High-consistency photoelectric memristor based on quasi-two-dimensional gallium nitride buffer layer

Abstract

The invention belongs to the technical field of brain-like computing chips, and provides a high-consistency photoelectric memristor based on a quasi-two-dimensional gallium nitride buffer layer. The objective of the invention is to solve the problems of poor consistency of the current memristor and low integration degree caused by a large amount of Joule heat generated by pure electric signal regulation and control. According to the main scheme, the memristor comprises a memristor bottom electrode, a memristor buffer layer, a memristor functional layer and a memristor top electrode which are sequentially arranged from bottom to top, wherein the memristor buffer layer is an independent quasi-two-dimensional gallium nitride film obtained through an anode electrochemical stripping technology. By introducing the quasi-two-dimensional gallium nitride buffer layer with the advantages of high electron mobility, high thermal stability, high chemical stability, strong radiation resistance, strong photoelectric effect and the like, on one hand, the reliability and consistency of the memristor are improved, on the other hand, optical signal regulation of a resistance state is realized, the generation of Joule heat of the device is reduced, and the performance of the memristor is improved. The high-density integration of the memristor is facilitated, and the potential application value of the memristor in an artificial neural network is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of neuromorphic computing chips, and particularly relates to a highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer. Background Art

[0002] In recent years, with the continuous maturity of neural network algorithms represented by recursive neural networks, convolutional neural networks, and deep neural networks, artificial intelligence has been widely applied in many fields such as autonomous driving, semantic understanding, knowledge search, speech and image recognition. The ultimate goal of artificial intelligence research is to achieve neuromorphic computing, that is, neuro-morphological computing, which aims to enable machines to have the ability to self-learn, remember, judge external information like humans, and complete a series of operations independently. Modern neurobiology believes that neural synapses are the basis of human learning and memory. The part where one neuron contacts another neuron is called a synapse. A synapse is the part where neurons are functionally connected and is also the key part for information transmission. Therefore, developing high-performance artificial neural synapses is the key to achieving energy-efficient neuromorphic computing. A memristor, as a new type of two-terminal device, is one of the best basic devices for realizing artificial neural synapses: First, the resistance value of the memristor can be adjusted under the action of an external signal, so it can simulate the plasticity of neural synapses; second, the memristor is a non-volatile device and can be used to store synaptic connection weights; at the same time, the magnitude of the current flowing through the memristor is obtained by multiplying its conductance value by the voltage value, corresponding to the weighted multiplication operation of synaptic weights and neuron excitation; in addition, the memristor also has the advantages of simple structure, low power consumption, small size, three-dimensional integration, and compatibility with CMOS technology.

[0003] However, so far, the research on memristors worldwide is still at the basic research level, and there is still a long way to go before full commercial application. One of the main obstacles is that the reliability, conductance volatility, and parameter discreteness of the devices cannot meet the requirements of artificial neural networks for neuromorphic computing. Therefore, how to improve the reliability and consistency of memristors has become a key issue for the practical application of memristors in the future. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems of poor consistency of current memristive devices and low integration due to a large amount of Joule heat generated by pure electrical signal regulation.

[0005] To achieve the above purpose, the present invention adopts the following technical means:

[0006] The present invention provides a highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer, which includes a memristor bottom electrode, a memristor buffer layer, a memristor functional layer, and a memristor top electrode arranged in sequence from bottom to top. The memristor buffer layer is an independent quasi-two-dimensional gallium nitride thin film peeled off from a growth substrate by anodic electrochemical exfoliation technology. Since natural gallium nitride does not exist in nature, the gallium nitride thin film is epitaxially grown on a hetero-substrate. The lattice mismatch between the hetero-substrate and gallium nitride will cause a large number of defects in the grown gallium nitride thin film, affecting the electrical performance of the corresponding device. However, for the quasi-two-dimensional gallium nitride thin film, since it is peeled off from the growth substrate, the internal stress in the lattice is released, so it has better lattice quality than the traditional bulk gallium nitride thin film.

