A self-powered photoelectric detector based on Ta2nise5 / InSe heterojunction and a preparation method thereof

Abstract

This invention relates to the field of self-powered photodetector technology, and discloses a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction and its fabrication method. The photodetector includes a substrate on which a Ta2NiSe5 layer and an InSe layer are disposed, wherein the InSe layer is at least partially stacked on top of the Ta2NiSe5 layer, thereby forming an n-n type van der Waals heterojunction between the overlapping portion of the Ta2NiSe5 and InSe layers. Metal electrodes are respectively disposed on both sides of the van der Waals heterojunction, and the metal electrodes are used to realize the electrical connection between the van der Waals heterojunction and an external circuit. The work functions of Ta2NiSe5 and InSe were measured to be 4.87 eV and 4.78 eV, respectively. After they come into contact, their Fermi levels align, generating a built-in electric field at the interface pointing from InSe to Ta2NiSe5 with a potential difference of approximately 90 mV. This structure achieves high carrier mobility while realizing efficient absorption across a wide wavelength range from ultraviolet to near-infrared. The photodetector achieved an open-circuit voltage of 0.24 V and a short-circuit current of 1.35 nA, indicating that it has excellent self-powered photoelectric conversion capability.

Description

Technical Field

[0001] This invention relates to the field of self-powered photodetector technology, and in particular to a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction and its fabrication method. Background Technology

[0002] Photodetectors are core components of optoelectronic systems and are widely used in imaging, sensing, and communication. Traditional photodetectors are mostly based on bulk materials such as silicon and III-V compounds, which suffer from limited spectral response, slow response speed, and the need for external bias voltage. Two-dimensional materials, due to their unique electrical and optical properties, have become a new platform for constructing high-performance photodetectors, such as self-powered photodetectors based on van der Waals heterostructures of two-dimensional materials.

[0003] In the prior art, a photodetector based on an α-In2Se3 / Ta2NiSe5 heterojunction was designed in the paper "Two-dimensional (2D) a-In2Se3 / Ta2NiSe5 heterojunction photodetector with high sensitivity and fast response in a wide spectral range" (https: / / doi.org / 10.1016 / j.matdes.2023.111799). This photodetector has a photoresponsivity of 12 A / W and a detectivity of 3.7. 10 13 Jones photodetectors exhibit response times of 25 μs / 423 μs and a spectral width of 405 nm - 1550 nm. With the development of technologies such as the Internet of Things (IoT), wearable electronics, and environmental monitoring, the demand for high-efficiency, low-power photodetectors is increasing. However, existing two-dimensional heterojunction self-powered photodetectors suffer from narrow response bands, high dark current, limited response speed, and insufficient self-powering performance. Therefore, it is necessary to develop new two-dimensional material heterojunction photodetectors to improve the overall performance of existing two-dimensional heterojunction self-powered photodetectors. Summary of the Invention

[0004] This invention discloses a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction and its fabrication method, which can improve the overall performance of existing two-dimensional heterojunction self-powered photodetectors.

[0005] The first aspect of this invention discloses a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction, the photodetector comprising: A substrate having a Ta2NiSe5 layer and an InSe layer disposed thereon, wherein the InSe layer is at least partially stacked on top of the Ta2NiSe5 layer, thereby forming an n-type van der Waals heterojunction between the overlapping portion of the Ta2NiSe5 layer and the InSe layer; Metal electrodes are provided on both sides of the van der Waals heterojunction, and the metal electrodes are used to realize the electrical connection between the van der Waals heterojunction and the external circuit.

[0006] As an optional implementation, in the first aspect of the present invention, the thickness of the Ta2NiSe5 layer is 20-50 nm, the thickness of the InSe layer is 20-50 nm, and the area of ​​the van der Waals heterojunction is 240-250 square micrometers.

[0007] As an optional implementation, in the first aspect of the present invention, the thickness of the Ta2NiSe5 layer is 36 nm, the thickness of the InSe layer is 23 nm, and the area of ​​the van der Waals heterojunction is 245.5 square micrometers.

[0008] As an optional implementation, in the first aspect of the present invention, the metal electrode is made of gold, and the substrate includes a single-crystal silicon layer and a silicon oxide layer, wherein the silicon oxide layer is provided with the Ta2NiSe5 layer and the InSe layer.

[0009] A second aspect of this invention discloses a method for fabricating a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction, the method comprising: Ta2NiSe5 and InSe thin films were obtained from Ta2NiSe5 and InSe crystals; A substrate is provided, an electrode region is defined on the substrate by photolithography, and a first metal electrode and a second metal electrode are deposited in the electrode region; The Ta2NiSe5 sheet is transferred to a predetermined position on the substrate so that it contacts the corresponding first metal electrode to obtain a Ta2NiSe5 layer. The InSe sheet is at least partially stacked on the Ta2NiSe5 layer and brought into contact with the corresponding second metal electrode to obtain the InSe layer.

[0010] As an optional implementation, in a second aspect of the invention, providing a substrate, defining electrode regions on the substrate using a photolithography process, and depositing a first metal electrode and a second metal electrode in the electrode regions, includes: A sacrificial substrate is provided, and a first trench and a second trench are etched on the front side of the sacrificial substrate by photolithography. Metal is filled in the first trench and the second trench to obtain a first metal electrode and a second metal electrode. A silicon oxide layer and a single-crystal silicon layer are sequentially deposited on the front side of the sacrificial substrate; A first connection hole and a second connection hole are etched in the silicon oxide layer and the single crystal silicon layer. The first connection hole and the second connection hole penetrate the silicon oxide layer and the single crystal silicon layer and correspond to the first metal electrode and the second metal electrode, respectively. Metal is filled into the first connecting hole and the second connecting hole to obtain a first metal connecting hole and a second metal connecting hole. One end of the first metal connecting hole is in contact with the first metal electrode, and the other end of the first metal connecting hole is exposed on the front side of the single crystal silicon layer. One end of the second metal connecting hole is in contact with the second metal electrode, and the other end of the second metal connecting hole is exposed on the front side of the single crystal silicon layer. A circuit chip is bonded to the front side of the single-crystal silicon layer so that the first metal connection hole and the second metal connection hole are electrically connected to the corresponding positions on the circuit chip. The sacrificial substrate is etched away along the reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode.

