An analysis was made of the effect of perturbations, which were produced by recombination at surfaces, trapping at impurities and stress fields, upon the room-temperature migration of point defects. Implantation of 40keV Si ions, through a striped mask, to doses of 1012 to 5 x 1013/cm3 at room temperature was used to inject point defects. Following implantation, defect-induced dopant deactivation, in the cross-section which was orthogonal to the direction of the stripes, was monitored by means of spreading resistance profiling. It was found that, in very pure epitaxial samples, dopant deactivation extended in depth to several microns beyond the region which was directly affected by the ions. The 2-dimensional deactivation profiles exhibited a strong recess at the surface, and a significant anisotropy; being markedly elongated in the lateral direction. An analysis of the data showed that the long-range migration of defects was interrupted by trapping at impurities (C and O) or by recombination at the surface. The lateral elongation of the profiles was attributed to an anisotropy in the defect diffusivity tensor which was produced by the strain field under the mask.

Surface, stress and impurity effects on room-temperature migration of ion beam-generated point defects S.Coffa, A.La Magna, V.Privitera, G.Mannino: Applied Physics Letters, 1998, 73[11], 1571-3