Light-emitting element and manufacturing method thereof, light-emitting diode and display device

Abstract

A light-emitting device includes a plurality of light-emitting diodes, a support structure and a first insulating layer, the first insulating layer includes a first portion and a second portion, the first portion at least covers a sidewall of the light-emitting diodes, and the second portion at least covers a sidewall of the light-emitting diodes. The second portion extends downward from the first portion and is connected to the support structure to form a bridging structure between the light emitting diode and the support structure. As mentioned above, the bridging structure is a structure parallel to the vertical direction of the side wall of the light-emitting diode, and connects and supports the light-emitting diode in the vertical direction. When the light-emitting diode is grabbed in the mass transfer process, the bridging structure is broken, and the broken surface of the bridging structure is the cross section of the second part of the first insulating layer, namely the surface parallel to the direction of the light-emitting surface of the light-emitting diode. Therefore, the side walls of the transferred light-emitting diodes are kept flush, the arrangement distance of the light-emitting diodes can be reduced, and meanwhile the mass transfer yield of the light-emitting diodes can be improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor devices, and in particular to a light-emitting element and a manufacturing method thereof, a light-emitting diode and a display device. Background Art

[0002] Micro Light Emitting Diode (Micro-LED) has the advantages of self-luminescence, high efficiency, low power consumption, high brightness, high stability, ultra-high resolution and color saturation, fast response speed and long life. It has been applied in display, optical communication, indoor positioning, biology and medical fields, and has a clear and promising market prospect.

[0003] There are still many technical challenges to be overcome for Micro-LED, one of which is how to improve the yield of mass transfer. In order to match different transfer schemes and chip applications, some special chip structure designs have been derived:

[0004] 1. Chip on wafer (COW), core transfer method: laser lift-off layer is epitaxial.

[0005] 2. Freestanding-Chip on carrier (FCOC), core transfer method: the laser peeling layer is an adhesive layer such as a glue layer.

[0006] 3. Tether-type chip on carrier (TCOC), core transfer method: stamp-type chip pick-up and placement (Pick&Place) technology.

[0007] There are many problems with the above technology, which affect the arrangement or yield of the chips after transfer. For example, when the TCOC anchor chain structure is transferred, due to design problems, the anchor chain often remains on the chip. When the spacing of the core particles is too small, it affects the actual use. The TCOC design must have a sacrificial layer process design. If the sacrificial layer is too thick, the process difficulty increases. If the sacrificial layer is too thin, the difficulty of mass transfer increases. The above-mentioned abnormal phenomenon of anchor chain residue or sacrificial layer thickness problem affects the yield of Micro-LED mass transfer, and then affects the yield and reliability of subsequent products. Summary of the invention

[0008] In view of the above-mentioned problems and defects in the mass transfer of Micro-LEDs in the prior art, the present application provides a light-emitting element and a manufacturing method thereof, a light-emitting diode and a display device to improve the mass transfer yield and appearance yield of light-emitting diodes.

[0009] To achieve the above-mentioned object and other related objects, the present invention provides a light-emitting element, which includes:

[0010] A plurality of light-emitting diodes, each of which comprises at least a semiconductor epitaxial stack, wherein the semiconductor epitaxial stack comprises a first semiconductor layer, an active layer and a second semiconductor layer sequentially stacked along a first direction;

[0011] A supporting structure, located below the light emitting diode, supporting the light emitting diode;

[0012] The first insulating layer includes a first portion and a second portion, wherein the first portion at least covers the side wall of the light-emitting diode, and the second portion extends downward from the first portion and is connected to the supporting structure to form a bridge structure between the light-emitting diode and the supporting structure.

[0013] Another aspect of the present application provides a method for manufacturing a light emitting element, comprising the following steps:

[0014] providing a substrate;

[0015] forming a bonding layer over the substrate;

[0016] Bonding a plurality of light emitting diodes on the bonding layer, wherein the light emitting diodes at least include a semiconductor epitaxial stack, and the semiconductor epitaxial stack includes a first semiconductor layer, an active layer, and a second semiconductor layer sequentially stacked along a first direction;

[0017] Etching the bonding layer so that the side wall of the bonding layer is flush with the side wall of the light emitting diode;

[0018] forming a first insulating layer from one side of the light emitting diode, the first insulating layer comprising a first portion and a second portion, wherein the first portion at least covers a side wall of the light emitting diode, and the second portion extends downward from the first portion and is connected to the support structure to form a bridge structure between the light emitting diode and the support structure;

[0019] The bonding layer is removed.

[0020] Another aspect of the present invention provides a light-emitting diode, which is a core particle obtained by transfer separation from the light-emitting element described in the present application, and the side wall of the core particle has the residual bridge structure.

[0021] Another aspect of the present invention provides a display device, which includes a circuit substrate and a plurality of light-emitting bodies fixed on the circuit substrate, wherein the light-emitting bodies include light-emitting diodes transferred in batches from the light-emitting elements described in the present application.

[0022] As described above, the light emitting element, light emitting diode and display device provided by the present invention have at least the following beneficial technical effects:

[0023] The light-emitting element of the present invention includes a plurality of light-emitting diodes, a support structure and a first insulating layer, wherein the first insulating layer includes a first part and a second part, wherein the first part at least covers the side wall of the light-emitting diode, and the second part extends downward from the first part and is connected to the support structure to form a bridge structure between the light-emitting diode and the support structure. As described above, the bridge structure between the light-emitting diode and the support structure is a part of the first insulating layer extending downward from the side wall of the light-emitting diode, that is, the bridge structure is a structure in the vertical direction parallel to the side wall of the light-emitting diode, and connects and supports the light-emitting diode in the vertical direction. When the light-emitting diode is captured during the mass transfer process, the bridge structure breaks, and its fracture surface is the cross-section of the second part of the first insulating layer, that is, the surface parallel to the light-emitting surface of the light-emitting diode. Therefore, the side wall of the light-emitting diode after the transfer remains flush, which is conducive to reducing the arrangement spacing of the light-emitting diode, and at the same time can improve the mass transfer yield of the light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The diagram shows a top view of the structure of a light emitting element in the prior art.

