Light-emitting element and light-emitting device

Abstract

The invention provides a light-emitting element and a light-emitting device. The light-emitting element comprises at least one light-emitting diode. The light emitting diode includes a substrate, an epitaxial structure, a first electrode, a specular layer, a first reflective layer, and a second reflective layer. The direction perpendicular to the front face of the substrate is the axial direction. The epitaxial structure comprises a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially stacked from the front face of the substrate. The first electrode is over and conductively connected to the second semiconductor layer. The mirror reflection layer is arranged between the first semiconductor layer and the substrate. The first reflecting layer is at least arranged on the surface of the second semiconductor layer covered by the back surface of the first electrode, and at least reflects part of light emitted to the back surface of the first electrode. The second reflection layer is of a DBR structure, is arranged between the mirror reflection layer and the first semiconductor layer, and at least reflects part or all of the incident light forming a preset included angle with the axial direction. Through the cooperation of the light-emitting side and the reflection structure of the backlight side, the shielding loss of the light-emitting side electrode is reduced, and lateral light emitting is increased.

Description

Technical Field

[0001] This application relates to the field of semiconductor devices, and more specifically, to a light-emitting element and a light-emitting device. Background Technology

[0002] With the rapid development of Augmented Reality (AR) and Virtual Reality (VR) technologies, the AR / VR market continues to expand. Micro LEDs (micro-light-emitting diodes), as one of the core components of AR / VR displays, are seeing increasing demand in the AR / VR field due to their advantages such as high brightness, high contrast, and fast response speed. As AR / VR devices become smaller and lighter, end-user applications are placing increasingly stringent demands on the reduction of Micro LED chip size. Chip size needs to be gradually reduced from the traditional 5μm level to the 2μm level, and even beyond the 2μm lower limit, to meet the design requirements of high integration and small size for AR / VR display modules.

[0003] In ultra-small Micro LEDs, a reflective system (such as a mirror or reflective film) is placed below the chip, while the main light-emitting surface is above. The bottom reflective system reflects the downward-propagating light from inside the chip back to the light-emitting direction, thereby improving light extraction efficiency. However, when the chip size shrinks to 2μm or less, the shading problem of the light-emitting surface caused by the electrodes (such as N-side or P-side electrodes) on the axial light-emitting side becomes severe. Due to the extremely small overall chip size, the electrodes occupy a large proportion of the area, resulting in the light-emitting surface being blocked by electrodes by more than 50%. In some ultra-small chips, the light-emitting surface is almost completely covered by electrodes, severely reducing chip brightness.

[0004] Although existing Micro LED products generally attempt to reduce light energy loss and improve light extraction efficiency by setting high-reflectivity reflective structures (such as metal mirrors and distributed Bragg reflectors) at the bottom of the chip, the limitations of this design are particularly obvious in ultra-small scale scenarios where the chip size breaks through the 2μm lower limit: even if the reflectivity of the bottom reflective structure is close to 100%, the reflected light still needs to be emitted through the light-emitting surface above the chip. The large area of ​​the light-emitting surface blocked by the axial electrode causes a large amount of reflected light to be absorbed or blocked by the electrode when it propagates to the light-emitting surface, and cannot be effectively extracted. Ultimately, the brightness performance of ultra-small Micro LEDs cannot meet the actual needs of AR / VR applications. Summary of the Invention

[0005] The purpose of this application is to provide a light-emitting element and a light-emitting device, which reduces the shading loss of the light-emitting electrode by coordinating the reflective structures on the light-emitting side and the backlight side, and guides the light to the sidewall of the epitaxial structure, thereby increasing the effective lateral light extraction rate and improving the brightness.

[0006] In a first aspect, this application provides a light-emitting element comprising at least one light-emitting diode. The light-emitting diode includes a substrate, an epitaxial structure, a first electrode, a specular reflective layer, a first reflective layer, and a second reflective layer.

[0007] The substrate has a front side and a back side disposed opposite to each other, with the extension direction perpendicular to the front side being called the axial direction. An epitaxial structure is formed on one side of the front side of the substrate, and the epitaxial structure includes a first semiconductor layer, an active layer, and a second semiconductor layer stacked sequentially from the front side of the substrate; the epitaxial structure has inclined sidewalls. A first electrode is located above the second semiconductor layer and is electrically connected to the second semiconductor layer. A mirror-reflective layer is disposed between the first semiconductor layer and the substrate.

[0008] A first reflective layer is disposed at least on the surface of the second semiconductor layer covering the back of the first electrode, and reflects at least a portion of the light rays incident on the back of the first electrode. The second reflective layer is a distributed Bragg reflection structure, disposed between the specular reflective layer and the first semiconductor layer, and reflects at least part or all of the incident light rays that are at a predetermined angle to the axial direction.

[0009] Secondly, this application provides a light-emitting device, including a circuit board and at least one light-emitting element fixed to the surface of the circuit board, wherein the light-emitting element is the aforementioned light-emitting element.

