  Prior studies have shown that photoluminescence from Er3+ impurities in
silicon is severely limited at room temperature by non-radiative relaxation and
solid solubility; and room temperature emission from Er3+ in oxide-based hosts
becomes diminished at high erbium concentrations. This work presents studies of
thin films (0.2 micron thick) prepared by vacuum co-evaporation from elemental
sources (Er, Si and Si/Ge) followed by vacuum annealing (600 degrees C);
materials of this type, which are produced with high Er3+ concentrations, are
shown to be capable of yielding strong room-temperature photoluminescence.
Alloy films of Si-Er-O and Si-Ge-Er-O, containing (20 +/- 2) at. % Er and
incorporating (16 +/- 2) at. % O (introduced via vacuum scavenging reactions),
exhibit emission bands with dominant components at 1.51 and 1.54 micron
(~0.04-micron overall spectral widths). Results are discussed in terms of Er-O
complex formation and effects of local randomness on cooperative inter-Er3+
energy transfer among thermal-broadened and local-field Stark-split 4I13/2 to
4I15/2 transitions. Advantages of scalability and low-cost associated with this
method of producing optically active silicon-based materials are discussed.
