First-principles study for orientation dependence of band alignments at 4H-SiC/SiO2 interface

The orientation dependence of band alignments and the formation of dipoles at 4H-SiC/SiO2 interface are theoretically investigated on the basis of first-principles calculations. The calculations demonstrate that the offsets of valence and conduction bands depend on the surface orientation and chemical bonds at 4H-SiC/SiO2 interface. The conduction band offset on the Si-face is larger than those on the C-face and m-face. Furthermore, it is found the atomic configurations at 4H-SiC/SiO2 interface results in the formation of dipoles, whose magnitude is large for Si-O and C-O bonds. The formation of large dipoles significantly changes the band structure of 4H-SiC, resulting in large conduction bands offset. Therefore, the formation of Si-O bond with large dipoles at the interface is of importance in order to obtain large conduction band offset. The calculated results give insights to improve the reliability in SiC metal-oxide-semiconductor field-effect transistors.