Evidence of Correlated Mobility Fluctuations in p-type Organic Thin Film Transistors

We report on the results of noise measurements in ptype organic thin-film transistors (OTFTs) extending from the subthreshold region into the strong accumulation region over four decades of drain current values. The low frequency noise produced by the devices can be successfully interpreted in the context of the multi-trap correlated number fluctuation - mobility fluctuation (CMF) theory, while neither phonon induced mobility fluctuation nor carrier number fluctuation mechanisms are capable of justifying the observed noise behavior. The Coulomb scattering parameter is found to be in the order of 107 Vs/C, about three orders of magnitude larger with respect to crystalline Silicon (c-Si) MOSFETs and comparable to what already reported in hydrogenated amorphous silicon (a-Si:H) TFTs, suggesting a much more relevant contribution coming from CMF in disordered materials.