Résumé
The intensity of Eu-related luminescence from ion-implanted GaN with a 10 nm thick AlN cap, both grown epitaxially by metal organic chemical vapor deposition (MOCVD) is increased markedly by high-temperature annealing at 1300 degrees C. Photoluminescence (PL) and PL excitation (PLE) studies reveal a variety of Eu centers with different excitation mechanisms. High-resolution PL spectra at low temperature clearly show that emission lines ascribed to D-5(0)-F-7(2) (similar to 622 nm), D-5(0)-F-7(3) (similar to 664 nm), and D-5(0)-F-7(1) (similar to 602 nm) transitions each consist of several peaks. PL excitation spectra of the spectrally resolved components of the D-5(0)-F-7(2) multiplet contain contributions from above-bandedge absorption by the GaN host, a GaN exciton absorption at 356 nm, and a broad subedge absorption band centred at similar to 385 nm. Marked differences in the shape of the D-5(0)-F-7(2) PL multiplet are demonstrated by selective excitation via the continuum/exciton states and the below gap absorption band. The four strongest lines of the multiplet are shown to consist of two pairs due to different Eu3+ centers with different excitation mechanisms. (c) 2005 American Institute of Physics.