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