Optoelectronic Transistor Research Articles

All-In-One Optoelectronic Transistors for Bio-Inspired Visual System.

Visual perception has profound effects on human decision-making and emotional responses. Replicating the functions of the human visual system through device development has been a constant pursuit in recent years. However, to fully simulate the various functions of the human visual system, it is often necessary to integrate multiple devices with different functions, resulting in complex, large-volume device structures and increased power consumption. Here, an optoelectronic transistor with comprehensive visual functions is introduced. By coupling diverse photoreceptive properties of the channel and electrical regulation through charge injection/ferroelectric switching from the hafnium-based gate, the devices can simulate functions of both photoreceptors in the retina and synapses in the visual cortex. A device array is constructed to confirm the perceptual functions of cone and rod cells. Subsequently, color discrimination and recognition for color images are achieved by combining the tunable perception and synapse functions. Then an intelligent traffic judgment system with this all-in-one device is developed, which is capable of making judgments and decisions regarding traffic signals and pedestrian movements. This work provides a potential solution for developing compact and efficient devices for the next-generation bio-inspired visual system.

Reconfigurable Sensing‐Memory‐Processing and Logical Integration Within 2D Ferroelectric Optoelectronic Transistor for CMOS‐Compatible Bionic Vision

AbstractNeuromorphic ferroelectric transistors integrating sensing and memory capabilities for photoelectric stimuli have provided a remarkable platform for multifunctional bionic vision. However, most hardware demonstrations utilizing ferroelectric transistors cannot implement multiple bio‐visual functions simultaneously under a small operating voltage with scalable material systems, which reduces the compatibility with complementary metal‐oxide‐semiconductor (CMOS) technology and blocks further bio‐visual applications. Herein, an optoelectronic transistor gated is constructed with ferroelectric LiNbO3, which exhibits sensing‐memory‐processing functions and logic integration simultaneously under a low operating voltage (≈1.5 V). Benefiting from the programmable photoinduction and strong ferroelectric polarization, the reliable and highly controllable synaptic characteristics and the bio‐visual selective learning behavior are successfully demonstrated. A high recognition accuracy (≈94.5%) in simulations is also achieved due to the unique linear synaptic plasticity. Furthermore, based on dual‐wavelength modulation, the full‐optical logics “AND” and “OR” are established within the same device. This work provides novel opportunities for the complex multifunctional bionic vision and toward large‐scale integration compatible with silicon‐based CMOS processes.

An Au25 nanocluster/MoS2 vdWaals heterojunction phototransistor for chromamorphic visual-afterimage emulation.

Color vision relies on three cone photoreceptors that are sensitive to different wavelengths of light. The interaction of three incident light wavelengths over time creates a fascinating color coupling perception, termed chromamorphic computing. However, the realization of this fascinating characteristic in semiconductor devices remains a great challenge. Herein, a mixed-dimensional optoelectronic transistor based on a novel metal nanocluster Au25(SC12H25)18 and two-dimensional MoS2 van der Waals (vdWaals) heterojunction is proposed for chromamorphic visual-afterimage emulation with red-green-blue three-color spatiotemporal coupling perception. This distinguished molecular-like electronic level of Au25 nanoclusters allows the transistor to have visible light-sensitive properties, endowing it with the ability to perceive color information. Moreover, the chromamorphic functions are realized using a color spatiotemporal coupling approach. By utilizing the photogating effect of light stimulus, the device exhibits visual experience-dependent plasticity in accordance with the Bienenstock-Cooper-Munro (BCM) learning rule. Most importantly, for the first time, intriguing visual afterimages could be implemented using a color sensitization approach based on a close relationship between visual persistence and negative afterimages. These results represent an important step towards a new generation of intelligent visual color perception systems for human-computer interaction, bionic robots, etc.

Azobenzene-based optoelectronic transistors for neurohybrid building blocks

Exploiting the light–matter interplay to realize advanced light responsive multimodal platforms is an emerging strategy to engineer bioinspired systems such as optoelectronic synaptic devices. However, existing neuroinspired optoelectronic devices rely on complex processing of hybrid materials which often do not exhibit the required features for biological interfacing such as biocompatibility and low Young’s modulus. Recently, organic photoelectrochemical transistors (OPECTs) have paved the way towards multimodal devices that can better couple to biological systems benefiting from the characteristics of conjugated polymers. Neurohybrid OPECTs can be designed to optimally interface neuronal systems while resembling typical plasticity-driven processes to create more sophisticated integrated architectures between neuron and neuromorphic ends. Here, an innovative photo-switchable PEDOT:PSS was synthesized and successfully integrated into an OPECT. The OPECT device uses an azobenzene-based organic neuro-hybrid building block to mimic the retina’s structure exhibiting the capability to emulate visual pathways. Moreover, dually operating the device with opto- and electrical functions, a light-dependent conditioning and extinction processes were achieved faithful mimicking synaptic neural functions such as short- and long-term plasticity.

