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The hydride vapor phase epitaxy (HVPE) process exhibits unexpected properties when growing GaN semiconductor nanowires (NWs). With respect to the classical well-known methods such as metal organic vapor phase epitaxy and molecular beam epitaxy, this near-equilibrium process based on hot wall reactor technology enables the synthesis of nanowires with a constant cylinder shape over unusual length. Catalyst-assisted HVPE shows a record short time process (less than 20 min) coupled to very low precursor consumption. NWs are grown at a fast solidification rate (50 μm h−1), facilitated by the high decomposition frequency of the chloride molecules involved in the HVPE process as element III precursors. In this work growth temperature and V/III ratio were investigated to determine the growth mechanism which led to such long NWs. Analysis based on the Ni–Ga phase diagram and the growth kinetics of near-equilibrium HVPE is proposed. [ABSTRACT FROM AUTHOR]

Hydride Vapor Phase Epitaxy (HVPE) growth process is still efficient for the growth of high quality GaN material. In situ-characterization techniques are extremely difficult to implement inside HVPE hot wall reactors. A method based on selective area growth coupled to spatially resolved optical spectroscopies, micro-photoluminescence and micro-reflectivity is developed for a control of GaN optical quality and strain at different growth stages. As highly reproducible HVPE process is used with a two-step epitaxial lateral overgrowth procedure to produce 80 µm thick GaN layers presenting a weak residual strain with high optical quality comparable to free-standing GaN layers. [ABSTRACT FROM AUTHOR]

GaN nanorods (NRs) with exceptional crystal-defined morphologieswere grown by near-equilibrium hydride vapor phase epitaxy (HVPE)on c-plane sapphire (0001) and silicon (111) substrates. Hexagonalfaceted individual, bunched, and hyperbunched GaN NRs were synthesizedby using a catalyst-free process. GaN NRs with a diameter in the rangeof 125–700 nm and a length in the range of 0.9–3 μmwere grown in a record short process time of 30 min. The influenceof growth temperature and ammonia gas flow rate was investigated toestablish the nucleation and the growth mechanisms of the GaN NRs.Shape and crystallographic facets of the NRs are discussed and a condensationgrowth mechanism is proposed for the formation of bunched GaN NRs.Emphasis is placed on the crystal symmetry of the nuclei in the firststage of growth. The morphology and the structural properties wereanalyzed by field emission scanning electron microscopy (SEM) andX-ray diffraction spectroscopy (XRD). [ABSTRACT FROM AUTHOR]

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]