Raman scattering and temperature-dependent photoluminescence properties of CdS/GaAs epilayers grown by hot-wall epitaxy

Hexagonal-structured CdS/GaAs epilayers were grown by the hot-wall epitaxy method. From the Raman spectrum, we found that the exciton-phonon coupling is deeply related to the dimensionality. The optical properties attributed to the thermal quenching phenomenon of CdS were studied through photoluminescence (PL) measurements as a function of temperature. With an increase in the temperature, PL intensities of free excitons were exponentially reduced and their spectral width showed a tendency to broaden. This tendency is related to the phonons generated by the lattice vibration of the host material in CdS. These findings led us to conclude that the phonons may be participating in the quenching process. Also, the temperature dependence of the band gap energy of CdS was well interpreted by E-g(T) = 2.5684 - (5.4 x 10(-4))T-2/(258.8 + T).