A novel vertical stepped doping poly-Si TFT (VSD-TFT) for leakage current improvement

•A poly-Si TFT structure is proposed to decrease leakage current.•The OFF-current reduces by creating two side barriers at the central barrier sides.•The ON-state current increases by a built-in electric field.•Results demonstrate that the on/off current ratio is improved too.•The channel doping density consists of five sections with different densities.

In this paper, we report a novel vertical stepped doping poly-Si thin film transistor (VSD-TFT) in which the channel doping density consists of five sections with different uniform densities in order to reduce the OFF-state leakage current and increase the ON-state current. The key idea in this work is to reduce the leakage current by creating two side barriers at two sides of central barrier and a built-in electric field for increasing the ON-state current. Using two-dimensional and two-carrier device simulation, we demonstrate that the OFF-state leakage current of the VSD-TFT decreases as compared with the C-TFT and the on/off current ratio is improved too.