Advanced Wide Bandgap Semiconductors for Future High-Power and Renewable Energy Applications

DrLin Cheng has 15+ years of wide bandgap semiconductor R&D and manufacturing experience in a combination of industry and academic settings. She received a BS degree in Material Science from Wuhan University of Technology, Wuhan, China, in 1988 and a PhD degree in Electrical Engineering from University of Cincinnati, Cincinnati, Ohio in 2003. Dr. Cheng is currently serving as a senior researcher to lead development of wide bandgap semiconductor power devices, such as SiCand GaN, at U.S. Army Research Laboratory in Adelphi, Maryland.  From Nov. 2008 to Oct. 2014, Dr. Cheng was with Cree Inc. in Durham, North Carolina, where her research interests included development of various SiChigh power devices.  In 2011 – 2014, she was appointed principle investigator and led the development of SiCtrench MOSFETs, DMOSFETs with high channel mobility, Cree’s 3rdgeneration SiCMOSFETs that are under transition to production, 3.3 kV – 15 kV MOSFETs, 10 kV – 22 kV GTOs, 10 kV – 18 kV light-triggered GTOs, and 3.3 kV – 23 kV power diodes under various internally and externally funded programs. Dr. Cheng also played key roles in development and commercialization of Cree's 1stand 2ndgeneration 1200 V SiCMOSFETs and development of 600 – 1200 V power BJTs and 10 kV – 27 kV SiCIGBTs.  To further help promote the development and manufacturing of wide bandgap power components and power electronics, Dr. Cheng has served on graduate students' committees in the Department of Electrical and Computer Engineering at North Carolina State University since October 2013 and Texas Tech University since February 2014, respectively.  Before joined Cree, Dr. Cheng was with SemiSouthLaboratories Inc. and Mississippi State University from May 2003 to Nov. 2008, where her research interests were focused on development of the SiCpower VJFETs and JBS diodes for various external and internal programs.  Dr. Cheng has authored and co-authored over 100 technical papers and presentations, including one short course and 13 invited talks.  She holds over 30 U.S. patents, patent applications and disclosures.  She was a technical committee member of the MRS Spring Meeting in 2008, the Intl’ Conference on SiC& Related Materials in 2013, the Intl’ Symposium on Power Semiconductor Devices and ICs from 2014 to 2018, and a reviewer for numerous journals, proceedings, and government proposals.  Dr. Cheng is a Senior Member of IEEE and a Member of the Materials Research Society.

Development in power semiconductors is vital for achieving the design goals set by industry.  The steadily increasing demand for high-power, high-voltage, high-frequency, and high-temperature operations of the power conversion, modulation, and distribution systems brings traditional silicon (Si) semiconductor ever closer to its fundamental material limits. The wide bandgap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), have attracted great attention over silicon for future high-power applications and energy savings due to their superior material properties.  Among the WBG semiconductors, power device technology based on SiCis most mature.  As evidence, with the rapid improvement of SiCmaterial quality in recent decades, the superior material properties of SiC, such as ~ 3x wider bandgap, ~ 3x higher thermal conductivity, and ~ 10x higher critical breakdown field strength than Si, have enabled 1200 V and 1700 V, 20 A and 50 A SiCSchottkydiodes and MOSFETs to meet the market demands in moderate to high power sectors for a variety of solar inverters, electric vehicles (EVs), fast chargers for EVs, and motor drive applications.  SiCpower modules rated at 1200 V, 100 – 300 A and 1700 V, 300 A have been introduced, and 1200 V, 880 A modules have successfully passed simulated testing of 11,783 miles on a road test at US Army Research Laboratory.  The improved SiCmaterial has also led to advances in high voltage bipolar devices such as GTO thyristors, IGBTs, and PiNdiodes in the 10 kV to 27 kV classes.  Work that remains is to improve the carrier lifetime and its uniformity at high-current injection levels, as well as to reduce basal plane dislocations and other defect densities in SiCthick epi-layers.  However, the progress made to date in achieving ultra-high voltage in 1 ~ 2 cm2SiCsingle switches is a testament to the continuously improving SiCmaterial quality.  In comparison to SiC, the potential, promises, and challenges of GaNpower device technology will be also discussed.