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Modeling of light-induced degradation due to Cu precipitation in p-type silicon. Pt.II: Comparison of simulations and experiments

: Vahlman, H.; Haarahiltunen, A.; Kwapil, W.; Schön, J.; Inglese, A.; Savin, H.


Journal of applied physics 121 (2017), No.19, Art. 195704, 12 pp.
ISSN: 0021-8979
ISSN: 1089-7550
Journal Article
Fraunhofer ISE ()
Solarzellen - Entwicklung und Charakterisierung; Photovoltaik; Silicium-Photovoltaik; Charakterisierung von Prozess- und Silicium-Materialien; Defektcharakterisierung; Defektsimulation

The presence of copper impurities is known to deteriorate the bulk minority carrier lifetime of silicon. In p-type silicon, the degradation occurs only under carrier injection (e.g., illumination), but the reason for this phenomenon called copper-related light-induced degradation (Cu-LID) has long remained uncertain. To clarify the physics of this problem, a mathematical model of Cu-LID was introduced in Paper I of this article. Within the model, kinetic precipitation simulations are interlinked with a Schottky junction model for electric behavior of metallic precipitates. As this approach enables simulating precipitation directly at the minority carrier lifetime level, the model is verified in this second part with a direct comparison to the corresponding degradation experiments and literature data. Convincing agreement is found with different doping and Cu concentrations as well as at increased temperature, and in the dark, both simulated degradation and measured degradation are very slow. In addition, modeled final lifetimes after illumination are very close to experimental final lifetimes, and a correlation with the final precipitate size is found. However, the model underestimates experimentally observed differences in the degradation rate at different illumination intensities. Nevertheless, the results of this work support the theory of Cu-LID as a precipitate formation process. Part of the results also imply that heterogeneous nucleation sites play a role during precipitate nucleation. The model reveals fundamental aspects of the physics of Cu-LID including how doping and heterogeneous nucleation site concentrations can considerably influence the final recombination activity.