Quantum dot based on self-assembly growth technology and preparation method thereof

Abstract

The invention discloses a quantum dot based on a self-assembly growth technology and a preparation method thereof. The preparation method comprises the following steps: selecting a GaAs substrate, heating to remove an oxide layer and degassing; growing a GaAs (gallium arsenide) buffer layer; raising the temperature, and growing an AlGaAs buffer layer; reducing the temperature of the substrate, and growing a GaAs buffer layer; reducing the temperature of the substrate, modifying the velocity-flow ratio of the V-group elements to the III-group elements in the growth cavity, and growing a layer of InGaAs quantum well; modifying the velocity-flow ratio of the V-group elements to the III-group elements in the growth cavity, growing an InAs material on the quantum well, and forming quantum dots through a self-assembly technology; and raising the temperature, growing an InAlAs stress buffer layer, growing an InGaAs cover layer, and growing a GaAs spacer layer. The stress buffer layer and the composite cover layer are used to reduce the stress on the quantum dots, so that the size of the quantum dots is increased, and finally the required quantum dots with special wavelengths are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor preparation, and in particular relates to a quantum dot based on self-assembly growth technology and a preparation method thereof. Background Art

[0002] InAs quantum dots have been widely studied for their ability to tune band gaps and optoelectronic properties. These quantum dots can adjust the band gap by changing their size, achieving emission and absorption of light of different wavelengths, covering a wide band from infrared to visible light, especially showing excellent performance in the infrared region, which makes them important in the development of devices such as tunable lasers and quantum dot lasers. The high quantum efficiency of InAs quantum dots means that they can efficiently convert light energy, which is particularly critical in the manufacture of high-performance infrared detectors and photovoltaic devices. InAs quantum dots can also be formed by self-assembly on the surface of semiconductor materials such as GaAs, which simplifies the manufacturing process and can effectively control the size and density of quantum dots, further improving their flexibility and reliability in practical applications. These characteristics, combined with their excellent performance in wide absorption range and high carrier mobility, make InAs quantum dots a hot research topic in the fields of optoelectronics and nanotechnology.

[0003] Although InAs quantum dots have shown great application prospects in many fields, they also face many challenges in practical research and application. Although self-assembly technology provides convenience for the growth and preparation of quantum dots, the uncertainty of this growth method and its sensitivity to growth conditions limit the application of InAs quantum dots in large-scale production. The main challenges brought by the self-assembly growth method include the problems of quantum dot uniformity and density. Since the optical properties of quantum dots are directly affected by their size, the growth conditions need to be precisely controlled to ensure the consistency of the geometric size of quantum dots. The non-uniformity of quantum dots will cause the luminescence spectrum of the device to become wider, thereby affecting the performance of the device. In addition, since the gain effect of quantum dots mainly depends on each quantum dot dispersed in space, the density of quantum dots directly affects its gain effect. In addition, when InAs quantum dots are grown on different substrates, they may face lattice matching problems, resulting in the generation of stress and defects such as dislocations. These defects will act as non-radiative recombination centers, reducing the photoelectric efficiency of quantum dots and the overall performance of the device. The stability problem in high temperature environment cannot be ignored. High temperature may cause the degradation of quantum dot structure, such as the diffusion of quantum dots or the enhancement of interactions between materials, thus affecting its photoelectric performance. In addition, the arsenic content in the material may raise environmental and health concerns, and appropriate safety measures need to be taken during use and waste disposal. These challenges need to be addressed through cross-innovation in materials science, nanotechnology, and chemical engineering to fully realize the application potential of InAs quantum dots in high-tech fields.

[0004] Based on the above problems, the present invention provides a quantum dot based on self-assembly growth technology and a preparation method thereof. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a quantum dot based on self-assembly growth technology and a preparation method thereof.

