Microstructure, optical, and photoluminescence properties of β-Ga2O3 films prepared by pulsed laser deposition under different oxygen partial pressures* *Project supported by the Guizhou Provincial Science and Technology Planning Project, China (Grant No. 2018-5781), the National Natural Science Foundation of China (Grant No. 51762010), the Guizhou Provincial Science and Technology Foundation, China (Grant Nos. 2020-1Y021 and 2020-1Y271), and the Guizhou Provincial

Abstract

The β-Ga2O3 films are prepared on polished Al2O3 (0001) substrates by pulsed laser deposition at different oxygen partial pressures. The influence of oxygen partial pressure on crystal structure, surface morphology, thickness, optical properties, and photoluminescence properties are studied by x-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), spectrophotometer, and spectrofluorometer. The results of x-ray diffraction and atomic force microscope indicate that with the decrease of oxygen pressure, the full width at half maximum (FWHM) and grain size increase. With the increase of oxygen pressure, the thickness of the films first increases and then decreases. The room-temperature UV-visible (UV-Vis) absorption spectra show that the bandgap of the β-Ga2O3 film increases from 4.76 eV to 4.91 eV as oxygen pressure decreasing. Room temperature photoluminescence spectra reveal that the emission band can be divided into four Gaussian bands centered at about 310 nm (∼ 4.0 eV), 360 nm (∼ 3.44 eV), 445 nm (∼ 2.79 eV), and 467 nm (∼ 2.66 eV), respectively. In addition, the total photoluminescence intensity decreases with oxygen pressure increasing, and it is found that the two UV bands are related to self-trapped holes (STHs) at O1 sites and between two O2-s sites, respectively, and the two blue bands originate from at Ga1 tetrahedral sites. The photoluminescence mechanism of the films is also discussed. These results will lay a foundation for investigating the Ga2O3 film-based electronic devices.