Influence of Cu contamination and hydrogenation on recombination activity of misfit dislocations in SiGe/Si epilayers

The EBIC contrast temperature-behaviour, c(T), was observed to exhibit a fingerprint characterizing the contamination level of the dislocations. In as-grown ''clean'' material the dislocations were found to show a very small contrast only, with a maximum around 50 K. For a Cu contamination of about 1 ppb the contrast increased markedly at low temperatures but remained invisible at room temperature. This c(T) behaviour is attributed to shallow traps. For a Cu contamination > 10 ppb the majority of dislocations exhibited contrast in the whole temperature range, being a consequence of near-midgap levels. Hydrogen plasma treatment of these dislocations was observed to passivate the contrast near room temperature but did not show a pronounced effect on the contrast at low temperatures, so that the very small contrast found for ''clean'' material was not restored by hydrogen. A Cu contamination treatment in the ppm range resulted in a dramatic increase of the contrasts in the whole temperature range. TEM investigations revealed in that material Cu silicide precipitates connected with the misfit dislocations.