Dynamic Gate Breakdown of p-Gate GaN HEMTs in Inductive Power Switching
Bixuan Wang, Ruizhe Zhang, Hengyu Wang, Quanbo He, Qihao Song, Qiang Li, Florin Udrea, Yuhao Zhang
Abstract
We employ a new circuit method to characterize the gate dynamic breakdown voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {BV}_{\text {dyn}}$ </tex-math></inline-formula> ) of Schottky-type p-gate GaN HEMTs in power converters. Different from prior pulse I-V and DC stress tests, this method features a resonance-like gate ringing with the pulse width down to 20 ns and an inductive switching concurrently in the drain-source loop. At the increased pulse width, the gate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {BV}_{\text {dyn}}$ </tex-math></inline-formula> shows a decrease and then saturation at 21~22 V. Moreover, the gate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {BV}_{\text {dyn}}$ </tex-math></inline-formula> increases with temperature and is higher under the hard switching than that under the drain-source grounding condition. In the 400 V hard switching at 150 °C, the gate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {BV}_{\text {dyn}}$ </tex-math></inline-formula> reaches 27.5 V. Such impact of the drain switching locus and temperature on the gate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {BV}_{\text {dyn}}$ </tex-math></inline-formula> is not seen in Si and SiC power transistors tested in the same setup. These results are explained by a physics model that accounts for the electrostatics in the p-GaN gate stack in hard switching and at high temperatures. This work unveils new physics critical to the gate robustness of p-gate GaN HEMTs and manifest the necessity of the gate robustness evaluation in inductive switching conditions.