Mid-infrared light detector and preparation method thereof

Abstract

The invention discloses a mid-infrared light detector and a preparation method thereof, and belongs to the technical field of light detection.The light detector comprises a piezoelectric substrate, and a Van der Waals heterojunction, an input interdigital transducer and an output interdigital transducer are arranged on the piezoelectric substrate; the input interdigital transducer and the output interdigital transducer are symmetrically arranged on two sides of the Van der Waals heterojunction; the input interdigital transducer is used for generating a surface acoustic wave according to the alternating current signal; and the output interdigital transducer is used for receiving the surface acoustic wave signal passing through the Van der Waals heterojunction and outputting the signal. According to the device, a periodic strain field and a piezoelectric field are formed on the surface of a substrate through surface acoustic waves, graphene plasmons are excited, mid-infrared light absorption is enhanced, photo-generated electron-hole space separation is promoted, photo-generated carrier recombination is inhibited, a photoelectric response signal is converted into an acoustoelectric signal, and the photoelectric response signal is converted into an acousto-electric signal. And high-performance mid-infrared light detection is realized by using the high-sensitivity response characteristic of the surface acoustic wave device to acoustoelectric interaction.

Description

Technical Field

[0001] The present invention relates to the field of light detection technology, and in particular to a mid-infrared light detector and a preparation method thereof. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] With the continuous emergence of new technology ecosystems such as artificial intelligence, smart cities, and the Internet of Things, photodetectors are developing towards high performance, small size, low energy consumption, low cost, and multifunctionality. Infrared light detectors that are sensitive to the mid-infrared band (3-8 μm) have important application value in the fields of infrared imaging and infrared guidance, and have become one of the research hotspots in the field of photodetection.

[0004] Two-dimensional materials represented by graphene, black phosphorus and transition metal chalcogenides have attracted widespread attention due to their layered structure, no surface dangling bonds, thickness-dependent band structure, strong light-matter interaction, and adjustable interlayer coupling properties. It is worth mentioning that some narrow-bandgap two-dimensional materials (black phosphorus, black arsenic phosphorus, PdSe2, Ta2NiSe5, etc.) have shown important application potential in the field of infrared detection due to their excellent optoelectronic properties, especially wide-spectrum absorption properties. Photoresponse intensity and detection sensitivity are the main indicators for measuring two-dimensional van der Waals mid-infrared photodetectors. The photoresponse intensity is the photogenerated current under unit light intensity, which represents the photoelectric conversion ability of the device; the detection sensitivity mainly characterizes the ability of the device to detect weak light signals. However, the main challenges faced by narrow-bandgap two-dimensional materials in infrared detection include: first, the low light absorption rate caused by the scale effect reduces the response intensity; second, the high background carrier concentration of narrow-bandgap two-dimensional materials leads to a large dark current, thereby reducing the detection sensitivity. To address this problem, the main technical means currently used is to use surface plasmon artificial microstructures to enhance light absorption through the resonant coupling of plasmons and infrared light, and to suppress dark current through local field regulation (such as ferroelectric field, interface built-in electric field, etc.). Such devices face challenges such as complex structure and difficult preparation process.

