Exciton polariton non-equilibrium photoelectric detector and preparation method thereof

Abstract

The invention relates to the technical field of photoelectric devices, in particular to an exciton polariton non-equilibrium photoelectric detector and a preparation method thereof, and the exciton polariton non-equilibrium photoelectric detector comprises a substrate, a metal bottom electrode layer, a two-dimensional exciton semiconductor material layer and a top transparent indium tin oxide (ITO) electrode layer which are sequentially stacked to form an open cavity type strong light-substance coupling structure. The two-dimensional exciton semiconductor material has relatively high exciton binding energy and oscillator strength, and can be strongly coupled with an in-cavity light field at room temperature to form a self-hybrid exciton polariton; the exciton polaritons are in a non-equilibrium state and participate in and regulate generation, distribution and transport of photon-generated carriers, so that the charge transport characteristic is improved, the effective diffusion length is increased, and the spectral response range is widened. And the transparent ITO electrode layer is also used as an anti-reflection coating, so that a light field in the cavity can be enhanced, strong coupling is promoted, and the detection performance is further improved. The preparation method is simple and controllable in process flow, and is suitable for stable preparation of devices and wide-spectrum and high-speed photoelectric detection application.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic device technology, specifically relating to an exciton polariton non-equilibrium photodetector and its fabrication method. Background Technology

[0002] As a core component in the field of optoelectronics, photodetectors are widely used in various important scenarios such as optical communication, optoelectronic imaging, environmental monitoring, and infrared detection. Their performance directly affects the overall operating efficiency and reliability of related systems. Among numerous photodetector materials, exciton semiconductor materials, with their excellent light absorption coefficient, have become a core component of optoelectronic devices such as photodiodes and photovoltaic devices, playing a crucial role in the light-to-electrical signal conversion process.

[0003] In optoelectronic devices based on exciton semiconductor materials, excitons are generated when incident light irradiates the material. These excitons need to diffuse to the material interface to be effectively separated into free carriers, thereby forming a detectable electrical signal. However, excitons themselves have strong binding energy and obvious localization characteristics, which limits their diffusion length and reduces their transmission efficiency. This problem has become a core bottleneck restricting the performance improvement of exciton-based optoelectronic devices.

[0004] To improve exciton transport capabilities, current research proposes a technique involving constructing an optical cavity to achieve energy resonance between the cavity and excitons, thereby forming exciton polaritons through strong light-matter interactions. Exciton polaritons combine the characteristics of excitons and cavity photons, exhibiting lower effective mass and a larger spatial spread, with transport behavior significantly superior to the intrinsic diffusion capability of excitons. Based on this principle, increased exciton diffusion length and enhanced photocurrent have been observed in some organic semiconductor devices by constructing optical cavities that match exciton energy levels. However, the aforementioned techniques still suffer from several insurmountable drawbacks: (1) Such schemes generally rely on additional external optical cavity structures, such as metal mirrors, distributed Bragg mirrors (DBR) and other optical cavity elements, which makes the device fabrication steps cumbersome and complicated, and puts forward extremely high requirements for thin film thickness uniformity and interface quality, increasing the fabrication cost and process difficulty. (2) Organic and some low-refractive-index exciton materials have low refractive indices, and the top metal electrode is prone to large light loss, making it difficult to form a stable and sufficiently strong light field inside the device, which limits their large-scale application in actual photodetectors and photovoltaic devices. (3) Existing detectors based on this scheme are difficult to cope with unbalanced infrared detection processes and cannot meet the application requirements of infrared band detection; (4) Although the open cavity structure can improve the light field distribution and increase the absorption efficiency to a certain extent, this structure is mostly used in the field of optical research. Its integration with optoelectronic devices is limited, and there is still uncertainty in achieving stable strong coupling conditions, making it difficult to realize practical application.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] To address the aforementioned technical problems in the prior art, this invention provides an exciton polariton non-equilibrium photodetector and its fabrication method, which solves the problems of complex device cavity structure, limited exciton diffusion, and narrow absorption bandwidth in the prior art.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, an exciton polariton non-equilibrium photodetector includes: a substrate layer, a metal bottom electrode layer, a two-dimensional exciton semiconductor functional layer, and a top transparent electrode layer, which are sequentially stacked along the light incident direction. The top transparent electrode layer and the two-dimensional exciton semiconductor functional layer form an interface optical interaction structure.

[0008] Furthermore, the two-dimensional exciton semiconductor functional layer is composed of a two-dimensional exciton material having a preset exciton binding energy and a preset light-matter interaction intensity; Strong room-temperature self-hybridized exciton-photon coupling occurs in the two-dimensional exciton semiconductor functional layer, generating exciton polaritons.

[0009] Furthermore, the two-dimensional exciton semiconductor functional layer is used for non-equilibrium self-hybridized exciton-polariton transport; The photodetector has spectral response characteristics corresponding to polariton branches under strong coupling conditions. The photodetector has a transient response speed on the order of nanoseconds and a response bandwidth on the order of megahertz under strong coupling.

