Quantum dot light source and preparation method thereof

Abstract

The invention provides a quantum dot light source and a preparation method thereof. The quantum dot light source can be applied to the technical field of semiconductors and quantum information. The quantum dot light source comprises a first doping layer, a quantum dot layer, a barrier layer, an energy level matching layer and a second doping layer which are sequentially stacked, the first doping layer is used for providing holes under electrical excitation; the quantum dot layer comprises a plurality of quantum dots, and the quantum dots are used for emitting fluorescence when holes from the first doped layer and electrons which are from the second doped layer and pass through the barrier layer are compounded in the quantum dots; the barrier layer is used for preventing holes from the quantum dot layer from passing through under electrical excitation and enabling electrons which come from the energy level matching layer and have energy equal to preset energy to pass through; the energy level matching layer is used for adjusting the energy of the electrons from the second doping layer to preset energy under electrical excitation; and the second doping layer is used for providing electrons under electrical excitation.

Description

Technical Field

[0001] The present invention relates to the fields of semiconductor and quantum information technologies, and more particularly, to a quantum dot light source and a method for preparing the same. Background Art

[0002] As a quantum light source with high practical value, semiconductor quantum dots are widely used in optical quantum communication and linear optical quantum computing. Quantum dots in these application scenarios almost all use the scheme of optical pulse resonance excitation to achieve higher optical quality. However, in the exploration of miniaturization and integration of semiconductor quantum dots as quantum light sources, the complex external optical excitation system and precise filtering facilities limit the potential of semiconductor quantum dots in integration. Quantum dots directly driven by electricity can just avoid these disadvantages.

[0003] However, the scheme of obtaining a quantum dot light source by electrically driving quantum dots is different from optical resonance excitation. The spectral components of electrically driven quantum dots are miscellaneous, and even after precise filtering operations on their fluorescence signals, the single-photon purity still cannot be improved to a relatively perfect level, which limits the application of such quantum light sources in quantum communication and quantum computing. Therefore, there is an urgent need for an electrically driven high-performance quantum dot scheme with a simpler structure, high spectral component purity, and suitable for large-scale integration. Summary of the Invention

[0004] In view of this, the present invention provides a quantum dot light source and a method for preparing the same.

[0005] According to one aspect of the present invention, there is provided a quantum dot light source, including: a first doped layer, a quantum dot layer, a barrier layer, an energy level matching layer, and a second doped layer that are sequentially stacked; the first doped layer is used to provide holes under electrical excitation; the quantum dot layer includes a plurality of quantum dots, and the quantum dots are used to emit fluorescence when holes from the first doped layer and electrons from the second doped layer and passing through the barrier layer recombine within the quantum dots; the barrier layer is used to prevent holes from the quantum dot layer from passing through under electrical excitation, and at the same time allow electrons from the energy level matching layer and having an energy equal to a predetermined energy to pass through; the energy level matching layer is used to adjust the energy of electrons from the second doped layer to a predetermined energy under electrical excitation; the second doped layer is used to provide electrons under electrical excitation.

[0006] According to an embodiment of the present invention, the quantum dot light source further includes: a first intrinsic layer disposed between the first doped layer and the quantum dot layer, and the first intrinsic layer is used to adjust the time for holes from the first doped layer to reach the quantum dot layer; a second intrinsic layer disposed between the energy level matching layer and the second doped layer, and the second intrinsic layer is used to adjust the time for electrons from the second doped layer to reach the energy level matching layer.

[0007] According to an embodiment of the present invention, the above-mentioned quantum dot light source further includes: a first metal layer disposed in the groove and attached to the second doped layer, and the first metal layer is used for electrically connecting to the first electrode of the power supply, wherein the groove penetrates through the first doped layer, the first intrinsic layer, the quantum dot layer, the barrier layer, the energy level matching layer, and the second intrinsic layer; a second metal layer disposed on the first doped layer and attached to the first doped layer, and the second metal layer is used for electrically connecting to the second electrode of the power supply.

[0008] According to an embodiment of the present invention, the above-mentioned energy level matching layer includes a quantum well or a superlattice structure.

[0009] According to an embodiment of the present invention, the material of the above-mentioned first doped layer includes at least one of the following: p-type doped gallium arsenide, p-type doped aluminum arsenide, p-type doped gallium aluminum arsenide; the material of the above-mentioned quantum dot layer includes one of the following: gallium arsenide, gallium aluminum arsenide, indium arsenide, indium gallium arsenide, indium phosphide; the material of the above-mentioned barrier layer includes one of the following: gallium arsenide, gallium aluminum arsenide; the material of the above-mentioned energy level matching layer includes one of the following: gallium arsenide, gallium aluminum arsenide, indium arsenide, indium gallium arsenide; the material of the above-mentioned second doped layer includes at least one of the following: n-type doped gallium arsenide, n-type doped aluminum arsenide, n-type doped gallium aluminum arsenide; the material of the above-mentioned first intrinsic layer includes one of the following: gallium arsenide, aluminum arsenide, gallium aluminum arsenide; the material of the above-mentioned second intrinsic layer includes one of the following: gallium arsenide, aluminum arsenide, gallium aluminum arsenide.

[0010] According to an embodiment of the present invention, the thickness of the above-mentioned first doped layer is between 20 nm and 400 nm; the thickness of the above-mentioned quantum dot layer is between 3 nm and 15 nm; the thickness of the above-mentioned barrier layer is between 0.5 nm and 5 nm; the thickness of the above-mentioned energy level matching layer is between 5 nm and 30 nm; the thickness of the above-mentioned second doped layer is between 20 nm and 400 nm; the thickness of the above-mentioned first intrinsic layer is between 40 nm and 400 nm; the thickness of the above-mentioned second intrinsic layer is between 40 nm and 400 nm.

[0011] According to an embodiment of the present invention, the above-mentioned quantum dot light source further includes a substrate disposed below the second doped layer.

[0012] According to an embodiment of the present invention, the material of the above-mentioned substrate includes gallium arsenide; the thickness of the above-mentioned substrate is between 300 μm and 1000 μm.

