Diffusion of aluminium to the surface and to dislocations in silicon

A quantitative study is made of the formation of p-n junctions produced by the preferential diffusion of aluminium relative to phosphorus in silicon. The concentration distributions for the flow of aluminium to the external surface, and to growing cylindrical precipitates which form at dislocations, are calculated and compared with experiment. Cylindrical p-n junctions have been produced round individual dislocations in silicon. The formation of an aluminium-oxygen complex in silicon leads to the precipitation of a second phase at crystal defects.