Photodetector and method for manufacturing a photodetector

Abstract

The application provides a photoelectric detector and a preparation method of the photoelectric detector. The photoelectric detector comprises at least two photoelectric response units. Each photoelectric response unit comprises a light-sensing region and an electrode electrically connected to the light-sensing region, and is used for converting incident light into an electric signal. The at least two photoelectric response units are arranged in a stacking mode along a light incidence direction, have corresponding spectral response ranges, and have coinciding orthographic projections of the light-sensing regions in a plane perpendicular to the light incidence direction. The application can improve the space utilization and detection accuracy of the photoelectric detector.

Description

Technical Field

[0001] This application relates to the field of photoelectric detection equipment, and more specifically, to a photodetector and a method for fabricating the photodetector. Background Technology

[0002] In the post-Moore's Law era, with the rapid development of micro-nano optoelectronic technology, photodetectors are undergoing a leap from single light intensity detection to multi-dimensional spectral sensing. Light is the carrier of material information, and different spectral bands carry differentiated physical and chemical characteristics: ultraviolet light corresponds to the high-energy electronic transitions and fine surface morphology features of materials; visible light carries rich color information and is an extension of human visual perception; near-infrared light has excellent penetrating power and molecular fingerprint recognition capabilities. In complex scenarios such as environmental monitoring, machine vision, and non-destructive testing in modern agriculture, target signals are often polychromatic light. In this case, the ability to achieve synchronous and independent detection across a wide spectral band of ultraviolet-visible-near-infrared light directly determines whether the system can accurately reproduce the true physicochemical properties of the target object.

[0003] However, existing broadband photodetectors face an inherent contradiction between "wide wavelength response" and "spectral discrimination capability." While traditional photodetectors (such as graphene- or perovskite-based devices) can cover a wide wavelength range from ultraviolet to infrared, they are essentially integrators of photon energy, outputting the current value of photogenerated carriers. They cannot distinguish whether the photocurrent is generated by ultraviolet, visible, or near-infrared photons. This detection mode leads to severe spectral information aliasing, making the system highly susceptible to false alarms or feature loss when faced with complex incident light (e.g., unable to distinguish between an ultraviolet radiation source and a beam of ordinary strong sunlight), thus losing the ability to accurately analyze and logically judge the scene.

[0004] To achieve spectral resolution, existing technologies often employ "external filters / spectral prisms" or "multiple detector planar arrays." However, this not only significantly increases the system's size and optical path complexity, limiting the integration of devices, but also causes parallax due to the spatial separation of detection units in different bands, leading to low detection accuracy. Summary of the Invention

[0005] The purpose of this application is to provide a photodetector and a method for preparing the photodetector, so as to improve the detection accuracy and space utilization of the photodetector.

[0006] In a first aspect, the present invention provides a photodetector, comprising at least two photoresponse units, each photoresponse unit comprising a photosensitive region and an electrode electrically connected to the photosensitive region, the photoresponse unit being used to convert incident light into an electrical signal; The at least two photoelectric response units are stacked along the light incident direction, and the spectral response ranges of the at least two photoelectric response units are different from each other; The photosensitive areas of the at least two photoresponse units overlap in their orthogonal projection onto a plane perpendicular to the light incident direction.

[0007] In the above implementation process, by coaxially aligning the photosensitive areas of the first photoelectric response unit and the second photoelectric response unit, their spatial positions coincide, avoiding different observation angles and thus parallax, ultimately improving detection accuracy. Simultaneously, the orthographic projection of the photosensitive areas of the first and second photoelectric response units coincides, improving space utilization.

[0008] In an optional embodiment, the photosensitive area is made of a semiconductor photoresponse material; The at least two photoresponse units are stacked along the light incident direction in order of decreasing band gap of the semiconductor photoresponse material.

[0009] In the above implementation process, the photoresponse material can be used as a semiconductor photoresponse material to utilize the bandgap difference of the semiconductor photoresponse material to realize a first photoresponse unit and a second photoresponse unit with different spectral response ranges. In an optional embodiment, a dielectric insulating layer is also included; wherein the dielectric insulating layer is disposed between two adjacent photoresponse units.

[0010] In the above implementation process, the dielectric insulating layer can insulate the photoelectric response units from each other, reducing the probability of mutual interference between the photoelectric response units.