[0013] According to an embodiment of the present invention, the volume of the above-mentioned quantum dot light source is between 1 mm 2 and 100 mm 2 .

[0014] According to another aspect of the present invention, there is provided a method for preparing the above-mentioned quantum dot light source, and the preparation method includes: sequentially growing a second doping layer, an energy level matching layer, a barrier layer, a quantum dot layer, and a first doping layer on a substrate.

[0015] For the quantum dot light source provided by the embodiment of the present invention, since the energy level matching layer can adjust the energy of electrons from the second doping layer to a predetermined energy under electrical excitation, and the barrier layer can prevent holes from the quantum dot layer from passing through under electrical excitation, while allowing electrons with an energy equal to the predetermined energy from the energy level matching layer to pass through, avoiding the recombination of electrons and holes in non-quantum dot layers, such as the first doping layer, the energy level matching layer, and the second doping layer, and generating fluorescence with a wavelength close to or consistent with that of the quantum dots, thereby avoiding the contamination of the optical properties of the quantum dots. At the same time, electrons can tunnel into the quantum dots at a specific voltage, and when holes from the first doping layer and electrons from the second doping layer passing through the barrier layer recombine in the quantum dots, the quantum dots can spontaneously emit fluorescence and emit fluorescence, realizing composite luminescence. This quantum dot light source structure is simpler, has a high spectral component purity, and is suitable for large-scale integrated high-performance quantum dot solutions driven by electricity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Through the following description of the embodiments of the present invention with reference to the drawings, the above and other objects, features, and advantages of the present invention will become clearer. In the drawings:

[0017] Figure 1 shows a schematic structural diagram of a quantum dot light source provided by an embodiment of the present invention;

[0018] Figure 2 shows a schematic structural diagram of a quantum dot light source provided by another embodiment of the present invention;

[0019] Figure 3 shows a schematic structural diagram of a quantum dot light source provided by still another embodiment of the present invention;

[0020] Figure 4 shows an energy schematic diagram of electrons and holes in each layer included in the quantum dot light source according to the embodiment of the present invention;

[0021] Figure 5 shows a spectrogram of a quantum dot light source in the related art;

[0022] Figure 6 shows a spectrogram of a quantum dot light source provided by an embodiment of the present invention;

[0023] Figure 7 shows a schematic diagram of the second-order correlation function value of a quantum dot light source in the related art;

[0024] Figure 8Schematic diagram showing the second-order correlation function value of a quantum dot light source according to an embodiment of the present invention;

[0025] Figure 9 Flowchart showing a method for preparing a quantum dot light source according to an embodiment of the present invention;

[0026] Figure 10A Schematic diagrams of some stages in the process of a method for preparing a quantum dot light source according to an embodiment of the present invention;

[0027] Figure 10B Schematic diagrams of some stages in the process of a method for preparing a quantum dot light source according to another embodiment of the present invention. Detailed implementation manners

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a thorough understanding of the embodiments of the present invention. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0029] The terms used herein are merely for describing specific embodiments and are not intended to limit the present invention. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0030] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0031] In the case of using expressions such as "at least one of A, B, and C", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include, but is not limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C).

[0032] In the related art, in order to integrate quantum dots on an optical excitation chip, a scheme has been developed to excite quantum dots using high-order modes of the light field and then collect the fundamental mode fluorescence, integrating the external optical filtering optical path, but at the same time introducing a more complex excitation optical path. Some developers have also explored the direct excitation of quantum dots by electrons and achieved certain progress in the fields of quantum communication and quantum computing, but their application scenarios are often limited by the optical quality of this scheme. Some developers have also grown quantum dot and quantum well structures on the same wafer and used the laser generated by the quantum well to excite the quantum dots in the form of band excitation, thereby obtaining better optical performance than direct electrical drive. This scheme has also been shelved due to the inability to further improve the optical quality.

[0033] Recently, there have been many successful attempts to integrate multiple quantum dots on the same chip or to integrate quantum dots and on-chip optical paths simultaneously. These schemes require exciting multiple slightly different quantum dots on the same sample. At this time, providing a dedicated excitation light path for each quantum dot becomes one of the main factors limiting the number of quantum dots that can be used simultaneously on the same chip. Quantum dots directly driven by electricity can just avoid this disadvantage.

[0034] The quantum dot light source obtained by electrically driving quantum dots has been proven to be able to generate single photons and entangled photon pairs. Its structure is simple, the optical path is simple, the cost is lower, and it is suitable for integrated applications. Among these schemes, different from optical resonance excitation, the spectral components of electrically driven quantum dots are complex. Even after precise filtering operations on its fluorescence signal, the purity of single photons still cannot be improved to a relatively perfect level, which limits the application of such quantum light sources in quantum communication and quantum computing.

[0035] In view of this, the present invention provides a quantum dot light source and a preparation method thereof, which can be applied to the fields of semiconductors and quantum information technology.

[0036] In order to overcome the shortcomings of the existing optical pulse resonance excitation of quantum dots, such as complex structure, low integration, and the complex spectral components of the quantum dot light source obtained by electrically driving quantum dots, the present invention proposes a new energy band structure design, which can further improve the purity of single photons obtained by electrically driving quantum dots, and can be combined with an optical resonator to improve the optical efficiency and increase its application value in quantum communication and quantum computing. It has a simpler structure, high spectral component purity, and is a high-performance quantum dot scheme suitable for large-scale integration.

[0037] Figure 1 The structural schematic diagram of the quantum dot light source provided according to an embodiment of the present invention is shown.

[0038] As Figure 1As shown, the quantum dot light source 100 includes a first doped layer 110, a quantum dot layer 120, a barrier layer 130, an energy level matching layer 140, and a second doped layer 150 that are stacked in sequence.

[0039] The first doped layer 110 is configured to provide holes under electrical excitation. Among them, the first doped layer can be a P-type doped layer.

