Far-infrared reflectance study of coupled longitudinal-optical phonon-hole plasmon modes and transport properties in heavily doped p-type GaAs

We measured room-temperature far-infrared reflectance spectra of ten p-type, Be-doped, molecular-beam-epitaxy-grown GaAs films with hole densities from 6.3 x 10(17) to 2.9 x 10(19) cm(-3) and examined the frequency-dependent dielectric function of coupled phonon-heavily damped hole plasmon modes in these samples without the complications that arise in Raman scattering experiments. Both a two-oscillator dielectric function epsilon(omega), and Kukharskii's factorized form epsilon(K)(omega) for the dielectric function, reproduce the data well. The plasmon-like modes clearly appear in the reflectance spectra, although they are suppressed in the Raman spectra, and we find that their frequencies are best given by finding the solutions of epsilon(omega)=0 in the complex omega-plane. The infrared data also accurately yield the hole drift mobilities when we consider values for the Hall scattering factor in p-type GaAs.