Nonmonotonic Instability of V TH and R ds,on in 650 V Schottky-Type p-GaN Gate HEMTs Under Short-Circuit: The Effect of Electric Field and Thermal Dynamics

In this work, the unique non monotonic instability behavior of threshold voltage ( ${V} _{\text {TH}}$ ) and on-resistance ( ${R} _{\text {ds,on}}$ ) in 650 V Schottky-type p-gallium nitride (GaN) gate high electron mobility transistors (HEMTs) and its correlation with the short-circuit (SC) stress intensity are observed and comprehensively studied. The instability of ${V} _{\text {TH}}$ and ${R} _{\text {ds,on}}$ , driven by the combined effects of electron trapping and hole injection, can be distinctly categorized into two regions according to the degradation mechanisms: 1) for the hot-electron trapping-dominated region ( ${V} _{\text {gs}} \le 4$ V & ${V} _{\text {dc}} =100$ V), the positive ${V} _{\text {TH}}$ drift and ${R} _{\text {ds,on}}$ degradation are dominated by the electron trapping in p-GaN gate-stack and drift region at the high electric field spot and2) for the hole injection-dominated region ( ${V} _{\text {gs}} \gt 4$ V and ${V} _{\text {dc}} \ge 100$ V), the higher gate stress voltage triggers prominent hole injection from the p-GaN gate, and it is further intensified by the pronounced self-heating effect induced by SC event, which is overwhelming to result in the ${V} _{\text {TH}}$ into a negative drift. Meanwhile, the elevated junction temperature tends to suppress the hot-electron trapping in the drift region, which mitigates ${R} _{\text {ds,on}}$ degradation. This work reveals profound and thorough understanding of device physics behind the unique instability behavior under short-circuit stress, which is of great interest to further enhance the device stability.