Light-operated artificial synaptic device and preparation method thereof

Abstract

The embodiment of the invention discloses a light-operated artificial synaptic device and a preparation method thereof. The artificial synaptic device comprises a substrate, a light-emitting layer and a synaptic function layer which are sequentially stacked in the thickness direction: the light-emitting layer is arranged on the substrate, and the light-emitting surface of the light-emitting layer faces the synaptic function layer; and the synaptic function layer is used for responding to the light signal emitted by the light-emitting layer and generating a conductivity change for simulating a biological synaptic behavior. According to the light-operated artificial synapse device provided by the invention, the light-emitting layer is integrated into the artificial synapse device, so that light signals do not need to be propagated for a long distance and can directly act on the synapse function layer in a directional manner, and the problem of low light coupling efficiency of the existing light-operated synapse is further solved.

Description

Technical Field

[0001] This invention relates to the field of artificial synapse technology, and in particular to a light-controlled artificial synapse device and its preparation method. Background Technology

[0002] An artificial synapse is a type of artificial neuron used to simulate the information transmission and storage functions of a biological nervous system. Optically controlled artificial synapses use light signals as an external excitation source to regulate the capture and release of charge carriers (electrons and holes) within the device, thereby achieving dynamic adjustment of synaptic weights and simulating the learning, memory, and information processing functions of biological synapses.

[0003] Currently, the low optical coupling efficiency of optically controlled artificial synapses has become a key technical bottleneck restricting their performance breakthrough. This problem stems from the reflection and scattering losses of optical signals at the device interface, as well as factors such as energy level mismatch and poor interface compatibility between the optical control layer and other functional layers of the device (such as electrode layers and transmission layers).

[0004] In existing technologies, researchers often try to reduce light energy loss by optimizing the thickness, crystallinity, or surface morphology of the light control layer material. However, due to the limitations of the overall device structure design, the improvement in light coupling efficiency is limited. Summary of the Invention

[0005] This invention provides a light-controlled artificial synapse device and its fabrication method. By integrating the light-emitting layer into the artificial synapse device, the problem of low optical coupling efficiency of existing light-controlled synapses is solved, making it suitable for low-power neuromorphic computing, intelligent visual perception and other scenarios.

[0006] In a first aspect, embodiments of the present invention provide a light-controlled artificial synapse device, comprising a substrate, a light-emitting layer, and a synaptic functional layer sequentially stacked along the thickness direction: the light-emitting layer is disposed on the substrate, with the light-emitting surface of the light-emitting layer facing the synaptic functional layer; the synaptic functional layer is used to generate a change in electrical conductivity that simulates biological synaptic behavior in response to the light signal emitted by the light-emitting layer.

[0007] Optionally, an optical coupling layer is also included, which is disposed between the light-emitting layer and the synaptic functional layer, and is used to focus the light signal emitted by the light-emitting layer.

[0008] Optionally, the light-emitting layer includes a miniLED array.

[0009] Optionally, it also includes a driving module, which is electrically connected to the miniLED array and is used to regulate the direction and amplitude of the conductance change of the synaptic functional layer by adjusting the wavelength and intensity of the light signal emitted by the miniLED array.

[0010] Optionally, the driving module is used to control the miniLED array layer to emit a light signal of a first wavelength and a first light intensity to enable the synaptic functional layer to produce a long-term enhancement effect; and / or to control the miniLED array layer to emit a light signal of a second wavelength and a second light intensity to enable the synaptic functional layer to produce a long-term suppression effect; wherein the first wavelength is smaller than the second wavelength, and the first light intensity is greater than the second light intensity.

[0011] Optionally, the first wavelength is 400-410nm blue light, with a first light intensity of 0.5-10mW / cm². 2 The second wavelength band is near-infrared light of 830-870nm, and the second light intensity is 0.1-0.5mW / cm². 2 .

[0012] Optionally, it also includes at least two electrodes electrically connected to the synaptic functional layer.

[0013] Optionally, the synaptic functional layer includes an n-type layer and a p-type layer; at least two electrodes include a source electrode and a drain electrode; the source electrode is electrically connected to the n-type layer for collecting electrons; the drain electrode is electrically connected to the p-type layer for collecting holes.

[0014] Optionally, an encapsulation layer may also be included, which covers the side of the synaptic functional layer away from the substrate.

