AVS 46th International Symposium
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       Session FP-MoA

Paper FP-MoA10
Role of Cations and Anions in Donor Doping of ZnS:Mn Thin Film Electroluminescent Phosphors

Monday, October 25, 1999, 5:00 pm, Room 604

Session: Luminescent Thin Films
Presenter: K.E. Waldrip, University of Florida
Authors: K.E. Waldrip, University of Florida
J.S. Lewis, III, University of Florida
Q. Zhai, University of Florida
M. Puga-Lambers, University of Florida, Microfabritech
M. Davidson, University of Florida, Microfabritech
P.H. Holloway, University of Florida
S.-S. Sun, Planar Systems, Inc.
Correspondent: Click to Email
Alternating current thin film electroluminescent ZnS:Mn phosphors have been deposited by RF magnetron sputter deposition on glass substrates coated with indium tin oxide (ITO) transparent conductor and an alumina-titania (ATO) composite dielectric. A co-dopant was introduced by an ex-situ diffusion method. The top dielectric and contact layers were deposited to complete the device. Control samples were processed exactly the same, with the exception that the co-dopants were not introduced. Co-doping ZnS:Mn thin film electroluminescent phosphors with potassium chloride resulted in a 50% increase in brightness and efficiency (150fL, 1.9L/W vs. 100fL, 1.3L/W), a 5% increase in threshold voltage, and an improvement in brightness vs. voltage stability. Electrical analysis revealed increases in the amount of transferred charge, leakage charge, internal phosphor field, and in the overall symmetry of the electrical characteristics with respect to applied voltage pulse polarity with KCl co-doping. The observations to date of the improved performance in co-doped ZnS:Mn can be explained by a donor doping mechanism in which chlorine acts as the shallowest and most abundant donor in the phosphor film. Interstitial potassium also behaves as a donor, and the theory rests on the assumption that there are more activated donors than acceptors. The purpose of the work presented here is to elucidate the role of the cation and the anion in the improved performance of co-doped ZnS:Mn phosphors. KF, KCl, KBr, LiCl, NaCl, ZnCl@SUB 2@ and K@SUB 2@S were tested as dopants to deconvolute the roles of the anion and the cation. The brightness and efficiency vs. voltage and threshold voltage for each sample will be reported against the control samples. SIMS and XTEM, as well as spectral distribution and electrical analysis will also be presented and correlated with the donor doping theory.