Ebic/Tem Investigation of Defects in Solar Cell Silicon

Abstract

ABSTRACTTwo examples are given of the application of EBIC and HVTEM to the study of defects in silicon.An hexagonal dislocation network in a coherent first order twin boundary in WEB silicon shows a three fold symmetry when imaged by EBIC. The observed variation of the minority carrier lifetime at the nodes is consistent with a model which assumes that jogs are particularly strong recombination sites at a dislocation.EBIC and STEM observations on unprocessed and processed EFG ribbon show that the phosphorus diffused junction depth is not uniform, and that a variety of chemical impurities precipitate out during processing. Two kinds of precipitates are found i) 10 nm or less in size, located at the dislocation nodes in sub-boundary like dislocation arrangements formed during processing and ii) large precipitates, the chemical composition of which has been partially identified. These large precipitates emit dense dislocations tangles into the adjacent crystal volume.