Light emitting diode and manufacturing method thereof

Abstract

The invention provides a light emitting diode and a manufacturing method thereof. The light emitting diode comprises a substrate, an epitaxial structure and a low refractive index layer, the epitaxial structure is located on the substrate, the low-refractive-index layer is located on the face, away from the epitaxial structure, of the substrate, the refractive index of the low-refractive-index layer is smaller than that of the substrate, and the refractive index of the low-refractive-index layer is larger than that of air; the light-emitting surface of the low-refractive-index layer is of an uneven structure.

Description

Technical Field

[0001] This disclosure relates to the field of light-emitting devices, and in particular to a light-emitting diode and a method for manufacturing the same. Background Technology

[0002] Light-emitting diodes (LEDs) have wide applications in displays, decoration, communications, and other fields. By employing different semiconductor materials and structures, LEDs can cover the full color range from ultraviolet to infrared.

[0003] In related technologies, a light-emitting diode includes a substrate and an epitaxial structure, with the epitaxial structure located on the substrate.

[0004] LEDs made using this structure have low brightness. Summary of the Invention

[0005] This disclosure provides a light-emitting diode (LED) and a method for manufacturing the same, which improves the brightness of the LED. The technical solution is as follows:

[0006] On one hand, a light-emitting diode (LED) is provided, the LED comprising: including:

[0007] Substrate, epitaxial structure, and low-refractive-index layer;

[0008] The epitaxial structure is located on the substrate, and the low refractive index layer is located on the side of the substrate away from the epitaxial structure. The refractive index of the low refractive index layer is less than the refractive index of the substrate and greater than the refractive index of air. The light-emitting surface of the low refractive index layer has an uneven structure.

[0009] Optionally, the thickness of the low-refractive-index layer is one-quarter of the wavelength of the light produced by the epitaxial structure.

[0010] Optionally, the low refractive index layer includes a plurality of protrusions located on one side of the substrate, the plurality of protrusions being arranged at intervals.

[0011] Optionally, the protrusion is a hemispherical protrusion or a pyramidal protrusion;

[0012] The diameter of the hemispherical protrusion or the length of the diagonal of the pyramidal protrusion is 1 to 5 micrometers;

[0013] The height of the protrusion is 1 to 3 micrometers;

[0014] The spacing between adjacent protrusions is 0.1 to 1 micrometer.

[0015] Optionally, the low refractive index layer is a silicon dioxide structure or a magnesium fluoride structure.

[0016] On the other hand, a method for manufacturing a light-emitting diode is provided, the method comprising:

[0017] Fabricating epitaxial structures on a substrate;

[0018] A low-refractive-index layer is formed on the side of the substrate away from the epitaxial structure. The refractive index of the low-refractive-index layer is less than that of the substrate, and the refractive index of the low-refractive-index layer is greater than that of air. The light-emitting surface of the low-refractive-index layer has an uneven structure.

[0019] Optionally, a temporary substrate is bonded to the side of the epitaxial structure away from the substrate;

[0020] Thinning the substrate;

[0021] A low-refractive-index thin film is formed on the side of the substrate away from the epitaxial structure;

[0022] The low-refractive-index thin film is patterned to obtain the low-refractive-index layer.

[0023] Optionally, the low-refractive-index thin film is patterned to obtain the low-refractive-index layer, including:

[0024] A photoresist film is deposited on the low refractive index film;

[0025] The photoresist film is exposed and developed to obtain a patterned photoresist mask;

[0026] The low-refractive-index thin film is dry-etched under the patterned photoresist mask to obtain the low-refractive-index layer;

[0027] Remove the patterned photoresist mask.

[0028] Optionally, the low-refractive-index thin film is deposited on the epitaxial structure using a PECVD process at a temperature below 300°C.

[0029] Optionally, the low refractive index layer is a silicon dioxide structure or a magnesium fluoride structure.

