Low Energy Proton Irradiation Effects on Commercial Enhancement Mode GaN HEMTs

Commercial enhancement mode GaN HEMTs are irradiated with low energy protons under different bias conditions. Negative threshold voltage (V
_th
) shifts are observed. In contrast, V
_th
shifts are positive under high voltage stress without proton irradiation. C-V measurements with floating terminals are performed before and after irradiation. Both I-V and C-V results show that a significant density of charged donor-like traps is introduced into these devices by low energy proton irradiation. These defects trap electrons, scatter charge carriers, and/or, in these enhancement mode devices, partially compensate the p-type doping in the p-GaN layer, thereby leading to the observed negative V
_th
shifts and G
_m
degradation. The floating terminal C-V measurements that are introduced in this study appear to be quite sensitive to traps in the AlGaN buffer layer, making this a potentially useful technique for future device characterization.