Optical phonon behaviors in ZnGeP2 single crystals from temperature dependent far-infrared reflectance spectra

Lattice vibration behaviors of ZnGeP2 single crystals derived from the far-infrared (FIR) reflectance spectra in the temperature range of 4–300 K are reported in this study. Dielectric permittivity dispersion is obtained for the polarization along the a- and c-axes of a single crystal. Phonon modes are described by the Lorentz oscillator model. Temperature dependence of the parameters of Lorentz oscillator model and their influence on the imaginary dielectric permittivity dispersion is discussed. Optical phonon behaviors are ascribed to thermal expansion of the lattice.