INFLUENCE OF COPPER CONTAMINATION ON RECOMBINATION ACTIVITY OF MISFITDISLOCATIONS IN SIGE SI EPILAYERS - TEMPERATURE-DEPENDENCE OF ACTIVITY AS A MARKER CHARACTERIZING THE CONTAMINATION LEVEL/

The technique of electron-beam-induced current (EBIC) has been used to study the recombination activity of misfit dislocations in Si/SiGe ep ilayers. EBIC contrast measurements recorded as a function of temperat ure (T = 80-300 K), c(T), were found to show a completely altered char acter following copper contamination of SiGe epilayers. In as-grown '' clean'' material the dislocations were found to exhibit a very small c ontrast at low temperature only. For a Cu contamination of about 1 ppb the contrast increased markedly at low temperatures but remained invi sible near room temperature. This c(T) behavior can be attributed to s hallow trap levels at the dislocations. For a Cu contamination around 15 ppb the majority of dislocations exhibited contrast in the whole te mperature range, being a consequence of near-midgap centers at the dis location. Hydrogen plasma treatment of these dislocations was observed to passivate the contrast near room temperature but did not show a pr onounced effect on the contrast at low temperatures, so that the very small dislocation contrast found for clean material was not restored b y hydrogen. A Cu contamination treatment in the ppm range resulted in a dramatic increase of the contrasts in the whole temperature range. I nvestigations by transmission electron microscopy (TEM) revealed in th at material copper precipitates connected with the misfit dislocations . In contrast to the low-contaminated material no direct decoration of the dislocations could be observed. TEM images revealed that the EBIC dislocation line contrast corresponded to bundles of up to 15 individ ual dislocations. (C) 1995 American Institute of Physics.