Photoelectric detector with gradient phase structure and method of manufacturing the same
Patent Information
- Application Number
- CN202611468028.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-21
- Publication Date
- 2026-10-27
AI Technical Summary
然而，薄膜内纵向梯度结构的能带和组分变化往往被限制在垂直厚度方向上，导致整片薄膜在宏观二维平面上仍表现出相对均匀的带隙分布
[0020]本发明提供了一种具有梯度相结构的光电探测器，该光电探测器在功能层引入SnS和Sn2S3混合相，并沿功能层的中心至外缘的径向方向上，形成 Sn2S3相对摩尔含量梯度增加的径向梯度结构。借助该径向梯度相结构，功能层能够在平面方向上形成连续变化的禁带宽度和能带分布，从而有利于光生载流子的分离、迁移和收集，并为多区域光电响应及近红外探测提供结构基础。
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Figure CN122995289A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optoelectronic technology, specifically to a photodetector with a gradient phase structure and its fabrication method. Background Technology
[0002] Photodetectors are functional devices that convert incident light signals into electrical signals, and are widely used in image sensing, environmental monitoring, optical communication, industrial inspection, biomedical detection, and infrared detection. As detection devices develop towards higher sensitivity, lower power consumption, wider spectral response, and greater integration, how to construct an effective built-in electric field within semiconductor thin films, improve the separation efficiency of photogenerated electrons and holes, and reduce carrier recombination losses has become an important research direction in this field.
[0003] In photodetectors, by constructing functional layers with gradient variations in composition, phase structure, doping concentration, or bandgap, spatially varying band structures can be formed within the thin film, providing a built-in driving force for the separation and migration of photogenerated carriers. Compared to homogeneous thin films, gradient structure thin films are beneficial for improving light absorption, carrier separation, and charge collection processes, and are therefore often used to enhance the response intensity, response speed, and stability of thin-film photodetectors.
[0004] Currently, related technologies construct a built-in electric field in the vertical direction by introducing a longitudinal gradient phase structure (i.e., a gradient change in composition or energy band along the thickness direction of the thin film) within the detector device. While this longitudinal gradient phase structure can shorten the carrier transport path within the device to some extent and establish a built-in electric field in the vertical direction, the band and composition changes of the longitudinal gradient structure within the thin film are often confined to the vertical thickness direction, resulting in a relatively uniform bandgap distribution across the entire thin film in a macroscopic two-dimensional plane. This in-plane physical symmetry makes it difficult for photogenerated carriers to have a driving force in the horizontal direction, hindering effective lateral transport and thus preventing the construction of high-performance, self-driven near-infrared photodetectors without external bias. Furthermore, it is difficult to form multiple functional regions with different response characteristics within the same thin film plane, thus limiting its application in on-chip multi-region functional integration and planar multispectral discrimination.
[0005] Therefore, it is necessary to design a photodetector with a gradient phase structure and its fabrication method to improve the above problems. Summary of the Invention
[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a photodetector with a gradient phase structure to improve the technical defects of photodetectors with longitudinal gradient phase structures, which are difficult to realize lateral carrier transport and regional multi-band photoelectric response in the planar space of thin films due to the uniformity of the bandgap structure in the plane.
[0007] To achieve the above and other related objectives, the present invention provides a photodetector with a gradient phase structure, the photodetector comprising a substrate, a functional layer and electrodes.
[0008] The functional layer is disposed on the substrate, and the functional layer includes SnS and Sn2S3; the electrode is disposed on the functional layer; the molar content of Sn2S3 in SnS and Sn2S3 increases in a gradient from the center to the outer edge of the functional layer in a radial direction.
[0009] In one example of the present invention, the bandgap of the functional layer is 0.93~1.3 eV.
[0010] In one example of the present invention, the bandgap width of the functional layer decreases in a gradient along the radial direction from the center to the outer edge of the functional layer.
[0011] In one example of the present invention, the functional layer has a photoelectric response to incident light with wavelengths of 400nm to 808nm.
[0012] In one example of the present invention, the substrate is a semiconductor substrate or an insulating substrate.
[0013] In one example of the present invention, the electrode is a ring electrode.
