DIELECTRIC RESPONSE OF THICK LOW DISLOCATION-DENSITY GE EPILAYERS GROWN ON (001)SI

Spectroscopic ellipsometry was used to measure the dielectric function s 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-po int parameters of Ge on Si were found to be indistinguishable from tha t of bulk single crystal Ge, indicating high optical quality. Dislocat ion density measurements using an iodine etch verified low surface def ect densities. We conclude that epitaxial Ge grown on Si at relatively low temperatures is suitable for optical device applications. (C) 199 6 American Institute of Physics.