Annealing induced phase transition and optical properties of Ga2O3 thin films synthesized by sputtering technique

Abstract Gallium oxide (Ga2O3) thin films were deposited on c-plane sapphire substrates at low temperature (RT) by magnetron sputtering method using Ga2O3 ceramic target and were post annealed at various temperatures ranging from 500 to 900 ℃ . The effect of annealing temperature on the surface morphology, crystalline structure, chemical composition and optical properties of Ga2O3 thin films were investigated. A phase separation is observed at 800 ℃ and α -phase Ga2O3 thin films is obtained at low annealing temperature while β -Ga2O3 at high temperature. With annealing temperature increases, the optical bandgap decreases from 5.47 to 5.00 eV and the surface morphology become more and more smooth. A broad emission band centered at 550 nm is observed for all samples which can be attributed to the donor acceptor pair (DAP) recombination related to the oxygen vacancies.