Structural Properties and Photoluminescence Study of CdSe/Si Epilayers Deposited by Laser Ablation

Structural and optical characterization of CdSe thin films deposited by laser ablation technique on silicon (100)- and (111)-oriented substrates are reported. The effect of the substrate orientation on the growth and luminescence features of the two types of epilayers are investigated. Photoluminescence spectra of CdSe films measured from 10 up to 300 K and as a function of the laser excitation intensity give detailed information on the extrinsic levels localized in the forbidden gap. Temperature dependence of the energy of the n = 1 exciton line has been fitted by the Varshni's equation and by an expression containing the Bose-Einstein occupation factor for phonons. Parameters related to the electron-phonon interaction have been obtained. Temperature dependence of the broadening of exciton linewidth has been studied in terms of an expression containing both exciton-optical phonon and exciton-acoustic phonons coupling constants. Evaluated fitting parameters have shown the dominant contribution of optical phonons in mechanism of the exciton line broadening.