Relationship between leakage current and the type of passivation layer of hydrogenated amorphous silicon thin-film transistors

The variations in the device characteristics of hydrogenated amorphous silicon thin film transistors according to the passivation layers and manufacturing processes have been studied. If a thin SiNx layer is used as a passivation layer, leakage current is increased over one order of magnitude after the deposition of transparent conducting oxide on the passivation layer. This phenomenon is the result of an accumulation of carriers in the active channel due to the surface charging on the passivation layer. The increase in leakage current is prohibited by using an organic passivation layer. The increase in thickness, the decrease in the dielectric constant and/or changes in passivation surface state as the organic layer is used instead of a SiNx layer cause the,reduction in leakage current. The knowledge acquired from this work is useful in fabricating reliable switching arrays for flat-panel displays.