Theoretical study of the mechanism of dry oxidation of4H-SiC

Possible defect structures, arising from the interaction of ${\mathrm{O}}_2$ molecules with an ideal portion of the $\mathrm{SiC}∕\mathrm{Si}{\mathrm{O}}_2$ interface, have been investigated systematically using density functional theory. Based on the calculated total energies and assuming thermal quasiequilibrium during oxidation, the most likely routes leading to complete oxidation have been determined. The defect structures produced along these routes will remain at the interface in significant concentration when stopping the oxidation process. The results obtained for their properties are well supported by experimental findings about the $\mathrm{SiC}∕\mathrm{Si}{\mathrm{O}}_2$ interface. It is found that carbon-carbon bonds can explain most of the observed interface states but not the high density near the conduction band of $4H$-SiC.