The Research Of Drain Current For Amorphous Zinc Oxide Thin Film Transistors Based On Surface Potential

Amorphous zinc oxide thin film transistors(a-Zn O TFTs) have increasingly broader application in active matrix liquid crystal display(AMLCD) devices, solid image sensors, chemical sensors and other fields. Compared with hydrogenated amorphous silicon(a-Si:H), amorphous zinc oxide(a-Zn O) devices have more complex electrical properties. In particular, aZn O have a higher mobility than a-Si:H. Thus, it is important to legitimately build a-Zn O TFTs physical models. Particularly, clarifying a-Zn O TFTs’ leakage current physical mechanism, and giving a function relationship consistent with the device characteristics, they will be not only provide a theoretical basis for a-Zn O TFTs’ preparation and circuit simulation.The research goal of this paper are systematically study the physical mechanism of a-Zn O TFTs devices in detail based on the surface potential, and establish a compact model of leakage current characteristics for a-Zn O TFTs by discussing the issue of mobility, so that the model has the condition to been embedded circuit emulator.Based on Poisson’s equation and Gauss’ s law, a compact and analytical model for the surface potential of a-Zn O TFTs has been derived in this paper, which adopts the non-iterative computations and considers both the exponential band-tail and deep states distributions of a-Zn O TFTs. In this paper, based on the mathematical transformation and Lambert W function, and adopted the effective charge density method, a new non-iterative algorithm and analytical surface potential of a-Zn O TFTs has been developed. And, compared with the calculated results of numerical iterative, the absolute errors of proposed model can attain-510 range, and the computational efficiency can also be improved. This algorithm avoids the iterative solution and reduces the simulation time, and the model provides the conditions for implementation which can be embedded in-circuit emulator.Thus, the drain current model of a-Zn O TFTs can be established based on the above noniterative calculation and analytic the surface potential solution. Compared the simulated results with experimental data at different drain-source voltage and gate-source voltage of a-Zn O TFTs devices, the output and transfer characteristics of drain current for a-Zn O TFTs can be shown, and then verify the validity and correctness of the proposed drain current model.In addition, to further study the drain current characteristics of a-Zn O TFTs. Through the analysis of power-law function of the mobility and the derivation of the effective channel mobility, and the error data analysis based on the two mobility for the drain current, the proposed model can select the optimum mobility equation to suitable for calculated the derived drain current.In summary, the proposed DC model of a-Zn O TFTs is based on the physical mechanism, and as a function of the surface potential. The relationship between the model parameters and device parameters is simple, and the model fitting the existing experimental data have a great performance. The proposed model need less computation, less mathematical expression, and its first derivative is continuous, so it meet the condition which can be embedded circuit emulator.