[0040] The quantum dot layer 120 includes a plurality of quantum dots. The quantum dots are configured to emit fluorescence when holes from the first doped layer 110 and electrons from the second doped layer 150 that pass through the barrier layer 130 recombine within the quantum dots.

[0041] The barrier layer 130 is configured to prevent holes from the quantum dot layer 120 from passing through under electrical excitation, while allowing electrons from the energy level matching layer 140 with an energy equal to a predetermined energy to pass through.

[0042] The energy level matching layer 140 is configured to adjust the energy of electrons from the second doped layer 150 to a predetermined energy under electrical excitation.

[0043] The second doped layer 150 is configured to provide electrons under electrical excitation. Among them, the second doped layer 150 can be an N-type doped layer

[0044] In the case where the barrier layer 130 and the energy level matching layer 140 are not added, the holes provided by the first doped layer 110 under electrical excitation can transition to the quantum dot layer 120 and the second doped layer 150. At the same time, the electrons provided by the second doped layer 150 under electrical excitation can transition to the first doped layer 110 and the quantum dot layer 120. As a result, electrons and holes will recombine in the quantum dot layer 120, the first doped layer 110, and the second doped layer 150, and the quantum dot layer 120, the first doped layer 110, and the second doped layer 150 will all emit light. At this time, when detecting the fluorescence emitted by the quantum dot layer 120, the light emitted by the first doped layer 110 and the second doped layer 150 will be detected simultaneously, making the spectral components of the detected light complex.

[0045] According to an embodiment of the present invention, the main function of the barrier layer 130 is to prevent holes and electrons with an energy not equal to the predetermined energy on both sides of this layer from passing through, avoiding their recombination in non-quantum dot layers (such as the first doped layer 110, the second doped layer 150, and the energy level matching layer 140, etc.) and generating fluorescence with a wavelength close to or consistent with that of the quantum dots, thereby avoiding contamination of the optical properties of the quantum dots.

[0046] According to an embodiment of the present invention, due to the introduction of the barrier layer 130, the electron-hole recombination in the quantum dot layer 120 is also suppressed simultaneously. Therefore, several additional energy level matching structures, namely the energy level matching layer 140, need to be added so that electrons can tunnel into the quantum dots in the quantum dot layer 120 at a specific voltage and recombine and emit light in the quantum dots.

[0047] According to an embodiment of the present invention, since the quantum dot light source provided by the embodiment of the present invention includes a barrier layer 130 and an energy level matching layer 140, it is possible to greatly suppress other components in the spectrum of the light obtained by electrically driving the quantum dots while retaining the spontaneous emission fluorescence component generated by the quantum dots, thereby obtaining a quantum dot light source of electrically driven quantum dots with spectral characteristics similar to those of optical resonance excitation.

[0048] According to an embodiment of the present invention, the quantum dot light source provided by the embodiment of the present invention can also be placed in an optical resonator with a certain Purcell effect to obtain a higher quantum efficiency and meet the requirements of quantum communication and quantum computing for quantum light sources.

[0049] For the quantum dot light source provided by the embodiment of the present invention, since the energy level matching layer can adjust the energy of electrons from the second doping layer to a predetermined energy under electrical excitation, and the barrier layer can prevent holes from the quantum dot layer from passing through under electrical excitation while allowing electrons with an energy equal to the predetermined energy from the energy level matching layer to pass through, avoiding the recombination of electrons and holes in non-quantum dot layers, such as the first doping layer, the energy level matching layer, and the second doping layer, to generate fluorescence with a wavelength close to or the same as that of the quantum dots, thereby avoiding the contamination of the optical performance of the quantum dots. At the same time, it can enable electrons to tunnel into the quantum dots at a specific voltage, and the quantum dots can spontaneously emit fluorescence and emit fluorescence when holes from the first doping layer and electrons from the second doping layer passing through the barrier layer recombine in the quantum dots, realizing recombination luminescence. This quantum dot light source structure is simpler, has a high spectral component purity, and is a high-performance quantum dot solution suitable for large-scale integration for electrical driving.

[0050] According to an embodiment of the present invention, by combining the barrier layer and the energy level matching layer with an electrically injected quantum dot single-photon source, the single-photon purity and entanglement fidelity are improved.

[0051] Figure 2 The structural schematic diagram of a quantum dot light source provided by another embodiment of the present invention is shown.

[0052] As Figure 2 shown, the quantum dot light source 100 includes a first doping layer 110, a first intrinsic layer 161, a quantum dot layer 120, a barrier layer 130, an energy level matching layer 140, a second intrinsic layer 162, a second doping layer 150, and a substrate 170 that are sequentially stacked and arranged.

[0053] Figure 2 and Figure 1 The first doping layer 110, quantum dot layer 120, barrier layer 130, energy level matching layer 140, and second doping layer 150 in [it] have similar structures and functions, and for the sake of simplicity, they will not be elaborated here.

[0054] The first intrinsic layer 161 is disposed between the first doping layer 110 and the quantum dot layer 120. The first intrinsic layer 161 is used to adjust the time for holes from the first doping layer 110 to reach the quantum dot layer 120. The second intrinsic layer 162 is disposed between the energy level matching layer 140 and the second doping layer 150. The second intrinsic layer 162 is used to adjust the time for electrons from the second doping layer 150 to reach the energy level matching layer 140.

[0055] According to an embodiment of the present invention, by using the first intrinsic layer to adjust the time for holes from the first doping layer to reach the quantum dot layer, and using the second intrinsic layer to adjust the time for electrons from the second doping layer to reach the energy level matching layer, so as to further adjust the time for electrons from the second doping layer to reach the quantum dot layer, and further ensure that the time for holes from the first doping layer to reach the quantum dot layer is the same as the time for electrons from the second doping layer to reach the quantum dot layer, thereby improving the fluorescence emission efficiency of the quantum dot layer.

