Equilibrium concentrations of defects in pure and B-doped silicon

Empirical tight-binding (ETB) calculations have been used in extensive searches for new point defect structures in pure silicon as well as silicon doped with boron. In general, these searches, which use a steepest-descents energy minimization from random starting structures, have produced the same set of simple defects in pure silicon (tetrahedral interstitials, split interstitials, and simple vacancies) which have been widely studied. However, a variety of boron interstitials, and several new di-interstitials (with and without boron) have been discovered. Similarities between these defects and defects found in ab initio and classical studies are discussed, as well as the accuracy of the theoretical results in general. A Stillinger-Weber (SW) model for Si-B interactions has been developed in order to obtain vibrational entropies for simple point defects. Using the SW potential, concentration prefactors have been obtained, and traditional Arrhenius plots for concentration have been produced. The theoretical equilibrium concentrations of self-interstitials are consistent with results obtained from Pt and Au In-diffusion experiments, and contrast with oxidation-enhanced diffusion/oxidation-retarded diffusion (OEO/ORD)-derived results. The theoretical results for point defect concentrations and binding energies are used to examine the assumptions of several diffusion models.