[0014] This invention also provides a method for fabricating a photodetector with a gradient phase structure, the method comprising the following steps: Provide substrate; A SnS thin film is formed on the substrate to obtain a substrate; At a first temperature, phosphorus vapor is introduced to induce a partial SnS phase transformation in the SnS film to Sn2S3, thereby forming a functional layer; wherein, from the center to the outer edge of the functional layer, the relative molar content of the Sn2S3 formed by the phase transformation increases in a gradient; the first temperature is 150℃~350℃; Electrodes are deposited on the functional layer to form a photodetector.
[0015] In one example of the present invention, providing a substrate further includes: performing a hydrophilic treatment on the surface of the substrate.
[0016] In one example of the present invention, the step of introducing phosphorus vapor at a first temperature to induce a partial SnS phase transformation in the SnS thin film to Sn2S3 includes: The red phosphorus and the substrate were placed in two temperature zones of the furnace body, respectively. The red phosphorus is heated at a second temperature, and the substrate is heated at the first temperature; an inert gas is introduced into the furnace to facilitate the transport of phosphorus vapor evaporated from the red phosphorus to the surface of the substrate and induce a partial SnS phase transformation in the SnS film to Sn2S3; the second temperature is 200℃~500℃.
[0017] In one example of the present invention, the step of introducing phosphorus vapor at a first temperature to induce a partial SnS phase transformation in the SnS thin film to Sn2S3 includes: The introduced phosphorus vapor forms a diffusion gradient within the SnS film, causing the relative content of Sn2S3 formed by phase transformation within the SnS film to decrease from the edge to the center region; the diffusion gradient decreases in the radial direction from the outer edge to the center of the SnS film.
[0018] In one example of the present invention, the distance between the red phosphorus and the substrate in the furnace body is 20-24 cm.
[0019] In one example of the present invention, the heating time for the substrate is 50 to 70 minutes.
[0020] This invention provides a photodetector with a gradient phase structure. The photodetector introduces a mixed SnS and Sn₂S₃ phase into the functional layer, forming a radial gradient structure with an increasing relative molar content of Sn₂S₃ along the radial direction from the center to the outer edge of the functional layer. This radial gradient phase structure allows the functional layer to form a continuously varying bandgap and band distribution in the planar direction, which is beneficial for the separation, migration, and collection of photogenerated carriers, and provides a structural basis for multi-region photoelectric response and near-infrared detection.
[0021] The photodetector fabrication method provided by this invention involves introducing phosphorus vapor into a SnS thin film at a first temperature. This causes the phosphorus vapor to form a diffusion gradient in the film that decreases from the outer edge to the center, thereby inducing a portion of the SnS in the SnS thin film to transform into Sn₂S₃. This results in a functional layer with a progressively increasing relative molar content of Sn₂S₃ along the direction from the center to the outer edge. The fabrication method provided by this invention overcomes the limitation that the SnS-to-Sn₂S₃ phase transition requires high temperature or high pressure conditions. Based on the chemical vapor deposition process for depositing SnS thin films, the introduction of phosphorus vapor enables the simultaneous fabrication of a continuous radial gradient structure at low temperatures, thus providing a convenient and effective fabrication method for radial gradient bandgap thin films. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.
[0023] Figure 1 This is a schematic diagram of a photodetector with a gradient phase structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the radial gradient phase structure of the functional layer in one embodiment of the present invention; in the figure, yellow atoms represent Sn atoms and gray atoms represent S atoms; Figure 3 This is a schematic diagram of the structure of the annular electrode in one embodiment of the present invention; Figure 4 This is an X-ray diffraction pattern measured at different locations from the center to the edge of the functional layer in one embodiment of the present invention; Figure 5 This is a schematic diagram of the bandgap variation of the functional layer from the center of the plane to the edge in one embodiment of the present invention; Figure 6 This is a schematic diagram of the bandgap region of the functional layer from the center of the plane to the edge in one embodiment of the present invention; Figure 7 The image shows the photoelectric response test results of a photodetector device under irradiation with 808nm wavelength lasers of different powers in one embodiment of the present invention. Figure 8 The image shows the photoelectric response test results of a photodetector device under laser irradiation at wavelengths of 400nm, 450nm, 500nm, 600nm, and 650nm, according to one embodiment of the present invention. Figure 9 This is a schematic flowchart of a preparation method in one embodiment of the present invention; Figure 10 This is a schematic diagram of the process for inducing a gradient phase transition in a SnS thin film according to an embodiment of the present invention.
