Infrared photodetector and method of making the same

Abstract

This invention discloses an infrared photodetector and its fabrication method. The infrared photodetector includes: an insulating substrate; a metasurface structure located on the insulating substrate, the metasurface structure comprising a plurality of arrayed metal structural units; a two-dimensional tellurium thin film located above the metasurface structure; and electrodes located on the two-dimensional tellurium thin film, the electrodes including a first electrode and a second electrode spaced apart at both ends of the two-dimensional tellurium thin film. This invention improves the light absorption efficiency of the two-dimensional tellurium thin film by fabricating a metasurface structure on an insulating substrate and then fabricating a two-dimensional tellurium thin film above the metasurface structure, thereby enhancing the local field by exciting local surface plasmon resonances in the metasurface structure.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, specifically relating to an infrared photodetector and its fabrication method. Background Technology

[0002] In recent years, infrared photodetectors have found important applications in military, medical, and industrial inspection fields. Two-dimensional materials such as graphene and black phosphorus have become research hotspots due to their unique photoelectric properties. Among them, two-dimensional tellurium (Te) thin films have shown potential in infrared detection due to their advantages such as high carrier mobility and a wide tunable bandgap range (0.31 eV to 1.21 eV).

[0003] However, existing tellurium-based photodetectors suffer from weak response in the mid-infrared band (e.g., 4μm, 6μm) due to limitations imposed by the band gap of tellurium materials and low light absorption efficiency. While existing technologies utilize heterojunction structures and photothermal effects to improve the performance of tellurium-based photodetectors, the response in the mid-infrared band remains unsatisfactory.

[0004] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a photodetector and its fabrication method. Summary of the Invention

[0005] The purpose of this invention is to provide an infrared photodetector and its preparation method, which can improve the light absorption efficiency of two-dimensional tellurium thin films, thereby improving the performance of the infrared photodetector.

[0006] To achieve the above objectives, an embodiment of the present invention provides the following technical solution:

[0007] An infrared photodetector, the infrared photodetector comprising:

[0008] Insulating substrate;

[0009] A metasurface structure is located on the insulating substrate, and the metasurface structure includes a plurality of arrayed metal structural units;

[0010] A two-dimensional tellurium thin film is located above the metasurface structure;

[0011] An electrode is located on the two-dimensional tellurium film, and the electrode includes a first electrode and a second electrode spaced apart at both ends of the two-dimensional tellurium film.

[0012] In one embodiment, the metal structure unit includes a first resonant unit and a second resonant unit spaced apart. The first resonant unit is a metal nanorod structure, and the second resonant unit has an opening facing the first resonant unit. The second resonant unit includes a first end and a second end, and the distance between the first end and the first resonant unit is not equal to the distance between the second end and the first resonant unit.

[0013] In one embodiment, the second resonant unit includes a main body and a first extension and a second extension extending from both ends of the main body toward the first resonant unit, respectively, wherein the lengths of the first extension and the second extension are not equal.

[0014] In one embodiment, the main body is arranged parallel to the first resonant unit, and the first extension and the second extension are arranged parallel to each other.

[0015] In one embodiment, the length of the first extension is greater than the length of the second extension, and the distance between the first resonant unit and the first extension is less than 1 μm.

[0016] In one embodiment, the infrared photodetector further includes an isolation layer located between the metasurface structure and the two-dimensional tellurium thin film.

[0017] In one embodiment, the isolation layer is an aluminum oxide layer, and the thickness of the isolation layer is 10nm~100nm.

[0018] Another embodiment of the present invention provides the following technical solution:

[0019] A method for fabricating an infrared photodetector, the method comprising the following steps:

[0020] Provide insulating substrate;

[0021] A metasurface structure is fabricated on the insulating substrate, the metasurface structure comprising a plurality of arrayed metal structural units;

[0022] A two-dimensional tellurium thin film is prepared on the metasurface structure;

[0023] An electrode is fabricated on the two-dimensional tellurium thin film, the electrode comprising a first electrode and a second electrode spaced apart on the two-dimensional tellurium thin film.

