CN111244221A - A high-speed and high-efficiency photodetector based on all-dielectric metalens - Google Patents

Abstract

The invention discloses a high-speed and high-efficiency photoelectric detector based on an all-dielectric superlens, and relates to the technical field of photoelectric detectors. The invention relates to a high-speed high-efficiency photoelectric detector based on an all-dielectric super lens, which comprises a detector and a super surface lens formed above the detector; the detector comprises a p-type layer, an intrinsic layer and an n-type layer which are sequentially arranged from bottom to top; the super-surface lens is a super-surface structure with gradient phase distribution, the super-surface lens has achromatic property, and the super-surface lens is configured to focus vertically incident light to the intrinsic layer. Compared with the prior art, the invention coordinates the contradiction between the responsivity and the bandwidth of the photoelectric detector, has the advantages of high speed and high efficiency, and solves the problem of wavelength sensitivity; moreover, the super-surface lens of the photoelectric detector is realized on an all-dielectric material, and has the advantages of low loss and high efficiency.

Description

A high-speed and high-efficiency photodetector based on all-dielectric metalens

technical field

The invention relates to the technical field of photodetectors, in particular to a high-speed and high-efficiency photodetector based on an all-dielectric superlens.

Background technique

In the era of high informationization, the amount of information is very large, and the speed of information transmission and processing is very fast. At the same time, photons and electrons are used as carriers of energy and information to realize high-speed, large-capacity, low crosstalk and low heat dissipation. Information transmission, This has prompted the development of optoelectronic integration technology. Photodetector is one of the indispensable devices in optoelectronic integrated circuits. It can convert optical signals into electrical signals by using the photoelectric effect of semiconductors, and establish the connection between optical signals and electrical signals. It is used in military, life, scientific research, etc. Therefore, the research on photodetectors has attracted more and more attention.

Responsivity and bandwidth are two very important physical quantities to measure the performance of photodetectors. For normal-incidence pin-type photodetectors, the thickness of the intrinsic layer directly affects the carrier transit time. The thicker the intrinsic layer, the longer the carrier transit time, thus limiting the response speed of the photodetector. From the viewpoint of response speed, in order to obtain high-speed photodetectors, the intrinsic layer should be as thin as possible. But, on the other hand, the thicker the intrinsic layer of a pin-type photodetector, the more photons are absorbed and the higher the quantum efficiency or responsivity of the photodetector. From the perspective of responsivity, the intrinsic layer of the pin-type photodetector should be as thick as possible. Therefore, the response speed (or bandwidth) and responsivity are two physical quantities that restrict each other in the photodetector. In order to reconcile the contradiction between the bandwidth and responsivity of photodetectors, a large number of cavity-enhanced photodetectors have been proposed successively. However, an inherent disadvantage of cavity-enhanced photodetectors is the extremely strong wavelength sensitivity, which greatly limits their applications.

In view of this, providing a new photodetector to reconcile the contradiction between responsivity and bandwidth while solving the problem of wavelength sensitivity will have great practical application value.

SUMMARY OF THE INVENTION

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

The present invention is achieved through the following technical solutions:

The present invention provides a high-speed and high-efficiency photodetector based on an all-dielectric super-lens, comprising a detector and a meta-surface lens formed above the detector;

The detector includes a p-type layer, an intrinsic layer and an n-type layer arranged in sequence from bottom to top;

The metasurface lens is a metasurface structure with a gradient phase distribution configured to focus normally incident light onto the intrinsic layer.

Further, the metasurface lens is composed of aperiodic rectangular dielectric resonant cavity arrays.

Further, the relationship between the phase distribution of the metasurface lens and the wavelength satisfies the following formula:

表示相位，λ表示入射光的波长，x表示相对所述元胞几何中心的位置坐标，f表示所述超表面透镜的焦距。In the formula,

represents the phase, λ represents the wavelength of the incident light, x represents the position coordinate relative to the geometric center of the cell, and f represents the focal length of the metasurface lens.

Further, the metasurface lens has achromatic properties.

Further, the metasurface lens is made of a dielectric material.

Further, the metasurface lens is formed by etching.

Further, the detector is a photodiode composed of III-V group compounds or IV group elements in the periodic table of elements.

Further, the detector is a silicon photodetector or a germanium photodetector.

Further, the detector further includes an electrode, the electrode includes a first electrode and a second electrode, the first electrode is formed on the p-type layer, and the second electrode is formed on the n-type layer .

