Examining the relationship between growth methods and defect structures in GaN (0001) substrates using Bragg diffraction imaging

This study compares defect structures of GaN substrates grown by ammonothermal and HVPE methods using either foreign or native seeds. Advanced characterization techniques, including Lang x-ray topography, rocking curve imaging, etching, and ToF-SIMS, were used. GaN crystals grown on native seeds, both Am-GaN and HVPE-GaN, showed a strong Borrmann effect and low lattice distortion (2–3 arcsec), indicating high structural quality. In contrast, substrates grown on foreign seeds exhibited a mosaic structure and high dislocation densities, with distortions up to 20 arcsec. The results highlight that using native seeds is essential for producing high-quality, low-defect GaN substrates.