All-dielectric metasurface enhanced photoelectric detector and preparation method thereof

Abstract

The invention provides an all-dielectric resonance enhanced photoelectric detector and a manufacturing method thereof, and belongs to the field of micro-nano processing and silicon-based photoelectric detectors. The enhanced photoelectric detector comprises a bottom SOI (Silicon On Insulator) substrate; the first Si doping layer is arranged above the substrate; the semiconductor absorption layer is arranged above the first Si doping layer, the interior of the semiconductor absorption layer is designed to be a periodic layered artificial unit, after incident light enters, remarkable local field enhancement is achieved on the layer, and photon-generated carriers are generated; the second Si doping layer is arranged above the semiconductor layer; and the deposition passivation layer is arranged on the uppermost layer and is used for protecting the surface of the metasurface. According to the high-speed photoelectric detector based on all-dielectric metasurface enhancement, the responsivity of the detector can be improved, and meanwhile the problem of mutual restriction between response bandwidth and the responsivity is solved.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano processing and photoelectric detection technology, and specifically relates to an all-dielectric meta-structure surface enhanced photoelectric detector and a preparation method thereof. Background Art

[0002] Photodetectors are important optoelectronic devices that convert optical signals into electrical signals and are widely used in fields such as optical fiber communication, environmental monitoring, and biomedical imaging. Photodetectors can be divided into two types according to the optical coupling method and actual application scenarios: surface-incident type and waveguide-coupled type. The surface-incident type has a simple structure and is widely used in fields such as optical communication and optical sensing. The waveguide-coupled type is easy to integrate with other waveguide-type active and passive devices, so it has advantages in the field of on-chip optical interconnection. However, due to the technical difficulties in coupling and monolithic integration, its application scenarios are relatively few. At present, surface-incident photodetectors are still the mainstream solution in the design of optical modules. However, there is a mutual constraint between the responsivity and the response bandwidth of the surface-incident photodetector. Increasing the thickness of the absorption layer can improve the responsivity of the detector and reduce the junction capacitance, but it also increases the transit time of the carriers in the absorption layer and reduces the response bandwidth of the detector. A sufficiently thin absorption layer can reduce the transit time of the carriers and increase the response bandwidth, but it reduces the responsivity of the detector. In order to solve the contradiction between the responsivity and the response bandwidth of the detector, the introduction of all-dielectric metasurfaces can ensure a higher light absorption rate in a thinner absorption layer.

[0003] Optical metasurfaces were originally mainly composed of metal nanostructure units, which can achieve significant local field enhancement on the device surface and affect the direction of electromagnetic radiation on the metasurface. However, metal materials have strong ohmic losses in the optical band, which reduces the efficiency and performance of the metasurface. All-dielectric metasurfaces do not have ohmic losses and support strong electric and magnetic resonances. The light field is mainly concentrated inside the dielectric nanostructure, which is conducive to enhancing the interaction between light and the medium. Summary of the invention

[0004] The technical problem solved by the present invention is to overcome the technical problem that the responsivity and response bandwidth of the existing surface-incident photoelectric detectors are mutually restricted, and to provide an all-dielectric meta-structure surface-enhanced photoelectric detector and a preparation method thereof.

[0005] The technical solution of the present invention is: an all-dielectric metastructure surface-enhanced photodetector, comprising: an SOI substrate, a first Si doping layer, a semiconductor absorption layer, a second Si doping layer, and a deposited passivation layer;

[0006] The SOI substrate is located at the bottom layer and is used to confine light in the semiconductor absorption layer;

[0007] A first Si doping layer is placed above the SOI substrate, for contacting a first electrode connected to an external circuit and enabling epitaxial growth of semiconductor material on the Si surface;

[0008] The semiconductor absorption layer is disposed above the first Si doped layer, and the layer is composed of a periodically arranged polygonal column array to form an all-dielectric metasurface, which is used to enhance the absorption of incident light and generate photogenerated carriers to form photocurrent;

[0009] The second Si doping layer is disposed above the semiconductor absorption layer and is used to contact a second electrode connected to an external circuit to achieve photocurrent transmission;

[0010] A deposited passivation layer is placed on top to protect the device.

[0011] The SOI substrate adopts a sandwich structure of silicon-insulator-silicon, specifically including a bottom silicon layer, a middle silicon dioxide insulating layer, and a top silicon layer.

[0012] The doping concentrations of the first Si doping layer and the second Si doping layer are both greater than 1×10 20 cm -3 .

