Retention in nonvolatile silicon transistors with an organic ferroelectric gate

Abstract

A silicone-based one-transistor nonvolatile memory cell has been implemented by integration of a ferroelectric polymer gate on a standard n-type metal oxide semiconductor field effect transistor. The polarization reversal in the gate results in a stable and reproducible memory effect changing the source-drain current by a factor 102–103, with the retention exceeding 2–3 days. Analysis of the drain current relaxation and time-resolved study of the spontaneous polarization via piezoforce scanning probe microscopy indicates that the retention loss is controlled by the interface-adjacent charge injection rather than the polarization instability. A semiquantitative model describes the time-dependent retention loss characterized by an exponential decay of the open state current of the transistor. The unique combination of properties of the ferroelectric copolymer of vinylidene fluoride and trifluoroethylene, including an adequate spontaneous polarization and low dielectric constant as well as rather benign processing demands, makes this material a promising candidate for memories fully compatible with silicon technology.