GaN epitaxial layers and nitride-based multiquantum well light emitting diode (LED) structures with conventional single GaN buffer and GaN/SiN double buffers were prepared by metalorganic chemical vapor deposition. It was found that we could reduce defect density and thus improve crystal quality of the GaN epitaxial layers by using GaN/SiN double buffers. It was also found that we could use such a GaN/SiN double buffer to achieve more reliable nitride-based LEDs. (C) 2003 Elsevier Ltd. All rights reserved.