Reaction of NO molecule at 4H-SiC/SiO2 interface: an ab initio study for the effect of NO annealing after dry oxidation

The reaction of the NO molecule at the 4H-SiC/SiO2 interface after dry oxidation is theoretically investigated on the basis of ab initio calculations. On the Si-face, the reaction of the NO molecule results in the dissociation of the C-C single bond and the formation of Si4-N bonds with the CO2 molecule. In contrast, the C=C double bond changes into the C-C bond with the formation of Si3-N bonds and CO2 desorption on the C-face. This C-C bond on the C-face can be removed by the incorporation of an additional NO molecule. For the resultant interface structures, no localized electronic states are generated around the energy gap of 4H-SiC, suggesting that the NO annealing process is crucial to reduce the carbon-related defects at the 4H-SiC/SiO2 interface. Furthermore, the reaction on the NO molecule at the interface with CO desorption after dry oxidation is discussed in order to clarify the behavior of the NO molecule during the annealing process at 4H-SiC/SiO2 interfaces.