It was noted that any defect or impurity contained some inherent stress and that, near to a free surface, its energy was reduced by relieving this stress. The defect stress was also coupled to the intrinsic surface stress. In general, the result was an enhancement of impurity solubility and diffusion near to the surface. Depending upon the assumptions that were made regarding the kinetics, the high impurity density near to the surface could be frozen in as the crystal grew, thus permitting the establishment of highly supersaturated solid solutions, such as high dopant concentrations in semiconductors. Calculations were performed for C near to the (001)Si surface in order to illustrate the solubility enhancement.

J.Tersoff: Physical Review Letters, 1995, 74[25], 5080-3