Arsenic segregation, pairing and mobility on the cores of partial dislocations in silicon

We studied the effects of arsenic on properties of dislocations in silicon. The theoretical investigation was carried out using ab initio total energy methods, based on the density functional theory. We find that the interaction of an arsenic impurity in the crystal with a dislocation results in a charge exchange, driving the dislocation core to a negative charge state. This interaction is essentially electrostatic and attractive, and leads to arsenic segregation. Although arsenic segregation to the core is energetically favourable, formation of arsenic pairs inside the core is energetically unfavourable. We also investigated the role of vacancies in arsenic diffusion inside the dislocation core.