Multi-band absorber and photoelectric detector suitable for visible-near infrared band

Abstract

The invention relates to measurement of intensity and spectral content of infrared light and visible light, in particular to a multiband absorber suitable for visible-near infrared bands and a photoelectric detector, and the absorber comprises a substrate layer, a transition metal nitride layer, a semiconductor layer and a distributed Bragg reflector which are stacked in sequence. According to the invention, visible-near infrared multiband efficient absorption can be realized, the efficiency of each absorption peak is high, and the broadband photoelectric detection requirement in the visible-near infrared band range can be covered; the transition metal nitride layer has high-temperature stability and long-term reliability, and the problem that traditional precious metal is prone to oxidation and failure in the visible-near infrared band can be solved; the target function can be achieved only through layered stacking of the substrate layer, the transition metal nitride layer, the semiconductor layer and the distributed Bragg reflector thin film, complex device design is not needed, complex nanometer processing technologies such as electron beam lithography are not needed, and the advantages of being simple in technology, low in cost and easy to prepare in a large area are achieved.

Description

Technical Field

[0001] This invention relates to the measurement of the intensity and spectral content of infrared and visible light (corresponding IPC classification number G01J), specifically to a multi-band absorber and a photodetector suitable for the visible-near infrared band. Background Technology

[0002] Multi-band photodetectors have significant application value in fields such as optical communication, spectral analysis, infrared imaging, and environmental monitoring. Traditional photoelectric absorption devices typically rely on the intrinsic band gap of materials to achieve absorption, making it difficult to simultaneously cover a wide wavelength range or achieve multi-peak absorption in a single device. Furthermore, they have limited absorption efficiency, complex device structures, and high fabrication costs.

[0003] In recent years, optical absorption in specific wavelength bands has been achieved by coupling distributed Bragg reflectors (DBRs) with metal layers to form Tamm-like plasmon modes. However, conventional noble metals such as gold (Au) and silver (Ag) suffer from poor thermal stability and low durability in the visible-near-infrared band, which limits the reliability and practical application of the devices. Summary of the Invention

[0004] In view of this, the present invention provides a multi-band absorber and a photodetector suitable for the visible-near infrared band, aiming to achieve efficient absorption of multiple peaks in the visible-near infrared band while also possessing durability, so as to meet the practical application requirements of multi-band photodetector.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A multi-band absorber suitable for the visible-near infrared band includes a substrate layer, a transition metal nitride layer, a semiconductor layer and a distributed Bragg reflector stacked sequentially.

[0006] As an optional implementation, the transition metal nitride layer is made of any one of titanium nitride (TiN), vanadium nitride (VN), zirconium nitride (ZrN), and hafnium nitride (HfN).

[0007] As an optional implementation, the distributed Bragg reflector includes N periodically alternating layers of first and second dielectric layers; one of the first and second dielectric layers is made of tantalum pentoxide (Ta2O5) and the other is made of silicon dioxide (SiO2); N is an integer ≥1.

[0008] As an optional implementation, N ≥ 2 and ≤ 8.

[0009] As an optional implementation, the thickness of the transition metal nitride layer is 60 nm to 120 nm; the thickness of the semiconductor layer is 18 nm to 25 nm; the thickness of the first dielectric layer and the second dielectric layer with a higher refractive index is 80 nm to 220 nm, and the thickness of the one with a lower refractive index is 120 nm to 300 nm.

[0010] As an alternative implementation, the semiconductor layer is made of molybdenum disulfide (MoS2).

[0011] As an alternative implementation, the substrate layer is made of silicon (Si).

[0012] A photodetector includes an absorber as described above.

[0013] In summary, compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention can achieve high-efficiency absorption in multiple visible-near infrared bands, with high efficiency for each absorption peak, and can cover the wide-band photoelectric detection needs in the visible-near infrared band range; it can be widely used in multi-band photoelectric detectors, Tamm plasmonic devices, and thermo-optical detection, balancing performance and application flexibility; the transition metal nitride layer has high-temperature stability and long-term reliability, which can overcome the problems of easy oxidation and failure of traditional noble metals in the visible-near infrared band; the structure is simple, and the target function can be achieved by simply stacking the substrate layer-transition metal nitride layer-semiconductor layer-distributed Bragg reflector thin film, without the need for complex device design or complex nanofabrication processes such as electron beam lithography, which has the advantages of simple process, low cost and easy large-area fabrication. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the stacked structure of the absorber described in this invention.

