Improved electroluminescence of ZnS : Mn thin films by codoping with potassium chloride

Alternating current thin film electroluminescent devices have been fabricat ed using sputter-deposited ZnS:Mn with and without codoped potassium chlori de via both in situ and ex situ methods. In situ codoping proved to be diff icult due to a memory effect in the deposition chamber. Samples codoped wit h potassium chloride via an ex situ diffusion method exhibited improvements in brightness of up to 70% (572 vs 337 cd/m(2)) and efficiency of up to 60 % (1.95 vs 1.25 lm/W) over noncodoped samples. The threshold voltage increa sed by approximate to5% (160 vs 168 V), and the brightness-versus-voltage c urve stabilized more rapidly for the devices. Several possible mechanisms t o explain these effects are discussed. While modest microstructural changes contribute to the improvements, changes in point defects which lead to mod ification of the space charge in the devices appears to be the dominant mec hanism. (C) 2001 American Institute of Physics.