Intermediate infrared detector and preparation method thereof

Abstract

The invention discloses an intermediate infrared detector and a preparation method thereof, the intermediate infrared detector comprises a substrate, a metal electrode, a semiconductor film layer and a quantum dot layer, and an electron collection layer is arranged between the semiconductor film layer and the quantum dot layer. The electron collection layer meets the requirement that built-in potential is generated between the semiconductor thin film layer and the quantum dot layer so that electrons can be driven to the electron transmission layer from the quantum dot layer and then driven to the semiconductor thin film layer. The electron collection layer is introduced between the semiconductor thin film layer and the quantum dot layer, and photo-induced electrons are transferred from the quantum dot layer to the semiconductor thin film layer, so that the charge transmission efficiency is improved, and the responsivity of the intermediate infrared detector is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic chips, and particularly relates to a mid-infrared detector and a preparation method thereof. Background Art

[0002] The mid-infrared detector, i.e., the mid-wave infrared detector, needs to have characteristics such as high sensitivity, low noise, and wide spectral response, which puts higher requirements on the materials of the detector. At present, although materials such as HgCdTe (mercury cadmium telluride) and type-II superlattices perform well in the field of mid- and long-wave detection, the growth process of HgCdTe requires precise control of the composition and temperature, and has poor uniformity and small substrate size, resulting in high costs. While the type-II superlattice material has advantages such as low cost, repeatability, and operability, there is a large gap in the minority carrier lifetime compared with HgCdTe, resulting in a high possibility of generation-recombination current in the depletion region of the detector.

[0003] For quantum dot materials such as mercury telluride, due to its small and adjustable bandgap, it is applied to mid- and long-wave infrared detectors. At present, photoconductive detectors based on such quantum dots have also been reported based on spin coating, spraying, or inkjet printing techniques on integrated electrode structures. However, due to the low carrier mobility, the responsivity of these detectors is low. For example, in a mercury telluride / graphene composite photodetector, due to the low built-in potential, the driving force of the photo-generated holes from the mercury telluride quantum dots to graphene is limited. Therefore, although these systems can achieve high gain, their charge collection ability is low, and thus the responsivity is relatively low.

[0004] The information disclosed in this background art section is only intended to increase the understanding of the overall background of the present invention, and should not be regarded as an admission or any form of implication that this information constitutes the prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a mid-infrared detector and a preparation method thereof, and the mid-infrared detector has a relatively high responsivity.

[0006] In order to achieve the above purpose, the technical solution provided by a specific embodiment of the present invention is as follows:

[0007] A mid-infrared detector includes a substrate, a metal electrode, a semiconductor thin film layer, and a quantum dot layer. An electron collection layer is provided between the semiconductor thin film layer and the quantum dot layer, and the electron collection layer is configured to generate a built-in potential between the semiconductor thin film layer and the quantum dot layer to drive electrons from the quantum dot layer to the electron transport layer, and then to the semiconductor thin film layer.

[0008] In one or more embodiments of the present invention, the electron collection layer is an n-type material.

[0009] In one or more embodiments of the present invention, the electron collection layer is one of a titanium dioxide layer, a zinc oxide layer, a chromium oxide layer, and a nickel oxide layer.

[0010] In one or more embodiments of the present invention, the thickness of the electron collection layer is 20 nm to 30 nm.

[0011] In one or more embodiments of the present invention, the quantum dot layer is a mercury telluride layer or a mercury selenide layer.

[0012] In one or more embodiments of the present invention, the thickness of the quantum dot layer is 80 nm to 90 nm.

[0013] In one or more embodiments of the present invention, the semiconductor thin film layer is one of a graphene thin film layer, a molybdenum disulfide layer, and a tungsten disulfide layer.

[0014] In one or more embodiments of the present invention, the thickness of the semiconductor thin film layer is 0.3 nm to 0.5 nm.