[0024] Component designation explanation 10. Substrate; 20. Functional layer; 30. Electrode. Detailed Implementation
[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.
[0026] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0027] In this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.
[0028] In the first aspect, please see Figures 1 to 3 This application provides a photodetector with a gradient phase structure, comprising a substrate 10, a functional layer 20, and an electrode 30. The functional layer 20 is disposed on one surface of the substrate 10 along its thickness direction, and the electrode 30 is disposed on the surface of the functional layer 20 away from the substrate 10. The electrode 30 is used for connection to an external test circuit or signal acquisition circuit.
[0029] like Figure 1 As shown, the substrate 10 can be made of semiconductor material or insulating material. Semiconductor material can be selected from, for example, single crystal silicon (Si), single crystal germanium (Ge), silicon germanium (SiGe) or silicon carbide (SiC); insulating material can be organic insulator, inorganic insulator or combination thereof, for example, insulating material can be silicon oxide (SiO2).
[0030] like Figure 1 and Figure 2 As shown, the functional layer 20 is disposed on the substrate 10. The functional layer 20 includes two phase structures: SnS and Sn2S3. Specifically, in the radial direction from the center to the outer edge of the functional layer 20, the relative molar content of Sn2S3 material in SnS and Sn2S3 shows a gradient increasing trend. This gradient does not require a clear abrupt interface between adjacent regions; it can manifest as a continuously varying phase content distribution or as an approximately continuous gradient change between multiple radial regions.
[0031] like Figure 3As shown, electrode 30 is a ring electrode. This ring electrode employs a concentric circle structure, meaning a central electrode is positioned in the central region of functional layer 20, and multiple ring electrodes are positioned outside the central electrode. By selecting different ring electrodes to connect to the central electrode, differences in photoelectric response across different radial span regions of functional layer 20 can be detected. This structure effectively matches the radial gradient phase structure of functional layer 20, ensuring that the charge collection direction of the device matches the radial bandgap change direction of functional layer 20.
[0032] Furthermore, it should be noted that the electrode 30 material can be any conductive material selected according to device requirements. For example, the electrode 30 can be made of gold, silver, platinum, titanium, chromium, aluminum, or composite metals. The electrode 30 can be formed through vacuum evaporation, magnetron sputtering, electron beam evaporation, or mask patterning processes. The thickness of the electrode 30, the width of the rings, the spacing between adjacent rings, and the number of electrodes 30 can be adjusted according to the target detection area, the number of test channels, and the device size, as long as electrical connection with the functional layer 20 and photoelectric signal acquisition are achieved.
[0033] like Figure 2 As shown, in some embodiments, the relative molar content of Sn2S3 within the functional layer 20 of the fabricated device increases continuously from 40% to 50% in the central region to 70% to 90% in the edge region. For example... Figure 4 The X-ray diffraction pattern shown confirms that the diffraction peak intensities of Sn2S3-related crystalline phases gradually increase in the radial direction from the center to the edge of functional layer 20. For example, the diffraction peaks corresponding to the Sn2S3(103) crystalline phase and the diffraction peaks corresponding to the superposition of SnS(040) and Sn2S3(211) crystalline phases all increase with radial position. This indicates that the relative molar content of Sn2S3 in functional layer 20 increases in a gradient along the radial direction, and a spatially continuous phase transition gradient has been successfully constructed in functional layer 20.
[0034] Because SnS and Sn₂S₃ have different band structures and light absorption characteristics, as the relative molar content of Sn₂S₃ in functional layer 20 increases radially, the band gap of functional layer 20 also changes with the radial position. Thus, functional layer 20 forms a band structure with spatially continuous variation characteristics in the planar radial direction. This endows the thin film with planar multispectral discrimination capability, enabling different wavelength bands of light response at different radial positions within the same thin film, thereby providing a physical basis for on-chip multi-region functional integration. The functional layer 20 of the photodetector undergoes a continuous compositional phase transition from its center to its edge, breaking the in-plane physical symmetry of the functional layer 20. This enables continuous spatial modulation of the device bandgap from the center to the edge of the functional layer 20 and spontaneously generates a transverse built-in electric field within the functional layer 20. This transverse built-in electric field can effectively drive the transverse separation efficiency of photogenerated carriers, overcoming the problem of the lack of transverse transport driving force in the longitudinal gradient structure. like Figure 5 and Figure 6 As shown, in some embodiments, the bandgap of the functional layer 20 is 0.93~1.3 eV. Furthermore, the bandgap of the functional layer 20 decreases gradually from the center to the outer edge in a radial direction. Specifically, in the radial direction, the bandgap of the functional layer 20 decreases from 1.3 eV in the central region to 0.93 eV in the edge region. This spatially continuous bandgap gradient allows the central region of the film to primarily absorb high-energy, short-wavelength light, while the edge region can absorb lower-energy, long-wavelength light, thereby extending the photoelectric response band of the photodetector to a continuous band from visible to near-infrared light.
