Interaction of iron with a grain boundary in boron-doped multicrystalline silicon

Abstract

The article presents a study of the interaction of iron with a grain boundary in boron-doped multicrystalline silicon. The sample was intentionally contaminated with iron to a few 1014 cm−3 and investigated by the electron-beam-induced-current technique (measurement of minority-carrier diffusion length, quantitative imaging) in the temperature range 80–300 K. The measurements were carried out for two different states of iron in the sample: (i) iron paired with boron, i.e., as FeB, and (ii) iron as interstitial iron Fei. The differences between diffusion lengths for these two states were used to estimate the iron concentration. The analysis of the data revealed a pronounced iron profile around the grain boundary, indicating gettering of about 4×1011 iron atoms per cm2. The recombination velocity of the grain boundary is about 5×105 cm s−1 at 300 K and is not changed by the FeB destruction treatment. The temperature dependence of the iron-related diffusion length components is discussed and found to be in satisfactory agreement with what is expected from Shockley–Read–Hall theory. Further, the diffusion length analysis revealed also a strong recombination channel of unidentified origin.