CN119677259B - Light emitting diode and light emitting device - Google Patents
Light emitting diode and light emitting deviceInfo
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- CN119677259B CN119677259B CN202411729577.6A CN202411729577A CN119677259B CN 119677259 B CN119677259 B CN 119677259B CN 202411729577 A CN202411729577 A CN 202411729577A CN 119677259 B CN119677259 B CN 119677259B
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Abstract
The application provides a light emitting diode and a light emitting device, wherein the light emitting diode comprises a substrate, an epitaxial structure, a first electrode, a first reflecting layer and a second reflecting layer. The substrate has a substrate front surface and a substrate back surface which are oppositely arranged, and the extending direction perpendicular to the substrate front surface is called an axial direction. The epitaxial structure is formed on one side of the front surface of the substrate and comprises a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially stacked from the front surface of the substrate. The first electrode is positioned above the second semiconductor layer and is in conductive connection with the second semiconductor layer, the first reflecting layer is arranged between the first electrode and the second semiconductor layer, the second reflecting layer is arranged between the first semiconductor layer and the substrate, and the surface of the second reflecting layer corresponding to at least the lower part of the first electrode is provided with a slope-shaped structure with an inclined wall surface. The technical scheme of the application optimizes the light extraction efficiency and reduces the light loss caused by electrode shielding.
Description
Technical Field
The application relates to the technical field of semiconductor devices and devices, in particular to a light emitting diode and a light emitting device.
Background
With the gradual expansion of the AR/VR (augmented reality technology/virtual reality technology) market, the application requirements of Micro LEDs (Micro light emitting diodes) in AR/VR are also increasing. And in the process of pursuing better compactness and portability at the application end, the size requirement of Micro LEDs is gradually reduced.
In AR/VR applications, micro LED products have high requirements on the chip size, which is often 5um, 2um, or even below 2 um. In order to meet the demand of chip miniaturization as much as possible, the packaging structure of Micro LED products generally adopts a vertical structure. In the vertical chip structure, the main light emitting direction is generally referred to as an axial direction (i.e., the direction from the back surface to the front surface of the epitaxial structure), an electrode structure is disposed on the axial light emitting surface, and the electrode structure on the light emitting surface can shield part of the light emitting surface, so that the light emitting brightness of the product is affected to a certain extent. Especially for the chip size below 2um, the size of the light-emitting surface also can shrink, and the electrode structure of the light-emitting surface almost completely shields the whole light-emitting surface, thereby seriously affecting the luminous brightness of the product.
Disclosure of Invention
The application aims to provide a light emitting diode and a light emitting device, which optimize light extraction efficiency and reduce light loss caused by electrode shielding.
In a first aspect, the application provides a light emitting diode, which comprises a substrate, an epitaxial structure, a first electrode, a first reflecting layer and a second reflecting layer. The substrate is provided with a substrate front surface and a substrate back surface which are oppositely arranged, and the extending direction perpendicular to the substrate front surface is called an axial direction. The epitaxial structure is formed on one side of the front surface of the substrate and comprises a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially stacked from the front surface of the substrate. The first electrode is positioned above the second semiconductor layer and is in conductive connection with the second semiconductor layer, the first reflecting layer is arranged between the first electrode and the second semiconductor layer, the second reflecting layer is arranged between the first semiconductor layer and the substrate, and the surface of the second reflecting layer corresponding to at least the lower part of the first electrode is provided with a slope-shaped structure with an inclined wall surface.
In a second aspect, the present application provides a light emitting device, including a circuit substrate and at least one light emitting diode fixed to a surface of the circuit substrate, where the light emitting diode is the light emitting diode.
