(Invited) Advances in SiC and GaN Power Device Development and Future Directions

Abstract

As wide bandgap semiconductors, devices based on SiC and GaN represent critical next-generation medium voltage and high voltage power switch technology. SiC device technology has matured rapidly over the past two decades, owing to advances in substrate quality, a fundamental understanding of epitaxial growth to characterize defects and identify and eliminate performance-limiting defects such as basal plane dislocations, and device breakthroughs such as the junction barrier Schottky (JBS) diode and DMOSFET. While lateral GaN-based HEMT technology has been highly successful for RF power amplifiers and is well-positioned to supersede GaAs-based MMICs, advances in vertical power device technology has been limited due to the lack of high quality native substrates. As large area substrates have become available by hydride vapor phase epitaxy (HVPE) and ammonothermal growth, several fundamental vertical power devices have recently been realized, including Schottky diodes with edge termination, trench MOSFETs, and CAVETs. However, significant fundamental materials challenges currently limit device performance, specifically the realization of repeatable thick drift layers with low background doping as well as a reliable selective area planar process for p-type doping. In this presentation, an overview of SiC and GaN device development at the U.S. Naval Research Laboratory will be summarized, first looking at SiC devices including the development of novel materials characterization techniques to understand the role of defects on device performance, reliability and failure analysis of devices, including BPD kinetics in PiN and MPS diodes, and novel device designs including grayscale termination processes, temperature compensated PiN diodes, and hybrid Si/SiC modules. Recent developments in GaN vertical device technology will also be presented, including the development of an ion implanted p-type doping process and preliminary materials characterization to understand the relationship between substrate quality, epitaxial layer quality, and device performance. Future directions for GaN device development enabled by the availability of bulk substrates will also be discussed, including implications for lateral devices, novel lateral device designs, and fundamental materials work based on the lessons learned from SiC.