Symposium Organizers
Mark Brongersma Stanford University
Donald S. Gardner Intel Corporation
Michal Lipson Cornell University
Jung H. Shin KAIST
I1: Si-Based Light Emitters
Session Chairs
Mark Brongersma
Don Gardner
Tuesday PM, April 18, 2006
Room 3007 (Moscone West)
9:30 AM - **I1.1
Light-emitting Porous Silicon and Silicon Nanowires: Past and Future.
Ulrich Goesele 1
1 Experimental Dept. II, Max Planck Institute of Microstructure Physics, Halle Germany
Show AbstractIn the early 1990ies, the observation of light-emitting porous silicon, consisting of an array of interconnected silicon quantum wires, induced a couple of thousand scientific publications because of the potential technological implications and the easy access to quantum phenomena present at room temperature. Porous silicon does not only show specific desirable optical properties but it also may act as an efficient explosive. In the meantime interest in silicon nanowires for future nanolectronics has increased fairly dramatically. The presentation will try to give an overview on the fabrication of porous silicon and some of its optical properties as well as the relation to the fabrication and properties of silicon nanowires and nanoparticles.
10:00 AM - I1.2
Size and Temperature Dependent Photophysics of Si Nanowires.
Alex Guichard 1 , David Barsic 1 , Ted Kamins 2 , Shashank Sharma 2 , Mark Brongersma 1
1 Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California, United States, 2 Quantum Science Research, Hewlett-Packard Laboratories, Palo Alto, California, United States
Show AbstractA study of the light emission from Si nanowires is presented. We demonstrate that efficient photoluminescence (PL) can be obtained from nanowires grown by chemical vapor deposition (CVD) at CMOS compatible TiSi2 catalyst sites. Small diameter Si nanowires have received little attention as a Si-based light emitter, but could overcome problems associated with charge injection and luminescence energy control in other nanostructured Si systems. In this study, we have investigated how the PL energy and lifetime changes with decreasing wire size, and show a luminescence blueshift with decreasing wire diameter and a final peak energy on the order of 1.6 eV. PL lifetimes are measured to be on the order of 40 μs. Transmission electron microscopy (TEM) studies reveal crystalline diameters on the order of 3nm, and the relationship of PL energy and lifetime with core diameter is in good agreement with various theoretical and experimental models of quantum confined charge carriers in Si. The temperature dependence of luminescence energy and intensity has also been explored, and low temperature luminescence photophysics of Si nanowires will be discussed. Challenges to fabrication of electroluminescent (EL) devices will also be explained. This research demonstrates that Si nanowires are a viable candidate for the realization of reliable and efficient Si-based EL devices.
10:15 AM - **I1.3
Tuned Spectral Emission from Silicon Nanocrystals Coupled to Metal Nanoisland Arrays.
Julie Biteen 1 , Luke Sweatlock 1 , Hans Mertens 2 , Nathan Lewis 1 , Albert Polman 2 , Harry Atwater 1
1 , California Institute of Technology, Pasadena, California, United States, 2 , AMOLF-FOM, Amsterdam Netherlands
Show Abstract10:45 AM - I1.4
Silicon Quantum Dots with Photoluminescence Quantum Yields as High as 67%.
Lorenzo Mangolini 1 , David Jurbergs 2 , Elena Rogojina 2 , Uwe Kortshagen 1
1 Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, United States, 2 , InnovaLight, Inc., Minneapolis, Minnesota, United States
Show AbstractSilicon’s indirect band gap character manifests in poor photo- and electroluminescence as well as long radiative lifetimes of the bulk material. While the optical properties of silicon nanocrystals are significantly enhanced compared to the bulk material, they can usually still not rival those of direct band gap semiconductors. In this presentation, we discuss a novel approach to the synthesis and surface passivation of silicon nanocrystals that enables achieving a so far unprecedented optical activity of silicon nanocrystals. Our synthesis approach is based on the dissociation of silane precursor gas in a nonthermal plasma and the formation of 3-5 nm nanocrystals within a few ms of residence time in the plasma. As we had shown previously, this simple and inexpensive single-step approach allows achieving very high mass yields of luminescent silicon nanocrystal material of up to 50 mg/h [Mangolini, Thimsen, and Kortshagen, Nano Letters 5(4), pp. 655-659 (2005)]. After the synthesis, silicon nanocrystal are collected on filters and their surfaces are passivated using a wet-chemical approach. Organic alkene or alkyne ligands are attached to the silicon nanocrystal surface in a reaction known as hydrosilylation. In this thermally activated reaction alkenes or alkynes bond with a hydrogen passivated silicon surface via a free-radical mechanism. A crucial aspect of our approach is the strict avoidance of exposure to air throughout the entire process. The synthesized powder is collected and transferred into the wet-chemical reactor under anaerobic conditions, and all chemical reactions are performed under air-sensitive chemistry procedures. Fourier transform infrared spectroscopy confirms that our samples show no trace of surface oxidation. Photoluminescence quantum yields of the materials have been measured. The highest values achieved have been as high as 67% for material that has a photoluminescence peak emission at about 790 nm. This very high quantum yield of silicon rivals the quantum yield of direct band gap semiconductors. This work was supported in part by the MRSEC Program of the National Science Foundation under award number DMR-0212302.
11:00 AM - I1:Si Emitters
BREAK
11:30 AM - **I1.5
Light Emission in Silicon-rich Nitride Nanostructures.
Luca Dal Negro 1 , Jae Hyung Yi 1 , Jurgen Michel 1 , Lionel C. Kimerling 1 , Sebastien Hamel 2 , Andrew Williamson 2 , Giulia Galli 2
1 Materials Science, MIT, Cambridge, Massachusetts, United States, 2 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractThe traditional approach to turn silicon (Si) into a light emitting material is to reduce its dimensionality to the nanometer scale, where both quantum confinement and surface chemistry effects improve the efficiency of light generation.Light-emitting Si-rich silicon nitride films (SRN) were fabricated by Plasma Enhanced Chemical Vapor Deposition (PE-CVD) and silicon nanocrystals (Si-nc’s) were formed by low temperature (500 - 900°C) thermal annealing. The presence of small (2 nm) Si-nc’s was demonstrated by micro-Raman scattering and transmission electron microscopy (TEM) analysis. Photoluminescence and absorption spectroscopy measurements have shown strongly Stokes-shifted, efficient broad band emission. The SRN emission dynamics and the emission temperature behavior were also studied and nanosecond fast, wavelength dependent recombination with negligible thermal quenching from 4 K to 330 K were observed. We studied the light emission mechanism in SRN by performing first-principles (DFT-LDA) theoretical simulations indicating that light emission in SRN originates from strongly localized, nitrogen-related exciton states at the surface of small Si clusters embedded in an amorphous silicon nitride network. Light emission from SRN systems can provide alternative routes towards the fabrication of optically active CMOS-devices.
12:00 PM - I1.6
Emission Properties Of Erbium-Doped Silicon Nanostructures In Silicon Nitride Under Electrical Excitation.
Jae Hyung Yi 1 , Luca Dal Negro 1 , Jurgen Michel 1 , Lionel C. Kimerling 1
1 DMSE, MIT, Cambridge, Massachusetts, United States
Show AbstractSilicon (Si) is the microelectronics material per excellence and many attempts in the last decade have been done to combine optical and electrical functions directly on a Si chip. Especially strong efforts have been devoted to obtain efficient light emission from Si-based structures. Quantum confinement and surface chemistry effects have allowed a significant improvement in light emission efficiency from Si-nanocrystals (Si-nc) embedded in SiOx matrices under optical pumping. However, the demonstration of efficient electroluminescence in these materials has been impeded so far by the lack of efficient carrier electrical injection in the insulating SiOx matrices and both injection current levels and device reliability severely limited the performances of SiOx-based light emitting structures. Therefore an alternative CMOS-compatible approach is needed, based on dielectric matrices where charge injection can be more easily achieved and efficiently emitting Si nanocrystals can be successfully embedded [1]. Recently we reported on nucleation of a high density of efficiently emitting (7% quantum efficiency at room temperature) Si nanoclusters embedded in amorphous silicon nitride and we showed by first-principles simulations [2,3] that nitrogen atoms at the surface of nanometer-sized silicon clusters play a crucial role in the light emission mechanism. In addition, we demonstrated [3] that the 1.55 μm Er ion emission can be significantly sensitized in these materials under resonant and non-resonant optical pumping. However, despite the opportunities of sensitized Er transitions in Si-nanocluster embedded in nitride matrices, there are few reports on the optical characteristics of Er-doped SRN system under electrical excitation. In this work we investigated the electrical and optical properties of Er-doped Si clusters in nitride matrices. Plasma Enhanced Chemical Vapor Deposition (PECVD) and rf sputtering were used for film deposition and thermal annealing was followed to induce the nucleation of small (1-3 nm) Si nanoclusters and to activate Er emission. Proof of concept p-i-n device structures have been fabricated to investigate the characteristics of the electrical transport and the electroluminescence of Er-doped Si-rich nitride. [1] L. Dal Negro, J. H. Yi, V. Nguyen, Y. Yi, J. Michel, L. C. Kimerling, “Spectrally enhanced light emission from aperiodic photonic structures”, Appl. Phys. Lett. 86, 261905 (2005).[2] L. Dal Negro, J. H. Yi, L. C. Kimerling, S. Hamel, A. Williamson, G. Galli, “Light Emission from Silicon-rich Nitride Nanostructures”, Appl. Phys. Lett., submitted (2005).[3] L. Dal Negro, J. H. Yi, M. Hiltunen, J. Michel, L. C. Kimerling, S. Hamel, A. J. Williamson, G. Galli, T.-W. F. Chang, V. Sukhovatkin, E. H. Sargent, “Light-emitting Silicon Nitride Systems and Photonic Structures”, J. Exper. Nanosci., submitted (2005).
12:30 PM - **I1.8
New Functionality Of C-Si:Er: Optical Memory Effect In Photo- And Electroluminescence.
I. Izeddin 1 , M. Forcales 1 , B. Andreev 2 , D. Kryzhkov 2 , W. Jantsch 3 , Tom Gregorkiewicz 1
1 , University of Amsterdam, Amsterdam Netherlands, 2 , Institute for Physics of Microstructures, RAS, Nizhny Novgorod Russian Federation, 3 , University of Linz, Linz Austria
Show AbstractIn spite of its natural constraint of a small and indirect bandgap, crystalline Si (c-Si) features some properties of an excellent optical material. In the past, we have reported persistent luminescence (afterglow) and optical memory in c-Si:Er at cryogenic temperatures using two-color spectroscopy with a free-electron laser. Following these fundamental findings, we now report on similar effects in electroluminescence at higher temperatures. We show full write-read-erase optical memory functionality for Si:Er structures grown using sublimation molecular beam epitaxy. These findings open new routes for the development of an optoelectronic converter with memory functions for Si-based photonic circuits operating in the 1.5 μm telecommunication wavelength. This ushers in the era of optical memory fully integrable with the CMOS platform.In the contribution, we will review optical memory effect as observed in photo and electroluminescence. We will explore practical limits of this effect in terms of operational temperature and retention time. We will present possible physical mechanism underlying the memory functionality and from that prospective compare the practical limits with the fundamental ones.
I2: Rare Earth-Doped Si Nanostructures
Session Chairs
Tuesday PM, April 18, 2006
Room 3007 (Moscone West)
2:30 PM - **I2.1
Silicon Dioxide Films Containing Silicon Nanocrystals and Erbium ions – Modification of Spontaneous Emission Rate and Energy Transfer Rate by Metal Thin Films.
Minoru Fujii 1
1 Department of Electrical & Electronics Engineering, Faculty of Engineering, Kobe University, Kobe Japan
Show Abstract3:00 PM - I2.2
Direct Measurement of the Er3+ Optical Absorption Cross-section in Different Oxide Thin Films.
W. M. M. Kessels 1 , B. Hoex 1 , I.M.P. Aarts 1 , T.T. Van 2 , J.P. Chang 2 , H. Mertens 3 , A. Polman 3 , M.C.M. Van de Sanden 1
1 Dept. of Applied Physics, Eindhoven Univ. of Technology, Eindhoven Netherlands, 2 Chemical and Biomolecular Engineering Department, University of California Los Angeles, Los Angeles, California, United States, 3 Center for Nanophotonics, FOM for Atomic and Molecular Physics, Amsterdam Netherlands
Show AbstractErbium-doped oxides are used as an optical gain medium in which Er3+ ions are excited to generate emission at 1.5 μm, which is the standard communication wavelength. Information on the absorption cross-sections is of key importance, although direct determination of these cross-sections is hampered due to sensitivity requirements. Here we show that the cavity ring-down technique, recently applied on thin films, is a direct and highly sensitive absorption measurement method that can be used to measure the optical absorption cross section of the Er3+ 4I15/2 → 4I13/2 intra-4f transition. Using this technique, samples with a thin Er-doped oxide film are placed inside a high quality linear optical cavity formed by two planoconcave highly reflecting mirrors, which is excited using a short laser pulse. Absorption values can be deduced from the decay rate of light, thereby preventing the most common limitation of standard absorption measurements as the decay rate is independent of the intensity of the light pulse. Furthermore, the effective sampling length is significantly enhanced by placing the sample inside an optical cavity, which also increases the sensitivity.This method has been applied to measure the absorption cross-section of Er3+ embedded in SiO2 and Si-rich oxide (10 at.% excess Si) films produced by ion implantation and thermal annealing. Maximum absorption values of 800 ppm were obtained and peak absorption cross-sections of (8±2)×10-21 cm2 at 1536 nm were found for both the SiO2 and Si-rich oxide [1]. This result also demonstrates that silicon nanoclusters in Si-rich oxide do not enhance the peak absorption cross-section as suggested by previous measurements using waveguides. The cavity ring-down method was also applied on very thin films, ~20 nm (determined based on the growth rate per ALD cycle), of Er-doped Y2O3 deposited by radical-enhanced atomic layer deposition (ALD) [2]. For these Y2O3 films, which can accommodate higher levels of Er doping and do not require thermal annealing, spectra were found with clearly resolved peaks due to Stark splitting of the excited and ground states. The Er3+ related absorption was 200-230 ppm which corresponds with a peak absorption cross section of (1.5±0.5)×10-20 cm2. Furthermore, an absorption peak was observed at ~1380 nm in the Er-doped Y2O3 which is most probably related to the first overtone of the O-H vibration. This absorption peak, with a maximum absorption value of 130 ppm, illustrates once more the sensitivity of the cavity ring-down method as no OH-related absorption could by observed by conventional infrared spectroscopy. [1] H. Mertens, A. Polman, I.M.P. Aarts, W.M.M. Kessels, and M.C.M. van de Sanden, Appl. Phys. Lett. 86, 241109 (2005).[2] T.T. Van and J. Chang, Appl. Phys. Lett. 87, 011907 (2005).
3:15 PM - I2.3
Broadband Sensitization of Erbium ion Emission at 1.54 μm in Er and Au or Ag Coimplanted Silica Glass.
Enrico Trave 1 , Giovanni Mattei 1 , Paolo Mazzoldi 1 , Giovanni Pellegrini 1 , Cinzia Sada 1 , Carlo Scian 1 , Carlo Battaglin 2
1 Dipartimento di Fisica, Universita' di Padova, Padova Italy, 2 Dipartimento di Chimica Fisica, Universita' di Venezia, Venezia Italy
Show Abstract3:30 PM - **I2.4
Band Offsets in Undoped and Er Doped Silicon Nanoparticles.
Tony van Buuren 1 2 , Rob Meulenberg 1 , April Montoya-Vaverka 1 , Trevor Willey 1 , Jon Lee 1 , Lou Terminello 1
1 Chemistry and Materials Science, LLNL, Livermore, California, United States, 2 , University of California Merced, Merced, California, United States
Show AbstractIf silicon nanoparticles are to be integrated into an optoelectronic device understanding how the band edges move as a function of particle size is required. Using elemental specific x-ray spectroscopy techniques [x-ray absorption (XAS) and soft x-ray emission (SXE)], we are able to monitor the band edge shifts as a function of silicon nanoparticle size and doping. Previously, we have reported that the band edges of both porous silicon and gas phase produced silicon nanoparticles shift as a function of particle size and the valence band shift was found to be twice as large as the conduction band. However this does not seem to be the case for silicon nanoparticles that are incorporated into an oxide matrix. In this case the valence band edge shift is on the same order as the conduction band edge shift. When less than 3% Er is incorporated into the silicon nanoparticle the conduction band edge shift remains the same as the undoped particle. The doped nanoparticles are fabricated in two manners: 1) by co-evaporation of Er and Si and 2) by Er deposition on the surface of undoped Si nanoparticles. In addition to monitoring band edge shifts as a function of both particle size and Er concentration. we are able to probe the chemical environment of the Er in the Si nanoparticle. In this presentation we discuss possible explanations for these observations in terms of surface termination and strain in the nanoparticle. This work was supported by the Division of Materials Sciences, Office of Basic Energy Science, and performed under the auspices of the U. S. DOE by LLNL under contract No. W-7405-ENG-48.
