This work presents an invention and investigation on the design of Organic Thin- Film Transistors (OTFT) with short-channel lengths required to achieve higher integration density organic circuits for various dc and RF applications. The dc and ac performance parameters of OTFT with channel lengths of 5 |am, 2 jam, 1.5 jam, 1.0 im, 0.9 nm and 0.7 |nm have been evaluated through carefully calibrated two-dimensional numerical simulation. The designed OTFT uses pentacene as the active layer in the bottom-contact configuration. The various performance parameter metrics i.e. threshold voltage (VTH), transconductance (Gm), gain (Av), ION/IOFF DIBL, cutoff frequency (fT) and Breakdown voltage (VBR) have been evaluated. The results have revealed that OTFTs with short-channel lengths show improved performance compared to long-channel transistors. The second order effects of threshold voltage (VTH) roll-off and DIBL are less pronounced in OTFTs. Results show that the VTH reduces only by 10.73% from L=5 im to L=0.7 im. The results have shown that OTFTs have a high ION/IOFF ratio of the order of 1013 thus effective for fast switching applications. The cut-off frequency of the simulated device for L=0.7 |im is 2.3 GHz suggesting the application of OTFTs for RF applications. The role of trap states on the device conduction has also been investigated. The simulation study has revealed that OTFTs exhibit well-defined mobility degradation and impact ionization behavior which becomes pronounced for channel lengths below 1 jim. Further the capacitive behavior of the designed device has been evaluated and it has been observed that the device capacitance can be defined from the MOSFET theory except for the role of trap states.
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