Normally-off Hydrogen-Terminated Diamond Field-Effect Transistor with SnO_x Dielectric Layer Formed by Thermal...

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/cm², and the maximum capacitance value is measured to be 0.207 μF/cm². According to the C-V results, trapped charge density and fixed charge density are determined to be 2.39 × 10¹² and 4.5 × 10¹¹ 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 cm²V^-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.