Electron beam induced current techniques were used to study the recombination activity of misfit dislocations in epilayers at temperatures of 80 to 300K. Completely altered characteristics were found, following the Cu contamination of SiGe epilayers. In as-grown clean material, the dislocations were found to exhibit a very slight contrast only at low temperatures. After Cu contamination of the order of ppb, the contrast increased markedly at low temperatures but remained invisible near to room temperature. This behavior was attributed to shallow trap levels at the dislocations. After Cu contamination to about 15ppb, most of the dislocations exhibited contrast over the entire temperature range. This was attributed to near-midgap centers at the dislocation. It was found that H plasma treatment of these dislocations passivated the contrast near to room temperature but did not have a pronounced effect upon the contrast at low temperatures. Thus, the very low dislocation contrast that was found in clean material was not restored by H. Copper contamination treatment in the ppm range led to a sharp increase in contrast over the entire temperature range. Transmission electron microscopy revealed Cu precipitates which were related to the misfit dislocations. Unlike slightly contaminated material, no direct decoration of the dislocations was observed. Transmission electron microscopic images revealed that the EBIC dislocation line contrast corresponded to bundles of up to 15 individual dislocations.

M.Kittler, C.Ulhaq-Bouillet, V.Higgs: Journal of Applied Physics, 1995, 78[7], 4573-83