Ferroelectric source follower for voltage-sensing nonvolatile memory and computing-in-memory

Abstract Memory arrays and computing-in-memory architecture based on emerging nonvolatile memory devices with a current-sensing scheme face several challenges when implemented in large-scale arrays, such as power and area penalties, voltage drop, and power-source limitations. Here, we demonstrate ferroelectric source followers as nonvolatile memory devices operating with a voltage-sensing scheme. The voltage output read out from the source terminal of a ferroelectric field-effect transistor is determined in a nonvolatile manner by the polarization state stored in a ferroelectric gate insulator, giving a higher output voltage at a lower threshold voltage. Device modeling reveals that the output voltage is described by a simple expression of the threshold voltage, gate bias, drain bias, and body-effect factor. Simple characteristics, low readout energy consumption (∼fJ) owing to an absence of steady current, and fast readout operation (∼ns) make ferroelectric source followers promising for voltage-sensing nonvolatile memory and voltage-sensing synapse as well as activation functions (biased rectified linear units) in computing-in-memory.