Analytical Current–Voltage Model for Double-Gate a-IGZO TFTs With Symmetric Structure for Above Threshold

This article presents an analytical model to reproduce the I - V characteristics of a double-gate (DG) amorphous indium-gallium-zinc oxide (a-IGZO) TFT with symmetric structure. This model for the above-threshold region is based on the gate voltage dependence of surface potential and potential at the center of the semiconductor layer, which are described by analytical expressions. Considering the densities of the free and localized carrier in the semiconductor, the total carrier density, which is equal to the effective carrier density, is calculated. The carrier mobility, calculated as the ratio between the free carrier and the effective carrier density, depends on the gate voltage as a power law with the power parameter γ different from zero, as it is typically represented for the amorphous TFT. The drain current model has only 13 model parameters and was validated with six different simulated transistor structures, as well as with an experimental device. A good coincidence of the modeled characteristics with both the simulated and experimental devices was obtained.