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

Widegap-channel Al
_0.65
Ga
_0.35
N/Al
_0.3
Ga
_0.7
N/AlN/SiC metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with ultrasonic spray pyrolysis deposition (USPD) grown Al
₂
O
₃
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 Al
_0.65
Ga
_0.35
N/Al
_0.3
Ga
_0.7
N/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.