Impact of carbon–carbon defects at the SiO2/4H-SiC (0001) interface: a first-principles calculation

Poor quality of the SiO2/4H-SiC (0001) interface is a long-standing issue limiting the performance of silicon carbide (SiC)-MOSFETs. However, the origin of the interface defects is still not fully understood. In this article, five types of carbon–carbon defects introduced to the SiO2/4H-SiC (0001) interface are systematically investigated by first-principle calculations. The thermal oxidation process of 4H-SiC is analyzed through the variation of the chemical potentials based on the chemical reaction equation. The trend of the formation energy with different oxidation conditions show that oxygen-poor condition is effective to suppress the formation of carbon–carbon defects. We obtain the accurate electronic structure with hybrid density functional and the distribution of electron states for the carbon–carbon defects. The interfacial carbon–carbon defects in SiC tend to cause gap states near the conduction band minimum (CBM). Furthermore, the calculated charge transition levels (CTLs) also show that the 0/− CTLs of the carbon–carbon defects are close to the CBM acting as acceptors. All the theoretical calculation results provide insight into understanding the atomic structures and electronic properties for the carbon–carbon defects at the SiO2/4H-SiC (0001) interface, which are fundamental to improve the performance of n-channel SiC-MOSFETs.