Solar-blind ultraviolet photoelectric synaptic device and preparation method thereof

Abstract

The invention relates to a solar-blind ultraviolet photoelectric synapse and a preparation method thereof. The solar-blind ultraviolet photoelectric synapse comprises a substrate; the bottom electrode is positioned on the substrate; the oxide layer is located on the surface of the bottom electrode, the material of the oxide layer is oxide with more than two oxidation states, and the oxide layer has light response to solar-blind ultraviolet light; and the transparent top electrode is positioned on the surface of the oxide layer. According to the invention, the oxide layer is arranged to absorb a large amount of solar-blind ultraviolet photons, so that the response rate and the performance of the device are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a solar-blind ultraviolet photosynapse and its fabrication method. Background Technology

[0002] Currently, near-ultraviolet-visible-infrared photoelectric synaptic devices face significant limitations in optical modulation applications: their operating wavelengths highly overlap with the solar spectrum, making the optical modulation process susceptible to interference from sunlight background noise; furthermore, these devices generally suffer from insufficient resistance to optical signal crosstalk. To overcome this technical bottleneck, solar-blind ultraviolet light sources can be used in photoelectric synaptic devices. Currently, most reported devices responding to solar-blind ultraviolet light are photodetectors, lacking neural computing capabilities. Therefore, developing photoelectric synapses with simple fabrication processes and solar-blind ultraviolet light response is a pressing technical problem in this field. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a solar-blind ultraviolet photoelectric synapse and its preparation method, which improves the device's responsivity and performance by absorbing a large number of solar-blind ultraviolet photons through an oxide layer.

[0004] To solve the above-mentioned technical problems, the present invention provides a solar-blind ultraviolet photosynapse, comprising: a substrate; a bottom electrode located on the substrate; an oxide layer located on the surface of the bottom electrode, wherein the oxide layer is made of an oxide having two or more oxidation states and the oxide layer has a photoresponse to solar-blind ultraviolet light; and a transparent top electrode located on the surface of the oxide layer.

[0005] Optionally, the material of the oxide layer includes at least two of Nb2O5, NbO2, V2O5, and VO2.

[0006] Optionally, the thickness of the oxide layer is 60 nm to 100 nm.

[0007] Optionally, the transparent top electrode includes at least one of an ITO electrode, a gold film, and a silver film, and the thickness of the transparent top electrode is 10 nm to 50 nm.

[0008] Optionally, the solar-blind ultraviolet photosynapse further includes: an adhesion layer located between the substrate and the bottom electrode, the material of the adhesion layer including at least one of titanium, nickel and chromium, and the thickness of the adhesion layer being 5 nm to 10 nm.

[0009] Optionally, the wavelength of the solar-blind ultraviolet light is 200nm to 280nm.

[0010] Accordingly, the present invention also provides a method for fabricating a solar-blind ultraviolet photosynapse, comprising: providing a substrate; forming a bottom electrode on the substrate; forming an oxide layer on the surface of the bottom electrode, wherein the oxide layer is made of an oxide having two or more oxidation states, and the oxide layer has a photoresponse to solar-blind ultraviolet light; and forming a transparent top electrode on the surface of the oxide layer.

[0011] Optionally, the process for forming the bottom electrode, the oxide layer, and the transparent top electrode includes magnetron sputtering.

[0012] Optionally, the process parameters for forming the oxide layer include: a magnetron sputtering power of 120W, a magnetron sputtering working pressure of 3.5mTorr, and a growth time of 3600s.

[0013] Optionally, an adhesion layer is formed on the substrate surface before forming the bottom electrode, and the process for forming the adhesion layer includes magnetron sputtering.

[0014] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: The solar-blind ultraviolet photosynapse provided by this invention includes a substrate, a bottom electrode, an oxide layer, and a transparent top electrode. Under solar-blind ultraviolet light excitation, photosynaptic plasticity is achieved. The bottom electrode is located on the substrate, the oxide layer is located on the surface of the bottom electrode, and the transparent top electrode is located on the surface of the oxide layer, thus forming the main body of the sandwich-structured photosynapse device. Since the oxide layer is made of an oxide with two or more oxidation states, and the oxide layer exhibits photoresponse to solar-blind ultraviolet light, multiple intermediate energy levels can be formed within the oxide bandgap. The introduction of these intermediate energy levels provides multi-step optical transition channels for charge carriers, allowing the photon absorption process to move beyond a single interband transition and absorb a large number of solar-blind ultraviolet photons. This increases the photon absorption probability and extends the lifetime of photogenerated charge carriers, thereby improving the device's responsivity to optical signals and overall device performance. Furthermore, since oxides have two or more oxidation states, reversible valence state transitions and the capture and release of photogenerated carriers can occur under light stimulation. After the light stimulation is removed, the energy barrier in the electron escape process prolongs the relaxation time of the current, further improving the device performance of the solar-blind ultraviolet photosynapse.

