The luminescence of Mn2+-activated ZnGa2O4

The luminescence of ZnGa2O4 and ZnGa2O4 doped with divalent manganese was studied by performing excitation, emission, and decay time measurements in the temperature range from 4.2 to 500 K. From the results of these measurements the following mechanism can be proposed. Excitation into the gallate host lattice leads to the formation of electron-hole pairs which recombine radiatively on either the gallate groups or Mn2+ or nonradiatively on quenching centers, depending on the temperature. In the first case a blue emission is observed, whereas the maximum of the green Mn2+ emission is at about 500 nm. At 4.2 K the effective distance of energy transport from excited gallate to emitting Mn2+ is estimated to be 40 Angstrom. Due to the increasing mobility of the exciton this value increases at higher temperatures. Furthermore, the luminescence properties are found to be dependent on the preparation conditions.