Benefits from Using Very Thin Channel Layer for TFTs

It is known from many published data on amorphous or polycrystalline silicon and on metal oxides based Thin Film Transistors (TFTs) that their electrical parameters improve when decreasing the thickness of the channel layer. The origin of this improvement is discussed here through electrostatic arguments only. In particular, it is shown that the behavior of the subthreshold swing with the thickness does not depend on the type of materials. The material and its electrical defects determine only the importance of the improvement but not the trend towards better electrical parameters. Meanwhile, in general, the electrical stability under gate stress enhances too. The improved stability is explained by the reduced electronic charge inside the channel layer, leading to a lower injection of electrons in the gate insulator.