Gallium oxide ultraviolet synaptic device and preparation method thereof

Abstract

The invention provides a gallium oxide ultraviolet synaptic device and a preparation method thereof, and relates to the technical field of microelectronics, and the gallium oxide ultraviolet synaptic device comprises a substrate layer, a gallium oxide light absorption layer and a patterned electrode which are sequentially arranged from bottom to top; the gallium oxide light absorption layer is used for generating photon-generated carriers under excitation of an ultraviolet light signal, and the gallium oxide light absorption layer has a ferroelectric characteristic, so that integration of an ultraviolet photosensitive characteristic and the ferroelectric characteristic is realized. The invention aims to provide a novel gallium oxide ultraviolet synapse device, the device not only has excellent sensitivity to ultraviolet light and can effectively simulate key functions of biological synapses, but also the gallium oxide light absorption layer has ferroelectric characteristics and can realize integration of ultraviolet photosensitive characteristics and ferroelectric characteristics, so that the device has good application prospects. And the method has important significance for further expanding the performance of the nerve synapse.

Description

Technical Field

[0001] The present invention relates to the field of microelectronics technology, in particular to a synaptic device, and in particular to a gallium oxide ultraviolet synaptic device and a preparation method thereof. Background Art

[0002] Neuromorphic computing is considered a promising AI computing approach for solving increasingly complex tasks. Due to the communication bottleneck of the von Neumann architecture—the separation of operation and storage units—which leads to hardware redundancy, power consumption, and computational latency, traditional von Neumann computing systems struggle to meet the practical requirements of neuromorphic computing. In contrast, the human brain possesses remarkable capabilities, capable of solving problems in parallel with low power consumption, distributed storage and processing, and self-learning. Research has shown that the dual capabilities of biological synapses for both computation and storage are key factors in the remarkable characteristics of the human brain. External stimuli (such as light, smell, sound, pressure, and chemicals) are detected and processed by sensory systems before reaching the brain. Within the sensory system, the visual system plays a crucial role in learning and memory, transmitting over 80% of environmental stimuli through the visual system and playing a key role in human perception. Therefore, simulating visual perception is crucial. Optoelectronic synaptic devices can convert visual stimuli into electronic information, integrating detection and memory to simulate vision. Due to its high bandwidth, low crosstalk and low power consumption, the concise structure enables faster computing speed, which makes it possible to solve the von Neumann communication bottleneck problem and neuromorphic computing that simulates the synaptic behavior of the human brain.

[0003] Furthermore, optoelectronic artificial synapses have broad application prospects in fields such as IoT smart sensors, biomedical electronics, artificial intelligence robotics, and neural prosthetics. They can operate effectively in a variety of environments, including astronomy, military science, and industrial engineering. As an effective method for simulating biological synapses, optoelectronic synaptic devices have attracted increasing attention and are undergoing in-depth research.

[0004] In recent years, gallium oxide has garnered significant attention for its widespread applications in power electronics, blind-spot UV photodetectors, and sensors. Binary metal oxide materials offer significant potential for practical application due to their simple chemical composition, ease of preparation, low cost, high stability, and compatibility with semiconductor processes. Gallium oxide, as a binary metal oxide, not only possesses these advantages but also exhibits wide bandgap semiconductor properties, offering strong radiation resistance and suitability for high-power, high-frequency applications.

[0005] Therefore, the development of optoelectronic neural devices based on gallium oxide is of great significance to the advancement of artificial intelligence and bioelectronics. Summary of the Invention

[0006] In response to the problems existing in the prior art, the present invention provides a gallium oxide ultraviolet synaptic device and a method for fabricating the same. The gallium oxide ultraviolet synaptic device comprises, arranged sequentially from bottom to top, a substrate layer, a gallium oxide light-absorbing layer, and a patterned electrode. The gallium oxide light-absorbing layer is configured to generate photogenerated carriers under the stimulation of an ultraviolet light signal. Furthermore, the gallium oxide light-absorbing layer exhibits ferroelectric properties, achieving the integration of ultraviolet sensitivity and ferroelectric properties. The present invention aims to provide a novel gallium oxide ultraviolet synaptic device that not only exhibits excellent sensitivity to ultraviolet light but also effectively simulates key biological synaptic functions, including but not limited to persistent photoconductivity (PPC), double-pulse facilitation (PPF), and transition plasticity from short-term memory (STM) to long-term memory (LTM). Furthermore, the gallium oxide light-absorbing layer exhibits ferroelectric properties, enabling the integration of ultraviolet sensitivity and ferroelectric properties, which is of great significance for further expanding the performance of neural synapses. The device offers advantages such as simple fabrication, high sensitivity, and excellent stability, making it highly suitable for industrial production.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] One of the objectives of the present invention is to provide a gallium oxide ultraviolet synapse device, comprising:

[0009] substrate layer.

