Negative-Voltage-Enabled Energy Efficient Nonvolatile Memories And In-Memory Computing Based On 2D Piezoelectric Transistors
This work addresses energy-efficiency and density limitations in non-volatile memories for computing applications, representing an incremental improvement over existing PeFET-based designs.
The paper tackles the trade-off between integration density and energy-efficiency in piezoelectric FET (PeFET) non-volatile memories by proposing designs that use negative voltage to reduce energy consumption, achieving read energy as low as 0.03x and write energy as low as 0.19x compared to prior designs, and enabling in-memory computing with 0.03x the energy of previous methods.
Piezoelectric FET (PeFET) is a promising non-volatile-memory (NVM) device that integrates a piezoelectric (PE)/ferroelectric (FE) capacitor with a 2D transistor. It uses the polarization of the FE capacitor for bit-storage and strain-induced bandgap change of the 2D channel during read. Previous PeFET-based NVM designs have shown immense promise in achieving high density and energy-efficiency compared to SRAM. However, a key limitation of these designs is that they must trade-off integration density to enhance energy-efficiency or augment the memory functionality with in-memory computing (IMC). In this work, we show that the unique structure of the PeFET presents an appealing opportunity to counter these limitations, thereby simultaneously achieving high density, high energy-efficiency, and IMC-compatibility. First, we highlight the key reasons for the limited energy-efficiency of the previous PeFET designs. Based on these insights, we propose two flavors of PeFET memories that utilize negative voltage (NeVo) to reduce the major energy-consuming components significantly. Compared to 6T-SRAM (prior PeFET-based NVMs), the proposed designs achieve substantial reductions in energy, lowering read energy to 0.08x(0.03x) and write energy to 0.19x(0.53x), respectively. We then leverage these cells to implement IMC primitives, such as addition, subtraction, and multiply-and-accumulate (MAC), achieving 0.03x the energy consumption of prior PeFET-based designs.