The two-dimensional growth and dislocation density of GaN epilayer were studied by using single-buffer layer and double-buffer layers grown on sapphire (00•1) by radio frequency plasma assisted molecular beam epitaxy. The double-buffer layers consist of two buffer layers deposited at 2 different temperatures T1 and T2 (T2>T1), and the high temperature annealing was performed after the buffer layer growth at T1. The surface morphology was observed by atomic force microscope, and the 2-dimensional growth of GaN epilayer was characterized by ω-scan rocking curve of X-ray diffraction. It was found that the root-mean-square roughness was decreased obviously and the full-width at half maximum of ω-scan rocking curve was reduced drastically when the GaN double-buffer layers were used. The dislocation density of the GaN epi-layer grown on double-buffer layers, which was estimated by two-dimensional triple axes mapping of X-ray diffraction measurement, was only a half as compared with that grown on single-buffer layer. It was shown that the quality of GaN epilayer was improved by using double-buffer layers.

Investigation of Dislocation Density of GaN with Single- and Double-Buffer Layer Grown on Sapphire (0001) by RF-Plasma Assisted MBE. Z.Zhao, M.Qi, A.Li: Materials Science and Engineering B, 2002, 95[3], 308-13