Erbium-doped films were grown on sapphire and silicon substrates by reactive sputtering, with different Er concentrations in the film. GaN films deposited at 800 K were determined to be polycrystalline by x-ray diffraction analysis, and retained their polycrystalline structure after annealing in nitrogen at 1250 K. The Er-doped films showed optical transmission beginning at about 360 nm, and the Er dose and film purity were determined with Rutherford backscattering spectroscopy. Photoluminescence and cathodoluminescence spectroscopy showed sharp emission lines corresponding to Er 3+ intra 4fn shell transitions over the range from 9 – 300 K. At above-bandgap optical and electron excitation, the 4S3/2 and 4F9/2 transition dominate, and are superposed on the “yellow band” emission. The infrared emission line at 1543 nm, corresponding to the Er 4I⅓ to 4I3/2 transition is also observed.