The interaction of Cu with dislocations was studied in Si-doped gallium arsenide by means of cathodoluminescence and transmission electron microscopy. Depending on the diffusion temperature :Ind cooling rate, several structures of defect complexes or microdefects surrounding the dislocations were found. The results could be explained by considering the local nonequilibrium of intrinsic point defects induced by Cu in-diffusion and outdiffusion. The kick-out mechanism was established as the responsible diffusion mechanism. The change in the solubility and the shift of the Fermi level must be taken into account in order to understand the defect formation. The generated defect distributions gave rise to bright or dark contrasts at dislocations in cathodoluminescence images. A Cottrell atmosphere of dissolved Cu is not sufficient to explain this behaviour. The formation of extended defects such as precipitates and small dislocation loops in the strain field of dislocations is the reason for the change of the material properties over a distance of several micrometres from the dislocation. A metastable phase of orthorhombic Cu5As2 was found in the precipitates at dislocations by energy-dispersive X-ray analysis and high-resolution transmission electron microscopy. [References: 23]

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