Growth and structure of sputtered gallium nitride films

GaN films have been deposited by radio frequency sputtering of a GaAs target with pure nitrogen. The growth, composition, and structure of the films deposited on quartz substrates have been studied by x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Films deposited below 300°C are amorphous and As rich. Above 300°C, polycrystalline, hexagonal GaN is formed, along with As rich amorphous phase, which reduces with increasing substrate temperature. At a substrate temperature of 700°C, GaN films, practically free of amorphous phase, and As (<0.5at.%) are formed. The preferred orientation depends strongly on the substrate temperature and is controlled by surface diffusion of adatoms during growth stage. Below 500°C, the surface diffusion between planes dominates and results in the (101¯1) preferred orientation. Above 500°C, the surface diffusion between grains takes over and results in (0002) preferred orientation.