High-Voltage and Low-Leakage-Current Gate Recessed Normally-Off GaN MIS-HEMTs With Dual Gate Insulator Employing PEALD-SiNx/RF-Sputtered-HfO2

To fabricate gate recessed normally-off AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors, we have employed a novel SiNx/HfO2 dual gate insulator. A plasma enhanced atomic layer deposition (PEALD) technique was used for very thin high quality SiNx (5 nm) as an interfacial layer followed by RF-sputtered HfO2 as a high-k dielectric for the second gate insulator structure. The PEALD SiNx interfacial layer effectively suppresses the forward gate leakage current and the current collapse. We have achieved excellent characteristics such as large threshold voltage of 1.65 V, high breakdown voltage of 900 V, extremely small off-state drain leakage current less than 10(-9) A/mm and high ON/OFF drain current ratio of similar to 10(9), low on-state resistance of 1.84 m Omega.cm(2), and small subthreshold slope of 85 mV/decade.