Extraction of intrinsic contact resistance in organic thin-film transistors with single channel length and high capacitance density

Abstract

Accurate characterization of the intrinsic contact resistance is important for the optimization of organic thin-film transistors (OTFTs), especially in devices with high gate capacitance density. This study reports on a method for the extraction of the intrinsic, or gate-voltage independent, contact resistance from OTFTs. In contrast to the transfer length method (TLM), this method can be applied to devices with single geometry. The method is an extension of the previously reported Y-function method and combines the model proposed by Luan and Neudeck to analyze the effect of the gate voltage on the contact resistance. This method is first applied to OTFTs with a bottom-gate top-contact geometry having varying gate capacitance density values. The intrinsic contact resistance is found to decrease with increased gate capacitance density with values ranging between 4 kΩ cm and under 1 kΩ cm when the gate capacitance is changed from 36.6 to 231.7 nF/cm2, respectively. These values are in good agreement with those obtained using TLM experiments. This method is also shown to be applicable to OTFTs with top-gate bottom-contact geometry.