Optical investigation of electronic states of Mn4+ ions in p-type GaN

The electronic states of manganese in p-type GaN are investigated usingphotoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. Aseries of sharp PL lines at 1.0 eV is observed in codoped GaN and attributed tothe intra d-shell transition 4T2(F)-4T1(F) of Mn4+ ions. PLE spectrum of theMn4+ [4T2(F)-4T1(F)] luminescence reveals intra center excitation processes viathe excited states of Mn4+ ions. PLE peaks observed at 1.79 and 2.33 eV areattributed to the intra-d-shell 4T1(P)-4T1(F) and 4A2(F)-4T1(F) transitions ofMn4+, respectively. In addition to the intra shell excitation processes, abroad PLE band involving charge-transfer transition of the Mn4+/3+ deep levelis observed, which is well described by the Lucovsky model. As determined fromthe onset of this PLE band, the position of the Mn4+/3+ deep level is 1.11 eVabove the valence band maximum, which is consistent with prior theory using abinitio calculations. Our work indicates 4+ is the predominant oxidation stateof Mn ions in p-type GaN:Mn when the Fermi energy is lower than 1.11 eV abovethe valence band maximum.Comment: 7 pages, 3 figures, To be publised in Appl. Phys. Let