Compact DC Modeling of Organic Thin-Film Transistors Including Their Parasitic Non-Linear Contact Effects Based on a Novel Extraction Method

This article presents a novel generic method for the extraction of the current-voltage characteristics of organic thin-film transistors (TFTs) that specifically accounts for the individual contributions of the source and drain contacts and their nonlinear behavior. Based on this extraction method, an analytical model has been derived that describes the behavior of the intrinsic TFT and of the source and drain contacts both in the linear and the saturation regimes. The essential feature of the proposed extraction method is that it does not depend on or assume any physical phenomena underlying the electrical characteristics of the contacts. Instead, it extracts the current-voltage characteristics of the contacts which can then be fit to any physics-based TFT model. This is beneficial both for circuit designers and for those developing physics-based TFT models. The proposed extraction method has been applied to organic TFTs fabricated on flexible plastic substrates in the staggered and coplanar device architectures using two different small-molecule organic semiconductors. The compact dc model has been used to simulate organic TFTs with channel lengths ranging from 4 to 100 μm and a transimpedance amplifier circuit based on TFTs with different channel lengths, and the results are in good agreement with the measurements.