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Vapor Phase Growth of GaN Crystals with Different Morphologies And Orientations on Graphite And Sapphire Substrates

GaN crystals were grown on graphite and sapphire substrates at 990–1050 °C by reaction of Ga2O with flowing NH3. Ga2O gas was produced at a constant rate (1.3 wt% min−1) by reaction of Ga2O3 with carbon at 1000–1060 °C. The effect of NH3 concentration (3–100 vol%) and the nature of the substrate on the morphology and orientation of the GaN crystals were determined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and selected area electron diffraction. It was found that sheet and plate-like crystals grew at different orientations to the substrate with different NH3 concentrations and substrates.

Single‐crystal layers of formula have been grown epitaxially on formula and sapphire substrates in an open‐tube system by reaction of the metal vapors with the nonmetal hydride gases. Various factors are discussed which were found to affect the epitaxial growth. These include the role of vapor compositions and growth temperatures in controlling stoichiometry and polymorphism, and the choice of substrate materials with particular emphasis on the effects of lattice and thermal expansion match between the substrate and the epitaxial layer. High crystalline quality of the epitaxially grown layers was evidenced by the Kikuchi lines present in their electron diffraction patterns. As‐grown layers of Formula and Formula , both undoped and doped, were high resistivity, while Formula was readily grown n‐type. These epitaxial layers showed at room temperature a bright, visible cathodoluminescence, and for each compound different emission colors were observed with specimens grown at different temperatures.


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