[0015] Figure 2 This is the absorption spectrum of the absorber described in Example 1.

[0016] Figure 3 The absorption spectrum of the absorber when gold (Au) is used instead of titanium nitride (TiN) in Example 1 is shown.

[0017] Figure 4 The absorption spectrum of the absorber when the precious metal silver (Ag) is used instead of titanium nitride (TiN) in Example 1 is shown.

[0018] Figure 5 The absorption spectrum of the absorber described in Example 1 is shown when the distributed Bragg mirror has different number of periods N.

[0019] Figure 6The absorption spectrum of the absorber described in Example 1 is shown under different combinations of the thicknesses of the first and second dielectric layers in the distributed Bragg mirror.

[0020] Figure 7 The absorption spectra of the absorber described in Example 1 are shown for different thicknesses of the transition metal nitride layer.

[0021] Figure 8 This is the absorption spectrum of the absorber described in Example 2.

[0022] Figure 9 This is the photoresponsivity diagram of the photodetector described in Example 3.

[0023] The reference numerals in the figures are defined as follows: 1. Substrate layer; 2. Transition metal nitride layer; 3. Semiconductor layer; 4. Distributed Bragg mirror; 41. First dielectric layer; 42. Second dielectric layer. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to specific embodiments.

[0025] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0026] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the stated number, while "above," "below," "within," etc. are understood to include the stated number. If terms such as "first," "second," etc., are used only to distinguish technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0027] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0028] Example 1 like Figure 1As shown, this invention introduces a multi-band absorber suitable for the visible-near-infrared band, comprising a substrate layer 1, a transition metal nitride layer 2, a semiconductor layer 3, and a distributed Bragg reflector 4 stacked sequentially. Light is incident from the side of the distributed Bragg reflector 4.

[0029] The substrate 1 can be made of silicon (Si), and its thickness is not limited.

[0030] The transition metal nitride layer 2 is made of any one of titanium nitride (TiN), vanadium nitride (VN), zirconium nitride (ZrN), and hafnium nitride (HfN), and its thickness can be set to 60 nanometers (inclusive) to 120 nanometers (inclusive).

[0031] The semiconductor layer 3 can be made of molybdenum disulfide (MoS2), with a thickness of 18 nm to 25 nm. While an excessively thin MoS2 layer offers high interface quality, it results in a short effective absorption path, making it difficult to achieve sufficient light energy capture. Conversely, an excessively thick MoS2 layer introduces additional optical losses and weakens the cavity resonance enhancement effect, hindering efficient light absorption. Therefore, selecting a MoS2 thickness of 18 nm to 25 nm ensures structural stability while achieving superior optical field coupling and absorption efficiency.

[0032] The distributed Bragg reflector 4 comprises N periodically alternating layers of first dielectric layers 41 and second dielectric layers 42, where N is an integer ≥ 1, preferably 2 ≤ N ≤ 8. One first dielectric layer 41 and one adjacent second dielectric layer 42 constitute one period. For example, when the number of periods N = 2, the layers are stacked sequentially: first dielectric layer 41, second dielectric layer 42, first dielectric layer 41, second dielectric layer 42; when the number of periods N = 3, the layers are stacked sequentially: first dielectric layer 41, second dielectric layer 42, first dielectric layer 41, second dielectric layer 42, first dielectric layer 41, second dielectric layer 42.

[0033] The refractive indices of the first dielectric layer 41 and the second dielectric layer 42 are different. For example, the refractive index of the first dielectric layer 41 may be greater than that of the second dielectric layer 42, or the refractive index of the first dielectric layer 41 may be less than that of the second dielectric layer 42.

