Internal-stress effects on Raman spectra ofInxGa1−xAs on InP

Raman spectra of ${\mathrm{In}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As are observed over a wide range of composition. A GaAs-like mode frequency ω is found to vary with the composition x as ω=-32.4$x^2$-18.6x+290.0 ${\mathrm{cm}}^{\mathrm{-}1}$. The internal stresses due to lattice mismatch are evaluated from the deviation of the GaAs-like LO mode frequency from the above experimental equation for small lattice mismatch. An increase is found in the internal stress toward the interface from the 5000-Å-thick surface layer. The stress effects on the lattice vibrations of the optical mode are discussed from a microscopic point of view.