Methods of making ingan quantum dots, ingan quantum dots, epitaxial structures, and optoelectronic devices
By controlling the growth temperature and NH3 flow rate, an InGaN quantum well layer was grown on a GaN buffer layer. InGaN quantum dots were directly grown by utilizing the strain energy release caused by lattice mismatch. This solved the problem of preparing high-quality InGaN quantum dots in the prior art, simplified the process, and improved the luminescence efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF SEMICONDUCTORS - CHINESE ACAD OF SCI
- Filing Date
- 2022-03-15
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies make it difficult to prepare high-quality InGaN quantum dots at low cost and high efficiency, which leads to spatial separation of the wave functions of electrons and holes and reduces the radiative recombination efficiency of electrons and holes. In particular, it is difficult to obtain InGaN/GaN quantum wells with high In content in the green light band.
By controlling the growth temperature and NH3 flow rate, an InGaN quantum well layer is grown on a GaN buffer layer. InGaN quantum dots are directly grown by utilizing the strain energy release caused by lattice mismatch. The diameter and density of the quantum dots are controlled by adjusting the NH3 flow rate, thus obtaining high-quality InGaN quantum dots.
The fabrication process was simplified, the process complexity was reduced, the luminescence performance of InGaN quantum dots was optimized, and the luminescence efficiency and performance of InGaN-based optoelectronic devices were improved.
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Figure CN114628554B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of semiconductor technology, and in particular to a method for preparing InGaN quantum dots, InGaN quantum dots, epitaxial structures, and optoelectronic devices. Background Technology
[0002] GaN-based semiconductor optoelectronic devices are important types of optoelectronic devices with wide applications in the ultraviolet and visible light bands. Blue-green light-emitting diodes (LEDs) and laser diodes (LDs) have considerable application prospects in semiconductor lighting and laser displays. However, traditional blue-green LEDs and laser diodes typically use InGaN / GaN quantum wells as the active region. InGaN / GaN quantum wells grown on polar surfaces suffer from a severe quantum confinement Stark effect, causing spatial separation of the wavefunctions of electrons and holes, reducing the radiative recombination efficiency of electrons and holes, and hindering quantum well luminescence. Especially in the green light band, InGaN / GaN quantum wells with higher In content are required. Obtaining high-quality quantum wells is a necessary condition for fabricating quantum well laser diodes, but high-quality InGaN / GaN quantum wells with high In content are still difficult to fabricate.
[0003] Current methods for preparing InGaN quantum dots are typically complex, difficult to control and operate, require precise processes, and are costly. Therefore, it is necessary to propose a new preparation method that can conveniently, quickly, and cost-effectively prepare high-quality InGaN quantum dots, thereby obtaining high-quality InGaN quantum dot epitaxial structures and optoelectronic devices. Summary of the Invention
[0004] To address the aforementioned issues, this disclosure proposes a method for preparing InGaN quantum dots, the InGaN quantum dots themselves, their epitaxial structure, and optoelectronic devices.
[0005] The method for preparing InGaN quantum dots disclosed herein includes: growing a GaN buffer layer on a substrate at a first temperature; raising the first temperature to a second temperature and growing an undoped GaN layer on the GaN buffer layer at the second temperature; lowering the second temperature to a set temperature and growing an InGaN quantum well layer on the undoped GaN layer; and introducing NH3 at the set temperature and continuing the growth reaction until a first time interval to obtain InGaN quantum dots on the InGaN quantum well layer, wherein the NH3 flow rate is 1–10 slm.
[0006] Furthermore, the method for preparing InGaN quantum dots proposed in this disclosure sets the temperature to 600–700 °C.
[0007] Furthermore, in the method for preparing InGaN quantum dots proposed in this disclosure, the thickness of the InGaN quantum well layer is 1–5 nm.
[0008] Furthermore, in the method for preparing InGaN quantum dots proposed in this disclosure, the material of the InGaN quantum well layer is In... x Ga 1-x N, wherein the In component x is continuously adjustable from 25% to 50%.
[0009] Furthermore, the method for preparing InGaN quantum dots proposed in this disclosure includes: preparing an InGaN quantum well layer containing a first component content to a first thickness, so that the InGaN quantum well layer does not relax, wherein the first component content is the In component content of the InGaN quantum well layer, and the first thickness is the thickness of the InGaN quantum well layer.
