The objective of the research presented in this thesis is to develop, implement,
and demonstrate the utility of an n-sheet, state-space alternating-current thin-film
electroluminescent (ACTFEL) device model. In this model, the phosphor layer is
discretized into n + 1 layers, with band-to-band impact ionization, space charge creation/
annihilation, and luminescent impurity excitation/do-excitation occurring only
at n sheets between the n + 1 layers. The state-space technique is a structured
approach in which the ACTFEL device physics implementation is separated from
the ACTFEL measurement circuit electrical response, resulting in a set of coupled,
first-order differential equations which are numerically evaluated. The device physics
implementation begins with electron injection from phosphor/insulator interfaces and
band-to-band impact ionization. Phosphor layer space charge generation via band-to-band
impact ionization and subsequent hole trapping, trap-to-band impact ionization,
and shallow donor trap emission are then added to the model. Finally, impact excitation
and radiative relaxation are added to the model to account for ACTFEL device
optical properties.
The utility of the n-sheet, state-space ACTFEL device model is demonstrated in
simulations which verify hypotheses regarding ACTFEL device measured characteristics.
The role of phosphor layer hole trapping and subsequent thermionic emission
in SrS:Cu ACTFEL device EL thermal quenching is verified via simulation. Leaky
ACTFEL device insulators are shown to produce high luminance but low efficiency. A
novel space charge estimation technique using a single transferred charge curve is presented
and verified via simulation. Hole trapping and trap-to-band impact ionization
are shown to produce realistic overshoot in C-V curves, and each results in a different
phosphor layer space charge distribution. DC coupling of the sense capacitor used
in the measurement circuit to the applied voltage source is required for the generation
of ACTFEL device electrical offset, as verified by simulation. Shallow donors are
identified as a probable SrS:Ce ACTFEL device leakage charge mechanism. A field-independent
emission rate time constant model is shown to yield realistic ZnS:Mn
ACTFEL device leakage charge trends. / Graduation date: 2001
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32679 |
| Date | 16 March 2001 |
| Creators | Hitt, John C. |
| Contributors | Wager, John F. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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