Mled and display device comprising same

Abstract

Disclosed in the present invention are an mLED and a display device comprising same. The mLED has a semiconductor layer sequence, wherein the semiconductor layer sequence comprises a back side and a front side, and comprises a first-type semiconductor layer and a second-type semiconductor layer in sequence from the front side, and an active layer is located between the first-type semiconductor layer and the second-type semiconductor layer; the back side of the semiconductor layer sequence is provided with a recess, which passes through the second-type semiconductor layer and the active layer to expose the first-type semiconductor layer; the back side of the semiconductor layer sequence comprises a first mesa within the recess, a second mesa on the second-type semiconductor layer, and a recess sidewall located between the first mesa and the second mesa; and the back side of the semiconductor layer sequence is provided with a first metal electrode electrically connected to the first-type semiconductor layer and a second metal electrode electrically connected to the second-type semiconductor layer, the first metal electrode and the second metal electrode are configured to be bonded to an external power supply, and the chromium content of the first metal electrode is greater than that of the second metal electrode, thereby solving the problem of chromium in the second metal electrode being prone to migrating.

Description

A micro light-emitting diode and its display device Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing, specifically relating to micro light-emitting diodes and display devices. Background Technology

[0002] Micro-LEDs (mLEDs) are currently a hot research topic as a next-generation display light source. They boast advantages such as low power consumption, high brightness, ultra-high resolution and color saturation, fast response speed, low energy consumption, and long lifespan. Furthermore, their power consumption is approximately 10% of that of LCDs and 50% of that of OLEDs. Compared to OLEDs, which are also self-emissive, mLEDs offer several times the brightness and can achieve high pixel density. These significant advantages make mLEDs a promising candidate to replace current OLEDs and LCDs as the light source for next-generation displays. However, mLEDs cannot yet be mass-produced due to numerous technical challenges that need to be overcome, one of the most important being improving the yield of micrometer-scale (μm) LED chips. Summary of the Invention

[0003] To improve the yield of micron-sized chips, this invention provides a micro-light-emitting diode with a semiconductor layer sequence, including a back side and a front side. Starting from the front side, it sequentially includes a first type semiconductor layer and a second type semiconductor layer, with an active layer located between them. The back side of the semiconductor layer sequence has a groove that penetrates the second type semiconductor layer and the active layer, exposing the first type semiconductor layer. The back side of the semiconductor layer sequence includes a first mesa within the groove, a second mesa on the second type semiconductor layer, and a groove sidewall located between them. The back side of the semiconductor layer sequence is provided with a first metal electrode electrically connected to the first type semiconductor layer and a second metal electrode electrically connected to the second type semiconductor layer. The chromium content of the first metal electrode is greater than that of the second metal electrode. The length of the second metal electrode is 2μm to 30μm. By reducing or eliminating the chromium content of the second metal electrode, chromium metal leakage is avoided in the micron-sized electrode structure.

[0004] This invention also provides a display device comprising a plurality of microlight-emitting diodes (LEDs) and a substrate. The LEDs are disposed on the substrate. The LEDs are characterized by being sealed with epoxy resin. Each LED has a semiconductor layer sequence, including a back side and a front side. Starting from the front side, the semiconductor layer sequence sequentially includes a first type semiconductor layer and a second type semiconductor layer, with an active layer located between them. The back side of the semiconductor layer sequence has a groove penetrating the second type semiconductor layer and the active layer, exposing the first type semiconductor layer. The back side of the semiconductor layer sequence includes a first mesa within the groove, a second mesa on the second type semiconductor layer, and a groove sidewall located between them. A first metal electrode electrically connected to the first type semiconductor layer and a second metal electrode electrically connected to the second type semiconductor layer are disposed on the back side of the semiconductor layer sequence. The first metal electrode has a higher chromium content than the second metal electrode, and the length of the second metal electrode is 2 μm to 30 μm. Under epoxy resin sealing conditions, the high stress of the epoxy resin may lead to chromium leakage. By eliminating the chromium content in the second metal electrode, the risk of chromium leakage is reduced.