[0015] In a second aspect, embodiments of the present invention also provide a method for fabricating a light-controlled artificial synapse device, characterized in that it is used to fabricate any one of the light-controlled artificial synapse devices in the first aspect; the method includes: providing a substrate; forming a light-emitting layer on one side of the substrate; and forming a synaptic functional layer on the side of the light-emitting layer opposite to the substrate.

[0016] This invention provides a light-controlled artificial synapse device and its fabrication method. The artificial synapse device includes a substrate, a light-emitting layer, and a synaptic functional layer sequentially stacked along its thickness direction. The light-emitting layer is disposed on the substrate, with its emitting surface facing the synaptic functional layer, replacing the traditional external light source illumination mode. The synaptic functional layer is used to generate a conductivity change simulating biological synaptic behavior in response to the light signal emitted by the light-emitting layer. The light-controlled artificial synapse device provided by this invention, by integrating the light-emitting layer into the artificial synapse device, allows the light signal to directly and directionally act on the synaptic functional layer without long-distance propagation, thereby solving the problem of low optical coupling efficiency in existing light-controlled synapses. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a light-controlled artificial synapse device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another light-controlled artificial synapse device provided in an embodiment of the present invention; Figure 3This is a partial structural schematic diagram of a light-controlled artificial synapse device provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a synaptic functional layer provided in an embodiment of the present invention; Figure 5 This is a schematic flowchart of a method for fabricating a light-controlled artificial synapse device according to an embodiment of the present invention. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] Figure 1 This is a schematic diagram of the structure of a light-controlled artificial synapse device provided in an embodiment of the present invention, with reference to... Figure 1 This invention provides a light-controlled artificial synapse device, comprising a substrate 10, a light-emitting layer 20, and a synaptic functional layer 30 stacked sequentially along the thickness direction: the light-emitting layer 20 is disposed on the substrate 10, and the light-emitting surface of the light-emitting layer 20 faces the synaptic functional layer 30; the synaptic functional layer 30 is used to generate a change in electrical conductivity that simulates biological synaptic behavior in response to the light signal emitted by the light-emitting layer 20.

[0021] The substrate 10 can be understood as the basic support structure of the device; the light-emitting layer 20 can be understood as a functional layer that can emit light of a specific wavelength under external excitation (such as an electrical signal) and is used as a light input stimulus source for artificial synapses; the synaptic functional layer 30 can be understood as a photoelectric response material layer, which changes its internal carrier concentration or distribution after receiving the light signal emitted by the light-emitting layer, thereby causing its conductivity to change reversibly and continuously to simulate biological synapses.

[0022] Specifically, the light-emitting layer 20 is fabricated on the substrate 10, with its light-emitting surface facing the synaptic functional layer 30. When a specific mode of electrical pulse (or light pulse) is applied to the light-emitting layer 20, it emits a light signal of corresponding intensity and duration. This light signal directly irradiates the synaptic functional layer 30. After the photosensitive material in the synaptic functional layer 30 absorbs photons, it generates photogenerated charge carriers (electron-hole pairs) or undergoes ion migration, resulting in a change in its conductivity. Through this change in conductivity, the signal changes of biological synapses under nerve pulse stimulation can be simulated.

[0023] For example, a Si / SiO2 composite substrate or a transparent sapphire substrate is selected; wherein the Si layer is p-type doped and used for current driving of the light-emitting layer 20, and the SiO2 layer serves as an insulating isolation layer.

[0024] Figure 2 This is a schematic diagram of another light-controlled artificial synapse device provided in an embodiment of the present invention, for reference. Figure 2 In an optional embodiment, the light-emitting layer 20 includes a miniLED array.

[0025] Specifically, the light-emitting layer 20 is composed of a miniLED array 21. Each miniLED pixel in this array can be driven by an independent electrical signal to emit a light signal with controllable intensity and timing, thereby achieving precise control of a specific unit or region in the synaptic device array.

[0026] In an optional embodiment, a Bragg reflector layer 22 is further included between the light-emitting layer 20 and the substrate 10. The Bragg reflector layer 22 is composed of alternating SiO2 / TiO2 layers. On the one hand, the Bragg reflector layer 22 is used to reflect the light emitted from the light-emitting layer 20 to improve the light extraction efficiency; on the other hand, it serves as a heat insulation layer.

[0027] Optionally, an optical coupling layer 40 is also included, which is disposed between the light-emitting layer 20 and the synaptic functional layer 30, and is used to focus the light signal emitted by the light-emitting layer 20.

