Europium (Eu) doped nitride semiconductors make it possible to create novel optical devices, such as a low threshold lasers and single photon emitters. However, not all europium ions are incorporated in semiconductor optical active site that can be excited through the GaN host. Therefore, it is important to develop methods to selectively incorporate europium ions in higher-efficiency optical sites. Hiroto Sekiguchi and his colleagues at Toyohashi University of Technology and Hamamatsu Photonics Ltd have improved the emission intensity from europium ions by magnesium co-dop...