High-k TiO2-dielectric Al0.25Ga0.75N/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs) grown on Si substrates by using nonvacuum ultrasonic spray pyrolysis deposition technique are reported for the first time. The effective oxide thickness is 1.45 nm with layer thickness/dielectric constant of 20 nm/53.6. Pulse I-V and low-frequency noise spectra (1/f) are conducted to characterize the interface property. The gate leakage current IGD is decreased by three orders at VGD = -50 V as compared with a reference Schottky-gate device. Superior device characteristics are achieved for the present MOS-HEMT (Schottky-gate HEMT) for the gate dimensions of 1 μ m × 100 μ m including drain-source current density IDS at VGS = 0 V (IDSS0) of 384 (342) mA/mm, maximum IDS (IDS, max) of 650 (511) mA/mm, maximum extrinsic transconductance (gm, max) of 107 (110) mS/mm, two-terminal gate-drain breakdown voltage (BVGD) of -155 (-105) V, turn-ON voltage (VON) of 3.8 (1.8) V, on-state breakdown (BVDS) of 139 (94) V, gate-voltage swing of 2.7 (1.7) V, and ON/OFF current ratio (ION/IOFF) of 4.5 × 105 (3.5 × 102).
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