Heterostructure ultraviolet phototransistor and preparation method and application thereof

Abstract

This invention relates to a heterostructure ultraviolet photoelectric synaptic transistor, its fabrication method, and its applications. The transistor's structure, from top to bottom, consists of a glass substrate, a gate dielectric layer, an active layer, and a source-drain electrode layer. It also includes a gate electrode disposed within the gate dielectric layer and in contact with the glass substrate. The active layer comprises an indium tin zinc oxide layer and a magnesium zinc oxide layer stacked sequentially. This invention leverages the superior electron mobility and channel stability of indium tin zinc oxide amorphous semiconductors and the intrinsic absorption characteristics of magnesium zinc oxide in the ultraviolet band to achieve a more sensitive transient response and precise synaptic weight update function. This has significant application value for simulating biological visual perception and the development of neuromorphic electronics.

Description

Technical Field

[0001] This invention relates to the field of neuromorphic computing technology, specifically to a heterostructure ultraviolet photosynaptic transistor, its fabrication method, and its applications. Background Technology

[0002] With the continuous expansion of big data processing and artificial intelligence applications, the demand for real-time processing of massive amounts of unstructured data has increased significantly. However, the traditional von Neumann computing architecture, based on the design principle of physical separation between storage and computing units, requires frequent data transfer between the processor and memory via a bus. This inherent "von Neumann bottleneck" leads to limited data transmission bandwidth and excessive power consumption, commonly known as the "memory wall" and "power wall" effects. When handling complex visual recognition and pattern classification tasks, the above architecture struggles to simultaneously meet the technical specifications of high computing power, low latency, and low energy consumption. In contrast, the biological brain exhibits superior energy efficiency and parallel processing capabilities, the core of which lies in the neural synapse mechanism: synapses are not only the hubs for signal transmission between neurons but also the common carriers of memory storage and logical operations, thus achieving architectural-level integration of storage and computing. Especially in biological visual perception systems, the retina directly converts external light signals into electrical impulse signals and completes feature extraction and integration of information in the visual cortex through the dynamic adjustment of synaptic weights. This integrated sensing, storage, and computing mechanism enables biological vision systems to efficiently process dynamic images and weak transient light signals with extremely low power consumption. Based on this, developing neuromorphic photoelectric synaptic transistors that can simulate biological visual perception and possess photoelectric signal conversion and synaptic plasticity modulation capabilities has become a key technological path to overcome the bottlenecks of existing computing architectures.

[0003] Wide-bandgap semiconductor materials (such as magnesium zinc oxide and gallium oxide) can effectively simulate the dynamic adjustment and memory behavior of biological synaptic weights due to their intrinsic absorption characteristics in the ultraviolet band and extremely long continuous photoconductivity, thereby constructing artificial photosynapses sensitive to the ultraviolet spectrum. These ultraviolet photosynaptic devices, integrating sensing, storage, and computing, show potential to replace traditional discrete sensing architectures in specific scenarios such as non-line-of-sight secure optical communication, high-voltage power grid corona discharge detection, industrial arc warning, and biomedical sterilization monitoring. However, existing devices based on metal oxide channels are often limited by carrier transport mechanisms. Their low electron mobility and slow defect state capture / release processes, while beneficial for simulating long-term memory, sacrifice the device's dynamic response bandwidth. This physical limitation makes it difficult for the device to capture short-duration weak light pulses, resulting in the loss of high-frequency information, and thus limiting the real-time reasoning and decision-making capabilities of neuromorphic vision systems in complex dynamic environments.

[0004] Chinese invention patent CN120051099A discloses an ultraviolet photoelectric synapse device based on a ZnO / GO heterostructure. This structure utilizes the abundant oxygen-containing functional groups in graphene oxide and the low defect density of ZnO-based materials to effectively reduce dark current and noise current, enabling weak light recognition and enhancing continuous photoconductivity. However, the device's operating frequency is still around 0.5Hz, and its response to ultraviolet light is relatively limited, making it unable to recognize and acquire high-frequency information. Summary of the Invention

[0005] The purpose of this invention is to provide a heterostructure ultraviolet photosynthetic transistor, its fabrication method, and its application.

[0006] The technical solution adopted in this invention is: A heterostructure ultraviolet phototransistor comprises a glass substrate, a gate dielectric layer, an active layer, and a source-drain electrode layer stacked sequentially, and a gate electrode disposed inside the gate dielectric layer and in contact with the glass substrate; the active layer comprises an indium tin zinc oxide layer and a magnesium zinc oxide layer stacked sequentially.

