Alternative regimes for the growth of GaN/InGaN quantum wells in a close coupled showerhead reactor have been investigated and their respective merits discussed. State-of-the-art characteristics have been seen from the best structures using 300 and 6 K photoluminescence, high-resolution X-ray diffraction. atomic force microscopy and transmission electron microscopy to characterize the material, The fabrication of high-quality electroluminescent devices from selected structures has shown the practical relevance of these studies, (C) 2002 Elsevier Science B.V. All rights reserved.