Photoluminescence spectra of Eu-doped GaN with various Eu concentrations

Variation of the luminescence spectra of Eu-doped GaN with varying Eu concentration ranging from 0.6 to 8.0 at. % was investigated. Eu-related luminescence originating from the D-5(0)-F-7(2) transition of Eu3+ was observed at about 622 nm. The luminescence basically consisted of three peaks. The relative intensity of the three peaks changed remarkably at the Eu concentration of around 2.0-3.5 at. % which corresponds to a structural phase transition from a single crystalline to a polycrystalline structure. This indicates that the incorporation site of Eu in GaN is very sensitive to the structural properties of the GaN host material.