[0010] Furthermore, the two-dimensional exciton material includes one or more of the following: transition metal chalcogenides, transition metal tellurides, or black phosphorus.

[0011] Furthermore, the transition metal chalcogenide includes one or more of molybdenum disulfide, tungsten disulfide, tungsten diselenide, and molybdenum ditelluride.

[0012] Furthermore, the top transparent electrode layer is an indium tin oxide electrode layer with a thickness of 10 nm to 100 nm.

[0013] Furthermore, the metal bottom electrode layer includes a transition metal bonding layer and a noble metal conductive layer stacked sequentially, wherein the transition metal bonding layer is attached to the surface of the substrate layer.

[0014] Furthermore, the transition metal bonding layer is a titanium metal layer with a thickness of 3 nm to 15 nm; the noble metal conductive layer is a gold metal layer with a thickness of 30 nm to 100 nm.

[0015] Furthermore, the substrate is a silicon / silicon dioxide substrate, comprising a silicon support layer and a silicon dioxide dielectric layer, wherein the silicon dioxide dielectric layer covers the surface of the silicon support layer and has a thickness of 200 nm to 300 nm; and the silicon support layer has a thickness of 500 μm.

[0016] Furthermore, the feature is that the thickness of the two-dimensional exciton semiconductor functional layer is 50 nm to 200 nm, and its thickness direction is a Fabry-Perot cavity structure with the resonant direction.

[0017] Secondly, a method for fabricating an exciton polariton non-equilibrium photodetector, comprising the aforementioned exciton polariton non-equilibrium photodetector, characterized in that it includes: S1. A metal bottom electrode layer is formed on the surface of the silicon dioxide dielectric layer of the substrate by a deposition process; S2. Transfer the two-dimensional exciton material to the surface of the metal bottom electrode layer away from the substrate module to form a two-dimensional exciton semiconductor functional layer; S3. A top transparent electrode layer is formed on the surface of the two-dimensional exciton semiconductor functional layer away from the metal bottom electrode layer by a deposition process to obtain an exciton polariton photodetector.

[0018] Compared with existing technologies, the exciton polariton non-equilibrium photodetector and its fabrication method provided by this invention include a substrate, a metal bottom electrode layer, a two-dimensional exciton semiconductor material layer, and a top transparent indium tin oxide (ITO) electrode layer stacked sequentially. The two-dimensional exciton semiconductor material has a large exciton binding energy and oscillator strength, and still exhibits a significant exciton effect at room temperature, enabling strong light-matter interaction and satisfying the strong coupling conditions for the formation of room-temperature self-hybridized exciton polaritons. The invention creatively achieves self-hybridization through the Fabry-Perot cavity structure of the two-dimensional exciton semiconductor functional layer itself, eliminating the need for additional external optical cavities or reflective elements, thus completely solving the problems of cumbersome fabrication and high cost caused by the reliance on complex cavity structures in existing technologies. The transparent ITO electrode layer also serves as an anti-reflection coating, enhancing the light field intensity in the open cavity structure and further promoting the stable realization of strong coupling.

[0019] The long-range transport characteristics of non-equilibrium exciton polaritons significantly overcome the bottleneck of traditional exciton diffusion length limitations, substantially improving charge separation and collection efficiency, enabling the internal quantum efficiency of the device to approach 1, while simultaneously broadening the spectral response range to a wide band. Combined with nanosecond-level transient response speed and megahertz-level response bandwidth, high-speed, high-sensitivity detection is achieved, with a photo-dark-current on / off ratio greater than [missing value]. Dark current density as low as Its overall performance far surpasses that of existing exciton-type photodetectors; by selecting two-dimensional exciton materials in the near-infrared or mid-infrared bands, it can be directly extended to infrared non-equilibrium state detection scenarios, filling the gap in the field of room-temperature high-efficiency exciton polariton photodetectors.

[0020] The fabrication method involves deposition and transfer processes to prepare each layer. The process is simple and controllable, with less stringent requirements for film thickness uniformity and interface quality, reducing the difficulty of large-scale production. At the same time, it ensures the consistency and stability of device performance, providing a feasible solution for the practical application of broadband, high-speed, and high-quantum-efficiency optoelectronic devices. Attached Figure Description