[0007] In the above technical solution, the material of the memristor bottom electrode is a high work function metal material that can form a Schottky contact with the gallium nitride material, including any one of gold, silver, aluminum, titanium, platinum, and nickel;

[0008] In the above technical solution, the thickness of the memristor bottom electrode is 20 - 80 nm;

[0009] In the above technical solution, the quasi-two-dimensional gallium nitride thin film is peeled off from the growth substrate by anodic electrochemical exfoliation technology; the electrolyte solution in the anodic electrochemical exfoliation process is one of HNO3 solution, H2SO4 solution, NaOH solution, and KOH solution; the applied voltage in the anodic electrochemical process is 10 - 50 V. The traditional thin film exfoliation technologies mainly include laser exfoliation and mechanical exfoliation. Among them, laser exfoliation uses high-energy laser, so it will cause great physical damage to the peeled thin film and can only be used to exfoliate thicker thin films; while mechanical exfoliation is generally used to exfoliate thinner thin films, but since it is manually operated, the thickness of the peeled thin film cannot be controlled, so the thickness of the thin film exfoliated by mechanical exfoliation technology is random. Compared with these two traditional exfoliation technologies, the anodic electrochemical exfoliation technology has the following advantages: First, since it is a chemical process of wet etching, it can avoid the great damage caused by high-energy laser; second, it can precisely control the thickness of the peeled thin film; third, during the anodic electrochemical exfoliation of the quasi-two-dimensional gallium nitride thin film, a large number of longitudinal nanopores will be formed while the quasi-two-dimensional gallium nitride thin film is being peeled off, which can greatly improve the absorption ability of the quasi-two-dimensional gallium nitride thin film for incident light, so it has a strong optoelectronic response.

[0010] In the above technical solution, the thickness of the quasi-two-dimensional gallium nitride thin film is very thin, 10 - 50 mm, almost a two-dimensional material. Therefore, in addition to the characteristics of traditional gallium nitride materials such as high electron mobility, high thermal stability, high chemical stability, strong anti-radiation characteristics, and strong optoelectronic effect, it also has the characteristics of being soft and easy to bend, and can be dry transferred through PDMS like two-dimensional materials.

[0011] In the above technical solution, the quasi-two-dimensional gallium nitride thin film is transferred onto the bottom electrode of the memristor through a dry transfer technique as the buffer layer of the memristor, and high-temperature thermal annealing is required after the transfer to enhance the Schottky contact between the quasi-two-dimensional gallium nitride buffer layer and the bottom electrode of the memristor; the high-temperature thermal annealing temperature is 400-600 °C; the high-temperature thermal annealing time is 3-5 minutes.

[0012] In the above technical solution, the material of the memristor functional layer is a binary metal oxide, including HfO x , TiO x , TaO x , ZrO x Any one of them. On the one hand, the binary metal oxide can be used as a functional layer to realize the switching between the high and low resistance states of the memristor, and on the other hand, it can also be used as a passivation layer to passivate the dangling bonds on the surface of the quasi-two-dimensional gallium nitride thin film;

[0013] In the above technical solution, the thickness of the binary metal oxide is 1-10 nm.

[0014] In the above technical solution, the top electrode of the memristor should have an ultraviolet light transmittance of more than 60% to ensure that the incident ultraviolet light can pass through the top electrode and be incident on the quasi-two-dimensional gallium nitride buffer layer;

[0015] In the above technical solution, the material of the top electrode of the memristor with high ultraviolet transmittance is any one of AlGaN, tin oxide, indium tin oxide, indium zinc oxide, and ultra-thin metal, and the thickness of the ultra-thin metal is 1-10 nm.

[0016] Because the present invention adopts the above technical means, it has the following beneficial effects:

[0017] 1. In the present invention, the introduced quasi-two-dimensional gallium nitride buffer layer, due to its high thermal stability, chemical stability, strong anti-radiation characteristics, etc., greatly inhibits the randomness of the formation of conductive filaments in the device, thereby improving the stability and reliability of the device and broadening the application scenarios of the memristor.

