Mg-doped β-Ga2O3 films with tunable optical band gap prepared on MgO (110) substrates by metal-organic chemical vapor deposition

The Mg-doped β-Ga2O3 (β-Ga2O3: Mg) films have been prepared on the MgO (110) substrates by the metal-organic chemical vapor deposition (MOCVD) technique. The Mg concentration was varied from 1% to 10% (atomic ratio). Post-deposition annealing was performed to investigate its influence on the film properties. The crystallinity was improved obviously after annealing for all the films, with a phase transition from amorphous to polycrystalline observed for the 1–7% Mg-doped films. The average transmittances for the β-Ga2O3: Mg films in the visible range were all over 90%, with an obvious increase observed in the ultraviolet (UV) region around 300 nm after annealing. The optical band gap of the β-Ga2O3: Mg films could be modulated from 4.93 to 5.32 eV before annealing, and from 4.87 to 5.22 eV after annealing.