[0015] In one or more embodiments of the present invention, the metal electrode includes an adhesion layer disposed on a substrate and an inert metal layer disposed on the adhesion layer. The material of the adhesion layer is chromium or titanium, and the material of the inert metal layer is gold;

[0016] The thickness of the adhesion layer is 15 nm to 30 nm, and the thickness of the inert metal layer is 70 nm to 85 nm.

[0017] The technical solution provided by another specific embodiment of the present invention is as follows:

[0018] A method for manufacturing a mid-infrared detector, comprising the following steps:

[0019] Provide a substrate and form a semiconductor thin film layer on the substrate;

[0020] Form a metal electrode connected to the semiconductor thin film layer on the substrate;

[0021] Form an electron collection layer on the surface of the semiconductor thin film layer;

[0022] Form a quantum dot layer on the surface of the electron collection layer to obtain a mid-infrared detector.

[0023] Compared with the prior art, the present invention introduces an electron collection layer between the semiconductor thin film layer and the quantum dot layer. By generating a built-in electric potential, electrons are driven from the quantum dot layer to the electron collection layer, and then to the semiconductor thin film layer, improving the charge transfer efficiency and enhancing the responsivity of the mid-infrared detector. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 Schematic diagram of the structure of a mid-infrared detector in an embodiment of the present invention;

[0026] Figures 2-6 Schematic diagram of the preparation process of a mid-infrared detector in an embodiment of the present invention.

[0027] Main reference numeral description:

[0028] 1. Substrate; 2. Semiconductor thin film layer; 3. Metal electrode; 4. Electron collection layer; 5. Quantum dot layer. Detailed implementation manners

[0029] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Graphene has an ultra-high carrier mobility, which means that electrons move very fast in graphene, facilitating the rapid separation and transmission of photo-generated carriers. This property enables graphene photodetectors to have the characteristics of high-speed response and low noise.

[0031] Mercury telluride is a narrow-bandgap semiconductor material with a bandgap width close to zero and can even exhibit a negative bandgap (i.e., the electron energy level is lower than the hole energy level), which endows mercury telluride quantum dots with metallic-like properties. By controlling the size of the quantum dots, their bandgap width can be adjusted, thereby realizing the regulation of optoelectronic properties.

[0032] The quantum dot / graphene composite photodetector generates a photoconductive mechanism by transferring photo-generated charges from the quantum dots to graphene. Combining the strong light absorption and bandgap tunability of the quantum dots for photo-generation of carriers, and the high mobility of single-layer graphene for efficient charge transport, an ultra-high gain is obtained. However, although these systems can achieve relatively high gains, their charge collection efficiency is poor.

[0033] Based on this, the present invention designs a mid-infrared detector with excellent charge collection. By adding an electron collection layer between the quantum dots and the semiconductor thin film layer (such as a graphene layer), electrons are driven from the quantum dots to the electron collection layer through the built-in potential, and then to the semiconductor thin film layer to improve charge collection.

[0034] A specific embodiment of the present invention provides a mid-infrared detector, such as Figure 1 shown, which includes a substrate 1, a metal electrode 3, a semiconductor thin film layer 2, and a quantum dot layer 5. An electron collection layer 4 is provided between the semiconductor thin film layer 2 and the quantum dot layer 5. The electron collection layer 4 is configured to generate a built-in potential between the semiconductor thin film layer 2 and the quantum dot layer 5 to drive electrons from the quantum dot layer 5 to the electron transport layer, and then to the semiconductor thin film layer 2.

[0035] Specifically, the electron collection layer 4 can generate a built-in potential to drive photo-generated electrons to the semiconductor thin film layer 2, thereby improving the mobility of photo-generated charge transfer in the quantum dots and enhancing the response speed and sensitivity of the detector.

[0036] Further, the electron collection layer is an n-type material, which is one of a titanium dioxide layer, a zinc oxide layer, a chromium oxide layer, and a nickel oxide layer, and has a thickness of 20 nm to 30 nm.

