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/[Formula: see text] interface for [Formula: see text] face (1[Formula: see text]00), [Formula: see text] face (11[Formula: see text]0), the C face (000[Formula: see text]), 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 [Formula: see text] 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.

Density functional theory study on the effect of NO annealing for SiC(0001) surface with atomic-scale steps

“…32,33) We have also reported that the insertion of the nitrided layers is an exothermic reaction and the nitrided layers are preferentially formed immediately below the SiO 2 region. 34) We plot in Fig. 5 the LDOS of the interface with steps after NO annealing and show the positions of the topmost interfacial SiC bilayers of the CBE states in the fifth column of Table I.…”