Impurity-induced microstructure of grain boundaries in cast silicon. Incidence on electrical properties

2014 The role of impurities in polysilicon for photocell has been investigated. Aluminium and carbon residual impurities in the Bridgman and HEM materials were particularly considered. The combination of local electrical, chemical and structural information with high spatial resolution, specifically in transmission electron microscopy, allowed to correlate the crystallography and chemistry with the electrical activity and barriers at grain boundaries. For aluminium it was shown that GB electrical property depends on the localization and environment of this dopant. The different ways for carbon to impair electrical properties are described. The correlation with other impurities and specially oxygen are considered and finally the predominant role of impurities is pointed out. Revue Phys. Appl. 22 (1987) 623-629 JUILLET 1981