A high-speed and high-efficiency photoelectric detector based on a full-dielectric superlens

Abstract

This invention discloses a high-speed, high-efficiency photodetector based on an all-dielectric metalens, relating to the field of photodetector technology. The high-speed, high-efficiency photodetector based on an all-dielectric metalens of this invention includes a detector and a metasurface lens formed on top of the detector; the detector includes a p-type layer, an intrinsic layer, and an n-type layer arranged sequentially from bottom to top; the metasurface lens is a metasurface structure with a gradient phase distribution, exhibiting achromatic properties, and is configured to focus perpendicularly incident light onto the intrinsic layer. Compared to existing technologies, this invention reconciles the contradiction between the responsivity and bandwidth of the photodetector, possessing the advantages of high speed and high efficiency, while simultaneously solving the wavelength sensitivity problem; moreover, the metasurface lens of the photodetector of this invention is implemented on an all-dielectric material, offering advantages of low loss and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of photodetector technology, and in particular to a high-speed, high-efficiency photodetector based on an all-dielectric superlens. Background Technology

[0002] In this highly information-driven era, the volume of information is enormous, and the speed of information transmission and processing is extremely rapid. Simultaneously, utilizing photons and electrons as energy and information carriers enables high-speed, high-capacity, low-crosstalk, and low-heat-dissipation information transmission, which has spurred the development of optoelectronic integrated circuit technology. Photodetectors are an indispensable component in optoelectronic integrated circuits. They utilize the photoelectric effect of semiconductors to convert optical signals into electrical signals, establishing a connection between optical and electrical signals. They play a crucial role in military, daily life, and scientific research, thus attracting increasing attention to research on photodetectors.

[0003] Responsivity and bandwidth are two crucial physical quantities for evaluating the performance of photodetectors. For vertically incident pin-type photodetectors, the thickness of the intrinsic layer directly affects the transit time of charge carriers. A thicker intrinsic layer results in a longer transit time, thus limiting the photodetector's response speed. From the perspective of response speed, the intrinsic layer should be as thin as possible to achieve a high-speed photodetector. However, on the other hand, a thicker intrinsic layer in a pin-type photodetector absorbs more photons, leading to higher quantum efficiency or responsivity. From the perspective of responsivity, the intrinsic layer of a pin-type photodetector should be as thick as possible. Therefore, response speed (or bandwidth) and responsivity are two mutually constraining physical quantities in photodetectors. To reconcile the trade-off between bandwidth and responsivity, numerous resonant cavity enhancement-type photodetectors have been proposed. However, an inherent drawback of resonant cavity enhancement-type photodetectors is their extremely high wavelength sensitivity, which significantly limits their applications.

[0004] In view of this, providing a new photodetector that reconciles the contradiction between responsivity and bandwidth while solving the problem of wavelength sensitivity will have great practical application value. Summary of the Invention

[0005] The purpose of this invention is to provide a high-speed, high-efficiency photodetector based on an all-dielectric superlens, so as to overcome the above-mentioned technical problems existing in photodetectors in the background art.

[0006] This invention is achieved through the following technical solution:

[0007] This invention provides a high-speed, high-efficiency photodetector based on an all-dielectric metalens, comprising a detector and a metasurface lens formed on top of the detector;

[0008] The detector comprises a p-type layer, an intrinsic layer, and an n-type layer arranged sequentially from bottom to top;

[0009] The metasurface lens is a metasurface structure with a gradient phase distribution, and the metasurface lens is configured to focus perpendicularly incident light onto the intrinsic layer.

[0010] Furthermore, the metasurface lens is composed of a non-periodic rectangular dielectric resonant cavity array.

[0011] Furthermore, the phase distribution of the metasurface lens is related to the wavelength by the following formula:

[0012]

[0013] In the formula, Let λ represent the phase, λ represent the wavelength of the incident light, x represent the position coordinates relative to the geometric center of the cell, and f represent the focal length of the metasurface lens.

[0014] Furthermore, the metasurface lens has achromatic properties.

[0015] Furthermore, the metasurface lens is made of a dielectric material.

[0016] Furthermore, the metasurface lens is formed by etching.

[0017] Furthermore, the detector is a photodiode composed of group III-V compounds or group IV elements from the periodic table.

[0018] Furthermore, the detector is a silicon photodetector or a germanium photodetector.

[0019] Furthermore, the detector also includes electrodes, which include a first electrode and a second electrode, wherein the first electrode is formed on the p-type layer and the second electrode is formed on the n-type layer.

