The Impact of Hot Electrons and Self-Heating During Hard-Switching in AlGaN/GaN HEMTs

In this article, we investigate the impact of hard-switching on the dynamic ON-resistance (RON) in the AlGaN/GaN high-electron mobility transistors (HEMTs). The pulsed measurements were taken on a set of GaN-on-Si wafers, showing a significant RON increase after hardswitching compared with soft-switching. The impact of hard-switching was found to be strongly dependent on the surface passivation stoichiometry. Both hot electrons and self-heating are generated during hard-switching and they were investigated separately. For the self-heating effect, we found that the heating energy dissipated during hard-switching followed a different trend to the dynamic RON, showing that self-heating was not responsible for the dynamic RON. Following hard-switching, we found that the recovery of the RON occurred on a time scale of microseconds, far too fast to be explained by buffer trapping. Consequently,we suggest that the hard-switchinginduced hot electrons are trapped on the surface and result in the dynamic RON. To support these conclusions, we undertook 2-D-TCAD simulations. Self-heating was found to be incompatible with the measurements, and surface-trapped hot electrons during hard-switching were shown to be consistent with the experimental observation. Based on the analysis, we find that modifying the field plates and stoichiometries of SiNx can be the possible solutions to suppress dynamic RON after hard-switching.