Deep Interface States in SiO 2/p-type α-SiC Structure

Thermally grown SiO2/p-SiC interfaces were characterized by a high-frequency C-V measurement using a light illumination technique. A large negative flatband shift at room temperature in a p-type SiC MOS capacitor is caused by fixed charges in SiO2 near the interface and holes captured at deep interface states. The contribution of both components to the voltage shift could be separated by utilizing illumination. By illumination under the deep depletion condition, deep states emit holes and become neutral. Therefore, only fixed charges affect the voltage shift after the emission of holes from the deep states. From this method, the total deep state density was estimated to be 4∼6 ×1012 cm-2 and the effective fixed charge density, 1 ∼2 ×1011 cm-2, indicating that the flatband shift is mainly caused by holes trapped at deep interface states.