Enhancement-Mode Characteristics of Al₀.₆₅Ga₀.₃₅N/Al₀.₃Ga₀.₇N/AlN/SiC MOS-HFETs

Abstract

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 ( $L_{GD}$ ) of $6~\boldsymbol {\mu }\text{m}$ and 14 $\boldsymbol {\mu }\text{m}$ have also been studied. The present E-mode Al0.65Ga0.35N/Al0.3Ga0.7N/AlN MOS-HFET (sample C) with $L_{GD} =6$ (14) $\boldsymbol {\mu }\text{m}$ has demonstrated improved maximum drain-source current density ( $I_{DS,max}$ ) of 206.3 (163.5) mA/mm at $V_{DS} =20$ V, maximum extrinsic transconductance ( $\text{g}_{m,max}$ ) of 32.9 (22.0) mS/mm, on/off-current ratio ( $I_{on}/I_{off}$ ) of 3.7 ${\times }\,\,10^{9}$ ( $1.8\,\,{\times }\,\,10^{9}$ ), two-terminal off-state gate-drain breakdown voltage ( $BV_{GD}$ ) of −370 (−475) V, and three-terminal on-state drain-source breakdown voltage ( $BV_{DS}$ ) of 330 395 V.

Keywords

• Widegap AlGaN channel
• MOS-HFET
• enhancement-mode
• Al₂O₃
• non-vacuum ultrasonic spray pyrolysis deposition