Al₂O₃-Dielectric InAlN/AlN/GaN Γ-Gate MOS-HFETs with Composite Al₂O₃/TiO₂ Passivation Oxides

Novel Al₂O₃-dielectric InAlN/AlN/GaN Γ-Gate metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with composite Al₂O₃/TiO₂ passivation oxides formed by using ultrasonic spray pyrolysis deposition (USPD)/RF sputtering, respectively, are investigated. The Γ-gate includes a 1-μm long active gate on the Al₂O₃ dielectric and a 1-μm long field-plate (FP) on the composite Al₂O₃/TiO₂ oxides. The present Γ-Gate MOS-HFET has demonstrated excellent on/off current ratio (Ion/Ioff) of 8.2 × 10¹⁰, subthreshold swing (SS) of 102.3 mV/dec, maximum extrinsic transconductance of (gm, max) of 210.1 mS/mm, maximum drain-source saturation current density (IDS, max) of 868.3 mA/mm, two-terminal off-state gate-drain breakdown voltage (BVGD) of -311.2 V, three-terminal drain-source breakdown voltage (BVDS) of 237 V at VGS = -10 V, and power-added efficiency (P.A.E.) of 39.9% at 2.4 GHz. A conventional Schottky-gate HFET and TiO₂-dielectric MOS-HFET were also prepared in comparison. The present design has shown superior DC/RF device performance. It is suitable for high-power RF circuit applications.