Research On The DC Model Of Organic Thin Film Transistors

Field effect transistor is one of the most basic devices in the field of microelectronics, especially in the integrated circuits. The organic semiconductor materials take the world's attention, because of low cost, simple processing technology, wide range of materials, good mechanical properties, and being compatible with traditional silicon-based technology. Organic thin film transistor based on organic semiconductor materials as a kind of field effect transistors becomes the object of research and development all over the world. The mobility of several organic polycrystalline thin films has achieved 1cm2/Vs. The performance has reached and exceeded the a-Si:H TFT. OTFT-based applied research develops gradually. Therefore, the research on the models of organic thin film transistors is significant.Without the models of silicon devices, inorganic semiconductor can not develop so fast. Similarly, as the applications of organic thin film transistors are more and more widely, the simulation models are more and more important. A precise model, can considerably improve the application of organic thin film transistors in the integrated circuits and verify the performance.The present paper mainly studies the DC model of organic thin film transistors. First of all, a great deal of literatures on analysis models of organic thin film transistors has been read. Several kinds of theories which are recognized, namely Multiple Trapping and Release model, grain boundary trapping model, Monte Carlo theory, et al. And from the existing numerous organic theories of thin film transistors, one kind of more reasonable theory is chosen as our research, namely variable range hopping theory. Each kind of influences to organic thin film transistors has been considered in the variable range hopping theory. So the using of the theory also becomes unusual widespread.Then, based on the variable range hopping theory, one kind of DC model of organic thin film transistor is proposed. By using current expression which is from the relationship between current density and conductivity, and the conductivity which is from the percolation theory, one DC current expression of organic thin film transistor based on the variable range hopping theory has been gained, via a series of integral transforms, mathematical calculations and approximations. Some parameters are from the experimental data. Through repetitious tries, a group of parameters are obtained which make a very good agreement between experimental data and the analytical model, with MATLAB. It verifies the accuracy of the current expression of organic thin film transistor. Therefore the DC simulation model of organic thin film transistors is obtained.At last, although the model based on variable range hopping theory is correct, it can not be used in some simulation software. One kind of DC model of organic thin film transistor based on HSPICE is proposed. In this paper, the Level 62 RPI TFT model is chosen. Through several tries, a group of parameters are gained which make a very good agreement between experimental data and the Level 62 RPI TFT model. It proves the validity of the model of organic thin film transistor based on Level 62 RPI TFT model. One kind of inverter which is made by p-type organic thin-film transistors is simulated by this model. And the result we get is not bad. This proves the practicability of the model of organic thin film transistor based on Level 62 RPI TFT model. This model provides a temporary solution for the designs and simulations of the integrated circuits based on organic thin film transistors.