AVS 47th International Symposium
    Flat Panel Displays Tuesday Sessions
       Session FP+VT-TuA

Paper FP+VT-TuA4
Current Density Saturation in FED Phosphors

Tuesday, October 3, 2000, 3:00 pm, Room 313

Session: Emissive Displays and Device Reliability
Presenter: J.S. Lewis, University of Florida
Authors: J.S. Lewis, University of Florida
G.O. Mueller, Agilent Labs
R. Mueller-Mach, Agilent Labs
T. Trottier, Agilent Labs
P.H. Holloway, University of Florida
Correspondent: Click to Email
In recent years interest in low voltage phosphors has been prompted by the development of field-emission displays (FED's) which operate in the 0.5-6 kV range. Taking into account factors such as dwell time, power density, intrinsic efficiency, and penetration depth, the current densities involved in FED operation are of similar magnitude as those used in CRT's and projection tubes. While brightness typically increases with current, efficiency decreases at higher current densities. Due to the different operating conditions, increased characterization and understanding of saturation at low voltages is needed. Quantification of current density is difficult, since electron beams used to excite the phosphors generally exhibit a Gaussian current distribution. This leads to variation of current density, and potentially saturation effects, over the beam area. Gaussian beam shapes cause more severe saturation in the center of the beam spot where current density is higher, and 'blooming' effects cause a change in beam size or shape as current increases. Deconvolution of these effects is difficult, but new experimental techniques have been developed which for the first time allow the determination of saturation effects in terms of absolute efficiency (under FED conditions). An approach was developed for the determination of the current distribution, and thus the saturation of intrinsic efficiency is obtained as a function of true local current density. The data can be used to model performance under any arbitrary current distribution. Results will be presented for a variety of traditional CRT and projection tube phosphors, as well as newer phosphors for use in FED's. The mechanisms for saturation will be discussed. *This work partially supported by the Phosphor Technology Center of Excellence.