Lattice vibrations and phonon-plasmon coupling in Raman spectra of p-typeIn0.53Ga0.47As

Raman spectra of p-type ${\mathrm{In}}_{0.53}$ ${\mathrm{Ga}}_{0.47}$As with doping levels ranging from p=2×${10}^{17}$ to 5×${10}^{19}$ ${\mathrm{ncm}}^{\mathrm{-}3}$ have been investigated. Analysis of the Raman line shape and its dependence on the free-hole density demonstrates four-mode behavior of optical phonons. Based on the oscillator strength and Faust-Henry factors of the optical phonons determined from the Raman data, and lattice-dynamic calculations of the phonon dispersion relations in ordered structures of ${\mathrm{InGaAs}}_2$, we show a relationship between the observed four-mode behavior and short-range order phase-separation effects.