Magic angle nano-cavity and topological body cavity preparation method based on quantum dot single photon source

Abstract

The invention discloses a preparation method of a magic angle nano-cavity and a topological body cavity based on a quantum dot single photon source, and the method comprises the steps: carrying out the preprocessing of a substrate, and enabling the substrate to comprise a quantum dot layer, a substrate layer, and a sacrificial layer located between the quantum dot layer and the substrate layer; treating the pretreated substrate by adopting oxygen plasma; photoresist is spin-coated on the surface of the quantum dot layer of the substrate, exposure and development are carried out, and a pattern is formed on the surface of the photoresist; transferring the pattern on the photoresist to the quantum dot layer through etching; and removing the sacrificial layer by wet etching to prepare two photonic crystal cavities, namely a magic angle nano cavity and a topological body cavity. Through fine electron beam exposure dose control, precise inductively coupled plasma gas component and etching rate control and appropriate corrosive liquid concentration and time control, a high-stability and high-repeatability photonic crystal suspension cavity structure, namely a magic angle nano cavity and a topological body cavity, with a line width of 30-50 nm is realized.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor quantum devices, and in particular to a method for preparing two types of photonic crystal microcavities, namely magic angle nanocavity and topological bulk cavity, based on quantum dot single photon source. Background Art

[0002] In an optical quantum network, quantum nodes can be used to generate, process and store optical quantum information. The quantum dot-microcavity coupling system is a high-performance quantum node with great application potential in the fields of photon quantum cloning, few-photon nonlinearity and quantum logic gates. The photon flow of a single quantum dot laser exhibits anti-bunching characteristics, and the number of photons emitted in a fixed time is more predictable than that of an ordinary laser. Compared with quantum light sources based on spontaneous radiation, the stimulated radiation of a single quantum dot in the lasing state is dominant, so the radiation photon line width is narrower, showing an optical nonlinear effect. However, at this stage, it is difficult to further improve the microcavity-quantum dot coupling strength, which affects the speed of microcavity-quantum dot energy exchange, resulting in low radiation rate, failure to achieve the expected "no threshold" and complex gain sources, which limits the research on single quantum stimulated radiation. Summary of the invention

[0003] In order to fill the above-mentioned gaps in the art, the present application aims to provide a method for preparing two types of photonic crystal microcavities, namely magic angle nanocavity and topological bulk cavity based on quantum dot single photon source.

[0004] According to one aspect of the present application, the present application provides a method for preparing a magic angle nanocavity and a topological body cavity based on a quantum dot single photon source, comprising:

[0005] Pre-processing a substrate, wherein the substrate comprises: a quantum dot layer, a substrate layer, and a sacrificial layer located between the quantum dot layer and the substrate layer;

[0006] A substrate pretreated with oxygen plasma treatment;

[0007] Spin-coating photoresist on the surface of the quantum dot layer of the substrate, exposing and developing, and forming a magic angle nanocavity pattern and / or a topological cavity pattern on the surface of the photoresist;

[0008] Transferring the magic angle nanocavity pattern and / or the topological cavity pattern to the quantum dot layer by etching;

[0009] The sacrificial layer is removed by wet etching to obtain magic-angle nanocavities and topological cavities.

[0010] According to some embodiments of the present application, the material of the quantum dot layer includes: GaAs or InP; the material of the substrate layer includes: GaAs or InP.

[0011] According to some embodiments of the present application, the material of the sacrificial layer includes: Al 0.8 Ga0.2 As or In 0.53 Ga 0.47 As;

[0012] According to some embodiments of the present application, the sacrificial layer material is Al 0.8 Ga 0.2 The thickness of As is 300-1000nm;

[0013] The sacrificial layer material is In 0.53 Ga 0.47 The thickness of As is 200 nm.

[0014] According to some embodiments of the present application, the thickness of the quantum dot layer is 200 nm;

[0015] The thickness of the substrate layer was 500 μm.

[0016] According to some embodiments of the present application, the pretreatment includes: soaking and cleaning in acetone, ethanol and deionized water in sequence, and then blowing dry with nitrogen.

