This thesis investigates two methods of optical excitation of alternating-current
thin-film electroluminescent (ACTFEL) devices. The two experimental methods investigated in this thesis are the photo-induced charge (PIQ) and luminescence (PIL),
and the subthreshold-voltage induced transferred charge (VIQ) techniques. PIQ/PIL
experiments utilize an above-bandgap laser pulse to investigate the transport properties
of photo-injected electrons and holes within the phosphor layer of the ACTFEL
device. VIQ experiments use a broadband xenon lamp pulse to optically reset traps
which are ionized by subthreshold bipolar voltage pulses. Both experiments characterize
traps within the phosphor layer.
PIQ/PIL experiments are performed on evaporated ZnS:Mn ACTFEL devices
possessing phosphor layers with thicknesses of 950, 700, and 300 nm. From the
PIQ/PIL experiment, an impact excitation threshold electric field for evaporated
ZnS:Mn is found to be ~1 MV/cm. Evidence of hole-trapping is also obtained from
the PIQ experiment. The holes in evaporated ZnS:Mn ACTFEL devices are found
to possess a drift length of ~180 �� 70 nm, a hole lifetime of ~2 ps, and a capture
cross-section of ~7 x 10������� cm��. It is speculated that the trap responsible for hole
capture is a zinc vacancy or zinc vacancy complex.
VIQ experiments are performed on evaporated, atomic layer epitaxy [ALE] (Cl),
and ALE (DEZ) ZnS:Mn ACTFEL devices. Data obtained via VIQ experiments yield
evidence for the generation of space charge below the EL conduction threshold, as well
as providing a means of estimating the physical location, energy depth, density, and
capture cross-section of traps responsible for VIQ. The depth of the traps responsible
for VIQ in evaporated, ALE (C1), and ALE (DEZ) ZnS:Mn are estimated to be ~1.1,
~0.3, and ~0.8 eV, respectively. It is speculated that the traps responsible for VIQ
are due to sulfur vacancies, chlorine, and oxygen, for evaporated, ALE (Cl), and
ALE (DEZ), respectively. / Graduation date: 1999
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33448 |
| Date | 10 November 1998 |
| Creators | Cleary, Bradford A. |
| Contributors | Plant, Thomas K. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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