[0018] 2. The quasi-two-dimensional gallium nitride buffer layer introduced in the present invention is obtained by anodic electrochemical exfoliation technology. The traditional thin film exfoliation technologies mainly include laser exfoliation and mechanical exfoliation. Among them, laser exfoliation uses high-energy lasers, which will cause great physical damage to the exfoliated thin film and can only be used for exfoliating relatively thick thin films. Mechanical exfoliation is generally used for exfoliating thin films with relatively thin thickness. However, since it is manually operated and the thickness of the exfoliated thin film cannot be controlled, the thickness of the thin film exfoliated by mechanical exfoliation technology is random. Compared with these two traditional exfoliation technologies, the anodic electrochemical exfoliation technology has the following advantages: First, since it is a chemical process of wet etching, it can avoid the great damage caused by high-energy lasers. Second, it can precisely control the thickness of the exfoliated thin film. Third, during the process of anodic electrochemical exfoliation of the quasi-two-dimensional gallium nitride thin film, a large number of longitudinal nanopores will be formed while the quasi-two-dimensional gallium nitride thin film is exfoliated, which can greatly improve the absorption ability of the quasi-two-dimensional gallium nitride thin film for incident light, so it has a strong photoelectric response.

[0019] 3. The quasi-two-dimensional gallium nitride buffer layer introduced in the present invention has a strong photoelectric effect. When ultraviolet light is applied to the device, a large number of photo-generated carriers will be formed inside the quasi-two-dimensional gallium nitride buffer layer. These photo-generated carriers can damage the integrity of the conductive filaments inside the functional layer and cause them to break, so that the device changes from a low-resistance state to a high-resistance state, realizing the optoelectronic regulation of the memristor resistance state. Compared with traditional pure electrical memristors, the introduction of optical signal regulation can effectively avoid the change of the device microstructure by the regulation signal and reduce the generation of Joule heat, further improving the stability of the memristor, which is beneficial to the high-density integration of the memristor and lays a solid foundation for the practical application of the memristor in artificial neural networks.

[0020] In summary, by introducing a quasi-two-dimensional gallium nitride buffer layer with advantages such as high electron mobility, high thermal stability, high chemical stability, strong anti-radiation characteristics, and strong photoelectric effect, the present invention improves the reliability and consistency of the memristor itself on the one hand, and realizes the optical signal regulation of the resistance state and reduces the generation of Joule heat of the device on the other hand, thereby further improving the device stability, being beneficial to the high-density integration of the memristor, and greatly improving the potential application value of the memristor in artificial neural networks. Brief Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the optoelectronic memristor structure;

[0022] Figure 2 It is a SEM image of the quasi-two-dimensional gallium nitride thin film. Detailed Embodiments

[0023] The following will give a detailed description of the embodiments of the present invention. Although the present invention will be described and illustrated in conjunction with some specific embodiments, it should be noted that the present invention is not limited to these embodiments only. On the contrary, any modifications or equivalent substitutions made to the present invention shall be covered within the scope of the claims of the present invention.

[0024] In addition, for a better illustration of the present invention, numerous specific details are given in the following specific embodiments. Those skilled in the art will understand that the present invention can also be implemented without these specific details.

[0025] The present invention uses a quasi-two-dimensional gallium nitride thin film with advantages such as high electron mobility, high thermal stability, high chemical stability, strong anti-radiation characteristics, and strong optoelectronic effects as the buffer layer of the memristor. The aims are as follows: on the one hand, by utilizing the characteristics of high electron mobility, high thermal stability, high chemical stability, and strong anti-radiation characteristics of the gallium nitride material, the reliability and consistency of the memristor itself are improved; on the other hand, when the memristor functional layer is in the low-resistance state, by applying light to the device, due to the strong optoelectronic effect of the gallium nitride material, the generated photo-generated carriers can damage the integrity of the conductive filaments inside the functional layer and cause them to break, thereby changing the device from the low-resistance state to the high-resistance state, realizing the optoelectronic regulation of the memristor resistance state. Compared with traditional pure electrical memristors, the introduction of optical signal regulation can effectively avoid the change of the device microstructure by the regulation signal and reduce the generation of Joule heat, further improving the stability of the memristor, being beneficial to the high-density integration of the memristor, and laying a solid foundation for the practical application of the memristor in artificial neural networks.