4:00 PM - I2:Rare Earth
BREAK
I3: Si-Compatible Light Emitters
Session Chairs
Tuesday PM, April 18, 2006
Room 3007 (Moscone West)
4:30 PM - **I3.1
Si-Based Light Sources and Lasers
Albert Polman 1
1 FOM Institute, AMOLF, Amsterdam Netherlands
Show Abstract5:00 PM - I3.2
PbSe Nanocrystal Excitation by a Si Nanocrystal Field Effect LED.
Robert Walters 1 , Josep Carreras 1 , Domenico Pacifici 1 , Sungjee Kim 1 , Harry Atwater 1
1 Applied Physics, California Institute of Technology, Pasadena, California, United States
Show AbstractField Effect Light Emitting Devices (FE-LEDs) enable the efficient electrical excitation of silicon nanocrystal arrays. These devices consist of MOS transistors with an embedded floating gate comprised of ~5E12 silicon nanocrystals/cm^2 (2-4nm diameter) isolated from the channel by an ~4nm tunnel oxide and isolated from the gate contact by an ~8nm thick control oxide layer. In contrast to traditional LEDs in which charges are driven into an active region by a constant current, the charges in this device are injected sequentially into the silicon nanocrystal array by Coulomb-field enhanced Fowler-Nordheim tunneling from the channel of the transistor. The gate contact is designed to allow for the transfer of energy from Si nanocrystals to organically synthesized PbSe nanocrystals that are drop cast on top of the FE-LED gate contact.We will present new observations of ~1550nm light emission from a hybrid FELED device in which PbSe nanocrystals are pumped via energy transfer from nearby silicon nanocrystals. Energy transfer to PbSe nanocrystals can occur via radiation and absorption of near-infrared photons (~780nm) or via non-radiative short range processes. Radiative energy transfer is limited by the slow recombination of excitons in silicon nanocrystals (~10-100kHz), while the short range non-radiative processes can be orders of magnitude faster.We will discuss observations of infrared electroluminescence in our device and comment on the role of radiative and non-radiative energy transfer processes. We will also present our analysis of the waveguiding and gain medium potential of the PbSe/FELED system for 1550nm light.
5:15 PM - I3.3
Light Emission Enhancement from Ion Beam Synthesized Nanocrystalline FeSi2-Si Structures by Multiple-cycle Implantation Approach
Judith Roller 1 5 , C.F. Chow 1 , Y.T. Chong 2 , S. P. Wong 1 3 , Quan Li 2 3 , M.A. Lourenco 4 , K.P. Homewood 4
1 Electronic Engineering, Chinese University of Hong Kong, Shatin Hong Kong, 5 Physics, University of Karlsruhe, Karlsruhe Germany, 2 Physics, Chinese University of Hong Kong, Shatin Hong Kong, 3 Materials Science and Technology Research Centre, Chinese University of Hong Kong, Shatin Hong Kong, 4 School of Electronics Engineering, Computer and Mathematics, University of Surrey, Guildford United Kingdom
Show AbstractWe have formed nanocrystalline (nc) FeSi2 embedded in Si by high dose Fe implantation into Si using a metal vapor vacuum arc ion source and studied the photoluminescence (PL) properties from these structures. We have also fabricated MOS diode structures containing implanted FeSi2 nanocrystals with a thin tunnel oxide layer of several nanometer thick and studied their electroluminescence (EL) properties. The PL and EL properties from these nc FeSi2-Si structures were measured as a function of temperature from 80 to 300 K. The dependence of the microstructures and light emission properties on the implantation and thermal annealing conditions were investigated. Our previous results showed that clear EL signals were obtained even at room temperature for some of the devices fabricated at appropriate processing conditions [1]. The PL intensity also exhibited an implant dose quenching effect which was shown to be related to the changes in the orientation relationship (OR) between the FeSi2 crystallites and the Si matrix with increasing dose [2]. In this work, we shall showed that by adopting a multiple-cycle implantation approach where a high implant dose is achieved by repeating two or more implantation-thermal annealing cycles each at a smaller dose, a higher PL and EL intensity can be obtained under appropriate conditions. The light emission properties and their dependence on the processing parameters will be discussed in conjunction with the microstructures determined by transmission electron microscopy. This work is partially supported by the Research Grants Council of Hong Kong SAR (ref. no. CUHK4231/03E), and C. N. Yang Optical Science Fund.[1] C.F. Chow et al., Mater. Sci. Eng. B (2005).[2] Y.T. Chong et al., Mater. Sci. Eng. B (2005).
5:30 PM - **I3.4
Towards the Era of Silicon Photonics through High Efficient Silicon-based Light Emitter.
G. Sung 1 , K.H. Kim 1 , N.-M. Park 1 , T.-Y. Kim 1 , K. S. Cho 1 , C. Huh 1 , J.H. Shin 1
1 , ETRI, Daejeon Korea (the Republic of)
Show AbstractCurrent electronic devices are strongly dominated by silicon technology. However silicon technology does not allow easy integration with optical component since silicon is a poor light emitter. The unique properties of Si nanocrystals (nc-Si) can be exploited to fabricate Si-based light source. In this presentation, we will introduce a quantum confinement effect in the nc-Si embedded in a silicon nitride formed by PECVD. The band gap of the nc-Si could be controlled from 1.38 to 3.02 eV by decreasing the nanocrystal size. In addition, we will demonstrate a silicon light emitter with a transparent doping layer on nc-Si embedded in silicon nitride active layer by using ITO and n-type wide bandgap semiconducting layer. The ability to control the emission properties of semiconductors with optical microcavities and photonic crystals is continuing to attract the attention of the photonics community. Therefore we will present some light-enhancement structures such as microcavity, photonic crystals, and surface modulation for achieving more efficient and new functional Si light emitters.
I4: Poster Session: Si and Rare Earth Based Light Emitting Materials
Session Chairs
Mark Brongersma
Jung Shin
Wednesday AM, April 19, 2006
Salons 8-15 (Marriott)
9:00 PM - I4.1
Effect of Ion Implantation on the Light-emitting Si Nanocrystals.
Gregory Kachurin 1 , S. Cherkova 1 , A. Gutakovsky 1 , D. Marin 1
1 , Institute of Semiconductor Physics, Novosibirsk Russian Federation
Show Abstract9:00 PM - I4.10
Structural and Photoluminescence Properties of Si clusters in Si-rich Silicon Nitride Films.
Abdelilah Slaoui 1 , Abdelatif Zerga 1 , Marzia Carrada 1
1 InESS, CNRS, Strasbourg France
Show Abstract9:00 PM - I4.11
The Photoluminescence Properties of Er3+ doped a-SiNx and a-SixC1−x Films.
Liu-Fang Bian 1 , Chu-Guang Zhang 1 , Wei De Chen 1 , L. B. Ma 2 , R. Song 2 , Z. X. Cao 2 , C. C. Hsu 1
1 , Institute of Semiconductors, Chinese Academy of Sciences, Beijing China, 2 , Institute of Physics, Chinese Academy of Sciences, Beijing China
Show AbstractEr doped Si-based materials have been recently attracting much interest because of its potential application in Si-based optoelectronic devices. In this work, amorphous SiNx (a-SiNx) and amorphous SixC1−x (a-SixC1−x) films were deposited onto Si (100) substrates by plasma-enhanced chemical vapor deposition. These films were implanted with Er3+ and were then characterized by x-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) measurements. The defined Stark structure from Er3+ PL spectrum for a-SiNx:Er were studied and discussed. Three strong peaks, P1 (1.528 μm), P2 (1.536 μm ) and P3 (1.550 μm), were clearly observed. The most intense emission P2 peak located at 1.536 μm showed the main emission was due to the transition 4I13/2 to 4I15/2 of Er3+ as commonly observed for Er3+ in Si. The other two PL peaks, P1 and P3, in the vicinity of main emission peak P2, are related to Er3+ centers from slightly different sites with lower site symmetry. The correlation between the visible PL from Si nanoclusters and infrared PL from Er3+ in a-SiNx:Er were studied. The PL properties of Er doped a-SixC1−x at room temperature and 10 K were also studied. The Er3+ 1.54 μm PL integrated intensity of Er-doped a-SixC1−x thin films decreases to about 62.7% when the temperature increases from 10 K to room temperature. Because of lower band gap of a-SiNx and a-SixC1−x comparing to silicon rich silicon oxide (SRSO), the two materials have advantage over SRSO for carrier injection. So the two materials may have practical use in fabricating light-emitting diode.
9:00 PM - I4.12
Er2SiO5 Nanotrees Formed by Wet Chemical Synthesis Using Vertically Aligned Si Nanowire Templates.
Kiseok Suh 1 , Jung Shin 1
1 Silicon Photonics Lab, Dept. of Physics, KAIST, Daejeon Korea (the Republic of)
Show Abstract Er-doping of Si-based materials has been the subject of intense investigation with the aim of developing an efficient, Si-based light source that can be used in Si microphotonics. However, the low solubility of Er has limited the maximum Er concentration that can be achieved without inducing Er precipitation to less than 1 at.% even for such well-establish host such as silica. Furthermore, incorporating Er in an amorphous host material results in a broad Er3+ luminescence peak, reducing the Er3+ emission cross section per unit wavelength. An interesting solution that has been proposed recently is using erbium silicates, since it can achieve an Er concentration in the excess of 10 at.%. Furthermore, since the Er3+ ions in such silicate crystals are located in a single class of site of a crystalline material, the resulting Er3+ luminescence peaks can be very narrow, effectively increasing the emission cross section at the peak wavelength. In this paper, we report on forming nanotrees of Er2SiO5 silicate crystals by wet chemical method using vertically aligned Si nanowires as templates. Saturated ErCl36H2O/EtOH solution was spin coated on vertically aligned Si nanowires of ~100nm diameter and ~1μm length grown via vapor-liquid-solid growth using SiCl4 and gold catalyst. Subsequent rapid thermal anneal at 900°C followed by another rapid thermal anneal at 1200°C in O2 and Ar environment, respectively, resulted in uniform transformation of Si nanowires into nanotrees of silicate crystals. The phase of the silicate crystals was determined via x-ray diffraction to be Er2SiO5, which is a stable phase in the Er2O3-SiO2 system. The high reactivity, large surface area, and isolation from direct contact with the Si substrate provided by Si nanowires is critical, as spin coating of blank Si substrates can lead to non-uniform formation of clumps of Er2O3 and Er2SiO5 phases instead. The nanotrees show sharp (less than 3 nm width at room temperature) at 1529 nm without any temperature quenching of Er3+ PL intensity, indicating their promise as the material basis for an efficient, Si-based light source.
9:00 PM - I4.13
Excited State Absorption in Erbium-Doped Silicon Rich Silicon Oxide.
Wei Loh 1 , Anthony Kenyon 2
1 Optoelectronics Research Centre, University of Southampton, Southampton United Kingdom, 2 Department of Electronic and Electrical Engineering, University College London, London United Kingdom
Show AbstractSilicon nanocluster (nc) sensitized Er-doped silica is a material system that has generated great interest, as it holds considerable promise for practical silicon-based lasers and optical amplifiers. There are numerous reports of 1550nm luminescence in this material system, and even experimental reports of optical gain in a fabricated waveguide. However, no lasing action has been achieved to date. In this contribution, we point out a key interaction – Er excited state absorption - in this material system; by highlighting and analyzing it here, we believe it will help point the way forward to efficient silicon-based lasers and optical amplifiers. In many reports, the Si nanoclusters, which are themselves luminescent, are found to have their broad photoluminescence (PL) peaks located near 1.6 eV (or a wavelength around 800nm), which has been attributed either to the silicon-oxygen double bond at the silicon-silica interface or to radiative recombination of confined excitons. Regardless of the cause, spectral hole-burning studies strongly indicate that resonant energy transfer does occur from the Si to the Er in the 800nm wavelength region. However, this energy transfer route may be highly problematic, due to an excited state absorption transition that is known from early work on erbium-doped fiber amplifiers (EDFAs). The basic reason why 800nm excitation of erbium is unattractive is simple: there are transitions around this energy that cause the Er metastable (4I13/2) state to be excited directly to higher level (4S3/2, 2H11/2) states. Excitations to these states serve no useful purpose, but merely pose a debilitating energy drain: EDFAs pumped at 800nm require about an order of magnitude more pump power to achieve the same gain as at 980nm, a level which suffers from no excited state absorption. We have conducted an analysis of this material system, incorporating excited state absorption in the model. The results of our analysis is compared with reported experimental data, and shown to explain the PL behaviour of the Si nc with Er concentration quite well. In addition, we are able to extract the Si nc-Er excited state energy transfer coefficient from the fit to experimental data, and estimate its value at 1x10-15 cm3/s. This is comparable to the Si nc-Er ground state transfer coefficient of 3x10-15 cm3/s, confirming that this transition is not of negligible impact, and should be considered in future designs and optimisation of this material system.
9:00 PM - I4.14
Energy Transfer by Gd to ion Implanted Ce and Er Atoms in Metal-Oxide-Silicon-based Light Emitting Diodes.
Slawomir Prucnal 1 , J.M. Sun 1 , H Reuther 1 , W Skorupa 1
1 , Institute of Ion Beam Physics and Materials Research,Forschungszentrum Rossendorf e.V., Dresden Germany
Show Abstract9:00 PM - I4.15
Flash lamp processing in the millisecond-range for Metal-Oxide-Silicon-based light emitting diodes
Slawomir Prucnal 1 , J.M. Sun 1 , A. Muecklich 1 , W. Skorupa 1
1 Ion Beam Physics and Material Research, FZR Rossendorf e.V, Dresden Germany
Show Abstract9:00 PM - I4.17
Monolithic Image and Particle Sensors Based on Thin-film on CMOS Technology: Advantages, Performances and Challenges.
Clement Miazza 1 , Nicolas Wyrsch 1 , Gregory Choong 1 , Dunand Sylvain 1 , Arvind Shah 1 , Christophe Ballif 1 , Nicolas Blanc 2 , Felix Lustenberger 2 , Rolf Kaufmann 2 , Danielle Moraes 3 , Mathieu Despeisse 3 , Pierre Jarron 3
1 Insititute of Microtechnology, University of Neuchatel, Neuchatel Switzerland, 2 Photonic Division, CSEM SA, Zurich Switzerland, 3 Experimental Physic Division, CERN, Geneva Switzerland
Show AbstractMonolithic image and particle sensors based on Thin Film on CMOS Technology (TFC) are becoming, due to the unique capabilities they provide, more and more attractive as an alternative to conventional sensors. In this technology, the detectors are vertically integrated on top of a CMOS chip. The chip is designed specifically for the application that is envisaged. The detector is, in the author’s case, a thin-film amorphous silicon (a-Si:H) diode, deposited within a VHF-PEVCD reactor. This deposition technique can provide high-quality, stress-free layers from a few hundred nm in thickness to several tens of micrometers. Therefore, this specific TFC concept enables one to: (i) separate the design of the photodiode and its placement from those of other pixel circuit elements; (ii) maximise photon or particle collection area within the array (thereby minimising dead areas that do not contribute to pixel sensitivity); (iii) optimise the a-Si:H detector so that it matches precisely the type and energy of the particles, or, alternatively, the spectrum of the photons to be detected.For both vision and particle detection, the use of this approach combined with the specific proprieties of a-Si:H diodes has lead to improved performances. In fact very high geometrical fill factors (FF > 90%), increased sensitivity (S > 60 V/(µJ/cm2)), high integration level and enhanced radiation hardness, coupled with low dark current values (10-100 pA/cm2) have been attained. This opens several possibilities in terms of applications with the following requirements, such as low light level detection, high dynamic range, high sensitivity, robustness for detection of particles, as well as for detection of X- and γ-rays.In this paper, an overview of these emerging TFC concepts is proposed with the aim of describing their advantages. The authors will, on one hand, define the potential of the technology, and, on the other hand, document some of the already reached performances. They will also illustrate the main challenges faced for the development of such monolithic sensors. The latest results achieved in both, vision and high energy physics field, as well as their potential applications are also presented here.