Compared with the prior art, the application has the beneficial effects that at least:
The design of the light-emitting diode optimizes the light extraction efficiency and reduces the light loss caused by electrode shielding. Specifically, when the light emitting diode generates light in an operating state, part of the light is emitted toward the bottom surface side of the first electrode. These rays are effectively reflected downwards by the first reflective layer and thus reach the second reflective layer. The second reflecting layer is particularly designed with a slope-shaped structure which not only receives the light reflected by the first reflecting layer, but also further reflects the light to the side wall direction of the epitaxial structure through the design of the inclined wall surface. The design leads part or all of light possibly blocked by the first electrode to be led out through the side wall of the epitaxial structure, thereby obviously reducing the shielding effect of the first electrode on the light emitted by the front surface of the light-emitting diode and ensuring the light-emitting brightness and efficiency of the light-emitting diode.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a cross-sectional view of a first light emitting diode according to an embodiment of the present application;
FIG. 2 is a cross-sectional view of a second light emitting diode according to an embodiment of the present application;
FIG. 3 is a cross-sectional view of a third light emitting diode according to an embodiment of the present application;
FIG. 4 is a cross-sectional view of a fourth light emitting diode according to an embodiment of the present application;
FIG. 5 is a cross-sectional view of a light emitting diode with roughened structure according to an embodiment of the present application;
FIG. 6 is a cross-sectional view of a light emitting diode with a lens structure according to an embodiment of the present application;
FIG. 7 is a cross-sectional view of a light emitting diode with an asymmetric slope structure according to an embodiment of the present application;
FIG. 8 is a cross-sectional view of a light emitting diode with a large arc slope structure according to an embodiment of the present application;
FIG. 9 is a cross-sectional view of a light emitting diode with a small arcuate ramp structure according to an embodiment of the present application;
FIG. 10 is a cross-sectional view of a light emitting diode with a trapezoid ramp structure according to an embodiment of the present application;
FIG. 11 is a cross-sectional view of a light emitting diode with a tapered ramp structure according to an embodiment of the present application;
FIG. 12 is a cross-sectional view of a ramp structure having a plurality of pointed cone-shaped raised structures according to an embodiment of the present application;
FIG. 13 is a cross-sectional view of a ramp structure having a plurality of arcuate raised structures according to an embodiment of the present application;
FIG. 14 is a cross-sectional view of a ramp structure having a plurality of convex structures of a blended shape, according to an embodiment of the present application;
FIG. 15 is a cross-sectional view of a light emitting diode with a first reflective layer having an inclined structure according to an embodiment of the present application;
fig. 16 is a block diagram of a light emitting device according to an embodiment of the present application.
100 Parts of light emitting diode, 1 part of substrate, 2 parts of epitaxial structure, 21 parts of first semiconductor layer, 22 parts of active layer, 23 parts of second semiconductor layer, 24 parts of roughening structure, 3 parts of first electrode, 4 parts of first reflecting layer, 41 parts of inclined structure, 5 parts of second reflecting layer, 51 parts of slope structure, 511 parts of protruding structure, 6 parts of lens, 7 parts of transparent packaging layer, 8 parts of second electrode, 200 parts of circuit substrate.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In order to meet the demands of chip miniaturization as much as possible, the chip size of Micro LED products is often 5um, 2um, or even below 2 um. In Micro LED products with miniaturized chips, 50% or more of the light-emitting surface can be shielded by the electrode structure of the light-emitting surface, especially the chips with the thickness of less than 2um, the whole light-emitting surface is almost shielded by the electrode structure, and the light-emitting brightness of the product is seriously affected. In order to solve this problem, the following technical means are provided.
The application provides a light emitting diode, which comprises a substrate, an epitaxial structure, a first electrode, a first reflecting layer and a second reflecting layer. The substrate is provided with a substrate front surface and a substrate back surface which are oppositely arranged, and the extending direction perpendicular to the substrate front surface is called an axial direction. The epitaxial structure is formed on one side of the front surface of the substrate and comprises a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially stacked from the front surface of the substrate. The first electrode is located above the second semiconductor layer and is electrically connected with the second semiconductor layer. The first reflecting layer is arranged between the first electrode and the second semiconductor layer. The second reflecting layer is arranged between the first semiconductor layer and the substrate, and at least the surface of the second reflecting layer corresponding to the lower part of the first electrode is provided with a slope-shaped structure with an inclined wall surface.
The design of the light-emitting diode optimizes the light extraction efficiency and reduces the light loss caused by electrode shielding. Specifically, when the light emitting diode generates light in an operating state, part of the light is emitted toward the bottom surface side of the first electrode. These rays are effectively reflected downwards by the first reflective layer and thus reach the second reflective layer. The second reflecting layer is particularly designed with a slope-shaped structure which not only receives the light reflected by the first reflecting layer, but also further reflects the light to the side wall direction of the epitaxial structure through the design of the inclined wall surface. The design leads part or all of light possibly blocked by the first electrode to be led out through the side wall of the epitaxial structure, thereby obviously reducing the shielding effect of the first electrode on the light emitted by the front surface of the light-emitting diode and ensuring the light-emitting brightness and efficiency of the light-emitting diode.
In an alternative scheme, the first semiconductor layer of the epitaxial structure is an N-type semiconductor layer, the second semiconductor layer is a P-type semiconductor layer, and the N-type semiconductor layer, the active layer and the P-type semiconductor layer can be all made of GaN-based or AlGaInP-based materials. The epitaxial structure can be prepared by chemical vapor deposition.
In the alternative, the first reflective layer and the second reflective layer may be DBR reflective structures or ODR reflective structures. DBR (Distributed Bragg Reflector ) and ODR (Omni-Directional Reflector, omnidirectional reflector) are two different reflective structures that function to enhance light reflection and increase light extraction efficiency in LED structures.
