Spectroscopic characterization of Praseodymium doped Gallium Nitride powder prepared by a Na flux method

The photoluminescence (PL) properties of Pr³⁺ doped GaN powders prepared by a Na flux method were investigated. Under above- and below-gap excitation, GaN:Pr powders exhibited intense red emission lines centered at ∼650 nm corresponding to the intra-4f transition ³P₀ → ³F₂ of Pr³⁺. In addition, weak infrared PL bands were observed from lower excited states of Pr³⁺ at ∼960, ∼1300, and ∼1500-1700 nm. A temperature dependent study of the red emission showed that the integrated PL intensity decreased by a factor of two under above-gap excitation for the temperature range 10-300 K. No significant thermal quenching of the red Pr³⁺ PL was observed under below-gap excitation. Time-resolved emission studies revealed that the decay transient of the red PL was characterized by a fast non-exponential decay followed by a slower decaying exponential component. The non-exponential decay can be attributed to cross-relaxation processes among Pr³⁺ ions, whereas the exponential component suggests the existence of isolated Pr³⁺ centers not affected by emission quenching through cross-relaxations.