Infrared photoelectric detector

Abstract

The invention relates to the technical field of photoelectric detectors, and discloses an infrared photoelectric detector which comprises a bottom layer, a heterojunction and a top layer which are sequentially stacked from bottom to top, the bottom layer is used for being electrically connected with a first electrode, the top layer is used for being electrically connected with a second electrode, the heterojunction at least partially covers the bottom layer, and the top layer is used for being electrically connected with a second electrode. The top layer at least partially covers the heterojunction, the top layer at least partially has light transmittance, and the heterojunction comprises a narrow band gap material layer. By means of the mode, the infrared photoelectric detector can achieve infrared detection which does not need complex refrigeration equipment and is high in response speed, wide in polarization response and spectral response range and high in stability.

Description

Technical Field

[0001] This application relates to the technical field of photodetectors, and more particularly to an infrared photodetector. Background Art

[0002] An infrared photodetector is a device that converts infrared light signals into electrical signals and is widely used in military (night vision goggles, missile guidance), medical (body temperature detection, medical imaging), environmental monitoring (gas detection, thermal imaging), and industrial inspection (non-destructive testing, temperature monitoring) and other fields. However, traditional devices are severely restricted in terms of portability, energy efficiency, and performance improvement due to problems such as reliance on complex cooling systems, slow response speed, limited spectral range, and insufficient stability.

[0003] Infrared detectors are mainly divided into photon detectors and thermal detectors. Photon detectors use the photoelectric effect to convert photons into electrical signals, such as mercury cadmium telluride (HgCdTe) detectors, quantum well infrared detectors, and indium antimonide (InSb) detectors, which achieve high-sensitivity, low-noise infrared detection by virtue of unique material properties, but in most cases, cryogenic cooling is required. Thermal detectors, on the other hand, perform infrared detection based on the change of material properties with temperature, such as thermopile detectors, pyroelectric detectors, and microbolometers, which mainly detect long-wave infrared and have a lower cost but a slower response.

[0004] Although these traditional infrared photodetectors have wide applications in their respective fields, their common problems such as the need for cooling, slow response speed, limited spectral range, and poor stability make it difficult to meet the growing high-performance requirements, and there is an urgent need to break through the existing limitations through the development of new materials and new technologies. Summary of the Invention

[0005] In view of the above problems, the embodiments of this application provide an infrared photodetector that can break through the performance bottleneck of traditional detectors and achieve infrared detection without complex cooling equipment, with a fast response speed, a wide spectral response range, polarization response, and high stability.

[0006] This application provides an infrared photodetector, which includes a bottom layer, a heterojunction, and a top layer stacked in sequence from bottom to top. The bottom layer is used for electrical connection with a first electrode, the top layer is used for electrical connection with a second electrode, the heterojunction at least partially covers the bottom layer, the top layer at least partially covers the heterojunction, the top layer at least partially has light transmittance, and the heterojunction includes a narrow bandgap material layer.

[0007] In an optional manner, the heterojunction includes a supporting layer made of a narrow bandgap material and a stacked layer made of a wide bandgap material. The stacked layer covers above the supporting layer, the stacked layer at least partially covers the supporting layer, the supporting layer at least partially covers the bottom layer, and the top layer at least partially covers the stacked layer.

[0008] In an alternative manner, the heterojunction includes a buffer layer made of a wide-bandgap material and a stacked layer made of a narrow-bandgap material. The stacked layer covers above the buffer layer. The stacked layer at least partially covers the buffer layer. The buffer layer at least partially covers the bottom layer. The top layer at least partially covers the stacked layer.

[0009] In an alternative manner, both the narrow-bandgap material and the wide-bandgap material are two-dimensional materials.

[0010] In an alternative manner, the stacked layer at least partially covers the bottom layer.

[0011] In an alternative manner, the narrow-bandgap material is any one of tellurium, black phosphorus, black arsenic, black arsenic phosphorus, platinum ditelluride, or platinum diselenide, and the wide-bandgap material is any one of tungsten diselenide, molybdenum disulfide, molybdenum diselenide, molybdenum ditelluride, indium selenide, indium triselenide, hafnium disulfide, hafnium diselenide, rhenium disulfide, rhenium diselenide, tin disulfide, tin diselenide, gallium sulfide, gallium selenide, germanium sulfide, or germanium selenide.

[0012] In an alternative manner, the heterojunction includes a buffer layer and a stacked layer. The stacked layer covers above the buffer layer. The bottom of the conduction band of the stacked layer is higher than that of the buffer layer. The top of the valence band of the stacked layer is lower than that of the buffer layer. The stacked layer and the buffer layer form a type-I heterojunction.

[0013] In an alternative manner, the heterojunction includes a buffer layer and a stacked layer. The stacked layer covers above the buffer layer. The bottom of the conduction band of the stacked layer is lower than that of the buffer layer. The top of the valence band of the stacked layer is higher than that of the buffer layer. The stacked layer and the buffer layer form a type-I heterojunction.

[0014] In an alternative manner, both the top layer and the bottom layer are made of a semiconductor-type two-dimensional material, a metallic two-dimensional material, or a semi-metallic two-dimensional material.

[0015] In an alternative manner, both the top layer and the bottom layer are made of graphene.

[0016] In an alternative manner, the bottom layer and the top layer are arranged with a lateral offset, and there is a spacing between the lateral projections of the bottom layer and the top layer.

