X-ray diffraction analysis of GaN and GaN/InGaN/GaN double-hetero structures grown on sapphire substrate by metalorganic chemical vapor deposition

The structural properties of the GaN layers and the GaN/InGaN/GaN double-hetero (DH) structures grown on sapphire (001) substrate using the metalorganic chemical vapor deposition (MOCVD) method were investigated using a high-resolution X-ray diffraction technique and transmission electron microscopy. Two experimental results were obtained. First, in the case of a single GaN layer, a transition of th film structure from grains, with relatively independent orientations at a thickness of 0.35 mu m, to a uniform film with a mosaic structure at a thickness of 1.4 mu m, occurred. Second, in the case of a DH structure, we observed an increased mosaicity of both the InGaN and the capping-GaN layers as the InGaN film thickness increased from 20 nm to 110 nm. This increase in the degree of mosaicity also leads to dislocations.