A balancing method for low Ron and high Vth normally-off GaN MISFET by preserving a damage-free thin AlGaN barrier layer

Abstract

Partially AlGaN recessed scheme based on selective area growth was experimentally demonstrated to improve the performance of normally-off GaN MISFET. The damage-free thin AlGaN barrier layer with lower Al-content in recessed region contributes to a positive Vth shift compared with the reference one (from 1.8 V to 2.5 V). At the same time this method realizes a high peak μκΣ of 2033 cm2/V·s and a low gate channel sheet resistance of 519 Ω/□ (@Vg = 12 V), which is a significant improvement compared with the fully recessed-gate device. The higher Al-contents AlGaN barrier layer regrown in accessed region is adopted to maintain high-conductivity 2DEG transport property. As a result, a maximum drain current of 645 mA/mm and a low on-resistance of 6.8 Ω-mni are obtained. The GaN MISFET also exhibits a low hysteresis, low gate leakage and slight current collapse. This technique could fabricate very promising normally-off GaN devices by designing thickness and Al-content of the controllable-growth thin AlGaN barrier layer.