[0017] In an alternative embodiment, the infrared photodetector further includes a substrate. The first electrode and the second electrode are respectively disposed on the left and right sides of the substrate. The heterojunction is disposed between the first electrode and the second electrode. One end of the bottom layer is electrically connected to the first electrode, and the other end of the bottom layer is electrically connected to the heterojunction. One end of the top layer is electrically connected to the heterojunction, and the other end of the top layer is electrically connected to the second electrode.

[0018] In an alternative embodiment, the infrared photodetector further includes a dielectric layer. The dielectric layer is disposed on the substrate. The first electrode and the second electrode are respectively disposed on the left and right sides of the dielectric layer. The heterojunction is disposed between the first electrode and the second electrode.

[0019] The infrared photodetector of the present application is formed by vertically stacking a bottom layer, a heterojunction, and a top layer in sequence. The bottom layer is used for electrical connection with the first electrode, the top layer is used for electrical connection with the second electrode, the heterojunction at least partially covers the bottom layer, the top layer at least partially covers the heterojunction, and the heterojunction includes a narrow bandgap material layer. When infrared light irradiates the detector, the narrow bandgap material layer in the heterojunction absorbs photons to generate electron-hole pairs, that is, photo-generated carriers. Due to the adoption of a specific heterojunction structure and materials, the dark current of the detector is suppressed. The photo-generated carriers can be efficiently separated under the action of the built-in electric field and move towards the top layer and the bottom layer respectively, and are finally collected by the electrodes to form a photocurrent, thereby realizing the detection of infrared light. Further, the narrow bandgap material can achieve high sensitivity, wide spectral response, polarization response, and fast response speed at room temperature, and at the same time, no complex refrigeration system is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments and descriptions thereof of this application are used to explain this application and do not constitute an improper limitation of this application.

[0021] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of this application. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0023] Figure 1It is a schematic structural diagram of an infrared detector provided by one embodiment of the present application.

[0024] Figure 2 It is a schematic structural diagram of an infrared detector provided by one embodiment of the present application.

[0025] Figure 3 It is an optical micrograph of the detector.

[0026] Figure 4 It is a photocurrent imaging diagram of the detector under 532nm laser excitation (where V WSe2 = +1V).

[0027] Figure 5 It is a photocurrent imaging diagram of the detector under 532nm laser excitation (where V WSe2 = -1V).

[0028] Figure 6 It is a photocurrent imaging diagram of the detector under 1550nm laser excitation (where V WSe2 = +1V).

[0029] Figure 7 It is a photocurrent imaging diagram of the detector under 1550nm laser excitation (where V WSe2 = -1V).

[0030] Figure 8 It is a responsivity diagram of the infrared detector to incident light of different wavelengths at room temperature.

[0031] Figure 9 It is a time-domain response current diagram of the infrared detector to periodically switched mid-infrared light of different wavelengths at room temperature.

[0032] Figure 10 It is the optical response performance of the infrared detector to 1550nm infrared light at room temperature.

[0033] Figure 11 It is the time-domain response curve and response time calibration of the infrared detector to periodically switched 1550nm infrared light at room temperature.

[0034] Figure 12 It is the time-domain optical response curve diagram of the infrared detector to 2500nm and 3000nm mid-infrared light with periodically changing polarization directions.

[0035] Figure 13 It is a polar coordinate diagram of the photocurrent response of the infrared detector changing with the polarization direction under 2500nm polarized light irradiation.

[0036] Figure 14 It is a polar coordinate diagram of the photocurrent response of the infrared detector changing with the polarization direction under 3000nm polarized light irradiation.

[0037] The reference numerals in the specific embodiments are as follows:

[0038] 1. Substrate, 2. Dielectric layer, 3. First electrode, 4. Bottom layer, 5. Support layer, 6. Stacked layer, 7. Top layer, 8. Protective layer, 9. Second electrode, 10. Heterojunction. Specific embodiments

[0039] Next, embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, so they are only examples and cannot be used to limit the protection scope of the present application. Many specific details are set forth in the following description in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0041] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meanings of "a plurality" and "several" are more than two, such as two, three, etc., unless otherwise specifically defined. Similarly, "multiple groups" means two or more groups (including two groups), and "multiple pieces" means two or more pieces (including two pieces). The mention of "embodiment" in this article means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0042] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: there is A, there is both A and B, and there is B. In addition, the character " / " in this article generally means that the associated objects before and after are in an "or" relationship.

[0043] In the description of the embodiments of the present application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of the present application.

[0044] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0045] In the present application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0046] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation manner.

[0047] In this application, "covering" means having a vertically aligned direct contact. The term "vertical" refers to a direction perpendicular to the substrate plane, while the term "lateral" can be used to denote a direction or region parallel to the substrate plane. When the second layer "covers" the first layer, the second layer and the first layer are vertically aligned and they are in direct contact with each other. In other words, the two layers have been sequentially disposed on a given region of the substrate. They are vertically aligned because the first layer is first disposed on that region and then the second layer is disposed on the same region. Thus, within that region, the first layer is located beneath the second layer in the vertical direction.

[0048] In this application, "overlying" means having a vertically aligned non-direct contact. When the second layer "overlies" the first layer, the second layer and the first layer are vertically aligned, but they are not in direct contact with each other. In other words, both layers have been disposed on a given region of the substrate, but an intermediate layer has been disposed between them. The three layers are all vertically aligned. The first layer is first disposed on that region, then the intermediate layer is disposed on the same region, and then the second layer is disposed on the same region. Within that region, the first layer is thus located beneath the intermediate layer and the second layer. The intermediate layer is located above the first layer but beneath the second layer in the vertical direction.

