The behavior of Si, after being initially δ-doped into very pure gas-source molecular beam epitaxial GaAs layers, was studied by using capacitance-voltage profiling. A non-linear behavior of the diffusivity of Si as a function of the reciprocal temperature was observed. This was explained in terms of a 2-component Arrhenius dependence in which the activation energies changed by 1.5eV. When Si diffusion was governed by the lower activation energy, the impurity profile grew in width as a linear function of the annealing time. Deviations of the measured Si diffusivity from classical impurity diffusion behavior were attributed to the existence of a non-equilibrium concentration of vacancies which was generated at the δ-source position during annealing.

J.E.Cunningham, T.H.Chui, W.Jan, T.Y.Kuo: Applied Physics Letters, 1991, 59[12], 1452-4