Bidirectionally Photoresponsive Optoelectronic Transistors with Dual Photogates for All‐Optical‐Configured Neuromorphic Vision

AbstractBio‐inspired neuromorphic vision sensors, integrating optical sensing, and processing functions have attracted significant attention for developing future low‐power and high‐efficiency imaging systems. However, the compulsory electrical signal modulation to achieve inhibitory behaviors in most reported neuromorphic vision sensors results in additional hardware and computational latency. Herein, bidirectional photoresponsive optoelectronic synapses based on In2O3/Al2O3/Y6 phototransistors are achieved, realizing all‐optical‐configured synaptic weight updates enabled by dual photogates. The inhibitory and excitatory photoresponses originate from the photogating effects provided by trapped photogenerated electrons in Al2O3 under near‐infrared light and the ionized oxygen vacancies in In2O3 under ultra‐violet light, respectively. The bidirectional phototransistor illustrates outstanding optoelectronic synaptic characteristics with low nonlinearity and asymmetry, demonstrating high efficiencies in both preprocessing and postprocessing tasks, such as noise reduction, contrast enhancement, and pattern recognition. The proposed dual‐photogate optoelectronic synapses provide effective strategies to construct high‐efficiency neuromorphic vision sensors and in‐sensor computing systems.

Flexibly Photo-Regulated Brain-Inspired Functions in Flexible Neuromorphic Transistors.

As an attractive prototype for neuromorphic computing, the difficultly attained three-terminal platforms have specific advantages in implementing the brain-inspired functions. Also, in these devices, the most utilized mechanisms are confined to the electrical gate-controlled ionic migrations, which are sensitive to the device defects and stoichiometric ratio. The resultant memristive responses have fluctuant characteristics, which have adverse influences on the neural emulations. Herein, we designed a specific transistor platform with light-regulated ambipolar memory characteristics. Also, based on its gentle processes of charge trapping, we obtain the impressive memristive performances featured by smooth responses and long-term endurable characteristics. The optoelectronic samples were also fabricated on flexible substrates successfully. Interestingly, based on the optoelectronic signals of the flexible devices, we endow the desirable optical processes with the brain-inspired emulations. We can flexibly emulate the light-inspired learning-memory functions in a synapse and further devise the advanced synapse array. More importantly, through this versatile platform, we investigate the mutual regulation of excitation and inhibition and implement their sensitive-mode transformations and the homeostasis property, which is conducive to ensuring the stability of overall neural activity. Furthermore, our flexible optoelectronic platform achieves high classification accuracy when implemented in artificial neural network simulations. This work demonstrates the advantages of the optoelectronic platform in implementing the significant brain-inspired functions and provides an insight into the future integration of visible sensing in flexible optoelectronic transistor platforms.

AReconfigurable Optoelectronic Synaptic Transistor with Stable Zr-CsPbI3 Nanocrystals for Visuomorphic Computing.

Reconfigurable phototransistor memory attracts considerable attention for adaptive visuomorphic computing, with highlyefficient sensing, memory, and processing functions integrated onto a single device. However, developing reconfigurable phototransistor memory remains a challenge due to the lack of anall-optically controlled transition between short-term plasticity (STP) and long-term plasticity (LTP). Herein, an air-stable Zr-CsPbI3 perovskite nanocrystal (PNC)-based phototransistor memory is designed,whichis capable of broadband photoresponses. Benefitting from the different electron capture ability of Zr-CsPbI3 PNCs to 650 and 405nm light, anartificial synapse and non-volatile memory can be created on-demand and quickly reconfigured within a single device for specific purposes. Owing to the optically reconfigurable and wavelength-aware operation between STP and LTP modes, the integrated blue feature extraction and target recognition can be demonstrated in a homogeneous neuromorphic vision sensor array. This work suggests a new way in developing perovskite optoelectronic transistors for highly efficient in-sensor computing.

