Insight into the energy level structure and luminescence process of color centers at SiO2/SiC interfaces

We investigated the correlation between electrically active defects and color centers at the SiO2/SiC interface, aiming to clarify the electronic and optical properties of the color centers. SiO2/SiC samples were formed by varying the oxidation temperature and oxygen partial pressure within 1400-1600 degrees C and 0.05%-100%, respectively. The results showed that the integrated photoluminescence intensity of the color centers is strongly correlated with the effective fixed charge density obtained from the flatband voltage shift in the capacitance-voltage characteristics. The effective fixed charges mainly originate from an acceptor level located at energies within (EC - 0.65)-(EC - 0.92) eV, which was estimated from the plateau capacitance of each sample. Therefore, the origin of color centers lies in a deep acceptor-type defect. Based on the results obtained, we discussed the possible luminescence process and the origin of color centers. Referring to previous theoretical calculations, we consider dicarbon antisite [(C2)Si] in near-interface SiC as a main candidate of the color centers found at the SiO2/SiC interface.