[0049] It should be noted that the expressions "partially covering" and "partially overlying" are used to refer to a partial vertical alignment where the region of the first layer is not completely covered or overlaid by the second layer. Open-ended qualifying expressions such as "at least partially covering" and "at least partially overlying" are used to refer to a partial vertical alignment.

[0050] Furthermore, the expression that an object is disposed (or deposited) "on a substrate" can mean that the object partially or completely covers (or is deposited to cover) the substrate, or that the object covers on the substrate (or is deposited to cover) a part or all of the substrate. In other words, an electrode "on a substrate" can be an electrode in direct contact with the substrate, or an electrode in direct contact with one or more intermediate layers covering the substrate. In other words, an electrode "on a substrate" can cover or cover a part of the substrate. In the case of a deposition method, it can be stipulated that multiple layers are sequentially deposited "on a substrate". Designating the order of such deposition steps corresponds to the order of depositing the layers on the substrate or certain regions of the substrate. Thus, this order determines which (preceding) layers a given layer covers or covers on a specific region of the substrate, and which (subsequent) layers will sequentially cover or cover a given layer on a specific region of the substrate.

[0051] As Figure 1 and Figure 2As shown in the figure, the present application provides an infrared photodetector. An infrared photodetector includes a bottom layer 4, a heterojunction 10, and a top layer 7 that are vertically stacked in sequence from bottom to top. The bottom layer 4 is used to be electrically connected to the first electrode 3, the top layer 7 is used to be electrically connected to the second electrode 9, the heterojunction 10 at least partially covers the bottom layer 4, the top layer 7 at least partially covers the heterojunction 10, at least part of the top layer 7 has light transmittance, and the heterojunction 10 includes a narrow-bandgap material layer.

[0052] The infrared photodetector of the present application is formed by vertically stacking a bottom layer 4, a heterojunction 10, and a top layer 7 in sequence. The bottom layer 4 is used to be electrically connected to the first electrode 3, the top layer 7 is used to be electrically connected to the second electrode 9, the heterojunction 10 at least partially covers the bottom layer 4, the top layer 7 at least partially covers the heterojunction 10, and the heterojunction 10 includes a narrow-bandgap material layer. When infrared light irradiates the detector, the narrow-bandgap material layer in the heterojunction 10 absorbs photons to generate electron-hole pairs, that is, photo-generated carriers. By sandwiching the heterojunction 10 between the bottom layer 4 and the top layer 7 to form a sandwich-like vertical structure, the photo-generated carriers (electrons and holes) in the middle-layer heterojunction 10 can be efficiently separated and transported to the electrodes on both sides under the action of the built-in electric field to form a photo-response current, thereby realizing the detection of infrared light. Further, the narrow-bandgap material can achieve high sensitivity, wide spectral response, and fast response speed at room temperature, and at the same time, no complex refrigeration system is required.

[0053] As Figure 1 shown in the figure, in some embodiments of the present application, the heterojunction 10 includes a support layer 5 made of a narrow-bandgap material and a stacked layer 6 made of a wide-bandgap material. The stacked layer 6 covers the support layer 5, the stacked layer 6 at least partially covers the support layer 5, the support layer 5 at least partially covers the bottom layer 4, the stacked layer 6 at least partially covers the bottom layer 4, the top layer 7 at least partially covers the stacked layer 6. Preferably, in order to generate as many photo-generated carriers as possible, the heterojunction 10 formed by the support layer 5 and the stacked layer 6 should have an appropriate overlapping area with the conductive material of the bottom layer 4 in the transverse direction. The top layer 7 and the bottom layer 4 are arranged in a transverse dislocation, and there is a spacing between the transverse projections of the top layer 7 and the bottom layer 4.

[0054] As Figure 1 shown in the figure, in some embodiments of the present application, the heterojunction 10 includes a support layer 5 made of a wide-bandgap material and a stacked layer 6 made of a narrow-bandgap material. The stacked layer 6 covers the support layer 5, the stacked layer 6 at least partially covers the support layer 5, the support layer 5 at least partially covers the bottom layer 4, the stacked layer 6 at least partially covers the bottom layer 4, the top layer 7 at least partially covers the stacked layer 6. Preferably, in order to generate as many photo-generated carriers as possible, the heterojunction 10 formed by the support layer 5 and the stacked layer 6 should have an appropriate overlapping area with the conductive material of the bottom layer 4 in the transverse direction. The top layer 7 and the bottom layer 4 are arranged in a transverse dislocation, and there is a spacing between the transverse projections of the top layer 7 and the bottom layer 4.

[0055] As Figure 2As shown, in some embodiments of the present application, the heterojunction 10 includes a buffer layer 5 made of a narrow bandgap material and a stack layer 6 made of a wide bandgap material. The stack layer 6 covers the buffer layer 5, and the stack layer 6 at least partially covers the buffer layer 5. The buffer layer 5 at least partially covers the bottom layer 4, and the top layer 7 at least partially covers the stack layer 6. Preferably, in order to generate as many photo-generated carriers as possible, the heterojunction 10 formed by the buffer layer 5 and the stack layer 6 should have an appropriate overlapping area with the conductive material of the top layer 7 in the transverse direction. The top layer 7 and the bottom layer 4 are arranged in a transverse dislocation, and there is a spacing between the transverse projections of the top layer 7 and the bottom layer 4.

