Experimental investigation on the instability for NiO/β-Ga2O3 heterojunction-gate FETs under negative bias stress

Abstract

A NiO/β-Ga2O3 heterojunction-gate field effect transistor (HJ-FET) is fabricated and its instability mechanisms are experimentally investigated under different gate stress voltage (V G,s) and stress times (t s). Two different degradation mechanisms of the devices under negative bias stress (NBS) are identified. At low V G,s for a short t s, NiO bulk traps trapping/de-trapping electrons are responsible for decrease/recovery of the leakage current, respectively. At higher V G,s or long t s, the device transfer characteristic curves and threshold voltage (V TH) are almost permanently negatively shifted. This is because the interface dipoles are almost permanently ionized and neutralize the ionized charges in the space charge region (SCR) across the heterojunction interface, resulting in a narrowing SCR. This provides an important theoretical guide to study the reliability of NiO/β-Ga2O3 heterojunction devices in power electronic applications.