Preparation method of magic angle nanocavity and topological body cavity based on quantum dot single photon source

Abstract

The application discloses a preparation method of a magic angle nanocavity and a topological body cavity based on a quantum dot single photon source, and comprises the following steps: pretreating a substrate, wherein the substrate comprises a quantum dot layer, a substrate layer and a sacrificial layer between the quantum dot layer and the substrate layer; treating the pretreated substrate by using oxygen plasma; spin-coating photoresist on the surface of the quantum dot layer of the substrate, performing exposure and development, and forming a pattern on the surface of the photoresist; transferring the pattern on the photoresist to the quantum dot layer by etching; and removing the sacrificial layer by wet etching to obtain two photonic crystal cavities, i.e., the magic angle nanocavity and the topological body cavity. Through fine electron beam exposure dose control, precise inductively coupled plasma gas component and etching rate control, and suitable etching liquid concentration and time control, the high stability and high repeatability of the photonic crystal suspended cavity structure, i.e., the magic angle nanocavity and the topological body cavity, with a line width of (30-50) nm are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor quantum devices, in particular to a preparation method of two kinds of photonic crystal microcavities of magic angle nanocavity and topological body cavity based on quantum dot single photon source. BACKGROUND

[0002] In an optical quantum network, quantum nodes can be used to generate, process and store optical quantum information, and the coupling system of quantum dot-microcavity is a high-performance quantum node, which has great application potential in the fields of photonic quantum cloning, few-photon nonlinearity and quantum logic gate. The photon flow of single quantum dot laser shows anti-bunching characteristics, and the number of photons emitted in a fixed time is more predictable than ordinary laser. Compared with quantum light sources based on spontaneous emission, single quantum dots are dominated by stimulated emission in the lasing state, so the radiation photon linewidth is narrower and exhibits optical nonlinear effects. However, the coupling strength of the microcavity-quantum dot at the present stage is difficult to further improve, which affects the energy exchange speed of the microcavity-quantum dot, causes low radiation rate, cannot reach the expected "threshold", and the gain source is complex, etc., which limits the research of single quantum stimulated emission. SUMMARY

[0003] In order to fill the above-mentioned gaps in the field, the present application aims to provide a preparation method of two kinds of photonic crystal microcavities of magic angle nanocavity and topological body cavity based on quantum dot single photon source.

[0004] According to an aspect of the present application, the present application provides a preparation method of magic angle nanocavity and topological body cavity based on quantum dot single photon source, which comprises:

[0005] The substrate is pretreated, and the substrate comprises: a quantum dot layer, a substrate layer and a sacrificial layer between the quantum dot layer and the substrate layer;

[0006] The pretreated substrate is treated by oxygen plasma;

[0007] Photoresist is spin-coated on the surface of the quantum dot layer of the substrate, and exposure and development are performed to form a magic angle nanocavity pattern and / or a topological body cavity pattern on the surface of the photoresist;

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

[0009] The sacrificial layer is removed by wet etching to obtain the magic angle nanocavity and the topological body cavity.

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

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

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

[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 this application, the thickness of the quantum dot layer is 200 nm;

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

[0016] According to some embodiments of this application, the pretreatment includes: sequentially immersing and washing in acetone, ethanol and deionized water, and then drying with nitrogen gas.

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

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

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

[0020] According to some embodiments of this application, the etching removal of the sacrificial layer is performed by wet etching.

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

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

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

[0024] The application provides a preparation method of two kinds of photonic crystal microcavities of magic angle nanocavity and topological body cavity based on quantum dot single photon source. Through fine electron beam exposure dose control, precise inductively coupled plasma gas component and etching rate control, and suitable etching liquid concentration and time control, a high stability and high repeatability photonic crystal suspended cavity structure of 30-50nm line width, i.e. magic angle nanocavity and topological body cavity, is realized.

