Miniature light emitting diode chip and display panel

Abstract

The invention relates to a micro light-emitting diode chip, which comprises a plurality of micro light-emitting diodes arranged in an array, and a current spreading structure located between the micro light-emitting diodes, where the current spreading structure is arranged to surround the micro light-emitting diodes, and the current spreading structure is configured to electrically contact the micro light-emitting diodes and at least partially reflect light emitted by the micro light-emitting diodes. According to the invention, the current expansion structure is arranged between the micro light-emitting diodes, and the current expansion structure can reflect the light emitted by the micro light-emitting diodes, thereby improving the light-emitting brightness of the micro light-emitting diode chip, and improving the light-emitting rate within the preset light-emitting angle.

Description

Technical Field

[0001] The present invention relates to the technical field of micro light emitting diodes, and particularly to a micro light emitting diode chip and a display panel. Background Art

[0002] Micro Light Emitting Diode (Micro-LED) is an emerging display technology. By miniaturizing traditional light emitting diodes, its size reaches the micron level, and these tiny LED arrays are integrated onto a chip, enabling the formation of a high-density display panel. As a semiconductor component that is small in size and can emit light, the micro light emitting diode device has the advantages of low power consumption, long lifespan, high brightness, high contrast, etc. With the gradual development of display technology, micro light emitting diode technology has gradually become a trend in new display technologies and has received increasing attention.

[0003] However, the light extraction efficiency (Wall-Plug Efficiency, WPE, also known as the electro-optical conversion efficiency) of existing micro light emitting diode devices is too low and needs to be further improved. Summary of the Invention

[0004] To solve at least some of the above problems in the prior art, the task of the present invention is to provide a micro light emitting diode chip, comprising:

[0005] a plurality of micro light emitting diodes arranged in an array; and

[0006] a current spreading structure located between the micro light emitting diodes, wherein the current spreading structure is arranged to surround the micro light emitting diodes, and the current spreading structure is configured to be in electrical contact with the micro light emitting diodes and at least partially reflect the light emitted by the micro light emitting diodes.

[0007] Further, the bottoms of adjacent current spreading structures are connected, and all current spreading structures are connected into a whole.

[0008] Further, the bottom size of the micro light emitting diode is larger than the top size.

[0009] Further, the longitudinal cross-section of adjacent two current spreading structures presents a bifurcated peak shape.

[0010] Further, the longitudinal cross-section shape of adjacent current spreading structures is asymmetrical.

[0011] Further, the current spreading structure is a multi-layer structure, wherein the current spreading structure includes one or more main metal layers.

[0012] Further, the material of the main metal layer is selected from one or more of Ti, Pt, Au, Al, and Ag.

[0013] Further, the current spreading structure further includes an isolation layer, which corresponds to each main metal layer one by one, and the isolation layer and the main metal layer are arranged alternately, and each main metal layer is located on the corresponding isolation layer.

[0014] Further, the current spreading structure further includes an adhesion layer, which is located at the bottommost layer of the current spreading structure, and the isolation layer and the main metal layer are located above the adhesion layer.

[0015] Further, the current spreading structure further includes an anti-diffusion layer, which corresponds to the isolation layer one by one, and each isolation layer is located on the corresponding anti-diffusion layer.

[0016] Further, there is a stacking gap in the current spreading structure.

[0017] Further, the micro light-emitting diode includes:

[0018] An epitaxial layer;

[0019] A first transparent conductive layer, which is located under the epitaxial layer;

[0020] A second transparent conductive layer, which is located on the side and top of the epitaxial layer; and

[0021] An insulating layer, which is located on the side of the epitaxial layer and the side of the first transparent conductive layer, and is located between the epitaxial layer and the second transparent conductive layer.

[0022] Further, the bottom of the current spreading structure is lower than the epitaxial layer.

[0023] Further, the top of the current spreading structure is higher than the top of the epitaxial layer; and / or

[0024] The top of the current spreading structure is flush with the top of the epitaxial layer; and / or

[0025] The top of the current spreading structure is 0 - 1 micrometer lower than the top of the epitaxial layer.

[0026] Further, the current spreading structure surrounds the epitaxial layer.

[0027] Further, the bottom size of the epitaxial layer is larger than the top size of the epitaxial layer.

[0028] Further, the epitaxial layer includes a first-type epitaxial layer, a second-type epitaxial layer, and a light-emitting layer located therebetween.

[0029] Further, the second type epitaxial layer is electrically connected to the first transparent conductive layer;

[0030] The first type epitaxial layer is electrically connected to the second transparent conductive layer.

[0031] Furthermore, the micro light emitting diode further includes a first bonding layer, which is located on a side of the first transparent conductive layer away from the epitaxial layer.

[0032] Furthermore, the first bonding layers of all the micro light emitting diodes are not connected to each other.

[0033] Furthermore, it also includes a driving backplane, which is electrically connected to the micro light emitting diode.

[0034] Furthermore, the driving backplane has driving electrodes, and each micro light emitting diode corresponds to one driving electrode.

[0035] Furthermore, a second bonding layer is provided on the surface of the driving electrode, the second bonding layer is bonded to the first bonding layer, and the second bonding layer is in electrical contact with the driving electrode.

