In this paper, we investigate the structural properties of AlGaN/GaN heterostructures grown by metal organic chemical vapor deposition on sapphire substrates with different thicknesses using high-resolution x-ray diffraction and Raman scattering methods. We discuss the microscopic nature of spatial-inhomogeneous deformations and dislocation density in the structures. Microdeformations within mosaic blocks and the sizes of regions of coherent diffraction are determined. We reveal a gradient depth distribution of deformations in the mosaic structure of nitride layers, as well as at the interface regions of the sapphire substrate on the microscale level using confocal micro-Raman spectroscopy. We determine that an increase in substrate thickness leads to a reduction in dislocation density in the layers and an increase in the elastic deformations. The features of the block structure of nitrides layers are shown to have a significant influence on their elastic properties.

Molecular beam epitaxy growth of multilayer In x Ga 1-x As/GaAs(001) structures with low indium content (x = 0.20-0.35) was studied by X-ray diffraction and photoluminescence in order to understand the initial stage of strain-driven island formation. The structural properties of these superlattices were investigated using reciprocal space maps, which were obtained around the symmetric 004 and asymmetric 113 and 224 Bragg diffraction, and x/2h scans with a high-resolution diffractometer in the triple axis configuration. Using the information obtained from the reciprocal space maps, the 004 x/2h scans were simulated by dynamical diffraction theory and the in-plane strain in the dot lattice was determined. We determined the degree of vertical correlation for the dot position (''stacking'') and lateral composition modulation period (LCM) (lateral ordering of the dots). It is shown that initial stage formation of nanoislands is accompanied by LCM only for [110] direction in the plane with a period of about 50 to 60 nm, which is responsible for the formation of a quantum wire like structure. The role of In x Ga 1-x As thickness and lateral composition modulation in the formation of quantum dots in strained In x Ga 1-x As/GaAs structures is discussed.

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Molecular beam epitaxy (MBE) grown In0.5Ga0.5As/GaAs multilayer structures with quantum dots chains (QDs), obtained under different growth conditions, were investigated by high‐resolution X‐ray diffractometry (HRXRD) and AFM. It was determined that self‐organized epitaxial growth of In0.5Ga0.5As/GaAs can lead to the formation of three‐dimensional quantum‐dot crystals with triclinic (distorted cubic) unit cell. The mechanisms of QDs ordering in dependence on As flux are analyzed.

Lateral ordering of InGaAs quantum dots on the GaAs (001) surface has been achieved in earlier reports, resembling an anisotropic pattern. In this work, we present a method of breaking the anisotropy of ordered quantum dots (QDs) by changing the growth environment. We show experimentally that using As(2) molecules instead of As(4) as a background flux is efficient in controlling the diffusion of distant Ga adatoms to make it possible to produce isotropic ordering of InGaAs QDs over GaAs (001). The control of the lateral ordering of QDs under As(2) flux has enabled us to improve their optical properties. Our results are consistent with reported experimental and theoretical data for structure and diffusion on the GaAs surface.