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 (Vth) instability. By implementing a depletion-mode (D-mode) MIS gate adjacent to Schottky-type p-GaN gate, the drain-induced bidirectional shift of dynamic Vth 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 (ID,sat) of 345 mA/mm, on-resistance (RON) of 13.2Ω·mm, and hard breakdown voltage (BV) of 1315 V, which are similar to the Conv-HEMT. The HG-HEMT demonstrates significantly improved dynamic Vth stability under drain bias, with a negligible dynamic Vth shift at on-state drain bias of 50 V, and a small positive dynamic Vth shift of +0.05 V after off-state drain bias of 400 V. As a comparison, Vth shifts of the Conv-HEMT are -0.28 V and +0.42 V, respectively. The improved dynamic Vth 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. © 1980-2012 IEEE.