Photoelectric detector and preparation method thereof
By using Bi1-xSbx alloy to construct a Type-II band-aligned heterojunction with a substrate in a photodetector, the problems of low absorption efficiency and large dark current in the ultraviolet and visible light bands of traditional photodetectors are solved, achieving high-efficiency photoelectric conversion and low-noise performance, which is suitable for optical communication and ultraviolet imaging.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-03-24
AI Technical Summary
Traditional photodetectors suffer from low absorption efficiency in the ultraviolet band, decreased quantum efficiency due to surface defects, and large dark current, which limits their performance improvement in the ultraviolet and visible light bands.
A type-II band-aligned heterojunction was constructed using a Bi1-xSbx alloy as the photodetector layer and substrate to form a strong built-in electric field, which reduced dark current and improved responsivity. Interface defects were optimized through magnetron co-sputtering technology and in-situ annealing process to achieve high-efficiency photoelectric conversion.
It expands the response range of photodetectors to the ultraviolet to visible light band, achieving a combination of high response speed, high quantum efficiency and low noise, meeting the needs of optical communication and ultraviolet imaging.
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Figure CN121728862A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of photodetector technology, and in particular to a photodetector and its fabrication method. Background Technology
[0002] With the rapid development of technologies such as optical communication, environmental monitoring, and optical imaging, the demand for high-performance photodetectors has extended from the visible light band to the ultraviolet light band. However, while traditional mainstream photodetectors (such as those based on silicon and InP materials) perform well in the visible light band, their ultraviolet detection performance faces significant bottlenecks. This is mainly due to three limitations: First, these materials have narrow intrinsic band gaps, resulting in low absorption efficiency for ultraviolet light; second, the dense defect states on the device surface lead to severe recombination of photogenerated carriers, reducing quantum efficiency; and finally, the large dark current severely restricts the signal-to-noise ratio and sensitivity of the detector.
[0003] Therefore, breaking through the limitations of existing material systems, exploring new wide-bandgap semiconductor materials, and designing corresponding optimized device structures have become key to improving the performance of ultraviolet photodetectors and promoting their practical applications. Summary of the Invention
[0004] This application provides a photodetector and its fabrication method to solve the problems of low absorption efficiency, decreased quantum efficiency due to surface defects, and large dark current of traditional materials in the ultraviolet band in related technologies.
[0005] The applicant discovered that topological insulators (TIs) are potential candidate materials for high-performance photodetectors due to their unique surface state properties. 1-x Sb x As a typical 3D topological insulator, the alloy, with its ultra-high carrier mobility and broad-spectrum response, has been considered an ideal choice for overcoming the defects of traditional semiconductor materials. By employing Bi... 1-x Sb x The alloy is used to construct a heterojunction structure between the photodetector layer and the substrate, which enables the photodetector to achieve excellent performance with high responsivity and low dark current in both visible and ultraviolet light bands.
[0006] Based on the above findings, this application provides the following technical solution: In a first aspect, this application provides a photodetector, the photodetector comprising: Substrate; A photodetector layer is disposed on at least a portion of the surface of the substrate and forms a heterostructure with Type-II band alignment between the photodetector layer and the substrate; A driving electrode is disposed on at least a portion of the surface of the photodetector layer away from the substrate.
[0007] The photodetector provided by this application forms a heterojunction with a Type-II energy band alignment between the light detection layer and the substrate, generating a strong built-in electric field, thereby significantly reducing the dark current and improving the responsivity, enabling the detector to maintain high-efficiency photoelectric conversion efficiency under zero bias. This structure effectively expands the light response range of the device in the ultraviolet to visible light band, and significantly improves the carrier migration efficiency due to the existence of the built-in electric field, ultimately achieving excellent comprehensive performance of high response speed, high quantum efficiency, and low noise.
[0008] In some embodiments, the material of the light detection layer includes bismuth antimonide alloy, with the chemical formula Bi 1-x Sb x , where 0 < x < 1. By using the bismuth antimonide alloy, with its ultra-high carrier mobility and broad-spectrum response ability, it works in synergy with the substrate to expand the response range of the photodetector and improve the quantum efficiency. Its surface states effectively enhance the quantum efficiency of the detector, thereby achieving higher sensitivity and lower noise.
[0009] In some embodiments, the thickness of the light detection layer is 20 - 100 nm. The light detection layer within the above thickness range can balance the light absorption efficiency and the defects caused by film stress.
