Optical investigation of electronic states of Mn4+ ions in p-type GaN -: art. no. 042505

The electronic states of manganese in p-type GaN are investigated using photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. A series of sharp PL lines at 1.0 eV is observed in codoped GaN and attributed to the intra d-shell transition T-4(2)(F)-T-4(1)(F) of Mn4+ ions. PLE spectrum of the Mn4+ [T-4(2)(F)-T-4(1)(F)] luminescence reveals intracenter excitation processes via the excited states of Mn4+ ions. PLE peaks observed at 1.79 and 2.33 eV are attributed to the intra-d-shell T-4(1)(P)-T-4(1)(F) and (4)A(2)(F)-T-4(1)(F) transitions of Mn4+, respectively. In addition to the intrashell excitation processes, a broad PLE band involving charge-transfer transition of the Mn4+/3+ deep level is observed, which is well described by the Lucovsky model. As determined from the onset of this PLE band, the position of the Mn4+/3+ deep level is 1.11 eV above the valence band maximum, which is consistent with prior theory using ab initio calculations. Our work indicates 4+ is the predominant oxidation state of Mn ions in p-type GaN:Mn when the Fermi energy is lower than 1.11 eV above the valence band maximum. (C) 2005 American Institute of Physics.