Electronic-structure study of the (110) inversion domain boundary in SiC

The linear muffin-tin-orbital (LMTO) band-structure method in conjunction with the local-density-functional method is used to study the electronic and total-energy properties of the (110) inversion domain boundary (IDB) in SiC. This type of boundary occurs frequently in compound semiconductors epitaxially grown on a stepped (001) surface of an elemental semiconductor. Fully self-consistent calculations are presented for a ten-layer superlattice model both for the unrelaxed structure and for a simple bond-rotation--bond-length relaxation model. Calculations for larger superlattices (up to 18 layers) are performed using a restricted self-consistency method which is shown to be in good agreement with the full calculation for the small superlattice. These latter calculations allow us to assess the convergence with cell size and prove helpful in the analysis of the energy of formation. As a result of electrostatic repulsion, a high energy of formation is obtained even when structural relaxation is taken into account. Several interface localized bands are obtained and remain present even after bond-length relaxation. They can qualitatively be interpreted in terms of the formation of Si-Si and C-C bonds near the interface. The p-like Si-Si bond related features lie above the SiC valence-band maximum in the semiconducting band gap. With relaxation we even find these states to be pushed up into the conduction band, leading to a semimetallic state and the formation of a two-dimensional electron gas near the IDB. The band-bending effects which can result from local pinning of the Fermi level near the IDB would significantly affect the electrical transport.