Tremendous enhancement of green emission from Er3+/In3+ co-doped β-Ga2O3 ultrawide bandgap semiconductors

Er3+ singly doped and Er3+/In3+ co-doped gallium oxide ceramics with intense green emission were prepared using the conventional solid-state reaction method. The Ga2-x-yErxInyO3 ceramics exhibit green and red emission at 555 and 673 nm, and follow the two-photon absorption process under the excitation of 980 nm. Systematical measurements of the upconversion luminescence spectra of Ga2-x-yErxInyO3 show that the optimal doping concentrations, sintering temperature and time are x = 0.015, y = 0.035, 1250 °C, and 8 h, respectively. For a fixed Er3+ doping concentration of x = 0.015, the green emission intensity at 555 nm can be enhanced by 60 folds through 3.5 mol% In3+ doping, which is attributed to reduced non-radiative decay and enhanced energy transfer from In3+ ions to Er3+ ions via defect states. The introduction of 3.5 mol% In3+ also increases the fluorescence lifetime by 235–272%. This observation provides compelling evidence for the presence of effective energy transfer between In3+ and Er3+ ions.