Dislocation density reduction during impurity gettering in multicrystalline silicon

H. J. Choi, M. I. Bertoni, J. Hofstetter, D. P. Fenning, D. M. Powell, S. Castellanos, T. Buonassisi

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Isothermal annealing above 1250 °C has been reported to reduce the dislocation density in multicrystalline silicon (mc-Si), presumably by pairwise dislocation annihilation. However, this high-temperature process may also cause significant impurity contamination, canceling out the positive effect of dislocation density reduction on cell performance. Here, efforts are made to annihilate dislocations in mc-Si in temperatures as low as 820 °C, with the assistance of an additional driving force to stimulate dislocation motion. A reduction of more than 60% in dislocation density is observed for mc-Si containing intermediate concentrations of certain metallic species after P gettering at 820 °C. While the precise mechanism remains in discussion, available evidence suggests that the net unidirectional flux of impurities in the presence of a gettering layer may cause dislocation motion, leading to dislocation density reduction. Analysis of minority carrier lifetime as a function of dislocation density suggests that lifetime improvements after P diffusion in these samples can be attributed to the combined effects of dislocation density reduction and impurity concentration reduction. These findings suggest there may be mechanisms to reduce dislocation densities at standard solar cell processing temperatures.

Original languageEnglish (US)
Article number6330974
Pages (from-to)189-198
Number of pages10
JournalIEEE Journal of Photovoltaics
Volume3
Issue number1
DOIs
StatePublished - Jan 1 2013
Externally publishedYes

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Keywords

  • Al gettering
  • P gettering
  • dislocation density
  • dislocation impurity interaction
  • multicrystalline silicon

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

Cite this

Choi, H. J., Bertoni, M. I., Hofstetter, J., Fenning, D. P., Powell, D. M., Castellanos, S., & Buonassisi, T. (2013). Dislocation density reduction during impurity gettering in multicrystalline silicon. IEEE Journal of Photovoltaics, 3(1), 189-198. [6330974]. https://doi.org/10.1109/JPHOTOV.2012.2219851