[0026] Embodiment 1

[0027] The present invention provides a highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer, as Figure 1 shown, including:

[0028] A memristor bottom electrode;

[0029] A memristor buffer layer, located above the memristor bottom electrode;

[0030] A memristor functional layer, located above the memristor buffer layer;

[0031] A memristor top electrode, located above the memristor functional layer;

[0032] The memristor buffer layer is a quasi-two-dimensional gallium nitride thin film with high electron mobility, high thermal stability, high chemical stability, strong anti-radiation characteristics, and strong optoelectronic response, as Figure 2 shown.

[0033] Embodiment 2

[0034] Based on Example 1, the bottom electrode material of the memristor is a high work function metal material that can form a Schottky contact with the gallium nitride material, including gold, silver, aluminum, titanium, platinum, and nickel; the thickness of the bottom electrode of the memristor is 20 - 80 nm, and a thinner electrode thickness facilitates the subsequent transfer of the quasi-two-dimensional gallium nitride buffer layer.

[0035] Example 3

[0036] Based on Example 1, the quasi-two-dimensional gallium nitride thin film is peeled off from the growth substrate by anodic electrochemical exfoliation technology; the electrolyte solution in the anodic electrochemical exfoliation process is one of HNO3 solution, H2SO4 solution, NaOH solution, and KOH solution; the applied voltage in the anodic electrochemical process is 10 - 50 V. The higher the voltage, the faster the peeling rate of the quasi-two-dimensional gallium nitride thin film, but too high a voltage will damage the integrity of the thin film.

[0037] Example 4

[0038] Based on Example 1, the thickness of the quasi-two-dimensional gallium nitride thin film is 10 - 50 nm. If it is too thin, it is difficult to peel off completely, and if it is too thick, it will affect its electrical properties. The quasi-two-dimensional gallium nitride thin film is very thin, almost a two-dimensional material. Therefore, in addition to the characteristics of traditional gallium nitride materials such as high electron mobility, high thermal stability, high chemical stability, strong anti-radiation characteristics, and strong photoelectric effect, it also has the characteristics of being soft and easy to bend, and can be dry transferred through PDMS like two-dimensional materials.

[0039] Example 5

[0040] Based on Example 4, the quasi-two-dimensional gallium nitride thin film is transferred onto the bottom electrode of the memristor through a dry transfer technique as a buffer layer of the memristor, and high-temperature thermal annealing is required after the transfer to enhance the Schottky contact between the quasi-two-dimensional gallium nitride buffer layer and the bottom electrode of the memristor; the high-temperature thermal annealing temperature is 400-600 °C; the high-temperature thermal annealing time is 3-5 minutes. The traditional thin film lift-off techniques mainly include laser lift-off and mechanical lift-off. Among them, laser lift-off uses high-energy laser, so it will cause great physical damage to the lifted-off thin film and can only be used to lift off thicker thin films; while mechanical lift-off is generally used to lift off thinner thin films, but because it is manually operated and the thickness of the lifted-off thin film cannot be controlled, the thickness of the thin film lifted off by the mechanical lift-off technique is random. Compared with these two traditional lift-off techniques, the anodic electrochemical lift-off technique has the following advantages: First, since it is a chemical process of wet etching, it can avoid the great damage caused by high-energy laser; Second, it can accurately control the thickness of the lifted-off thin film; Third, during the anodic electrochemical lift-off of the quasi-two-dimensional gallium nitride thin film, a large number of longitudinal nanopores will be formed on the quasi-two-dimensional gallium nitride thin film while being lifted off, which can greatly improve the absorption ability of the quasi-two-dimensional gallium nitride thin film for incident light, so it has a strong photoelectric response.

