Dephasing of LO-phonon–plasmon hybrid modes inn-type GaAs

Abstract

The relaxation dynamics of coherent phononlike LO-phonon--plasmon hybrid modes is investigated in $n$-doped GaAs using an infrared time-resolved coherent anti-Stokes Raman scattering technique. Measurements performed for different crystal temperatures in the range 10--300 K as a function of the electron density injected by doping show a large reduction of the hybrid mode dephasing time compared to the bare LO-phonon one for densities larger than ${10}^{16}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}.$ The results are interpreted in terms of coherent decay of the LO-phonon--plasmon mixed mode in the weak-coupling regime and yield information on the plasmon and electron relaxation. The estimated average electron momentum relaxation times are smaller than those deduced from Hall mobility measurements, as expected from our theoretical model.