9:00 PM - I4.18
Synthesis of Erbium Doped Si-rich SiOx by Radio-Frequency Magnetron Cosputtering using Si/SiO/Er2O3 Target
Chia-Yang Chen 1 , Chun-Jung Lin 1 , Gong-Ru Lin 1
1 Department of Photonics & Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu Taiwan
Show AbstractErbium doped Si-rich SiOx (SiOx:Er3+) film has emerged as one of the luminescent materials for fiber-optic communication applications at wavelength of 1.52-1.57 μm. Typically, the SiOx:Er3+ can be synthesized using RF co-sputtering of Si chips and Er or Er2O3 pellets placed on the SiO2 target. Alternatively, Gourbilleau et al. prepared the SiOx:Er3+ films using a target with Er2O3 pellets on a pure SiO2 substrate in a plasma containing hydrogen environment. With the participation of Si chips and the hydrogen gas was attempted to increase the Si and reduce oxygen contents, respectively, in the deposited SiOx:Er3+ film. This facilitates an optimized precipitation of nc-Si in the SiOx:Er3+ after annealing. To tentatively increase the excess Si density, we propose for the first an oxygen-educed Si/SiO/Er2O3 target and demonstrate a parametric analysis for optimal sputtering condition of SiOx:Er3+ synthesis. The proposed technique also attempts to simultaneously increase the doping density of Er ions in the film without using pure Er pellets since which required additional ionization process in the as-deposited film. The use of Er2O3 thus preserves the Er3+ ions to improve light emission from the intra-4f transition at around 1.54 μm. With an optimized target area ratio of Si:SiO:Er2O3 = 35:52:13, the SiOx:Er3+ film RF sputtered at an RF sputtering power varying from 80 W to 170 W, and thermally annealed at 1000oC for 30-300 min is demonstrated. The maximum density of Si and Er are occurred at RF power of 100W. According to the RBS analysis,. The more Si and Er contents indicate the larger amount of the density of nc-Si and Er3+, respectively. The maximum IR-PL intensity at the wavelength of 1535 nm is observed from the SiOx:Er3+ sample annealed at 1000oC for the 240 min. Strong IR-PL peak at a wavelength of 1535 nm by pumping SiOx:Er3+ with a 532nm DPSS green laser is observed, as attributed to the energy transfer from nc-Si to the intra-4f transitions between the first excited state (4I13/2) and the ground state (4I15/2) of Er3+ ion. The PL spectra at 700-900 nm and 1520-1570nm obtained by using a 325 nm He-Cd laser and a 980 nm DFB laser are carried out to find out the evolution on the densities of nc-Si and Er3+ ions at different annealing temperatures and durations. Low annealing temperature and short annealing time cause weak IR-PL intensity, as attributed to low density of precipitated nc-Si. In contrast, high annealing temperature causes the decrease of IR-PL intensity with the elimination of Er3+ ions due to its segregation into erbium oxide or precipitation in the SiO2 host. Moreover, longer annealing time also decreases the IR-PL intensity, as the density of precipitated Si nanocrystals slightly reduces in the SiOx:Er3+ film with constant excess Si atoms. These results indicate that the Si/SiO/Er2O3 target can be successfully employed for sputtering growth of SiOx:Er3+ with enhanced near-infrared luminescence.
9:00 PM - I4.3
Radiative Versus Non-radiative Decay Processes Studied by Time-resolved Photoluminescence for Multi-layered Si Nanocrystals Fabricated by Ion Beam Sputtering and Annealing.
Sung Kim 1 , Yong Min Park 1 , Suk-Ho Choi 1 , Kyung Joong Kim 2
1 Dept. of Physics and Applied Physics, College of Electronics and Information, Kyung Hee University, Yongin, Kyungkido, Korea (the Republic of), 2 Nano Surface Group, Korea Research Institute of Standards and Science, Taejon Korea (the Republic of)
Show AbstractIon beam sputtering has been used to fabricate 50-period SiO2/SiOx multilayers, which have been subsequently annealed to form Si nanocrystals (NCs) in the SiOx layer. The PL intensity of the samples with x < 1.4 increases with increasing temperature up to 100 K, but above 100 K, it decreases. For the samples with x ≥ 1.4, the PL intensity shows a monotonic decrease with increasing temperature. For most samples, the time-resolved PL starts to decay following a stretched exponential function at about 300 s after excitation by 20-ps pulse laser. The PL lifetime of Si NCs ranges form 55 to 300 μs depending on the energy, the temperature, and the size of NCs. The lifetime is shorter at the higher energy of the PL spectra or for smaller NCs, which is well explained by the state filling effect. Possible mechanism based on the transitions associated with singlet and triplet states is proposed to explain the radiative versus non-radiative decay processes related to the observed temperature-dependent PL behaviors.
9:00 PM - I4.4
Growth and Photoluminescence Characteristics of Si Nanocrystals in Ion-beam-sputtered SiOx Layers Depending on Their Thickness and the Existence of SiO2 Capping Layer.
Min Choul Kim 1 , Yong Min Park 1 , Sung Kim 1 , Suk-Ho Choi 1 , Kyung Joong Kim 2 , Kwang-Hyun Ahn 3 , Song-Ho Byeon 3
1 Dept. of Physics and Applied Physics, College of Electronics and Information, Kyung Hee University, Yongin, Kyungkido, Korea (the Republic of), 2 Nano Surface Group, Korea Research Institute of Standards and Science, Taejon Korea (the Republic of), 3 College of Environment and Applied Chemistry, Kyung Hee University, Yongin, Kyungkido, Korea (the Republic of)
Show AbstractIon beam sputtering has been employed in ultra-high vacuum to fabricate thin Si-rich SiOx layers of 2 to 20 nm thickness, which have been subsequently annealed at 1100 oC for 20min to form Si nanocrystals (NCs). Annealing temperature dependence was also studied from 600 to 1100 oC for the samples of 12 nm thickness. The x value was controlled and determined using in-situ X-ray photoemission spectroscopy. NC-related photoluminescence (PL) spectra appear when the thickness of SiOx is ≥ 6 nm, and are blue-shifted from 850nm to 730nm by increasing x from 0.8 to 1.8. When x > 1.2, the PL peak redshifts with increasing the layer thickness, but when x < 1.2, the PL peak of thicker layers shows anomalous higher-energy shifts. At x = 1.2, the samples show mixed behaviors of the PL shifts. By capping the SiOx layer with a 2 nm SiO2, the PL is blue-shifted with its intensity enhanced due to the rescaling of the overall film stoichiometry. Possible growth and luminescence mechanisms of Si NCs are proposed to explain the experimental results.
9:00 PM - I4.5
Control of Er/Tm interaction in Er and Tm doped silicon nano-clusters: for optimization of rare earth luminescence
Se-Young Seo 1 2 , Margit Zacharias 1 , Jung Shin 2
1 , Max-Planck-Institute for Microstructurephysics, Halle Germany, 2 Physics, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractSilicon-based microphotonics aims to realize the monolithic highly-integrated optical components on a chip with help of mature CMOS process. The increase of bandwidth of a single optical waveguide is needed in order to reduce the device size further. In multiplexing system, ultra broad light sources/amplifiers are compulsory components, but ‘state of art’ broadband amplifiers are rather bulky, because they have been realized by the serial combination of individual amplifiers. Nanocluster silicon (nc-Si) can excite different rare earth (RE) ions at the same time, thanks to non-resonant Auger-type interaction between nc-Si and RE ions. Thus nc-Si co-doped with Er3+ ('C' band) and Tm3+ ('L' and 'U' band) can be applied to compact infrared light source/amplifier which cover almost entire communication window of silica fiber. For Er and Tm homogenously doped nc-Si, strong Er3+ → Tm3+ energy transfer was however reported, and need to be controlled for micro-photonic application. In this work, we present the efficient methods to control Er/Tm interaction in Er and Tm co-doped nc-Si films for efficient RE luminescences. The Er/Tm energy transfer are controlled via the adjustment of relative ratio of excited Tm3+ to excited Er3+ ion or the adjustment of distance between Er and Tm. The excited ion ratio is adjusted varying annealing temperature. For only Er or Tm doped nc-Si films, both Er3+ and Tm3+ luminescence could be optimized at 950—1050 °C anneal. And the intensity ratio of Tm3+ to Er3+ luminescence is decreased by four times, with increase of annealing temperature from 700 °C to 1250 °C. The result imply that an excited Er3+ ion is faced with less Tm3+ ions at higher annealing temperature if Er and Tm ions are homogenously co-doped to nc-Si films. After examination of anneal temperature dependence of RE luminescence, Er → Tm energy transfer rate was found to decrease significantly from 1 × 104 to 4 × 103 sec-1, and it is consistent with the decrease of the excited ion ratio. In addition, due to weaker Er/Tm interaction at higher anneal temperature, optimum Er3+ luminescence could be achieved at rather higher anneal temperature(1050—1150 °C) in co-doped films, compared to only Er doped films. In order to adjust the Er—Tm distance, we used nm-scale Er/Tm separated silicon nanostructures. One example of these nanostructures is alternatively Er and Tm doped SRSO layers. We deposited the each doped layers of from 0 to 72 nm, and the energy transfer rate is strongly decreased from 5 × 103 to 70 s−1 with increase of layer thickness. At the same time 50-folds enhancement of Er3+ luminescence is observed while the Tm3+ PL intensity is unaffected. We also suggest another example of distance controlled nanostructure, Si/SiO2:Er/Si/SiO2:Tm superlattices films, and discuss their RE luminescence and Er/Tm interaction. The models of Er/Tm interaction in each cases and the comparison to experiments are also discussed in this presentation.
9:00 PM - I4.6
Effects of Crystallinity on the Er3+ Excitation in Er-doped SiOx/SiO2 Superlattices.
Jee Soo Chang 1 , Moon-Seung Yang 1 , Jung Shin 1 , Kyung Joong Kim 2 , Dae won Moon 2
1 Physics, Korea Advanced Institute of Science & Technology(KAIST), Daejeon Korea (the Republic of), 2 Nano surface group, Korea Research Institute of Standards and Science(KRISS), Daejon Korea (the Republic of)
Show AbstractNanocluster Si (nc-Si) sensitization of Er3+ has attracted a great interest for its applications in Si photonics as a promising light source at 1.54 μm. While it is often assumed that the nc-Si are crystalline, it is not required by the physics of nc-Si sensitization. Furthermore, there have been reports that amorphous nc-Si may be a better sensitizer for erbium. On the other hand, the high temperature annealing required to crystallize nc-Si not only leads to crystallization of nc-Si, but also to to many other changes such as differences in nc-Si size and density, annealing of non-radiative defects, and Er precipitate formation. These can all affect Er3+ luminescence properties, making unambiguous identification of the effect of crystallinity difficult. In this work, we report on using SRSO/SiO2:Er superlattice (SL) structure to investigate the effect of crystallinity on the Er3+ excitation. By isolating Er ions into pure SiO2 layers, it is possible to investigate the formation and crystallization of nc-Si separately from Er3+ luminescence properties. Two series of SiOx/SiO2:Er superlattices with stoichiometry of x=1.6 and 1.8 was deposited by the UHV-ion beam sputtering method. After deposition, SLs were annealed in a sequence of 20 min at 600°C, 5min at a temperature ranging from 650°C~1100°C, and 5 min at 600°C to form Si nanoclusters in the SiOx layer. Phase separation of SiOx into nc-Si at different annealing temperatures was identified by XPS analysis, while crystallinity of nc-Si was identified by high-reslolution TEM. We find that while formation of nc-Si occurs at temperatures as low as 700°C, crystallization requires temperatures in the excess of 1050°C, with the nc-Si from x=1.6 film being larger than that from the x=1.8 film. The Er3+ luminescence efficiency, on the other hand, remains the same above 800°C, allowing us to unambiguously investigate the effect of nc-Si crystallinity on Er3+ excitation efficiency. We find that silicon suboxides are ineffective in sensitizing Er3+, and that presence of nc-Si is required for effective sensitization. However, little effect is observed from nc-Si crystallinity on the effective excitation cross section of Er3+. Instead, a much greater effect is observed from the nc-Si size, with smaller nc-Si being far more efficient than the larger ones irrespective of crystallinity such that the highest Er3+ PL intensity and efficiency is observed from the x=1.8 film that was annealed at 1050°C. Based on the result, we conclude that for nc-Si sensitization of Er3+, formation of the highest density of smallest possible nc-Si while suppressing non-radiative defect formation and Er precipitation is far more critical than forming high-quality crystalline nc-Si.
9:00 PM - I4.7
The Effect of Hole Confinement on Luminescence Efficiency of Er in group IV Semiconductors.
Karen Vernon-Parry 1 , Jan Evans-Freeman 1 , Phil Dawson 2
1 Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield United Kingdom, 2 Physics Department, University of Manchester, Manchester United Kingdom
Show Abstract9:00 PM - I4.8
Visible photo- and Electro-luminescence from Tb-doped Silicon Oxy-nitride.
Hoon Jeong 1 , Jung Shin 1
1 Physics, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractThere is a growing interest doping CMOS-compatible dielectrics with rare earths to develop light emitters in the visible range that can be monolithically integrated with other photonic and electronic devices. So far, much of the research effort was focused on rare-earth doping of silica due to its ability to be used directly in the well-understood MOS-type diode structure. Unfortunately, silica has an extremely large bandgap that makes efficient injection of carrier difficult, thereby requiring very high operating voltages that can lead to short device lifetimes. An interesting alternative is rare earth doping of silicon nitride. Nitrogen is as effective in optically activating rare earth ions as oxygen, and silicon nitrides have a bandgap of only about 4 eV, allowing easier injection of current. Furthermore, nitrogen bonds tend to be quite robust, which may lead to more stable device operations. In this paper, we report on Tb-doped oxynitride films grown by plasma-enhanced chemical vapor deposition (PECVD). 220±20 nm thick Tb-doped oxynitride films were grown using inductively-coupled PECVD with concurrent sputtering of Tb. The film composition was varied by varying the gas flow rates. For comparison, a similar set of oxynitride films without Tb was also deposited. After deposition, the films were annealed for 30 min at temperatures ranging from 550 to 950°C in flowing Ar environment. The Si and Tb content were kept constant at 39±1 at. % and 0.25±0.02 at. %, respectively, while the O/N ratio was varied between 0.14 and 0.44. Note that in all cases, we have no excess Si as the oxygen and nitrogen content are higher than that necessary to form stoichiometric Si3 N4 and SiO2. We find that Tb3+ ions can be excited via carrier recombination, but that excitation of carriers into the extended, above-bandgap states is necessary as the band-tail states are ineffective in transferring energy to Tb3+ ions despite energy resonance. We also find that strong Tb3+ photoluminescence can be obtained even from as-deposited films without the need for a high temperature anneal. Visible electroluminescence could be obtained from mesa-type diodes were fabricated using Tb-doped oxynitride films. Strong electroluminescence required reverse bias and a p-type substrate, indicating that impact excitation via electrons from the substrate to be the dominant excitation mechanism. Blue photoluminescence could be obtained from similarly prepared, Tm-doped oxynitride films, indicating that multi-color emission may be possible using a single oxynitride host. Detailed analysis of the Tb electroluminescence as well as possibility of blue electroluminescence from Tm-doped films will also be given.
9:00 PM - I4.9
Nanocluster Si Sensitization of Er3+ Using Silicon-rich Silicon Nitride.
Moon-Seung Yang 1 , Jung Shin 1 , Kyung Joong Kim 2
1 Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon Korea (the Republic of), 2 Nano-Surface, Korea Research Institute of Standards and Science (KRISS), Daejeon Korea (the Republic of)
Show Abstract
Symposium Organizers
Mark Brongersma Stanford University
Donald S. Gardner Intel Corporation
Michal Lipson Cornell University
Jung H. Shin KAIST
I5: Si-Based Light Sources I
Session Chairs
Wednesday AM, April 19, 2006
Room 3007 (Moscone West)
9:30 AM - **I5.1
Electrically-Pumped Nanocrystal Sources for Si Photonics
Harry Atwater 1
1 Applied Physics, California Institute of Technology, Pasadena, California, United States
Show AbstractEfficient light-emitting devices are key components of future Si-based optoelectronic systems. In this talk we will describe recent developments in Si CMOS compatible near-infrared sources using field effect electroluminescence, a newly-identified charge injection process for CMOS-based light emitting devices. Field-effect light emitting devices (FE-LEDs) are MOS transistors with nanocrystals embedded in the gate dielectric. Excitons are electrically programmed in FE-LEDs by sequential electron and hole injection from the MOS channel and pulsed light emission is observed upon injection of the second carrier. A device performance analysis suggests potential for these devices to enable chip-based sources for optical power at 850 nm at the 1-200 microwatt/device level. We will also describe plasmon-enhanced light emission from Si nanocrystals that can increase the radiative rate of Si nanocrystal emitters, and will discuss approaches to using Si-nanocrystal based FE-LEDs to achieve emission in the 1300-1550 nm wavelength range. Finally, electrically-pumped device designs for field effect light emitting devices operating at 1550 nm for amplifier and laser applications will be discussed.
10:00 AM - I5.2
Interface- and Size- Controlled Silicon Nanocrystals Applicable for Nonvolatile Memory or Photonic Device.
Kyong Hee Joo 1 , Sang Ryol Yang 1 , Seung-Hyun Lim 1 , Seung-Jae Baik 1 , Yong-Won Cha 1 , Young-Kwan Cha 2 , In-Seok Yeo 1 , U-In Chung 1 , Joo Tae Moon 1 , In Kyeong Yoo 2 , Suk-Ho Choi 3
1 Memory Devision, Samsing Electronics, Yongin Korea (the Republic of), 2 U-Team, Samsung Advanced Institute of Technology, Yongin Korea (the Republic of), 3 Physics and Applied Physics, Kyung Hee University, Yongin Korea (the Republic of)
Show Abstract10:15 AM - I5.3
Application of Luminescent Nanocrystalline Silicon Particles to Display Field
Keisuke Sato 1 , Satoshi Yanagisawa 1 , Kenji Hirakuri 1
1 Dept. of Electronic and Computer Engineering, Tokyo Denki University, Hikigun, Saitama, Japan
Show AbstractElectroluminescent (EL) device using Nanocrystalline silicon (nc-Si) particles has been expected for the attractive applications to a Si-based flat panel displays (FPD) including EL displays, flexible displays and light emitting diodes, because it exhibits visible luminescence by the carrier injection into the nc-Si region. However, the luminous efficiency of EL device is very low for the FPD applications. In this paper, we have fabricated the EL device consists of the top electrode/nc-Si region/substrate/back electrode to obtain the luminescence with the high efficiency. Moreover, the luminescence and electrical properties of EL device have also studied.The silicon dioxide (SiO2) layer embedding nc-Si particles was formed on a p-type Si (100) substrate by cosputtering of Si/SiO2 targets and subsequent annealing at high temperature in a furnace. The SiO2 layer, then, was etched in a hydrofluoric (HF) acid steam for 5min to extract the nc-Si particles onto the substrate. After HF treatment, the nc-Si particles were dispersed uniformly from the substrate into the ethanol solution by a supersonic vibration treatment. After that, the nc-Si particles in the ethanol solution adhered to the luminous region between each SiO2 layer, formed on the substrate. The top and back electrodes were utilized an indium tin oxide and aluminum, respectively.The EL device showed the rectification characteristics on a current-voltage curve. Moreover, the luminescence from the EL device was bright that could be clearly discerned by the naked eye after applying it the direct current voltage above 4.5 V. This was achieved by the realization of efficient and easy carrier injection into the radiative recombination centers at the nc-Si surface vicinity of luminous layer from the top electrode and substrate sides, because the nc-Si region is in direct contacted with the top electrode and substrate.
