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, gr owth uniformity and crystal quality were investigated in a horizontal gallium nitride vapor-phase epitaxy reactor. The effects of these para meters, were studied through the comparison of numerical model predict ions to experimentally observed values. Gas-phase reactions between Gr oups III and V sources and deposition of material on the wall are show n to lead to reduced overall growth rates and may be responsible for i nferior crystal quality. A low ammonia concentration is correlated wit h the deposition of polycrystalline films. A low V/III ratio and ammon ia concentration lead to inferior crystalline quality and increased ye llow luminescence. An optimum HVPE growth process requires selection o f reactor geometry and operating conditions to minimize gas-phase reac tions and wall deposition while providing a uniform reactant distribut ion across the substrate.