[0034] The thickness design of distributed Bragg reflectors is typically based on the quarter-wavelength condition to achieve maximum reflectivity at the target center wavelength. For a distributed Bragg reflector structure composed of alternating high- and low-refractive-index materials, the following condition must be satisfied at the design center wavelength λ0: n H ×d H =λ0 / 4 and n L ×d L =λ0 / 4, where nH d represents the refractive index of a high-refractive-index material. H n represents the thickness of the high refractive index material. L d represents the refractive index of a low-refractive-index material. L The thickness of the low-refractive-index material is given. Based on the aforementioned quarter-wavelength matching condition, the position of the central reflection band of the distributed Bragg reflector is directly related to the optical thickness of each layer. Therefore, when the material thickness deviates from the design value, its reflection bandgap and the resulting cavity mode or Tamm mode resonance conditions will change, thus affecting the absorption spectrum response of the device. By combining the target operating wavelength range and the actual refractive index parameters of the material in the visible-near-infrared region for reverse calculation and optimization design, a reasonable range of structural parameters can be obtained. Therefore, in this invention, the thickness range of the first dielectric layer 41 and the second dielectric layer 42 with the higher refractive index can be set to 80 nm (inclusive) to 220 nm (inclusive), and the thickness range of the one with the lower refractive index can be set to 120 nm (inclusive) to 300 nm (inclusive) to ensure that the reflection bandgap covers the target absorption wavelength range and also takes into account the multimode resonance modulation requirements.

[0035] One of the first dielectric layer 41 and the second dielectric layer 42 can be made of tantalum pentoxide (Ta2O5), and the other can be made of silicon dioxide (SiO2). The refractive index of tantalum pentoxide (Ta2O5) is greater than that of silicon dioxide (SiO2).

[0036] In Example 1, the substrate layer 1 is made of silicon (Si); the transition metal nitride layer 2 is made of titanium nitride (TiN) with a thickness of 100 nm; the semiconductor layer 3 is made of molybdenum disulfide (MoS2) with a thickness of 20 nm; the first dielectric layer 41 is made of tantalum pentoxide (Ta2O5) with a thickness of 200 nm; the second dielectric layer 42 is made of silicon dioxide (SiO2) with a thickness of 270 nm; and the number of periods N of the distributed Bragg reflector 4 is 8. The absorption spectrum of this absorber is shown below. Figure 2 As shown.

[0037] Figure 2 In the graph, the horizontal axis represents the wavelength of light (in nanometers), and the vertical axis represents the light absorption rate of the absorber. The green curve represents the light absorption rate when the absorber only includes semiconductor layer 3 (MoS2). The red curve represents the light absorption rate when the absorber includes a combination of transition metal nitride layer 2 (TiN), semiconductor layer 3 (MoS2), and distributed Bragg mirror 4 (DBR). The blue curve represents the light absorption rate when the absorber only includes distributed Bragg mirror 4 (DBR). The yellow curve represents the light absorption rate when the absorber only includes transition metal nitride layer 2 (TiN).

[0038] from Figure 2 It can be clearly seen that only when the absorber includes a combination of a transition metal nitride layer 2 (TiN), a semiconductor layer 3 (MoS2), and a distributed Bragg reflector 4 (DBR) can multi-band absorption peaks be generated in the visible-near infrared band range of 550 nm to 1000 nm.

[0039] This is because the Distributed Bragg Reflector 4 (DBR), as a highly reflective photonic bandgap structure, provides strong reflection and precise phase modulation capabilities within its bandgap, enabling the incident light to form an effective optical cavity within the structure. This cavity satisfies the phase-matching condition at the interface with the transition metal nitride layer 2 (TiN), thereby exciting multiple Tamm-like surface resonances and cavity modes. The transition metal nitride layer 2 (TiN) is the primary energy dissipation center. Under the influence of the resonantly enhanced local electromagnetic field, it efficiently converts the trapped light energy into electronic excitation through ohmic loss, achieving strong absorption. The semiconductor layer 3 (MoS2) provides intrinsic semiconductor absorption and participates in cavity field distribution modulation, further enhancing the light-matter interaction in the metal-semiconductor region. Due to the photon confinement effect of the distributed Bragg reflector 4 (DBR) and the plasmon dissipation mechanism of the transition metal nitride layer 2 (TiN), the structure forms multiple discrete resonant enhancement absorption peaks in the 550 nm to 1000 nm wavelength range. This causes light to be reflected and interfered with multiple times in the structure and dissipated step by step, thus exhibiting multi-band high absorption characteristics in the visible to near-infrared range.