Implement the present invention, have the following beneficial effects:

The high-speed and high-efficiency photodetector based on the all-dielectric superlens of the present invention can focus the vertically incident light into the intrinsic layer by setting the superlens structure in the photodetector, thereby improving the quantum efficiency of the photodetector; The structural parameters of the metalens can reduce the focal length of the metalens, so that a thinner intrinsic layer can be obtained, and the response speed of the photodetector can be improved. Moreover, the metalens structure has achromatic properties, which solves the problem of wavelength sensitivity of photodetectors. Compared with the prior art, the invention balances the contradiction between the responsivity and the bandwidth of the photodetector, has the advantages of high speed and high efficiency, and simultaneously solves the problem of wavelength sensitivity. In addition, the metasurface lens in the photodetector of the present invention is realized on an all-dielectric material, and the all-dielectric metasurface lens can overcome the problems of large loss and low efficiency of the surface plasmon metasurface lens, and has the advantages of low loss and high efficiency. advantage.

Description of drawings

In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description The drawings are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

1 is a schematic diagram of a unit structure of a superlens according to an embodiment of the present invention;

2 is a diagram showing the value of w2 in a phase modulation range of 0 to 2π when w1 and g take different values in the embodiment of the present invention;

3 is a schematic structural diagram of a photodetector according to an embodiment of the present invention;

4 is a schematic structural diagram of another photodetector according to an embodiment of the present invention;

The reference numerals correspond to: 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, 7-second electrode.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

In the description of the present invention, it should be understood that the terms "first", "second" and the like are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It is to be understood that the data so used may be interchanged under appropriate circumstances such that the embodiments of the invention described herein can be practiced in sequences other than those illustrated or described herein.

Example

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 above the detector; the detector is a pin-type detector, and the detector includes a bottom-up detector. The p-type layer, the intrinsic layer 3 and the n-type layer are arranged in sequence; the meta-surface lens 5 is a meta-surface structure with gradient phase distribution, and the meta-surface lens 5 is configured to focus normal incident light to the intrinsic layer 3 .

In this embodiment, by arranging the metasurface lens 5 on the detector, the focusing of the vertically incident light on the intrinsic layer 3 can be realized, the photoelectric conversion efficiency can be improved, and thus the quantum efficiency or responsivity of the photodetector can be improved.

In this embodiment, the metasurface lens 5 is composed of an aperiodic rectangular dielectric resonant cavity array.

In a specific embodiment, referring to FIG. 1 , the metasurface lens 5 is composed of an aperiodic rectangular dielectric resonant cavity array, wherein each cell includes two rectangular column structures, which are a first rectangular column and a second rectangular column respectively. column.

In a specific embodiment, considering the phase modulation of 0-2π, the height of the rectangular column structure and the width of the cell satisfy: t=s, where t represents the height of the rectangular column structure, s represents the width of the cell, The width of the cells is on the order of hundreds of nanometers.

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

Further, the relationship between the phase distribution of the metasurface lens 5 and the wavelength satisfies the following formula:

表示相位，λ表示入射光的波长，x表示相对元胞几何中心的位置坐标，f表示超表面透镜的焦距。In the formula,

represents the phase, λ represents the wavelength of the incident light, x represents the position coordinate relative to the geometric center of the cell, and f represents the focal length of the metasurface lens.

In a specific embodiment, the width and spacing of the first rectangular column and the second rectangular column satisfy: 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 distance between the first rectangular column and the second rectangular column.

In a specific embodiment, the position coordinates x relative to the geometric center of the cell can be marked with p, p1, and p2, respectively. Continuing to refer to FIG. 1, p, p1, and p2 are respectively defined as:

p=w1+w2+g;

p1 = -p/2;

p2=p1+w1+g;

When t=s=550nm, when w1 and g take different values, the value of the second rectangular column width w2 that can achieve phase modulation in the range of 0 to 2π calculated by simulation is shown in Figure 2, where , the abscissa phase represents the phase. According to the phase distribution formula of the metasurface lens 5, corresponding to a certain focal length f, at the position x (x=±ns) of the nth (n=0, 1, 2, . . . ) cell, a The value of the group [w1,w2,g] is such that the actual phase there satisfies the phase distribution formula. The function of the rectangular dielectric cavity is that the metasurface lens 5 can be achromatic by adjusting the values of [w1, w2, g], so as to solve the problem of the wavelength sensitivity of the photodetector. The more the number of cells, the better the focusing effect. The actual number of cells used can be determined according to the actual needs.