[0021] Figure 1 This is a structural diagram of the exciton polariton non-equilibrium photodetector provided in Embodiment 1 of the present invention; Figure 2 This is a top view of the exciton polariton non-equilibrium photodetector provided in Embodiment 3 of the present invention; Figure 3 This is an optical microscope image of the exciton polariton non-equilibrium photodetector provided in Embodiment 3 of the present invention; Figure 4 The thickness-dependent reflectance spectrum of the exciton exciton non-equilibrium photodetector prepared from tungsten disulfide sheets of different thicknesses provided in Embodiment 4 of the present invention is shown. Figure 5 The thickness-dependent reflectance spectrum test results of the exciton polariton non-equilibrium photodetector prepared from tungsten disulfide sheets of different thicknesses provided in Embodiment 4 of the present invention are shown. Figure 6 The external quantum efficiency spectrum test results of the exciton polariton non-equilibrium photodetector prepared by tungsten disulfide thin sheets of different thicknesses provided in Embodiment 4 of the present invention are shown in the figure. Figure 7 The graph shows the relationship between the external and internal quantum efficiencies of the exciton polariton non-equilibrium photodetectors prepared from tungsten disulfide sheets of different thicknesses provided in Embodiment 4 of the present invention and the thickness of the tungsten disulfide sheet. Figure 8 The dark current density versus photocurrent density characteristic curves of the exciton polariton non-equilibrium photodetector prepared from tungsten disulfide sheets of different thicknesses provided in Embodiment 4 of the present invention. Figure 9 The graph shows the test results of the responsivity of the exciton polariton non-equilibrium photodetector prepared from tungsten disulfide sheets of different thicknesses provided in Embodiment 4 of the present invention. Figure 10 The transient optical response test results of the exciton polariton non-equilibrium photodetector prepared by tungsten disulfide thin sheets of different thicknesses provided in Embodiment 4 of the present invention under the condition of laser incident at a wavelength of 520 nm are shown in the figure. Figure 11 The graph shows the test results of the photoresponse signal of the exciton polariton non-equilibrium photodetector prepared by tungsten disulfide thin sheets of different thicknesses provided in Embodiment 4 of the present invention as a function of modulation frequency under the condition of laser incident at a wavelength of 520 nm. Attached image description: 1. Top transparent indium tin oxide electrode layer; 2. Tungsten disulfide sheet; 3. Metal bottom electrode layer; 4. Silicon / silicon dioxide substrate. Detailed Implementation

[0022] The technical solution of the present invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0023] It should be noted that, unless otherwise specifically stated, the relative arrangement and numerical expressions of the components and steps described in these embodiments should not be construed as limiting the scope of the invention.

[0024] The following description of exemplary embodiments is merely illustrative and is not intended to limit the invention or its application or use in any way. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail herein, but where applicable, such techniques, methods, and apparatus should be considered part of this specification.

[0025] Example 1 See Figure 1 , Figure 1 This is a structural diagram of an exciton polariton non-equilibrium photodetector proposed in this invention, comprising a substrate layer, a metal bottom electrode layer, a two-dimensional exciton semiconductor functional layer, and a top transparent electrode layer stacked sequentially along the light incident direction; the top transparent electrode layer and the two-dimensional exciton semiconductor functional layer form an interface optical interaction structure, which is the core foundation for achieving a strong coupling state. Specifically, it includes: D1. Substrate: A silicon / silicon dioxide substrate is used, wherein the silicon support layer is 500 μm thick, and a silicon dioxide dielectric layer covers the surface of the silicon support layer with a thickness of 200 nm to 300 nm, specifically 200 nm, 230 nm, 260 nm, 290 nm, or 300 nm; the size of the silicon / silicon dioxide substrate is 0.5 cm to 1 cm × 0.5 cm to 1 cm, and the metal bottom electrode layer is attached to the surface of the silicon dioxide dielectric layer away from the silicon support layer; the thickness of the dielectric layer of this substrate is matched with the refractive index, providing a stable optical environment for the formation of a strong coupling state; D2, Metal bottom electrode layer: It is a composite layer structure, including a transition metal bonding layer and a noble metal conductive layer stacked sequentially; the transition metal bonding layer is a titanium metal layer with a thickness of 3nm to 15nm, preferably 5nm to 10nm, more preferably 7nm to 9nm, and is directly attached to the surface of the silicon dioxide dielectric layer of the substrate layer. The noble metal conductive layer is a gold metal layer with a thickness of 30nm to 100nm, preferably 50nm to 80nm, more preferably 60nm to 75nm, specifically 60nm, 70nm, 80nm, 90nm, or 100nm. The metal bottom electrode layer is preferably a segmented composite structure, its planar outline sequentially including: a first rectangular portion, a trapezoidal transition portion, a second rectangular portion, and a square end portion, wherein the width of the first rectangular portion is smaller than the width of the second rectangular portion, the upper base of the trapezoidal transition portion connects to the first rectangular portion, and the lower base connects to the second rectangular portion, and the side length of the square end portion is greater than the width of the second rectangular portion. The first rectangular portion serves as the contact area of ​​the two-dimensional exciton semiconductor material layer, and the square end portion serves as the wire bonding area of ​​the electrode, used to realize the electrical connection of the electrode to the external testing system, facilitating testing.

