Modeling of lifetime distribution in a multicrystalline silicon ingot

The lifetime distribution of a multicrystalline silicon ingot of 250 mm diameter and 100 mm height, grown by unidirectional solidification has been modeled. The model computes the combined effect of interstitial iron and dislocation distribution on minority carrier lifetime of the ingot based on the Shockley Read Hall (SRH) recombination model for iron point defects and Donolato's model for recombination on dislocations. The iron distribution model was based on the solid state diffusion of iron from the crucible and coating to the ingot during its solidification and cooling, taking into account segregation of iron to the melt and back diffusion after the end of solidification. The dislocation density distribution is determined from experimental data obtained by PVScan analysis from a vertical cross section slice. The calculated lifetime is fitted to the measured one by fitting parameters relating the recombination strength and the local concentration of iron.