[0056] As Figure 2 shown, in some embodiments of the present application, the heterojunction 10 includes a buffer layer 5 made of a wide bandgap material and a stack layer 6 made of a narrow bandgap material. The stack layer 6 covers the buffer layer 5, and the stack layer 6 at least partially covers the buffer layer 5. The buffer layer 5 at least partially covers the bottom layer 4, and the top layer 7 at least partially covers the stack layer 6. Preferably, in order to generate as many photo-generated carriers as possible, the heterojunction 10 formed by the buffer layer 5 and the stack layer 6 should have an appropriate overlapping area with the conductive material of the top layer 7 in the transverse direction. The top layer 7 and the bottom layer 4 are arranged in a transverse dislocation, and there is a spacing between the transverse projections of the top layer 7 and the bottom layer 4.

[0057] Among them, the upper and lower order of the narrow bandgap material and the wide bandgap material can be swapped. Preferably, the narrow bandgap material is on the top. The relative positional relationship between the stack layer 6 and the bottom layer 4 can be selected according to the actual situation. The stack layer 6 can partially cover the bottom layer 4 (for example Figure 1 shown), or the stack layer 6 can also be arranged in a transverse dislocation with the bottom layer 4, and there is a spacing between the transverse projections of the stack layer 6 and the bottom layer 4 (for example Figure 2 shown).

[0058] In some embodiments of the present application, both the narrow bandgap material and the wide bandgap material are two-dimensional materials. Due to their high carrier mobility, direct bandgap, strong light-matter interaction and other characteristics, the detectors prepared from them can achieve high-performance photoelectric detection such as high sensitivity, wide spectral response and high-speed response at room temperature without a complex refrigeration system.

[0059] In some embodiments of the present application, the narrow bandgap material is any one of Te (tellurium), BP (black phosphorus), b-As (black arsenic), b-AsP (black arsenic phosphorus), PtTe2 (platinum ditelluride), or PtSe2 (platinum diselenide). Among them, preferably, black phosphorus shows great application potential in the fields of infrared photodetection and broadband photodetection due to its broad spectral response and high sensitivity. The wide bandgap materials are any one of WSe2 (tungsten diselenide), WS2 (tungsten disulfide), MoS2 (molybdenum disulfide), MoSe2 (molybdenum diselenide), MoTe2 (molybdenum ditelluride), InSe (indium selenide), In2Se3 (diindium triselenide), HfS2 (hafnium disulfide), HfSe2 (hafnium diselenide), ReS2 (rhenium disulfide), ReSe2 (rhenium diselenide), SnS2 (tin disulfide), SnSe2 (tin diselenide), GaS (gallium sulfide), GaSe (gallium selenide), GeS (germanium sulfide), or GeSe (germanium selenide). Among them, molybdenum disulfide and tungsten diselenide, as typical representatives of transition metal chalcogenides, are expected to be applied to next-generation optoelectronic devices and transistor devices due to their tunable bandgaps, excellent mechanical stability, and potential for low-cost large-scale mass production. These materials have different band structures and optoelectronic properties, and through reasonable combination, effective detection of infrared light in different bands can be achieved.

[0060] In some embodiments of the present application, the heterojunction 10 is a type-I heterojunction 10, a type-II heterojunction 10, or a type-III heterojunction 10. These heterojunction 10 structures can effectively regulate the transport characteristics of carriers and improve the separation efficiency of photo-generated carriers. Those skilled in the art can select the structure of the heterojunction according to the actual usage scenario.

[0061] In some embodiments of the present application, the heterojunction 10 includes a substrate layer 5 and a stacked layer 6. The stacked layer 6 covers the substrate layer 5. The bottom of the conduction band of the stacked layer 6 is higher than the bottom of the conduction band of the substrate layer 5, and the top of the valence band of the stacked layer 6 is lower than the top of the valence band of the substrate layer 5. The stacked layer 6 and the substrate layer 5 form a type-I heterojunction 10.

[0062] In some embodiments of the present application, the heterojunction 10 includes a substrate layer 5 and a stacked layer 6. The stacked layer 6 covers the substrate layer 5. The bottom of the conduction band of the stacked layer 6 is lower than the bottom of the conduction band of the substrate layer 5, and the top of the valence band of the stacked layer 6 is higher than the top of the valence band of the substrate layer 5. The stacked layer 6 and the substrate layer 5 form a type-I heterojunction 10.

[0063] In summary, by performing bandgap matching between narrow-bandgap materials and other two-dimensional materials with good stability to form type-I van der Waals heterojunctions, the conduction band and valence band of the narrow-bandgap materials are clamped by the conduction band and valence band of the wide-bandgap materials. Such a band structure and a vertically stacked device structure not only facilitate the suppression of the dark current of the detector and enhance the efficient transport of photo-generated carriers, but also enable wide-spectrum detection from visible light to mid-infrared. This structure can more effectively separate photo-generated electrons and holes, reduce the recombination rate of carriers during transport, and reduce interface scattering and noise, thereby improving the stability and light response performance of the device.

[0064] In some embodiments of the present application, both the top layer 7 and the bottom layer 4 are made of any one of semiconductor-type two-dimensional materials, metallic two-dimensional materials, or semi-metallic two-dimensional materials. The heterojunction 10 is sandwiched between the bottom layer 4 and the top layer 7 to form a sandwich-like vertical structure, thereby efficiently transporting the carriers (electrons and holes) in the middle-layer heterojunction 10 to the electrodes on both sides.