[0011] As an optional implementation, in a second aspect of the invention, providing a sacrificial substrate, wherein a first trench and a second trench are etched on the front side of the sacrificial substrate by a photolithography process, includes: A sacrificial substrate is provided, and a first wide trench region and a second wide trench region are defined on the front side of the sacrificial substrate using a first mask, and a first wide trench and a second wide trench are etched in the first wide trench region and the second wide trench region. A carbon-based material layer is deposited on the front side of the sacrificial substrate, and then the carbon-based material layer is ground flat to fill the first wide trench and the second wide trench with the carbon-based material. An epitaxial layer of thickness d is epitaxially grown on the front side of the sacrificial substrate. The material of the epitaxial layer is the same as that of the sacrificial substrate layer, and d is greater than the thickness of the Ta2NiSe5 sheet and the InSe sheet. A first narrow trench region and a second narrow trench region are defined on the front side of the sacrificial substrate using a second mask, wherein the first narrow trench region and the second narrow trench region are located above the first wide trench and the second wide trench, respectively, and the width of the first narrow trench region and the second narrow trench region is smaller than the width of the first wide trench region and the second wide trench region. The first narrow trench region and the second narrow trench region are etched downwards to etch the first narrow trench and the second narrow trench in the epitaxial layer, and the carbon-based material in the first wide trench and the second wide trench is etched away to obtain a first trench that connects the first narrow trench and the first wide trench, and a second trench that connects the second narrow trench and the second wide trench.

[0012] As an optional implementation, in a second aspect of the invention, metal is filled into the first trench and the second trench to obtain a first metal electrode and a second metal electrode, comprising: A first metal electrode is obtained by filling the first trench with metal, wherein the first metal electrode includes a first wide metal electrode located in the first wide trench and a first narrow metal electrode located in the first narrow trench, and the first wide metal electrode and the first narrow metal electrode are fixedly connected. The second metal electrode is obtained by filling the second trench with metal, wherein the second metal electrode includes a second wide metal electrode located in the second wide trench and a second narrow metal electrode located in the second narrow trench, and the second wide metal electrode and the second narrow metal electrode are fixedly connected.

[0013] As an optional implementation, in a second aspect of the invention, etching away the sacrificial substrate along its reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode includes: The sacrificial substrate is etched away along its reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode, wherein: There is a first gap of thickness d between the first wide metal electrode and the silicon oxide layer. The first gap is used to contact the Ta2NiSe5 sheet so that a portion of the Ta2NiSe5 sheet is accommodated within the first gap. A second gap of thickness d exists between the second wide metal electrode and the silicon oxide layer. The second gap is used to contact the InSe sheet so that a portion of the InSe sheet is accommodated within the first gap.

[0014] The third aspect of the present invention discloses a photoelectric sensor, wherein the photoelectric sensor is provided with a plurality of self-powered photodetectors based on Ta2NiSe5 / InSe heterojunction as disclosed in the first aspect of the present invention, arranged according to a preset rule, or a plurality of electro-photodetectors prepared using the self-powered photodetector preparation method based on Ta2NiSe5 / InSe heterojunction disclosed in the second aspect of the present invention, arranged according to a preset rule.

[0015] Compared with the prior art, the present invention has the following beneficial effects: For two-dimensional heterojunction photodetectors, existing technologies mostly employ pn junctions or np structures. These structures have slow response speeds (millisecond-level) and often require external bias voltages. Furthermore, commonly used two-dimensional heterojunctions in existing technologies (such as MoS2 / WSe2, InSe / MoS2, etc.) are mostly type-II band-aligned structures, with their response bands mainly concentrated in the visible light range and weak near-infrared response. This invention innovatively uses Ta2NiSe5 with a bandgap of only 0.36 eV as a narrow bandgap component to form an n-type heterojunction with InSe, resulting in a type-I band-aligned structure.

[0016] The working principle of this photodetector is based on the strong built-in electric field formed at the heterojunction interface and band engineering. Characterized by Kelvin probe force microscopy (KPFM), the work functions of Ta2NiSe5 and InSe were measured to be 4.87 eV and 4.78 eV, respectively. After they come into contact, the Fermi levels align, generating a built-in electric field at the interface with a potential difference of about 90 mV, pointing from InSe to Ta2NiSe5. This structure achieves high efficiency absorption across a wide band from ultraviolet to near-infrared while maintaining high carrier mobility.