[0006] The technical solution adopted by the present invention to solve the technical problem is: A method for preparing quantum dots based on self-assembly growth technology, the method comprising the following steps: S100: Selecting a GaAs substrate, heating the GaAs substrate to remove an oxide layer and degassing; S200: Growth of GaAs buffer layer on GaAs substrate using molecular beam epitaxy technology; S300: raising the temperature of the GaAs substrate to grow an AlGaAs buffer layer on the GaAs buffer layer; S400: lowering the substrate temperature and growing another GaAs buffer layer on the AlGaAs buffer layer; S500: lowering the substrate temperature again, and modifying the rate flow ratio of the group V element and the group III element in the growth chamber, and growing a layer of InGaAs quantum well on the GaAs buffer layer; S600: Modify the rate flow ratio of group V elements and group III elements in the growth chamber again, grow InAs material on the InGaAs quantum well, and form InAs quantum dots through self-assembly technology; S700: Further increase the temperature on the InAs quantum dots to grow an InAlAs stress buffer layer, followed by growing an InGaAs cap layer, and then growing a GaAs spacer layer on the InGaAs cap layer to complete the preparation of the quantum dots.

[0007] Preferably, S100 specifically includes: The GaAs substrate is heated to 550°C~620°C in an arsenic-rich environment to remove the oxide layer, and is kept at 600°C~650°C for 10 minutes for a degassing step.

[0008] Preferably, S200 is specifically: The GaAs buffer layer is grown at a high temperature of 500°C to 600°C using molecular beam epitaxy technology, with a thickness of no less than 150nm.

[0009] Preferably, S300 specifically includes: The substrate temperature is raised to 620°C~650°C to grow the AlGaAs buffer layer. The thickness of the buffer layer ranges from 50nm to 1400nm, and the aluminum component is maintained at 30%~45%.

[0010] Preferably, S400 specifically includes: The substrate temperature is lowered to 500°C~600°C to grow a GaAs buffer layer with a thickness of 30nm~70nm.

[0011] Preferably, S500 is specifically: The substrate temperature is lowered to a suitable temperature for InGaAs quantum wells, ranging from 450°C to 600°C, and the flow rate ratio of group V and group III elements in the growth chamber is modified to a range of 15 to 45 to achieve suitable growth conditions for high-performance quantum dots.

[0012] Preferably, S600 specifically includes: The rate flow ratio of group V elements and group III elements in the growth chamber is modified within the range of 10 to 50, InAs material with a thickness of 1nm to 2nm is grown on the InGaAs quantum well, and InAs quantum dots are formed through self-assembly technology.

[0013] Preferably, S700 specifically includes: The temperature is further increased by 10~40℃ on the InAs quantum dots to grow InAs with a thickness of 1~5nm. x Al 1-x As stress buffer layer, in which the x component of InAlAs is 10-30%; then a 3-8nm thick InGaAs cap layer is grown; then a 4nm~10nm thick GaAs spacer layer is grown on the InGaAs cap layer; then the substrate is heated to 500℃~600℃ to grow a high-temperature GaAs spacer layer, and the thickness of the spacer layer is 30nm~100nm.

[0014] Quantum dots based on self-assembly growth technology include quantum dots formed by the above-mentioned quantum dot preparation method based on self-assembly growth technology.

[0015] The quantum dots based on self-assembly growth technology and the preparation method thereof use a stress buffer layer and a composite capping layer of InAlAs / InGaAs to reduce the stress on the InAs quantum dots, thereby increasing the size of the quantum dots and ultimately obtaining quantum dots of the required special wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of a method for preparing quantum dots based on self-assembly growth technology in one embodiment of the present invention; Figure 2 Schematic diagram of the growth structure of quantum dots in one embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0018] In one embodiment, Figure 1 and Figure 2 As shown, a method for preparing quantum dots based on self-assembly growth technology comprises the following steps: S100: Selecting a GaAs substrate, heating the GaAs substrate to remove an oxide layer and degassing; S200: Growth of GaAs buffer layer on GaAs substrate using molecular beam epitaxy technology; S300: raising the temperature of the GaAs substrate to grow an AlGaAs buffer layer on the GaAs buffer layer; S400: lowering the substrate temperature and growing another GaAs buffer layer on the AlGaAs buffer layer; S500: lowering the substrate temperature again, and modifying the rate flow ratio of the group V element and the group III element in the growth chamber, and growing a layer of InGaAs quantum well on the GaAs buffer layer; S600: further modifying the rate flow ratio of the group V elements and the group III elements in the growth chamber, growing InAs materials on the InGaAs quantum wells, and forming InAs quantum dots by self-assembly technology; S700: Further increase the temperature on the InAs quantum dots to grow an InAlAs stress buffer layer, followed by growing an InGaAs cap layer, and then growing a GaAs spacer layer on the InGaAs cap layer to complete the preparation of quantum dots of a specific wavelength.

