Simulation And Experimental Study On Growth Of GaN Nanowires By Sublimation

As the third generation of new semiconductor materials,GaN,because of its wide bandgap,anti-radiation,chemical stability and other characteristics are widely used in the development of optoelectronic components.In recent years,with the in-depth study of GaN material properties,the researchers found that not only can grow GaN films,but also can grow GaN one-dimensional nano-materials,which has aroused widespread concern at home and abroad.In this thesis,GaN nanowires are grown by the self-designed sublimation method growth system.It mainly includes two parts,namely based on computational fluid dynamics numerical simulation and experimental preparation of GaN nanowires.In order to shorten the design cycle of the sublimation method and improve the design of the cavity structure,the numerical simulation of the two-dimensional model is carried out from the aspects of growth temperature,height of the substrate relative to the base and the height of the base relative to the reaction chamber.The effects of Ga,NH3 molar concentration distribution and GaN growth rate on the growth of GaN nanowires were studied.The growth uniformity of GaN nanowires was better under the growth conditions with the growth temperature of 1050?,the relative height of the substrate 6mm and the relative height of the base 25 mm.In addition,the flow field distribution in the reaction chamber was analyzed by numerical simulation after add ing the gas N2 with different flow rates under the optimized growth conditions.The GaN nanowires were grown from NH3 flow rate,growth time,catalyst and buffer layer by means of sublimation method.The surface morphology of GaN nanowires was analyzed by scanning electron microscopy(SEM).It is found that the graphene intercalation,the NH3 flow rate,the reaction time,the presence or absence of the catalyst and the GaN buffer layer have a great influence on the morphology of the GaN nanowires by comparing the SEM images of the samples.At the appropriate ammonia flow rate,the GaN nanowires can be grown on the graphene without catalyst,the nanowires are about 80 nm in diameter and about 10 ?m in length.After introducing the buffer layer and the catalyst,the GaN nanowires show a pattern of vertical alignment.The results show that graphene,buffer layer and catalyst provide the basis for the nucleation of GaN nanostructures,and the optimized nanowire structure can be grown under certain conditions.Through the numerical simulation and experimental preparation,it can provide theoretical basis for improving the cavity structure and optimizing the growth process of the growth system,which has a great significance for the experimental growth of the GaN nanometer array.