[0017] According to some embodiments of the present application, the exposure voltage is 80-150 kV;

[0018] According to some embodiments of the present application, the voltage is 125 kV.

[0019] According to some embodiments of the present application, when the material of the quantum dot layer is GaAs, the exposure dose is 340-380 μC / cm 2 When the material of the quantum dot layer is InP, the exposure dose is 280-310μC / cm 2 .

[0020] According to some embodiments of the present application, etching to remove the sacrificial layer is wet etching;

[0021] According to some embodiments of the present application, the wet etching solution includes 2%-10% HF or H3PO4:H2O2:H2O etching solutions with different ratios.

[0022] According to another aspect of the present application, a magic angle nanocavity and a topological body cavity of a quantum dot single photon source prepared by the above preparation method are also provided.

[0023] Compared with the prior art, this application has at least the following beneficial effects:

[0024] The present application provides a method for preparing two types of photonic crystal microcavities, namely magic angle nanocavity and topological bulk cavity, based on quantum dot single photon source. Through fine electron beam exposure dose control, precise inductively coupled plasma gas composition and etching rate control, and appropriate etching solution concentration and time control, a photonic crystal suspended cavity structure with high stability and high repeatability of 30-50nm line width - magic angle nanocavity and topological bulk cavity is achieved.

[0025] The two types of photonic crystal microcavities, magic angle nanocavity and topological bulk cavity, of the present application have the highest quality factor and are robust to structural shape. They can greatly enhance the coupling between a single quantum dot and the cavity mode, providing an ideal platform for studying stimulated radiation of a single quantum dot. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a schematic diagram of the preparation method of an exemplary embodiment of the present application.

[0027] Figure 2 Schematic diagram of the structure of the magic angle nanocavity and the topological cavity according to the exemplary embodiment of the present application.

[0028] Figure 3 Scanning electron microscope images of suspended magic angle nanocavity and topological bulk cavity photonic crystal samples according to example embodiments of the present application. DETAILED DESCRIPTION

[0029] The technical solution of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0030] It is particularly important to point out that similar substitutions and modifications made to the present application are obvious to those skilled in the art, and they are all deemed to be included in the present application. Relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present application to implement and apply the technology of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments.

[0031] If no specific conditions are specified in this application, the preparation shall be carried out under conventional conditions or the conditions recommended by the manufacturer. The raw materials or excipients used, as well as the reagents or instruments used, for which the manufacturers are not specified, are all conventional products that can be obtained commercially.

[0032] The application is described in detail below.

[0033] Photonic crystals are periodic dielectric structures with photonic band gaps. Light waves are periodically modulated to produce energy band structures and band gaps. Light waves whose energy falls in the band gap cannot propagate, thus controlling the movement of photons. Semiconductor photonic crystal lasers are divided into two categories: the first category is photonic crystal defect lasers, whose resonant cavity modes are designed within the optical energy gap, so light cannot exist in areas outside the defect and can only resonate in this defect area. This type of photonic crystal laser can obtain a higher quality factor, a smaller mode volume, a larger Purcell effect, and a low threshold condition. Among these photonic crystal microcavities, the magic angle nanocavity can obtain the highest ratio of quality factor to mode volume, so the coupling strength between it and the quantum dot can be greatly enhanced. In addition, by changing the relative rotation angle between the two sets of photonic crystals that constitute the magic angle nanocavity, the quality factor of the flat band mode can be greatly changed, while keeping the subwavelength-level mode volume basically unchanged. Based on this, the coupling strength of the single quantum dot-magic angle nanocavity system can be greatly changed by adjusting the interlayer rotation angle, so that the system can be freely converted in different coupling intervals. The second type is the photonic crystal band edge laser. Since the group velocity of light waves at the band edge approaches zero, standing waves will be formed when specific Bragg reflection conditions are met. Light waves at specific wavelengths satisfy the conservation of energy and momentum and emit vertically, with the advantages of large-area light output, single-mode operation, low divergence angle, and high output power. In this type of photonic crystal laser, the topological cavity provides a new laser mode selection mechanism due to the topological protection of the special edge / interface state receptor band dispersion, which makes the emission have excellent directionality. This feature greatly enhances the coupling strength of the topological cavity and quantum dots, providing an excellent experimental system for studying the lasing of quantum dots.

[0034] These two types of photonic crystal microcavities have obvious advantages over the single-photon sources such as micro-column cavities, target eye cavities and micro-disk cavities that are currently being studied more. For example, the preparation method is simpler, the structure is more stable, no reflectors are required to increase the brightness of quantum dots, the air layer generated by the suspended structure can replace the deposited silicon dioxide dielectric layer to prevent light leakage, and it has ultra-high coupling with quantum dots. However, to date, there are very few studies on the magic angle nanocavity-quantum dot coupling system and the topological body cavity-quantum dot coupling system to improve the performance of single-photon sources such as sensitivity, emission intensity, Q value, Purcell factor, and photon extraction efficiency. In particular, the ultra-high coupling characteristics with quantum dots generated by the structure of these two microcavities themselves, and the physical properties of stimulated radiation in the lasing state of single quantum dots are still to be studied. This application is mainly committed to solving the process preparation problems of the two types of photonic crystal microcavities, magic angle nanocavities and topological body cavities, to obtain a single quantum dot laser device with a stable structure, good process repeatability, and extremely high photonic crystal microcavity-quantum dot coupling at an extremely small size of 30-50nm.

[0035] Based on the above background, the technical problems to be solved by this application include:

[0036] 1. The high coupling problem between quantum dots and photonic crystal cavities.

[0037] 2. Transfer the photonic crystal cavity on the layout to the electron beam glue covered on the substrate surface, with the error controlled within 10nm.

[0038] 3. Accurately transfer the photonic crystal structure on the electron beam glue to the substrate quantum dot layer.

[0039] 4. Find a corrosive solution with extremely high selectivity for quantum dot layer materials and sacrificial layer materials to obtain a photonic crystal-quantum dot coupling cavity in a stable suspended state.

[0040] In order to solve the above technical problems, the magic angle nanophotonic crystal cavity of the present application is different from the magic angle structure of the existing two layers of graphene twisted angle to form an electronic system. The present application uses fine micro-nano processing methods to make two sets of photonic crystal lattices rotated at a certain angle in the same layer of semiconductor material to form a moiré supercell, which can greatly change the quality factor of the flat band mode while keeping the sub-wavelength mode volume basically unchanged. Based on this, the interaction between light and matter is enhanced, and adjusting the rotation angle of the two sets of lattices can change the coupling strength of the quantum dot-magic angle nanocavity system.

[0041] The topological photonic crystal cavity of the present application is a new type of crystal structure that introduces the concept of topology based on photonic crystals. The present application uses sophisticated micro-nano processing methods to prepare robust boundary state topological cavities of different forms. Due to the topological protection of the special edge state receptor band dispersion, the emission has excellent directionality. This characteristic greatly enhances the coupling strength of the topological cavity and quantum dots.

[0042] This application uses sophisticated micro-nano processing technology to achieve a smaller size of photonic crystal structure than that prepared by existing technology, that is, the size of the two types of photonic crystal cavity patterns are both in the hundreds of nanometers, and the connection points are in the 30-50nm size range; the structural performance is more excellent, that is, the magic angle nanostructure and the hexagonal topological structure both make the coupling strength of the photonic crystal microcavity-quantum dot system higher, and the coupling area is larger than the existing micro-column cavity and target eye cavity, which solves the problem of weak coupling strength that has always existed in single quantum dot lasers. The magic angle nanocavity and topological body cavity preparation technology provided by this application provides a carrier for studying physical properties such as stimulated radiation of single quantum dots and photonic crystal microcavity-quantum dot coupled radiation processes, provides new ideas for realizing quantum nodes, and promotes the development of higher quality quantum light sources.

[0043] This application demonstrates the micro-nano fabrication technology solutions for these two types of photonic crystal cavities by fabricating magic-angle nanocavities and topological bulk cavities respectively through two material systems, GaAs and InP.

[0044] The technical solution of this application includes:

[0045] Substrate preparation: epitaxially grown GaAs or InP substrate structure such as Figure 1 As shown in (a), the top layer is GaAs or InP layer containing InAs quantum dots, and the middle layer is Al 0.8 Ga 0.2 As or In 0.53 Ga 0.47 As sacrificial layer, the bottom layer is GaAs or InP substrate layer. The substrate can be dissociated into substrates of 5*5mm size along the crystal direction.

[0046] Substrate pretreatment: Soak the substrate in acetone, ethanol and deionized water for 5-10 minutes, then blow dry with nitrogen. Use oxygen plasma to bombard the substrate surface to improve the hydrophilicity of the substrate surface and improve the surface adhesion to ensure that the subsequent spin-coated electron beam glue is well bonded to the substrate surface.

[0047] Generate photoresist pattern: Spin-coat a layer of electron beam resist (photoresist) on the substrate surface and bake it at high temperature to form a mask for the photonic crystal cavity, such as Figure 1 (b) As shown. A high-voltage electron beam lithography machine is used to transfer the photonic crystal pattern with a precision of hundreds of nanometers from the layout to the electron beam glue. Figure 1 (c) as shown.

[0048] Etching photoresist pattern: Use an inductively coupled plasma etcher to dry etch the substrate, accurately transfer the pattern on the electron beam resist to the substrate quantum dot layer, and remove the remaining residual glue after etching. Figure 1 (d) as shown.

[0049] Removing the sacrificial layer: The middle sacrificial layer is removed by wet etching to obtain a stable suspension structure, such as Figure 1 (e) as shown.

[0050] Among them, the exposure voltage is 80-150kv, and 125kV is selected. Compared with the commonly used 30kV voltage, the exposure has small forward scattering, low proximity effect, good collimation, and the error between the actual graphic size obtained by exposure and the designed size is about 10nm. The corners of the triangular graphics are also sharper, which is very important for the 30-50nm line width that needs to be achieved.

[0051] The exposure doses of magic angle nanocavity and topological cavity are different. The exposure doses of topological cavities of different sizes are also different. At the same time, the exposure doses of GaAs and InP are also different. Through detailed dose testing, it can be determined that the exposure dose of GaAs photonic crystal is 340-380μC / cm 2 The exposure dose of InP photonic crystal is between 280-310μC / cm2 between.

[0052] The etching gas composition and etching rate are crucial to the widening of the pattern line width. The chamber temperature, gas composition, upper and lower electrode power, pressure and time required by GaAs and InP are all different and need to be finely controlled.

[0053] Different materials require different etching solutions, and different material thicknesses also require different concentrations of etching solutions. 0.8 Ga 0.2 For As material, choose 2%-10% HF etching solution. For 200nm thick In 0.53 Ga 0.47 As material, select H3PO4:H2O2:H2O etching solution.

[0054] The magic angle nanocavity of the present application is a moiré supercell structure obtained by rotating two sets of moiré lattices with the central air hole as the axis by angles -θ° and +θ° in the XY plane, respectively. The value of θ is selected according to the coupling strength requirement, such as Figure 2 (a) shows that the topological cavity is formed by two different sets of hexagonal lattices arranged periodically inside and outside, respectively. The boundary between the two hexagonal lattices forms topological characteristics, such as Figure 2 (b) and 2(c) show a regular hexagonal topological cavity and an irregular "Q"-type topological cavity structure, respectively.

[0055] The technical solution of the present application is further described below in conjunction with specific embodiments.

[0056] Example 1

[0057] Fabrication of magic-angle nanocavities

[0058] The epitaxial growth substrate includes, from top to bottom: a 200nm thick GaAs layer containing InAs quantum dots, a 300-1000nm thick Al 0.8 Ga 0.2 As sacrificial layer, 500μm thick GaAs substrate layer. The substrate was dissociated into 5×5mm size along the crystal direction, soaked in acetone, ethanol and deionized water for 5min respectively, and blown dry with a nitrogen gun. The substrate surface was bombarded with oxygen plasma equipment, and the organic solvent and impurity particles remaining on the substrate surface were cleaned again. The specific parameters were: O2 gas flow rate was set to 50sccm, RF power was set to 100W, and bombardment time was 1min.

