LED chip and preparation method thereof

Abstract

The application provides an LED chip and a preparation method thereof. A substrate is provided with a plurality of protrusions, and a light-emitting structure is stacked on one side surface of the substrate with the protrusions. The cross-sectional area of the protrusions gradually decreases along a first direction. The cross-sectional area difference corresponding to the unit height of the protrusions along the first direction is a change rate, and the curve of the change rate and the height of the protrusions is in a "V" shape. The first direction is perpendicular to the substrate and points from the substrate to the light-emitting structure. The obtained protrusion shape based on the above setting makes the light form a more comprehensive reflection direction in the protrusions, thereby expanding the light-emitting angle of the LED chip. Thus, the backlight design can be simplified during subsequent display assembly, and the application is especially suitable for micro-LED chips (such as Mini-LED or Micro-LED, etc.).

Description

Technical Field

[0001] This invention relates to the field of light-emitting diodes, and more particularly to an LED chip and its fabrication method. Background Technology

[0002] With the continuous development of semiconductor light-emitting technology, the applications of LEDs are changing rapidly, especially in display technology. At the same time, due to the need for high resolution in LED displays, the spacing and size of LED chips are becoming smaller and smaller, such as Mini-LEDs and other micro-light-emitting devices.

[0003] Mini-LEDs are LED chips with dimensions on the order of 100 micrometers, primarily used in backlighting and direct-view displays. In terms of size, a single Mini-LED chip ranges from 50-200 μm in diameter, with a pixel pitch of approximately 0.5-1 mm. Compared to traditional LED chip backlighting products, this smaller pixel pitch allows for the integration of more LED backlight beads onto a single display screen. This divides the screen into more finely divided backlight zones, facilitating more precise localized light emission adjustment and achieving contrast levels approaching those of OLED screens. Furthermore, compared to OLED screens, Mini-LED backlit screens offer advantages such as longer lifespan and reduced burn-in resistance.

[0004] However, the current Mini-LED chips have a relatively small light-emitting angle, mostly between 130 and 140°. In order to achieve a better display effect, more backlight chips and backlight design need to be integrated. However, the accumulation of multiple backlight chips can also generate more heat, which puts higher demands on the heat dissipation of the equipment. Therefore, the application of Mini-LED in larger-scale displays is extremely challenging.

[0005] In view of this, the inventor has specifically designed an LED chip and its preparation method, which leads to this invention. Summary of the Invention

[0006] The purpose of this invention is to provide an LED chip and its fabrication method to solve the problem of small light emission angle in micro light-emitting devices.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] An LED chip, comprising:

[0009] A substrate having a plurality of protrusions on its surface;

[0010] A light-emitting structure, which is stacked on one side surface of the substrate having a protrusion, is used to provide electrons and holes and perform radiative recombination to emit light;

[0011] Wherein, the cross-sectional area of ​​the protrusion gradually decreases along the first direction; the difference in cross-sectional area per unit height of the protrusion along the first direction is the rate of change, and the curve of the rate of change and the protrusion height is "V" shaped; the first direction is perpendicular to the substrate and points from the substrate to the light-emitting structure.

[0012] Preferably, if the height of the protrusion is H, then the height of the cross section corresponding to the minimum rate of change is 0.4H to 0.8H, including the endpoint values.

[0013] Preferably, a plane is formed between adjacent protrusions.

[0014] Preferably, the sum of the projected areas of all the protrusions on the substrate surface is S1, and the area of ​​the substrate is S2, then 0.2*S2≤S1≤0.8*S2.

[0015] Preferably, a recess is provided on the surface of the substrate facing away from the light-emitting structure, and the recess and the protrusion are offset along the first direction.

[0016] Preferably, the depth of the depression is less than the height of the protrusion.

[0017] Preferably, the number of depressions is less than the number of protrusions.

[0018] Preferably, a buffer layer is provided on the plane.

[0019] Preferably, if the LED chip is a flip-chip structure, then the light-emitting structure includes:

[0020] An epitaxial stack, comprising at least a first type semiconductor layer, an active layer, and a second type semiconductor layer stacked sequentially along the first direction, wherein a local area of ​​the epitaxial stack is etched to a portion of the first type semiconductor layer to form a groove and a mesa; wherein the first type semiconductor layer covers each of the protrusions.

[0021] A reflective structure is mounted on the tabletop;

[0022] An insulating layer is disposed on the sidewall of the groove;

[0023] The first electrode is in contact with the first type of semiconductor layer by being stacked in the groove;

[0024] The second electrode is in contact with the second type of semiconductor layer by being stacked on the mesa.