[0011] In an optional embodiment, the photosensitive area and the electrode form a detection circuit; wherein the detection circuits of each photoelectric response unit are independent of each other.

[0012] In the above implementation process, the photosensitive area and the electrode form a detection circuit, wherein the detection circuits of each photoelectric response unit are independent of each other, thereby reducing the probability of mutual interference between photoelectric response units.

[0013] In an optional embodiment, the photodetector includes three photoresponse units; The spectral response ranges of the three photoelectric response units correspond to the ultraviolet light band, the visible light band, and the infrared light band, respectively.

[0014] In the above implementation process, three photoelectric response units can detect ultraviolet light, visible light, and infrared light.

[0015] Secondly, the present invention provides a method for fabricating a photodetector, the method being used to fabricate a photodetector as described in any of the foregoing embodiments, the method comprising: At least two photoresponse units of semiconductor photoresponse material are transferred onto the substrate of the photoresponse unit to form the photosensitive area of ​​each photoresponse unit, and electrodes of each photoresponse unit are prepared to form the at least two photoresponse units; wherein the photosensitive area of ​​each photoresponse unit is electrically connected to the corresponding electrode. The at least two photoelectric response units are stacked along the light incident direction, such that the photosensitive areas of each photoelectric response unit coincide on the orthographic projection of a plane perpendicular to the light incident direction; wherein the spectral response ranges of the at least two photoelectric response units are different from each other.

[0016] In the above-mentioned process, the above-mentioned preparation method can be used to prepare a photodetector that can improve space utilization and has higher detection accuracy.

[0017] In an optional embodiment, before transferring the semiconductor photoresponse materials of at least two photoresponse units onto the substrate of the photoresponse unit, the fabrication method further includes: A precursor solution of a liquid thermosetting polymer is spin-coated onto the surface of the substrate of the photoelectric response unit, and the liquid thermosetting polymer is cured and baked. After the precursor solution solidifies, a thin film is formed on the surface of the substrate of the photoelectric response unit, and the thin film is a dielectric support layer.

[0018] In the above-described process, the first-formed dielectric support layer can provide support during the transfer of the single-layer photoresponse unit and can also be used as an insulating layer between the response units. Furthermore, compared to existing fabrication processes, this step does not hinder material transfer or subsequent electrode fabrication before material transfer. Ultimately, it facilitates the transfer of the dielectric support layer along with the device on top of it to the first layer of photoresponse units using a stamp, thus avoiding the need to re-transfer the insulating layer.

[0019] In an optional embodiment, stacking the at least two photoresponse units along the light incident direction includes: The composite layer of the photoelectric response unit is peeled off from the substrate of the photoelectric response unit using a viscoelastic stamp. The composite layer of the photoelectric response unit includes a semiconductor photoelectric response material and an electrode, and the dielectric support layer. The composite layer of the photoelectric response unit is transferred above another photoelectric response unit and its position is adjusted so that the photosensitive areas of each photoelectric response unit coincide on the orthographic projection on a plane perpendicular to the light incident direction.

[0020] In the above implementation process, viscoelastic stamps can be used for transfer and stacking, simplifying the transfer process.

[0021] In an optional embodiment, the curing and baking of the liquid thermosetting polymer includes: The liquid thermosetting polymer is baked at a temperature of 100~150℃ for 2 minutes to solidify the liquid thermosetting polymer.

[0022] In the above-mentioned process, after the liquid thermosetting polymer is cured under these conditions, it is easy to use a viscoelastic stamp to separate the dielectric support layer from the underlying silicon wafer without damage.

[0023] In an optional embodiment, after the liquid thermosetting polymer has cured, the preparation method further includes: The thermosetting polymer is baked at a temperature of 200~300℃ for 30~60 minutes.

[0024] In the above process, the thermosetting polymer after baking and curing can improve the resistance of the dielectric support layer to acid and organic reagent corrosion. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic flowchart of a method for fabricating a photodetector provided in an embodiment of this application; Figure 2 This is a schematic diagram of a broadband stacked device for ultraviolet, visible, and near-infrared wavelengths provided in an embodiment of this application; Figure 3 This is a fabrication process flow diagram of a broadband stacked device in the ultraviolet, visible, and near-infrared bands provided in an embodiment of this application; Figure 4 This is an optical image comparing a viscoelastic stamp before and after peeling, provided in an embodiment of this application. Detailed Implementation

[0026] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0027] In a first aspect, the present invention provides a photodetector, comprising at least two photoresponse units, each photoresponse unit comprising a photosensitive region and an electrode electrically connected to the photosensitive region, the photoresponse unit being used to convert incident light into an electrical signal; The at least two photoelectric response units are stacked along the light incident direction, and the spectral response ranges of the at least two photoelectric response units are different from each other; The photosensitive areas of the at least two photoresponse units overlap in their orthogonal projection onto a plane perpendicular to the light incident direction.

[0028] In this embodiment, the photoelectric response unit refers to the physical functional layer that can convert the energy of incident photons into current or voltage. It is the basic module for the detector to realize photoelectric signal conversion. It can be a photodiode based on III-V compound or a photoconductive device based on organic semiconductor.

[0029] In this embodiment, the photosensitive area refers to the semiconductor material area in the photoelectric response unit that actually performs the light absorption function. The area of ​​this area directly determines the sensitivity and resolution of the device. It can be a rectangular pixel area or a circular photosensitive surface.

[0030] In this embodiment, orthographic projection coincidence means that the geometric centers of the upper and lower photosensitive areas are aligned and there is no overlap error in a view perpendicular to the direction of light propagation. This coincidence can be achieved by submicron-level photolithography alignment or by self-aligned growth process.

[0031] In this embodiment, including at least two photoelectric response units means including two photoelectric response units, or it can include three or more photoelectric response units, wherein each photoelectric response unit has a different spectral response range.

[0032] In the above implementation process, by coaxially aligning the photosensitive areas of the first photoelectric response unit and the second photoelectric response unit, their spatial positions coincide, avoiding different observation angles and thus parallax, ultimately improving detection accuracy. Simultaneously, the orthographic projection of the photosensitive areas of the first and second photoelectric response units coincides, improving space utilization.

[0033] In an optional embodiment, the photosensitive area is made of a semiconductor photoresponse material; The at least two photoresponse units are stacked along the light incident direction in order of decreasing band gap of the semiconductor photoresponse material.

[0034] In this embodiment, semiconductor photoelectric response material refers to semiconductor material whose bandgap energy can match the energy of a specific photon. The spectral response range is divided by selecting materials with different bandgap, which can be silicon (Si) or gallium arsenide (GaAs).

[0035] In this embodiment, the order of decreasing bandgap refers to the fact that the bandgap width (Eg) of each layer of material decreases sequentially from the first layer to the bottom layer when light is incident, so as to achieve the layer-by-layer absorption of photons of different energies. It can be a three-layer structure of "gallium nitride (GaN) / silicon (Si) / germanium (Ge)" or a two-layer structure of "gallium phosphide (GaP) / gallium arsenide (GaAs)".

[0036] In the above implementation process, the photoelectric response material can be used as a semiconductor photoelectric response material, so as to utilize the band gap difference of the semiconductor photoelectric response material to realize the first photoelectric response unit and the second photoelectric response unit with different spectral response ranges.

[0037] In an optional embodiment, a dielectric insulating layer is further included; wherein the dielectric insulating layer is disposed between two adjacent photoresponse units. In the above implementation, the dielectric insulating layer isolates the photoresponse units from each other, reducing the probability of mutual interference between the photoresponse units.

[0038] In an optional embodiment, the photosensitive area and the electrode form a detection circuit; wherein the detection circuits of each photoelectric response unit are independent of each other.

[0039] In this embodiment, the detection circuit refers to the conductive path connecting the photosensitive area and the external readout integrated circuit (ROIC), which is used to extract the photogenerated current and perform integration and amplification. It can be an active pixel circuit containing an integrating capacitor and an operational amplifier, or it can be a simple resistive load circuit.

[0040] In the above implementation process, the photosensitive area and the electrode form a detection circuit, wherein the detection circuits of each photoelectric response unit are independent of each other, thereby reducing the probability of mutual interference between photoelectric response units.

[0041] In an optional embodiment, the photodetector includes three photoresponse units; The spectral response ranges of the three photoelectric response units correspond to the ultraviolet light band, the visible light band, and the infrared light band, respectively.

[0042] In the above implementation process, three photoelectric response units can detect ultraviolet light, visible light, and infrared light.

