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Tight-binding molecular dynamics simulations of semiconductor alloys: clusters, surfaces, and defects

We extend the tight-binding molecular dynamics technique to simulations of III - V semiconductor alloy clusters, surfaces, and defects. The total energy of the alloy system is calculated using a newly developed tight-binding parametrization of ab initio band structures of bulk alloys and their pure components, for different structures and lattice parameters. The non-local binding in the lattice is compensated by pairwise repulsion to reproduce the ab initio total energies. Molecular dynamics techniques are incorporated into the tight-binding total energy scheme following the prescription of Khan and Broughton (Khan F S and Broughton J Q 1989 Phys. Rev. B 39 8592). The method is used to study small clusters, the GaAs(110) surface, and an As vacancy in bulk GaAs. Good agreement with previous studies and available experimental results is obtained in each case.