IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Electronics Tuesday Sessions
       Session EL-TuP

Paper EL-TuP23
Improved Efficiency and Space Charge Effects in ZnS:Mn ACTFEL Devices Co-Doped with KCl

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Electronic Materials Poster Session
Presenter: J.S. Lewis, MCNC
Authors: J.S. Lewis, MCNC
M.R. Davidson, University of Florida
Q. Zhai, University of Florida
K. Waldrip, University of Florida
P.H. Holloway, University of Florida
Correspondent: Click to Email
Alternating-current thin-film electroluminescent (ACTFEL) phosphors have been studied and improved with respect to brightness, efficiency, and stability. It is shown that ex-situ co-doping of the sputter deposited ZnS:Mn active layer with K and Cl results in 53% improvement in brightness, 62 % improvement in efficiency, and better 100-hour accelerated aging stability. This improvement was demonstrated to result from a 75% increase in excitation efficiency for conduction electrons, combined with a small decrease in both light outcoupling and non-radiative recombination. By studying the electrical behavior of the co-doped devices as compared to the undoped devices, it was determined that there is a reduced amount of static space charge in the films, resulting in a larger average field, increased excitation efficiency, and increased charge multiplication. The reduced space charge is attributed to the addition of charge compensating zinc vacancy-chlorine complexes and isolated chlorine point defects, which are acceptor and donor defects, respectively, and the reduction of zinc vacancy deep hole traps. It is postulated that there is sufficient electron multiplication or donor ionization to create a situation in which the current limit is set by the phosphor resistance rather than a capacitance or density of states. The increased efficiency is discussed in a framework of generic ACTFEL device efficiency common to all ACTFEL phosphors. Work supported by DARPA Grant # MDA97-1-0003 through the Phosphor Technology Center of Excellence.