Analysis of the current conduction in poly-Si thin film transistors

Abstract

The current conduction in polycrystalline silicon thin film transistors is analyzed in weak inversion, partially weak and strong inversion, and strong inversion regions. These operation regions can be determined from the dependence of the surface potential on the gate voltage under various channel potentials. In each different operation region, the source of the current conduction is analyzed based on the surface potential under the different channel potentials by some simple formulas. In comparison with other works and the calculated current components—the diffusion and drift current in the strong inversion, the current conduction is verified for both fully and partially depleted devices. It is found that the diffusion current dominates in the weak inversion region. Both diffusion and drift currents are important in the partially weak and strong inversion region. In the strong inversion region, the current conduction is determined by the drift component. It yields a new way to analyze the current conduction in polycrystalline silicon thin film transistors.