NEAR-BAND-EDGE PHOTOLUMINESCENCE IN RELAXED SI1-XGEX 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 sampl es was dominated at low temperature and low excitation densities by re combination of excitons bound to alloy fluctuations exhibiting the sma llest full width at half-maximum, 2.44 meV, reported for relaxed epita xial Si1-xGex layers. Excitons bound to phosphorous and boron were als o observed as was free exciton recombination. (C) 1995 American Instit ute of Physics.