A Novel Scalable Energy-Efficient Synaptic Device: Crossbar Ferroelectric Semiconductor Junction

A novel ferroelectric semiconductor junction (FSJ) based two-terminal memristor is demonstrated as a synaptic device for the first time. In this novel FSJ device, a metal-ferroelectric semiconductor (FS)-metal crossbar structure is used, instead of a metal-ferroelectric insulator-metal structure for a conventional ferroelectric tunnel junction (FTJ), so that an ultra-thin ferroelectric insulator is not required. Meanwhile, the FSJ also offers energy efficiency advantage over the conventional filament-based resistive random access memory (RRAM) device because the conductance of the FSJ scales with the junction area. Experimentally, a ferroelectric semiconductor α-In₂Se₃ based crossbar FSJ (c-FSJ) as a synaptic device is demonstrated. Ferroelectric resistive switching is clearly observed in both planar FSJ (p-FSJ) by in-plane polarization switching and c-FSJ by out-of-plane polarization switching. Conductance potentiation and depression in the c-FSJ are measured and benchmarked at both original size and projected to 32 nm node with different synaptic devices. α-In₂Se₃ c-FSJ shows good on-line learning accuracy (~92 %), low latency and energy consumption due to the short write pulse width and large R_ON.