[0030] The beneficial effects of the technical solutions provided in this disclosure are:

[0031] In related technologies, light is emitted from the epitaxial structure, passes through the substrate and enters the air. However, the refractive index of the substrate is greater than that of air. When the angle of incidence is greater than the critical angle, total internal reflection will occur, resulting in a decrease in the brightness of the light-emitting diode.

[0032] In this embodiment, the low-refractive-index layer is located on the side of the substrate away from the epitaxial structure. The refractive index of the low-refractive-index layer is less than that of the substrate and greater than that of air. Therefore, the low-refractive-index layer can change the path of light, thereby changing the incident angle of light entering the air, allowing more light to enter the air, thus improving the brightness of the light-emitting diode. The light-emitting surface of the low-refractive-index layer has an uneven structure. When light is transmitted inside the uneven structure, each reflection on the inner wall of the uneven structure causes the light to deviate from the critical angle of total internal reflection, thereby breaking the condition of total internal reflection and making it easier for light to escape from the protrusion, thus improving the light extraction efficiency. Attached Figure Description

[0033] 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.

[0034] Figure 1 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure;

[0035] Figure 2 This is a flowchart of a method for manufacturing a light-emitting diode provided in an embodiment of the present disclosure;

[0036] Figure 3 This is a flowchart of another method for manufacturing a light-emitting diode provided in this disclosure embodiment;

[0037] Figure 4 This is a structural diagram of a light-emitting diode manufacturing process provided in an embodiment of this disclosure;

[0038] Figure 5 This is a structural diagram of a light-emitting diode manufacturing process provided in an embodiment of this disclosure;

[0039] Figure 6 This is a structural diagram of a light-emitting diode manufacturing process provided in an embodiment of this disclosure;

[0040] Figure 7 This is a structural diagram of a light-emitting diode manufacturing process provided in an embodiment of this disclosure;

[0041] Figure 8 This is a structural diagram of a light-emitting diode manufacturing process provided in an embodiment of this disclosure;

[0042] Figure 9 This is a structural diagram of a light-emitting diode manufacturing process provided in an embodiment of this disclosure;

[0043] Figure 10 This is an optical path diagram of a light-emitting diode provided by related technologies;

[0044] Figure 11 This is an optical path diagram of a light-emitting diode provided in an embodiment of this disclosure.

[0045] The attached figures are labeled as follows:

[0046] 10: Substrate; 20: Epitaxial structure; 30: Low refractive index layer; 40: Electrode structure;

[0047] 200: Epitaxial patterning unit; 201: Bonding layer; 202: Temporary substrate;

[0048] 301: Protrusion;

[0049] L1: Spacing between two extended graphic units; L2: Spacing between adjacent protrusions; R: Diameter of a hemispherical protrusion or length of the diagonal of a pyramidal protrusion; H: Height of the protrusion. Detailed Implementation

[0050] 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.

[0051] Figure 1 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure. See also... Figure 1 The light-emitting diode includes:

[0052] Substrate 10, epitaxial structure 20 and low refractive index layer 30.

[0053] The epitaxial structure 20 is located on the substrate 10, and the low-refractive-index layer 30 is located on the side of the substrate 10 away from the epitaxial structure 20. The refractive index of the low-refractive-index layer 30 is less than the refractive index of the substrate 10, and the refractive index of the low-refractive-index layer 30 is greater than the refractive index of air. The light-emitting surface of the low-refractive-index layer 30 has an uneven structure.

[0054] In related technologies, light is emitted from the epitaxial structure, passes through the substrate and enters the air. However, the refractive index of the substrate is greater than that of air. When the angle of incidence is greater than the critical angle, total internal reflection will occur, resulting in a decrease in the brightness of the light-emitting diode.

