An experimental study was made of Si out-diffusion from GaAs, by using pre-doped samples. The results showed that the Si diffusivity depended upon the As4 vapor-phase pressure in the ambient, and upon the electron concentration in the crystal. It was concluded that, in GaAs, diffusion of the Si donor species which occupied Ga sites, SiGa+, was governed by the triply negatively charged Ga vacancies, VGa3-. However, the present VGa3--dominated SiGa+ out-diffusivities were larger, by many orders of magnitude, than those which were obtained under Si in-diffusion conditions. A tentative explanation of this large difference was given in terms of an undersaturation of VGa3- in intrinsic material during in-diffusion experiments, and of a supersaturation of VGa3- which developed during the out-diffusion of Si from n-type Si-doped material.

H.M.You, U.M.Gösele, T.Y.Tan: Journal of Applied Physics, 1993, 73[11], 7207-16