[0007] Preferably, the thickness of the indium tin zinc oxide layer is 10 nm to 40 nm.

[0008] Preferably, the thickness of the magnesium zinc oxide layer is 10 nm to 40 nm.

[0009] Preferably, the gate dielectric layer is composed of one of aluminum oxide, silicon dioxide, zirconium oxide, and hafnium oxide.

[0010] Preferably, the thickness of the gate dielectric layer is 100nm~300nm.

[0011] Preferably, the gate electrode is composed of Al.

[0012] Preferably, the thickness of the gate electrode is 80nm~120nm.

[0013] Preferably, the source electrode in the source-drain electrode layer is one of ITO electrode, Al electrode, and Au electrode; the thickness of the source electrode layer is 50nm~200nm.

[0014] Preferably, the drain electrode in the source-drain electrode layer is one of ITO electrode, Al electrode, and Au electrode; the thickness of the drain electrode layer is 50nm~200nm.

[0015] A method for fabricating a heterostructure ultraviolet photosynthetic transistor as described above includes the following steps: (1) A gate electrode and a gate dielectric layer are sequentially deposited on one side of a glass substrate; (2) An indium tin zinc oxide layer and a magnesium zinc oxide layer are sequentially deposited on the surface of the gate dielectric layer to form an active layer; (3) Deposit source and drain electrodes on the surface of the active layer to form a source and drain electrode layer.

[0016] Furthermore: Indium tin zinc oxide (ITI) layers were deposited using multi-target co-sputtering. The process parameters for multi-target co-sputtering were as follows: the chamber pressure was set to 0.4–0.6 Pa during sputtering; the gas atmosphere used was oxygen and argon, with flow rates set to 3–8 sccm and 8–12 sccm, respectively; the sputtering temperature was set to 25 °C; the targets used for sputtering ITI were polycrystalline indium tin oxide (ITI) and polycrystalline zinc oxide (ZNO); the sputtering time was 90 s; the sputtering power of the polycrystalline ITI target was set to 100 W; and the sputtering power of the polycrystalline ZNO target was set to 130 W.

[0017] Magnesium zinc oxide was deposited on the surface of an indium tin zinc oxide layer by multi-target co-sputtering. The process parameters for multi-target co-sputtering were as follows: the chamber pressure was set to 0.4~0.6 Pa during sputtering, the gas atmosphere used was oxygen and argon, the flow rates were set to 3~8 sccm and 8~12 sccm respectively, the sputtering temperature was set to 25℃, the target materials used for sputtering magnesium zinc oxide were polycrystalline magnesium oxide and polycrystalline zinc oxide, the sputtering time was 90 s, the sputtering power of the polycrystalline magnesium oxide target was set to 70 W, and the sputtering power of the polycrystalline zinc oxide target was set to 130 W.

[0018] An array substrate comprising the aforementioned heterostructure ultraviolet photosynthetic transistor.

[0019] A neuromorphic computer comprising the aforementioned heterostructured ultraviolet photosynaptic transistor.

[0020] The ultraviolet photosynaptic transistor of this invention innovatively employs an indium tin zinc oxide / magnesium zinc oxide heterostructure as the active layer. By utilizing the conduction band difference within the heterostructure, this ultraviolet photosynaptic transistor exhibits advantages such as fast response speed and stable performance, which can improve the overall decision-making speed of neuromorphic computing systems and is suitable for large-scale applications in the field of neuromorphic computing.

[0021] Specifically: (1) The ultraviolet phototransistor of the present invention uses an indium tin zinc oxide / magnesium zinc oxide heterostructure as the active layer. Indium tin zinc oxide amorphous semiconductor has excellent electron mobility and channel stability, but its capture efficiency for photogenerated carriers is low, making it difficult to independently achieve efficient photosynaptic plasticity modulation. Magnesium zinc oxide, as a ternary oxide semiconductor with a wide bandgap, exhibits excellent intrinsic absorption characteristics in the ultraviolet band and can generate high-density photogenerated electron-hole pairs. However, the magnesium zinc oxide material itself is limited by its low electron mobility, resulting in poor transport efficiency of photogenerated carriers and limiting the dynamic response speed of the device. Therefore, by constructing an indium tin zinc oxide / magnesium zinc oxide heterostructure, a unique Type-II heterojunction band arrangement is formed. This mechanism enables the efficient injection of photogenerated carriers from the magnesium zinc oxide layer into the high-mobility indium tin zinc oxide transport channel. This not only achieves rapid separation of photogenerated electrons and holes, suppressing recombination losses, but also utilizes the charge trapping / release mechanism at the interface to rapidly adjust the channel conductivity. This endows the photoelectric synaptic device with a more sensitive transient response and precise synaptic weight update capability. Finally, due to the high film quality and suitable oxygen vacancy concentration of the active layer, this heterostructure ultraviolet photoelectric synaptic transistor possesses superior electrical characteristics that are difficult to find in other ultraviolet photoelectric synaptic transistors, thus demonstrating broader application prospects.

