Miniature light emitting diode and preparation method thereof
By controlling the thickness and material combination of the Micro LED reflective layer, the problem of poor reflection effect was solved, achieving a display effect with high brightness and high contrast, and reducing the difficulty and cost of transfer.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BOE HUACAN OPTOELECTRONICS (GUANGDONG) CO LTD
- Filing Date
- 2025-12-11
- Publication Date
- 2026-05-05
AI Technical Summary
Micro LEDs suffer from poor reflection due to improper reflective layer thickness, which affects display quality and increases the difficulty and cost of mass transfer.
By controlling the thickness of the reflective layer between 0.9 μm and 1.3 μm and using alternating layers of high and low refractive index materials, the reflectivity is ensured to be no less than 95%, which is suitable for the small size of Micro LEDs and reduces the difficulty of transfer.
It achieves high brightness and high contrast display effects, reduces the complexity and cost of mass transfer, and improves light energy utilization.
Smart Images
Figure CN121985647A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of optoelectronic manufacturing technology, and in particular to a micro light-emitting diode and its fabrication method. Background Technology
[0002] Micro LEDs are ultra-small light-emitting diodes with side lengths ranging from a few micrometers to tens of micrometers. Due to their small size, Micro LEDs can be arranged more densely to significantly improve resolution. They also have self-emissive properties and are superior to LCD displays in terms of high brightness, high contrast, high responsiveness, and energy saving.
[0003] In related technologies, in order to improve the light-emitting effect of light-emitting diodes, a distributed Bragg reflector (DBR) layer is usually set on the backlight side of the light-emitting diode.
[0004] Because of the small size of micro LEDs, an excessively thick DBR layer would increase the height of the micro LED, which would increase the difficulty of subsequent mass transfer; while an excessively thin DBR layer would affect its reflection effect. Summary of the Invention
[0005] This disclosure provides a miniature light-emitting diode and its fabrication method, which can improve the poor reflectivity of the reflective layer in miniature light-emitting diodes. The technical solution is as follows: On one hand, this disclosure provides a light-emitting diode, which includes an epitaxial layer and a reflective layer located on one side of the epitaxial layer. The thickness of the reflective layer is 0.9 μm to 1.3 μm, and the center wavelength reflectivity of the reflective layer is greater than or equal to 95%.
[0006] In one implementation of this disclosure, when the emission color of the epitaxial layer is blue, the thickness of the reflective layer is 0.9 μm to 1.1 μm; when the emission color of the epitaxial layer is green, the thickness of the reflective layer is 0.9 μm to 1.1 μm; and when the emission color of the epitaxial layer is red, the thickness of the reflective layer is 1 μm to 1.3 μm.
[0007] In another implementation of the present disclosure, the reflective layer includes 7 to 8 alternating layers of first material layer and 7 to 8 layers of second material layer, wherein the refractive index of the first material layer is greater than the refractive index of the second material layer.
[0008] In another implementation of the present disclosure, the epitaxial layer emits light in blue; the thickness of the first material layer is 47 nm to 50 nm, and the thickness of the second material layer is 77 nm to 80 nm.
[0009] In another implementation of the present disclosure, the reflective layer has a reflectivity of 95% or greater for light with wavelengths from 400 nm to 540 nm.
[0010] In another implementation of the present disclosure, the epitaxial layer emits green light; the thickness of the first material layer is 54 nm to 57 nm, and the thickness of the second material layer is 88 nm to 91 nm.
[0011] In another implementation of the present disclosure, the reflective layer has a reflectivity of 95% or greater for light with wavelengths from 480 nm to 600 nm.
[0012] In another implementation of the present disclosure, the epitaxial layer emits light in red; the thickness of the first material layer is 62nm to 68nm, and the thickness of the second material layer is 100nm to 110nm.
[0013] In another implementation of the present disclosure, the reflective layer has a reflectivity of 95% or greater for light with wavelengths from 540 nm to 710 nm.
