A Complete Crystallographic Study Of Gan Epitaxial Morphologies In Selective Area Growth By Hydride Vapour Phase Epitaxy (sag-hvpe)

摘要

GaN structures have been fabricated by selective area growth by hydride vapour phase epitaxy (SAG-HVPE) on parallel stripes-patterned equivalent <1100> sapphire and <1120> GaN/sapphire substrates, and on parallel stripes-patterned <1120> sapphire and < 1100 > GaN/sapphire structures. The growth morphologies of the GaN stripes were systematically investigated by scanning electron microscopy (SEM). HVPE-GaN layers exhibit (0001), (1100) and (1101) or (2203) facets on <1120> GaN/sapphire substrates, while on the equivalent < 1100 > sapphire direction only (0001) and (1100) facets coexist. On the <1100> GaN/sapphire substrate direction, (0001), (1122) and (3362) facets compose the growth structures. Special emphasis was paid to the analysis of the crystal growth mechanisms. A crystallographic tool was developed to calculate the facets growth rates, the condensation surfaces and the surface recovered by GaN stripe in order to establish a correlation between the growth morphologies and the experimental conditions. It is shown that the growth rates of the facets, and so the morphologies, depend on the variations of the H_2 ratio in the total flow rate.