[0020] Implementing this invention has the following beneficial effects:

[0021] This invention relates to a high-speed, high-efficiency photodetector based on an all-dielectric metalens. By incorporating a metalens structure within the photodetector, perpendicularly incident light can be focused onto the intrinsic layer, thereby improving the quantum efficiency of the photodetector. Furthermore, by adjusting the structural parameters of the metalens, the focal length can be reduced, resulting in a thinner intrinsic layer and improved response speed. Moreover, the metalens structure possesses achromatic properties, resolving the wavelength sensitivity issue of the photodetector. Compared to existing technologies, this invention reconciles the trade-off between responsivity and bandwidth, offering high speed and efficiency while simultaneously addressing wavelength sensitivity. Additionally, the metasurface lens in this photodetector is implemented on an all-dielectric material, overcoming the high loss and low efficiency problems of surface plasmon metasurface lenses, thus exhibiting low loss and high efficiency. Attached Figure Description

[0022] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the unit structure of the superlens according to an embodiment of the present invention;

[0024] Figure 2 This is a diagram showing the values ​​of w2 within the phase modulation range of 0 to 2π when w1 and g take different values ​​in this embodiment of the invention.

[0025] Figure 3 This is a schematic diagram of the structure of the photodetector according to an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the structure of another photodetector according to an embodiment of the present invention;

[0027] The corresponding reference numerals in the figures are: 1-substrate, 2-p+-Si layer, 2'-p+-Ge layer, 3-intrinsic layer, 4-n+-Si layer, 4'-n+-Ge layer, 5-metasurface lens, 6-first electrode, and 7-second electrode. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] In the description of this invention, it should be understood that the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.

[0030] Example

[0031] This embodiment provides a high-speed and high-efficiency photodetector based on an all-dielectric metalens, including a detector and a metasurface lens 5 formed on top of the detector; the detector is a pin-type detector, which includes a p-type layer, an intrinsic layer 3 and an n-type layer arranged sequentially from bottom to top; the metasurface lens 5 is a metasurface structure with a gradient phase distribution, and the metasurface lens 5 is configured to focus vertically incident light onto the intrinsic layer 3.

[0032] In this embodiment, by setting a metasurface lens 5 on the detector, the vertically incident light can be focused on the intrinsic layer 3, which improves the photoelectric conversion efficiency and thus improves the quantum efficiency or responsivity of the photodetector.

[0033] In this embodiment, the metasurface lens 5 is composed of a non-periodic rectangular dielectric resonant cavity array.

[0034] In one specific implementation, see Figure 1 The metasurface lens 5 is composed of a non-periodic rectangular dielectric resonant cavity array, wherein each cell includes two rectangular pillar structures, namely the first rectangular pillar and the second rectangular pillar.

[0035] In one specific implementation, considering phase modulation from 0 to 2π, the height of the rectangular pillar structure and the width of the cell satisfy: t = s, where t represents the height of the rectangular pillar structure and s represents the width of the cell, which is on the order of hundreds of nanometers.

[0036] It should be noted that in some other implementations, the width of the cell can be other sizes, and the relationship between the height of the rectangular column structure and the width of the cell can also be adjusted according to actual needs, as long as the same function can be achieved.

[0037] Furthermore, the phase distribution of the metasurface lens 5 is related to the wavelength by the following formula:

[0038]

[0039] In the formula, Let λ represent the phase, λ represent the wavelength of the incident light, x represent the position coordinates relative to the geometric center of the cell, and f represent the focal length of the metasurface lens.

[0040] In one specific implementation, the first rectangular column and the second rectangular column satisfy the following in terms of width and spacing: w1, w2, g ≥ 0, w1 + w2 + g ≤ s, where w1 represents the width of the first rectangular column, w2 represents the width of the second rectangular column, and g represents the spacing between the first rectangular column and the second rectangular column.

[0041] In one specific implementation, the position coordinate x relative to the geometric center of the cell can be labeled with p, p1, and p2, respectively. (See further...) Figure 1 Let p, p1, and p2 be defined as follows:

[0042] p = w1 + w2 + g;

[0043] p1 = -p / 2;

[0044] p2 = p1 + w1 + g;

[0045] When t = s = 550 nm, the simulation results show that the width w2 of the second rectangular pillar, which can achieve phase modulation in the range of 0 to 2π, can be obtained by taking different values ​​of w1 and g. Figure 2 As shown, the horizontal axis "phase" represents the phase. According to the phase distribution formula of the metasurface lens 5, for a certain focal length f, at the position x (x = ±ns) of the nth (n = 0, 1, 2, ...) cell, a set of values ​​for [w1, w2, g] can always be found that makes the actual phase at that point satisfy the phase distribution formula. The function of the rectangular dielectric resonant cavity is to enable the metasurface lens 5 to have achromatic characteristics by adjusting the values ​​of [w1, w2, g], thereby solving the problem of wavelength sensitivity of the photodetector. The more cells there are, the better the focusing effect; the actual number of cells used can be determined according to actual needs.

