Influence of growth temperature on the crystalline quality of hexagonal GaN layer on GaAs (111)A by metalorganic hydrogen chloride vapor phase epitaxy

Growth of thick hexagonal GaN layer on GaAs (111)A surfaces by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE) was studied in the temperature range from 920 degreesC to 1000 degreesC. Cross section of the layer (25 mum) grown at 960 degreesC or below revealed a columnar structure through the layer. On the other hand, in the 1000 degreesC grown layer, the columnar structure disappeared in the process of growth, which brought a drastic change in surface morphology from a rugged surface to a mirror-like surface. Photoluminescence (PL) property of the grown layer was also improved with increase of the growth temperature. It was shown that a GaN layer thicker than 100 mum grown on a GaAs (111)A surface at 1000 degreesC would be a promising candidate for the preparation of high quality freestanding GaN substrate for homoepitaxy.