Characterization of Threshold Voltage Shift in SiC MOSFETs Under Nanosecond-Range Switching and Its Impact on High- Frequency Applications

Dynamic threshold voltage shifts (DTVS) in silicon carbide (SiC) MOSFETs are investigated using an ultrafast characterization method that incorporates nanosecond-range switching. A positive gate bias causes a positive DTVS and a negative gate bias causes a negative DTVS, which is observed within a timescale range of 40 ns-1 s. At a gate bias of -10 V, the negative DTVS can reach approximately -4 V, which changes the threshold voltage from positive to negative. A mechanism involving carrier trapping at/near the SiO2 /SiC interface is proposed. Then, the impact of DTVS on dynamic behavior is evaluated by a double-pulse test (DPT) under different off-state gate biases ({V} -{text {GS,OFF}} ). A negative DTVS causes the channel turn-on earlier, increasing the current overshoot ({I} -{text {OS}} ) during the turn-on process. As {V} -{text {GS,OFF}} decreases from 0 to -10 V, the turn-on loss ({E} -{text {ON}} ) increases by 11.2% at a load current of 10 A. Moreover, the {E} -{text {ON}} changes from an increase to a decrease when the turn-on gate resistance ({R} -{text {G,ON}} ) increases from 10 to 50-Omega . Therefore, for a specific gate driving condition, an optimized {R} -{text {G,ON}} can be chosen to compromise the DTVS-induced {E} -{text {ON}} change.