Instability of the Noise Level in Polymer Field-Effect Transistors with Non-Stationary Electrical Characteristics

摘要

The low frequency noise (LFN) properties of field-effect transistors (FETs) using polymers as the semiconducting substrate material are investigated and explained in terms of the charge carrier transport in polymer thin-film structure. Three mechanisms contribute to the carrier transport ― charge injection from source electrode into polymer, charge hopping between polymer molecules for drift transport toward the drain, and charge buildup, probably at polymer-oxide interface. Charge buildup is responsible for non-stationary electrical characteristics, but does not contribute significantly to the LFN. Charge hopping determines the maximum value of the mobility and the minimum value of mobility 1/f noise. The variations of the PFET characteristics are mainly due to dispersion in the injection barrier of source-to-polymer contact. High disorder in the polymer at the source contact can increase the leakage current in PFET and can introduce number fluctuation S_(G_N) in the polymer conduction on top of the mobility fluctuation. S_(G_N) is proportional to the DC power applied to the injection barrier and should be assumed as a voltage source, since carrier hopping in the polymer reduces the effect of the injection noise. At present, the physical origin of S_(G_N) is not fully understood.