Investigation of the bipolar degradation of SiC MOSFET body diodes and the influence of current density

Bipolar degradation continues to be a key issue that should be taken into account in 4H-SiC devices using bipolar operation modes. The generation and expansion of recombination-induced stacking faults (SFs) in 4H-SiC devices results in a forward-voltage drift, which has been widely discussed in the literature. In this work, 1.2 kV SiC MOSFET body diodes were stressed at different current densities to investigate the influence of crystal-induced voltage drifts like bipolar degradation caused by stacking faults (SFs), expansion from pre-existing basal plane dislocations (BPDs) or conversion points. Additionally, thermomechanical failures (gate-oxide damage, front-side metallization degradation, bond-wire heel crack and lift-off) inevitably occurred due to high surge-current stress. The measurement results illustrate the spectrum of degradation by applying different current densities to the body diode of SiC MOSFETs.