Gallium oxide ultraviolet optical synapse device, control system and preparation method thereof

Abstract

The application relates to a gallium oxide ultraviolet optical synapse device, a control system and a preparation method thereof. The device comprises a substrate, a silicon carbide conductive layer and a gallium oxide absorption layer which are stacked in sequence, a heterojunction is formed between the silicon carbide conductive layer and the gallium oxide absorption layer as a carrier transport layer, a groove extending to the silicon carbide conductive layer is etched in the gallium oxide absorption layer, an electrode is prepared in the groove, and the electrode is isolated from the gallium oxide absorption layer through the groove, so that the technical problem that the deep ultraviolet detection function and the optical synapse regulation are difficult to be considered is solved.

Description

Technical Field

[0001] This application relates to the field of storage technology, and in particular to a gallium oxide ultraviolet synaptic device, a control system, and a method for fabricating the same. Background Technology

[0002] In complex mathematical operations, storage units and computing units are usually separated. When processing large-scale unstructured visual information, this results in high data transmission energy consumption and computational latency.

[0003] Neuromorphic devices couple the processes of information perception, storage, and processing within the same physical unit, which can reduce data handling and improve perceptual computing efficiency, making them an important piece of hardware for building low-power artificial vision systems.

[0004] In recent years, optoelectronic synaptic devices have become an important technology branch in neuromorphic devices due to their advantages such as high bandwidth, strong parallelism and low power consumption, and are used in fields such as brain-like visual perception hardware.

[0005] However, existing opto-synaptic devices use low-bandgap materials such as MoS2, IGZO, perovskite, and graphene, as well as organic semiconductors or perovskite materials. They can only achieve photoelectric detection or photocurrent modulation, but they are prone to responding to visible light, near-ultraviolet light, or broadband light, making it difficult to achieve highly selective photosynaptic modulation in the deep ultraviolet band. Furthermore, they have shortcomings in terms of environmental stability, process compatibility, and high-temperature reliability. Summary of the Invention

[0006] Based on this, a photodetector is provided to solve the technical problem of the difficulty in simultaneously achieving deep ultraviolet detection function and photosynaptic modulation.

[0007] In a first aspect, embodiments of this application provide a gallium oxide ultraviolet synapse device, comprising:

[0008] A substrate, a silicon carbide conductive layer, and a gallium oxide absorber layer are stacked sequentially, with the silicon carbide conductive layer serving as a carrier transport layer and forming a heterojunction with the gallium oxide absorber layer;

[0009] The gallium oxide absorber layer has trenches etched extending to the silicon carbide conductive layer; electrodes are formed in the trenches, and the electrodes are isolated from the gallium oxide absorber layer through the trenches.

[0010] In one embodiment, the silicon carbide conductive layer is in electrical contact with the electrode to form a current readout channel, the thickness of the silicon carbide conductive layer includes 200 nm, and / or the substrate is a flexible substrate, the substrate material including polyimide (PI) or mica sheet.

[0011] In one embodiment, the electrode includes a source and a drain, the source being in electrical contact with the silicon carbide conductive layer for applying a source bias voltage;

[0012] The drain electrode is in electrical contact with the silicon carbide conductive layer to apply a drain bias voltage.

[0013] In one embodiment, the device is externally connected to a pulsed light source controller via the electrodes. The pulsed light source controller applies a bias voltage to the source and the drain, and emits ultraviolet light pulses to the device. The gallium oxide absorption layer absorbs the charge carriers generated by the silicon carbide conductive layer, thereby enhancing the absorption of the charge carriers generated by the ultraviolet light by the gallium oxide absorption layer, so as to generate an excitatory postsynaptic current (EPSC).

[0014] Secondly, embodiments of this application also provide a control system for a gallium oxide ultraviolet synaptic device, including a pulsed light source controller and the aforementioned gallium oxide ultraviolet synaptic device;

[0015] The pulsed light source controller is used to control the optical power density, pulse width, pulse interval, and number of pulses of the ultraviolet light pulse, so as to realize at least one of the following neural synaptic functions through the gallium oxide ultraviolet synaptic device:

[0016] Excitatory postsynaptic currents (EPSC), double-pulse facilitated pulse currents (PPF), short-term memory, long-term memory, and the learning-forgetting-relearning pathway.

