Interference effects in the light scattering spectra of semiconductors

Abstract

We investigate the effect of plasmon-phonon coupling on the spectrum of laser light scattered by doped semiconductors under high-excitation conditions. A model consisting of the plasmon and LO-phonon subsystems in conditions of quasiequilibrium, characterized by uniform internal temperatures, is used. The scattering cross section is derived through an appropriate generalization of the fluctuation-dissipation theorem and the use of Bogoliubov's Green's-function formalism. The Coulomb interaction between electrons is treated within the random-phase approximation and the Frohlich Hamiltonian is used to describe the electronphonon interaction. The phonon lifetime and plasma lifetime, other than Landau damping, are introduced in a phenomenological way. Numerical calculations for the case of a nondegenerate conduction-electron gas in GaAs are presented. The analysis is completed with a discussion of resonant Raman scattering when "hot" electrons are considered for the intermediate states of the scattering amplitude.

Optical properties of semiconductors via pump-probe experiments: statistical-thermodynamical approach, hot plasma and coherent phonon states

“…where τ , predominantly the decay of the LO phonon at mode Q, varies around 7 ps [24,34,37]. We recall that β c (t) = 1/k B T * c (t), the evolution of the carriers' quasitemperature is given in figure 1, and n 6.5 × 10 17 cm −3 is practically constant in time in the given interval when the observation and measurement was performed.…”

“…a in the effective mass approximation. Two others are the hybrid optical plasma-LO phonon excitations, with the dispersion relation [33,34]…”

“…Finally, in the given conditions the lifetime of the upper hybrid (optical plasmon-LO phonon) mode L + is much larger than the one of the lower hybrid mode L − . This is a result of the fact that the L + mode at the given density n is predominantly of the longitudinaloptical vibration type, and then its lifetime is of the order of picoseconds while the L − mode is predominantly a plasma oscillation, with lifetime of the order of femtoseconds [24,34]. Consequently, the modulation of the reflectivity coefficient occurs in terms of the frequency ω + (Q) which is 8.85 THz for a concentration of photoinjected carriers of roughly 6.5 × 10 17 cm −3 , in coincidence within the experimental error with the observed one of 8.8 ± 0.15 THz.…”

A NONEQUILIBRIUM STATISTICAL ENSEMBLE FORMALISM MaxEnt–NESOM: Basic Concepts, Construction, Application, Open Questions and Criticisms

“…171 is investigated the effect of plasmon-phonon coupling on the spectrum of laser light scattered by doped semiconductors under high-excitation conditions. A model consisting of the plasmon and LO-phonon subsystems in conditions of quasiequilibrium, characterized by uniform internal temperatures, was used.…”