[0028] Specifically, the optical coupling layer 40 is disposed between the light-emitting layer 20 and the synaptic functional layer 30. When the light-emitting layer 20 is excited by light, the emitted light signal, which has a certain degree of divergence, enters the optical coupling layer 40. The microlens array or grating inside the optical coupling layer 40 focuses the originally divergent light and projects it onto a specific area of ​​the synaptic functional layer 30, thereby reducing the spatial loss of light energy during transmission and improving the efficiency of the light signal in exciting the synaptic functional layer 30, thus achieving more precise synaptic control and lower device operating power consumption.

[0029] For example, embodiments of the present invention may provide two solutions as the optical coupling layer 40. Solution 1: Figure 3This is a partial structural schematic diagram of a light-controlled artificial synapse device provided in an embodiment of the present invention, with reference to... Figure 3 The optical coupling layer 40 includes a SiO2 microlens array 41 (thickness 100-500nm), with the diameter of a single microlens unit being consistent with that of the miniLED chip 21 (50-200μm) and the focal length being 50-100nm, matching the thickness of the synaptic functional layer; Scheme 2: PMMA optical waveguide layer (thickness 200-300nm), with waveguide channels defined by photolithography, and the channel cross-section corresponding one-to-one with the miniLED chip.

[0030] Optionally, it also includes a driving module 50, which is electrically connected to the miniLED array and is used to regulate the direction and amplitude of the conductivity change of the synaptic functional layer 30 by adjusting the wavelength and intensity of the light signal emitted by the miniLED array.

[0031] Specifically, the driving module 50 is electrically connected to each pixel or pixel group of the miniLED array. The driving module 50 can apply driving signals with different voltages, currents, pulse widths, or wavelengths to a specific miniLED pixel, thereby precisely adjusting the wavelength and intensity of the light signal emitted by that pixel. Photons of different wavelengths may be absorbed by different active substances or energy levels in the synaptic functional layer 30, thereby generating different types of charge carriers or triggering different ion migration paths; different light intensities directly determine the excitation intensity, and the two together determine the path and degree of the change in the internal state of the synaptic functional layer 30, thereby regulating the direction (corresponding to the enhancement or suppression of synaptic weights) and amplitude (corresponding to the magnitude of the weight change) of its conductance change.

[0032] Optionally, the driving module 50 is used to control the miniLED array to emit a light signal with a first wavelength and a first light intensity so that the synaptic functional layer 30 produces a long-term enhancement effect; and / or control the miniLED array to emit a light signal with a second wavelength and a second light intensity so that the synaptic functional layer 30 produces a long-term suppression effect; wherein the first wavelength is smaller than the second wavelength, and the first light intensity is greater than the second light intensity.

[0033] The first band and the first light intensity can be understood as a combination of driving parameters set by the driving module 50, which usually corresponds to a shorter wavelength (such as blue light) and a higher brightness; the second band and the second light intensity can be understood as another combination of driving parameters set by the driving module 50, which usually corresponds to a longer wavelength (such as red light) and a lower brightness; the long-term enhancement effect can be understood as the synaptic functional layer 30 experiencing a significant and prolonged increase in conductivity after being stimulated by specific light; the long-term inhibition effect can be understood as the synaptic functional layer 30 experiencing a significant and prolonged decrease in conductivity after being stimulated by specific light.

[0034] Specifically, the driving module 50 has at least two driving modes. When simulating long-term enhancement effects, it controls the miniLED array to emit a first-band, first-intensity optical signal, triggering strong carrier injection or rapid ion migration, resulting in a significant and sustained increase in conductivity. When simulating long-term suppression effects, it controls the miniLED array to emit a second-band, second-intensity optical signal, triggering ion relocation or defect state filling, resulting in a slow and sustained decrease in conductivity.

[0035] Optionally, the first wavelength is 400-410nm blue light, with a first light intensity of 0.5-10mW / cm². 2 The second wavelength band is near-infrared light of 830-870nm, and the second light intensity is 0.1-0.5mW / cm². 2 .

[0036] Specifically, the blue light wavelength is 400-410nm, and the power density is 0.5-10mW / cm². 2 Blue light, with its high-energy photons and moderate intensity, can induce strong carrier injection or rapid ion migration, leading to a significant and sustained increase in conductivity. Wavelength: 830-870 nm; Power density: 0.1-0.5 mW / cm². 2 Near-infrared light, with its low-energy photons and weak intensity, may trigger ion re-entry or defect state filling, leading to a slow and persistent decrease in conductivity.

