High power devices in wide bandgap semiconductors

Abstract

Silicon carbide (SiC) semiconductor devices for high power applications are now commercially available as discrete devices. Recently Schottky diodes are offered by both USA and Europe based companies. Active switching devices such as bipolar junction transistors (BJTs), field effect transistors (JFETs and MOSFETs) are now reaching the market. The interest is rapidly growing for these devices in high power and high temperature applications. The main advantages of wide bandgap semiconductors are their very high critical electric field capability. From a power device perspective the high critical field strength can be used to design switching devices with much lower losses than conventional silicon based devices both for on-state losses and reduced switching losses. This paper will review the current state of the art in active switching device performance for both SiC and GaN devices. SiC material quality and epitaxy processes have greatly improved and degradation free 100 mm wafers are readily available. This is encouraging since also bipolar devices now are attractive with good long term stability. SiC wafers still have a too high cost to be fully cost efficient. However, the SiC wafer roadmap looks very favorable as volume production takes off. For GaN materials the main application area is geared towards the lower power rating level up to 1 kV on mostly lateral FET designs. The cost advantage is interesting for GaN when grown on Si substrates to bring down costs.