[0065] Preferably, in some embodiments of the present application, both the top layer 7 and the bottom layer 4 are made of graphene (Graphene, Gr). Graphene has high electron mobility, good electrical conductivity, thermal conductivity, and optical transparency. Using it for the top layer 7 and the bottom layer 4 can reduce the interface defects and Schottky barriers caused by the metal-semiconductor contact, improve the speed of the photo-response current, and is also conducive to the efficient transport of photo-generated carriers. In addition, the optical transparency of graphene can ensure that the heterojunction 10 can effectively receive infrared light signals and convert them into electrical signals for output. Further, the heterojunction 10 is sandwiched between two layers of graphene to form a sandwich-like vertical structure, thereby efficiently separating and transporting the carriers (electrons and holes) in the middle-layer heterojunction 10 to the metal electrodes on both sides.

[0066] In some embodiments of the present application, the bottom layer 4 and the top layer 7 are arranged with a lateral offset, and there is a spacing between the lateral projections of the bottom layer 4 and the top layer 7, that is, the top layer 7 does not cover the bottom layer 4. This offset design helps to optimize the electrical performance and light absorption characteristics of the device. At the same time, there is no overlapping area between the top layer 7 and the bottom layer 4 in the lateral direction, which can reduce the problem of excessive dark current caused by the tunneling effect.

[0067] In some embodiments of the present application, the infrared photodetector further includes a protective layer 8 made of an inert insulating material. The protective layer 8 made of an inert insulating material surrounds the outside of the heterojunction 10. By setting the protective layer 8, the stability and the ability to resist water and oxygen erosion of the device can be improved. At least part of the protective layer 8 has light transmittance to ensure that the detector can effectively receive infrared light signals and convert them into electrical signals for output. In some embodiments of the present application, the protective layer 8 made of an inert insulating material can be selected as hexagonal boron nitride (hBN), and the protective layer 8 is fully transparent.

[0068] In some embodiments of the present application, the infrared photodetector further includes a substrate 1, a first electrode 3 and a second electrode 9 are respectively disposed on the left and right sides of the substrate 1, a heterojunction 10 is disposed between the first electrode 3 and the second electrode 9, one end of the bottom layer 4 is electrically connected to the first electrode 3, the other end of the bottom layer 4 is electrically connected to the heterojunction 10, one end of the top layer 7 is electrically connected to the heterojunction 10, and the other end of the top layer 7 is electrically connected to the second electrode 9. The substrate 1 can be made of, for example, single crystal silicon (Si), calcium fluoride (CaF2), sapphire (Al2O3), quartz (SiO2), silicon nitride (Si3N4), aluminum nitride (AlN), germanium (Ge), gallium arsenide (GaAs), gallium nitride (GaN), etc.

[0069] In some embodiments of the present application, the infrared photodetector further includes a substrate 1 and a dielectric layer 2, the dielectric layer 2 is disposed on the substrate 1, a first electrode 3 and a second electrode 9 are respectively disposed on the left and right sides of the substrate 1, a heterojunction 10 is disposed between the first electrode 3 and the second electrode 9, and the dielectric layer can be formed by reaction of the material of the substrate 1, or can be prepared by deposition or epitaxial growth methods.

[0070] In some embodiments of the present application, one end of the bottom layer 4 overlaps on the top of the first electrode 3, the other end of the bottom layer 4 extends downward along the inner side of the first electrode 3, and then extends horizontally to the bottom of the heterojunction 10, one end of the top layer 7 overlaps on the top of the heterojunction 10, and the other end of the top layer 7 extends downward along the inner side of the second electrode 9, and then extends horizontally to the top of the second electrode 9. This structural layout helps to achieve stable support of the infrared photodetector, and at the same time can ensure effective connection between the electrodes and the detector. In addition, it can also optimize the integration and performance of the device.

[0071] In some embodiments of the present application, at least one conductive source electrode and at least one conductive drain electrode are deposited on the substrate 1. The materials of the source electrode and the drain electrode can be gold (Au) electrodes, silver (Ag) electrodes, platinum (Pt) electrodes, palladium (Pd) electrodes, copper (Cu) electrodes, aluminum (Al) electrodes, magnesium (Mg) electrodes, titanium (Ti) electrodes, chromium (Cr) electrodes, indium (In) electrodes, nickel (Ni) electrodes, cobalt (Co) electrodes, iron (Fe) electrodes, etc., or formed by sequentially depositing multiple metals.

[0072] Specifically, the structure of the infrared photodetector of the optimal embodiment of the present application is selected below for detailed introduction and description:

[0073] The infrared photodetector is placed on the silicon wafer substrate 1 with metal electrodes. The infrared photodetector has a total of 5 layers of materials from bottom to top, which are: the first layer (bottom layer 4) is a conductive layer material for connecting the first metal electrode (the first electrode 3, i.e., the drain electrode) and the heterojunction 10; the second layer (support layer 5) is a wide-bandgap two-dimensional material, and the material of the second layer can be WSe2 (tungsten diselenide), WS2 (tungsten sulfide), MoS2 (molybdenum disulfide), MoSe2 (molybdenum selenide), MoTe2 (molybdenum telluride), InSe (indium selenide), In2Se3 (diindium triselenide), HfS2 (hafnium disulfide), HfSe2 (hafnium selenide), ReS2 (rhenium disulfide), ReSe2 (rhenium selenide), SnS2 (tin disulfide), SnSe2 (tin selenide), GaS (gallium sulfide), GaSe (gallium selenide), GeS (germanium sulfide) or GeSe (germanium selenide), etc.; the third layer (stacked layer 6) is a narrow-bandgap material for infrared light sensing, and the material of the third layer can be Te (tellurium), BP (black phosphorus), b-As (black arsenic), b-AsP (black arsenic phosphorus), PtTe2 (platinum telluride) or PtSe2 (platinum selenide), etc.; the fourth layer (top layer 7) is a conductive layer material for connecting the heterojunction 10 and the second metal electrode (the second electrode 9, i.e., the source electrode); the fifth layer (protective layer 8) is a protective layer 8 made of an inert insulating material responsible for isolating water and oxygen.