[0026] Specifically, the preferred size ranges for each functional segment of the metal bottom electrode are as follows: The first rectangular portion has a width of 20μm to 50μm and a length of 80μm to 150μm. It is used to form a stable and low contact resistance contact interface with the two-dimensional exciton semiconductor material layer to ensure the efficient transport of charge carriers in the strongly coupled state. Transition trapezoidal section: upper base width 20μm to 50μm, lower base width 30μm to 60μm, height 80μm to 150μm, used to realize the gradual expansion of the current path from the small area contact area to the large area transmission area, reduce the concentration of local current density, and avoid affecting the stability of the strong coupling state; The second rectangular section has a width of 80μm to 150μm and a length of 200μm to 500μm. It is used to form the main current channel and improve the current carrying capacity, adapting to the enhanced photogenerated carrier output requirements under strong coupling conditions. Square end: 150μm to 300μm in side length, used for external electrode connection, providing sufficient mechanical area and reliability for probe contact or gold wire bonding.

[0027] D3. Two-dimensional exciton semiconductor functional layer: composed of two-dimensional exciton material tungsten disulfide, with a thickness of 50 nm to 200 nm, more preferably 75 nm to 200 nm, specifically 77.9 nm, 151.2 nm, or 196 nm; its thickness direction is a Fabry-Perot cavity structure in the resonant direction, which can be used as a self-hybridized microcavity to bind photons, achieving strong coupling between self-hybridized excitons and photons at room temperature, thereby generating exciton polaritons. The exciton polaritons are in a non-equilibrium state and carry out transport, which can enhance charge transport characteristics, make the device exhibit spectral response characteristics corresponding to the polariton branch, and improve the transient response speed and response bandwidth of the device. The coupling strength is 86.5 meV to 96.5 meV; this functional layer covers the surface of the first rectangular part of the metal bottom electrode layer, and is formed by peeling off tungsten disulfide crystals with preset exciton binding energy and preset light-matter interaction strength. The preset parameters are the key prerequisites for achieving the strong coupling state.

[0028] Two-dimensional exciton materials include one or more of transition metal chalcogenides, transition metal tellurides, or black phosphorus; transition metal chalcogenides include one or more of molybdenum disulfide, tungsten disulfide, tungsten diselenide, and molybdenum ditelluride. All of the above materials possess the high exciton binding energy and oscillator strength required to achieve a strong coupling state.

[0029] D4. Top transparent electrode layer: Indium tin oxide electrode layer 1, with a thickness of 10nm to 100nm, more preferably 30nm to 80nm, and more preferably 40nm to 50nm. Its planar profile is completely consistent with the metal bottom electrode layer, covering the surface of the two-dimensional exciton semiconductor functional layer away from the metal bottom electrode layer, and forming an interface optical interaction structure with the two-dimensional exciton semiconductor functional layer. This electrode layer also serves as an anti-reflection coating, which can enhance the intensity of the optical field in the cavity and provide key support for the stable formation and maintenance of the strong coupling state. Specifically, the planar shape of the top transparent indium tin oxide (ITO) electrode layer is preferably consistent with that of the metal bottom electrode layer, including a first rectangular contact portion, a transition trapezoidal portion, a second rectangular transmission portion and an end connection portion connected in sequence. This structure can achieve precise alignment of the upper and lower electrodes without increasing the complexity of the device layout, which is beneficial to ensuring the consistency and stability of the vertical current path of the FP cavity.

[0030] The preferred size ranges for each functional segment are as follows: The first rectangular contact portion has a width of 20μm to 50μm and a length of 80μm to 150μm; the upper base of the transition trapezoidal portion has a width of 20μm to 50μm, the lower base has a width of 30μm to 60μm, and a height of 80μm to 150μm; the second rectangular transmission portion has a width of 80μm to 150μm and a length of 200μm to 500μm; the end connection portion has a side length of 150μm to 300μm and is used for reliable connection with external test ports or wire bonding areas.

[0031] The aforementioned size range matches the bottom metal electrode, enabling the upper and lower electrodes to form a consistent coverage profile across the entire device area. This results in a more uniform distribution of current injection and light absorption, ensuring the stability of the strongly coupled state across the entire device. Furthermore, this invention does not limit the ITO electrode size to be completely identical to the metal electrode. Those skilled in the art can make reasonable adjustments to the local dimensions based on process alignment accuracy, optical transmittance, and current carrying requirements. The core requirement is to meet the optical field and carrier transport requirements of the strongly coupled state.

[0032] Example 2 The present invention proposes a method for fabricating an exciton polariton non-equilibrium photodetector, the specific steps of which include: S1. A metal bottom electrode layer is formed on the surface of the silicon dioxide dielectric layer of the substrate by a deposition process; Specifically, the substrate (silicon / silicon dioxide substrate) is pretreated by sequentially cleaning it with acetone, isopropanol, and deionized water to remove surface impurities. Impurity removal prevents light scattering and ensures the quality of the light field in the subsequent strongly coupled state. Electron beam lithography is used to expose the metal bottom electrode region on the surface of the silicon dioxide dielectric layer of the substrate, followed by development. Then, using a thermal evaporation deposition system, titanium and gold metal layers are sequentially deposited at a deposition rate of 0.1 to 0.5 Å / s (selectable from 0.1, 0.2, 0.3, 0.4, or 0.5 Å / s) to form a composite metal bottom electrode layer. Precise control of the deposition rate ensures the flatness of the electrode layer and avoids interface roughness affecting the strongly coupled state. After deposition, the remaining photoresist is sequentially stripped using acetone, isopropanol, and deionized water to obtain the formed metal bottom electrode layer.