ODR reflective structures are based on the waveguide effect and total reflection principle of light, with multiple reflections inside a mirror to achieve transmission and reflection of light. ODR is typically composed of two parallel reflective surfaces, one of which is partially coated to provide high reflectivity, and the other of which is totally reflective. When light rays are emitted from the reflecting surface of the partial coating, the light beams can be reflected for multiple times through the reflecting surface of the partial coating according to the magnitude of the incident angle. During these reflections, the direction of light transmission changes, but the total energy remains inside the mirror. When the incident angle reaches a certain condition, the critical angle is exceeded, and the light cannot be transmitted out of part of the coating surface, so that the total reflection phenomenon occurs. At this time, the light rays can be reflected back and forth between the partially coated reflecting surface and the fully reflecting surface for multiple times, and the light rays are kept to be transmitted inside the mirror. ODR can reflect light beams from one location to another, enabling transmission and reflection of light.
The DBR reflecting structure is a reflector formed by alternately and periodically stacking films with different refractive indexes. When light passes through these films of different refractive indices, the light reflected from the layers interferes constructively due to the change in phase angle and then combines with each other to give strongly reflected light. The DBR reflectivity is determined by the refractive index difference of the materials of the layers making up the DBR and the number of DBR periods.
In general, ODR and DBR each have unique advantages and applicable scenarios. ODR is suitable for applications requiring broad coverage and beam control due to its omnidirectional reflectivity, while DBR is suitable for applications requiring specific wavelength reflection and laser stabilization due to its high reflectivity and wavelength selectivity. Depending on the different design requirements and application requirements, a person skilled in the art will choose a suitable reflective structure.
In an alternative, the projected boundary of the first electrode to the front surface of the first reflective layer may completely coincide with the boundary of the front surface region of the first reflective layer, or the projected boundary of the first electrode to the front surface of the first reflective layer may be located within the boundary of the front surface region of the first reflective layer.
For example, for light emitting diodes with a chip size of 2um or more, the size of the first electrode may be smaller than the size of the second semiconductor layer, i.e. the first electrode may not completely cover the second semiconductor layer, and the first reflective layer may completely cover the front surface of the second semiconductor layer or cover a part of the front surface of the second semiconductor layer, but the front surface area of the first reflective layer at least includes the shielding area of the first electrode. For another example, for light emitting diodes with a chip size below 2um, the size of the first electrode may be substantially equal to the size of the second semiconductor layer, i.e. the first electrode substantially completely covers the second semiconductor layer, where the first reflective layer is arranged to completely cover the front surface of the second semiconductor layer to completely contain the shielding region of the first electrode.
In an alternative, the first reflective layer completely covers the surface of the second semiconductor layer, so that light is guided out from the sides of the epitaxial structure.
The light emitting diode of the present application includes a second electrode formed on the back side of the substrate in conductive connection with the first semiconductor layer.
In an alternative, the epitaxial structure has sloped sidewalls. For example, the included angle beta of the side wall of the epitaxial structure relative to the back surface of the epitaxial structure can be 30-70 degrees, so that the possibility of escaping light from the epitaxial structure is increased, the propagation path of the light in the epitaxial structure is reduced to a certain extent, the absorption of the light by the material is reduced, and the light output efficiency is improved.
In an alternative scheme, the side wall of the epitaxial structure is provided with a coarsening structure, the height difference range of the coarsening structure can be set to be 0.1-0.5 um, and the coarsening structure can be a regular graphical structure or an irregular graphical structure. In addition, passivation treatment can be performed after the roughening structure is manufactured. The coarsening structure improves the extraction efficiency of light inside the vertical structure chip.
The light emitting diode comprises a transparent packaging layer which at least covers the surface of the epitaxial structure. The transparent packaging layer may be a multi-layer stacked structure, for example, may include an antireflection film layer and a protection film layer stacked in sequence. The transparent encapsulation layer can play roles in reflection prevention and protection. The transparent packaging layer (particularly the anti-reflection film layer) increases the intensity of emergent light mainly by reducing the reflection of light at the interface between the chip and the air, thereby improving the light extraction efficiency. The transparent packaging layer (particularly the protective film layer) can provide mechanical protection for the chip, prevent the chip from being exposed in the air for a long time or being mechanically damaged, and improve the stability and the reliability of the chip.