[0017] Under illumination, Ta₂NiSe₅ and InSe simultaneously absorb photons and generate electron-hole pairs. Under the influence of the built-in electric field, photogenerated electrons drift towards the InSe side, while holes migrate towards the Ta₂NiSe₅ side, thus achieving efficient spatial separation of charge carriers. Under zero bias, the separated charge carriers accumulate between the electrodes, forming a significant photovoltaic effect. Experimental measurements yielded an open-circuit voltage of 0.24 V and a short-circuit current of 1.35 nA, indicating that this photodetector possesses excellent self-powered photoelectric conversion capability. Therefore, the two-dimensional heterojunction photodetector disclosed in this invention improves the overall performance of existing two-dimensional heterojunction self-powered photodetectors. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a structural diagram of a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction; Figure 2 This is a microscope image of a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction; Figure 3This is an atomic force microscope image of a Ta2NiSe5 / InSe heterostructure; Figure 4 It is a Raman diagram of the Ta2NiSe5 / InSe heterojunction; Figure 5 This is a linear IV characteristic curve of the Ta2NiSe5 / InSe heterojunction; Figure 6 This is the broadband response spectrum of the Ta2NiSe5 / InSe heterojunction; Figure 7 It is a graph of photocurrent as a function of laser power density; Figure 8 This is a graph showing the responsivity and detectivity of the Ta2NiSe5 / InSe heterojunction; Figure 9 This is a schematic diagram of the external quantum efficiency of the Ta2NiSe5 / InSe heterojunction and the on / off ratio of the photodetector; Figure 10 This is a schematic diagram of the open-circuit voltage Voc and short-circuit current Isc of the Ta2NiSe5 / InSe heterojunction under different optical power densities; Figure 11 This is the response time diagram of the Ta2NiSe5 / InSe heterojunction; Figure 12 This is a flowchart of a method for fabricating a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction; Figure 13 This is a schematic diagram of the first and second trenches etched using photolithography. Figure 14 This is a schematic diagram showing how metal is filled into the first and second trenches to obtain the first and second metal electrodes. Figure 15 This is a schematic diagram showing the sequential deposition of a silicon oxide layer and a single-crystal silicon layer on the front side of a sacrificial substrate. Figure 16 This is a schematic diagram showing the etching of the first and second connecting holes in the silicon oxide layer and the single-crystal silicon layer; Figure 17 This is a schematic diagram of the first metal connection hole and the second metal connection hole; Figure 18 This is a schematic diagram of bonding a circuit chip to the front side of a single-crystal silicon layer; Figure 19 This is a schematic diagram showing the process of etching away the sacrificial substrate along the reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode. Figure 20 This is a schematic diagram of depositing a carbon-based material layer on the front side of a sacrificial substrate; Figure 21This is a schematic diagram of an epitaxial layer with a thickness of d being epitaxially grown on the front side of a sacrificial substrate; Figure 22 This is a schematic diagram showing a first groove that connects a first narrow groove and a first wide groove, and a second groove that connects a second narrow groove and a second wide groove; Figure 23 This is a schematic diagram of another type of first and second metal electrode. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product, or end that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or ends.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] This invention discloses a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction and its fabrication method, which is used to improve the overall performance of existing two-dimensional heterojunction self-powered photodetectors. Detailed descriptions follow.

[0024] Example 1 This invention discloses a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction, such as... Figure 1 As shown, the photodetector includes: A substrate having a Ta2NiSe5 layer and an InSe layer disposed thereon, wherein the InSe layer is at least partially stacked on top of the Ta2NiSe5 layer, thereby forming an n-type van der Waals heterojunction between the overlapping portion of the Ta2NiSe5 layer and the InSe layer. Metal electrodes are provided on both sides of the van der Waals heterojunction, which are used to realize the electrical connection between the van der Waals heterojunction and the external circuit.

[0025] For two-dimensional heterojunction photodetectors, existing technologies mostly employ pn junctions or np structures. These structures have slow response speeds (millisecond-level) and often require external bias voltages. Furthermore, commonly used two-dimensional heterojunctions in existing technologies (such as MoS2 / WSe2, InSe / MoS2, etc.) are mostly type-II band-aligned structures, with their response bands mainly concentrated in the visible light range and weak near-infrared response. In contrast, this invention creatively uses Ta2NiSe5 with a band gap of only 0.36 eV as a narrow band gap component to form an n-type heterojunction with InSe, which is a type-I band-aligned structure.

[0026] The working principle of this photodetector is based on the strong built-in electric field formed at the heterojunction interface and band engineering. In this embodiment, the work functions of Ta2NiSe5 and InSe were measured to be 4.87 eV and 4.78 eV, respectively, using Kelvin probe force microscopy (KPFM). After contact, the Fermi levels align, generating a built-in electric field at the interface pointing from InSe to Ta2NiSe5 with a potential difference of approximately 90 mV. This structure achieves efficient absorption across a wide wavelength range from ultraviolet to near-infrared while maintaining high carrier mobility.

[0027] Under illumination, Ta₂NiSe₅ and InSe simultaneously absorb photons and generate electron-hole pairs. Under the influence of the built-in electric field, photogenerated electrons drift towards the InSe side, while holes migrate towards the Ta₂NiSe₅ side, thus achieving efficient spatial separation of charge carriers. Under zero bias conditions, the separated charge carriers accumulate between the electrodes, forming a significant photovoltaic effect. In this embodiment, an open-circuit voltage of 0.24 V was obtained through actual measurement. OC ) and a short-circuit current of 1.35 nA (I SC The results (405 nm, 25.48 mW / cm²) indicate that the photodetector possesses excellent self-powered photoelectric conversion capability. Therefore, the two-dimensional material heterojunction photodetector disclosed in this embodiment of the invention improves the overall performance of existing two-dimensional heterojunction self-powered photodetectors.

[0028] In one optional embodiment, the thickness of the Ta2NiSe5 layer is 20-50 nm, the thickness of the InSe layer is 20-50 nm, and the area of ​​the van der Waals heterojunction is 240-250 square micrometers. More optionally, the thickness of the Ta2NiSe5 layer is 36 nm, the thickness of the InSe layer is 23 nm, and the area of ​​the van der Waals heterojunction is 245.5 square micrometers.

[0029] For the self-powered photodetector based on the Ta2NiSe5 / InSe heterojunction in this optional embodiment, the underlying Ta2NiSe5 film has a thickness of 36 nm and a band gap of approximately 0.36 eV, exhibiting a high 161.25 cm²·V. - ¹·s - ¹ It exhibits high carrier mobility and good air stability; the top InSe film has a thickness of 23 nm or 24 nm and a band gap of about 1.24 eV, and possesses high light absorption coefficient and carrier mobility.