[0033] S2. Transfer the two-dimensional exciton material to the surface of the metal bottom electrode layer away from the substrate module to form a two-dimensional exciton semiconductor functional layer; Specifically, a mechanical peeling method is used to peel off two-dimensional exciton semiconductor materials with uniform thickness and smooth surface from bulk transition metal chalcogenides, transition metal tellurides or black phosphorus crystals. The uniformity of material thickness and the smoothness of the surface are the core process requirements for achieving a stable and strong coupling state. First, the two-dimensional exciton semiconductor material obtained by stripping is transferred to the surface of polydimethylsiloxane. Then, it is precisely transferred from polydimethylsiloxane to the end region of the metal bottom electrode layer on the transfer stage, so that the material and the metal bottom electrode layer are closely attached to form a two-dimensional exciton semiconductor functional layer. The close attachment can reduce interface defects and avoid energy loss in the strong coupling state.

[0034] S3. A top transparent electrode layer is formed on the surface of the two-dimensional exciton semiconductor functional layer away from the metal bottom electrode layer by a deposition process to obtain an exciton polariton photodetector.

[0035] Specifically, electron beam lithography is used to expose the top transparent indium tin oxide (ITO) electrode layer on the surface of the two-dimensional exciton semiconductor functional layer, followed by development. The ITO layer is then prepared by magnetron sputtering or ion beam sputtering at a deposition rate of 0.1 to 0.5 Å / s (selectable from 0.1 Å / s, 0.2 Å / s, 0.3 Å / s, 0.4 Å / s, or 0.5 Å / s). Precise control of the deposition rate ensures a balance between the optical transmittance and conductivity of the electrode layer, providing optimal optical support for the strong coupling state. After deposition, the remaining photoresist is stripped using acetone, isopropanol, and deionized water in sequence to obtain the top transparent ITO electrode layer, ultimately forming an exciton polariton non-equilibrium photodetector capable of stably achieving a strong coupling state.

[0036] Example 3 This embodiment employs a method for fabricating an exciton polariton non-equilibrium photodetector proposed in this invention. The specific fabrication steps include: First, the silicon / silicon dioxide substrate 4 is pretreated by sequentially cleaning it with acetone, isopropanol and deionized water to remove surface impurities. The silicon layer in the substrate is 500 μm thick and the silicon dioxide layer is 280 nm thick. The overall size of the substrate is 0.5 cm × 0.5 cm. After cleaning, it is dried for later use. The parameters of this substrate provide a basis for matching optical refractive index and cavity length for strong coupling.

[0037] Next, the metal bottom electrode layer 3 is fabricated. Electron beam lithography is used to expose the metal bottom electrode region on the surface of a clean silicon / silicon dioxide substrate 4. After exposure, a photoresist mask with a preset pattern is formed by development. Subsequently, a titanium metal layer with a thickness of 3 nm and a gold metal layer with a thickness of 100 nm are deposited sequentially at a deposition rate of 0.2 Å / s using a thermal evaporation deposition process. After deposition, the remaining photoresist is stripped sequentially using acetone, isopropanol and deionized water to obtain the metal bottom electrode layer 3. The planar contour of the metal bottom electrode layer 3 includes a first rectangular portion (approximately 30 μm × 120 μm), a trapezoidal transition portion (upper base approximately 30 μm, lower base approximately 100 μm, height approximately 35 μm), a second rectangular portion (approximately 315 μm × 100 μm), and a square connecting portion (approximately 200 μm × 200 μm). This structural design can ensure low-loss transmission of carriers in a strongly coupled state.

[0038] Next, a two-dimensional exciton semiconductor functional layer was prepared. A tungsten disulfide sheet 2 with uniform thickness, a flat surface, and a thickness range of 50 nm to 200 nm was peeled off from a bulk tungsten disulfide crystal using a mechanical peeling method. This thickness range is a key size range for achieving Fabry-Perot cavity resonance and strong coupling. The peeled tungsten disulfide sheet 2 was then transferred to a pre-cut polydimethylsiloxane surface. The substrate with the prepared metal bottom electrode layer 3 was fixed on the transfer stage, and the tungsten disulfide sheet 2 on the polydimethylsiloxane surface was transferred to the metal bottom electrode layer 3 by micromanipulation to form a two-dimensional exciton semiconductor functional layer. During the transfer process, it was ensured that the material was free of wrinkles and impurities to guarantee the stability of the strong coupling state.

