AVS 50th International Symposium
    Thin Films Wednesday Sessions
       Session TF2-WeA

Paper TF2-WeA7
Infrared Electroluminescent Zinc Sulfide: Rare Earth Doped Thin Film Devices

Wednesday, November 5, 2003, 4:00 pm, Room 329

Session: Optical Thin Films and Photovoltaics II
Presenter: A.S. Kale, University of Florida
Authors: A.S. Kale, University of Florida
W. Glass, University of Florida
N. Shepherd, University of Florida
M.R. Davidson, University of Florida
P.H. Holloway, University of Florida
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ZnS doped rare earth fluoride thin films have been fabricated by RF magnetron sputtering in the conventional metal-insulator-semiconductor-metal electroluminescence (EL) configuration as a novel source for IR radiation. These ACTFEL (alternating current thin film electroluminescent) devices have promise for applications in fiber optic communication and industrial gas sensors as well as consumer electronic devices. ZnS thin films, typically 1µm thick, doped with ErF@sub 3@ and NdF@sub 3@ have been studied for their IR versus visible emissions. Electroluminescence has been investigated after different annealing temperatures (as deposited to 475°C) at a fixed time (60min) to study the influence of annealing on the IR brightness. An extremely sharp temperature dependence has been found in the IR emission, where anneals at 425°C sharply increase the emission intensity, while temperatures 25°C higher or lower result in sharply attenuated emission. The origin of this effect will be discussed. Emission spectra and efficiency from 0.35 to 1.55µm will be reported. For Er doped films, there is no shift in 4f-4f emission wavelengths versus annealing temperature, but shifts of up to 10 nm are seen for Nd doped ZnS thin films. This shift in wavelengths in Nd has been attributed to crystal field effects on the mixed 5d-4f as well as the 4f-4f transitions. Room as well as low temperature time resolved decay measurements are presented to compare the nature of specific energy transitions and energy transfer mechanisms as function of device temperature.