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

beta-Ga2O3 epitaxial thin films were deposited by laser molecular beam epitaxy (LMBE) and annealed at 800 degrees 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. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement