Normally-Off p-GaN Gated AlGaN/GaN MIS-HEMTs with ALD-Grown Al₂O₃/AlN Composite Gate Insulator

A metal-insulator-semiconductor p-type GaN gate high-electron-mobility transistor (MIS-HEMT) with an Al₂O₃/AlN gate insulator layer deposited through atomic layer deposition was investigated. A favorable interface was observed between the selected insulator, atomic layer deposition-grown AlN, and GaN. A conventional p-type enhancement-mode GaN device without an Al₂O₃/AlN layer, known as a Schottky gate (SG) p-GaN HEMT, was also fabricated for comparison. Because of the presence of the Al₂O₃/AlN layer, the gate leakage and threshold voltage of the MIS-HEMT improved more than those of the SG-HEMT did. Additionally, a high turn-on voltage was obtained. The MIS-HEMT was shown to be reliable with a long lifetime. Hence, growing a high-quality Al₂O₃/AlN layer in an HEMT can help realize a high-performance enhancement-mode transistor with high stability, a large gate swing region, and high reliability.