Impact of Vₜₕ 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 ( <tex-math notation="LaTeX">Vₜₕ</tex-math> ) instability phenomenon. Both positive and negative <tex-math notation="LaTeX">Vₜₕ</tex-math> shifts are reported when device undertakes the voltage bias, but the impact of this <tex-math notation="LaTeX">Vₜₕ</tex-math> instability phenomenon on device switching behaviors is less investigated. In this study, the drain-source voltage ( <tex-math notation="LaTeX">Vds</tex-math> ) induced bidirectional <tex-math notation="LaTeX">Vₜₕ</tex-math> shift in hard-switching condition is characterized and decoupled by an H-bridge based double-pulse test (DPT). Subsequently, the influence of <tex-math notation="LaTeX">Vₜₕ</tex-math> shift on switching behaviors is theoretically analyzed and demonstrated through SPICE simulation and experiment, showing how a positive shifted <tex-math notation="LaTeX">Vₜₕ</tex-math> can reduce the device turn-on commutation speed and increase the switching losses, and vice versa. The results suggest that the <tex-math notation="LaTeX">Vₜₕ</tex-math> instability phenomenon should be considered in accurate switching modeling.