Impact of $V_\mathsf {th}$ Instability of Schottky-Type p-GaN Gate HEMTs on Switching Behaviors

Schottky-type p-GaN gate gallium nitride high electron mobility transistors suffer from threshold voltage ($V_\mathsf {th}$) instability phenomenon. Both positive and negative $V_\mathsf {th}$ shifts are reported when device undertakes the voltage bias, but the impact of this $V_\mathsf {th}$ instability phenomenon on device switching behaviors is less investigated. In this study, the drain-source voltage ($V_\mathsf {ds}$) induced bidirectional $V_\mathsf {th}$ shift in hard-switching condition is characterized and decoupled by an H-bridge based double-pulse test. Subsequently, the influence of $V_\mathsf {th}$ shift on switching behaviors is theoretically analyzed and demonstrated through SPICE simulation and experiment, showing how a positive shifted $V_\mathsf {th}$ can reduce the device turn-on commutation speed and increase the switching losses, and vice versa. The results suggest that the $V_\mathsf {th}$ instability phenomenon should be considered in accurate switching modeling.