Density functional calculations for structures and energetics of atomic steps and their implication for surface morphology on Si-face SiC polar surfaces

Abstract

We perform large-scale density-functional calculations using the real-space finite-difference scheme endorsed by the Gordon Bell prize in 2011 that reveal detailed atomic and electronic structures of atomic steps on silicon carbide (SiC) polar surfaces for the first time. The accurate structural optimization elucidates characteristic atomic reconstruction among the upper and lower edge atoms, which is peculiar to compound semiconductors having both covalent and ionic nature. The calculated formation energies of all the possible atomic steps lead us to unequivocally identify the abundant atomic steps on the Si-face SiC polar surfaces. The energetics thus obtained for the atomic steps provides a natural and persuasive microscopic reason for the difference in the step morphology observed experimentally, i.e., the meandering and straight step edges depending on the inclined direction on the polar vicinal SiC surfaces. Electron states caused by those atomic steps are also calculated, which assists in the identification of the atomic steps by future experiments.