[0022] (2) This invention utilizes the unique continuous photoconductivity of oxide semiconductors to enable the heterostructure ultraviolet photosynaptic transistor to possess photoelectric memory characteristics, successfully simulating various biological synaptic functions such as double-pulse heterogeneity, excitatory postsynaptic current, short-term enhancement to long-term enhancement, and pulse frequency-dependent plasticity. This provides a stable development scheme for simulating biological visual perception functions and the development of neuromorphic electronics. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the heterostructure ultraviolet photosynthetic transistor of the present invention.

[0024] Explanation of reference numerals in the attached figures: 10, glass substrate; 20, gate electrode; 30, gate dielectric layer; 40, indium tin zinc oxide layer; 50, magnesium zinc oxide layer; 60, source electrode; 70, drain electrode.

[0025] Figure 2 This diagram illustrates the energy levels and carrier transfer mechanism before and after contact in a heterostructure.

[0026] Figure 3 The transfer characteristic curve of the heterostructure ultraviolet photosynthetic transistor in the embodiment is shown.

[0027] Figure 4The curves show the transfer characteristics of the ultraviolet photosynaptic transistor in Comparative Example 1.

[0028] Figure 5 The diagram shows the change in excitatory postsynaptic current of the heterostructure ultraviolet photosynaptic transistor in response to a single ultraviolet pulse signal with a wavelength of 365nm and a pulse duration of 250ms.

[0029] Figure 6 The graph shows the change in excitatory postsynaptic current of the ultraviolet photosynaptic transistor in Comparative Example 1 in response to a single ultraviolet pulse signal with a wavelength of 365nm and a pulse duration of 250ms.

[0030] Figure 7 The diagram shows the postsynaptic current change of the heterostructure ultraviolet photosynaptic transistor in the embodiment to a double-pulse ultraviolet signal with a wavelength of 365nm and a pulse duration of 50ms.

[0031] Figure 8 This example simulates the pulse frequency-dependent plasticity of a heterostructured ultraviolet photosynaptic transistor. Detailed Implementation

[0032] The invention will be explained and illustrated below with examples.

[0033] Example: A heterostructured ultraviolet photosynthetic transistor (structural schematic shown in figure) Figure 1 As shown, it consists of a glass substrate 10, a gate electrode 20, a gate dielectric layer 30, an indium tin zinc oxide layer 40, a magnesium zinc oxide layer 50, a source electrode layer 60, and a drain electrode layer 70; wherein the gate electrode layer 20 is disposed inside the gate dielectric layer 30 and is in contact with the glass substrate 10.

[0034] The fabrication method of an indium tin zinc oxide / magnesium zinc oxide heterostructure ultraviolet photosynaptic transistor is as follows: 1) Substrate pretreatment: The Al / alumina substrate with a thickness of 300nm was placed in deionized water and isopropanol, and ultrasonically cleaned for 20min each. Then, it was dried with nitrogen to obtain the pretreated Al / alumina substrate.

