It is known that the width of the memory loop of the brightness-voltage characteristic in ZnS:Mn a-c thin film electroluminescence devices depends on the Mn doping concentration and on the ZnS:Mn film thickness. In this study we have varied the ZnS thickness fraction doped with Mn and its location. The results of this study show that the memory loop widens incrementally with the ZnS thickness fraction doped with Mn. We infer that the Mn doping is affecting the high-field bulk conductivity of the ZnS. © 1980, The Electrochemical Society, Inc. All rights reserved.