[0055] In this embodiment, the low-refractive-index layer is located on the side of the substrate away from the epitaxial structure. The refractive index of the low-refractive-index layer is less than that of the substrate and greater than that of air. Therefore, the low-refractive-index layer can change the path of light, thereby changing the incident angle of light entering the air, allowing more light to enter the air, thus improving the brightness of the light-emitting diode. The light-emitting surface of the low-refractive-index layer has an uneven structure. When light is transmitted inside the uneven structure, each reflection on the inner wall of the uneven structure causes the light to deviate from the critical angle of total internal reflection, thereby breaking the condition of total internal reflection and making it easier for light to escape from the protrusion, thus improving the light extraction efficiency.

[0056] In this embodiment of the disclosure, the thickness of the low-refractive-index layer is one-quarter of the wavelength of the light generated by the epitaxial structure.

[0057] In this implementation, the thickness of the low-refractive-index layer is one-quarter of the wavelength of the light generated by the epitaxial structure. Due to the principle of constructive interference, this thickness can enhance the light.

[0058] In this embodiment of the disclosure, the low refractive index layer 30 includes a plurality of protrusions 301 located on one side of the substrate 10, the plurality of protrusions 301 being arranged at intervals.

[0059] In this implementation, the low refractive index layer includes multiple protrusions located on one side of the substrate. The multiple protrusions are arranged at intervals. When light is transmitted inside the protrusions, each reflection on the inner wall of the protrusion will cause the light to deviate from the critical angle of total internal reflection, thereby destroying the condition of total internal reflection and making it easier for light to escape from the protrusions, thus improving the light extraction efficiency.

[0060] In other embodiments, the low-refractive-index layer 30 may also be a monolithic structure, with the side of the monolithic structure away from the substrate being uneven.

[0061] In this embodiment of the disclosure, the protrusion 301 is a hemispherical protrusion or a pyramidal protrusion;

[0062] The diameter of a hemispherical protrusion or the length of the diagonal R of a pyramidal protrusion is 1 to 5 micrometers;

[0063] The height H of protrusion 301 is 1 to 3 micrometers;

[0064] The spacing L2 between adjacent protrusions 301 is 0.1 to 1 micrometer.

[0065] In this implementation, the protrusions are hemispherical or pyramidal, which facilitates light escape and improves the brightness of the LED. The diameter of the hemispherical protrusion or the length of the diagonal of the pyramidal protrusion is 1–5 micrometers. The area of ​​the protrusion's base surface is not too large, as a large base surface area would reduce the number of protrusions, thus decreasing the protrusion's ability to refract light. The area of ​​the protrusion's base surface is not too small, as a narrow base surface area increases the precision requirements for etching, and defects are easily generated in the low-refractive-index layer during etching, leading to a decrease in the LED's yield. The height of the protrusion is 1–3 micrometers. The height of the protrusions should not be too high, as this would result in an excessively thin low-refractive-index layer, reducing the light refraction capability. Conversely, the protrusions should not be too low, as this would cause the angle of incidence to be greater than or equal to the critical angle for total internal reflection, leading to partial total internal reflection and reduced LED brightness. The spacing between adjacent protrusions should be 0.1–1 micrometer. Too wide a spacing would allow some light to enter the external environment through the gap, easily causing total internal reflection and reducing light extraction efficiency. Similarly, too narrow a spacing would easily damage the epitaxial structure during etching, reducing LED yield.

[0066] For example, protrusion 301 is a hemispherical protrusion;

[0067] The diameter R of the hemispherical protrusion is 3 micrometers;

[0068] The height H of protrusion 301 is 2 micrometers;

[0069] The spacing L2 between adjacent protrusions 301 is 0.5 micrometers.

[0070] In this embodiment, the low refractive index layer 30 is a silicon dioxide structure or a magnesium fluoride structure.

[0071] In this implementation, the low refractive index layer is a silicon dioxide structure or a magnesium fluoride structure. The refractive index of the silicon dioxide structure or the magnesium fluoride structure is located between the refractive index of the substrate and the refractive index of air, which can play a transition role between the substrate and the air. Light can pass through the low refractive index layer and then enter the air, reducing the critical angle and allowing more light to enter the air, thereby improving the brightness of the light-emitting diode.

