Abstract
Thin film transistors based on high-mobility organic semiconductors are prone to contact problems that complicate the interpretation of their electrical characteristics and the extraction of important material parameters such as the charge carrier mobility. Here we report on the gated van der Pauw method for the simple and accurate determination of the electrical characteristics of thin semiconducting films, independently from contact effects. We test our method on thin films of seven high-mobility organic semiconductors of both polarities: device fabrication is fully compatible with common transistor process flows and device measurements deliver consistent and precise values for the charge carrier mobility and threshold voltage in the high-charge carrier density regime that is representative of transistor operation. The gated van der Pauw method is broadly applicable to thin films of semiconductors and enables a simple and clean parameter extraction independent from contact effects.
Highlights
Thin film transistors based on high-mobility organic semiconductors are prone to contact problems that complicate the interpretation of their electrical characteristics and the extraction of important material parameters such as the charge carrier mobility
We show that the gate in the gated van der Pauw (gVDP) structure creates transport conditions similar to thin film transistors (TFT) operation
We propose a simple model for the interpretation of gVDP characteristics, allowing for an extraction of mobility and threshold voltage VT
Summary
Thin film transistors based on high-mobility organic semiconductors are prone to contact problems that complicate the interpretation of their electrical characteristics and the extraction of important material parameters such as the charge carrier mobility. Mobility is conveniently extracted from thin film transistors (TFT) characteristics using the standard gradual channel approximation model[6,7] This approach evaluates the mobility of charges during their transport through the high-density accumulation layer at the semiconductor-dielectric interface[8,9]. A more accurate, yet simple, method is highly desirable for the proper evaluation of mtfsc, the charge carrier mobility in thin films of organic semiconductors in the high-charge density accumulation layer In this definition, mtfsc characterizes the contact-independent translational motion of charge carriers across the thin film semiconductor material, over distances that may be larger than typical grain size. We fabricate devices based on thin films of seven different organic semiconductors and show that their measurements are independent of Rc and are representative of the electrical characteristics of the thin film in the high-charge density regime This validates the gVDP method as a simple and accurate technique to extract mtfsc
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