Near band-edge photoluminescence in relaxed Si_1-xGe_x layers

Near band-gap photoluminescence was observed at low temperatures from relaxed Si1-xGex layers with 0.17<x<0.32 grown on Si(001) by ultrahigh vacuum chemical vapor deposition. The luminescence from undoped samples was dominated at low temperature and low excitation densities by recombination of excitons bound to alloy fluctuations exhibiting the smallest full width at half-maximum, 2.44 meV, reported for relaxed epitaxial Si 1-xGex layers. Excitons bound to phosphorous and boron were also observed as was free exciton recombination.© 1995 American Institute of Physics.