An Analytical Model for the Transfer Characteristics of a Polycrystalline Silicon Thin-Film Transistor With a Double Exponential Grain-Boundary Trap-State Energy Dispersion

For a thin-film transistor (TFT) built on excimer-laser crystallized polycrystalline silicon, the dependence of the effective ldquograin-boundary mobilityrdquo on the gate-to-source voltage can be divided into two subregimes exhibiting different power-law characteristics. An expression for the effective mobility is developed using a procedure previously proposed for a TFT built on polycrystalline silicon exhibiting only single power-law dependence. The additional power-law component is reflected in the model by a pair of measurable and physically meaningful parameters. The procedure for determining these parameters is described and demonstrated. Both the measured and calculated transfer characteristics are reported and compared. The double power-law dependence implies a grain-boundary trap-state energy dispersion characterized by two exponential functions. This is presently verified.