[0035] 2) The pre-treated substrate is fixed in a patterned metal mask, and an indium tin zinc oxide with a thickness of 15 nm is deposited by multi-target co-sputtering. The process parameters of multi-target co-sputtering are as follows: the chamber pressure is set to 0.5 Pa during sputtering, the gas atmosphere used is oxygen and argon, the flow rates are set to 10 sccm and 3 sccm respectively, the sputtering temperature is set to 25℃, the target materials used for sputtering indium tin oxide are polycrystalline indium tin oxide and polycrystalline zinc oxide, the sputtering time is 90 s, the sputtering power of the polycrystalline indium tin oxide target is set to 100 W, and the sputtering power of the polycrystalline zinc oxide target is set to 130 W. 3) The substrate sputtered with indium tin zinc oxide is fixed in a patterned metal mask, and magnesium zinc oxide with a thickness of 15 nm is deposited by multi-target co-sputtering. The process parameters of multi-target co-sputtering are as follows: the chamber pressure is set to 0.5 Pa during sputtering, the gas atmosphere used is oxygen and argon, the flow rates are set to 6 sccm and 10 sccm respectively, the sputtering temperature is set to 25℃, the target materials used for sputtering magnesium zinc oxide are polycrystalline magnesium oxide and polycrystalline zinc oxide, the sputtering time is 90 s, the sputtering power of polycrystalline magnesium oxide target is set to 70 W, and the sputtering power of polycrystalline zinc oxide target is set to 130 W. 4) The substrate with the prepared heterostructure active layer is placed in a patterned metal mask and fixed. A polycrystalline indium tin oxide (ITO) thin film with a thickness of 80 nm is deposited on the surface of the active layer by magnetron sputtering using a polycrystalline ITO target as the source-drain electrode layer. The channel width and length between the source and drain electrodes are 300 μm and 100 μm, respectively. The magnetron sputtering process parameters are as follows: the cavity pressure is set to 0.5 Pa during sputtering, the gas atmosphere used is oxygen and argon, the flow rates are set to 3 sccm and 10 sccm, respectively, the sputtering temperature is set to 25 °C, the sputtering power of the polycrystalline ITO target is set to 70 W, and the sputtering time is set to 10 min. 5) Place the substrate with the prepared heterostructure active layer and source-drain electrode layer on a heating stage and anneal continuously at 360°C for 3 hours in an air atmosphere. The heterostructure ultraviolet phototransistor is thus obtained.

[0036] Figure 2 This diagram illustrates the energy levels and carrier transfer mechanism before and after the contact of the heterostructure. In this device, indium tin zinc oxide (IZO) and magnesium zinc oxide (MgZO) form a unique Type-II heterojunction band arrangement. Photogenerated carriers are generated using the intrinsic ultraviolet absorption properties of the MgZO thin film, with its higher conduction band position driving efficient electron injection into the IZO channel. Simultaneously, the deeper valence band position of the IZO film constitutes a hole-blocking barrier. This design achieves effective spatial separation of electrons and holes, significantly extending carrier lifetime and enhancing the grating effect, thus endowing the device with excellent synaptic plasticity.

[0037] Comparative example: An ultraviolet photosynaptic transistor based on indium tin zinc oxide is disclosed, which differs from the embodiment in that the heterojunction active layer is replaced with an indium tin zinc oxide monolayer structure with a thickness of 30 nm. During sputtering, the flow rates of oxygen and argon are set to 3 sccm and 10 sccm, respectively. Otherwise, it is completely identical to the heterostructure ultraviolet photosynaptic transistor of the embodiment.

[0038] Performance testing a) The electrical performance of the ultraviolet photosynaptic transistors of Examples 1 and Comparative Example 1 was tested using an Agilent B1500 semiconductor parameter analyzer. The resulting transfer characteristic curves are shown below. Figure 3 and Figure 4 As shown.

[0039] contrast Figure 3 and Figure 4 It can be seen that the heterostructure ultraviolet photosynthetic transistor in the embodiment has good switching characteristics, low subthreshold swing and high switching current ratio. Compared with the ultraviolet photosynthetic transistor in Comparative Example 1, it can be found that the threshold voltage has a certain degree of negative drift. This is because the introduction of the interface state of the heterostructure will increase the surface carrier density.

[0040] b) The response current of the heterostructure ultraviolet photosynaptic transistor in Example 1 and the ultraviolet photosynaptic transistor in Comparative Example 1 to a 365nm ultraviolet single-pulse signal was tested in air using an Agilent B1500 semiconductor parameter analyzer. The postsynaptic current changes were obtained as follows: Figure 5 and Figure 6 As shown.

[0041] contrast Figure 5 and Figure 6 It can be seen that when exposed to ultraviolet light with a wavelength of 365nm and an illumination time of 250ms, the maximum response current of the heterostructure ultraviolet photosynaptic transistor in the example is 91.75nA, and after a rapid decay of 1s, there is still a post-response current of about 20nA; while in Comparative Example 1, the maximum response current of the ultraviolet photosynaptic transistor is 36.58nA, and after a rapid decay of 1s, the value of the post-response current is about 10nA.

[0042] As can be seen from the postsynaptic current response curve of the ultraviolet single-pulse signal, the ultraviolet photoelectric synaptic transistor with a heterostructure composed of magnesium zinc oxide layer and indium tin zinc oxide layer has better photoresponse characteristics. At the same time, the built-in electric field formed by the band shift at the heterostructure interface suppresses the recombination of photogenerated carriers, thereby giving the photoelectric synaptic device a more sensitive transient response capability and more accurate photoelectric memory characteristics.

