The growth of GaN from solution in Ga under high N2 pressure resulted in very low-dislocation density (<100/cm2) crystals usually in the form of hexagonal platelets, but of size limited to 1cm (lateral) and 100μm (thickness). Nevertheless, even with such small and thin substrates, the blue–violet lasers with optical power as high as 100 to 200mW were reproducibly constructed. Deposition of GaN by HVPE on the pressure grown plate-like or needle-like crystals allows stable crystallization (in terms of flatness of the crystallization front and uniformity of the new grown material) at a rate of about 100μm/h on both types of seeds. For the needle-like seeds, stable crystallization by HVPE was possible also in multiple growth processes resulting in bulk prismatic crystals with diameter exceeding 5mm. The crystallization by HVPE on the high-pressure seeds was analyzed with the use of defect selective etching and X-ray data for thick (a few mm) platelets grown on the plate-like seeds, prismatic bulk crystals grown on needle-like seeds and the cross-section samples sliced from the bulk material in different crystallographic orientations. The results of application of the new grown material for epitaxial growth of quantum structures in both polar and non-polar directions, was shortly reported.

Crystallization of Low Dislocation Density GaN by High-Pressure Solution and HVPE Methods. I.Grzegory, B.Łucznik, M.Boćkowski, S.Porowski: Journal of Crystal Growth, 2007, 300[1], 17-25