Influence of annealing atmosphere on the performance of a β-Ga2O3 thin film and photodetector

β-Ga2O3 epitaxial thin films were deposited by laser molecular beam epitaxy (LMBE) and annealed at 800°C for 30 minutes in air and oxygen atmospheres, respectively. Photodetectors were fabricated using as-grown and annealed Ga2O3 epilayers. The influence of the annealing atmosphere on the crystal structure and optical properties of Ga2O3 films was investigated. X-ray diffraction (XRD) measurements show that the in-plane compressive strain of Ga2O3 thin films could be relaxed after high temperature thermal annealing. Compared with the as-grown sample, the annealed samples exhibit a red shift of absorption edge in the transmittance spectra, indicating a reduced bandgap. According to the XPS measurement results, the atomic ratios of O to Ga also increased for the annealed samples. Moreover, the oxygen-annealed photodetector achieves a larger photocurrent, higher responsivity and better time-dependent photoresponse than the other two samples, which may be attributed to the decrease in the number of oxygen vacancies.