In this embodiment, by adjusting the structural parameters of the metasurface lens, the focal length of the metasurface lens can be reduced, so that the thickness of the intrinsic layer 3 can be effectively reduced, and a thinner intrinsic layer can be obtained, which is beneficial to improve the photodetector response speed or bandwidth.

It should be noted that the structure of the meta-surface lens 5 is not unique, and any meta-surface structure with focusing properties belongs to the meta-surface lens of the present invention. In some other embodiments, according to the above formula, parameters such as s and t can be adjusted as required, and other numbers of cells and other structural parameters can be obtained through simulation calculation, and the adjustment of the structural parameters of the metasurface lens is also within the protection scope of the present invention.

In the photodetector of this embodiment, by introducing a superlens structure into the photodetector, the focusing of incident light in the intrinsic layer can be realized, thereby greatly improving the quantum efficiency of the photodetector. On the other hand, by adjusting the structural parameters of the metalens, the focal length of the metalens can be changed to obtain a thinner intrinsic layer, which can improve the response speed of the photodetector and has the advantages of high speed and high efficiency.

In a specific embodiment, the metasurface lens 5 has achromatic properties.

In a specific embodiment, the meta-surface lens 5 is made of a dielectric material, which overcomes the problems of large loss and low efficiency of the surface plasmon meta-lens, and has the advantages of low loss and high efficiency.

In this embodiment, since the meta-surface lens has achromatic properties, the problem of wavelength sensitivity of the photodetector can be solved. In addition, because the meta-surface lens is realized on all-dielectric materials, the surface plasmon meta-lens structure is overcome. The problem of large loss and low efficiency has the advantages of small loss and high efficiency.

As a specific implementation manner, the detector further includes a substrate 1 , and the p-type layer, the intrinsic layer 3 and the n-type layer are sequentially arranged on the substrate 1 .

As a specific embodiment, the detector further includes electrodes, the electrodes include a first electrode 6 and a second electrode 7, the first electrode 6 is formed on the p-type layer, the second electrode 7 is formed on the n-type layer, and the first electrode 6 is formed on the n-type layer. Both the electrode 6 and the second electrode 7 are metal electrodes.

As an optional embodiment, referring to FIG. 3, the detector is a silicon photodetector, and the silicon photodetector includes a substrate 1, a p+-Si layer 2, an i-Si layer and an n+-Si layer 4, and the i-Si layer As the intrinsic layer 3 , the meta-surface 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 preparation method of silicon photodetector includes the following steps:

S1, cleaning and preparing the wafer, including substrate 1, p+-Si layer 2, i-Si layer and n+-Si layer 4;

S2, epitaxially growing a silicon layer on the n+-Si layer 4 of the wafer prepared in step S1;

S3, spin coating a layer of photoresist on the silicon layer epitaxially grown in step S2, and perform exposure and development;

S4, etching to form a corresponding metasurface lens structure;

S5, photoresist coating, exposure development and etching are performed in two steps, the first step is to etch to the p+-Si layer 2, and the second step is to etch to the base layer 1;

S6. Metal electrodes are deposited on the p+-Si layer 2 and the n+-Si layer 4, which are the first electrode 6 and the second electrode 7 respectively.

As an optional embodiment, referring to FIG. 4 , the detector is a germanium photodetector, and the germanium photodetector includes a substrate 1, a p+-Si layer 2, a p+-Ge layer 2', an i-Ge layer, and an n+-Ge layer. Layer 4' and n+-Si layer 4, i-Ge layer is used as intrinsic layer 3, wherein meta-surface lens 5 is formed above n+-Si layer 4, p+-Si layer 2 is connected to first electrode 6, n+-Si layer 4 is connected to the second electrode 7. The preparation method of germanium photodetector includes the following steps:

S1, cleaning and preparing 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;

S2, epitaxially growing a silicon layer on the n+-Si layer 4 of the wafer prepared in step S1;

S3, spin coating a layer of photoresist on the silicon layer epitaxially grown in step S2, and perform exposure and development;

S4, etching to form a corresponding metasurface lens structure;

S5, photoresist coating, exposure development and etching are performed in two steps, the first step is to etch to the p+-Si layer 2, and the second step is to etch to the base layer 1;

S6. Metal electrodes are deposited on the p+-Si layer 2 and the n+-Si layer 4, which are the first electrode 6 and the second electrode 7 respectively.

