Analysis of ZnS:Mn‐Type ac Thin‐Film Electroluminescent Display Devices with Bulk Traps

Analysis of a ZnS:Mn‐type ac thin‐film electroluminescent device with a deep level in the bulk of the phosphor layer was performed. Both donor‐ and acceptor‐type levels were considered. Calculations of field, current, and luminescence as a function of the interface‐state‐level energy (ECD) showed that a trailing‐edge peak in the luminescence waveform appears when ECD is less than 0.5 eV. It was found that an acceptor‐type bulk level can, under certain conditions, lead to oscillations in the electron flux and the device current. A reasonable match between theoretical and experimental luminescence waveforms could be obtained for ECD = 0.8 eV. However, theory and experiment could not be matched simultaneously at three different drive conditions consisting of three different slew rates for the drive pulses. Further refinement of the model is necessary for predicting the ACTFEL drive response for all drive conditions. These refinements include the energy distribution of hot electrons, probability of impact excitation, and carrier multiplication in the phosphor layer.