MRS Meetings and Events


EL11.12.07 2023 MRS Fall Meeting

MOCVD Grown High-Al Content β-(AlxGa1-x)2O3 for Enabling 2DEGs

When and Where

Nov 30, 2023
3:45pm - 4:00pm

Hynes, Level 2, Room 210



Cameron Gorsak1,Jonathan McCandless1,Katie Gann1,Huili Xing1,Debdeep Jena1,Michael Thompson1,Hari Nair1

Cornell University1


Cameron Gorsak1,Jonathan McCandless1,Katie Gann1,Huili Xing1,Debdeep Jena1,Michael Thompson1,Hari Nair1

Cornell University1
The unique properties of <i>β</i>-Ga<sub>2</sub>O<sub>3 </sub>including its ultra-wide bandgap of ~4.8 eV, critical breakdown field of ~8 MV/cm, availability of large-area native substrates, and controllable n-type doping have enabled rapid development in both growth and device processing. However, compared to other wide bandgap semiconductors, the intrinsic channel mobility is relatively low. A potential pathway to overcome this mobility limit is through two-dimensional electron gas (2DEG) formed at the interface of δ-doped <i>β</i>-(Al<i><sub>x</sub></i>Ga<sub>1-<i>x</i></sub>)<sub>2</sub>O<sub>3 </sub>and undoped <i>β</i>-Ga<sub>2</sub>O<sub>3</sub>. In this work, abrupt and smooth heterojunctions were growth at high Al concentrations using metal organic chemical vapor deposition (MOCVD) with TEGa and TEAl precursors.<br/>Prior to growth, (010) <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> substrates were etched in hydrofluoric acid (HF) for 30 minutes to minimize parasitic interfacial Si doping. In pure <i>β</i>-Ga<sub>2</sub>O<sub>3</sub>, we have demonstrated mobilities of 156 and 114 cm<sup>2</sup>/Vs for 1x10<sup>17</sup> and 1x10<sup>18</sup> /cm<sup>3</sup> Si doping, respectively, with sub-nm RMS roughness. However, as the Al concentration increases, multiple material challenges must be addressed including potential segregation, dopant activation, and maintaining film smoothness. Using TMAl and TEGa precursors, we demonstrate sub-2 nm RMS roughness for 130 nm <i>β</i>-(Al<sub>0.09</sub>Ga<sub>0.91</sub>)<sub>2</sub>O<sub>3 </sub>films. However, the growth temperature of 900 °C is too high for δ-doping; to reduce the growth temperature, TMAl was replaced with TEAl as the Al precursor due to the reduced cracking temperature. Additionally, TEAl shows potentially lower carbon incorporation because it pyrolyzes via β-hydrogen elimination whereas the pyrolysis of TMAl can leave behind highly reactive methyl radicals that may incorporate into the film.<br/>Surface roughness, carrier activation, and mobility as a function of Al concentration and doping conditions are reported.<br/>Combining effective substrate etching to remove a parasitic conducting channel with smooth highly doped <i>β</i>-(Al<i><sub>x</sub></i>Ga<sub>1-<i>x</i></sub>)<sub>2</sub>O<sub>3 </sub>will enable high mobility 2DEGs which will open the opportunity for devices with high switching speeds to operate in extreme environments.


alloy | metalorganic deposition

Symposium Organizers

Stephen Goodnick, Arizona State University
Robert Kaplar, Sandia National Laboratories
Martin Kuball, University of Bristol
Yoshinao Kumagai, Tokyo University of Agriculture and Technology

Symposium Support

Taiyo Nippon Sanson

Publishing Alliance

MRS publishes with Springer Nature