Photoluminescence of a-GeN alloys doped with different rare-earth ions

Amorphous (a-)GeN alloys independently doped with Pr, Sm, Ho, and Er rare-earth (RE) elements were prepared by co-sputtering a Ge + RE target in an atmosphere of pure nitrogen. Room-temperature photoluminescence experiments indicate relatively strong visible light emission characteristic of each RE3+ ion that was obtained after laser annealing the surface of the films by means of an optical microscope and 488.0 nm photons. Typically, the irradiation exposures were 20 s long with an average power density of ≈2 mW μm−2. Laser anneal induces the crystallization of the irradiated areas, as confirmed by Raman spectroscopy, and activates the RE-related photoluminescence. According to the present experimental results, RE-related light emission originates mostly from the surface of the a-GeN films and is tentatively attributed to a reduction in the density of defects and/or to the presence of Ge crystallites. The potential of these compounds in applications such as (micro-)devices will also be outlined.