[0017] Thirdly, embodiments of this application also provide a method for fabricating a gallium oxide ultraviolet synaptic device, comprising:

[0018] Substrate preparation;

[0019] A silicon carbide conductive layer is prepared on the substrate;

[0020] A gallium oxide absorber layer is prepared above the silicon carbide conductive layer;

[0021] The gallium oxide absorber layer is etched down to the silicon carbide conductive layer to form a trench;

[0022] An electrode is fabricated within the trench, and the electrode is isolated from the gallium oxide absorber layer by the trench.

[0023] In one embodiment, a silicon carbide conductive layer is formed over the substrate, including:

[0024] Magnetron sputtering was used to deposit silicon carbide thin films with a thickness of 200 nm by sputtering for 60 minutes under conditions of argon flow rate of 10 sccm to 30 sccm, radio frequency power of 80 W to 120 W, and gas pressure of 1 Pa.

[0025] The silicon carbide thin film was annealed at 900°C in an argon atmosphere to prepare the silicon carbide conductive layer.

[0026] And / or, a gallium oxide absorber layer is formed over the silicon carbide conductive layer, comprising:

[0027] A gallium oxide thin film with a thickness of 80 nm was obtained by sputtering for 30 minutes under the conditions of argon flow rate of 10 sccm to 30 sccm, radio frequency power of 80 W to 120 W, and gas pressure of 1 Pa.

[0028] The gallium oxide thin film was annealed at 600°C in an argon atmosphere to prepare the gallium oxide absorber layer.

[0029] In one embodiment, the preparation of the substrate includes:

[0030] Flexible substrates are prepared using polyimide (PI) or mica sheets.

[0031] In one embodiment, the gallium oxide absorber layer is etched down to the silicon carbide conductive layer to form a trench, including:

[0032] Laser direct writing and etching technology is used to develop and etch the surface of the gallium oxide absorption layer to remove gallium oxide and expose silicon carbide. Electrode areas are then marked in the exposed silicon carbide area using overlay technology.

[0033] In one embodiment, the method further includes:

[0034] The electrode is connected to a pulsed light source controller, which applies a bias voltage to the electrode and emits ultraviolet light pulses to the device. The gallium oxide absorption layer absorbs the charge carriers generated by the silicon carbide conductive layer, thereby enhancing the absorption of the charge carriers generated by the ultraviolet light by the gallium oxide absorption layer to generate an excitatory postsynaptic current (EPSC).

[0035] The pulsed light source controller adjusts the optical power density, pulse width, pulse interval, and number of pulses of the ultraviolet light pulse to achieve at least one of the following neural synaptic functions through the gallium oxide ultraviolet synaptic device:

[0036] Excitatory postsynaptic currents (EPSC), double-pulse facilitated pulse currents (PPF), short-term memory, long-term memory, and the learning-forgetting-relearning pathway.

[0037] This application provides a gallium oxide ultraviolet synaptic device, a control system, and a fabrication method thereof. Carrier transport is achieved through a silicon carbide conductive layer formed on a substrate. Since deep ultraviolet light can be absorbed through the gallium oxide absorption layer, the energy band of the silicon carbide and gallium oxide heterojunction is modulated by the source and drain electrodes that are electrically in contact with silicon carbide. Furthermore, the state changes of the carriers (generation, separation, injection, capture, and release) can generate a tunable synaptic photoelectric response, thereby achieving both deep ultraviolet detection and photosynaptic modulation functions. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic diagram of a gallium oxide ultraviolet synaptic device structure provided in an embodiment of this application;

[0040] Figure 2 A schematic diagram illustrating the response of a gallium oxide ultraviolet synaptic device to EPSC under stimulation by a single deep ultraviolet light pulse, as provided in an embodiment of this application.

[0041] Figure 3 A schematic diagram illustrating the response of a gallium oxide ultraviolet synaptic device to double-pulse facilitation under double-pulse stimulation, provided in an embodiment of this application.

