The interaction of Cu with dislocations was studied in Si-doped material by using cathodoluminescence and transmission electron microscopic methods. Depending upon the diffusion temperature and cooling rate, several defect-complex structures or micro-defects surrounding the dislocations were found. The results could be explained by considering the local non-equilibrium of intrinsic point defects that were introduced by Cu in-diffusion and out-diffusion. The kick-out mechanism was shown to be the diffusion mechanism which was responsible. The change in the solubility, and the shift in the Fermi level, had to be taken into account in order to understand defect formation. The defect distributions which were generated gave rise to bright or dark contrasts at dislocations in cathodoluminescence images. A Cottrell atmosphere of dissolved Cu did not entirely explain this behaviour. The formation of extended defects, such as precipitates and small dislocation loops, in the strain field of dislocations was suggested to be the reason for a change in the material properties at up to several micrometres from the dislocations. Metastable orthorhombic Cu5As2 phase was found, in precipitates at dislocations, by means of energy-dispersive X-ray analysis and high-resolution transmission electron microscopy.

Copper Diffusion in Dislocation-Rich Gallium Arsenide H.S.Leipner, R.F.Scholz, F.Syrowatka, J.Schreiber, P.Werner: Philosophical Magazine A, 1999, 79[11], 2785-802