Effect of Threshold Voltage Hysteresis on Switching Characteristics of Silicon Carbide MOSFETs

Threshold voltage ( ${V}_{\text {TH}}$ ) hysteresis affects the reliability of silicon carbide (SiC) MOSFETs. To evaluate the ${V}_{\text {TH}}$ hysteresis effect on switching characteristics, this article first investigates the ${V}_{\text {TH}}$ hysteresis in the static characteristics of three SiC MOSFETs with different gate structures. The results illustrate the density of the interface states in different gate structures. Then, the effect of ${V}_{\text {TH}}$ hysteresis on dynamic characteristics under varying OFF-state starting voltages ( ${V}_{\text {G}}^{ \mathrm{\scriptscriptstyle OFF}}$ ) is evaluated by experiment. Furthermore, the effect mechanism of ${V}_{\text {TH}}$ hysteresis and ${V}_{\text {G}}^{ \mathrm{\scriptscriptstyle OFF}}$ on switching characteristics is analyzed. Under the effect of the ${V}_{\text {TH}}$ hysteresis, a smaller ${V}_{\text {G}}^{ \mathrm{\scriptscriptstyle OFF}}$ reduces ${V}_{\text {TH}}$ when the device turns on. This phenomenon leads to a reduction in the turn-on delay and consequently lowers the turn-on loss. Therefore, the ${V}_{\text {TH}}$ hysteresis is a significant factor for gate driver design of SiC MOSFETs.