[0042] Figure 4 A schematic diagram illustrating the synaptic weight modulation behavior of the gallium oxide ultraviolet synaptic device provided in this application embodiment under stimulation by different numbers of ultraviolet light pulses;

[0043] Figure 5 A schematic diagram illustrating the learning-forgetting-relearning link of the gallium oxide ultraviolet synaptic device provided in the embodiments of this application;

[0044] Figure 6 This is a schematic diagram of the fabrication process of the gallium oxide ultraviolet synaptic device provided in the embodiments of this application;

[0045] Figure 7 This is a schematic diagram of the fabrication process of the gallium oxide ultraviolet synaptic device provided in the embodiments of this application. Detailed Implementation

[0046] To facilitate understanding of this application, it will be described in more detail below. However, it should be understood that this application can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular implementations or embodiments only and is not intended to be limiting of this application. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0048] The first embodiment of this application provides a gallium oxide ultraviolet synapse device, see [link to relevant documentation]. Figure 1 The following are included:

[0049] A substrate 101, a silicon carbide conductive layer 102, and a gallium oxide absorber layer 103 are stacked sequentially. The silicon carbide conductive layer 102 serves as a carrier transport layer and forms a heterojunction with the gallium oxide absorber layer 103.

[0050] The gallium oxide absorber layer 103 has trenches etched in it that extend to the silicon carbide conductive layer 102; an electrode 104 is fabricated in the trenches, and the electrode 104 is isolated from the gallium oxide absorber layer 103 by the trenches.

[0051] In some optional embodiments of this application, the gallium oxide absorber layer is made of Ga2O3.

[0052] The silicon carbide conductive layer makes electrical contact with the electrode to form a current readout channel. A gallium oxide absorber layer is disposed above the silicon carbide conductive layer, serving as a deep ultraviolet light absorber and defect trapping layer, used to receive deep ultraviolet light irradiation and generate photogenerated carriers.

[0053] Ga₂O₃, with a bandgap of approximately 4.9 eV, is an ultrawide bandgap semiconductor material exhibiting strong absorption in the deep ultraviolet region (<300 nm). Oxygen vacancies and defect states in Ga₂O₃ films can serve as photogenerated carrier trapping centers, resulting in sustained photoconductivity and memory effects. SiC, with a bandgap of approximately 3.2 eV, possesses high thermal stability and excellent electron mobility, making it suitable as a lateral carrier transport layer and current readout channel. This application's embodiments construct heterostructures based on SiC and Ga₂O₃, utilizing Ga₂O₃ for deep ultraviolet absorption and defect trapping, and SiC for photogenerated carrier transport and current readout. Furthermore, the bandgap at the heterostructure interface between SiC and Ga₂O₃ facilitates the separation and injection of photogenerated carriers.

[0054] In some optional embodiments of this application, the electrode includes a source and a drain. The source is in electrical contact with the silicon carbide conductive layer and is used to apply a source bias voltage. The drain is in electrical contact with the silicon carbide conductive layer and is used to apply a drain bias voltage.

[0055] For example, the gallium oxide absorber layer can be located between the source and drain, and isolated by trenches. In some optional embodiments of this application, the gallium oxide ultraviolet synaptic device is externally connected to a pulsed light source controller through the source and drain. The pulsed light source controller applies a bias voltage to the source and drain and emits ultraviolet light pulses to the gallium oxide ultraviolet synaptic device. The gallium oxide absorber layer absorbs the charge carriers generated by the silicon carbide conductive layer, thereby enhancing the absorption of ultraviolet light-generated charge carriers by the gallium oxide absorber layer to generate EPSC (Excitatory Postsynaptic Current).

[0056] The pulsed light source controller may include, but is not limited to, a pulse generator and a xenon lamp. The xenon lamp can be excited by a pulse signal emitted by the pulse generator to emit ultraviolet light pulses, wherein the wavelength of the ultraviolet light pulses may include, but is not limited to, deep ultraviolet light in the range of 240 to 280 nm, for example, 254 nm or 265 nm.

[0057] This application also provides a control system for a gallium oxide ultraviolet synaptic device, including the gallium oxide ultraviolet synaptic device and a pulsed light source controller. The pulsed light source controller is used to control the optical power density, pulse width, pulse interval, and number of pulses of the ultraviolet light pulses, so as to realize at least one of the following neural synaptic functions through the gallium oxide ultraviolet synaptic device:

[0058] Excitatory postsynaptic currents (EPSC), double-pulse facilitated pulse currents (PPF), short-term memory, long-term memory, and the learning-forgetting-relearning pathway.