[0025] Preferably, the reflective structure includes an insulating reflector, and the second electrode forms contact with the second type of semiconductor layer by embedding the insulating reflector through a through-hole;

[0026] Alternatively, the reflective structure includes a metal mirror, with the second electrode stacked on the surface of the metal mirror.

[0027] Preferably, the insulating mirror extends to the sidewall of the epitaxial stack and the sidewall of the groove.

[0028] Preferably, the insulating reflector includes a DBR reflector.

[0029] Preferably, the insulating layer extends beyond the exposed surface of the epitaxial stack.

[0030] The present invention also provides a method for fabricating an LED chip, wherein the LED chip is a flip-chip structure, and the fabrication method includes the following steps:

[0031] S01. A substrate is provided, the surface of which has a plurality of protrusions and a plane is formed between adjacent protrusions;

[0032] Wherein, the cross-sectional area of ​​the protrusion gradually decreases along the first direction; the difference in cross-sectional area per unit height of the protrusion along the first direction is the rate of change, and the curve of the rate of change and the protrusion height is "V" shaped; the first direction is perpendicular to the substrate and points from the substrate to the light-emitting structure;

[0033] S02. A buffer layer is formed, wherein the buffer layer is disposed within the plane;

[0034] S03. Growing an epitaxial stack, the epitaxial stack comprising at least a first type semiconductor layer, an active layer, and a second type semiconductor layer stacked sequentially along the growth direction; wherein the first type semiconductor layer covers each of the protrusions;

[0035] S04. Etching a portion of the epitaxial stack to a portion of the first type semiconductor layer to form a plurality of grooves and mesa, wherein the grooves and mesa are disposed opposite to each other.

[0036] S05. By deeply etching the epitaxial stack to expose the substrate surface, a plurality of LED units are formed by spacing them between each other through channels;

[0037] S06. A reflective structure is formed, which is disposed on the platform of each of the LED units;

[0038] S07. An insulating layer is formed on the sidewall of the groove;

[0039] S08, depositing the first and second electrodes;

[0040] The first electrode forms contact with the first type of semiconductor layer by being stacked in the groove;

[0041] The second electrode forms contact with the second type of semiconductor layer by being stacked on the mesa.

[0042] Preferably, if the height of the protrusion is H, then the height of the cross section corresponding to the minimum rate of change is 0.4H to 0.8H, including the endpoint values.

[0043] Preferably, a recess is provided on the surface of the substrate facing away from the light-emitting structure, and the recess and the protrusion are offset along the first direction.

[0044] As can be seen from the above technical solution, the LED chip provided by the present invention has a substrate with multiple protrusions, and the light-emitting structure is stacked on the surface of the substrate with the protrusions. The cross-sectional area of ​​the protrusions gradually decreases along a first direction; the difference in cross-sectional area per unit height of the protrusion along the first direction is the rate of change, and the curve of the rate of change versus the protrusion height is V-shaped. The first direction is perpendicular to the substrate and points from the substrate to the light-emitting structure. Based on the protrusion shape obtained by the above arrangement, light forms a more comprehensive reflection direction on the protrusions, thereby expanding the light-emitting angle of the LED chip. This simplifies the backlight design during subsequent display assembly, and is particularly suitable for micro LED chips (such as Mini-LED or Micro-LED).

[0045] Then, by setting the height of the protrusion to H, the height of the cross-section corresponding to the minimum rate of change is 0.4H to 0.8H, so that the inflection point of the rate of change of the cross-sectional area of ​​the protrusion is located in the region of the middle height, thereby expanding the light reflection direction of a single protrusion and further expanding the light emission angle of the LED chip.

[0046] Finally, a recess is provided on the surface of the substrate facing away from the light-emitting structure, and the recess and the protrusion are offset along the first direction. That is, while ensuring the light emission angle, the spatial offset between the recess and the protrusion enables a better optical path transmission system for the light emitted by the active layer; in particular, after passing through the interfaces between the epitaxial material, the substrate and the air, the light will not overlap in the vertical direction, thereby reducing secondary reflection of light in vertical space, allowing light to escape from the light-emitting device better and effectively improving its luminous efficiency.

