Modeling of silicon atoms diffusion in GaAs in view of nonuniform distribution of point defects

Abstract

A simulation of Si diffusion in layer-doped GaAs crystals during annealing in the ambients with no excess of Ga or As and in As-rich conditions has been carried out. A model of diffusion due to “silicon atom–gallium vacancy” pairs taking into account the nonuniform distribution of point defects responsible for diffusion and amphoteric behavior of silicon in GaAs has been used for the calculation of dopant concentration profiles. A number of parameters, such as intrinsic diffusivity of silicon, average migration length of gallium vacancies etc, has been derived from the fitting to the experimental data. For all annealing conditions, the surface acts as a strong sink for gallium vacancies inducing vacancy diffusion to the surface. The values of the average migration length for gallium vacancies are approximately the same for all investigated cases and are equal to ∼0.4 μm. It is shown that in the range of a dopant concentration up to 5 n i silicon diffusion is governed by the neutral gallium vacancies V Ga ×, but, if silicon concentration is near or exceeds 10 n i, the dominant defect responsible for dopant diffusion is the triply negatively charged gallium vacancies V Ga 3−.