Abstract
The important role of the surface morphology of the CVD grown GaN buffer layer in the epitaxy of GaN film on Al 2 O 3 (0001) was studied by x-ray diffraction at different buffer layer growth temperatures. The results show that the buffer layer grown at lower temperature resulting in a smoother surface provides a good basis for growing a good working GaN films. While the buffer layers grown at higher temperatures have better crystalline qualities, such as smaller rocking curve widths, high diffraction intensities and longer coherent lengths, consequently grow into worse epitaxial GaN films owing to the highly rough surfaces on the top of buffer layers. © 2012 The Physical Society of the Republic of China.