[0005] Other beneficial effects of the present invention will be described step by step through the embodiments and accompanying drawings. Attached Figure Description

[0006] 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, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0007] Figures 1 and 2 are schematic cross-sectional views of micro-light-emitting diode chips and micro-display devices in the prior art, respectively.

[0008] Figures 3 and 4 are respectively a cross-sectional view and a top view of the first embodiment of the present invention;

[0009] Figure 5 is a cross-sectional schematic diagram of the second embodiment of the present invention;

[0010] Figure 6 is a cross-sectional schematic diagram of the third and fourth embodiments of the present invention.

[0011] The diagram is labeled as follows: 110, Semiconductor layer sequence; 111, First type semiconductor layer; 112, Second type semiconductor layer; 113, Active layer; 210, First metal electrode; 211, First layer of the first metal electrode; 220, Second metal electrode; 221, First layer of the second metal electrode; 222, Second layer of the second metal electrode; 300, Passivation layer; 400, Transparent conductive layer; 500, Substrate; C1, Micro LED; G1, Groove; K1, First opening; K2, Second opening; K12, First electrode hole; K22, Second electrode hole; M1, First mesa; M2, Second mesa; P1, Silicone; P2, Epoxy resin; S1, Groove sidewall; L1, Length of the second metal electrode; L2, Length of the first layer of the second metal electrode. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0013] In some embodiments, a micro-light-emitting diode is provided, having a semiconductor layer sequence including a back side and a front side. Starting from the front side, it sequentially includes a first type semiconductor layer and a second type semiconductor layer, with an active layer located between them. The back side of the semiconductor layer sequence has a groove that penetrates the second type semiconductor layer and the active layer, exposing the first type semiconductor layer. The back side of the semiconductor layer sequence includes a first mesa within the groove, a second mesa on the second type semiconductor layer, and a groove sidewall located between them. The back side of the semiconductor layer sequence is provided with a first metal electrode electrically connected to the first type semiconductor layer and a second metal electrode electrically connected to the second type semiconductor layer. Metal migration depends on high temperature and high humidity conditions. Under the catalysis of water vapor, chromium-containing ions migrate. The second metal electrode has a high electric field, and the chromium in the second metal electrode is more easily migrated than the chromium in the first metal electrode. The chromium content of the first metal electrode is set to be greater than that of the second metal electrode. The length of the second metal electrode is 2 μm to 30 μm. As the size of the second metal electrode continues to shrink, the metal encapsulation decreases, making chromium leakage more likely. Reducing the chromium content of the second metal electrode helps to reduce the risk of chromium leakage.

[0014] In some embodiments, the first metal electrode is in contact with the first type of semiconductor layer via chromium, while the second metal electrode does not contain chromium, i.e., it is not connected to the second type of semiconductor layer via chromium, or it is not connected to the transparent conductive layer via chromium.

[0015] In some embodiments, the length of the second metal electrode is 5 μm to 30 μm. Increasing the minimum length of the second metal electrode compensates for the loss of adhesion due to the reduced chromium content and reduces the risk of the second metal electrode detaching.

[0016] In some embodiments, the first metal electrode is completely disposed within the groove, which is a non-closed step; three of the four sides of the groove are exposed, and the other side is a sidewall of the groove, or two of the four sides of the groove are exposed, and the other two sides are sidewalls of the groove.

[0017] In some embodiments, the first metal electrode extends from the groove to the second platform, and the height of the groove sidewall is 0.5 μm to 2 μm.

[0018] In some embodiments, the projected area of ​​the back surface of the first metal electrode and / or the second metal electrode is 25 μm. 2 Up to 100μm 2 The projected area of ​​the first back surface of the second metal electrode is 30 μm. 2 Up to 100μm 2 To maximize the area of ​​the first layer of the second metal electrode, the adhesion of the electrode should be increased.

[0019] In some embodiments, the distance between the first metal electrode and the second metal electrode is 4 μm to 10 μm.

