Simulation of Iron Distribution after Crystallization of mc Silicon

Abstract

Interstitial iron (Fei) and iron-boron pairs influence or even limit the recombination lifetime in industrial block cast multicrystalline (mc) silicon, though the proportions in the total iron concentration are generally small. Most of the iron in mc silicon is precipitated and less recombination active. This work aims for a better understanding of the distribution of iron in its different states (precipitated or dissolved) over the block height, as well as in regions of different crystal quality. In experimental studies several features of iron in mc silicon were observed, which occur due to the high extended defect density. In our 2-dimensional model for mc silicon, trapping of interstitial Fe at extended defects and precipitation at the extended defects are taken into account. The results are compared with NAA-data and spatial resolved measurements of the Fei concentration.