Photoluminescence investigation of ferromagnetic Ga _1-x Mn _x N layers with GaN templates grown on sapphire (0 0 0 1) substrates

We have investigated the temperature and composition dependent photoluminescence (PL) spectra in Ga _1-x Mn _x N layers (where x ≈ 0.1-0.8%) grown on sapphire (0 0 0 1) 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 Ga _1-x Mn _x N layers decreased with increasing temperature and manganese composition. The band-gap energy of the Ga _1-x Mn _x N layers was modeled by the Varshni equation and the parameters were determined to be α = 2.3 × 10 ^-4 , 2.7 × 10 ^-4 , 3.4 × 10 ^-4 eV/K and β = 210, 210, and 230 K for the manganese composition x = 0.1%, 0.2%, and 0.8%, respectively. As the Mn concentration in the Ga _1-x Mn _x N layers increased, the temperature dependence of the band-gap energy was clearly reduced.