The authors report on the optical and magnetic properties of GaN epilayers, grown by metal-organic chemical vapor deposition, with in situ Er doping at concentrations up to ∼ 1021 cm-3. Using ultraviolet laser excitation, all samples exhibited photoluminescence near 1540 nm with the integrated intensity approximately proportional to the Er concentration. Data from superconducting quantum interference device measurements indicated room temperature ferromagnetic ordering in all Er-doped GaN epilayers. The saturation magnetization in these samples also followed a nearly linear fit to the Er concentration. X-ray diffraction spectra did not reveal evidence of any second phases over this range of Er concentrations.