Sputter deposition and electroluminescence of Zn2GeO4:Mn

Radio frequency magnetron sputter-deposited Zn(2)GcO(4):Mn was investigated as a potential green-emitting phosphor fur thin-film electroluininescent devices. Thin Films similar to 0.4 mu m thick were tested at a frequency of 60 Hz at 40 V above threshold. The best device values were L-40 = 74 cd/m(2), E-40 = 0.19 lm/W, and CIE x = 0.300 and y = 0.664. The films were transparent and smooth, resulting in extremely poor outcoupling of light. This suggests that the internal efficiency of the devices may be significantly higher than reflected by the values of L-40 and E-40. Photoluminescent excitation spectra showed a defect state lying 614 meV froln the bandedge. Electrical characterization before and after aging showed a very large amount of dynamic space charge was present in as deposited devices. This space charge disappeared after aging just 30 min at 3.5 kHz and resulted in a threshold voltage increase from 180 to 220 V. (C) 2000 The Electrochemical Society. S0013-3651(00)01-126-5. All rights reserved.