RAMAN-SCATTERING STUDIES OF SI1-XGEX EPITAXIAL LAYERS GROWN BY ATMOSPHERIC-PRESSURE CHEMICAL-VAPOR-DEPOSITION

Room temperature Raman spectra are reported of Si1-xGex epitaxial laye rs on Si substrates (0.08 less than or equal to x less than or equal t o 0.2). The samples were grown using atmospheric pressure chemical vap or deposition techniques. Layer thicknesses varied from 0.03-10 mu m. The relative frequency shift of the Si-Si phonon mode for the SiGe str ained epilayers from an incommensurate pseudo-alloy of the same compos ition is used as a quantitative measure of the lattice relaxation fact or. For thicknesses below a critical value the Raman data indicate tha t the films are highly strained and the growth is commensurate with th e substrate whereas thicker films are partially or fully relaxed.