Al_0.75Ga_0.25N/Al_xGa_1-xN/Al_0.75Ga_0.25N/AlN/SiC Metal–Oxide–Semiconductor Heterostructure Field-Effect Transistors With Symmetrically-Graded Widegap Channel

Abstract

Novel Al0.75Ga0.25N/AlxGa1-xN/Al0.75Ga0.25N/AlN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with symmetrically-graded widegap AlxGa1-xN channel (x = 0.75 → 0.25 → 0.75) grown on a SiC substrate are investigated. Al2O3 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 (LG), the present widegap V-shape-channel MOS-HFET has shown improved maximum drain-source current density (IDS,max) of 299.3 A/mm at VDS = 20 V, IDS density at VGS = 0 V (IDSS0) of 153.9 mA/mm, on/off-current ratio (Ion/Ioff) of 1.4 × 107, extrinsic transconductance (gm,max) of 16.7 mS/mm, two-terminal off-state gate-drain breakdown voltage (BVGD) of -379 V, and three-terminal on-state drain-source breakdown voltage (BVDS) 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.

Keywords

• AlₓGa₁−ₓN
• MOS-HFET
• symmetrically-graded
• widegap channel
• Al₂O₃
• non-vacuum ultrasonic spray pyrolysis deposition