Analysis of the Enhancing Effect of Rare Earth Ion Co-Doping on the Red Emission of CaGa2S4:Mn2+ in View of Its Decay Time

When certain trivalent rare earth elements (REEs) are co-doped with Mn2+ in CaGa2S4, the Mn2+ red emission of the compounds is enhanced. To clarify its mechanism, its decay curves of the Mn2+ red emission from CaGa2S4:Mn2+, REE3+ are investigated. For these analyses, we present a tentative transition model including the trap levels due to REE3+ together with a process enabling electron supply from REE3+ to the excited 3d state of Mn2+. This model can explain the enhancing effect on the Mn2+ red emission.