Influence of Hole Injection on Associated Recovery Phenomena in GaN-Based GITs Subjected to Hot Electron Trapping

Abstract

Hot carrier degradation (HCD) is one of the major reliability concerns in power devices, leading to an increase in on-resistance degradation over time. To investigate the physical origin of HCD and the recovery behavior related to it, GaN gate injection transistor (GIT) structures are investigate more closely in this work. Therefore, the devices under test are periodically stressed in measurement-stress-measurement (MSM) sequences and evaluated after each stress cycle. In selected devices, the MSM cycles are extended by a static resetting pulse (SRP) where holes are injected into the gate-drain access region by applying a positive gate bias to the gate p-n junction. These holes were previously believed to neutralize negative charges trapped in defects in the SiN passivation layer of the device, recovering RDSon. We show that only a fraction of the degradation is actually recovered and propose an alternative explanation for recovery: instead of neutralization of electrons by detrapping, free holes in the access region could also temporarily shield the 2D electron gas (2DEG) from the negatively charged defects. These holes would disappear again as the stress is reapplied, which is the main reason for the extensive recovery that is observed for the semi-on stress scenario.