GaN structures have been fabricated by selective area growth by hydride vapour phase epitaxy (SAG-HVPE) on parallel stripes-patterned equivalent < 1 (1) over bar 0 0 > sapphire and < 1 1 (2) over bar 0 > GaN/sapphire substrates, and on parallel stripes-patterned < 1 1 (2) over bar 0 > sapphire and < 1 (1) over bar 0 0 > GaN/sapphire structures. The growth morphologies of the GaN stripes were systematically investigated by scanning electron microscopy (SEM). HVPE-GaN layers exhibit (0 0 0 1), {1 1 (1) over bar 0 0} and {1 (1) over bar 0 1} or {2 (2) over bar 0 3} facets on < 1 1 (2) over bar 0 > GaN/sapphire substrates, while on the equivalent < 1 (1) over bar 0 0 > sapphire direction only (0 0 0 1) and {1 (1) over bar 0 0} facets coexist. on the < 1 (1) over bar 0 0 > GaN/sapphire substrate direction, (0 0 0 1), {1 1 (2) over bar 2} and {3 3 (6) over bar 2} 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. (C) 2009 Published by Elsevier B.V.