[0047] The present invention also provides a method for preparing an LED chip, which achieves the beneficial effects of the LED chip mentioned above, and its process is simple and convenient, making it easy to mass-produce. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of the structure of the LED chip provided in an embodiment of the present invention;

[0050] Figure 2 This is a top view of the LED chip provided in an embodiment of the present invention;

[0051] Figures 3.1 to 3.9 This is a schematic diagram of the structure corresponding to the steps of the LED chip fabrication method provided in the embodiments of the present invention;

[0052] Symbols in the figure: 1. Substrate, 1.1. Protrusion, 1.2. Plane, 2. Buffer layer, 3. Type I semiconductor layer, 4. Active layer, 5. Type II semiconductor layer, 6. Groove, 7. Mesa, 8. Reflective structure, 9. Insulating layer, 10. First electrode, 11. Second electrode, 12. Recess. Detailed Implementation

[0053] To make the content of this invention clearer, the following description, in conjunction with the accompanying drawings, further illustrates the invention. This invention is not limited to this specific embodiment. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0054] like Figure 1 , Figure 2 As shown, an LED chip includes:

[0055] Substrate 1, the surface of which has a plurality of protrusions 1.1;

[0056] A light-emitting structure is stacked on one side surface of the substrate 1 with a protrusion 1.1, for providing electrons and holes and performing radiative recombination light emission;

[0057] Wherein, the cross-sectional area of ​​the protrusion 1.1 gradually decreases along the first direction; the difference in cross-sectional area per unit height of the protrusion 1.1 along the first direction is the rate of change, and the curve of the rate of change and the height of the protrusion 1.1 is "V" shaped; the first direction is perpendicular to the substrate 1 and points from the substrate 1 to the light-emitting structure.

[0058] It should be noted that the material type of substrate 1 is not limited in this embodiment. For example, substrate 1 can be, but is not limited to, sapphire substrate 1, silicon substrate 1, etc.

[0059] It should be noted that the specific value of the rate of change is not elaborated in this embodiment. As long as the curve of the rate of change and the height of the protrusion 1.1 is "V" shaped, the cross-section of the protrusion 1.1 changes relatively gently in a certain area to obtain a larger diffuse reflection area.

[0060] Based on the above embodiments, in one embodiment of the present invention, the height of the protrusion 1.1 is H, and the height of the cross-section corresponding to the minimum rate of change is 0.4H to 0.8H, including the endpoint value. This makes the inflection point of the rate of change of the cross-sectional area of ​​the protrusion 1.1 located in the region of intermediate height, thereby expanding the diffuse reflection surface of a single protrusion 1.1 to further expand the light emission angle of the LED chip.

[0061] Based on the above embodiments, in one embodiment of the present invention, a plane 1.2 is formed between adjacent protrusions 1.1.

[0062] Based on the above embodiments, in one embodiment of the present invention, the sum of the projected areas of all the protrusions 1.1 on the surface of the substrate 1 is S1, and the area of ​​the substrate 1 is S2, then 0.2*S2≤S1≤0.8*S2.

[0063] Based on the above embodiments, in one embodiment of the present invention, a recess is provided on the surface of the substrate 1 facing away from the light-emitting structure, and the recess and the protrusion 1.1 are offset along the first direction.

[0064] Based on the above embodiments, in one embodiment of the present invention, the depth of the recess is less than the height of the protrusion 1.1.

[0065] Based on the above embodiments, in one embodiment of the present invention, the number of the recesses is less than the number of the protrusions 1.1.

[0066] Based on the above embodiments, in one embodiment of the present invention, a buffer layer 2 is provided on the plane 1.2.

[0067] Based on the above embodiments, in an embodiment of the present invention, if the LED chip is a flip-chip structure, then the light-emitting structure includes:

[0068] An epitaxial stack, the epitaxial stack comprising at least a first type semiconductor layer 3, an active layer 4 and a second type semiconductor layer 5 stacked sequentially along the first direction, wherein a local area of ​​the epitaxial stack is etched to a portion of the first type semiconductor layer 3 to form a groove 6 and a mesa 7; wherein the first type semiconductor layer 3 covers each of the protrusions 1.1;

[0069] A reflective structure 8 is disposed on the platform 7;

[0070] An insulating layer 9 is disposed on the sidewall of the groove 6;

[0071] The first electrode 10 is in contact with the first type semiconductor layer 3 by being stacked on the groove 6;

[0072] The second electrode 11 is in contact with the second type semiconductor layer 5 by being stacked on the mesa 7.

[0073] It is worth mentioning that, in the above embodiments, the types of the first type semiconductor layer 3, the active layer 4 and the second type semiconductor layer 5 of the epitaxial stack can also be unrestricted in the LED chip of this embodiment. For example, the first type semiconductor layer 3 can be, but is not limited to, a gallium nitride layer, and correspondingly, the second type semiconductor layer 5 can be, but is not limited to, a gallium nitride layer.

