Electronic structure and bonding at SiC/AlN and SiC/BP interfaces

The (110) interfaces SiC/AlN and SiC/BP between the cubic (sphalerite) crystals of these semiconductors are studied within the local-density-functional framework using the linear muffin-tin orbital method and the supercell approach. The preferred bonding configurations are found to be Si-N and C-Al for the former and Si-B and C-P for the latter. Both correspond to cation-anion bonding when the anomalous ion character of BP is taken into account. The latter is independently confirmed by our calculations. The interface energies are calculated as the limits of half the superlattice energies of formation and are found to be 0.45 and 0.50 eV for SiC/AlN and SiC/BP, respectively. Combined with a simple bond-breaking model for the surface energies they are used to estimate the adhesion energies, which are shown to be comparable in magnitude to the surface energies of the individual materials. The energy of formation of the 1+1 superlattices, which is effectively a 50% mixed compoud, is calculated and used to make a crude estimate of the energy of formation and the maximum miscibility-gap temperature of the solid solutions. The band structures of the bulk compounds are presented, including an approximate correction of the band gap. The band alignment is found to be of type I for SiC/AlN and of type II for SiC/BP with the higher valence-band maximum in BP. Strain effects in the case of SiC/BP are briefly discussed. The interface electronic structures including interface states and resonances are analyzed in terms of the local densities of states.