Influence of N2 and O2 annealing treatment on the optical bandgap of polycrystalline Ga2O3:Cu films

Abstract Cu-doped Ga 2 O 3 thin films were deposited by electron beam evaporation with subsequent annealing at 1000 °C in N 2 and O 2 for 1 h. The influence of the annealing atmosphere on the crystal structure, surface morphology and optical properties of Ga 2 O 3 :Cu films was investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and transmittance and photoluminescence (PL) spectroscopy. The optical bandgap deduced from the absorption spectrum was greater for the O 2 annealed than for N 2 annealed samples. In both cases the bandgap was wider than for bulk β-Ga 2 O 3 . The grain size and surface roughness were sensitive to the annealing atmosphere. Results confirmed that the annealed samples were polycrystalline β-Ga 2 O 3 with some amorphous phase. We hypothesize that annealing in oxygen led to recrystallization of the Ga 2 O 3 :Cu film. Annealing treatment improved the crystal quality of Ga 2 O 3 :Cu films and the PL intensity of the samples increased.