[0074] Based on the above embodiments, in one embodiment of this application, the reflective structure 8 includes an insulating reflector, and the second electrode 11 forms contact with the second type semiconductor layer 5 by embedding the insulating reflector through a through hole;

[0075] In other embodiments of this application, the reflective structure 8 may include a metal reflector, and the second electrode 11 is stacked on the surface of the metal reflector.

[0076] Based on the above embodiments, in one embodiment of this application, the insulating reflector extends to the sidewall of the epitaxial stack and the sidewall of the groove 6.

[0077] Based on the above embodiments, in one embodiment of this application, the insulating reflector includes a DBR reflector.

[0078] Based on the above embodiments, in one embodiment of this application, the insulating layer 9 extends the exposed surface of the epitaxial stack.

[0079] The present invention also provides a method for fabricating an LED chip, wherein the LED chip is a flip-chip structure, and the fabrication method includes the following steps:

[0080] S01, such as Figure 3.1 As shown, a substrate 1 is provided, the surface of the substrate 1 having a plurality of protrusions 1.1, and a plane 1.2 is formed between adjacent protrusions 1.1;

[0081] Wherein, the cross-sectional area of ​​the protrusion 1.1 gradually decreases along the first direction; the difference in cross-sectional area per unit height of the protrusion 1.1 along the first direction is the rate of change, and the curve of the rate of change and the height of the protrusion 1.1 is "V" shaped; the first direction is perpendicular to the substrate 1 and points from the substrate 1 to the light-emitting structure;

[0082] It should be noted that the type of substrate 1 is not limited in this embodiment. For example, substrate 1 can be, but is not limited to, sapphire substrate 1, silicon substrate 1, etc.

[0083] Based on the above embodiments, in one embodiment of the present invention, the height of the protrusion 1.1 is H, and the height of the cross-section corresponding to the minimum rate of change is 0.4H to 0.8H, including the endpoint value. This makes the inflection point of the rate of change of the cross-sectional area of ​​the protrusion 1.1 located in the region of intermediate height, thereby expanding the diffuse reflection surface of a single protrusion 1.1 to further expand the light emission angle of the LED chip.

[0084] Based on the above embodiments, in one embodiment of the present invention, a plane 1.2 is formed between adjacent protrusions 1.1.

[0085] Based on the above embodiments, in one embodiment of the present invention, the sum of the projected areas of all the protrusions 1.1 on the surface of the substrate 1 is S1, and the area of ​​the substrate 1 is S2, then 0.2*S2≤S1≤0.8*S2.

[0086] S02, such as Figure 3.2 As shown, a buffer layer 2 is formed, and the buffer layer 2 is disposed within the plane 1.2;

[0087] It should be noted that the type of buffer layer 2 is not limited in this embodiment. For example, buffer layer 2 can be an AlN buffer layer 2.

[0088] It should be noted that the buffer layer 2 does not cover the protrusion 1.1.

[0089] S03, such as Figure 3.3 As shown, an epitaxial stack is grown, the epitaxial stack including at least a first type semiconductor layer 3, an active layer 4 and a second type semiconductor layer 5 stacked sequentially along the growth direction; wherein, the first type semiconductor layer 3 covers each of the protrusions 1.1;

[0090] It is worth mentioning that, in the above embodiments, the types of the first type semiconductor layer 3, the active layer 4 and the second type semiconductor layer 5 of the epitaxial stack can also be unrestricted in the LED chip of this embodiment. For example, the first type semiconductor layer 3 can be, but is not limited to, a gallium nitride layer, and correspondingly, the second type semiconductor layer 5 can be, but is not limited to, a gallium nitride layer.

[0091] S04, such as Figure 3.4 As shown, a local area of ​​the epitaxial stack is etched to a portion of the first type semiconductor layer 3 to form a plurality of grooves 6 and mesa 7, wherein the grooves 6 and mesa 7 are disposed opposite to each other.

[0092] S05, such as Figure 3.5 As shown, by deeply etching the epitaxial stack to expose the surface of the substrate 1, a plurality of LED units are formed by spacing them between each other through channels;

[0093] It should be emphasized that, in order to highlight the technical points of the present invention, only a single LED unit in the micro-light-emitting device is shown in the figure in the embodiments of the present invention. In actual use, the surface of the substrate 1 may contain tens of thousands of LED units, depending on the specific situation. This application does not limit this.