[0025] The two kinds of photonic crystal microcavities of magic angle nanocavity and topological body cavity of the application have the highest quality factor and are robust to the structure shape, can greatly enhance the coupling of a single quantum dot and a cavity mode, and provide an ideal platform for studying stimulated radiation of a single quantum dot. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The figure is a preparation method flowchart of an example embodiment of the application.

[0027] Figure 2 The figure is a structure schematic diagram of the magic angle nanocavity and topological body cavity of an example embodiment of the application.

[0028] Figure 3 The figure is a scanning electron microscope diagram of the suspended magic angle nanocavity and topological body cavity photonic crystal sample of an example embodiment of the application. DETAILED DESCRIPTION

[0029] The technical solutions of the application will be described clearly and completely in combination with the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without making creative efforts are within the protection scope of the application.

[0030] It is particularly pointed out that similar replacements and changes made for the application are obvious to those skilled in the art, and they are considered to be included in the application. The related personnel can obviously make changes or appropriate changes and combinations to the methods and applications described herein without departing from the content, spirit and scope of the application, to realize and apply the technology of the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments.

[0031] Unless specified otherwise, the application is carried out according to the conventional conditions or the conditions recommended by the manufacturer. The raw materials or excipients used, and the reagents or instruments used, which are not specified by the manufacturer, are all conventional products that can be obtained from the market.

[0032] The application will be described in detail below.

[0033] Photonic crystal is a periodic dielectric structure with photonic band gap, light waves are modulated periodically, energy band structure is generated, band gap appears, and light waves falling in the band gap cannot propagate, thereby the movement of photons can be controlled. Semiconductor photonic crystal lasers are divided into two categories: the first category is photonic crystal defect type laser, the resonant cavity mode is designed in the optical energy gap, so light cannot exist in the area outside the defect, but only resonates in the defect area. This type of photonic crystal laser can obtain higher quality factor, smaller mode volume, larger Purcell effect and low threshold condition. In this type of photonic crystal microcavity, 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 constituting the magic angle nanocavity, the quality factor of the flat band mode can be greatly changed, while the subwavelength mode volume remains basically unchanged. Based on this, by adjusting the interlayer rotation angle, the coupling strength of the single quantum dot-magic angle nanocavity system can be greatly changed, so that the system can be freely converted in different coupling intervals. The second category is photonic crystal energy band edge type laser, because the group velocity of light waves at the energy band edge tends to zero, a standing wave will be formed when the specific Bragg reflection condition is met. The light wave of a specific wavelength satisfies the energy and momentum conservation to appear vertical plane emission, which has the advantages of large area light emission, single mode operation, low divergence angle and high output power. In this type of photonic crystal laser, the topological body cavity provides a new laser mode selection mechanism due to the topological protection of the special edge / interface state acceptor band dispersion, which makes the emission have excellent directivity. This characteristic greatly enhances the coupling strength of the topological body cavity and the quantum dot coupling, providing an excellent experimental system for studying quantum dot lasing.

[0034] These two photonic crystal microcavities have obvious advantages compared with the single photon source of the microcolumn cavity, target eye cavity and microdisk cavity which are currently studied more, such as simpler preparation method, more stable structure, no need of mirror to improve quantum dot brightness, air layer produced by suspended structure can replace deposited silica dielectric layer to prevent light leakage and have ultra-high coupling with quantum dots, etc. However, so far, there are few studies on the sensitivity, emission intensity, Q value, Purcell factor, photon extraction efficiency, etc. of single photon source of the magic angle nanocavity-quantum dot coupling system and the topological body cavity-quantum dot coupling system. Especially, the ultra-high coupling characteristics of these two microcavities with quantum dots need to be studied in the physical characteristics of stimulated radiation under single quantum dot lasing. The present application is mainly devoted to solving the process preparation problem of the magic angle nanocavity and the topological body cavity of the two photonic crystal microcavities, and obtaining a single quantum dot laser device with extremely small size of 30-50 nm, stable structure, good process repeatability and extremely high photonic crystal microcavity-quantum dot coupling.

