A method for growing indium arsenide quantum dot single-photon source using molecular beam epitaxy

Abstract

The present invention relates to a method for growing an indium arsenide quantum dot single-photon source using molecular beam epitaxy, comprising the following steps: (1) growing indium arsenide quantum dots on a substrate using molecular beam epitaxy in a stationary growth manner, and adjusting the indium beam current size to a rate suitable for the growth of the indium arsenide quantum dots; (2) adjusting the growth time of the indium arsenide quantum dots based on the growth time of the indium arsenide quantum dots formed by observing a reflection high-energy electron diffractometer, so that the single-photon source region of the sample is located at the center of the entire sample during stationary growth; and (3) fixing the growth time of the indium arsenide quantum dots, changing the growth mode to a combination of rotational growth and stationary growth, and adjusting the time distribution of the rotational growth and stationary growth during the growth process to achieve regulation of the distribution of the single-photon source region. The present invention achieves regulation of the distribution of the indium arsenide quantum dot single-photon source region, greatly increasing the effective area of ​​the quantum dot single-photon source on the sample, and improving the wafer yield and utilization rate.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor materials, and in particular relates to a method for growing an indium arsenide quantum dot single-photon source by using molecular beam epitaxy. Background Art

[0002] A fast, efficient, and low-error single-photon source is essential for realizing quantum information processing applications. Quantum information processing, including quantum communication and quantum computing, relies on high-efficiency, low-error single-photon sources. Because single-photon sources have excellent luminescence properties and can provide stable and reliable qubits, they are the foundation for building optical quantum information networks. Their high efficiency and low error have broad application prospects in fields such as quantum communication and quantum computing. Furthermore, single-photon sources are also being used in data centers, 5G signal processing, autonomous driving, optical computing, and other fields, providing new research areas and development directions for next-generation on-chip optoelectronic information systems.

[0003] Semiconductor quantum dot materials, due to the surrounding potential barrier, confine electrons and holes in the conduction and valence bands within the quantum dot. Because carrier motion within the quantum dot is restricted in all three dimensions, resulting in separated energy levels, the confined electrons and holes exhibit a density of states similar to a delta function. The fermionic nature of electrons allows for spectral isolation of individual optical transitions involving individual electrons, thereby enabling single-photon emission. Because semiconductor quantum dots exhibit discrete energy levels similar to atoms, they are often referred to as artificial atoms. Quantum dots have been studied in a variety of material systems as candidate materials for single-photon sources. Currently, the best performing quantum dot-based single-photon sources are made from III-V semiconductor materials. Among these, the most common quantum dots are InAs quantum dots on gallium arsenide (GaAs) materials, which exhibit exceptional luminescence properties and are easily integrated with other semiconductor structures and manufacturing technologies. InAs quantum dots typically emit light at wavelengths between 850 and 1000 nm and are typically grown using molecular beam epitaxy using the Stranski-Krastanov (SK) growth method. Considerable research has been conducted on controlling the density of self-assembled quantum dots in the SK mode using molecular beam epitaxy (MBE). This allows individual structures to be isolated and used to generate single photons. Currently, single-photon emission from epitaxial quantum dots, quantum key distribution, electrically pumped single-photon emission, integration with many different types of optical microcavities, strong coupling with optical microcavities, photon blockade, resonant excitation, photon indistinguishability measurements, and single-photon lasers have all been achieved in the InAs / GaAs quantum dot material system.

[0004] InAs quantum dots grown using molecular beam epitaxy are distributed in a single plane. Only when the surface density of quantum dots is low enough can it be possible to spatially excite a single quantum dot using light or electrical injection to achieve single photon emission. However, growing InAs quantum dots under conventional conditions usually results in a very high surface density of InAs quantum dots, which is usually as high as 1E10 / cm 2 , adjacent quantum dots are too close to interfere with each other and are not suitable for single-photon emission. The density of quantum dots can be reduced by reducing the thickness of the InAs layer deposition, but due to the SK growth mode of quantum dots, quantum dots cannot be produced when the InAs layer thickness is less than the critical thickness, and when the InAs thickness exceeds the critical thickness, it is very easy to produce InAs quantum dots with too high a surface density. Therefore, the thickness of the InAs layer suitable for generating a single-photon source is in a very small range, which is very difficult to calibrate and control, and is the main challenge of molecular beam epitaxy for growing single-photon source quantum dots. In order to solve this difficulty, people have proposed to use the non-uniform distribution of the source furnace beam in molecular beam epitaxy growth, and intentionally keep the sample in a static state during the growth process to obtain a continuously monotonically changing InAs layer thickness on the sample surface. In this region where the InAs layer thickness continuously changes, low-surface-density InAs quantum dots suitable for single-photon source emission can be found. Although the above method can produce single-photon source InAs quantum dots, its efficiency is extremely low. Only a small area on the entire sample can be found in an area suitable for generating single-photon sources. Most areas cannot be used, either because there are no quantum dots or the surface density of quantum dots is too high. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for growing an indium arsenide quantum dot single-photon source by molecular beam epitaxy, which regulates the distribution area of ​​the quantum dot single-photon source by combining rotational growth with stationary growth.

