Simple polysilicon thin film transistor structure for achieving high on/off current ratio independent of gate bias

Abstract

The ON and OFF characteristics of poly-Si TFTs described in this paper have been improved, with respect to conventional structure TFTs, by using a special device structure and a new process. To eliminate the anomalous leakage current we have used an offset gate structure while for increasing the device ON-current a fixed quantity of positive charges are introduced in the passivation layer on the top of the offset region. The presence of these charges result in accumulation of electrons at the surface which increase the surface conductivity of the offset region. Thus the proposed approach does not require any second gate electrode or use of ion implantation to achieve a high ON-current in poly-Si offset gate TFT structures.