[0005] As a metal-like material, graphene can generate surface plasmons. Graphene surface plasmons have excellent properties such as high light field compression, highly enhanced local electromagnetic field, dynamically adjustable spectral response and low intrinsic loss, which greatly promotes the development of wide-band surface enhanced spectroscopy (covering the near-infrared to terahertz bands). There are usually two ways to prepare nanostructures that excite graphene surface plasmons: one is to pattern periodic nanostructures onto graphene through photolithography; the other is to couple graphene with other surface plasmon structures (metal nanoparticles, quantum dots, gratings, etc.). Obviously, these two methods are difficult to avoid causing the degradation of graphene's electrical properties (especially mobility), and the electrode or edge scattering reduces the plasmon lifetime, thereby reducing the detection sensitivity and responsiveness of the relevant detectors. On the other hand, in order to improve the polarization sensitivity of the device, that is, the ratio of the dichroicity of the photogenerated current, the design and preparation of surface plasmon structures with specific polarization selectivity requires the use of precise nano-processing technology to improve accuracy. The preparation process is complicated, which not only increases the difficulty of research and production, but also increases the cost. At the same time, metal nanostructures may deform under long-term light or high temperature conditions, which will affect the performance stability of surface plasmons and the long-term reliability of photodetectors. In addition, once the above-mentioned plasmon structures are prepared, it is difficult to control them on-chip. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a mid-infrared light detector and its preparation method. On the one hand, the periodic strain field and piezoelectric field formed by surface acoustic waves on the surface of the piezoelectric substrate can form a graphene grating, thereby exciting graphene plasmons to enhance mid-infrared light absorption; on the other hand, the strain field and piezoelectric field generated by surface acoustic waves are used to promote the spatial separation of photogenerated carriers (electron-hole pairs) and inhibit the recombination of photogenerated carriers. Then, the photoelectric response signal is converted into an acoustic-electric signal, and the high-sensitivity response mechanism of the surface acoustic wave device to the acoustic-electric interaction is used to improve the device responsiveness and detection sensitivity.

[0007] To achieve the above object, the present invention adopts the following technical solution: In the first aspect, a mid-infrared light detector is proposed, comprising a piezoelectric substrate, on which a van der Waals heterojunction, an input interdigital transducer and an output interdigital transducer are arranged; the input interdigital transducer and the output interdigital transducer are symmetrically arranged on both sides of the van der Waals heterojunction; An input interdigital transducer is used to generate a surface acoustic wave according to an alternating current signal; The output interdigital transducer is used to receive the surface acoustic wave signal after passing through the van der Waals heterojunction and output the signal.

[0008] Furthermore, the input IDT and the output IDT each include a pair of bus electrodes and multiple pairs of interdigital electrodes; the multiple pairs of interdigital electrodes are located between the pair of bus electrodes and connected to the bus electrodes.

[0009] Furthermore, the van der Waals heterojunction is located on a delay line between the input IDT and the output IDT.

[0010] Furthermore, the van der Waals heterojunction includes a graphene layer and a narrow bandgap two-dimensional semiconductor.

[0011] Furthermore, the narrow bandgap two-dimensional semiconductor is multilayered.

[0012] Furthermore, narrow-bandgap two-dimensional semiconductors are two-dimensional materials that can realize mid-infrared light detection.

[0013] Furthermore, the graphene layer is a single layer or a double layer.

[0014] Furthermore, the piezoelectric substrate is made of piezoelectric material.

[0015] Furthermore, the input IDT and the output IDT are made of metal-like material or metal material.

[0016] In the second aspect, a method for preparing a mid-infrared light detector is proposed, comprising: preparing a piezoelectric substrate; An input interdigital transducer and an output interdigital transducer are prepared on a piezoelectric substrate; A van der Waals heterojunction is fabricated between the input IDT and the output IDT.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The invention proposes a mid-infrared light detector and a preparation method thereof. The detector comprises a piezoelectric substrate, on which a van der Waals heterojunction, an input interdigital transducer and an output interdigital transducer are arranged; the input interdigital transducer and the output interdigital transducer are symmetrically arranged on both sides of the van der Waals heterojunction; the input interdigital transducer and the output interdigital transducer each comprise a pair of bus electrodes and a plurality of pairs of interdigital electrodes; the plurality of pairs of interdigital electrodes are located between a pair of bus electrodes and are connected to the bus electrodes; the input interdigital transducer is used to generate a surface acoustic wave according to an alternating current signal; the output interdigital transducer The device is used to receive the surface acoustic wave signal after passing through the van der Waals heterojunction and output the signal; through the periodic strain field and piezoelectric field generated by the surface acoustic wave on the surface of the piezoelectric substrate, a modulated optical grating is formed to modulate the plasmon, effectively enhance the interaction between the plasmon and the mid-infrared wave, and improve light absorption; at the same time, the periodic strain field generated by the acoustic surface promotes the spatial separation of photogenerated electrons and holes, suppresses recombination, and then uses the high-sensitivity response mechanism of the surface acoustic wave device to the acoustic-electric interaction to achieve high-performance mid-infrared light detection.

