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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]

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: Selective area growth experiments were carried out by hydride vapour phase epitaxy (HVPE) on (100) GaAs-patterned substrates for the making of GaAs tips to be used as spin injectors. The tips exhibited various morphological profiles bounded by low and high index faces. Sharp apices were formed by the intersection of four perfectly crystal-defined {110} facets. The tip height and the apex sharpness have been optimized through the control of the crystal intrinsic growth anisotropy as a function of the experimental growth parameters. A good agreement was obtained between the morphologies of the selectively grown tips and kinetic Wulff constructions based on knowledge of the growth rate anisotropy that was independently determined on low index substrates. This demonstrates that a strictly surface kinetics dependent growth regime was established. HVPE appears to be a rapid, reliable tool for the making of morphologically controlled microtips on large area wafers. [Copyright &y& Elsevier]