[0036] Furthermore, it also includes a microlens, which is arranged on the micro light emitting diode, and adjacent microlenses are connected.

[0037] Furthermore, there is a gap between adjacent microlenses, and the gap is located between two adjacent current spreading structures.

[0038] Furthermore, an air gap is provided inside the microlens, and the air gap is located between the epitaxial layer and the current spreading structure.

[0039] The present invention also provides a display panel, which includes the micro light emitting diode chip.

[0040] The present invention has at least the following beneficial effects: a current expansion structure is arranged between micro-LEDs, and the current expansion structure can reflect the light emitted by the micro-LEDs, thereby increasing the luminous brightness of the micro-LED chip and increasing the light output rate within a preset light output angle. A current expansion structure is arranged between micro-LEDs, and the current expansion structure can reflect the light emitted by the micro-LEDs to avoid light absorption by the side walls, thereby increasing the total light output. At the same time, the current expansion structure with reflection capability can also prevent light from entering adjacent micro-LEDs, thereby avoiding light crosstalk between adjacent micro-LEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] To further clarify the above and other advantages and features of the embodiments of the present invention, a more specific description of the embodiments of the present invention will be presented with reference to the accompanying drawings. It can be understood that these drawings only depict typical embodiments of the present invention and thus will not be considered as limiting its scope. In the drawings, for clarity, the same or corresponding components will be denoted by the same or similar reference numerals.

[0042] Figure 1 A top view schematic diagram of a micro light-emitting diode display chip according to an embodiment of the present invention is shown;

[0043] Figure 2 A top view schematic diagram of a current spreading structure according to an embodiment of the present invention is shown;

[0044] Figure 3 A longitudinal cross-sectional schematic diagram of a micro light-emitting diode display chip according to an embodiment of the present invention is shown;

[0045] Figure 4 A longitudinal cross-sectional schematic diagram of a current spreading structure according to an embodiment of the present invention is shown;

[0046] Figure 5 A longitudinal cross-sectional schematic diagram of a current spreading structure according to another embodiment of the present invention is shown;

[0047] Figure 6 A longitudinal cross-sectional schematic diagram of a micro light-emitting diode chip according to another embodiment of the present invention is shown; and

[0048] Figure 7 A longitudinal cross-sectional schematic diagram of a micro light-emitting diode chip with a microlens according to an embodiment of the present invention is shown. Detailed Description of the Embodiments

[0049] It should be noted that the components in the respective drawings may be exaggerated for illustration purposes and not necessarily drawn to scale.

[0050] In the present invention, the embodiments are merely intended to illustrate the solutions of the present invention and should not be construed as restrictive.

[0051] In the present invention, unless otherwise specified, the quantifiers "a" and "one" do not exclude the scenario of multiple elements.

[0052] It should also be noted here that in the embodiments of the present invention, for clarity and simplicity, only a part of the components or assemblies may be shown, but those of ordinary skill in the art can understand that, under the teachings of the present invention, the required components or assemblies can be added according to the specific scenario needs.

[0053] It should also be noted here that within the scope of the present invention, terms such as "identical", "equal", "equivalent" do not mean that the two values are absolutely equal, but allow for a certain reasonable error, that is, these terms also cover "substantially identical", "substantially equal", "substantially equivalent".

[0054] It should also be noted here that in the description of the present invention, the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than explicitly or implicitly indicating that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as explicitly or implicitly indicating relative importance.

[0055] In addition, the embodiments of the present invention describe the process steps in a specific order. However, this is only for the convenience of distinguishing each step and does not limit the sequence of each step. In different embodiments of the present invention, the sequence of each step can be adjusted according to the adjustment of the process.

[0056] In the present application, the term "configured" means setting the shape, structure, material, and / or function of the target object to achieve the desired technical effect, where "configured" includes various alternative technical means for achieving this technical effect, and these technical means become obvious under the teaching of the present application.

[0057] In the present invention, the term "horizontal profile" has the following meaning: for a regular shape, it refers to the horizontal dimension, and for an irregular shape, it refers to the maximum horizontal dimension. For example, for a hemispherical microlens, its horizontal profile refers to its bottom diameter, and for a cylindrical micro light-emitting diode, its horizontal profile refers to the diameter of its cylinder cross-section. The maximum horizontal profile refers to the maximum value of the dimension.

[0058] Figure 1 Shows a top view schematic diagram of a micro light-emitting diode chip according to an embodiment of the present invention; Figure 2 Shows a top view schematic diagram of a current spreading structure according to an embodiment of the present invention;

[0059] Figure 3 Shows a longitudinal cross-sectional schematic diagram of a micro light-emitting diode chip according to an embodiment of the present invention; Figure 4 Shows a longitudinal cross-sectional schematic diagram of a current spreading structure according to an embodiment of the present invention; Figure 5 Shows a longitudinal cross-sectional schematic diagram of a current spreading structure according to another embodiment of the present invention.

[0060] As Figure 1 and 3 shown, the micro light-emitting diode chip includes a plurality of micro light-emitting diodes 101 arranged in an array and a current spreading structure 102.