[0018] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0020] Figure 1 The figure is a schematic diagram of the overall structure of a mid-infrared light detector disclosed in an embodiment.

[0021] Wherein: 1. piezoelectric substrate, 2. graphene layer, 3. narrow bandgap two-dimensional semiconductor, 4. bus electrode, 5. interdigital electrode, 6. input interdigital transducer, 7. output interdigital transducer. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0023] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0024] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0025] In the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention, and do not specifically refer to any part or element in the present invention and should not be understood as limitations on the present invention.

[0026] In the present invention, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. Relevant scientific research or technical personnel in this field can determine the specific meanings of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0027] Example 1 In order to solve the problems that the current infrared detector preparation process is complicated, the cost is high, and the micro-nano structure of the plasmon is difficult to change after it is made, in this embodiment, a mid-infrared light detector is disclosed, the detector adopts a surface acoustic wave delay line device structure, selects a suitable piezoelectric substrate, designs and prepares an input interdigital transducer, an output interdigital transducer, and a van der Waals heterojunction containing a graphene layer and a narrow bandgap two-dimensional semiconductor located on the delay line on the piezoelectric substrate, and forms a modulated graphene optical grating through the periodic strain field and piezoelectric field generated by the surface acoustic wave, so as to achieve the modulation effect on the graphene plasmon, and effectively enhance the interaction between the graphene plasmon and the mid-infrared wave. At the same time, the strain field and the piezoelectric field can promote the spatial separation of photogenerated electrons and holes and suppress recombination. Then, the photoelectric response signal is converted into an acoustic-electric signal, and high-performance mid-infrared detection is achieved by means of the highly sensitive response mechanism of the surface acoustic wave device to the acoustic-electric interaction. The main advantages of the detector are: first, the formation of graphene gratings and the generation of plasmons do not require special processing technology, which effectively avoids damage to the material; second, the graphene grating period can be modulated by changing the electrical excitation frequency of the interdigital transducer, while traditional graphene patterning or metal structure coupling is difficult to change once prepared; third, the strain field and local electric field generated by surface acoustic waves are both micro-nano scale and controllable, which can effectively suppress the recombination of photogenerated carriers; fourth, the detector can realize passive wireless detection to meet the needs of complex and harsh environments, and is easy to integrate with integrated circuits to form detection chips and systems. In the future, it can be integrated into smart terminal devices, which is easy to carry, monitor in real time, and quickly feedback detection information, making the detector more intelligent and in line with the needs of contemporary people.

[0028] This embodiment discloses a mid-infrared light detector, such as Figure 1 As shown, it includes a piezoelectric substrate 1, on which a van der Waals heterojunction, an input interdigital transducer 6 and an output interdigital transducer 7 are arranged; the input interdigital transducer 6 and the output interdigital transducer 7 are symmetrically arranged on both sides of the van der Waals heterojunction; An input interdigital transducer 6 is used to generate a surface acoustic wave according to an alternating current signal; The output interdigital transducer 7 is used to receive the surface acoustic wave signal after passing through the van der Waals heterojunction and output the signal.

