Anisotropic Diffusion Lengths in Germanium and Silicon Crystals containing Parallel Arrays of Edge Dislocations †

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Abstract
Techniques for introducing parallel arrays of edge dislocations into germanium and silicon by means of plastic bending are described. Crystals of germanium with a similar arrangement of dislocations, but with a, higher mean minority carrier lifetime than for those subjected to plastic bending, may be grown by pulling from the melt using a suitably orientated dislocated seed crystal. In crystals containing parallel arrays of edge dislocations the diffusion length is no longer independent of direction but is greater when measured along the dislocations than across them. The model used to explain the results suggests that the anisotropies observed will be more marked for crystals in which the dislocations are highly polygonized.