[0043] Secondly, the present invention provides a method for fabricating a photodetector, the method being used to fabricate a photodetector as described in any of the foregoing embodiments, the method comprising: At least two photoresponse units of semiconductor photoresponse material are transferred onto the substrate of the photoresponse unit to form the photosensitive area of ​​each photoresponse unit, and electrodes of each photoresponse unit are prepared to form the at least two photoresponse units; wherein the photosensitive area of ​​each photoresponse unit is electrically connected to the corresponding electrode. The at least two photoelectric response units are stacked along the light incident direction, such that the photosensitive areas of each photoelectric response unit coincide on the orthographic projection of a plane perpendicular to the light incident direction; wherein the spectral response ranges of the at least two photoelectric response units are different from each other.

[0044] In the above-described process, the above-described preparation method can be used to prepare a photodetector that can improve space utilization and has higher detection accuracy.

[0045] In an optional embodiment, before transferring the semiconductor photoresponse materials of at least two photoresponse units onto the substrate of the photoresponse unit, the fabrication method further includes: A precursor solution of a liquid thermosetting polymer is spin-coated onto the surface of the substrate of the photoelectric response unit, and the liquid thermosetting polymer is cured and baked. After the precursor solution solidifies, a thin film is formed on the surface of the substrate of the photoelectric response unit, and the thin film is a dielectric support layer.

[0046] In the above-described process, the first-formed dielectric support layer can provide support during the transfer of the single-layer photoresponse unit and can also be used as an insulating layer between the response units. Furthermore, compared to existing fabrication processes, this step does not hinder material transfer or subsequent electrode fabrication before material transfer. Ultimately, it facilitates the transfer of the dielectric support layer along with the device on top of it to the first layer of photoresponse units using a stamp, thus avoiding the need to re-transfer the insulating layer.

[0047] In an optional embodiment, stacking the at least two photoresponse units along the light incident direction includes: The composite layer of the photoelectric response unit is peeled off from the substrate of the photoelectric response unit using a viscoelastic stamp. The composite layer of the photoelectric response unit includes a semiconductor photoelectric response material and an electrode, and the dielectric support layer. The composite layer of the photoelectric response unit is transferred above another photoelectric response unit and its position is adjusted so that the photosensitive areas of each photoelectric response unit coincide on the orthographic projection on a plane perpendicular to the light incident direction.

[0048] In the above implementation process, viscoelastic stamps can be used for transfer and stacking, simplifying the transfer process.

[0049] In an optional embodiment, the curing and baking of the liquid thermosetting polymer includes: The liquid thermosetting polymer is baked at a temperature of 100~150℃ for 2 minutes to solidify the liquid thermosetting polymer.

[0050] In the above-mentioned process, after the liquid thermosetting polymer is cured under these conditions, it is easy to use a viscoelastic stamp to separate the dielectric support layer from the underlying silicon wafer without damage.

[0051] In an optional embodiment, after the liquid thermosetting polymer has cured, the preparation method further includes: The thermosetting polymer is baked at 200-300℃ for 30-60 minutes. In this process, the baked and cured thermosetting polymer improves the resistance of the dielectric support layer to acid and organic reagent corrosion.

[0052] In one specific embodiment of this application, a method for fabricating a broadband vertically integrated photodetector with spectral resolution is provided. This method utilizes a polyimide (PI)-assisted dry transfer technique to align and stack two-dimensional material devices with different band structures in the vertical direction. (See also...) Figure 1 , Figure 1 This is a schematic flowchart illustrating a method for fabricating a photodetector according to an embodiment of this application. Figure 1 As shown, it specifically includes the following steps: S1: Fabrication of the underlying near-infrared detection unit. Silicon / quartz / glass is selected as the target substrate and cleaned. Molybdenum ditelluride (MDT) is transferred to the substrate surface using a mechanical lift-off method. Subsequently, electrodes (such as Cr / Au) are fabricated at both ends of the MDT material using photolithography and magnetron sputtering processes to construct the underlying photodetector unit, which is mainly used to respond to near-infrared light signals.