10:30 AM - I5.4
Transparent Current Spreading Ni/Ag/ITO Contact to Si Quantum Dot Light-emitting Diodes.
Chul Huh 1 , Nae-Man Park 1 , Tae-Youb Kim 1 , Kyung-Hyun Kim 1 , Jae-Heon Shin 1 , Kwan Sik Cho 1 , Gun Yong Sung 1
1 Future Technology Reseach Division, Electronics and Telecommunications Research Institute, Daejeon Korea (the Republic of)
Show Abstract10:45 AM - I5.5
Enhanced Light-extraction Efficiency of Silicon Quantum Dot Light-emitting Diode by Nano-roughened Surfaces.
Baek-Hyun Kim 1 , Il-Kyu Park 1 , Tae-Wook Kim 1 , Chang-Hee Cho 1 , Seong-Ju Park 1 , Nae-Man Park 2 , Gun-Yong Sung 2
1 Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju Korea (the Republic of), 2 , Electronics and Telecommunications Research Institute, Daejeon Korea (the Republic of)
Show AbstractFor a silicon quantum dot (Si QD) light-emitting diode (LED) with an absorbing substrate and a planar surface, only a few % of the internally emitted light can escape to the surrounding air due to the high refractive index of Si3N4 as well as the absorption in the metal pad for current injection, even if the internal quantum efficiency close to 100 % is reached. In order to increase the light-extraction efficiency from LEDs, it is necessary to change a shape of LEDs, which the photons can easily escape outside. In this study, we report on the enhanced light-extraction efficiency of a Si QD LED by a nano-roughened Si surface using wet etching. Nano-roughened Si surface was formed on the p-Si wafers (100) having the concentration of about 1015 cm-3. It was reported that the etching rate of Si is about 200 times larger on the (100) than on the (111) surface in KOH solution.1 Hence, we employed the same wet chemical etching method to etch the Si top surface. A nano-roughened Si surface was formed on the Si top surface by a wet etching process using a 13.5 wt. % KOH solution at room temperature for 10 min. A silicon nitride film containing Si QDs was grown on the nano-roughened Si surface using the flow rate of SiH4 of 190 sccm and an additional flow rate of NH3 of 10 sccm.2 The plasma power, pressure, and growth temperature were maintained at 10 W, 1.0 torr, and 300 oC, respectively. The current-voltage (I-V) characteristics of an LED with nano-roughened surfaces were reduced to 8.9 V from 11.7 V of an LED without surface roughening at the same current of 20 mA. By employing the nano-roughened top and bottom surfaces of an LED structure, the light-extraction was also improved about 400 % compared to that without surface roughening at the same current of 90 mA. The enhancement in the electrical and optical properties were attributed to the increase in the surface area and the angular randomization of photons emitted in Si QDs, resulting in an increase in the light-extraction efficiency of the Si QD LED.[1] D. L. Kendall , J. Vac. Sci. Technol. A 8, 3598 (1990).[2] B. H. Kim, C. H. Cho, T. W Kim, N. M. Park, G. Y. Sung, and S. J. Park, Appl. Phys. Lett. 86, 091908 (2005).
11:00 AM - I5:Si Sources
BREAK
I6: Si-Based Light Sources II
Session Chairs
Wednesday PM, April 19, 2006
Room 3007 (Moscone West)
11:30 AM - **I6.1
Light Emitting Devices Based on Si Nanostructures.
Alessia Irrera 1 , Giorgia Franzo' 1 , Fabio Iacona 2 , Calogero D. Presti 1 , Isodiana Crupi 1 , Andrea Canino 1 , Delfo Sanfilippo 3 , Gianfranco Di Stefano 3 , Angelo Piana 3 , PierGiorgio Fallica 3 , Francesco Priolo 1
1 , MATIS- CNR-INFM and Dipartimento di Fisica e Astronomia, Universita' di Catania , Catania Italy, 2 , IMM-CNR, Catania Italy, 3 , STMicroelectronics, Catania Italy
Show AbstractWe present the structural, electrical and optical properties of light emitting MOS devices, where the dielectric layer consists of a substoichiometric SiOx (x < 2) thin film deposited by plasma enhanced chemical vapor deposition. After deposition the films were annealed to induce the separation of the Si and SiO2 phases with the formation of Si nanoclusters embedded in the insulating matrix. It is shown that amorphous silicon nanostructures may constitute an interesting system for the monolithic integration of optical functions in the Si VLSI technology. In fact, they exhibit an intense room temperature electroluminescence (EL) in the visible/near infrared region with the advantage to be formed at a temperature of 900 °C, remarkably lower than the temperature needed for the formation of Si nanocrystals (1100 °C or higher). In order to improve the light extraction, these devices were integrated with a properly designed photonic crystal structure. Standard low cost optical lithography was successfully employed to fabricate a two-dimensional photonic crystal onto the polysilicon layer acting also as the top electrode of the device. We measured a vertical emission with the extracted radiation enhanced by over a factor of 4, without the aid of any buried reflector. In addition, we will present data on light emitting devices based on Er-doped Si nanoclusters. We demonstrate that in presence of Er the EL from Si nanostructures is quenched suggesting that, similarly to photoluminescence (PL) experiments, Er is excited mainly through the recombination of electron-hole pairs localized within the nanostructures. In contrast to PL and to current belief, we show that EL efficiency is mainly limited by an Auger-type process of excited Er ions with the carriers trapped in the structure. The current injection has the two-fold role of producing excitation through electron-hole recombination and inducing quenching through Auger. Indeed, we demonstrate that unbalanced injection of carriers (electrons versus holes) is one of the main processes limiting luminescence efficiency. This phenomenon is studied in detail and, on the basis of its understanding, we propose novel device structures in which sequential injection of electrons and holes can improve quantum efficiency by avoiding Auger processes. These achievements open the way to a new generation of nanostructured silicon active devices in which photonic and electronic functions are integrated together.
12:00 PM - I6.2
Optical Activation and Electrical Stabilization of the Ultra Violet Electroluminescence from SiO2:Gd Gate Oxide Layers by Fluorine and Potassium Co-implantations.
Slawomir Prucnal 1 , Jiaming Sun 1 , H. Reuther 1 , W. Skorupa 1
1 , Institute of Ion Beam Physics and Material Research, Forschungszentrum Rossendorf, POB 510119, D-01314 Dresden Germany
Show Abstract12:15 PM - I6.3
Efficient Evanescent-Wave Coupling from a SiON Waveguide to a Si p-i-n Photodetector
Donghwan Ahn 1 , Ching-yin Hong 1 , Lionel Kimerling 1 , Jurgen Michel 1
1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWe have fabricated vertical p-i-n Si photodetectors that are monolithically integrated with compact silicon-oxynitride channel waveguides. 830nm light guided by the waveguide was coupled to the photodetector through evanescent-wave coupling. The photocurrent and the unabsorbed optical power that remained in the through waveguide were measured and compared for several photodetector lengths. We found a >90% photon coupling efficiency from the waveguide to the photodetector. Using a 1.2μm×1.2μm square waveguide (ncore=1.52) the coupling rate was 1/αcoupling~50μm and the mode-matching efficiency between the input waveguide and the waveguide on top of Si photodetector in the coupling region was about 86%. During device processing, a CMP process to planarize the lower SiO2 cladding is necessary. Generally, the subsequent opening of oxide window will results in a step-like feature in the waveguide. The effect of the coupling structure design on the coupling behavior was studied by varying the step height at the transition interface as well as introducing a vertical taper to avoid abrupt effective index changes. The mode-matching efficiency was highest when a 0.2μm step was intentionally introduced. Mode analysis and BPM/FDTD simulations show that waveguide offset compensates for the mode mismatch at the transition interface. We furthermore compared the coupling efficiency of low and high index-contrast waveguide. Higher index-contrast rectangular waveguides (0.9μm×0.3μm waveguide with core refractive index of 1.58 and 1.2μm×0.4μm waveguide with core refractive index of 1.67) showed different coupling behavior. The coupling rate was significantly higher than in the previous case (1/αcoupling ~17μm and 26μm) and total quantum efficiency was about 80%. Our Si photodetector with surface-normal, free space illumination has a total quantum efficiency of 41% for 830nm light.
12:30 PM - **I6.4
Efficiency and Stability Issues of Metal-Oxide-Silicon-based Light Emitting Diodes made by Rare Earth Ion Implantion
Wolfgang Skorupa 1 2 , Jiaming Sun 1 , Slawomir Prucnal 1 4 , Manfred Helm 1 2 , Lars Rebohle 2 , Thoralf Gebel 2 , Alexei Nazarov 3 , Igor Osiyuk 3 , Igor Tjagulski 3 , Jerzy Zuk 4
1 FWIM, Forschungszentrum Rossendorf e.V., Dresden Germany, 2 , nanoparc GmbH, Dresden Germany, 4 , Maria Curie-Sklodowska-University, Lublin Poland, 3 , Institute of Semiconductor Physics, Kyiv Ukraine
Show AbstractCombining silicon-based electronic circuits with optoelectronic functionality is one of the key challenges for the future semiconductor technology. Such work must not only be devoted to the wavelength of 1.54 µm because there are more applications needing light sources from all the UV to IR wavelength range. In our work we employed ion beam processing to embed different rare earth (RE) luminescent centers (Gd3+, Ce3+, Tm3+, Tb3+, Eu3+, Er3+) into the silicon dioxide layer of a purpose-designed Metal-Oxide-Silicon-based Light Emitting Diodes (MOSLEDs) with advanced electrical performance. Efficient electroluminescence was obtained from UV to infrared with a transparent top electrode made of indium-tin oxide. The distinct differences in efficiency of the various rare earth atoms will be discussed as well as problems of electrical stability of such devices due to hot electron injection and charge trapping phenomena. Several developments for improving the device stability will be proposed related to charge compensation and elimination of the defects in SiO2.
I7: SiGe-Based Light Emitters and Modulators
Session Chairs
Wednesday PM, April 19, 2006
Room 3007 (Moscone West)
2:30 PM - **I7.1
Photoluminescence in Composition-Controlled Three-Dimensional Si/Si1-xGex Nanostructures
Leonid Tsybeskov 1
1 , NJIT, Newark, New Jersey, United States
Show AbstractDetailed photoluminescence (PL) measurements in series of multilayer Si/Si1-xGex samples with an island-like morphology and precisely controlled chemical composition in the range of 0.096 ≤ x ≤ 0.61 are presented. In the samples with x continuously increasing from 0.096 to 0.55, a red shift in the PL peak position, an increase in the activation energy of the PL thermal quenching and PL quantum efficiency (better than 1%) are found. Time-resolved PL measurements reveal complex carrier recombination dynamics with characteristic lifetimes ranging from nanoseconds to tens of millisecond. In our model, efficient carrier recombination mainly occurs at sharp, quasi-type II Si/SiGe interfaces with only several milli-electron volts barrier for electrons and deep potential wells for holes localized within Ge-rich Si1-xGex islands. Several avenues toward efficient, room temperature operating Si-Ge light emitters will be discussed.
3:15 PM - I7.3
Pure Germanium Isotopes for Investigating Interdiffusion in Uncapped Self-Assembled Ge/Si Nanostructures.
Oussama Moutanabbir 1 , Satoru Miyamoto 1 , Yoshiyuki Tabuchi 1 , Kohei Itoh 1
1 Applied Physics and Physico-Informatics, Keio University, Yokohama Japan
Show AbstractThe formation and growth of Ge layers on Si surfaces has been a subject of great interest in the last decade, both from a fundamental point of view and for potential applications in optoelectronics. In this work, we report a new approach for highlighting subtleties in the growth of Ge/Si nanostructures using isotopic variations of Stranski-Krastanov 3D islands. We propose a 2-steps growth process to investigate the contribution of wetting layer (WL) Ge atoms to 3D nanostructures nucleation and growth. First, 2D WL is grown by deposition of pure 76Ge and, in the second step; 2D-3D transition is assured by an additional evaporation of pure 70Ge. All-70Ge nanostructures (WL and 3D islands) are used as reference structures. Ge/Si nanostructures were characterized by polarized Raman scattering in backscattering configuration. Raman spectra of all-70Ge heterostructures show a narrow peak at ~302 cm-1 associated to 70Ge -70Ge mode, whereas 2-steps nanostructures spectra show two main features: A broadband centered at ~298 cm-1 most likely composed by 70Ge -70Ge mode and 76Ge -70Ge mixed mode, and a relatively small peak at ~291 cm-1 attributed to 76Ge-76Ge mode. These isotopic shifts in Ge-Ge optical phonon induced by 76Ge "impurities" is used as a marker to evidence and quantitatively analyze the mass transport from 2D WL to 3D Ge/Si islands. By exploring a wide range of kinetics growth parameters, a plausible mechanistic picture of 2D WL stability after nucleation of 3D islands is presented and discussed. Additionally, Ge/Si islands average composition and strain were quantitatively analyzed using Ge-Ge and Si-Ge optical phonon frequencies as a function of substrate orientation at growth temperature (TG) ranging from 340 to 630 oC. For both orientations (001) and (111), Ge-Ge mode frequency shifts down with TG. However, Si-Ge mode is only observed for TG above a critical temperature suggesting that the growth at lowest temperatures produces pure Ge nanostructures. We found that substrate orientation slightly affects Si-Ge interdiffusion critical temperature. Expectedly, Si diffusion induces lateral strain relaxation morphologically associated to the growth of larger islands. Consequently, by increasing substrate temperature the average island composition becomes Si richer, changing from pure Ge to Ge0.7Si0.3/Si(001) and Ge0.83Si0.17/Si(111) at the highest growth temperature (630 oC). Strain relaxation has been found to be relatively more pronounced for (100) orientation. Statistical analyses of AFM images show that Ge/Si(111) islands lateral dimension and height exhibit a relatively high uniformity independently on growth temperature, whereas Ge/Si(001) nanostructures size uniformity is highly affected by substrate temperature: The highest island size dispersion is observed at intermediate TG. Complementary results of wet chemical etching, transmission electron microscopy and x-ray photoelectron spectroscopy will be presented and discussed.
3:30 PM - **I7.4
Ge/SiGe Quantum Well Photonic Devices.
James Harris 1 , Yu-Hsuan Kuo 1 , Yong Kyu Lee 1 , Yangsi Ge 1 , Shen Ren 1 , Jonathan Roth 1 , Glenn Solomon 1 , Theodore Kamins 1 , David Miller 1
1 Electrical Engineering, Stanford University, Stanford, California, United States
Show AbstractThe increasing pressure of higher speed, greater bandwidth and decreasing dimensions are creating a serious challenge for between chip and ultimately on-chip communications. Because of the fundamental energy band properties of Si, it is inherently a very poor optoelectronic material. Ge on the other hand, while an indirect bandgap material, has a direct bandgap much like that of III-V materials that is only 130 meV above the indirect minima and it can be utilized to form direct bandgap like excitons, absorption and quantum confined Stark shifts with bias. Since Ge can be grown on Si with appropriate buffer layers, devices based upon these effects can be directly integrated with Si ICs to enable optical modulation. I will describe our work to produce a high-speed electroabsorption modulator and comment on the prospects for additional integrated photonic devices.
I8: Microresonators
Session Chairs
Wednesday PM, April 19, 2006
Room 3007 (Moscone West)
4:30 PM - **I8.1
Demonstration of Erbium Doped Micro-disk Lasers on a Silicon Chip.
