The luminescence of ZnGa 2 0 and ZnGa 2 0 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 Mn 2+ or nonradiatively on quenching centers, depending on the temperature. In the first case a blue emission is o served, whereas the maximum of the green Mn 2+ emission is at about 500 nm. At 4.2 K the effective distance of energy transport from excited gallate to emitting Mn 2+ is estimated to be 40 A. 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.