Mid gap photoluminescence from GaN:Mn, a magnetic semiconductor

The defect and morphology of GaN monocrystals with Mn content 10(19) cm(-3) were examined by fluorescence confocal microscopy and spectroscopy. The fluorescence spectral investigation was carried out in a region very close to the defect centers. Contrary to earlier results, we did observe a characteristic fluorescence line of Mn corresponding to the T-4(1) --> (6)A(1) and T-4(1) --> (6)A(1) transitions, suggesting the predominant presence of Mn2+ (d(5)). In addition, strong emission lines were observed at 1.60 and at 1.85 eV when the sample was excited with light of 436 and 365 nm, respectively. An energy scheme is proposed to explain the observed data coherently. (C) 2003 Elsevier Ltd. All rights reserved.