[0013] The passivation layer material is silicon dioxide or silicon nitride.

[0014] The semiconductor material used in the semiconductor absorption layer is InGaAs, GaAs of group III-V or Ge of group IV.

[0015] The all-dielectric metasurface inside the semiconductor absorption layer is composed of a polygonal column array, and the overall outline of the all-dielectric metasurface is square or circular; the geometric parameters of each unit in the polygonal column array include: period, semiconductor absorption layer thickness, semiconductor absorption layer etching thickness, and length from each vertex of the polygon to the center.

[0016] The all-dielectric metasurface inside the semiconductor absorption layer is processed by full etching or partial etching.

[0017] The all-dielectric metasurface material is doped with P-type and N-type respectively, and the doping concentration is greater than 1×10 19 cm -3 , where the P-type layer, the intrinsic layer and the N-type layer constitute a PIN-type diode structure.

[0018] The absorption rate of the all-dielectric metasurface in the detection band is between 80% and 98.82%;

[0019] A method for preparing the detector comprises:

[0020] Using molecular beam epitaxy to grow a first Si doping layer, a semiconductor absorption layer, and a second Si doping layer required for the detector on the top silicon of the SOI substrate;

[0021] Made of spin-coated glass or photoresist, the mask is patterned by electron beam exposure, UV exposure or nanoimprinting. After development, Ti or Au is deposited by EBE as a mark for multiple exposures of subsequent detectors. The photoresist is dissolved in a solvent to complete the stripping.

[0022] Spin-coated glass or photoresist, pattern the mask by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE etching to a specific thickness to complete the processing of the full dielectric metasurface;

[0023] Spin-coated glass or photoresist, pattern the mask by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE etching to above the first Si doping layer to complete the first-order mesa processing;

[0024] Made of spin-coated glass or photoresist, the mask is patterned by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE etching is performed above the silicon dioxide insulating layer in the middle of the SOI substrate to complete the second-order mesa processing;

[0025] Low temperature deposition of silicon dioxide or silicon nitride to complete the passivation layer processing;

[0026] Made of spin-coated glass or photoresist, the mask is patterned by electron beam exposure, UV exposure or nanoimprinting. After development, the passivation layer is over-etched by ICP or RIE to complete the window opening.

[0027] The advantages of the present invention over the prior art are: the all-dielectric metasurface enhanced photodetector of the present invention introduces optical resonance on the all-dielectric metasurface through reasonable structural design to achieve enhanced light absorption within a specific spectral range. Compared with the prior art, the all-dielectric metasurface enhanced photodetector does not need to use a reflector to construct a resonant cavity, avoiding complex process manufacturing problems; in addition, the all-dielectric metasurface does not have the ohmic loss of the metal metasurface in the optical band, avoiding the influence of the heat generated after energy conversion on the stability of the device; at the same time, the thinner semiconductor absorption layer greatly solves the yield problem of micro-nano processing; it has the characteristics of small junction capacitance and low dark current, thereby solving the contradiction between high responsiveness and high response bandwidth, and improving the performance of the surface-incident photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the three-dimensional structure of the all-dielectric metasurface enhanced photodetector according to the first embodiment of the present invention;

[0029] Figure 2This is a front view of the structure of the all-dielectric metasurface enhanced photodetector according to the first embodiment of the present invention;

[0030] Figure 3 It is a top view of the all-dielectric metastructure surface-enhanced photodetector structure according to the first embodiment of the present invention and an enlarged schematic diagram of a polygonal nanocolumn unit;

[0031] Figure 4 It is a wide range spectral response curve of the all-dielectric meta-structure surface enhanced photodetector according to the first embodiment of the present invention;

[0032] Figure 5 This is a diagram of the electric field distribution in the xz direction inside the all-dielectric metasurface enhanced photodetector according to the first embodiment of the present invention;

[0033] Figure 6 This is a diagram showing the electric field distribution in the xy direction inside the all-dielectric metasurface-enhanced photodetector according to the first embodiment of the present invention;

[0034] Figure 7 is the C-band spectral response curve of the all-dielectric meta-structure surface-enhanced photodetector according to the second embodiment of the present invention;

[0035] Figure 8 is the O-band spectral response curve of the all-dielectric meta-structure surface-enhanced photodetector according to the third embodiment of the present invention;

[0036] Fig. 9 is a near-infrared band spectral response curve of the all-dielectric meta-structure surface-enhanced photodetector according to the third embodiment of the present invention; DETAILED DESCRIPTION

[0037] Implementation Plan 1

[0038] Figure 1 It is a schematic diagram of the three-dimensional structure of the all-dielectric metasurface enhanced photodetector of implementation scheme 1.