[0030] To verify the performance of the self-powered photodetector in this optional embodiment, this optional embodiment fabricated as follows: Figure 1 The self-powered photodetector based on the Ta2NiSe5 / InSe heterojunction shown is illustrated under a microscope as follows. Figure 2 As shown.

[0031] against Figure 2 The Ta2NiSe5 / InSe heterojunction shown in this alternative embodiment has its performance verified through the following tests, specifically: (1) Figure 3 An atomic force microscopy (AFM) image of a Ta2NiSe5 / InSe heterojunction.

[0032] Figure 3 Experimental results show that: Material identification: The location and stacking area of ​​Ta2NiSe5 and InSe materials can be clearly distinguished.

[0033] Thickness measurement: Through profile analysis, the thickness of the Ta2NiSe5 layer was measured to be 36.4 nm, and the thickness of the InSe layer was 23.9 nm.

[0034] Interface quality: The surface of the overlapping area of ​​the heterojunction is smooth and free of bubbles or wrinkles.

[0035] (2) Figure 4 Raman diagram of Ta2NiSe5 / InSe heterojunction Figure 4 The Raman spectra show different wavenumbers (cm). -1 The Raman scattering intensity peak at ( ). The Raman peak corresponds to the characteristic lattice vibration mode of the material.

[0036] Figure 4 Experimental results show that the Raman peaks of the heterojunction are a simple superposition of the characteristics of the two materials. There is no peak shift or new peak, indicating that the interface between the two materials is well bonded, no chemical reaction occurs, and significant strain is generated.

[0037] (4) Figure 5 Linear IV characteristic curves of Ta2NiSe5 / InSe heterojunction Figure 5 The current-voltage (IV) curve shows the variation of the current flowing through the device with the applied voltage under different conditions (typically in darkness and under different lighting conditions).

[0038] Figure 5 Experimental results show that: Contact type: The curve in the figure passes through zero and is a straight line, indicating that an ohmic contact, rather than a Schottky contact, is formed between the electrode and the material. This is the ideal situation in this embodiment, avoiding the impact of additional contact resistance on device performance.

[0039] Preliminary verification of light response: The curve under illumination shifts compared to the curve under dark conditions, indicating that the device responds to light.

[0040] (5) Figure 6 Broadband response spectrum of Ta2NiSe5 / InSe heterojunction Figure 6 The spectral response diagram shows the responsivity (photocurrent / optical power) or photocurrent magnitude of the device under incident light at different wavelengths (from ultraviolet to near infrared).

[0041] Figure 6 Experimental results show that: Detection range: Figure 6 This demonstrates that the device has broadband detection capability, and it can be read out that the device has a significant response in the wavelength range of 365nm-940nm. Figure 6 The multiple response peaks indicate that the device performs optimally at wavelengths of 365nm, 405nm, 685nm, 780nm, and 940nm.

[0042] (6) Figure 7 The photocurrent is a function of the laser power density.

[0043] Figure 7 The fitted curve in a double logarithmic coordinate system shows the photocurrent (Ig). ph The relationship between the incident laser power density (P) and the power density is expressed using a power-law function I. ph ∝P θ Perform fitting.

[0044] Figure 7Experimental results show that: The fitted exponent θ value reveals the dynamic process of carrier recombination. If θ≈1, it indicates a single-molecule recombination mechanism, which usually corresponds to high-quality materials with few defects. If θ<1, it indicates the existence of bimolecular recombination or trap-assisted recombination. Figure 7 In the figure, θ=0.99: This value is slightly less than 1, indicating that the device has high quality and few defects.

[0045] (7) Figure 8 Responsivity and detectivity of Ta2NiSe5 / InSe heterojunction Figure 8 Under 405 nm laser irradiation and zero bias conditions, the responsivity (R) and specific detectivity (D) are plotted together as a function of a variable such as optical power density or wavelength.

[0046] Figure 8 Experimental results show that under 405 nm laser irradiation and zero bias conditions, the device exhibits excellent self-powered photodetector performance: responsivity (R) reaches 43.17 mA / W and specific detectivity (D*) reaches 1.21 × 10¹² Jones.

[0047] (8) Figure 9 The external quantum efficiency (EQE) of the Ta2NiSe5 / InSe heterojunction and the photodetector's on / off ratio Figure 9 Under 405 nm laser irradiation and zero bias conditions, EQE and light-dark ratio were plotted together.

[0048] External quantum efficiency (EQE): represents the percentage of electrons generated and collected for each incident photon.

[0049] Light-to-dark ratio (I) on / I off ): This represents the ratio of the device's current under illumination to that under darkness, reflecting its signal recognition capability.

[0050] Figure 9 Experimental results show that under 405 nm laser irradiation and zero bias conditions, the external quantum efficiency (EQE) of this device is 12.95%, and the light-to-dark ratio exceeds 10. 5 .

[0051] (9) Figure 10 Open-circuit voltage Voc and short-circuit current Isc of Ta2NiSe5 / InSe heterojunction under different optical power densities Figure 10 These are two key photovoltaic parameters extracted from the IV curve: open-circuit voltage Voc and short-circuit current Isc.

[0052] Open circuit voltage (Voc): The voltage across the device when it is open-circuited (no current output).

[0053] Short-circuit current (Isc): The current flowing through a device when it is short-circuited (no voltage output).

[0054] Figure 10 Experimental results show that: Confirmation of photovoltaic effect: The existence of non-zero Voc and Isc is direct evidence that the device has self-powering capability (photovoltaic effect).

[0055] Performance trends: Isc typically increases linearly or sublinearly with light intensity. Voc increases logarithmically with light intensity and tends to saturate at high light intensities.

[0056] (10) Figure 11 Response time diagram of Ta2NiSe5 / InSe heterojunction Figure 11 The oscilloscope screenshot, taken under 405 nm laser irradiation and zero bias conditions, shows the transient response curve of the device's photocurrent as a function of time under periodically switched laser irradiation. The curve is read from 10% to 90% (rise time, ... ) and from 90% to 10% (time of decline, The time required defines the response speed.

