The focus of this thesis involves development of highly transparent, n-channel, accumulation-
mode thin-film transistors employing a zinc tin oxide (ZTO) channel layer. ZTO-based
transparent thin-film transistors (TTFTs) show improved device performance compared
to ZnO-based TTFTs. An estimated peak effective mobility for these devices as high
as ~100 cm² V⁻¹sec⁻¹ has been observed, although effective mobilities in the range of 20-50 cm²V⁻¹sec⁻¹ are more common. This performance inconsistency may be due, in part,
to the large device dimensions employed in developmental test structures and/or to shadow
mask misalignment. Typical drain current on-to-off ratios are > 10⁶. Variation in the post-deposition
annealing cycle is found to be an effective means to control the threshold voltage
and to improve device performance. Optical characterization of these devices indicates
~84% transparency in the visible spectrum as viewed through the source/drain. Another
aspect of this thesis research involves the utilization and extension of quantitative polycrystalline
TFT device models with the intention of guiding the design and optimization of future
TFTs. In particular, subthreshold conduction is assessed in order to estimate the bulk (and/or
grain boundary) and interface trap densities. This leads to a consideration of threshold voltage
and channel mobility extraction, as well as establishment of the turn-on voltage, V[subscript turn-on]
Finally, a third aspect of this thesis research involves a new radio-frequency (RF) magnetron
sputtering system, custom-designed and constructed at OSU by Chris Tasker. Contributions
to the development of this tool include assisting in the design and implementation of the
computer-controlled interlocks utilized for operation of the tool. The experimental flexibility
of this new tool is discussed with respect to its applicability in the design and fabrication of
future TTFTS. / Graduation date: 2004
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30002 |
| Date | 07 August 2003 |
| Creators | Chiang, Hai Q. |
| Contributors | Wager, John F. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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