[0014] On the other hand, this disclosure provides a method for fabricating a light-emitting diode, the method comprising: providing a substrate; forming an epitaxial layer on the substrate; forming a reflective layer on the surface of the epitaxial layer, the reflective layer having a thickness of 0.9 μm to 1.3 μm, and the reflectivity of the center wavelength of the reflective layer being greater than or equal to 95%.
[0015] The beneficial effects of the technical solutions provided in this disclosure include at least the following: The light-emitting diode provided in this disclosure controls the reflective layer thickness to be between 0.9 μm and 1.3 μm. Compared to related technologies where the DBR layer is often designed to be thicker to maintain high reflectivity, the extremely small size of Micro LEDs means that an excessively thick DBR layer would significantly increase the overall device height. This would lead to higher precision requirements for adsorption, alignment, and bonding during subsequent mass transfer, making it difficult to guarantee yield. By controlling the reflective layer thickness to around 1 μm, it can be adapted to the small size of Micro LEDs, avoiding the increased complexity of the transfer process due to height increase, and effectively reducing the difficulty of mass transfer.
[0016] Furthermore, the core function of the reflective layer is to reflect unused photons back to the light-emitting surface, thereby improving light extraction efficiency. In this embodiment, the reflective layer with a thickness of approximately 1 μm ensures that the reflectivity of the reflective layer at the center wavelength (corresponding to the RGB three primary color emission wavelengths) is not less than 95%. Even with a relatively thin thickness, it can still effectively cover the RGB spectrum range required for full-color display. This ensures sufficient reflection of red, green, and blue light, avoiding light efficiency loss due to insufficient reflection, and also solves the defect of insufficient reflectivity of excessively thin DBR layers in related technologies, achieving a high-brightness and high-contrast display effect. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure; Figure 2 This is a diagram showing the relationship between wavelength and reflectivity in a reflective layer corresponding to a blue light epitaxial layer, provided in an embodiment of this disclosure. Figure 3 This is a diagram showing the relationship between wavelength and reflectivity in a reflective layer corresponding to a green epitaxial layer, provided in an embodiment of this disclosure. Figure 4 This is a diagram showing the relationship between wavelength and reflectivity in a reflective layer corresponding to a red light epitaxial layer, provided in an embodiment of this disclosure. Figure 5 This is a flowchart of a method for fabricating a light-emitting diode according to an embodiment of this disclosure.
[0019] The markings in the diagram are explained as follows: 10. Epitaxial layer; 20. Reflective layer; 21. First material layer; 22. Second material layer. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.
[0021] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” “third,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” “right,” “top,” and “bottom,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.
[0022] Figure 1 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure. For example... Figure 1 As shown, the light-emitting diode includes an epitaxial layer 10 and a reflective layer 20 located on one side of the epitaxial layer 10. The thickness of the reflective layer 20 is 0.9 μm to 1.3 μm, and the center wavelength reflectivity of the reflective layer 20 is greater than or equal to 95%.
[0023] The light-emitting diode provided in this disclosure controls the thickness of the reflective layer 20 to be between 0.9 μm and 1.3 μm. Compared to related technologies where the DBR layer is often designed to be a thicker structure to accommodate high reflectivity, the microLED itself is very small. An excessively thick DBR layer would significantly increase the overall height of the device, leading to higher precision requirements for adsorption, alignment, and bonding during subsequent mass transfer, making it difficult to guarantee yield. By controlling the thickness of the reflective layer 20 to around 1 μm, it can be adapted to the small size of the microLED, avoiding the complexity of the transfer process caused by increased height, and effectively reducing the difficulty of mass transfer.