[0035] like Figure 7 and Figure 8 As shown, in some embodiments, under the aforementioned radial gradient phase structure, the functional layer 20 exhibits photoelectric response to incident light in the wavelength range of 400 nm to 808 nm. Furthermore, because the functional layer 20 has different SnS / Sn2S3 phase ratios and different bandgap widths from its center to its outer edge, the device can generate photocurrent responses of varying intensities when light illuminates different radial regions. For example... Figure 7 As shown, under illumination in the 400nm~650nm wavelength range, the photodetector device demonstrates that it achieves a spatially resolved, broadband photoelectric response in the visible to near-infrared light band by reading the photocurrent between the central electrode 30 and different radial ring electrodes 30. Specifically, the central electrode 30 region of the functional layer 20 exhibits a relatively stronger photoelectric response to short-wavelength illumination (e.g., 400nm~500nm); the span from the center to the edge of the functional layer 20 shows a relatively stronger photoelectric response to orange, red, and even near-infrared wavelengths (600nm~800nm). This characteristic allows the same functional layer 20 to be used not only for near-infrared photoelectric detection but also to provide a material basis for broadband response, spatially resolved detection, and on-chip integrated photodetector devices.
[0036] Furthermore, in some embodiments, the thickness of the functional layer 20 is any value within the range of 150nm to 340nm, for example, it can be 150nm, 170nm, 190nm, 200nm, 210nm, 230nm, 250nm, 270nm, 290nm, 300nm, 320nm, or 340nm. Optionally, the thickness of the functional layer 20 can be 210nm. It should be noted that the thickness of the functional layer 20 has no effect on its radial bandgap distribution structure or photoelectric response band, but only on the light absorption rate. Therefore, the specific thickness of the functional layer 20 is not limited and can be adaptively adjusted according to photoelectric detection requirements.
[0037] Currently, the fabrication of radially gradient composition thin films is more challenging than that of vertically gradient composition thin films. This is especially true for tin-sulfur system materials, which, despite possessing various thermodynamically stable phases (such as orthorhombic SnS, layered semiconductor SnS2, and triclinic Sn2S3), exhibit demanding phase transition conditions from orthorhombic SnS to triclinic Sn2S3. Even bulk materials require high temperature and pressure environments for this phase transition to occur. This further increases the difficulty of fabricating radially gradient tin selenide thin films. Therefore, developing efficient and controllable fabrication techniques for tin selenide radially gradient phase structure thin films has significant research value and application prospects.
[0038] like Figure 9 As shown, to improve the above-mentioned problems, this application also provides a method for fabricating a photodetector with a gradient phase structure, the method comprising the following steps: S1, Provide substrate 10.
[0039] S2. A SnS thin film is formed on the substrate 10 to obtain a substrate.
[0040] S3. At a first temperature, phosphorus vapor is introduced to induce a gradient phase transformation of some SnS in the SnS film from the edge to the center to Sn2S3, so as to form a functional layer 20; the relative molar content of Sn2S3 formed by the phase transformation increases in a gradient direction from the center to the outer edge of the functional layer 20.
[0041] S4. Electrode 30 is deposited on the functional layer 20 to form a photodetector.
