STRUCTURAL-PROPERTIES OF INN FILMS GROWN ON SAPPHIRE SUBSTRATES BY MICROWAVE-EXCITED METALORGANIC VAPOR-PHASE EPITAXY

The structural properties of InN films grown on (0001) sapphire (alpha-Al2O3) substrates are investigated by reflection high-energy electron-diffraction and x-ray-diffraction methods. The epitaxial relationship between the InN layer and the alpha-Al2O3 substrate is revealed to be (0001)InN//(0001)alpha-Al2O3 with [1010BAR]InN//[1010BAR]alpha-Al2O3, which is different from that of AIN and GaN epitaxial films. The x-ray rocking curve measurements prove that the crystalline quality of as-grown InN films is not so good, while it can be significantly improved by thermal annealing at temperatures of 450-500-degrees-C within 10 min in nitrogen ambient. The improvement of quality is ascribed to the rearrangement of mosaic crystallites in the films through the movement of their boundaries during a short period of time.