The hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) have been widely used as switching device for large-area electronics such as active matrix liquid crystal displays (AM-LCDs). a-Si TFT is particularly advantageous to the production of large screen displays and facilitates mass production.
When employing an a-Si:H layer, the main objectives are to enhance the field effect mobility and to reduce the off-state current under light illumination. The increase of field effect mobility results in wide application of a-Si:H TFTs in high resolution LCDs. On the other hand, a-Si:H has high photoconductivity which results in high off-state current of a-Si:H TFT under light illumination. The off-state leakage current under light illumination is, in particular, a serious problem in the projection and/or multimedia displays that require high intensity backlight illumination.
Minimizing the off-current increase by a-Si photosensitivity is an important design consideration for achieving highimage-quality LCDs. TFT off-current increase by photoillumination of a-Si decreases the charge stored on the pixel during the TFT off-time, and results in gray-scale shading, flicker, crosstalk and other display nonuniformity in the LCD.
The fluorine incorporated amorphous silicon [a-Si:H(:F)] and amorphous silicon (a-Si:H) were illuminated with backlight to investigate electrical characteristics. The effect of different [SiF4] / [ SiH4] ratio on the performance of a-Si:H(:F) TFTs was also studied. We found the density of states in the gap of a-Si:H(:F) will be modified by the introduction of F into a-Si:H and resulting the shift of the Fermi level toward the valence band edge. The density-of-states increasing cause more recombination centers for electrons and holes to increase the carrier recombination rate. The shift in the Fermi level leads to a reduction of the photoconductivity of a-Si:H(:F). Due to these two important factor, the photo leakage current decreases.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0801106-145749 |
| Date | 01 August 2006 |
| Creators | Yang, Po-Cheng |
| Contributors | none, none, none, none |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0801106-145749 |
| Rights | unrestricted, Copyright information available at source archive |
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