Electric-field enhanced thermionic emission model for carrier injection mechanism of organic field-effect transistors: Understanding of contact resistance

We developed an electric-field enhanced thermionic emission model combined with an equivalent circuit for a three-terminal organic transistor structure to interpret the gate-voltage dependent contact resistance. In the model the contact resistance is composed of two components: (i) the interfacial resistance not only influenced by interfacial energy barrier but also strongly dependent on active layer thickness, and (ii) the bulk resistance that is affected only by active layer itself. The model having physical meaning in the fitting parameters, different from the previous with simple power functions, can well fit the voltage dependence for a series of independent data. In addition, the bulk resistance component can be extracted and is estimated reasonable for the first time, which is demonstrated not to be neglected even for the devices with high effective mobility. The developed model will be helpful for understanding of contact resistance and charge carrier injection behavior in the organic thin film transistors.