[0019] In one embodiment, S100 specifically includes: The GaAs substrate is heated to 550°C~620°C in an arsenic-rich environment to remove the oxide layer, and is kept at 600°C~650°C for 10 minutes for a degassing step.

[0020] In one embodiment, S200 specifically includes: The GaAs buffer layer is grown at a high temperature of 500°C to 600°C using molecular beam epitaxy technology, with a thickness of no less than 150nm.

[0021] Specifically, the growth thickness of the GaAs buffer layer can be changed according to demand. Generally speaking, the thickness is not less than 150 nm to obtain a relatively flat GaAs epitaxial layer to facilitate subsequent growth.

[0022] Furthermore, this buffer layer can be doped with P-type or N-type depending on the substrate and structure. The thickness range is relatively arbitrary, and 200nm~1um is actually acceptable. The doping concentration is generally similar to that of the substrate.

[0023] In one embodiment, S300 specifically includes: The substrate temperature is raised to 620°C~650°C to grow the AlGaAs buffer layer. The thickness of the buffer layer ranges from 50nm to 1400nm, and the aluminum component is maintained at 30%~45%.

[0024] In one embodiment, S400 specifically includes: The substrate temperature is lowered to 500°C~600°C to grow a GaAs buffer layer with a thickness of 30nm~70nm.

[0025] In one embodiment, S500 specifically includes: The substrate temperature is lowered to a suitable temperature for InGaAs quantum wells, ranging from 450°C to 600°C, and the flow rate ratio of group V and group III elements in the growth chamber is modified to a range of 15 to 45 to achieve suitable growth conditions for high-performance quantum dots.

[0026] Specifically, the flow rate ratio of group V elements (arsenic) and group III elements (indium + gallium) in the growth chamber is modified to be in the range of 15 to 45.

[0027] In one embodiment, S600 specifically includes: The rate flow ratio of group V elements and group III elements in the growth chamber is modified within the range of 10 to 50, InAs material with a thickness of 1 to 2 nm is grown on the InGaAs quantum well, and InAs quantum dots are formed through self-assembly technology.

[0028] Specifically, the general characteristic value of the rate flow ratio of group V elements and group III elements in the growth chamber is 30. Through the self-assembly technology, InAs growth is transformed from two-dimensional growth to three-dimensional growth, thereby forming InAs quantum dots.

[0029] In one embodiment, S700 specifically includes: The temperature is further increased by 10~40℃ on the InAs quantum dots to grow InAs with a thickness of 1~5nm. x Al 1-xAs stress buffer layer, in which the x component of InAlAs is 10-30%; then a 3-8nm thick InGaAs cap layer is grown; then a 4nm~10nm thick GaAs spacer layer is grown on the InGaAs cap layer; then the substrate is heated to 500℃~600℃ to grow a high-temperature GaAs spacer layer, and the thickness of the spacer layer is 30nm~100nm.

[0030] Specifically, the composition, temperature and thickness of InAlAs need to be precisely controlled, otherwise the performance of the quantum dots will not meet expectations; in addition, the thickness of the spacer layer can be adjusted according to the required modulation speed.

[0031] By using a composite cap layer of InAlAs / InGaAs, and especially controlling the growth method and growth conditions (composition, thickness and growth temperature) of InAlAs, the emission wavelength of quantum dots can be further red-shifted.

[0032] Quantum dots based on self-assembly growth technology include specific wavelength quantum dots formed by the above-mentioned quantum dot preparation method based on self-assembly growth technology.