[0010] Furthermore, in the method for preparing InGaN quantum dots proposed in this disclosure, the first thickness is 2-3 nm.
[0011] Furthermore, in the method for preparing InGaN quantum dots proposed in this disclosure, the substrate material is sapphire or gallium nitride.
[0012] Another aspect of this disclosure proposes an InGaN quantum dot, which is prepared by the aforementioned method for preparing InGaN quantum dots.
[0013] This disclosure also proposes an InGaN quantum dot epitaxial structure, comprising: a substrate; a GaN buffer layer, an undoped GaN layer, an InGaN quantum well layer, and an InGaN quantum dot sequentially epitaxially disposed on the substrate; wherein the InGaN quantum dot epitaxial structure is prepared by the aforementioned method for preparing InGaN quantum dots.
[0014] This disclosure also proposes a blue-green light optoelectronic device, which includes the aforementioned InGaN quantum dot epitaxial structure.
[0015] This disclosure has the following beneficial effects:
[0016] (1) InGaN quantum dots can be directly obtained on the substrate by means of the growth characteristics of the InGaN layer material growth process. This method has the advantages of simple steps and easy operation, which significantly reduces the process complexity of obtaining InGaN quantum dots.
[0017] (2) In the process of obtaining InGaN quantum dots, InGaN quantum dots with different diameters and densities were obtained by changing the NH3 flow rate, which further optimized the luminescence performance of InGaN quantum dots, including the emission wavelength and luminescence intensity, and promoted the application of InGaN quantum dots in InGaN-based optoelectronic devices. Attached Figure Description
[0018] Figure 1This is a schematic diagram of the method for preparing InGaN quantum dots disclosed in this paper;
[0019] Figure 2 This is a schematic diagram of the InGaN quantum dot epitaxial structure obtained in this disclosure;
[0020] Figure 3 This is an AFM three-dimensional structure diagram of InGaN quantum dots obtained under different NH3 flow rates according to embodiments of this disclosure;
[0021] Figure 4 These are cross-sectional comparison images of InGaN quantum dots obtained under different NH3 flow rates according to embodiments of this disclosure.
[0022] In the picture:
[0023] 101 - Substrate; 102 - GaN buffer layer; 103 - Undoped GaN layer; 104 - InGaN quantum well layer; 105 - InGaN quantum dot. Detailed Implementation
[0024] One aspect of this disclosure provides a method for preparing InGaN quantum dots, which utilizes the release of strain energy of the quantum well itself due to lattice mismatch during the growth of the quantum well to control the critical thickness of the quantum well growth, thereby directly growing InGaN quantum dots. At the same time, the diameter of the quantum dot growth can be adjusted, which is more conducive to obtaining high-quality InGaN quantum dots, thereby enabling the preparation of high-quality InGaN quantum dot optoelectronic devices.
[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.
[0026] Figure 1 This is a schematic diagram of the method for preparing InGaN quantum dots disclosed in this paper. Figure 2 This is a schematic diagram of the InGaN quantum dot epitaxial structure prepared in this disclosure. (Refer to...) Figure 1 , Figure 2 The method for preparing InGaN quantum dots disclosed herein will be described in detail.
[0027] The method for preparing InGaN quantum dots disclosed herein includes:
[0028] S101, a GaN buffer layer is grown on the substrate.
[0029] According to some embodiments of this disclosure, a GaN low-temperature buffer layer with poor crystal quality is first grown on a substrate at a low temperature.
[0030] In these embodiments, the substrate material used can be sapphire or gallium nitride. The growth temperature for growing the GaN low-temperature buffer layer on the substrate is 560°C, and the growth thickness is 20–30 nm.
[0031] S102, grow an undoped GaN layer on the GaN buffer layer.
[0032] According to some embodiments of this disclosure, the growth temperature for growing an undoped GaN layer on a GaN buffer layer is 1100°C, and the growth thickness is 2–3 μm. In these embodiments, the grown undoped GaN layer is a high-quality undoped GaN layer.
[0033] In S101 to S102 above, some embodiments of this application employ a two-step method to first grow a GaN buffer layer, and then grow an undoped GaN layer on the GaN buffer layer.
[0034] S103, lower the growth temperature to the set temperature, and grow an InGaN quantum well layer on the undoped GaN layer.