[0043] Figure 7 The image shows the excitatory postsynaptic current response curve of a heterostructure ultraviolet photosynaptic transistor to two ultraviolet light pulses with a wavelength of 365 nm and an illumination time of 50 ms, where the interval between pulses is 50 ms. The photopower factor (PPF) of this ultraviolet photosynaptic transistor is 168%, indicating that the device exhibits significant photoresponse and memory characteristics even under extremely short light pulses.

[0044] Figure 8This paper presents the excitatory postsynaptic current response curves of a heterostructure ultraviolet photosynaptic transistor to ten consecutive ultraviolet light pulses with a wavelength of 365 nm and an irradiation time of 50 ms. The response current value increases significantly with increasing pulse frequency, realizing the transition from short-term plasticity to long-term plasticity. This successfully simulates the frequency-dependent plasticity of neural synapses and provides important theoretical support for the construction of neuromorphic computing devices.

Claims

1. A heterostructure ultraviolet photosynthetic transistor, characterized in that, The structure of the transistor, from top to bottom, consists of a glass substrate, a gate dielectric layer, an active layer, and a source-drain electrode layer; it also includes a gate electrode disposed inside the gate dielectric layer and in contact with the glass substrate; the active layer comprises an indium tin zinc oxide layer and a magnesium zinc oxide layer stacked sequentially.

2. The heterostructure ultraviolet photosynthetic transistor according to claim 1, characterized in that, The thickness of the indium tin zinc oxide layer is 10 nm to 40 nm; the thickness of the magnesium zinc oxide layer is 10 nm to 40 nm.

3. The heterostructure ultraviolet photosynthetic transistor according to claim 1, characterized in that, The gate dielectric layer is composed of one of the following: aluminum oxide, silicon dioxide, zirconium oxide, and hafnium oxide.

4. The heterostructure ultraviolet photosynthetic transistor according to claim 1, characterized in that, The gate electrode is composed of Al; the thickness of the gate electrode is 80 nm to 120 nm.

5. The heterostructure ultraviolet photosynthetic transistor according to claim 1, characterized in that, The source electrode in the source-drain electrode layer is one of ITO electrode, Al electrode, and Au electrode; the thickness of the source electrode layer is 50nm~200nm.

6. The heterostructure ultraviolet photosynthetic transistor according to claim 1, characterized in that, The drain electrode in the source-drain electrode layer is one of ITO electrode, Al electrode, and Au electrode; the thickness of the drain electrode layer is 50nm~200nm.

7. A method for fabricating a heterostructure ultraviolet photosynthetic transistor as described in any one of claims 1 to 6, characterized in that, Includes the following steps: (1) A gate electrode and a gate dielectric layer are sequentially deposited on one side of a glass substrate; (2) An indium tin zinc oxide layer and a magnesium zinc oxide layer are sequentially deposited on the surface of the gate dielectric layer to form an active layer; (3) Deposit source and drain electrodes on the surface of the active layer to form a source and drain electrode layer.

8. The preparation method according to claim 7, characterized in that, Indium tin zinc oxide (ITI) layers were deposited using multi-target co-sputtering. The process parameters for multi-target co-sputtering were as follows: the chamber pressure was set to 0.4–0.6 Pa during sputtering; the gas atmosphere used was oxygen and argon, with flow rates set to 3–8 sccm and 8–12 sccm, respectively; the sputtering temperature was set to 25 °C; the targets used for sputtering ITI were polycrystalline indium tin oxide (ITI) and polycrystalline zinc oxide (ZNO); the sputtering time was 90 s; the sputtering power of the polycrystalline ITI target was set to 100 W; and the sputtering power of the polycrystalline ZNO target was set to 130 W.

9. The preparation method according to claim 7, characterized in that, Magnesium zinc oxide was deposited on the surface of an indium tin zinc oxide layer by multi-target co-sputtering. The process parameters for multi-target co-sputtering were as follows: the chamber pressure was set to 0.4~0.6 Pa during sputtering, the gas atmosphere used was oxygen and argon, the flow rates were set to 3~8 sccm and 8~12 sccm respectively, the sputtering temperature was set to 25℃, the target materials used for sputtering magnesium zinc oxide were polycrystalline magnesium oxide and polycrystalline zinc oxide, the sputtering time was 90 s, the sputtering power of the polycrystalline magnesium oxide target was set to 70 W, and the sputtering power of the polycrystalline zinc oxide target was set to 130 W.

10. The application of the heterostructure ultraviolet photosynaptic transistor of claim 1 in the fabrication of biomimetic sensing devices, neuromorphic memories, or brain-like computing chips.

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