Ammonia assisted low temperature growth of In2O3 (111) epitaxial films on c-sapphire substrates by chemical vapor deposition technique

The authors report the growth of bixbyite In2O3 (111) epitaxial layers on c-plane sapphire substrates by a chemical vapor deposition route, in which growth takes place under the flow of oxygen and ammonia in a furnace. Indium metal is used as the source for indium. It has been found that In2O3 films with high epitaxial quality can be grown by optimizing the growth temperature and the flow rate of NH3. Ammonia plays a catalytic role in the growth process. At growth temperatures less than 550 degrees C, inclusion of a rhombohedral phase, which is known to be thermodynamically stable only at high pressure, has been detected in the film. X-ray photoelectron spectroscopy does not show the presence of nitrogen in these films. An x-ray diffraction study reveals a sharp increase of disorder in these films as the growth temperature increases beyond 550 degrees C. The bandgap of the material is also found to decrease with the increase of disorder.