[0037] Further, the quantum dot layer is a mercury telluride layer or a mercury selenide layer, and has a thickness of 80 nm to 90 nm

[0038] Specifically, mercury telluride quantum dots have high carrier mobility and low resistance, which contribute to the efficient movement of electrons in the transport layer. Moreover, the infrared absorption spectrum range of mercury telluride quantum dots is wide and adjustable, enabling more effective capture and conversion of light energy, thereby improving the photoelectric conversion efficiency. Mercury selenide has high carrier mobility and long carrier lifetime, which helps to improve the response speed and detection efficiency of the detector.

[0039] Further, the semiconductor thin film layer is one of a graphene thin film layer, a molybdenum disulfide layer, and a tungsten disulfide layer, and has a thickness of 0.3 nm to 0.5 nm.

[0040] Specifically, graphene has excellent electrical properties and extremely high carrier mobility, capable of rapidly transporting photo-generated carriers, thus improving the response speed of the detector. Molybdenum disulfide has excellent optical and electrical properties and high carrier mobility. Tungsten disulfide has high conductivity and excellent carrier mobility. Both molybdenum disulfide and tungsten disulfide can play an important role in improving the sensitivity and response speed of the detector.

[0041] Further, the substrate 1 includes a substrate and a dielectric layer provided on the substrate. The substrate material is silicon, the dielectric layer material is silicon dioxide, and the thickness of the dielectric layer is 250 nm to 300 nm.

[0042] Furthermore, the metal electrode 3 includes an adhesion layer provided on the substrate 1 and an inert metal layer provided on the adhesion layer. The material of the adhesion layer is chromium or titanium, and the material of the inert metal layer is gold. The thickness of the adhesion layer is 15 nm to 30 nm, and the thickness of the inert metal layer is 70 nm to 85 nm. Selecting the above types of materials to prepare the metal electrode 3 and controlling the thickness of the metal electrode 3 can enable the metal electrode 3 to efficiently transfer photo-generated carriers to the external circuit and realize the conversion from optical signals to electrical signals.

[0043] Another specific embodiment of the present invention provides a method for manufacturing a mid-infrared detector, including steps 1-4.

[0044] Step 1: Provide the substrate 1 and form a semiconductor thin film layer 2 on the substrate 1.

[0045] Specifically, the substrate 1 includes a silicon substrate, and the surface of the silicon substrate has a silicon dioxide dielectric layer with a thickness of 250 nm to 300 nm. The semiconductor thin film layer 2 is a graphene thin film layer or a molybdenum disulfide layer or a tungsten disulfide layer. Taking the graphene thin film layer as an example, the graphene thin film grown by chemical vapor deposition is transferred onto the substrate 1, and then the actual required part of the graphene thin film layer is formed by oxygen plasma etching.

[0046] Furthermore, growing the graphene thin film by chemical vapor deposition is a conventional method. For example: Select and clean the SiO2 / Si substrate to ensure its surface is clean and free of impurities; put the substrate into the CVD chamber, heat it to a high temperature (such as 1000 °C) and perform an annealing treatment to activate the surface of the substrate; at a high temperature, introduce a hydrocarbon gas (such as methane) as a carbon source and auxiliary gases such as hydrogen into the CVD chamber; the hydrocarbon gas decomposes on the surface of the substrate, and carbon atoms rearrange on the surface of the substrate to form graphene. After growth is completed, let the substrate cool naturally or control the cooling rate, and then transfer the graphene from the substrate to the substrate 1. Among them, the transfer uses a conventional method, such as wet transfer.

[0047] Step 2: Form a metal electrode 3 connected to the semiconductor thin film on the substrate 1.

[0048] Furthermore, the metal electrode 3 is composed of an adhesion layer located on the substrate 1 and an inert metal layer located on the adhesion layer. The material of the adhesion layer is chromium or titanium, and the material of the inert metal layer is gold. The metal electrode 3 is prepared by deposition.

[0049] Step 3: Form an electron collection layer 4 on the surface of the semiconductor thin film layer 2.

[0050] Specifically, the electron collection layer 4 is one of a titanium dioxide layer, a zinc oxide layer, a chromium oxide layer, and a nickel oxide layer. The electron collection layer 4 is formed by atomic layer deposition and then the required part of the electron collection layer 4 is formed by etching. The atomic layer deposition is carried out by a conventional method.

[0051] Step 4: Form a quantum dot layer 5 on the electron collection layer 4.

[0052] Specifically, the quantum dot layer 5 is a mercury telluride layer or a mercury selenide layer, and the quantum dot layer 5 is obtained by spin-coating quantum dot ink on the electron collection layer 4.

[0053] The present invention will be further described in detail below in conjunction with specific embodiments.

[0054] Embodiment 1

[0055] A mid-infrared detector is prepared by the following method:

[0056] As Figure 2 shown, a substrate is provided. The substrate includes a silicon substrate, and a silicon dioxide dielectric layer with a thickness of 285 nm is on the surface of the silicon substrate. A graphene thin film obtained by chemical vapor deposition is transferred to the surface of the silicon dioxide dielectric layer. As Figure 3 , a layer of photoresist is spin-coated on the surface of the graphene thin film, exposed and developed to leave a photoresist structure, and then the graphene thin film is etched by oxygen plasma, and then the photoresist is removed by an acetone solution to obtain a required semiconductor thin film layer with a thickness of 0.3 nm.

[0057] As Figure 4 , a photoresist is spin-coated on the surface of the substrate, exposed and developed to leave a photoresist structure, and then metal is deposited. The metal electrode consists of two layers of metal. The bottom layer is an adhesion layer made of chromium with a thickness of 20 nm, and the upper layer is an inert metal layer made of gold with a thickness of 80 nm. Then the photoresist is washed off by an acetone solution, and the metal thin film on the surface of the photoresist is peeled off together to form a metal electrode connected to the semiconductor thin film layer.

[0058] As Figure 5 , a zinc oxide layer with a thickness of 20 nm is deposited on the surface of the graphene thin film by atomic layer deposition. As Figure 6 , a layer of photoresist is spin-coated on the surface of the zinc oxide layer, exposed and developed to leave a required photoresist structure, and then the zinc oxide layer is etched by dry etching, and the photoresist is removed by acetone to obtain a required electron transport layer.

[0059] Take quantum dot ink (Zhongxin Thermal Imaging, No. Xin-LWCQD-1), spin-coat it on the surface of the zinc oxide layer, and after drying, a quantum dot layer with a thickness of 80 nm is formed to obtain a mid-infrared detector with the structure shown in Figure 1 shown.

[0060] Embodiment 2

[0061] A mid-infrared detector is prepared by the following method:

[0062] Provide a substrate. The substrate includes a silicon substrate, and the surface of the silicon substrate has a silicon dioxide dielectric layer with a thickness of 285 nm. Transfer the graphene film grown by chemical vapor deposition to the surface of the silicon dioxide dielectric layer. Spin-coat a layer of photoresist on the graphene film, expose and develop to leave a photoresist structure, then etch the graphene film by oxygen plasma, and then remove the photoresist with an acetone solution to obtain the required semiconductor thin film layer with a thickness of 0.5 nm.

[0063] Spin-coat a photoresist on the substrate surface, expose and develop to leave a photoresist structure, and then deposit metal. The metal electrode consists of two layers of metal. The bottom layer is an adhesion layer made of chromium with a thickness of 20 nm, and the upper layer is an inert metal layer made of gold with a thickness of 80 nm. Then use an acetone solution to wash away the photoresist and strip the metal thin film on the photoresist surface together to form a metal electrode connected to the semiconductor thin film layer.

