Effect of annealing on the properties of Ga2O3:Mg films prepared on α-Al2O3 (0001) by MOCVD

• The Mg-doped Ga2O3 films were prepared on α-Al2O3(0001) substrates by MOCVD for the first time.
• Structural, electrical and optical properties of the films as a function of Mg concentration and annealing were investigated.
• Phase transition from amorphous to polycrystalline structure of monoclinic β-Ga2O3 was observed after annealing.
• Excellent optical transparency in the UV and visible wavelength regions was achieved.
• Tunable optical band gap was obtained.

The Mg-doped Ga2O3 (Ga2O3:Mg) films have been prepared on the α-Al2O3(0001) substrates by metalorganic chemical vapor deposition (MOCVD). The Mg doping was varied from 0 to 10% (atomic ratio). The effect of annealing on the structural, electrical and optical properties of the films was investigated in detail. After annealing, the 0–3% Mg-doped films changed from amorphous to polycrystalline structure of monoclinic β-Ga2O3 with a single orientation along the (2¯01) direction, while no obvious phase transition was observed for the rest of the samples. The average transmittances for the Ga2O3:Mg films in the visible range were over 90%, with an obvious increase observed in the ultraviolet (UV) region around 300 nm after annealing. Tunable optical band gap from 4.96 to 5.4 eV was obtained before annealing, which varied in a different range of 4.88–5.36 eV after annealing.