A High‐Performance In‐Memory Photodetector Realized by Charge Storage in a van der Waals MISFET

Abstract

explosive increase in data information, however, significantly challenges the conventional von Neumann architecture in which sensing, memory, and computing functions are realized by discrete devices. In this circumstance, the integration of multifunctions in a single device, such as in-memory photodetectors, is regarded as an ideal solution to this problem. [7][8][9][10] These devices can not only dramatically simplify the conventional image sensor circuitry, but also be applied as a wide variety of photonic synaptic devices for neuromorphic computing and objects recognition in a complex environment. [11,12] Accordingly, it is necessary to explore novel materials and innovative device structures in photodetection with integrated working modes, which can accommodate the explosive data flows. [13] Among numerous novel materials, 2D materials are promising type of media for the evolution of in-memory photodetection. [14][15][16] On the one hand, 2D-material-based flash memories demonstrate ultrafast (nano seconds) operation speeds and long-term non-volatile property (10 years), owing to the atomically sharp interface and optimized barrier height. [17][18][19] On the other hand, their superior optoelectronic characteristics make them ideal photodetecting materials, considering their unique features of absences of dangling bonds [20][21][22] and tunable bandgaps. [23][24][25] Regarding the current research into 2D-material-based highperformance in-memory photodetectors, charge-storage effect is a practical approach. [15] Different from the working flow of normal photo detectors, this kind of in-memory photodetectors generally photosensitize at a positive or negative gate voltage to realize non-volatile charge writing and erasing. [26,27] In this vein, a few attempts at achieving charge storage have been carried out, which however yielded unsatisfactory photodetection or memory performances. [27][28][29][30] For instance, the MoS 2 / functionalized SiO 2 device with interface charge trap yields low readout photocurrent (<10 nA) and short non-volatile retention characteristic (≈20 s). [27] The floating gate structure of MoS 2 /h-BN/MoS 2 on Si/SiO 2 substrate showed longer retention time (>10 4 s) but suffers from the weakness of low readout photocurrent (only ≈100 nA). [28] Furthermore, the chargestorage mechanisms of almost all in-memory photo detectors are only at the hypothesis stage, lacking direct experimentalThe emerging data-intensive applications in optoelectronics are driving innovation toward the fused integration of sensing, memory, and computing to break through the restrictions of the von Neumann architecture. However, the present photodetectors with only optoelectronic conversion functions cannot satisfy the growing demands of the multifunctions required in single devices. Here, a novel route for the integration of non-volatile memory into a photodetector is proposed, with a WSe 2 /h-BN van der Waals heterostructure on a Si/SiO 2 substrate to realize in-memory photodetection. This photodetector exhibits a...

Rapid Charge Storage and Release at Etching‐Assist Electret in Organic Transistors for Memories, Photodetectors, and Artificial Synapses

“…Under the positive gate voltage and UV light irradiation, the C 12 -BTBT layer absorbs light to generate photo-excited holeelectron pairs, subsequently, the electrons are injected into the LUMO level of the PS layer under the gate electric field, so that the transfer curve of the transistor shifts more to the positive direction. [10,[61][62] According to the above experimental results, we conclude that after introducing charge trapping sites on the PS surface by plasma treatment, holes can be rapidly injected into PS in a short time to form surface electrets, which shifts the threshold voltage of the transistor to the negative direction, so that the transistor maintains high resistance state (i.e., low drain current) in a wide range of gate voltage. Nevertheless, the surface electret charges are sensitive to UV light and can be rapidly released under UV light irradiation, allowing the transistor to revert to a low resistance state (i.e., high drain current) within a certain gate voltage range.…”

“…Therefore, this photosensitive transistor is suitable for use as a photodetector, but a setup process of introducing surface electret by negative gate-bias stress is essential before each detection, which ensures that the response of the drain current is proportional to the UV light intensity. [10,63] The holes injected into PS can be released under UV light, and the device operation is sensitive to light intensity. Therefore, the changes in device state caused by electret charge release under UV light can be used as the basis of photodetectors.…”

“…[1][2] Insulators could trap charges from the external electrical or photonic stimulus, referring to electrets, which are being developed for transistors, memories, and bio-mimic systems. [3][4][5][6][7][8][9][10][11][12] However, as compared with electrical conductors, insulators intrinsically have high electrical resistance, thus the charge injection and release typically require high voltage or long applied duration, which limits their applications in highspeed devices. [13] Nanocomposites [14][15][16] or floating-gate [17][18] architectures have been developed to improve the charge storage and release capability, which has been commercially applied for memory applications.…”

Near-infrared heterojunction field modulated phototransistors with distinct photodetection/photostorage switching features for artificial visuals

“…34 In particular, multi-functional high performance optoelectronic devices are highly pursued, where the image sensing and processing functions in separated vision chips can integrate together for promoting the efficiency of the vision system. Nowadays, more functions in computing photonic chips are being developed, such as edge computing, 35 in memory detection, 36 motion detection 37 and broadband convolutional processing. 38 Here, by utilizing electronic extraction layer ZnO and a faceon orientation of D-A molecular packing in a D-A/graphene system, we explore the graphene/ZnO/PTB7-Th:IEICO-4F BHJ field-effect transistor with prominent infrared broadband photo-response (488-1064 nm) and photo-storage phenomena.…”

“…34 In particular, multi-functional high performance optoelectronic devices are highly pursued, where the image sensing and processing functions in separated vision chips can integrate together for promoting the efficiency of the vision system. Nowadays, more functions in computing photonic chips are being developed, such as edge computing, 35 in memory detection, 36 motion detection 37 and broadband convolutional processing. 38…”