Research in High Voltage Thin Film Transistors (HVTFTs) has been driven by the need for devices with reduced on-state resistance and high blocking capability to improve the performance of large area electronic applications. Conventional HVTFTs give unsatisfactory performance because of the high on-state resistance, low breakdown voltage (Offset Drain HVTFT), high possibility of oxide failure and requirement for extra external bias line (Metal Field Plate HVTFT) etc. This thesis presents a novel high voltage thin film transistor structure - Semi-Insulating Field Plate HVTFT (SIFP HVTFT) which utilises a semi-insulating layer as the field plate to modify the conductivity in the offset region. The new structure has demonstrated and enhanced on-state performance relative to conventional offset drain device and a much improved blocking capability compared with all existing high voltage thin film transistor structures. Unlike conventional offset drain TFTs, during the "on-state", the channel formed under the gate can be extended into the offset region by the potential on the semi-insulating field plate which is controlled by the bias on the gate and the drain. Equivalent circuit models for the SIFP HVTFT have been developed for the device analysis. New concepts such as "extended channel" have been proposed for the first time to illustrate the device physics underlying the improvement in performance of the new device. The superior blocking capability is attributed to a very small leakage current flowing through the semi-insulating field plate which increases the radius of potential curvature near the drain. This leakage current, however, does not significantly contribute to the main current flowing through the device. It is concluded that the SIFP HVTFT presents a new concept to the high voltage thin film transistor family and has clearly shown many advantages over conventional HVTFTs.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:597542 |
| Date | January 1998 |
| Creators | Chen, Y. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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