Electron-beam-induced current study of grain boundaries in multicrystalline silicon

Abstract

The effects of grain boundary (GB) character and impurity contamination on the recombination activity of grain boundaries (GBs) in multicrystalline silicon (mc-Si) were systematically studied through an electron-beam-induced current (EBIC) technique. First, clean GBs of various characters were checked at 300 and 100K. The EBIC contrasts of these GBs were in the same range of 0%–2% at 300K and 2%–4% at 100K, suggesting that the recombination activity of clean GBs is weak and the GB character has no significant effect on it. Second, the effect of impurities was studied by comparing the EBIC contrasts of the same type of the GBs in mc-Si with different Fe contamination levels. The recombination activity of GBs became stronger as the contamination level rose. The variation in the recombination activity related to the GB character was also observed in these specimens. The random or high-Σ GBs showed a stronger EBIC contrast than the low-Σ GBs. Moreover, we found that the EBIC contrast was not uniform along one Σ3 GB. In a clean mc-Si, the variation in the EBIC contrast of different parts of the Σ3 GB was 1% at 300K, whereas it was more than 10% in the contaminated mc-Si. This indicates that not only the GB character but also the GB plane would affect the recombination activity of GBs. These results suggest that the recombination activity of GBs is principally determined by the gettering ability of GBs. Specifically, that random GBs may have the strongest gettering ability, whereas Σ3 {111} has the weakest.