[0025] Figure 2 Shown is a schematic top view of the structure of a light emitting element provided in the first embodiment of the present invention.

[0026] Figure 3 Display as Figure 2 Schematic diagram of the cross-sectional structure in the AA direction.

[0027] Figure 4 Display as Figure 2 Schematic diagram of the cross-sectional structure in the BB direction.

[0028] Figure 5 Another alternative embodiment is shown along Figure 2 Schematic diagram of the cross-sectional structure in the same direction as BB.

[0029] Figure 6 Display as Figure 5 A partial enlarged schematic diagram of the bridge structure.

[0030] Figure 7 It is shown that the bridge structure breaks and then Figure 1 Schematic diagram of the structure of the light-emitting diode picked up.

[0031] Figure 8 Shown is a schematic diagram of the top view structure of the light emitting element provided in the second embodiment of the present application.

[0032] Fig. 9 Display as Figure 8 Schematic diagram of the cross-sectional structure in the AA direction.

[0033] Fig.10 Shown is a schematic diagram of the top view structure of the light-emitting element provided in Example 3 of the present application.

[0034] Fig.11 Shown is a schematic diagram of the top view structure of the light-emitting element provided in Example 4 of the present application.

[0035] Fig.12 Schematic diagram of the top view of the light emitting element provided in Example 5 of the present application.

[0036] Figures 13 to 15 A schematic diagram showing the structure formed by each step of the method for manufacturing a light-emitting element provided in Example 6 of the present application.

[0037] Fig.16 Shown is a schematic diagram of the structure of a light-emitting element provided in Embodiment 7 of the present invention.

[0038] Fig.17 Shown is a schematic diagram of the structure of a light-emitting element provided in Embodiment 8 of the present invention.

[0039] Fig.18 Shown is a schematic diagram of the structure of a display device provided in Embodiment 9 of the present invention.

[0040] Reference numerals

[0041] 10. Micro-LED; 11. Bridge arm.

[0042] 100, light-emitting element; 101, supporting structure; 102, first insulating layer; 1021, first part; 1022, second part; 1023, third part; 103, bonding layer; 200, light-emitting diode; 201, semiconductor epitaxial stack; 2011, first semiconductor layer; 2012, active layer; 2013, second semiconductor layer; 204, first table; 205, second table; 206, light-emitting surface; 2051, first electrode; 2052, second electrode; 2053, first contact electrode; 2054, second contact electrode; 202, second insulating layer.

[0043] 300, display device; 301, light emitting body; 302, circuit substrate. DETAILED DESCRIPTION

[0044] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0045] It should be noted that the illustrations provided in the embodiments of the present application only illustrate the basic concept of the present invention in a schematic manner. Although the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation, the form, quantity, positional relationship and proportion of each component in actual implementation can be changed at will under the premise of realizing the technical solution of the present invention, and the component layout form may also be more complicated.

[0046] like Figure 1 As shown, in the prior art, during mass transfer, a bridge arm 11 is formed at the two opposite side walls of Micro-LED 10, and the bridge arm 11 is usually an insulating material layer tightly connected to the side wall of Micro-LED 10. When transferring Micro-LED 10, it is necessary to grab Micro-LED 10, and the bridge arm 11 is broken to achieve grabbing. However, due to the above-mentioned characteristics of the bridge arm 11, it cannot be guaranteed that the breaking positions of different bridge arms are fixed when breaking; in addition, the cross-section of the bridge arm 11 after breaking is usually also displayed as a stamp-like torn cross-section rather than a flat cross-section. This will affect the appearance of Micro-LED 10, and then affect the yield of mass transfer, and therefore also affect the yield and reliability of subsequent devices. In order to solve this problem, the present invention provides a light-emitting element and a light-emitting diode. It is now described in detail through the following specific embodiments.

[0047] In order to solve the above-mentioned defects and shortcomings of the prior art, the present invention provides a light-emitting element, which includes:

[0048] A plurality of light-emitting diodes, each of which comprises at least a semiconductor epitaxial stack, wherein the semiconductor epitaxial stack comprises a first semiconductor layer, an active layer and a second semiconductor layer sequentially stacked along a first direction;

[0049] A supporting structure, located below the light emitting diode, supporting the light emitting diode;

[0050] The first insulating layer includes a first portion and a second portion, wherein the first portion at least covers the side wall of the light-emitting diode, and the second portion extends downward from the first portion and is connected to the supporting structure to form a bridge structure between the light-emitting diode and the supporting structure.

[0051] The bridge structure between the light-emitting diode and the support structure is a part of the first insulating layer extending downward from the side wall of the light-emitting diode, that is, the bridge structure is a structure in the vertical direction parallel to the side wall of the light-emitting diode, connecting and supporting the light-emitting diode in the vertical direction. When the light-emitting diode is grabbed during the mass transfer process, the bridge structure breaks, and its fracture surface is the cross-section of the second part of the first insulating layer, that is, the surface parallel to the light-emitting surface of the light-emitting diode. Therefore, the side wall of the light-emitting diode after transfer remains flush, which is conducive to reducing the arrangement spacing of the light-emitting diode, and at the same time can improve the mass transfer yield of the light-emitting diode.

[0052] Optionally, the thickness of the first insulating layer is greater than or equal to 0.1 μm.

[0053] The thickness of the first insulating layer can ensure that the first insulating layer protects the semiconductor stack, that is, the light-emitting diode, so that the light-emitting diode is protected from damage by external moisture and impurities; on the other hand, it can ensure that when the light-emitting diodes are transferred in batches, they can be broken at the bridge structure to ensure the transfer yield.

[0054] Optionally, a minimum distance between the light emitting diode and the supporting structure is d2, and 0.1 μm≤d2≤50 μm.

[0055] The minimum distance between the light-emitting diode and the supporting structure is set to avoid damage to the light-emitting diode caused by contact with the supporting structure on the one hand, and to minimize the height of the bridge structure on the other hand to ensure its mechanical support strength and support stability.

[0056] Optionally, the bridging structure further comprises a third portion extending on the surface of the supporting structure, wherein the third portion is connected to the second portion.

[0057] The third part can further increase the mechanical support stability of the bridge structure.