[0042] In this preparation method, a SnS thin film is first formed on a substrate 10. Then, phosphorus vapor is introduced as a chemical inducer. The phosphorus vapor diffuses into the interlayer structure of the SnS thin film from the edge to the center, promoting the rearrangement of Sn-S bonds and even the reconstruction of the crystal structure within the film. This lowers the kinetic energy barrier for the SnS to Sn2S3 phase transition, allowing the SnS thin film to undergo a phase transition at a relatively low initial temperature. Simultaneously, because the diffused phosphorus vapor forms a diffusion concentration gradient that decreases from the outer edge to the center in the film, the effect of phosphorus vapor in inducing the phase transition in the SnS thin film decreases from the edge to the center. This results in a gradient distribution of the Sn2S3 phase structure introduced into the film, and a functional layer 20 with a gradient increase in the relative molar content of Sn2S3 from the center to the outer edge.
[0043] The above preparation method utilizes the radial diffusion differences of phosphorus vapor in SnS thin films to induce phase transitions of varying degrees in the SnS thin films under low-temperature conditions, thereby forming a continuously varying SnS / Sn2S3 phase structure from the center to the outer edge in the monolithic functional layer 20. This method does not require high-temperature and high-pressure processing, nor does it require multiple depositions of thin films with different compositions. The process flow is relatively simple and suitable for preparing planar radial gradient thin films.
[0044] In some embodiments, in step S1, the substrate 10 may be a semiconductor substrate 10 or an insulating substrate 10 for growing the thin film. Furthermore, to improve the bonding stability between the SnS thin film and the substrate 10 and to reduce the impact of surface contaminants on subsequent thin film growth and phosphorus-induced phase transition, the substrate 10 may be cleaned before depositing the SnS thin film. Specifically, the substrate 10 may be ultrasonically cleaned sequentially with acetone, ethanol, and deionized water, followed by drying with nitrogen. If necessary, ultraviolet ozone treatment, oxygen plasma treatment, or low-temperature drying treatment may also be used to remove organic residues on the surface of the substrate 10 and improve surface cleanliness.
[0045] In step S2, a SnS thin film can be formed on the substrate 10 using magnetron sputtering, thermal evaporation, chemical vapor deposition, pulsed laser deposition, or other thin film formation processes feasible in the art. For example, in some embodiments, radio frequency magnetron sputtering can be used to form the SnS thin film on the substrate 10. Specifically, the sputtering chamber is first evacuated to a vacuum state to reduce the influence of oxygen and water vapor on the film composition; then, argon gas is introduced into the chamber as the working gas, and a SnS thin film is sputtered on the surface of the substrate 10 using a SnS target. The argon gas flow rate can be controlled between 20 sccm and 60 sccm, the radio frequency power of the SnS target can be controlled between 50 W and 100 W, and the sputtering time can be controlled between 10 minutes and 30 minutes. During the preparation process, the thickness, density, and crystallinity of the SnS thin film can be adjusted as needed by adjusting the sputtering power, gas flow rate, and deposition time. After deposition, a substrate consisting of the substrate 10 and the SnS thin film is obtained.
[0046] like Figure 10 As shown, in some embodiments, step S3 includes the following steps: S31. Place the red phosphorus and the substrate in two temperature zones of the furnace body, respectively.
[0047] like Figure 10 As shown, in step S31, a tube furnace with dual temperature zones is used to perform a gradient phase transition of the thin film components. Specifically, bulk red phosphorus is placed in a quartz boat, which is then placed in the first temperature zone of the tube furnace; the substrate prepared in step S2 is placed in the second temperature zone of the tube furnace. In the tube furnace, the quartz boat containing the red phosphorus and the substrate are positioned in the same direction, and the distance between the red phosphorus and the substrate is controlled to be any distance within the range of 20cm to 24cm, for example, the spacing can be 20cm, 21cm, 22cm, 23cm, or 24cm.
[0048] S32. The red phosphorus is heated at a second temperature, and the substrate is heated at the first temperature. An inert gas is introduced into the furnace to facilitate the transport of phosphorus vapor evaporated from the red phosphorus to the surface of the substrate and induce a partial SnS phase transformation in the SnS film to Sn2S3, thereby forming a functional layer 20 in which the relative molar content of Sn2S3 increases in a gradient from the center to the outer edge.
[0049] like Figure 10 As shown, in step S32, a protective gas is introduced into the tube furnace, and the introduced inert gas flows from the first temperature zone to the second temperature zone. The first temperature zone is heated to the second temperature, causing the blocky red phosphorus to evaporate and form phosphorus vapor under the second temperature heating. The phosphorus vapor is transported to the substrate surface by the inert gas, and the second temperature zone is heated to the first temperature, and the substrate is heated at the first temperature for 50-70 minutes.
