Normally-Off GaN Power Device Based on Stack AlGaN Barrier Structure and P-Type NiO Gate Electrode

Abstract

In this study, we propose a novel normally-off AlGaN/GaN HFET based on stack AlGaN barrier structure and p-type NiO gate. The residual thin AlGaN barrier (with low Al content) is adopted to alleviate mobility degradation. Besides, p-type conductive NiO formed by thermal oxidation at 500 °C was used as gate electrode, which contribute to the positive shift of threshold voltage. Combining NiO gate and thin barrier structure, normally-off device with a threshold voltage of +1.1 V is realized. Temperature dependent transfer characteristics show that the normally-off device presents good thermally stability within the temperature range from 25 to 150 °C.