[0064] Deposit a titanium dioxide layer with a thickness of 30 nm on the surface of the graphene film layer by atomic layer deposition. Then spin-coat a layer of photoresist on the surface of the titanium dioxide layer, expose and develop to leave the required photoresist structure, then etch the titanium dioxide layer by dry etching, and remove the photoresist with acetone to obtain the required electron transport layer.

[0065] Take quantum dot ink (Zhongxin Thermal Imaging, No. Xin-LWCQD-1), spin-coat it on the surface of the titanium dioxide layer, and after drying, form a quantum dot layer with a thickness of 90 nm.

[0066] Example 3

[0067] A mid-infrared detector is prepared by the following method:

[0068] Provide a substrate. The substrate includes a silicon substrate, and the surface of the silicon substrate has a silicon dioxide dielectric layer with a thickness of 285 nm. Transfer the graphene film grown by chemical vapor deposition to the surface of the silicon dioxide dielectric layer. Spin-coat a layer of photoresist on the graphene film, expose and develop to leave a photoresist structure, then etch the graphene film by oxygen plasma, and then remove the photoresist with an acetone solution to obtain the required semiconductor thin film layer with a thickness of 0.3 nm.

[0069] Spin-coat a photoresist on the substrate surface, expose and develop to leave a photoresist structure, and then deposit metal. The metal electrode consists of two layers of metal. The bottom layer is an adhesion layer made of chromium with a thickness of 20 nm, and the upper layer is an inert metal layer made of gold with a thickness of 80 nm. Then use an acetone solution to wash away the photoresist and strip the metal thin film on the photoresist surface together to form a metal electrode connected to the semiconductor thin film layer.

[0070] Deposit a chromium oxide layer with a thickness of 25 nm on the surface of the graphene thin film layer by atomic layer deposition. Then, spin-coat a layer of photoresist on the surface of the chromium oxide layer, expose and develop it to leave the required photoresist structure, and then dry-etch the chromium oxide layer and remove the photoresist with acetone to obtain the required electron transport layer.

[0071] Take quantum dot ink (Zhongxin Thermal Imaging, No. Xin-LWCQD-1), spin-coat it on the surface of the chromium oxide layer, and after drying, form a quantum dot layer with a thickness of 80 nm.

[0072] Example 4

[0073] A mid-infrared detector is prepared by the following method:

[0074] Provide a substrate, the substrate includes a silicon substrate, and the surface of the silicon substrate has a silicon dioxide dielectric layer with a thickness of 285 nm. Transfer the graphene thin film grown by chemical vapor deposition to the surface of the silicon dioxide dielectric layer. Spin-coat a layer of photoresist on the surface of the graphene thin film, expose and develop it to leave the photoresist structure, and then dry-etch the graphene thin film with oxygen plasma and remove the photoresist with an acetone solution to obtain the required semiconductor thin film layer with a thickness of 0.3 nm.

[0075] Spin-coat a photoresist on the surface of the substrate, expose and develop it to leave the photoresist structure, and then deposit metal. The metal electrode consists of two layers of metal. The bottom layer is an adhesion layer made of chromium with a thickness of 15 nm, and the upper layer is an inert metal layer made of gold with a thickness of 85 nm. Then, wash off the photoresist with an acetone solution and strip the metal thin film on the surface of the photoresist to form a metal electrode connected to the semiconductor thin film layer.

[0076] Deposit a nickel oxide layer with a thickness of 20 nm on the surface of the graphene thin film layer by atomic layer deposition. Then, spin-coat a layer of photoresist on the surface of the nickel oxide layer, expose and develop it to leave the required photoresist structure, and then dry-etch the nickel oxide layer and remove the photoresist with acetone to obtain the required electron transport layer.

[0077] Take quantum dot ink (Zhongxin Thermal Imaging, No. Xin-LWCQD-1), spin-coat it on the surface of the nickel oxide layer, and after drying, form a quantum dot layer with a thickness of 90 nm.