[0024] Furthermore, the core function of the reflective layer 20 is to reflect unused photons back to the light-emitting surface, thereby improving light extraction efficiency. In this embodiment, the reflective layer 20, with a thickness of approximately 1 μm, ensures that the reflectivity of the reflective layer 20 at the center wavelength (corresponding to the RGB three primary color emission wavelengths) is not less than 95%. Even with a relatively thin thickness, it can still effectively cover the RGB spectrum range required for full-color display. This ensures sufficient reflection of red, green, and blue light, avoiding light efficiency loss due to insufficient reflection, and also solves the defect of insufficient reflectivity of excessively thin DBR layers in related technologies, achieving a high-brightness and high-contrast display effect.
[0025] Optionally, when the emission color of the epitaxial layer 10 is blue, the thickness of the reflective layer 20 is 0.9 μm to 1.1 μm.
[0026] The center wavelength of blue light is relatively short (450nm to 470nm), corresponding to a lower optical thickness required for effective reflection. By controlling the thickness of the reflective layer 20 to between 0.9μm and 1.1μm (close to twice the optical thickness range of the blue light wavelength), the reflection requirements of blue light can be precisely matched, while avoiding optical path redundancy caused by excessive thickness.
[0027] Furthermore, a thinner reflective layer 20 can effectively reduce the penetration loss of blue light inside the reflective layer 20. When light propagates in a medium, the smaller the thickness, the lower the probability of photons being absorbed or scattered. Especially for high-energy blue light, the reduction in penetration loss directly increases the proportion of photons reflected back to the light-emitting surface.
[0028] Furthermore, the reflective layer 20 of this thickness range is highly compatible with the tiny size of Micro LEDs, ensuring the feasibility of mass transfer (such as adsorption accuracy and alignment tolerance) and maintaining high reflection efficiency through a center wavelength reflectivity of not less than 95%, thus achieving efficient utilization and low-loss output of blue light.
[0029] Optionally, when the emission color of the epitaxial layer 10 is green, the thickness of the reflective layer 20 is 0.9 μm to 1.1 μm.
[0030] The central wavelength of green light is in the middle range (520nm to 540nm), and its reflection requirements are between those of blue and red light. Designing the thickness of the reflective layer 20 to be 0.9μm to 1.1μm not only allows for matching the peak wavelength of green light with a reasonable optical thickness (approximately twice the optical thickness covering the dominant wavelength range), but also reduces the transmission loss of green light within the reflective layer 20 through thinning. Although the energy of green light is lower than that of blue light but higher than that of red light, an excessively thick reflective layer 20 would cause more photons to be absorbed due to multiple refractions / scatterings, while a thin layer of 0.9μm to 1.1μm can minimize this loss.
[0031] Meanwhile, the reflective layer 20 of this thickness is compatible with the microstructure of Micro LED, which avoids the risk of increasing the difficulty of mass transfer due to the increase in height, and ensures efficient reflection of green light through a center wavelength reflectivity of not less than 95%.
[0032] Optionally, when the emission color of the epitaxial layer 10 is red, the thickness of the reflective layer 20 is 1 μm to 1.3 μm.
[0033] Red light has the longest central wavelength (620nm to 640nm), requiring a greater optical thickness for effective reflection matching. By allowing the thickness of the reflective layer 20 to be relaxed to 1μm to 1.3μm (approximately twice the optical thickness range of the red light wavelength), the long-wavelength characteristics of red light can be precisely matched, ensuring strong reflection of photons in the red light band and avoiding a decrease in long-wavelength reflectivity due to insufficient thickness. Although the thickness is slightly greater than that of blue / green light, it is still within the thin-layer range, significantly reduced compared to the several-micrometer thickness of the DBR layer in related technologies. This approach does not increase the overall height of the Micro LED, and by controlling the upper limit of thickness, it reduces the penetration loss of red light in the reflective layer 20. Red light has the lowest energy; if the reflective layer 20 is too thick, photons are more prone to attenuation due to multiple interface reflections or medium absorption. The 1μm to 1.3μm thickness balances reflection requirements with loss control.
[0034] Furthermore, the reflective layer's center wavelength reflectivity of not less than 95% ensures efficient red light recovery and enables synergistic optimization of red, green, and blue colors within the same process framework, supporting high-performance displays of full-color Micro LED.