Tobias Kippenberg 1 , Jeroen Kalkman 2 , Anna Tchebotareva 2 , Albert Polman 2 , Kerry Vahala 3
1 , Max Planck Institute of Quantum Optics, Garching Germany, 2 , Center for Nanophotonics, FOM Institute AMOLF, Amsterdam Netherlands, 3 , California Institute of Technology, Pasadena, California, United States
Show AbstractErbium ions embedded in silica provide gain in the 1.55 micron range. However, due to the small cross section of erbium population inversion of Er doped glasses require high pump intensities, or equivalently low loss microcavities for lasing operation. Here we demonstrate lasing in silica microdisks on a silicon wafer. By controlling of both the Er-ion distribution, as well as the mode distribution, high Q silica microdisk could be fabricated, with simultaneously excellent modal overlap with the erbium ions. Control of the Erbium ions was achieved by using ion-implantation of oxidized silicon wafer. The oxide thickness was 1 micron, and the implantation energy was chosen as to obtain the center of the Erbium distribution at 500 nm depth. A total of 1.2x10(15) ions per square-cm were implanted. Under condition of optimal coupling, lasing under these Er implantation conditions requires intrinsic cavity losses of less than 0.03 dB per cm equating to a quality factor (Q) of >2 million. These quality factors are readily available in toroidal micro-cavities[1], which use a laser assisted reflow process, and have been used to create Er-microlasers on Si for the first time [2, 3]. Here, we explore a different route and use engineering of the cavity mode to reduce scattering losses and to increase the intrinsic Q-factor. The method has been reported previously [4] and only involves CMOS compatible fabrication steps. This step allows to achieve Q-factors in excess of 10 million. The observed high Q is attributed to the wedged-shaped edge of the disk microcavity, which is believed to isolate modes from the disk perimeter and thereby reduce scattering losses. This method was successfully employed to the erbium implanted oxidized silicon wafers. The microdisk cavities had a diameter of 60 micron and the Q-factors at 1450 nm were observed to be in excess of 1 million, consistent with erbium absorption in this wavelength band. The microcavities were directly coupled to a tapered optical fiber. Upon pumping at 1450 nm the transmission in the fiber exhibited several peaks throughout the erbium emission band, clearly demonstrating that the erbium ions were coupled to the pump-mode. Upon increase in pump power a gradual transition was observed from spontaneous emission to stimulated emission. From linear interpolation the threshold was estimated to be 35 micro Watts. 1.Armani, D.K., et al., Ultra-high-Q toroid microcavity on a chip. Nature, 2003. 421(6926): p. 925-928.2.Polman, A., et al., Ultralow-threshold erbium-implanted toroidal microlaser on silicon. Applied Physics Letters, 2004. 84(7): p. 1037-1039.3.Yang, L., D.K. Armani, and K.J. Vahala, Fiber-coupled erbium microlasers on a chip. Applied Physics Letters, 2003. 83(5): p. 825-826.4.Kippenberg, T.J., et al., Fabrication and coupling to planar high-Q silica disk microcavities. Applied Physics Letters, 2003. 83(4): p. 797-799.
5:00 PM - I8.2
Whispering-gallery-mode of Visible nc-silicon Luminescence in Microdisk Arrays Based on Size Controlled Si Nanocrystals.
Se-Young Seo 1 , Rong-Jun Zhang 1 , Alexey Milenin 1 , Manfred Reiche 1 , Margit Zacharias 1
1 , Max-Planck-Institute for Microstructurephysics, Halle Germany
Show AbstractSilicon photonics has gathered a lot of interest during the past years. Highly integrated photonic devices based on Si with high performance and low fabrication cost are expected at least partially to functionally replace the present electronic devices. For the on-chip integration of all silicon photonic components, individual silicon photonic component with smart functions and small device size must be developed. Even though many silicon nano- or micro-photonic devices such as waveguide, filters, or modulator have been introduced so far, a micro sized silicon light source have been still under consideration, due to the lack of optical activity of silicon itself. With the benefit of quantum confinement effect, nanocrystalline silicon (nc-Si) can efficiently emit light at visible range, and can be utilized as base material for silicon light source. With respect to device size, microdisk (MD) resonators, which have excellent Q value and much advantages for lasing, have been regarded as possible structure for micro-sized light source. In this work, we present MD resonators with embedded nc-Si/SiO2 superlattices (SLs) containing nanocrystals of a size of 3 nm. Arrays of circular disks and squares were defined by standard photolithography and anisotropic etching. Using isotropic etching, the microstructures are finally isolated from silicon substrate. Luminescence measurement were done pumping the nc-Si SL on top of the microdiscs. A luminescence peaked at ~800 nm was found which is typical for 3 nm sized nc-Si. A similar luminescence profile was observed comparing SL films, microsquare arrays, and MDs arrays. However, small peaks superimposed on nc-Si luminescence were observed from the MD arrays only. These regular spaced sharp peaks are attributed to whispering-gallery-modes(WGMs) of MDs. After deduction of nc-Si spontaneous luminescence from overall spectrum, the WGM can clearly be observed. Obviously the disk thickness is thin enough to support only one fundamental axial mode (TE0 mode). Solving two-dimensional Helmholtz equation and using boundary condition, the observed peaks were assigned with azimuthally modes ranged 40 to 65 for 1st radial mode. No more higher radial modes seem to exist, and the lack of both higher axial and higher radial mode allow mode spacing to be rather broad (15 nm for MD array with 8.8 mm disk diameter). The overall Q factor of the MD array (not single microdisk) was found to be 400 which imply the excellent mass fabrication of MDs with size difference less than 1%. We will discuss the advantages of size controlled nc-Si for MD application. The device performance and field characteristics of single micro disk will be presented.
5:15 PM - I8.3
Evidence for Stimulated Emission in Silicon Nanocrystal Microspheres
Hui Chen 1 , Joo-Yeon Sung 3 , Anuranjita Tewary 4 , Mark Brongersma 4 , Jung Shin 3 , Philippe Fauchet 2
1 Department of Physics, Univ. of Rochester, Rochester, New York, United States, 3 Department of Physics, Korea Advanced Institute of Science and Technology, Taejon Korea (the Republic of), 4 Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California, United States, 2 Department of Electrical and Computer Engineering, Univ. of Rochester, Rochester, New York, United States
Show AbstractSilicon has been used in all photonic functions except lasing. An on-chip electrically injected silicon laser is an important building block for on-chip optical interconnects, which was identified by the International Technology Roadmap of Semiconductors as one of the most promising solutions to the “electrical interconnect bottleneck”. We report evidence for stimulated emission in silicon nanocrystal microspheres under strong pulsed excitation. A narrow emission lineshape near 590 nm is observed and the features of this emission lineshape are consistent with stimulated emission and lasing.Our samples are high-Q silica microspheres coated with silicon nanocrystals (Si-nc). An amplified Ti sapphire laser system (200 fs, 1 kHz, 405 nm) is used to excite the sample. The photoluminescence (PL) spectra are taken under different excitation intensities to explore the possibility of lasing. At low pumping intensities, the PL spectra are broad and featureless, as expected from other Si-nc samples. When the pumping intensity increases above a certain level a clear PL peak at 590 nm emerges. This peak is observed during the first 50 ns after excitation and is accompanied by the active suppression of the luminescence in the 550 to 650 nm range. The peak width is much narrower than the spontaneous emission FWHM reported in all silicon nanocrystal samples including our microspheres. After isolating the signal from the background spontaneous emission, the peak intensity shows a definite threshold with a super-linear increase afterward. All these features match the four commonly recognized signatures of lasing: spectral narrowing, lifetime shortening, a well-defined threshold and a super-linear increase afterward. This suggests that we have observed stimulated emission in our silicon nanocrystal microspheres. Preliminary control experiments also suggest that the presence of silicon nanocrystals is necessary to observe the stimulated emission signal. We will report results of additional control experiments, including those obtained on similar film deposited on a planar substrate using the variable stripe length method. These experiments should help us determine the origin of the stimulated emission, i.e., excitonic recombination or defect-related recombination.This work was supported in part by the Semiconductor Research Corporation.
5:30 PM - **I8.4
Microphotonics Applications of Silicon Microspheres
Ali Serpenguzel 1
1 Physics Department, Microphotonics Research Laboratory, Koc University, Istanbul Turkey
Show AbstractSilicon microspheres with high quality factors morphology dependent resonances are used for resonant detection and filtering of light in the near infrared. The light is coupled to the silicon microsphere with optical fiber half couplers in the near-IR. The observed morphology dependent resonances have quality factors of 100000. The experimentally measured quality factors are limited by the sensitivity of the experimental setup. These optical resonances provide the necessary narrow linewidths, that are needed for high resolution optical filtering applications, Raman lasers, modulators, CMOS-compatible detectors in the near-IR. In addition to filtering, detection, and switching applications of this microphotonic system in the near-IR, we have studied the response of the silicon microsphere in the far-IR (THz) region. The silicon microsphere shows promise as a building block for silicon microphotonics, a complementary technology to the already well established CMOS microelectronics technology for the realization of future microelectro-photonic integration.
I9: Poster Session: Si Compatible Materials and Devices
Session Chairs
Don Gardner
Michal Lipson
Thursday AM, April 20, 2006
Salons 8-15 (Marriott)
9:00 PM - I9.1
SiGe nanophotonics: The growth and optical properties of SiGe nanowires.
Jee-Eun Yang 1 , Chang-Beom Jin 1 , Yosep Yang 1 , Chan-Gyung Park 1 , Moon-Ho Jo 1
1 materials science and engineering, postech, Pohang Korea (the Republic of)
Show Abstract9:00 PM - I9.10
Laser-induced Structural Modifications in Nanocrystalline Silicon/Amorphous Silicon Dioxide Superlattices
Boris Kamenev 1 , Haim Grebel 1 , Leonid Tsybeskov 1
1 , NJIT, Newark, New Jersey, United States
Show AbstractWe theoretically calculate and experimentally determine thermal conductivity and laser melting threshold in nanocrystalline Si/amorphous SiO2 superlattices. Using pulsed photoexcitation slightly above the melting threshold, we observe two types of laser-induced structural modifications: (i) disappearance of nanocrystalline Si phase due to breakdown of a superlattice structure and merge of Si nanocrystals in the samples with thin (≤ 2 nm) SiO2 layers and (ii) photo-induced amorphization of Si nanocrystals in the samples with thicker (≥ 5 nm) SiO2 layers. The observed Si nanocrystal amorphization strongly increases optical absorption and intensity of visible photoluminescence (PL). We also find that high intensity, single-pulse laser irradiation creates a short-lived thermal wave. We show that complex PL dynamics, at least in part, are due to thermal emission.
9:00 PM - I9.11
Evaluation of Heavy Metal Impurity Behaviors in the n/n+ and p/p+ Epitaxial Wafer by Means of Microwave Photoconductive Decay Method.
Hochan Ham 1 , Sungwook Lee 1 , Byung-seop Hong 1 , Bo-young Lee 1
1 Application & Analysis team, R&D center, LG Siltron Inc., Kumi City, Gyeongsangbuk-do, Korea (the Republic of)
Show Abstract9:00 PM - I9.12
A Comparative Study of CVD-Grown a-SiCxOyHz Materials for Silicon Photonics.
Spyros Gallis 1 , Vasileios Nikas 1 , Mengbing Huang 1 , Eric Eisenbraun 1 , Alain Kaloyeros 1
1 College of Nanoscale Science and Engineering, The University at Albany - SUNY, Albany, New York, United States
Show AbstractThe present investigators have previously demonstrated strong luminescence at 1540 nm from erbium-doped amorphous silicon oxycarbide (a-SiCxOyHz:Er) materials.1 Herein, pertinent details are presented regarding the role of the growth conditions and post-deposition thermal treatment in engineering the compositional, structural, and optical characteristics of these novel Si-based materials, leading to optimized luminescence performance. The hydrogenated a-SiCxOyHz films, with thicknesses in the range of 280 to 380nm, were deposited in a hot-wall quartz tube reactor by thermal chemical vapor deposition (TCVD) at a substrate temperature of 800°C. A single source oligomer, 2,4,6-trimethyl-2,4,6-trisila-heptane (C7H22Si3) was utilized as the supply of Si and C, along with ultra-high purity oxygen and argon as, respectively, co-reactant and dilution gas. By varying the oxygen flow rate, three different classes of a-SiCxOyHz materials were synthesized, as driven by their carbon (x) and oxygen (y) concentrations: (i) SiC-like (SiC1.00O0.10H0.20); (ii) Si-C-O (SiC0.50O1.00H0.20); and (iii) SiO2-like (SiC0.15O1.70H0.20). A comparative investigation of the effects of annealing on the structural, chemical and optical properties of these three classes of films was carried out by employing various analytical techniques, including x-ray photoelectron spectroscopy (XPS), ion scattering, Fourier transform infrared spectroscopy (FTIR), nuclear reaction analysis (NRA), and spectroscopic ultraviolet-visible ellipsometry (SE). In particular, it was found that film refractive index varied from ~2.6 for the SiC-like samples, to ~1.8 for Si-C-O samples, to ~1.5 for the SiO2-like samples. Interestingly, the energy band gap of the Si-C-O matrix films was found to decrease from 3.6 eV to 2.9 eV, as the annealing temperature was increased from 500°C to 1100°C. Additionally, it was found that the decrease in the energy bandgap of these materials is caused by desorption of hydrogen from the films at elevated annealing temperatures (>900°C), as documented by NRA and FTIR measurements. This behavior was attributed to a reduction in the concentration of hydrogen-related bonds as a function of increased annealing temperature. FTIR and XPS analyses of the elemental electronic environment in the Si-C-O matrix indicated that Si-C-O films were composed primarily of Si-C-O networks. Detailed FTIR analysis also determined the onset for formation of embedded SiC nanocrystals in the amorphous film matrix at an annealing temperature of 1100°C, interestingly as evident only for the SiC-like samples. A strong correlation was established between the existence of Si-C-O networks and the strong Er3+ luminescence from amorphous Er-doped Si-C-O (a-SiC0.50O1.00H0.20:Er) films, suggesting that TCVD-grown amorphous Si-C-O is a very promising matrix for realizing high-performance photonics devices based on Er-doped silicon materials.1.S. Gallis et al. , Appl. Phys. Lett., 87, 091901 (2005).
9:00 PM - I9.13
Nonlinear Optical Response of the Complete Photonic Band Gap in Silicon Inverse Opal
Hong Wei 1 , David Underwood 2 , David Blank 2 , David Norris 1
1 Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 2 Department of Chemistry, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractWe utilized colloidal self-assembly to obtain silicon inverse opals that possess a complete photonic band gap at 1.37µm. Optical pump-probe techniques were then employed to spectrally resolve the nonlinear reflectivity change near the energy of the photonic band gap. Our data show that the initial change in the reflectivity near the photonic band gap can be near 50% with a rise time as short as 500fs. We compared these findings with calculated spectra obtained by combining the transfer matrix method with the Drude model for excited free carriers in silicon. The initial time dependence of the reflectivity spectrum was found to originate in two terms: (i) the pump-induced shift of the photonic band gap and (ii) the pump-induced absorption. At longer times, relaxation of free carriers transfers energy to the silicon lattice and increases its temperature. This causes a spectral shift of the photonic band gap after ~15ps due to temperature induced changes in the refractive index of the silicon. Interestingly, we found (both in experiment and simulation) that this shift can be either red or blue depending on the thickness of the oxide layer on the silicon. The oxide causes a temperature-dependent stress, which strongly affects the refractive index. Finally, the implications of these observations for potential uses of these materials will be discussed.
9:00 PM - I9.14
Oxidation of Structured Silicon Thin Films for Inverse Silicon Square Spiral Photonic Crystal Fabrication
Mark Summers 1 , Michael Brett 1
1 Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada
Show AbstractPhotonic Band Gap (PBG) crystals are artificially engineered structures of periodically alternating dielectric materials that enable manipulation of light in unique ways. As proposed by O. Toader and S. John, large bandwidth PBG crystals based on the diamond lattice can be constructed by fabricating a two-dimensional periodic array of silicon square spirals. Furthermore, an improved photonic crystal can be constructed by fabricating the inverse of this structure, such that void square spirals are situated in a silicon backfill. This structure yields a theoretical maximum PBG of 24%, while the direct silicon square spiral structure yields a theoretical maximum of 16%. [1]The direct silicon square spiral structure has previously been successfully fabricated using the glancing angle deposition (GLAD) process [2]. The GLAD fabrication process uses advanced substrate motion and oblique incidence deposition to engineer precise nanostructures such as helices, chevrons, or polygonal spirals. These nanostructures are grown with lateral and longitudinal periodicity using a pre-patterned substrate consisting of a tetragonal array of relief structures. Upon successful fabrication of the direct silicon square spiral structure, it was proposed that fabrication of the inverse structure could be completed using a backfill process with a silica template [2]. A periodic array of silica square spirals would be fabricated using the GLAD technique. The template would then be filled with amorphous silicon using low-pressure chemical vapour deposition (LPCVD). To reveal the inverse silicon structure, the silica template would be removed by means of chemical etching with an isotropic chemical etchant. Creation of a suitable template for the inversion of silicon square spirals is an important step in the realization of the inverse silicon square spiral PBG crystal. However, we have seen empirically that silica square spiral films grown directly via the GLAD technique are structurally inferior to silicon films. We present an intermediate step for the fabrication of a suitable template, whereby a silicon structure is fabricated with appropriate geometries and subsequently oxidized. The procedure has been optimized to ensure a thorough oxidization of the silicon posts, while minimally distorting the structure of the square spiral template.REFERENCES:[1] O. Toader and S. John, Science 292, 1133-1135, (2001).[2] S. R. Kennedy, M. J. Brett, O. Toader, and S. John, Nano Letters 2, 59-62 (2002).
9:00 PM - I9.15
Active Photonic Crystals Based multiplexer.
