Precipitation of interstitial iron in multicrystalline silicon

Abstract

The internal gettering of iron in silicon via iron precipitation at low processing temperatures is known to improve solar cell efficiencies. Studies have found that the optimal temperature lies in the range of 500°C-600°C. In this paper, we present experimental results on quantitatively analysing the precipitation of interstitial Fe in multicrystalline silicon wafers during the 500°C-600°C thermal annealing processes. The concentration and the spatial distribution of interstitial Fe in mc-Si were measured by the photoluminescence imaging technique. It was found that, apart from the processing temperature, the Fe precipitation time constant is highly dependent on the supersaturation ratio and the density and types of the precipitation sites.