Design of normally-off p-GaN/AlGaN/GaN heterojunction field-effect transistors with re-grown AlGaN barrier

In this paper, a novel p-GaN/AlGaN/GaN HFET with re-grown AlGaN is designed by using Silvaco TCAD. It demonstrates that a thin AlGaN barrier with relatively small Al content beneath the p-GaN positively shifts the threshold voltage and helps to obtain normally-off operation, while it also degrades the drain current obviously due to the low 2DEG concentration. On the other hand, the re-grown AlGaN barrier in the access regions can recover the 2DEG concentration and enhance the drain current partially. In addition, the field plate structure formed during the AlGaN re-growth process is beneficial to suppress the electric filed crowding and premature breakdown effectively under forward gate bias. By optimizing the device parameters, normally-off p-GaN/AlGaN/GaN HFET with balanced output current, threshold voltage and breakdown voltage is designed.