X-ray analysis for micro-structure of AlN/GaN multiple quantum well systems
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The structural properties of AlN/GaN multiple quantum well (MQW) structures grown on c-plain sapphire substrate are studied by means of high-resolution X-ray diffraction (HRXRD). A new method to consider the influence of the depth variation of the dislocations density and well (barrier) thicknesses on the X-ray diffraction spectra was developed. The influence of the dislocation type on the diffraction peak broadening is based on the mosaic model of a crystal. The represented simulations of the experimental spectra are based on the dynamical theory of X-ray diffraction in agreement with the developed model. The calculations of X-ray diffraction spectra for AlN/GaN MQW considering the depth variation of dislocation density and layers thicknesses explain well the observed broadening and asymmetry of the satellites peaks of the measured spectra, especially for higher-order reflections. In addition, in this paper was demonstrated, that the commonly used Williamson–Hall plot analysis is consistent for MQW structures with the dislocations density > 1 × 108 cm−2. The developed methods allow fast and reliable determination of layers thicknesses, dislocations densities and strain profiles.
This work has been funded by the Program of Fundamental Researches of The National Academy of Sciences of Ukraine “Fundamental Problems of New Nanomaterials and Nanotechnologies”. Furthermore, the authors thank PhD Hryhorii V. Stanchu for useful discussions and critical reading of the manuscript.
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