[0072] In another implementation, the extension structure 20 may also include multiple extension graphic units 200, and the spacing between two adjacent extension graphic units 200 may be equal to the spacing between adjacent protrusions 301.

[0073] In this embodiment of the disclosure, the spacing L1 between two adjacent epitaxial pattern units 200 can be 3 to 5 μm.

[0074] For example, the spacing L1 between two adjacent epitaxial pattern units 200 is 4 μm.

[0075] In the embodiments of this disclosure, the substrate 10 can be any one of a sapphire patterned substrate, a Si substrate, a SiC substrate, etc., and this disclosure does not limit the material of the substrate.

[0076] For example, substrate 10 is a patterned sapphire substrate.

[0077] For example, sapphire has a refractive index of 1.76 to 1.78 for visible light wavelengths, while air has a refractive index of 1.

[0078] Assuming light travels from medium n1 (higher refractive index) to medium n2 (lower refractive index), the formula for calculating the critical angle θc is:

[0079] θc = arcsin(n2 / n1)

[0080] Sapphire is a uniaxial crystal with anisotropic refractive index (the refractive index of the ordinary ray is about 1.768, and the refractive index of the extraordinary ray is about 1.760). Here, we use the standard value of 1.76 for sapphire calculation, that is, n1 = 1.76, and n2 is the refractive index of air, which is taken as n2 = 1.

[0081] Substituting into the formula: θc=arcsin(1 / 1.76)=arcsin(0.5681818)

[0082] The calculated result is approximately 34.6°, meaning the critical angle θc for total internal reflection is 34.6°.

[0083] In other words, when the angle of incidence of light is greater than the critical angle of 34.6°, the light will not be refracted into the air, but will be completely reflected back into the sapphire. The light is trapped inside the sapphire and cannot pass through, resulting in a reduction in the effective emitted light.

[0084] By fabricating a low-refractive-index layer 30 on sapphire, the critical angle can be reduced. Let the refractive index of the low-refractive-index layer 30 be n. c (1 <n c <1.76), if n c When θ = 1.38, θcc = arcsin(1.38 / 1.76), and the calculated result is approximately 51.5°, which is 16.9° larger than the original critical angle of 34.6°. This expands the range of angles from which light can pass through into the air, thus increasing the effective emitted light and improving the brightness of the LED.

[0085] In this embodiment of the disclosure, the thickness of the substrate 10 is 90–200 μm.

[0086] For example, the thickness of the substrate 10 is 150 μm.

[0087] In this embodiment of the disclosure, the epitaxial structure 20 includes: a first semiconductor layer, an active layer, and a second semiconductor layer stacked sequentially.

[0088] In this embodiment of the disclosure, the first semiconductor layer may be a P-type semiconductor layer, and the second semiconductor layer may be an N-type semiconductor layer.

[0089] In another example, the first semiconductor layer can be an N-type semiconductor layer and the second semiconductor layer can be a P-type semiconductor layer.

[0090] In this embodiment of the disclosure, the active layer can be a multi-quantum well layer, for example, a multi-quantum well layer can include multiple periodically alternating stacked quantum well layers and quantum barrier layers.

[0091] In this embodiment of the disclosure, the light-emitting diode further includes an electrode structure 40, which is connected to the epitaxial structure 20.

[0092] Figure 2 This is a flowchart illustrating a method for manufacturing a light-emitting diode (LED) according to an embodiment of this disclosure. See also... Figure 2 The method includes the following steps:

[0093] S11. Growing an epitaxial structure on a substrate.

[0094] S12. A low refractive index layer is formed on the side of the substrate away from the epitaxial structure. The refractive index of the low refractive index layer is less than the refractive index of the substrate, and the refractive index of the low refractive index layer is greater than the refractive index of air. The light-emitting surface of the low refractive index layer has an uneven structure.