[0050] In this process, phosphorus vapor transported to the second temperature region diffuses in a gradient decreasing from the edge to the interior of the SnS film. The phosphorus vapor penetrating into the interlayer of the SnS film promotes lattice structure reconstruction, thereby lowering the kinetic energy barrier for the SnS to Sn₂S₃ phase transition. This allows a portion of the SnS on the substrate to undergo a phase transition at the first temperature. Furthermore, since the concentration of phosphorus vapor penetrating into the SnS film gradually decreases from the outer edge to the center, the effect of phosphorus vapor in inducing the phase transition in the SnS film decreases from the edge to the center. Consequently, the Sn₂S₃ content formed by the phase transition within the functional layer 20 decreases in a gradient from the outer edge to the center in the radial direction.
[0051] In some embodiments, in step S32, the first temperature for heating the second temperature zone can be any value within the range of 150°C to 350°C, for example, 150°C, 200°C, 250°C, 300°C, or 350°C. The second temperature for heating the first temperature zone can be any value within the range of 200°C to 500°C, for example, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, or 500°C.
[0052] In some embodiments, in step S4, an electrode 30 is deposited on the surface of the functional layer 20 using an electron beam evaporation apparatus and a metal mask to fabricate a photodetector with a gradient phase structure. In step S4, the formed electrode 30 can be a ring electrode, comprising a central electrode 30 located at the center of the plane of the functional layer 20 and a plurality of annular ring electrodes 30 arranged around the central electrode 30.
[0053] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A photodetector with a gradient phase structure, characterized in that, include: Substrate; A functional layer is disposed on the substrate, the functional layer comprising SnS and Sn2S3; Electrodes are disposed on the functional layer; In particular, the molar content of Sn2S3 in SnS and Sn2S3 increases in a gradient from the center to the outer edge of the functional layer in the radial direction.
2. The photodetector according to claim 1, characterized in that, The bandgap of the functional layer is 0.93~1.3eV.
3. The photodetector according to claim 2, characterized in that, Along the radial direction from the center to the outer edge of the functional layer, the bandgap width of the functional layer decreases in a gradient.
4. The photodetector according to claim 1, characterized in that, The functional layer has a photoelectric response to incident light with wavelengths of 400nm to 808nm.
5. The photodetector according to claim 1, characterized in that, The substrate is a semiconductor substrate or an insulating substrate.
6. The photodetector according to claim 1, characterized in that, The electrode is a circular ring electrode.
7. A method for fabricating a photodetector with a gradient phase structure, characterized in that, include: Provide substrate; A SnS thin film is formed on the substrate to obtain a substrate; At a first temperature, phosphorus vapor is introduced to induce a partial SnS phase transformation in the SnS film to Sn2S3, thereby forming a functional layer; wherein, from the center to the outer edge of the functional layer, the relative molar content of the Sn2S3 formed by the phase transformation increases in a gradient; the first temperature is 150℃~350℃; Electrodes are deposited on the functional layer to form a photodetector.
8. The preparation method according to claim 7, characterized in that, The step of introducing phosphorus vapor at the first temperature to induce a partial SnS phase transformation in the SnS film to Sn2S3 includes: The red phosphorus and the substrate were placed in two temperature zones of the furnace body, respectively. The red phosphorus is heated at a second temperature, and the substrate is heated at the first temperature; an inert gas is introduced into the furnace to facilitate the transport of phosphorus vapor evaporated from the red phosphorus to the surface of the substrate and induce a partial SnS phase transformation in the SnS film to Sn2S3; the second temperature is 200℃~500℃.
9. The preparation method according to claim 7 or 8, characterized in that, The step of introducing phosphorus vapor at the first temperature to induce a partial SnS phase transformation in the SnS film to Sn2S3 includes: The introduced phosphorus vapor forms a diffusion gradient within the SnS film, causing the relative content of Sn2S3 formed by phase transformation within the SnS film to decrease from the edge to the center region; the diffusion gradient decreases in the radial direction from the outer edge to the center of the SnS film.
10. The preparation method according to claim 8, characterized in that, In the furnace body, the distance between the red phosphorus and the substrate is 20-24 cm; and / or, the heating time for the substrate is 50-70 minutes.