Regensburg 2025 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 15: Crystal Structure Defects / Real Structure / Microstructure
KFM 15.8: Vortrag
Donnerstag, 20. März 2025, 11:45–12:00, H9
Dislocation correlations in GaN epitaxial films revealed by EBSD and XRD — •Domenik Spallek, Vladimir M. Kaganer, Philipp John, Oliver Brandt, and Jonas Lähnemann — Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany
Threading dislocations in group-III nitrides are omnipresent and are a challenge especially in heteroepitaxial growth for device applications. However, the correlation of individual dislocations with each other and the resulting screening of the strain is often disregarded although it is a necessity to describe elastic energies in an extended crystal.
In this study, two GaN epitaxial layers with threading dislocation densities (TDD) of 5× 108 cm−2 and 1.8× 1010 cm−2 are investigated by x-ray diffraction (XRD) and high-resolution electron backscatter diffraction (HR-EBSD), complemented by Monte Carlo simulations to model and interpret the experimental results.
While the XRD measurement directly gives quantitative results about the average strain in the illuminated area, a cross-correlation analysis of Kikuchi patterns results in spatially-resolved maps for the components of the strain and rotation tensors. Through an analysis of the strain-strain correlation functions for the measured and simulated maps, it is found that the spatial resolution in the HR-EBSD maps is highly anisotropic. Furthermore, we discover that the strain is significantly underestimated for higher dislocation densities. As main result, the screening distances for dislocations were determined as 2 µm and 0.3 µm for the sample with the lower and higher TDD, respectively.
Keywords: Gallium nitride; Dislocations; Dislocation correlation; Electron backscatter diffraction; X-ray diffraction