Influence of defects and impurities on the deteriorated border region in multicrystalline silicon ingots

Abstract

AbstractThe origin of the lower minority carrier lifetime in the border region of multicrystalline silicon (mc‐Si) ingots was investigated. Based on minority carrier lifetime measurements and chemical analyses, distributions of defects and impurities were studied. It is found that the content of oxygen, carbon and other metal impurities in the border region were almost at the same level as that in the bulk, while the concentration of Fe‐B pairs is significantly higher. More interestingly, the dislocation density in the border region was observed to be much lower than that in the adjacent part. It is elucidated that the lower dislocation density in the border region leads to more iron existing in the form of Fe‐B pairs, which could be responsible for the low lifetime. In addition, it is shown that the low minority carrier lifetime in the border region can be improved effectively by phosphorous gettering. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)