Controlled Optoelectronic Response in van der Waals Heterostructures for In‐Sensor Computing

AbstractIn‐sensor computing with visual information, which can integrate photo‐sensing, data storage, and computation functions within the same physical element, has promised a fundamentally different architecture for future machine vision technology with extreme energy and time efficiency. The elementary devices required to fulfil the goal of such a new sensory computation scheme would demand a bold functional variation to the existing sensor and data processing hardware. Here, a van der Waals (vdW) heterostructure‐based optoelectronic transistor that can act as an integrated photoreceptor, memory, and computation unit by exploiting its own physical attributes is demonstrated. It is found that diverse photoelectric control of device conductance can lead to versatile photoresponse characteristics, including memristive behaviors, retention‐, polarity‐ and strength‐tunable photoconductance, photoelectric‐coupling effect, etc. Exploiting the photoelectric‐coupling effect, reconfigurable and nonvolatile optoelectronic logic functions are realized in this device, featuring a logic‐in‐sensor unit. With the same device, both short‐ and long‐term synaptic plasticity can be faithfully emulated, rendering it an optoelectronic synaptic transistor. Moreover, a psychologic human memory model is implemented with the device, showing the emulation of memorization and learning processes. This prototypical demonstration provides a promising hardware system for visual information in‐sensor computing capable of addressing complex computation tasks.

Multifunctional Memory-Synaptic Hybrid Optoelectronic Transistors for Neuromorphic Computing

Multifunctional neuromorphic devices, integrating the acquisition, computation, and processing of information, have exceptional advantages to simulate biological behaviors and become one of the foundations of future neuromorphic computing. However, the realization of sensor-memory-calculation in a single device remains a great challenge. Herein, memory-synaptic hybrid optoelectronic transistors were developed with hydrolyzed silica-coated lead-free double perovskite Cs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> AgBiBr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> and organic semiconductors, which exhibited sensor-memory-calculation behavior. This work offers a novel strategy for constructing multifunctional neuromorphic devices, which will further inspire the development of floating-gate device in future neuromorphic computing.

Bioinspired organic optoelectronic synaptic transistors based on cellulose nanopaper and natural chlorophyll-a for neuromorphic systems

Inspired by human brains, optoelectronic synapses are expected as one of significant steps for constructing neuromorphic systems. In addition, intensive attention has been paid to biodegradable and biocompatible materials for developing green electronics. In this regard, environmentally friendly organic optoelectronic synaptic transistors based on wood-derived cellulose nanopaper (WCN) as dielectric/substrate and nature chlorophyll-a as photoactive material are demonstrated. Both WCN and chlorophyll-a are biocompatible and biodegradable materials from natural organisms. Versatile synaptic behaviors have been well mimicked by the modulation of both electrical and optical signals. More significantly, optical wireless communication is experimentally emulated and the information processing capability is also verified in pattern recognition simulation. Furthermore, the flexible synaptic transistors exhibit no apparent synaptic performance degradation even when the bending radius is reduced to 1 mm. Our work may develop a promising approach for the development of green and flexible electronics in neuromorphic visual systems.

Fully Printed Optoelectronic Synaptic Transistors Based on Quantum Dot-Metal Oxide Semiconductor Heterojunctions.

Optoelectronic synaptic transistors with hybrid heterostructure channels have been extensively developed to construct artificial visual systems, inspired by the human visual system. However, optoelectronic transistors taking full advantages of superior optoelectronic synaptic behaviors, low-cost processes, low-power consumption, and environmental benignity remained a challenge. Herein, we report a fully printed, high-performance optoelectronic synaptic transistor based on hybrid heterostructures of heavy-metal-free InP/ZnSe core/shell quantum dots (QDs) and n-type SnO2 amorphous oxide semiconductors (AOSs). The elaborately designed heterojunction improves the separation efficiency of photoexcited charges, leading to high photoresponsivity and tunable synaptic weight changes. Under the coordinated modulation of electrical and optical modes, important biological synaptic behaviors, including excitatory postsynaptic current, short/long-term plasticity, and paired-pulse facilitation, were demonstrated with a low power consumption (∼5.6 pJ per event). The InP/ZnSe QD/SnO2 based artificial vision system illustrated a significantly improved accuracy of 91% in image recognition, compared to that of bare SnO2 based counterparts (58%). Combining the outstanding synaptic characteristics of both AOS materials and heterojunction structures, this work provides a printable, low-cost, and high-efficiency strategy to achieve advanced optoelectronic synapses for neuromorphic electronics and artificial intelligence.

