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X-ray diffraction is one of the most popular experimental methods employed for determination of dislocation densities, as it can recognize both the strain fields and the local lattice rotations produced by dislocations. The main challenge of the quantitative analysis of the dislocation density is the formulation of a suitable microstructure model, which describes the dislocation arrangement and the effect of the interactions between the strain fields from neighboring dislocations reliably in order to be able to determine the dislocation densities precisely. The aim of this study is to prove the capability of X-ray diffraction and two computational methods, which are frequently used for quantification of the threading dislocation densities from X-ray diffraction measurements, in the special case of partially bunched threading dislocations. The first method is based on the analysis of the dislocation-controlled crystal mosaicity, and the other one on the analysis of diffuse X-ray scattering from threading dislocations. The complementarity of both methods is discussed. Furthermore, it is shown how the complementarity of these methods can be used to improve the results of the quantitative analysis of bunched and thus inhomogeneously distributed threading dislocations and to get a better insight into the dislocation arrangement. [ABSTRACT FROM AUTHOR]

In this article, we combine diffuse x-ray scattering with a Monte Carlo simulation method for the determination of the dislocation density in thin heteroepitaxial layers. As a model, we consider GaN epitaxial layers containing threading dislocations perpendicular to the surface. The densities of particular types of threading dislocations following from the comparison of measured and simulated distributions of diffusely scattered x-ray intensity are compared with the dislocation densities determined by etching. A good agreement was found. [ABSTRACT FROM AUTHOR]

Presents information on a study wherein a theory describing x-ray diffuse scattering from misfit dislocations in epitaxial layers was developed. Methods; Results; Discussion.

High-resolution X-ray diffraction in coplanar and noncoplanar geometries has been used to investigate the influence of an SiN x nano-mask in the reduction of the threading dislocation (TD) density of high-quality AlGaN epitaxial layers grown on sapphire substrates. Our developed model, based on a Monte Carlo method, was applied to the simulation of the reciprocal-space maps of a two-layer system. Good agreement was found between the simulation and the experimental data, leading to an accurate determination of the dislocation densities as a function of the overgrowth layer thickness. The efficiency of the SiN x nano-mask was defined as the ratio of the TD densities in the AlGaN layers below and above the mask. A significant improvement in the AlGaN layer quality was achieved by increasing the overgrowth layer thickness, and a TD density reduction scaling law was established. [ABSTRACT FROM AUTHOR]

Abstract: For the first time self-organized epitaxially grown semiconductor islands were investigated by a full three-dimensional mapping of the scattered X-ray intensity in reciprocal space. Intensity distributions were measured in a coplanar diffraction geometry around symmetric and asymmetric Bragg reflections. The 3D intensity maps were compared with theoretical simulations based on continuum-elasticity simulations of internal strains in the islands and on kinematical scattering theory whereby local chemical composition and strain profiles of the islands were retrieved. [Copyright &y& Elsevier]

Abstract: A statistical theory of X-ray scattering from dislocations oriented parallel or perpendicular to the surface in semiconductor thin film is presented. We apply this theory to two particular cases. At first, we derive formulae for diffusively scattered X-ray intensity from screw threading dislocations in GaN thin film in high-density approximation. Correlation in dislocation positions is involved in calculations. Diffuse X-ray scattering is calculated in case of PbTe thin films with various thicknesses in the second case. From the fit, the dislocation density was determined. [Copyright &y& Elsevier]

We used high-resolution x-ray reciprocal space mapping in noncoplanar grazing-incidence geometry for the determination of the density of edge threading dislocations in c-oriented GaN epitaxial layers and we compared the measured intensity distributions with results of numerical Monte Carlo simulations of diffuse scattering. We demonstrated that a combination of diffraction data taken in coplanar symmetric and noncoplanar grazing-incidence geometries makes it possible to obtain the densities of screw and edge threading dislocations. [ABSTRACT FROM AUTHOR]

Densities of Mn ions in epitaxial layers of (Ga,Mn)As were determined by anomalous x-ray diffraction, i.e., by a measurement of the dependence of the intensity of weak diffraction 002 on the photon energy around the Mn K absorption edge. From the measured data it was possible to determine the density of Mn ions in substitutional positions and the difference in the Mn densities in two possible interstitial positions in the GaAs lattice. The data demonstrate that the rate of the out-diffusion of the Mn interstitials from the Ga tetrahedrons significantly exceeds that from the As tetrahedrons. [ABSTRACT FROM AUTHOR]

Diffuse x-ray scattering from epitaxial layers with screw dislocations perpendicular to the surface is calculated assuming correlated dislocation positions. The resulting intensity distribution was compared with a reciprocal-space map measured in a symmetric diffraction from a hexagonal GaN(0001) layer, and a good correspondence was achieved. From the fit, both the dislocation density and their correlation length were determined. [ABSTRACT FROM AUTHOR]

Epitaxial growth of topological insulatorbismuth telluride bymolecular beam epitaxy onto BaF2(111) substrates is studiedusing Bi2Te3and Te as source materials. Bychanging the beam flux composition, different stoichiometric phasesare obtained, resulting in high quality Bi2Te3and Bi1Te1epilayers as shown by Raman spectroscopyand high-resolution X-ray diffraction. From X-ray reciprocal spacemapping, the residual strain, as well as size of coherently scatteringdomains are deduced. The Raman modes for the two different phasesare identified and the dielectric functions derived from spectroscopicellipsometry investigations. Angular resolved photoemission revealstopologically protected surface states of the Bi2Te3epilayers. Thus, BaF2is a perfectly suited substratematerial for the bismuth telluride compounds. [ABSTRACT FROM AUTHOR]