[0078] Comparative example

[0079] A mid-infrared detector is prepared by the following method:

[0080] Provide a substrate, which includes a silicon substrate. The surface of the silicon substrate has a silicon dioxide dielectric layer with a thickness of 285 nm. Transfer the graphene film grown by chemical vapor deposition to the surface of the silicon dioxide dielectric layer. Spin-coat a layer of photoresist on the surface of the graphene film, expose and develop to leave a photoresist structure, then etch the graphene film by oxygen plasma, and then remove the photoresist using acetone solution to obtain the required semiconductor thin film layer with a thickness of 0.3 nm.

[0081] Spin-coat photoresist on the surface of the substrate, expose and develop to leave a photoresist structure, and then deposit metal. The metal electrode consists of two layers of metal. The bottom layer is an adhesion layer made of chromium with a thickness of 20 nm, and the upper layer is an inert metal layer made of gold with a thickness of 80 nm. Then use acetone solution to wash away the photoresist and strip the metal thin film on the surface of the photoresist together to form a metal electrode connected to the semiconductor thin film layer.

[0082] Take quantum dot ink (Zhongxin Thermal Imaging, No. Xin-LWCQD-1), spin-coat it on the surface of the graphene film, and after drying, form a quantum dot layer with a thickness of 80 nm.

[0083] Test the mid-infrared detectors in the examples and comparative examples by using mid-wave infrared light. The results show that compared with the comparative examples, the mid-infrared detectors in the examples of the present invention have higher responsivity, indicating that by setting an electron collection layer between the semiconductor thin film layer and the quantum dot layer, the present invention can improve the charge transfer rate, thereby enhancing the responsivity of the mid-infrared detector.

[0084] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0085] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard 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. A mid-infrared detector comprising a substrate, a metal electrode, a semiconductor thin film layer and a quantum dot layer, characterized in that: An electron collection layer is provided between the semiconductor thin film layer and the quantum dot layer, and the electron collection layer is sufficient to generate a built-in potential between the semiconductor thin film layer and the quantum dot layer to drive electrons from the quantum dot layer to the electron transport layer, and then to the semiconductor thin film layer.

2. The mid-infrared detector according to claim 1, characterized in that: The electron collection layer is an n-type material.

3. The mid-infrared detector according to claim 2, characterized in that: The electron collection layer is one of a titanium dioxide layer, a zinc oxide layer, a chromium oxide layer, and a nickel oxide layer.

4. The mid-infrared detector according to claim 1, characterized in that: The thickness of the electron collection layer is 20nm to 30nm.

5. The mid-infrared detector according to claim 1, characterized in that: The quantum dot layer is a mercury telluride layer or a mercury selenide layer.

6. The mid-infrared detector according to claim 1, characterized in that: The thickness of the quantum dot layer is 80nm-90nm.

7. The mid-infrared detector according to claim 1, characterized in that: The semiconductor film layer is one of a graphene film layer, a molybdenum disulfide layer and a tungsten disulfide layer.

8. The mid-infrared detector according to claim 1, characterized in that: The thickness of the semiconductor thin film layer is 0.3nm-0.5nm.

9. The mid-infrared detector according to claim 1, characterized in that: The metal electrode comprises an adhesion layer disposed on the substrate and an inert metal layer disposed on the adhesion layer, the material of the adhesion layer is chromium or titanium, and the material of the inert metal layer is gold; The thickness of the adhesion layer is 15nm-30nm, and the thickness of the inert metal layer is 70nm-85nm.

10. A method for preparing a mid-infrared detector according to any one of claims 1 to 9, characterized in that: The steps include: Providing a substrate, and forming a semiconductor thin film layer on the substrate; forming a metal electrode connected to the semiconductor thin film layer on the substrate; Forming an electron collection layer on the surface of the semiconductor thin film layer; A quantum dot layer is formed on the surface of the electron collection layer to obtain a mid-infrared detector.

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