[0024] In one embodiment, the step of fabricating a two-dimensional tellurium thin film over the metasurface structure includes:

[0025] A two-dimensional tellurium thin film was deposited on the metasurface structure using magnetron sputtering.

[0026] The deposited two-dimensional tellurium film was annealed.

[0027] In one embodiment, the step of fabricating a metasurface structure on the insulating substrate includes:

[0028] Patterned photoresist layers are formed on insulating substrates using electron beam lithography, nanoimprint lithography, or laser direct writing.

[0029] Deposit a metal layer on an insulating substrate and a photoresist layer;

[0030] A metasurface structure is formed on an insulating substrate by removing the photoresist layer and the metal layer thereon through a stripping process.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention improves the light absorption efficiency of the two-dimensional tellurium thin film by preparing a metasurface structure on an insulating substrate and then preparing a two-dimensional tellurium thin film on top of the metasurface structure, thereby enhancing the local field by exciting local surface plasmon resonance of the metasurface structure.

[0033] The present invention employs a metal structure unit in the metasurface structure composed of a first resonant unit and a second resonant unit with an asymmetric structure, which can excite Fano resonance, thereby forming a stronger electric field enhancement factor in the two-dimensional tellurium thin film and further improving the performance of the infrared photodetector.

[0034] The infrared photodetector fabrication method of the present invention is simple and easy to integrate and mass-produce. Attached Figure Description

[0035] 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 recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the infrared photodetector in Embodiment 1 of the present invention;

[0037] Figure 2 This is a schematic diagram of the metal structural unit in Embodiment 1 of the present invention;

[0038] Figures 3a-3d This is a process flow diagram of the infrared photodetector fabrication method in Embodiment 1 of the present invention.

[0039] Explanation of key figure labels:

[0040] 10 - Insulating substrate, 101 - Silicon substrate, 102 - Silicon oxide layer, 20 - Metasurface structure, 201 - Metal structure unit, 2011 - First resonant unit, 2012 - Second resonant unit, 20121 - Main body, 20122 - First extension, 20123 - Second extension, 30 - Two-dimensional tellurium thin film, 401 - First electrode, 402 - Second electrode, 50 - Isolation layer. Detailed implementation manners

[0041] In order to enable those skilled in the art to better understand the technical solutions in this disclosure, the following will clearly and completely describe the technical solutions in the embodiments of this disclosure with reference to the accompanying drawings in the embodiments of this disclosure. Obviously, the described embodiments are only a part of the embodiments of this disclosure, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this disclosure without creative efforts shall fall within the scope of protection of this disclosure.

[0042] This invention discloses an infrared photodetector, comprising:

[0043] An insulating substrate;

[0044] A metasurface structure located on the insulating substrate, the metasurface structure comprising a plurality of metal structure units arranged in an array;

[0045] A two-dimensional tellurium thin film located above the metasurface structure;

[0046] Electrodes located on the two-dimensional tellurium thin film, the electrodes comprising a first electrode and a second electrode spaced apart at both ends of the two-dimensional tellurium thin film.

[0047] This invention also discloses a method for manufacturing an infrared photodetector, comprising the following steps:

[0048] Providing an insulating substrate;

[0049] Preparing a metasurface structure on the insulating substrate, the metasurface structure comprising a plurality of metal structure units arranged in an array;

[0050] Preparing a two-dimensional tellurium thin film above the metasurface structure;

[0051] Preparing electrodes on the two-dimensional tellurium thin film, the electrodes comprising a first electrode and a second electrode spaced apart on the two-dimensional tellurium thin film.

[0052] The following further illustrates this invention with specific examples.

[0053] Example 1:

[0054] As Figure 1 shown, the infrared photodetector in this embodiment comprises:

[0055] Insulating substrate 10;

[0056] Metasurface structure 20, located on the insulating substrate 10, the metasurface structure 20 includes a plurality of metal structure units 201 arranged in an array;

[0057] Two-dimensional tellurium thin film 30, located above the metasurface structure 20;

[0058] Electrodes, located on the two-dimensional tellurium thin film 30, the electrodes include a first electrode 401 and a second electrode 402 spaced at both ends of the two-dimensional tellurium thin film 30.

