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We report on band-gap luminescence in strain-symmetrized, (Si) /(Ge)"superlattices grown on a step-graded, alloy buffer with a reduced dislocation density, using Sb as a surfactant. The luminescence efficiency for a (Si)9/(Ge)6 and (Si)6/(Ge)& superlattice is strongly enhanced compared with a corresponding Slo 6Geo 4 alloy reference sample. The luminescence signals can be attributed to interband transitions

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Silver-doped silicon was investigated by using transmission and photothermal ionization spectroscopy (PTIS). A spectrum of sharp lines was detected between 6200 and 6700 cm '. In PTIS, strong phonon-assisted Fano resonances were observed which involved f TO and g LO intervalley phonons. It was therefore possible to identify the silver-related center as a donor. The Ag spectrum differs from previously reported donor spectra in silicon in the sense that excitations to excited p states do not dominate. 2po and 3po lines were weakly observed, and none of the usually strong p+ lines were detected. By comparing spectra of P and neutral Te with the spectrum obtained for Ag, it is shown that the Ag spectrum is dominated by excitations to s states.

We report for the first time on room temperature electroluminescence in the region 1.3–1.7 μm from a strain-adjusted Si6Ge4 superlattice. These results, together with photoluminescence, short-circuit photocurrent spectroscopy, and voltage-intensity and current-intensity measurements indicate that the observed electroluminescence consists of two emission bands which are believed to be caused by defect and interband recombination processes.