[0095] In related technologies, light is emitted from the epitaxial structure, passes through the substrate and enters the air. However, the refractive index of the substrate is greater than that of air. When the angle of incidence is greater than the critical angle, total internal reflection will occur, resulting in a decrease in the brightness of the light-emitting diode.

[0096] In this embodiment, the low-refractive-index layer is located on the side of the substrate away from the epitaxial structure. The refractive index of the low-refractive-index layer is less than that of the substrate and greater than that of air. Therefore, the low-refractive-index layer can change the path of light, thereby changing the incident angle of light entering the air, allowing more light to enter the air, thus improving the brightness of the light-emitting diode. The light-emitting surface of the low-refractive-index layer has an uneven structure. When light is transmitted inside the uneven structure, each reflection on the inner wall of the uneven structure causes the light to deviate from the critical angle of total internal reflection, thereby breaking the condition of total internal reflection and making it easier for light to escape from the protrusion, thus improving the light extraction efficiency.

[0097] Figure 3 This is a flowchart of another method for manufacturing a light-emitting diode (LED) according to an embodiment of this disclosure. See also... Figure 3 The method includes the following steps:

[0098] S21. Sequentially fabricate a second semiconductor layer, an active layer, and a first semiconductor layer on a substrate to form an epitaxial structure.

[0099] In this embodiment of the disclosure, the substrate can be any one of sapphire substrate, Si substrate and SiC substrate, and the material of the substrate is not limited in this embodiment of the disclosure.

[0100] For example, the substrate is a sapphire substrate.

[0101] In one example, step S21 includes:

[0102] The first step is to fabricate the first semiconductor layer.

[0103] In this embodiment of the disclosure, the first semiconductor layer may be a P-type semiconductor layer.

[0104] In another example, the first semiconductor layer can be an N-type semiconductor layer.

[0105] The second step is to create the active layer.

[0106] In this embodiment of the disclosure, the active layer is a multi-quantum well layer, comprising multiple periodically alternating quantum well layers and quantum barrier layers.

[0107] For example, a metal-organic chemical vapor deposition (MOCVD) apparatus is used to alternately grow multiple quantum well layers and quantum barrier layers on the surface of the first semiconductor layer.

[0108] The third step is to fabricate the second semiconductor layer.

[0109] In this embodiment of the disclosure, the second semiconductor layer may be an N-type semiconductor layer.

[0110] In another example, the second semiconductor layer can be a P-type semiconductor layer.

[0111] The epitaxial layer structure described above is merely an example. In other embodiments, the epitaxial layer and its material can be adjusted and optimized according to different semiconductor material systems and device application requirements.

[0112] Figure 4 This is a structural diagram of a light-emitting diode (LED) fabrication process provided in an embodiment of this disclosure. See also... Figure 4 The epitaxial structure 20 is located on the substrate 10.

[0113] S22. Perform graphical processing on the extensional structure to obtain multiple extensional graphical units.

[0114] In one example, step S22 includes:

[0115] The first step is to deposit a photoresist film on the epitaxial structure.

[0116] The second step is to expose and develop the photoresist film to obtain a photoresist mask.

[0117] The third step involves etching the epitaxial structure under the cover of a photoresist mask to obtain multiple epitaxial pattern units.

[0118] In this embodiment of the disclosure, the epitaxial structure is etched by inductively coupled plasma etching (ICP).

[0119] The fourth step is to remove the photoresist mask.

[0120] Figure 5 This is a structural diagram of a light-emitting diode (LED) fabrication process provided in an embodiment of this disclosure. See also... Figure 5 The extensional structure 20 includes multiple extensional graphic units 200.

[0121] S23. Fabricate the electrode structure, which is located on the epitaxial structure.

[0122] Figure 6 This is a structural diagram of a light-emitting diode (LED) fabrication process provided in an embodiment of this disclosure. See also... Figure 6 The electrode structure 40 is located on multiple epitaxial patterning units 200.