[0057] Figure 11 Experimental results show that under 405 nm laser irradiation and zero bias conditions, the response time is 30 μs increase and 28 μs decrease.

[0058] In summary, under 405 nm laser illumination and zero bias conditions, this device exhibits excellent self-powered photodetector performance: a responsivity (R) of 43.17 mA / W, a specific detectivity (D*) of 1.21 × 10¹² Jones, an external quantum efficiency (EQE) of 12.95%, and a photo-to-dark ratio exceeding 10. 5 The response time is 30 μs for rising and 28 μs for falling.

[0059] The device exhibits a wide spectral response, covering the band from 365 nm (ultraviolet) to 940 nm (near infrared), achieving broadband detection capability from ultraviolet (365 nm) to near infrared (940 nm). This is attributed to the use of a heterojunction constructed from Ta2NiSe5, a narrow bandgap material with a bandgap of only 0.36 eV, and InSe, with a bandgap of 1.24 eV. In contrast, existing technologies mostly use material combinations with wider bandgap (such as MoS2 / WSe2, InSe / GaSe, etc.), whose photon absorption range is mainly limited to the visible light band.

[0060] Long-term stability tests show that after being stored at room temperature for 6 months, its photoelectric response performance remains basically unchanged, demonstrating good environmental stability and reliability.

[0061] In terms of self-powered performance, the device achieves an open-circuit voltage of 0.24 V and a short-circuit current of 1.35 nA at zero bias. This excellent self-powered capability is the result of efficient separation of photogenerated carriers driven by a strong built-in electric field achieved through precise band engineering design. In contrast, existing self-powered detectors often have weak photovoltaic output due to imperfect band alignment or insufficient built-in electric field.

[0062] The above experiments show that precisely controlling the Ta2NiSe5 and InSe thin films within the range of 20-50 nm can produce better results. Excessive thickness will reduce the built-in electric field strength and affect the carrier separation efficiency, while excessive thinness will easily cause instability in the material structure.

[0063] Finally, the self-powered photodetector based on the Ta2NiSe5 / InSe heterojunction in this optional embodiment is compared with the electro-photodetector described in "Two-dimensional (2D) a-In2Se3 / Ta2NiSe5 heterojunction photodetector with high sensitivity and fast response in a wide spectral range" as follows: This optional embodiment uses InSe as the wide bandgap material for constructing a heterojunction with Ta2NiSe5, while the α-In2Se3 / Ta2NiSe5 heterojunction device uses α-In2Se3. The two differ fundamentally in crystal structure, bandgap parameters (such as bandgap size and electron affinity), and interface characteristics. Specifically, the bandgap of InSe (approximately 1.24 eV) is smaller than that of α-In2Se3 (approximately 1.46 eV), resulting in different bandgap shifts at the interface between InSe and Ta2NiSe5, thus affecting the strength of the built-in electric field and carrier transport behavior. This optional embodiment, by controlling the material thickness, forms a built-in electric field of approximately 90 mV at the interface; while the work function difference between α-In2Se3 and Ta2NiSe5 is larger (approximately 0.25 eV), resulting in a stronger built-in electric field. This optional embodiment suppresses the dark current to 10 mV. - ¹ 5While the α-In2Se3 / Ta2NiSe5 heterojunction device exhibits a high dark current, it limits its low-light detection capability. This alternative embodiment focuses more on applications such as low power consumption and low-light imaging; while the α-In2Se3 / Ta2NiSe5 heterojunction device focuses more on high sensitivity and wide-band coverage, and its technical approach relies on a large built-in electric field. Therefore, the two differ significantly in their technical starting point and the technical problems they address.

[0064] In another optional embodiment, the metal electrode is made of gold, and the substrate includes a single-crystal silicon layer and a silicon oxide layer, wherein a Ta2NiSe5 layer and an InSe layer are disposed on the silicon oxide layer.

[0065] Example 2 like Figure 12 As shown, this embodiment of the invention discloses a method for fabricating a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction. This method can be used to fabricate the self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction disclosed in Embodiment 1 of this invention. Specifically, the method includes: S1. Obtain Ta2NiSe5 thin films and InSe thin films from Ta2NiSe5 crystal and InSe crystal.

[0066] Among them, mechanical peeling method can be used, and in mass production, roller peeling method can be used to prepare Ta2NiSe5 thin films and InSe thin films.

[0067] S2. Provide a substrate, determine the electrode region on the substrate by photolithography, and deposit a first metal electrode and a second metal electrode in the electrode region.

[0068] In this embodiment of the invention, the substrate can be a wafer containing an insulating layer, such as a substrate comprising a single-crystal silicon layer and a silicon oxide layer, wherein the silicon oxide layer is used to support the metal electrodes and subsequent heterojunctions. The substrate can also be a chip containing photodetector circuitry, fabricated using a specific process, such as a photoelectric sensor chip including a readout circuitry.

[0069] S3. Transfer the Ta2NiSe5 thin film to a preset position on the substrate so that it contacts the corresponding first metal electrode to obtain the Ta2NiSe5 layer.

[0070] In this embodiment of the invention, a dry transfer technique can be used to transfer Ta2NiSe5 thin films to a predetermined position on a substrate.

[0071] S4. At least partially stack the InSe thin film on the Ta2NiSe5 layer and make it contact the corresponding second metal electrode to obtain the InSe layer.

[0072] like Figure 1 As shown, InSe sheets are at least partially stacked on the Ta2NiSe5 layer, thereby forming an n-type van der Waals heterojunction between the overlapping Ta2NiSe5 layer and the InSe layer. At the same time, the Ta2NiSe5 layer and the InSe layer are each connected to an external control circuit or readout circuit through metal electrodes.

