ABSTRACT
The effect of nucleation morphology on GaN epilayer structural characteristics has been investigated, as these are revealed by both symmetric and asymmetric x-ray diffraction rocking curve scans. Heteroepitaxially grown GaN layers contain threading dislocations of considerable density and are commonly described in terms of the model of the mosaic crystal. For the case of parameter optimization in GaN annealing experiments, structural evaluation using only symmetric x-ray rocking curves is not a safe method. Anneal time was the only variable for the deposition of the nucleation layers (NL) and was chosen to span the time-temperature transformation space. NL-a is an as grown layer and is provided for comparison. The histogram of NL-b clearly shows an evolving ripening process; the distribution of nuclei size broadens and moves to higher grain sizes. Ripening has progressed further in NL-c where a bimodal-like distribution is evident.
