High Dynamic Stability in Enhancement-Mode Active-Passivation p-GaN Gate HEMT

The dynamic stability of E-mode active-passivation p-GaN gate HEMT (AP- HEMT) is investigated, including dynamic $V_{\text{th}}$ shift, dynamic $R_{\text{ON}}$ degradation, and dynamic leakage current. The AP-HEMT features an ohmic-type gate/p-GaN contact that results in a stable dynamic $V_{\text{th}}$, as the charge storage effect associated with the floating p-GaN layer is avoided. At a 650- V $V_{\text{DS}}$ stress, the AP- HEMT exhibits a low dynamic $R_{\text{ON}}$/static $R_{\text{ON}}$ ratio of 1.4, which can be attributed to the presence of the p-GaN active-passivation layer that screens the influence of surface traps. The hole injection in the p-GaN gate HEMT is expected to increase the dynamic OFF-state leakage current, as the holes reduce the energy barrier of the buffer layer. Despite a larger injector area, the AP-HEMT exhibits a lower dynamic leakage current increase, which is due to the relocation of the electric field peak from the gate edge towards the drain. This relocation suppresses the lowering of the energy barrier under the gate. Overall, the unique device structure of the AP-HEMT leads to a negligible dynamic $V_{\text{th}}$ shift, a low dynamic $R_{\text{ON}}$, and a small OFF-state dynamic leakage increase.