Photoinduced Multi‐Bit Nonvolatile Memory Based on a van der Waals Heterostructure with a 2D‐Perovskite Floating Gate

Abstract

inevitable, which reduces the reliability in high-density integration. Furthermore, uncontrollable interface is detrimental to the retention time and operation speed of the memory device. 2D van der Waals (vdW) crystals manifest ultra-thin layered structure, highly anisotropic in-and outof-plane conductivity and superior carrier migration, [6] which are promising to solve the above problems. Over the past decade, 2D vdW atomic crystals, such as graphene, MoS 2 , ReS 2 , etc., are widely used as the composed elements in FGNVM, [7][8][9][10][11] and extended device structures are proposed to improve the performance. [12,13] It has been demonstrated that the FGNVM based on vdW heterostructure could enable atomically sharp interface for ultrafast operation at tens of nanosecond. [14][15][16] Nonetheless, the investigation is still in the initial stage and much research work has to be carried out before the commercialization of the vdW-heterostructure-based nonvolatile memory. In conventional FGNVM, the program/erase operations are accomplished by electrical stimuli. The repetitive voltage drives not only increase the power consumption, but also deteriorate the reliability and stability of the device. [17] Light, as an efficient non-contact signal, has a small energy dissipation when traveling through the free space. Therefore, using light illumination as an auxiliary programming method is beneficial to realize long-distance quantum communication, while effectively minimizing the power consumption, so as to improve the reliability The development of floating-gate nonvolatile memory (FGNVM) is limited by the charge storage, retention and transfer ability of the charge-trapping layer.Here, it is demonstrated that due to the unique alternate inorganic/organic chain structure and superior optical sensitivity, an insulating 2D Ruddlesden-Popper perovskite (2D-RPP) layer can function both as an excellent chargestorage layer and a photosensitive layer. Optoelectronic memory composed of a MoS 2 /hBN/2D-RPP (MBR) van der Waals heterostructure is demonstrated. The MBR device exhibits unique light-controlled charge-storage characteristics, with maximum memory window up to 92 V, high on/off ratio of 10 4 , negligible degeneration over 10 3 s, >1000 program/erase cycles, and write speed of 500 µs. Dependent on the initial states, the MBR optoelectronic memory can be programmed in both positive photoconductivity (PPC) and negative photoconductivity (NPC) modes, with up to 11 and 22 distinct resistance states, respectively. The optical program power for each bit is as low as 36/10 pJ for PPC/NPC. The results not only reveal the potential of 2D-RPP as a superior charge-storage medium in floating-gate memory, but also provides an effective strategy toward fast, low-power and stable optical multi-bit storage and neuromorphic computing.

Fast, Multi‐Bit, and Vis‐Infrared Broadband Nonvolatile Optoelectronic Memory with MoS2/2D‐Perovskite Van der Waals Heterojunction

“…2D Ruddlesden-Popper perovskite (2D-RPP) materials with unique inorganic/organic alternating chain structure have received attention recently in non-volatile floating gate memory. [19,20] Due to the insulating nature of the long organic chain, it is possible that the organic chain layer itself functions as an insulating tunneling layer as that in FG structure, while the trapping ability of charge are determined by the chain length and the multiple defect states in the inorganic layer. [21] Besides, 2D-RPP are photosensitive materials that provide tunable band structures via component engineering, which is essential in interface band alignment design and broadband photoelectric application.…”

Uncovering the Role of Crystal Phase in Determining Nonvolatile Flash Memory Device Performance Fabricated from MoTe2-Based 2D van der Waals Heterostructures

“…When the laser pulses are irradiated on the device, considerable photogenerated electron/hole pairs will be induced in the semiconducting channel, which is shown in Figure S12g. Since holes are easier to tunnel through the h-BN insulating layer than electrons, more holes tunnel into the floating gate layer to recombine with the stored electrons, resulting in a reduced net charge in the floating gate layer . With the number of optical pulses increasing, optical-induced multilevel switching states can be obtained.…”

Advanced Optoelectronic Devices for Neuromorphic Analog Based on Low‐Dimensional Semiconductors

“…Photogenerated electrons (holes) in the channel unable to recombine with carriers of opposite polarity and accumulate in the channel, resulting in persistent EPSC does not disappear but maintains for a period of time instead of immediate disappearance. [94][95][96][97][98][99] Tran et al [89] reported a floating gate field effect transistor based on MoS 2 /h-BN/graphene heterostructure (Figure 8a). The fabricated optical memory device could control electron tunneling to the graphene floating gate layer to modulate the resistance of the MoS 2 channel and realize the programmable function of optical memory by using the source-drain voltage and light illumination.…”