[0056] According to an embodiment of the present invention, by using the first doping layer to provide holes under electrical excitation, using the quantum dot layer including a plurality of quantum dots to emit fluorescence when holes from the first doping layer and electrons from the second doping layer passing through the barrier layer recombine within the quantum dots, using the barrier layer to prevent holes from the quantum dot layer from passing through under electrical excitation while allowing electrons from the energy level matching layer with an energy equal to a predetermined energy to pass through, using the energy level matching layer to adjust the energy of electrons from the second doping layer to the predetermined energy under electrical excitation, using the second doping layer to provide electrons under electrical excitation, using the first intrinsic layer to adjust the time for holes from the first doping layer to reach the quantum dot layer, and using the second intrinsic layer to adjust the time for electrons from the second doping layer to reach the energy level matching layer, the combination of the electrical system and the optical system is realized, and while ensuring a high electron injection efficiency, the optical efficiency can also be improved.

[0057] The substrate 180 is disposed below the second doping layer 150.

[0058] The substrate 180 is used to provide a stable support structure for epitaxially growing other layer structures in the quantum dot light source 100 except the substrate.

[0059] The physical structure of the substrate 180 is relatively stable. The substrate 180 can provide a flat and continuous single crystal interface for epitaxial growth.

[0060] Figure 3The structural schematic diagram of a quantum dot light source provided according to another embodiment of the present invention is shown.

[0061] As Figure 3 shown, the quantum dot light source 100 includes a first doped layer 110, a first intrinsic layer 161, a quantum dot layer 120, a barrier layer 130, an energy level matching layer 140, a second intrinsic layer 162, a second doped layer 150, and a substrate 170 that are sequentially stacked, and also includes a first metal layer 181 and a second metal layer 182.

[0062] Figure 3 and Figure 2 The first doped layer 110, the first intrinsic layer 161, the quantum dot layer 120, the barrier layer 130, the energy level matching layer 140, the second intrinsic layer 162, the second doped layer 150, and the substrate 170 in

[0063] have similar structures and functions, and for simplicity, they will not be elaborated here.

[0064] The first metal layer 181 is disposed in the groove and is in contact with the second doped layer 150. The first metal layer 181 is used to electrically connect to the first electrode of the power supply. Among them, the groove penetrates through the first doped layer 110, the first intrinsic layer 161, the quantum dot layer 120, the barrier layer 130, the energy level matching layer 140, and the second intrinsic layer 162. The second metal layer 182 is disposed on the first doped layer 110 and is in contact with the first doped layer 110. The second metal layer 182 is used to electrically connect to the second electrode of the power supply.

[0065] When the power supply applies a predetermined voltage to the quantum dot light source 100 through the first electrode and the second electrode, electrons and holes recombine in the quantum dots included in the quantum dot light source 100, and the quantum dots emit fluorescence with a relatively high single-photon purity.

[0066] For example, the energy level matching layer 140 includes a quantum well or a superlattice structure.

[0067] For example, the energy level matching layer 140 can be a quantum well layer. By using the quantum well layer, electrons from the second doped layer can tunnel into the quantum dots in the quantum dot layer 120 at a specific voltage and recombine and emit light in the quantum dots.

[0068] The energy level matching layer 140 can be a superlattice structure layer. By using the superlattice structure layer, electrons from the second doped layer can tunnel into the quantum dots in the quantum dot layer 120 at a specific voltage and recombine and emit light in the quantum dots.

[0069] The material of the first doping layer 110 includes at least one of the following: P-type doped gallium arsenide, P-type doped aluminum arsenide, P-type doped gallium aluminum arsenide. The material of the quantum dot layer 120 includes one of the following: gallium arsenide, gallium aluminum arsenide, indium arsenide, indium gallium arsenide, indium phosphide. The material of the barrier layer 130 includes one of the following: gallium arsenide, gallium aluminum arsenide. The material of the energy level matching layer 140 includes one of the following: gallium arsenide, gallium aluminum arsenide, indium arsenide, indium gallium arsenide. The material of the second doping layer 150 includes at least one of the following: N-type doped gallium arsenide, N-type doped aluminum arsenide, N-type doped gallium aluminum arsenide. The material of the first intrinsic layer 161 includes one of the following: gallium arsenide, aluminum arsenide, gallium aluminum arsenide. The material of the second intrinsic layer 162 includes one of the following: gallium arsenide, aluminum arsenide, gallium aluminum arsenide. The material of the substrate 170 includes gallium arsenide;

[0070] The thickness of the first doping layer 110 is between 20 nm and 400 nm. For example, the thickness of the first doping layer 110 can be 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm.

[0071] The thickness of the quantum dot layer 120 is between 3 nm and 15 nm. For example, the thickness of the quantum dot layer 120 can be 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 13 nm, or 15 nm.

[0072] The thickness of the barrier layer 130 is between 0.5 nm and 5 nm. For example, the thickness of the barrier layer 130 can be 0.5 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 4.5 nm, or 5 nm.

[0073] The thickness of the energy level matching layer 140 is between 5 nm and 30 nm. For example, the thickness of the energy level matching layer 140 can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, or 30 nm.

[0074] The thickness of the second doping layer 150 is between 20 nm and 400 nm. For example, the thickness of the second doping layer 150 can be 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm.

[0075] The thickness of the first intrinsic layer 161 is between 40 nm and 400 nm. For example, the thickness of the first intrinsic layer 161 can be 40 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm.

[0076] The thickness of the second intrinsic layer 162 is between 40 nm and 400 nm. For example, the thickness of the second intrinsic layer 162 can be 40 nm, 50 nm, 90 nm, 100 nm, 120 nm, 200 nm, 250 nm, 300 nm, 350 nm or 400 nm.

[0077] The thickness of the substrate 170 is between 300 μm and 1000 μm. For example, the thickness of the substrate 170 can be 300 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm or 1000 μm.

[0078] The volume of the quantum dot light source 100 is between 1 mm 2 and 100 mm 2 The quantum dot light source 100 has a small volume, a simple structure and is easy to be integrated.

[0079] According to the embodiments of the present invention, the thickness of each layer, the material parameters of each layer and the doping concentration of the doping layer included in the quantum dot light source 100 are calculated according to the following operations:

[0080] First, substitute the preset thickness of each layer, the preset material parameters of each layer and the preset doping concentration of the doping layer into the Poisson equation and solve it to calculate the energy bands of each layer of the quantum dot light source corresponding to these preset parameters under non-operating voltage and operating voltage.

[0081] Second, calculate the potential energies of electrons and holes in each layer according to the energy bands of each layer under non-operating voltage and operating voltage, substitute the corresponding potential energies into the Schrödinger equation and solve it to calculate the ground state wave functions of electrons and holes in the quantum dot layer and the energy level matching layer under non-operating voltage (i.e., without applying operating voltage) and operating voltage; then calculate the probabilities of the ground state electrons in the energy level matching layer and the holes in the quantum dot layer tunneling through the barrier layer under operating voltage according to the ground state wave functions of electrons and holes in the quantum dot layer and the energy level matching layer under non-operating voltage and operating voltage; calculate the probabilities of the ground state electrons in the second doping layer and the holes in the first doping layer tunneling through the barrier layer under operating voltage according to the ground state wave functions of electrons and holes in the first doping layer and the second doping layer under non-operating voltage and operating voltage.

[0082] Third, calculate the fluorescence wavelength of the fluorescence emitted by the quantum dots in the quantum dot layer according to the preset thickness of each layer, the preset material parameters of each layer and the ground state wave functions of electrons and holes in the quantum dot layer under operating voltage; substitute the fluorescence wavelength of the fluorescence emitted by the quantum dots, the preset thickness of each layer and the preset material parameters into the Maxwell equations and solve it to calculate the efficiency of the fluorescence of this wavelength being collected by the objective lens.

[0083] According to the probability results obtained above, adjust parameters such as the preset thickness of each layer, the preset material parameters of each layer, and the preset doping concentration of the doping layer, and re - perform the above - mentioned first to third steps until, at the working temperature (4K (Kelvin)) and the target working voltage, the probability results meet the following conditions, and obtain the parameters such as the thickness of each layer, the material parameters of each layer, and the doping concentration of the doping layer included in the final quantum dot light source: 1) The probability that electrons in the conduction band of the second doping layer cross or tunnel through the barrier layer is less than one - thousandth; 2) The probability that holes in the valence band of the first doping layer cross or tunnel through the barrier layer is less than one - thousandth; 3) The probability that holes in the quantum dot layer cross or tunnel through the barrier layer is less than one - thousandth; 4) The probability that electrons in the energy level matching layer cross or tunnel through the barrier layer is greater than 60%; 5) The efficiency that the fluorescence emitted by the quantum dots can be collected by the objective lens is greater than 40%.

[0084] According to an embodiment of the present invention, after obtaining the parameters such as the thickness of each layer, the material parameters of each layer, and the doping concentration of the doping layer included in the final quantum dot light source, the energies of electrons and holes in each layer are matched, so that the final quantum dot light source can meet Figures 1 to 3 the functions of the quantum dot light source 100 as shown

[0085] According to an embodiment of the present invention, the doping concentration of the doping layer can be selected according to actual situations and is not limited herein. For example, the doping concentration of the doping layer can be in the range of 1×10 18 / CM 3 ~2×10 19 / CM 3 .

[0086] Table 1 shows the parameters used for each layer of the quantum dot light source provided by the embodiment of the present invention.

[0087] Table 1

[0088]

[0089] Among them, GaAs is gallium arsenide. AlAs is aluminum arsenide. Al 0.2 GaAs is aluminum gallium arsenide, and 0.2 represents that the proportion of aluminum is 0.2. By analogy, the proportion of aluminum in other aluminum gallium arsenides in Table 1 can be obtained.

[0090] As can be seen from Table 1, a substrate, 5.5 pairs of Bragg reflectors, a second doped layer, a second intrinsic layer, an energy level matching layer, a barrier layer, a quantum dot layer, a first intrinsic layer, a first doped layer, a third intrinsic layer, and a fourth intrinsic layer can be grown in sequence to obtain a quantum dot light source. The 5.5 pairs of Bragg reflectors can serve as a reflective layer to improve the photon collection efficiency. That is, photons emitted towards the substrate are reflected by the 5.5 pairs of Bragg reflectors towards the objective lens, achieving an improvement in the photon collection efficiency. The third intrinsic layer and the fourth intrinsic layer are used to keep the total thickness of the quantum dot light source unchanged when the doped layer is moved towards the quantum dot layer. The thickness of the substrate can also be 650000 nm.

[0091] The second doped layer may include a gallium arsenide doped sub-layer and a first gallium aluminum arsenide doped sub-layer. Both the gallium arsenide doped sub-layer and the first gallium aluminum arsenide doped sub-layer are N-type doped, and the doping concentrations are both 2×10 18 / CM 3 . The material of the gallium arsenide doped sub-layer is gallium arsenide, and the thickness is 5 nm. The material of the first gallium aluminum arsenide doped sub-layer is gallium aluminum arsenide, and the thickness is 30 nm.

[0092] The first doped layer may include a second gallium aluminum arsenide doped sub-layer and a third gallium aluminum arsenide doped sub-layer. Both the second gallium aluminum arsenide doped sub-layer and the third gallium aluminum arsenide doped sub-layer are P-type doped, and the doping concentrations are 1×10 19 / CM 3 and 2×10 18 / CM 3 .

[0093] The quantum dot layer includes a first gallium aluminum arsenide sub-layer, a second gallium aluminum arsenide sub-layer, and quantum dots. The materials of the first gallium aluminum arsenide sub-layer and the second gallium aluminum arsenide sub-layer are both gallium aluminum arsenide, and the thicknesses are 9 nm and 15 nm respectively. By analogy, the materials and thicknesses of other layers can be obtained.

[0094] Figure 4 Shows an energy schematic diagram of electrons and holes in each layer included in the quantum dot light source according to an embodiment of the present invention.

[0095] Figure 4 In (a) shows the energies of electrons and holes in each layer included in the quantum dot light source provided by the embodiment of the present invention under a non-operating voltage. Figure 4 In (b) shows the energies of electrons and holes in each layer included in the quantum dot light source provided by the embodiment of the present invention under an operating voltage.

[0096] As Figure 4As shown in (a) of [reference], when the quantum dot light source is at a non-operating voltage, the energy of electrons in the conduction bands of each layer changes according to the trend shown by energy line 101. When the quantum dot light source is at a non-operating voltage, the energy of holes in the valence bands of each layer changes according to the trend shown by energy line 102. 103 represents the electrons in the conduction band. 104 represents the holes in the valence band. 141 represents the hole energy in the energy level matching layer 140. 121 represents the energy of electrons in the quantum dot layer 120.

[0097] As can be seen from Figure 4 in (a) of [reference], when the quantum dot light source 100 is at a non-operating voltage, the energy 121 of electrons in the quantum dot layer 120 is less than the electron energy in the barrier layer 130, and the energy of holes in the quantum dot layer 120 is greater than the hole energy in the barrier layer 130. Neither the electrons nor the holes in the quantum dot layer 120 can pass through or tunnel through the barrier layer 130. The energy 141 of holes in the energy level matching layer 140 is greater than the hole energy in the barrier layer 130, and the energy of electrons in the energy level matching layer 140 is less than the electron energy in the barrier layer 130. Neither the electrons nor the holes in the energy level matching layer 140 can pass through or tunnel through the barrier layer 130.

[0098] As Figure 4 shown in (b) of [reference], 122 represents the energy of holes in the quantum dot layer 120. 142 represents the electron energy in the energy level matching layer 140. When the quantum dot light source 100 is at an operating voltage, under electrical excitation, the energy level matching layer 140 adjusts the energy of electrons from the second doping layer 150 to a predetermined energy, that is, adjusts the electron energy 142 in the energy level matching layer 140 to a predetermined energy, so that the electrons reaching the predetermined energy can pass through the barrier layer 130 and reach the quantum dot layer 120. At the same time, after the holes provided by the first doping layer 110 under electrical excitation reach the quantum dot layer 120, the energy of the holes in the quantum dot layer 120 is greater than the hole energy in the barrier layer 130, and the holes in the quantum dot layer 120 cannot pass through or tunnel through the barrier layer 130. When the quantum dots included in the quantum dot layer 120 recombine the holes from the first doping layer 110 and the electrons from the second doping layer 150 that pass through the barrier layer 130 within the quantum dots, fluorescence 105 is emitted. Thus, the quantum dot light source 100 improves the single-photon purity and entanglement fidelity by combining the barrier layer 130 and the energy level matching layer 140 with an electrically injected quantum dot single-photon source.

[0099] Figure 5 shows the spectral diagram of a quantum dot light source in the related art. Figure 6 shows the spectral diagram of a quantum dot light source according to an embodiment of the present invention.

[0100] In Figure 5 and Figure 6Among them, the abscissa is the wavelength in nanometers, and the ordinate is the counting rate in counts per second. Among them, the counting rate represents the number of photons collected per unit time.

[0101] By applying a target voltage to the quantum dot light source, the quantum dot light source can emit fluorescence. Fluorescence of different wavelengths is collected and corresponding photons are counted to obtain Figure 5 and Figure 6 the spectral diagram shown.

[0102] From Figure 5 it can be seen that for a predetermined wavelength, near this wavelength, the quantum dot light source in the related art emits fluorescence corresponding to multiple wavelengths. When collecting the fluorescence corresponding to this predetermined wavelength, the spectral components are complex and the single-photon purity is low.

[0103] From Figure 6 it can be seen that for a predetermined wavelength, the quantum dot light source provided in this application basically only emits fluorescence corresponding to this predetermined wavelength. When collecting the fluorescence corresponding to this predetermined wavelength, the spectral components are single and the single-photon purity is high.

[0104] Figure 7 shows a schematic diagram of the second-order correlation function value of the quantum dot light source in the related art. Figure 8 shows a schematic diagram of the second-order correlation function value of the quantum dot light source according to an embodiment of the present invention.

[0105] In Figure 7 and Figure 8 the abscissa is time in nanoseconds, and the ordinate is the photon count in counts. Among them, time 0 represents any acquisition moment. The photon count is the second-order correlation function value, which represents the number of photons of the fluorescence emitted by the quantum dot light source incident on the acquisition device at each acquisition moment. The black line is the measured result, and the red line is the fitting result after fitting the measured data.

[0106] Comparing Figure 7 and Figure 8 for the photon counts at time 0, it can be seen that the photon count of the quantum dot light source in the related art is close to 50, indicating that the fluorescence emitted by the quantum dots in the quantum dot light source in the related art is greatly affected by stray light and the single-photon purity is low. The photon count of the quantum dot light source in this application is close to 0, which represents this application, indicating that the fluorescence emitted by the quantum dots in the quantum dot light source in this application is less affected by stray light and the single-photon purity is high.

[0107] It should be noted that the structure of the quantum dot light source provided in the embodiment of the present invention is an electron tunneling structure, which is only an example of the structure of the quantum dot light source. The structure of the quantum dot light source can also be a hole tunneling structure, or an electron-hole simultaneous tunneling structure.

[0108] For example, in the case where the quantum dot light source structure is a hole tunneling structure, the quantum dot light source may include a first doped layer, a first intrinsic layer, a hole energy level matching layer, a hole barrier layer, a quantum dot layer, a second intrinsic layer, a second doped layer, and a substrate, which are sequentially stacked.