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

[0036] I. High coupling of quantum dots and photonic crystal cavities.

[0037] II. Transferring the photonic crystal cavities on the layout to the electron beam glue on the surface of the substrate, with an error of 10nm.

[0038] III. Accurately transferring the photonic crystal structure on the electron beam glue to the quantum dot layer of the substrate.

[0039] IV. Finding a highly selective etching liquid for the quantum dot layer material and the sacrificial layer material, and obtaining a stable suspended photonic crystal-quantum dot coupling cavity.

[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-layer graphene twist angle electronic system. The present application uses fine micro-nano processing means to make two sets of photonic crystal lattices with a certain angle of rotation in the same layer of semiconductor material to form a moire supercell, which can greatly change the quality factor of the flat band mode while keeping the mode volume basically unchanged. Based on this, the interaction between light and matter is enhanced, and the coupling strength of the quantum dot-magic angle nanocavity system can be changed by adjusting the rotation angle of the two lattices.

[0041] The topological body photonic crystal cavity of the present application is a new type of crystal structure based on the introduction of the concept of topology to the photonic crystal. The present application prepares different forms of robust boundary state topological body cavities through fine micro-nano processing means. Due to the topological protection of the special edge state acceptor band dispersion, the emission has excellent directivity. This characteristic greatly enhances the coupling strength of the topological body cavity and the quantum dot.

[0042] The present application realizes smaller photonic crystal structure size than the existing technology through fine micro-nano processing technology, i.e. the size of the two photonic crystal cavity patterns is in the order of hundreds of nanometers, and the connection is in the size range of 30-50nm; the structure performance is more excellent, i.e. the magic angle nanostructure and the hexagonal topological structure both make the coupling strength of the photonic crystal microcavity-quantum dot system higher, the coupling area is larger than the existing microcolumn cavity and target eye cavity, and the problem of weak coupling strength existing in the current single quantum dot laser is solved. The magic angle nanocavity and topological body cavity preparation technology provided by the present application provides a carrier for studying the physical characteristics such as single quantum dot stimulated radiation and photonic crystal microcavity-quantum dot coupling radiation process, provides a new idea for realizing quantum nodes, and promotes the research and development of higher quality quantum light sources.

[0043] The present application uses two material systems of GaAs and InP to correspondingly prepare magic angle nanocavities and topological body cavities to demonstrate the micro-nano processing preparation technical solutions of the two photonic crystal cavities.

[0044] The technical solutions of the present application include:

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

[0046] Substrate pretreatment: The substrate is sequentially immersed in acetone, ethanol and deionized water for 5-10 min, and then dried with nitrogen. The surface of the substrate is bombarded with oxygen plasma to improve the hydrophilicity of the substrate surface and improve the surface adhesion, so that the electron beam glue for subsequent spin coating is well combined with the substrate surface.

[0047] Generating a photoresist pattern: A layer of electron beam resist (photoresist) is spin-coated on the surface of the substrate, and high-temperature baking is performed to form a pattern, which is used as a mask for the photonic crystal cavity, as shown in Figure 1 (b). A high-voltage electron beam exposure machine is used to transfer the nanometer-precision photonic crystal pattern from the layout to the electron beam glue, as shown in Figure 1 (c).

[0048] Etching the photoresist pattern: An inductively coupled plasma etching machine is used to perform dry etching on the substrate to accurately transfer the pattern on the electron beam resist to the substrate containing quantum dots, and after removing the residual photoresist left after etching, as shown in Figure 1 (d).

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

[0050] 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 actual pattern size obtained by exposure has an error of about 10nm from the designed size, and the angle of the triangular pattern is also sharper, which is very important for the 30-50nm line width that needs to be achieved.

