Red emission properties of europium doped GaN powders prepared by a Na flux method

Temperature dependent and time-resolved photoluminescence (PL) studies were performed on the red emission properties of Eu doped GaN powders prepared by a Na flux method. The Eu³⁺ doped GaN powder showed bright red emission (∼622 nm) at room temperature, which corresponds to the intra-4f Eu ³⁺ transition ⁵D₀→ ⁷F ₂. It was observed that under above-gap excitation the integrated Eu³⁺ PL intensity was quenched by a factor of ∼20 for the temperature range 10 to 300 K. In contrast, the emission lifetime was only slightly temperature dependent with an average value of ∼242 μs at room temperature. Photoluminescence excitation (PLE) measurements performed in the visible spectral region revealed a weak defect-related and broad excitation band superimposed by narrow intra-4f absorption lines of Eu³⁺ ions. Moreover, PLE studies for the ⁵F₀ → ⁷D₀ transition demonstrated the existence of multiple Eu³⁺ centers in the investigated GaN powder.