Investigation of the Progressive Gate Breakdown Behaviors in p-GaN Gate HEMTs

In this work, multiple time-dependent gate breakdown (BD) experiments are performed on p-GaN gate high-electron-mobility transistors (HEMTs) under constant gate voltage stress. Progressive gate BD behaviors are observed during the time-dependent failure process. It is found that the time-to-BD (<inline-formula> <tex-math notation="LaTeX">${t}_{\text {BD}}$ </tex-math></inline-formula>) has a positive dependence on temperature but a weak relevance to p-GaN gate length. Moreover, it is confirmed that the Schottky junction first (1st) degenerates after the 1st stage jump of <inline-formula> <tex-math notation="LaTeX">${I}_{G}$ </tex-math></inline-formula> and the p-i-n junction fails in the subsequent process. The underlying failure mechanisms are revealed by further analyzing the degradation behaviors and the carrier transport mechanisms before/after the Schottky junction degrades. Hole Fowler–Nordheim (FN) tunneling at the metal gate/p-GaN interface guides the first degradation of the Schottky junction. Afterward, the trap-assisted electron tunneling across the AlGaN layer indicates the failure of the p-i-n junction. These two processes sequentially facilitate defect generation within the p-GaN and the AlGaN layer, resulting in a percolation path between the gate and the source terminal.