Structural and optical properties of InN films prepared by radio frequency magnetron sputtering

Indium nitride (InN) films were prepared by a radio frequency magnetron sputtering in N2/Ar mixed gases. The results on X-ray diffraction measurements indicated that all of the InN films deposited were hexagonal crystalline InN. The c-axis lattice constant of the InN film deposited at room temperature was decreased with the increase of Ar composition ratio in N2/Ar mixed gas. For the InN film deposited in pure N2 gas it was also decreased with the increase of substrate temperature, which was related to the relative nitrogen concentration in the InN film. The results on X-ray diffraction and Raman spectroscopy measurements indicated that the InN films with large c-axis lattice constant were disordered crystalline film and had nitrogen-rich stoichiometry. The optical band-gap energies of the disordered InN films were always large values of 1.42–1.85 eV, whereas that of high quality InN film deposited on GaN/Al2O3 substrate at 450 °C in pure N2 gas, was 0.84 eV.