Accurate Evaluation of Threshold Voltage Hysteresis in SiC MOSFET Under Switching Stress

In this letter, a novel method is proposed for accurately evaluating the transient recoverable threshold voltage (Vth) shift of silicon carbide (SiC) mosfet caused by hysteresis effect. Based on a resistive load circuit with the multistage gate drive module, the method achieves a fast switching from high-frequency bipolar switching gate bias stress to V-th acquisition. Furthermore, the method is experimentally verified with a 1200-V commercial SiC mosfet. The Vth shift is evaluated after bipolar switching stress, and the time interval between stress and measurement, i.e., the test delay, is reduced to 100 ns. In addition, the V-th shift with different test delays after 500-kHz bipolar stress is evaluated. The results demonstrate that the positive and negative V-th shifts measured after a delay time of 1 mu s can be underestimated by more than 32% and 22%, respectively, when compared to a shorter test delay of 100 ns.