[0010] The gallium oxide absorption layer is arranged on the surface of the substrate layer and is used to generate photogenerated carriers under the stimulation of ultraviolet light signals; moreover, the gallium oxide absorption layer has ferroelectric properties, realizing the integration of ultraviolet photosensitivity and ferroelectric properties.

[0011] A patterned electrode is arranged on the surface of the gallium oxide light absorbing layer and is used for collecting the photogenerated carriers and outputting electrical signals.

[0012] The gallium oxide UV synaptic device described in this invention is extremely sensitive to ultraviolet light and has successfully simulated various properties of biological synapses, including persistent photoconductivity (PPC), paired-pulse facilitation (PPF), and cognitive behavior during the transition from short-term memory (STM) to long-term memory (LTM). Furthermore, the gallium oxide light-absorbing layer possesses ferroelectric properties, enabling the integration of UV sensitivity and ferroelectricity, which is of great significance for further expanding the performance of neural synapses. The device also boasts simple preparation, high sensitivity, low energy consumption, and excellent stability, making it highly suitable for industrial production.

[0013] As a preferred technical solution of the present invention, the substrate layer is made of a material selected from any one of silicon, silicon carbide, sapphire or gallium nitride, and the substrate layer is made of an insulating material.

[0014] As a preferred technical solution of the present invention, the gallium oxide light-absorbing layer is an ε-Ga2O3 light-absorbing layer and has oxygen vacancy defects.

[0015] It should be noted that the gallium oxide light-absorbing layer described in the present invention is an ε-Ga2O3 light-absorbing layer. Although β-Ga2O3 light-absorbing layers have been widely studied, their deposition temperature is relatively high and they are not easy to mass-produce. Relatively speaking, ε-Ga2O3 light-absorbing layers have been less studied, but scientists have recently discovered that they have many excellent properties. First, their structure is highly symmetrical and is a hexahedral structure, which has a good match with the GaN direct structure. Secondly, they have the largest bandgap width and the highest theoretical breakdown field strength, and have epitaxial growth conditions at lower temperatures. In addition, it is particularly important that ε-Ga2O3 has unique ferroelectric properties, which give ε-Ga2O3 broad application prospects in neuro-photoelectric devices.

[0016] It should be noted that the ε-Ga2O3 light-absorbing layer is designed to be oxygen-deficient and has oxygen vacancy defects, so that the oxygen vacancy defects can be used to achieve a persistent photoconductivity effect (PPC), further expanding the various sensing functions of gallium oxide materials in synaptic devices.

[0017] As a preferred technical solution of the present invention, the thickness of the gallium oxide light absorbing layer is 5-1000 nm, for example, 200 nm, 230 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 370 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc., but is not limited to the listed values. Other values not listed within the above numerical range are also applicable.

[0018] As a preferred technical solution of the present invention, the wavelength range of ultraviolet light to which the gallium oxide light-absorbing layer can respond is 200-400 nm, such as 230 nm, 254 nm, 265 nm, etc., but is not limited to the listed values. Other values not listed within the above numerical range are also applicable.

[0019] As a preferred technical solution of the present invention, the material for preparing the patterned electrode includes any one of Ti, Cr, Ag, Pt, Au, Al, Ni, Cu or ITO, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of Ti and Au metal superposition, a combination of Cr and Au metal superposition, a combination of Ti and Pt metal superposition, etc.

[0020] As a preferred technical solution of the present invention, the patterned electrode includes any one of periodic square electrodes, periodic circular electrodes or periodic interdigitated electrodes, or a combination of at least two of them.

[0021] As a preferred technical solution of the present invention, the diameter of the periodic square electrode is 1-1000μm, for example, 1μm, 10μm, 30μm, 50μm, 70μm, 100μm, 300μm, 500μm, 800μm or 1000μm, etc., but is not limited to the listed values. Other unlisted values within the above numerical range are also applicable.

