Fundamental and second-order phonon processes in CdTe and ZnTe

Fundamental and higher-order photon-phonon interactions dominate the far infrared absorption and dispersion spectrum of most semiconductors and dielectrics. We present a detailed investigation of the temperature dependence of the dielectric function of the important II-VI semiconductors CdTe and ZnTe in the frequency range below 3 THz, between 10 and 300 K. From the dielectric function we determine the temperature dependence of the fundamental trans verse-optical (TO) frequency in CdTe and ZnTe as well as the TO phonon damping rate in CdTe, and the dynamic ionic charge of both crystals is infer-red from the measurements. Furthermore, our experimental data enable unambiguous assignment of low-frequency absorption bands to sum and difference combinations of fundamental phonon modes at critical points away from the Brillouin zone center.