Structure and energetics of carbon defects in SiC (0001)/SiO2 systems at realistic temperatures: Defects in SiC, SiO2, and at their interface

We report systematic first-principles calculations that reveal the atomic configurations, stability, and energy levels of carbon defects in SiC (0001)/SiO2 systems. We clarify the stable position (i.e., in SiC, SiO2, or at SiC/SiO2 interfaces) of defects depending on the oxidation environment (an oxygen-rich or -poor condition). At finite temperatures, the chemical potential of atomic species was corrected referring to thermochemical tables in order to obtain the temperature-dependent defect formation energies. Under an oxygen-rich condition, we found that the dicarbon antisite [(C2)Si] in SiC is one of the favorable defects at a typical oxidation temperature of 1600 K and it creates a localized level near the conduction band edge of SiC, being a critical defect for n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs). A variety of carbon-dimer defects at a SiC/SiO2 interface, such as Si—CO—CO2, Si—CO—CO—Si, and Si—(CO)—CO2, are stable under the oxygen-rich condition at 1600 K, and they create localized levels relatively close to the valence band edge of SiC, thus being critical defects for p-channel MOSFETs. In the viewpoint of static energetics, our results suggest that the oxidation of SiC under a high-temperature oxygen-poor condition is effective in suppressing the generation of carbon defects.