Method to Study Dynamic Depletion Behaviors in High-Voltage ($BV=1.4\ \text{kV}$) p-GaN Gate HEMT on Sapphire Substrate

This study presents an investigation of high-voltage enhancement-mode p-GaN gate HEMTs on a sapphire substrate. The breakdown voltage of the devices shows a linear relationship with the $L_{\text{GD}}$. For $L_{\text{GD}}=27 \mu\mathrm{m}$, the device exhibits a high breakdown voltage of 1412 V. The threshold voltage is 0.9 V. The $R_{\text{on}}$ is $17.7\ \ \Omega\cdot \text{mm}$, and the specific on-resistance $R_{\text{sp}}$ is $6.73\ \mathrm{m}\Omega\cdot \text{cm}^{2}$. To measure the depletion region directly for high-voltage devices, depletion-testing structures were fabricated alongside the HEMTs. The depletion lengths were determined based on the I-$V$ characteristics of the structures, with the pinch-off voltage of the I-$V$ characteristics correlated to the depletion length. Additionally, using pulse waveforms as the gate control signals, the formation of the depletion region under dynamic conditions was revealed.