[0035] Optionally, the reflective layer 20 includes 7 to 8 alternating layers of first material layer 21 and 7 to 8 layers of second material layer 22.
[0036] The refractive index of the first material layer 21 is greater than that of the second material layer 22.
[0037] For example, the first material layer 21 is a titanium oxide layer and a tantalum oxide layer.
[0038] For example, the second material layer 22 is a silicon oxide layer.
[0039] In the above implementation, a DBR layer can be formed by alternately stacking materials with different refractive indices. The DBR layer can precisely control the reflection peak for the RGB center wavelength. Furthermore, by adjusting the number of each material layer to 7 to 8 layers, the total thickness of the reflective layer 20 can be more easily controlled within 0.9 μm to 1.1 μm. This enhances reflection through multi-layer interference while avoiding the increased difficulty of mass transfer caused by excessive overall thickness. At the same time, the thinner reflective layer 20 also reduces the light penetration path within the reflective layer 20, reducing energy loss caused by light absorption or scattering, and further improving light energy utilization.
[0040] Secondly, titanium oxide and tantalum oxide are selected as high refractive index layers, and silicon oxide is selected as a low refractive index layer. Both are mature and stable materials in semiconductor processes, and have good compatibility with epitaxial layer 10. In addition, titanium oxide and tantalum oxide have high transmittance and chemical stability in the visible light band, which avoids the problems of easy oxidation and poor thermal stability of metal reflective layer 20, and ensures long-term reliability.
[0041] Table 1 below shows the material layer thickness of the reflective layer adapted to epitaxial layers with different luminous colors.
[0042] Table 1
[0043] Optionally, as shown in Table 1, when the emission color of the epitaxial layer 10 is blue, the thickness of the first material layer 21 is 47 nm to 50 nm, and the thickness of the second material layer 22 is 77 nm to 80 nm.
[0044] For example, as shown in Table 1, when the epitaxial layer 10 emits blue light, there are 8 first material layers 21 and 7 second material layers 22. The thickness of each first material layer 21 is set to 47 nm to 50 nm, and the thickness of each second material layer 22 is 77 nm to 80 nm.
[0045] Because the center wavelength of blue light is relatively short, this thickness combination is an optical thickness calculated precisely based on the blue light wavelength. As shown in Table 1, the total thickness of the reflective layer 20 is 937 nm. This thickness of the reflective layer 20 enables it to form strong interference reflection for blue light, effectively improving the reflectivity of blue light at the center wavelength and ensuring a reflectivity ≥95%. Furthermore, the relatively thin thickness and the number of 7 to 8 layers are suitable for the small size of blue Micro LEDs, avoiding an excessive increase in the overall device height and reducing the difficulty of mass transfer.
[0046] Figure 2 This is a graph showing the relationship between wavelength and reflectivity in the reflective layer 20 corresponding to the blue light epitaxial layer 10, provided in an embodiment of this disclosure. For example... Figure 2 As shown, the reflective layer 20 has a reflectivity of 95% or greater for light with wavelengths from 400 nm to 540 nm.
[0047] As shown in the experimental data, the reflective layer exhibits a reflectivity of over 95%, and even exceeding 99%, for wavelengths from 400nm to 540nm. In LEDs, this wavelength range encompasses blue light and part of green light, representing a crucial light-emitting region. High reflectivity reflects a significant number of photons that might otherwise be transmitted back to the light-emitting surface, greatly improving light utilization and enhancing the LED's luminous intensity. For miniature LEDs, given their tiny size, maximizing light utilization is even more critical; this reflectivity compensates for potential light loss due to their small size.
[0048] Optionally, as shown in Table 1, the epitaxial layer 10 emits green light. The thickness of the first material layer 21 is 54 nm to 57 nm, and the thickness of the second material layer 22 is 88 nm to 91 nm.
