查看文章

We have studied by means of Raman scattering the LO phonon-plasmon coupled modes in n− In 0.53 Ga 0.47 As, for carrier densities between 5× 10 16 and 5× 10 19 cm− 3. In addition to the L+ mode, whose frequency rapidly increases with carrier density, two other coupled modes are detected that shift to lower frequencies as the carrier density increases. The observed carrier-density dependence of the latter two modes markedly differs from the coupled-mode behavior reported so far for ternary alloys, exemplified by that of the Al x Ga 1− x As alloys. Such a dependence is correctly described by a line-shape model based on the Lindhard-Mermin dielectric function, suitably generalized to ternary alloys. Landau damping effects are shown to play a major role in the carrier-density dependence of the lower-energy coupled modes. These effects are clearly observed in In 0.53 Ga 0.47 As because the small electron …