A physically-based model for drift in Al2O3-gate pH ISFET´s

A physical model is presented which quantitatively describes drift in Al₂O₃-gate pH ISFET´s. Drift is postulated to be associated with a chemical modification of the Al₂O₃ surface as a result of exposure to the aqueous electrolyte. The time dependence of drift is modeled by a hopping transport mechanism, known as dispersive transport. Chemical modification of the Al₂ O₃ surface leads to a change in the overall insulator capacitance with time, which gives rise to a monotonic temporal change in the threshold voltage of the ISFET. The validity of the proposed model is experimentally tested by fitting measured drift characteristics of Al₂O₃-gate pH ISFET´s and examining the physical plausibility of the fitting parameters