[0046] In this embodiment, by adjusting the structural parameters of the metasurface lens, the focal length of the metasurface lens can be reduced, thereby effectively reducing the thickness of the intrinsic layer 3 and obtaining a thinner intrinsic layer, which is beneficial to improving the response speed or bandwidth of the photodetector.

[0047] It should be noted that the structure of the metasurface lens 5 is not unique; any metasurface structure with focusing characteristics belongs to the metasurface lens of this invention. In other embodiments, according to the above formula, parameters such as s and t can be adjusted as needed, and other numbers of cells and other structural parameters can be obtained through simulation calculations. The adjustment of the structural parameters of the metasurface lens is also within the protection scope of this invention.

[0048] The photodetector in this embodiment, by introducing a superlens structure, can achieve focusing of incident light into the intrinsic layer, thereby greatly improving the quantum efficiency of the photodetector. Furthermore, by adjusting the structural parameters of the superlens, the focal length of the superlens can be changed to obtain a thinner intrinsic layer, thereby improving the response speed of the photodetector and offering the advantages of high speed and high efficiency.

[0049] In one specific implementation, the metasurface lens 5 has achromatic properties.

[0050] In one specific embodiment, the metasurface lens 5 is made of a dielectric material, which overcomes the problems of high loss and low efficiency of surface plasmon superlenses, and has the advantages of low loss and high efficiency.

[0051] In this embodiment, since the metasurface lens has achromatic properties, the problem of wavelength sensitivity of the photodetector can be solved. In addition, since the metasurface lens is realized on an all-dielectric material, it overcomes the problems of high loss and low efficiency of surface plasmon superlens structures, and has the advantages of low loss and high efficiency.

[0052] In one specific implementation, the detector also includes a substrate 1, with a p-type layer, an intrinsic layer 3, and an n-type layer sequentially disposed on the substrate 1.

[0053] In one specific implementation, the detector also includes electrodes, including a first electrode 6 and a second electrode 7. The first electrode 6 is formed on a p-type layer, and the second electrode 7 is formed on an n-type layer. Both the first electrode 6 and the second electrode 7 are metal electrodes.

[0054] As an optional implementation method, see [link / reference]. Figure 3 The detector is a silicon photodetector, comprising a substrate 1, a p+-Si layer 2, an i-Si layer, and an n+-Si layer 4. The i-Si layer serves as the intrinsic layer 3. A metasurface lens 5 is formed above the n+-Si layer 4. The p+-Si layer 2 is connected to a first electrode 6, and the n+-Si layer 4 is connected to a second electrode 7. The fabrication method of the silicon photodetector includes the following steps:

[0055] S1. Cleaning and preparing the wafer, including substrate 1, p+-Si layer 2, i-Si layer and n+-Si layer 4;

[0056] S2. An epitaxial silicon layer is grown on the n+-Si layer 4 of the wafer prepared in step S1.

[0057] S3. Spin-coat a layer of photoresist onto the silicon layer epitaxially grown in step S2, and then expose and develop it.

[0058] S4. Etching forms the corresponding metasurface lens structure;

[0059] S5. Photoresist coating, exposure, development and etching are performed in two steps. The first step is to etch down to the p+-Si layer 2, and the second step is to etch down to the substrate layer 1.

[0060] S6. Deposit metal electrodes on the p+-Si layer 2 and the n+-Si layer 4, respectively, as the first electrode 6 and the second electrode 7.

[0061] As an optional implementation method, see [link / reference]. Figure 4 The detector is a germanium photodetector, which includes a substrate 1, a p+-Si layer 2, a p+-Ge layer 2', an i-Ge layer, an n+-Ge layer 4', and an n+-Si layer 4. The i-Ge layer serves as the intrinsic layer 3. A metasurface lens 5 is formed above the n+-Si layer 4. The p+-Si layer 2 is connected to the first electrode 6, and the n+-Si layer 4 is connected to the second electrode 7. The fabrication method of the germanium photodetector includes the following steps:

[0062] S1. Clean and prepare the wafer, including substrate 1, p+-Si layer 2, p+-Ge layer 2', i-Ge layer, n+-Ge layer 4', and n+-Si layer 4;

[0063] S2. An epitaxial silicon layer is grown on the n+-Si layer 4 of the wafer prepared in step S1.

[0064] S3. Spin-coat a layer of photoresist onto the silicon layer epitaxially grown in step S2, and then expose and develop it.

