Off-axis implantation of 80 keV Eu ions into epitaxial c -plane InAlN/GaN bilayers confines rare-earth REdoping largely to the InAlN layer. Rutherford backscattering spectrometry and x-ray diffraction show good correlations between the Eu 3+ emission linewidth and key structural parameters of In x Al 1−x N films on GaN in the composition range near lattice matching (x∼0.17) . In contrast to GaN:Eu, selectively excited photoluminescencePL and PL excitation spectra reveal the presence of a single dominant optical center in InAlN. Eu 3+ emission from In 0.13 Al 0.87 N:Eu also shows significantly less thermal quenching than GaN:Eu. InAlN films are therefore superior to GaN for RE optical doping.