Red up-conversion emission from nanocrystalline GaN powders co-doped with Er³⁺ and Yb³⁺

The synthesis, structure, and spectroscopy of frequency upconverting lanthanide doped GaN nanocrystals (NCs) are presented. The crystalline wurtzite GaN NCs were synthesized via a nitridation reaction of β-Ga₂O₃ in a flow of anhydrous ammonia. The average sizes of GaN nanocrystallites as determined from XRD and TEM measurements was 30 nm. The photoluminescence (PL) spectra under 980 nm laser diode excitation was measured and analyzed. It was found that GaN Er³⁺ and Yb³⁺ doped nanocrystalline powders exhibit strong red up-conversion (UC) emission. The mechanisms and pathways of UC are also briefly discussed.