[0020] In some embodiments, the second mesa is located on the side of the second type semiconductor layer away from the active layer. A passivation layer is disposed on the second mesa, covering at least from the second mesa to the first mesa. The passivation layer has a first opening on the first mesa and a second opening on the second mesa. A first metal electrode is electrically connected to the first type semiconductor layer through the first opening, and a second metal electrode is electrically connected to the second type semiconductor layer through the second opening. A transparent conductive layer is disposed between the second metal electrode and the second type semiconductor layer.

[0021] In some embodiments, the maximum aperture of the second opening is 2 μm to 20 μm, ensuring that the second metal electrode and the second type of semiconductor layer have sufficient connectivity to compensate for the loss of adhesion due to the reduction or elimination of chromium content.

[0022] In some embodiments, a passivation layer is disposed between a second metal electrode and a second type of semiconductor layer, with the second metal electrode extending from a second opening to the upper surface of the back side of the passivation layer. The thickness of the passivation layer is 0.5 μm to 3 μm.

[0023] In some embodiments, the second metal electrode is not disposed between the passivation layer and the second type of semiconductor layer, or the second metal electrode is not disposed between the passivation layer and the transparent conductive layer.

[0024] In some embodiments, the back surface of the first metal electrode corresponding to the first opening has a first electrode hole, and the back surface of the second metal electrode corresponding to the second opening has a second electrode hole. The opening area of ​​the first electrode hole is smaller than the opening area of ​​the second electrode hole. Increasing the opening area of ​​the second electrode hole limits the effective contact area of ​​the first metal electrode as it extends from the groove to the second platform. This embodiment increases the contact area between the second metal electrode and the second type of semiconductor layer or transparent conductive layer on its front side, while also increasing the bonding area when the first metal electrode is bonded to the outside, thus reducing the risk of bond detachment.

[0025] In some embodiments, the opening area of ​​the first electrode hole accounts for 10% to 40% of the back surface area of ​​the first metal electrode, and the opening area of ​​the second electrode hole accounts for 15% to 50% of the back surface area of ​​the second metal electrode, thereby increasing the bonding area when the first metal electrode is bonded to the outside and reducing the risk of bond detachment.

[0026] In some embodiments, the first metal electrode and the second metal electrode have n metal layers, where n is an integer greater than or equal to 2. The first layer of the first metal electrode, near the first mesa, contains chromium and is used to connect to the first type of semiconductor layer. The first layer of the second metal electrode, near the second mesa, does not contain chromium and is in contact with a transparent conductive layer, which is electrically connected to the second type of semiconductor layer.

[0027] In some embodiments, the length of the first layer of the second metal electrode is greater than 2 μm to 25 μm. The first layer of the second metal electrode serves as a contact layer with the second type semiconductor layer or transparent conductive layer. The material includes, for example, nickel, aluminum, titanium, platinum, gold, or an alloy of any combination thereof. The adhesion of the first layer to the second type semiconductor layer and transparent conductive layer is lower than that of chromium. Therefore, increasing the length is beneficial to improving the overall adhesion of the second metal electrode.

[0028] In some embodiments, the first layer of the second metal electrode comprises titanium, which has high adhesion and is not easily migrated under an electric field.

[0029] In some embodiments, the first metal electrode is an N-type electrode and the second metal electrode is a P-type electrode.

[0030] In some embodiments, the micro-LED is sealed with epoxy resin. The micro-LED has a semiconductor layer sequence, including a back side and a front side. Starting from the front side, it sequentially includes a first type semiconductor layer and a second type semiconductor layer, with an active layer located between them. The back side of the semiconductor layer sequence has a groove that penetrates the second type semiconductor layer and the active layer, exposing the first type semiconductor layer. The back side of the semiconductor layer sequence includes a first mesa within the groove, a second mesa on the second type semiconductor layer, and a groove sidewall located between them. The back side of the semiconductor layer sequence is provided with a first metal electrode electrically connected to the first type semiconductor layer and a second metal electrode electrically connected to the second type semiconductor layer. The chromium content of the first metal electrode is greater than that of the second metal electrode, and the length of the second metal electrode is 2 μm to 30 μm. Because epoxy resin has high stress, chromium leakage from the second metal electrode is likely to occur. Therefore, reducing or eliminating the chromium content of the first electrode is beneficial for improving product yield.