[0010] In some embodiments, the material of the substrate includes InP. Selecting the above material as the substrate can naturally form a heterojunction with a Type-II energy band alignment with the light detection layer. This structure can generate a strong built-in electric field, further optimizing the carrier migration efficiency, so that the detector can obtain a lower dark current and a higher photoelectric responsivity under zero bias, greatly improving the performance of the detector.
[0011] In some embodiments, the thickness of the substrate is 100 - 625 μm. The substrate within the above thickness range is suitable for the COMS process.
[0012] In some embodiments, the material of the driving electrode includes at least one of Ag, Au, C, Cu, Ti, and In. Selecting the above materials as the driving electrode can reduce the surface barrier.
[0013] In some embodiments, the light response wavelength of the photodetector is 300 - 800 nm. The light response wavelength of the photodetector within this range expands the response range of the photodetector from the infrared band of traditional materials to the visible and ultraviolet light bands, meeting the requirements of fields such as optical communication and ultraviolet imaging, and expanding the response range of the photodetector and improving the quantum efficiency through the synergistic effect of the surface states of the material and the interband transition of the substrate.
[0014] In a second aspect, this application provides a method for manufacturing the above-mentioned photodetector, including the following steps: Provide substrate; A photodetector layer is prepared on at least a portion of the surface of the substrate; A drive motor is fabricated on at least a portion of the surface of the photodetector layer away from the substrate.
[0015] The fabrication method provided in this application enables the natural formation of a Type-II band-aligned heterojunction between the photodetector layer and the substrate, successfully reducing the interface defect density and improving the crystal quality of the thin film. This method is simple, scalable, suitable for large-scale production, and has good commercialization prospects.
[0016] In some embodiments, the step of fabricating the photodetector layer includes: The photodetector layer is formed on at least a portion of the substrate surface by depositing the material of the photodetector layer using magnetron co-sputtering technology, followed by in-situ annealing.
[0017] By using magnetron co-sputtering technology and in-situ annealing process, the interface defect density was successfully reduced and the crystal quality of the thin film was improved, so that a heterojunction with Type-II band alignment was naturally formed between the photodetector layer and the substrate.
[0018] In some embodiments, the in-situ annealing temperature is 200-300°C, and the time is 0.1-1 h. By limiting the in-situ annealing temperature and time within the above range, it is beneficial to obtain films of better quality. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is a schematic diagram of the structure of a photodetector provided in an embodiment of this application.
[0021] Figure 2 The current versus voltage (IT) curve of the photodetector provided in Embodiment 1 of this application under 650nm illumination.
[0022] Reference numerals: photodetector 100, substrate 10, photodetector layer 20, driving electrode 30. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0024] The rapid development of fields such as optical communication, environmental monitoring and optical imaging has placed higher demands on the photoelectric performance of photodetectors in the ultraviolet to visible light band.
[0025] Currently, photodetectors in this band mostly use traditional semiconductor materials such as silicon and indium phosphide. Although these materials perform well in the infrared region, their inherent characteristics expose significant limitations in the ultraviolet and visible light bands: on the one hand, the band gap of the material itself limits its efficient absorption of ultraviolet light; on the other hand, the devices suffer from problems such as high surface defect density and large dark current, making it difficult to further improve ultraviolet detection efficiency and signal-to-noise ratio.
[0026] In recent years, topological insulators have provided a new technological path for developing high-performance optoelectronic devices due to their topologically protected gapless surface states, extremely high carrier mobility, and wide spectral response characteristics. Among them, Bi... 1-x Sb x As a typical three-dimensional topological insulator, alloys are considered to be potential materials for overcoming the aforementioned defects of traditional semiconductor materials.
[0027] However, how to make Bi 1-x Sb x Combining the superior physical properties of materials with mature semiconductor processes to construct device structures with efficient charge separation capabilities and stable performance remains a technical problem to be solved in this field. Therefore, this invention proposes a novel photodetector and its fabrication method.
[0028] The term "Type-II band-aligned heterojunction" in this application refers to a special band arrangement formed at the interface of two different semiconductor materials. In this structure, the conduction band bottom and valence band top of one material are both lower in energy than the corresponding bands of the other material, resulting in an "interleaved" band arrangement at the interface. This unique band shift forces photogenerated electrons and holes to spontaneously separate and migrate into different material layers in space—electrons converge and become confined in the conduction band of the lower-energy material (such as InP in this case), while holes converge and become confined in the higher-energy material (such as Bi in this case). 1-x Sb xIn the valence band of the alloy, this physical separation effect creates a strong built-in electric field at the interface, which greatly accelerates the separation and transport of charges and effectively suppresses the recombination of electrons and holes.
