Enhancement-Mode Characteristics of Al.Ga.N/Al.Ga.N/AlN/SiC MOS-HFETs

Widegap-channel Al0.65Ga0.35N/Al0.3Ga0.7N/AlN/SiC metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with ultrasonic spray pyrolysis deposition (USPD) grown Al2O3 gate-oxide demonstrating enhancement-mode (E-mode) operation are investigated for the first time. The E-mode operation was achieved by using fluorine ions (F-) implantation. In comparison, conventional Schottky-gate device (sample A) and MOS-HFET (sample B) showing depletion-mode (D-mode) operation were fabricated on the same epitaxial structure. The device characteristics with respect to different gate-to-drain spacings (LGD) of 6μ m and 14 μm have also been studied. The present E-mode Al0.65Ga0.35N/Al0.3Ga0.7N/AlN MOS-HFET (sample C) with LGD =6 (14)μ m has demonstrated improved maximum drain-source current density (IDS,max) of 206.3 (163.5) mA/mm at VDS =20 V, maximum extrinsic transconductance (g m,max) of 32.9 (22.0) mS/mm, on/off-current ratio (I on/Ioff) of 3.7 ×,109 (1.8\,×,\,109), two-terminal off-state gate-drain breakdown voltage (BVGD) of-370 (-475) V, and three-terminal on-state drain-source breakdown voltage (BVDS) of 330 395 V.