OPTICAL AND ELECTRONIC-PROPERTIES OF SIGEC ALLOYS GROWN ON SI SUBSTRATE

Metastable Si1-x-yGexCy alloys were grown by molecular beam epitaxy on (100) Si substrates. Solid elemental sources were used for the Si and Ge beams, and a resistively heated graphite filament was used for the C beam. Up to 3 at % of C was incorporated in the alloy layers. Optic al transmission measurements showed that the absorption edge of thick layers increased to higher energies with increasing C fraction, and re vealed the presence of Si-C and Ge-C vibrational modes in the infrared . Al low temperatures, the alloys showed significant photoluminescence . The bandgap energies of thick layers increased linearly with the C f raction and followed a linear dependence of the bandgap on composition . Measurements of the valence band density of states using X-ray photo electron spectroscopy indicated that the valence band energy maximum i ncreased with the C fraction relative to that of SiGe alloys of simila r composition. Our results indicated that SiGeC alloys are promising m aterials for Si-based heterostructure devices.