Avalanche Capability Characterization of 1.2 kV SiC Power MOSFETs Compared with 900V Si CoolMOS

The failure mode and operation robustness under extreme condition are critical factors to maximize the potential of SiC MOSFET for high power energy conversion application. In this paper, the avalanche performances of commercial 1.2 kV SiC MOSFET and 900 V Si CoolMOS are characterized and evaluated by signal-pulse unclamped inductive switching (UIS) circuits. The two key parameters related about avalanche capability are calculated to evaluate avalanche capability, including the maximum avalanche current and maximum avalanche energy. Furthermore, the power device models based on physical structure are established by TCAD simulation software. Different mechanisms of avalanche failure are found. The avalanche failure for SiC MOSFET is caused by the parasitic BJT turn-on mechanism, and the avalanche failure for Si CoolMOS is caused by the large avalanche current under gate oxide bottom. The characterization results combined with simulation indicate that the avalanche capability of SiC MOSFET is much better than Si CoolMOS for the larger maximum avalanche current and energy.