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

Abstract

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.