Thermal Stability of EL2 in GaAs

Different samples originating from the same LEC ingot have been used in order to determine the variation of the EL2 concentration versus depth after different types of thermal annealing ( 450 and 850°C : the temperatures generally used in technological processes ). The annealing of EL2 near the surface at 850°C has been interpreted as the result of the deviation from the stoichiometry near the surface, due to [As] variation induced by vacancy diffusion. At 450°C, the annealing of EL2 can only be explained by the dissociation of a complex, followed by the migration of one of the constituants, confirming that the EL2 defect is the complex AsGa- Asi.