Lattice site location and luminescence studies of AlxGa1−xN alloys doped with thulium ions

Abstract

Rare earth doped AlGaN is being considered for the development of new optoelectronic devices. This wide band gap compound provides lower thermal quenching of rare earth intra-4fn transitions making room temperature operation possible. In this work a detailed study of AlxGa1−xN (x=0.15, 0.77) samples grown by halide vapor phase epitaxy on (0001) sapphire implanted with Tm is presented. The samples were implanted at room temperature with 300keVTm ions to fluences of 1×1014cm−2 and 1×1015cm−2. The damage accumulation and the rare earth lattice site location are investigated by Rutherford Backscattering/Channeling Spectrometry. The structural measurements show a higher resistance of the lattice to irradiation damage with the increase of the AlN content. The analysis of angular scans along different axes using the Monte Carlo code FLUX allows the determination of the rare earth lattice sites. Results for Al0.15Ga0.85N show that Tm ions occupy two preferential sites: the high symmetry substitutional Ga/Al site and a site displaced by ∼0.3Å along the c-axis from this regular site.Rapid thermal annealing treatments at 1200°C under N2 ambient were performed to remove implantation damage and promote the optical activation of rare earth intra-4fn transitions. Photoluminescence measurements were performed to characterize the thulium ions spectroscopic transitions. The effects of thermal annealing and fluence on the fraction of rare earth optically active ions are exploited and discussed.