[0029] The surface of the piezoelectric substrate 1 can form a periodic strain field and a piezoelectric field by using surface acoustic waves, so that the graphene undergoes periodic deformation, and the carriers present a periodic spatial distribution, forming a graphene optical grating, exciting graphene plasmons, enhancing mid-infrared light absorption, and improving response intensity and detection sensitivity; using surface acoustic waves to form a periodic strain field and a piezoelectric field on the surface of the piezoelectric substrate, the conduction band and the valence band of the two-dimensional semiconductor also undergo periodic changes, so that the photogenerated electrons and holes are separated in space, and the photogenerated carriers are inhibited from recombination; under the mechanism of the acoustic-electric effect, the photogenerated carriers generated by the van der Waals heterojunction under light undergo acoustic-electric coupling with the surface acoustic wave device, thereby causing changes in the transmission characteristics of the device, causing acoustic wave frequency shift and transmission loss. With the help of the highly sensitive response mechanism of the surface acoustic wave device to the acoustic-electric interaction, high detection sensitivity is achieved, wherein the surface acoustic wave device refers to the piezoelectric substrate and the interdigital transducer component after removing the van der Waals heterojunction part.

[0030] The piezoelectric substrate is made of piezoelectric materials, such as lithium niobate (LiNbO3), zinc oxide (ZnO) or lead zirconate titanate piezoelectric ceramics (PZT).

[0031] The van der Waals heterojunction is located on the delay line between the input IDT 6 and the output IDT 7 .

[0032] The van der Waals heterojunction includes a graphene layer 2 and a narrow bandgap two-dimensional semiconductor 3. The graphene layer 2 is superimposed on a piezoelectric substrate 1, and the narrow bandgap two-dimensional semiconductor 3 is superimposed on the graphene layer 2, or the narrow bandgap two-dimensional semiconductor 3 is superimposed on the piezoelectric substrate 1, and the graphene layer 2 is superimposed on the narrow bandgap two-dimensional semiconductor 3.

[0033] The van der Waals heterojunction is connected to the piezoelectric substrate by mechanical exfoliation or growth deposition.

[0034] The narrow bandgap two-dimensional semiconductor 3 is a multilayer.

[0035] Narrow bandgap two-dimensional semiconductor materials include black phosphorus, black arsenic phosphide, palladium diselenide (PdSe2) or tantalum nickel ditelluride (Ta2NiSe5) and other two-dimensional materials that can realize mid-infrared light detection.

[0036] The graphene layer 2 is a single layer or a double layer.

[0037] The two IDTs have the same structure and material. The input IDT 6 and the output IDT 7 both include a pair of bus electrodes 4 and multiple pairs of interdigital electrodes 5 . The multiple pairs of interdigital electrodes 5 are located between the pair of bus electrodes 4 and connected to the bus electrodes 4 .

[0038] Specifically, the input interdigital transducer 6 and the output interdigital transducer 7 each include a pair of bus electrodes 4 and multiple pairs of interdigital electrodes 5; a pair of bus electrodes 4 include a first bus electrode and a second bus electrode in parallel; each pair of interdigital electrodes 5 includes a first finger portion and a second finger portion, a plurality of first fingers are arranged on one side of the first bus electrode, and a plurality of second fingers cooperating with the first fingers are arranged on a side of the second bus electrode close to the first return electrode; the plurality of second fingers are interlaced with the plurality of first fingers to form an interdigital transducer.

[0039] The input IDT and the output IDT are made of metal-like materials or metal materials, wherein the metal material is one or more of gold, silver, indium, copper or titanium, etc.; the metal-like material is graphene, etc.

[0040] A mid-infrared light detector disclosed in this embodiment does not require the preparation of metal electrodes on the van der Waals heterojunction, and the optical response of the device is characterized by testing the frequency, phase change or transmission loss of the surface acoustic wave under light by an interdigital transducer; the response spectrum range can cover the mid-infrared band; a modulated graphene optical grating is formed by the periodic strain field and piezoelectric field generated by the surface acoustic wave, which excites the graphene surface plasmons and enhances the absorption of mid-infrared light, and the strain field and local electric field generated by the surface acoustic wave are both micro-nano scale and controllable; the formation of the graphene grating and the generation of plasmons do not require special processing technology, which effectively avoids damage to the material; the graphene grating period can be adjusted by changing the frequency of the input interdigital transducer alternating current signal, while traditional graphene patterning or metal structure coupling is difficult to change and on-chip control once prepared.