[0010] Compared with existing technologies, the beneficial effects of this application include at least the following: The light-emitting element of this application, through the synergistic design of the reflective structures on the light-emitting side and the backlight side, constructs a more complete light energy recovery and guidance system. The first reflective layer focuses and solves the problem of electrode shading loss, and achieves direction resetting through light recombination radiation to reduce light absorption loss; the second reflective layer focuses and solves the problem of directional propagation of non-axial light, and guides light to converge towards the sidewall through reflection. The combined effect of the two not only reduces the light energy loss caused by the first electrode shading, but also taps into the potential of non-axial light emission from the sidewall, optimizing light utilization efficiency from two dimensions: reducing loss and improving effective light emission, ultimately achieving an effective improvement in the brightness of the light-emitting element, which is especially suitable for scenarios requiring ultra-small size, high brightness light-emitting devices. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a top view schematic diagram of a light-emitting element shown in an embodiment of this application.

[0013] Figure 2 for Figure 1 A schematic diagram of the first cross-section of the light-emitting element along AA.

[0014] Figure 3 for Figure 1 A schematic diagram of the second cross-section of the light-emitting element along AA.

[0015] Figure 4 for Figure 1 A schematic diagram of the third cross-section of the light-emitting element along AA.

[0016] Figure 5 for Figure 1 A schematic diagram of the fourth cross-section of the light-emitting element along AA.

[0017] Figure 6 This is a cross-sectional schematic diagram of a first type of light-emitting element with a microlens, as shown in an embodiment of this application.

[0018] Figure 7 This is a cross-sectional schematic diagram of a second type of light-emitting element with microlenses, as shown in an embodiment of this application.

[0019] Figure 8 for Figure 1 A schematic diagram of the fifth cross-section of the light-emitting element along AA.

[0020] Figure 9 This is a cross-sectional schematic diagram of a light-emitting device according to an embodiment of this application.

[0021] In the figure: 100, light-emitting element; 101, light-emitting diode; 1, substrate; 2, epitaxial structure; 21, first semiconductor layer; 22, active layer; 23, second semiconductor layer; 3, first electrode; 4, specular reflection layer; 5, first reflective layer; 6, second reflective layer; 7, transparent encapsulation layer; 8, second electrode; 9, top mirror layer; 10, microlens structure; 11, roughened structure; 200, light-emitting device; 201, circuit board. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] This application provides a light-emitting element, which includes at least one light-emitting diode. The light-emitting diode includes a substrate, an epitaxial structure, a first electrode, a specular reflective layer, a first reflective layer, and a second reflective layer.

[0025] The substrate has a front side and a back side disposed opposite to each other, with the extension direction perpendicular to the front side being called the axial direction. An epitaxial structure is formed on one side of the front side of the substrate, and the epitaxial structure includes a first semiconductor layer, an active layer, and a second semiconductor layer stacked sequentially from the front side of the substrate; the epitaxial structure has inclined sidewalls. A first electrode is located above the second semiconductor layer and is electrically connected to the second semiconductor layer. A mirror-reflective layer is disposed between the first semiconductor layer and the substrate.

[0026] The first reflective layer is a distributed Bragg reflection structure or a specular reflection structure, and is disposed at least on the surface of the second semiconductor layer covering the back of the first electrode, reflecting at least a portion of the light rays incident on the back of the first electrode. The second reflective layer is a distributed Bragg reflection structure, disposed between the specular reflection layer and the first semiconductor layer, and reflects at least a portion or all of the incident light rays that form a predetermined angle with the axial direction.

[0027] The light-emitting element of this application offers at least the following advantages:

[0028] First, the first reflective layer reduces the loss of axial light caused by the first electrode blocking it, thus improving the efficiency of light reuse.

[0029] For example, when the first reflective layer is a specular reflective structure, light rays incident on the back side of the first electrode are directly reflected back by the first reflective layer. Some of the light rays may exit directly from the sidewall of the epitaxial structure, while some light rays are reflected back into the active layer, where they recombine and emit photons. Since the propagation direction of the recombinated photons is random, at least some of the re-emitted photons no longer target the back side of the first electrode. This reduces the light absorption loss caused by the first electrode blocking the light, increases the probability of these photons exiting from the sidewall of the epitaxial structure, and lays the foundation for improved brightness.

[0030] For example, when the first reflective layer is a distributed Bragg reflector structure, it is disposed between the first electrode and the second semiconductor layer, and the first reflective layer is configured to have high reflectivity for axially incident light (e.g., reflectivity greater than or equal to 80%). When axially incident light emitted from the active layer strikes the back of the first electrode, relying on the high reflectivity of the first reflective layer for axially incident light, most of the axially incident light can be reflected back to the active layer, where it recombines and emits photons. Since the propagation direction of the recombinated photons is random, the number of photons striking the back of the first electrode along the axial direction can be reduced to a certain extent, thereby reducing the light absorption loss caused by the first electrode being blocked, increasing the probability of these photons escaping from the sidewall of the epitaxial structure, and laying the foundation for improved brightness.

