Raman scattering and terahertz spectroscopic characteristics of longitudinal optical phonons in i-GaAs/n-GaAs epitaxial structures

We have investigated longitudinal optical phonons (LO) characteristics in i-GaAs/n-GaAs epitaxial structures. The LO phonons and LO phonon-plasmon coupled modes were observed in the Raman scattering spectra, whereas only the coherent LO phonon was detected in terahertz spectroscopy. We conclude that the initial polarization is responsible for emission of the co-herent-LO-phonon terahertz wave.