Anharmonic phonon decay in CdSe_xTe_1-x compound thin films

Resonant Raman scattering experiments were employed to investigate composition dependence of exciton-phonon coupling and anharmonic phonon decay in CdSexTe1-x thin films with x values between 0 and 1. The energy variations of the CdTe- and CdSe-like longitudinal optical phonons (LO) with compositions were found to be well described by the random-element isodisplacement model. Frohlich interaction was enhanced in CdSexTe1-x films with x values of similar to 0.2, and strong additive combination phonons mLO(1) + nLO(2) have been observed, here, m and n are integers describing Raman scattering orders. The experimental results demonstrate that the anharmonic decay of the additive combination LO1 + LO2 mode was dominated by the cascade relaxation process, namely, the decay can be described by successive decaying of the individual LO1 and LO2 modes. Transverse acoustical phonon (TA), whose phonon density of states varies rapidly with alloy composition, played critical role in the anharmonic decay for the CdSexTe1-x films with different compositions.