EFFECT OF INTERFACIAL BONDING ON THE STRUCTURAL AND VIBRATIONAL PROPERTIES OF INAS GASB SUPERLATTICES/

We have studied InAs/GaSb superlattices (SL's grown with either InSb-l ike or GaAs-like interfaces (IF's) on top of a GaSb buffer layer on (1 00) GaAs substrates. The InAs layer thickness was varied from 4 to 14 monolayers (ML) while the GaSb layer thickness was kept fixed at 10 ML . The type of LF bonds realized was verified by Raman scattering from mechanical IF modes. High-resolution x-ray diffraction using one- and two-dimensional mapping of symmetric and asymmetric reflections allowe d us to determine independently the lattice parameters parallel and pe rpendicular to the growth direction. The GaSb buffer layer was found t o be fully relaxed whereas the SL's with InSb-like IF's were coherentl y strained to the in-plane lattice parameter of the GaSb buffer for In As layer thicknesses exceeding 6 ML. The strain distribution within th e SL's with GaAs-like IF's was obtained from simulations of the x-ray reflection profiles. The SL's were found to be coherently strained clo se to the GaSb buffer and showed increasing strain relaxation with inc reasing distance from the buffer layer. In addition, these simulations provide an accurate determination of the SL periods. Well-resolved Ra man spectra of backfolded longitudinal acoustic (LA) phonons were obse rved showing for SL's with InSb-like IF's folded LA phonon lines up to the seventh order. The spectrum of quasiconfined optical SL phonons w as examined by Raman spectroscopy and by IR reflection. A detailed ana lysis of the IR reflection spectra allowed an independent determinatio n of the individual layer widths within the SL stack, including the sp atial extent of the GaAs-like IF mode.