Crystallization of low dislocation density GaN by high-pressure solution and HVPE methods

Abstract

The growth of GaN from solution in gallium under high N 2 pressure results in very low-dislocation density (<100 cm −2) crystals usually in the form of hexagonal platelets, but of size limited to 1 cm (lateral) and 100 μm (thickness). Nevertheless, even with such small and thin substrates, the blue–violet lasers with optical power as high as 100–200 mW are 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 100 μm/h on both types of seeds. For the needle-like seeds, stable crystallization by HVPE is possible also in multiple growth processes resulting in bulk prismatic crystals with diameter exceeding 5 mm. The crystallization by HVPE on the high-pressure seeds is analyzed with the use of defect selective etching and X-ray data for thick (a few of 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, is shortly reported.