[0040] Figure 3 and Figure 4 The absorption spectra are shown respectively when the transition metal nitride layer 2 (TiN) in the absorber described in Example 1 is replaced by noble metal gold (Au) or silver (Ag). Figure 3 and Figure 4 In the diagram, the horizontal axis represents the wavelength of light (in nanometers), and the vertical axis represents the absorption rate of the absorber.

[0041] from Figure 3 and Figure 4 As can be seen, the transition metal nitride layer 2 in the absorber can still maintain multi-band resonant absorption characteristics after being replaced by noble metals gold (Au) or silver (Ag). This is because the distributed Bragg mirror 4 (DBR) and the metal interface can still form cavity enhancement and Tamm-like modes.

[0042] However, compared to structures using transition metal nitrides such as titanium nitride (TiN) as the transition metal nitride layer 2, the absorption change in the visible band is not significant, while the absorption intensity in the near-infrared band is significantly reduced. This phenomenon is mainly due to the low intrinsic loss of gold (Au) and silver (Ag) in the near-infrared region, making it difficult to effectively convert electromagnetic energy into dissipative absorption. In contrast, transition metal nitrides such as titanium nitride (TiN) combine plasmon resonance characteristics with moderate ohmic loss, enabling stronger light energy dissipation and multi-order resonant coupling under cavity enhancement, thus achieving more efficient multi-peak absorption characteristics in the visible to near-infrared range, which is beneficial for improving the overall photoelectric conversion efficiency.

[0043] In addition, the present invention uses refractory metal nitrides such as titanium nitride (TiN), vanadium nitride (VN), zirconium nitride (ZrN), and hafnium nitride (HfN) to form a transition metal nitride layer 2, which has high temperature stability and long-term reliability, and can overcome the problems of easy oxidation and failure of traditional precious metals in the visible-near infrared band.

[0044] This invention employs molybdenum disulfide (MoS2) connected to a transition metal nitride layer 2 and a distributed Bragg mirror 4. This is because MoS2, as a two-dimensional semiconductor material, possesses atomic-level thickness and high interface uniformity, enabling it to bond tightly with the transition metal nitride layer 2 and the distributed Bragg mirror 4, forming a high-quality interface structure. This structure facilitates strong coupling between light and materials, thereby enhancing localized light absorption. Simultaneously, MoS2 itself has a suitable bandgap and tunable optical absorption characteristics, covering the multi-peak absorption requirements from the visible to near-infrared bands, allowing the absorber to achieve efficient energy capture over a wide spectral range. The two-dimensional nature of MoS2 also results in lower optical loss and higher carrier mobility, which is beneficial for the rapid transport and efficient utilization of photoexcited carriers, thereby improving absorption efficiency and overall device response performance.

[0045] The absorber described in this invention is tunable, such as... Figure 5 As shown, the target absorption band of the absorber can be controlled by adjusting the number of periods N of the distributed Bragg mirror 4 (DBR).

[0046] Figure 5 In the diagram, the horizontal axis represents the wavelength of light (in nanometers), and the vertical axis represents the absorption rate of the absorber. Curves of different colors represent the absorption rates of the absorber when the distributed Bragg reflector (DBR) has different number of periods N.

[0047] from Figure 5As can be seen, the number of absorption peaks of the absorber decreases as the number of periods N of the distributed Bragg mirror 4 (DBR) decreases, and the position of the absorption peaks also changes accordingly. This indicates that the absorber is tunable and the target absorption band of the absorber can be controlled by adjusting the number of periods N of the distributed Bragg mirror 4 (DBR).

