Deep Source Metal Trenches in GaN-On-Si HEMTs for Relieving Current Collapse

The dynamic on-resistance increase during power switching is one of the challenges of GaN-based HEMTs (high-electron-mobility transistors) for power electronic applications. Both the surface traps and buffer traps reduce channel carriers, resulting in decreased operating current during power switching. In this work, we propose a source metal trench toward the buffer region to alleviate channel carriers' trapping in the buffer region. We compare the dynamic behaviors of the HEMTs with the source trench fabricated within and out of the mesa region. The results indicate less dynamic on-resistance increase at higher drain and gate stress voltages of the device with source trench in the mesa, as compared with the device with source trench fabricated away from mesa, or the one without a trench. We further develop physical models, including multiple current-conducting paths, reduction of buffer traps through source trench, and the re-distribution of the electric field profile, to explain the phenomenon.