[0058] Optionally, the second portions are formed in pairs at two opposite side walls of the light emitting diode, and at least one pair of the second portions is provided at two opposite side walls of the light emitting diode.

[0059] Optionally, the bridging structures are symmetrically distributed on the side walls of the light emitting diode; or asymmetrically distributed on the side walls of the light emitting diode.

[0060] The formation position and distribution characteristics of the bridge structure increase the design diversity and applicability of the bridge structure, and can be flexibly designed according to the actual size of the light-emitting diode, application requirements, etc.

[0061] Optionally, a width of the second portion is smaller than a width of a side wall of the light emitting diode where the second portion is located.

[0062] The width of the second part is relatively small, so that the second part can be easily broken when a large number of light-emitting diodes are transferred, thereby ensuring the transfer yield.

[0063] Optionally, a width of the second portion is 1 / 10 to 1 / 4 of a width of a side wall of the light emitting diode where the second portion is located.

[0064] The width of the second part can be flexibly designed according to the actual size of the light-emitting diode, as well as the mechanical support and fracture requirements of mass transfer, to ensure the mechanical support stability of the second part as a bridging structure, while ensuring that it is easier to break during mass transfer.

[0065] Optionally, the longitudinal cross-section of the second part is a trapezoidal structure, wherein the short side a of the trapezoidal structure is close to the boundary of the first part, the long side b of the trapezoidal structure is opposite and parallel to the short side a, and the waist c of the trapezoidal structure is connected to the short side a and the long side b, wherein b>a, and a:b:c=(0.1~1):(1~5):(1~2).

[0066] Optionally, the angle between the short side a and the waist c is between 120° and 150°.

[0067] The longitudinal section of the second part is formed into a trapezoid, and the short side of the trapezoid is located on the side connected to the first part, which is conducive to breaking during large-scale transfer. The long side is connected to the third part on the supporting structure, which can increase the stability of the second part as a bridging structure.

[0068] Optionally, a side of the first semiconductor layer away from the active layer is a light emitting surface of the light emitting diode, and on a side opposite to the light emitting surface, the semiconductor stack is formed with a first mesa and a second mesa, the second mesa is formed by the first semiconductor layer and is located around the first mesa, and the first portion of the first insulating layer extends from the side wall of the light emitting diode to cover at least a portion of the light emitting surface.

[0069] The first insulating layer can extend from the side wall of the semiconductor stack to the light emitting surface, thereby increasing the adhesion between the first insulating layer and the semiconductor stack, increasing its stability, and increasing the protection of the light emitting diode.

[0070] Optionally, the surface area of ​​the light emitting surface covered by the first part is S1, and the surface area of ​​the light emitting surface is S2, wherein: S1≥0.1*S2.

[0071] The coverage of the first part does not exceed the range of the light-emitting surface corresponding to the first table, thereby minimizing the reflection or refraction of the light emitted from the light-emitting surface and ensuring the light-emitting effect of the light-emitting diode. When S1=S2, that is, the first part completely covers the light-emitting surface, the protection of the light-emitting diode can be increased. At this time, the first insulating layer can be made of a material layer with good light transmittance, or a material layer with anti-reflection effect.

[0072] Optionally, a second insulating layer is further included, wherein the second insulating layer covers surfaces of the first mesa and the second mesa, and the first portion of the first insulating layer covers a side wall of the second insulating layer.

[0073] The first part of the first insulating layer covers the side wall of the second insulating layer, so that the second insulating layer and the first insulating layer form a continuous structure, thereby increasing the protection effect on the light emitting diode.

[0074] Optionally, the material of the first insulating layer and / or the second insulating layer is SiO2, SiN x 、SiO x N y , a combination of one or more of Ti2O3 and Al2O3.

[0075] The first insulating layer and the second insulating layer can be made of the same material or different materials, and can be selected according to actual needs.

[0076] Optionally, the side length or height of the light emitting diode is between 2 μm and 100 μm.

[0077] The provision of the first insulating layer can make the size of the light emitting diode as small as possible.

[0078] Another aspect of the present application provides a method for manufacturing a light emitting element, comprising the following steps:

[0079] providing a substrate;

[0080] forming a bonding layer over the substrate;

[0081] Bonding a plurality of light emitting diodes on the bonding layer, wherein the light emitting diodes at least include a semiconductor epitaxial stack, and the semiconductor epitaxial stack includes a first semiconductor layer, an active layer, and a second semiconductor layer sequentially stacked along a first direction;

[0082] Etching the bonding layer so that the side wall of the bonding layer is flush with the side wall of the light emitting diode;

[0083] forming a first insulating layer from one side of the light emitting diode, the first insulating layer comprising a first portion and a second portion, wherein the first portion at least covers a side wall of the light emitting diode, and the second portion extends downward from the first portion and is connected to the support structure to form a bridge structure between the light emitting diode and the support structure;

[0084] The bonding layer is removed.

[0085] There is no need to set a sacrificial layer or similar structure between the light-emitting diode and the supporting structure, which saves process steps, helps save costs, and reduces the complexity and difficulty of the process.

[0086] Optionally, a minimum thickness of the bonding layer is greater than or equal to 0.1 μm and less than or equal to 50 μm.

[0087] The thickness of the bonding layer can ensure the minimum distance between the light-emitting diode and the supporting structure, which is conducive to forming a stable and easy-to-break bridge structure.

[0088] Another aspect of the present invention provides a light-emitting diode, which is obtained by transfer separation from the light-emitting element described in the present application, and has a first portion of a first insulating layer and a remaining second portion at a side wall of the light-emitting diode.

[0089] Even if the above-mentioned residual second portion exists in the light-emitting diode after the transfer, the second portion is located in the thickness direction of the light-emitting diode, so the side wall of the light-emitting diode is flush as a whole, which is beneficial to the subsequent arrangement.

[0090] Optionally, the height of the second portion remaining on the side wall of the light-emitting diode is d4, and the height of the light-emitting diode exceeding the first portion is d1, wherein

[0091] The height of the remaining second portion is less than the height of the first table of the light-emitting diode or less than the thickness of the electrode structure of the light-emitting diode, so it will not exceed the light-emitting diode in the thickness direction of the light-emitting diode, and thus will not affect the transfer and arrangement of the light-emitting diode. At the same time, the missing second portion is retained at the side wall of the light-emitting diode, so that the continuity of the first insulating layer and the second insulating layer is not destroyed, and the protection of the light-emitting diode by the two is guaranteed.