Principia Dardano 1 2 , Vito Mocella 1 , Luigi Moretti 3 , Luigi Sirleto 1 , Ivo Rendina 1
1 Sez. di Napoli, CNR-IMM, Napoli Italy, 2 Dip. Scienze Fisiche, Federico II University, Napoli Italy, 3 , Mediterranea University, Reggio Calabria Italy
Show AbstractIn this communication a new tunable wavelength demultiplexer based on silicon Photonic Crystals (PhCs) and Liquid Crystals (LCs) is proposed. The device has a T-shaped bidimensional PhC waveguiding structure of silicon rods, arranged in a square lattice infiltrated with LCs. The light enters in a simple PhC waveguide, realised removing a line of rods in the basic PhC structure, and propagates in the left-side or right-side waveguides depending on the fact that its frequency is lower or greater than a “switch frequency” characterizing the static device operation. The left-side and right-side waveguides are respectively outlined by rows of silicon rods with different radii. The size of the rod radius r of the basic PhC structure has been determined in order to maximize the band gap for the TM polarization. To reach this goal the gap map (i.e., the map of the range of frequency forbidden versus the radius of the silicon rods) has been studied. The analysis shows that the widest band gap (i.e., Δω=(0,3023÷0,2557)x2πc/a) occurs when r=0.228a, a being the lattice constant of the basic PhC. In the same way we find the radii of the rods in the left and right waveguides (r1 and r2, respectively) so that the light experiences complementary gaps in the two branches of T-shaped structure. The size of the radii in the left and right branches has been matched to cover entirely, without intersections, the gap Δω of the basic PhC structure. In particular, we found that for r1=0.154a, the gap is Δω1= (0.3043÷0.2780) x2πc/a. Whereas for r2 =0.294a, the gap is Δω2= (0.2780÷0.2537)x2πc/a. Then, the resulting switch frequency is ωswitch = (0.2780)x2πc/a in the static device. So if we want to match the switch wavelength at 1.55μm, the radius r will be 100nm, while r1 and r2 will be 70nm and 125nm, respectively. Hitherto, it has been supposed that the PhC “background” is formed by a nematic liquid crystal (NLC), embedding the whole structure, with its molecules aligned, without any applied electric field, in a direction perpendicular to the rods. In this case the light propagating in the waveguides feels the ordinary refractive index of the NLC. By applying an electric field, and therefore reorienting the NLC molecule direction along the rods, the propagating light experiences the NLC extraordinary refractive index. In this way the dielectric constant of the NLC “background” material changes from εb=2.25 (Δnlc=0,0) to εb=2.89 (Δnlc=0,2). This leads to a shift of ωswitch (i.e., Δωlc=(0.2835÷0.2725)x2πc/a) corresponding to a wavelength shift Δλlc of 61nm covering the C-band of the infrared optical communication wavelengths. These performances confirm the great potentiality that infiltration of liquid crystals in photonic band-gap structures presents. The carried out results open new prospects in the application area of wavelength division multiplexing.
9:00 PM - I9.16
Predictive Process Simulation of the FIB-based Fabrication of Metallic Nanoparticle Waveguides.
Lars Roentzsch 1 , Karl-Heinz Heinig 1
1 FWIT, Research Center Rossendorf, Dresden Germany
Show AbstractChains of metallic nanoparticles may be applied as surface-plasmon-polariton (SPP) waveguides. Moreover, nanoparticle waveguide structures with small bend radii, e.g. L-turns or beam splitting T-junctions, are of technological interest. In this contribution, we present reaction pathways of the fabrication of 1D metallic nanostructures by focused metal ion implantation and subsequent thermal treatment. Nanowires (NWs) as well as structures consisting of metallic nanoparticle chains were found. The search for reaction pathways was performed by kinetic Monte Carlo simulations including realistic focused ion beam (FIB) implantation profiles which were determined by spatially dependent dynamic ion range calculations. During annealing, buried NWs and more complex structures (e.g. T- or X-junctions) form that are embedded in the matrix along the FIB implantation trace. The diameter of the synthesized NWs is about five times smaller than the width of the FIB implantation trace. The dominating driving force of NW formation is a free energy gain by phase separation and by reduction of high interface curvatures. During long-term thermal annealing, NWs disintegrate into regular chains of nanodots because of the built-up of long-wavelength interface undulations (Rayleigh instability). Crosses, corners or ends of NWs are subject to a preferential disintegration. Thus, by choosing appropriate geometries and implantation conditions, SPP waveguides based on multiple nanodot chains, e.g. L-turns, X- or T-junctions, might be fabricated by FIB implantation. The simulations were performed for focused Co ion implantation into Si since CoSi2 might be a metallic waveguide material with several advantages: monocrystalline embedding into c-Si with coherent (and defect-free) interfaces, CMOS-compatibility, and surface plasmon resonance in the infrared where Si is transparent.
9:00 PM - I9.17
Vapours Sensing In Porous Silicon With Raman Scattering.
Maria Antonietta Ferrara 1 2 , Luigi Sirleto 1 , Ivo Rendina 1
1 IMM, CNR , Napoli, Na, Italy, 2 DIMET, University of Reggio Calabria, Reggio Calabria Italy
Show AbstractAdsorption and wetting phenomena are due to the action of molecular interactions between a fluid and the adsorbent, which is usually considered to be rigid. In the adsorption phenomena the adsorbent also experiences the action of the molecular forces, and some substrate deformation must exist, as indeed revealed by numerous observation of adsorption strains. Measurements of adsorption strains in porous silicon are actually of great interest, however in our case they are useful in order to prove the possibility to tune the Raman peak [1]. In fact, Raman scattering can be used to measure strain induced in substrate. Compressive stress will result in an increase of the Raman frequency shift, while tensile stress results in a decrease.When porous silicon is exposed to vapour, capillary condensation in the silicon pores have been observed [2]. When the vapour is stable in a large volume, the liquid phase can condense in a confined volume, and is then separated from the vapour phase by a concave spherical meniscus [1]; the maximum capillary stress occurs when the meniscus enter the pores.In this experiment a porous silicon multilayer obtained by electro-chemical etching on p+ type (ρ=8-12mΩ cm) standard silicon wafer is used. The multilayer structure is made alternating high and low porosities layers with 57 and 79% porosity, respectively. The total porous silicon sample thickness is 5 micron.Raman spectra are measured in backscattering configuration using an He-Ne laser at 633nm. The first step was the measure of the Raman spectra in unperturbed porous silicon multilayer. The peak is observed at about 652.7 nm, this result is in agreement with the shift, with respect to the pump wavelength, due to the optical phonon frequency in porous silicon (corresponding at 15.7 THz red-shifted).Afterwards, with the aim of study the influence of the chemical species infiltration in porous silicon, a small amount of volatile liquids were added to the vial containing the sample. The vapours saturated rapidly the vial atmosphere, after that the acquisition of spectra were carried out. The Raman peak is obtained at about 648.5 nm for isopropanol, and at about 649.6 nm for ethanol. So, we measure a shift of Raman spectra with respect to the unperturbed case of 4.2 nm for isopropanol, and of 3.1 nm for ethanol. We note that the Raman shift is reversible.In this work, we investigate adsorption strains in porous silicon by Raman measurements. We prove that when the porous silicon structure is exposed to vapor of isopropanol or ethanol, a reversible blue shift of the Raman spectra is observed.REFERENCES1. G. Dolino, D. Bellet, and C. Faivre, “Adsorption strains in porous silicon”, Physical Review B, vol. 54, No. 24, 1996.2. A.V. Neimark, P.I. Ravikovitch, Micro. Meso. Mat. 44-45 (2001) 697-707.
9:00 PM - I9.18
Room Temperature Coulomb Blockade Effect in Silicon Quantum Dots in Silicon Nitride Film.
Chang-Hee Cho 1 , Baek-Hyun Kim 1 , Seong-Ju Park 1
1 Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju Korea (the Republic of)
Show AbstractNanostructured electronic devices are expected to provide a breakthrough in electronics industry forced into a successive miniaturization and ultra low power operation. In particular, single electron transistors (SETs) allow us to propose new device concepts such as a single electron logic, single electron memory, and high precision electrometry using a quantum phenomenon known as Coulomb blockade effect to control the transfer of individual electrons in the SETs [1, 2]. In this work, the Coulomb blockade effect was observed in silicon quantum dots (Si QDs) at room temperature. The Si QDs were spontaneously grown in silicon nitride film by plasma-enhanced chemical vapor deposition using SiH
4 and NH
3 gases. The metal-insulator-metal device containing the Si QDs showed a clear Coulomb staircase and differential conductance peaks at room temperature, indicating that the single electron addition energy of the Si QDs is about 67 meV. The size distribution of the Si QDs measured by high-resolution transmission electron microscopy suggested that the single electron addition energy of 67 meV is close to the charging energy of the largest Si QDs with the diameter of 4.7 nm among the assembly of Si QDs with various sizes, since the electrons can start to tunnel through the largest Si QDs due to their smallest band-gap and charging energy.1.C. W. J. Beenakker, Phys. Rev. B 44, 1646 (1991).2.M. H. Devoret, D. Esteve, and C. Urbina, Nature (London) 360, 547 (1992).*
[email protected]9:00 PM - I9.19
Surface Structure of Al-induced Clusters on Si(001) using CAICISS.
J. H. Seo 1 , C. N. Whang 1 , K.-H. Yoo 1 , S. S. Kim 2 , D. S. Choi 3 , K. H. Chae 4
1 Institute of Physics & Applied Physics , Yonsei university, Seoul Korea (the Republic of), 2 Department of Techno-marketing, Mokwon Universit, Taejeon Korea (the Republic of), 3 Department of Physics, Kangwon National University, Chuncheon Korea (the Republic of), 4 Division of Materials Science and Technology, Korea Institute of Science and Technology, SEOUL Korea (the Republic of)
Show AbstractWe have studied the atomic arrangement of the Al-induced nanoclusters on Si(001) using coaxial impact collision ion scattering spectroscopy (CAICISS). Al atoms were deposited on a clean Si(001) surface in the 0.5-monolayer (ML) coverage and annealed at 500°C. CAICISS result can be proposed that the Al atoms occupy selectively T4 site and at one end of a Si dimer as substituted a Al atom for a Si atom in a dimer. To determine the structure of the Al-induced nanoclusters definitely, classical ion trajectory simulations using scattering and recoiling imaging code (SARIC) have been performed for the recently proposed most possible four different cluster models (Bunk et al [Appl. Surf. Sci. 123-124 (1998) 104], Zotov et al [Phys. Rev. B 57 (1998) 12492], kotlyar et al [Surf. Sci. 506 (2002) 80] and mixed Al-Si nanocluster model [Surf. Sci. 504 (2002) 101]). Our CAICISS spectra and simulation results show that the Bunk model is best plausible one of the other three models. It is suggested that Al-Si dimer oriented with a bonding length (Δz) of 1.00 ± 0.05 Å on topmost layer.
9:00 PM - I9.2
Low-temperature Hetero-epitaxial Ggrowth of Ge on Si by High Density Plasma Chemical Vapor Deposition.
Malcolm Carroll 1 , Josephine Sheng 1 2 , Jason Verley 1 , Jim Banks 2
1 Microphotonic Systems, Sandia National Labs, Albuquerque, New Mexico, United States, 2 Electrical Engineering, University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractDemand for integration of optoelectronic functionality with silicon complementary metal oxide semiconductor (CMOS) technology has for many years motivated the investigation and development of low temperature formation of amorphous, poly-crystal and single crystal germanium on silicon (Ge/Si) heterostructures1. Epitaxial growth is often preferred for these applications because of the better crystal quality (e.g., minority carrier lifetimes) and some detector applications are still of interest despite the large number of misfit and threading dislocation defects at the Ge/Si interface2. A common challenge to the integration of Ge into or after CMOS device flows is, however, the thermal budget required to produce high quality epitaxy, which is frequently limited by the pre-epitaxy in-situ bakes necessary to clean the surface of oxygen and carbon (T > 780C)3. The high temperature constrains the use of epitaxy particularly to before CMOS device completion. Plasma enhanced chemical vapor deposition (PECVD), alternatively, is able to both prepare clean surfaces and grow SiGe epitaxy at much lower temperatures than classic low pressure CVD for several different specialized PECVD configurations (e.g., remote plasma4, and low-energy dc plasma5). In this paper, we examine the crystallinity of Ge depositions on (100), 150 mm silicon wafers with or without plasma oxide caps, and produced by high density plasmas (HDP) of argon-germane mixes at pressures between 1-25 mtorr, powers from 175-5000W and at temperatures between 250-500C. When the plasma pressure is lowered below a critical point ellipsometry indicates a transition from poly-Ge deposition to oxide removal without appreciable Ge deposition on oxide capped Si. Transmission electron microscopy and X-ray diffraction indicate that the oxide removing phase of the HDP argon-germane plasma assists in initiating Ge epitaxy on uncapped silicon surfaces, which otherwise produce poly-crystal Ge when relying on alternative standard native oxide removal methods such as ex-situ dilute HF dips or in-situ NF3 plasmas. The use of this epitaxy initialization step demonstrates, therefore, an alternative way to produce Ge epitaxy at temperatures less than 500C using a commercially available HDP-CVD chamber typically used for CMOS dielectric deposition6. Surface roughness, stress, background chemical content and minority carrier lifetimes as well as selective Ge epitaxy will also be discussed.Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.1 G. Masini, et al., APL 80, 3268 (2002).2 L. Colace, et al., APL 76 (10), 1231 (2000).3 M. S. Carroll, et al., JECS 147, 4652 (2000).4 K. Fukuda, et al., APL. 59 (22), 2853 (1991).5 C. Rosenblad, et al., J. Vac. Sci. Tech. A 16 (5), 2785 (1998).6 Applied Materials, Centura Ultima HDP-CVD (150 mm)
9:00 PM - I9.3
In situ Doped Ge Film on Si for Near-infrared Ge Photodetectors.
Jer-shen Maa 1 , Douglas Tweet 1 , Jong-Jan Lee 1 , Greg Stecker 1 , Mark Burgholzer 1 , Ray Hill 1 , Sheng Teng Hsu 1
1 , Sharp Labs of America, Camas, Washington, United States
Show AbstractWe have fabricated Ge/Si p-i-n photodetoctors by using in-situ boron-doped and phosphorus-doped Ge epitaxial layers as well as undoped Ge layer on Si (100) substrates from chemical vapor deposition. P- and n-Ge layers were deposited from GeH4/B2H6/Ar and GeH4/PH3/Ar, respectively. A cluster tool with dual CVD chambers was used to prevent cross contamination of these doping gases. Boron-doped Ge and undoped Ge were deposited in the same chamber, high purity intrinsic Ge film was achieved without extensive chamber cleaning after the deposition of boron-doped layer, as demonstrated both by SIMS and by diode characteristics. Phosphorus-doped Ge was deposited in a second CVD chamber, no additional acivation step was needed. Surface roughness was within nm range by applying a two-step deposition, first by depositing a thin Ge layer at a lower temperature. Cycle annealing of Ge was used to reduce the threading dislocation density, during which a passivating cap layer was used to prevent the degradation of surface roughness. Photodetectors with low dark current and high quantum efficiency were fabricated and high responsitivity was demonstrated at 1.55 micron.
9:00 PM - I9.4
Visible-Blind UV/IR Photodetectors Integrated on Si Substrates.
David Starikov 1 2 , John Boney 2 1 , Rajeev Pillai 2 , Abdelhak Bensaoula 2
1 , Integrated Micro Sensors Inc., Houston, Texas, United States, 2 CAM, University of Houston, Houston, Texas, United States
Show AbstractCurrently used flame detectors that are composed of discrete UV and IR solid-state components are bulky, sustain temperatures only up to 125°C, and are not capable of detecting a multi-band optical signal with high spatial resolution. Most current solid-state IR sensing devices require intensive one or even two-stage cooling. Existing imaging devices combined with image processing systems are expensive and lack resistance to harsh environments. This is necessary in order to place the sensor in close vicinity of the possible hazard source.Group III-nitride semiconductor materials are superior for advanced multi-band optical sensor fabrication due to their wide direct band gap and high thermal, chemical, mechanical, and radiation tolerance. The objective of the current work is development of new miniature, single-chip integrated, inexpensive and reliable high-temperature UV/IR fire and hazardous object sensors. Miniature, inexpensive chip-based dual-color high-temperature and radiation-resistant solar-blind optical sensor would allow early false alarm-free fire detection through distributed sensors, placed closer to potential flame sources, and provide a fast and reliable response in separated UV and IR bands with high spatial and time resolution. Moreover, development of such sensors would enable fabrication of multi-pixel focal arrays for multi-band solar-blind cameras, which can be used in harsh environments for flame detection in industrial and aerospace applications, as well as for object/target recognition in military missions.Demonstration of a TO-8 packaged UV/IR visible-blind photodetector based on a single-chip integration of III nitride materials on commercial Si wafers will be presented. The UV-sensitive photodetector structure is based on Schottky diodes fabricated on AlGaN layers grown by RF MBE on Si wafers. The IR-sensitive part of the photodetector is based on Schottky diodes fabricated on the same Si substrate also serving as a filter for the visible wavelength range. The spectral responses measured separately in the UV- and IR-sensitive structures represent two spectral bands from 248 to 377nm, and from 830 to 1132 nm, with corresponding peaks at 354 nm and 1000 nm, respectively. The responsivities at the maximum wavelengths for the UV- and IR-sensitive structures calculated after system calibration were 0.006 and 0.08 A/W, respectively.
