Improved Stability of Fully Recessed Normally-Off GaN MIS-HEMTs With SiN x /AlN Dielectric Stack

This work presents a comparative study of GaN metal-insulator-semiconductor high-electron-mobility-transistors (MIS-HEMTs) employing LPCVD-SiNx/ALD-AlN or PEALD-SiO2/ALD-AlN dielectric stacks. The SiNx/AlN MIS-HEMTs exhibit a minimal threshold voltage shift (ΔVTH) of -0.24 V with an on/off current ratio up to 108under 150∘C, compared to ΔVTH= 2.0 V for SiO2/AlN MIS-HEMTs. Under gate bias stress, SiNx/AlN devices show ΔVTHof -0.90 V (positive) and -0.45 V (negative), versus -1.75 and 3.31 V for SiO2/AlN devices. After maintaining 104s of off-state drain-bias stress, SiNx/AlN MIS-HEMT achieves a small ΔVTHof -0.45 V. The improved stability is attributed to the better interface quality of SiNx/AlN stack, enabled by the low-pressure chemical vapor deposition (LPCVD) process and nitrogen-rich environment. These findings underscore the potential of LPCVD-SiNx/ALD-AlN dielectric stacks in advancing GaN MIS-HEMTs for high-performance and reliable power switching applications.