The influence of V/III ratio on GaN grown on patterned sapphire substrate with low temperature AlN buffer layer by hydride vapor phase epitaxy

In this paper, 2-4 in. GaN wafers with high crystal quality were obtained with optimized V/III ratio of source gases on the patterned sapphire substrate (PSS) covered by a sputtered thin AlN buffer layer by using hydride vapor phase epitaxy (HVPE) growth technology. It was found that the morphology and crystal quality of the top GaN layer were significantly different with the variation of V/III ratio of source gases in initial nucleation growth step. Transparent single crystalline GaN layer could be obtained under relatively low V/III ratio of source gases, while it transferred to yellow and polycrystalline structure with increasing of V/III ratio of source gases. This is mainly attributed to the significant transition of GaN nucleation process with different crystallographic plane of AlN buffer layer, and corresponding variation of GaN growth mode at different V/III ratio of source gases, supported by surface, lateral SEM characterization, high-resolution X-ray diffraction (XRD) measurement, and detailed growth mechanism analysis. Moreover, the crystal quality of GaN grown under optimized condition can be further improved by increasing the thickness of GaN. It would offer a simple way to obtain GaN templates with high crystal quality at relatively low cost.