Dislocation Cells and Grain Boundaries

It is noteworthy that the distribution of very low dislocation densities below 200 cm turns out to be inhomogeneous. As was observed by Birkmann et al. 

One of the characteristic structural features in semiconductor compounds, which is not yet completely clarified, is the patterning of dislocations into a cellular 

Furthermore, the relation between acting stress and cell dimension was investigated. From postgrowth deformation experiments on numerous metals and dielectrics a universal relation between cell diameter and shear stress x is known [79] 

Gompared to GaAs in InP crystals, often a missing cell structure is reported even if the dislocation density exceeds 10 cm [66]. Obviously, under standard LEG growth conditions in undoped as-grown InP crystals the cell formation is much more restrained [82]. Only at markedly higher stresses over 20 MPa, as was applied in postgrowth deformation experiments [83], also in InP crystals does a cellular dislocation network with d between 2 and 10 pm appear. 

In both undoped as-grown GdTe and PbTe crystals the presence of cellular structures is obvious. Mean cell dimensions in the range of 100 — 200 pm at EPD of 5 X 10 and 2 X 10 cm respectively, have been detected in GdTe crystals grown 

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