[0031] Furthermore, the second reflective layer guides the directional propagation of non-axial light, enhancing the sidewall light extraction efficiency. The second reflective layer, in the form of a distributed Bragg reflector structure, is positioned between the specular reflective layer and the first semiconductor layer. When non-axial light emitted from the active layer strikes the second reflective layer, its high reflectivity towards non-axial incident light allows most of the light to be reflected towards the sidewalls of the epitaxial structure. This directional guidance significantly increases the probability of photons escaping from the sidewalls of the epitaxial structure, preventing non-axial light from being absorbed by the substrate or other structures due to disordered propagation, further increasing the total amount of light emitted from the sidewalls, and thus improving the overall brightness of the chip.

[0032] In summary, the light-emitting element of this application constructs a more complete light energy recovery and guidance system through the coordinated design of the reflective structures on the light-emitting side and the backlight side. The first reflective layer focuses and solves the problem of electrode shading loss, and achieves direction resetting through light recombination radiation to reduce light absorption loss; the second reflective layer focuses and solves the problem of directional propagation of non-axial light, and guides light to converge towards the sidewall through reflection. The combined effect of the two not only reduces the light energy loss caused by the first electrode shading, but also taps into the potential of non-axial light emission from the sidewall, optimizing light utilization efficiency from two dimensions: reducing loss and improving effective light emission. Ultimately, this achieves an effective improvement in the brightness of the light-emitting element, which is particularly suitable for scenarios requiring ultra-small size and high brightness light-emitting devices.

[0033] In an optional embodiment, the first reflective layer is a distributed Bragg reflector structure with a reflectivity of R1 for axially incident light, which can be configured to R1 ≥ 80%. In a further embodiment, R1 ≥ 90% or R1 ≥ 95%.

[0034] In an alternative scheme, when both the first and second reflective layers are distributed Bragg reflection structures, the first and second reflective layers can be fabricated by epitaxial growth processes, and the first and second reflective layers are part of the epitaxial structure.

[0035] In the alternative scheme, the second reflective layer makes an angle of θ with the axial direction. The reflectivity of the incident light is higher than that of the incident light along the axial direction, where 20° ≤ ≤70°. In a further embodiment, 30°≤ ≤60°.

[0036] In the alternative scheme, the second reflective layer makes an angle of θ with the axial direction. The reflectivity of the incident light is R2, which can be configured to be R2≥80%. In a further embodiment, R2≥90% or R2≥95%.

[0037] It should be noted that "incident ray along the axial direction" can refer to an incident ray with an angle of 0° to the axial direction. Alternatively, considering error factors, "incident ray along the axial direction" can refer to an incident ray with an angle of β to the axial direction, where 0°≤β≤10°.

[0038] In one alternative design, the angle between the sidewalls of the epitaxial structure and the back surface of the epitaxial structure ranges from 20° to 70°. In a further design, the angle between the sidewalls of the epitaxial structure and the back surface of the epitaxial structure ranges from 30° to 60°. The inclined sidewalls of the epitaxial structure increase the chance of light escaping from the epitaxial structure, reduce the light propagation path within the epitaxial structure to some extent, decrease light absorption by the material, and improve light output efficiency.

[0039] In an alternative embodiment, the first reflective layer is composed of alternating layers of two materials with different refractive indices, each layer having a thickness of [missing information]. .in, The wavelength of the light emitted by the active layer. is the refractive index of the corresponding material layer in the first reflective layer.

[0040] For example, if the first reflective layer is composed of alternating layers of material A and material B with different refractive indices, then the thickness of material layer A is... Then the thickness of material layer B is Material layers A and B can be made of at least two different materials selected from SiO2, TiO2, ZnO2, ZrO2, and Cu2O3. Specifically, they can be formed by alternating layers of high-refractive-index and low-refractive-index materials. For example, material layer A can be the low-refractive-index material SiO2, and material layer B can be the high-refractive-index material TiO2. Furthermore, in order to achieve the target reflectivity, those skilled in the art can reasonably determine the number of overlap pairs between material layers A and B.

[0041] In an alternative design, the second reflective layer is composed of alternating layers of two materials with different refractive indices. The thickness of the layer material is .in, The wavelength of the light emitted by the active layer. For the second reflective layer The refractive index of the layer material, The angle between the incident ray and the axis is denoted as .

[0042] For example, if the second reflective layer is composed of alternating layers of material C and material D with different refractive indices, then the thickness of material layer C is... Then the thickness of material layer D is The materials of material layer C and material layer D can be at least two different materials selected from SiO2, TiO2, ZnO2, ZrO2, and Cu2O3. Specifically, they can be formed by alternating layers of high-refractive-index and low-refractive-index materials. For example, material layer C can be the low-refractive-index material SiO2, and material layer D can be the high-refractive-index material TiO2. Furthermore, in order to achieve the target reflectivity, those skilled in the art can reasonably determine the number of overlap pairs of material layer C and material layer D.

[0043] In an alternative embodiment, if the projection of the first electrode onto the front surface of the epitaxial structure is within the front surface boundary of the epitaxial structure, meaning the first electrode does not completely obscure the front surface of the epitaxial structure, then the first reflective layer can be provided only in the projection area of ​​the first reflective layer onto the front surface of the epitaxial structure. That is, the projection boundary of the first reflective layer onto the front surface of the epitaxial structure coincides with the projection boundary of the first electrode onto the front surface of the epitaxial structure. Alternatively, the projection boundary of the first electrode onto the front surface of the epitaxial structure can be located within the projection boundary of the first reflective layer onto the front surface of the epitaxial structure. Or, the projection boundary of the first reflective layer onto the front surface of the epitaxial structure can coincide with the front surface boundary of the epitaxial structure.

