An analytical model for short-channel organic thin-film transistors

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Abstract
An analytical model that describes the operation of α‐hexathienylene (α‐6T) thin‐film‐transistors (TFTs) is presented. The current‐voltage characteristics of TFTs with channel lengths ranging from 1.5 to 25 μm have been calculated after modifying the equations that describe the characteristics of conventional enhancement mode p‐channel metal‐oxide‐semiconductor field‐effect‐transistors. The calculated current‐voltage characteristics are compared with the experimental data. The model takes into account the non‐inversion‐mode operation of α‐6T TFTs as well as short channel effects such as series parasitic resistance, channel length shortening, apparent threshold voltage, and apparent field‐effect mobility. Furthermore, the field‐effect mobility is observed to depend on longitudinal electric fields which are higher than 105 V/cm, and this effect is also included in the model. The highest field‐effect mobility measured is 0.03 cm2/V s. From an analysis of measured data, the carrier mobility of field‐induced positive carriers in α‐6T is estimated to be at least as high as 0.08 cm2/V s.