Luminescence enhancement of ZnGa2O4:Mn2+ by Ge4+ and Li+ doping

Structural and optical properties of ZnGa2O4:Ge4+ and ZnGa2O4:Ge4+, Li+, Mn2+ phosphors were investigated by using X-ray diffraction (XRD), photoluminescence (PL) and cathodoluminescence (CL) measurements. The XRD patterns show that Ge-doped ZnGa2O4 has a spinel phase and its lattice constant increases with respect to ZnGa2O4. Emission wavelength shifts from 400 to 360 nm in comparison with ZnGa2O4 when Ge is doped in ZnGa2O4 and a peak related with oxygen defect was observed in Ge-doped ZnGa2O4. The CL luminance of ZnGa2O4:Ge4+, Li+, Mn2+ phosphors is seven times brighter than that of ZnGa2O4:Mn2+. This drastic luminance improvement can be attributed to Ge doping in ZnGa2O4 acting as donor ion and Li doping resulting in increasing conductivity of ZnGa2O4. These results indicate that ZnGa2O4:Ge4+, Li+, Mn2+ phosphors hold promise for potential applications in field-emission display devices with high brightness operating in green spectral regions.