Defect formation chemistry of EL2 center at E_c-0.83 eV in ion-implanted gallium arsenide

Deep level defects after annealing were investigated for horizontal Bridgman GaAs implanted with donor species (Si, S, Se) and with a combination of these donors and oxygen. It was demonstrated that the EL2 defect level at E_c-0.83 eV and its concentration were identical for both cases, implanted with and without oxygen, and that oxygen could not be involved in the formation of EL2. Based upon the assumption of stoichiometry balance, a possible model for defect formation mechanism was constructed by considering diffusion and chemical reactions during ion implantation and annealing process. Using this model, the EL2 center may be assigned to a simple antisite defect - As in a Ga site if no complexes of higher orders were assumed to form. The model predicts that the donor impurities act as a catalyst during the formation of the EL2 defect but are not involved in the actual coordination of the defect or complex formation. Finally, the defect concentration profiles were shown to be controlled by the resulted stoichiometry deviation due to implantation and by different diffusivity of the implanted species as predicted by our model.