[0094] S06, such as Figure 3.6 As shown, a reflective structure 8 is formed, which is disposed on the platform 7 of each of the LED units;

[0095] In one embodiment of this application, the reflective structure 8 includes an insulating mirror. Further, in another embodiment, the insulating mirror extends to the sidewall of the epitaxial stack and the sidewall of the groove 6. As a preferred embodiment, the insulating mirror includes a DBR mirror.

[0096] In other embodiments of this application, the reflective structure 8 may include a metal reflector, and therefore, the metal reflector is only disposed on the platform 7.

[0097] S07, such as Figure 3.7 As shown, an insulating layer 9 is formed, which is disposed on the sidewall of the groove 6;

[0098] Based on the above embodiments, in one embodiment of this application, the insulating layer 9 includes a material layer such as silicon oxide and silicon nitride.

[0099] Based on the above embodiments, in one embodiment of this application, the insulating layer 9 includes an insulating material layer with a high thermal conductivity, such as one or more of AlN layer, BN layer, and Al2O3 layer.

[0100] S08, such as Figure 3.8 As shown, the first electrode 10 and the second electrode 11 are deposited.

[0101] The first electrode 10 forms contact with the first type semiconductor layer 3 by being stacked on the groove 6;

[0102] The second electrode 11 forms contact with the second type semiconductor layer 5 by being stacked on the mesa 7.

[0103] Based on the above embodiments, in one embodiment of this application, the first electrode 10 and the second electrode 11 include, but are not limited to, one or more combinations of metals such as Cr, Ni, Al, Ti, Pt, Au, Sn, Ag, and Cu.

[0104] S09, such as Figure 3.9 As shown, the substrate 1 is thinned, and several recesses 12 are formed on the surface of the substrate 1 facing away from the light-emitting structure;

[0105] Based on the above embodiments, in one embodiment of this application, the recess and the protrusion 1.1 are offset along the first direction.

[0106] Based on the above embodiments, in one embodiment of the present invention, the depth of the recess is less than the height of the protrusion 1.1.

[0107] Based on the above embodiments, in one embodiment of the present invention, the number of the recesses is less than the number of the protrusions 1.1.

[0108] As can be seen from the above technical solution, the LED chip provided by the present invention has a substrate 1 with multiple protrusions 1.1, and the light-emitting structure is stacked on the surface of the substrate 1 with the protrusions 1.1. The cross-sectional area of ​​the protrusions 1.1 gradually decreases along a first direction; the difference in cross-sectional area per unit height of the protrusions 1.1 along the first direction is the rate of change, and the curve of the rate of change and the height of the protrusions 1.1 is "V"-shaped. The first direction is perpendicular to the substrate 1 and points from the substrate 1 to the light-emitting structure. Based on the shape of the protrusions 1.1 obtained by the above configuration, light forms a more comprehensive reflection direction on the protrusions 1.1, thereby expanding the light-emitting angle of the LED chip. This simplifies the backlight design during subsequent display assembly, and is especially suitable for micro LED chips (such as Mini-LED or Micro-LED).

[0109] Then, by setting the height of the protrusion 1.1 to H, the height of the cross-section corresponding to the minimum rate of change is 0.4H to 0.8H, so that the inflection point of the rate of change of the cross-sectional area of ​​the protrusion 1.1 is located in the region of the middle height, thereby expanding the light reflection direction of a single protrusion 1.1, so as to further expand the light emission angle of the LED chip.

[0110] Finally, a recess is provided on the surface of the substrate 1 facing away from the light-emitting structure, and the recess and the protrusion 1.1 are offset along the first direction. That is, while ensuring the light emission angle, the spatial offset between the recess and the protrusion allows the light emitted by the active layer to achieve a better optical path transmission system; in particular, after passing through the interfaces between the epitaxial material, the substrate and the air, the light will not overlap in the vertical direction, thereby reducing secondary reflection of light in vertical space, allowing light to escape from the light-emitting device better and effectively improving its luminous efficiency.

[0111] The present invention also provides a method for preparing an LED chip, which achieves the beneficial effects of the LED chip mentioned above, and its process is simple and convenient, making it easy to mass-produce.

[0112] Example 2

[0113] The difference between this embodiment and Embodiment 1 is that the LED chip provided in this embodiment has a front-mounted structure. Therefore, in this embodiment, the LED chip does not need to have a reflective structure 8 on the surface of each LED unit. The specific structure is shown in Figure 3. The preparation method can refer to the preparation method shown in Embodiment 1, but the relevant steps of the reflective structure 8 can be omitted. This embodiment will not elaborate on this.

