Growth and structure of sputtered gallium nitride films

Abstract

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 degrees C are amorphous and As rich. Above 300 degrees C, polycrystalline, hexagonal GaN is formed, along with As rich amorphous phase, which reduces with increasing substrate temperature. At a substrate temperature of 700 degrees C, GaN films, practically free of amorphous phase, and As (< 0.5 at. %) are formed. The preferred orientation depends strongly on the substrate temperature and is controlled by surface diffusion of adatoms during growth stage. Below 500 degrees C, the surface diffusion between planes dominates and results in the (10 (1) over bar1) preferred orientation. Above 500 degrees C, the surface diffusion between grains takes over and results in (0002) preferred orientation. (C) 2007