AlGaN/GaN MISHEMTs on silicon using atomic layer deposited ZrO2 as gate dielectrics

Abstract

Conventional Schottky-metal gate based GaN HEMTs (SB-HEMTs) suffer undesirable high gate leakage current (Igleak) issue. To reduce the Igleak, varieties of gate insulators like Si3N4, SiO2, Al2O3, Ga2O3, HfO2, Sc2O3 etc. have been demonstrated to obtain high quality metal-insulator-semiconductor (MIS) structure. ZrO2, with a high dielectric constant (18-25 [1]) and large bandgap (5.2-7.8 eV [2]), is a good candidate for gate insulation layer. Compared with ZrO2 prepared by other techniques, atomic layer deposited (ALD) technique has the benefits of nanometer scalability, high uniformity, good coverage, low defect density, etc. S. Abermann et al. [3] and A. Alexewicz et al. [4] have reported InAlN/GaN MISHEMTs using ALD ZrO2. However to-date, comprehensive study was not carried out in AlGaN/GaN MISHEMTs on Si with ALD ZrO2 as insulator layer. In this paper, we demonstrated AlGaN/GaN MISHEMTs with ALD ZrO2 as the gate dielectric layer on Si substrate. The use of ALD ZrO2 dielectrics can effectively suppress the reverse gate leakage current and improve gate voltage up to +5 V.