9:00 PM - I9.5
Modeling Misfit Dislocation Arrays for the Growth of Low-Defect Density AlSb on Si
Anitha Jallipalli 1 , Ganesh Balakrishnan 1 , Shenghong Huang 1 , Arezou Khoshakhlagh 1 , Ralph Dawson 1 , Diana Huffaker 1
1 Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractWe present analytical models and experimental results to describe low-defect density growth (~ 6 x 10^5/cm.sq.) of highly mismatched antimonides on Si and GaAs substrates, with strain relief achieved at the growth interface through periodic 90° misfit dislocations. We use molecular mechanics based modeling techniques to understand, at the atomic level, the spontaneous formation and energetics of these 90° misfit dislocations. We have modeled, grown and characterized two systems extensively, these are - AlSb on Si with approximately 13% mismatch and GaSb on GaAs with 7.83% lattice mismatch. Growth of these materials by molecular beam epitaxy (MBE) and subsequent high-resolution transmission electron microscopy (HR-TEM) has indicated that there is no tetragonal distortion in these two systems despite the high lattice mismatch. Instead, the mismatched epi-layers spontaneously form interfacial, periodic, 90-degree, misfit dislocation arrays that run along the [110] and the [1-10] directions and relieve almost 100% of the strain in a few monolayers of deposition. To model this form of strain relief, we use existing theories of strain relief adapted for very high strain conditions and we also use bond energetics to model the strain-relieving interface. The bond energetics approach involves calculating bond distortion energy for every interfacial bond. This can be expressed as the sum of bond stretching energy, bond-bending energy, energy required for stretch-bend interaction, torsional energy, dipole-dipole energy and Vanderwaal forces (if any) for each bond. The interfacial dislocations in these systems are periodic and so are the deviation in bond lengths & bond angles, this restricts our calculation space to a finite number of elements. We shall also demonstrate extensive growth and characterization results of the materials grown with a particular emphasis on the strain-relieving interface to show excellent agreement of the experimental data with the proposed models. The high quality and low-defect density in AlSb grown on Si, has helped us demonstrate optically pumped IR VCSELs & edge emitters monolithically on Si (001) and this data will also be presented. [1,2][1]. G. Balakrishnan, S. H. Huang, A. Khoshakhlagh, P.Hill, A.Amtout , S. Krishna, G.P. Donati, L.R. Dawson and D.L.Huffaker : ‘Room-temperature optically-pumped InGaSb quantum well lasers monolithically grown on Si(100) substrate’, Electron. Lett. 41, 531 (2005).[2] G. Balakrishnan, S. Huang, L. R. Dawson, Y.-C. Xin, P. Conlin, and D. L. Huffaker: “Growth mechanisms of highly mismatched AlSb on a Si substrate”, Appl. Phy. Lett. 86, 034105 (2005).
9:00 PM - I9.6
Spatially Resolved Characterization of Microstructure, Defects and Tilts in GaN Layers Grown on Si(111) Substrates by Maskless Cantilever Epitaxy.
Rozaliya Barabash 1 , G. Ice 1 , W. Liu 1 , O. Barabash 1 , C. Roder 2 , S. Figge 2 , S. Einfeldt 2 , D. Hommel 2 , T. Katona 3 , J. Speck 4 , S. DenBaars 4
1 Metals and Ceramics Div., Oak Ridge National Laboratory, Oak Ridge TN, Tennessee, United States, 2 , University of Bremen, Bremen Germany, 3 Electrical and Computer Engineering Department, University of California, Santa Barbara, santa Barbara, California, United States, 4 Materials Department, University of California, Santa Barbara, santa Barbara, California, United States
Show AbstractThe spatially resolved distribution of strain, misfit and threading dislocations, and crystallographic orientation in uncoalesced GaN layers grown on Si(111) substrates by maskless cantilever epitaxy was studied by white beam Laue x-ray microdiffraction, high-resolution monochromatic x-ray diffraction and scanning electron microscopy. Tilt boundaries formed at the column/wing interface depending on the growth conditions. Two types of misfit dislocations were observed during cantilever epitaxial growth of GaN layers Si(111) substrates due to relaxation processes. Density of misfit dislocations as well as their arrangement within different dislocation arrays was quantified. The measurements revealed that the free-hanging wings are tilted upward at room temperature in the direction perpendicular to the stripes. A depth dependent deviatoric strain gradient is found in the GaN. Moreover, a crystallographic tilt between the GaN[0001] and the Si[111] surface normal was observed parallel to the stripes. Two different kinds of tilt (parallel and perpendicular to the stripe direction) manifest themselves by mutually orthogonal displacement of the (0006)GaN Laue spot relative to the Si (444) Laue spot. Origin of tilts is discussed with respect to the miscut of the Si(111) surface and misfit dislocations formed at the interface.
9:00 PM - I9.7
GaAs to Si Integration via Isothermal Solidification Metal Waferbonding.
Justin Bickford 1 , Paul Yu 1 , S.S. Lau 1
1 Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, United States
Show Abstract Waferbonding allows lattice-mismatched materials such as GaAs and Si to be integrated with much lower bulk defect densities than by traditional epitaxial growth techniques. Waferbonding using metal can provide linear electrical interfaces, thus allowing the bond to also act as an electrical contact between bonded devices. Taking advantage of the low-temperature bonding property of the isothermal solidification method, large differences in Thermal Coefficients of Expansion (TEC) between materials create less stress during bonding and thus yield better quality bonded material and interfaces. A metal bonding layer would also act as a mirror-like optical reflector and should provide superior heat conduction in contrast to oxide interlayer waferbonding. 1cm x 1cm x 500μm (100) Si and (100) GaAs pieces have been successfully waferbonded using the low-temperature isothermal solidification metal bonding method. The process is capable of producing void-free bonds across the entire area; the joint quality was examined using Scanning Acoustic Microscopy (SAM). The In-Pd metal alloy used to bond the samples has provided non-spiking ohmic interfaces for all four combinations of ~1e18cm-3 doped bonded materials; p-GaAs to p-Si, p-GaAs to n-Si, n-GaAs to p-Si, and n-GaAs to n-Si. 2μm thick MOCVD grown doped-GaAs layers with an InGaP etchstop layer have also been successfully waferbonded to doped-Si substrates, proving that the process can bond samples comparable to device grown material. Measurement structures fabricated from such samples have resolved the lumped specific contact resistance of the bond layer for the n-GaAs to p-Si case to be ~ 1.03e(sup)-5(/sup).
9:00 PM - I9.8
Theoretical Investigation of Strain-balanced GaP1-xNx/GaAsyNy superlattices lattice-matched to Si(001) for 1.5-1.8 eV photonic applications
Lekhnath Bhusal 1 2 , Wenkai Zhu 1 2 , Alex Freundlich 1 2
1 Photovolatics and Nanostructures Laboratories, Texas Center for Advanced Materials , Houston, Texas, United States, 2 Physics Department, University of Houston, Houston, Texas, United States
Show AbstractDilute nitrides alloys of GaP1-x-yAsyNx alloys have attracted much attention since they exhibit a direct bandgap and their lattice constant matches the one of silicon for y=4.7x-0.1. Thus these alloys offer interesting perspectives for the monolithic integration of III-V optoelectronics with the silicon technology. For practically achievable nitrogen composition (x<=0.04), the band gap of GaP1-x-yAsyNx alloys lattice matched to Si is limited to about 1.75 eV. One may attempt to expand the operation wavelength of these dilute nitrides by fabricating a short period strain-balanced GaP1-xNx/GaAs1-yNy superlattice on silicon where ultra-thin layers of GaAs1-yNy (compressively strained) and GaP1-xNx (tensilely strained) are alternated and where the thickness of each layer is maintained to below the onset of the lattice relaxation.In this work we present a theoretical study of the electronic band structure of these strain-balanced (and lattice matched to Si) superlattices in the vicinity of the center of the Brilloin zone (Γ-point). A six-band Kane Hamiltonian modified to account for the strain effect and a the band anti-crossing model are used to describe the electronic states of the highly strained zinc blende GaP1-xNx and GaAs1-yNy ternaries. The evolution of the conduction band minima and valence subbands maxima of GaP1-xNx and GaAs1-yNy indicates the occurrence of a type I band alignment for the superlattices involving the mj=+/-3/2, +/-1/2 valence subbands in the range of compositions of interest.A transfer matrix method has been used to determine the electron and hole minibands of the superlattice structure, predicting the evolution of the band edge transition energies for different nitrogen compositions and alloying/thickness combinations. The results of calculations show the potential to obtain room-temperature photon absorption/emission energies as low as 1.57 eV for a typical nitrogen composition of 4%. The proposed strain balanced structure, thus offers the potential for bandgap engineering ranging from the near IR to visible with host of major applications in silicon-based optoelectronics and multi-bandgap photovoltaics.
9:00 PM - I9.9
Enhanced Broad Band Cathodoluminescence of Nano-Structured Zinc Silicate Films.
Young-Hwan Kim 1 , Woon-Jo Cho 2 , Yu-Jin Park 1 3 , Soo-Jin Lee 2 , Yong Tae Kim 1
1 Semiconductor Materials and Devices Laboratory, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 Nano Device Research Center, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 3 Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractLow-dimensional ZnO materials compatible with silicon-based electronic materials are important from the viewpoint of practical applications of these materials. Compared to a conventional ZnO film, we report here an enhanced (3 times) and broaden (6 times) cathodoluminescence properties of nano-structured zinc silicate films containing ZnO nanoparticles with average size of ~5nm. The films were fabricated on Si (100) substrates by rf sputtering. ZnO pellets with a diameter of ~10mm were placed on 2-inch Si target and number of ZnO pellet was varied to control film composition. Optical and structural properties were characterized by photoluminescence, cathodoluminescence, XRD, TEM, RBS, and FTIR, etc. From the results of cathodoluminescence measurements, typically, the film with composition of Zn/Si=1.56 which was annealed at 700 oC exhibited a strong and broad emission band at the wavelength of ~400 nm with FWHM of ~100 nm. On the other hand, pure ZnO film showed sharp emission peak at 385 nm with FWHM of ~15 nm. This band was found to be very sensitive to both film composition and annealing temperature. TEM image of this film shows that crystallized nanoparticles with average size of ~5nm are densely distributed in the amorphous matrix. SAD and XRD analysis reveal that the nanoparticles are composed of both ZnO and Zn2SiO4. Therefore, the strong and broad emission band at 400 nm is suggested to be attributed to ZnO nanoparticles, considering that Zn2SiO4 is known to have only one 525 nm emission band. The origin of this 400 nm broad band emission from nano-structured zinc silicate thin films will be discussed more analytically. This work is supported by the Korea Institute of Science and Technology under Contract No. 2E18540.
Symposium Organizers
Mark Brongersma Stanford University
Donald S. Gardner Intel Corporation
Michal Lipson Cornell University
Jung H. Shin KAIST
I10: Active Si Photonic Devices
Session Chairs
Thursday AM, April 20, 2006
Room 3007 (Moscone West)
9:30 AM - **I10.1
Proposal for Mid-infrared Silicon Raman lasers
Bahram Jalali 1 , Varun Raghunathan 1 , Ramesh Shori 1 , Oscar Stafsudd 1
1 Electrical Engineering Department, University of California, Los Angeles, Los Angeles, California, United States
Show AbstractSilicon Photonics has achieved some key milestones in recent years in its quest towards realizing low cost, high speed optoelectronic components. The enormous infrastructure available for Silicon device manufacturing and the economy of scales have been the motivating factors in this direction. In particular, Raman scattering has been successfully used to demonstrate Lasers[1,2] and amplifiers[3,4] on pure Silicon chip. In these demonstrations, schemes like low duty cycle pulse pumping and reverse-biased carrier sweep out were employed to minimize the impact of nonlinear losses due to free carrier absorption processes. However, the maximum output power of the Raman laser is limited by the nonlinear losses and the presence of free carriers also increases the on-chip heat dissipation. In addition to this, the need for an external optical pump poses a question regarding the place of Silicon Raman lasers at telecom wavelengths, where the III-V laser technology has already made significant impact.The two-photon absorption effect which is responsible for creation of free carriers in Silicon is found to reduce significantly when pumped at energy less than half the band gap (~2.2μm)[5]. This implies that Silicon Raman lasers pumped at mid infrared(MIR) wavelengths can operate without the competing nonlinear loss mechanisms. The linear absorption loss data[6] for Silicon also suggests that the low-loss window extends from 1.1-8μm in wavelength. In addition to this, the absence of suitable semiconductor lasers at MIR wavelengths along with the high damage threshold of Silicon is expected to make it a potentially viable material for realizing MIR wavelength Raman devices. MIR wavelengths in the range of 2-5μm is an important band for free space communications, bio-chemical detection and certain medical applications. Most gases and biological compounds have fundamental resonances at the MIR and can be detected using these sources. The strong absorption of water and skin cells at these wavelengths renders theses sources as attractive tools for dentistry, eye surgery etc. The implementation of Silicon Raman devices at these wavelengths could potentially miniaturize the devices used in these applications. Moreover, the inherent Stokes tunability with pump wavelength and the prospects of cascaded stokes emission could help achieve wavelengths not easily reachable using other schemes.This talk proposes a new technology, ie. Silicon Raman lasers that operate at MIR wavelengths, and discusses its applications. Silicon is compared with other standard material used as MIR sources. To support this vision, measurement of linear and nonlinear losses of Silicon at both telecom and MIR wavelengths will be presented.1.O. Boyraz et. al.,Opt. Express, 12, 5269(2004)2.H. Rong et. al.,Nature, 13,725(2005)3.V. Raghunathan et. al.,CLEO, CMU1, Baltimore(2005)4.R. Jones et. al. Nature,13,519(2005)5.R.A. Soref, private communications6.“Properties of Silicon”,INSPEC(1998)
10:00 AM - I10.2
Thermo-electrical Analysis of an Optoelectronic Modulator Integrated in a SOI Rib Waveguide Operating in the Gb/s Regime.
Mario Iodice 1 , Giuseppe Coppola 1 , Rocco Zaccuri 1
1 , IMM-CNR, Napoli Italy
Show Abstract10:15 AM - I10.3
Microstrutural, Optical and electro-optical Properties Of Ba0.5Sr0.5TiO3 Thin Film Deposited By Pulsed Laser Deposition For Active Low Loss Waveguide Applications.
Mounir Gaidi 1 2 , Marcello Ferrera 1 3 , Fulvio Cusimano 1 3 , Robin Helsten 1 , Yongwoo Park 1 , Jose Azana 1 , Roberto Morandotti 1 , Pasquale Cusumano 3 , Mohamed Chaker 1
1 , INRS-EMT, Varennes, Quebec, Canada, 2 , Adtek Photomask Inc, Monteral, Quebec, Canada, 3 Department of Electrical Engineering, University of Palermo, Palermo Italy
Show Abstract10:30 AM - I10.4
High Sensitivity Sensor Based on Porous Silicon Waveguide
Sharon Weiss 1 , Guoguang Rong 1 , Jarkko Saarinen 2 , John Sipe 2
1 Electrical Engineering & Computer Science, Vanderbilt University, Nashville, Tennessee, United States, 2 Department of Physics and Institute for Optical Sciences, University of Toronto, Toronto, Ontario, Canada
Show AbstractWe report on a new sensor design for ultra-sensitive detection of chemical and biological species. The sensor combines the advantages of the large internal surface area of porous silicon and the high electromagnetic field strength localized in a waveguide mode. Light of a specific wavelength and at a specific angle is coupled into a porous silicon waveguide that contains the target material to be detected. Any change of the refractive index of the waveguide will alter the way light propagates in the waveguide and will cause a measurable deviation in the angle at which light exits the sensor. Since the porous silicon pore size is small compared to the wavelength of light, the presence of the target species in the pores will cause the effective refractive index of the waveguide to change. The key advantage of this sensor design, compared to the current state-of-the-art surface plasmon resonance (SPR) sensors, is that the electric field is strongest in the location where the biological and chemical species are detected (e.g., inside the waveguide). Therefore, due to the extremely sharp waveguide resonance, the sensitivity of the porous silicon waveguide sensor to small changes in refractive index is superior. Rigorous calculations based on a pole expansion predict a nearly 60-fold enhancement of the sensitivity of the porous silicon sensor as compared to an SPR sensor. Experimental demonstrations of the porous silicon waveguide sensor show a substantial, 6.6 degree angular deviation of the light coupled out of the waveguide in response to the infiltration of isopropyl alcohol. The influence of the porous silicon porosity and thickness as well as the silicon substrate doping level will be examined. Demonstrations of the sensor response to smaller refractive index changes, for example, due to the binding of DNA sequences, and an investigation of the minimum detectable concentration level will also be presented.
