Raman and photoluminescence investigations of disorder in ZnSe films deposited on n-GaAs

We report Raman and photoluminescence studies of ZnSe films deposited on a (100) $n$-GaAs substrate by pulsed laser deposition. We have investigated the disorder in the thin films of ZnSe by analyzing the asymmetry of the ZnSe LO modes. We find that the best fit of the line shape is obtained using the spatial correlation model and invoking the presence of a zone edge LO phonon. This zone edge LO phonon is attributed to the presence of disorder in the material. The intensity of this disorder activated zone edge phonon is found to correlate very well with the results of the crystal quality obtained from x-ray diffraction. In addition we have studied the variation of the depletion widths in the GaAs substrate as a function of the deposition parameters of ZnSe, using the intensity ratios of the LO and L_ modes of an $n$-GaAs substrate. We have also analyzed the origin of the deep center luminescence observed in these films. The information is found to be complementary and consistent with that obtained by Raman spectroscopy and the variations expected due to different deposition conditions.