[0059] For example, using 254nm deep ultraviolet light, the optical power density is P1 (μW / cm²). 2Two consecutive ultraviolet light pulses are input, with a pulse width of 0.5s and a pulse interval of 0.8s, which in turn generates two EPSC peaks A1 and A2.

[0060] Figure 2 This is a schematic diagram illustrating the response of a gallium oxide ultraviolet synaptic device to generate an excitatory postsynaptic current under stimulation by a single deep ultraviolet light pulse, as provided in an embodiment of this application.

[0061] For example, under the same source bias voltage, drain bias voltage, and the same ultraviolet light pulse conditions (such as a source and drain bias voltage of 1V and an optical power density of P1μW / cm²), 2 Two consecutive 254nm deep ultraviolet (DUV) light pulses (pulse width 0.3s, pulse interval 0.7s) are applied. The EPSC peak value A1 after the first UV pulse and the EPSC peak value A2 after the second UV pulse are recorded (or, A1 and A2 can be the peak increments relative to the dark-state baseline current I0). When A2 is greater than A1, it indicates that the second stimulus response is stronger than the first stimulus response, and the gallium oxide UV synaptic device achieves the two-pulse facilitated function. The PPF index can be expressed as PPF = A2 / A1 × 100%. See also Figure 3 As shown, Figure 3 Paired pulse facilitated response of gallium oxide ultraviolet synaptic devices under dual-pulse stimulation is provided.

[0062] For example, short-term memory can be achieved based on multi-pulse stimulation: fixed source and drain bias voltages (e.g., both 1V); using 254nm deep ultraviolet light with a power density of P2 (μW / cm²). 2 Five, ten, and fifteen consecutive ultraviolet light pulses were set, with a pulse width of 0.5 s and a pulse interval of 0.8 s. The peak current, residual current, and decay process after the light stimulation was removed were recorded as changes in the decay state of short-term memory.

[0063] In an optional embodiment of this application, short-term memory can refer to the current enhancement and spontaneous decay process within the range of 0.1s to 100s after the ultraviolet light pulse is removed. For example, the current maintenance and recovery process within the range of seconds to tens of seconds after the ultraviolet light pulse is removed can be considered as short-term memory. The specific timescale of short-term memory can be determined by the time required for the source and drain currents to decay to near the dark-state baseline current after the ultraviolet light pulse is removed.

[0064] Figure 4This diagram illustrates the synaptic weight regulation behavior of a gallium oxide ultraviolet (GaO) synaptic device provided in this application under stimulation with different numbers of ultraviolet (UV) light pulses. The GaO UV synaptic device can continuously adjust the current and / or conductance by changing the number of UV light pulses, thereby simulating the increase and decrease of synaptic weight. For example, varying the number of UV light pulses (5, 10, 20, and 50) controls the number of stimulations to the synaptic weight. As the number of UV light pulses increases from 5 to 10, 20, and 50 respectively, the postsynaptic current of the GaO UV synaptic device gradually increases, indicating that continuous light stimulation can effectively regulate the device's conductance. Since current is proportional to conductance at a fixed readout voltage, the gradual increase in current reflects the continuous increase in synaptic weight. After the UV light pulses stop, the current gradually decreases over time, corresponding to the forgetting process in biological synapses. The more pulses there are, the more significant the conductance enhancement of the gallium oxide ultraviolet synaptic device. It can be seen that the gallium oxide ultraviolet synaptic device can achieve multi-level synaptic weight control by adjusting the number of ultraviolet light pulses.

[0065] Assuming that the time required for the source and drain currents of a gallium oxide ultraviolet synaptic device to decay to near the dark-state baseline current after the deep ultraviolet light pulse is removed is 10 seconds, then the short-time memory of the gallium oxide ultraviolet synaptic device can be recorded as 10 seconds.