[0123] S24. Bond a temporary substrate to the side of the epitaxial structure away from the substrate.

[0124] In one example, step S24 includes:

[0125] The first step is to fabricate a bonding layer on the epitaxial structure.

[0126] In another example, a bonding layer can be fabricated on a temporary substrate to bond the temporary substrate to the epitaxial structure.

[0127] The second step is to bond the epitaxial structure to the temporary substrate using a bonding layer.

[0128] In the embodiments disclosed herein, the temporary substrate can be any one of a sapphire substrate, a Si substrate, or the like.

[0129] In the embodiments disclosed herein, the thickness of the temporary substrate can be 200–1000 μm.

[0130] For example, the thickness of the temporary substrate is 800 μm.

[0131] In this embodiment of the disclosure, a temporary substrate is bonded to the epitaxial structure through a bonding layer under conditions of pressure of 1000-12000 kg and temperature of 150-300 °C.

[0132] For example, a temporary substrate is bonded to the epitaxial structure through a bonding layer under conditions of 5000 kg pressure and 200 °C temperature.

[0133] In this embodiment of the disclosure, the bonding layer is made of any one of photoresist, benzocyclobutene, and silicone.

[0134] For example, the bonding layer is made of silicone.

[0135] Figure 7 This is a structural diagram of a light-emitting diode (LED) fabrication process provided in an embodiment of this disclosure. See also... Figure 7 The bonding layer 201 covers the epitaxial structure 20, and the temporary substrate 202 is connected to the bonding layer 201.

[0136] S25, thinning of the substrate.

[0137] In the embodiments disclosed herein, the thickness of the thinned substrate is 90–200 μm.

[0138] For example, the thickness of the thinned substrate is 150 μm.

[0139] Figure 8 This is a structural diagram of a light-emitting diode (LED) fabrication process provided in an embodiment of this disclosure. See also... Figure 8 ,exist Figure 7 The substrate was thinned by 10 on the basis of the previous method.

[0140] S26. Fabricate a low-refractive-index thin film on the side of the substrate away from the epitaxial structure.

[0141] In this embodiment of the disclosure, a low refractive index thin film is deposited on the epitaxial structure using a plasma-enhanced chemical vapor deposition (PECVD) process at a temperature below 300°C.

[0142] In this implementation, a low-refractive-index thin film is deposited on the epitaxial structure using a PECVD process at a temperature below 300°C. The low-temperature deposition allows for the deposition of a refractive-index thin film without compromising the quality of the epitaxial structure.

[0143] In this embodiment of the disclosure, the refractive index of the refractive film is located between the refractive index of the substrate and the refractive index of air.

[0144] S27. Pattern the low-refractive-index thin film to obtain a low-refractive-index layer.

[0145] In one example, step S27 includes:

[0146] The first step is to deposit a photoresist film on a low-refractive-index film.

[0147] The second step is to expose and develop the photoresist film to obtain a patterned photoresist mask.

[0148] The third step involves dry etching the low-refractive-index thin film under the cover of a patterned photoresist mask to obtain a low-refractive-index layer.

[0149] The fourth step is to remove the patterned photoresist mask.

[0150] In this embodiment, the low refractive index layer is a silicon dioxide structure or a magnesium fluoride structure.

[0151] In this implementation, the low refractive index layer is a silicon dioxide structure or a magnesium fluoride structure. The refractive index of the silicon dioxide structure or the magnesium fluoride structure is located between the refractive index of the substrate and the refractive index of air, which can play a transition role between the substrate and the air. Light can pass through the low refractive index layer and then enter the air, reducing the critical angle and allowing more light to enter the air, thereby improving the brightness of the light-emitting diode.

[0152] In this embodiment of the disclosure, the thickness of the low-refractive-index layer is one-quarter of the wavelength of the light generated by the epitaxial structure.