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

[0052] Etching gas composition and etching rate are very important to the linewidth broadening. GaAs and InP need different chamber temperature, gas composition, power of upper and lower electrode, pressure and time, which need to be finely controlled.

[0053] Different materials need different etching solution, and different thickness of materials need different concentration of etching solution. For 300-1000nm thick Al 0.8 Ga 0.2 As material, 2%-10% HF etching solution is selected. For 200nm thick In 0.53 Ga 0.47 As material, H3PO4:H2O2:H2O etching solution is selected.

[0054] The magic angle nanocavity of the present application is a moire supercell structure obtained by rotating two sets of moire lattices by angles -θ° and +θ° in the XY plane respectively with the central air hole as the axis, and the value of θ is selected according to the coupling strength requirement, such as θ = 0°, θ = 30°, θ = 60°, θ = 90°, θ = 120°, θ = 150°, θ = 180°, θ = 210°, θ = 240°, θ = 270°, θ = 300°, θ = 330°, θ = 360°, etc. Figure 2 (a). The topological body cavity is formed by periodically arranging two different hexagonal lattices inside and outside respectively, and the boundary between the two hexagonal lattices forms a topological characteristic, such as Figure 2 (b) and 2(c) respectively show a regular hexagonal topological body cavity and an irregular "Q" type topological body cavity structure.

[0055] The technical solutions of the present application will be further introduced below in combination with specific embodiments.

[0056] Embodiment 1

[0057] Preparation of magic angle nanocavity

[0058] Epitaxial growth substrate, from top to bottom including: 200nm thick GaAs layer containing InAs quantum dots, 300-1000nm thick Al 0.8 Ga 0.2 As sacrificial layer, 500μm thick GaAs substrate layer. The substrate is dissociated along the crystal direction to 5×5mm size, soaked in acetone, ethanol and deionized water for 5min respectively, and dried with nitrogen gun. The substrate surface is bombarded with oxygen plasma equipment, and the residual organic solvents and impurity particles on the substrate surface are cleaned at the same time. The specific parameters are: O2 gas flow is set to 50sccm, radio frequency power is set to 100W, and bombardment time is 1min.

[0059] A layer of electron beam resist ZEP520A was spin-coated on the surface of the substrate, and the experimental parameters were as follows: 300 rpm for 6 seconds, acceleration to 3000 rpm for 60 seconds, and a thickness of about 380 nm. Then the substrate with the uniform coating was placed on a hot plate for baking and curing, at a temperature of 180 °C for 180 seconds.

[0060] Exposure was performed by using an electron beam exposure device (model ELS-F125, Elionix, Japan). The parameters were as follows: a writing field size of 200 x 200 μm, an acceleration voltage of 125 kV, a beam current of 300 pA, a step size of 2 nm, and an aperture size of 120 μm. The magic angle nanocavity structure is shown in Fig. 1 (a), and the exposure dose of the GaAs material was 350 μC / cm Figure 2 2 .

[0061] Dry etching was performed by using an inductively coupled plasma etching machine (model Plasma Pro 100 Cobra, Oxford Instruments, UK). The substrate to be etched was adhered to a single crystal silicon wafer with heat-conducting silicone oil, and the area of the single crystal silicon outside the substrate was covered with a polyimide high-temperature adhesive tape. The substrate was placed in the pre-vacuum chamber of the etching machine, and after the vacuum reached the preset value, it was transferred to the etching chamber. The etching parameters were as follows: the substrate table temperature was set to 20 °C, the He gas blowing pressure on the back of the substrate was 10 Torr, the process pressure was 1 mTorr, the upper electrode (ICP) power was 200 W, the lower electrode (Bias) power was 40 W, the etching gas was a mixture of chlorine (Cl2), boron trichloride (BCl3), and argon (Ar) with a gas component flow rate of Cl2 / BCl3 / Ar = 3 / 5 / 7 sccm, and the process time was 1 min 50 s.