[0022] Preferably, the side length of the periodic circular electrode is 1-1000μm, for example, 1μm, 10μm, 30μm, 50μm, 70μm, 100μm, 300μm, 500μm, 800μm or 1000μm, etc., but is not limited to the listed values. Other values not listed within the above numerical range are also applicable.

[0023] Preferably, the interdigitated electrode has an interdigitated width of 1-3000 μm, such as 1 μm, 10 μm, 30 μm, 50 μm, 70 μm, 100 μm, 300 μm, 500 μm, 800 μm, 1000 μm, 1500 μm, 2000 μm, 2500 μm or 3000 μm, etc., and a spacing of 1-3000 μm, such as 1 μm, 10 μm, 50 μm, 100 μm, 300 μm, 500 μm, 700 μm. , 1000μm, 1300μm, 1500μm, 2000μm, 2500μm, 2800μm or 3000μm, etc., the number of finger pairs is 3-300 pairs, for example, 3 pairs, 5 pairs, 10 pairs, 30 pairs, 50 pairs, 80 pairs, 100 pairs, 130 pairs, 150 pairs, 180 pairs, 200 pairs, 230 pairs, 250 pairs, 280 pairs or 300 pairs, etc., but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

[0024] A second object of the present invention is to provide a method for preparing the gallium oxide ultraviolet synapse device described in the first object, the method comprising the following steps:

[0025] A substrate layer is prepared, a gallium oxide light absorbing layer is deposited on the substrate layer, and a patterned electrode is prepared on the surface of the gallium oxide light absorbing layer; wherein the deposition includes any one of metal organic chemical vapor deposition, magnetron sputtering or atomic layer deposition.

[0026] As a preferred technical solution of the present invention, the oxygen flow rate used in the growth process of the gallium oxide light absorbing layer is in the range of 170-350sccm, for example, 170sccm, 200sccm, 230sccm, 250sccm, 280sccm, 300sccm, 310sccm or 350sccm. During the growth process of the gallium oxide light absorbing layer, the present invention uses an oxygen flow rate lower than the standard oxygen flow rate of 440sccm to increase the oxygen vacancy defects in the ε-Ga2O3 light absorbing layer.

[0027] Compared with the existing technical solutions, the present invention has at least the following beneficial effects:

[0028] (1) The gallium oxide ultraviolet synaptic device of the present invention is extremely sensitive to ultraviolet light and can successfully simulate the various properties of biological synapses, including persistent photoconductivity (PPC), double-pulse facilitation (PPF), and cognitive behavior of the transition from short-term memory (STM) to long-term memory (LTM). Moreover, the gallium oxide light-absorbing layer has ferroelectric properties, which can realize the integration of ultraviolet light sensitivity and ferroelectric properties, which will be of great significance for further expanding the performance of neural synapses.

[0029] (2) The gallium oxide ultraviolet synaptic device described in the present invention has the advantages of simple preparation, high sensitivity, low energy consumption, and good stability, and is very suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of the gallium oxide ultraviolet synapse device according to Example 1 of the present invention;

[0031] In the figure, 101 is a substrate layer; 102 is a gallium oxide light absorbing layer; 103 is a patterned electrode;

[0032] Figure 2 is the PPC curve of the gallium oxide ultraviolet synapse device described in Example 1 of the present invention;

[0033] Figure 3 is the PPF curve of the gallium oxide ultraviolet synapse device described in Example 1 of the present invention;

[0034] Figure 4 is a transition curve from STM to LTM caused by the gallium oxide ultraviolet synaptic device described in Example 1 of the present invention under different light exposure durations;

[0035] Figure 5 is a transition curve from STM to LTM caused by the gallium oxide ultraviolet synaptic device described in Example 1 of the present invention under different light intensities;

[0036] Figure 6is the learning curve of the gallium oxide ultraviolet synapse device described in Example 1 of the present invention;

[0037] Figure 7 This is the hysteresis loop of the gallium oxide ultraviolet synapse device described in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0039] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0040] Example 1

[0041] This embodiment provides a gallium oxide ultraviolet synaptic device, such as Figure 1 As shown, the gallium oxide ultraviolet synapse device described in this embodiment includes:

[0042] Substrate layer 101.

