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.