Method to Study Dynamic Depletion Behaviors in High-Voltage ($BV=1.4\ \text{kV}$) p-GaN Gate HEMT on Sapphire Substrate
Jiawei Cui, Yanlin Wu, Junjie Yang, Jingjing Yu, Teng Li, Xuelin Yang, Bo Shen, Maojun Wang, Jin Wei
Abstract
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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L_{\text{GD}}$</tex> . For <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L_{\text{GD}}=27 \mu\mathrm{m}$</tex> , the device exhibits a high breakdown voltage of 1412 V. The threshold voltage is 0.9 V. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$R_{\text{on}}$</tex> is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$17.7\ \ \Omega\cdot \text{mm}$</tex> , and the specific on-resistance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$R_{\text{sp}}$</tex> is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$6.73\ \mathrm{m}\Omega\cdot \text{cm}^{2}$</tex> . 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- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V$</tex> characteristics of the structures, with the pinch-off voltage of the I- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V$</tex> 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.