[0073] It should be noted that the step numbering in the embodiments of the present invention is only used to distinguish different steps and does not explicitly or implicitly indicate the order between different steps. For example, step S1 may be performed alongside step S2, or may be performed after step S2.

[0074] For the performance of the self-powered photodetector based on the Ta2NiSe5 / InSe heterojunction prepared by the above method, please refer to the description in Embodiment 1 of this invention. It is particularly important to emphasize the following in this embodiment: Regarding electrode fabrication, existing technologies mostly employ direct deposition of metal electrodes, resulting in high contact resistance. In this invention, the Au electrode achieves an ohmic contact with the material through dry transfer, thus achieving extremely low dark current (10⁻⁶) in terms of detection sensitivity. - ¹ 5 A) and high contrast ratio (>10) 5 This is attributed to the clean interface formed by dry transfer and the strong built-in electric field (approximately 90 mV) generated by the work function difference (0.09 eV). Existing technologies often result in high dark current due to interface defects or built-in electric fields. In the embodiments of the present invention, the built-in electric field is of appropriate size and the interface of the ohmic contact is clean, resulting in a smaller impact of dark current.

[0075] As mentioned above, the substrate can also be a chip containing photoelectric detection circuitry, prepared by a certain process, such as a photoelectric sensor chip including a readout circuitry. Therefore, in an optional embodiment, this invention creatively proposes a method for preparing a substrate containing a circuit chip. The substrate provided in the above embodiment, the electrode region defined on the substrate by photolithography, and the deposition of a first metal electrode and a second metal electrode in the electrode region, can include: S21. Provide a sacrificial substrate, and etch a first trench and a second trench on the front side of the sacrificial substrate using a photolithography process, such as... Figure 13 As shown, metal is filled into the first trench and the second trench to obtain a first metal electrode and a second metal electrode, as follows. Figure 14 As shown.

[0076] In this optional embodiment, the sacrificial substrate is used to assist in the precise generation of the metal electrode in the early stage and to assist in the connection between the metal electrode and the silicon oxide layer. The sacrificial layer can be removed by etching in the later stage. Optionally, the sacrificial layer is made of a material that is easy to etch, such as various metal oxide layers or single crystal silicon layers.

[0077] S22. Sequentially deposit a silicon oxide layer and a single-crystal silicon layer on the front side of the sacrificial substrate, such as... Figure 15 As shown.

[0078] Unlike existing technologies, the silicon oxide layer and the single-crystal silicon layer in this optional embodiment are obtained by deposition on a sacrificial substrate, which facilitates control over their thicknesses. After the silicon oxide layer and the single-crystal silicon layer are deposited sequentially on the front side of the sacrificial substrate, the metal electrode fabricated on the sacrificial substrate will be more firmly bonded to the silicon oxide layer.

[0079] S23. Etch a first connection hole and a second connection hole in the silicon oxide layer and the single-crystal silicon layer. The first connection hole and the second connection hole penetrate the silicon oxide layer and the single-crystal silicon layer and correspond to the first metal electrode and the second metal electrode, respectively. Figure 16 As shown.

[0080] The first and second connecting holes are for preparing to form a metal connection after the metal is filled. The drilling direction of the first and second connecting holes is from the single crystal silicon layer to the silicon oxide layer. The drilling ends when the metal electrode is contacted. The size of the connecting hole is smaller than the size of the metal electrode.

[0081] S24. Fill the first connecting hole and the second connecting hole with metal to obtain the first metal connecting hole and the second metal connecting hole.

[0082] In this configuration, one end of the first metal connection hole contacts the first metal electrode, and the other end of the first metal connection hole is exposed on the front side of the monocrystalline silicon layer; one end of the second metal connection hole contacts the second metal electrode, and the other end of the second metal connection hole is exposed on the front side of the monocrystalline silicon layer, such as... Figure 17 As shown in the figure. The first and second metal connection holes are used to transmit electrical signals between the circuit chip and the metal electrodes.

[0083] S25. Bond a circuit chip to the front side of the single-crystal silicon layer so that the first metal connection hole and the second metal connection hole are electrically connected to the corresponding positions on the circuit chip, such as... Figure 18 As shown.

[0084] In this optional embodiment, the circuit chip can be a chip that receives photoelectric information, processes photoelectric signals, or stores photoelectric signals. It can be a chip fabricated using semiconductor technology, with corresponding external connection parts, such as metal contact parts, on its top. The metal base part can be connected to the first metal connection hole and the second metal connection hole to receive the signal detected by the photodetector.

[0085] In this optional embodiment, the bonding between chips or wafers can be accomplished using any bonding method in the prior art. The bonded circuit chip is combined with the single-crystal silicon layer to form a new substrate.

[0086] S26. Etch away the sacrificial substrate along the reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode, as shown. Figure 19 As shown.

[0087] In this optional embodiment, the sacrificial substrate is used to assist in the precise fabrication of the metal electrode in the early stages and to facilitate the connection between the metal electrode and the silicon oxide layer. Figure 18 Once the metal electrodes, silicon oxide layer, single-crystal silicon layer metal interconnects, and circuit chips shown are all fabricated, the sacrificial layer can be removed by etching. Since the sacrificial substrate is made of a material that is easier to etch, the silicon oxide layer and metal electrodes can be precisely preserved after the sacrificial substrate is etched away.

[0088] As can be seen, this optional embodiment provides a method for fabricating a substrate containing a circuit chip. It creatively utilizes a sacrificial substrate to assist in the precise generation of metal electrodes and the connection between the metal electrodes and the silicon oxide layer. Since both the silicon oxide layer and the single-crystal silicon layer are deposited on the sacrificial substrate in this optional embodiment, their thickness and size are easier to control, and the quality of the finished product is easier to control.

