A Novel Insight Into the Mechanism of Bipolar Degradation in 4H-SiC MOSFET

In converter applications, the body diode SiC MOSFET is often repurposed as freewheeling diode to reduce cost and save space, it potentially leads the device to bipolar degradation. This paper analyzes and compares the bipolar degradation mechanisms of a 1200 V SiC MOSFET under both DC and pulsed current stress conditions. The study reveals that degradation under DC stress occurs at a faster rate than that under pulsed stress, due to the contraction of dislocations in the device during the off-state of pulsed current, the overall degradation becomes slower. At lower DC current densities, the bipolar degradation process exhibits an activation phase before degradation, with longer activation and degradation time observed as current density decreases.