Microstructure and optical properties of sputter-deposited Ga2O3 films

We report on the properties of gallium oxide (Ga2O3) thin films deposited on c-plane sapphire substrates using radio frequency magnetron sputtering under various conditions. The parameters varied included the composition of the deposition gas, the substrate temperature, and postdeposition annealing temperature. The optical characteristics obtained by UV-VIS spectroscopy showed excellent transparency of 90%–95% for all the films obtained. The structural and compositional properties of the films were determined using x-ray diffraction and energy dispersive spectrometry measurements. The films deposited in Ar at 400 °C showed diffraction peaks at 18.6°, 37.2°, and 58.2°, which are attributed to diffraction peaks from ( 2 ¯ 0 1 ), ( 4 ¯ 0 2 ), and ( 6 ¯ 0 3 ) planes of β-Ga2O3. Postdeposition annealing in N2 at 400–900 °C did not make any improvement in the crystalline quality of the films. The addition of tin in the films produced transparent films whose optical bandgaps decreased with increasing tin concentration in the films.