Ammonothermal growth of high-quality GaN crystals on HVPE template seeds

High quality GaN crystals have been successfully grown by the ammonothermal method in alkaline ammonia solutions using hydride vapor phase epitaxy (HVPE) seeds. The grown crystals, over 1 mm thick, are clear and possess excellent structural and optical properties. The crystalline structure of the as-grown bulk GaN is as good as, or better than the HVPE seeds as measured by high resolution X-ray rocking curves with 100 arcsec of full width at half maximum (FWHM) on (0 0 2) and 90 arcsec on (1 0 2) diffractions. The crystal quality is improved through a process of careful seed selection and controlled heating during nucleation, so that the ammonothermal growth replicates the seed crystals on both the nitrogen and gallium faces. The results are confirmed by low temperature photoluminescence spectra resolving donor-bound and free excitons as well as multiple phonon replicas, and further by room temperature cathodoluminescence indicating reduced yellow-band emission. Successful growth of high quality GaN crystals on HVPE seeds will facilitate the scale-up to large area growth by use of large area GaN HVPE templates as seeds.