MSE Seminar: Dr. Hongping Zhao, Ohio State University

Wednesday, May 1, 2024
3:30 p.m.
Room 2110 Chemical and Nuclear Engineering Building
Sherri Tatum
301 405 5240

Next Generation Power Electronics: From Wide Bandgap GaN to Ultrawide Bandgap Ga2O3 and (AlxGa1-x)2O

Abstract: Wide bandgap gallium nitride (GaN) with intrinsic breakdown field of 3.5 MV/cm and a high electron mobility (phonon limited mobility >2000 cm2/Vs), possesses Baliga figure-of-merit at least 5 times superior to SiC and nearly 1000 times better than Si, enabling substantial reduction in conduction and switching losses in power electronics. While extensive research has focused on lateral power switching transistors with substantial industry involvement, vertical GaN devices are at a relatively less mature stage. Achieving high quality thick GaN drift layer with controllable doping level at low-1015 cm-3 and low defects determines vertical power device performance and reliability. In this talk, laser-assisted metalorganic chemical vapor deposition (MOCVD) development of GaN-on-GaN for high performance vertical PN diodes will be discussed. Record breakdown voltage exceeding 10 kV of vertical GaN PN diodes was demonstrated recently. 

Additionally, MOCVD epitaxy of several other WBG and UWBG semiconductors will be discussed. Derived conceptually from III-nitrides, II-IV-nitrides replace two group III atoms with a pair of group II and group IV atoms, opening new possibilities for band structure and device engineering. This talk will highlight MOCVD developments of two types of II-IV-N2 (ZnGeN2 and ZnSnN2) and their applications in light emitters.

UWBG gallium oxide (Ga2O3) represents an emerging semiconductor material promising for power electronics applications. With a bandgap energy of 4.8 eV, β-Ga2O3 is predicted to have a critical field strength of 8 MV/cm, enabling power switching devices with much lower conduction losses. Tremendous progresses have been made in the past decade on developing high quality Ga2O3 substrates, thin film epitaxy, defects and doping control, and device demonstrations. This talk will discuss our recent MOCVD developments of Ga2O3, doping, alloys, phase stabilization and heterostructures at OSU. MOCVD growth of (010) β-Ga2O3 results in high purity material with low compensation concentration, high electron mobility and wide range of n-type doping. Challenges and opportunities for developing (AlxGa1-x)2O3 on Ga2O3 substrates with different crystal orientations ((010), (100), (-201), (001)) will be discussed. MOCVD growth of metastable α-phase (AlxGa1-x)2O3 with Al composition from 0-100% and exploration of MOCVD growth window of κ-phase Ga2O3 will also be covered.  

Bio: Hongping Zhao is a professor in the Department of Electrical and Computer Engineering, and the Department of Materials Science and Engineering at The Ohio State University (Columbus, Ohio, USA). Prior to her current position, Prof. Zhao was an Assistant Professor in the Department of Electrical Engineering and Computer Science at Case Western Reserve University (Cleveland, Ohio, USA). She earned her PhD in Electrical Engineering from Lehigh University (Bethlehem, Pennsylvania, USA) in 2011. Prof. Zhao’s research expertise is centered in wide bandgap and ultra-wide bandgap semiconductor materials and devices. Her current research focuses on the material synthesis and device physics of III-nitrides, II-IV-nitrides, Ga2O3, etc. She currently serves as an Associate Editor for the journal Applied Physics Letters, and Journal of Crystal Growth. She is also serving as the technical program committee for the ICMOVPE XXI, IWGO 2024, IEDM 2023/2024, and an invited organizer for EMC. Prof. Zhao is serving as the general conference chair for GOX 2024.

Audience: Graduate  Faculty  Staff 

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