[0049] For example, as shown in Table 1, when the epitaxial layer 10 emits green light, the first material layer 21 has 7 layers and the second material layer 22 has 7 layers. The number of first material layers 21 in the reflective layer 20 corresponding to green light is less than the number of first material layers 21 in the reflective layer 20 corresponding to blue or red light. This results in a thinner reflective layer 20, which reduces the loss of light transmission.
[0050] The thickness of each first material layer 21 is set to 54nm to 57nm, and the thickness of each second material layer 22 is 88nm to 91nm.
[0051] Because the wavelength of green light is moderate, this thickness combination is optically designed to precisely match the wavelength of green light, forming efficient interference reflection. This results in the reflective layer 20 having a reflectivity of ≥95% for the center wavelength of green light, enhancing the green light reflection efficiency. As shown in Table 1, the total thickness of the reflective layer 20 is 1013.8 nm. This thickness makes the reflective layer 20 relatively thin overall, reducing the penetration loss of green light and minimizing light energy loss.
[0052] Figure 3 This is a graph showing the relationship between wavelength and reflectivity in the reflective layer 20 corresponding to the green epitaxial layer 10 provided in this embodiment of the disclosure. Figure 3 As shown, the reflective layer 20 has a reflectivity of 95% or greater for light with wavelengths from 480 nm to 600 nm.
[0053] As shown in the experimental data, the reflective layer 20 exhibits a reflectivity exceeding 95%, even reaching over 99%, for light with wavelengths from 480nm to 600nm (covering green light and parts of the blue and yellow light bands). This effectively improves light energy utilization and display quality. This wavelength range includes green light and adjacent colors, to which the human eye is most sensitive. The high reflectivity reflects a large number of photons that might otherwise be lost during transmission back to the light-emitting surface, enhancing the luminous intensity of mid-band light such as green light and resulting in a more balanced overall spectrum. For micro-LEDs, this design reduces the penetration loss of mid-band light in the reflective layer 20, avoiding energy waste and improving luminous efficiency.
[0054] Optionally, as shown in Table 1, the epitaxial layer 10 emits red light, the first material layer 21 has a thickness of 62 nm to 68 nm, and the second material layer 22 has a thickness of 100 nm to 110 nm.
[0055] For example, as shown in Table 1, when the epitaxial layer 10 emits red light, the first material layer 21 has 8 layers and the second material layer 22 has 7 layers.
[0056] Because red light has a long wavelength, this thickness combination is an optically precise design based on the red light wavelength, enabling efficient interference reflection. This allows the reflective layer 20 to achieve a reflectivity of over 95%, or even over 99%, for the central wavelength of red light, thus enhancing red light reflection efficiency. The thicker second material layer 22 is adapted to the long-wave characteristics of red light, better reflecting long-wavelength photons. Simultaneously, this thickness is not excessively large, avoiding an overly significant increase in the overall thickness of the reflective layer 20. This prevents the massive transfer challenges posed to the tiny red Micro LED and also reduces the penetration loss of red light in the reflective layer 20, allowing more red light to be reflected back to the light-emitting surface, thereby increasing the red light luminescence intensity.
[0057] Figure 4 This is a graph showing the relationship between wavelength and reflectivity in the reflective layer 20 corresponding to the red epitaxial layer 10 provided in this embodiment of the disclosure. Figure 4 As shown, the reflective layer 20 has a reflectivity of 95% or greater for light with wavelengths from 540 nm to 710 nm.
[0058] The experimental data shows that the reflective layer 20 exhibits a reflectivity exceeding 95%, even reaching over 99%, for light wavelengths from 540nm to 710nm (covering green, yellow, orange, and red light), effectively recovering photons in this wavelength range. This range includes green light, which is sensitive to the human eye, and the predominantly red light. High reflectivity reduces light transmission loss, enhances the secondary excitation efficiency of these key colors, and effectively improves overall brightness and energy efficiency. For Micro LEDs, this design ensures sufficient reflection of long-wavelength light such as red and green, avoiding energy waste and improving color saturation and contrast. Simultaneously, the reflective layer 20 remains thin, ensuring compatibility with mass transfer processes.
