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Influence of metal-organic vapor phase epitaxy reactor environment on the silicon bulk lifetime

: Ohlmann, J.; Feifel, M.; Rachow, T.; Benick, J.; Janz, S.; Dimroth, F.; Lackner, D.


IEEE Journal of Photovoltaics 6 (2016), No.6, pp.1668-1672
ISSN: 2156-3381
Journal Article
Fraunhofer ISE ()

III-V multijunction solar cells grown on a Si solar cell are an attractive approach to reduce the cost of high-efficiency solar cells. When using the Si wafer as an active solar cell, it is crucial to avoid degradation of the minority carrier lifetime in the Si during the metal-organic vapor phase epitaxy (MOVPE) process. After heating a Si wafer in a MOVPE reactor under a H2 atmosphere, we observed a strong degradation of its lifetime. By analyzing the annealed samples with photoluminescence and quasi-steady-state photoconductance, we found an iron contamination of up to 2 × 1012 cm-3. The measured iron concentration could be identified as the major source for the decrease of the minority carrier lifetimes of the Si wafers. By using diffusion barriers, we identified the graphite susceptor as the main source of the iron contamination. This knowledge offers pathways to preserve the minority carrier lifetime in the Si wafers during the MOVPE process.