[0059] Spin coat a layer of electron beam resist ZEP520A on the substrate surface, the experimental parameters are: 300rpm for 6 seconds, accelerate to 3000rpm for 60 seconds, the thickness of the glue is about 380nm. Then put the substrate with glue on a hot plate for baking and curing, the temperature is 180℃, the time is 180 seconds.

[0060] The exposure was performed using an electron beam exposure device (ELS-F125, Elionix, Japan). The parameters were: writing field size 200×200 μm, acceleration voltage 125 kV, beam current 300 pA, step length 2 nm, aperture size 120 μm. Figure 2 (a) shows that the exposure dose of GaAs material is 350μC / cm 2 .

[0061] An inductively coupled plasma etcher (Plasma Pro100Cobra, Oxford Instruments, UK) was used for dry etching: the substrate to be etched was adhered to the single crystal silicon wafer with thermal conductive silicone oil, and the single crystal silicon area outside the substrate was covered with polyimide high temperature tape. It was placed in the pre-vacuum chamber of the etcher, and after the vacuum reached the preset value, it was transferred to the etching chamber. The etching parameters were: the substrate stage temperature was set to 20°C, the pressure of He gas purge on the back of the substrate was 10Torr, the process pressure was 1mTorr, the upper electrode (ICP) power was 200W, the lower electrode (Bias) power was 40W, and the etching gas was a mixed gas of chlorine (Cl2), boron trichloride (BCl3) and argon (Ar), the gas component flow rate was Cl2 / BCl3 / Ar=3 / 5 / 7sccm, and the process time was 1min50s.

[0062] Remove the residual glue after etching: soak in N,N-dimethylacetamide for 5 minutes, then wash with acetone, ethanol, and deionized water for 2 minutes. Then use an oxygen plasma degumming machine to clean the small area of ​​residual glue and residual organic solvent. The O2 flow rate is set to 50sccm, the RF power is set to 100W, and the processing time is 10 minutes.

[0063] Wet etching of Al 0.8 Ga 0.2 As sacrificial layer, forming a stable suspension structure: prepare a 10% HF solution, and etch the sacrificial layer with a thickness of 1000nm for 30s. After etching, transfer the sample to the first deionized water beaker, shake it gently for 5s, and then transfer the sample to the second pure water beaker and soak it for 10min. Then transfer the sample to isopropanol and soak it for 3min. Slowly remove the sample from the isopropanol, place it in the air, and wait for the isopropanol to evaporate naturally.

[0064] Example 2

[0065] Preparation of topological body cavity

[0066] The epitaxial growth substrate includes, from top to bottom: a 200nm thick InP layer containing InAs quantum dots, a 200nm thick In 0.53 Ga 0.47 As sacrificial layer, 500μm thick InP substrate layer. The substrate was dissociated into 5×5mm size along the crystal direction, soaked in acetone, ethanol and deionized water for 5min respectively, and blown dry with a nitrogen gun. The substrate surface was bombarded with oxygen plasma equipment, and the organic solvent and impurity particles remaining on the substrate surface were cleaned again. The specific parameters were: O2 gas flow rate was set to 50sccm, RF power was set to 100W, and bombardment time was 1min.

[0067] Spin coat a layer of electron beam resist ZEP520A on the substrate surface, the experimental parameters are: 300rpm for 6 seconds, accelerate to 3000rpm for 60 seconds, the thickness of the glue is about 380nm. Then put the substrate with glue on a hot plate for baking and curing, the temperature is 180℃, the time is 180 seconds.

[0068] The exposure was performed using an electron beam exposure device (ELS-F125, Elionix, Japan). The parameters were: writing field size 200×200 μm, acceleration voltage 125 kV, beam current 300 pA, step length 2 nm, aperture size 120 μm. Figure 2 As shown in (b) and (c), the exposure dose of InP material is 300μC / cm 2 、290μC / cm 2 .