[0109] In the case where the quantum dot light source structure is a hole tunneling structure, the first doped layer is used to provide holes under electrical excitation. The first intrinsic layer is used to adjust the time for the holes from the first doped layer to reach the hole energy level matching layer. The hole energy level matching layer is used to adjust the energy of the holes from the first doped layer to the predetermined hole energy under electrical excitation. The hole barrier layer is used to prevent the electrons from the quantum dot layer from passing through under electrical excitation, while allowing the holes with an energy equal to the predetermined hole energy from the hole energy level matching layer to pass through. The quantum dot layer includes a plurality of quantum dots, and the quantum dots are used to spontaneously emit fluorescence and emit fluorescence when the electrons from the second doped layer and the holes from the first doped layer that pass through the hole barrier layer recombine within the quantum dots. The second intrinsic layer is used to adjust the time for the electrons from the second doped layer to reach the quantum dot layer. The second doped layer is used to provide electrons under electrical excitation.

[0110] For example, in the case where the structure of the quantum dot light source is an electron-hole simultaneous tunneling structure, the quantum dot light source may include a first doped layer, a first intrinsic layer, a hole energy level matching layer, a hole barrier layer, a quantum dot layer, a barrier layer, an energy level matching layer, a second intrinsic layer, a second doped layer, and a substrate, which are sequentially stacked.

[0111] In the case where the structure of the quantum dot light source is an electron-hole simultaneous tunneling structure, the first doped layer is used to provide holes under electrical excitation. The first intrinsic layer is used to adjust the time for the holes from the first doped layer to reach the hole energy level matching layer. The hole energy level matching layer is used to adjust the energy of the holes from the first doped layer to the predetermined hole energy under electrical excitation. The hole barrier layer is used to prevent the electrons from the quantum dot layer from passing through under electrical excitation, while allowing the holes with an energy equal to the predetermined hole energy from the hole energy level matching layer to pass through. The quantum dot layer includes a plurality of quantum dots, and the quantum dots are used to spontaneously emit fluorescence and emit fluorescence when the electrons from the second doped layer that pass through the barrier layer and the holes from the first doped layer that pass through the hole barrier layer recombine within the quantum dots. The barrier layer is used to prevent the holes from the quantum dot layer from passing through under electrical excitation, while allowing the electrons with an energy equal to the predetermined energy from the energy level matching layer to pass through. The energy level matching layer is used to adjust the energy of the electrons from the second doped layer to the predetermined energy; the second intrinsic layer is used to adjust the time for the electrons from the second doped layer to reach the energy level matching layer. The second doped layer is used to provide electrons under electrical excitation.

[0112] Figure 9The figure shows a flowchart of a method for preparing a quantum dot light source according to an embodiment of the present invention.

[0113] As Figure 9 shown, the method for preparing a quantum dot light source may include operation S910. Figure 9 The method for preparing a quantum dot light source shown can be used for the above-mentioned quantum dot light source.

[0114] In operation S910, a second doped layer, an energy level matching layer, a barrier layer, a quantum dot layer, and a first doped layer are sequentially grown on a substrate.

[0115] According to an embodiment of the present invention, for operation S910, sequentially growing a second doped layer, an energy level matching layer, a barrier layer, a quantum dot layer, and a first doped layer on a substrate may include: growing a second intrinsic layer on the second doped layer before growing the energy level matching layer; growing a first intrinsic layer on the quantum dot layer before growing the first doped layer.

[0116] Figure 9 The method for preparing a quantum dot light source shown may further include: etching a groove penetrating through the first doped layer, the first intrinsic layer, the quantum dot layer, the barrier layer, the energy level matching layer, and the second intrinsic layer. Depositing a first metal layer on the second doped layer; depositing a second metal layer on the first doped layer.

[0117] It should be noted that the part of the method for preparing a quantum dot light source in the embodiment of the present invention corresponds to the part of the quantum dot light source in the embodiment of the present invention. For the description of the part of the method for preparing a quantum dot light source, specifically refer to the part of the quantum dot light source, and details will not be repeated here.

[0118] After obtaining Figure 2 the quantum dot light source shown, it can be further processed according to Figure 10A and Figure 10B the preparation process shown to obtain Figure 3 the quantum dot light source shown.

[0119] Figure 10A The figure shows some stage diagrams in the process of a method for preparing a quantum dot light source according to an embodiment of the present invention. Figure 10B The figure shows some stage diagrams in the process of a method for preparing a quantum dot light source according to another embodiment of the present invention.

[0120] After obtaining Figure 2After the quantum dot light source shown, photoresist can be applied to protect the quantum dot light source. Subsequently, the quantum dot light source is diced into small pieces of 10 mm × 10 mm. The photoresist is removed using an N-Methyl-2-Pyrrolidone (NMP) solution, and then cleaned with Iso-Propyl Alcohol (IPA) and deionized water to obtain multiple quantum dot light sources 1000 of 10 mm 2 .

[0121] In Figure 10A , for the quantum dot light source 1000, in the th step, after spin-coating the photoresist, the designed pattern is exposed, and a first photoresist layer 1001 including the designed pattern is formed on the top layer of the quantum dot light source 1000. In the th step, an etching solution with a ratio of concentrated sulfuric acid: hydrogen peroxide: water = 1:1:50 is used to etch the designed pattern area, resulting in a groove that penetrates the first doped layer, the first intrinsic layer, the quantum dot layer, the barrier layer, the energy level matching layer, and the second intrinsic layer of the quantum dot light source 1000. Among them, this exposure - development - etching process will be carried out three times, and the functions are respectively: isolating the area that may be damaged during dicing from the active area, precisely calibrating the etching rate of the solution, and exposing the N-doped layer, that is, the second doped layer.

[0122] In the th step, the first photoresist layer 1001 is removed. In the th step, the quantum dot light source 1000 processed in the th step is spin-coated, exposed, and developed, and a second photoresist layer 1002 including the designed pattern is formed on the top layer. In the th step, metal for the N-doped region is deposited using electron beam evaporation. The material of the metal in the N-doped region is AuGe-Ni-Au, where AuGe-Ni-Au consists of three layers: the outermost layer is gold (Au), the middle layer is nickel (Ni), and the bottom layer is gold germanium alloy (AuGe).

[0123] Subsequently, in the Figure 10B th step of , the second photoresist layer 1002 is removed using the lift-off process, and only the metal 1081 in the N-doped region is retained.

