Al0.75Ga0.25N/AlxGa1-xN/Al0.75Ga0.25N/AlN/SiC Metal–Oxide–Semiconductor Heterostructure Field-Effect Transistors With Symmetrically-Graded Widegap Channel

Abstract

Novel Al 0.75 Ga 0.25 N/Al x Ga 1-x N/Al 0.75 Ga 0.25 N/AlN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with symmetrically-graded widegap Al x Ga 1-x N channel (x = 0.75 → 0.25 → 0.75) grown on a SiC substrate are investigated. Al 2 O 3 was devised as the gate dielectric by using a non-vacuum ultrasonic spray pyrolysis deposition (USPD) technique. Device characteristics with respect to different etch depths of the source/drain recesses were studied. For a 2-μm gate length (L G ), the present widegap V-shape-channel MOS-HFET has shown improved maximum drain-source current density (I DS,max ) of 299.3 A/mm at V DS = 20 V, I DS density at V GS = 0 V (I DSS0 ) of 153.9 mA/mm, on/off-current ratio (I on /I off ) of 1.4 × 10 7 , extrinsic transconductance (g m , max ) of 16.7 mS/mm, two-terminal off-state gate-drain breakdown voltage (BV GD ) of -379 V, and three-terminal on-state drain-source breakdown voltage (BV DS ) of 339 V. Besides, superior deep-UV sensing performance with high spectral responsivity (SR) of 1780 (810.2) A/W at wavelength λ = 250 (300) nm are also achieved.