A thin film transistor (TFT) is a special kind of field effect transistor made by depositing thin films for the metallic contacts, semiconductor active layer, and dielectric layer.
The channel region of a TFT is a thin film that is deposited onto a substrate (often glass, since the primary application of TFTs is in liquid crystal displays).
Most TFTs are not transparent themselves, since many of them are based on hydrogenated amorphous silicon (a-Si:H), which bandgap is assumed to be less than that of crystalline silicon (1.12eV). However, because indium tin oxide (ITO) are usually employed for the electrodes, terminals and interconnections are often transparent.
Because the substrate cannot stand for the high annealing temperature, the deposition process has to be completed under relatively low temperature. Chemical vapor deposition, physical vapor deposition (usually sputtering) are applied. Also the first solution processed transparent TFTs (TTFTs), based on zinc oxide were reported in 2003 by researchers at Oregon State University.Wager, John. OSU Engineers Create World’s First Transparent Transistor. College of Engineering, Oregon State University, Corvallis, OR: OSU News & Communication, 2003. 29 July 2007.
The best known application of thin-film transistors is in TFT LCDs, a variant of LCD technology. Transistors are embedded within the panel itself, reducing crosstalk between pixels and improving image stability. As of 2004, all but the cheapest color LCD screens use this technology. TFT panels are heavily used in digital radiography applications including Mammography and General Radiography.
The new AMOLED (Active-Matrix OLED) screens also contain a TFT layer.
See also
- Liquid crystal display television
References
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