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 (GaN-HEMTs) 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 (DPT). 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.