[0153] In this implementation, the thickness of the low-refractive-index layer is one-quarter of the wavelength of the light generated by the epitaxial structure. Due to the principle of constructive interference, this thickness can enhance the light.

[0154] In this embodiment of the disclosure, the low refractive index layer includes a plurality of protrusions located on one side of the substrate, the plurality of protrusions being arranged at intervals.

[0155] In this implementation, the low refractive index layer includes multiple protrusions located on one side of the substrate. The multiple protrusions are arranged at intervals. When light is transmitted inside the protrusions, each reflection on the inner wall of the protrusion will cause the light to deviate from the critical angle of total internal reflection, thereby destroying the condition of total internal reflection and making it easier for light to escape from the protrusions, thus improving the light extraction efficiency.

[0156] In other embodiments, the low-refractive-index layer may also be a monolithic structure, with the side of the monolithic structure away from the substrate being uneven.

[0157] In this embodiment of the disclosure, the protrusion is a hemispherical protrusion or a pyramidal protrusion;

[0158] The diameter of a hemispherical protrusion or the length of the diagonal of a pyramidal protrusion is 1 to 5 micrometers;

[0159] The height of the protrusion is 1 to 3 micrometers;

[0160] The spacing between adjacent protrusions is 0.1 to 1 micrometer.

[0161] In this implementation, the protrusion is hemispherical or pyramidal, which facilitates light escape and improves the brightness of the LED. The diameter of the hemispherical protrusion or the length of the diagonal of the pyramidal protrusion is 1–5 micrometers. The area of ​​the protrusion's base is not too large, as a large base area would reduce the number of protrusions, thus decreasing their light refraction capability. The area of ​​the protrusion's base is not too small, as a narrow base area increases the precision requirements for etching, making the low-refractive-index layer prone to defects during etching, thereby reducing the LED yield. The height of the protrusion is 1–3 micrometers. The protrusions should not be too high, as this would result in an excessively thin low-refractive-index layer, reducing the light refraction capability. Conversely, the protrusions should not be too low, as this would cause the incident angle of light to be greater than or equal to the critical angle for total internal reflection, leading to partial total internal reflection and reduced LED brightness. The spacing between adjacent protrusions should be 0.1–1 micrometer. Too wide a spacing would allow some light to enter the external environment through the gap, easily causing total internal reflection and reducing light extraction efficiency. Similarly, too narrow a spacing would easily damage the epitaxial structure during etching, reducing LED yield.

[0162] For example, the protrusion is a hemispherical protrusion; the diameter of the hemispherical protrusion is 3 micrometers; the height of the protrusion is 2 micrometers; and the spacing between adjacent protrusions is 0.5 micrometers.

[0163] In this embodiment, the low refractive index layer is a silicon dioxide structure or a magnesium fluoride structure.

[0164] In this implementation, the low refractive index layer is a silicon dioxide structure or a magnesium fluoride structure. The refractive index of the silicon dioxide structure or the magnesium fluoride structure is located between the refractive index of the substrate and the refractive index of air, which can play a transition role between the substrate and the air. Light can pass through the low refractive index layer and then enter the air, reducing the critical angle and allowing more light to enter the air, thereby improving the brightness of the light-emitting diode.

[0165] Figure 9 This is a structural diagram of a light-emitting diode (LED) fabrication process provided in an embodiment of this disclosure. See also... Figure 9 The low-refractive-index layer 30 includes multiple protrusions 301.

[0166] S28. Peel off the temporary substrate and remove the bonding layer.

[0167] In this embodiment of the disclosure, a laser is used to remove the temporary substrate.

[0168] S29, Cracked LED.

[0169] In this embodiment of the disclosure, the multiple epitaxial pattern units of the light-emitting diode before it is scratched correspond to multiple sets of protrusion structures.

[0170] After being scratched, each epitaxial pattern unit of the light-emitting diode corresponds to a set of protrusion structures.

