Effect of reactor geometry and growth parameters on the uniformity and material properties of GaN/sapphire grown by hydride vapor-phase epitaxy

The effects of flow rate variation and geometry on the growth rate, growth uniformity and crystal quality were investigated in a horizontal gallium nitride vapor-phase epitaxy reactor. The effects of these parameters, were studied through the comparison of numerical model predictions to experimentally observed values. Gas-phase reactions between Groups III and V sources and deposition of material on the wall are shown to lead to reduced overall growth rates and may be responsible for inferior crystal quality. A low ammonia concentration is correlated with the deposition of polycrystalline films. A low V/III ratio and ammonia concentration lead to inferior crystalline quality and increased yellow luminescence. An optimum HVPE growth process requires selection of reactor geometry and operating conditions to minimize gas-phase reactions and wall deposition while providing a uniform reactant distribution across the substrate.