[0066] In testing the short-time memory of gallium oxide ultraviolet synaptic devices, the baseline current I0 under no-light conditions can be recorded first, and the peak current I0 can be recorded after applying a 254nm ultraviolet light pulse. peak If the current rises rapidly after 254nm ultraviolet light stimulation, and does not immediately recover to I0 after the 254nm ultraviolet light stimulation is removed, but remains above I0 for a short period and gradually decays, then the gallium oxide ultraviolet synaptic device is judged to have short-term memory or STP (Short-Term Plasticity). This decay process can be fitted using I(t) = I0 + Aexp(-t / τ) or a double exponential function, where I(t) represents the source-drain current measured at time t after the deep ultraviolet light pulse is removed, I0 represents the dark-state baseline current under no-light conditions, τ represents the current decay time constant, t represents the time from the removal of the deep ultraviolet light pulse until time t, and A represents the current increment or fitted amplitude caused by light stimulation. The source-drain current refers to the current between the drain and source of a MOSFET. When the MOSFET is in the off state, a small leakage current is generated due to some physical effects (such as tunneling and leakage effects).

[0067] For example, the synaptic behavior of gallium oxide ultraviolet synaptic devices, which maintain an enhanced conductivity state for a long time after stimulation by no less than 5 consecutive ultraviolet light pulses or a high light dose, can be used as a characterization of long-term memory or LTP (long-term plasticity).

[0068] The long-term memory of continuous ultraviolet light pulses can be, but is not limited to, 20, 50, 60, etc., or the state exhibited in gallium oxide ultraviolet synaptic devices after strong stimulation with a high light dose. This long-term memory can last for more than 1 minute, for example, from several minutes to more than 10 minutes.

[0069] For example, see Figure 5 As shown, a learning-forgetting-relearning link is realized based on multi-pulse stimulation: 50 consecutive ultraviolet light pulses are used as learning stimuli, and 50 ultraviolet light pulses are applied again as relearning stimuli after intervals of 1 min, 5 min, and 10 min, thereby realizing the learning-forgetting-relearning link.

[0070] In some optional embodiments of this application, the substrate can be a silicon substrate with a silicon dioxide insulating layer on its surface. The substrate can be a Si / SiO2 stack, quartz, glass, sapphire, or polyimide (PI) substrate, etc. A Si / SiO2 stack substrate refers to a layered structure in which a silicon dioxide insulating layer is formed on the surface of a silicon substrate.

[0071] For example, using Si / SiO2 as the substrate material, Si / SiO2 substrates have the advantages of flat surface, good process compatibility, and strong insulation. They can not only withstand the annealing process of SiC and Ga2O3 thin films, but also facilitate photolithography patterning and electrode overlay. They are suitable for verifying the structural design, fabrication process and synaptic function of deep ultraviolet neural optoelectronic devices with SiC / Ga2O3 heterostructure interfaces.

[0072] For example, deep ultraviolet light pulses such as 254nm and 265nm can be used to stimulate excitatory postsynaptic currents (EPSC), double-pulse facilitation (PPF), short-term memory, long-term memory, and synaptic behaviors such as learning-forgetting-relearning.

[0073] In other alternative embodiments, deep ultraviolet light in the range of 240nm to 280nm can also be used as the photostimuli source, such as 265nm deep ultraviolet light, to achieve a similar photoinduced synaptic response.

[0074] In an optional embodiment of this application, the parameters of the ultraviolet light emitted to the gallium oxide ultraviolet synaptic device can be recorded.

[0075] For example, the optical power density P, pulse width Y, pulse interval Z, pulse number N, and the corresponding EPSC current-time curve generated by the gallium oxide ultraviolet synaptic device can be recorded using a source meter, semiconductor parameter analyzer, or data acquisition system. The synaptic memory state of the gallium oxide ultraviolet synaptic device is not stored as digital parameters, but rather exists as changes in charge trapping / releasing states in Ga2O3 layer oxygen vacancies, thin film defect states, SiC / Ga2O3 interface states, and the conductivity state of the silicon carbide conductive layer.

[0076] As shown in Table 1, Table 1 is a mapping table of the internal changes of the gallium oxide ultraviolet synaptic device, the modulation parameters of the pulse signal, and the synaptic memory state provided in the embodiments of this application.

