Raman and photoluminescence investigations of impurities in zinc-rich ZnxCd1−xSe

Thin films of zinc-rich ZnxCd1−xSe were grown on GaAs substrate using metal-organic-chemical-vapor-deposition (MOCVD) technique. Bound-longitudinal-optical (B-LO) phonon modes in the first-order and higher-order Raman spectra of ZnxCd1−xSe have been observed for the first time. Presence of these phonon modes are ascribed to impurities in the sample incorporated from the substrate. The modes are explained within the purview of a model used earlier for bound modes in GaP. Photoluminescence spectroscopy also reveals a deep energy band which suppresses the near band edge emission for x = 0.8, an alloy composition for which B-LO phonons are observed.