From the viewpoint of application in power electronics, SiC possesses the greatest advantage of having SiO2 as its native oxide. Unfortunately, the usual thermal oxidation produces an unacceptably high density of interface states, with a complex energy distribution. Deep states were assumed to be caused by C excess at the interface, while the slow electron traps, called NIT, with especially high density near the conduction band of 4H-SiC (which would be the best polytype for power devices), were expected to originate from oxide defects near the interface. Unlike the case of the Si/SiO2 interface, simple H passivation does not help to reduce the high trap density. A possible passivation method for both deep states and NIT was post-oxidation annealing or oxidation in the presence of NO or N2O molecules. Here systematic and sophisticated theoretical calculations were presented of a model of the 4H-SiC/SiO2 interface, in order to establish the main reaction routes and the most important defects that were created during dry oxidation, and may give rise to the observed interface traps. The effect of N in suppressing them was also investigated.

The Mechanism of Defect Creation and Passivation at the SiC/SiO2 Interface. P.Deák, J.M.Knaup, T.Hornos, C.Thill, A.Gali, T.Frauenheim: Journal of Physics D, 2007, 40[20], 6242-53