Bias-induced threshold voltages shifts in thin-film organic transistors

An investigation into the stability of metal-insulator-semiconductor (MIS) transistors based on α-sexithiophene is reported. In particular, the kinetics of the threshold voltage shift upon application of a gate bias has been determined. The kinetics follow stretched-hyperbola-type behavior, in agreement with the formalism developed to explain metastability in amorphous-silicon thin-film transistors. Using this model, quantification of device stability is possible. Temperature-dependent measurements show that there are two processes involved in the threshold voltage shift, one occurring at $\text{T≈220\hspace{0.17em}}\mathrm{K}$ and the other at $\text{T≈300\hspace{0.17em}}\mathrm{K}.$ The latter process is found to be sample dependent. This suggests a relation between device stability and processing parameters.