Estimation of Indium Composition in GaxIn1-xN/GaN Layers from V-Pit Diameter Measurements

Threading dislocations in Ga _x In _1−x N/GaN heterostructures give rise to the formation of V-pits, which act as effective strain-relief centers by redistributing elastic stress along their inclined facets. The geometry and size of these V-pits therefore directly reflect the strain state of the epilayer and its dependence on indium composition and layer thickness. Building on this physical understanding, we present a practical method to estimate the indium composition (x) in Ga _x In _1−x N/GaN layers by measuring the diameter of V-pits from microscopy images and using the layer thickness obtained from growth parameters. V-pits, which are inverted hexagonal pyramidal defects originating at threading dislocations, play a key role in strain relaxation in GaInN/GaN epilayers. Based on theoretical considerations and published experimental data, an empirical relation is developed that links V-pit diameter and layer thickness to indium composition. The relation follows a hyperbolic-type dependence, consistent with the gradual and saturating nature of strain relaxation mediated by V-pit formation. Validation against literature data obtained from X-ray reciprocal space mapping, transmission electron microscopy, and scanning electron microscopy shows good agreement between predicted and measured compositions. Contour and three-dimensional representations derived from the model allow rapid estimation of the indium composition once the V-pit diameter and layer thickness are known, eliminating the need for high-resolution X-ray diffraction measurements. The approach is applicable to layers grown under comparable growth temperatures and substrate dislocation densities to those used for calibration, and offers a fast, non-destructive methodology for process monitoring and optimization in GaInN/GaN -based devices, including LEDs, HEMTs, and solar cells.