[0006] The present invention provides a method for growing an indium arsenide quantum dot single-photon source using molecular beam epitaxy, comprising the following steps:

[0007] (1) Growing indium arsenide quantum dots on a substrate by molecular beam epitaxy in a static growth manner, and adjusting the indium beam size to a rate suitable for the growth of indium arsenide quantum dots;

[0008] (2) Based on the growth time of the InAs quantum dots formed by reflection high energy electron diffractometer (RHEED), the growth time of the InAs quantum dots was adjusted so that the single photon source region of the sample was located at the center of the entire sample during stationary growth;

[0009] (3) The growth time of indium arsenide quantum dots is fixed, and the growth mode is changed to a combination of rotational growth and static growth. The regional distribution of the single-photon source is controlled by adjusting the time distribution of rotational growth and static growth during the growth process.

[0010] Furthermore, in step (1), the indium beam size is adjusted gradually until a rate suitable for the growth of indium arsenide quantum dots is found.

[0011] Furthermore, in the step (3), the time proportion of rotational growth is increased during the growth process, the time proportion of static growth is reduced, and the single-photon source area of ​​the indium arsenide quantum dots is enlarged.

[0012] The principle of this invention is that the amount of indium arsenide (InAs) layer deposited is determined by the arsenic beam current and the InAs growth time. During the growth process, the substrate is held stationary, and the arsenic beam current on the sample surface, from the nearest end to the farthest end of the arsenic source, is gradually reduced. By maintaining a fixed growth time, the thickness of the InAs layer gradually decreases, thereby gradually reducing the surface density of indium quantum dots. Because the single-photon source requires a very high density of InAs quantum dots, the region of the single-photon source that meets these requirements is relatively narrow. If the substrate is rotated at a constant speed during the growth process, a uniformly thick InAs layer is grown on the sample surface, resulting in a uniform quantum dot density distribution. Combining rotational growth with stationary growth during the growth process can change the average indium beam current corresponding to different regions on the sample, enabling regulation of the distribution of the InAs quantum dot single-photon source. This inventive method is of great significance for improving the distribution and utilization of quantum dot single-photon source regions in actual production.

[0013] Beneficial effects

[0014] The present invention realizes the distribution regulation of the indium arsenide quantum dot single-photon source area, greatly increases the effective area of ​​the quantum dot single-photon source on the sample, improves the wafer yield and utilization rate, is easy to use, accurate and reliable, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the process of splitting the epitaxial wafer in the embodiment.

[0016] Figure 2 These are the results of atomic force microscopy tests on samples S1, S3, S5, S7, and S9 in the examples.

[0017] Figure 3 These are the test results of the luminescence wavelength and luminescence intensity of indium arsenide quantum dots on the S2 sample.

[0018] Figure 4 These are the test results of the luminescence wavelength and luminescence intensity of indium arsenide quantum dots on the S3 sample.

[0019] Figure 5 These are the test results of the luminescence wavelength and luminescence intensity of indium arsenide quantum dots on the S4 sample.

[0020] Figure 6 These are the test results of the luminescence wavelength and luminescence intensity of indium arsenide quantum dots on the S5 sample.

[0021] Figure 7 These are the test results of the luminescence wavelength and luminescence intensity of indium arsenide quantum dots on the S6 sample.

[0022] Figure 8 These are the test results of the luminescence wavelength and luminescence intensity of indium arsenide quantum dots on the S7 sample.

[0023] Figure 9 The S5 sample in the embodiment is observed to emit light in the single-photon region by qCMOS.

[0024] Figure 10 The S6 sample in the embodiment is observed to emit light in the single-photon region using qCMOS.

[0025] Figure 11 This is an example of regulating the distribution area of ​​the quantum dot single-photon source in the embodiment. DETAILED DESCRIPTION

[0026] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0027] Example 1

[0028] In this embodiment, the epitaxial growth of InAs quantum dots uses a solid source molecular beam epitaxy (SSMBE) system with two solid group V sources of As and Sb, three group III sources of Ga, Al and In, and three doping sources of Si, GaTe and Be.