[0053] S2: Fabrication of the intermediate visible light detection unit (using PI-assisted process). Take a cleaned temporary substrate (such as silicon / quartz / glass) and spin-coat a liquid polyimide (PI) precursor solution onto its surface. Spin-coating parameters are: rotation speed 2000~4000 rpm, time 30~60 seconds, followed by curing and baking at 120~300℃ to form a solid PI film with a thickness of 1~3μm. Molybdenum disulfide material is transferred onto the PI film surface using mechanical exfoliation. Electrodes are then fabricated at both ends of the molybdenum disulfide using micro / nano fabrication processes (photolithography, deposition). At this point, the PI layer serves both as a flexible support layer for this device and as an interlayer insulating medium for subsequent stacking.

[0054] S3: Fabricate the top-layer ultraviolet light detection unit (using PI-assisted process). Repeat a process similar to step S2, transferring germanium diselenide material onto the PI film on another temporary substrate using mechanical lift-off, and fabricating the corresponding electrodes. This layer device is mainly used to respond to ultraviolet light signals.

[0055] S4: Vertical Stacking and Alignment Release. Using a viscoelastic stamp, the "PI thin film-molybdenum disulfide device-electrode" composite layer prepared in step S2 is peeled off entirely from the temporary substrate. With the assistance of a micro-alignment platform, this composite layer is transferred above the bottom molybdenum ditelluride device prepared in step S1, and its position is adjusted so that the molybdenum disulfide channel region is aligned with the molybdenum ditelluride channel region below. Subsequently, the Z-axis is manipulated to slowly lower the viscoelastic stamp until it adheres to the bottom device, and then the platform temperature is raised to 60~120°C and maintained for 2~10 minutes. Afterwards, the Z-axis is slowly raised. Due to the difference in van der Waals interactions between the different materials, the composite layer separates from the viscoelastic stamp and remains above the bottom device. Similarly, the "PI thin film-germanium diselenide device-electrode" composite layer prepared in step S3 is peeled off using a viscoelastic stamp and aligned and released above the intermediate molybdenum disulfide device.

[0056] This specific implementation achieves filterless band resolution at the single-device scale, solving the problem of traditional wideband detectors' full-band response but inability to distinguish between wavelengths. Because traditional wideband detectors are integrating detectors, they respond to all photons with energies above the bandgap, making it impossible to differentiate photon energy (wavelength). This specific implementation creatively constructs a vertical bandgap structure of germanium diselenide (bandgap ~2.7 eV) / molybdenum disulfide (bandgap ~1.5 eV) / molybdenum ditelluride (bandgap ~1 eV). Utilizing the intrinsic absorption characteristics of semiconductor materials, the top-layer germanium diselenide preferentially absorbs ultraviolet light, the middle-layer molybdenum disulfide absorbs visible light, and the bottom-layer molybdenum ditelluride absorbs near-infrared light. This design eliminates the need for any external filters or beam splitters, enabling independent detection of the ultraviolet, visible, and near-infrared bands on a single optical axis, greatly simplifying the optical structure of the multispectral detection system and reducing cost and size.

[0057] Furthermore, this specific method, by combining mechanical exfoliation with PI-assisted transfer, significantly improves the cleanliness and electrical performance of the device interface. Traditional two-dimensional material transfer processes typically use a support layer represented by PMMA (Polymethylmethacrylate) polymers. After transfer, these layers must be removed using organic solvents such as acetone. This process is not only cumbersome but also easily leaves difficult-to-remove polymer residues on the surface of the two-dimensional material, leading to increased carrier scattering and decreased photoelectric responsivity. This invention combines mechanical exfoliation of the two-dimensional material with PI film-assisted transfer. After the device is exfoliated and fabricated on the PI film, polyimide is used as the transfer medium and retained in situ as an interlayer insulating layer, also known as a dielectric insulating layer. This process avoids the introduction of polymers from the source, fundamentally eliminating the risk of interface contamination from organic solvent cleaning, ensuring atomic-level cleanliness of the two-dimensional material surface, thereby significantly improving the responsivity and detectivity of the photodetector.

[0058] Furthermore, this specific implementation achieves zero-parallax multi-band detection, significantly improving the fill factor of the imaging system. Traditional RGB or multispectral detectors often employ planar array arrangements, resulting in spatial displacement of the detection pixels for different bands. This leads to parallax during imaging and greatly reduces the effective photosensitive area of ​​the chip. This specific implementation uses a vertically stacked structure, where the photosensitive areas of the three bands completely overlap in space (Z-axis aligned), eliminating spatial parallax and improving the detection accuracy of the photodetector. Simultaneously, this structure can achieve a higher pixel density within the same area. Therefore, this photodetector is particularly suitable for applications requiring extremely high positional accuracy, such as machine vision and microscopic imaging.

