Analytical Model of Apparent Threshold Voltage Lowering Induced by Contact Resistance in Amorphous Silicon Thin Film Transistors

In this paper, we have shown that in a-Si TFT\´s the apparent threshold voltage extracted by conventional methods is lowered by the presence of the source/drain contact resistance, especially at short channel lengths and the analytical model presented to explain this effect is in good agreement with the experimental data. This model is particularly useful for AMOLED applications where the contact resistance has a crucial role in determining the driving current and thus the brightness of the pixels. In this abstract, we (i) show that this series resistance causes a large lowering of the "apparent" threshold voltage when it is extracted by conventional methods, and (ii) develop an analytical model to explain this effect. The model is supported by experimental data at different channel lengths and series resistances.