Polymeric Thin Film Transistors Modeling in the Presence of Non-Ohmic Contacts

This chapter discusses a model for polymeric thin film transistors, PTFTs, based on the unified model and parameter extraction method (UMEM), previously developed by these authors for thin film transistors, which includes specific features of OTFTs, as initial drain current and subthreshold behavior. In this case, the model shows the presence of non-ohmic contacts at drain and source. UMEM, has been previously used with a-Si:H, polysilicon and nanocrystalline TFTs and as compared with previous methods, it provides a more rigorous and accurate determination of the main electrical parameters of TFTs. Device parameters are extracted in a simple and direct way from the experimental measurements, with no need for assigning predetermined values to any model parameter or using optimization methods. In this case, the extraction procedure is complemented to include the extraction of the model parameters related to the non-ohmic contacts at drain and source. The model was implemented in Verilog-A and included for application in Spice simulators. Good consistency was found between the simulations in Spice using the model and the measured devices, as shown herein.