In an alternative, the projected boundary of the first electrode to the front surface of the substrate may exceed the projected boundary of the ramp structure to the front surface of the substrate. That is, after the light vertically directed to one side of the bottom surface of the first electrode is reflected back by the first reflecting layer, only part of the reflected light is received by the slope structure and reflected to the side wall direction of the epitaxial structure, so as to reduce the light loss and improve the light-emitting brightness and the light-emitting efficiency.
In an alternative, the projection boundary of the first electrode to the front side of the substrate does not exceed the projection boundary of the ramp-like structure to the front side of the substrate. Therefore, after the light rays vertically shot to one side of the bottom surface of the first electrode are reflected by the first reflecting layer, the totally reflected light rays can be received by the slope-shaped structure as much as possible and reflected to the side wall direction of the epitaxial structure, so that the light loss is reduced, and the luminous brightness and luminous efficiency are remarkably improved.
In the alternative, the ramp structure may be an asymmetric structure. The inclined wall surface of the slope-shaped structure below the first electrode can incline towards the same side so as to reflect most of light to the single side wall of the epitaxial structure and improve the luminous brightness of the single side wall.
In an alternative scheme, the central position of the whole slope structure is axially coincident with the central position of the first electrode, the whole slope structure is in a symmetrical structure relative to the central position of the whole slope structure, and the central position of the first electrode is axially coincident with the central position of the epitaxial structure, so that the light quantity reflected to the side walls on two sides of the epitaxial structure by the slope structure is basically the same, and the light-emitting brightness of the two side walls of the epitaxial structure is basically the same.
In an alternative, the ramp-like structure comprises at least one protruding structure provided with inclined side walls for reflecting light.
In the alternative, the surface topography of the sloped sidewalls of the raised structures may be planar, arcuate, or a combination of both. For example, the cross-sectional shape of the raised structures may be triangular, tapered, trapezoidal, circular arc, etc.
In the alternative, the raised structures may be asymmetric structures.
In the alternative, the raised structures may be symmetrical structures, i.e. each raised structure has inclined side walls symmetrically arranged about its own central position.
In an alternative, the ramp-like structure includes a plurality of raised structures distributed in an array along the back side of the epitaxial structure. The inclined wall surfaces of the plurality of convex structures can receive the light rays reflected by the first reflecting layer at multiple angles as much as possible, so that the brightness loss is reduced.
In an alternative scheme, the height difference between the top end and the root of the protruding structure ranges from 0.2 um to 1um.
In an alternative, the light emitting diode further comprises a lens covering the front surface and at least part of the side walls of the epitaxial structure for guiding part of the light emitted in the epitaxial structure in the axial direction. The term "partial ray" as used herein refers mainly to a ray of light emitted from the side of the epitaxial structure at a large angle, which is severely deviated from the axial direction, and the outgoing ray of light at a large angle is directed as axially as possible by means of a lens. The term "guide axial direction" as used herein does not necessarily mean that the guide axial direction is completely coincident with the axial direction, but means that the angle between the light emission direction and the axial direction is reduced, and the guide axial direction may be coincident with the axial direction or may have a certain angle.
In an alternative, at least the back side of the corresponding first reflective layer under the first electrode is provided with an inclined structure. When light in the epitaxial structure vertically or obliquely irradiates to the lower part of the first electrode, the light irradiates to the inclined structure of the first reflecting layer, and the inclined structure reflects the light. Since the inclined structure has an inclined surface, light rays perpendicularly emitted to the bottom surface of the first electrode are emitted by the inclined surface of the inclined structure to the surface of the second reflective layer in an inclined manner, and the second reflective layer is further directed toward the sidewall of the epitaxial structure.
In the alternative, the inclined structure of the first reflective layer may take the same or similar structure as the slope structure of the second reflective layer. Meanwhile, the inclined structure can be arranged to be symmetrical about the axial center line where the central position of the first electrode is located.
The application also provides a light-emitting device, which comprises a circuit substrate and at least one light-emitting diode fixed on the surface of the circuit substrate, wherein the light-emitting diode is the light-emitting diode in the scheme.
For a more detailed description of the light emitting diode of the present application, the following examples are provided. It should be noted that the technical features and technical solutions in the following embodiments may be combined with each other on the premise of no conflict.
Example 1
As shown in fig. 1, the present embodiment provides a light emitting diode, which includes a substrate 1, an epitaxial structure 2, a first electrode 3, a first reflective layer 4, and a second reflective layer 5.
The substrate 1 has a substrate front surface and a substrate back surface which are disposed opposite to each other, and an extending direction perpendicular to the substrate front surface is referred to as an axial direction. The epitaxial structure 2 is formed on the substrate front side, and the epitaxial structure 2 includes a first semiconductor layer 21, an active layer 22, and a second semiconductor layer 23 stacked in this order from the substrate front side. The first electrode 3 is located above the second semiconductor layer 23 and is electrically connected to the second semiconductor layer 23. The first reflective layer 4 is disposed between the first electrode 3 and the second semiconductor layer 23. The second reflective layer 5 is disposed between the first semiconductor layer 21 and the substrate 1, and at least a surface of the second reflective layer 5 under the first electrode 3 is configured as a slope structure 51 having an inclined wall surface.