Evolutionary 2D organic crystals for optoelectronic transistors and neuromorphic computing

Abstract Brain-inspired neuromorphic computing has been extensively researched, taking advantage of increased computer power, the acquisition of massive data, and algorithm optimization. Neuromorphic computing requires mimicking synaptic plasticity and enables near-in-sensor computing. In synaptic transistors, how to elaborate and examine the link between microstructure and characteristics is a major difficulty. Due to the absence of interlayer shielding effects, defect-free interfaces, and wide spectrum responses, reducing the thickness of organic crystals to the 2D limit has a lot of application possibilities in this computing paradigm. This paper presents an update on the progress of 2D organic crystal-based transistors for data storage and neuromorphic computing. The promises and synthesis methodologies of 2D organic crystals (2D OCs) are summarized. Following that, applications of 2D OCs for ferroelectric non-volatile memory, circuit-type optoelectronic synapses, and neuromorphic computing are addressed. Finally, new insights and challenges for the field’s future prospects are presented, pushing the boundaries of neuromorphic computing even farther.

A robust neuromorphic vision sensor with optical control of ferroelectric switching

The rapid development of the artificial intelligence field has increased the demand for retina-inspired neuromorphic vision sensors with integrated sensing, memory, and processing functions. Here, we present a neuromorphic vision sensor with an optoelectronic transistor structure consisting of monolayer molybdenum disulfide and barium titanate ferroelectric film. Beyond conventional electrical tuning of ferroelectric polarization, the optoelectronic transistor can exhibit a light-dosage tunable synaptic behavior with a high switching ratio and good non-volatility, enabled by photo-induced ferroelectric polarization reversal. The wavelength-dependent optical sensing and multi-level optical memory properties are utilized to achieve the in-sensor neuromorphic visual pre-processing. A simulated artificial neural network built from the proposed vision sensors with neuromorphic pre-processing function demonstrated that the image recognition rate for the Modified National Institute of Standards and Technology (MNIST) handwritten dataset could be significantly improved by reducing redundant data. The obtained results suggest that 2D semiconductor/ferroelectric optoelectronic transistors can provide a promising hardware implementation towards constructing high-performance neuromorphic visual systems

Nonvolatile Reconfigurable 2D Schottky Barrier Transistors.

Nonvolatile reconfigurable transistors can be used to implement highly flexible and compact logic circuits with low power consumption in maintaining the configuration. In this paper, we build nonvolatile reconfigurable transistors based on 2D CuInP2S6/MoTe2 heterostructures. The ferroelectric polarization-induced electron and hole doping in the heterostructure are investigated. By introducing the ferroelectric doping into the source/drain contacts, we demonstrate reconfigurable Schottky barrier transistors, whose polarity (n-type or p-type) can be dynamically programmed, where the configuration is nonvolatile in nature. These transistors exhibit a tunable photoresponse, where the n-n doping state leads to negative photocurrent, whereas the p-p doping state gives rise to a positive photocurrent. The transistor with asymmetric (n-p or p-n) contacts exhibits a strong photovoltaic effect. These reconfigurable logic and optoelectronic transistors will enable a new type of device fabric for future computing systems and sensing networks.

Ternary MoSe2xTe2−2x alloy with tunable band gap for electronic and optoelectronic transistors

Two-dimensional transition metal dichalcogenide (2D TMDs) alloys, consisting of three or more elements, offer a luxury variety of chemical and physical properties through elemental ratio alteration, thus may provide ideal candidate with tunable band gap for specific electrical applications. In this work, we demonstrate a high-quality layered MoSe2xTe2−2x (x = 0 ∼ 1) alloy synthesized via one-step chemical vapor transport method for high-performance electronic and optoelectronic transistors. Our characterizations reveal the obtained ternary alloy forming high-quality single crystal layers with 2H phase. Interestingly, the electronic transistors fabricated on MoSe2xTe2−2x thin layers (6 ∼ 7 layers) display an anomalous transition from ambipolar to n-type in conductive characteristics with the increase of substitution x value. The subsequent photoelectrical measurements exhibit that high on-off ratio for every ratio (x = 0.18, 0.38, 0.67, 0.83) with optical band gap in the range of 1.6 eV and 1.1 eV (near infrared). The optimized MoSe0.37Te1.63–based transistor can achieve up to ∼107 Ion/Ioff and 105 Iph/Idark ratio, 100 mA W−1 photo-responsivity and 2.38% external quantum efficiency with high photoresponsivity. Thus, such ternary MoSe2xTe2−2x alloys may pose a great potential for 2D-based electronic and photoelectronic applications.

