The effect of phosphorus diffusion gettering on recombination at grain boundaries in HPMC-silicon wafers

Abstract

The influence of phosphorus diffusion gettering on recombination at grain boundaries has been studied in a commercially cast high performance multicrystalline silicon block. Wafers from four different heights have been studied with high resolution photoluminescence-imaging. The recombination at grain boundaries was studied from linescans perpendicular to the grain bounadary of interest. The change in recombination activity at grain boundaries after gettering has been correlated with grain orientation measured by electron backscatter diffraction and classified according to Brandon criterion. The relative change in carrier lifetime after gettering depends on the height in the cast, and is very sensitive to the injection level. Iron concentrations were also found from photoluminescence-imaging of iron in Fei and FeB states, respectively. After gettering recombination grain boundaries in the middle section of the ingot has become strongly recombination active. Fei, has been efficiently removed and no longer constitute the main recombination path at any height.