A fin-gate p-GaN HEMT with high threshold voltage and improved dynamic performance

Abstract

A novel fin-gate p-GaN (FPG) HEMT is proposed to simultaneously increase threshold voltage (V_th) and improve dynamic performance of the p-GaN HEMT. The fin-gate structure works as a normally-on p-channel MESFET between gate and source by forming a Schottky-type contact on sidewall and a source-connected Ohmic-type contact on top of the fin. Thus, the V_th can change with the shutdown voltage of the p-channel MESFET, which can be modulated by the doping concentration and width of the fin-p-GaN. By optimizing the fin structure, a high positive V_th of 4V is achieved without transconductance and breakdown voltage degradation in this work. It breaks the restriction between V_th and on-resistance for conventional p-GaN HEMT. The dynamic characteristics of the FPG HEMT are investigated by SPICE simulations. Owing to the well-grounded p-GaN through the normally-on MESFET, the recovery process of the dynamic shift in V_th (ΔV_th) after on/off-state stress can be accelerated by two orders of magnitude. It means an imperceptible dynamic degradation and a great potential in high frequency application for the FPG HEMT.