[0044] Preferably, if the first electrode completely blocks the front side of the epitaxial structure, then it is preferable to make the projection boundary of the first reflective layer onto the front side of the epitaxial structure coincide with the front boundary of the epitaxial structure.

[0045] In an optional design, the sidewalls of the epitaxial structure are roughened, with the height difference of the roughened structure ranging from 0.1 to 0.5 μm. The roughened structure can be a regular or irregular patterned structure. Furthermore, the roughened structure can be passivated after fabrication. The roughened structure improves the light extraction efficiency within the chip.

[0046] The light-emitting element of this application includes a light-emitting diode (LED) comprising a transparent encapsulation layer that at least covers the sidewalls of the epitaxial structure, the front surface and sidewalls of the first reflective layer, and the sidewalls of the second reflective layer. The transparent encapsulation layer can be a multi-layered structure, for example, it may include an anti-reflection film layer and a protective film layer stacked sequentially. The transparent encapsulation layer serves both anti-reflection and protection functions. The anti-reflection film layer primarily improves light extraction efficiency by reducing light reflection at the chip-air interface and increasing the intensity of emitted light. The protective film layer provides mechanical protection for the chip, preventing long-term exposure to air or mechanical damage, thereby improving the chip's stability and reliability.

[0047] In the light-emitting element of this application, the light-emitting diode includes a second electrode, which is formed on the back side of the substrate and electrically connected to the first semiconductor layer.

[0048] In an alternative embodiment, the light-emitting diode may further include a top mirror layer disposed between the first electrode and the first reflective layer, wherein the projection boundary of the top mirror layer onto the back side of the first electrode at least completely covers the back side boundary of the first electrode and does not exceed the front side boundary of the epitaxial structure.

[0049] When some of the non-axial outgoing light rays are directed toward the back of the first electrode, the reflection effect of the top mirror layer can cause the non-axial outgoing light rays to return to the active layer or be emitted along the sidewall, thereby further reducing light loss.

[0050] In an alternative embodiment, the light-emitting diode may also include a microlens structure for changing the direction of light emitted from the sidewalls of the epitaxial structure. Specifically, the microlens structure can redirect the light emitted from the sidewalls to the axial direction. "Redirecting to the axial direction" does not necessarily mean that it is completely aligned with the axial direction, but rather that it reduces the angle between the light emission direction and the axial direction. They may be aligned or there may be a certain angle.

[0051] For example, in an alternative solution, the microlens structure can be positioned on the side of the epitaxial structure to guide the light emitted from the sidewall of the epitaxial structure axially; or, the microlens structure can be made of a transparent material to cover the epitaxial structure, so as to guide the large-angle light emitted from the sidewall as axially as possible.

[0052] This application also provides a light-emitting device, including a circuit board and at least one light-emitting element fixed to the surface of the circuit board, wherein the light-emitting element is the aforementioned light-emitting element.

[0053] To provide a more detailed description of the light-emitting element of this application, the following embodiments are provided. It should be noted that the technical features and solutions in the following embodiments can be used in combination with each other without conflict.

[0054] Example 1

[0055] This embodiment provides a light-emitting element, which includes at least one light-emitting diode 101.

[0056] like Figure 1 and Figure 2 As shown, the light-emitting diode 101 includes a substrate 1, an epitaxial structure 2, a first electrode 3, a specular reflective layer 4, a first reflective layer 5, and a second reflective layer 6.

[0057] The substrate 1 has a front side and a back side disposed opposite to each other, with the extension direction perpendicular to the front side of the substrate referred to as the axial direction. An epitaxial structure 2 is formed on one side of the front side of the substrate, and the epitaxial structure 2 includes a first semiconductor layer 21, an active layer 22, and a second semiconductor layer 23 stacked sequentially from the front side of the substrate; the epitaxial structure 2 has inclined sidewalls. A first electrode 3 is located above the second semiconductor layer 23 and is electrically connected to the second semiconductor layer 23. A mirror-reflective layer 4 is disposed between the first semiconductor layer 21 and the substrate 1.

[0058] The first reflective layer 5 is a distributed Bragg reflection structure, which is disposed at least on the surface of the second semiconductor layer 23 covering the back of the first electrode 3, and has high reflectivity for incident light along the axial direction. The second reflective layer 6 is a distributed Bragg reflection structure, which is disposed between the specular reflective layer 4 and the first semiconductor layer 21, and reflects at least part or all of the incident light that is at a predetermined angle to the axial direction.