[0059] Optionally, such as Figure 1 As shown, the light-emitting diode also includes a substrate, and the epitaxial layer 10 is located on the surface of the substrate.
[0060] For example, the substrate is a sapphire substrate. Sapphire substrates have high light transmittance, meaning they are transparent. Furthermore, sapphire material is relatively hard and chemically stable, giving the light-emitting diode (LED) good luminous efficacy and stability.
[0061] In this embodiment of the disclosure, the epitaxial layer 10 includes a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer sequentially stacked on a substrate.
[0062] In this embodiment of the disclosure, one of the first semiconductor layer and the second semiconductor layer is a p-type layer, and the other of the first semiconductor layer and the second semiconductor layer is an n-type layer.
[0063] For example, the first semiconductor layer is a p-type layer and the second semiconductor layer is an n-type layer.
[0064] Optionally, the first semiconductor layer is a magnesium-doped p-type GaN layer. The thickness of the p-type GaN layer can be from 0.5 μm to 3 μm.
[0065] Optionally, the multi-quantum-well layer includes alternating InGaN quantum well layers and GaN quantum barrier layers. Specifically, the multi-quantum-well layer may include 3 to 8 alternating stacked InGaN quantum well layers and GaN quantum barrier layers.
[0066] As an example, in an embodiment of this disclosure, the multi-quantum-well layer includes five alternating stacked InGaN quantum-well layers and GaN quantum-barrier layers.
[0067] Optionally, the thickness of the multi-quantum well layer can be from 150 nm to 200 nm.
[0068] In this embodiment of the disclosure, the second semiconductor layer is Al. x Ga （1-x） N material layers, where x is greater than or equal to 0 and less than or equal to 1.
[0069] For example, when x is 0, the second semiconductor layer is a GaN layer. For instance, the first semiconductor layer is a silicon-doped n-type GaN layer. The thickness of the n-type GaN layer can be from 0.5 μm to 3 μm.
[0070] Figure 5 This is a flowchart illustrating a method for fabricating a light-emitting diode according to an embodiment of this disclosure. Figure 5 As shown, the preparation method includes: S11: Provide a substrate.
[0071] S12: An epitaxial layer is formed on the substrate.
[0072] The epitaxial layer may include a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer sequentially stacked on the substrate.
[0073] S13: A reflective layer is formed on the surface of the epitaxial layer.
[0074] The thickness of the reflective layer is 0.9 μm to 1.3 μm, and the reflectivity of the center wavelength of the reflective layer is greater than or equal to 95%.
[0075] The light-emitting diodes fabricated using the method disclosed in this embodiment have a reflective layer thickness controlled between 0.9 μm and 1.3 μm. Compared to related technologies where the DBR layer is often designed to be thicker to maintain high reflectivity, the extremely small size of Micro LEDs means that an excessively thick DBR layer would significantly increase the overall device height, leading to higher precision requirements for adsorption, alignment, and bonding during subsequent mass transfer, making it difficult to guarantee yield. By controlling the reflective layer thickness to around 1 μm, it can be adapted to the small size of Micro LEDs, avoiding the increased complexity of the transfer process due to height increase, and effectively reducing the difficulty of mass transfer.
[0076] Furthermore, the core function of the reflective layer is to reflect unused photons back to the light-emitting surface, thereby improving light extraction efficiency. In this embodiment, the reflective layer with a thickness of approximately 1 μm ensures that the reflectivity of the reflective layer at the center wavelength (corresponding to the RGB three primary color emission wavelengths) is not less than 95%. Even with a relatively thin thickness, it can still effectively cover the RGB spectrum range required for full-color display. This ensures sufficient reflection of red, green, and blue light, avoiding light efficiency loss due to insufficient reflection, and also solves the defect of insufficient reflectivity of excessively thin DBR layers in related technologies, achieving a high-brightness and high-contrast display effect.
