Effect of annealing temperature on luminescence in Eu implanted GaN

Europium red photoluminescence (5D0 → 7F2) in implanted GaN samples is investigated as a function of the annealing temperature. For above bandgap excitation a remarkable increase of the photoluminescence (PL) is observed for samples annealed at 1300 °C. Excitation density dependent measurements at 12 K reveal the existence of two major incorporation sites for Eu3+ ions in GaN samples. Spectral characteristics of the two Eu3+ centers are described. Eu3+5D0 lifetimes and effective excitation cross-sections specific to each Eu3+ center are determined in various samples. Results suggest that one center corresponds to Eu3+ ions in Ga substitutional sites with a corresponding rather low effective excitation cross-section compared to the other center which exhibits a higher excitation cross-section and is probably associated to a more distorted local environment.