The light emitting diode of the present embodiment includes a second electrode 8 formed on the back surface side of the substrate 1 in conductive connection with the first semiconductor layer 21. The specific conductive connection position between the second electrode 8 and the first semiconductor layer 21 is not shown in the drawings.
The light emitting diode of this embodiment comprises a transparent encapsulation layer 7 covering at least the surface of the epitaxial structure 2. The transparent encapsulation layer 7 may be a multi-layered stacked structure, and may include an antireflection film layer and a protection film layer stacked in sequence, for example. The transparent encapsulation layer 7 may play a role in anti-reflection and protection. The transparent encapsulation layer 7 (particularly, an antireflection film layer) increases the intensity of outgoing light mainly by reducing reflection of light at the interface between the chip and air, thereby improving light extraction efficiency. The transparent encapsulation layer 7 (especially, the protection film layer can provide mechanical protection for the chip, prevent the chip from being exposed in the air for a long time or being mechanically damaged, and improve the stability and reliability of the chip).
It should be noted that, referring to fig. 4, the light emitting diode of the present embodiment may include a substrate 1 and a plurality of epitaxial structures 2 formed on the same substrate 1 and independent of each other.
The light emitting diode of the embodiment has the advantages that the design optimizes the light extraction efficiency and reduces the light loss caused by the shielding of the electrode. Specifically, when the light emitting diode generates light in an operating state, a part of the light is emitted toward the bottom surface side of the first electrode 3. These rays are effectively reflected downwards by the first reflective layer 4 and thus reach the second reflective layer 5. The second reflective layer 5 is particularly designed with a slope-like structure 51 which receives not only the light reflected from the first reflective layer 4, but also further reflects the light by its inclined wall surface design, leading to the sidewall direction of the epitaxial structure 2. The design leads part or all of light possibly blocked by the first electrode 3 to be led out through the side wall of the epitaxial structure 2, thereby obviously reducing the shielding effect of the first electrode 3 on the front light of the light-emitting diode and ensuring the light-emitting brightness and efficiency of the light-emitting diode.
In this embodiment, the first semiconductor layer 21 of the epitaxial structure 2 may be an N-type semiconductor layer, the second semiconductor layer 23 is a P-type semiconductor layer, and the N-type semiconductor layer, the active layer 22, and the P-type semiconductor layer are all made of GaN-based materials. The epitaxial structure 2 may be prepared by chemical vapor deposition.
In the present embodiment, the first reflective layer 4 and the second reflective layer 5 may be DBR reflective structures or OBR reflective structures. DBR (Distributed Bragg Reflector ) and OBR (Organic Bragg Reflector, organic bragg reflector) are two different reflective structures that function to enhance light reflection and improve light extraction efficiency in LED structures. The type of the reflection structure selected can be reasonably determined by a person skilled in the art according to actual requirements and characteristics of the reflection structure.
In this embodiment, as shown in fig. 1 to 3, the projection boundary of the first electrode 3 to the front surface of the first reflective layer 4 may completely coincide with the front surface region boundary of the first reflective layer 4, or the projection boundary of the first electrode 3 to the front surface of the first reflective layer 4 may be located within the front surface region boundary of the first reflective layer 4.
For example, for light emitting diodes with a chip size of 2um or more, referring to fig. 1 and 2, the size of the first electrode 3 may be smaller than the size of the second semiconductor layer 23, that is, the first electrode 3 may not completely cover the second semiconductor layer 23, and the first reflective layer 4 may completely cover the front surface of the second semiconductor layer 23 or cover a part of the front surface of the second semiconductor layer 23, but the front surface area of the first reflective layer 4 at least includes the shielding area of the first electrode 3. For another example, for a light emitting diode with a chip size below 2um, referring to fig. 3, the size of the first electrode 3 may be substantially equal to the size of the second semiconductor layer 23, i.e. the first electrode 3 substantially completely shields the second semiconductor layer 23, and the first reflective layer 4 is disposed to completely cover the front surface of the second semiconductor layer 23 to completely contain the shielding region of the first electrode 3.
In this embodiment, the first reflective layer 4 may be arranged to entirely cover the surface of the second semiconductor layer 23 so that light is guided out from the sides of the epitaxial structure 2.
