Next-Generation High-Power RF Sources – Establishing GaN IMPATT Technology and Beyond with Ultra-Wide Bandgap Semiconductors

Abstract:

Gallium nitride (GaN) has emerged as a transformative material in RF applications with the market projected to surpass $ 2 billion by 2029. The exceptional power density, efficiency, and thermal robustness of GaN-based high electron mobility transistors (HEMTs) have been pivotal in driving this growth, establishing GaN as a dominant solution in 5G base stations, radar systems, and satellite communications. However, continuous device innovations remain critical for further technology advancement. Today, improvements in material growth and fabrication processes are unlocking new possibilities for novel device architectures in GaN. A prime example is the impact ionization avalanche transit time (IMPATT) diode, which presents another promising path to achieving high-frequency RF systems with high output power in a compact form factor.

In this talk, I will primarily present our research in making the first mm-wave GaN IMPATT oscillator, operating from Ka- to V-band. I will first discuss our material design and edge termination strategies that ensure uniform avalanche in GaN pn diodes. Next, I will illustrate the integration of these avalanche diodes into a full RF oscillator system, addressing challenges in packaging and circuit design. Finally, I will showcase our latest work on diffusion-based doping techniques in GaN and Ga₂O₃ and explore how these unconventional processes unlock new device architectures and pave the way for next-generation power electronics and RF devices.

Bio:

Zhengliang Bian is currently a final-year Ph.D. candidate at Stanford University, working in Wide-Bandgap Lab supervised by Prof. Srabanti Chowdhury. He received a B.Eng. from Tsinghua University in 2019 and an M.S. in Electrical Engineering from Stanford University in 2023. His research focuses on (ultra)wide bandgap materials for power electronics and RF applications, spanning material design, device fabrication, packaging, and circuit integration. Notably, his work led to the development of the first GaN IMPATT oscillator operating at mm-wave frequencies, which was selected for presentation at the IEDM in both 2023 and 2024. His research has resulted in 17 journal and conference papers, including articles featured as the cover in EDL, editor’s picks in APL, and news coverage in Compound Semiconductor Magazine.