[0039] Finally, the top transparent electrode layer was fabricated and the detector was formed. Electron beam lithography was used to expose the top transparent indium tin oxide (ITO) electrode layer 1 on the surface of the two-dimensional exciton semiconductor functional layer. After exposure, development was performed. An indium tin oxide layer with a thickness of 50 nm was deposited by ion beam sputtering at a deposition rate of 0.2 Å / s. The planar contour dimensions of the indium tin oxide layer were completely consistent with those of the metal bottom electrode layer 3. Its thickness and deposition process parameters were optimized to maximize the enhancement of the intracavity light field and promote the formation of a strong coupling state. After deposition, the remaining photoresist was stripped using acetone, isopropanol and deionized water in sequence, and finally an exciton polariton non-equilibrium photodetector that can stably realize a strong coupling state was obtained.

[0040] A top view of the exciton polariton non-equilibrium photodetector prepared in this embodiment is shown below. Figure 2 As shown, the optical microscope image is as follows Figure 3 As shown, the microscopic morphology reveals that each layer has a flat structure and clear interfaces, providing structural assurance for the stability of the strongly coupled state.

[0041] Example 4 This embodiment tests the performance of the exciton polariton non-equilibrium photodetector prepared in Example 3. The test object is the exciton polariton non-equilibrium photodetector prepared in Example 3 using tungsten disulfide sheets of different thicknesses (50nm to 200nm). The focus is on verifying the decisive role of the strong coupling state on the device performance. The specific test items, conditions and results are as follows: Thickness-dependent reflectance spectroscopy measurements were performed without external bias voltage, and the test wavelengths covered the exciton resonance correlation band. The test results are as follows: Figure 4 As shown, Figure 4 In the figure, 'a' represents the experimentally measured reflectance spectrum and its corresponding calculation result using the Transmission Matrix Method (TMM). Figure 4 Figure b shows the thickness-wavelength-dependent reflectance distribution calculated using the transfer matrix method, fitted using a coupled oscillator model. The experimentally measured reflectance spectrum shows good agreement with the results calculated using the transfer matrix method (black dashed line). The dispersion relations of the upper polariton branch (UPB) and lower polariton branch (LPB) are shown, and the spectra under different thickness conditions are appropriately shifted in the longitudinal direction. Near the exciton resonance (tungsten disulfide exciton energy is approximately 1.97 eV), the device exhibits large and broadband optical absorption characteristics. Figure 4 In the case of b, the exciton polariton state exhibits a minimum characteristic in the reflectance spectrum, and this minimum shows obvious anti-crossing behavior, which proves that the device has successfully achieved strong coupling between self-hybridized excitons and photons, which is a typical spectral feature of strong coupling states. After fitting the dispersion relation for different Fabry-Perot cavity mode orders, the Rabi splitting energies corresponding to the first three cavity mode orders (l=1, 2, 3) are respectively =152.62meV, 173.38meV and 171.42meV, the significant values ​​of the Rabi splitting energy further verify the formation of the strongly coupled state.

[0042] Angle-resolved reflectance spectroscopy tests were conducted under different incident angles and without external bias voltage. The test results are as follows: Figure 5As shown, the energy of the cavity mode inside the device varies with the incident angle, and the corresponding polarization state exhibits a significant angle dependence. In devices with a thickness greater than approximately 50 nm in the two-dimensional exciton semiconductor material, anti-crossing features in the reflection spectrum can be clearly observed. These anti-crossing features are the core criterion for determining the strong coupling state, indicating that a mixed exciton-photon state has been formed between the cavity mode and the exciton. In thinner devices, only approximately dispersion-free exciton resonance features are observed, and no effective strong coupling state has been formed. The angle-resolved dispersion relation under different thickness conditions is fitted using a coupled oscillator model. Devices with thicknesses of approximately 77.9 nm, 151.2 nm, and 221 nm correspond to the zero-detuning conditions of the first, second, and third order Fabry-Perot cavity modes, respectively. The fitted coupling strengths are 86.5 meV, 91.7 meV, and 93.9 meV, respectively, further quantifying the strength of the strong coupling state.

[0043] External quantum efficiency (EQE) spectral measurements were performed in the wavelength range of 450 nm to 800 nm without an external bias voltage. The results are as follows: Figure 6 As shown, Figure 6 In the figure, 'a' represents the EQE spectrum of devices with different thicknesses. Figure 6 Figure b shows a comparison between the experimental results of the EQE peak position varying with thickness and the fitting results of the coupled oscillator model. When the tungsten disulfide sheet thickness is greater than 50 nm (forming a strong coupling state), the EQE spectrum shows response peaks corresponding to the lower polariton branch and the upper polariton branch on both sides of the bare exciton resonance energy, and the energy separation between the response peak and the bare exciton resonance is greater than their respective linewidths. When the tungsten disulfide sheet thickness is less than or equal to 50 nm (not forming a strong coupling state), the EQE spectrum shows a single response peak only at the bare exciton resonance position. The peak positions of the EQE spectra extracted from devices of different thicknesses change systematically with the thickness of the tungsten disulfide sheet, and the trend is consistent with the calculation results based on the coupled oscillator model, proving that the strong coupling state directly modulates the spectral response characteristics of the device.