[0029] This application provides a photodetector and its fabrication method to solve the problems of low absorption efficiency, decreased quantum efficiency due to surface defects, and large dark current of traditional materials in the ultraviolet and visible light bands in related technologies.
[0030] In one aspect, this application provides a photodetector 100, with reference to Figure 1 The photodetector 100 includes: Substrate 10; A photodetector layer 20 is disposed on at least a portion of the surface of the substrate 10 and forms a heterostructure with Type-II band alignment between the photodetector layer 20 and the substrate 10. A driving electrode 30 is disposed on at least a portion of the surface of the photodetector layer 20 away from the substrate 10.
[0031] The photodetector provided in this application generates a strong built-in electric field by forming a Type-II band-aligned heterojunction between the photodetector layer and the substrate. This significantly reduces dark current and improves responsivity, enabling the detector to maintain high photoelectric conversion efficiency at zero bias. This structure effectively extends the optical response range of the device from ultraviolet to visible light, and the presence of the built-in electric field significantly improves carrier migration efficiency, ultimately achieving excellent overall performance with high response speed, high quantum efficiency, and low noise.
[0032] Furthermore, the driving electrodes can also be arranged in a symmetrical dual-electrode structure on both sides of the photodetector layer, directly covering the upper surface of the photodetector layer (or partially embedded in the edge of the photodetector layer), forming a symmetrical contact layout on the left and right or front and back.
[0033] For details, see Figure 1 As shown, in the structure of the photodetector 100, the substrate 10 serves as the basic support layer, on which a photodetector layer 20 is disposed to receive ultraviolet light incident from above and perform photoelectric conversion and other related detection operations; driving electrodes 30 are symmetrically arranged on both sides of the photodetector layer 20 to provide driving signals to the photodetector layer 20 or to transmit electrical signals generated by detection, and the various parts work together to realize the photodetector function.
[0034] Furthermore, the working process of the photodetector 100 is as follows: When light irradiates the light detection layer, the material absorbs the photon energy to generate electron-hole pairs; in the Type-II energy band alignment structure formed by the light detection layer and the substrate, the conduction band and valence band edges are staggered, and electrons and holes are respectively confined in different material layers. This energy band step promotes the rapid separation of photo-generated carriers in the opposite direction under the action of the built-in electric field, effectively suppressing the recombination loss; the separated electrons and holes migrate towards the driving electrodes respectively to form a photocurrent signal; the driving electrodes collect these carriers and convert them into measurable electrical signals to achieve the light detection function. This structure optimizes the carrier separation efficiency through energy band engineering and significantly improves the optoelectronic conversion performance.
[0035] In some embodiments provided by the present application, the material of the light detection layer 20 includes bismuth antimonide alloy with the chemical formula Bi 1-x Sb x , where 0 < x < 1. By using the bismuth antimonide alloy, with its ultra-high carrier mobility and broad-spectrum response ability, and in cooperation with the substrate, the response range of the photodetector is expanded, and the quantum efficiency is improved. Its surface states effectively enhance the quantum efficiency of the detector, thus achieving higher sensitivity and lower noise.
[0036] In some embodiments provided by the present application, the thickness of the light detection layer 20 is 20 - 100 nm. The light detection layer within the above thickness range can balance the light absorption efficiency and the defects caused by film stress.
[0037] In some embodiments provided by the present application, the material of the substrate 10 includes InP. Selecting the above material as the substrate can naturally form a heterojunction with a Type-II energy band alignment with the light detection layer. This structure can generate a strong built-in electric field, further optimizing the carrier migration efficiency, so that the detector can obtain a lower dark current and a higher optoelectronic responsivity under zero bias voltage, greatly improving the performance of the detector.
[0038] In some embodiments provided by the present application, the thickness of the substrate 10 is 100 - 625 μm. The substrate within the above thickness range can be applicable to the COMS process.
[0039] In some embodiments provided by the present application, the material of the driving electrode 30 includes at least one of Ag, Au, C, Cu, Ti, and In. Selecting the above materials as the driving electrode can reduce the surface barrier.
