Piezoelectric Strain FET (PeFET)-Based Nonvolatile Memories

We propose nonvolatile memory (NVM) designs based on piezoelectric strain FET (PeFET) utilizing piezoelectric/ferroelectric material (PE/FE such as PZT) coupled with 2-D transition metal dichalcogenide (2-D-TMD such as MoS
$_{{2}}{)}$
-based transistor. The proposed NVMs store bit information in the form of polarization (
${P}$
) of FE/PE, use electric-field driven
${P}$
-switching for write, and employ piezoelectricity-induced dynamic bandgap modulation of 2-D-TMD channel for bit sensing. We analyze PeFET with COMSOL-based 3-D modeling, showing that circuit-driven optimization of PeFET geometry is essential to achieve effective strain transduction and adequate bandgap modulation for NVM read. We achieve distinguishability of up to
$11\times $
in binary states of PeFETs. We propose various flavors of PeFET NVMs, namely: 1) high-density (HD) NVM featuring a compact access-transistor-less bit-cell; 2) 1T-1PeFET NVM with segmented architecture, targeted for optimized write energy and latency; and 3) cross-coupled (CC) NVM offering a tradeoff between area and latency. PeFET NVMs offer up to
$7\times $
smaller cell area, 66% lower write energy, 87% lower read energy, and 44% faster read compared to 2-D-FET static random access memory (SRAM). This comes at the cost of high write latency in PeFET NVMs, which can be minimized by virtue of optimized PE geometry.