[0092] Another aspect of the present invention provides a display device, which includes a circuit substrate and a plurality of light-emitting bodies fixed on the circuit substrate, wherein the light-emitting bodies include light-emitting diodes transferred in batches from the light-emitting elements described in the present application.

[0093] The display device has the above-mentioned light-emitting diode of the present application, and therefore has a higher yield rate during the transfer process, thereby ensuring the display effect of the display device.

[0094] Embodiment 1

[0095] This embodiment provides a light emitting element, such as Figure 2 As shown, the light emitting element 100 of this embodiment includes a plurality of light emitting diodes 200, a supporting structure 101 and a first insulating layer 102. Figure 2 and Figure 3 As shown, the light emitting diode 200 is connected by the first insulating layer 102 and supported on the support structure 101. The support structure 101 of the present application includes a substrate, and in an optional embodiment, the substrate can be any suitable substrate capable of playing a supporting role, such as a sapphire substrate, a glass substrate, a ceramic substrate, etc.

[0096] like Figure 3 As shown, the light emitting diode 200 in this embodiment is a micro light emitting diode 200, which refers to a micron-sized light emitting diode 200. Since the size of the micro light emitting diode 200 is small, the micro light emitting diode 200 in this embodiment mainly refers to a light emitting diode 200 with a size (including length, width or height) ranging from greater than or equal to 2 μm to less than 5 μm, from greater than or equal to 5 μm to less than 10 μm, from greater than or equal to 10 μm to less than 20 μm, from greater than or equal to 20 μm to less than 50 μm or from greater than or equal to 50 μm to less than or equal to 100 μm. The above-mentioned several are generally understood to be greater than or equal to 1.

[0097] Also refer to Figure 3 The light emitting diode 200 at least comprises a semiconductor epitaxial stack 201, which comprises a first semiconductor layer 2011, an active layer 2012 and a second semiconductor layer 2013 stacked in sequence along a first direction (i.e., the Z direction in the figure). In this embodiment, the semiconductor epitaxial stack 201 is formed into a mesa structure, specifically, comprising a first mesa 204 and a second mesa 205, wherein the first mesa 204 is formed by the first semiconductor layer 2011 exposed by the depression of the semiconductor epitaxial stack 201; the second mesa 205 is formed by the stacked first semiconductor layer 2011, the active layer 2012 and the second semiconductor layer 2013. The first mesa 204 is the light radiation area of ​​the light emitting diode 200, and the side of the first semiconductor layer 2011 away from the active layer 2012 is the light emitting surface 206 of the light emitting diode 200. In order to improve the light extraction efficiency of the light emitting diode 200 , the surface of the first semiconductor layer 2011 on the light extraction surface 206 side may be roughened to form a roughened structure.

[0098] In an alternative embodiment, the first semiconductor layer 2011 may be composed of a III-V group or a II-VI group compound semiconductor and may be doped with a first dopant. The first semiconductor layer 2011 may be composed of a compound semiconductor having a chemical formula of In x1 Al y1 Ga 1-x1-y1 N (0≤x1≤1, 0≤y1≤1, 0≤x1+y1≤1) semiconductor material, such as GaN, AlGaN, InGaN, InAlGaN, etc., or a material selected from AlGaAs, GaP, GaAs, GaAsP and AlGaInP. In addition, the above-mentioned 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 2011 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 2011 doped with the first dopant is a p-type semiconductor layer.

[0099] like Figure 3 As shown, the active layer 2012 is arranged between the first semiconductor layer 2011 and the second semiconductor layer 2013. The active layer 2012 is a region for providing light radiation for electron and hole recombination. Different materials can be selected according to different luminous wavelengths. The active layer 2012 can be a periodic structure of a single quantum well or multiple quantum wells. The active layer 2012 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 material in the active layer 2012, it is expected to radiate light of different wavelengths.

[0100] The second semiconductor layer 2013 is formed on the active layer 2012 and may be composed of a group III-V or group II-VI compound semiconductor. The second semiconductor layer 2013 may be doped with a second dopant. The second semiconductor layer 2013 may be composed of a compound semiconductor having a chemical formula In x2 Al y2 G a1-x2-y2N (0≤x2≤1, 0≤y2≤1, 0≤x2+y2≤1) semiconductor material, or a material 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 2013 doped with the second dopant is a p-type semiconductor layer. The second dopant may 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 2013 doped with the second dopant is an n-type semiconductor layer. When the first semiconductor layer 2011 is an n-type semiconductor layer, the second semiconductor layer 2013 is a p-type semiconductor layer; conversely, when the first semiconductor layer 2011 is a p-type semiconductor layer, the second semiconductor layer 2013 is an n-type semiconductor layer.

[0101] It is understandable that the semiconductor epitaxial stack 201 may also include other layer materials, such as a current spreading layer, a window layer or an ohmic contact layer, etc., which are arranged as different multilayers according to different doping concentrations or component contents. The epitaxial stack structure can be formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), epitaxial growth (Epitaxy Growth Technology) and atomic beam deposition (ALD). In this embodiment, the semiconductor epitaxial stack 201 is preferably composed of AlGaInP-based materials, and the semiconductor epitaxial stack 201 radiates red light. However, the present invention is not limited to red light micro-LEDs, and the present invention is also applicable to blue-green light micro-LEDs.

[0102] Reference Figure 2 , Figure 3 and Figure 4, the first insulating layer 102 connects the light-emitting diode 200 and the support structure 101, and supports the light-emitting diode 200. The first insulating layer 102 covers at least the sidewall portion of the light-emitting diode 200, and extends downward along the sidewall of the light-emitting diode 200 to the support structure 101, forming a continuous structure on the surface of the support structure 101 to support a plurality of light-emitting diodes 200. For ease of description, the portion of the first insulating layer 102 covering the sidewall of the light-emitting diode 200 is defined as a first portion 1021, the portion extending downward from the first portion 1021 to the support structure 101 is defined as a second portion 1022, and the first insulating layer 102 extending from the first portion 1021 on the support structure 101 between adjacent light-emitting diodes 200 is defined as a third portion 1023. The second portion 1022 and the third portion 1023 form a bridge structure between a plurality of light-emitting diodes 200 and the support structure 101. Figure 2 As shown, in this embodiment, the second parts 1022 are formed in pairs at two opposite side walls of the light emitting diode 200, and the two opposite side walls of the light emitting diode 200 have at least one pair of second parts 1022. The third part 1023 can further increase the mechanical support stability of the bridge structure.