[0061] The size of each micro light-emitting diode chip does not exceed 1 cm, preferably does not exceed 20 microns. The micro light-emitting diodes are formed in an array in the micro light-emitting diode chip, and the resolution is, for example, 720*480, 640*480, 1920*1080, 1280*720, 2K or 4K. The diameter of the micro light-emitting diode structure is in the nanometer range, for example, 20 nm to 100 nm. Each micro light-emitting diode can form at least a part of the pixel element on the micro light-emitting diode chip.

[0062] In some embodiments, the pitch of the micro light-emitting diode array, that is, the minimum center-to-center distance between the micro light-emitting diodes, can be between about 2 microns and about 50 microns.

[0063] In some embodiments, the number of pixels on the micro light-emitting diode chip can be between several thousand and several million.

[0064] The current spreading structure 102 is located between the micro light-emitting diodes 101. The current spreading structure 102 surrounds the micro light-emitting diodes 101. The current spreading structure 102 is electrically connected to the micro light-emitting diodes 101.

[0065] The micro light-emitting diode 101 and the current spreading structure 102 will be introduced in detail below in sequence.

[0066] As Figure 3 shown, the micro light-emitting diode 101 includes a first transparent conductive layer 104, an epitaxial layer 103, an insulating layer 105 and a second transparent conductive layer 106.

[0067] In an embodiment of the present invention, the epitaxial layer 103 is located between the first transparent conductive layer 104 and the second transparent conductive layer 106. The epitaxial layer 103 is located above the first transparent conductive layer 104, and the first transparent conductive layer 104 contacts the bottom surface of the epitaxial layer 103.

[0068] The size of the first transparent conductive layer 104 is larger than the size of the epitaxial layer 103.

[0069] In an embodiment of the present invention, the second transparent conductive layer 106 is located on the top and side of the epitaxial layer 103, and the second transparent conductive layers 106 of all the micro light-emitting diodes are electrically connected to each other, and the second transparent conductive layer 106 is also electrically connected to the current spreading structure 102.

[0070] In an embodiment of the present invention, the material of the first transparent conductive layer 104 and / or the second transparent conductive layer 106 may include indium tin oxide (In2O5Sn), thereby improving the conductivity and light extraction effect.

[0071] It should be noted that the material of the first transparent conductive layer 104 and / or the second transparent conductive layer 106 may also include other suitable materials, such as fluorine-doped tin oxide (FTO), zinc oxide (ZnO).

[0072] In an embodiment of the present invention, the insulating layer 105 is located on the side of the epitaxial layer 103 and the side of the first transparent conductive layer 104, and the insulating layers 105 of all the micro light-emitting diodes are interconnected. The insulating layer 105 is used to isolate the first transparent conductive layer 104 and the second transparent conductive layer 106. Further, the insulating layer 105 is transparent.

[0073] In other embodiments, the insulating layer 105 covers the side of the first transparent conductive layer 104, the side of the epitaxial layer 103, and a partial area on the top.

[0074] Since the size of the first transparent conductive layer 104 is larger than the size of the bottom of the epitaxial layer 103, a step is formed. The insulating layer 105 and the second transparent conductive layer 106 cover the sides of the first transparent conductive layer 104 and the epitaxial layer 103. Due to the step at the first transparent conductive layer 104, there will also be a step in the insulating layer 105 and the second transparent conductive layer 106.

[0075] In an embodiment of the present invention, the bottom size of the epitaxial layer 103 is larger than the top size of the epitaxial layer 103. It should be noted that the lateral cross-sectional shape of the epitaxial layer 103 is not limited to a circle, and may also be other suitable shapes, such as a rectangle, a square, or a polygon, etc.

[0076] As Figure 3 shown, the epitaxial layer 103 includes a first type epitaxial layer 1031, a second type epitaxial layer 1032, and a light-emitting layer 1033 located therebetween.

[0077] In an embodiment of the present invention, the first type epitaxial layer 1031 is located above the light-emitting layer 1033, and the second type epitaxial layer 1032 is located below the light-emitting layer 1033. The second type epitaxial layer 1032 is electrically connected to the first transparent conductive layer 104, and the first type epitaxial layer 1031 is electrically connected to the second transparent conductive layer 106.

[0078] In some embodiments, the light-emitting layer is formed by a plurality of stacked quantum well layers, especially superlattice-stacked quantum well layers. Preferably, the superlattice-stacked quantum well layers include multiple pairs of quantum well layers stacked with quantum barrier layers.

[0079] In some embodiments, the first-type epitaxial layer is a semiconductor material having a first-type epitaxial layer and includes a plurality of semiconductor layers. The main matrix material of the first-type epitaxial layer may be, but is not limited to, composed of at least two or more elements among Ga, N, As, P, In, and Al. In addition, the first-type epitaxial layer may include, but is not limited to, a confinement layer and a waveguide layer from top to bottom; in addition, in some embodiments, an ohmic contact layer may be formed on the confinement layer. In some embodiments, the second-type epitaxial layer is a semiconductor material having a second conductivity type and includes a plurality of semiconductor layers. The main matrix material of the second-type epitaxial layer may be, but is not limited to, composed of materials such as Ga, N, As, P, In, or Al. In addition, the second-type epitaxial layer may include, but is not limited to, a waveguide layer, a confinement layer, a transition layer, and a window layer from top to bottom; in addition, an ohmic contact layer may be formed below the window layer. In one embodiment, the first conductivity type is different from the second conductivity type.