[0114] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0115] It should also be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes the aforementioned element.

[0116] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An LED chip, characterized in that, include: A substrate having a plurality of protrusions on its surface; A light-emitting structure, which is stacked on one side surface of the substrate having a protrusion, is used to provide electrons and holes and perform radiative recombination to emit light; Wherein, the cross-sectional area of ​​the protrusion gradually decreases along the first direction; the difference in cross-sectional area per unit height of the protrusion along the first direction is the rate of change, and the curve of the rate of change and the protrusion height is "V" shaped; the first direction is perpendicular to the substrate and points from the substrate to the light-emitting structure; Wherein, the LED chip is a flip-chip structure; the height of the protrusion is H, then the height of the cross section corresponding to the minimum rate of change is 0.4H~0.8H, including the endpoint values; A recess is provided on the surface of the substrate facing away from the light-emitting structure, and the recess and the protrusion are offset along the first direction.

2. The LED chip according to claim 1, characterized in that, A plane is formed between adjacent protrusions.

3. The LED chip according to claim 2, characterized in that, The sum of the projected areas of all the protrusions on the substrate surface is S1, and the area of ​​the substrate is S2. Then, 0.2*S2≤S1≤0.5*S2.

4. The LED chip according to claim 2, characterized in that, A buffer layer is provided on the plane.

5. The LED chip according to claim 1, characterized in that, The light-emitting structure includes: An epitaxial stack, comprising at least a first type semiconductor layer, an active layer, and a second type semiconductor layer stacked sequentially along the first direction, wherein a local area of ​​the epitaxial stack is etched to a portion of the first type semiconductor layer to form a groove and a mesa; wherein the first type semiconductor layer covers each of the protrusions. A reflective structure is mounted on the tabletop; An insulating layer is disposed on the sidewall of the groove; The first electrode is in contact with the first type of semiconductor layer by being stacked in the groove; The second electrode is in contact with the second type of semiconductor layer by being stacked on the mesa.

6. The LED chip according to claim 5, characterized in that, The reflective structure includes an insulating reflector, and the second electrode forms contact with the second type of semiconductor layer by embedding the insulating reflector through a through hole; Alternatively, the reflective structure includes a metal mirror, with the second electrode stacked on the surface of the metal mirror.

7. The LED chip according to claim 6, characterized in that, The insulating mirror extends to the sidewall of the epitaxial stack and the sidewall of the groove.

8. The LED chip according to claim 6, characterized in that, The insulating reflector includes a DBR reflector.

9. The LED chip according to any one of claims 5 to 8, characterized in that, The insulating layer covers the exposed surface of the epitaxial stack.

10. A method for fabricating an LED chip, characterized in that, If the LED chip has a flip-chip structure, the fabrication method includes the following steps: S01. A substrate is provided, the surface of which has a plurality of protrusions and a plane is formed between adjacent protrusions; Wherein, the cross-sectional area of ​​the protrusion gradually decreases along the first direction; the difference in cross-sectional area per unit height of the protrusion along the first direction is the rate of change, and the curve of the rate of change and the protrusion height is "V" shaped; the first direction is perpendicular to the substrate and points from the substrate to the light-emitting structure; S02. A buffer layer is formed, wherein the buffer layer is disposed within the plane; S03. Growing an epitaxial stack, the epitaxial stack comprising at least a first type semiconductor layer, an active layer, and a second type semiconductor layer stacked sequentially along the first direction; wherein the first type semiconductor layer covers each of the protrusions; S04. Etching a local area of ​​the epitaxial stack to a portion of the first type semiconductor layer to form a plurality of grooves and mesa, the grooves and mesa being disposed opposite to each other; S05. By deeply etching the epitaxial stack to expose the substrate surface, a plurality of LED units are formed by spacing them between each other through channels; S06. A reflective structure is formed, which is disposed on the platform of each of the LED units; S07. An insulating layer is formed on the sidewall of the groove; S08, depositing the first and second electrodes; The first electrode forms contact with the first type of semiconductor layer by being stacked in the groove; The second electrode forms contact with the second type of semiconductor layer by being stacked on the mesa; Wherein, the height of the protrusion is H, then the height of the cross section corresponding to the minimum rate of change is 0.4H~0.8H, including the endpoint values; A recess is provided on the surface of the substrate facing away from the light-emitting structure, and the recess and the protrusion are offset along the first direction.

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