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

Photoluminescence and cathodoluminescence (CL) spectra of stoichiometric an d 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 t he width, the larger the intensity. Experimental results and spectral analy ses 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 V-o(+) (th e single negatively charged interstitial oxygen ion O-i(-)) center in the p article. (C) 2001 American Institute of Physics.