[0033] The present invention proposes a quantum dot based on self-assembly growth technology and a preparation method thereof, using a stress buffer layer to reduce the stress on the InAs quantum dot, thereby increasing the size of the quantum dot, and finally obtaining the quantum dot of the required special wavelength. The substrate selected in the present invention can be a GaAs substrate (or a Si substrate and other GaAs VS). Since the In atoms have a tendency to move on the surface rather than being immediately fixed on the lattice points during the growth of quantum dots, especially in a high temperature environment, it will not only lead to a slowdown in the nucleation rate and a change in the growth dynamics, but also further affect the photoelectric properties of the quantum dots. In order to reduce its influence, the present invention adopts the use of Al element, mainly because In and Al form stable bonds. Therefore, adding InAlAs before the InGaAs layer can effectively increase the size of the quantum dot, thereby causing the wavelength to redshift, so as to achieve the purpose of controlling the wavelength.

[0034] The above is a detailed introduction to a quantum dot based on self-assembly growth technology and a preparation method thereof provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention, and the description of the above embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing quantum dots based on self-assembly growth technology, characterized in that: The method comprises the following steps: S100: Selecting a GaAs substrate, heating the GaAs substrate to remove an oxide layer and degassing; S200: Growth of GaAs buffer layer on GaAs substrate using molecular beam epitaxy technology; S300: raising the temperature of the GaAs substrate to grow an AlGaAs buffer layer on the GaAs buffer layer; S400: lowering the substrate temperature and growing another GaAs buffer layer on the AlGaAs buffer layer; S500: lowering the substrate temperature again, and modifying the rate flow ratio of the group V element and the group III element in the growth chamber, and growing a layer of InGaAs quantum well on the GaAs buffer layer; S600: Modify the rate flow ratio of group V elements and group III elements in the growth chamber again, grow InAs material on the InGaAs quantum well, and form InAs quantum dots through self-assembly technology; S700: Further increase the temperature on the InAs quantum dots to grow an InAlAs stress buffer layer, followed by growing an InGaAs cap layer, and then growing a GaAs spacer layer on the InGaAs cap layer to complete the preparation of the quantum dots.

2. The method according to claim 1, characterized in that S100 is specifically: The GaAs substrate is heated to 550°C~620°C in an arsenic-rich environment to remove the oxide layer, and is kept at 600°C~650°C for 10 minutes for a degassing step.

3. The method according to claim 2, characterized in that S200 is specifically: The GaAs buffer layer is grown at a high temperature of 500°C to 600°C using molecular beam epitaxy technology, with a thickness of no less than 150nm.

4. The method according to claim 3, characterized in that: S300 is specifically: The substrate temperature is raised to 620°C~650°C to grow the AlGaAs buffer layer. The thickness of the buffer layer ranges from 50nm to 1400nm, and the aluminum component is maintained at 30%~45%.

5. The method according to claim 4, characterized in that S400 is specifically: The substrate temperature is lowered to 500°C~600°C to grow a GaAs buffer layer with a thickness of 30nm~70nm.

6. The method according to claim 5, characterized in that S500 is specifically: The substrate temperature is lowered to a suitable temperature for InGaAs quantum wells, ranging from 450°C to 600°C, and the flow rate ratio of group V and group III elements in the growth chamber is modified to a range of 15 to 45 to achieve suitable growth conditions for high-performance quantum dots.

7. The method according to claim 6, characterized in that S600 is specifically: The rate flow ratio of group V elements and group III elements in the growth chamber is modified within the range of 10 to 50, InAs material with a thickness of 1nm to 2nm is grown on the InGaAs quantum well, and InAs quantum dots are formed through self-assembly technology.

8. The method according to claim 7, characterized in that S700 is specifically: The temperature is further increased by 10~40℃ on the InAs quantum dots to grow InAs with a thickness of 1~5nm. x Al 1-x As stress buffer layer, in which the x component of InAlAs is 10-30%; then a 3-8nm thick InGaAs cap layer is grown; then a 4-10nm thick GaAs spacer layer is grown on the InGaAs cap layer; then the substrate is heated to 500℃~600℃ to grow a high-temperature GaAs spacer layer, and the thickness of the spacer layer is 30nm~100nm.

9. Quantum dots based on self-assembly growth technology, characterized in that: The invention comprises quantum dots formed by the preparation method according to any one of claims 1 to 8.

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