[0065] S4. Etching forms the corresponding metasurface lens structure;

[0066] S5. Photoresist coating, exposure, development and etching are performed in two steps. The first step is to etch down to the p+-Si layer 2, and the second step is to etch down to the substrate layer 1.

[0067] S6. Deposit metal electrodes on the p+-Si layer 2 and the n+-Si layer 4, respectively, as the first electrode 6 and the second electrode 7.

[0068] In other embodiments, the germanium photodetector may not include the p+-Ge layer 2', and the present invention does not limit this.

[0069] In other embodiments, the detector may also be a photodiode composed of group III-V compounds or group IV elements from the periodic table, with a metasurface lens disposed thereon to focus perpendicularly incident light onto the intrinsic layer, thereby improving the quantum efficiency and response speed of the photodetector.

[0070] In this embodiment, the photodetector incorporates a superlens structure, enabling the focusing of incident light into the intrinsic layer, thereby significantly improving the quantum efficiency of the photodetector. Furthermore, by adjusting the structural parameters of the superlens, the focal length can be altered to obtain a thinner intrinsic layer, thus enhancing the photodetector's response speed. Moreover, since the superlens structure introduced into the photodetector possesses achromatic properties, the superlens photodetector overcomes the wavelength sensitivity problem. Finally, the superlens structure in this embodiment is implemented on an all-dielectric material, which overcomes the high loss and low efficiency issues of surface plasmon superlenses, offering advantages such as low loss and high efficiency.

[0071] The above embodiments of the present invention have the following beneficial effects: The high-speed and high-efficiency photodetector based on an all-dielectric superlens of the present invention, by setting a superlens structure in the photodetector, can focus perpendicularly incident light onto the intrinsic layer, thereby improving the quantum efficiency of the photodetector; by adjusting the structural parameters of the superlens, the focal length of the superlens can be reduced, thereby obtaining a thinner intrinsic layer and improving the response speed of the photodetector. Moreover, the superlens structure has achromatic characteristics, solving the problem of wavelength sensitivity of the photodetector. Compared with the prior art, the present invention reconciles the contradiction between the responsivity and bandwidth of the photodetector, and has the advantages of high speed and high efficiency, while solving the problem of wavelength sensitivity. In addition, the metasurface lens in the photodetector of the present invention is realized on an all-dielectric material. The all-dielectric metasurface lens can overcome the problems of high loss and low efficiency of surface plasmon metasurface lenses, and has the advantages of low loss and high efficiency.

[0072] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A high-speed, high-efficiency photodetector based on an all-dielectric superlens, characterized in that, It includes a detector and a metasurface lens (5) formed above the detector; the metasurface lens (5) is made of a dielectric material; The detector comprises a p-type layer, an intrinsic layer (3), and an n-type layer arranged sequentially from bottom to top; The metasurface lens (5) is a metasurface structure with a gradient phase distribution. The metasurface lens (5) is configured to focus perpendicularly incident light onto the intrinsic layer (3). The metasurface lens (5) is composed of a non-periodic rectangular dielectric resonant cavity array. Each cell includes two rectangular pillar structures. The two rectangular pillar structures include a first rectangular pillar and a second rectangular pillar. The structural parameters of the metasurface lens include the width of each cell, the width of each rectangular pillar, the spacing between the first rectangular pillar and the second rectangular pillar, and the height of each rectangular pillar. By adjusting the structural parameters, the focal length of the metasurface lens is shortened, thereby reducing the thickness of the intrinsic layer.

2. The high-speed, high-efficiency photodetector based on an all-dielectric superlens according to claim 1, characterized in that, The phase distribution of the metasurface lens (5) is related to the wavelength by the following formula: In the formula, Let λ represent the phase, λ represent the wavelength of the incident light, x represent the position coordinates relative to the geometric center of the cell, and f represent the focal length of the metasurface lens.

3. The high-speed, high-efficiency photodetector based on an all-dielectric superlens according to claim 1, characterized in that, The metasurface lens (5) has achromatic properties.

4. The high-speed, high-efficiency photodetector based on an all-dielectric superlens according to claim 1, characterized in that, The metasurface lens (5) is formed by etching.

5. The high-speed, high-efficiency photodetector based on an all-dielectric superlens according to claim 1, characterized in that, The detector is a photodiode composed of group III-V compounds or group IV elements from the periodic table.

6. The high-speed, high-efficiency photodetector based on an all-dielectric superlens according to claim 1, characterized in that, The detector is a silicon photodetector or a germanium photodetector.

7. The high-speed, high-efficiency photodetector based on an all-dielectric superlens according to claim 1, characterized in that, The detector also includes electrodes, which include a first electrode (6) and a second electrode (7), wherein the first electrode (6) is formed on the p-type layer and the second electrode (7) is formed on the n-type layer.

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