Study of threading dislocation density reduction in AlGaN epilayers by Monte Carlo simulation of high-resolution reciprocal-space maps of a two-layer system

High‐resolution X‐ray diffraction in coplanar and noncoplanar geometries has been used to investigate the influence of an SiNx 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 SiNx 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.