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

Novel Al
₂
O
₃
-dielectric InAlN/AlN/GaN Γ-Gate metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with composite Al
₂
O
₃
/TiO
₂
passivation oxides formed by using ultrasonic spray pyrolysis deposition/RF sputtering, respectively, are investigated. The r-gate includes a 1-μm long active gate on the Al
₂
O
₃
dielectric and a 1-μm long field-plate on the composite Al
₂
O
₃
/TiO
₂
oxides. The present Γ-Gate MOS-HFET has demonstrated excellent on/off current ratio (I
_on
/I
_off
) of 8.2 x 1010, subthreshold swing of 102.3 mV/dec, maximum extrinsic transconductance of (g
_m,max
) of 210.1 mS/mm, maximum drain-source saturation current density (I
_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
_GS
= -10 V, and power-added efficiency of 39.9% at 2.4 GHz. A conventional Schottky-gate HFET and TiO
₂
-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.