[0035] According to some embodiments of this disclosure, the set temperature used when growing an InGaN quantum well layer on an undoped GaN layer is 600–700°C.
[0036] According to some embodiments of this disclosure, the material of the InGaN quantum well layer is In x Ga 1-x N, wherein the In component x is continuously adjustable from 25% to 50%.
[0037] Traditional blue-green light-emitting diodes (LEDs) and laser diodes typically use InGaN / GaN quantum wells as the active region. InGaN / GaN quantum wells grown on polar surfaces suffer from a severe quantum confinement Stark effect, causing spatial separation of the wavefunctions of electrons and holes, reducing the radiative recombination efficiency of electrons and holes, and hindering quantum well luminescence. Especially in the green light band, InGaN / GaN quantum wells with higher In content are required. Therefore, this disclosure controls the In content to 25%–50%, which is continuously adjustable. The luminous efficiency of the optoelectronic device is controlled by adjusting the In content.
[0038] According to some embodiments of this disclosure, the thickness of the InGaN quantum well layer grown on the undoped GaN layer is 1–5 nm.
[0039] According to some embodiments of this disclosure, the set temperature for growing an InGaN quantum well layer on an undoped GaN layer is 650°C, and the growth thickness is 2–3 nm. This ensures that the In component in the InGaN layer material is fully incorporated while satisfying the critical conditions for generating strained quantum dots. This is because, in this disclosure, the InGaN quantum well layer is grown on an undoped GaN layer using a layer-island growth mode to reach a certain thickness, thereby obtaining naturally grown InGaN quantum dots.
[0040] S104, maintaining the set temperature, introduces NH3 to continue the growth reaction until the first time, and obtains InGaN quantum dots on the InGaN quantum well layer.
[0041] Maintaining the set temperature from the previous step, NH3 is introduced into the reaction vessel, and the growth time is extended to allow the growth reaction to continue, thereby generating InGaN strained quantum dots on the InGaN well layer.
[0042] In this process, extending the growth time is to achieve the transformation of the InGaN quantum well layer growth mode from layered growth to island-like growth. When the thickness of the island-grown InGaN quantum well layer is greater than the lattice mismatch threshold thickness, that is, when the strain energy reaches the InGaN quantum dot formation energy, InGaN quantum dots will spontaneously form on the grown InGaN quantum well layer. The lattice mismatch threshold thickness is approximately 3 nm.
[0043] The strain energy of the InGaN quantum well layer is related to the In content and thickness of the InGaN quantum well layer. To obtain InGaN quantum dots, it is necessary to ensure that the thickness and In content of the InGaN quantum well layer are within the critical values for relaxation, thereby preventing the obtained InGaN strained quantum dots from decreasing due to relaxation.
[0044] According to some embodiments of this disclosure, during the preparation of the InGaN quantum well layer, the InGaN quantum well layer containing a first component content is prepared to reach a first thickness so that the InGaN quantum well layer does not relax, wherein the first component content is the In component content of the InGaN quantum well layer, and the first thickness is the thickness of the InGaN quantum well layer.
[0045] According to some embodiments of this disclosure, the thickness of the InGaN quantum well layer that generates strained quantum dots without relaxation is 2–3 nm.
[0046] In this process, NH3 is introduced into the reaction vessel to promote the formation of InGaN quantum dots. According to some embodiments of this disclosure, the flow rate of the introduced NH3 is 1–10 slm.
[0047] According to some embodiments of this disclosure, the growth diameter and density of InGaN quantum dots can be controlled by adjusting the flow rate of NH3 during the growth of InGaN quantum dots.
[0048] According to some embodiments of this disclosure, increasing the NH3 flow rate increases the diameter of the InGaN quantum dots, and the density of the InGaN quantum dots first increases and then decreases, reaching its maximum when the NH3 flow rate is 5 slm.
[0049] According to some embodiments of this disclosure, when the NH3 flow rate is 2–4 slm, the density increase of InGaN quantum dots is not significant, numerically around 2.7 × 10⁻⁶. 10 cm -2 Up to 3×10 10 cm -2 When the NH3 flow rate exceeds 5 slm, the H2 decomposed from NH3 has a significant corrosive effect on InGaN quantum dots, and there are almost no InGaN quantum dots on the InGaN quantum well layer, but rather a flat interface.
