  Photoluminescence is observed at room temperature from phonon-assisted
band-to-band emission in Si (1.067 eV peak) using unpatterned bulk p-type
silicon wafer samples that were spin-coated with Er-doped (6 at. %) silica-gel
films (0.13 micron) and vacuum annealed; the strongest emission was obtained at
~700 degrees C. Comparative study of annealing behavior indicates two-orders of
magnitude efficiency enhancement. Emission from Er+3 ions in the silica film is
used to gauge relative emission strengths. Mechanisms for inducing emission
from silicon utilizing stresses in sol-gel-films are discussed.
