Reliability Analysis for 1200V SiC MOSFETs under Repetitive Surge Current Operation with Negative Gate-source Bias

In new energy vehicle electric drive inverters and DC/DC power conversion systems, the body diode of silicon carbide MOSFETs (SiC MOSFETs) is increasingly utilized as a freewheeling element due to its inherently low reverse recovery charge. While prior research has extensively characterized the single-pulse surge current capability of commercial SiC MOSFET body diodes, critical gaps remain in understanding their long-term reliability under repetitive surge stress. In this study, the failure mechanisms of SiC MOSFETs with different structures are systematically elucidated based on the quantitative coupling of the evolution characteristics of static electrical parameters and the degree of device degradation, combined with the chip morphology damage patterns revealed by microstructure characterization techniques. The experimental results show that device degradation is mainly concentrated in three key regions: the increase of interface state density in the gate-oxide layer, the accumulation of lattice defects in the drift region, and the concentration of thermo-mechanical stresses in the encapsulation layer.