Luminescence spectroscopy of europium doped gallium nitride powder prepared by a Na flux method

The red emission properties of Eu doped gallium nitride (GaN) powder prepared by a Na flux method were characterized by time-resolved photoluminescence (PL) and site-selective PL excitation studies. Under above-gap excitation (325 nm), Eu ³⁺ doped GaN powders exhibited bright red luminescence at ∼622 nm ( ⁵D ₀ → ⁷F ₂ transition). The room-temperature emission lifetime was determined to be ∼242 μs and increased only slightly at 10 K with a value of ∼252 μs. At the same time, the integrated Eu ³⁺ PL intensity was quenched by a factor of ∼20 for the temperature range from 10 to 300 K. Low temperature PL excitation studies in the region of the ⁷F ₀ → ⁵D ₀ transition of Eu ³⁺ ions indicated the existence of multiple Eu ³⁺ centers with distinct excitation and emission properties in GaN:Eu powder.