Organic Thin Film Transistor Gas Sensor Device and Circuit Level Optimization

Organic Thin Film Transistors are simulated for gas sensing application both in a single transistor and circuit configurations. Circuits with different configurations and different active organic materials are simulated. Results of simulation are compared with experiment. Combined transistor in parallel, series, and inverter configurations gave a better performance than single transistors in terms of gas analyte sensing. Drift-diffusion (DD) simulation model is used in which the basic equations used are similar to those used for a single-crystal device except that traps and defects are included in the model. It is assumed that traps due to grain boundaries are uniformly distributed throughout the film. Both exponential and Gaussian trap distributions are introduced in the simulation. Gas sensing is accounted for by doping dependent mobility model in the organic active material. Interface traps and charges at the interface between the polymer channel and gate insulator are incorporated. The density of doping in the polymer and the quantity of traps and interface charges are extracted by matching the simulation I-V curves with experiment. Parameters extracted from simulations show good agreement with that of experiment.