[0062] The residual coating after etching was removed by immersing in N,N-dimethylacetamide for 5 min, and then sequentially washing with acetone, ethanol, and deionized water for 2 min. Then, the residual coating and the residual organic solvent were cleaned by an oxygen plasma coating removal machine, with an O2 flow rate of 50 sccm, a radio frequency power of 100 W, and a processing time of 10 min.

[0063] Wet etching of Al 0.8 Ga 0.2 As sacrificial layer to form a stable suspended structure: a 10% HF solution was prepared, and the 1000 nm thick sacrificial layer was etched for 30 s. After etching, the sample was transferred to the first deionized water beaker, gently shaken for 5 s, and then transferred to the second pure water beaker for immersion for 10 min. Then, the sample was transferred to isopropyl alcohol for immersion for 3 min. The sample was slowly taken out of the isopropyl alcohol and placed in the air, and the isopropyl alcohol was allowed to naturally evaporate completely.

[0064] Example 2​

[0065] Preparation of topological cavities

[0066] The epitaxial growth substrate, from top to bottom, includes: a 200nm thick InP layer containing InAs quantum dots, a 200nm thick In... 0.53 Ga 0.47 As a sacrificial layer, a 500μm thick InP substrate layer was used. The substrate was dissected along the crystal orientation into 5×5mm pieces, and then immersed in acetone, ethanol, and deionized water for 5 minutes each, followed by drying with a nitrogen gun. The substrate surface was then bombarded with oxygen plasma to simultaneously clean residual organic solvents and impurity particles. The specific parameters were: O2 gas flow rate set to 50 sccm, RF power set to 100W, and bombardment time set to 1 minute.

[0067] A layer of electron beam resist ZEP520A was spin-coated onto the substrate surface. The experimental parameters were: 300 rpm for 6 seconds, accelerated to 3000 rpm for 60 seconds, and the resist thickness was approximately 380 nm. The substrate with the uniformly coated resist was then placed on a hot plate for baking and curing at 180°C for 180 seconds.

[0068] Exposure was performed using an electron beam lithography system (Elionix ELS-F125, Japan). The parameters were: write field size 200 × 200 μm, accelerating voltage 125 kV, beam current 300 pA, step size 2 nm, and aperture size 120 μm. The topological cavity structure is as follows... Figure 2 As shown in (b) and (c), the exposure dose of the InP material is 300 μC / cm. 2 290μC / cm 2 .

[0069] Dry etching was performed using an inductively coupled plasma etching machine (Plasma Pro100Cobra, Oxford Instruments, UK). The substrate to be etched was adhered to a monocrystalline silicon wafer using thermally conductive silicone oil. The monocrystalline silicon areas outside the substrate were covered with polyimide high-temperature tape. The wafer was placed in the pre-vacuum chamber of the etching machine. Once the vacuum reached the preset value, it was transferred to the etching chamber. The etching parameters were as follows: substrate stage temperature set to 25°C, He gas purging pressure on the sample back side at 10 Torr, process pressure at 4 mTorr, upper electrode (ICP) power at 1000W, lower electrode (Bias) power at 150W, etching gas mixture of methane (CH4), chlorine (Cl2), and argon (Ar) with flow rates of CH4 / Cl2 / Ar = 12 sccm / 6 sccm / 3 sccm, and process time at 30 s.

[0070] Removal of the post-etching residue: soak in N,N-dimethylacetamide for 5 min, then clean with acetone, ethanol, and deionized water for 2 min, respectively. Then clean the small area of residue and the residual organic solvent with an oxygen plasma machine, with O2 flow rate of 50 sccm, RF power of 100 W, and processing time of 10 min.

