Unified electrical model for the contact regions of staggered Thin Film Transistors

Abstract

In this work, we propose an unified compact model, which includes the effects of both source and drain contact regions, to describe the electrical characteristics of staggered thin film transistors (TFTs). The model is based on a generic drift analytical expression that describes the intrinsic channel of the transistor. Despite the distributed two-dimensional nature of the contacts in staggered configurations, two-terminal components are usually preferred to model the source and drain contact regions. In this regard, a model based on versatile simple expressions that describe the current-voltage relations of both contact regions are proposed in this work. These expressions are based on the physics underlying a metal-organic-metal structure. They can be adapted to different transport conditions, such as ohmic, space-charge-limited transport or Schottky-like contacts. This adaptation is controlled with the value of a single parameter that modifies the concavity or convexity of these expressions. The model works together with an evolutionary parameter extraction procedure, presented in a previous work for TFTs with negligible drain contact effects, and adapted here to this proposed model for staggered transistors. The results of the model and the evolutionary procedure have been validated with published experimental data of different TFTs, mostly organic thin film transistors (OTFTs). The model and evolutionary procedure agrees with other procedures tested successfully in the literature which were defined to cope with specific kinds of contacts in the TFTs. In this regard, our model and evolutionary parameter extraction procedure unify these previous procedures.