Random Access Memory Based on In-plane Ferroelectricity

Technology

The memory device has at least one semiconductor layer, one writing electrode and one reading electrode. The semiconductor layer is made of ferroelectric material having an in-plane polarization component switchable between two opposite directions. These two polarization states represent the “0” and “1” bit of the information. Such robust ferroelectricity at room temperature in atomic-thick thin films is viable in specific materials such as SnTe. The writing electrode applies a writing voltage to the semiconductor layer and switches the in-plane polarization component between the two directions. The reading electrode applies a reading voltage that measures the tunneling current substantially perpendicular to the direction of the in-plane polarization component. Different in-plane polarization direction bends the local electronic band structure of the semiconductor layer differently, resulting a very sensitive dependence of the electric tunneling potential perpendicular to the semiconductor layer on the direction of the in-plane polarization. This enables a nondestructive polarization state readout. An additional thin insulator layer can be sandwiched between the semiconductor layer and the two electrodes in order to prolong the lifetime of the in-plane polarization state and prevent electric leakage through the electrode.

Problem Addressed

Conventional memory devices using out-of-plane polarization of ferroelectric materials have several drawbacks. First, the reading process is destructive and a reset electric field is usually applied to maintain the initial polarization, which increases the device complexity and power consumption. Second, the material typically has a thickness greater than a required threshold thickness to build up the polarization field; therefore this limits the smallest possible size of the device. The proposed memory is based on in-plane polarized ferroelectric state. The reading process is nondestructive and the memory device can be as thin as one unit cell (UC) of the ferroelectric material.

Advantages

• Low power consumption
• Fast write operations
• Durable storage
• Small device size

Publications

Kai Chang, et al. "Discovery of Robust In-Plane Ferroelectricity in Atomic-Thick SnTe." Science 353, 274-278 (2016). DOI: 10.1126/science.aad8609.