[0077] Table 1

[0078]

[0079] In optional embodiments of this application, if the optical power density P increases, the number of deep ultraviolet photons absorbed by Ga2O3 increases, the number of photogenerated carriers increases, interface charge trapping is enhanced, the EPSC peak value increases, the residual current increases, the learning intensity is enhanced, and short-term memory transitions to long-term memory. If the pulse width Y increases, the single illumination time is prolonged, the single pulse light dose increases, more carriers are trapped by defect states and interface states, the EPSC duration is prolonged, the decay is slower, and the memory retention capability is enhanced. If the pulse interval Z decreases, the carrier release and recombination time between adjacent pulses is shortened, the accumulation of conductivity states is enhanced, the second or subsequent EPSC peak value is higher than the previous EPSC peak value, and the dual-pulse facilitation or short-term plasticity is enhanced. If the pulse interval Z increases, the carrier release between adjacent pulses is more complete, the residual effect of the previous pulse is weakened, the enhancement degree of subsequent EPSC is reduced, and the forgetting process is enhanced. If the number of pulses N increases, multiple light stimulations cause charge trapping accumulation, the conductivity of the silicon carbide conductive layer continues to increase, the EPSC peak value and residual current gradually increase, and multi-pulse learning, long-term memory, or long-term enhancement are achieved.

[0080] For example, under solar-blind deep ultraviolet light stimulation, the gallium oxide (GaO) absorber layer absorbs photons and generates photogenerated carriers. Due to the bandgap and built-in electric field at the SiC / Ga2O3 heterojunction interface, the photogenerated carriers can undergo spatial separation near the interface. Some photogenerated electrons can be injected into the silicon carbide conductive layer and participate in lateral current transport under source-drain bias, while others are captured by oxygen vacancies, thin film defects, or SiC / Ga2O3 interface states in the GaO absorber layer. This carrier transport, capture, and release process can modulate the channel conductivity and interface barrier of the GaO ultraviolet synaptic device, thereby enabling the device to generate a photoelectric response similar to the postsynaptic current in biological systems under ultraviolet light pulse stimulation. By applying source-drain voltages across the GaO ultraviolet synaptic device, these photogenerated electrons can be further driven to migrate within the silicon carbide conductive layer, thus forming a photocurrent similar to the postsynaptic current (PSC) generated at the posterior end of a nerve synapse. When a high-frequency, high-intensity deep ultraviolet light pulse is applied to a gallium oxide ultraviolet synaptic device, a large number of photogenerated electrons are injected into the silicon carbide conductive layer. Simultaneously, holes within the gallium oxide absorption layer are continuously trapped in interface or defect states, further lowering the heterojunction barrier. This process creates a stable charge-trapping distribution within the gallium oxide ultraviolet synaptic device, allowing it to maintain a high conductivity state even after illumination ceases, effectively achieving long-term potentiation (LTP) in biological synapses.

[0081] The synaptic memory state of gallium oxide ultraviolet synaptic devices is achieved through a combination of internal charge trapping / releasing, interface barrier modulation, and channel conductance changes. External testing systems are only used to set ultraviolet light pulse parameters, apply source-drain bias voltages, and read current signals. These external testing systems may include pulse source controllers and current-voltage controllers. Therefore, the synaptic weights corresponding to the optical stimulation history are not stored in external memory but are manifested as reversible modulation of the device's own conductance state.

[0082] In the learning-forgetting-relearning process, continuous ultraviolet light pulses correspond to learning and memory writing, the spontaneous current decay after the ultraviolet light pulses are removed corresponds to forgetting, and the application of ultraviolet light pulses again corresponds to relearning. This process is used to characterize the repeatable synaptic weight adjustment capability of gallium oxide ultraviolet synaptic devices under deep ultraviolet stimulation.

[0083] See Figure 6 and Figure 7 As shown in the embodiments of this application, a method for fabricating a gallium oxide ultraviolet synaptic device is also provided, comprising:

[0084] S701: Substrate preparation;

[0085] S702: A silicon carbide conductive layer is prepared on top of the substrate;

[0086] S703: A gallium oxide absorber layer is prepared above the silicon carbide conductive layer;

[0087] S704: Etch the gallium oxide absorber layer down to the silicon carbide conductive layer to form a trench;

[0088] S705: An electrode is fabricated in a trench, and the electrode is isolated from the gallium oxide absorber layer by the trench.

[0089] In an optional embodiment of this application, the substrate can be prepared in the following manner:

[0090] Select at least one of Si / SiO2 composite material, quartz, sapphire, glass, PI, flexible mica sheet, etc. as the substrate, cut it to a suitable size, such as 2cm×2cm; clean it in sequence with acetone, anhydrous ethanol and deionized water, ultrasonic cleaning for about 5 minutes in each step, and then dry it with N2.