10:45 AM - I10.5
Ferroelectric Perovskite Oxide Integration for Active Silicon Photonic Devices
Matthew Dicken 1 , Axel Scherer 1 , Harry Atwater 1
1 Applied Physics, California Institute of Technology, Pasadena, California, United States
Show AbstractIntegration of electro-optic materials with integrated silicon photonics will allow for active control of devices (cavity resonant frequency, photonic crystal waveguide dispersion) to be developed in a manner compatible with CMOS processes, e.g, similar to those that current employ barium strontium titanate capactors in front-end processing. Ferroelectric perovskite oxides, such as barium titanate (BT), are an interesting candidate for thin film optical devices because of their large electro-optic coefficients and electrically switchable structural and optical properties. The ability to electrically modulate the refractive index of BT thin films has previously yielded electro-optic waveguide modulators and interferometers fabricated on bulk MgO oxide substrates. However, a more desirable strategy for integrated photonics is to enable similar functionality for silicon-on-insulator (SOI) photonic devices. Recently, we have developed a process to integrate ferroelectric thin films of barium titanate with silicon-based substrates using biaxially-oriented thin film template layers of MgO deposited by ion beam assisted deposition (IBAD). We have been able to grow optical quality thin films of 200 nm thickness barium titanate by molecular beam epitaxy on silicon, silicon-on-insulator (110nm thick Si on 1.5um thick Box layers), and 5nm thickness amorphous Si3N4 films with using IBAD: MgO template layers. These barium titanate films exhibit single crystal-like optical properties in the wavelength range from 300-2200nm as determined using variable angle spectroscopic ellipsometry. Piezoresponse force microscopy has been used to characterize the ferroelectric properties of the film, indicating clamped piezoelectric coefficients of 10pm/V and coercive fields of 500 kV/cm. Optical engineering using modal analysis and beam propagation models has been used to design the mode profile and predict the electro-optic response of BT/SOI photonic structures. Measurements of loss and dispersion in BT/SOI photonic crystal waveguides and the potential for creating tunable photonic crystal resonators, in silicon-on-insulator devices using BT/SOI thin film integration will be discussed.
11:00 AM - I10: Si Photonic
BREAK
I11: Si Microphotonics
Session Chairs
Thursday PM, April 20, 2006
Room 3007 (Moscone West)
11:30 AM - **I11.1
A Roadmap for Silicon-based On-chip Optical Interconnects
Philippe Fauchet 1 , Eby Friedman 1 , David Albonesi 2 , Mikhail Haurylau 1 , Hui Chen 3 , Jidong Zhang 1 , Guoqing Chen 1 , Nicholas Nelson 1
1 ECE, University of Rochester, Rochester, New York, United States, 2 ECE, Cornell University, Ithaca, New York, United States, 3 Physics and Astronomy, University of Rochester, Rochester, New York, United States
Show AbstractUsing the International Technology Roadmap for Semiconductors (ITRS) as a starting point, we derive the requirements for silicon-based intrachip optical interconnects and identify the areas where progress is urgently needed. First, we make predictions valid until year 2016 for electrical interconnects relying on state-of-the-art VLSI modeling approaches. We then perform a complete analysis of an optical interconnect system consisting of three main on-chip components (light modulators, waveguides, and photodetectors) and assuming an off-chip light source. The performance of electrical and optical interconnect systems are then compared from the viewpoint of various metrics, including delay, power-delay product, bandwidth density, power dissipation, and timing jitter. This part of our work demonstrates the advantages of using high-refractive index (e.g., silicon) as opposed to low-refractive index (e.g., polymers or silica) components, makes it clear that resonant modulators are necessary, and clearly identifies several system-level advantages of optical interconnects. We also find that wavelength division multiplexing is necessary and show how the need for it increases in time.Armed with the results of this analysis, we identify the primary challenges facing intrachip optical interconnects. First, the size, delay, and power consumption of silicon-based modulators must be significantly reduced. Second, the introduction of wavelength division multiplexing necessitates the development of ultra-compact wavelength selective components. Third, efficient on-chip light amplifiers and (potentially on-chip) light sources need to be developed. Progress toward these goals will be briefly discussed.This work was supported by NSF (CCR-0304574), with additional support by SRC and AFOSR.
12:00 PM - **I11.2
Fiber on a Chip: Nonlinear Optics in Siliconwires
Richard Osgood 1 , Oliver Chen 1 , Andy Hsieh 1 , Nicolae Panoiu 1 , Jerry Dadap 1 , Frank Dulkeith 2 , Sharee McNab 2 , Yurii Vlasov 2
1 , Columbia University, New York, New York, United States, 2 IBM Watson Labs, IBM, Yorktown Heights, New York, United States
Show AbstractFiber optics is an enabling technology not only for light transport but also a means to manipulate the phase, timing, envelope, and wavelength of optical pulses. Using recent technology it is now possible to accomplish these fiber-optic functions entirely on-chip using SOI-based materials. In this paper, we will describe the use of siliconwires to accomplish many of these nonlinear optical functions. The experiments make use of variety of laser waveforms from CW to femtosecond to pump low-propagation- and low-insertion-loss Si waveguides on wafer-bonded SOI wafers. The waveguides are 400nm by 200nm channel guides with 3dB/cm propagation loss and 3dB input and output loss at 1.55μm wavelength. With these waveguides, we have demonstrated Raman amplification, four-wave mixing, self-phase modulation, optical limiting, and pulse shaping. A key feature of such integrated nonlinear devices is that their dispersion can be engineered via waveguide geometry so that both positive and negative second-order dispersion can be fabricated into the waveguide. Our experimental work has also been guided by the development of a full, rigorous theoretical treatment of nonlinear propagation in the crystal-silicon waveguide, which fully accounts for strong modal confinement and Si-optical-nonlinearity anisotropy. Our work will discuss our experimental measurements at Columbia and IBM of nonlinear gain, four-wave mixing, pulse shaping, and self-phase modulation and the comparison with behavior expected on the basis of our theoretical treatment.
12:30 PM - **I11.3
Silicon Microphotonics: Hardware for the Information Age.
Lionel Kimerling 1
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractThe optical components industry stands at the threshold of a major expansion that will restructure its business processes and sustain its profitability for the next three decades. This growth will establish a cost effective platform for the partitioning of electronic and photonic functionality to extend the processing power of integrated circuits and the performance of optical communications networks. The traditional dimensional shrink approach to the scaling of microprocessor technology is encountering barriers in materials and power dissipation that dictate more distributed, parallel architectures. The performance requirement for this short link interconnection is crossing the 10 MBp/s km threshold that dictates optical carrier utilization. This new direction will ignite a major change in leadership of the industry from information transmission (telecom) to information processing (computing, imaging); and it will open significant new markets with high volume applications. The talk will give an overview of the evolving silicon microphotonic technology platform – components and monolithic integration - and assess its capability in meeting the challenges – processing, interconnection and high volume production - of the next phase of the Information Age.
I12: Photonic Crystals I
Session Chairs
Thursday PM, April 20, 2006
Room 3007 (Moscone West)
2:30 PM - **I12.1
Low Loss and Slow Light Photonic Crystal Waveguides in SOI.
Thomas Krauss 1 , Michael Settle 1 , Michael Salib 2 , Albert Michaeli 3
1 School of Physics and Astronomy, University of St. Andrews, Fife United Kingdom, 2 , Intel Corporation, Santa Clara, California, United States, 3 , Intel Corporation, Kyriat Gat Israel
Show AbstractThe field of photonic crystals has made tremendous progress in recent years, and has evolved from an academic curiosity to an area where practical applications are beginning to appear feasible. This is in part due to a better understanding of the useful parameter-space, but mainly due to tremendous technological improvements. Only true control on the nanometre-scale, in terms of roughness and lithographic accuracy, has enabled losses to drop below the critical 10 dB/cm limit. While most structures are made using e-beam lithography, it is essential to adopt mass-manufacturing processes if volume applications are envisaged. For the same reason, waveguides on a solid cladding are preferred, discounting the, in principle, superior “air-bridge’ approach. Pursuing this approach and using 193 nm lithography in a CMOS fab, we have now achieved losses approaching the 10 dB/cm level.
3:00 PM - I12.2
Tuning of Integrated Silicon Based Photonic Bandgap Structures
Mikhail Haurylau 1 , Jidong Zhang 1 , Sean Anderson 2 , Kenneth Marshall 3 , Philippe Fauchet 1 2 3
1 Department of the Electrical and Computer Engineering, University of Rochester, Rochester, New York, United States, 2 The Institute of Optics, University of Rochester, Rochester, New York, United States, 3 The Laboratory for Laser Energetics, University of Rochester, Rochester, New York, United States
Show AbstractThe development of a comprehensive integrated photonic system requires a set of flexible optical functional units, such as switches or tunable filters, that are compatible with the mainstream fabrication technology. Silicon based photonic bandgap (PBG) structures are a likely platform for such systems; however they lack flexibility if only silicon is used as an active material. When the host material is a semiconductor such as silicon with poor electrooptic properties, this tuning can be achieved by infiltrating the structure with an active optical material. This approach combines the benefits of microelectronic silicon processing with the optical performance of a variety of materials that can be infiltrated in the last step of fabrication. The key to the performance of such structures is to confine both light and electric field inside the active material. The confinement of light can easily be achieved by using PBG structures, where the optical modes can be designed to reside inside a low-refractive index material. In contrast, the confinement of the electric field inside the active material was considered to be impossible due to the high conductivity of the silicon host. The silicon host can indeed provide a bypass route for electric field lines away from the active material, an effect that is known as electric field screening . We analyze the switching of electrooptic material in such structures and introduce design rules that help achieve electrical tuning. In particular, a design concept that eliminates electric field screening effects is proposed for the first time. The developed rules and concepts are demonstrated via electrical tuning of liquid crystals inside 2-D silicon PBG structures. Integrated silicon-on-insulator based PBG devices and porous silicon 2-D PBG structures and membranes are fabricated and then infiltrated with liquid crystal molecules. Electric field switching at fields lower than 1 V/μm is observed using both polarized light microscopy and direct PBG spectrum measurements. The design rules can be applied across different combinations of semiconductor PBG structures and active optical materials.
3:15 PM - I12.3
Patterned Porous Silicon Structures for Microphotonics.
Daniel Gargas 1 , Ovidiu Muresan 1 , Donald Sirbuly 2 , Steven Buratto 1
1 Chemistry, University of California Santa Barbara, Santa Barbara, California, United States, 2 Chemistry, University of California, Berkeley, California, United States
Show AbstractMicrostructures of porous silicon photonic crystals fabricated by soft lithography are presented for use in microphotonics. In our experiments a porous silicon Bragg reflector is brought into contact with a patterned PDMS stamp. The stamp is then peeled from the film removing the porous Si from regions in contact with the film leaving behind a patterned structure. [1] The removed porous Si multilayers can be then be transferred from the PDMS stamp to a polymer film by this same contact and peel procedure to create patterned porous Si Bragg reflectors on polymer substrates. Details of our lithographic technique will be presented. We have also used this lithographic technique to create microscale and nanoscale patterned porous Si structures for a number of new applications including porous Si waveguides, amplified stimulated emission in waveguides, patterned Bragg mirrors and chemical sensors based on reflectivity and luminescence. Details of these applications will also be discussed. [1] Sirbuly D.J.; Lowman G.M.; Scott B.; Stucky G.D.; and Buratto S.K.: Adv. Mater. 15, 149 (2003).
3:30 PM - I12.4
Birefringence in Si-rich SiO2 Thin Films Deposited through Reactive RF Sputtering.
Michael Stolfi 1 , Luca Dal Negro 1 , John LeBlanc 2 , John Haavisto 2 , Lionel Kimerling 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , Charles Stark Draper Laboratory, Cambridge, Massachusetts, United States
Show AbstractSi-rich SiO2 thin films have attracted considerable attention due to the demonstration of efficient light emission and optical gain from Si nanocrystals as well as rare-earth emission enhancement due to energy transfer from Si nanocrystals. Birefringence in this materials system has been reported for Si nanocrystal samples prepared through annealing of Si/SiO2 superlattices where the birefringence was attributed to the anisotropic superlattice structure [1]. We have deposited Si-rich SiO2 thin films on silica substrates through reactive RF magnetron sputtering to investigate the film birefringence as a function of preparation conditions. The film birefringence was measured using a Metricon prism coupler at λ = 1551 nm. For Si-rich SiO2 films we have observed a positive birefringence (nTM > nTE) which increases with increasing silicon content for as deposited films. In comparison, the birefringence measured in as deposited Ge-doped stoichiometric SiO2, with an index of refraction nTE = 1.475, was negligible. The dependence of the birefringence on annealing temperature is also influenced by the silicon content. Films with moderate silicon contents (nTE = 1.685, ~38 at% Si) demonstrated birefringence reduction after annealing at 1100 °C while films with high silicon content (nTE = 1.952, ~50 at% Si) demonstrated birefringence enhancement after annealing at 1100 °C. Preliminary results show a birefringence of more than 3% can be generated in films with high silicon content (nTE = 1.952, ~50 at% Si) annealed at 1100 °C. The role of film stress and film nanostructure in the origin of the birefringence will be discussed. [1] F. Riboli et al. Appl.Phys.Lett. 85 (7). 2004.
3:45 PM - I12: Phot Crys 1
BREAK
I13: Photonic Crystals II
Session Chairs
Thursday PM, April 20, 2006
Room 3007 (Moscone West)
4:15 PM - **I13.1
SOI with Er:SiOx Overcladding: Microphotonic Design and Fabrication for Ultra-compact Amplifying Circuits and Low-threshold, Broadband Si-based Lasers.
Oskar Painter 1
1 Engineering and Applied Science, CalTech, Pasadena, California, United States
Show Abstract4:45 PM - I13.2
Simulations of Sub-wavelength Silicon-based Metallo-dielectric Photonic Crystals for Sensing.
Rana Biswas 1 , Changgeng Ding 1 , Irina Puscasu 2 , Martin Pralle 2 , Mark McNeal 2 , James Daly 2 , Anton Greenwald 2 , Edward Johnson 2 , Srinivas Neginhal 1
1 Dept. of Physics & ECpE, MRC, Ames Lab, Iowa State University, Ames, Iowa, United States, 2 , Ion Optics Inc., Waltham, Massachusetts, United States
Show AbstractA novel silicon-based metallo-dielectric photonic crystal has been fabricated by Ion-Optics [1] for infrared sensing applications, and detection of gaseous species. This structure is a novel tunable narrow-band emitter at infrared wavelengths, that has promise for silicon microphotonics applications. A rigorous S-matrix (scattering matrix) theory is developed to simulate and understand the optical properties of this structure. The device consists of a sub-wavelength array of holes in a metal layer residing on a silicon photonic crystal. The S-matrix approach simulates the reflection and transmission through this structure by solution of eigenmodes within each layer, utilizing realistic material absorption and dispersion. We find in the simulations sharp resonant absorption and corresponding resonant emission modes, at wavelengths close to the lattice spacing, in agreement with measurement. There is an enormous enhancement of the fields within the sub-wavelength apertures with maxima near the edges of the holes and minima in the interior of the apertures, for the resonant modes. Analysis of the dominant eigenmodes connects the resonances to surface plasmon modes at the metal-dielectric interfaces. The thin metal layer with a sub-wavelength array of holes for a range of hole sizes, exhibits the well-known extraordinary transmission peaks for with our simulation approach. The plasmonic resonances in the subwavelength array of holes will be related to those in the full silicon based structure. The role of the silicon photonic crystal and will be analysed through systematic simulations. Simulations of the emission at different wavelength ranges will be presented. Off-normal photonic properties will be analysed. Results will be presented for the emission, photonic properties and plasmonic modes when the hole shape is distorted as well as when simple defects are introduced into the lattice, for new photonics applications on silicon-based platforms.[1] I. Puscasu, et al J. Applied Physics 98, 013531 (2005).Supported by the NSF.
5:00 PM - I13.3
Size and Position Control of Chains or Arrays of Nanoparticles by Surface-plasmon-polariton-induced Thermocapillarity.
Lars Roentzsch 1 , Karl-Heinz Heinig 1
1 FWIT, Research Center Rossendorf, Dresden Germany
Show AbstractSurface free energy minimization, driven by capillary forces, may lead to morphological changes of wires (e.g. disintegration into a droplet chain which is known as Rayleigh instability) and layers (dewetting). At nano-scale dimensions, capillary effects are much more pronounced than in macroscopic systems due to the large surface-to-volume ratio. On the other hand, capillary-driven self-organization processes are subject to increasing fluctuation with decreasing dimensions, which mostly prevent the formation of regular structures with long-range order.In this contribution, we predict by means of atomistic Monte Carlo simulations a novel method to fabricate size- and position controlled 1D- and 2D-patterns of nanoparticles. Our prediction rests on the temperature dependence of surface tension – the origin of the well-known thermocapillarity. Uncompensated forces occur due to surface temperature gradients. These forces may have considerable impact in the nanoworld, thus, leading to material transport and structure formation on short time and length scales. A surface tension gradient (also responsible for the Marangoni effect) triggers the biased migration of atoms from hot to cold regions by surface diffusion. A periodic temperature gradient on the surface of a wire or a layer may be achieved by a surface-plasmon-polariton (SPP) wave or even by a SPP wave interference pattern. For SPP excitations with long wavelengths (e.g. by a CO2 laser), sufficiently strong steady-state temperature gradients may be produced. However, pulsed operation might be necessary for shorter wavelengths. We predict by kinetic Monte Carlo simulations that the regularity of nanodroplet chains, that form during a self-organized disintegration of nanowires, might be considerably improved by SPPs. If the SPP wavelength is commensurable with the inherent Rayleigh wavelength of the nanowire disintegration, the SPP-induced temperature undulations control the Rayleigh instability. Thus, a regular and long-range order in nanodroplet size and position may be achieved. Similarly, this principle may be used for the fabrication of regular and long-range 2D nanodroplet patterns, if interference patterns of SPP waves on thin layers are achieved.