CN108365517B - Preparation method and prepared structure of two-color single-photon source structure - Google Patents

Abstract

The invention provides a preparation method of a bicolor single photon source structure, which comprises the following steps: s1, growing and preparing a nanowire single quantum dot structure on a semiconductor substrate; s2, partially flattening the nanowire single quantum dot structure to expose a stress island at the top end of the nanowire; and S3, manufacturing a two-dimensional film by using a mechanical stripping method, and transferring the two-dimensional film to a stress island to finish the preparation.

Description

Preparation method and prepared structure of two-color single-photon source structure

technical field

The invention relates to the technical field of semiconductor materials and devices, and more particularly, to a preparation method and a prepared structure of a two-color single-photon source structure integrating nanowire quantum dots and two-dimensional material films.

Background technique

In recent years, quantum information technologies based on the principles of quantum mechanics, such as quantum computers, quantum key distribution, quantum teleportation and other applications have gradually shown great social and economic prospects. Among them, high-quality single-photon sources and entangled photon sources are the prerequisites to ensure accurate information encoding and efficient transmission and storage, and are an important basis for the practical application of quantum information technologies such as optical quantum computing and quantum secure communication in the future.

Low-density quantum dots grown in Stranski-Krastanov (SK) mode are used to prepare due to their ability to periodically optically pump or electrically inject electrons and holes in a two-level-like system, and have atom-like spectra at low temperatures single photon source. It has the advantages of high oscillator strength, narrow spectral line width, tunable wavelength, and easy integration. Coupling the quantum dot with the tapered nanowire structure can enhance the quantum dot with a wide spectral range. By designing the top of the tapered, the far-field light spot is approximately Gaussian distribution, and the efficiency of entering the fiber after passing through the lens can reach 99% . However, in the currently reported nanowire quantum dot quantum light sources, the deterministic coupling of self-organized quantum dots and nanowire structures and the expansion of wavelengths still need to be solved urgently.

Single-photon sources based on two-dimensional material defect emission or localized exciton state emission have been proven to have the advantages of simple fabrication and adjustable wavelength. The present invention proposes to integrate it with the nanowire quantum dot structure to construct a self-aligned, highly integrated semiconductor two-color single-photon emission source, which will be used for subsequent quantum optical experiments (two-color single-photon sum frequency, difference frequency, quantum communication Multi-dimensional reuse, etc.) provide favorable conditions, so it has very important theoretical research and practical application value.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high-brightness exciton state that can generate defect luminescence or localization in a two-dimensional thin film by using the stress island at the top of the nanowire, and then construct it together with the exciton state emitted by its own single quantum dot. Preparation method of two-color single-photon source structure.

In order to achieve the above purpose of the invention, the technical scheme adopted is:

The preparation method of the dual-color single-photon source structure includes the following steps:

S1. Growing and preparing a nanowire single quantum dot structure on a semiconductor substrate;

S2. Partially planarize the nanowire single quantum dot structure to expose the stress island at the top of the nanowire;

S3. The two-dimensional film is fabricated by a mechanical lift-off method, and the two-dimensional film is transferred to the stress island to complete the fabrication.

Preferably, the material of the semiconductor substrate is GaAs, InP or Si.

Preferably, the height of the single quantum dot structure of the nanowire is 2-3 μm, the quantum dot is located in the axial position of the nanowire, the diameter of the position should meet the single transverse mode condition, and the shape of the apex angle of the nanowire is a cone, The angle of the taper angle is ^2o .

Preferably, the height of the stress island exposed at the top of the nanowire after the planarization is in the range of 150-200 nm.

Preferably, the step S1 prepares the nanowire single quantum dot structure by means 1) or 2):

1) Nanowire single quantum dot structure grown by droplet autocatalysis;

2) Grow self-organized quantum dots, the density of self-organized quantum dots is less than 10 ^-8 /cm ^-2 , and then use quantum dot fluorescence imaging method, and use electron beam exposure combined with inductively coupled plasma etching technology to prepare.