[0091] Fabricating a silicon carbide conductive layer over a substrate may include:

[0092] Magnetron sputtering was used to deposit silicon carbide thin films with a thickness of 200 nm by sputtering for 60 minutes under conditions of argon flow rate of 10 sccm to 30 sccm, radio frequency power of 80 W to 120 W, and gas pressure of 1 Pa.

[0093] Silicon carbide thin films were annealed at 900°C in an argon atmosphere to prepare a silicon carbide conductive layer.

[0094] In addition to magnetron sputtering, silicon carbide conductive layers can be prepared by, but are not limited to, pulsed laser deposition, chemical vapor deposition, plasma-enhanced chemical vapor deposition, atomic layer deposition, or thin film transfer.

[0095] The preparation of a gallium oxide absorber layer may include, but is not limited to:

[0096] A gallium oxide thin film with a thickness of 80 nm was obtained by sputtering for 30 minutes under the conditions of argon flow rate of 10 sccm to 30 sccm, radio frequency power of 80 W to 120 W, and gas pressure of 1 Pa.

[0097] Gallium oxide thin films were annealed at 600°C in an argon atmosphere to prepare gallium oxide absorber layers.

[0098] In addition to magnetron sputtering, gallium oxide absorber layers can be prepared by, but are not limited to, atomic layer deposition, pulsed laser deposition, sol-gel, spin coating annealing, chemical vapor deposition, or electron beam evaporation.

[0099] Laser direct writing and etching techniques can be used to develop and etch the gallium oxide absorber layer, removing the gallium oxide and exposing the silicon carbide. Electrode areas are then marked using overlay techniques in the exposed silicon carbide regions. Electrodes are then fabricated in these electrode areas.

[0100] In addition to Ti / Al alloy electrodes, other conductive materials such as Ti / Au alloy, Au, Ag, Pt, graphene, silver nanowires, and carbon nanotube transparent conductive films can also be used for electrodes.

[0101] The electrodes can be of various structures, such as parallel electrodes, interdigitated electrodes, transparent covered electrodes, or arrayed row and column electrodes, without any restrictions.

[0102] In one embodiment, the method further includes:

[0103] The electrode is connected to a pulsed light source controller, which applies a bias voltage to the electrode and emits ultraviolet light pulses to the device. The gallium oxide absorption layer absorbs the charge carriers generated by the silicon carbide conductive layer, thereby enhancing the absorption of the charge carriers generated by the ultraviolet light by the gallium oxide absorption layer to generate an excitatory postsynaptic current (EPSC).

[0104] The pulsed light source controller adjusts the optical power density, pulse width, pulse interval, and number of pulses of the ultraviolet light pulse to achieve at least one of the following neural synaptic functions through the gallium oxide ultraviolet synaptic device:

[0105] Excitatory postsynaptic currents (EPSC), double-pulse facilitated pulse currents (PPF), short-term memory, long-term memory, and the learning-forgetting-relearning pathway.

[0106] The gallium oxide ultraviolet synaptic device of this application can be used in the fields of deep ultraviolet neural photodetector, artificial vision, deep ultraviolet image recognition, neuromorphic sensing front end, and optoelectronic storage device.

[0107] In some alternative embodiments, if the gallium oxide ultraviolet synaptic device employs a flexible substrate, it can be further used in wearable and attachable deep ultraviolet sensing systems.

[0108] In some alternative embodiments, the flexible substrate can be polyimide (PI) or mica. For example, when the flexible substrate material is PI, the thickness of the PI layer can be between 0.02 mm and 0.2 mm. When the flexible substrate material is a thin mica sheet, its thickness can be between 0.025 mm and 0.1 mm. Thin mica sheets have a certain degree of flexibility and high temperature resistance, and can be used in flexible or bendable device structures that require high processing temperatures.

[0109] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application.

Claims

1. A gallium oxide ultraviolet synaptic device, characterized in that, include: A substrate, a silicon carbide conductive layer, and a gallium oxide absorber layer are stacked sequentially, with the silicon carbide conductive layer serving as a carrier transport layer and forming a heterojunction with the gallium oxide absorber layer; The gallium oxide absorber layer has trenches etched extending to the silicon carbide conductive layer; electrodes are formed in the trenches, and the electrodes are isolated from the gallium oxide absorber layer through the trenches.

