Effect of Atomic-Layer-Deposition Method on Threshold Voltage Shift in AlGaN/GaN Metal–Insulator–Semiconductor High Electron Mobility Transistors

Abstract

We have investigated the mechanism for threshold voltage (Vth) shift of AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) for power applications. In this study, atomic layer deposited (ALD)-Al2O3 was used in AlGaN/GaN MIS-HEMTs as gate insulator films, and we focused on plasma-induced damages at the GaN/Al2O3 interface, when O2 plasma was used as the oxidant source for the ALD method. We clarified that the deep trap sites which were located around 2.58–3.26 eV from the conduction band edge were generated in the oxidized-GaN layer at the GaN/Al2O3 interface due to plasma-induced damages, and this caused the Vth shift when using O2 plasma. Therefore, we controlled the initial oxidant source, and demonstrated the reductions in the Vth shift and the gate leakage current by applying hybrid–Al2O3 structure (lower H2O vapor–Al2O3/upper O2 plasma–Al2O3) for AlGaN/GaN MIS-HEMTs.