[0077] The process of preparing the epitaxial layer in steps S11 to S12 may include the following steps: First, a substrate is provided.
[0078] The substrate can be a sapphire substrate, a silicon substrate, or a silicon carbide substrate. The substrate can be a flat substrate or a patterned substrate.
[0079] As an example, in this embodiment of the disclosure, the substrate is a sapphire substrate. Sapphire substrates are a commonly used substrate, with mature technology and low cost. Specifically, it can be a patterned sapphire substrate or a flat sapphire substrate.
[0080] The sapphire substrate can be pretreated by placing it in an MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber and baking it for 12 to 18 minutes. As an example, in this embodiment of the present disclosure, the sapphire substrate is baked for 15 minutes.
[0081] Specifically, the baking temperature can be from 1000℃ to 1200℃, and the pressure inside the MOCVD reaction chamber during baking can be from 100mbar to 200mbar.
[0082] Growing an epitaxial layer on a substrate can include: sequentially forming a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer on a sapphire substrate using MOCVD technology.
[0083] The first semiconductor layer is a p-type layer, and the second semiconductor layer is an n-type layer.
[0084] Optionally, the first semiconductor layer is a magnesium-doped p-type GaN layer. The thickness of the p-type GaN layer can be from 0.5 μm to 3 μm.
[0085] When growing p-type GaN layers, the growth pressure of p-type GaN layers can be from 200 Torr to 600 Torr, and the growth temperature of p-type GaN layers can be from 800℃ to 1000℃.
[0086] Optionally, the multi-quantum-well layer includes alternating InGaN quantum well layers and GaN quantum barrier layers. Specifically, the multi-quantum-well layer may include 3 to 8 alternating stacked InGaN quantum well layers and GaN quantum barrier layers.
[0087] When growing multiple quantum well layers, the MOCVD reaction chamber pressure is controlled at 200 torr. When growing InGaN quantum well layers, the reaction chamber temperature is 760℃ to 780℃. When growing GaN quantum barrier layers, the reaction chamber temperature is 860℃ to 890℃.
[0088] As an example, in an embodiment of this disclosure, the multi-quantum-well layer includes five alternating stacked InGaN quantum-well layers and GaN quantum-barrier layers.
[0089] Optionally, the thickness of the multi-quantum well layer can be from 150 nm to 200 nm.
[0090] Optionally, the second semiconductor layer is a silicon-doped n-type GaN layer. The thickness of the n-type GaN layer can be from 0.5 μm to 3 μm.
[0091] The growth temperature of the n-type GaN layer can be from 1000℃ to 1100℃, and the growth pressure of the n-type GaN layer can be from 100 torr to 300 torr.
[0092] The coating conditions for preparing the reflective layer in step S13 are shown in Table 2 below.
[0093] Table 2
[0094] In Table 2, BEAM represents the ion beam, ACC represents the accelerating voltage, and E / B represents the proportion of ions in the total ion beam.
[0095] As shown in Table 2, step S13 may include the following steps: First, the wafer with the epitaxial layer is cleaned.
[0096] Specifically, this can include: setting an ion source with a power of 800W, controlling the voltage of the ion beam to 750V, and the current of the ion beam to 750mA to excite oxygen ions, combined with an ACC acceleration voltage of 600V, and effectively removing contaminants by bombarding the substrate surface with high-energy oxygen ions (150% E / B ratio).
[0097] Gas1 is supplied with 50 sccm of oxygen to provide an oxidation environment, and 12 sccm of argon to help maintain plasma stability and ensure surface cleanliness.
[0098] Next, SiO2 and TiO2 were deposited alternately.
[0099] In this embodiment of the disclosure, the coating process is performed in a vacuum environment. Exemplarily, the vacuum coating within the coating reaction chamber can be configured to 10... -3 pa.