2. The device according to claim 1, characterized in that, The silicon carbide conductive layer is in electrical contact with the electrode to form a current readout channel, and the thickness of the silicon carbide conductive layer includes 200 nm; And / or, the substrate is a flexible substrate, and the substrate material includes polyimide (PI) or mica sheets.

3. The device according to claim 1, characterized in that, The electrode includes a source and a drain, and the source is in electrical contact with the silicon carbide conductive layer for applying a source bias voltage. The drain electrode is in electrical contact with the silicon carbide conductive layer to apply a drain bias voltage.

4. The device according to claim 3, characterized in that, The device is externally connected to a pulsed light source controller via the electrodes. The pulsed light source controller applies a bias voltage to the source and the drain, and emits ultraviolet light pulses to the device. The gallium oxide absorption layer absorbs the charge carriers generated by the silicon carbide conductive layer, thereby enhancing the absorption of the charge carriers generated by the ultraviolet light by the gallium oxide absorption layer, so as to generate an excitatory postsynaptic current (EPSC).

5. A control system for a gallium oxide ultraviolet synaptic device, characterized in that, Includes a pulsed light source controller and the device as described in any one of claims 1 to 4; The pulsed light source controller is used to control the optical power density, pulse width, pulse interval, and number of pulses of the ultraviolet light pulse, so as to realize at least one of the following neural synaptic functions through the gallium oxide ultraviolet synaptic device: Excitatory postsynaptic currents (EPSC), double-pulse facilitated pulse currents (PPF), short-term memory, long-term memory, and the learning-forgetting-relearning pathway.

6. A method for fabricating a gallium oxide ultraviolet synaptic device, characterized in that, include: Substrate preparation; A silicon carbide conductive layer is prepared on the substrate; A gallium oxide absorber layer is prepared above the silicon carbide conductive layer; The gallium oxide absorber layer is etched down to the silicon carbide conductive layer to form a trench; An electrode is fabricated within the trench, and the electrode is isolated from the gallium oxide absorber layer by the trench.

7. The preparation method according to claim 6, characterized in that, A silicon carbide conductive layer is prepared over the substrate, comprising: Magnetron sputtering was used to deposit silicon carbide thin films with a thickness of 200 nm by sputtering for 60 minutes under conditions of argon flow rate of 10 sccm to 30 sccm, radio frequency power of 80 W to 120 W, and gas pressure of 1 Pa. The silicon carbide thin film was annealed at 900°C in an argon atmosphere to prepare the silicon carbide conductive layer. And / or, a gallium oxide absorber layer is formed over the silicon carbide conductive layer, comprising: A gallium oxide thin film with a thickness of 80 nm was obtained by sputtering for 30 minutes under the conditions of argon flow rate of 10 sccm to 30 sccm, radio frequency power of 80 W to 120 W, and gas pressure of 1 Pa. The gallium oxide thin film was annealed at 600°C in an argon atmosphere to prepare the gallium oxide absorber layer.

8. The preparation method according to claim 6, characterized in that, The preparation of the substrate includes: Flexible substrates are prepared using polyimide (PI) or mica sheets.

9. The preparation method according to claim 6, characterized in that, Etching the gallium oxide absorber layer down to the silicon carbide conductive layer to form a trench includes: Laser direct writing and etching technology is used to develop and etch the surface of the gallium oxide absorption layer to remove gallium oxide and expose silicon carbide. Electrode areas are then marked in the exposed silicon carbide area using overlay technology.

10. The preparation method according to claim 6, characterized in that, The method further includes: The electrode is connected to a pulsed light source controller, which applies a bias voltage to the electrode and emits ultraviolet light pulses to the device. The gallium oxide absorption layer absorbs the charge carriers generated by the silicon carbide conductive layer, thereby enhancing the absorption of the charge carriers generated by the ultraviolet light by the gallium oxide absorption layer to generate an excitatory postsynaptic current (EPSC). The pulsed light source controller adjusts the optical power density, pulse width, pulse interval, and number of pulses of the ultraviolet light pulse to achieve at least one of the following neural synaptic functions through the gallium oxide ultraviolet synaptic device: Excitatory postsynaptic currents (EPSC), double-pulse facilitated pulse currents (PPF), short-term memory, long-term memory, and the learning-forgetting-relearning pathway.

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