Organic thin film transistors with asymmetrically placed source and drain contact

This work describes the impact of different source/drain contact arrangements on organic thin film transistor’s speed characterized by unity gain frequency. 2D numerical simulations are used to analyze four different device structures resulting from placement of either of the contacts at the bottom or on top of organic semiconductor film. It is shown that variations in contact placement result in differences in device speed due to differences in transconductance and gate–drain capacitances. An asymmetrical device structure with source at the bottom and drain at the top is found to yield the highest unity gain frequency at a carefully chosen semiconductor film thickness.

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► We highlight a significant impact of the contact placement on device transconductance and capacitance and device speed.
► It allows us to propose two new structures for OTFT with asymmetric placement of source and drain contact.
► BSTDC OTFT structure can offer significantly higher device speed while compared with its identical TC structure.
► This benefit results from its higher device transconductance and lower device capacitance at saturation region of operation.
► The proposed device becomes feasible if mobility and contact resistance in BC OTFT become as good as or better than TC OTFT.