[0050] According to some embodiments of this disclosure, the diameter and density of InGaN quantum dots can be changed by altering the flow rate of NH3, thereby changing the photoelectric properties of InGaN quantum dots and thus improving the performance of InGaN-based optoelectronic devices.
[0051] According to some embodiments of this disclosure, when the NH3 flow rate is 1–10 slm, the diameter of the InGaN quantum dots can be controlled within the range of 10–50 nm, and the density of the InGaN quantum dots can be controlled within the range of 1 × 10⁻⁶ nm, depending on the NH3 flow rate. 10 cm -2 Up to 1×10 11 cm -2 .
[0052] According to some embodiments of this disclosure, the height of the InGaN quantum dots obtained is 1–5 nm.
[0053] The following three specific examples illustrate how changing the flow rate of NH3 can visually demonstrate the variations in the diameter and density of the prepared InGaN quantum dots.
[0054] Example 1
[0055] Step 1: Grow a GaN low-temperature buffer layer with poor crystal quality on a sapphire substrate at a low temperature of 560℃, with a growth thickness of 20nm;
[0056] Step 2: A high-quality undoped GaN layer with a thickness of 2 μm is grown on the GaN low-temperature buffer layer at 1100 °C;
[0057] Step 3: Reduce the growth temperature to 650℃ and grow an InGaN quantum well layer on the undoped GaN layer. The InGaN quantum well layer material is InGaN containing 30% In content, and the growth thickness is 3nm.
[0058] Step 4: Maintain the growth temperature at 650℃, introduce NH3 into the reaction vessel at a flow rate of 1 slm, and allow the reaction to proceed for 1 hour to obtain InGaN quantum dots on the InGaN quantum well layer.
[0059] The AFM three-dimensional structure diagram of the InGaN quantum dots prepared in this embodiment is shown below. Figure 3 As shown in the first image.
[0060] Example 2
[0061] Step 1: Grow a GaN low-temperature buffer layer with poor crystal quality on a sapphire substrate at a low temperature of 560℃, with a growth thickness of 20nm;
[0062] Step 2: A high-quality undoped GaN layer with a thickness of 2 μm is grown on the GaN low-temperature buffer layer at 1100 °C;
[0063] Step 3: Reduce the growth temperature to 650℃ and grow an InGaN quantum well layer on the undoped GaN layer. The InGaN quantum well layer material is InGaN containing 30% In content, and the growth thickness is 3nm.
[0064] Step 4: Maintain the growth temperature at 650℃, introduce NH3 into the reaction vessel at a flow rate of 2 slm, and allow the reaction to proceed for 1 hour to obtain InGaN quantum dots on the InGaN quantum well layer.
[0065] The AFM three-dimensional structure diagram of the InGaN quantum dots prepared in this embodiment is shown below. Figure 3 As shown in the second image.
[0066] Example 3
[0067] Step 1: Grow a GaN low-temperature buffer layer with poor crystal quality on a sapphire substrate at a low temperature of 560℃, with a growth thickness of 20nm;
[0068] Step 2: A high-quality undoped GaN layer with a thickness of 2 μm is grown on the GaN low-temperature buffer layer at 1100 °C;
[0069] Step 3: Reduce the growth temperature to 650℃ and grow an InGaN quantum well layer on the undoped GaN layer. The InGaN quantum well layer material is InGaN containing 30% In content, and the growth thickness is 3nm.
[0070] Step 4: Maintain the growth temperature at 650℃, introduce NH3 into the reaction vessel at a flow rate of 4 slm, and allow the reaction to proceed for 1 hour to obtain InGaN quantum dots on the InGaN quantum well layer.
[0071] The AFM three-dimensional structure diagram of the InGaN quantum dots prepared in this embodiment is shown below. Figure 3 As shown in the third image.
[0072] Reference Figure 3 It can be seen that as the NH3 flux increases from 1 slm to 2 slm, the InGaN quantum dot density increases from approximately 2 × 10⁻⁶. 10 cm -2 Increased to approximately 2.7 × 10 10 cm -2 The InGaN quantum dot density varies considerably; however, as the NH3 flux increases from 2 slm to 4 slm, the InGaN quantum dot density decreases from approximately 2.7 × 10⁻⁶. 10 cm -2 Increased to approximately 3×10 10 cm -2 The density of InGaN quantum dots does not change significantly.