[0031] In some embodiments, the first metal electrode is in contact with a first type of semiconductor layer via chromium, and the second metal electrode does not contain chromium.

[0032] Referring to Figures 1 and 2, in the prior art, silicone P1 is usually used as the encapsulation material. Silicone P1 has the technical effect of low stress. The micro light-emitting diode includes: a semiconductor layer sequence 110, which has a first type semiconductor layer 111 and a first type semiconductor layer 112, with an active layer 113 located between them. A first metal electrode 210 is electrically connected to the first type semiconductor layer 111, and a second metal electrode 220 is electrically connected to the first type semiconductor layer 112.

[0033] On the one hand, in order to replace existing technologies, when the client uses epoxy resin as the encapsulation material, the stress of the encapsulation adhesive increases, making it easier for the chromium in the first layer 221 of the second metal electrode 220 to leak. On the other hand, since the size of the micro LED chip is at the micrometer level and significantly smaller than that of the traditional LED chip, the size of the second metal electrode 220 also needs to be continuously reduced. The first layer 221 of the second metal electrode 220 usually serves as a contact layer to provide adhesive force, and the second layer or above of the second metal electrode 220 serves as a protective layer to cover the first layer 221 of the second metal electrode 220 and prevent the material of the first layer 221 of the second metal electrode 220 from leaking. As the size of the second metal electrode 220 continues to shrink, the covering effect of the second layer 222 of the second metal electrode 220 decreases, making it easier for the material of the first layer 221 of the second metal electrode 220 to leak.

[0034] Referring to Figures 3 and 4, in the first embodiment of the present invention, a micro-light-emitting diode (LED) is provided. The LED is rectangular, with a short side length of 10 μm to 30 μm and a long side length of 15 μm to 40 μm. For example, the size of the LED is 10 μm * 25 μm. The LED has a semiconductor layer sequence 110, which includes a back side and a front side. Starting from the front side, the semiconductor layer sequence 110 includes a first type semiconductor layer 111 and a first type semiconductor layer 112 in sequence, with an active layer 113 located between them. The first type semiconductor layer 111 of the LED is at least partially removed from the front side, for example, through a substrate stripping and epitaxial thinning process. The back side of semiconductor layer sequence 110 has a groove G1, which serves as a Mesa trench, providing a window for fabricating electrodes. The groove G1 penetrates the first type semiconductor layer 112 and the active layer 113, exposing the first type semiconductor layer 111. The back side of semiconductor layer sequence 110 includes a first mesa M1 within the groove G1, a second mesa M2 on the first type semiconductor layer 112, and a sidewall S1 of the groove G1 located between the two. The back side of semiconductor layer sequence 110 is provided with a first metal electrode 210 electrically connected to the first type semiconductor layer 111 and a second metal electrode 220 electrically connected to the first type semiconductor layer 112. The chromium content of the first metal electrode 210 is greater than that of the second metal electrode 220. The first metal electrode 210 and the second metal electrode 220 are used for bonding to an external power source. The length L1 of the second metal electrode 220 is 2 μm to 30 μm. In this embodiment, the semiconductor layer sequence 110 is gallium nitride-based, the first type semiconductor layer 111 is an N-type semiconductor layer, the first type semiconductor layer 112 is a P-type semiconductor layer, the first metal electrode 210 is an N-type electrode, and the second metal electrode 220 is a P-type electrode.

[0035] In some embodiments of this example, the length L1 of the second metal electrode 220 is 5 μm to 30 μm.

[0036] In some embodiments of this example, the projected area of ​​the back surface of the first metal electrode 210 and / or the second metal electrode 220 is 25 μm. 2 Up to 100μm 2 .

[0037] In some embodiments of this example, the second metal electrode 220 is not plated with chromium metal; for example, the chromium content of the second metal electrode 220 is zero. The distance between the first metal electrode 210 and the second metal electrode 220 is 4 μm to 10 μm.

[0038] In this embodiment, the first metal electrode 210 extends from the groove G1 to the second mesa M2 on the first type semiconductor layer 112. Two of the four sides of the groove G1 are exposed, and the other two sides are the sidewalls S1 of the groove G1. The height of the sidewalls S1 of the groove G1 is 0.5 μm to 2 μm.