[0039] like Figure 1-Figure 3 As shown, the all-dielectric metasurface enhanced photodetector includes an SOI substrate 1, a first Si doped layer 2, a semiconductor absorption layer 3, and a second Si doped layer 4 arranged in sequence from bottom to top; wherein the SOI substrate 1 includes a bottom silicon 10, a silicon dioxide insulating layer 11, and a top silicon 12; the inside of the semiconductor absorption layer 3 is an all-dielectric metasurface 30 composed of a polygonal nanocolumn array; the all-dielectric metasurface 30 is composed of polygonal nanocolumn units 301 arranged periodically or non-periodically. The enlarged schematic diagram of the polygonal nanocolumn unit 301 is shown in FIG. Figure 3As shown, the electromagnetic response of the polygonal nanocolumn unit 301 can be adjusted by adjusting its geometric parameters, which include the period of the array, the thickness of the semiconductor absorption layer, the etching thickness of the semiconductor absorption layer, the length from each vertex of the polygon to the center, and the breakage.

[0040] In the exemplary embodiment, the first Si doping layer 2 and the second Si doping layer 4 serve as electrode contact layers, and the doping concentrations of the first Si doping layer 2 and the second Si doping layer 4 are both greater than 1×10 20 cm -3 To form a good ohmic contact.

[0041] In an exemplary embodiment, a low temperature deposited silicon dioxide or silicon nitride passivation layer 5 is used to protect the device.

[0042] In the exemplary embodiment, the semiconductor absorption layer metasurface material is made of germanium (Ge), and is doped with P-type and N-type, with the doping concentration being greater than 1×10 19 cm -3 , where the P-type layer, intrinsic layer and N-type layer form a PIN diode structure. Based on semiconductor theory, when the incident light hits the detector light absorption layer, the photon energy is absorbed by the semiconductor material. If the photon energy is greater than or equal to the band gap energy of the material, it will excite the valence band electrons to transition to the conduction band, leaving a hole in the valence band and generating an electron-hole pair. Under the action of reverse bias, the electron-hole pair quickly separates under the action of the built-in electric field to form a high-speed photocurrent.

[0043] The time it takes for photogenerated carriers to form photocurrent and be received by the external electrode is called response time, which is a key parameter to measure the speed of the detector's response to light signals. The response time is mainly related to the carrier's transit time in the depletion region and the detector's RC constant. The transit time can be expressed as:

[0044]

[0045] Where W is the width of the depletion region, V d is the saturation drift velocity of the carrier. The detector frequency determined by the transit time can be expressed as:

[0046]

[0047] The influence of external circuit characteristics on the detector frequency can be expressed as:

[0048]

[0049] Where S is the area of ​​the detector, ε0 is the vacuum dielectric constant, and ε r is the relative dielectric constant of the depletion region material. Finally, the 3dB bandwidth of the detector can be expressed as:

[0050]

[0051] In addition, responsivity is usually used to characterize the ability of the detector to convert optical signals into electrical signals, which can be expressed as:

[0052]

[0053] Where α is the light absorption coefficient of the absorption layer material, d is the propagation length of light in the absorption layer, which is positively correlated with W, R is the surface reflectivity of the detector to light, and ξ is the percentage of electron-hole pairs that can ultimately form the detector current.

[0054] From equation (4), it can be seen that reducing the depletion region width W can increase the overall response frequency of the detector, while equation (5) reveals that reducing the depletion region width W will also reduce the responsivity of the detector, which restricts the responsivity and response frequency. Therefore, a solution to the contradiction between the two is to achieve higher light absorption efficiency in a thinner Ge absorption layer through the optimization of a unique optical structure.

[0055] In an exemplary embodiment, an all-dielectric metasurface is introduced to increase the absorption coefficient α of the absorption layer. In this embodiment, the polygonal nanorod unit 301 has a period of 0.66 μm, a height of 220 nm, and a length from the vertex to the midpoint of the hexagon is 0.235 μm. Figure 4 The spectral response curve of the detector in a wide range is shown. The maximum absorption rate is 98.82% at a wavelength of 1063nm.

[0056] In the exemplary embodiment, when the incident light is incident vertically through the all-dielectric polygonal nanocolumn array 30, the in-phase electromagnetic response of the unit structure 301 in the array forms a collective resonance, which is the array effect. The array effect hinders the far-field radiation of the electromagnetic wave, so that the energy can be tightly bound inside the polygonal nanounit structure, thereby enhancing the interaction between light and the medium.

