The tutorial focuses on the fundamentals and applications of heterogeneously integrated structures using 1D, 2D, and 3D materials from the growth of various dimensional materials, and various lift-off technologies to heterogeneous integration of electronic/optoelectronic/biomedical devices.
Lattice-Mismatched Heterostructures and the Applications to WBG and UWBG Semiconductor
Devices Zhenqiang Ma, University of Wisconsin, Madison
Semiconductor heterostructures are rooted in the theory conceived by Nobel Laureate Hebert Kroemer in 1957. Since then, the four classes, namely, GaAs-, InP-, Si/Ge-, and III-nitrides-based heterostructures, have revolutionized the electronics and optoelectronics that set the foundation of today's communications, lighting, sensing, infotainment, etc. These heterostructures were universally formed by epitaxy techniques uniquely governed and enabled by the stringent requirements of lattice matching. Limited by this requirement, realizing heterostructures between lattice-mismatched semiconductors has been a decades-long obstacle, although the materials space to explore and the number of heterostructures that can be made are vast compared to its lattice-matched counterparts. In this tutorial, lattice-mismatched heterostructures, or arbitrary heterostructures, formed via semiconductor grafting based on a quantum tunneling gluing approach are described. The tutorial will include the history of attempts at forming lattice-mismatched heterostructures, physical principles of bypassing the lattice constraints, fabrication methods and scalability, and a set of application examples involving wide bandgap (WBG) and ultra-wide bandgap (UWBG) semiconductor devices.
Advanced Heterogeneous Integration Enabled by 3D Freestanding Membranes—From Material Growths to Applications
Jeehwan Kim, Massachusetts Institute of Technology
For the future of electronics such as bioelectronics, 3D integrated electronics, and bendable electronics, the need for flexibility and stackability of electronic products has substantially grown up. However, conventional wafer-based single-crystalline semiconductors cannot catch up with such trends because they are bound to thick rigid wafers such that they are neither flexible nor stackable. Although polymer-based organic electronic materials are more compatible as they are mechanically compliant and less costly than inorganic counterparts, their electronic/photonic performance is substantially inferior to that of single-crystalline inorganic materials. Such performance-mechanical compliance dilemma could be resolved by developing methods to obtain cheap, flexible, stackable, single-crystalline inorganic systems. Such dream electronic systems could be realized by producing single-crystalline freestanding membranes. For the past few decades, various layer transfer techniques (a.k.a layer liftoff techniques) have been developed to produce single-crystalline freestanding membranes. In today's talk, I will present the survey of the layer liftoff techniques and go over how these strategies unlock new ways of manufacturing advanced electronic systems. In addition, I will introduce unprecedented artificial heterostructure devices enabled by stacking of those freestanding 3D material membranes, e.g., the world's smallest vertically-stacked full-color micro-LEDs, the world's best multiferroic devices, chip-less wireless e-skin, and reconfigurable hetero-integrated chips with AI accelerators.
Semiconductor Nanomaterials for Bioelectronic Systems
John A. Rogers, Northwestern University
Advanced electronic/optoelectronic systems built using classes of nanomaterials that enable intimate integration with living organisms will accelerate progress in biomedical research; they will also serve as the foundations for new approaches to monitoring and treating diseases. Specifically, capabilities for injecting miniaturized electronic elements, light sources, photodetectors, multiplexed sensors, programmable microfluidic networks and other components into precise locations of soft tissues or for softly laminating them onto the surfaces of vital organs will open up unique and important opportunities in tracking and manipulating biological processes. This presentation describes concepts in materials science and assembly techniques that underpin these types of technologies, including bioresorbable, or `transient', devices designed to disappear into the body on timescales matched to natural processes. Examples include skin-like devices for health monitoring, `cellular-scale' optofluidic neural probes for optogenetics research, systems for control of bladder function by closed-loop neuromodulation and bioelectronic `medicines' for accelerated regeneration of damaged peripheral nerves and temporary cardiac pacing.
Mixed-Dimensional Heterostructures for Electronic and Energy Technologies
Mark C. Hersam, Northwestern University
Layered two-dimensional (2D) materials interact primarily via van der Waals bonding, which has created new opportunities for heterostructures that are not constrained by epitaxial growth. However, it is important to acknowledge that van der Waals interactions are not limited to interplanar interactions in 2D materials. In principle, any passivated, dangling bond-free surface interacts with another via non-covalent forces. Consequently, layered 2D materials can be integrated with a diverse range of other materials, including those of different dimensionality, to form mixed-dimensional van der Waals heterostructures . Furthermore, chemical functionalization provides additional opportunities for tailoring the properties of 2D materials  and the degree of coupling across heterointerfaces . To efficiently explore the vast phase space for mixed-dimensional heterostructures, our laboratory employs solution-based additive assembly. In particular, constituent nanomaterials (e.g., carbon nanotubes, graphene, transition metal dichalcogenides, black phosphorus, boron nitride, and indium selenide) are isolated in solution, and then deposited into thin films with scalable additive manufacturing methods . By achieving high levels of nanomaterial monodispersity and printing fidelity, a variety of electronic and energy applications can be enhanced including photodetectors, optical emitters, supercapacitors, and batteries [5-7]. Furthermore, by integrating multiple nanomaterials into heterostructures, an unprecedented device function can be realized including anti-ambipolar transistors, gate-tunable Gaussian heterojunction transistors, and neuromorphic memtransistors [8-10]. In addition to technological implications for electronic and energy technologies, this talk will explore several fundamental issues including band alignment, doping, trap states, and charge/energy transfer across van der Waals heterointerfaces.
Freestanding Organic-Inorganic Hybrid Materials for Flexible Electronic and Optoelectronic Devices
Sheng Xu, University of California, San Diego
Organic-inorganic halide perovskites have demonstrated tremendous potential for next-generation electronic and optoelectronic devices due to their remarkable carrier dynamics. Current studies are mostly focused on polycrystals, since controlled growth of high-quality single crystals is challenging. In this presentation, I will discuss strategies that enabled the first chemical epitaxial growth of single-crystal hybrid halide perovskites. Using advanced microfabrication, homo-/hetero-epitaxy, and a low-temperature solution method, single crystals can be grown with controlled locations, morphologies, orientations, and strain levels. By a lifting-off approach, single-crystal thin films can be transferred from the epitaxial substrate to a general flexible substrate. This approach opens up broad opportunities for hybrid halide perovskite materials based on flexible high-performance electronic and optoelectronic devices.
Epitaxy of III-Nitrides on 2D Materials—Interface Manipulation
Abdallah Ougazzaden, Georgia Tech
The instructor will discuss the epitaxy of III-nitrides semiconductors on 2D materials by either MOVPE or MBE. The discussion will include 1) Epitaxy of single-crystal III-nitride films on transferred 2D materials on different kinds of substrates such as single-crystal sapphire and polycrystalline diamond, 2) Interface manipulation between III-nitrides and 2D materials, 3) Separation of wafer-scale epitaxial III-nitride films on 2D materials, and 4) Fabrication of transferable III-nitrides-based light emitting devices.