Structural and luminescent properties of ZnTe film grown on silicon by metalorganic chemical vapor deposition

Reported here are the structural and luminescent properties of ZnTe films grown on Si substrates by metalorganic chemical vapor deposition (MOCVD). ZnO intermediate layers annealed at different temperature are employed to buffer the thermal and chemical difference between the ZnTe epilayers and silicon substrates. With increasing the annealing temperature of ZnO buffer layer, the crystallization of ZnTe assessed by x-ray diffraction is improved. Temperature dependent photoluminescence (PL) of the ZnTe epilayer is processed to evaluate the optical properties of our samples. The PL spectra are characterized by an asymmetry line shape labeled E, and it can be dissolved into two Gaussian lines with energy discrepancy of about 18.5 meV. The origins of these two Gaussian lines are thought to be free and bound excitons emission, respectively. The dependence of luminescence on temperature indicates that the emission from bound excitons dominates the spectrum below 157 K. While above 157 K, the bound excitons are detrapped to become free excitons, and free excitons emission becomes dominant. Also, the broadening of the emission line resulting from the ionized impurity scattering cannot be neglected above 157 K. Temperature dependence of the full width at half maximum and peak energy of the spectra can be comprehended well under the framework of the two-dissociation-process theory, which, in turn, further strengthens the validity of the origin of the spectra. (C) 2002 American Vacuum Society.