Tight-binding description for the bound electronic states of isolated single and paired native defects in beta -SiC.

Abstract

A theoretical analysis is presented for existing photoluminescence (PL) and deep-level-transient-spectroscopy (DLTS) data, characterizing the optically active impurities and lattice defects in \ensuremath{\beta}-SiC films gown by the chemical-vapor-deposition technique. Results are reported for the band structure of \ensuremath{\beta}-SiC based on a tight-binding theory and calculations are presented in the Green's-function framework for the electronic energy states of ${\mathit{sp}}^{3}$-bonded native, substitutional (isolated), and pair defects occupying either Si and/or C sites. Local distortions around impurity atoms are estimated in terms of a simple, but first-principles, bond-orbital model. To account for the off-diagonal elements in the perturbation matrix, the effects of lattice relaxations are systematically included. For bound electronic states of several isolated and complex defects, the results are discussed and compared with existing theoretical results and experimental (PL and DLTS) data.