Estimating the Crystallographic Structure of AlGaN/GaN Heterostructure Buffer Layers Using Symmetric and Asymmetric X-ray Schemes

The possibility of using symmetric and asymmetric X-ray schemes on an XMD-300 single-crystal diffractometer to estimate the crystal structure of AlGaN/GaN heterostructure buffer layers is investigated. The developed algorithm for calculating the angles of incidence of a primary X-ray beam, angles of emergence of the diffracted beam to the AlN/GaN/Al2O3 heterostructure surface, and diffraction angles for certain crystallographic planes of these materials allows us to obtain reflections from the $$(10\bar {1}4),$$ $$(10\bar {1}3),$$ and $$(11\bar {2}2)$$ planes, which lie at angles to the surface. A study of the $$11\bar {2}2$$ reflection shows that the crystal lattice of the transition layer between the Al2O3 substrate and bulk GaN buffer layer is turned to the basal plane normal by an azimuthal angle of 30°. The embedding of С and Fe to the GaN buffer layer during a certain chosen growth process leads to a change in the GaN crystal structure, specifically, to the filling of vacant tetrapores through which the $$(10\bar {1}3)$$ plane passes.