Effect of grain boundary character of multicrystalline Si on external and internal (phosphorus) gettering of impurities

We investigated the effect of the grain boundary (GB) character of multicrystalline Si (mc-Si) on the efficiency of external and internal gettering of impurities during phosphorus diffusion gettering (PDG). We utilized seed crystals with an artificially designed GB configuration to grow mc-Si ingots with different artificial GB characters. PDG combined with an originally developed multiple-cycle gettering technique at low temperature was introduced on intentionally Fe-contaminated mc-Si samples to enhance external and internal gettering. A significant positive PDG effect was observed after PDG combined with the multiple-cycle technique, as evidenced by the increase in lifetimes after PDG. A bright cloud-like photoluminescence signal around contaminated GBs was observed for artificial sigma 5-GBs and tilt-GBs after PDG, suggesting the enhancement of the internal gettering efficiency by leaving a cleaner area around the GBs. This result suggests the importance of the control of crystal defect character as well as impurities in mc-Si ingots, which could strongly affect the PDG efficiency. Copyright (c) 2016 John Wiley & Sons, Ltd.