Anomalous dispersion with excitation wavelength of longitudinal optical phonon–plasmoncoupled modes in n-InGaAs

Abstract

We have studied the wavevector dispersion of theL+ coupled modein n-type In0.53Ga0.47As by means of Raman scattering using several excitation wavelengthsin the range between 457.9 and 720 nm. The optical properties ofIn0.53Ga0.47As in the range of excitation energies used are strongly affected by the presence of theE1 and E1+Δ1 critical points, and set an upper limit to the wavevector that can be probed by decreasingthe excitation wavelength in Raman scattering experiments. The Raman scattering resultsare analysed using a Lindhard–Mermin model, and it is found that optical absorptionstrongly affects the coupled-mode Raman peaks excited with the more energetic lines.