Dielectric response of thick low dislocation-density Ge epilayers grown on (001) Si

Spectroscopic ellipsometry was used to measure the dielectric functions of epitaxial and bulk Gr at photon energies from 1.5 to 5.2 eV. The epitaxial Ge was grown at 400 degrees C by molecular beam epitaxy on (001) Si substrates. The optical response and the interband critical-point parameters of Ge on Si were found to be indistinguishable from that of bulk single crystal Ge, indicating high optical quality. Dislocation density measurements using an iodine etch verified low surface defect densities. We conclude that epitaxial Ge grown on Si at relatively low temperatures is suitable for optical device applications. (C) 1996 American Institute of Physics.