In this embodiment, as shown in fig. 3, the projection boundary of the first electrode 3 to the front surface of the substrate may exceed the projection boundary of the slope structure 51 to the front surface of the substrate. That is, after the light perpendicularly emitted to the bottom surface of the first electrode 3 is reflected by the first reflecting layer 4, only part of the reflected light is received by the slope structure 51 and reflected to the sidewall direction of the epitaxial structure 2, so that the light loss can be reduced to a certain extent, and the light emitting brightness and the light emitting efficiency can be improved.
In the present embodiment, as shown in fig. 1,2, and 7 to 14, it is preferable to set the projection boundary of the first electrode 3 to the front surface of the substrate not to exceed the projection boundary of the slope-like structure 51 to the front surface of the substrate. In this way, after the light rays vertically emitted to the bottom surface side of the first electrode 3 are reflected by the first reflecting layer 4, the light rays totally reflected back can be received by the slope structure 51 as much as possible and reflected to the side wall direction of the epitaxial structure 2, so as to greatly reduce the light loss and remarkably improve the light-emitting brightness and the light-emitting efficiency.
In the present embodiment, as shown in fig. 7, the slope-like structure 51 may be an asymmetric structure. The inclined wall surface of the slope structure 51 below the first electrode 3 may incline towards the same side so as to reflect most of light to the single side wall of the epitaxial structure 2, and improve the light-emitting brightness of the single side wall.
In this embodiment, as shown in fig. 8 to 14, it is preferable that the central position of the entire slope structure 51 coincides with the central position of the first electrode 3 in the axial direction, the entire slope structure 51 has a symmetrical structure about its own central position, and the central position of the first electrode 3 coincides with the central position of the epitaxial structure 2 in the axial direction, which makes the amounts of light reflected by the slope structure to the side walls on both sides of the epitaxial structure substantially the same, so that the light emission luminance of the side walls on both sides of the epitaxial structure is substantially the same.
In the present embodiment, as shown in fig. 7 to 14, the slope-like structure 51 includes at least one protrusion structure 511, and the protrusion structure 511 is provided with inclined side walls for reflecting light. For example, the slope-like structure 51 shown in fig. 7 to 11 has only one convex structure 511, and the slope-like structure 51 shown in fig. 12 to 14 has a plurality of convex structures 511.
In this embodiment, as shown in fig. 7 to 11, the surface morphology of the inclined side wall of the protrusion structure 511 may be a plane, an arc surface, or a combination of both. The cross-sectional shape of the protruding structures may be triangular (fig. 7), pointed cone (fig. 11), trapezoid (fig. 10), circular arc (fig. 8 and 9), etc.
In this embodiment, the bump structure 511 may be an asymmetric structure. As shown in fig. 7, the convex structure 511 is triangular, but the inclination and the side length of the side walls at the two sides are different, so as to realize the light reflection capability of the two sides with different.
In this embodiment, the bump structure 511 may be a symmetrical structure. As shown in fig. 8 to 11, it is preferable that each of the convex structures 511 has inclined side walls symmetrically disposed about its own center position.
In this embodiment, as shown in fig. 8 to 14, the ramp-like structure 51 includes a plurality of bump structures 511, and the plurality of bump structures 511 are distributed in an array along the back surface of the epitaxial structure 2. The inclined wall surfaces of the plurality of convex structures 511 can receive the light reflected by the first reflective layer 4 at multiple angles as much as possible, so as to reduce the brightness loss.
Meanwhile, in this embodiment, as shown in fig. 8 to 14, the central position of the whole slope structure 51 coincides with the central position of the first electrode 3 in the axial direction, the whole slope structure 51 has a symmetrical structure about its own central position, and the light reflection efficiency can be further improved by matching with the plurality of convex structures 511 arranged in an array, and the light emitting brightness and brightness uniformity of the two sidewalls of the epitaxial structure 2 can be improved.
In this embodiment, the ramp-like structure 51 may include a plurality of raised structures 511 that are identical in structure. As shown in fig. 12, the ramp structure 51 includes a plurality of convex structures 511 having a pointed cone shape. As shown in fig. 13, the slope-like structure 51 includes a plurality of convex structures 511 having a circular arc shape.
In this embodiment, the ramp-like structure 51 may include a plurality of raised structures 511 that differ in structure. As shown in fig. 14, the slope-like structure 51 includes a pointed cone-shaped convex structure 511 and a circular arc-shaped convex structure 511, which are alternately distributed.
It should be noted that, when the slope structure 51 has a bump structure 511 as shown in fig. 8, the area of the second reflective layer 5 corresponding to the bottom surface of the epitaxial structure 2 may be integrally bump to form a bump structure 511 with a relatively large size.