[0040] In some embodiments provided in this application, the photodetector 100 has a light response wavelength of 300-800 nm. This range of photodetector wavelengths extends the response range of the photodetector from the infrared band of conventional materials to the visible and ultraviolet bands, meeting the needs of fields such as optical communication and ultraviolet imaging. Furthermore, through the synergistic effect of material surface states and substrate band transitions, the response range of the photodetector is expanded and quantum efficiency is improved.
[0041] Secondly, this application provides a method for preparing the above-described photodetector, comprising the following steps: Step S100: Provide a substrate; In this step, by selecting a substrate of a specific material, a crystal template and mechanical support can be provided for the subsequent construction of heterojunctions.
[0042] It should be noted that the material of the substrate is not specifically limited, and those skilled in the art can make flexible choices as needed. According to a specific embodiment of this application, the material of the substrate is InP, and the crystal orientation of the InP crystal is (100), abbreviated as InP(100).
[0043] Step S200: Prepare a photodetector layer on at least a portion of the surface of the substrate; In this step, a photodetector layer is prepared on at least a portion of the surface of the substrate.
[0044] Furthermore, after depositing the material of the photodetector layer on at least a portion of the surface of the substrate using magnetron co-sputtering technology, in-situ annealing is performed to form the photodetector layer on at least a portion of the surface of the substrate.
[0045] It should be noted that the material of the photodetector layer is not particularly limited, and those skilled in the art can choose it flexibly as needed. According to a specific embodiment of this application, the material of the photodetector layer is a bismuth antimonide alloy with the chemical formula Bi. 1-x Sb x 0 <x<1。
[0046] Specifically, Bi was deposited on an InP(100) substrate using magnetron co-sputtering technology. 1-x Sb x The sputtering power and element ratio of the alloy thin film are controlled by adjusting the power of the Bi and Sb baffles.
[0047] Furthermore, Bi 1-x Sb x The alloy thin film was grown at room temperature and then annealed in situ under an argon atmosphere at a temperature of 200-300℃ for 0.1-1 h, which was beneficial for improving Bi content. 1-x Sbx The quality of the alloy film.
[0048] Furthermore, during the annealing process, Bi 1-x Sb x A Type-II band-aligned heterojunction is naturally formed between the thin film and the InP substrate, generating a strong built-in electric field that can further optimize carrier migration efficiency. Moreover, this heterojunction structure can achieve low dark current and high photoresponsivity under zero bias, which greatly improves the performance of the detector.
[0049] Therefore, through Bi 1-x Sb x The synergistic effect of surface states and InP interband transitions expands the response range of photodetectors and improves quantum efficiency.
[0050] Step S300: Prepare a drive motor on at least a portion of the surface of the photodetector layer away from the substrate.
[0051] This step establishes an efficient external charge collection and transport channel by fabricating a driving electrode on the upper surface of the photodetector layer opposite to the heterojunction interface. This channel can effectively export photogenerated carriers (especially holes) separated by the built-in electric field of the Type-II heterojunction to the external circuit, thereby converting the efficient internal photoelectric conversion process into a measurable high-response electrical signal output, and finally completing the complete functional closed loop from photon detection to electrical signal output.
[0052] There are no special limitations on the manufacturing method of the drive motor. This method is a conventional process and will not be described in detail. Those skilled in the art can make flexible choices as needed.
[0053] The technical solutions provided in this application will be described in detail below with reference to the embodiments.
[0054] Unless otherwise specified, the InP(100) wafer material used in Example 1 is a substrate material purchased from Newmicro Semiconductor.
[0055] Example 1 Embodiment 1 of this application provides a photodetector, which has a layered structure and comprises, from bottom to top: Substrate: An InP(100) wafer with a thickness of 625μm was used as the substrate.
[0056] Photodetector layer: Bi 0.5 Sb 0.5 An alloy thin film, 50 nm thick, is grown on an InP substrate and together with the substrate forms a heterojunction with Type-II band alignment.
[0057] Driving electrode: The material is chromium / gold (Cr / Au), fabricated on Bi...0.5 Sb 0.5 Thin film surface.
[0058] 2. Preparation method The method for fabricating the photodetector includes the following steps: Step S100, Substrate preparation: Perform standard cleaning on the InP substrate to remove surface contaminants and oxides.
