X-ray analysis for micro-structure of AlN/GaN multiple quantum well systems

Abstract

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.