[0015] The method for fabricating a solar-blind ultraviolet photosynapse provided by the present invention is used to fabricate the aforementioned solar-blind ultraviolet photosynapse, and therefore also possesses the technical effects of the aforementioned solar-blind ultraviolet photosynapse, which will not be elaborated further here. Furthermore, the method for fabricating the solar-blind ultraviolet photosynapse is compatible with existing CMOS processes, has a simple fabrication process, and is suitable for large-scale production. Attached Figure Description

[0016] Figures 1 to 4This is a schematic diagram of the structure of each step in the preparation method of the solar-blind ultraviolet photosynapse provided in the embodiments of the present invention; Figure 5 This is a response diagram of the solar-blind ultraviolet photosynapse provided in the embodiment of the present invention to different light pulse powers under solar-blind ultraviolet light with a wavelength of 250nm; Figure 6 This is a response diagram of the solar-blind ultraviolet photosynapse provided in this embodiment of the invention to different light pulse durations under solar-blind ultraviolet light with a wavelength of 250nm; Figure 7 This is a current response diagram of the solar-blind ultraviolet photosynapse provided in an embodiment of the present invention to solar-blind ultraviolet light with a wavelength of 200nm; Figure 8 This is a current response diagram of the solar-blind ultraviolet photosynapse provided in this embodiment of the invention to solar-blind ultraviolet light with a wavelength of 280nm.

[0017] Explanation of reference numerals in the attached figures: 100, Substrate; 110, Adhesion layer; 200, Bottom electrode; 300, Oxide layer; 400, Transparent top electrode. Detailed Implementation

[0018] As described in the background section, most devices responsive to solar-blind ultraviolet light are photodetectors, and the materials used for this response are mostly organic or two-dimensional materials. Gallium oxide is a CMOS-compatible oxide, but its fabrication conditions are demanding and require a fixed phase. Therefore, developing a simple fabrication process for a photosynapse responsive to solar-blind ultraviolet light is a pressing technical problem in this field.

[0019] To address the aforementioned technical problems, the present invention provides a solar-blind ultraviolet photoelectric synapse and its fabrication method. By using an oxide layer with two or more oxidation states, the absorption probability of photons is increased and the lifetime of photogenerated carriers is extended, thereby improving the device's response rate to optical signals and device performance.

[0020] To make the above-mentioned objectives, features, and beneficial effects of the present invention more apparent and understandable, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that 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 a 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. Additionally, directional terms such as above, below, up, down, upward, downward, left, right, etc., are used relative to exemplary embodiments as they are shown in the figures, with upward or upper directions pointing towards the top of the corresponding figure and downward or lower directions pointing towards the bottom of the corresponding figure.

[0022] Figures 1 to 4 This is a schematic diagram of the structure of each step in the preparation method of the solar-blind ultraviolet photosynapse provided in the embodiments of the present invention.

[0023] Please refer to Figure 1 Substrate 100 is provided.

[0024] Specifically, the substrate 100 is made of silicon. The substrate 100 may also include at least one of the following materials: Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors. Alternatively, the substrate 100 may include a silicon substrate, silicon-on-insulator (SSOI), silicon-on-insulator (S-SiGeOI), silicon-on-insulator (SiGeOI), or germanium-on-insulator (GeOI), etc. The size of the substrate 100 may be 6 inches, 8 inches, 12 inches, etc., and there is no limitation thereto.

[0025] Please refer to Figure 2 A bottom electrode 200 is formed on the substrate 100.

[0026] In this embodiment, the bottom electrode 200 is used to form a stable Schottky barrier, thereby amplifying the changes in photocurrent.

[0027] Specifically, the material of the bottom electrode 200 may include platinum.

[0028] In this embodiment, the process for forming the bottom electrode 200 includes magnetron sputtering technology.

[0029] Specifically, the method for forming the bottom electrode 200 includes sputtering deposition in an argon atmosphere, with a magnetron sputtering power of 120W and a chamber working pressure of 3mToor.

[0030] In this embodiment, before forming the bottom electrode 200, an adhesion layer 110 is formed on the surface of the substrate 100.

[0031] In this embodiment, the adhesion layer 110 is located between the substrate 100 and the bottom electrode 200.

[0032] Specifically, the material of the adhesive layer 110 includes at least one of titanium, nickel, and chromium.

[0033] Specifically, the thickness of the adhesion layer 110 is 5nm to 10nm.

[0034] Specifically, the process for forming the adhesion layer 110 includes magnetron sputtering technology.

[0035] Please refer to Figure 3 An oxide layer 300 is formed on the surface of the bottom electrode 200.

