Contact resistance in pentacene thin film transistors

We present results of the contact resistance extraction for Pd and Au top-contact and Pd bottom-contact pentacene TFTs. The extracted gold TFT contact resistance depends on the gate-source voltage V_GS, but shows no dependence on drain-source voltage V_DS . The TFT channel resistance is comparable to or exceeds the contact resistance at L < 10 μm. Therefore, L < 10 μm Au TFT performance can be limited by the contacts instead of the channel. We propose a circuit simulating the bottom-contact TFT contact resistance, which is drain bias dependent. We verified the circuit applicability by extracting and comparing the TFT channel resistances at |V_DS| = 0.1 V and in the "linear" regime of TFT operation. The circuit allowed us to extract the physically meaningful Pd bottom-contact TFT resistance values and Pd top-contact TFT gate-voltage dependent R_s. Despite higher initial series resistance R_s for the Pd-contact TFTs, the series resistance in the "linear" region of the TFT operation is much smaller and only several times larger that the gold top-contact TFT series resistance