[0044] The quantum efficiency variation with thickness was measured under conditions of incident light wavelength of 650 nm and no external bias voltage. The test results are as follows: Figure 7 As shown, Figure 7 The graphs show the relationship between the external quantum efficiency (EQE) and internal quantum efficiency (IQE) of devices with different thicknesses and the material thickness. Figure 7As shown in Figure a, with the increase of the thickness of the tungsten disulfide sheet, the EQE exhibits obvious oscillating characteristics, with obvious peaks appearing near the thickness of the tungsten disulfide sheet at approximately 75 nm (corresponding to the first-order Fabry-Perot cavity mode, forming a strong coupling state) and 145 nm (corresponding to the second-order Fabry-Perot cavity mode, forming a strong coupling state). During the process of transitioning from the weak coupling region to the strong coupling state, the overall EQE level at the wavelength of 650 nm is significantly improved, with the maximum value increasing by more than one order of magnitude compared to the weak coupling state, reaching up to approximately 20 times. like Figure 7 As shown in Figure b, the IQE also exhibits significant oscillatory behavior with the thickness of the tungsten disulfide sheet. The IQE increases significantly when the thickness enters the strongly coupled state region, and a significant enhancement peak appears near the zero detuning condition. When the IQE corresponds to the first-order polariton mode, it can approach 1, proving that the strongly coupled state is the core mechanism for improving quantum efficiency.

[0045] See Figure 8 , Figure 8 Dark current density versus photocurrent density characteristic curves of exciton exciton non-equilibrium photodetectors prepared from tungsten disulfide sheets of different thicknesses. like Figure 8 As shown, under operating conditions with an applied bias voltage of 0V, the photodetector exhibits a low dark current level, with its dark current density reaching as low as [missing value]. This result indicates that the device exhibits low intrinsic noise current characteristics under zero-bias operation.

[0046] Meanwhile, under the same zero-bias condition, the device exhibits significant differences between the illuminated and dark states, with the photocurrent to dark current ratio being greater than [missing value]. The results show that the efficient transport of exciton polaritons in the strongly coupled state reduces carrier recombination loss, which in turn reduces dark current noise and enhances photocurrent signal, giving the device a high on / off ratio.

[0047] See Figure 9 , Figure 9 Figure showing the test results of the responsivity of exciton polariton non-equilibrium photodetectors prepared from tungsten disulfide sheets of different thicknesses; During the test, the responsivity of the photodetector was measured under incident light with a wavelength of 600 nm under an applied bias voltage of 0V, and the relationship between the device responsivity and the thickness of the tungsten disulfide sheet was calculated.

[0048] like Figure 9As shown, the device responsivity exhibits a distinct oscillating variation with the thickness of the tungsten disulfide sheet. The responsivity significantly increases near the zero-detuned thickness region of the strongly coupled state, reaching its maximum value near the zero-detuned thickness corresponding to the first-order Fabry-Perot cavity mode. The device achieves a maximum responsivity of approximately 0.35 A / W under conditions of a wavelength of 600 nm and an incident light power of 15 μW.

[0049] The above results show that the light absorption efficiency and carrier transport capability are both enhanced under strong coupling, thereby significantly improving the responsivity performance of the photodetector.

[0050] See Figure 10 , Figure 10 The transient optical response test results of exciton polariton non-equilibrium photodetectors prepared from tungsten disulfide sheets of different thicknesses under laser incident conditions at a wavelength of 520 nm are shown in the figure. like Figure 10 As shown, under operating conditions of an applied bias voltage of 0V and an incident laser wavelength of 520nm, the transient response of the photodetector was tested, and its photoresponse rise time was measured to be approximately 288.8ns and its fall time to be approximately 16.5ns. This result indicates that exciton polaritons generated under strong coupling conditions possess low effective mass and long-range transport characteristics, significantly accelerating the carrier transport process and thus improving the response speed of the photodetector.

[0051] See Figure 11 , Figure 11 The test results of the photoresponse signal of exciton polariton non-equilibrium photodetectors prepared from tungsten disulfide sheets of different thicknesses as a function of modulation frequency under laser incident at a wavelength of 520 nm are shown in the figure. like Figure 11 As shown, the frequency response curve can be used to determine the photodetector's... The 3dB cutoff frequency is approximately 1.21MHz, indicating that this two-dimensional photodetector based on the strong coupling state of room-temperature self-hybridized exciton polaritons can still achieve a response bandwidth in the megahertz range under zero bias conditions. This proves that the strong coupling state is the core guarantee for achieving high-speed detection and is suitable for high-speed photodetector applications.

