Theoretical analysis of 4H-SiC/SiO 2 interface structures and band alignments: effects of NO annealing

Abstract The orientation dependence of the effects of N atoms incorporation on structural stability, band alignments, and dipole formation at 4H-SiC/SiO 2 interface is theoretically investigated on the basis of first-principles calculations. The calculations demonstrate that the upper limit for thermodynamically stable N atoms incorporation is strongly dependent on crystal orientation, with C-face accommodating the most, followed by m -face, and Si-face the least. Considering this stable incorporation range, the calculated conduction band (valence band) offset is found to increase (decrease) on Si-face and C-face by the incorporation of N atoms, while it conversely decreases (increase) on m -face. Furthermore, it is found that the incorporation of N atoms induces a significant change in the interface dipole. This modification of the dipole shifts the 4H-SiC valence band, which in turn determines the final band alignment. This result suggests that the incorporation of N atoms on Si-face and C-face is of importance in order to obtain a large conduction band offset with an enhanced interface dipole, thereby achieving high resistance to electron leakage current. The calculated results provide atomic-scale insights into the mechanism of NO annealing and enable the orientation-dependent design of reliable SiC metal-oxide-semiconductor field-effect transistors.