RAMAN-LINE-SHAPE STUDY OF INXGA1-XAS ON INP AND GAAS SUBSTRATES

Raman scattering of InxGa1-xAs epitaxial layers on InP and GaAs substr ates have been investigated with a wide range of composition. It is fo und that the asymmetric broadening of LO phonon modes varies with comp osition as well as substrate. With the spatial correlation model, the Raman line shapes of the GaAs-like mode in InxGa1-xAs epitaxial layers have been analyzed. It is found that the one-parameter spatial correl ation model cannot explain the experimental results. According to the measurements of double-crystal x-ray diffraction (DXRD), we find stron g correlation between the full width at half maximum of DXRD measureme nts and the line shapes of the Raman spectra. Thus, it is suggested th at the Raman line shapes depend not only on the alloy disorder but als o on the degree of structural dislocation in the heteroepitaxial syste m. Structural dislocation will change the intrinsic linewidth of the R aman spectrum which introduces an additional fitting parameter in the spatial-correlation model. Thus, our results provide a framework for t he use of the two-parameter spatial-correlation model in the study of the compositional dependence of the Raman spectra in epilayer structur es.