[0039] In some embodiments of this example, the second platform M2 is rectangular, with a single-side dimension of 5μm to 35μm. Experiments have shown that a rectangle at a small size helps to increase the current density of the product, thereby improving the product brightness.

[0040] In some embodiments of this example, the first metal electrode 210 is completely disposed within the groove G1, which is a non-closed step; three of the four sides of the groove G1 are exposed, and the other side is the sidewall S1 of the groove G1.

[0041] In this embodiment, the second mesa M2 is located on the side of the first type semiconductor layer 112 away from the active layer 113. A passivation layer 300 is disposed on the second mesa M2, covering at least from the second mesa M2 to the first mesa M1. The passivation layer 300 has a first opening K1 on the first mesa M1 and a second opening K2 on the second mesa M2. The first metal electrode 210 is electrically connected to the first type semiconductor layer 111 through the first opening K1, and the second metal electrode 220 is electrically connected to the first type semiconductor layer 112 through the second opening K2. The maximum aperture of the second opening K2 is 2μm to 20μm. A transparent conductive layer 400 is disposed between the second metal electrode 220 and the first type semiconductor layer 112.

[0042] The passivation layer 300 is made of materials including silicon dioxide, silicon nitride, aluminum oxide, or titanium oxide, and mainly serves as an electrical insulator. In some cases, a DBR structure can also be used to increase light reflection. The passivation layer 300 is disposed between the second metal electrode 220 and the first type semiconductor layer 112. The second metal electrode 220 extends from the second opening K2 to the upper surface of the back side of the passivation layer 300. The thickness of the passivation layer 300 is 0.5 μm to 3 μm. In this embodiment, the second metal electrode 220 is not disposed between the passivation layer 300 and the first type semiconductor layer 112, or the second metal electrode 220 is not disposed between the passivation layer 300 and the transparent conductive layer 400.

[0043] In this embodiment, the back surface of the first metal electrode 210 corresponding to the first opening K1 has a first electrode hole K12, and the back surface of the second metal electrode 220 corresponding to the second opening K2 has a second electrode hole, wherein the opening area of ​​the first electrode hole K12 is smaller than the opening area of ​​the second electrode hole. The opening area of ​​the first electrode hole K12 accounts for 10% to 40% of the area of ​​the back surface of the first metal electrode 210, and the opening area of ​​the second electrode hole accounts for 15% to 50% of the area of ​​the back surface of the second metal electrode 220. It should be noted that, due to the different shapes of the grooves G1, the first electrode hole K12 is caused by the first opening K2 and the groove G1 together, and may not have a completely closed boundary. It is sufficient to ensure a sufficient bonding area, which does not affect the implementation of this embodiment.

[0044] Referring to Figure 5, in the second embodiment of the present invention, the difference from Embodiment 1 is that the first metal electrode 210 and the second metal electrode 220 have n metal layers, where n is an integer greater than or equal to 2. The first layer 211 of the first metal electrode 210, located near the first mesa M1, contains chromium and is used to connect to the first type semiconductor layer 111. The first layer 221 of the second metal electrode 220, located near the second mesa M2, does not contain chromium and is in contact with a transparent conductive layer 400. The transparent conductive layer 400 is electrically connected to the first type semiconductor layer 112. In this embodiment, the first type semiconductor layer 111 is an N-type semiconductor layer, the first type semiconductor layer 112 is a P-type semiconductor layer, the first metal electrode 210 is an N-type electrode, and the second metal electrode 220 is a P-type electrode.

[0045] The length L2 of the first layer 221 of the second metal electrode 220 is greater than 2 μm to 25 μm. The first layer 221 of the second metal electrode 220 serves as a contact layer with the first type semiconductor layer 112 or the transparent conductive layer 400. The material includes, for example, nickel, aluminum, titanium, platinum, gold, or an alloy of any combination thereof. Its adhesion to the first type semiconductor layer 112 and the transparent conductive layer 400 is lower than that of chromium; therefore, increasing the length L2 is beneficial for improving the overall adhesion of the second metal electrode 220. In this embodiment, titanium is preferably used for the first layer 221 of the second metal electrode 220. The transparent conductive layer 400 is, for example, ITO. In this embodiment, the length L2 of the first layer 221 of the second metal electrode 220 refers to the longest dimension.

