Characterization of Ill-V heterostructures grown by selective-area epitaxy using double-crystal X-ray diffractometry with high lateral resolution

X-ray diffraction studies were performed on different Ill-V heterostuctures grown by planar and embedded selective area epitaxy (SAE) using metal-organic vapour phase epitaxy (MOVPE) and metal-organic molecular beam epitaxy (MOMBE). In order to characterize the heterostructures at the boundaries of masked areas, a convergent-beam double-crystal X-ray diffractometer for laboratory X-ray sources was developed, allowing rocking curve measurements with high lateral resolution. The X-ray beam was focused onto the sample as a line focus by means of a cylindrically curved mirror. A position-sensitive proportional counter was used for the parallel recording of rocking curves along the line focus, resulting in a spatial resolution of 20 mu m*50 mu m. With this set-up rocking curve measurements across the growth/non-growth boundaries of selectively grown heterostructures were performed. These measurements indicate compositional changes in a region of 100 mu m at the boundaries of layers grown by SAE using MOVPE. The changes for MOMBE grown SAE are on a scale of only a few micrometres and are not resolved with this system.