[0059] Furthermore, in the above specific embodiments, the stacking order of the detector materials follows a bandgap gradient, i.e., the bandgap of the upper layer material > the bandgap of the middle layer material > the bandgap of the bottom layer material. Any combination of materials that follows this physical law can be used as an alternative.

[0060] Furthermore, in the above specific embodiments, the top material (UV-responsive layer) can be germanium diselenide or a wide bandgap two-dimensional material (such as hexagonal boron nitride (h-BN), gallium selenide (GaSe), zinc oxide nanosheets (ZnO), perovskite thin films). As long as the material has a sufficiently large bandgap (> 2 eV), mainly absorbs ultraviolet light, and is transparent to visible / infrared light, it can replace germanium diselenide.

[0061] Furthermore, in the above specific embodiments, the middle layer material can be molybdenum disulfide. Alternatives include other transition metal chalcogenides (such as tungsten diselenide (WSe2), tungsten disulfide (WS2), and molybdenum diselenide (MoSe2)). Any material with a band gap between 1.5 eV and 2 eV that can effectively respond to visible light and transmit near-infrared light can replace molybdenum disulfide.

[0062] Furthermore, in the above specific embodiments, the underlying material (near-infrared response layer) can be molybdenum distellide or a narrow bandgap material (such as black phosphorus (BP), platinum diselenide (PtSe2), graphene, colloidal quantum dots, etc.). It should be noted that materials with a narrow bandgap (< 1.2 eV) that can effectively absorb the transmitted low-energy photons can all replace molybdenum distellide.

[0063] Furthermore, in the above specific embodiments, the insulating / supporting material can be polyimide (PI). Other thermosetting or photosensitive polymers, such as SU-8 photoresist, BCB (benzocyclobutene), PMMA (polymethyl methacrylate), PVA (polyvinyl alcohol), etc., can also be used.

[0064] Furthermore, in the above specific embodiments, an alternative to the insulating layer formation method is proposed: In the current approach, PI serves as both a support layer and an insulating layer, and the PI film is peeled off and transferred to the underlying device using a viscoelastic stamp. An alternative approach involves first depositing alumina / silicon dioxide or transferring boron nitride onto the underlying device, then transferring the next layer of material using a conventional wet / dry method, followed by removing the transfer medium. While this method is more cumbersome and may introduce contamination, it can still achieve a vertically stacked structure.

[0065] Furthermore, in the above specific embodiments, regarding the direction of illumination, light can enter from the top of the photodetector. Accordingly, the stacking order is wide bandgap material on top, narrow bandgap material on the bottom, and the bottom substrate is silicon. Alternatively, when light enters from the back using a transparent substrate (such as quartz, sapphire, PET, etc.), the light enters from the substrate, and the stacking order needs to be reversed: wide bandgap material at the bottom (closely attached to the transparent substrate), followed by medium bandgap material, and the top layer is narrow bandgap material.

[0066] Furthermore, in the above specific embodiments, the photodetector can be a three-layer stack, namely, a stack of ultraviolet, visible, and near-infrared layers. It can also be a two-layer stack, for example, only realizing the UV / VIS band or VIS / NIR band stack; or it can be a multi-layer stack, such as further subdividing the visible light band by adding blue light response layer, red light response layer and green light response layer materials.

[0067] Furthermore, in the above specific embodiments, as an example, such as Figure 2As shown, the photodetector comprises, from bottom to top: Substrate: Silicon (Si / SiO2) substrate with a 300nm oxide layer.

[0068] The underlying device (mainly responding in the near-infrared band) consists of mechanically stripped molybdenum ditelluride and Cr / Au source / drain electrodes.

[0069] The first insulating layer is a polyimide film with a thickness of approximately 2 μm.

[0070] The middle layer device (mainly responding in the visible light band) consists of mechanically stripped molybdenum disulfide and Cr / Au source / drain electrodes, located above the first isolation layer.

[0071] The second insulating layer is a polyimide film with a thickness of approximately 2 μm.

[0072] Top-level device (mainly responding in the ultraviolet band): It consists of mechanically stripped germanium diselenide and Cr / Au source / drain electrodes, located above the second isolation layer.

