Off-state breakdown and leakage current transport analysis of AlGaN/GaN high electron mobility transistors

•Breakdown properties of GaN HEMTs are studied by drain current injection method.•Buffer-leakage induced breakdown is revealed at high drain current injection level.•The buffer-leakage induced breakdown should be defect-related in present devices.

Off-state breakdown characteristics of AlGaN/GaN high-electron-mobility transistors have been studied based on drain current injection method. It is found that at low drain current injection level, the observed premature breakdown is caused by excess gate-to-drain leakage current. Nevertheless, at high drain injection current level, buffer-leakage-dominated breakdown proceeds gate-leakage-dominated breakdown as the gate bias increases from pinch-off voltage to deep-depletion voltage. In both breakdown regions, the breakdown voltages show negative temperature coefficients. The buffer-leakage-induced breakdown should be defect-related, which is confirmed by temperature-dependent buffer leakage measurements.