An analytical modeling approach to the electrical behavior of the bottom-contact organic thin-film transistors in presence of the trap states

Abstract

In this paper, a complete analytical model of the conduction behavior of organic thin-film transistors (OTFTs) within the framework of trap states has been presented. The aim of the work is to develop modeling equations which can be evolved into compact models generic to OTFTs rather than relying on the MOSFET-based models for the modeling and simulation of organic-based devices. The exponential density of trap states and the trap decay rate has been included in the modeling equations of the bottom-contact OTFTs with pentacene as the active layer. In this work, we propose for the first time a modeling approach to mobility. The mobility model takes into account the low-field mobility enhancement as well as high-field mobility degradation because of the presence of defect states. The current–voltage equations in the linear and saturation regimes have been modified to include the effect of trap states. The influence of trap states on the device capacitance has been modeled, and it has been found that the high density of trap states leads to deviation in the capacitance characteristics of OTFTs. Results obtained from the modeling equations of surface potential, total charge density, mobility and current–voltage relations show performance degradation with the increase in the density of trap states. The results predicted from the analytical modeling equations are in excellent agreement with the reported electrical behavior of the OTFTs, thus proving the feasibility of the proposed model. The proposed analytical model is valid for OTFTs in the linear and saturation regimes even for short-channel length transistors.