[0069] An inductively coupled plasma etcher (Plasma Pro100Cobra, Oxford Instruments, UK) was used for dry etching: the substrate to be etched was adhered to the single crystal silicon wafer with thermal conductive silicone oil, and the single crystal silicon area outside the substrate was covered with polyimide high temperature tape. It was placed in the pre-vacuum chamber of the etcher, and after the vacuum reached the preset value, it was transferred to the etching chamber. The etching parameters were: the substrate stage temperature was set to 25°C, the pressure of He gas purge on the back of the sample was 10Torr, the process pressure was 4mTorr, the upper electrode (ICP) power was 1000W, the lower electrode (Bias) power was 150W, and the etching gas was a mixed gas of methane (CH4), chlorine (Cl2) and argon (Ar), the gas component flow rate was CH4 / Cl2 / Ar=12sccm / 6sccm / 3sccm, and the process time was 30s.

[0070] Remove the residual glue after etching: soak in N,N-dimethylacetamide for 5 minutes, then wash with acetone, ethanol, and deionized water for 2 minutes. Then use an oxygen plasma degumming machine to clean the small area of ​​residual glue and residual organic solvent. The O2 flow rate is set to 50sccm, the RF power is set to 100W, and the processing time is 10 minutes.

[0071] Wet etching In 0.53 Ga 0.47 As sacrificial layer, forming a stable suspension structure: prepare H3PO4:H2O2:H2O=2:3:30 etching solution, the etching time is 24s. After etching, transfer the sample to the first deionized water beaker, shake gently for 5s, then transfer the sample to the second pure water beaker and soak for 10min. Then transfer the sample to isopropanol and soak for 3min. Slowly take the sample out of the isopropanol, place it in the air, and wait for the isopropanol to evaporate naturally.

[0072] Example 3

[0073] Fabrication of magic angle nanocavities and topological cavities

[0074] The epitaxial growth substrate includes, from top to bottom: a 200nm thick GaAs layer containing InAs quantum dots, a 300-1000nm thick Al 0.8 Ga 0.2 As sacrificial layer, 500μm thick GaAs substrate layer. The substrate was dissociated into 5×5mm size along the crystal direction, soaked in acetone, ethanol and deionized water for 5min respectively, and blown dry with a nitrogen gun. The substrate surface was bombarded with oxygen plasma equipment, and the organic solvent and impurity particles remaining on the substrate surface were cleaned again. The specific parameters were: O2 gas flow rate was set to 50sccm, RF power was set to 100W, and bombardment time was 1min.

[0075] Spin coat a layer of electron beam resist ZEP520A on the substrate surface, the experimental parameters are: 300rpm for 6 seconds, accelerate to 3000rpm for 60 seconds, the thickness of the glue is about 380nm. Then put the substrate with glue on a hot plate for baking and curing, the temperature is 180℃, the time is 180 seconds.

[0076] The exposure was performed using an electron beam exposure device (ELS-F125, Elionix, Japan). The parameters were: writing field size 200×200μm, acceleration voltage 125kV, beam current 300pA, step length 2nm, aperture size 120μm. Magic angle nanocavity and topological cavity structures such as Figure 2 As shown in (a), (b), and (c), the exposure dose of GaAs material for magic angle nanocavity and topological cavity is 350 μC / cm 2 、360μC / cm2 .

[0077] An inductively coupled plasma etcher (Plasma Pro100Cobra, Oxford Instruments, UK) was used for dry etching: the substrate to be etched was adhered to the single crystal silicon wafer with thermal conductive silicone oil, and the single crystal silicon area outside the substrate was covered with polyimide high temperature tape. It was placed in the pre-vacuum chamber of the etcher, and after the vacuum reached the preset value, it was transferred to the etching chamber. The etching parameters were: the substrate stage temperature was set to 20°C, the pressure of He gas purge on the back of the substrate was 10Torr, the process pressure was 1mTorr, the upper electrode (ICP) power was 200W, the lower electrode (Bias) power was 40W, and the etching gas was a mixed gas of chlorine (Cl2), boron trichloride (BCl3) and argon (Ar), the gas component flow rate was Cl2 / BCl3 / Ar=3 / 5 / 7sccm, and the process time was 1min50s.