[0074] Furthermore, the material of the first layer uses graphene with high electron mobility and good flexibility as the guiding electrode to connect the first metal electrode with the wide-bandgap material of the second layer. Such a setting can reduce the interface defects and Schottky barriers caused by the metal-semiconductor contact and improve the light response current speed. The wide-bandgap material of the second layer and the narrow-bandgap material of the third layer are vertically stacked to form the heterojunction 10 responsible for infrared detection; at the same time, in order to generate and separate as many photo-generated carriers as possible, the heterojunction 10 formed by the second layer and the third layer materials should have an appropriate overlapping area with the conductive material of the first layer in the transverse direction. The material of the fourth layer also uses graphene with high electron mobility. The material of the fourth layer acts as an electrode to connect the narrow-bandgap material of the third layer with the metal electrode, and in order to reduce the excessive dark current caused by tunneling, the conductive material of the fourth layer does not have an overlapping area with the conductive material of the first layer in the transverse direction; the heterojunction 10 is sandwiched in the middle by two layers of graphene to form a sandwich-like vertical structure, so as to efficiently separate and transport the carriers (electrons and holes) in the middle layer heterojunction 10 to the metal electrodes on both sides. The material of the fifth layer uses a stable, flat and highly transparent protective material (such as hexagonal boron nitride) to be stacked above the material vulnerable to water and oxygen erosion to improve the stability of the device.

[0075] Furthermore, the heterojunction 10 composed of a wide-bandgap material (the capping layer 5) and a narrow-bandgap material (the stacked layer 6) is a key component for achieving infrared response. Its working principle is to form a type-I van der Waals heterojunction by matching the energy bands of the narrow-bandgap material with other two-dimensional materials with good stability, that is, the conduction band bottom of the narrow-bandgap material is lower than that of the wide-bandgap material, and the valence band top is higher than that of the wide-bandgap material. In this way, the conduction band and valence band of the narrow-bandgap material are completely clamped by the conduction band and valence band of the wide-bandgap material. Such an energy band structure and the vertically stacked device structure not only help to suppress the dark current of the detector, enhance the efficient transport of photo-generated carriers, but also enable wide-spectrum detection from visible light to mid-infrared. This structure can more effectively separate photo-generated electrons and holes, reduce the recombination rate of carriers during transport, and reduce interface scattering and noise, thereby improving the stability and light response performance of the device.

[0076] Therefore, for the PN heterojunction based on this type-I heterojunction energy band structure, when a reverse bias voltage is applied, a sufficiently large external electric field can be formed, and an additional potential barrier can be provided to suppress the tunneling current, increase the ratio of the response current to the dark current, and achieve high-contrast detection of infrared light. At the same time, using graphene as the electrode and sandwiching the heterojunction 10 in the middle of the vertical sandwich structure is beneficial to the separation of photo-generated carriers in the energy band arrangement structure of the type-I heterojunction, effectively improving the transport of photo-generated carriers in the device and achieving ultrafast infrared light switch response detection.

[0077] The specific preparation steps of the infrared photodetector of this application are as follows:

[0078] Substrate: A highly doped p-type silicon wafer substrate with a 300-nm oxide layer.

[0079] Preparation of source and drain electrodes: The substrate 1 is ultrasonically cleaned with isopropyl alcohol and ultrapure water for 20 minutes in sequence, then cleaned with ultraviolet ozone for 20 minutes to remove contaminants, and then a copper mesh with a specific hollow shape is adhered to the substrate 1 with a high-temperature tape, or an electrode pattern is prepared using a photolithography process with photoresist, and a bilayer metal of Cr (15 nm) / Au (50 nm) is deposited using an electron beam evaporation system (where Cr bonds Au to the substrate 1), and finally, the substrate 1 with metal source and drain electrodes is obtained.

[0080] Lift-off and dry transfer: In a glove box filled with nitrogen, bulk graphene, tungsten diselenide, black phosphorus, and hexagonal boron nitride are mechanically exfoliated onto a polydimethylsiloxane (PDMS) stamp using tape. Then, under an optical microscope, these two-dimensional layered materials are stacked onto the substrate 1 in sequence with the help of the PDMS stamp to construct a two-dimensional van der Waals structure.

[0081] An infrared photodetector with the above structure was fabricated. The substrate 1 is a highly doped p-type silicon wafer with a 300-nm oxide layer. The metal source electrode is a Cr and Au electrode. The thickness of Cr on the oxide layer is about 5 - 20 nm, and the thickness of Au on Cr is 20 - 200 nm. The bottom conductive layer is graphene with a thickness of 5 - 20 nm. The second layer of wide-bandgap material, tungsten diselenide, has a thickness of 10 - 30 nm. The third layer of narrow-bandgap material, black phosphorus, has a thickness of 10 - 100 nm. The fourth layer of conductive material, graphene, has a thickness of 5 - 20 nm. The fifth layer of protective layer 8 material, hexagonal boron nitride, has a thickness of 10 - 50 nm.