[0071] Wet etching In 0.53 Ga 0.47 As sacrificial layer, forming stable suspended structures: prepare an etching solution of H3PO4:H2O2:H2O = 2:3:30, and etch for 24 s. After etching, transfer the sample to a first beaker of deionized water, and gently shake for 5 s. Then transfer the sample to a second beaker of pure water, and soak for 10 min. Then transfer the sample to isopropyl alcohol, and soak for 3 min. Slowly take the sample out of the isopropyl alcohol, and place it in the air, waiting for the isopropyl alcohol to naturally evaporate completely.

[0072] Example 3

[0073] Preparation of magic-angle nanocavity and topological cavity

[0074] Epitaxially grow the substrate, which includes, from top to bottom: a GaAs layer with InAs quantum dots with a thickness of 200 nm, 300-1000 nm of Al 0.8 Ga 0.2 As sacrificial layer, and a 500-μm-thick GaAs substrate layer. Dissociate the substrate along the crystal direction into 5x5 mm in size, and soak in acetone, ethanol, and deionized water for 5 min, and dry with a nitrogen gun. Bombard the surface of the substrate with an oxygen plasma device, while secondarily cleaning the residual organic solvent and impurity particles on the surface of the substrate, with the following parameters: O2 flow rate of 50 sccm, RF power of 100 W, and bombardment time of 1 min.

[0075] Spin a layer of electron beam resist ZEP520A on the surface of the substrate, with the following experimental parameters: 300 rpm for 6 sec, accelerate to 3000 rpm for 60 sec, and a thickness of about 380 nm. Then place the substrate with the uniformed resist on a hot plate for baking and curing, with a temperature of 180°C and a time of 180 sec.

[0076] Use an electron beam exposure device (model ELS-F125 from Japan Elionix) for exposure, with the following parameters: writing field size of 200x200 μm, acceleration voltage of 125 kV, beam current of 300 pA, step size of 2 nm, and aperture size of 120 μm. The magic-angle nanocavity and topological cavity structures are as shown in Figure 2 (a) (b) (c), and the exposure dose of GaAs material for the magic-angle nanocavity and topological cavity is 350 μC / cm 2 , 360 μC / cm2 .

[0077] Dry etching was performed by using an inductively coupled plasma etching machine (Oxford Instruments, Plasma Pro 100 Cobra). The substrate to be etched was adhered to a single crystal silicon wafer with heat-conducting silicone oil, and the area of the single crystal silicon outside the substrate was covered with a polyimide high-temperature tape. It was placed in the pre-vacuum chamber of the etching machine, and after the vacuum reached the preset value, it was transferred to the etching chamber. The etching parameters were as follows: the substrate table temperature was set to 20°C, the He gas blowing pressure on the back of the substrate was 10 Torr, the process pressure was 1 mTorr, the upper electrode (ICP) power was 200 W, the lower electrode (Bias) power was 40 W, the etching gas was a mixture of chlorine (Cl2), boron trichloride (BCl3) and argon (Ar), the gas component flow rate was Cl2 / BCl3 / Ar = 3 / 5 / 7 sccm, and the process time was 1 min 50 s.

[0078] Removal of residual glue after etching: soak in N,N-dimethylacetamide for 5 min, and then sequentially clean with acetone, ethanol and deionized water for 2 min. Then use an oxygen plasma glue removal machine to clean the small range of residual glue and residual organic solvents, set the O2 flow rate to 50 sccm, the radio frequency power to 100 W, and the processing time to 10 min.

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

[0080] The scanning electron microscope images of the suspended magic-angle nanocavity and topological body cavity photonic crystal samples prepared in the above embodiments of the present application are shown in FIGS. 1 and 2. Figure 3 As can be seen from the figures, the 30 nm line width connection at the edge of the magic-angle nanocavity and the 50 nm line width connection at the edge of the topological body cavity are complete, the suspended structure is stable, the pattern has no deformation, and the size is consistent with the design. For micro-column cavities and ring-shaped Bragg cavities, quantum dots must be in the center of the cavity to be well coupled. The photonic crystal cavity prepared by this method has a stable suspended structure and a larger effective coupling area, and the quantum dots can still be well coupled within a certain range from the center, greatly improving the coupling probability and device success rate. The photonic crystal cavity has the highest quality factor, and has great advantages in studying stimulated emission under single quantum dot stimulated emission.