[0036] The oxide layer 300 is made of an oxide having two or more oxidation states, and the oxide layer 300 is photoresponsive to solar-blind ultraviolet light.

[0037] In this embodiment, the material of the oxide layer 300 includes at least two of Nb2O5, NbO2, V2O5 and VO2.

[0038] Specifically, both Nb2O5 and NbO2 can exist in crystalline and amorphous states, as can both V2O5 and VO2.

[0039] In this embodiment, the thickness of the oxide layer 300 is 60 nm to 100 nm.

[0040] In this embodiment, the process for forming the oxide layer 300 may include magnetron sputtering technology.

[0041] Specifically, the method for forming oxide layer 300 includes sputtering deposition in a mixed atmosphere of oxygen and argon, with a magnetron sputtering power of 120W, a chamber working pressure of 3.5mToor, and a growth time of 3600s.

[0042] Preferably, the gas volume ratio of oxygen to argon is 3:10.

[0043] In this embodiment, the wavelength of the solar blinding ultraviolet light is 200nm to 280nm.

[0044] Please refer to Figure 4 A transparent top electrode 400 is formed on the surface of the oxide layer 300.

[0045] In this embodiment, the transparent top electrode 400 may include at least one of an ITO electrode, a gold film, and a silver film.

[0046] In this embodiment, the thickness of the transparent top electrode 400 is 10 nm to 50 nm.

[0047] In this embodiment, the process of forming the transparent top electrode 400 may include magnetron sputtering technology.

[0048] Specifically, the method for forming the transparent top electrode 400 includes: sputtering deposition in an argon atmosphere, with a magnetron sputtering power of 80W and a cavity working pressure of 3mToor.

[0049] The performance of the solar-blind ultraviolet photosynapse device according to an embodiment of the present invention was tested.

[0050] Please refer to Figure 5 Under different light pulse powers of 250nm wavelength solar-blind ultraviolet light, the photoelectric response amplitude of the solar-blind ultraviolet photosynapse provided in this embodiment of the invention gradually increases with the increase of light pulse power, indicating that the device has good adjustable response characteristics to light pulse power. At the same time, the response gradually decays over time after the light pulse ends, exhibiting dynamic behavior characteristics similar to biological synaptic short-term memory, which can realize photosynaptic plasticity.

[0051] In this embodiment, photoelectronic synaptic plasticity refers to the adjustable change in the electrical state (usually conductivity / current) of a device under light stimulation. This change can accumulate, be maintained, and exhibit learning, memory, and forgetting behaviors similar to those of biological synapses.

[0052] Please refer to Figure 6 Under solar-blind ultraviolet light with a wavelength of 250 nm, the photoelectric response amplitude of the device gradually increases with the extension of the light pulse duration, indicating that the light pulse duration can effectively regulate the transient response intensity of the device. When the light pulse is removed, the response gradually decays over time and returns to its initial state, exhibiting dynamic response characteristics similar to biological synaptic short-term memory.

[0053] Please refer to Figure 7 Under solar-blind ultraviolet light with a wavelength of 200nm, the solar-blind ultraviolet photosynapse provided in this embodiment of the invention exhibits a significant photocurrent response, and the response process shows a reversible change with the on and off of the illumination. The current peak is obvious, the decay time is slow, the device has a high responsivity, and the performance is good.

[0054] Please refer to Figure 8 Under solar-blind ultraviolet light with a wavelength of 280nm, the solar-blind ultraviolet photosynapse provided in this embodiment of the invention exhibits a significant photocurrent response with a high peak current and a long current relaxation time.

[0055] In this embodiment, the fabrication method of the solar-blind ultraviolet photosynapse includes providing a substrate 100, forming a bottom electrode 200 on the substrate 100, forming an oxide layer 300 on the surface of the bottom electrode 200, and forming a transparent top electrode 400 on the surface of the oxide layer 300. Under solar-blind ultraviolet light excitation, the fabricated device achieves photosynaptic plasticity. The bottom electrode 200 is located on the substrate 100, the oxide layer 300 is located on the surface of the bottom electrode 200, and the transparent top electrode 400 is located on the surface of the oxide layer 300, thus constituting the main body of the solar-blind ultraviolet photosynapse device with a sandwich structure. Since the oxide layer 300 is made of an oxide with two or more oxidation states, and since the oxide layer 300 exhibits photoresponse to solar-blind ultraviolet light, multiple intermediate energy levels can be formed within the oxide bandgap. The introduction of these intermediate energy levels provides multi-step optical transition channels for charge carriers, allowing the photon absorption process to move beyond a single interband transition and absorb a large number of solar-blind ultraviolet photons. This increases the photon absorption probability and extends the lifetime of photogenerated charge carriers, thereby improving the device's responsivity to optical signals and its performance. Furthermore, because the oxide has two or more oxidation states, reversible valence state transitions and the capture and release of photogenerated charge carriers can occur under photostimulation. After the photostimulation is removed, the energy barrier during electron escape prolongs the current relaxation time, further improving the device performance of the solar-blind ultraviolet photosynapse. Simultaneously, the fabrication method of the solar-blind ultraviolet photosynapse provided in this embodiment is compatible with existing CMOS processes, is simple to fabricate, and is suitable for large-scale production.

