ABSORPTION OF INFRARED RADIATION BY AN ELECTRON-PLASMA IN THE CASE OFSCATTERING BY IMPURITIES AND PLASMON PHONON EXCITATIONS IN SEMICONDUCTORS

The method of cumulants was applied in the framework of the fluctuatio n-dissipation theorem to obtain expressions for the coefficient repres enting absorption of infrared radiation by an electron plasma in a sem iconductor. A detailed analysis is made of the interaction of electron s with impurities and with plasmon-phonon excitations using the random -phase approximation. Numerical calculations are reported for GaAs. It is shown that the damping of phonons has a strong effect on the posit ion and width of the absorption resonance peaks. The proposed method c an be generalized to the case of an arbitrary electron-phonon and elec tron-impurity coupling.