Al2O3-Dielectric InAlN/AlN/GaN ${\Gamma}$ -Gate MOS-HFETs With Composite Al2O3/TiO2 Passivation Oxides

Abstract

Novel Al2O3-dielectric InAlN/AlN/GaN ${\Gamma }$ -Gate metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with composite Al2O3/TiO2 passivation oxides formed by using ultrasonic spray pyrolysis deposition/RF sputtering, respectively, are investigated. The ${\Gamma }$ -gate includes a 1- ${\mu }\text{m}$ long active gate on the Al2O3 dielectric and a 1- ${\mu }\text{m}$ long field-plate on the composite Al2O3/TiO2 oxides. The present ${\Gamma }$ -Gate MOS-HFET has demonstrated excellent on/off current ratio ( $I_{\mathrm{ on}}/I_{\mathrm{ off}}$ ) of $8.2 \times 10^{10}$ , subthreshold swing of 102.3 mV/dec, maximum extrinsic transconductance of ( $g_{m,{\mathrm{ max}}}$ ) of 210.1 mS/mm, maximum drain-source saturation current density ( $I_{\mathrm{ DS,max}}$ ) 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 $V_{\mathrm{ GS}}= -10$ V, and power-added efficiency 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.