Silicon Carbide Junction Field‐Effect Transistors (SiC JFETs)

Wide bandgap semiconductors like silicon carbide (SiC) are currently being developed for high-power/high-temperature applications. Silicon carbide (SiC) is ideally suited for power switching because of its high saturated drift velocity, its high critical field strength, its excellent thermal conductivity, and its mechanical strength. For power devices, the 10-fold 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 bandgap of SiC allows operation at high temperatures where conventional Si devices fail. In this article, we will review the SiC single-implant no epitaxial regrowth vertical channel junction field-effect transistor (JFET). The feasibility of efficient 1200 V normally OFF JFET operation will be investigated. The all-SiC JFET-based cascode switch will be introduced and aspects of its operation evaluated. High-temperature direct-current (dc) characteristics of JFETs and 1200 V normally OFF cascode switches will be discussed. Large-area high-current JFETs and their current sharing and switching performances will be presented. Aspects of JFET fabrication, including their edge termination, will be provided. JFET wafer yields and parameter uniformities will be presented. Hard and unclamped inductive JFET switching evaluations will be introduced. Finally, a 9-kV JFET will be introduced and its reliability under bipolar stress will be examined. Keywords: Silicon carbide; power switching; high voltage; high temperature; SiC