[0124] In the th step, the quantum dot light source 1000 processed in the 6th step is cleaned and sent into a rapid thermal annealing furnace. It is annealed under the protection of a vacuum or nitrogen atmosphere, with the highest temperature between 410 °C and 430 °C and the time not exceeding 90 seconds. Subsequently, the vacuum or nitrogen atmosphere is maintained, and it is taken out after waiting for natural cooling to less than 100 °C, so that the metal 1081 in the N-doped region makes good contact and bonding with the second doped layer in the quantum dot light source 1000.

[0125] In the th step, after spin-coating the quantum dot light source 1000 processed in the th step, expose the designed pattern by exposure, and a third photoresist layer 1003 including the designed pattern is formed on the top layer. In the th step, deposit the metal in the P-doped region by electron beam evaporation. The material of the metal in the P-doped region is titanium and gold. Subsequently, in the th step, use the lift-off process to remove the third photoresist layer 1003, and only the metal 1082 in the P-doped region is retained.

[0126] Finally, use the method of atomic layer deposition (ALD) to deposit an alumina thin film with a thickness of about 15 nm on the entire surface of the quantum dot light source obtained after the

[0127] th step, which plays a role in protection and passivation. Subsequently, spin-coat and expose the area on the metal that needs to be connected to the printed circuit board (PCB). Use an etching solution to remove the passivation layer on it. th step, the quantum dot light source structure can be spin-coated with a protective photoresist, and then use steps similar to the

[0128] th step to etch and slice the spin-coated quantum dot light source structure to obtain several small pieces of about 2.5 mm × 2.5 mm. After cleaning, store them.

[0129] Those skilled in the art can understand that the features recited in the various embodiments and / or claims of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly recited in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features recited in the various embodiments and / or claims of the present invention can be combined and / or combined in various ways. All such combinations and / or combinations fall within the scope of the present invention.

[0130] The embodiments of the present invention have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Although the embodiments have been described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art can make various substitutions and modifications, and these substitutions and modifications should fall within the scope of the present invention.

Claims

1. A quantum dot light source, characterized in that, The quantum dot light source includes: a first doped layer, a quantum dot layer, a barrier layer, an energy level matching layer, and a second doped layer that are stacked in sequence; The first doped layer is configured to provide holes under electrical excitation; The quantum dot layer includes a plurality of quantum dots. The quantum dots are configured to emit fluorescence when holes from the first doped layer and electrons from the second doped layer that pass through the barrier layer recombine within the quantum dots; The barrier layer is configured to prevent holes from the quantum dot layer from passing through under electrical excitation, and at the same time allow electrons from the energy level matching layer with an energy equal to a predetermined energy to pass through; The energy level matching layer is configured to adjust the energy of electrons from the second doped layer to a predetermined energy under electrical excitation; The second doped layer is configured to provide electrons under electrical excitation.

2. The quantum dot light source according to claim 1, characterized in that The quantum dot light source further includes: A first intrinsic layer disposed between the first doped layer and the quantum dot layer. The first intrinsic layer is configured to adjust the time for holes from the first doped layer to reach the quantum dot layer; A second intrinsic layer disposed between the energy level matching layer and the second doped layer. The second intrinsic layer is configured to adjust the time for electrons from the second doped layer to reach the energy level matching layer.

3. The quantum dot light source according to claim 2, wherein The quantum dot light source further includes: A first metal layer disposed in the groove and in contact with the second doped layer. The first metal layer is configured to be electrically connected to the first electrode of the power supply. Wherein, the groove penetrates through the first doped layer, the first intrinsic layer, the quantum dot layer, the barrier layer, the energy level matching layer, and the second intrinsic layer; A second metal layer disposed on the first doped layer and in contact with the first doped layer. The second metal layer is configured to be electrically connected to the second electrode of the power supply.

4. The quantum dot light source according to claim 1, wherein The energy level matching layer includes a quantum well or a superlattice structure.

5. The quantum dot light source according to claim 2, wherein The material of the first doped layer includes at least one of the following: P-type doped gallium arsenide, aluminum arsenide, aluminum gallium arsenide; The material of the quantum dot layer includes one of the following: gallium arsenide, aluminum gallium arsenide, indium arsenide, indium gallium arsenide, indium phosphide; The material of the barrier layer includes one of the following: gallium arsenide, aluminum gallium arsenide; The material of the energy level matching layer includes one of the following: gallium arsenide, aluminum gallium arsenide, indium arsenide, indium gallium arsenide; The material of the second doped layer includes at least one of the following: N-type doped gallium arsenide, aluminum arsenide, aluminum gallium arsenide; The material of the first intrinsic layer includes one of the following: gallium arsenide, aluminum arsenide, aluminum gallium arsenide; The material of the second intrinsic layer includes one of the following: gallium arsenide, aluminum arsenide, aluminum gallium arsenide.

6. The quantum dot light source according to claim 5, characterized in that, The thickness of the first doped layer is between 20 nm and 400 nm; The thickness of the quantum dot layer is between 3 nm and 15 nm; The thickness of the barrier layer is between 0.5 nm and 5 nm; The thickness of the energy level matching layer is between 5 nm and 30 nm; The thickness of the second doped layer is between 20 nm and 400 nm; The thickness of the first intrinsic layer is between 40 nm and 400 nm; The thickness of the second intrinsic layer is between 40 nm and 400 nm.

7. The quantum dot light source according to claim 5, wherein The quantum dot light source further includes a substrate disposed below the second doped layer.

8. The quantum dot light source according to claim 7, wherein The material of the substrate includes gallium arsenide; The thickness of the substrate is between 300 μm and 1000 μm.

9. The quantum dot light source according to claim 5, wherein The volume of the quantum dot light source is between 1 mm 2 and 100 mm 2 .

10. A method for preparing the quantum dot light source according to any one of claims 1 to 9, characterized in that, The preparation method includes: sequentially growing a second doped layer, an energy level matching layer, a barrier layer, a quantum dot layer, and a first doped layer on the substrate.

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