[0103] like Figure 2 As shown, in this embodiment, the first portion 1021 of the first insulating layer 102 extends from the side wall of the light emitting diode 200 to cover part of the light emitting surface 206, and the surface area of ​​the light emitting surface 206 covered by the first portion 1021 is defined as S1, and the surface area of ​​the light emitting surface 206 is defined as S2, wherein S1 and S2 satisfy: S1 ≥ 0.1 * S2, and further, in this embodiment, the above S1 is less than S2. That is, the first portion 1021 extends from the side wall of the light emitting diode 200 to cover the edge of the light emitting surface 206, and does not completely cover the light emitting surface 206.

[0104] Also refer to Figure 3 The second portion 1022 extends from the first portion 1021 to the surface of the support structure 101, forming a bridge structure between the light emitting diode 200 and the support structure 101. The bridge structure enables the light emitting diode 200 to be located above the support structure 101 and spaced apart from the support structure 101. Figure 3As shown, there is a gap between the light-emitting diode 200 and the support structure 101. Further, there is a minimum distance d2 between the light-emitting diode 200 and the surface of the support structure 101, and 0.1μm≤d2≤50μm, further, 5μm≤d2≤30μm, 10μm≤d2≤20μm. The limitation of the minimum distance allows a gap to be provided between the light-emitting diode 200 and the support structure 101, which can prevent the light-emitting diode 200 from contacting with the support structure 101 and cause damage, and on the other hand, minimize the height of the bridge structure to ensure its mechanical support strength and support stability.

[0105] like Figure 4 As shown, in this embodiment, the width of the second portion 1022 is smaller than the width of the side wall of the light emitting diode 200 where the second portion 1022 is located. Figure 4 As shown, the width referred to here is the span of the structure in the X direction in the figure. Further, the width of the side wall of the light-emitting diode 200 where the second part 1022 is located is defined as W1, and the width of the second part 1022 is defined as W2, W2 = (1 / 10 ~ 1 / 4) W1. For example, the width of the second part 1022 can be 0.2μm≤W2≤10μm, and further, 1μm≤W2≤5μm, for example, W2 can be 0.5μm, 2μm, 3μm, 4μm, 6μm, 8μm, etc. As described above, the width of the second part 1022 is set to be smaller than, or even much smaller than, the width of the side wall of the light-emitting diode 200 where it is located, to ensure that the second part 1022 can be easily broken when the light-emitting diode 200 is transferred in large quantities, thereby ensuring the transfer yield. Furthermore, the width of the second portion 1022 can be flexibly designed according to the actual size of the LED 200 and the mechanical support and fracture requirements of mass transfer, thereby ensuring the mechanical support stability of the second portion 1022 as a bridging structure and ensuring that it is easier to fracture during mass transfer.

[0106] In an optional embodiment, if Figure 5 and Figure 6As shown, the longitudinal cross-section of the second part 1022 is a trapezoidal structure, that is, the surface shape of the second part 1022 in the height direction is a trapezoidal structure. The boundary close to the first part 1021 is the short side a of the trapezoidal structure, the long side b of the trapezoidal structure is opposite and parallel to the short side a, the waist c of the trapezoidal structure is connected to the short side a and the long side b, and the height of the trapezoidal structure is h, wherein b>a, and a:b:c=(0.1~1):(1~5):(1~2); further, a:b:c=1:2:(1~2), the height h of the trapezoidal structure is equal to or slightly greater than the minimum distance d2 between the light-emitting diode 200 and the support structure 101, and when h is slightly greater than d2, h is equal to the sum of d2 and the height of the second table 205. The angle between the short side a and the waist c is between 120° and 150°. As described above, the longitudinal section of the second part 1022 is formed into a trapezoid, and the short side of the trapezoid is located on the side connected to the first part 1021, which is conducive to breaking during large-scale transfer. The long side is connected to the third part 1023 on the support structure 101, which can increase the stability of the second part 1022 as a bridging structure.

[0107] In an optional embodiment, the material of the first insulating layer 102 is SiO2, SiN x 、SiO x N y , Ti2O3 and Al2O3, and further, the first insulating layer 102 is a material layer with better light transmittance, such as SiO2 layer. The thickness of the first insulating layer 102 is greater than or equal to 0.1 μm. Figure 3 As shown, the first insulating layer 102 has a covering thickness d3 ≥ 0.1 μm on the side wall of the light-emitting diode 200, for example, further, between 0.5 μm and 5 μm, further, between 2 μm and 3 μm. This thickness can ensure that the first portion 1021 covering the side wall of the light-emitting diode and at least part of the light-emitting surface 206 can effectively prevent damage to the light-emitting diode 200 caused by external water vapor, impurities, etc.; on the other hand, it can ensure the strength of the second portion 1022 as a bridge structure, and at the same time ensure that it can be easily broken during the transfer process.

[0108] In an optional embodiment, refer again to Figure 3A second insulating layer 202 is also formed on the side of the light emitting diode 200 opposite to the light emitting surface 206. The second insulating layer 202 covers the surfaces of the first table 204 and the second table 205, and forms a continuous structure with the first part 1021 of the first insulating layer 102 at the side wall of the first table 204. The first part 1021 of the first insulating layer 102 and the second insulating layer 202 jointly protect the light emitting diode 200 from damage by external water vapor, impurities, etc. Optionally, the second insulating layer 202 can be a layer of the same material as the first insulating layer 102, or a layer of a different material. In this embodiment, the second insulating layer 202 is preferably formed as a layer of material with a good reflective effect, so as to reflect as much as possible the light radiated by the semiconductor epitaxial stack 201 to the light emitting surface 206 side for emission, thereby improving the light emitting effect of the light emitting diode 200. Optionally, the second insulating layer 202 is a Bragg reflector (DBR) structure, which is formed by alternately stacking two insulating dielectric layer materials with different refractive indices, such as SiO2, SiN x In an optional embodiment, the second insulating layer 202 may also cover the sidewalls of the light emitting diode 200 . In this case, the first insulating layer 102 covers the second insulating layer 202 .