[0059] In this embodiment, the first semiconductor layer 21 may be composed of a III-V or II-VI compound semiconductor and may be doped with a first dopant. The first semiconductor layer 21 may be made of a material with the chemical formula In. x1 Al y1 Ga 1-x1-y1 The first semiconductor layer 21 is composed of N (0≤x1≤1, 0≤y1≤1, 0≤x1+y1≤1) semiconductor materials, such as GaN, AlGaN, InGaN, InAlGaN, etc., or materials selected from AlGaAs, GaP, GaAs, GaAsP, and AlGaInP. Furthermore, the first dopant can be an n-type dopant, such as any one or more of Si, Ge, Sn, Se, and Te. When the first dopant is an n-type dopant, the first semiconductor layer 21 doped with the first dopant is an n-type semiconductor layer. The first dopant can also be a p-type dopant, such as any one or more of Mg, Zn, Ca, Sr, and Ba; in this case, the first semiconductor layer 21 doped with the first dopant is a p-type semiconductor layer.

[0060] An active layer 22 is disposed between a first semiconductor layer 21 and a second semiconductor layer 23. The active layer 22 provides a region for electron-hole recombination and light radiation. Different materials can be selected depending on the emission wavelength. The active layer 22 can be a periodic structure with a single quantum well or multiple quantum wells. The active layer 22 includes a well layer and a barrier layer, wherein the barrier layer has a larger band gap than the well layer. By adjusting the composition ratio of the semiconductor materials in the active layer 22, it is desired to radiate light of different wavelengths.

[0061] The second semiconductor layer 23 is formed above the active layer 22 and may be composed of a III-V or II-VI compound semiconductor. The second semiconductor layer 23 may be doped with a second dopant. The second semiconductor layer 23 may be made of a material with the chemical formula In. x2 Al y2 G a1-x2-y2 The semiconductor layer 23 is composed of N (0≤x²≤1, 0≤y²≤1, 0≤x²+y²≤1) semiconductor materials, or materials selected from AlGaAs, GaP, GaAs, GaAsP, and AlGaInP. When the second dopant is a p-type dopant, such as any one or more of Mg, Zn, Ca, Sr, and Ba, the second semiconductor layer 23 doped with the second dopant is a p-type semiconductor layer. The second dopant can also be an n-type dopant, such as any one or more of Si, Ge, Sn, Se, and Te. When the second dopant is an n-type dopant, the second semiconductor layer 23 doped with the second dopant is an n-type semiconductor layer. When the first semiconductor layer 21 is an n-type semiconductor layer, the second semiconductor layer 23 is a p-type semiconductor layer; conversely, when the first semiconductor layer 21 is a p-type semiconductor layer, the second semiconductor layer 23 is an n-type semiconductor layer.

[0062] It is understandable that the epitaxial structure 2 may also include other layer materials, such as current spreading layers, window layers, or ohmic contact layers, and may be configured as different multilayers depending on the doping concentration or composition content. The epitaxial structure 2 can be formed by methods such as physical vapor deposition (PVD), chemical vapor deposition (CVD), epitaxy growth technology, and atomic layer deposition (ALD).

[0063] In this embodiment, the reflectivity of the first reflective layer 5 to incident light along the axial direction is R1, which can be configured to R1≥80%. In a further embodiment, R1≥90% or R1≥95%.

[0064] In this embodiment, both the first reflective layer 5 and the second reflective layer 6 are distributed Bragg reflective structures. The first reflective layer 5 and the second reflective layer 6 can be fabricated by epitaxial growth process, and the first reflective layer 5 and the second reflective layer 6 are part of the epitaxial structure 2.

[0065] In this embodiment, the second reflective layer 6 has an angle of 6° with the axial direction. The reflectivity of the incident light is higher than that of the incident light along the axial direction, where 20° ≤ ≤70°. In a further embodiment, 30°≤ ≤60°.

[0066] In this embodiment, the second reflective layer 6 has an angle of 6° with the axial direction. The reflectivity of the incident light is R2, which can be configured to be R2≥80%. In a further embodiment, R2≥90% or R2≥95%.

[0067] It should be noted that "incident ray along the axial direction" can refer to an incident ray with an angle of 0° to the axial direction. Alternatively, considering error factors, "incident ray along the axial direction" can refer to an incident ray with an angle of β to the axial direction, where 0°≤β≤10°.

[0068] In an optional embodiment, the angle between the sidewall of the epitaxial structure 2 and its back surface ranges from 20° to 70°. In a further embodiment, the angle between the sidewall of the epitaxial structure 2 and its back surface ranges from 30° to 60°. The inclined sidewall of the epitaxial structure 2 increases the chance of light escaping from it, reduces the light propagation path within the structure, decreases light absorption by the material, and improves light output efficiency.

[0069] In this embodiment, the first reflective layer 5 is composed of alternating layers of two materials with different refractive indices, each layer having a thickness of [missing information]. .in, The wavelength of the light radiated from active layer 22. is the refractive index of the corresponding material layer in the first reflective layer 5.

[0070] For example, if the first reflective layer 5 is composed of alternating layers of material A and material B with different refractive indices, then the thickness of material layer A is... Then the thickness of material layer B is Material layers A and B can be made of at least two different materials selected from SiO2, TiO2, ZnO2, ZrO2, and Cu2O3. Specifically, they can be formed by alternating layers of high-refractive-index and low-refractive-index materials. For example, material layer A can be the low-refractive-index material SiO2, and material layer B can be the high-refractive-index material TiO2. Furthermore, in order to achieve the target reflectivity, those skilled in the art can reasonably determine the number of overlap pairs between material layers A and B.

