The floating body effect of a WSe₂ transistor with volatile memory performance

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• The floating body effect is crucial for single-transistor capacitor-less (1T0C) dynamic random access memory (DRAM) cells, enabling miniaturization beyond conventional capacitor limits.
• Existing 1T0C DRAM implementations primarily use traditional CMOS technology, limiting exploration in emerging semiconductor systems.
• Exfoliated multilayer tungsten diselenide (ML WSe2) presents an underexplored material system for advanced memory applications.

Purpose of the Study:

• To investigate the feasibility of using exfoliated ML WSe2 for 1T0C DRAM applications.
• To demonstrate the role of the floating body effect in WSe2-based 1T0C DRAM.
• To explore the underlying physical mechanisms enabling WSe2 1T0C DRAM functionality.

Main Methods:

• Fabrication and electrical characterization of dual-gate transistors with varying top-gate lengths using exfoliated ML WSe2.
• Analysis of device characteristics to confirm the floating body effect and distinct memory states.
• In situ electrostatic force microscopy (EFM) and density functional theory (DFT) calculations to elucidate charge injection mechanisms.

Main Results:

• Demonstrated successful implementation of 1T0C DRAM functionality in ML WSe2 transistors.
• Confirmed the critical role of the floating body effect, modulated by hole population, in achieving distinct memory states.
• Identified band-to-band (B2B) tunneling, driven by effective electrostatic modulation, as the mechanism for hole injection.

Conclusions:

• Exfoliated ML WSe2 is a viable material for realizing 1T0C DRAM, overcoming traditional channel thickness limitations.
• The floating body effect in ML WSe2 enables distinct memory states essential for DRAM operation.
• This work presents a significant advancement towards overcoming inherent limitations in DRAM cell design using novel 2D materials.