GaN films were grown on silica substrates by metalorganic chemical vapor deposition as a function of film thickness. It was found that yellow luminescence (YL) emission increased as the (10 1 1) atomic facets became dominant. It was assumed that gallium vacancies and impurity complexes on the atomic facets of (10 1 1) were responsible for the YL emissions. Furthermore, the YL emitters were not concentrated near the interface between the substrate and the film but distributed through the entire film. (C) 2003 Elsevier Science B.V. All rights reserved.