[0037] Continue to refer to Figure 2 In an optional embodiment, it further includes at least two electrodes 60, which are electrically connected to the synaptic functional layer 30.

[0038] Specifically, at least two electrodes 60 are disposed on the surface of the synaptic functional layer 30. When it is necessary to measure or utilize the change in conductivity of the synaptic functional layer 30, a reading voltage (or current) is applied to it through these two electrodes 60, and the current flowing through it (or the voltage generated) is measured. The magnitude of this measurement signal directly reflects the conductivity value of the synaptic functional layer 30 after stimulation by a specific light signal.

[0039] Figure 4 This is a schematic diagram of the structure of a synaptic functional layer provided in an embodiment of the present invention, with reference to... Figure 4 In an optional embodiment, the synaptic functional layer 30 includes an n-type layer 31 and a p-type layer 32; at least two electrodes 60 include a source electrode 61 and a drain electrode 62; the source electrode 61 is electrically connected to the n-type layer 31 for collecting electrons; and the drain electrode 62 is electrically connected to the p-type layer 32 for collecting holes.

[0040] Specifically, the synaptic functional layer 30 is composed of a heterostructure, including an n-type layer 31 and a p-type layer 32 (such as MoS2 and WS2). The source electrode 61 is electrically connected to the n-type layer 31, and the drain electrode 62 is electrically connected to the p-type layer 32. When the light signal emitted by the light-emitting layer 20 irradiates the heterojunction interface, electron-hole pairs are generated therein. Due to the built-in electric field, electrons tend to migrate to the n-type layer 31 and are collected by the source electrode 61, while holes tend to migrate to the p-type layer 32 and are collected by the drain electrode 62. By measuring the current between the source electrode 61 and the drain electrode 62, the equivalent conductance determined by the separation and transport of photogenerated carriers can be directly detected. This conductance value will reversibly change with the history of illumination (intensity, wavelength, time), thereby simulating the long-term plasticity of synaptic weights. This structure utilizes the built-in electric field of the heterojunction to achieve efficient photoelectric conversion and carrier separation, providing a clear physical mechanism and excellent electrical response for photo-controlled artificial synapses.

[0041] In an optional embodiment, for example, at least two electrodes 60 include a source electrode 61, a drain electrode 62, and a gate electrode 63, the gate electrode being isolated from the synaptic functional layer for assisting in the regulation of carrier mobility.

[0042] Continue to refer to Figure 2 In an optional embodiment, an encapsulation layer 70 is also included, which covers the side of the synaptic functional layer 30 opposite to the substrate 10.

[0043] Specifically, an encapsulation layer 70 is provided on the side of the synaptic functional layer 30 facing away from the substrate 10. The encapsulation layer 70 completely covers the entire synaptic functional layer 30, effectively blocking water and oxygen molecules in the air from corroding and degrading the synaptic functional layer 30 material and electrodes, while also preventing damage to the synaptic layer from high-temperature environments.

[0044] For example, the encapsulation layer is an Al2O3 thin film with a thickness of 50-100 nm.

[0045] Figure 5 This is a schematic flowchart of a method for fabricating a light-controlled artificial synapse device according to an embodiment of the present invention. (Refer to...) Figure 5 The present invention also provides a method for fabricating a light-controlled artificial synapse device, used to fabricate any one of the light-controlled artificial synapse devices in the first aspect, the method comprising: S110 provides a substrate.

[0046] Specifically, the substrate 10 is first provided and cleaned (e.g., a silicon wafer or sapphire substrate with a silicon oxide insulating layer on the surface), and surface contaminants are removed and the surface is activated by solvent cleaning and plasma treatment.

[0047] For example, a p-type 1-Si / SiO2 substrate is selected and ultrasonically cleaned and dried in sequence with acetone, isopropanol, and deionized water.

[0048] S120, A light-emitting layer is formed on one side of the substrate.

[0049] Specifically, the pre-prepared miniLED array is peeled off from its original growth substrate (such as sapphire) and transferred to the surface of a pre-treated substrate 10 (such as Si / SiO2). After transfer, it is fixed using UV-curable adhesive. Subsequently, positive and negative electrodes are formed on the transferred miniLED chip using a vacuum evaporation process.