[0171] Figure 10 This is an optical path diagram of a light-emitting diode (LED) provided by related technologies. See also... Figure 10 Some of the light is totally reflected, resulting in low brightness of the LED.

[0172] Figure 11 This is an optical path diagram of a light-emitting diode provided in an embodiment of this disclosure. See also... Figure 11 ,exist Figure 10 Some of the light that is totally reflected also enters the air, increasing the brightness of the LED.

[0173] In this embodiment, creating hemispherical or pyramidal protrusions on the surface of the refractive film, similar to epitaxy, can alter the incident angle through microstructure. The inclined surface of the protrusion can reduce the actual incident angle of light at the interface, effectively forming a refractive index gradient layer. This reduces abrupt reflections at the interface, allowing light that would otherwise undergo total internal reflection to pass through. Furthermore, light can undergo multiple reflections and refractions within the protrusion, extending the path and providing more opportunities for light to escape. In addition, this low refractive index layer can convert light into diffuse reflection, reducing local glare and improving brightness.

[0174] 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: Substrate (10), epitaxial structure (20) and low refractive index layer (30); The epitaxial structure (20) is located on the substrate (10), and the low refractive index layer (30) is located on the side of the substrate (10) away from the epitaxial structure (20). The refractive index of the low refractive index layer (30) is less than the refractive index of the substrate (10), and the refractive index of the low refractive index layer (30) is greater than the refractive index of air. The light-emitting surface of the low refractive index layer (30) has an uneven structure.

2. The light-emitting diode according to claim 1, characterized in that, The thickness of the low refractive index layer (30) is one-quarter of the wavelength of the light produced by the epitaxial structure (20).

3. The light-emitting diode according to claim 1 or 2, characterized in that, The low refractive index layer (30) includes a plurality of protrusions (301) located on one side of the substrate (10), the plurality of protrusions (301) being arranged at intervals.

4. The light-emitting diode according to claim 3, characterized in that, The protrusion (301) is a hemispherical protrusion or a pyramidal protrusion; The diameter of the hemispherical protrusion or the length of the diagonal of the pyramidal protrusion is 1 to 5 micrometers; The height of the protrusion (301) is 1 to 3 micrometers; The spacing between adjacent protrusions (301) is 0.1 to 1 micrometer.

5. The light-emitting diode according to claim 1 or 2, characterized in that, The low refractive index layer (30) is a silicon dioxide structure or a magnesium fluoride structure.

6. A method for manufacturing a light-emitting diode, characterized in that, The method includes: Fabricating epitaxial structures on a substrate; A low-refractive-index layer is formed on the side of the substrate away from the epitaxial structure. The refractive index of the low-refractive-index layer is less than that of the substrate, and the refractive index of the low-refractive-index layer is greater than that of air. The light-emitting surface of the low-refractive-index layer has an uneven structure.

7. The method according to claim 6, characterized in that, The fabrication of the low-refractive-index layer includes: A temporary substrate is bonded to the side of the epitaxial structure away from the substrate; Thinning the substrate; A low-refractive-index thin film is formed on the side of the substrate away from the epitaxial structure; The low-refractive-index thin film is patterned to obtain the low-refractive-index layer.

8. The method according to claim 7, characterized in that, The low-refractive-index thin film is patterned to obtain the low-refractive-index layer, comprising: A photoresist film is deposited on the low refractive index film; The photoresist film is exposed and developed to obtain a patterned photoresist mask; The low-refractive-index thin film is dry-etched under the patterned photoresist mask to obtain the low-refractive-index layer; Remove the patterned photoresist mask.

9. The method according to claim 7, characterized in that, Fabrication of low refractive index thin films includes: The low-refractive-index thin film is deposited on the epitaxial structure using a PECVD process at a temperature below 300°C.

10. The method according to any one of claims 6 to 9, characterized in that, The low refractive index layer is a silicon dioxide structure or a magnesium fluoride structure.

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