ZnO is a promising material for light emitters in the UV region. For MOCVD growth no well-suited O-precursor is available. Three different high-purity oxygen precursors. i.e. iso-propanol. acetone. and N2O were tested for the growth of ZnO on GaN/Si(1 1 1) template. For iso-propanol pre-reactions are observed influencing the growth rate and limiting the growth temperature to below 500 degreesC. Best layer quality is obtained around 450 degreesC at 300 mbar reactor pressure and a VI-II ratio larger than 40. ZnO grown in a similar growth regime but using acetone Lis O-precursor exhibits a surface constructed from nanometer sized filaments. Most of the acetone-grown films have growth orientations of (1 0 1 1). Using N2O higher growth temperatures Lire needed due to the poor decomposition of this gas. However, no prereactions are observed and (0 0 0 2) oriented layers with good X-ray omega-scans at ZnO-positions can be obtained around 800 degreesC at 300 mbar and a VI-II ratio above 600. (C) 2002 Elsevier Science B.V. All rights reserved.