Degradation of 4H-SiC MOSFET body diode under repetitive surge current stress

In this work, repetitive surge current stress is applied on the body diode of SiC MOSFET to examine the degradation of the body diode. The repetitive surge tests are conducted at $25^{\circ}\mathrm{C}$ and $125^{\circ}\mathrm{C}$. Static characteristics and reverse recovery transient of the DUT’s body diode are measured after each 50 surge pulses to monitor the electrical parameter variations. Increase in body diode resistance and decrease in reverse recovery charge are observed after hundreds of stress cycles. Meanwhile, the transfer curve and I-V curve of the DUT are measured. No obvious shift of threshold voltage is observed, indicating no gate oxide degradation occurred. Based on the analysis of the resistance components of body diode and MOSFET, bipolar degradation is demonstrated to be the mechanism leading to the degradation.