Plasmon-phonon Interaction Research Articles

Far-infrared study of free carriers and the plasmon-phonon interaction in CdTe

The reflectivity of $n\ensuremath{-}\mathrm{CdTe}$ has been measured between 16 and 203 ${\mathrm{cm}}^{\ensuremath{-}1}$ at room temperature. The single-crystal samples had carrier concentrations $N$ between 5 \ifmmode\times\else\texttimes\fi{} ${10}^{16}$ and 1 \ifmmode\times\else\texttimes\fi{} ${10}^{18}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. The data could be fitted by using classical lattice theory and Drude-type free-carrier theory with an energy-independent scattering time. The values of $N$ and mobility $\ensuremath{\mu}$ obtained from the fits agreed reasonably well with Hall and resistivity values. The agreement was not improved by the introduction of an energy-dependent scattering time for either polar-mode or ionized-impurity scattering. The plasmon-phonon minima were observed and their frequencies were found to be strongly influenced by $\ensuremath{\mu}$ as well as by $N$. The optical lattice parameters were determined as follows: ${\ensuremath{\epsilon}}_{s}=10.2$, ${\ensuremath{\epsilon}}_{\ensuremath{\infty}}=7.1$, ${\ensuremath{\omega}}_{t}=141$ ${\mathrm{cm}}^{\ensuremath{-}1}$, and $\ensuremath{\Gamma}=8.7$ ${\mathrm{cm}}^{\ensuremath{-}1}$. These results agree well with previous measurements.

Longitudinal optical phonon-plasmon coupling in GaAs

The longitudinal optical phonon-plasmon interaction theory of Varga has been used to explain the normal-incidence reflectivity of some doped GaAs samples. Varga's theory with phonon damping is more realistic over the whole region of wavelengths. The two wavelength minima predicted by Varga's theory have also been determined over the entire range of concentration and a good agreement with the experimental data is found. The effective-mass values have also been determined and a good comparison with the other values has been found.

Intervalley Transfer, Plasma Frequency, and Plasmon-LO-Phonon Interaction inn-Type Gallium Antimonide

A theoretical study is made of the effects of intervalley transfer on the plasma frequency and plasmon-LO-phonon interaction in highly doped $n$-type gallium antimonide. Because of the difference in masses between the central and secondary valleys, both the plasma frequency and the plasmon-phonon interaction undergo large changes when an appreciable transfer from the central to the secondary valleys occurs as a result of raising the temperature from 0\ifmmode^\circ\else\textdegree\fi{}K to room temperature.

Longitudinal Optical Phonon-Plasmon Coupling in CdS

The longitudinal optical phonon-plasmon interaction theory of Varga is shown to be applicable to Gadoped CdS through the region of the first reflectivity minumum (2.5 to about 30 μ). The theoretical reflectivity vs wavelength for several concentrations of Ga-doped CdS are compared with experiment. The agreement between theory and experiment is particularly good for high dopant concentrations. A plot of the wavelength at minimum reflectivity vs impurity concentrations shows that the Varga theory does well in explaining the data. When phonon damping is introduced into the Varga dielectric function, the reflectivity over the whole region of resonance is more realistic. Finite plasmon lifetime is not considered since no data are available for CdS.