Resonant Photoluminescence Excitation in GaAs Grown Directly on Si

We describe new results observed during resonant excitation in the excitonic region of GaAs grown directly on Si by organometallic vapor phase epitaxy. Two resolved features were found in the light hole photoluminescence (PL) region, one identified with a free exciton process and the other with donor-related transitions. Features which track the laser excitation line were observed and identified with a process in which a donor is excited from the n=l ground state to an n=2 excited state. The PL excitation spectra associated with these features have spectral widths as narrow as 1.5 meV. PL spectral widths of ~3 meV have been attained for the heavy hole exciton band, representing the narrowest value obtained for OMVPE material and an improvement of about 30% over our best previous results.