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-GS,V-OFF). A negative DTVS causes the channel turn-on earlier, increasing the current overshoot (I-OS) during the turn-on process. As V-GS,V-OFF decreases from 0 to - 10 V, the turn-on loss (E-ON) increases by 11.2% at a load current of 10 A. Moreover, the E-ON changes from an increase to a decrease when the turn-on gate resistance (R-G,R-ON) increases from 10 to 50 Omega. Therefore, for a specific gate driving condition, an optimized R-G,R-ON can be chosen to compromise the DTVS-induced E-ON change.