Sodium Enhanced Oxidation: Absence of Shallow Interface Traps after Removal of Sodium Ions from the SiO2/4H-SiC Interface

We investigate the strong passivation of shallow interface traps located near the SiC conduction band after enhanced oxidation of Si-face 4H-SiC in the presence of sodium. We find that removing the sodium ions present at the SiO2/SiC interface since oxidation by way of bias stress or annealing does not lead to a significant increase in the density of interface traps. The presence of sodium ions at the SiO2/SiC interface is therefore not responsible for the passivation of such interface traps in oxides formed by sodium enhanced oxidation.