[0080] In some embodiments, the first-type epitaxial layer is an N-type GaN layer or an N-type AlGaN layer, and the second-type epitaxial layer is a P-type GaN layer or a P-type AlGaN layer. That is, the material of the second-type epitaxial layer may be a material layer composed of at least two or more elements among Ga, N, As, Al, In, P of the second conductivity type, and the first-type epitaxial layer may be a material layer composed of at least two or more elements among Ga, N, As, Al, In, P of the first conductivity type. In one embodiment, the light-emitting layer includes a multi-quantum well layer and an electron blocking layer, and the multi-quantum well layer is an InGaN / GaN multi-quantum well layer or an InGaN / AlGaN multi-quantum well layer or an InGaAs / AlGaAs multi-quantum well layer. In another embodiment, the first-type epitaxial layer may also be a P-type GaN layer or a P-type AlGaN layer, and the second-type epitaxial layer is an N-type GaN layer or an N-type AlGaN layer.

[0081] In some embodiments, the light-emitting layer includes at least one quantum well layer. The thickness of the quantum well layer is between 20 nm and 40 nm, for example, the thickness is 30 nm. In some embodiments, the material of the quantum well layer is GaInP / (Al x Ga 1-x ) y In 1-y P, where the range of x is 0.5 to 0.9, and the range of y is 0.3 to 0.5. For example, x is 0.8 and y is 0.5. In some embodiments, the relationship between x and y is that x is 1 to 2 times y. In some embodiments, the light-emitting layer is a multi-quantum well (MQW).

[0082] In some embodiments, one of the first-type epitaxial layer and the second-type epitaxial layer is an N-type semiconductor layer, and the other is a P-type semiconductor layer. In some embodiments, the N-type semiconductor layer further includes a doped N-type contact layer and an N-type cladding layer. The N-type cladding layer is formed on the doped N-type contact layer. The material of the N-type cladding layer is Al x In 1-x P, where the range of x is from 0.1 to 0.5, for example, x is 0.5. In addition, in these embodiments, the thickness of the N-type cladding layer is not greater than 350 nm. For example, the thickness of the N-type cladding layer is 320 nm. The doping concentration of the N-type cladding layer is 5e 17 cm -3 to 1e 18 cm -3 . In some embodiments, the N-type semiconductor layer further includes a doped N-type contact layer and an N-type cladding layer formed on the doped N-type contact layer. The material of the doped N-type contact layer is GaAs. In some embodiments, the thickness of the doped N-type contact layer is from 10 nm to 30 nm. In some embodiments, the doping concentration of the doped N-type contact layer is 2e 18 cm -3 to 1e 19 cm -3 . In some embodiments, the N-type semiconductor layer further includes an N-type spacer layer formed on the N-type cladding layer. The material of the N-type spacer layer is (Al x Ga 1-x ) y In 1-y P, where the range of x is from 0.5 to 0.9, and the range of y is from 0.1 to 0.5. For example, x is 0.8 and y is 0.5. In some embodiments, the relationship between x and y is that x is 1 to 2 times y. The thickness of the N-type spacer layer is from 50 nm to 75 nm, for example, 65 nm. In some embodiments, the P-type semiconductor layer includes a P-type cladding layer and a doped P-type contact layer. The P-type cladding layer is formed on the light-emitting layer, and the doped P-type contact layer is formed on the P-type cladding layer.

[0083] In some embodiments, the material of the P-type cladding layer is Al x In 1-x P, where x is from 0.3 to 0.5, for example, x is 0.5. In such embodiments, the thickness of the P-type cladding layer is not greater than 380 nm. For example, the thickness of the P-type cladding layer is 360 nm.

[0084] In some embodiments, the material of the doped P-type contact layer is GaAs. The thickness of the doped P-type contact layer is from 10 nm to 30 nm, for example, 20 nm.

[0085] In some embodiments, the P-type semiconductor layer further includes a P-type spacer layer formed under the P-type cladding layer, a first doped P-type transition layer formed on the P-type cladding layer, and a second doped P-type transition layer formed on the first doped P-type transition layer. In some embodiments, the material of the P-type spacer layer is (Al x Ga 1-x ) y In 1-y P, where the range of x is 0.5 to 0.9 and the range of y is 0.3 to 0.5. For example, x is 0.8 and y is 0.5. In some embodiments, the relationship between x and y is that x is 1 to 2 times y. In some embodiments, the thickness of the P-type spacer layer is 50 nm to 70 nm, such as 65 nm.

[0086] In some embodiments, the material of the first doped P-type transition layer is (Al x Ga 1-x ) y In 1-y P, where the range of x is 0.1 to 0.3 and the range of y is 0.3 to 0.5. For example, x is 0.17 and y is 0.5. In some embodiments, the relationship between x and y is that y is 1 to 5 times x. In some embodiments, the thickness of the first doped P-type transition layer is 20 nm to 40 nm, such as 30 nm.

[0087] In some embodiments, the material of the second doped P-type transition layer is Al x Ga 1-x As, where the range of x is 0.5 to 0.9, for example x is 0.6. In some embodiments, the thickness of the second doped P-type transition layer is 10 nm to 30 nm, such as 20 nm.