[0082] In some embodiments of the present application, the metal source electrode is a Cr and Au electrode. The thickness of Cr on the oxide layer is about 15 nm, and the thickness of Au on Cr is 50 nm. The bottom conductive layer is graphene with a thickness of 17 nm. The second layer of two-dimensional material, tungsten diselenide, has a thickness of 13 nm. The third layer of narrow-bandgap material, black phosphorus, has a thickness of 44 nm. The fourth layer of conductive material, graphene, has a thickness of 8 nm. The fifth layer of protective layer 8 material, hexagonal boron nitride, has a thickness of 34 nm.

[0083] In some embodiments of the present application, the thickness of Cr on the oxide layer is about 15 nm, and the thickness of Au on Cr is 50 nm. The bottom conductive layer is graphene with a thickness of 16 nm. The second layer of two-dimensional material, tungsten diselenide, has a thickness of 12 nm. The third layer of narrow-bandgap material, black phosphorus, has a thickness of 36 nm. The fourth layer of conductive material, graphene, has a thickness of 20 nm. The fifth layer of protective layer 8 material, hexagonal boron nitride, has a thickness of 28 nm.

[0084] In some embodiments of the present application, the thickness of Cr on the oxide layer is about 12 nm, and the thickness of Au on Cr is 50 nm. The bottom conductive layer is graphene with a thickness of 12 nm. The second layer of two-dimensional material, tungsten diselenide, has a thickness of 30 nm. The third layer of narrow-bandgap material, black phosphorus, has a thickness of 47 nm. The fourth layer of conductive material, graphene, has a thickness of 10 nm. The fifth layer of protective layer 8 material, hexagonal boron nitride, has a thickness of 23 nm.

[0085] Please refer to Figures 3 to 7 , Figure 3 which is the optical micrograph of the detector, Figure 4 and WSe2 this Figure 5 is the photocurrent imaging of the detector under 532-nm laser excitation (where V WSe2 = +1 V), Figure 6 and WSe2 this Figure 7This is the photocurrent imaging diagram of the detector under 1550 nm laser excitation (where V WSe2 =-1 V). Under the excitation of 532 nm laser and 1550 nm laser, it can be clearly observed that the photocurrent response regions at different bias voltages are all concentrated within the heterojunction 10, and no obvious photocurrent response is observed at both ends of the electrodes, indicating that ohmic contact is formed after graphene contacts with the metal electrodes, which is beneficial to the formation of the type-I energy band alignment of the heterojunction; at the same time, the photocurrent in the response region evenly covers the overlapping region of the first, second, and third layer materials (the bottom layer 4 and the heterojunction 10), indicating that the prepared photodetector has good contact at each interface, its built-in electric field is evenly distributed, and it has an efficient carrier separation and collection mechanism, which is beneficial to achieving high-speed optical switch response detection. According to the analysis of the photocurrent imaging diagram, in the visible light band, both positive and negative biases respond. However, in the infrared band, mainly the BP-WSe2 heterojunction plays a role, and an infrared response can be generated when this junction is reverse-biased, thus realizing effective detection in the infrared band.

[0086] Please refer to Figure 8 , Figure 8 This is the responsivity diagram of the infrared detector to incident light of different wavelengths at room temperature, and the results show that the detector can effectively detect the mid-infrared band.

[0087] Please refer to Figure 9 , Figure 9 This is the time-domain response current diagram of the infrared detector to different wavelengths of periodic switched mid-infrared light at room temperature. The results show that its optical response current and dark current platforms are stable. Without additional refrigeration equipment, there is no obvious thermal accumulation effect, and the device response is stably maintained at the microsecond level.

[0088] Please refer to Figure 10 , Figure 10 This is the optical response performance of the infrared detector to 1550 nm infrared light at room temperature, where the maximum responsivity is 25.68 A / W, and its optical response current can reach the nanoscale.

[0089] Please refer to Figure 11 , Figure 11 This is the time-domain response curve and response time calibration of the infrared detector to periodic switched 1550 nm infrared light at room temperature. Among them, the rise time is defined as the time required for the optical response current to increase from 10% to 90%, and the fall time is defined as the time required for the optical response current to decrease from 90% to 10%. According to the measurement results, the device shows a high-speed and stable response, with a rise time of 66 ns and a fall time of 127 ns. According to the formula f -3dB =0.35 / t r calculation, the device bandwidth is 2.8 MHz, which can be used for high-speed near-infrared communication.

[0090] Please refer toFigure 12 , Figure 12 is the time-domain optical response curve of the infrared detector to mid-infrared light at 2500 nm and 3000 nm with a periodically changing polarization direction. Due to the anisotropic optical properties of BP, this device has mid-infrared polarization resolution characteristics. A half-wave plate is placed in the optical path, and the mid-infrared polarized light is modulated in polarization direction by a rapidly rotating half-wave plate and then irradiated on the infrared detector. An oscilloscope is used to record the continuous change of the photocurrent response on the infrared detector. The results show that the infrared detector has a sensitive and stable polarized light response ability.

