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 Rc of 0.5 Ω∙mm was obtained and the 2DHG sheet density was as high as 1.0.1013 cm-2 with a corresponding mobility of 104 cm2 /V∙s. The fabricated diamond MOSFET with gate length of 0.5 μm showcased a high current density of 750 mA/mm, a low on-resistance of 24 Ω∙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.