[0057] In an exemplary embodiment, Figure 5 , Figure 6 This is the light field distribution inside the all-dielectric metasurface enhanced photodetector. It can be seen that part of the light energy is confined in the Si layer, and the other part is confined in the Ge layer. For the light band used in the simulation, the light energy distributed in the Ge layer will be directly absorbed; while Si is completely transparent in the communication C band and O band, and the energy in the Si layer will not be absorbed; in addition, the refractive index of Ge is larger than that of Si, and even if some energy exists in the Si layer, the light energy will gradually be evanescently coupled into the Ge layer and then absorbed by Ge.

[0058] In an exemplary embodiment, a method for preparing an all-dielectric metasurface-enhanced photodetector is as follows:

[0059] S1. Using molecular beam epitaxy to grow the first Si doping layer, semiconductor absorption layer, and second Si doping layer required for the detector on the top silicon of the SOI substrate;

[0060] S2. Spin-coated glass or photoresist, patterning the mask by electron beam exposure, UV exposure or nanoimprinting, and after development, EBE deposits Ti or Au as a mark for subsequent multiple exposures of the detector, and then puts the dissolving agent into the photoresist to complete the stripping;

[0061] S3. Spin-coated glass or photoresist, pattern the mask by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE etching to a specific thickness to complete the processing of the all-medium metasurface;

[0062] S4. Spin-coated glass or photoresist, pattern the mask by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE etching to above the first Si doping layer to complete the first-order mesa processing;

[0063] S5. Spin-coated glass or photoresist, pattern the mask by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE etching to the top of the silicon dioxide insulating layer in the middle of the SOI substrate to complete the second-order mesa processing;

[0064] S6. Low temperature deposition of silicon dioxide or silicon nitride to complete the passivation layer processing;

[0065] S7. Spin-coated glass or photoresist, patterning the mask by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE over-etching the passivation layer to complete the window opening;

[0066] It should be noted that the limitations on the various steps involved in this solution, without affecting the implementation of the specific solution, are not deemed to limit the order of the steps. The steps written in front can be executed first, or later, or even simultaneously. As long as this solution can be implemented, it should be deemed to fall within the scope of protection of this application.

[0067] The present application is described above in conjunction with specific implementation methods, but it should be clear to those skilled in the art that these descriptions are exemplary and are not intended to limit the scope of protection of the present application. Those skilled in the art can make various modifications and variations to the present application based on the spirit and principles of the present application, and these modifications and variations are also within the scope of the present application.

[0068] Implementation Plan 2

[0069] Please refer to Figure 3 , Figure 7This implementation scheme is generally the same as the implementation scheme, with the only difference being that the parameters of the basic unit of the all-dielectric metasurface are changed to meet the photoelectric detection applications in different communication bands.

[0070] In the exemplary embodiment, the polygonal nanocolumn unit 301 has a period of 0.588 μm, a height of 220 nm, and a length from a hexagonal vertex to a midpoint of 0.395 μm. Figure 7 The spectral response curve of the detector in the C-band range is shown. The maximum absorbance is 84.1% at a wavelength of 1550nm.

[0071] The rest of this embodiment is the same as embodiment 1. The features not explained in this embodiment are all based on the explanations in embodiment 1 and will not be described in detail here.

[0072] Implementation Plan 3

[0073] Please refer to Figure 3 , Figure 8 This implementation scheme is generally the same as the implementation scheme, with the only difference being that the parameters of the basic unit of the all-dielectric metasurface are changed to meet the photoelectric detection applications in different communication bands.

[0074] In the exemplary embodiment, the polygonal nanocolumn unit 301 has a period of 0.615 μm, a height of 220 nm, and a length from a hexagonal vertex to a midpoint of 0.249 μm. Figure 7 The spectral response curve of the detector in the O-band range is shown. The maximum absorbance is 90.3% at a wavelength of 1314nm.

[0075] The rest of this embodiment is the same as embodiment 1. The features not explained in this embodiment are all based on the explanations in embodiment 1 and will not be described in detail here.

[0076] Implementation Plan 4

[0077] Please refer to Figure 3 , Fig. 9 This implementation scheme is generally the same as the implementation scheme, with the only difference being that the parameters of the basic unit of the all-dielectric metasurface are changed to meet the photoelectric detection applications in different communication bands.