[0071] In this embodiment, the second reflective layer 6 is composed of alternating layers of two materials with different refractive indices. The thickness of the layer material is .in, The wavelength of the light radiated from active layer 22. For the second reflective layer 6, the first The refractive index of the layer material, The angle between the incident ray and the axis is denoted as .

[0072] For example, if the second reflective layer 6 is composed of alternating layers of materials C and D with different refractive indices, then the thickness of material layer C is... Then the thickness of material layer D is The materials of material layer C and material layer D can be at least two different materials selected from SiO2, TiO2, ZnO2, ZrO2, and Cu2O3. Specifically, they can be formed by alternating layers of high-refractive-index and low-refractive-index materials. For example, material layer C can be the low-refractive-index material SiO2, and material layer D can be the high-refractive-index material TiO2. Furthermore, in order to achieve the target reflectivity, those skilled in the art can reasonably determine the number of overlap pairs of material layer C and material layer D.

[0073] The light-emitting element of this embodiment offers at least the following advantages:

[0074] First, the first reflective layer 5 reduces the loss of axial light rays due to the blocking of the first electrode 3, thereby improving light reuse efficiency. The first reflective layer 5, in the form of a distributed Bragg reflector structure, is disposed between the first electrode 3 and the second semiconductor layer 23. (See also...) Figure 2As shown in the light path S1, when the axial light emitted from the active layer 22 strikes the back of the first electrode 3, the first reflective layer 5, with its high reflectivity for axially incident light (e.g., incident light with an angle of 0° to 10° with the axis), can reflect most of the axially incident light back into the active layer 22. There, the light recombines and radiates photons. Because the propagation direction of the recombinated photons is random, the number of photons striking the back of the first electrode 3 along the axis can be reduced to some extent. This reduces the light absorption loss caused by the first electrode 3 being blocked, increases the probability of these photons escaping from the sidewall of the epitaxial structure 2, and lays the foundation for improved brightness.

[0075] Furthermore, the second reflective layer 6 guides the directional propagation of non-axial light, enhancing the light extraction efficiency of the sidewalls. The second reflective layer 6, in the form of a distributed Bragg reflector structure, is disposed between the specular reflective layer 4 and the first semiconductor layer 21, see [reference needed]. Figure 2 As shown in the light path S2, when the non-axial light emitted from the active layer 22 strikes the second reflective layer 6, the high reflectivity of the second reflective layer 6 for non-axial incident light (e.g., incident light at an angle of 30° to 60° with the axis) allows most of the non-axial incident light to be reflected towards the sidewall of the epitaxial structure 2. This directional guidance significantly increases the probability of photons escaping from the sidewall of the epitaxial structure 2, preventing non-axial light from being absorbed by the substrate or other structures due to disordered propagation, further increasing the total amount of light emitted from the sidewall, and thus improving the overall brightness of the chip.

[0076] In summary, the light-emitting element of this embodiment, through the collaborative design of dual distributed Bragg reflector layers on the light-emitting side and the backlight side, constructs a more complete light energy recovery and guidance system. The first reflector layer 5 focuses on solving the problem of axial light loss due to electrode shading, and achieves direction resetting through light recombination radiation to reduce light absorption loss; the second reflector layer 6 focuses on solving the problem of non-axial light directional propagation, and guides light to converge towards the sidewall through reflection. The combined effect of the two not only reduces the axial light energy loss caused by the shading of the first electrode 3, but also taps into the potential of non-axial light emission from the sidewall, optimizing light utilization efficiency from two dimensions: reducing loss and improving effective light emission. Ultimately, this effectively improves the brightness of the light-emitting element, making it particularly suitable for scenarios requiring ultra-small size and high brightness light-emitting devices.

[0077] In addition, see Figure 2As shown in the light path of S3, the second reflective layer 6 has low reflectivity for axially incident light (e.g., incident light with an angle of 0° to 10° to the axis). This portion of the axially incident light passes through the second reflective layer 6 and reaches the specular reflective layer 4. Under the action of the specular reflective layer 4, the axially incident light returns to the active layer 22, recombines, and emits photons. Since the propagation direction of the recombinated photons is random, it can further reduce the loss of axial light to a certain extent, contributing to the improvement of brightness.

[0078] In this embodiment, as Figure 3 As shown, the projection of the first electrode 3 onto the front surface of the epitaxial structure 2 is located within the boundary of the front surface region of the epitaxial structure 2, meaning that the first electrode 3 does not completely obscure the front surface of the epitaxial structure 2. Therefore, the first reflective layer 5 can be provided only in the projection area of ​​the first reflective layer 5 onto the front surface of the epitaxial structure 2, meaning that the projection boundary of the first reflective layer 5 onto the front surface of the epitaxial structure 2 coincides with the projection boundary of the first electrode 3 onto the front surface of the epitaxial structure 2.

