Preparation of AlN and GaN thin films by reactive ion beam sputtering and optical properties

Amorphous AIN and GaN films have been fabricated on sapphire and quartz glass substrates by reactive ion beam sputtering. The properties of the films have been studied by X-ray diffraction, X-ray photoemission spectroscopy, and electrical and optical measurements. All of the prepared films are amorphous. AIN films contain some oxygen impurities and the fundamental absorption edges are smaller than that of crystalline A1N. The photoluminescence spectrum at 300 K from the AIN film also supports that the film contains some oxygen. The absorption edges of the prepared GaN films are larger than that of polycrystalline GaN. The GaN films contain some Al impurities and that makes the band gap large. The electrical resistivity of the AIN and GaN films is higher than 10(11) Omega cm, and both films are insulators.