Photoluminescence studies of Si/Si_{1 - x}Ge_x quantum wells and Si_mGe_n superlattices

We report on photoluminescence studies of Si/Si_{1 - x}Ge_x quantum wells with systematically varied growth temperatures and well thicknesses. Well resolved band gap luminescence could be observed in quantum well structures grown at temperatures above 600 °C while for structures grown at lower temperatures defect-related lines dominate the luminescence spectra. We also present photoluminescence and electroluminescence studies for a strain-symmetrized Si₅Ge₅ superlattice. The photoluminescence observed below the band gap of the corresponding alloy is shown to be enhanced by growing the superlattice on a thick, single-step alloy buffer layer. Absorption measurements on the superlattice show an onset of the absorbance at an energetic position close to the observed photoluminescence. These findings provide strong evidence for band gap related photoluminescence and electroluminescence in a strain-symmetrized Si₅Ge₅ superlattice.