Analysis of distributed threshold voltage transistors

The device physics of the distributed threshold voltage thin-film transistor is described. This transistor features a low and constant off-current over a wide range of gate voltages. The origin of this feature is investigated using a gradual channel model. It is pointed out, however, that the gradual channel approximation represents a worst-case analysis; there is room for obtaining even better characteristics by taking into account the limit imposed by the generation rate of carriers. The results are applicable not only to amorphous-silicon thin-film transistors, but also to polysilicon thin-film transistors