[0088] In some embodiments, the doping concentration of the second doped P-type transition layer is greater than the doping density of the first doped P-type transition layer. The doping concentration of the doped P-type contact layer is 1 to 10 times the doping concentration of the second doped P-type transition layer.

[0089] In some embodiments, the doping concentration of the doped P-type contact layer is greater than the doping concentration of the second doped P-type transition layer. Additionally, in some embodiments, the doping concentration of the second doped P-type transition layer is 2 to 4 times the doping concentration of the first doped P-type transition layer.

[0090] For example, the doping concentration of the first doped P-type transition layer is greater than 1e 18 cm -3 , and the doping density of the second doped P-type transition layer is between 2e 18 cm -3 -4e 18 cm -3In the range of 5e 18 cm -3 .

[0091] In the embodiment of the present invention, the micro-LED 101 further includes a first bonding layer 107, which is located on the side of the first transparent conductive layer 104 away from the epitaxial layer 103, that is, the first bonding layer 107 is located below the first transparent conductive layer 104. The number of the first bonding layers 107 is the same as the number of the epitaxial layers 103. The first bonding layer 107 of each micro-LED 101 is independent, and all the first bonding layers 107 are not connected to each other.

[0092] The size of the first bonding layer 107 is greater than or equal to the size of the first transparent conductive layer 104 .

[0093] In the embodiment of the present invention, the insulating layer 105 also covers the side surfaces of the first bonding layer 107 .

[0094] like Figure 3 As shown, the current spreading structure 102 has an inner wall 1021 facing the micro-LED and an outer wall 1022 facing away from the micro-LED. The lower ends of the outer walls 1022 between adjacent current spreading structures 102 are connected.

[0095] The surface of the current spreading structure 102 facing the light emitting diode 101 has light reflection capability, for example, it is made of metal, so that the current spreading structure 102 can at least partially reflect the light emitted by the light emitting diode 101. Figure 3 As shown, the reflection process is that the light emitted from the light-emitting layer of the light-emitting diode 101 passes through the transparent layer thereon (for example, the second transparent conductive layer), and then the first part of these lights (whose emission angle is small enough so as not to hit the current expansion structure 102 on the side, within the preset light output angle, such as within plus or minus 20°) is directly emitted, and the second part of these lights (whose emission angle is large enough to hit the current expansion structure 102 on the side) hits the current expansion structure 102 and is emitted after reflection, changing the direction of the light path to within the preset light output angle, thereby effectively improving the light output rate. Preferably, the proportion of light reflected by the current expansion structure 102 to the light emitted by the light-emitting diode 101 can be, for example, 10%-60%. By providing a current expansion structure 102 with light reflection capability, the amount of light absorbed by the side wall can be significantly reduced, thereby significantly improving the total light output. At the same time, the current expansion structure 102 can also isolate light to prevent light crosstalk between adjacent light-emitting diodes 101.

[0096] In an embodiment of the present invention, the current spreading structure 102 is electrically connected to the second transparent conductive layer 106. By arranging the current spreading structure 102 to surround the second transparent conductive layer 106 of the micro light-emitting diode 101 in an electrically contacting manner, the electrical contact area between the current spreading structure 102 and the micro light-emitting diode 101 can be significantly increased, so that the active layer (light-emitting layer) of the micro light-emitting diode 101 can emit light more uniformly, effectively avoiding the situation that only the electrically contacted part or the vicinity thereof emits light or the light-emitting brightness of the electrically contacted part or the vicinity thereof is too high.

[0097] The size of the bottom of the current spreading structure is larger than that of the top. Since the bottoms of adjacent current spreading structures 102 are connected, the longitudinal cross-section of two adjacent current spreading structures 102 presents a forked peak shape.

[0098] Furthermore, the longitudinal cross-sectional shapes of two adjacent current spreading structures 102 may be asymmetric, and the heights may be different, which are not limited herein.

[0099] The bottoms of adjacent current spreading structures 102 are connected. Furthermore, all the current spreading structures 102 are integrated into a whole, and the overall top view shape is as Figure 2 shown.

[0100] In this embodiment, the top view shape (i.e., the cross-sectional shape) of the micro light-emitting diode 101 is circular, and the top view shape of the overall current spreading structure is the remaining grid shape after removing the circle (as Figure 2 ).

[0101] In other embodiments, the top view shape of the micro light-emitting diode 101 may also be other appropriate shapes, such as a rectangle, a square, or a regular polygon, etc. The top view shape of the overall current spreading structure may also be the remaining shape after removing other appropriate shapes, such as the remaining grid shape after removing a rectangle, a square, or a polygon.

[0102] In an embodiment of the present invention, the bottom of the current spreading structure 102 is lower than the epitaxial layer 103 of the micro light-emitting diode 101.

[0103] In an embodiment of the present invention, the top of the current spreading structure 102 may be higher than the top of the epitaxial layer 103; the top of the current spreading structure 102 may also be flush with the top of the epitaxial layer 103; the top of the current spreading structure 102 may also be lower than the top of the epitaxial layer 103 (for example, slightly lower than the top of the epitaxial layer 103 by 0-1 micrometer). In a chip, the above 1, 2, or 3 situations may exist simultaneously.

