Analysis of Reverse Breakdown Mechanisms and Bias-Dependent Conduction Path Evolution in p-GaN HEMTs

This article presents a comprehensive experimental study of reverse breakdown in p-GaN high-electron-mobility transistors (HEMTs), emphasizing the drain-to-source bias ($\textit{V}_{\text {ds}}$) dependence of conduction paths and electric-field peak migration. The source current exhibits a turning point with negative$\textit{V}_{\text {ds}}$increasing, whereas the gate current rises only when$\textit{V}_{\text {ds}}$exceeds a critical value. This transition is attributed to an electric-field peak shift effect. At low reverse bias, conduction is dominated by the source current. As$\textit{V}_{\text {ds}}$increases, impact ionization emerges with the electric-field distribution located in the AlGaN barrier near the gate–source edge. With$\textit{V}_{\text {ds}}$going beyond −12 V, the gate current increases significantly, accompanied by degradation of AlGaN and p-GaN. At higher reverse bias around −15 V, the electric-field peak shifts into the p-GaN region, where Schottky contact degradation triggers a rapid rise in gate current and$\textit{I}_{\text {g}}$breakdown. These findings provide full-spectrum experimental evidence, corroborated by TCAD simulations, to establish the mechanisms of reverse conduction path evolution in p-GaN HEMTs and offer critical guidance for enhancing device robustness under reverse conduction operation.