Preferably, the step S2 uses SU8 series photoresist/benzocyclobutene and corresponding exposure technology to partially planarize the nanowire single quantum dot structure.

Preferably, the material of the two-dimensional thin film is tungsten diselenide or hexagonal boron nitride.

Meanwhile, another object of the present invention is to provide a dual-color single-photon source structure prepared by applying the above preparation method.

Compared with the prior art, the beneficial effects of the present invention are:

The invention adopts the stress island at the top of the nanowire to better three-dimensionally confine the defect state carriers of the two-dimensional film, can prepare a more efficient single photon source, and further improve the working temperature. On the other hand, the dual-color single-photon source proposed by the present invention has the advantages of self-alignment, adjustable wavelength, high emission efficiency, good controllability and simple preparation process, and has the possibility of large-scale preparation of dual-color quantum devices. Therefore, it has great application potential in the field of quantum information.

Description of drawings

Figure 1 is a schematic flow chart of the preparation method.

Figure 2 is a schematic representation of the prepared structures.

FIG. 3 is a SEM image of the prepared nanowire quantum dot structure.

Detailed ways

The accompanying drawings are for illustrative purposes only, and should not be construed as limitations on this patent;

The present invention will be further elaborated below in conjunction with the accompanying drawings and embodiments.

Example 1

This embodiment provides a method for preparing a dual-color single-photon source structure. Figure 1 is a flow chart of the preparation method. With reference to Figure 2, the preparation method provided by the present invention includes the following steps:

The first step is to grow and prepare a nanowire single quantum dot structure 2 on the semiconductor substrate 1 .

In this embodiment, the nanowire single quantum dot structure 2 can be prepared by way 1) or way 2):

1) Single quantum dot structure 2 of GaN/AlN or InAs/InP nanowires grown by droplet autocatalysis; the quantum dots are located in the axial direction of the nanowires, and the substrate 1 has no selectivity;

2) Grow InAs/GaAs, GaAs/AlGaAs or InAs/InP self-organized quantum dots, the density of self-organized quantum dots is less than 10 ^-8 /cm ^-2 , and then use quantum dot fluorescence imaging method, and use electron beam exposure combined with inductive coupling Prepared by plasma etching technology. The SEM image of a typical nanowire quantum dot structure is shown in Figure 3. The growth of these two methods can be selected by molecular beam epitaxy or metal organic compound chemical vapor deposition method.

It should be noted that, in order to generate single-photon emission of nanowire quantum dots with high extraction efficiency, as shown in Figure 2, the size of the nanowire single quantum dot structure 2 should be satisfied, and its height is about 2-3 μm, and the quantum dots are located in the nanowire. In the axial direction of , the diameter of the position where the quantum dot is located must satisfy the single transverse mode condition, the vertex angle of the nanowire single quantum dot structure 2 must be tapered, and the angle of the tapered angle is about 2 ^o .

The second step is to partially planarize the nanowire single quantum dot structure 2 to expose the stress island 3 at the top of the nanowire.

In the above scheme, the nanowire single quantum dot structure 2 is partially planarized by using SU8 series photoresist/benzocyclobutene and corresponding exposure technology. Wherein, as shown in FIG. 2 , the height of the stress island 3 exposed at the top of the nanowire after planarization is in the range of 150-200 nm. It is convenient to apply suitable stress to the two-dimensional thin film 4 to generate localized excitons 5 with high brightness.

In the third step, the two-dimensional film 4 is fabricated by using a mechanical peeling method, and the two-dimensional film 4 is transferred to the stress island 3 to complete the preparation.

The material of the two-dimensional thin film 4 is a two-dimensional material such as tungsten diselenide (WSe ₂ ) or hexagonal boron nitride (hBN) for defect emission and localized exciton state emission.

So far, the preparation process is introduced.

Example 2

This embodiment provides a dual-color single-photon source structure, and the preparation process is shown in FIG. 1 , and the prepared structure is shown in FIGS. 2 and 3 .