In this embodiment, the range of the difference between the top and the root of the protrusion 511 may be 0.2-1 um, for example, the values of 0.2um, 0.3um, 0.4um, 0.5um, 0.6um, 0.7um, 0.8um, 0.9um, and 1um.
As shown in fig. 16, the present embodiment further provides a light emitting device, which includes a circuit substrate 200 and at least one light emitting diode 100 fixed to a surface of the circuit substrate 200, wherein the light emitting diode 100 is the aforementioned light emitting diode.
Example two
As shown in fig. 5, this embodiment provides a light emitting diode, unlike the first embodiment, the sidewall of the epitaxial structure 2 of this embodiment is provided with a roughened structure 24.
In this embodiment, the epitaxial structure 2 may be provided with inclined sidewalls. The angle β of the sidewall of the epitaxial structure 2 with respect to the back surface of the epitaxial structure 2 may be in the range of 30 ° to 70 °, for example 30 °, 35 °, 40 °,45 °,50 °, 55 °, 60 °, 65 °, 70 °, etc. The epitaxial structure 2 is provided with the inclined side wall, so that the possibility of escaping light from the epitaxial structure 2 is increased, the propagation path of the light in the epitaxial structure 2 is reduced to a certain extent, the absorption of the light by materials is reduced, and the light output efficiency is improved.
In this embodiment, the sidewall of the epitaxial structure 2 is provided with the roughened structure 24, and the height difference range of the roughened structure 24 may be set to 0.1-0.5 um.
Coarsening structure 24 may be a regular patterned structure or an irregular patterned structure. In addition, passivation may be performed after roughening 24 is made. For example, roughened structures 24 may be pyramid-shaped pointed cone structures distributed in an array on the sidewalls of epitaxial structure 2.
In this embodiment, the roughened structure 24 can be used to improve the extraction efficiency of light inside the vertical structure chip. Meanwhile, the internal light extraction efficiency of the mini light emitting diode can be further improved and the light emitting brightness can be improved by matching with the reflection guiding function of the inclined side wall of the epitaxial structure 2 and the slope-shaped structure 51.
In this embodiment, the roughened structure 24 may be disposed on the surface of the second semiconductor layer 23 of the epitaxial structure 2 not covered by the first electrode 3 and the first reflective layer 4, so as to improve the light extraction efficiency of the front portion.
Example III
As shown in fig. 6, this embodiment provides a light emitting diode, which, unlike the first or second embodiment, further includes a lens 6.
In particular, the lens 6 covers the front face and at least part of the side walls of the epitaxial structure 2 for guiding part of the light rays exiting the epitaxial structure 2 in the axial direction.
Here, "partial rays" refer mainly to rays of light of a large angle emerging from the side of the epitaxial structure 2, which deviate significantly from the axial direction, and the emerging rays of light of a large angle are directed as axially as possible by means of the lens 6. The term "guide axial direction" as used herein does not necessarily mean that the guide axial direction is completely coincident with the axial direction, but means that the angle between the light emission direction and the axial direction is reduced, and the guide axial direction may be coincident with the axial direction or may have a certain angle.
Example IV
As shown in fig. 15, this embodiment provides a light emitting diode, and unlike the first, second or third embodiments, the first reflective layer 4 of the light emitting diode of this embodiment is provided with an inclined structure 41.
Specifically, the inclined structure 41 of the first reflecting layer 4 may take the same or similar structure as the slope structure 51 on the second reflecting layer 5.
In the present embodiment, as shown in fig. 15, at least the back surface of the first reflection layer 4 corresponding to the lower side of the first electrode 3 is provided with an inclined structure 41. When light in the epitaxial structure 2 is directed vertically or obliquely below the first electrode 3, it is directed to the inclined structure 41 of the first reflective layer 4, and the inclined structure 41 reflects the light. Since the inclined structure 41 has an inclined surface, light perpendicularly directed to the bottom surface of the first electrode 3 is directed by the inclined surface of the inclined structure 41 in an inclined manner to the surface of the second reflective layer 5, and the second reflective layer 5 is further directed toward the sidewall of the epitaxial structure 2.
In the present embodiment, the inclined structure 41 is preferably provided in a symmetrical structure about the axial center line where the center position of the first electrode 3 is located.