[0073] When the NH3 flow rate is increased to more than 5 slm, the H2 decomposed from NH3 has a significant corrosive effect on quantum dots. Therefore, there are almost no quantum dots, but rather a flat interface, which is not shown in the figure here.
[0074] Reference Figure 4 These are comparative cross-sectional images of InGaN quantum dots obtained under different NH3 flow rates in the aforementioned embodiments, from... Figure 4 It is evident that the diameter of InGaN quantum dots increases with increasing NH3 flux.
[0075] In the embodiments of this disclosure, the diameter of the InGaN quantum dot is changed by altering the NH3 flow rate, which changes the confinement effect of the InGaN quantum dot on charge carriers, thereby changing the photoelectric properties of the InGaN quantum dot and thus improving the performance of InGaN-based optoelectronic devices.
[0076] Based on the above embodiments, this disclosure also proposes an InGaN quantum dot, which is prepared by the method for preparing InGaN quantum dots described in the foregoing embodiments. Furthermore, the diameter of the InGaN quantum dot can be changed by altering the NH3 flow rate; that is, the diameter of the InGaN quantum dot increases with increasing NH3 flow rate.
[0077] According to the above embodiments, this disclosure also proposes an InGaN quantum dot epitaxial structure, comprising: a substrate; a GaN buffer layer, an undoped GaN layer, an InGaN quantum well layer, and an InGaN quantum dot sequentially epitaxially disposed on the substrate; wherein the InGaN quantum dot epitaxial structure is prepared by the method for preparing InGaN quantum dots in the foregoing embodiments.
[0078] Based on the above embodiments, this disclosure also proposes a blue-green light optoelectronic device, which includes the InGaN quantum dot epitaxial structure prepared in the foregoing embodiments.
[0079] This disclosure utilizes the release of strain energy of the quantum well itself due to lattice mismatch during the growth of the quantum well, and controls the critical thickness of the quantum well growth to directly grow InGaN quantum dots. Furthermore, the growth diameter of the InGaN quantum dots can be adjusted by changing the flow rate of NH3, which is beneficial for obtaining high-quality InGaN quantum dots and InGaN quantum dot epitaxial structures, thereby enabling the fabrication of high-quality optoelectronic devices.
[0080] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing InGaN quantum dots, characterized in that, include: At the first temperature, a GaN buffer layer is grown on the substrate; The first temperature is raised to a second temperature, and an undoped GaN layer is grown on the GaN buffer layer at the second temperature; The second temperature is lowered to a set temperature, and an InGaN quantum well layer is grown on the undoped GaN layer. At the set temperature, NH3 is introduced, and the growth reaction continues until the first time interval, thereby obtaining InGaN quantum dots on the InGaN quantum well layer. The NH3 flow rate is 1–10 slm. With variations in the NH3 flow rate, the diameter of the InGaN quantum dots can be controlled within the range of 10–50 nm, and the density of the InGaN quantum dots can be controlled within the range of 1 × 10⁻⁶. 10 cm -2 Up to 1×10 11 cm -2 ; The set temperature is 600~700℃; the thickness of the InGaN quantum well layer is 1~5nm; and the material of the InGaN quantum well layer is In. x Ga 1-x N, wherein the In component x is continuously adjustable from 25% to 50%.
2. The method for preparing InGaN quantum dots according to claim 1, characterized in that, include: An InGaN quantum well layer containing a first component content is prepared to reach a first thickness so that the InGaN quantum well layer does not relax, wherein the first component content is the In component content of the InGaN quantum well layer, and the first thickness is the thickness of the InGaN quantum well layer.
3. The method for preparing InGaN quantum dots according to claim 2, characterized in that, The first thickness is 2~3nm.
4. The method for preparing InGaN quantum dots according to claim 1, characterized in that, The substrate material is sapphire or gallium nitride.
5. An InGaN quantum dot, characterized in that, The InGaN quantum dots are prepared by the method described in any one of claims 1 to 4.
6. An InGaN quantum dot epitaxial structure, characterized in that, include: Substrate; A GaN buffer layer, an undoped GaN layer, an InGaN quantum well layer, and InGaN quantum dots are sequentially epitaxially deposited on the substrate; wherein... The InGaN quantum dot epitaxial structure is prepared by the method described in any one of claims 1 to 4.
7. A blue-green light optoelectronic device, characterized in that, The blue-green light optoelectronic device includes the InGaN quantum dot epitaxial structure as described in claim 6.