Growth of thick hexagonal GaN layer on GaAs (111)A surfaces for freestanding GaN by metalorganic hydrogen chloride vapor phase epitaxy

Thick hexagonal GaN was grown on GaAs (111)A surfaces by metalorganic hydrogen chloride vapor phase epitaxy(MO-HVPE) in the temperature range from 920 degrees C to 1000 degrees 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 degrees C. However, the full-width at half maximum (FWHM) in the omega mode X-ray diffraction (XRD) of the GaN (0002) plane increased with increasing growth temperature above 960 degrees C, due to the bending of the grown layer. The bending could be suppressed by growing a thicker layer, even at 1000 degrees C. A mirror-like GaN layer with the FWHM value of 4.7 min was obtained by growing a 100-mu m-thick layer at 1000 degrees 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.