[0078] Remove the residual glue after etching: soak in N,N-dimethylacetamide for 5 minutes, then wash with acetone, ethanol, and deionized water for 2 minutes. Then use an oxygen plasma degumming machine to clean the small area of ​​residual glue and residual organic solvent. The O2 flow rate is set to 50sccm, the RF power is set to 100W, and the processing time is 10 minutes.

[0079] Wet etching of Al 0.8 Ga 0.2 As sacrificial layer, forming a stable suspension structure: prepare a 4% HF solution, and etch the 300nm thick sacrificial layer for 12s. After etching, transfer the sample to the first deionized water beaker, shake it gently for 5s, and then transfer the sample to the second pure water beaker and soak it for 10min. Then transfer the sample to isopropanol and soak it for 3min. Slowly take the sample out of the isopropanol, place it in the air, and wait for the isopropanol to evaporate naturally.

[0080] The scanning electron microscope images of the suspended magic angle nanocavity and topological bulk cavity photonic crystal samples prepared in the above embodiments of the present application are as follows: Figure 3 As shown. It can be seen that the pattern at the 30nm line width connection at the edge of the magic angle nanocavity and the 50nm line width connection at the triangle of the topological cavity is complete, the suspension structure is stable, the pattern is not deformed, and it is consistent with the design size. For micro-pillar cavities and annular Bragg cavities, quantum dots must be well coupled at the center of the cavity. The photonic crystal cavity prepared by this method has a stable suspension structure and a larger effective coupling area. The quantum dots can still be well coupled within a certain range away from the center, which greatly improves the coupling probability and device success rate. The photonic crystal cavity has the highest quality factor and has great advantages in studying stimulated radiation in the lasing state of a single quantum dot.

[0081] The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. It should be noted that, for ordinary technicians in this technical field, several improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for preparing magic angle nanocavity and topological body cavity based on quantum dot single photon source, characterized in that: include: Preprocessing a substrate, wherein the substrate comprises: a quantum dot layer, a substrate layer, and a sacrificial layer located between the quantum dot layer and the substrate layer; treating the pretreated substrate with oxygen plasma; Spin-coating photoresist on the surface of the quantum dot layer of the substrate, performing exposure and development, and forming a magic angle nanocavity pattern and / or a topological cavity pattern on the surface of the photoresist; Transferring the magic angle nanocavity pattern and / or the topological cavity pattern to the quantum dot layer by etching; The sacrificial layer is removed by wet etching to obtain the magic angle nanocavity and the topological body cavity.

2. The preparation method according to claim 1, characterized in that: The material of the quantum dot layer includes GaAs or InP; the material of the substrate layer includes GaAs or InP.

3. The preparation method according to claim 2, characterized in that: The material of the sacrificial layer includes: Al 0.8 Ga 0.2 As or In 0.53 Ga 0.47 As; Optionally, the sacrificial layer material is Al 0.8 Ga 0.2 The thickness of As is 300-1000nm; The sacrificial layer material is In 0.53 Ga 0.47 The thickness of As is 200 nm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The thickness of the quantum dot layer is 200 nm; The thickness of the substrate layer is 500 μm.

5. The preparation method according to claim 1, characterized in that: The pretreatment comprises: sequentially immersing and cleaning in acetone, ethanol and deionized water, and then drying with nitrogen.

6. The preparation method according to claim 1, characterized in that: The exposure voltage is 80-150 kV; Optionally, the voltage is 125 kV.

7. The preparation method according to claim 1, characterized in that: When the material of the quantum dot layer is GaAs, the exposure dose is 340-380 μC / cm 2 When the material of the quantum dot layer is InP, the exposure dose is 280-310 μC / cm 2 .

8. The preparation method according to claim 1, characterized in that: The etching to remove the sacrificial layer is wet etching; Optionally, the wet etching solution includes 2%-10% HF or H3PO4:H2O2:H2O etching solution.

9. Magic angle nanocavity based on quantum dot single photon source, characterized in that: The method is prepared by any one of claims 1 to 8.

10. A topological cavity based on a quantum dot single photon source, characterized in that: The method is prepared by any one of claims 1 to 8.

Images