Prospects of bipolar power devices in silicon carbide

There has been a rapid improvement in SiC materials and power devices during the last few years. SiC unipolar devices such as Schottky diodes, JFETS and MOSFETs have been developed extensively and advantages of insertion such devices in the power systems have been demonstrated. However, for high power systems such as high voltage converters, bipolar devices are preferable due to their low on-resistance. In this work, a detailed review of the current situation and future trends in SiC power switches, especially BJTs, IGBTs, and GTOs, is given with an emphasis on the device designs and characterization. On the contrary to Silicon BJTs, SiC BJTs exhibit a positive temperature coefficient for the on-state voltage drop, which makes SiC BJTs easily paralleled. In addition, a current gain of 50-70 has been routinely achieved on SiC BJTs which can significantly simplify the gate drive circuits. SiC IGBTs are suitable as the power switches in the range of 10 - 20 kV due to the conductivity modulation and simple gate driver. SiC GTOs have shown superior high current handling capabity even at high temperatures making the preferable device for high power pulse applications. This paper discusses the state-of-the-art achievements on these devices and identifies the key issues in SiC materials and device processing which will influence the future SiC power bipolar device commercialization.