Structure and properties of gallium nitride thin films deposited on Si (111) by using radio-frequency magnetron sputtering

The structure and the properties of gallium nitride (GaN) thin films prepared by using a radiofrequency (RF) magnetron sputtering method are reported. The GaN thin films were deposited on p-type (111)-oriented silicon substrates at room temperature in a pure nitrogen atmosphere. X-ray photoelectron spectra showed that the films were mainly composed of gallium and nitrogen. An oxygen impurity was found to be incorporated into the films during the deposition. The refractive index of the GaN films was measured to be 2.36 at a wavelength of 633 nm. The optical bandgap of the GaN films was determined to be approximately 3.31 eV. From the grazing incidence X-ray reflectivity measurements, the density and the surface roughness of the GaN films were estimated to be 5.827 g/cm(3) and 2.95 nm, respectively. The X-ray diffraction analysis revealed that the crystalline phase of the GaN films changed from wurtzite to zinc-blende as the working gas pressure was reduced. The observed phase change was found to be independent of the orientation of the Si substrate, but to be strongly correlated with the biaxial compressive stress.