[0073] Based on the above photodetector, please refer to Figure 3 , Figure 3 This is one of the methods provided in this application embodiment, and the specific preparation steps are as follows: Underlying device fabrication: The Si / SiO2 substrate was sequentially ultrasonically cleaned for 10 minutes each in acetone, ethanol, and deionized water. Bulk molybdenum ditelluride (MoDDI) was peeled off and transferred to the substrate surface using a mechanical peeling method with adhesive tape. MoDDI flakes of uniform thickness (20–40 nm) were selected using an optical microscope. Electrode patterns were then defined using DMD lithography, and 20 nm Cr / 100 nm Au were deposited as source / drain electrodes via magnetron sputtering to complete the underlying device fabrication.

[0074] Mid-layer device fabrication (PI-assisted method): A clean temporary silicon wafer substrate was used, and a liquid polyimide precursor was spin-coated. The spin-coating parameters were set as follows: low speed 1500 rpm (15 seconds), high speed 3000 rpm (45 seconds). The sample was then placed on a hot stage and cured at 120°C for 2 minutes, followed by a temperature increase to 200°C for 20 minutes. The resulting PI film was approximately 2 μm thick and exhibited good mechanical flexibility. Molybdenum disulfide flakes were transferred onto the cured PI film surface using a mechanical exfoliation method. Similarly, Cr / Au electrodes were fabricated at both ends of the molybdenum disulfide using micro / nano fabrication processes (DMD lithography + magnetron sputtering deposition).

[0075] Intermediate Layer Peeling and Stacking: Using a viscoelastic stamp, the intermediate layer device surface prepared in the above steps is slowly contacted. By peeling off the PDMS stamp, the entire "PI film-molybdenum disulfide device-electrode" can be completely peeled off from the temporary silicon substrate. Optical images before and after peeling are shown below. Figure 4 As shown. Subsequently, using an alignment and transfer platform equipped with a high-precision micro-manipulation stage, under the view of an optical microscope, the middle layer device on the PDMS stamp was moved directly above the bottom molybdenum ditelluride device. The position was adjusted so that the molybdenum disulfide channel overlapped with the lower molybdenum ditelluride channel along the optical path on the Z-axis. Then, the Z-axis was slowly lowered to bring the PI layer into contact with the bottom device. Assisted release was performed at a temperature below 120°C, and the PMDS (polydimethylsiloxane) stamp was removed. At this point, the "PI film-molybdenum disulfide device-electrode" was completely transferred above the bottom device, and the PI layer also served as the insulating medium between the bottom and middle layers.

[0076] Fabrication and stacking of the top-layer device: Repeating the above process steps, the "PI thin film-germanium diselenide device-electrode" is aligned and released above the middle-layer molybdenum disulfide device. This achieves the fabrication of a vertically integrated photodetector with broad-spectrum multi-band resolution.

[0077] Furthermore, in the above specific implementation, as another example, it is not limited to a specific material combination, and can be applied as long as it conforms to the principle of band gradient (material 1 band > material 2 band > material 3 band). The difference from the first example is that this example uses a different combination of two-dimensional materials.

[0078] In this example, boron nitride is used as the top layer material, with a band gap of approximately 6 eV, and it primarily responds to deep ultraviolet light. In this example, the middle layer material is tungsten disulfide, with a band gap of approximately 1.7 eV, and it primarily responds to visible light. In this example, black phosphorus is used as the base material, with a band gap of approximately 0.3 eV and a response band that extends to the mid-infrared band. In this example, because black phosphorus is unstable in air, the fabrication of the bottom-layer BP device and subsequent stacking in this embodiment must be carried out in a nitrogen-filled glove box. This embodiment demonstrates the universality of the vertical stacking architecture proposed in this invention, allowing for flexible material replacement according to actual detection band requirements.

[0079] Furthermore, in the above specific embodiments, as another example, this example is applicable to flexible wearable electronic devices. In this example, the structure of the photodetector is adjusted as follows: a flexible and transparent polyethylene terephthalate (PET) substrate is selected as the substrate, and the illumination method adopts back-incident, that is, the device enters the device through the transparent substrate. To match the back-incident light path, the material stacking order is reversed from that in Embodiment 1, that is, the bottom layer (closely adjacent to the PET layer) uses a wide bandgap material germanium diselenide, the middle layer uses a medium bandgap material molybdenum disulfide, and the top layer uses a narrow bandgap material molybdenum distelluride.

