Asymmetric Electrical Properties of Corbino a-Si:H TFT and Concepts of Its Application to Flat Panel Displays

Inverted stagger hydrogenated-amorphous-silicon (a-Si:H) Corbino thin-film transistors (TFTs) were fabricated with a five-photomask process used in the processing of the active-matrix liquid-crystal displays (AM-LCD). The authors show that the a-Si:H Corbino TFT has the asymmetric electrical characteristics under different drain-bias conditions. To accommodate for these differences when the electrical device parameters are extracted, the authors developed asymmetric geometric factors. The ON-OFF current ratio can be significantly enhanced by choosing the outer electrode as the drain, while the field-effect mobility and threshold voltage are identical when different drain-bias conditions are used. Finally, the authors developed concepts of its possible application to AM-LCDs and active-matrix organic light-emitting displays