Using a combination of the local-basis ab initio program SIESTA and the activation-relaxation technique the diffusion mechanisms of the Ga vacancy in GaAs were studied. Vacancies were found to diffuse to the second neighbour using two different mechanisms, as well as to the first and fourth neighbours following various mechanisms. It was found that the height of the energy barrier was sensitive to the Fermi level and generally increases with the charge state. Migration pathways themselves could be strongly charge dependent and may appear or disappear as a function of the charge state. These differences in transition state and migration barrier were explained by the charge transfer that takes place during the vacancy migration.

Charge-Dependent Migration Pathways for the Ga Vacancy in GaAs. F.El-Mellouhi, N.Mousseau: Physical Review B, 2006, 74[20], 205207 (9pp)