[0052] In summary, the present invention has the following advantages: 1. A two-dimensional photodetector based on room-temperature self-hybridized exciton polaritons eliminates the need for external optical cavities or additional reflective structures. It utilizes the inherent high exciton binding energy and strong light-matter interaction of two-dimensional exciton semiconductor materials, combined with the optical impedance mismatch between the top ITO electrode and the material layer, to naturally form a Fabry-Perot cavity mode within the device, thus achieving a strong coupling state of self-hybridized exciton polaritons at room temperature. This self-hybridization mechanism effectively avoids the energy loss and integration difficulties associated with complex cavity structures in traditional exciton devices, significantly reducing fabrication complexity and cost, and facilitating large-scale production. 2. By utilizing the hybrid states (E-Ps) formed by self-hybridized exciton polaritons, lower effective mass and delocalized wavefunctions are achieved, thus enabling long-range transport characteristics. This directly improves charge separation and collection efficiency, effectively solving the problem of limited exciton diffusion length in traditional exciton semiconductors, thereby achieving faster response speeds; 3. It significantly enhances the light field intensity, enabling the generation of self-hybridized exciton polaritons near the material band gap, while maintaining strong non-resonant absorption above the band gap. This achieves a wider absorption bandwidth and higher photon capture efficiency, solving the problem of limited absorption in traditional two-dimensional exciton materials, improving the quantum efficiency of the device, and meeting the application requirements of broadband photoelectric detection. 4. Excellent band scalability. By selecting two-dimensional exciton semiconductor materials with band gaps in the near-infrared or mid-infrared bands, the photodetector can be extended to the field of infrared non-equilibrium photoelectric detection and control; 5. With its fast response speed (suitable for high-speed detection scenarios), high quantum efficiency, and stable and reliable characteristics, it is particularly suitable for applications in broadband photoelectric detection, imaging, and communication, filling the gap in existing technologies for high-efficiency exciton polariton photoelectric detectors at room temperature.

[0053] The above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An exciton polariton non-equilibrium photodetector, characterized in that, include: A substrate layer, a metal bottom electrode layer, a two-dimensional exciton semiconductor functional layer, and a top transparent electrode layer are sequentially stacked along the light incident direction; The top transparent electrode layer and the two-dimensional exciton semiconductor functional layer form an interface optical interaction structure.

2. The exciton polariton non-equilibrium photodetector according to claim 1, characterized in that, The two-dimensional exciton semiconductor functional layer is composed of a two-dimensional exciton material with a preset exciton binding energy and a preset light-matter interaction intensity; Strong room-temperature self-hybridized exciton-photon coupling occurs in the two-dimensional exciton semiconductor functional layer, generating exciton polaritons.

3. The exciton polariton non-equilibrium photodetector according to claim 2, characterized in that, The two-dimensional exciton semiconductor functional layer is used for non-equilibrium self-hybridized exciton-polariton transport; The photodetector has spectral response characteristics corresponding to polariton branches under strong coupling conditions. The photodetector has a transient response speed on the order of nanoseconds and a response bandwidth on the order of megahertz under strong coupling.

4. The exciton polariton non-equilibrium photodetector according to claim 2, characterized in that, The two-dimensional exciton material includes one or more of the following: transition metal chalcogenides, transition metal tellurides, or black phosphorus.

5. The exciton polariton non-equilibrium photodetector according to claim 4, characterized in that, The transition metal chalcogenides include one or more of molybdenum disulfide, tungsten disulfide, tungsten diselenide, and molybdenum ditelluride.

6. The exciton polariton non-equilibrium photodetector according to claim 1, characterized in that, The top transparent electrode layer is an indium tin oxide electrode layer with a thickness of 10 nm to 100 nm.

7. The exciton polariton non-equilibrium photodetector according to claim 1, characterized in that, The metal bottom electrode layer includes a transition metal bonding layer and a noble metal conductive layer stacked sequentially, wherein the transition metal bonding layer is attached to the surface of the substrate layer.

8. The exciton polariton non-equilibrium photodetector according to claim 7, characterized in that, The transition metal bonding layer is a titanium metal layer with a thickness of 3nm to 15nm; the noble metal conductive layer is a gold metal layer with a thickness of 30nm to 100nm.

9. The exciton polariton non-equilibrium photodetector according to claim 1, characterized in that, The substrate is a silicon / silicon dioxide substrate, including a silicon support layer and a silicon dioxide dielectric layer. The silicon dioxide dielectric layer covers the surface of the silicon support layer and has a thickness of 200 nm to 300 nm. The thickness of the silicon support layer is 500 μm.

10. The exciton polariton non-equilibrium photodetector according to claim 1, characterized in that, The thickness of the two-dimensional exciton semiconductor functional layer is 50 nm to 200 nm, and its thickness direction is the resonant direction of the Fabry-Perot cavity structure.

11. A method for fabricating an exciton polariton non-equilibrium photodetector, comprising fabricating the exciton polariton non-equilibrium photodetector according to any one of claims 1-9, characterized in that, include: S1. A metal bottom electrode layer is formed on the surface of the silicon dioxide dielectric layer of the substrate by a deposition process; S2. Transfer the two-dimensional exciton material to the surface of the metal bottom electrode layer away from the substrate module to form a two-dimensional exciton semiconductor functional layer; S3. A top transparent electrode layer is formed on the surface of the two-dimensional exciton semiconductor functional layer away from the metal bottom electrode layer by a deposition process to obtain an exciton polariton photodetector.

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