Normally-off Hydrogen-Terminated Diamond Field-Effect Transistor with SnO x Dielectric Layer Formed by Thermal Oxidation of Sn.

SnO x films were deposited on a hydrogen-terminated diamond by thermal oxidation of Sn. The X-ray photoelectron spectroscopy result implies partial oxidation of Sn film on the diamond surface. The leakage current and capacitance-voltage properties of Al/SnO x /H-diamond metal-oxide-semiconductor diodes were investigated. The maximum leakage current density value at -8.0 V is 1.6 × 10 -4 A/cm 2 , and the maximum capacitance value is measured to be 0.207 μF/cm 2 . According to the C-V results, trapped charge density and fixed charge density are determined to be 2.39 × 10 12 and 4.5 × 10 11 cm -2 , respectively. Finally, an enhancement-mode H-diamond field effect transistor was obtained with a V TH of -0.5 V. Its I DMAX is -21.9 mA/mm when V GS is -5, V DS is -10 V. The effective mobility and transconductance are 92.5 cm 2 V -1 s -1 and 5.6 mS/mm, respectively. We suspect that the normally-off characteristic is caused by unoxidized Sn, whose outermost electron could deplete the hole in the channel.