[0091] Please refer to Figure 13 , Figure 13 is the polar coordinate diagram of the photocurrent response of the infrared detector changing with the polarization direction under the irradiation of 2500 nm polarized light. And according to the formula:

[0092]

[0093] the normalized photocurrent of the device was fitted. As the angle changes from 0° to 360°, the device shows different photocurrent responses at different angles. The anisotropy of the photocurrent response was further confirmed by the polar coordinate diagram, and the result shows that the polarization ratio (PR) is 1.58, where the calculation of PR is based on the following formula:

[0094]

[0095] Please refer to Figure 14 , Figure 14 is the polar coordinate diagram of the photocurrent response of the infrared detector changing with the polarization direction under the irradiation of 3000 nm polarized light. Its polarization ratio was calculated to be 1.535.

[0096] In summary, this application constructs a stable vertical heterojunction 10 based on narrow-bandgap two-dimensional materials, forms a type-I heterojunction energy band arrangement structure through energy band matching, gives full play to the long-wavelength detection advantage of narrow-bandgap materials, and realizes wide-spectrum detection from visible light to mid-infrared at room temperature. This device can work at room temperature, has high responsivity and ultrafast response speed, and significantly improves the performance of infrared light detection.

[0097] Furthermore, a sandwich structure of graphene sandwiching the heterojunction 10 is adopted, enabling efficient transport of photo-generated carriers, effectively accelerating the photocurrent response speed of the device, and enabling high-speed and stable transmission of a large amount of data in the near-infrared to mid-infrared band. The photocurrent response of this device is not affected by the thermal effect in the infrared band under uncooled room temperature conditions, and the rising / falling edges and on / off response platforms are stable, ensuring reliable optical communication performance.

[0098] Meanwhile, the high-performance infrared photodetector based on the narrow-bandgap two-dimensional material heterojunction 10 of the present application can utilize the optical anisotropy of two-dimensional materials, have a sensitive response ability to polarized light, and achieve the detection of polarized light in the infrared band at room temperature.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way.

[0100] The various technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0101] The above embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. An infrared photoelectric detector, characterized in that: include: A bottom layer, a heterojunction, and a top layer are stacked in sequence from bottom to top, wherein the bottom layer is used to be electrically connected to a first electrode, the top layer is used to be electrically connected to a second electrode, the heterojunction at least partially covers the bottom layer, the top layer at least partially covers the heterojunction, the top layer is at least partially light-transmissive, and the heterojunction comprises a narrow bandgap material layer.

2. The infrared photoelectric detector according to claim 1, characterized in that: The heterojunction comprises a support layer made of a narrow bandgap material and a stacked layer made of a wide bandgap material, the stacked layer covers the support layer, the stacked layer at least partially covers the support layer, the support layer at least partially covers the bottom layer, and the top layer at least partially covers the stacked layer; or The heterojunction includes a support layer made of a wide bandgap material and a stacked layer made of a narrow bandgap material, wherein the stacked layer covers the support layer, the stacked layer at least partially covers the support layer, the support layer at least partially covers the bottom layer, and the top layer at least partially covers the stacked layer.

3. The infrared photoelectric detector according to claim 2, characterized in that: The narrow bandgap material and the wide bandgap material are both two-dimensional materials, and / or the stack at least partially covers the bottom layer.

4. The infrared photoelectric detector according to claim 3, characterized in that: The narrow bandgap material is any one of tellurium, black phosphorus, black arsenic, black arsenic phosphorus, platinum ditelluride or platinum diselenide, and the wide bandgap material is any one of tungsten diselenide, tungsten disulfide, molybdenum disulfide, molybdenum diselenide, molybdenum ditelluride, indium selenide, indium triselenide, hafnium disulfide, hafnium diselenide, rhenium disulfide, rhenium diselenide, tin disulfide, tin diselenide, gallium sulfide, gallium selenide, germanium sulfide or germanium selenide.

5. The infrared photoelectric detector according to claim 1, characterized in that: The heterojunction comprises a support layer and a stacked layer, wherein the stacked layer covers the support layer, the conduction band bottom of the stacked layer is higher than the conduction band bottom of the support layer, the valence band top of the stacked layer is lower than the valence band top of the support layer, and the stacked layer and the support layer form a type I heterojunction; or The heterojunction includes a supporting layer and a stacked layer, wherein the stacked layer covers the supporting layer, the conduction band bottom of the stacked layer is lower than the conduction band bottom of the supporting layer, the valence band top of the stacked layer is higher than the valence band top of the supporting layer, and the stacked layer and the supporting layer form a type I heterojunction.

6. The infrared photoelectric detector according to claim 1, characterized in that: The top layer and the bottom layer are both made of semiconductor two-dimensional materials, metallic two-dimensional materials, or semi-metallic two-dimensional materials.

7. The infrared photoelectric detector according to claim 6, characterized in that: The top layer and the bottom layer are both made of graphene.

8. The infrared photoelectric detector according to claim 1, characterized in that: The bottom layer and the top layer are laterally offset, and there is a distance between the lateral projections of the bottom layer and the top layer.

9. The infrared photoelectric detector according to claim 1, characterized in that: It also includes a substrate, the first electrode and the second electrode are respectively arranged on the left and right sides of the substrate, the heterojunction is arranged between the first electrode and the second electrode, one end of the bottom layer is electrically connected to the first electrode, the other end of the bottom layer is electrically connected to the heterojunction, one end of the top layer is electrically connected to the heterojunction, and the other end of the top layer is electrically connected to the second electrode.

10. The infrared photoelectric detector according to claim 9, characterized in that: It also includes a dielectric layer, which is arranged on the substrate, the first electrode and the second electrode are arranged on the left and right sides of the dielectric layer respectively, and the heterojunction is arranged between the first electrode and the second electrode.

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