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

Conventional Schottky-metal gate based GaN HEMTs (SB-HEMTs) suffer undesirable high gate leakage current (I_gleak) issue. To reduce the I_gleak, 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.