Enhanced Photon-Generated Hole Spreading in p-GaN Gate Double-Channel HEMT for Suppression of Back-Gating Effect from Si Substrate

This work presents a comprehensive study of the back-gating effect in $p$-GaN gate double-channel high-electronmobility transistor (DC-HEMT) under UV light illumination. Our findings reveal that the upper channel plays an effective role of hole-spreading that facilitates hole transport and mitigates the back-gating effect. When a Schottky-type p-GaN gate HEMT is subject to UV band-to-band illumination, electron-hole pairs are excited in the access region and subsequently separated by the vertical electric field induced by the negative substrate voltage ($V_{\text {Sub }}$). The photon-generated electrons migrate toward the two 2DEG channels thereby reducing the access region resistance. Regarding the photongenerated holes, they tend to move downward to the GaN buffer layer but are partially blocked and stored by the thin AIN barrier between the two GaN channels. The accumulated holes can then spread along the lower portion of the upper channel, effectively screening the effect of the $V_{\text {SUB }}$ and resulting in a minimal impact on the device characteristics. These findings highlight the great potential of the $\boldsymbol{p}$-GaN gate double-channel platform for power integration by harnessing photon-generated carriers to suppress the back-gating effect.