Direct Growth of GaN on (0001) Sapphire by Low Pressure Hydride Vapour Phase Epitaxy

A two-step process for GaN on (0001) sapphire based on low-temperature GaN nucleation in low pressure hydride vapour phase epitaxy using a conventional reactor is described. The process allows reproducibly for subsequent growth of high-quality GaN layers eliminating the need for ex-situ pregrowth processes like sputtering of ZnO or use of MOVPE-grown templates. By means of electron microscopy and thin film X-ray diffraction it is shown that the nucleation procedure yields high-density nucleation centers of the same orientation as the substrate and promotes the lateral growth of epitaxial GaN films.