[0048] from Figure 5 It can also be seen that when the number of periods N of the distributed Bragg reflector 4 (DBR) is 2, the absorber still has two strong absorption peaks, and the peak intensity remains at a high level, indicating that effective multi-band absorption can still be formed even with a small number of periods. Meanwhile, as the number of periods increases, the absorption bands become more numerous and stronger, but the structural complexity and manufacturing cost also increase accordingly. Therefore, while considering absorption performance, structural stability, and process feasibility, this invention sets the range of the number of periods N to 2 (inclusive) to 8 (inclusive) to meet the requirements of different operating bands and multi-mode control.

[0049] like Figure 6 As shown, the target absorption band of the absorber can also be controlled by adjusting the thickness of the first dielectric layer 41 and the second dielectric layer 42 in the distributed Bragg reflector 4.

[0050] Figure 6 In the graph, the horizontal axis represents the wavelength of light (in nanometers), and the vertical axis represents the light absorption rate of the absorber. The blue curve represents the light absorption rate of the absorber described in Example 1 after the thickness of tantalum pentoxide (Ta2O5) is halved in each cycle. The yellow curve represents the light absorption rate of the absorber described in Example 1 after the thickness of silicon dioxide (SiO2) is halved in each cycle. The red curve represents the light absorption rate of the absorber described in Example 1. from Figure 6 As can be seen, the resonant position and number of absorption peaks of the absorber are highly sensitive to the thickness of the silicon dioxide (SiO2) and tantalum pentoxide (Ta2O5) layers. Reducing the thickness of these layers will cause the resonant position to shift significantly and the number of absorption peaks to decrease, indicating that the device is tunable and the target absorption band of the absorber can be controlled by adjusting the thickness of the first dielectric layer 41 and the second dielectric layer 42 in the distributed Bragg reflector 4.

[0051] The present invention can also optimize the absorption rate of the absorber in the target absorption band by adjusting the thickness of the transition metal nitride layer 2.

[0052] like Figure 7 As shown, the horizontal axis represents the wavelength of light (in nanometers), and the vertical axis represents the absorption rate of the absorber. The curves of different colors represent the absorption rates of the absorber when the transition metal nitride layer 2 made of titanium nitride (TiN) has different thicknesses (in nanometers).

[0053] from Figure 7 As can be seen, the absorption peak intensity is quite sensitive to the thickness of the titanium nitride (TiN) layer. As the thickness of the titanium nitride (TiN) layer decreases, the absorption peak gradually decreases, indicating that the matching relationship between metal loss and intracavity field enhancement has a significant impact on absorption performance. This shows that the absorber also has good tunability, and the absorption rate of the target absorption band can be optimized by adjusting the thickness of the transition metal nitride layer 2.

[0054] It can also be noted that when the titanium nitride (TiN) layer thickness is 60 nm, the absorber can still maintain an absorption rate of over 88%, indicating that it has a certain structural margin while ensuring high absorption efficiency. However, when the titanium nitride (TiN) layer thickness is greater than 120 nm, the metal layer approaches an optically opaque state, making it difficult for the intracavity electromagnetic field to be effectively coupled to the metal / DBR interface region. This results in weakened resonance modulation capability and increased material loss, which is detrimental to device performance optimization. Therefore, this invention sets the thickness range of the transition metal nitride layer 2 to 60 nm (inclusive) to 120 nm (inclusive) to achieve a balance between high absorption efficiency and structural tunability.

[0055] Example 2 In Example 2, the substrate layer 1 is made of silicon (Si); the transition metal nitride layer 2 is made of vanadium nitride (VN) with a thickness of 100 nm; the semiconductor layer 3 is made of molybdenum disulfide (MoS2) with a thickness of 20 nm; the first dielectric layer 41 is made of tantalum pentoxide (Ta2O5) with a thickness of 200 nm; the second dielectric layer 42 is made of silicon dioxide (SiO2) with a thickness of 270 nm; and the number of periods N of the distributed Bragg reflector 4 is 8. The absorption spectrum of this absorber is shown below. Figure 8 As shown.

[0056] from Figure 8 As can be seen from the example, the absorber described in Example 2 also has multi-band high absorption characteristics in the visible-near infrared band range of 550 nm to 1000 nm.