[0104] Preferably, the top of the current spreading structure 102 is higher than the top of the epitaxial layer 103 of the micro light-emitting diode 101. By making the height of the top of the current spreading structure 102 greater than the height of the top plane of the epitaxial layer 103 of the micro light-emitting diode 101, a higher current spreading structure 102 can be obtained, further increasing the chance of light reflection and the light extraction efficiency.

[0105] As Figure 4 shown, the current spreading structure 102 can be divided into a first part 1023 whose inner wall is in direct contact with the micro light-emitting diode, and a second part 1024 whose inner wall is not in direct contact with the micro light-emitting diode. The second part 1024 is located above the first part 1023. As shown in the figure, it is divided by a dashed line. Below the dashed line is the first part 1023, and above the dashed line is the second part 1024. The inner wall of the first part 1023 is in electrical contact with the second transparent conductive layer 106.

[0106] The second part 1024 of the current spreading structure 102 has a three-dimensional shape. As Figure 4 shown, in one embodiment, the three-dimensional shape of the second part 1024 is a cup shape with an open bottom. The angle α between the inner wall of the second part 1024 and the horizontal direction is at least 90°, so that the light incident on the inner wall from the micro light-emitting diode 101 is reflected to the outside of the micro light-emitting diode 101.

[0107] The cup-shaped structure forms the effect of a reflective cup. When the light at a large angle of the micro light-emitting diode irradiates the inner wall of the cup-shaped metal, the light path reflection increases the light extraction efficiency at a small angle. The cup-shaped structure can achieve a better light-concentrating effect.

[0108] As Figure 5 shown, in another embodiment, the three-dimensional shape of the second part 1024 is a bowl shape with an open bottom. The inner wall of the second part 1024 is arc-shaped, and the angle β between the tangent of each point on the inner wall and the horizontal direction is at least 90°, so that the light incident on the inner wall from the micro light-emitting diode 101 is reflected to the outside of the micro light-emitting diode 101.

[0109] In other embodiments, the number of current spreading structures 102 can also be 1 / 4 or 1 / 9 of the number of micro light-emitting diodes 101. Each current spreading structure 102 surrounds 4 micro light-emitting diodes 101, or 9 micro light-emitting diodes 101, without limitation.

[0110] The current spreading structure can increase the current spreading between adjacent micro light-emitting diodes, reduce the resistance between adjacent micro light-emitting diodes, and reduce losses. The current spreading structure can quickly and evenly spread the current to all micro light-emitting diodes.

[0111] In an embodiment of the present invention, the current spreading structure 102 may be a multi-layer structure, and the current spreading structure 102 includes one or more main metal layers.

[0112] In an embodiment of the present invention, the material of the main metal layer may be one or more of Pt, Au, Al, and Ag.

[0113] In some embodiments, the current spreading structure 102 may further include: isolation layers corresponding to each layer of the main metal layer one by one; wherein, the isolation layers and the main metal layers are arranged alternately, and each layer of the main metal layer is located on the corresponding isolation layer.

[0114] By adopting isolation layers corresponding to each layer of the main metal layer one by one, and the isolation layers and the main metal layers are arranged alternately, and each layer of the main metal layer is located on the corresponding isolation layer, the influence of electromigration in the current spreading structure 102 can be effectively suppressed by setting the isolation layers. Especially when the density of the micro light-emitting diodes 101 in the micro light-emitting diode chip is relatively large, the possibility of increasing the height of the current spreading structure 102 can be obtained by setting the isolation layers, and then the light extraction efficiency can be further improved by the higher current spreading structure 102.

[0115] Furthermore, the isolation layer may include: a titanium (Ti) metal layer. It should be noted that the material of the isolation layer may also include other suitable materials, such as titanium nitride (TiN).

[0116] In some embodiments, the current spreading structure 102 may further include: an adhesion layer located at the bottom layer of the current spreading structure 102, and the isolation layers and the main metal layers are located above the adhesion layer.

[0117] By forming an adhesion layer between the adhesion layer and the micro light-emitting diodes 101, and the isolation layers and the main metal layers are located on the adhesion layer, the bottom stability of the current spreading structure 102 can be effectively improved by the adhesion of the adhesion layer. Especially when the density of the micro light-emitting diodes 101 in the micro light-emitting diode chip is relatively large, the possibility of increasing the height of the current spreading structure 102 can be obtained by setting the adhesion layer, and then the light extraction efficiency can be further improved by the higher current spreading structure 102.

[0118] Furthermore, the adhesion layer may include: a chromium (Cr) metal layer. It should be noted that the material of the adhesion layer may also include other suitable materials, such as one or more of the following: titanium (Ti), titanium nitride (TiN), tungsten (W).

[0119] In an embodiment of the present invention, the current spreading structure 102 may further include: anti-diffusion layers corresponding to the isolation layers one by one, and each layer of the isolation layer is located on the corresponding anti-diffusion layer.

