2.1 W/mm Output Power Density at 10 GHz for H-Terminated Diamond MOSFETs With (111)-Oriented Surface

This paper presents high performance hydrogen-terminated diamond MOSFETs fabricated on a (111)-oriented single-crystal diamond substrate. The diamond surface was passivated by a high-quality Al2O3 grown by ALD at 350°C as well as a secondary passivation layer Si3N4 deposited by PECVD. After passivation, a low ohmic contact resistance
$R_{c}$
of
$0.5 \Omega \cdot $
mm was obtained and the 2DHG sheet density was as high as
$1.0\times 10\,\,^{\mathrm{ 13}}\,\,{\mathrm{ cm}}^{-2}$
with a corresponding mobility of
$104 {\mathrm{ cm}}^{2} /\text{V}\cdot \text{s}$
. The fabricated diamond MOSFET with gate length of
$0.5 ~\mu \text{m}$
showcased a high current density of 750 mA/mm, a low on-resistance of
$24 \Omega \cdot $
mm, and a high off-state breakdown voltage of 117 V. Thanks to the high current density and low on-resistance, a record high output power density of 2.1 W/mm was achieved at 10 GHz with drain biased at a low voltage of −30 V. These results demonstrate that the output current and output power can be improved by using a (111)-oriented diamond, which is benefit for high-frequency and high-power RF devices.