Structure-property correlation of europium doped β-GaO: an experimental and first-principle study

In this work, the structure-properties correlation of Eu-doped β-gallium oxides was studied by both experimental as well as first-principle studies. The thin films were grown by the PVD co-sputtering method on a quartz substrate and analyzed further. The results showed that thin film fabricated were nanocrystalline structures with an average grain size of ∼ 0.029 ± 0.005 μm, and preferably oriented towards the (-201) plane. The band gap energy (Eg) of intrinsic β-GaO measured from the Tauc plot shows a decreasing trend, as the band energy gap decreases from 3.98 to 3.88 eV on Eu doping, while the optical transmittance doesn’t show any effect. Further, a first-principal study was conducted, and the simulated result of the band structure of β-GaO on Eu doping also follows the same decreasing trend as the experimental results. The electronic band structure of intrinsic β-GaO reduces to 3.41 eV from 4.9 eV on Eu doping. The total and partial density of states (DOS) results suggested that the reason behind the decreasing trend of the band structure of β-GaO may be due to the dominance of the 4f states orbital in the lower conduction band on Eu doping in the tetrahedral site. The reflectance and energy loss function shows a reduction due to Eu doping, although the transmittance and absorption edge remains unaffected. There was a redshift in the absorption spectra observed of intrinsic β-GaO on Eu doping, which improves the visible light absorption. It is suggested that co-doping with other rare earth metals may be able to tune the Eg and make it useful for monolithic and phosphor-free LEDs applications.