[0120] By forming an anti-diffusion layer corresponding one-to-one with the isolation layer, and each isolation layer being located on the corresponding anti-diffusion layer, the stability of the current spreading structure 102 can be improved by the characteristics of the anti-diffusion layer, such as high hardness and good anti-corrosion effect. Especially when the density of the micro light-emitting diodes 101 in the micro light-emitting diode chip is relatively large, by setting the anti-diffusion layer, it is possible to increase the height of the current spreading structure 102, and then further improve the light extraction efficiency through the higher current spreading structure 102.

[0121] The anti-diffusion layer may include: a platinum (Pt) metal layer, a nickel (Ni) metal layer. It should be noted that the anti-diffusion layer can be a single-layer platinum metal layer, or a single-layer nickel metal layer, or a stack of a single-layer platinum metal layer and a single-layer nickel metal layer.

[0122] Figure 6 The longitudinal cross-sectional schematic diagram of a micro light-emitting diode chip according to another embodiment of the present invention is shown.

[0123] In some embodiments, as Figure 6 shown, there is a stacking gap 1025 in the current spreading structure 102.

[0124] The current spreading structure 102 can be formed by a metal evaporation method. The stacking gap 1025 is formed during the metal evaporation process. The existence of the stacking gap has the advantage of reducing the film stress in the current spreading structure 102. The number of the stacking gaps 1025 is not fixed, and the position of the stacking gaps 1025 in the current spreading structure 102 is not fixed. For example, the stacking gaps 1025 exist in the second part and / or the first part of the current spreading structure 102. Figure 6 The number and position of the stacking gaps 1025 in

[0125] Figure 7 The longitudinal cross-sectional schematic diagram of a micro light-emitting diode chip with a microlens according to an embodiment of the present invention is shown.

[0126] As Figure 7 shown, the micro light-emitting diode chip further includes a microlens 300. The microlens 300 is disposed above the micro light-emitting diode. At least one microlens 300 is disposed above the epitaxial layer 103 of the micro light-emitting diode to form a microlens array. The adjacent microlenses 300 are connected to each other, and the horizontal contour of the microlens 300 is larger than the maximum horizontal contour of the micro light-emitting diode.

[0127] As Figure 7As shown, in an embodiment of the present invention, there is a gap 301 between adjacent microlenses. In an embodiment of the present invention, the bottom of the gap 301 is higher than the top of the epitaxial layer 103. In another embodiment of the present invention, the bottom of the gap 301 is lower than the top of the epitaxial layer 103 and higher than the bottom of the epitaxial layer 103. In another embodiment of the present invention, the bottom of the gap is above the current spreading structure 102. Specifically, as shown, the gap 301 is located between two adjacent current spreading structures (i.e., between the forked peaks).

[0128] In addition, as Figure 7 shown, in an embodiment of the present invention, there may also be an air gap 302 inside the microlens. Each lens may have multiple air gaps, and the sizes and lengths of the respective air gaps may be the same or different. At the same time, in the same chip, the number and / or position and / or size of the air gaps in different microlenses may be the same or different. As shown, in some embodiments of the present invention, the air gap 302 is located at the edge of the microlens 300. Specifically, for example, it may be located on both sides of the epitaxial layer 103. Preferably, it is located between the epitaxial layer 103 and the current spreading structure 102. At the same time, as shown, in some embodiments of the present invention, the top of the air gap 302 is higher than the top of the epitaxial layer 103, and its bottom may be higher than the top of the epitaxial layer 103 or lower than the top of the epitaxial layer 103. As shown, in some embodiments of the present invention, the bottom of the air gap 302 is higher than the top of the current spreading structure 102. In still other embodiments of the present invention, the bottom of the air gap 302 is lower than the top of the current spreading structure 102. It should be noted that in other embodiments of the present invention, there may be no air gap 302 inside the microlens.

[0129] In an embodiment of the present invention, as Figure 3 shown, the micro light-emitting diode chip further includes: a driving backplane 201, and the micro light-emitting diode 101 is disposed on the driving backplane 201. The driving backplane 201 may adopt an integrated circuit (IC) board. The epitaxial layer 103 is electrically connected to the driving backplane 201, and the driving backplane 201 is used to control the lighting and extinguishing of the epitaxial layer 103.

[0130] In some embodiments, the integrated circuit board may be electrically connected to each micro light-emitting diode in the micro light-emitting diode array through separate metal interconnections.

[0131] In some embodiments, each micro light-emitting diode may be individually electrically controlled by the integrated circuit board.

[0132] In some embodiments, the integrated circuit board may be electrically connected to the electrodes of the micro light-emitting diode chip through metal interconnections.

[0133] In an embodiment of the present invention, the driving backplane 201 has driving electrodes 202, and each micro light-emitting diode 101 corresponds to one driving electrode 202. The driving electrodes 201 may be conductive vias, such as copper vias.

[0134] In an embodiment of the present invention, a second bonding layer 203 is disposed on the surface of the driving electrode 202. The second bonding layer 203 is in electrical contact with the driving electrode 202; the second bonding layer 203 is bonded to the first bonding layer 107.

[0135] In an embodiment of the present invention, a display panel is further provided, which includes the above-mentioned micro light-emitting diode chip.

[0136] Although some embodiments of the present invention have been described in this application document, those skilled in the art can understand that these embodiments are merely shown as examples. Those skilled in the art can conceive of numerous variant schemes, alternative schemes, and improvement schemes under the teaching of the present invention without departing from the scope of the present invention. The appended claims are intended to define the scope of the present invention and thereby cover the methods and structures within the scope of these claims themselves and their equivalent transformations.