Novel p-n junctions based on ambipolar two-dimensional crystals

Two-dimensional (2D) materials have a unique crystal structure and excellent properties, which renders it possible to be used to construct novel artificial nanostructures and design novel nanodevices, thereby achieving a breakthrough in the semiconductor field. In this review paper, the basic behaviors of the ambipolar 2D crystals and the fabrication method of the van der Waals heterostructures are first introduced. We mainly summarize the applications of the ambipolar 2D crystals for novel electrical-field-tunable 2D p-n junctions and p-n heterojunctions (field-effect p-n heterojunction transistor) and non-volatile storable p-n junctions, and other aspects of the relevant structural design, electronic and optoelectronic properties. Then we further introduce their potential applications of logic rectifiers, field-effect optoelectronic transistors, multi-mode non-volatile memories, rectifier memories, optoelectronic memories, photovoltaics, etc. Finally, we provide an outlook of the future possible studies of this new type of p-n junctions in the relevant fields.

Reconfigurable van der Waals Heterostructured Devices with Metal-Insulator Transition.

Atomically thin two-dimensional (2D) materials range from semimetallic graphene to insulating hexagonal boron nitride to semiconducting transition-metal dichalcogenides. Recently, metal-insulator-semiconductor field effect transistors built from these 2D elements were studied for flexible and transparent electronics. However, to induce ambipolar characteristics for alternative power-efficient circuitry, ion-gel gating is often employed for high capacitive coupling, limiting stable operation at ambient conditions. Here, we report reconfigurable MoTe2 optoelectronic transistors with all 2D components, where the device can be reconfigured by both drain and gate voltages. Eight different configurations for each fixed voltage are spatially resolved by scanning photocurrent microscopy. In addition, metal-insulator transitions are observed in both electron and hole carriers under 2 V due to strong Coulomb interaction in the system. Furthermore, the vertical tunneling photocurrent through multiple van der Waals layers between the gate and source contacts is measured. Our reconfigurable devices offer potential building blocks for system-on-a-chip optoelectronics.

GaAs–AlGaAs heterostructure thyristors with completely optical transfer of emitter current

Several variants of thyristors based on GaAs-AlGaAs heterostructures with optical transfer of the emitter current are considered. The possibility that thyristors with fully optical transfer of the emitter current can be, in principle, created is demonstrated by means of the results of a study of n-p-n and p-n-p optoelectronic transistors in which the emitter current is converted into light, this light, in turn, being converted into a collector current. Structures of optoelectronic switches of this kind are presented. A switch comprising three constituent transistors has been suggested and fabricated taking into account specific features of the technique for growth of undoped GaAs layers and fabrication of high-voltage p0-n0 junctions with back-ground impurities from these layers, which makes the turn-on delay cardinally shorter and raises the working frequency.

Excitonic switches operating at around 100 K

Photonic and optoelectronic devices may offer the opportunity to realize efficient signal processing at speeds higher than in conventional electronic devices. Switches form the building blocks for circuits, and fast photonic switches have been realized1,2,3,4,5,6. Recently, a proof of principle demonstration of exciton optoelectronic devices was reported7,8. The potential advantages of excitonic devices include high operation and interconnection speed, small dimensions and the opportunity to combine many elements into integrated circuits. Here, we demonstrate experimental proof of principle for the operation of excitonic switching devices at temperatures around 100 K. The devices are based on an AlAs/GaAs coupled quantum well structure and include the exciton optoelectronic transistor (EXOT), the excitonic bridge modulator (EXBM), and the excitonic pinch-off modulator (EXPOM). A two orders of magnitude increase in the operation temperature compared to earlier devices (1.5 K; refs 7,8) is achieved. Exciton optoelectronic devices have been demonstrated previously at an operating temperature of 1.5 K. Here, experimental proof-of-principle for excitonic switching devices at approximately 100 K is demonstrated. Excitonic devices promise high operation speed and optoelectronic integration in compact dimensions.

Control of Exciton Fluxes in an Excitonic Integrated Circuit

Efficient signal communication uses photons. Signal processing, however, uses an optically inactive medium, electrons. Therefore, an interconnection between electronic signal processing and optical communication is required at the integrated circuit level. We demonstrated control of exciton fluxes in an excitonic integrated circuit. The circuit consists of three exciton optoelectronic transistors and performs operations with exciton fluxes, such as directional switching and merging. Photons transform into excitons at the circuit input, and the excitons transform into photons at the circuit output. The exciton flux from the input to the output is controlled by a pattern of the electrode voltages. The direct coupling of photons, used in communication, to excitons, used as the device-operation medium, may lead to the development of efficient exciton-based optoelectronic devices.