Signatures of Positive Gate Over-Drive Induced Hole Trap Generation and its Impact on p-GaN Gate Stack Instability in AlGaN/GaN HEMTs

In this work, we probe the physical mechanism responsible for Vth and gate current instability in p-GaN Schottky gated AlGaN/GaN HEMTs. Devices exhibited a negative Vth shift accompanied by a distinct increase in gate current, followed by gate failure, when driven at positive gate over-drives. Temperature and frequency dependent CV analysis is carried out along with capacitive-DLTS measurements to probe and validate the physical mechanism responsible for the observed gate instabilities. Generation of hole traps with an energy level of 0.43eV, in response to gate bias stress is found to trigger gate instability, subsequently leading to device failure.