[0080] In this example, the process was adjusted as follows: First, GeSe2 devices were directly fabricated on a PET substrate. Then, following the PI-assisted transfer method described in Example 1, MoS2 and MoTe2 devices were sequentially stacked on top. It should be noted that due to the poor temperature resistance of the PET substrate, the curing temperature of the PI layer needs to be reduced to 150°C, and the baking time correspondingly extended to 2 hours to ensure the formation of the PI film. This embodiment demonstrates that the technical solution proposed in this invention is not only applicable to rigid silicon substrates but also to the field of flexible transparent electronics, and can be adapted to different optical path designs by adjusting the stacking order.

[0081] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0082] Furthermore, the units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0083] Furthermore, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0084] It should be noted that if the function is implemented as a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0085] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0086] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A photodetector, characterized in that, Includes at least two photoelectric response units; Each of the photoelectric response units includes a photosensitive area and an electrode electrically connected to the photosensitive area, and the photoelectric response unit is used to convert incident light into an electrical signal; The at least two photoelectric response units are stacked along the light incident direction, and the at least two photoelectric response units have corresponding spectral response ranges; The photosensitive areas of the at least two photoresponse units overlap in their orthogonal projection onto a plane perpendicular to the light incident direction.

2. The photodetector according to claim 1, characterized in that, The photosensitive area is made of semiconductor photoelectric response material; The at least two photoresponse units are stacked along the light incident direction in order of decreasing band gap of the semiconductor photoresponse material.

3. The photodetector according to claim 1, characterized in that, It also includes a dielectric insulating layer; wherein the dielectric insulating layer is disposed between two adjacent photoelectric response units.

4. The photodetector according to claim 1, characterized in that, The photosensitive area and the electrode form a detection circuit; wherein the detection circuits of each photoelectric response unit are independent of each other.

5. The photodetector according to claim 2, characterized in that, The photodetector includes three photoelectric response units; The spectral response ranges of the three photoelectric response units correspond to the ultraviolet light band, the visible light band, and the infrared light band, respectively.

6. A method for fabricating a photodetector, characterized in that, The preparation method includes: At least two photoresponse units of semiconductor photoresponse material are transferred onto the substrate of the photoresponse unit to form the photosensitive area of ​​each photoresponse unit, and electrodes of each photoresponse unit are prepared to form the at least two photoresponse units; wherein the photosensitive area of ​​each photoresponse unit is electrically connected to the corresponding electrode. The at least two photoelectric response units are stacked along the light incident direction, such that the photosensitive areas of each photoelectric response unit coincide on the orthographic projection of a plane perpendicular to the light incident direction; wherein the at least two photoelectric response units have corresponding spectral response ranges.

7. The preparation method according to claim 6, characterized in that, Before transferring the semiconductor photoresponse materials of at least two photoresponse units onto the substrate of the photoresponse unit, the fabrication method further includes: A precursor solution of a liquid thermosetting polymer is spin-coated onto the surface of the substrate of the photoelectric response unit, and the liquid thermosetting polymer is cured and baked. After the precursor solution solidifies, a thin film is formed on the surface of the substrate of the photoelectric response unit, and the thin film is a dielectric support layer.

8. The preparation method according to claim 7, characterized in that, Stacking the at least two photoresponse units along the light incident direction includes: The composite layer of the photoelectric response unit is peeled off from the substrate of the photoelectric response unit using a viscoelastic stamp; wherein the composite layer of the photoelectric response unit includes a semiconductor photoelectric response material and an electrode, and the dielectric support layer; The composite layer of the photoelectric response unit is transferred above another photoelectric response unit, and the positions of each photoelectric response unit are adjusted; wherein, after the position adjustment, the photosensitive areas of each photoelectric response unit coincide on the orthographic projection on a plane perpendicular to the light incident direction.

9. The preparation method according to claim 8, characterized in that, The curing and baking of the liquid thermosetting polymer includes: The liquid thermosetting polymer is baked at a temperature of 100~150℃ for a preset time to solidify it.

10. The preparation method according to claim 9, characterized in that, After the liquid thermosetting polymer has cured, the preparation method further includes: The thermosetting polymer is baked at a temperature of 200~300℃ for 30~60 minutes.

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