In other embodiments, the germanium photodetector may also not include the p+-Ge layer 2', which is not limited in the present invention.

In other embodiments, the detector can also be a photodiode composed of III-V group compounds or IV group elements in the periodic table, on which a metasurface lens is arranged to focus the normal incident light to the intrinsic layer, thereby Improve the quantum efficiency and response speed of photodetectors.

In the photodetector of this embodiment, by introducing a superlens structure into the photodetector, the focusing of incident light in the intrinsic layer can be realized, thereby greatly improving the quantum efficiency of the photodetector. On the other hand, by adjusting the structural parameters of the metalens, the focal length of the metalens can be changed to obtain a thinner intrinsic layer, which can improve the response speed of the photodetector. Moreover, due to the achromatic properties of the metalens structure introduced in the photodetector, the metalens photodetector can overcome the problem of wavelength sensitivity. Finally, the superlens structure in the photodetector of this embodiment is realized on an all-dielectric material, and the all-dielectric superlens can overcome the problems of large loss and low efficiency of the surface plasmon superlens, and has the advantages of low loss and high efficiency.

The above-mentioned embodiments of the present invention have the following beneficial effects: the high-speed and high-efficiency photodetector based on the all-dielectric superlens of the present invention can focus the vertically incident light into the intrinsic layer by arranging the superlens structure in the photodetector, Thus, the quantum efficiency of the photodetector is improved; by adjusting the structural parameters of the superlens, the focal length of the superlens can be reduced, so that a thinner intrinsic layer can be obtained, and the response speed of the photodetector is improved. Moreover, the metalens structure has achromatic properties, which solves the problem of wavelength sensitivity of photodetectors. Compared with the prior art, the invention balances the contradiction between the responsivity and the bandwidth of the photodetector, has the advantages of high speed and high efficiency, and simultaneously solves the problem of wavelength sensitivity. In addition, the metasurface lens in the photodetector of the present invention is realized on an all-dielectric material, and the all-dielectric metasurface lens can overcome the problems of large loss and low efficiency of the surface plasmon metasurface lens, and has the advantages of low loss and high efficiency. advantage.

The above are the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made, and these improvements and modifications may also be regarded as It is the protection scope of the present invention.

Claims (9)

1. A high-speed and high-efficiency photoelectric detector based on an all-dielectric superlens is characterized by comprising a detector and a super-surface lens (5) formed above the detector;

the detector comprises a p-type layer, an intrinsic layer (3) and an n-type layer which are sequentially arranged from bottom to top;

the super-surface lens (5) is a super-surface structure with a gradient phase distribution, and the super-surface lens (5) is configured to focus vertically incident light to the intrinsic layer (3).

2. The all-dielectric-superlens-based high-speed high-efficiency photodetector according to claim 1, characterized in that the super-surface lens (5) is composed of an array of non-periodic rectangular dielectric resonant cavities.

3. The all-dielectric-superlens-based high-speed and high-efficiency photodetector according to claim 2, characterized in that the phase distribution of the supersurface lens (5) with respect to wavelength satisfies the following formula:

in the formula (I), the compound is shown in the specification,

denotes the phase, λ denotes the wavelength of the incident light, x denotes the position coordinates with respect to the geometric center of the cell, and f denotes the focal length of the super-surface lens.

4. The all-dielectric-superlens-based high-speed high-efficiency photodetector of claim 3, characterized in that the supersurface lens (5) has achromatic properties.

5. The all-dielectric-superlens-based high-speed high-efficiency photodetector according to claim 1, characterized in that the supersurface lens (5) is made of dielectric material.

6. The all-dielectric-superlens-based high-speed high-efficiency photodetector according to claim 1, characterized in that the super-surface lens (5) is formed by etching.

7. The all-dielectric-superlens-based high-speed high-efficiency photodetector of claim 1, wherein the detector is a photodiode formed of a group III-V compound or a group IV element of the periodic table.

8. The all-dielectric superlens based high-speed high-efficiency photodetector of claim 1, wherein the detector is a silicon photodetector or a germanium photodetector.

9. The all-dielectric-superlens-based high-speed high-efficiency photodetector of claim 1, further comprising electrodes, the electrodes comprising a first electrode (6) and a second electrode (7), the first electrode (6) being formed on the p-type layer and the second electrode (7) being formed on the n-type layer.

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