[0079] Alternatively, the projected boundary of the first reflective layer 5 onto the front side of the epitaxial structure 2 can be located between the projected boundary of the first electrode 3 onto the front side of the epitaxial structure 2 and the boundary of the front side region of the epitaxial structure 2. Or, as... Figure 2 As shown, the projection boundary of the first reflective layer 5 onto the front side of the epitaxial structure 2 can be made to coincide with the front boundary of the epitaxial structure 2.

[0080] In this embodiment, as Figure 4 As shown, if the first electrode 3 completely blocks the front side of the epitaxial structure 2, it is preferable to make the projection boundary of the first reflective layer 5 onto the front side of the epitaxial structure 2 coincide with the boundary of the front area of ​​the epitaxial structure 2.

[0081] In this embodiment, as Figure 2 As shown, the light-emitting diode 101 includes a transparent encapsulation layer 7, which at least covers the sidewalls of the epitaxial structure 2, the front side and sidewalls of the first reflective layer 5, and the sidewalls of the second reflective layer 6. The transparent encapsulation layer 7 can be a multi-layered structure, for example, it may include an anti-reflection film layer and a protective film layer stacked sequentially. The transparent encapsulation layer 7 serves both anti-reflection and protective functions. The anti-reflection film layer mainly increases the intensity of emitted light by reducing light reflection at the chip-air interface, thereby improving light extraction efficiency. The protective film layer provides mechanical protection for the chip, preventing long-term exposure to air or mechanical damage, thus improving the chip's stability and reliability.

[0082] In this embodiment, as Figure 2 As shown, the light-emitting diode 101 includes a second electrode 8, which is formed on the back side of the substrate 1 and electrically connected to the first semiconductor layer 21.

[0083] Example 2

[0084] This embodiment also provides a light-emitting element, but unlike the first embodiment, this embodiment also includes a top mirror layer.

[0085] Specifically, such as Figure 5 As shown, in the light-emitting element 100 of this embodiment, the light-emitting diode 101 includes a top mirror layer 9, which is disposed between the first electrode 3 and the first reflective layer 5, and the projection boundary of the top mirror layer 9 onto the back side of the first electrode 3 at least completely covers the back side boundary of the first electrode 3, and does not exceed the front side boundary of the epitaxial structure 2.

[0086] The solution in this embodiment can further solve the problem of loss of non-axial light rays: see Figure 5 As shown in the light path of S4, when some non-axial light rays emitted from the active layer 22 (e.g., incident light rays with an angle of 30° to 60° with the axis) are directed toward the back of the first electrode 3, the top mirror layer 9 can reflect these light rays, which might otherwise be absorbed by the first electrode 3, back to the active layer 22 or be emitted directly along the sidewall of the epitaxial structure 2, thereby further reducing light loss and helping to improve the light utilization efficiency of the light-emitting element 100.

[0087] Example 3

[0088] This embodiment also provides a light-emitting element. The difference from Embodiment 1 or Embodiment 2 is that the sidewall of the epitaxial structure in this embodiment is further provided with a roughened structure.

[0089] Specifically, such as Figure 4 As shown, the sidewall of the epitaxial structure 2 is provided with a roughened structure 11. The height difference of the roughened structure 11 can be set to 0.1~0.5µm. The roughened structure 11 can be a regular patterned structure or an irregular patterned structure. In addition, the roughened structure 11 can be passivated after fabrication. On the one hand, the roughened structure 11 can improve the light emission efficiency; on the other hand, the roughened structure 11 can improve the docking stability with the transparent encapsulation layer 7.

[0090] Example 4

[0091] This embodiment also provides a light-emitting element, but unlike any of the embodiments in Embodiments 1 to 3, this embodiment also includes a microlens structure.

[0092] Specifically, such as Figure 6 and Figure 7 As shown, in the light-emitting element 100 of this embodiment, the light-emitting diode 101 may also include a microlens structure 10 for changing the direction of light emitted from the sidewall of the epitaxial structure 2.

[0093] Specifically, the microlens structure 10 can redirect the light emitted from the sidewall to the axial direction. "Redirecting to the axial direction" does not necessarily mean that it is completely aligned with the axial direction, but rather that it reduces the angle between the light emission direction and the axial direction. They may be aligned or there may be a certain angle.

[0094] For example, such as Figure 7 As shown, the microlens structure 10 can be disposed on the side of the epitaxial structure 2 to guide the light emitted from the sidewall of the epitaxial structure 2 axially.

[0095] Or, such as Figure 6 As shown, the microlens structure 10 is made of transparent material and can cover the epitaxial structure 2 to guide the large-angle light rays emitted from the sidewall as much as possible along the axis.

[0096] Example 5

[0097] This embodiment also provides a light-emitting element, but the difference from any of the embodiments in Embodiment 1, Embodiment 3, and Embodiment 4 is that the first reflective layer 5 in this embodiment is a specular reflection structure, rather than a distributed Bragg reflection structure.

[0098] like Figure 8 As shown, the first reflective layer 5 is a specular reflective structure. It can be disposed only on the back surface of the first electrode 3, or it can cover the entire light-emitting surface of the epitaxial structure 2. The first reflective layer 5 contains conductive holes to enable electrical conduction between the first electrode 3 and the second semiconductor layer 23.