[0041] A mid-infrared light detector disclosed in this embodiment can promote the separation of photogenerated electron-hole pairs through periodic strain fields and piezoelectric fields, inhibit the recombination of photogenerated carriers, and improve the device's responsiveness and detection sensitivity.

[0042] A mid-infrared light detector disclosed in this embodiment connects an input IDT to an AC power supply, provides an AC signal to the input IDT through the AC power supply, generates a surface acoustic wave through the AC signal input to the input IDT, and reaches the output IDT after passing through a van der Waals heterojunction; the output IDT receives the surface acoustic wave signal after passing through the van der Waals heterojunction and outputs it, feeds back a light response by analyzing the frequency, phase or transmission loss changes of the surface acoustic wave signal output by the output IDT, and determines a light detection result, thereby realizing passive wireless detection.

[0043] The mid-infrared light detector disclosed in this embodiment can be easily integrated with an integrated circuit to form a detection chip and system. In the future, it can be integrated into smart terminal devices such as mobile phones. It is easy to carry around, monitor in real time, and quickly feedback detection information, making the detector more intelligent and meeting the needs of contemporary people.

[0044] Example 2 In this embodiment, a method for preparing a mid-infrared light detector disclosed in Embodiment 1 is disclosed, comprising: preparing a piezoelectric substrate; An input interdigital transducer and an output interdigital transducer are prepared on a piezoelectric substrate; A van der Waals heterojunction is fabricated between the input IDT and the output IDT.

[0045] Among them, the input interdigital transducer and the output interdigital transducer are prepared on the piezoelectric substrate through processes such as photolithography or metal deposition.

[0046] Van der Waals heterojunctions were prepared on piezoelectric substrates by mechanical exfoliation or CVD techniques.

[0047] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A mid-infrared light detector, characterized in that: The piezoelectric substrate comprises a van der Waals heterojunction, an input interdigital transducer and an output interdigital transducer, which are arranged on the piezoelectric substrate; the input interdigital transducer and the output interdigital transducer are symmetrically arranged on both sides of the van der Waals heterojunction; An input interdigital transducer is used to generate a surface acoustic wave according to an alternating current signal; The output interdigital transducer is used to receive the surface acoustic wave signal after passing through the van der Waals heterojunction and output the signal.

2. A mid-infrared light detector as claimed in claim 1, characterized in that: The input interdigital transducer and the output interdigital transducer both include a pair of bus electrodes and a plurality of pairs of interdigital electrodes; the plurality of pairs of interdigital electrodes are located between the pair of bus electrodes and are connected to the bus electrodes.

3. A mid-infrared light detector as claimed in claim 1, characterized in that: The van der Waals heterojunction is located on the delay line between the input IDT and the output IDT.

4. A mid-infrared light detector as claimed in claim 1, characterized in that: The van der Waals heterojunction consists of a graphene layer and a narrow-bandgap two-dimensional semiconductor.

5. A mid-infrared light detector as claimed in claim 4, characterized in that: Narrow bandgap two-dimensional semiconductors are multilayered.

6. A mid-infrared light detector as claimed in claim 4, characterized in that: Narrow bandgap two-dimensional semiconductors are two-dimensional materials that can realize mid-infrared light detection.

7. A mid-infrared light detector as claimed in claim 4, characterized in that: The graphene layer is either a single layer or a double layer.

8. A mid-infrared light detector as claimed in claim 1, characterized in that: The piezoelectric substrate is made of piezoelectric material.

9. A mid-infrared light detector as claimed in claim 1, characterized in that: The input interdigital transducer and the output interdigital transducer are made of metal-like material or metal material.

10. The method for preparing a mid-infrared light detector according to any one of claims 1 to 9, characterized in that: include: preparing a piezoelectric substrate; An input interdigital transducer and an output interdigital transducer are prepared on a piezoelectric substrate; A van der Waals heterojunction is fabricated between the input IDT and the output IDT.

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