The predominant mobile fluorine defect in silicon was determined by means of density-functional based simulations. Among the mobile defects FV2, FV, F, and FI, it was found that the extra fluorine atom dominated diffusion. In p-type silicon, it was neutral and in n-type silicon it was negatively charged. The calculated concentration of this defect was by a factor of at least 10(6) higher compared to the other mobile defects. During migration of both F0 and F- the fluorine atom moves from one bond-centered configuration into a neighbouring one. For the negatively, neutral, and positively charged mobile defects the relative mobility was determined by molecular dynamics simulations at 1000C. Defect concentrations were derived from calculated cluster formation energies for a large number of clusters.

Ab initio Study of Fluorine in Silicon - Large Clusters and the Dominant Mobile Defect. K.Vollenweider, B.Sahli, W.Fichtner: Physical Review Letters, 2009, 103[7], 075503