[0057] Example 3 Example 3 also introduces a photodetector, which includes a first electrode, a second electrode, and the absorber described in Examples 1 and 2. One of the first and second electrodes is electrically connected to the transition metal nitride layer 2, and the other is electrically connected to the semiconductor layer 3. This photodetector can be used to collect charge carriers generated by illumination and output photoelectric signals. It can be used for multi-band photodetection and can achieve multi-peak efficient absorption in the visible-near-infrared band range of 550 nm to 1000 nm.

[0058] This invention also simulated and calculated the photoelectric response application of the photodetector described in Example 3, and obtained the following results: Figure 9 The light responsivity diagram is shown.

[0059] Figure 9 In the diagram, the horizontal axis represents the wavelength of light (in nanometers), and the vertical axis represents the photodetector's responsivity to light (in milliamperes per watt). This responsivity is used to measure the photoelectric conversion capability of the photodetector.

[0060] In this invention, a Schottky barrier is formed at the interface between molybdenum disulfide (MoS2) and a transition metal nitride layer 2 (e.g., TiN). When the photodetector is irradiated with visible-near-infrared light, the incident light energy is absorbed by the multi-peak Tamm plasmon-like modes coupled to the DBR–TiN layer, generating hot electrons in the titanium nitride (TiN) layer. Some of these hot electrons, whose energy exceeds the height of the Schottky barrier at the MoS2 / TiN interface, can be injected into the MoS2 semiconductor, forming a photocurrent. By controlling the number of DBR layer periods, thickness, and material, simultaneous control of multi-band light absorption and hot electron generation can be achieved, thereby obtaining a tunable photoelectric response in the 550 nm–1000 nm wavelength range.

[0061] In this invention, molybdenum disulfide (MoS2) possesses a moderate band gap and excellent interface tunability. It can form a Schottky barrier of suitable height when in contact with transition metal nitrides such as titanium nitride (TiN), which mainly ensures that hot electrons can effectively cross the barrier for injection, while maintaining low dark current and good rectification characteristics. At the same time, as a two-dimensional material, molybdenum disulfide (MoS2) has advantages such as atomic-level thickness, high interface cleanliness, and low carrier scattering, which are conducive to improving hot electron transport efficiency and interface tunability, thereby improving the overall photoelectric detection performance.

[0062] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, various improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multi-band absorber suitable for the visible-near-infrared band, characterized in that: It includes a substrate layer (1), a transition metal nitride layer (2), a semiconductor layer (3), and a distributed Bragg reflector (4) stacked in sequence.

2. A multi-band absorber suitable for the visible-near-infrared band as described in claim 1, characterized in that: The transition metal nitride layer (2) is made of any one of titanium nitride (TiN), vanadium nitride (VN), zirconium nitride (ZrN), and hafnium nitride (HfN).

3. A multi-band absorber suitable for the visible-near-infrared band as described in claim 1, characterized in that: The distributed Bragg reflector (4) comprises N periodically alternating layers of first dielectric layer (41) and second dielectric layer (41). One of the first dielectric layer (41) and the second dielectric layer (42) is made of tantalum pentoxide (Ta2O5), and the other is made of silicon dioxide (SiO2); N is an integer ≥ 1.

4. A multi-band absorber suitable for the visible-near-infrared band as described in claim 3, characterized in that: The N ≥ 2 and ≤ 8.

5. A multi-band absorber suitable for the visible-near-infrared band as described in claim 3, characterized in that: The thickness of the transition metal nitride layer (2) is 60 nanometers to 120 nanometers; The thickness of the semiconductor layer (3) is 18 nanometers to 25 nanometers; The thickness of the first dielectric layer (41) and the second dielectric layer (42) with a higher refractive index is 80 nm to 220 nm, and the thickness of the one with a lower refractive index is 120 nm to 300 nm.

6. A multi-band absorber suitable for the visible-near-infrared band as described in claim 1, characterized in that: The semiconductor layer (3) is made of molybdenum disulfide (MoS2).

7. A multi-band absorber suitable for the visible-near-infrared band as described in claim 1, characterized in that: The substrate layer (1) is made of silicon (Si).

8. A photodetector, characterized in that: Includes the absorber as described in any one of claims 1-7.

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