[0046] In some embodiments of this example, the projected area of ​​the back surface of the first layer 221 of the second metal electrode 220 is 30 μm. 2 Up to 100μm 2 The area of ​​the first layer 221 of the second metal electrode 220 should be increased as much as possible to enhance electrode adhesion.

[0047] Referring to Figure 6, in a third embodiment of the present invention, a display device is provided, wherein a micro-light-emitting diode C1 is sealed by epoxy resin P2, and the micro-light-emitting diode C1 is bonded and fixed on a substrate 500, having a semiconductor layer sequence 110. The semiconductor layer sequence 110 includes a back side and a front side, and starting from the front side, it sequentially includes a first type semiconductor layer 111 and a first type semiconductor layer 112, with an active layer 113 located between them. The back side of the semiconductor layer sequence 110 has a groove G1, which penetrates the first type semiconductor layer 112 and the active layer 113, exposing the first type semiconductor layer 111. A type of semiconductor layer 111 and a semiconductor layer sequence 110 include, on the back side, a first mesa M1 within a groove G1, a second mesa M2 on a type of semiconductor layer 112, and a sidewall S1 of the groove G1 located between them. The back side of the semiconductor layer sequence 110 is provided with a first metal electrode 210 electrically connected to the first type of semiconductor layer 111 and a second metal electrode 220 electrically connected to the first type of semiconductor layer 112. The chromium content of the first metal electrode 210 is greater than that of the second metal electrode 220, and the length L1 of the second metal electrode 220 is 2 μm to 30 μm. Because the epoxy resin P2 has high stress, chromium leakage from the second metal electrode 220 is likely to occur. Therefore, reducing or eliminating the chromium content of the first electrode is beneficial to improving product yield. Using the micro-light-emitting diode of Example 1 for sealing effectively improves the overall performance and yield of the display device.

[0048] In a fourth embodiment of the present invention, a display device is provided, which differs from embodiment 3 in that it employs the micro-light-emitting diode chip of embodiment 2. The first metal electrode 210 is in contact with the first type semiconductor layer 111 through the first layer 211 chromium of the first metal electrode, and the first layer 221 of the second metal electrode 220 does not contain chromium. This improves the overall performance and yield of the display device.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A micro light-emitting diode (LED) having a semiconductor layer sequence, the semiconductor layer sequence including a back side and a front side, the front side sequentially including a first type semiconductor layer and a second type semiconductor layer, an active layer located between the two, the back side of the semiconductor layer sequence having a groove penetrating the second type semiconductor layer and the active layer, exposing the first type semiconductor layer, the back side of the semiconductor layer sequence including a first mesa within the groove, a second mesa on the second type semiconductor layer, and a groove sidewall located between the two, the back side of the semiconductor layer sequence being provided with a first metal electrode electrically connected to the first type semiconductor layer and a second metal electrode electrically connected to the second type semiconductor layer, characterized in that: The first metal electrode has a higher chromium content than the second metal electrode, and the length of the second metal electrode is 2 μm to 30 μm.

2. A micro light-emitting diode according to claim 1, characterized in that: The first metal electrode is in contact with the first type of semiconductor layer through chromium, and the second metal electrode does not contain chromium.

3. A micro light-emitting diode according to claim 1, characterized in that: The length of the second metal electrode is 5 μm to 30 μm.

4. A micro light-emitting diode according to claim 1, characterized in that: The first metal electrode is completely disposed within the groove, which is a non-closed step; three of the four sides of the groove are exposed, and the other side is the sidewall of the groove, or two of the four sides of the groove are exposed, and the other two sides are the sidewalls of the groove.

5. A micro light-emitting diode according to claim 1, characterized in that: The first metal electrode extends from the groove to the second platform, and the height of the groove sidewall is 0.5 μm to 2 μm.

