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Abstract: The synthesis of GaN by selective area growth using Hydride Vapor Phase Epitaxy (SAG-HVPE) is reported for stripes patterned along and GaN on c-plane sapphire substrates. A systematic control of the GaN morphologies was carried out by both cross-sectional and surface Scanning Electron Microscopy (SEM). A complete HVPE cartography of GaN-SAG revealed domains of zero growth rates at high concentration of hydrogen in the carrier gas. The determination of the mechanisms that govern the growth of GaN morphologies was particularly emphasized. A theoretical model based on thermodynamic and kinetic analyses of the grown (0001) GaN layers was discussed, in combination with experiments on unmasked (0001) GaN and patterned GaN/c-plane sapphire substrates. Long HVPE runs were performed to demonstrate that the prevailing growth mechanism, for high hydrogen concentration in the carrier gas, is a mechanism based on a dechlorination by GaCl2 gas species. This mechanism leads to growth blockade of GaN growth and constitutes a very interesting issue for shaping GaN material as an alternative to top-down micro- and nano-technologies. [Copyright &y& Elsevier]

Abstract: GaN structures have been grown by selective area growth (SAG) in an atmospheric hydride vapour phase epitaxy (HVPE) reactor on c-plane sapphire and metal organic vapour phase epitaxy (MOVPE) grown GaN/c-plane sapphire substrates. The substrates were patterned in two perpendicular crystallographic directions 〈11−20〉 and 〈1−100〉. The growth morphologies of the GaN stripes were systematically investigated by scanning electron microscopy (SEM). A complete cartography of GaN SAG was established, after varying the growth temperature and the V/III ratio on both types of substrate. The cartography permits to fix the appropriate parameters for growing GaN quasi-substrates or GaN nano-structures with controlled morphology. [Copyright &y& Elsevier]

Abstract: GaN structures have been fabricated by selective area growth by hydride vapour phase epitaxy (SAG-HVPE) on parallel stripes-patterned equivalent 〈11¯00〉 sapphire and 〈112¯0〉 GaN/sapphire substrates, and on parallel stripes-patterned 〈112¯0〉 sapphire and 〈11¯00〉 GaN/sapphire structures. The growth morphologies of the GaN stripes were systematically investigated by scanning electron microscopy (SEM). HVPE-GaN layers exhibit (0001), {11¯00} and {11¯01} or {22¯03} facets on 〈112¯0〉 GaN/sapphire substrates, while on the equivalent 〈11¯00〉 sapphire direction only (0001) and {11¯00} facets coexist. On the 〈11¯00〉 GaN/sapphire substrate direction, (0001), {112¯2} and {336¯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 H2 ratio in the total flow rate. [Copyright &y& Elsevier]

Abstract: GaN layers have been grown on patterned c-plane (0001) sapphire and (0001) GaN Metal Organic Vapour-Phase Epitaxy (MOVPE)/sapphire substrates by Hydride Vapour-Phase Epitaxy (HVPE) using the epitaxial lateral overgrowth (ELO) process in a single HVPE reactor. The crystal growth mechanisms via the lateral and vertical extensions were analysed with respect to the theoretical results based on the phenomenological model. The best experimental conditions supporting a high lateral extension were deduced. Coalescence of growth structures was favoured and high-quality uniform GaN layers about 10μm thick were successfully grown directly on low-cost sapphire substrates. The properties of GaN layers were systematically investigated by scanning electron microscopy (SEM). GaN films exhibited a mirror-like surface without defects through the thickness. [Copyright &y& Elsevier]