Eu+3 and Cr+3 doping for red cathodoluminescence in ZnGa2O4

Abstract

Cathodoluminescence emission spectra and photoluminescence (PL) excitation spectra were used to evaluate Eu+3 and Cr+3 as activators for red luminescence in ZnGa2O4. In the ZnGa2O4:Eu materials red emission from Eu+3 and blue intrinsic emission were observed. The blue intrinsic emission increased relative the Eu+3 emission with increasing current density and is attributed to preferential current saturation of the Eu+3 activators. In addition, PL excitation measurements revealed that the inefficient energy transfer from the ZnGa2O4 host to the Eu+3 is due to poor spectral overlap between the ZnGa2O4 emission and the Eu+3 absorption. Cr-doping resulted in a saturated red-color, and no host emission was observed over the entire current density regime investigated. The PL excitation of the ZnGa2O4:Cr revealed good overlap between the ZnGa2O4 host and the Cr+3 absorption. Efficient energy transfer to the Cr+3 activators occurs via multipolar interactions.