Optical properties of Mn4+ ions in GaN:Mn codoped with Mg acceptors

The optical properties of Mn–Mg-codoped epitaxial GaN were studied. Addition of Mg acceptors quenches the weak manganese-related photoluminescence (PL) band at 1.3eV in GaN:Mn and a series of sharp PL peaks are observed at 1eV in codoped epilayers. The change in PL spectra indicates that the Mg addition stabilizes the Mn4+ charge state by decreasing the Fermi level. The 1eV PL peaks are tentatively attributed to intracenter transitions involving Mn4+ ions. Spin-allowed 3d-shell T24–T14 transitions and their phonon replicas are involved. The relative intensities of the sharp peaks are strongly dependent on the excitation wavelength, indicating that the optically active Mn4+ centers involved in the separate peaks are different. The temperature dependence of the PL spectrum suggests the presence of at least three distinct Mn4+ complex centers.