[0089] In the above embodiments, since the Ta2NiSe5 and InSe wafers are disposed on the silicon oxide layer and contacted with the corresponding metal electrodes using a dry transfer method, the contact stability between the Ta2NiSe5 and InSe wafers and the metal electrodes depends entirely on the accuracy of the dry transfer and the quality of the wafers themselves. To further improve the stability of the electrical connection between the Ta2NiSe5 and InSe wafers and the metal electrodes, in another optional embodiment, a sacrificial substrate is provided. A first trench and a second trench are etched on the front side of the sacrificial substrate using a photolithography process, including: A sacrificial substrate is provided, and a first wide trench region and a second wide trench region are defined on the front side of the sacrificial substrate using a first mask. The first wide trench and the second wide trench are etched in the first wide trench region and the second wide trench region. For example, the first wide trench and the second wide trench are etched in the first wide trench region and the second wide trench region defined by the photolithographic mask using photolithography, or the first wide trench and the second wide trench are etched in the first wide trench region and the second wide trench region defined by the first mask using dry etching.

[0090] A carbon-based material layer is deposited on the front side of the sacrificial substrate, such as... Figure 20 As shown, the carbon-based material layer is then ground flat to fill the first and second wide trenches with carbon-based material. Conventional wafer grinding techniques can be used to remove the carbon-based material on the surface of the sacrificial substrate, leaving the carbon-based material inside the trenches. Here, carbon-based material mainly refers to carbon-based materials. Its role here is to fill the trenches so that they are not filled with epitaxial material during the next epitaxial growth process.

[0091] An epitaxial layer of thickness d is epitaxially grown on the front side of the sacrificial substrate. The material of the epitaxial layer is the same as that of the sacrificial substrate layer, and d is greater than the thickness of the Ta2NiSe5 and InSe wafers. Figure 21 As shown.

[0092] A first narrow trench region and a second narrow trench region are defined on the front side of the sacrificial substrate using a second mask, wherein the first narrow trench region and the second narrow trench region are located above the first wide trench and the second wide trench, respectively, and the width of the first narrow trench region and the second narrow trench region is smaller than the width of the first wide trench region and the second wide trench region. Etching downwards along the first narrow trench region and the second narrow trench region to etch the first narrow trench and the second narrow trench in the epitaxial layer, and etching away the carbon-based material in the first wide trench and the second wide trench, resulting in a first trench connecting the first narrow trench and the first wide trench, and a second trench connecting the second narrow trench and the second wide trench, as shown. Figure 22 As shown.

[0093] Thus, both the first and second trenches are T-shaped, resulting in T-shaped metal electrodes within them. This creates a gap of thickness *d* between the metal electrodes and the silicon oxide layer. These gaps can accommodate Ta₂NiSe₅ and InSe flakes, thereby improving the stability of the contact between the Ta₂NiSe₅ and InSe flakes and the metal electrodes. In practice, the Ta₂NiSe₅ and InSe flakes can be partially accommodated within the gaps of the T-shaped metal electrodes, and then a conductive layer can be deposited. This conductive layer fills the unoccupied areas within the gaps during deposition, further stabilizing the contact between the Ta₂NiSe₅ and InSe flakes and the metal electrodes.

[0094] In this optional embodiment, further optionally, metal is filled into the first trench and the second trench to obtain a first metal electrode and a second metal electrode, including: A first metal electrode is obtained by filling a first trench with metal, wherein the first metal electrode includes a first wide metal electrode located in a first wide trench and a first narrow metal electrode located in a first narrow trench, and the first wide metal electrode and the first narrow metal electrode are fixedly connected. A second metal electrode is obtained by filling a second trench with metal, wherein the second metal electrode includes a second wide metal electrode located in a second wide trench and a second narrow metal electrode located in a second narrow trench, and the second wide metal electrode and the second narrow metal electrode are fixedly connected.

[0095] The final first and second metal electrodes are as follows: Figure 23 As shown.

[0096] In this optional embodiment, further optionally, the sacrificial substrate is etched away along the reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode, including: The sacrificial substrate is etched away along its reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode, wherein: There is a first gap of thickness d between the first wide metal electrode and the silicon oxide layer. The first gap is used to contact the Ta2NiSe5 sheet so that a portion of the Ta2NiSe5 sheet can be accommodated within the first gap. There is a second gap of thickness d between the second wide metal electrode and the silicon oxide layer. The second gap is used to contact the InSe sheet so that a portion of the InSe sheet can be accommodated within the first gap.

[0097] Example 3 This invention discloses a photoelectric sensor, which is provided with a plurality of self-powered photodetectors based on a Ta2NiSe5 / InSe heterojunction as disclosed in Embodiment 1 of this invention, arranged according to a preset rule, or a plurality of electro-photodetectors prepared using the self-powered photodetector preparation method based on a Ta2NiSe5 / InSe heterojunction disclosed in Embodiment 2 of this invention, arranged according to a preset rule.

[0098] When industrial mass production is required, the photodetector disclosed in Embodiment 1 or 2 of this invention can be set as a pixel or an imaging point in the sensor to obtain a novel photoelectric sensor.

[0099] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are only used to illustrate the technical solutions of the present invention, not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction, characterized in that, The photodetector includes: A substrate having a Ta2NiSe5 layer and an InSe layer disposed thereon, wherein the InSe layer is at least partially stacked on top of the Ta2NiSe5 layer, thereby forming an n-type van der Waals heterojunction between the overlapping portion of the Ta2NiSe5 layer and the InSe layer; Metal electrodes are provided on both sides of the van der Waals heterojunction, and the metal electrodes are used to realize the electrical connection between the van der Waals heterojunction and the external circuit.

2. The self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction according to claim 1, characterized in that, The thickness of the Ta2NiSe5 layer is 20-50 nm, the thickness of the InSe layer is 20-50 nm, and the area of ​​the van der Waals heterojunction is 240-250 square micrometers.

