Insights into the greatly boosted red photoluminescence emission in Ga2O3:Eu3+/Ti4+ composite ultrawide bandgap semiconductors

Abstract

Two series of Ga2O3:Eu3+/Ti4+ ceramic phosphors with nominal composition of Ga2-xEuxO3 (Ga2O3:xEu3+) and Ga1.965-yEu0.035TiyO3 (Ga2O3:0.035Eu3+/yTi4+) were prepared using a high-temperature solid-state reaction method. Photoluminescence measurements show that the optimal doping concentration, sintering temperature and time are x=0.035, y=0.07, 1300°C, and 8 hours, respectively. Under the excitation of 394 nm, the Ga2O3:Eu3+ phosphors emit light-pink light centred at 592 nm (5D0 → 7F1) and red light centred at 613 nm (5D0 → 7F2), with the optimal Eu3+ concentration of 3.5%. The co-doping of Eu3+/Ti4+ in Ga2O3:0.035Eu3+/yTi4+ phosphors results in greatly enhanced photoluminescent emission intensity and extended decay time. The boosted red emission is mainly attributed to enhanced absorption of 394-nm photons due to the red shift of the bandgap and the energy transfer from Ti4+ to Eu3+ ions. An analysis of the CIE coordinate diagrams reveals that Ti4+ doping not only increases the purity of the emitted red light but also increases the stability of the red emission intensity and chromaticity against temperature variation. Our results demonstrate the efficient energy transfer from Ti4+ to Eu3+ and highlight that Ti4+ ions doping could be an efficient approach to improve the overall photoluminescence characteristics of Ga2O3-based luminescence materials.