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

Abstract

First-principles, spin-polarized local-density-functional calculations are used to model interstitial iron ͑Fe i ͒ and its complexes with substitutional aluminum in dilute Si x Ge 1−x alloys ͑x Ͻ 8%͒. We considered both the effect of direct bonding between Fe i or Fe i Al with Ge atoms in the x → 0 limit and the evolution of the defect properties with the alloy composition. It is found that Fe i prefers Si-rich regions, but when placed near a Ge atom, its ͑0 / +͒ level is shifted toward the conduction band. However, the ionization energy of Fe ͑+/+2͒ -Al − is only slightly changed by the presence of neighboring Ge atoms in the proximity. It is also found that indirect alloying effects shift the donor levels of Fe i and FeAl at a fast rate toward the valence band. The acceptor levels, however, remain approximately at the same distance from E v .

Electrical and structural properties of In-implanted Si1−xGex alloys

“…Such an approach for modeling random Si 1Àx Ge x alloys has been previously justified. [26][27][28] The validity of the models was further confirmed, as the Si-Ge bond lengths and the topological rigidity parameter (without In atoms present) agreed well with those in the published literature. 29,30 III.…”

Effect of Ge doping on the kinetics of iron–boron pair association and dissociation in photovoltaic silicon

“…3(b) shows that as the iron atom leaves away from the Ge atom, the relative energy goes down in the directions of both /1 01S and /1 01 S. Thus, it is expected that Fe will avoid Ge atoms. A. Carvalho et al reported the same result by a first principle calculation in Si x Ge 1 À x alloys [27]. The diffusion barrier of Fe away from Ge is lower than the diffusion barrier of Fe back to Ge, and the active energy of iron diffusion from a site to d site is even lower than the barrier of iron diffusion in CZ system, as shown in Fig.…”

Influence of germanium doping on the performance of high-performance multi-crystalline silicon

“…But the electrical activity of FeB complexes was stronger than that of Ge-Fe complexes [20] and FeB complexes could be a stronger recombination center that leaded to a bigger influence on the minority carrier lifetime than Ge-Fe complexes. Moreover, because Ge doping could increase the diffusion barrier of interstitial iron [14] and reduce the amount of FeB complexes in the Ge-doped mc-Si ingot, Ge doping could improve the minority carrier lifetime of the mc-Si wafers.…”