The migration of impurity atoms in solid-phase epitaxially grown layers was studied by means of back-scattering spectrometry. The samples were amorphized by Ge implantation into [100]- or [111]-oriented samples. The amorphized regions were then recrystallized by furnace annealing. Asymmetrically enhanced diffusion was observed in the case of [111]-type samples; for both As and Ge implantation. A striking result was that, in the case of [111]-type samples, there was extensive smearing of the profiles while, in the case of [100]-type samples, this was hardly detectable. It was recalled that it was well known that the re-growth features of [100]-type and [111]-type amorphized Si were different. In essential agreement with previous observations, it was found here (using cross-sectional electron microscopy) that the re-grown layer on [111]-type material was characterized by extensive multiple twinning. A 2-step annealing treatment usually led to a superior crystalline perfection, as confirmed by the cross-sectional transmission electron microscopy of samples which had first been annealed at 650C, and then at 1050C. The diffusion of Ge was then also reduced. Overall, the extent of diffusion was related to defects.

R.Turan, T.G.Finstad: Philosophical Magazine A, 1991, 63[3], 519-25