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.
- Light absorption and reflection