Copper diffusion in dislocation-rich gallium arsenide

The interaction of Cu with dislocations was studied in Si-doped gallium ars enide by means of cathodoluminescence and transmission electron microscopy. Depending on the diffusion temperature :Ind cooling rate, several structur es of defect complexes or microdefects surrounding the dislocations were fo und. The results could be explained by considering the local nonequilibrium of intrinsic point defects induced by Cu in-diffusion and outdiffusion. Th e kick-out mechanism was established as the responsible diffusion mechanism . The change in the solubility and the shift of the Fermi level must be tak en 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 su ch as precipitates and small dislocation loops in the strain field of dislo cations is the reason for the change of the material properties over a dist ance of several micrometres from the dislocation. A metastable phase of ort horhombic Cu5As2 was found in the precipitates at dislocations by energy-di spersive X-ray analysis and high-resolution transmission electron microscop y.