[0056] Accordingly, embodiments of the present invention also provide a solar-blind ultraviolet photosynapse, comprising: a substrate 100, a bottom electrode 200, an oxide layer 300, and a transparent top electrode 400.

[0057] Specifically, the bottom electrode 200 is located on the substrate 100.

[0058] Specifically, the oxide layer 300 is located on the surface of the bottom electrode 200. The material of the oxide layer 300 is an oxide having two or more oxidation states, and the oxide layer 300 has a photoresponse to solar-blind ultraviolet light.

[0059] Specifically, the transparent top electrode 400 is located on the surface of the oxide layer 300.

[0060] In this embodiment, the material of the oxide layer 300 includes at least two of Nb2O5, NbO2, V2O5 and VO2.

[0061] In this embodiment, the thickness of the oxide layer 300 is 60 nm to 100 nm.

[0062] In this embodiment, the transparent top electrode 400 includes at least one of an ITO electrode, a gold film, and a silver film.

[0063] Specifically, the thickness of the transparent top electrode 400 is 10nm to 50nm.

[0064] In this embodiment, the solar-blind ultraviolet photosynapse further includes an adhesion layer 110.

[0065] Specifically, the adhesion layer 110 is located between the substrate 100 and the bottom electrode 200.

[0066] Specifically, the material of the adhesive layer 110 includes at least one of titanium, nickel, and chromium.

[0067] Specifically, the thickness of the adhesion layer 110 is 5nm to 10nm.

[0068] In this embodiment, the wavelength of the solar blinding ultraviolet light is 200nm to 280nm.

[0069] Specifically, the materials, formation process, working principle, specific implementation method and beneficial effects of the solar-blind ultraviolet photosynapse in the embodiments of the present invention can be found in the preparation method of the solar-blind ultraviolet photosynapse in the embodiments of the present invention, and will not be repeated here.

[0070] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A solar-blind ultraviolet photosynapse, characterized in that, include: Substrate; The bottom electrode is located on the substrate; An oxide layer is located on the surface of the bottom electrode. The oxide layer is made of an oxide having two or more oxidation states and is photoresponsive to solar-blind ultraviolet light. A transparent top electrode is located on the surface of the oxide layer.

2. The solar-blind ultraviolet photosynapse as described in claim 1, characterized in that, The oxide layer is made of at least two of Nb2O5, NbO2, V2O5, and VO2.

3. The solar-blind ultraviolet photosynapse as described in claim 2, characterized in that, The oxide layer has a thickness of 60 nm to 100 nm.

4. The solar-blind ultraviolet photosynapse as described in claim 1, characterized in that, The transparent top electrode includes at least one of an ITO electrode, a gold film, and a silver film, and the thickness of the transparent top electrode is 10 nm to 50 nm.

5. The solar-blind ultraviolet photosynapse as described in claim 1, characterized in that, Also includes: An adhesion layer is located between the substrate and the bottom electrode. The material of the adhesion layer includes at least one of titanium, nickel, and chromium, and the thickness of the adhesion layer is 5 nm to 10 nm.

6. The solar-blind ultraviolet photosynapse as described in claim 1, characterized in that, The wavelength of the solar blinding ultraviolet light is 200nm to 280nm.

7. A method for preparing a solar-blind ultraviolet photosynapse, characterized in that, include: Provide substrate; A bottom electrode is formed on the substrate; An oxide layer is formed on the surface of the bottom electrode. The oxide layer is made of an oxide having two or more oxidation states and is photoresponsive to solar-blind ultraviolet light. A transparent top electrode is formed on the surface of the oxide layer.

8. The method for preparing a solar-blind ultraviolet photosynapse as described in claim 7, characterized in that, The process for forming the bottom electrode, the oxide layer, and the transparent top electrode includes magnetron sputtering technology.

9. The method for preparing a solar-blind ultraviolet photosynapse as described in claim 8, characterized in that, The process parameters for forming the oxide layer include: magnetron sputtering power of 120W, magnetron sputtering working pressure of 3.5mTorr, and growth time of 3600s.

10. The method for preparing a solar-blind ultraviolet photosynapse as described in claim 7, characterized in that, Also includes: Before forming the bottom electrode, an adhesion layer is formed on the surface of the substrate, and the process for forming the adhesion layer includes magnetron sputtering.

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