[0041] Example 6

[0042] Based on Example 1, the memristor functional layer material is a binary metal oxide, such as HfOx, TiOx, TaOx, ZrOx. On the one hand, the binary metal oxide can be used as a functional layer to realize the switching between the high and low resistance states of the memristor, and on the other hand, it can also be used as a passivation layer to passivate the surface dangling bonds of the quasi-two-dimensional gallium nitride thin film, thereby improving the electrical performance of the whole device; the thickness of the binary metal oxide is 1-10 nm.

[0043] Example 7

[0044] Based on Example 1, the top electrode of the memristor should have an ultraviolet light transmittance of more than 60% to ensure that the incident ultraviolet light can pass through the top electrode and be incident on the quasi-two-dimensional gallium nitride buffer layer; the material of the top electrode of the memristor with high ultraviolet transmittance is any one of AlGaN, tin oxide, indium tin oxide (ITO), indium zinc oxide, and ultra-thin metal (1-10 nm).

Claims

1. A highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer, characterized in that It includes a memristor bottom electrode, a memristor buffer layer, a memristor functional layer, and a memristor top electrode, which are arranged in sequence from bottom to top. The memristor buffer layer is an independent quasi-two-dimensional gallium nitride thin film obtained by anodic electrochemical exfoliation technology from a growth substrate.

2. The highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer according to claim 1, wherein The material of the memristor bottom electrode is a high work function metal material that can form a Schottky contact with the gallium nitride material, including any one of gold, silver, aluminum, titanium, platinum, and nickel.

3. The highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer according to claim 2, wherein, The thickness of the memristor bottom electrode is 20 - 80 nm.

4. A highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer according to claim 1, characterized in that: The electrolyte solution for the anodic electrochemical exfoliation process is one of HNO3 solution, H2SO4 solution, NaOH solution, and KOH solution; the applied voltage in the anodic electrochemical process is 10 - 50 V.

5. The highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer according to claim 1, wherein: The thickness of the quasi-two-dimensional gallium nitride thin film is 10 - 50 nm.

6. The highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer according to claim 5, characterized in that: The quasi-two-dimensional gallium nitride thin film is transferred onto the memristor bottom electrode as a memristor buffer layer through dry transfer technology, and high-temperature thermal annealing is required after transfer to enhance the Schottky contact between the quasi-two-dimensional gallium nitride buffer layer and the memristor bottom electrode; the high-temperature thermal annealing temperature is 400 - 600 °C; the high-temperature thermal annealing time is 3 - 5 mins.

7. The highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer according to claim 1, wherein The memristor functional layer material is a binary metal oxide, including HfO x , TiO x , TaO x , ZrO x Any one of them. On the one hand, the binary metal oxide can be used as a functional layer to realize the switching between the high and low resistance states of the memristor. On the other hand, it can also be used as a passivation layer to passivate the surface dangling bonds of the quasi-two-dimensional gallium nitride thin film.

8. A highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer according to claim 7, wherein, The thickness of the binary metal oxide is 1 - 10 nm.

9. The high-consistency optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer according to claim 1, wherein The memristor top electrode should have an ultraviolet light transmittance of more than 60% to ensure that the incident ultraviolet light can pass through the top electrode and be incident on the quasi-two-dimensional gallium nitride buffer layer.

10. A highly consistent optoelectronic memristor based on a quasi-two-dimensional gallium nitride buffer layer according to claim 9, characterized in that, The material of the memristor top electrode with high ultraviolet transmittance is any one of AlGaN, tin oxide, indium tin oxide, indium zinc oxide, and ultra-thin metal, and the thickness of the ultra-thin metal is 1 - 10 nm.

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