Theoretical and Experimental Analyses of Safe Operating Area (SOA) of 1200-V 4H-SiC BJT

The safe operating area (SOA) of 1200-V SiC bipolar junction transistor (BJT) is investigated by experiments and simulations. The SiC BJT is free of the second breakdown even under the turn-off power density of 3.7 MW/cm². The theoretical boundary of reverse-biased SOA caused by the false turn-on is obtained by simulations. The short-circuit capability of the 1200-V SiC BJT is also investigated theoretically and experimentally. Self-heating is considered by the nonisothermal simulation, and 1800-K maximum local temperature is the simulated critical temperature of device failure. The surface condition is very critical for short-circuit capability. From simulations, when the interface trap density increases, the critical temperature decreases. This is believed to be the reason why the experimental results show much shorter short-circuit withstand time than the simulation showed.