Density functional theory calculations for investigation of atomic structures of 4H-SiC/SiO2 interface after NO annealing

Abstract

We propose the atomic structures of the 4H-SiC/SiO2 interface for a face (11¯00), m face (112¯0), the C face (0001¯), and Si face (0001) after NO annealing using the OH-terminated SiC surface models. Our proposed structures preferentially form at the topmost layers of the SiC side of the interface, which agrees with the experimental finding of secondary-ion mass spectrometry; that is, the N atoms accumulate at the interface. In addition, the areal N-atom density is of the order of 1015atom/cm2 for each plane, which is also consistent with the experimental result. Moreover, the electronic structure on the interface after NO annealing in which the CO bonds are removed and the nitride layer only at the interface is inserted, is free from gap states, although some interface models before NO annealing include the gap states arising from the CO bonds near the valence band edge of the bandgap. Our results imply that NO annealing can contribute to the reduction in the density of interface defects by forming the nitride layer.