3. The self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction according to claim 2, characterized in that, The thickness of the Ta2NiSe5 layer is 36 nm, the thickness of the InSe layer is 23 nm, and the area of ​​the van der Waals heterojunction is 245.5 square micrometers.

4. The self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction according to any one of claims 1-3, characterized in that, The metal electrode is made of gold, and the substrate includes a single-crystal silicon layer and a silicon oxide layer, wherein the silicon oxide layer is provided with the Ta2NiSe5 layer and the InSe layer.

5. A method for fabricating a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction, characterized in that, The method includes: Ta2NiSe5 and InSe thin films were obtained from Ta2NiSe5 and InSe crystals; A substrate is provided, an electrode region is defined on the substrate by photolithography, and a first metal electrode and a second metal electrode are deposited in the electrode region; The Ta2NiSe5 sheet is transferred to a predetermined position on the substrate so that it contacts the corresponding first metal electrode to obtain a Ta2NiSe5 layer. The InSe sheet is at least partially stacked on the Ta2NiSe5 layer and brought into contact with the corresponding second metal electrode to obtain the InSe layer.

6. The method for fabricating a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction according to claim 5, characterized in that, The provision of a substrate, wherein electrode regions are defined on the substrate by photolithography, and a first metal electrode and a second metal electrode are deposited in the electrode regions, comprising: A sacrificial substrate is provided, and a first trench and a second trench are etched on the front side of the sacrificial substrate by photolithography. Metal is filled in the first trench and the second trench to obtain a first metal electrode and a second metal electrode. A silicon oxide layer and a single-crystal silicon layer are sequentially deposited on the front side of the sacrificial substrate; A first connection hole and a second connection hole are etched in the silicon oxide layer and the single crystal silicon layer. The first connection hole and the second connection hole penetrate the silicon oxide layer and the single crystal silicon layer and correspond to the first metal electrode and the second metal electrode, respectively. Metal is filled into the first connecting hole and the second connecting hole to obtain a first metal connecting hole and a second metal connecting hole. One end of the first metal connecting hole is in contact with the first metal electrode, and the other end of the first metal connecting hole is exposed on the front side of the single crystal silicon layer. One end of the second metal connecting hole is in contact with the second metal electrode, and the other end of the second metal connecting hole is exposed on the front side of the single crystal silicon layer. A circuit chip is bonded to the front side of the single-crystal silicon layer so that the first metal connection hole and the second metal connection hole are electrically connected to the corresponding positions on the circuit chip. The sacrificial substrate is etched away along the reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode.

7. The method for fabricating a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction according to claim 6, characterized in that, The provision of a sacrificial substrate, wherein a first trench and a second trench are etched on the front side of the sacrificial substrate using a photolithography process, includes: A sacrificial substrate is provided, and a first wide trench region and a second wide trench region are defined on the front side of the sacrificial substrate using a first mask, and a first wide trench and a second wide trench are etched in the first wide trench region and the second wide trench region. A carbon-based material layer is deposited on the front side of the sacrificial substrate, and then the carbon-based material layer is ground flat to fill the first wide trench and the second wide trench with the carbon-based material. An epitaxial layer of thickness d is epitaxially grown on the front side of the sacrificial substrate. The material of the epitaxial layer is the same as that of the sacrificial substrate layer, and d is greater than the thickness of the Ta2NiSe5 sheet and the InSe sheet. A first narrow trench region and a second narrow trench region are defined on the front side of the sacrificial substrate using a second mask, wherein the first narrow trench region and the second narrow trench region are located above the first wide trench and the second wide trench, respectively, and the width of the first narrow trench region and the second narrow trench region is smaller than the width of the first wide trench region and the second wide trench region. The first narrow trench region and the second narrow trench region are etched downwards to etch the first narrow trench and the second narrow trench in the epitaxial layer, and the carbon-based material in the first wide trench and the second wide trench is etched away to obtain a first trench that connects the first narrow trench and the first wide trench, and a second trench that connects the second narrow trench and the second wide trench.

8. The method for fabricating a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction according to claim 7, characterized in that, Filling the first trench and the second trench with metal yields a first metal electrode and a second metal electrode, comprising: A first metal electrode is obtained by filling the first trench with metal, wherein the first metal electrode includes a first wide metal electrode located in the first wide trench and a first narrow metal electrode located in the first narrow trench, and the first wide metal electrode and the first narrow metal electrode are fixedly connected. The second metal electrode is obtained by filling the second trench with metal, wherein the second metal electrode includes a second wide metal electrode located in the second wide trench and a second narrow metal electrode located in the second narrow trench, and the second wide metal electrode and the second narrow metal electrode are fixedly connected.

9. The method for fabricating a self-powered photodetector based on a Ta2NiSe5 / InSe heterojunction according to claim 8, characterized in that, Etching away the sacrificial substrate along its reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode includes: The sacrificial substrate is etched away along its reverse side to expose the silicon oxide layer, the first metal electrode, and the second metal electrode, wherein: There is a first gap of thickness d between the first wide metal electrode and the silicon oxide layer. The first gap is used to contact the Ta2NiSe5 sheet so that a portion of the Ta2NiSe5 sheet is accommodated within the first gap. A second gap of thickness d exists between the second wide metal electrode and the silicon oxide layer. The second gap is used to contact the InSe sheet so that a portion of the InSe sheet is accommodated within the second gap.

10. A photoelectric sensor, characterized in that, The photoelectric sensor is provided with a plurality of self-powered photodetectors based on Ta2NiSe5 / InSe heterojunction as described in any one of claims 1-4, arranged according to a preset rule, or a plurality of electro-photodetectors prepared by the method for preparing self-powered photodetectors based on Ta2NiSe5 / InSe heterojunction as described in any one of claims 5-9, arranged according to a preset rule.

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