The above description is only a few embodiments of the present application and is not intended to limit the present application, and various modifications and variations will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (20)
1. A light emitting diode, comprising:
A substrate (1) having a substrate front surface and a substrate back surface which are disposed opposite to each other, an extending direction perpendicular to the substrate front surface being referred to as an axial direction;
An epitaxial structure (2) formed on one side of the front surface of the substrate, wherein the epitaxial structure (2) comprises a first semiconductor layer (21), an active layer (22) and a second semiconductor layer (23) which are sequentially stacked from the front surface of the substrate;
a first electrode (3) located above the second semiconductor layer (23) and electrically connected to the second semiconductor layer (23);
a first reflective layer (4) provided between the first electrode (3) and the second semiconductor layer (23);
And a second reflection layer (5) provided between the first semiconductor layer (21) and the substrate (1), wherein at least the surface of the second reflection layer (5) corresponding to the lower part of the first electrode (3) is provided with a slope-like structure (51) having an inclined wall surface.
2. A light emitting diode according to claim 1, characterized in that the epitaxial structure (2) has inclined side walls.
3. A light emitting diode according to claim 2, characterized in that the angle of the side walls of the epitaxial structure (2) with respect to the back side of the epitaxial structure (2) is in the range of 30 ° -70 °.
4. A light emitting diode according to claim 2, characterized in that the side walls of the epitaxial structure (2) are provided with roughened structures (24).
5. The led of claim 4, wherein said roughened structures (24) have a height difference in the range of 0.1-0.5 um.
6. A light emitting diode according to claim 1, further comprising a lens (6) covering the front face and at least part of the side walls of the epitaxial structure (2) for guiding part of the light emitted in the epitaxial structure (2) in the axial direction.
7. A light emitting diode according to claim 1, characterized by comprising a transparent encapsulation layer (7) covering at least the surface of the epitaxial structure (2).
8. A light emitting diode according to claim 1, characterized by comprising a second electrode (8) formed on the back side of the substrate (1) in electrically conductive connection with the first semiconductor layer (21).
9. A light emitting diode according to claim 1, characterized in that the first reflective layer (4) completely covers the surface of the second semiconductor layer (23).
10. A light emitting diode according to claim 1, characterized in that at least the back side of the corresponding first reflective layer (4) below the first electrode (3) is provided with an inclined structure (41).
11. The light emitting diode according to claim 10, characterized in that the inclined structure (41) is symmetrical about an axial center line where the central position of the first electrode (3) is located.
12. A light emitting diode according to claim 1, characterized in that the projection boundary of the first electrode (3) towards the front side of the substrate does not exceed the projection boundary of the ramp structure (51) towards the front side of the substrate.
13. A light emitting diode according to claim 1, characterized in that the central position of the whole of the ramp-like structure (51) coincides with the central position of the first electrode (3) in the axial direction, the whole of the ramp-like structure (51) being symmetrical about its own central position.
14. A light emitting diode according to claim 13, characterized in that the central position of the first electrode (3) coincides axially with the central position of the epitaxial structure (2).
15. The light emitting diode according to any one of claims 1 to 14, characterized in that the ramp-like structure (51) comprises at least one protruding structure (511), the protruding structure (511) being provided with inclined side walls.
16. The led of claim 15, wherein said raised structures (511) have sloped sidewalls symmetrically disposed about their own center location.
17. The led of claim 15, wherein the sloped sidewall has a planar surface, an arcuate surface, or a combination thereof.
18. The light emitting diode according to claim 15, wherein the ramp-like structure (51) comprises a plurality of the raised structures (511), the plurality of raised structures (511) being distributed in an array along the back side of the epitaxial structure (2).
19. The led of claim 15, wherein the height difference between the tips and the roots of said bump structures (511) is in the range of 0.2-1 um.
20. A light-emitting device comprising a circuit substrate and at least one light-emitting diode fixed to a surface of the circuit substrate, the light-emitting diode comprising the light-emitting diode according to any one of claims 1 to 19.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102709420A (en) * | 2012-06-21 | 2012-10-03 | 安徽三安光电有限公司 | A gallium nitride based light emitting diode |
| CN109768138A (en) * | 2018-12-28 | 2019-05-17 | 华灿光电（浙江）有限公司 | A kind of light-emitting diode chip for backlight unit and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR20120078385A (en) * | 2010-12-31 | 2012-07-10 | 갤럭시아포토닉스 주식회사 | Light emitting diode having reflective body of substrate and its light emitting diode package |
| CN203250787U (en) * | 2013-04-19 | 2013-10-23 | 天津三安光电有限公司 | Light-emitting diode with scattering structure and lighting system |
| CN214588889U (en) * | 2021-04-14 | 2021-11-02 | 安徽三安光电有限公司 | Light-emitting diode |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102709420A (en) * | 2012-06-21 | 2012-10-03 | 安徽三安光电有限公司 | A gallium nitride based light emitting diode |
| CN109768138A (en) * | 2018-12-28 | 2019-05-17 | 华灿光电（浙江）有限公司 | A kind of light-emitting diode chip for backlight unit and preparation method thereof |
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