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Organic Field Effect Transistors for Large Format Electronics

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Final rept.

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The work performed for this program was carried out at SVT Associates and the University of Minnesota. We have succeeded in demonstrating an Organic Field Effect Transistor OFET. We investigated a bottom-contact transistor structure in which the source and drain contacts are deposited directly on the gate oxide followed by the deposition of the active organic layer. Two-dimensional simulations for these structures were carried out and the I-V characteristics calculated. Barrier lowering due to image charge effects was found to play a critical role in determining device characteristics because the source contact acts as a reverse biased Schottky contact and without this effect the drain current would be severely limited. One important consequence of this is that if material in the immediate vicinity of the contacts is depleted of carriers due to traps or other defects the current can be significantly reduced. Even though this layer may constitute as little as 1 of the channel material, device performance is disproportionately affected by it. Actual bottom-contact OFET devices were fabricated and tested. Various organic materials were deposited onto the contactoxide layer. We have obtained device I-V curves with characteristic transistor behavior similar to the modeling result. It was found that ultraviolet light can greatly enhance current magnitude. These results represent significant accomplishments toward achieving our Phase I program goals. In summary, the major results of this Phase I program are 1 Development of two-dimensional model showing importance of a image charge related barrier lowering on current magnitude b material quality in the immediate vicinity of the sourcedrain contacts 2 Fabricated and tested OFETs with various organic materials 3 Demonstrated working OFETs with channel lengths of 10, 20 and 30 micrometers.

Subject Categories:

  • Electrical and Electronic Equipment
  • Computer Programming and Software
  • Electricity and Magnetism

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