We have investigated optical property of GaGdN grown on GaN template by radio-frequency plasma-assisted molecular beam epitaxy by varying the concentration of Gd. All the samples exhibit photoluminescence emission at the near band edge of 356 nm, a blue luminescence (BL) band around 420 nm and a green luminescence (GL) band around 500 nm, instead of yellow luminescence (YL) band around 550 nm frequently observed in n-GaN layer. The band edge emission is independent of the Gd concentration. This shows that the values of band gap for the GaGdN layers are the same as that of GaN. The temperature dependencies of the GL band intensity and peak wavelength are very similar to those of the YL band observed in the GaN epitaxial layers on the GaN templates. On the other hand, with increasing the Gd concentration, the BL bands observed in the GaGdN layers are red-shifted and their intensities decrease. The BL band intensity remains unchanged in the temperature range of 20-60 K. It rapidly decreases at temperature above 100 K, and disappears at 200 K. The BL band is red-shifted in the temperature range of 4-200 K and its value is about twice larger than that of the GL band. (c) 2013 Elsevier B.V. All rights reserved.