Fixed charges investigation in Al₂O₃/hydrogenated-diamond metal-oxide-semiconductor capacitors Available to Purchase

Electrical properties of Al₂O₃/hydrogenated-diamond (H-diamond) metal-oxide-semiconductor (MOS) capacitors are investigated and discussed in this study. Al₂O₃ gate dielectrics are deposited at 120, 200, and 300 °C by an atomic layer deposition technique. For the H-diamond MOS capacitors with Al₂O₃ deposited at 120, 200, and 300 °C, leakage current densities at an electric field of 3.0 MV cm⁻¹ are 8.4 × 10⁻⁴, 7.1 × 10⁻⁶, and 7.5 × 10⁻⁵ A cm⁻², respectively. A small decrease in the maximum capacitance of the Al₂O₃ (120 °C)/H-diamond MOS capacitor is observed when the measurement frequency is increased from 1 kHz to 100 kHz. However, the maximum capacitances of the Al₂O₃ (200 °C)/H-diamond and Al₂O₃ (300 °C)/H-diamond MOS capacitors are stable. Experimental flatband voltage in the capacitance–voltage curve of the Al₂O₃ (120 °C)/H-diamond MOS capacitor shifts to the left with respect to theoretical flatband voltage. However, they shift to the right for the Al₂O₃ (200 °C)/H-diamond and Al₂O₃ (300 °C)/H-diamond MOS capacitors. Therefore, when the deposition temperature of Al₂O₃ is increased from 120 to 300 °C, polarity of the fixed charges in the H-diamond MOS capacitors changes from positive to negative. This phenomenon is explained by the variations of negatively charged acceptors at the Al₂O₃/H-diamond interface and oxygen vacancies in the Al₂O₃ film.