Large Memory Window of van der Waals Heterostructure Devices Based on MOCVD-Grown 2D Layered Ge4Se9

Abstract

Van der Waals (vdW) heterostructure has drawn much interest over the last decade owing to its absence of dangling bonds and their intriguing low-dimensional properties. The emergence of 2D materials has enabled the achievement of significant progress in both the discovery of physical phenomena and the realization of superior devices. Here, we are the first to introduce the group IV metal chalcogenide of 2D-layered Ge4Se9 as a new selection of insulating vdW material. We synthesized 2D-layered Ge4Se9 with a rectangular shape using the MOCVD system using liquid germanium precursor at 240 °C. By stacking the Ge4Se9 and MoS2, we fabricated the vdW heterostructure devices with a giant memory window of 129 V by sweeping back gate range of ±80 V. The gate-independent decay time reveals that the large hysteresis is induced by the interfacial charge transfer, which originates from the low band offset. Moreover, we observed repeatable conductance changes over the 2,250 pulses with low non-linearity values of 0.26 and 0.95 for potentiation and depression curves, respectively. The energy consumption of MoS2/Ge4Se9 device was about 15 fJ for operating energy and the learning accuracy of image classification reached 88.3%, which further proves the great potential of artificial synapses.