[0059] Among them, the insulating substrate 10 includes a silicon substrate 101 and a silicon oxide layer 102 located on the silicon substrate 101. The insulating substrate 10 provides support for the device structure, and the silicon oxide layer 102 serves as an electrical insulating layer, which can effectively block the leakage current path that may be generated by the silicon substrate 101 and ensure the stability of the infrared photodetector.

[0060] As an artificially designed two-dimensional ultrathin material, the metasurface structure is composed of periodically arranged sub-wavelength basic units. The sub-wavelength basic unit in this embodiment is a metal structure unit. The free electrons on the metal surface will generate collective oscillations under the irradiation of electromagnetic waves with the same frequency as it. By designing the shape and size of the metal structure, localized surface plasmon resonance can be generated, that is, localized surface plasmon resonance (Localized Surface Plasmon Resonance, LSPR). Under the irradiation of infrared light, the localized surface plasmon resonance excited by the metasurface structure with size parameters matching the incident light can generate a localized field enhancement, thereby improving the light absorption efficiency of the two-dimensional tellurium thin film and enhancing the responsivity of the infrared photodetector.

[0061] Refer Figure 2 As shown, the metal structure unit 201 in this embodiment includes a first resonant unit 2011 and a second resonant unit 2012 arranged at intervals. The first resonant unit 2011 is a metal nanorod structure. The second resonant unit 2012 has an opening facing the first resonant unit. The second resonant unit 2012 includes a first end and a second end. The distance between the first end and the first resonant unit 2011 is not equal to the distance between the second end and the first resonant unit 2011. That is, the second resonant unit 2012 is an asymmetric C-shaped split-ring resonator structure.

[0062] Specifically, the second resonant unit 2012 includes a main body portion 20121 and a first extension portion 20122 and a second extension portion 20123 respectively extending from both ends of the main body portion 20121 toward the first resonant unit 2011. The length of the first extension portion 20122 is not equal to the length of the second extension portion 20123.

[0063] More specifically, in this embodiment, the first resonant unit 2011 is located on the left side, and the second resonant unit 2012 is located on the right side. The main body 20121 is arranged parallel to the first resonant unit, and the first extension 20122 and the second extension 20123 are arranged parallel to each other, that is, the first extension 20122 and the second extension 20123 are respectively arranged perpendicular to the first resonant unit 2011. Furthermore, in this embodiment, the length of the first extension 20122 is greater than the length of the second extension 20123, and the distance between the first resonant unit 2011 and the first extension 20122 is less than 1 μm, ensuring that the second resonant unit 2012 and the first resonant unit 2011 maintain a nanometer-level coupling gap.

[0064] Furthermore, the materials used for the metal structural units include, but are not limited to, highly conductive metals such as gold, silver, and aluminum. In this embodiment, the metal structural unit is preferably composed of a 60nm gold metal layer.

[0065] The metal structure unit in this embodiment comprises two parts, left and right. The first resonant unit on the left serves as a broadband radiative resonant unit, possessing a large net electric dipole moment. It is used to directly and efficiently couple incident infrared light into free space and excite broadband electric dipole resonance, constituting the continuous state of this optical system. The second resonant unit on the right maintains a nanometer-scale coupling distance with the first resonant unit and exhibits an asymmetrical C-shape. This asymmetry breaks the geometric symmetry of the structural plane, which can excite a narrowband subradiative state with a high quality factor, constituting the discrete state of this optical system. When infrared light is incident, it excites the broadband radiative state of the first resonant unit in the metal structure unit, and through near-field capacitive coupling, further excites the narrowband subradiative state of the second resonant unit on its side. The broadband continuous state and the narrowband discrete state of the optical system undergo strong destructive interference in the near-field space, producing an asymmetrical sharp Fano resonance line shape in the macroscopic reflection or transmission spectrum. Due to the strong interference effect of Fano resonance, a highly compressed and amplified local electric field extreme region, i.e., electric field hot spot, is generated at the tiny coupling gap between the first and second resonant units. These locally enhanced electric fields can further greatly enhance the light absorption cross section of the two-dimensional tellurium thin film in a specific resonant frequency band, thereby breaking through the limitation of the intrinsic band gap of tellurium material on light absorption rate.

