Nonlinear dependencies of Si diffusion in δ-doped GaAs

We examine atomic diffusion of Si, when initially δ doped into very pure GaAs layers grown by gas source molecular beam epitaxy. A nonlinear Si diffusion coefficient versus inverse temperature is observed as a two-component Arrhenius dependence in which the activation energies change by 1.5 eV. Furthermore, when Si diffusion is thermally activated with the lower energy kinetics, the corresponding impurity profile grows in width linearly with the anneal time. We explain the above departures of measured Si diffusivity from classical impurity diffusion via a nonequilibrated concentration of vacancies generated at the δ position during the anneal.