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 ona (111)-oriented single-crystal diamond substrate. The diamond surface was passivated by a high-quality Al(2)O(3 )grown by ALD at 350 degrees C as well as a secondary passivation layer Si(3)N(4 )deposited by PECVD.After passivation, a low ohmic contact resistance R(c)of 0.5 Omegamm was obtained and the 2DHG sheetdensity was as high as 1.0x1013cm-2with a corresponding mobility of 104 cm(2)/Vs. The fabricated diamond MOSFET with gate length of 0.5 mu m showcased a high current density of 750 mA/mm, a lowon-resistance of 24 Omegamm, and a high off-state breakdown voltage of 117 V. Thanks to the high currentdensity and low on-resistance, a record high output power density of 2.1 W/mm was achieved at 10 GHzwith drain biased at a low voltage of-30 V. These results demonstrate that the output current andoutput power can be improved by using a (111)-oriented diamond, which is benefit for high-frequencyand high-power RF devices.