[0109] After the light emitting diode 200 is picked up from the light emitting element 100 of this embodiment so that the second portion 1022 of the first insulating layer 102 is broken, the following is obtained: Figure 7 The light emitting diode 200 shown has a side wall consisting of the first portion 1021 of the first insulating layer 102 and a small amount of the remaining second portion 1022. The side wall is flat as a whole, which is beneficial to the subsequent arrangement of the light emitting diodes 200 and to improving the transfer yield.

[0110] Embodiment 2

[0111] This embodiment also provides a light emitting element. The light emitting element 100 of this embodiment includes a plurality of light emitting diodes 200, a support structure 101 and a first insulating layer 102. Figure 8 and Fig. 9 As shown, the light emitting diode 200 is connected by the first insulating layer 102 and supported on the supporting structure 101. The same points as the first embodiment are not repeated here, and the difference is that:

[0112] like Figure 8 and Fig. 9As shown, in the light emitting element 100 of this embodiment, the first portion 1021 of the first insulating layer 102 extends from the side wall of the light emitting diode 200 to cover the entire light emitting surface 206. That is, in this embodiment, the surface area S1 of the light emitting surface 206 covered by the first portion 1021 and the surface area S2 of the light emitting surface 206 satisfy: S1 = S2. At this time, the material of the first insulating layer 102 is preferably a material layer with good light transmittance or anti-reflection effect.

[0113] Embodiment 3

[0114] This embodiment also provides a light emitting element. The light emitting element 100 of this embodiment includes a plurality of light emitting diodes 200, a support structure 101 and a first insulating layer 102. The light emitting diodes 200 are connected by the first insulating layer 102 and supported on the support structure 101. The similarities with the first and second embodiments are not repeated here. The differences are as follows:

[0115] In this embodiment, Fig.10 As shown, in this embodiment, a pair of bridge structures located on two opposite side walls of the light emitting diode 200 are distributed asymmetrically, for example, they can be distributed staggered with each other, thereby better supporting the light emitting diode 200.

[0116] Embodiment 4

[0117] This embodiment also provides a light emitting element. The light emitting element 100 of this embodiment includes a plurality of light emitting diodes 200, a support structure 101, and a first insulating layer 102. The light emitting diodes 200 are connected by the first insulating layer 102 and supported on the support structure 101. The same points as those of the first to third embodiments are not repeated here. The difference is that:

[0118] In this embodiment, in a group of side walls opposite to the light emitting diode 200, a plurality of second portions 1022 are formed on each side wall, and the plurality of second portions 1022 are distributed at intervals. The plurality of second portions 1022 can be evenly distributed on the side walls, or can be distributed on the side walls in any form. Fig.11 As shown, taking the example of two second parts 1022 on one side wall, the two second parts 1022 on the same side wall are symmetrically distributed along the center line of the side wall, and further, the second parts 1022 on two opposite side walls are symmetrically distributed along the midpoint connection line of another group of opposite side walls of the light emitting diode 200. The symmetrically distributed second parts 1022 are conducive to uniform force and facilitate the breaking of the second parts 1022.

[0119] Embodiment 5

[0120] This embodiment also provides a light emitting element. The light emitting element 100 of this embodiment includes a plurality of light emitting diodes 200, a support structure 101, and a first insulating layer 102. The light emitting diodes 200 are connected by the first insulating layer 102 and supported on the support structure 101. The same points as those of the first to fourth embodiments are not repeated here. The difference is that:

[0121] In this embodiment, Fig.12 As shown, the second portion 1022 as a bridge structure is located at two relatively short opposite side walls of the light emitting diode 200. At this time, other configurations of the second portion 1022 may be the same as any configuration of the first to fourth embodiments.

[0122] Embodiment 6

[0123] This embodiment provides a method for manufacturing a light emitting element, the method comprising the following steps:

[0124] like Fig.13 As shown, first, a substrate is provided; the substrate can be any suitable substrate that can play a supporting role, such as a sapphire substrate, a glass substrate, a ceramic substrate, etc.

[0125] A bonding layer 103 is formed on the substrate; the bonding layer 103 may be a material layer having certain adhesion and being easy to separate, such as BCB glue, silica gel, UV glue or resin. The minimum thickness of the bonding layer 103 is greater than or equal to 0.1 μm and less than or equal to 50 μm. This ensures the minimum distance between the light-emitting diode 200 and the substrate, prevents the light-emitting diode 200 from touching the substrate and being damaged, and facilitates the subsequent transfer of the light-emitting diode 200.

[0126] Afterwards, the same Fig.13 As shown, a plurality of light-emitting diodes 200 are bonded on the bonding layer 103, and the light-emitting diodes 200 at least include a semiconductor epitaxial stack 201, and the semiconductor epitaxial stack 201 includes a first semiconductor layer 2011, an active layer 2012, and a second semiconductor layer 2013 stacked in sequence along a first direction; the side of the first semiconductor layer 2011 of the light-emitting diode 200 away from the active layer 2012 is a light-emitting surface 206, and the light-emitting diode 200 is bonded to the bonding layer 103 with the light-emitting surface 206 facing upward, thereby facilitating further operations on the light-emitting surface 206 of the light-emitting diode 200. For example, the light-emitting surface 206 can be roughened after bonding, so that the light-emitting surface 206 forms a roughened surface, thereby improving the light-emitting efficiency.

[0127] Afterwards, if Fig.14As shown, the bonding layer 103 is etched so that the sidewall of the bonding layer 103 is flush with the sidewall of the light-emitting diode 200; the redundant bonding layer 103 between the light-emitting diodes 200 facilitates the subsequent formation of a bridge structure extending downward along the sidewall of the light-emitting diode 200.