[0081] The above description of the embodiments is only used to help understand the method and its core idea of the application. It should be pointed out that, for those skilled in the art, some improvements and modifications can be made to the application without departing from the principles of the application, and these improvements and modifications also fall within the protection scope of the claims of the application.

Claims

1. A method for fabricating a magic-angle nanocavity based on a quantum dot single-photon source, characterized in that, include: The substrate undergoes pretreatment. The substrate includes: a quantum dot layer, a substrate layer, and an Al layer located between the quantum dot layer and the substrate layer. 0.8 Ga 0.2 As the sacrificial layer; The pretreated substrate is treated with oxygen plasma; Photoresist is spin-coated onto the surface of the quantum dot layer on the substrate, and then exposed and developed to form a magic angle nanocavity pattern on the photoresist surface. The magic-angle nanocavity pattern is transferred to the quantum dot layer by etching; The sacrificial layer was removed by wet etching with 4%-10% HF to obtain the magic angle nanocavity; Wherein, the Al 0.8 Ga 0.2 The thickness of the As sacrificial layer is 300-1000 nm; The exposure voltage is 80-150 kV.

2. The preparation method according to claim 1, characterized in that, The quantum dot layer of the magic angle nanocavity is made of GaAs; the substrate layer is made of GaAs.

3. The preparation method according to claim 1 or 2, characterized in that, The thickness of the quantum dot layer is 200 nm; The thickness of the substrate layer is 500 μm.

4. The preparation method according to claim 1, characterized in that, The pretreatment includes: sequentially immersing and washing in acetone, ethanol, and deionized water, and then drying with nitrogen gas.

5. The preparation method according to claim 1, characterized in that, The exposure voltage is 125 kV.

6. The preparation method according to claim 2, characterized in that, The exposure dose of the quantum dot layer is 340-380 μC / cm. 2 .

7. A method for fabricating a topological cavity based on a quantum dot single-photon source, characterized in that, include: The substrate undergoes preprocessing. The substrate includes: a quantum dot layer, a substrate layer, and an In layer located between the quantum dot layer and the substrate layer. 0.53 Ga 0.47 As the sacrificial layer; The pretreated substrate is treated with oxygen plasma; Photoresist is spin-coated onto the surface of the quantum dot layer on the substrate, and then exposed and developed to form a topological cavity pattern on the photoresist surface. The topological cavity pattern is transferred to the quantum dot layer by etching; The sacrificial layer was removed by wet etching using a 2:3:30 H3PO4:H2O2:H2O etchant to obtain the topological cavity. Wherein, the In 0.53 Ga 0.47 The thickness of the As sacrificial layer is 200 nm; The exposure voltage is 80-150 kV.

8. The preparation method according to claim 7, characterized in that, The quantum dot layer of the topological cavity is made of InP; the substrate layer is made of InP.

9. The preparation method according to claim 7 or 8, characterized in that, The thickness of the quantum dot layer is 200 nm; The thickness of the substrate layer is 500 μm.

10. The preparation method according to claim 7, characterized in that, The pretreatment includes: sequentially immersing and washing in acetone, ethanol, and deionized water, and then drying with nitrogen gas.

11. The preparation method according to claim 7, characterized in that, The exposure voltage is 125 kV.

12. The preparation method according to claim 8, characterized in that, The exposure dose of the quantum dot layer is 280-310 μC / cm. 2 .

13. A magic-angle nanocavity based on a quantum dot single-photon source, characterized in that, Prepared using any of the preparation methods described in claims 1-6.

14. A topological cavity based on a quantum dot single-photon source, characterized in that, Prepared using any of the preparation methods described in claims 7-12.

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