Cathodoluminescence imaging of misfit dislocations in Si/SiGe epitaxial layers: the influence of transition metal contamination

Abstract

Cathodoluminescence (CL) spectroscopy and CL imaging have been used to characterize misfit dislocations in as-grown Si/SiGe epilayers and those contaminated with transition metal. The misfit dislocations in the as-grown layers showed no radiative recombination (D bands) but only the band exciton features from the Si substrate. CL monochromatic imaging with the Si substrate luminescence revealed dark line contrast, associated with non-radiative recombination at the misfit dislocations. Following contamination with low levels (10 10 −10 12 atoms cm −2 ) of the transition metals Cu, Au, Fe or Ni and annealing, the D bands (D1–D4) were observed. CL images indicated that D1 and D2 are associated with point defects and that D3 and D4 are related to radiative recombination at the misfit dislocations. After higher contamination with Cu, Au or Ni, when the misfit dislocations were decorated by metal-related microprecipitates, the radiative recombination at the dislocation was quenched. The CL dark line contrast was observed from all the samples, independent of contamination treatment.