Understanding carrier trapping in multicrystalline silicon

The physical origin of minority carrier trapping centers in multicrystalline silicon is explored in both gettered and non-gettered material. The experimental evidence suggests that there are two types of trap present. One species can be removed by gettering and is related to the presence of boron–impurity pairs or complexes. The other type is impervious to gettering and is correlated to the dislocation density. Annealing experiments reveal that the trapping centers caused by boron–impurity complexes can be dissociated, and that these trapping centers do not contribute to recombination. The effect of trapping centers on open-circuit voltage is shown to be negligible when the trap density is less than the dopant density.