[0066] It is worth noting that the metasurface structure in this embodiment also has extremely strong wavelength selectivity and high structural tunability. The lengths of the first and second extensions in the second resonant unit can be adjusted according to the required detection band to regulate its "asymmetry", thereby achieving precise control of the position and linewidth of the Fano resonance peak, making it perfectly adaptable to the target detection band required in different application scenarios.

[0067] It should be understood that in practical applications, parameters such as the period of the metal structural unit, the length of the first resonant unit, the length of the first extension and the second extension, the spacing between the first resonant unit and the second resonant unit, and the linewidth of the first resonant unit and the second resonant unit should be strictly designed according to the target detection band and the specific material of the metasurface structure, so that it can excite Fano resonance under the irradiation of infrared light in the target band.

[0068] Compared with conventional metasurface structures composed of symmetrical metal structural units, the metasurface structure in this embodiment can excite Fano resonance, greatly suppress radiation loss, has a higher quality factor, and can provide a stronger electric field enhancement factor locally in two-dimensional tellurium thin films, thereby bringing more significant photocurrent gain.

[0069] Furthermore, the infrared photodetector in this embodiment also includes an isolation layer 50 located between the metasurface structure 20 and the two-dimensional tellurium thin film 30. The isolation layer can prevent the two-dimensional tellurium thin film from directly contacting the metasurface structure, effectively preventing the increase of dark current, and at the same time can introduce an interface electric field to induce the grating effect.

[0070] Specifically, the isolation layer is an aluminum oxide layer with a thickness of 10nm~100nm.

[0071] Preferably, the isolation layer in this embodiment is a 10nm thick alumina layer. Because the metasurface structure in this embodiment can excite Fano resonance, the locally enhanced electric field can effectively penetrate the 10nm thick alumina layer above it, thereby improving the light absorption rate of the two-dimensional tellurium thin film.

[0072] More specifically, in this embodiment, the thickness of the two-dimensional tellurium thin film 30 is 30 nm.

[0073] The method for fabricating the infrared photodetector in this embodiment includes the following steps:

[0074] S1, Reference Figure 3a As shown, an insulating substrate 10 is provided.

[0075] In this embodiment, the insulating substrate 10 includes a silicon substrate 101 and a silicon oxide layer 102 located on the silicon substrate 101.

[0076] Specifically, this step also includes cleaning the insulating substrate to remove surface impurities.

[0077] S2, Reference Figure 3b As shown, a metasurface structure 20 is fabricated on an insulating substrate 10. The metasurface structure 20 includes a plurality of arrayed metal structural units 201.

[0078] In this embodiment, the metal structure unit includes a first resonant unit and a second resonant unit arranged at intervals. The first resonant unit is a metal nanorod structure, and the second resonant unit is an asymmetric C-shaped open resonant ring structure.

[0079] Specifically, this step includes:

[0080] 1. A patterned photoresist layer is formed on an insulating substrate using electron beam lithography, nanoimprint lithography, or laser direct writing.

[0081] Preferably, in this embodiment, after standard electron beam lithography processes such as spin coating, baking, electron beam exposure, development, and fixing, a patterned photoresist layer is formed on the insulating substrate.

[0082] 2. Deposit a metal layer on the insulating substrate and the photoresist layer.

[0083] Specifically, in this embodiment, a 60nm gold metal layer is deposited on an insulating substrate and a photoresist layer using a vapor deposition process.

[0084] 3. The photoresist layer and the metal layer on it are removed by a stripping process to form a metasurface structure on an insulating substrate.

[0085] S3, Reference Figure 3c As shown, a two-dimensional tellurium thin film 30 is prepared on top of the metasurface structure 20.

[0086] Specifically, in this embodiment, before preparing the two-dimensional tellurium thin film, a 10 nm aluminum oxide layer is deposited on the insulating substrate and the metasurface structure as an isolation layer 50 by an atomic layer deposition process.

