Photoluminescence and cathodoluminescence studies of stoichiometric and oxygen-deficient ZnO films

Photoluminescence and cathodoluminescence ~CL! spectra of stoichiometric and oxygen-deficient ZnO films grown on sapphire were examined. It was found that the intensities of the green and yellow emissions depend on the width of the free-carrier depletion region at the particle surface; the thinner the width, the larger the intensity. Experimental results and spectral analyses suggest that the mechanism responsible for the green ~yellow! emission is the recombination of a delocalized electron close to the conduction band with a deeply trapped hole in the single ionized oxygen vacancy Vo 1 ~the single negatively charged interstitial oxygen ion Oi ) center in the particle. © 2001 American Institute of Physics. @DOI: 10.1063/1.1361288#