[0029] First, InAs quantum dots were grown epitaxially on a GaAs substrate by static growth. The epitaxial wafer was then split, and the middle piece was taken and divided into ten equal pieces. The samples were named S1-S10 from the cut edge to the top. The indium beam current gradually increased from S1 to S10. Figure 1 As shown. The indium beam current at position S1 is 2.15×10 -8 Torr, the indium beam current at S10 position is 2.26×10 -8The beam current difference is about 5%. Samples S1, S3, S5, S7, and S9 were selected for atomic force microscopy testing, and the test range was 1×1μm. 2 , the test results are as follows Figure 2 As shown in the figure, for samples S1 and S3, the indium beam current is low at this location, and only atomic steps in the indium arsenide wetting layer are observed. Due to the thin InAs layer, no quantum dots are formed. As the indium beam current increases, quantum dots begin to appear on sample S5. As the indium beam current further increases, the density of indium arsenide quantum dots gradually increases in samples S7 and S9. The atomic force microscopy test results well confirm the indium beam current distribution at different locations on the sample surface.

[0030] Then the luminescence test of indium arsenide quantum dots was carried out on samples S2-S7. The test results are as follows: Figures 3 to 8 As shown. For samples S2, S3, and S4, only the luminescence peaks of the GaAs and InAs immersion layers can be observed, but not the quantum dots. The luminescent quantum dots cannot be seen using qCMOS. For samples S5 and S6, the luminescence peaks of the quantum dots can be observed. The wavelength of the quantum dots is between 870 and 890 nm, and the narrowest line width is 0.08 nm. The luminescence brightness of the quantum dots on these samples is sufficient and the distribution is appropriate. In addition, the luminescent quantum dots can be observed using qCMOS, as shown in the following figure. Figure 9 and Figure 10 As shown in Figure 2, for the S7 sample, the emission wavelength of the InAs quantum dot red-shifts, the luminescence brightness decreases, and the signal disappears near the S8 position.

[0031] Combining the results of atomic force microscopy and luminescence testing, it can be concluded that for samples S1-S10, the appropriate area is on the S5-S6 samples (with a width of approximately 2 cm). The luminous wavelength of the quantum dots is between 870-890 nm, the luminous brightness is sufficient, and the distribution is appropriate. This area is the quantum dot single-photon source area. The S5-S6 samples are in the center of the entire epitaxial wafer, and the beam current at this position is the average beam current of the rotating growth. The horizontal axis is the position of the substrate from the source furnace, the vertical axis is the beam distribution, and the dotted line range is the single-photon source area, as shown in the figure. Figure 11 As shown. Through superlattice calibration, we obtained an indium beam current of 2.2×10 -8 Torr, the corresponding indium arsenide growth rate is 0.03nm / s, and the total indium arsenide growth time is 17s. When the sample is stationary, the beam current corresponding to the S1-S10 position is A1-B1, and the indium beam current at point A1 is 2.15×10 -8 Torr, the indium beam current at point B1 is 2.26×10 -8The static growth lasts for 17 seconds, and the area that satisfies the single-photon source emission is CD. Keeping the total growth time unchanged at 17 seconds, the rotational growth is combined with the static growth and the proportion of rotational growth is gradually increased. A1-B1 will rotate closer to A2-B2 within the shadow range, and the area that satisfies the single-photon source emission will gradually increase. When the total time of 17 seconds is fully rotational growth, the average indium beam current at each point on the entire sample is equal to 2.2×10 -8 To, at this time corresponding Figure 11 By using the A2-B2 curve in the figure, we can obtain a sample in which the entire epitaxial wafer meets the requirements of a single-photon source.

[0032] Therefore, if the total growth time remains constant and the sample's state is switched from static to rotational growth, a sample can be obtained that meets the requirements of a single-photon source throughout the entire epitaxial wafer. By combining rotational growth with stationary growth during epitaxial growth, while maintaining a constant indium beam current and total time, and adjusting the ratio of rotational to stationary growth time, the distribution area of ​​the single-photon source of the InAs quantum dots can be controlled. The longer the rotational growth time is allocated, the larger the single-photon source distribution area.

Claims

1. A method for growing an indium arsenide quantum dot single-photon source using molecular beam epitaxy, characterized in that: The steps include: (1) Growing indium arsenide quantum dots on a substrate by molecular beam epitaxy in a static growth manner, and adjusting the indium beam size to a rate suitable for the growth of indium arsenide quantum dots; (2) According to the growth time of the indium arsenide quantum dots formed by observing the reflection high-energy electron diffractometer, the growth time of the indium arsenide quantum dots was adjusted so that the single photon source region of the sample was located at the center of the entire sample during static growth; (3) The growth time of indium arsenide quantum dots is fixed, and the growth mode is changed to a combination of rotational growth and static growth. The regional distribution of the single-photon source is controlled by adjusting the time distribution of rotational growth and static growth during the growth process.

2. The method according to claim 1, wherein: In step (1), the indium beam size is gradually adjusted until a rate suitable for the growth of indium arsenide quantum dots is found.

3. The method according to claim 1, wherein: In the step (3), the time proportion of rotational growth during the growth process is increased, the time proportion of static growth is reduced, and the single-photon source area of ​​the indium arsenide quantum dots is enlarged.

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