[0087] More specifically, this step includes:

[0088] 1. A two-dimensional tellurium thin film is deposited on the isolation layer of a metasurface structure by magnetron sputtering.

[0089] 2. Anneal the deposited two-dimensional tellurium film.

[0090] S4, Reference Figure 3d As shown, an electrode is fabricated on a two-dimensional tellurium thin film, the electrode including a first electrode and a second electrode spaced apart on the two-dimensional tellurium thin film.

[0091] As can be seen from the above technical solution, the present invention has the following beneficial effects:

[0092] This invention improves the light absorption efficiency of the two-dimensional tellurium thin film by preparing a metasurface structure on an insulating substrate and then preparing a two-dimensional tellurium thin film on top of the metasurface structure, thereby enhancing the local field by exciting local surface plasmon resonance of the metasurface structure.

[0093] The present invention employs a metal structure unit in the metasurface structure composed of a first resonant unit and a second resonant unit with an asymmetric structure, which can excite Fano resonance, thereby forming a stronger electric field enhancement factor in the two-dimensional tellurium thin film and further improving the performance of the infrared photodetector.

[0094] The infrared photodetector fabrication method of the present invention is simple and easy to integrate and mass-produce.

[0095] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0096] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An infrared photodetector, characterized in that, The infrared photodetector includes: Insulating substrate; A metasurface structure is located on the insulating substrate, and the metasurface structure includes a plurality of arrayed metal structural units; A two-dimensional tellurium thin film is located above the metasurface structure; An electrode is located on the two-dimensional tellurium film, and the electrode includes a first electrode and a second electrode spaced apart at both ends of the two-dimensional tellurium film.

2. The infrared photodetector according to claim 1, characterized in that, The metal structure unit includes a first resonant unit and a second resonant unit spaced apart. The first resonant unit is a metal nanorod structure. The second resonant unit has an opening facing the first resonant unit. The second resonant unit includes a first end and a second end. The distance between the first end and the first resonant unit is not equal to the distance between the second end and the first resonant unit.

3. The infrared photodetector according to claim 2, characterized in that, The second resonant unit includes a main body and a first extension and a second extension extending from both ends of the main body toward the first resonant unit, respectively. The lengths of the first extension and the second extension are not equal.

4. The infrared photodetector according to claim 3, characterized in that, The main body is arranged parallel to the first resonant unit, and the first extension and the second extension are arranged parallel to each other.

5. The infrared photodetector according to claim 3, characterized in that, The length of the first extension is greater than the length of the second extension, and the distance between the first resonant unit and the first extension is less than 1 μm.

6. The infrared photodetector according to claim 1, characterized in that, The infrared photodetector also includes an isolation layer located between the metasurface structure and the two-dimensional tellurium thin film.

7. The infrared photodetector according to claim 6, characterized in that, The isolation layer is an aluminum oxide layer, and the thickness of the isolation layer is 10nm~100nm.

8. A method for fabricating an infrared photodetector, characterized in that, The preparation method includes the following steps: Provide insulating substrate; A metasurface structure is fabricated on the insulating substrate, the metasurface structure comprising a plurality of arrayed metal structural units; A two-dimensional tellurium thin film is prepared on the metasurface structure; An electrode is fabricated on the two-dimensional tellurium thin film, the electrode comprising a first electrode and a second electrode spaced apart on the two-dimensional tellurium thin film.

9. The method for preparing an infrared photodetector according to claim 8, characterized in that, The steps for fabricating a two-dimensional tellurium thin film on the metasurface structure include: A two-dimensional tellurium thin film was deposited on the metasurface structure using magnetron sputtering. The deposited two-dimensional tellurium film was annealed.

10. The method for preparing an infrared photodetector according to claim 8, characterized in that, The steps for fabricating metasurface structures on the insulating substrate include: Patterned photoresist layers are formed on insulating substrates using electron beam lithography, nanoimprint lithography, or laser direct writing. Deposit a metal layer on an insulating substrate and a photoresist layer; A metasurface structure is formed on an insulating substrate by removing the photoresist layer and the metal layer thereon through a stripping process.

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