6. A micro light-emitting diode according to claim 1, characterized in that: The projected area of ​​the back surface of the first metal electrode and / or the second metal electrode is 25 μm. 2 Up to 100μm 2 .

7. A micro light-emitting diode according to claim 1, characterized in that: The distance between the first metal electrode and the second metal electrode is 4 μm to 10 μm.

8. A micro light-emitting diode according to claim 1, characterized in that: The second mesa is located on the side of the second type semiconductor layer away from the active layer. A passivation layer is disposed on the second mesa, covering at least from the second mesa to the first mesa. The passivation layer has a first opening on the first mesa and a second opening on the second mesa. A first metal electrode is electrically connected to the first type semiconductor layer through the first opening, and a second metal electrode is electrically connected to the second type semiconductor layer through the second opening. A transparent conductive layer is disposed between the second metal electrode and the second type semiconductor layer.

9. A micro light-emitting diode according to claim 8, characterized in that: The maximum aperture of the second opening is 2 μm to 20 μm.

10. A micro light-emitting diode according to claim 8, characterized in that: A passivation layer is disposed between a second metal electrode and a second type semiconductor layer. The second metal electrode extends from the second opening to the upper surface of the back side of the passivation layer. The second metal electrode is not disposed between the passivation layer and the second type semiconductor layer, or the second metal electrode is not disposed between the passivation layer and the transparent conductive layer.

11. A micro light-emitting diode according to claim 8, characterized in that: The thickness of the passivation layer is 0.5 μm to 3 μm.

12. A micro light-emitting diode according to claim 8, characterized in that: The back surface of the first metal electrode corresponding to the first opening has a first electrode hole, and the back surface of the second metal electrode corresponding to the second opening has a second electrode hole, wherein the opening area of ​​the first electrode hole is smaller than the opening area of ​​the second electrode hole.

13. A micro light-emitting diode according to claim 12, characterized in that: The opening area of ​​the first electrode hole accounts for 10% to 40% of the back surface area of ​​the first metal electrode, and the opening area of ​​the second electrode hole accounts for 15% to 50% of the back surface area of ​​the second metal electrode.

14. A micro light-emitting diode according to claim 1, characterized in that: The first metal electrode and the second metal electrode have n metal layers, where n is an integer greater than or equal to 2. The first layer of the first metal electrode, near the first mesa, contains chromium and is used to connect to the first type of semiconductor layer. The first layer of the second metal electrode, near the second mesa, does not contain chromium and is in contact with a transparent conductive layer, which is electrically connected to the second type of semiconductor layer.

15. A micro light-emitting diode according to claim 14, characterized in that: The length of the first layer of the second metal electrode is greater than 2 μm to 25 μm.

16. A micro light-emitting diode according to claim 14, characterized in that: The first layer of the second metal electrode includes nickel, aluminum, titanium, platinum, gold, or any combination of these alloys.

17. A micro light-emitting diode according to claim 1, characterized in that: The first metal electrode is an N-type electrode, and the second metal electrode is a P-type electrode.

18. A display device comprising a plurality of micro light-emitting diodes and a substrate, wherein the micro light-emitting diodes are disposed on the substrate, characterized in that, The micro-light-emitting diode is sealed with epoxy resin. The micro-light-emitting diode has a semiconductor layer sequence, including a back side and a front side. Starting from the front side, it sequentially includes a first type semiconductor layer and a second type semiconductor layer, with an active layer located between them. The back side of the semiconductor layer sequence has a groove that penetrates the second type semiconductor layer and the active layer, exposing the first type semiconductor layer. The back side of the semiconductor layer sequence includes a first mesa within the groove, a second mesa on the second type semiconductor layer, and a groove sidewall located between them. The back side of the semiconductor layer sequence is provided with a first metal electrode electrically connected to the first type semiconductor layer and a second metal electrode electrically connected to the second type semiconductor layer. The first metal electrode has a higher chromium content than the second metal electrode, and the length of the second metal electrode is 2 μm to 30 μm.

19. A display device according to claim 18, characterized in that: The first metal electrode is in contact with the first type of semiconductor layer through chromium, and the second metal electrode does not contain chromium.

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