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.