Normally-off HEMTs With Regrown p-GaN Gate and Low-Pressure Chemical Vapor Deposition SiNx Passivation by Using an AlN Pre-Layer

Abstract

Normally-off HEMTs have been fabricated with regrown p-GaN gate and SiNx passivation by Low-pressure chemical vapor deposition (LPCVD) using an AlN pre-layer, featuring a high-temperature passivation-first technique with no incompatibility issues. Through careful surface treatments, high-quality interfaces (regrown p-GaN/AlGaN and SiNx/AlGaN), as well as a stable p-GaN contact, can be achieved, enabling a robust gate operation and improved dynamic performance. The as-fabricated device exhibits a low reverse gate leakage of 2 nA/mm @ VGD = −200 V, a stable forward gate current of $10~\mu \text{A}$ /mm @ VGS = 5 V, a positive threshold voltage of +1.7 V @ ${I}_{\text {DS}} = {10}\,\,\mu \text{A}$ /mm with a high saturation current of 435 mA/mm, a high Ion/Ioff ratio of ${5}\times {10}^{10}$ , and a low Ron,d/Ron,s ratio of 1.5. The as-developed technique with the LPCVD SiNx passivation and p-GaN gate regrowth may provide a way to enhance the performance of p-GaN E-HEMTs.