We have investigated the temperature and composition dependent photoluminescence (PL) spectra in Ga1-xMnxN layers (where x approximate to 0.1-0.8%) grown on sapphire (0001) substrates using the plasma-enhanced molecular beam epitaxy technique. The efficient PL is peaked in the red (1.86 eV), yellow (2.34 eV), and blue (3.29 eV) spectral range. The band-gap energy of the Ga1-xMnxN layers decreased with increasing temperature and manganese composition. The band-gap energy of the Ga1-xMnxN layers was modeled by the Varshni equation and the parameters were determined to be alpha = 2.3 x 10(-4), 2.7 x 10(-4), 3.4 x 10(-4) eV/K and beta = 210, 210, and 230 K for the manganese composition x = 0.1%, 0.2%, and 0.8%, respectively. As the Mn concentration in the Ga1-xMnxN layers increased, the temperature dependence of the band-gap energy was clearly reduced. (C) 2008 Elsevier B. V. All rights reserved.