Ab initio total-energy calculations for iron-acceptor pairs in silicon

First-principles study of Fe and FeAl defects in SiGe alloys

“…19,25 Local-density-functional spin-polarized ͑LSDA͒ Green's function calculations [28][29][30] and recently fully relaxed generalized gradient approximation ͑GGA͒ calculations 18,31 were used to model the electronic structure of interstitial iron, reproducing the observed spin-1 and spin-3/2 for Fe i and Fe i + , respectively, and finding a donor level in the lower half of the band gap in agreement with experiment. Iron-acceptor pairing was also the object of previous theoretical studies, [16][17][18] which found that the C 3v configuration is the most stable for Fe i B but a C 2v configuration, where Fe i is at the second-nearest T site of the substitutional acceptor atom, is almost degenerate in energy with the trigonal form for Fe i Al and Fe i Ga, and energetically favorable for the larger acceptors In and Tl. 17,18 Both the orthorhombic and trigonal forms of each pair were found to exist in three charge states ͑−, 0, and +͒.…”

“…2 The formation of iron-acceptor pairs at temperatures below 80-100°C is accompanied by a decrease in the concentration of isolated Fe i , and they remain stable up to a higher temperature stage ͑100-200°C͒ when a recovery of the concentration of isolated Fe i is observed. 2 The Fe i B complex, formed by an interstitial iron close to a substitutional boron aligned along the ͗111͘ crystallographic direction, [16][17][18] has a well-known donor level at about E v + 0.1 eV. This electrical level arises from the Fe i +/+2 transition level, pulled into the band gap due to the electrostatic interaction with B − .…”

Interstitial Fe in Si and its interactions with hydrogen and shallow dopants

“…25,67 In situations were the impurity can be assume to reside at undistorted high-symmetry sites-as is the case here ͑see below͒-these calculations are better suited than our pseudopotential method to reproduce the EPR and ENDOR data. We do not focus on this aspect of the problem.…”

Lattice sites of implanted Fe in Si

“…9 Based on these EPR observations most theoretical approaches focused on iron on ideal tetrahedral interstitial sites ͑see Refs. 10-14 and references therein͒, but, with the exception of Feacceptor pairs, 15 never in a configuration of symmetry lower than T d .…”