Double-floating-gate memory device based on energy band engineered van der Waals heterostructure

Abstract

Floating-gate memory devices based on two-dimensional van der Waals heterostructures are considered as promising candidates for next-generation nonvolatile memories. Here, we report a nonvolatile double-floating-gate (DFG) memory device based on a ReS2/boron nitride/black phosphorus (BP)/boron nitride/graphene heterostructure. By comparing with a single-floating-gate device we fabricated, the device shows enlarged memory window, high on–off ratio, and improved retention performance. Based on these findings, we propose energy band diagrams showing how the memory performance can be improved by energy band engineering through designing the van der Waals heterostructure. In the DFG structure, electrons could transfer between the ReS2 channel and BP as well as between BP and graphene, providing greater controllability for electron tunneling and injection. By choosing graphene and BP as two floating gates, an energy barrier rising from the conduction-band offset between multilayer graphene and BP is set up to efficiently prevent charge leakage from the graphene floating gate and, thus, improve the memory performance. Our work demonstrates an effective way for future designs of high-performance nonvolatile flash memories.