[0059] Step S200, Deposition of the photodetector layer: The cleaned substrate is placed in a magnetron sputtering system. High-purity Bi and Sb targets are used as sputtering sources, and co-sputtering is performed at room temperature in an argon atmosphere. By precisely controlling the sputtering power of the Bi and Sb targets, the composition of the deposited alloy film is made of Bi. 0.5 Sb 0.5 By controlling the sputtering time, the film thickness was controlled to 50 nm. After film deposition, an argon atmosphere was maintained within the sputtering chamber, and in-situ annealing was immediately performed. The annealing temperature was 240℃, and the annealing time was 30 minutes. This process promoted film crystallization, reduced interface defect density, and drove Bi... 0.5 Sb 0.5 A high-quality Type-II heterojunction is formed at the interface between the thin film and the InP substrate.
[0060] Step S300, Prepare the driving electrode: In Bi 0.5 Sb 0.5 Metal is deposited on the thin film by evaporation using a photomask.
[0061] Figure 2 The figure shown is a current-voltage (IT) curve of the photodetector provided in Embodiment 1 of this application under 650nm illumination. It can be seen that the response time is 16ms and the recovery time is 24ms.
[0062] The photodetectors in Examples 2-5 are prepared in a similar manner to those in Example 1, but some experimental parameters are different. The specific differences are described below and in Table 1.
[0063] Table 1
[0064] Comparative Example 1 Comparative Example 1 provides a photodetector with the same structure as the photodetector in Example 1, except that there is no heterojunction with Type-II band alignment between the photodetector layer and the substrate.
[0065] Comparative Example 2 Comparative Example 2 provides a photodetector with the same structure and preparation method as the photodetector in Example 1, except that the in-situ annealing process is omitted during the preparation of the photodetector.
[0066] Performance testing The performance of the photodetectors in Examples 1-5 and Comparative Examples 1-2 was tested, including the dark current, responsivity, spectral response range, and response / recovery time.
[0067] The test results are shown in Table 2.
[0068] Table 2 Test Results
[0069] Combining Tables 1 and 2, it can be seen that the responsivity and response / recovery time of Examples 1-5 are significantly better than those of Comparative Example 1. This indicates that the heterojunction structure with Type-II band alignment can improve photoelectric conversion efficiency and response speed, and effectively suppress dark current.
[0070] Due to the lack of in-situ annealing, the response of Comparative Example 2 (0.3 A / W) was significantly lower than that of Examples 1-5.
[0071] The above results demonstrate that the photodetector provided in this application generates a strong built-in electric field by forming a Type-II band-aligned heterojunction between the photodetector layer and the substrate, thereby significantly reducing dark current and improving responsivity, enabling the detector to maintain high photoelectric conversion efficiency at zero bias. This structure effectively extends the optical response range of the device in the ultraviolet to visible light band, and significantly improves carrier migration efficiency due to the presence of the built-in electric field, ultimately achieving excellent comprehensive performance of high response speed, high quantum efficiency, and low noise.
[0072] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.
[0073] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.
[0074] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A photodetector, characterized in that, The photodetector includes: Substrate; A photodetector layer is disposed on at least a portion of the surface of the substrate and forms a heterojunction with Type-II band alignment between the photodetector layer and the substrate; A driving electrode is disposed on at least a portion of the surface of the photodetector layer away from the substrate.
2. The photodetector as described in claim 1, characterized in that, The photodetector layer is made of bismuth antimonide alloy, with the chemical formula Bi. 1-x Sb x 0 <x<1。 3. The photodetector as described in claim 1, characterized in that, The thickness of the photodetector layer is 20-100 nm.
4. The photodetector as described in claim 1, characterized in that, The substrate is made of InP.
5. The photodetector as described in claim 1, characterized in that, The thickness of the substrate is 100-625 μm.
6. The photodetector as described in claim 1, characterized in that, The material of the driving electrode includes at least one of Ag, Au, C, Cu, Ti and In.
7. The photodetector as described in claim 1, characterized in that, The photodetector has a photoresponse wavelength of 300-800 nm.
8. A method for preparing a photodetector as described in any one of claims 1-7, characterized in that, include: Provide substrate; A photodetector layer is prepared on at least a portion of the surface of the substrate; A drive motor is fabricated on at least a portion of the surface of the photodetector layer away from the substrate.
9. The method as described in claim 8, characterized in that, The steps for fabricating the photodetector layer include: The photodetector layer is formed on at least a portion of the substrate surface by depositing the material of the photodetector layer using magnetron co-sputtering technology, followed by in-situ annealing.
10. The method as described in claim 9, characterized in that, The in-situ annealing temperature is 200-300℃, and the time is 0.1-1h.