CHARACTERIZATION OF ALN BUFFER LAYERS ON (0001)-SAPPHIRE SUBSTRATES

It is now established that low-temperature grown buffer layers are nee ded to improve the structural and electronic properties of GaN layers grown on sapphire. We studied the recrystallization of AIN buffer laye rs grown by low-pressure MOVPE as a function of annealing time. The Wa rren-Averbach method was applied to the analysis of broadening and lin e shape of the (0 0 0 2) and (0 0 0 4) X-ray diffraction peaks. This m ethod yielded a separation of the grain size distribution from microst rain effects. The evolution of the relative frequency distribution of the grain size with annealing is correlated with atomic force microsco py experiments. The distribution of the reflecting-planes orientation was determined by X-ray rocking-curve experiments, (C) 1998 Elsevier S cience B.V. All rights reserved.