Optical and structural characterization of high crystalline β-Ga2O3 films prepared using an RF magnetron sputtering

beta-Ga2O3 films have been prepared on sapphire (0001) substrate using an RF magnetron sputtering. The highly oriented beta-Ga2O3 films with a high crystallinity could be obtained at Ts above 700 degrees C. The sputtered film in pure Ar showed a low optical band-gap and a strong optical absorption in UV and visible region, possibly due to non-stoichiometry, oxygen-deficiency. Raman modes of beta-Ga2O3 started to evolve at Ts of 400 degrees C and then, were clearly defined and dominant at Ts above 600 degrees C in a good consistence with XRD result. In the PL spectra at Ts above 600 degrees C, UV emission peaked at 3.75 eV and red-emission composed of broad band and sharp peaks were predominant. These emissions are the first report in PL spectra of beta-Ga2O3 and have been tentatively assigned to high energy excitons caused by electrons trapped with holes at deeper acceptor level, and optical transition between deep donor level and delocalized/clustered acceptor levels, respectively. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Beta-Ga2O3 films were prepared on sapphire substrates using RF magnetron sputtering, showing low optical band-gap and high absorption in UV and visible regions. Raman modes and photoluminescence spectra revealed the existence of high energy excitons and optical transitions at high temperatures, indicative of good crystallinity and unique optical properties of the films.