Investigations on Al2O3-Dielectric Wide-Gap Al0.3Ga0.7N Channel MOS-HFETs with Composite Al2O3/In Situ SiN Passivation

Abstract

Al05Ga0.5N/n-Al0.3Ga0.7N/AlN metal-oxide-semiconductor heterostructure field- effect transistors (MOS-HFETs), grown on a SiC substrate, with composite Al2O3/in situ SiN passivation and Al2O3 gate dielectric are investigated. 20 nm thick high-k Al2O3 was deposited by using a non-vacuum ultrasonic spray pyrolysis deposition (USPD) method. Comparative studies between an in situ SiN-passivated Schottky-gate HFET (sample A) and a composite Al2O3/SiN-passivated MOS-HFET were made. Besides, electrical and deep-UV sensing characteristics for devices with different gate-drain separations (L GD ) of 6 μm and 14 μm were also studied. Improved device performances have been obtained for the present sample B (A) with L GD = 6/14 μm separately, including maximum drain-source current density (I DS, max) of 634.4/463.1 (421.8/301.1) mA mm−1, maximum extrinsic transconductance (g m, max) of 25.2/17.9 (19.1/15.2) mS mm−1, on/off-current ratio (I on /I off ) of 7.4 × 107/5.4 × 107 (4.5 × 105/5.4 × 104), two-terminal off-state gate-drain breakdown voltage (BV GD ) of −420/−480 (−320/−390) V, and three-terminal on-state drain-source breakdown voltage (BV DS ) of 310/380 (220/300) V at 300 K. Superior spectral responsivity (SR) of 885.6 A W−1 under 250 nm deep-UV radiation has also been achieved for the present MOS-HFET.