Contact effects, Stability and Noise Investigation in Organic Thin-Film Transistors

--In this work we report on the results of DirectCurrent (DC) and Low-Frequency Noise (LFN) measurements in p-type staggered top-gate Organic Thin-Film-Transistors (OTFTs). The analysis involves the effects of Source/Drain contacts and the stability characteristics of OTFTs induced by Gate and Drain bias stress. Noise data are interpreted in the context of a multi-trap correlated-mobility-fluctuations (CMFs) model, showing that noise is dominated by acceptor-like traps. The influence of noise sources at contacts is found to be negligible. However contacts affect the measured noise by a non negligible differential resistance. The product between the scattering parameter and the effective mobility DPeff?2?107 cm2/C, which measures the strength of CMFs, is similar to what reported for a-Si:H and much higher with respect to c-Si MOSFETs revealing a strong correlation between CMFs and the state of disorder of the active layer. Instability is observed in presence of Drain bias stress and for sufficient short channel length (<10Pm). The measured shift in LFNMs appears correlated with the shift of the measured channel current. In the context of the CMF model the noise shift can be interpreted as due to the increase of DPeff caused by the increased scattering between the charged channel carriers and the charged traps at the interface.