P-GaN/p-AlGaN/AlGaN/GaN heterojunction field-effect transistor with a threshold voltage of 6 V

In this study, we proposed a novel p-GaN/p-AlGaN/AlGaN/GaN heterojunction field-effect transistor (HFET). When a selective etching process is used to precisely etch the p-GaN layer of a conventional p-GaN/AlGaN/GaN HFET structure, over-etching-induced surface damage can degrade the device characteristics. By inserting a p-AlGaN layer between p-GaN and AlGaN, the over-etching-induced plasma damage at the surface of the p-AlGaN layer can subsequently be removed using a low-damage atomic layer etching process. As a result, the surface damage issue can be mitigated. An additional benefit of using the p-AlGaN layer is a higher threshold voltage. The fabricated p-GaN/p-AlGaN/AlGaN/GaN HFET exhibited a remarkably high threshold voltage of 6 V with a specific on-resistance of 7.47 m·Ωcm ² .