| Summary: | Widegap-channel Al<sub>0.65</sub>Ga<sub>0.35</sub>N/Al<sub>0.3</sub>Ga<sub>0.7</sub>N/AlN/SiC metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with ultrasonic spray pyrolysis deposition (USPD) grown Al<sub>2</sub>O<sub>3</sub> 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<sup>−</sup>) 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 (<inline-formula> <tex-math notation="LaTeX">$L_{GD}$ </tex-math></inline-formula>) of <inline-formula> <tex-math notation="LaTeX">$6~\boldsymbol {\mu }\text{m}$ </tex-math></inline-formula> and 14 <inline-formula> <tex-math notation="LaTeX">$\boldsymbol {\mu }\text{m}$ </tex-math></inline-formula> have also been studied. The present E-mode Al<sub>0.65</sub>Ga<sub>0.35</sub>N/Al<sub>0.3</sub>Ga<sub>0.7</sub>N/AlN MOS-HFET (sample C) with <inline-formula> <tex-math notation="LaTeX">$L_{GD} =6$ </tex-math></inline-formula> (14) <inline-formula> <tex-math notation="LaTeX">$\boldsymbol {\mu }\text{m}$ </tex-math></inline-formula> has demonstrated improved maximum drain-source current density (<inline-formula> <tex-math notation="LaTeX">$I_{DS,max}$ </tex-math></inline-formula>) of 206.3 (163.5) mA/mm at <inline-formula> <tex-math notation="LaTeX">$V_{DS} =20$ </tex-math></inline-formula> V, maximum extrinsic transconductance (<inline-formula> <tex-math notation="LaTeX">$\text{g}_{m,max}$ </tex-math></inline-formula>) of 32.9 (22.0) mS/mm, on/off-current ratio (<inline-formula> <tex-math notation="LaTeX">$I_{on}/I_{off}$ </tex-math></inline-formula>) of 3.7 <inline-formula> <tex-math notation="LaTeX">${\times }\,\,10^{9}$ </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">$1.8\,\,{\times }\,\,10^{9}$ </tex-math></inline-formula>), two-terminal off-state gate-drain breakdown voltage (<inline-formula> <tex-math notation="LaTeX">$BV_{GD}$ </tex-math></inline-formula>) of −370 (−475) V, and three-terminal on-state drain-source breakdown voltage (<inline-formula> <tex-math notation="LaTeX">$BV_{DS}$ </tex-math></inline-formula>) of 330 395 V.
|
|---|