Effects of spatial dispersion in the temperature dependence of the optical absorption in ZnSe heteroepitaxial layers and CdTe and ZnTe crystals

The absorption-edge spectra have been studied in the temperature range from 4 to 300 K for single-crystals of CdTe, ZnTe and heteroepitaxial layers of ZnSe. In all cases the frequency integrated absorption coefficient K is found to increase monotonously with temperature T up to T = T* and keeps constant above T*. The temperatures T*, depending on semiconducting materials, might be considered as critical ones corresponding to a change in polaritonic energy transport mechanism due to the lack of spatial dispersion at T > T*. The temperature dependence of K gives the possibility to calculate oscillator strengths or longitudinal-transverse splitting Delta(LT) as 0.45, 0.65 and 1.6 meV for CdTe, ZnTe and ZnSe, respectively.