A phenomenological methodology was used to characterize the intrinsic diffusion of Sn in GaAs, based on the coupled motion of substitutional and interstitial Sn atoms. Both the rapid diffusivity of interstitial Sn atoms and their transformation to substitutionals by occupying Ga vacancies were processes that led to the anomalous so-called double-profile diffusion curve observed in highly-doped samples. The model was developed for samples annealed at 973 to 1123K. The resultant model, developed and perhaps only applicable over this temperature range, couls be extendable to a wider temperature range provided that the underlying mechanism was unchanged. The methodology consists of using key aspects of the diffusion profiles along with the mass conservation criterion to predetermine bounds which prescribe the values of the parameters used to model the experimental data. This fitting procedure allowed for a more rapid assessment of the model parameters by providing physical bounds on their values as derived from the experimental profiles. The proposed diffusion mechanism combines the simultaneous diffusion of both interstitial and substitutional Sn atoms as well as key defect reactions characterizing their mutual equilibrium with the background vacancy concentration.

Phenomenological Modeling of Diffusion Profiles - Sn in GaAs. M.G.Debs, T.F.Kuech: Journal of Applied Physics, 2006, 99[12], 123710 (7pp)