The Origin and Nature of Contact Resistance in a-Si:H TFTs

Abstract

ABSTRACTThe origin of contact resistance in a-Si:H TFTs is investigated by formulating a model for the contact limited current. The Model accounts for the independent contributions of the Metal–n+a-Si:H interface resistance and the space charge limited conduction through the intrinsic a-Si:H film. Using our contact current model we investigated the I–V behavior of an n–i–n structure with a thin a-Si:H layer (=700Å) and found that the resistance of the Metal–n+a-Si:H interface is nonlinear. We incorporated the contact limited current expression into a full TFT Model and simulated the TFT performance for a wide range of Metal–n+a-Si:H interface resistance values and intrinsic a-Si:H film thicknesses. We found that the Metal–n+a-Si:H interface resistance dominates over space charge limited conduction for the thicknesses of intrinsic a-Si:H films used in AM-LCD switches. This trend is sustained even when the effective resistance of the Metal–n+a-Si:H interface decreases due to the nonlinear current conduction across it.