Light scattering by a multicomponent plasma coupled with longitudinal-optical phonons: Raman spectra ofp-type GaAs:Zn

Abstract

The LO-phonon\char21{}hole-plasmon coupling is investigated for $p$-type III-V semiconductors. Due to a large carrier damping, only one coupled LO-phonon\char21{}plasmon mode (CPPM) appears. Expressions for the theoretical Raman scattering efficiency of a multicomponent plasma are derived in the random phase approximation. They take into account wave-vector-dependent intraband transitions within the heavy- and light-hole bands as well as interband transitions between them. Finite lifetime effects were included in a generalized Mermin approximation. The theoretical band shapes of the CPPM at different temperatures are compared with Raman measurements of Zn-doped $p$-type GaAs in the hole concentration range ${p=10}^{17}$\char21{}${10}^{20}$ ${\mathrm{cm}}^{\ensuremath{-}3}.$ At low temperatures the contribution of the interband transitions cannot be neglected in the frequency range of the CPPM, resulting in a mode broadening. Agreement between the theoretical band shapes and the Raman spectra is obtained without any fit parameter if the hole concentration $p$ and the mobility $\ensuremath{\mu}$ are derived from the measured Hall values ${p}_{H}$ and ${\ensuremath{\mu}}_{H}$ evaluated on the basis of a two-band model of the conductivity. Raman measurements of the CPPM in Zn-doped $p$-type GaP show a different temperature dependence, which is explained by the different ratio of the light- to the heavy-hole effective mass on the interband transitions.