I. Introduction
Wide-band-gap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) have superior characteristics to silicon (Si). Many universities and/or manufacturers are now cooperating and competing to develop the next-generation, ultra low-loss, high-speed power devices using wide-band-gap semiconductors [1]–[9]. Infineon Technologies and Cree have already put 300-V, 600-V, and 1,200-V SiC-SBDs (Schottky barrier diodes) on the market. These SiC-SBDs have been tested in power electronic circuits to evaluate their effectiveness in reducing power loss [10]. In addition, SiC-JFETs (junction field-effect transistors) and SiC-MOSFETs (metal-oxide-semiconductor field-effect transistors) are now shifting from laboratory levels toward commercial levels. Mitsubishi Electric and Rohm in December 2004, and National Institute of Advanced Industrial Science and Technology of Japan (AIST) in March 2005 independently announced that they had developed SiC-MOSFETs with reduced channel resistances [8], [9].