[0043] The gallium oxide light absorbing layer 102 is disposed on the surface of the substrate layer 101 and is used to generate photogenerated carriers under the stimulation of an ultraviolet light signal.

[0044] The patterned electrode 103 is disposed on the surface of the gallium oxide light absorbing layer 102 and is used to collect the photogenerated carriers and output electrical signals.

[0045] This embodiment provides a method for preparing a gallium oxide ultraviolet synaptic device, the method comprising the following steps:

[0046] (1) Prepare the sapphire substrate layer and clean it with alcohol, deionized water, and acetone in sequence.

[0047] (2) Preparation of gallium oxide light absorbing layer: Using MOCVD equipment to further grow ~300nm ε-Ga2O3 light absorbing layer on the sapphire substrate layer described in step (1), the TMGa flow rate is 495sccm, the O2 flow rate is 350sccm; the pressure is 20kPa; the deposition temperature is 500℃; and the deposition time is 35min.

[0048] (3) Preparing a patterned electrode: On the surface of the gallium oxide light-absorbing layer in step (2), a Ag metal electrode is prepared. The electrode is a periodic interdigitated electrode with an interdigit width of 100 μm, a spacing of 50 μm, and four pairs of interdigits.

[0049] Using a semiconductor parameter measurement instrument and probe station, a 254nm LED light source was used as the experimental light source. The power of the light source was set to 0.63mW, the reading voltage was set to 5V, and the pulse interval was set to 10s. The PPC curve was measured. The power of the light source was set to 0.63mW, the reading voltage was set to 5V, the duration of a single light pulse was set to 2s, and the interval between two light pulses was set to 1s. The PPF curve was measured. The laser power was set to 0.63mW, the reading voltage was set to 5V, the duration of a single light pulse was set to 2s, and the interval between two light pulses was set to 2s. Initial stimulation was performed with 30 consecutive light pulses to measure the learning curve. The voltage range was set to -10V to 10V, and the number of test points was set to 101. The hysteresis loop characteristics of the device were measured using a Radiant ferroelectric voltage and probe station.

[0050] The PPC curve of the gallium oxide ultraviolet synaptic device described in Example 1 is as follows: Figure 2 As shown in the figure, it can be seen that when the sample is irradiated with a 254nm light source, the conductivity of the sample increases significantly, and a charge capture process occurs. After the illumination ends, the conductivity decreases, but it cannot immediately return to the initial value. The sample has a significant PPC effect. After fitting with a stretched exponential function, it is found that its relaxation time is 17.2s, which can be used to construct biological synaptic devices.

[0051] The PPF curve of the gallium oxide ultraviolet synaptic device described in Example 1 is as follows: Figure 3 As shown in the figure, it can be seen that after the sample is irradiated with continuous light pulses with a duration of 2s and an interval of 1s, the second current peak is significantly higher than the first peak, resulting in a PPF phenomenon. The ratio of A2 / A1 is 1.35. The synaptic response is significantly enhanced after two stimulations, indicating short-range plasticity.

[0052] The transition curves of the gallium oxide ultraviolet synaptic device in Example 1 from short-term memory to long-term memory under different illumination durations are as follows: Figure 4 As shown in the figure, it can be clearly seen that when the illumination pulse duration increases from 2s to 50s, the corresponding postsynaptic current increases from 0.14μA to 0.38μA. In addition to the gain effect of the illumination pulse duration on the postsynaptic current, the increase in light intensity will also cause the increase in the postsynaptic current of the device. The transition curve of the gallium oxide ultraviolet synaptic device in Example 1 from short-term memory to long-term memory under different light intensities is shown in the figure. Figure 5 As shown in the figure, it is obvious that when the light intensity is from 0.6mw / cm 2 Increased to 2.3mw / cm 2 The corresponding postsynaptic current increased from 0.14 μA to 0.49 μA. The above two cases are consistent with the performance of biological synapses. After the light stimulation conditions change, the device has achieved a transition from STM to LTM.

[0053] The learning curve of the gallium oxide ultraviolet synaptic device described in Example 1 is as follows: Figure 6 As shown in the figure, it can be seen that the device has the ability to learn. In the first learning process, under 30 consecutive pulse stimulations, the excitatory postsynaptic current increased significantly. After that, after a period of forgetting, during the second learning process, only 7 consecutive light pulses were used to make the excitatory synaptic current reach the peak current that could only be reached by 23 pulses in the first time. This phenomenon is similar to the learning-forgetting-learning process of the human brain, further verifying that our device has the learning ability of biological synapses.

