1200 V SiC vertical-channel-JFETs and cascode switches

Wide band gap semiconductors like silicon carbide (SiC) are currently being developed for high power/temperature applications. Silicon carbide is ideally suited for power switching due to its high saturated drift velocity, its high critical field strength, its excellent thermal conductivity, and its mechanical strength. For power devices, the tenfold increase in critical field strength of SiC relative to Si allows high voltage blocking layers to be fabricated significantly thinner than those of comparable Si devices. This reduces device on-state resistance and the associated conduction and switching losses, while maintaining the same high voltage blocking capability. The specific on-state resistance of 4H-SiC is approximately 400 times lower than that of Si at a given breakdown voltage. This allows for high current operation at relatively low forward voltage drop. In addition, the wide band gap of SiC allows operation at high temperatures where conventional Si devices fail. In this article, we will review Northrop Grumman's single-implant no-epitaxial-regrowth vertical-channel JFET. The feasibility of efficient 1200 V normally-off VJFET operation will be investigated. The all-SiC VJFET based cascode switch will be introduced and aspects of its operation evaluated. High temperature DC characteristics of VJFETs and 1200 V normally-off cascode switches will be discussed. Finally, the development of large-area high-current 1200 V VJFETs and their edge termination performance will be presented. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim