Why is nonvolatile ferroelectric memory field-effect transistor still elusive?

TLDR

A memory FET based on a metal‑ferroelectric‑semiconductor gate stack promises random access, high speed, low power, high density, and nonvolatility, yet reported devices retain data for only a few days, far short of the ten‑year requirement. This study investigates the depolarization field and finite gate leakage as the main causes of short retention in ferroelectric memory transistors and proposes a solution involving single‑crystal, single‑domain ferroelectric growth on silicon. The authors analyze retention loss mechanisms, recommend single‑crystal, single‑domain ferroelectric on Si to mitigate them, and propose employing the device as a capacitor‑less DRAM cell.

Abstract

In principle, a memory field-effect transistor (FET) based on the metal-ferroelectric-semiconductor gate stack could be the building block of an ideal memory technology that offers random access, high speed, low power, high density and nonvolatility. In practice, however, so far none of the reported ferroelectric memory transistors has achieved a memory retention time of more than a few days, a far cry from the ten-year retention requirement for a nonvolatile memory device. This work will examine two major causes of the short retention (assuming no significant mobile ionic charge motion in the ferroelectric film): 1) depolarization field and 2) finite gate leakage current. A possible solution to the memory retention problem will be suggested, which involves the growth of single-crystal, single domain ferroelectric on Si. The use of the ferroelectric memory transistor as a capacitor-less DRAM cell will also be proposed.