[0128] Then, if Fig.15 As shown, a first insulating layer 102 is formed from one side of the light-emitting diode 200, and the first insulating layer 102 includes a first portion 1021 and a second portion 1022, wherein the first portion 1021 at least covers the side wall of the light-emitting diode 200, and the second portion 1022 extends downward from the first portion 1021 and is connected to the support structure 101 to form a bridge structure between the light-emitting diode 200 and the support structure 101; Fig.15 As shown, an insulating material layer is deposited on one side of the light emitting diode 200 (more specifically, on the light emitting surface 206 of the light emitting diode 200), for example, SiO2, SiN x , TiO2, Al2O3 and other non-metallic materials. Then, the insulating material layer is etched using a photomask to remove the portion of insulating material covering the side wall of the bonding layer 103 to form the second portion 1022. At the same time, part of the insulating material on the surface of the substrate can be further removed to form the third portion 1023 of the first insulating layer 102. The arrangement and related features of each portion of the first insulating layer 102 can refer to the description of the above-mentioned embodiments 1 to 5.

[0129] Finally, the bonding layer 103 is removed. Figure 3 For example, the bonding layer 103 is removed by wet or dry etching, so that a hollow structure is formed between the light emitting diode 200 and the substrate.

[0130] As described above, the manufacturing method of this embodiment only forms the bonding layer 103 between the light emitting diode 200 and the substrate, and then obtains the bridge structure capable of supporting the light emitting diode 200 by removing the bonding layer 103. The manufacturing process is simple and easy to operate, which is conducive to cost saving.

[0131] Embodiment 7

[0132] This embodiment provides a light emitting diode 200, which is a micro light emitting diode 200, and is a core particle transferred and separated from the light emitting element 100 of the first to fifth embodiments. It includes a semiconductor epitaxial stack 201, and the semiconductor epitaxial stack 201 includes a first semiconductor layer 2011, an active layer 2012, and a second semiconductor layer 2013 stacked in sequence. The relevant configuration of the semiconductor epitaxial stack 201 can refer to the relevant description of the first embodiment.

[0133] like Fig.16As shown, the light emitting diode 200 of this embodiment further includes an electrode structure, which is located above the second insulating layer 202. The first electrode 2051 is formed on the first mesa 204 and is electrically connected to the first semiconductor layer 2011. In some embodiments, a first contact electrode 2053 is further formed between the first electrode 2051 and the first semiconductor layer 2011 to form an ohmic contact with the first semiconductor layer 2011. The second electrode 2052 of the electrode structure is formed on the second mesa 205 and is electrically connected to the second semiconductor layer 2013. In some embodiments, a second contact electrode 2054 is further formed between the second electrode 2052 and the second semiconductor layer 2013 to form an ohmic contact with the second semiconductor layer 2013.

[0134] In an optional embodiment, the material of the first contact electrode 2053 and the second contact electrode 2054 may be Au / AuZn / Au or Au / BeAu / Au or AuGeNi multilayer structure, and the first electrode 2051 and the second electrode 2052 may be formed by one or a combination of two or more materials selected from Au, Ag, Al, Pt, Ti, Ni and Cr. In some embodiments, the first electrode 2051 and the second electrode 2052 may be formed by reflective metal Au or Al, thereby improving the light extraction efficiency of the light emitting diode 200 and improving the light emitting brightness of the light emitting diode 200. Fig.16 In the light emitting diode 200 shown, the first electrode 2051 is formed on the first table 204 and extends above the second table 205, flush with the second electrode 2052. The design of the first electrode 2051 bridging the second table 205 facilitates subsequent packaging and improves packaging yield.

[0135] Also refer to Fig.16 The light emitting surface 206 and the side wall of the light emitting diode 200 retain the first part 1021 of the first insulating layer 102, and the first part 1021 preferably covers the side wall of the second insulating layer 202, and the two form a continuous structure. There is also a residual second part 1022 on the side wall of the light emitting diode 200. Fig.16 In the light emitting diode shown in FIG. 1 , the remaining second portion 1022 extends from the second mesa 205 toward the first mesa 204. Fig.16, the height of the first mesa 204 is defined as d1. It can be understood that the height d1 defined here broadly includes the mesa portion of the semiconductor stack and the total height of the second insulating layer 202 and the electrode portion formed above the mesa. The second portion 1022 extends from the first portion 1021, and the height of the extension is less than or equal to 1 / 2 of the height d1 of the first mesa 204 of the light-emitting diode 200, and further, less than or equal to 1 / 4 of the height d1 of the first mesa 204 of the light-emitting diode 200. Since the remaining second portion 1022 extends along the height direction of the light-emitting diode 200, it will not affect the appearance of the light-emitting diode 200. The side wall of the light-emitting diode 200 is a flush structure as a whole, which is beneficial to the arrangement of the light-emitting diode 200, improves the transfer yield, and the reliability of subsequent devices; in addition, the height of the second portion 1022 is small, less than the above-mentioned height d1, so during the transfer, the remaining second portion 1022 will not affect the welding of the light-emitting diode 200 after transfer.

[0136] Embodiment 8

[0137] This embodiment provides a light emitting diode 200, which is a micro light emitting diode 200, and is a core particle transferred and separated from the light emitting element 100 of the first to fifth embodiments. It includes a semiconductor epitaxial stack 201, and the semiconductor epitaxial stack 201 includes a first semiconductor layer 2011, an active layer 2012, and a second semiconductor layer 2013 stacked in sequence. The relevant configuration of the semiconductor epitaxial stack 201 can refer to the relevant description of the first embodiment.

[0138] like Fig.17 As shown, the light emitting diode of this embodiment is different from the light emitting diode of the seventh embodiment in that: in this embodiment, the mesa structure 205 of the semiconductor stack 201 is formed as a closed hole structure, and the side wall of the light emitting diode is a one-stage structure. At this time, the height of the electrode structure (specifically, the first electrode 2051 and the second electrode 2052) formed above the second insulating layer 202 is defined as d5. Fig.17 In the light-emitting diode shown, the remaining second portion 1022 extends from the side wall of the light-emitting diode along the height direction of the light-emitting diode, and the extended height is d4, and the height d4 is less than or equal to 1 / 2 of d5, and further, less than or equal to 1 / 4 of the height d5. Since the remaining second portion 1022 extends along the height direction of the light-emitting diode 200, it will not affect the appearance of the light-emitting diode 200, and the side wall of the light-emitting diode 200 is a flush structure as a whole, which is beneficial to the arrangement of the light-emitting diode 200, improves the transfer yield, and the reliability of subsequent devices; in addition, the extended height of the second portion 1022 is small, less than the above-mentioned height d5, so during the transfer, the remaining second portion 1022 will not affect the welding of the light-emitting diode 200 after transfer.