[0050] In an optional embodiment, before forming the light-emitting layer on one side of the substrate, a DBR layer 22 is further prepared on the substrate 10.

[0051] In an optional embodiment, after forming the light-emitting layer on one side of the substrate, an optical coupling layer 40 is further formed between the light-emitting layer 20 and the synaptic functional layer 30.

[0052] Specifically, a light coupling layer 40 is deposited on the surface of the miniLED array using PECVD, and then a microlens array 41 is fabricated by photolithography and ICP etching.

[0053] S130. A synaptic functional layer is formed on the side of the light-emitting layer away from the substrate.

[0054] Specifically, a synaptic functional layer 30 is grown on top of the luminescent layer 20.

[0055] For example, a two-step chemical vapor deposition method can be used: first, a WS2 layer 31 is grown in the corresponding region of the miniLED array as a p-type semiconductor layer; then, a MoS2 layer 32 is grown in the adjacent or overlapping region as an n-type semiconductor layer, and the two form a heterojunction at the interface to respond to the light signal emitted by the miniLED below.

[0056] In an optional embodiment, after forming the synaptic functional layer on the side of the light-emitting layer facing away from the substrate, the method further includes depositing a dielectric layer 71, an electrode layer 80, and an encapsulation layer 70 on the synaptic functional layer: the electrode layer 80 includes at least two electrodes 60, each including a source electrode 61, a drain electrode 62, and a gate electrode 63. The source electrode 61 contacts the MoS2 layer 32, the drain electrode 62 contacts the WS2 layer 31, and the gate electrode 63 covers the dielectric layer 71; the encapsulation layer 70 covers the entire electrode layer 80.

[0057] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A light-controlled artificial synapse device, characterized in that, It includes a substrate, a light-emitting layer, and a synaptic functional layer, which are stacked sequentially along the thickness direction: The light-emitting layer is disposed on the substrate, with the light-emitting surface of the light-emitting layer facing the synaptic functional layer; The synaptic functional layer is used to generate electrical conductance changes that mimic biological synaptic behavior in response to light signals emitted by the light-emitting layer.

2. The light-controlled artificial synapse device according to claim 1, characterized in that, It also includes an optical coupling layer, which is disposed between the light-emitting layer and the synaptic functional layer, and is used to focus the light signal emitted by the light-emitting layer.

3. The light-controlled artificial synapse device according to claim 1, characterized in that, The light-emitting layer includes a miniLED array.

4. The light-controlled artificial synapse device according to claim 3, characterized in that, It also includes a driving module, which is electrically connected to the miniLED array and is used to regulate the direction and amplitude of the conductivity change of the synaptic functional layer by adjusting the wavelength and intensity of the light signal emitted by the miniLED array.

5. The light-controlled artificial synapse device according to claim 4, characterized in that, The driving module is used to control the miniLED array layer to emit a light signal of a first wavelength and a first intensity, so as to cause the synaptic functional layer to produce a long-term enhancement effect; and / or The miniLED array layer is controlled to emit a light signal with a second wavelength and a second intensity, so that the synaptic functional layer produces a long-term suppression effect. Wherein, the first wavelength band is smaller than the second wavelength band, and the first light intensity is greater than the second light intensity.

6. The light-controlled artificial synapse device according to claim 5, characterized in that, The first wavelength band is blue light in the range of 400-410nm, and the first light intensity is 0.5-10mW / cm². 2 The second wavelength band is near-infrared light of 830-870nm, and the second light intensity is 0.1-0.5mW / cm². 2 .

7. The light-controlled artificial synapse device according to claim 1, characterized in that, It also includes at least two electrodes that are electrically connected to the synaptic functional layer.

8. The light-controlled artificial synapse device according to claim 7, characterized in that, The synaptic functional layer includes an n-type layer and a p-type layer; The at least two electrodes include a source electrode and a drain electrode; the source electrode is electrically connected to the n-type layer for collecting electrons; the drain electrode is electrically connected to the p-type layer for collecting holes.

9. The light-controlled artificial synapse device according to claim 1, characterized in that, It also includes an encapsulation layer that covers the side of the synaptic functional layer opposite to the substrate.

10. A method for fabricating a light-controlled artificial synapse device, characterized in that, Used to prepare the light-controlled artificial synapse device according to any one of claims 1-8; The method includes: Provide substrate; A light-emitting layer is formed on one side of the substrate; A synaptic functional layer is formed on the side of the light-emitting layer opposite to the substrate.

Images