Effects of wet-ROA on shallow interface traps of n-type 4H-SiC MOS capacitors

The effects of wet re-oxidation annealing (wet-ROA) on the shallow interface traps of n-type 4H-SiC metal-oxide-semiconductor (MOS) capacitors were investigated by Gray-Brown method and angle-dependent X-ray photoelectron spectroscopy technique. The results present the energy distribution of the density of interface traps (D_it) from 0 to 0.2 eV below SiC conduction band edge (E_C) of the sample with wet-ROA for the first time, and indicate that wet-ROA could reduce the D_it in this energy range by more than 60%. The reduction in D_it is attributed to the reaction between the introduced oxygen and the SiO_xC_y species, which results in C release and SiO_xC_y transformation into higher oxidation states, thus reducing the SiO_xC_y content and the SiO_xC_y interface transition region thickness.