[0054] The hysteresis loop of the gallium oxide ultraviolet synaptic device described in Example 1 is as follows: Figure 7 As shown in the figure, as the external electric field strength increases, the polarization strength first increases. When the electric field is reversed, the polarization strength also reverses, forming a closed loop. When a voltage of 10 volts is applied, the residual intensity is ~0.3μC / cm 2 , the coercive field strength is ~250kV / cm, so the ε-Ga2O3 in Example 1 has obvious ferroelectric properties. The successful development of this material integrating ferroelectric properties with ultraviolet photosensitivity will be of great significance for further expanding the performance of neural synapses.

[0055] In summary, the gallium oxide ultraviolet synaptic device described in the present invention is extremely sensitive to ultraviolet light and has successfully simulated various properties of biological synapses, including persistent photoconductivity (PPC), double-pulse facilitation (PPF), and cognitive behavior of the transition from short-term memory (STM) to long-term memory (LTM). Moreover, the gallium oxide light-absorbing layer has ferroelectric properties, which can achieve the integration of ultraviolet photosensitivity and ferroelectric properties, which will be of great significance for further expanding the performance of neural synapses. It also has the advantages of simple preparation, high sensitivity, low energy consumption, and good stability, making it very suitable for industrial production.

[0056] While the present invention is described through the above-described embodiments to illustrate the detailed structural features of the present invention, the present invention is not limited to these detailed structural features, nor does it necessarily rely on these detailed structural features for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

[0057] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0058] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0059] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A gallium oxide ultraviolet synaptic device, characterized in that: include: substrate layer; A gallium oxide light-absorbing layer is provided on the surface of the substrate layer and is used to generate photogenerated carriers under the stimulation of an ultraviolet light signal; moreover, the gallium oxide light-absorbing layer has ferroelectric properties, realizing the integration of ultraviolet light-sensitive properties and ferroelectric properties; A patterned electrode is arranged on the surface of the gallium oxide light absorbing layer and is used for collecting the photogenerated carriers and outputting electrical signals.

2. The gallium oxide ultraviolet synapse device according to claim 1, characterized in that: The substrate layer is made of a material selected from any one of silicon, silicon carbide, sapphire or gallium nitride.

3. The gallium oxide ultraviolet synapse device according to claim 1, characterized in that: The gallium oxide light-absorbing layer is an ε-Ga2O3 light-absorbing layer and has oxygen vacancy defects.

4. The gallium oxide ultraviolet synapse device according to claim 1, characterized in that: The thickness of the gallium oxide light-absorbing layer is 5-1000 nm.

5. The gallium oxide ultraviolet synapse device according to claim 1, characterized in that: The wavelength range of ultraviolet light to which the gallium oxide light-absorbing layer can respond is 200-400 nm.

6. The gallium oxide ultraviolet synapse device according to claim 1, characterized in that: The material for preparing the patterned electrode includes any one of Ag, Pt, Au, Al, Ni, Cu or ITO, or a combination of at least two of them.

7. The gallium oxide ultraviolet synapse device according to claim 1, characterized in that: The patterned electrodes include any one of periodic square electrodes, periodic circular electrodes, and periodic interdigitated electrodes, or a combination of at least two of them.

8. The gallium oxide ultraviolet synapse device according to claim 7, characterized in that: The diameter of the periodic square electrode is 1-1000 μm; And / or, the side length of the periodic circular electrode is 1-1000 μm; And / or, the interdigital width of the periodic interdigital electrode is 1-3000 μm, the spacing is 1-3000 μm, and the number of interdigital pairs is 3-300 pairs.

9. A method for preparing the gallium oxide ultraviolet synapse device according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: A substrate layer is prepared, a gallium oxide light absorbing layer is deposited on the surface of the substrate, and a patterned electrode is prepared on the surface of the gallium oxide light absorbing layer; wherein the deposition includes any one of metal organic chemical vapor deposition, magnetron sputtering or atomic layer deposition.

10. The preparation method according to claim 9, characterized in that The oxygen flow rate used during the growth of the gallium oxide light absorbing layer is in the range of 170-350 sccm.

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