Growth of Thick Hexagonal GaN Layer on GaAs (111)A Surfaces for Freestanding GaN by Metalorganic Hydrogen Chloride Vapor Phase Epitaxy

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Abstract
Thick hexagonal GaN was grown on GaAs (111)A surfaces by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE) in the temperature range from 920°C to 1000°C. Both the surface morphology and the photoluminescence (PL) property of the grown layer were greatly improved with increase of the growth temperature up to 1000°C. However, the full-width at half maximum (FWHM) in the ω mode X-ray diffraction (XRD) of the GaN (0002) plane increased with increasing growth temperature above 960°C, due to the bending of the grown layer. The bending could be suppressed by growing a thicker layer, even at 1000°C. A mirror-like GaN layer with the FWHM value of 4.7 min was obtained by growing a 100-µm-thick layer at 1000°C, which indicates that the growth of a thick GaN layer on the GaAs (111)A surface is a promising method for the preparation of freestanding GaN substrates.