On the mechanism of recombination at oxide precipitates in silicon

Abstract

Oxide precipitates are well known to degrade minority carrier lifetime in silicon, but the mechanism by which they act as recombination centres is not fully understood. We report minority carrier lifetime measurements on oxide precipitate-containing silicon which has been intentionally contaminated with iron. Analysis of the injection-dependence of lifetime demonstrates the same recombination centres exist in iron-contaminated and not intentionally contaminated samples, with the state density scaling with iron loss from the bulk. This shows that recombination activity arises from impurity atoms segregated to oxide precipitates and/or surrounding crystallographic defects.

X-ray micro-beam characterization of lattice rotations and distortions due to an individual dislocation

“…Their behaviour is of fundamental importance for the performance of thermoelectric devices 2 , nano-electronics 3,4 and solar cells 5,6 . In structural engineering alloys, used for high-performance aerospace applications, dislocation-mediated slip is one of the main deformation mechanisms 7 .…”

Competitive gettering of iron in silicon photovoltaics: Oxide precipitates versus phosphorus diffusion

“…In this paper, we present results using a methodology which relies on the analysis of injection-dependent minority carrier lifetime measurements 14 and our prior correlation between recombination activity and the amount of iron segregated to oxide precipitates and associated defects. 5 Combining this with well-established techniques for measuring bulk iron concentrations by photodissociation of iron boron pairs [15][16][17] enables the simultaneous quantification of levels of iron in the bulk and that segregated to oxide precipitates and associated defects. This allows for the study of the efficacy of PDG at removing iron from oxide precipitates and associated defects, and the bulk.…”

“…Strain fields surrounding extended defects provide low energy sites for segregation of impurity atoms and the formation of precipitates. The presence of impurities at extended defects enhances their recombination activity, [3][4][5] which, in the context of a photovoltaic solar cell, will reduce the conversion efficiency.…”

“…9,13 We have recently shown a strong correlation between the quantity of iron segregated to the oxide precipitates and associated defects (surrounding dislocations and stacking faults) and the resulting recombination activity. 5 As solar silicon is at risk of contamination by transition metal impurities from the crucible or during cell processing, it is important to understand how the interaction of impurities with oxide precipitates evolves during cell processing.…”

Hydrogénation effect on low temperature internal gettering in multicrystalline silicon

“…The details of how impurities are distributed within the material govern the material's performance. For instance, the electrical activity of dislocations or oxide precipitates is governed by the degree to which they are decorated by metallic impurities [1,2] and concentrating a fixed impurity concentration into a lower density of larger metallic precipitates can lower overall recombination activity [3]. Among the various metallic impurities present in mc-Si material, iron is one of the most detrimental to the minority carrier lifetime (henceforth referred to as just "lifetime") [4,5].…”