Its preparation process is as follows:

S1. Growing and preparing a nanowire single quantum dot structure 2 on a semiconductor substrate 1;

S2. Partially planarize the nanowire single quantum dot structure 2 to expose the stress island 3 at the top of the nanowire;

S3. Use the mechanical peeling method to fabricate the two-dimensional thin film 4, and transfer the two-dimensional thin film 4 to the stress island 3 to complete the preparation.

In the above scheme, the two-color single-photon source structure provided by the present invention can use the stress island 3 at the top of the nanowire to make the two-dimensional film 4 generate defect luminescence or localized high-brightness exciton state 5, and then combine with its own single quantum dot. The emitted exciton states are co-constructed.

In this embodiment, the material of the semiconductor substrate 1 is GaAs, InP or Si.

In this embodiment, the height of the nanowire single quantum dot structure 2 is 2-3 μm, the quantum dots are located in the axial position of the nanowire, and the diameter of the position should meet the single transverse mode condition, and the shape of the vertex angle of the nanowire is Conical, the angle of the cone angle is ^2o .

In this embodiment, the height of the stress island 3 exposed at the top of the nanowire after planarization is in the range of 150-200 nm.

In this embodiment, the step S1 prepares the nanowire single quantum dot structure 2 by means 1) or 2), and the growth of these two structures can be selected by molecular beam epitaxy or metal organic compound chemical vapor deposition method:

1) Single quantum dot structure of GaN/AlN, InAs/InP nanowires grown by droplet autocatalysis, the quantum dots are located in the axial direction of the nanowires, and the substrate has no selectivity;

2) Grow InAs/GaAs, GaAs/AlGaAs or InAs/InP self-organized quantum dots, the density should be less than 10 ^-8 /cm ^-2 , and then use the quantum dot fluorescence imaging method, and use electron beam exposure combined with inductively coupled plasma etching prepared by etching technique.

In this embodiment, the step S2 uses photoresist/benzocyclobutene and corresponding exposure technology to partially planarize the nanowire single quantum dot structure 2 .

In this embodiment, the material of the two-dimensional thin film 4 is tungsten diselenide or hexagonal boron nitride.

Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the embodiments of the present invention. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (6)

1. the preparation method of two-color single photon source structure is characterized in that: comprise the following steps: S1. Growing and preparing a nanowire single quantum dot structure on a semiconductor substrate, the height of the nanowire single quantum dot structure is 2-3 μm, the quantum dot is located in the axial position of the nanowire, and the diameter of the position needs to satisfy the single quantum dot structure. For the transverse mode condition, the shape of the apex angle of the nanowire is a cone, and the angle of the cone angle is 2°; S2. Partially flatten the nanowire single quantum dot structure to expose the stress island at the top of the nanowire, and the height of the stress island exposed at the top of the nanowire after the flattening is 150-200 nm; S3. The two-dimensional film is fabricated by a mechanical lift-off method, and the two-dimensional film is transferred to the stress island to complete the fabrication. 2 . The method for preparing a dual-color single-photon source structure according to claim 1 , wherein the material of the semiconductor substrate is GaAs, InP or Si. 3 . 3. The method for preparing a dual-color single-photon source structure according to claim 1, wherein the step S1 prepares a nanowire single quantum dot structure by means of 1) or 2): 1) Nanowire single quantum dot structure grown by droplet autocatalysis; 2) growing self-organized quantum dots, the density of self-organizing quantum dots is less than 10 ^-8 /cm ^-2 , and then using the quantum dot fluorescence imaging method, and using electron beam exposure combined with inductively coupled plasma etching technology to prepare. 4. the preparation method of two-color single photon source structure according to claim 1, is characterized in that: described step S2 adopts SU8 series photoresist/benzocyclobutene and corresponding exposure technology to nanowire single quantum dot structure Partial leveling is performed. 5 . The method for preparing a dual-color single-photon source structure according to claim 1 , wherein the two-dimensional thin film is made of tungsten diselenide or hexagonal boron nitride. 6 . 6. A dual-color single-photon source structure, characterized in that: it is prepared by the preparation method of any one of claims 1 to 5.

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