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.

Automated summary

In this article, five types of carbon-carbon defects introduced to the SiO2/4H-SiC (0001) interface are systematically investigated through first-principle calculations. The thermal oxidation process of 4H-SiC is analyzed, and it is found that oxygen-poor condition effectively suppresses the formation of carbon-carbon defects. The electronic structure and distribution of electron states for the carbon-carbon defects are obtained, revealing that they cause gap states near the conduction band minimum and act as acceptors.