Ultraviolet (UV) detection and electrical characteristics of In 0.17 Al 0.83 N/AlN/GaN metaloxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with Al 2 O 3 gate-dielectric and passivation formed by using ultrasonic spray pyrolysis deposition (USPD) are studied with respect to a conventional Schottky-gate HFET. The present MOS-HFET (Schottky-gate HFET) has demonstrated superior spectral responsivity (SR) of 360 (340) A/W at 350 nm at V GS = 5(3) V and V DS = 6(7) V, maximum drain-source saturation current density (I DS,max ) of 810.5 (546.6) mA/mm, maximum extrinsic transconductance of (g m,max ) of 180.4 (221.2) mS/mm, gate-voltage swing (GVS) of 2.4 (0.5) V, on/off current ratio (I on /I off ) of 5.5 × 10 8 (1.7 × 10 5 ), two-terminal off-state gate-drain breakdown voltage (BV GD ) of −158.5 (−127) V, three-terminal drain-source breakdown voltage (BV DS ) of 162 (83.4) V at V GS = −10 V, and power-added efficiency (P.A.E.) of 26.3% (16.5%) at 2.4 GHz at 300 K. In addition to the improved device performance, this paper demonstrates, for the first time, the UV sensing based on an InAlN/AlN/GaN MOS-HFET design.

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