Ab initio theoretical study of an oxygen vacancy defect at the 4 H -SiC ( 0001 ) / SiO 2 interface

In order to study the electronic structures of the $\text{SiC}/{\text{SiO}}_{2}$ interface, which is made by the oxidation of SiC, we constructed the structural models for the dangling-bond free interfaces of $4H\text{-SiC}/{\text{SiO}}_{2}$ with the substrate orientations of (0001) and $(11\overline{2}0)$. We carried out ab initio calculations to find that a stretched oxygen atom appears in the near-interface region of the ${\text{SiO}}_{2}$ insulator for the $4H\text{-SiC}(0001)/{\text{SiO}}_{2}$ interface but not for the $4H\text{-SiC}(11\overline{2}0)/{\text{SiO}}_{2}$ interface. We argue the origin of the experimentally found oxygen vacancy defect near the $\text{SiC}(0001)/{\text{SiO}}_{2}$ interface.