[0100] Furthermore, during the coating process, the coating reaction chamber is heated to a temperature of 120°C to 150°C.
[0101] The SiO2 layer is deposited at a rate of 8 Å / s, the BEAM voltage is increased to 1200V, the oxygen ion energy is enhanced, and the SiO2 densification is promoted. Gas1 is introduced with 50 sccm of oxygen to provide an oxidation environment, and 8 sccm of argon is introduced to balance the ratio of ions to neutral particles.
[0102] The TiO2 deposition rate is 4 Å / s. The BEAM voltage is increased to 1300V to further enhance the ion bombardment intensity. The ACC at 900V optimizes the film stress. Gas1 is introduced with 85 sccm of oxygen to suppress titanium ion defects and 8 sccm of argon to reduce excessive sputtering.
[0103] Before each layer of coating is applied, the power of the ion source is controlled at 1200W, the voltage of the ion beam is controlled at 1200V, the current of the ion beam is controlled at 1200mA, the film surface is bombarded with an ACC voltage of 900V, the bombardment time is controlled at 40s to 50s, and the gas Gas1 is 5sccm of oxygen to remove interface contaminants and make the film layer more compact.
[0104] At the same time, a stable argon plasma of 8 sccm is maintained to avoid uneven oxidation of the film.
[0105] The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.
Claims
1. A light-emitting diode, characterized in that, The light-emitting diode includes an epitaxial layer (10) and a reflective layer (20) located on one side of the epitaxial layer (10). The thickness of the reflective layer (20) is 0.9 μm to 1.3 μm, and the center wavelength reflectivity of the reflective layer (20) is greater than or equal to 95%.
2. The light-emitting diode according to claim 1, characterized in that, When the emission color of the epitaxial layer (10) is blue, the thickness of the reflective layer (20) is 0.9 μm to 1.1 μm; When the luminescent color of the epitaxial layer (10) is green, the thickness of the reflective layer (20) is 0.9 μm to 1.1 μm; When the emission color of the epitaxial layer (10) is red, the thickness of the reflective layer (20) is 1 μm to 1.3 μm.
3. The light-emitting diode according to claim 2, characterized in that, The reflective layer (20) comprises 7 to 8 alternating layers of first material layer (21) and 7 to 8 layers of second material layer (22), wherein the refractive index of the first material layer (21) is greater than the refractive index of the second material layer (22).
4. The light-emitting diode according to claim 3, characterized in that, The epitaxial layer (10) emits light in blue; The thickness of the first material layer (21) is 47 nm to 50 nm, and the thickness of the second material layer (22) is 77 nm to 80 nm.
5. The light-emitting diode according to claim 4, characterized in that, The reflective layer (20) has a reflectivity of 95% or greater for light with wavelengths from 400 nm to 540 nm.
6. The light-emitting diode according to claim 3, characterized in that, The epitaxial layer (10) emits green light; The thickness of the first material layer (21) is 54 nm to 57 nm, and the thickness of the second material layer (22) is 88 nm to 91 nm.
7. The light-emitting diode according to claim 6, characterized in that, The reflective layer (20) has a reflectivity of 95% or greater for light with wavelengths from 480 nm to 600 nm.
8. The light-emitting diode according to claim 3, characterized in that, The epitaxial layer (10) emits light in red; The thickness of the first material layer (21) is 62nm to 68nm, and the thickness of the second material layer (22) is 100nm to 110nm.
9. The light-emitting diode according to claim 8, characterized in that, The reflective layer (20) has a reflectivity of 95% or greater for light with wavelengths from 540 nm to 710 nm.
10. A method for fabricating a light-emitting diode, characterized in that, The preparation method includes: Provide a substrate; An epitaxial layer is formed on the substrate; A reflective layer is formed on the surface of the epitaxial layer, the thickness of the reflective layer is 0.9 μm to 1.3 μm, and the reflectivity of the center wavelength of the reflective layer is greater than or equal to 95%.