[0078] In the exemplary embodiment, the polygonal nanocolumn unit 301 has a period of 0.5 μm, a height of 220 nm, and a length from a hexagonal vertex to a midpoint of 0.2 μm. Figure 7 The spectral response curve of the detector in the near infrared band is shown. The maximum absorption rate is 89% at 850nm wavelength.

[0079] The rest of this embodiment is the same as embodiment 1. The features not explained in this embodiment are all based on the explanations in embodiment 1 and will not be described in detail here.

Claims

1. An all-dielectric metasurface enhanced photodetector, characterized in that: include: SOI substrate, first Si doping layer, semiconductor absorption layer, second Si doping layer, deposited passivation layer; The SOI substrate is located at the bottom layer and is used to confine light in the semiconductor absorption layer; A first Si doping layer is placed above the SOI substrate, for contacting a first electrode connected to an external circuit and enabling epitaxial growth of semiconductor material on the Si surface; The semiconductor absorption layer is disposed above the first Si doped layer, and the layer is composed of a periodically arranged polygonal column array to form an all-dielectric metasurface, which is used to enhance the absorption of incident light and generate photogenerated carriers to form photocurrent; The second Si doping layer is disposed above the semiconductor absorption layer and is used to contact a second electrode connected to an external circuit to achieve photocurrent transmission; A deposited passivation layer is placed on top to protect the device.

2. The all-dielectric metasurface enhanced photodetector according to claim 1, characterized in that: The SOI substrate adopts a sandwich structure of silicon-insulator-silicon, specifically including a bottom silicon layer, a middle silicon dioxide insulating layer, and a top silicon layer.

3. The all-dielectric metasurface enhanced photodetector according to claim 1, characterized in that: The doping concentrations of the first Si doping layer and the second Si doping layer are both greater than 1×10 20 cm -3 .

4. The all-dielectric metasurface enhanced photodetector according to claim 1, characterized in that: The passivation layer material is silicon dioxide or silicon nitride.

5. The all-dielectric metasurface enhanced photodetector according to claim 1, characterized in that: The semiconductor material used in the semiconductor absorption layer is InGaAs, GaAs of group III-V or Ge of group IV.

6. The all-dielectric metasurface enhanced photodetector according to claim 1, characterized in that: The all-dielectric metasurface inside the semiconductor absorption layer is composed of a polygonal column array, and the overall outline of the all-dielectric metasurface is square or circular; The geometric parameters of each unit in the polygonal column array include: period, thickness of semiconductor absorption layer, etching thickness of semiconductor absorption layer, and length from each vertex of the polygon to the center.

7. The all-dielectric metasurface enhanced photodetector according to claim 6, characterized in that: The all-dielectric metasurface inside the semiconductor absorption layer is processed by full etching or partial etching.

8. The all-dielectric metasurface enhanced photodetector according to claim 6, characterized in that: The all-dielectric metasurface material is doped with P-type and N-type respectively, and the doping concentration is greater than 1×10 19 cm -3 , where the P-type layer, the intrinsic layer and the N-type layer constitute a PIN-type diode structure.

9. The all-dielectric metasurface enhanced photodetector according to claim 6, characterized in that: The absorption rate of the all-dielectric metasurface in the detection band is between 80% and 98.82%.

10. A method for preparing the detector according to claim 1, characterized in that: include: Using molecular beam epitaxy to grow a first Si doping layer, a semiconductor absorption layer, and a second Si doping layer required for the detector on the top silicon of the SOI substrate; Made of spin-coated glass or photoresist, the mask is patterned by electron beam exposure, UV exposure or nanoimprinting. After development, Ti or Au is deposited by EBE as a mark for multiple exposures of subsequent detectors. The photoresist is dissolved in a solvent to complete the stripping. Spin-coated glass or photoresist, pattern the mask by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE etching to a specific thickness to complete the processing of the full dielectric metasurface; Spin-coated glass or photoresist, pattern the mask by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE etching to above the first Si doping layer to complete the first-order mesa processing; Made of spin-coated glass or photoresist, the mask is patterned by electron beam exposure, UV exposure or nanoimprinting, and after development, ICP or RIE etching is performed above the silicon dioxide insulating layer in the middle of the SOI substrate to complete the second-order mesa processing; Low temperature deposition of silicon dioxide or silicon nitride to complete the passivation layer processing; Made of spin-coated glass or photoresist, the mask is patterned by electron beam exposure, UV exposure or nanoimprinting. After development, the passivation layer is over-etched by ICP or RIE to complete the window opening.

Images