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Published online by Cambridge University Press: 28 February 2011
A theoretical study of native defect complexes in GaAs is reported here. These calculations are based on tight-binding Hamiltonians and employ a large cluster recursion method to obtain the changes of local densities of states. A new description of the tight-binding matrix elements developed by us is used to take into account the lattice relaxation and to provide the interaction matrix elements between the antisite defect and its neigiitors. We have examined the complexes GaAsVGa, (VGa)2, VGaAsGaVGa, VGaAsGaVGa, AsGaVAs and VAsAsGaVAs. The results indicate that the use of realistic interaction between the antisite atom and its neighloors is essential to obtain an accurate result for the midgap state of the isolated antisite and that the GaAsVGa,AsGaVAs, (VGa)2 may be responsible for the A,D hole traps and the electron trap C as proposed recently by Zou et al. using a thermochemical model. Both VGaAsGaVGa and VGaAsGaVAs are found to produce states in the gap. It is not possible to exclude either of them as a candidate for the EL2 state. A detailed analysis of the states induced by the defect complexes is made.