[0099] When the first reflective layer 5 is a specular reflective structure, it can reflect incident light along the axial direction (see...). Figure 8 The light path S1 can also reflect incident light rays that are at an angle to the axis (see [reference]). Figure 8 (Middle ray path S4).

[0100] Example 6

[0101] like Figure 9 As shown, this embodiment also provides a light-emitting device 200, including a circuit board 201 and at least one of the aforementioned light-emitting elements 100 fixed to the surface of the circuit board 201. The light-emitting element 100 includes one or more light-emitting diodes 101. The light-emitting element 100 is the light-emitting element 100 in any of the foregoing embodiments.

[0102] The above description is only a partial embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A light-emitting element, characterized in that, Includes at least one light-emitting diode (101), said light-emitting diode (101) comprising: The substrate (1) has a front side and a back side of the substrate that are disposed opposite to each other, and the extending direction perpendicular to the front side of the substrate is called the axial direction; An epitaxial structure (2) is formed on one side of the front side of the substrate. The epitaxial structure (2) includes a first semiconductor layer (21), an active layer (22), and a second semiconductor layer (23) stacked sequentially from the front side of the substrate. The epitaxial structure (2) has inclined sidewalls. The first electrode (3) is located above the second semiconductor layer (23) and is electrically connected to the second semiconductor layer (23); A mirror-reflective layer (4) is disposed between the first semiconductor layer (21) and the substrate (1); A first reflective layer (5) is disposed at least on the surface of the second semiconductor layer (23) covering the back of the first electrode (3), and it reflects at least a portion of the light rays incident on the back of the first electrode (3). The second reflective layer (6) is a distributed Bragg reflection structure, disposed between the mirror reflective layer (4) and the first semiconductor layer (21), which reflects at least part or all of the incident light rays that are at a predetermined angle to the axis.

2. The light-emitting element according to claim 1, characterized in that, The first reflective layer (5) is a distributed Bragg reflection structure, which reflects at least part or all of the incident light along the axial direction.

3. The light-emitting element according to claim 2, characterized in that, The first reflective layer (5) and the second reflective layer (6) are fabricated by an epitaxial growth process, and the first reflective layer (5) and the second reflective layer (6) are part of the epitaxial structure (2).

4. The light-emitting element according to claim 1, characterized in that, The first reflective layer (5) is a specular reflective structure.

5. The light-emitting element according to claim 2, characterized in that, The first reflective layer (5) has a reflectivity of R1 for incident light along the axial direction, wherein R1 ≥ 80%.

6. The light-emitting element according to claim 1, characterized in that, The second reflective layer (6) has an angle of θ with the axial direction. The reflectivity of the incident light is higher than that of the incident light along the axial direction, where 20° ≤ ≤70°.

7. The light-emitting element according to claim 6, characterized in that, The second reflective layer (6) has an angle of θ with the axial direction. The reflectivity of the incident light is R2, where R2≥80%.

8. The light-emitting element according to claim 6, characterized in that, The angle between the sidewall of the epitaxial structure (2) and the back surface of the epitaxial structure (2) is in the range of 20° to 70°.

9. The light-emitting element according to claim 2, characterized in that, The first reflective layer (5) is composed of alternating layers of two materials with different refractive indices, each layer having a thickness of [missing information]. ; in, The wavelength of the light radiated by the active layer (22) is... is the refractive index of the corresponding material layer in the first reflective layer (5).

10. The light-emitting element according to claim 6, characterized in that, The second reflective layer (6) is composed of alternating layers of two materials with different refractive indices, each layer having a thickness of [missing information]. ; in, The wavelength of the light radiated by the active layer (22) is... The refractive index of the corresponding material layer in the second reflective layer (6) is... The angle between the incident ray and the axis is denoted as .

11. The light-emitting element according to claim 1, characterized in that, The projection boundary of the first reflective layer (5) onto the front side of the epitaxial structure (2) coincides with the front boundary of the epitaxial structure (2).

12. The light-emitting element according to claim 1, characterized in that, The light-emitting diode (101) includes a transparent encapsulation layer (7) that at least covers the sidewall of the epitaxial structure (2), the front and sidewall of the first reflective layer (5), and the sidewall of the second reflective layer (6).

13. The light-emitting element according to claim 1, characterized in that, The light-emitting diode (101) includes a second electrode (8) formed on the back side of the substrate (1) and electrically connected to the first semiconductor layer (21).

14. The light-emitting element according to claim 2, characterized in that, The light-emitting diode (101) further includes a top mirror layer (9) disposed between the first electrode (3) and the first reflective layer (5), and the projection boundary of the top mirror layer (9) onto the back of the first electrode (3) at least completely covers the back boundary of the first electrode (3) and does not exceed the front boundary of the epitaxial structure (2).

15. The light-emitting element according to claim 1, characterized in that, The light-emitting diode (101) also includes a microlens structure (10), which is disposed on the side of the epitaxial structure (2) or covers the epitaxial structure (2) to change the direction of light emitted from the sidewall of the epitaxial structure (2).

16. A light-emitting device, characterized in that, It includes a circuit board and at least one light-emitting element fixed to the surface of the circuit board, the light-emitting element including the light-emitting element according to any one of claims 1 to 15.

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