Surface potential based current model for organic thin film transistor considering double exponential density of states

Abstract

Surface potential based models are one among the best known compact models for thin film transistors. However, their use in computer aided design (CAD) tools is restricted due to the fact that they need computationally intensive and iterative approach to obtain the device characteristics. Existing techniques for computing surface potential use region wise approximations, smoothing functions and empirical methods to solve for surface potential. These techniques, often result in in-consistent results, large errors especially in transition regions. Moreover, solutions obtained using such approximations quiet often fail to establish a relation with intrinsic device parameters. This work, proposes a computationally efficient, compact, accurate and a physically based closed form solution for surface potential in case of organic thin film transistors (OTFTs). The analytical expression obtained for surface potential is a non-iterative (single step) and extremely accurate with an absolute error less than 1% compared with numerical solution. Further, the surface potential expression derived is incorporated in the all-region I–V characteristics expression of an OTFT. The I–V characteristic curves obtained using the analytical solution for surface potential are able to accurately model both linear and saturation behaviour of an OTFT.