Optical Properties of Sputter-Deposited Gallium Oxide Thin Films

We report on studies conducted on gallium oxide (Ga$_{\mathrm{2}}$O$_{\mathrm{3}})$ thin films grown on c-plane sapphire substrates by RF magnetron sputtering from a 99.9{\%} pure ceramic target. Single and poly crystalline thin films were obtained by varying the composition of Ar and O$_{\mathrm{2}}$ gas used in the deposition; substrate temperature and post deposition annealing treatment. The optical characteristics were obtained by UV-VIS spectroscopy measurements which yielded transmission of 90 - 95{\%}, optical bandgaps of 4.7- 4.8 eV. Structural characteristics were analyzed through x-ray diffraction measurements. A single diffraction peak at 2$\theta \quad =$ 37$^{\mathrm{o}}$, assigned to the (4 0 1) plane was obtained for a film annealed at 1000 $^{\mathrm{o}}$C for 1hour in N2 atmosphere. An attempt to dope the films using Sn for n-type conductivity was made. Optical bandgaps of 6{\%}, 9{\%} and 10{\%} Sn-doped Gallium oxide films were 4.72, 4.57 and 4.56 eV, respectively.