[0139] Embodiment 9

[0140] This embodiment provides a display device such as Fig.18 As shown, the display device 300 includes a circuit substrate 302 and a plurality of luminous bodies 301 fixed on the circuit substrate 302. A driving circuit is provided in the circuit substrate 302. The luminous bodies 301 are electrically connected to the driving circuit so as to be controlled to light up or extinguish by the driving circuit. In this embodiment, the luminous bodies 301 are light-emitting diodes 200 transferred in batches from any one or more light-emitting elements 100 provided in Embodiments 1 to 5, i.e., the light-emitting diodes 200 provided in Embodiments 7 and / or 8.

[0141] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A light emitting element, characterized in that: include: A plurality of light-emitting diodes, each of which comprises at least a semiconductor epitaxial stack, wherein the semiconductor epitaxial stack comprises a first semiconductor layer, an active layer and a second semiconductor layer sequentially stacked along a first direction; A supporting structure, located below the light emitting diode, supporting the light emitting diode; The first insulating layer includes a first portion and a second portion, wherein the first portion at least covers the side wall of the light-emitting diode, and the second portion extends downward from the first portion and is connected to the supporting structure to form a bridge structure between the light-emitting diode and the supporting structure.

2. The light emitting element according to claim 1, characterized in that The thickness of the first insulating layer is greater than or equal to 0.1 μm.

3. The light emitting element according to claim 1, wherein: The minimum distance between the light emitting diode and the supporting structure is d2, and 0.1 μm≤d2≤50 μm.

4. The light emitting element according to claim 3, characterized in that The bridge structure further includes a third portion extending on the surface of the support structure, the third portion being connected to the second portion.

5. The light emitting element according to claim 1, characterized in that The second portions are formed in pairs at two opposite side walls of the light emitting diode, and at least one pair of the second portions is provided at two opposite side walls of the light emitting diode.

6. The light emitting element according to claim 5, characterized in that The bridge structures are symmetrically distributed on the side walls of the light emitting diode; or asymmetrically distributed on the side walls of the light emitting diode.

7. The light emitting element according to claim 5 or 6, characterized in that: The width of the second portion is smaller than the width of the side wall of the light emitting diode where the second portion is located.

8. The light emitting element according to claim 5 or 6, characterized in that: The width of the second portion is 1 / 10 to 1 / 4 of the width of the side wall of the light emitting diode where the second portion is located.

9. The light emitting element according to claim 1, wherein: The longitudinal cross-section of the second part is a trapezoidal structure, wherein the short side a of the trapezoidal structure is close to the boundary of the first part, the long side b of the trapezoidal structure is opposite and parallel to the short side a, and the waist c of the trapezoidal structure is connected to the short side a and the long side b, wherein b>a, and a: b: c=(0.1~1): (1~5): (1~2).

10. The light emitting element according to claim 9, characterized in that The included angle between the short side a and the waist c is between 120° and 150°.

11. The light emitting element according to claim 1, wherein The side of the first semiconductor layer away from the active layer is the light emitting surface of the light emitting diode. On the side opposite to the light emitting surface, the semiconductor stack is formed with a first mesa and a second mesa. The first mesa is formed by the first semiconductor layer and is located around the second mesa. The first portion of the first insulating layer extends from the side wall of the light emitting diode to cover at least a portion of the light emitting surface.

12. The light emitting element according to claim 11, characterized in that The surface area of ​​the light emitting surface covered by the first part is S1, and the surface area of ​​the light emitting surface is S2, wherein: S1≥0.1*S2.

13. The light emitting element according to claim 11, characterized in that A second insulating layer is also included, wherein the second insulating layer covers surfaces of the first mesa and the second mesa, and the first portion of the first insulating layer covers a side wall of the second insulating layer.

14. The light emitting element according to claim 13, characterized in that: The material of the first insulating layer and / or the second insulating layer is SiO2, SiN x 、SiO x N y , a combination of one or more of Ti2O3 and Al2O3.

15. The light emitting element according to claim 1, wherein: The side length or height of the light emitting diode is between 2 μm and 100 μm.

16. A method for manufacturing a light emitting element, characterized in that: The following steps are involved: providing a substrate; forming a bonding layer over the substrate; Bonding a plurality of light emitting diodes on the bonding layer, wherein the light emitting diodes at least include a semiconductor epitaxial stack, and the semiconductor epitaxial stack includes a first semiconductor layer, an active layer, and a second semiconductor layer sequentially stacked along a first direction; Etching the bonding layer so that the side wall of the bonding layer is flush with the side wall of the light emitting diode; forming a first insulating layer from one side of the light emitting diode, the first insulating layer comprising a first portion and a second portion, wherein the first portion at least covers a side wall of the light emitting diode, and the second portion extends downward from the first portion and is connected to the support structure to form a bridge structure between the light emitting diode and the support structure; The bonding layer is removed.

17. The method for manufacturing a light emitting element according to claim 16, wherein: The minimum thickness of the bonding layer is greater than or equal to 0.1 μm and less than or equal to 50 μm.

18. A light emitting diode, characterized in that: The light-emitting diode is a core particle obtained by transfer separation from the light-emitting element according to any one of claims 1 to 17, and has a first portion of the first insulating layer and a remaining second portion at a side wall of the light-emitting diode.

19. The light emitting diode according to claim 18, characterized in that: The height of the second portion remaining on the side wall of the light emitting diode is d4, and the height of the light emitting diode exceeding the first portion is d1, wherein 20. A display device, characterized in that: It comprises a circuit substrate and a plurality of luminous bodies fixed on the circuit substrate, wherein the luminous bodies comprise light emitting diodes transferred in batches from the light emitting elements according to any one of claims 1 to 15.

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