Hybrid p-GaN/MIS Gate HEMT Suppressing Drain-Induced Dynamic Threshold Voltage Instability

This letter demonstrates a hybrid p-GaN/MIS gate HEMT (HG-HEMT) to suppress the drain-induced dynamic threshold voltage ( ${V}_{\text {th}}\text {)}$ instability. By implementing a depletion-mode (D-mode) MIS gate adjacent to Schottky-type p-GaN gate, the drain-induced bidirectional shift of dynamic ${V}_{\text {th}}$ is significantly reduced. The fabricated HG-HEMT exhibits decent performances compared to the conventional Schottky-type p-GaN gate HEMT (Conv-HEMT), with saturation current ( ${I}_{\text {D, {sat}}}\text {)}$ of 345 mA/mm, on-resistance ( ${R}_{\text {ON}}\text {)}$ of $13.2~\Omega \cdot $ mm, and hard breakdown voltage ( BV ) of 1315 V, which are similar to the Conv-HEMT. The HG-HEMT demonstrates significantly improved dynamic ${V}_{\text {th}}$ stability under drain bias, with a negligible dynamic ${V}_{\text {th}}$ shift at on-state drain bias of 50 V, and a small positive dynamic ${V}_{\text {th}}$ shift of +0.05 V after off-state drain bias of 400 V. As a comparison, ${V}_{\text {th}}$ shifts of the Conv-HEMT are −0.28 V and +0.42 V, respectively. The improved dynamic ${V}_{\text {th}}$ stability of the HG-HEMT is owing to a D-mode MIS-gate region that shields the interplay between drain and the p-GaN region. The proposed HG-HEMT paves the way for highly stable GaN power electronics applications.