ECE EDS: Wenshen Li - High-Voltage beta-Ga2O3 Vertical Power Diodes and Transistors

Description

Abstract : beta-Ga2O3 is an ultra-wide-bandgap (4.5-4.7 eV) semiconductor material that possess disruptive potential in handling high power. Recently, a new Center-of-Excellence has been established on-campus by Cornell and the Air Force Research Laboratory (AFRL), aiming to develop growth and processing methodologies of Ga2O3. In this talk, I will discuss our recent development of high-voltage b-Ga2O3 vertical power diodes and transistors. For high voltage and high current applications, vertical power semiconductor devices are generally preferred over the lateral counterparts. The development of vertical power devices relies on the ability to epitaxially grow thick drift layers with low defect density and precisely-controlled net doping concentration, often on the order of 101 6 cm-3 or lower. One of the unique advantages of b-Ga2O3 over SiC and GaN is the availability of melt-growth methods for the production of high quality single-crystal substrates, which enables high quality epitaxial growth and a potentially low-cost device platform. The ultra-high critical breakdown field of 6-8 MV/cm in b-Ga2O3 is another key advantage of this material. Due to the high critical field, the conduction loss b-Ga2O3 can be even lower than SiC and GaN, which already enabled higher-efficiency power devices than Si. While the high critical field allows for significant advantage in efficiency, it also brings tremendous challenge to the management of the electric field in power devices, especially with the absence of native p-type doping in Ga2O3 up till now. Here, I will show that effective field management near the device active region can be achieved with vertical-fin structures. Over 2-kV breakdown voltage has been achieved in those devices, which represents the state-of-the-art of Ga2O3 power devices. Bio: Wenshen Li received the B.S. degree in Microelectronics from Tsinghua University, Beijing, China, in 2015, and M. S. degree in Electrical and Computer Engineering in from Cornell University in 2018. He is currently pursuing the Ph.D. degree in electrical engineering with Cornell University. His current research interests include GaN and Ga2O3 power devices. He has published 6 journal papers as the first author and has given 10 oral conference presentations, including in the International Electron Devices Meeting (IEDM) and an invited talk in the 235th ECS meeting. He has won the Honorary mention for Best Student Paper Award in Compound Semiconductor Week, 2018.