Claims

1. A micro light-emitting diode chip, characterized in that, Comprising: Multiple micro light-emitting diodes arranged in an array; And A current spreading structure located between the micro light-emitting diodes, wherein the current spreading structure is arranged to surround the micro light-emitting diodes, and the current spreading structure is configured to be in electrical contact with the micro light-emitting diodes and at least partially reflect the light emitted by the micro light-emitting diodes.

2. The micro light-emitting diode chip according to claim 1, wherein, The bottoms of adjacent current spreading structures are connected, and all current spreading structures are integrated into one body.

3. The micro light-emitting diode chip according to claim 1, characterized in that, The bottom size of the micro light-emitting diode is larger than the top size.

4. The micro light-emitting diode chip according to claim 2, wherein The longitudinal cross-section of adjacent two current spreading structures presents a forked peak shape.

5. The micro light-emitting diode chip according to claim 4, wherein, The longitudinal cross-section shape of adjacent current spreading structures is asymmetric.

6. The micro light-emitting diode chip according to claim 1, wherein The current spreading structure is a multi-layer structure, wherein the current spreading structure includes one or more main metal layers.

7. The micro light-emitting diode chip according to claim 6, wherein The material of the main metal layer is selected from one or more of Ti, Pt, Au, Al, and Ag.

8. The micro light-emitting diode chip according to claim 6, characterized in that, The current spreading structure further includes isolation layers, which correspond to each main metal layer one by one, and the isolation layers and the main metal layers are arranged in an interleaved manner, and each main metal layer is located on the corresponding isolation layer.

9. The micro light-emitting diode chip according to claim 8, wherein, The current spreading structure further includes an adhesion layer, which is located at the bottommost layer of the current spreading structure, and the isolation layers and the main metal layers are located above the adhesion layer.

10. The micro light-emitting diode chip according to claim 9, wherein, The current spreading structure further includes anti-diffusion layers, which correspond to the isolation layers one by one, and each isolation layer is located on the corresponding anti-diffusion layer.

11. The micro light-emitting diode chip according to claim 6, characterized in that, There are overlapping gaps in the current spreading structure.

12. The micro light-emitting diode chip according to claim 1, wherein, The micro light-emitting diode includes: An epitaxial layer; A first transparent conductive layer located under the epitaxial layer; A second transparent conductive layer located on the side and top of the epitaxial layer; and An insulating layer located on the side of the epitaxial layer and the side of the first transparent conductive layer, and located between the epitaxial layer and the second transparent conductive layer.

13. The micro light-emitting diode chip according to claim 12, wherein The bottom of the current spreading structure is lower than the epitaxial layer.

14. The micro light-emitting diode chip according to claim 12, characterized in that, The top of the current spreading structure is higher than the top of the epitaxial layer; and / or The top of the current spreading structure is flush with the top of the epitaxial layer; and / or The top of the current spreading structure is 0 - 1 micrometer lower than the top of the epitaxial layer.

15. The micro light-emitting diode chip according to claim 12, wherein The current spreading structure surrounds the epitaxial layer.

16. The micro light-emitting diode chip according to claim 12, characterized in that, The bottom size of the epitaxial layer is larger than the top size of the epitaxial layer.

17. The micro light-emitting diode chip according to claim 12, wherein, The epitaxial layer includes a first type epitaxial layer, a second type epitaxial layer, and a light-emitting layer located between the two.

18. The micro light-emitting diode chip according to claim 17, wherein, The second type epitaxial layer is electrically connected to the first transparent conductive layer; The first type epitaxial layer is electrically connected to the second transparent conductive layer.

19. The micro light-emitting diode chip according to claim 12, characterized in that, The micro light-emitting diode further includes a first bonding layer located on the side of the first transparent conductive layer facing away from the epitaxial layer.

20. The micro light-emitting diode chip according to claim 19, wherein, The first bonding layers of all micro light-emitting diodes are not connected to each other.

21. The micro light-emitting diode chip according to claim 19, wherein, It further includes a driving backplane, which is electrically connected to the micro light-emitting diodes.

22. The micro light-emitting diode chip according to claim 21, wherein The driving backplane has driving electrodes, and each micro light-emitting diode corresponds to one driving electrode.

23. The micro light-emitting diode chip according to claim 22, wherein, A second bonding layer is provided on the surface of the driving electrode, the second bonding layer is bonded to the first bonding layer, and the second bonding layer is in electrical contact with the driving electrode.

24. The micro light-emitting diode chip according to claim 17, wherein, It further includes microlenses, which are arranged above the micro light-emitting diodes, and adjacent microlenses are connected to each other.

25. The micro light-emitting diode display chip according to claim 24, wherein, There is a gap between adjacent microlenses, and the gap is located between adjacent two current spreading structures.

26. The micro light-emitting diode display chip according to claim 24 or 25, characterized in that, The interior of the microlens has an air gap, and the air gap is located between the epitaxial layer and the current spreading structure.

27. A display panel, comprising a micro light-emitting diode chip according to any one of claims 1 to 26.

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