Micro light-emitting diode chip and preparation method thereof, and display panel

Abstract

The present invention discloses a micro-LED chip, a method for manufacturing the same, and a display panel. The micro-LED chip includes an epitaxial wafer and a first electrode. The epitaxial wafer includes a stacked first cladding layer and a first current spreading layer. The first cladding layer is located on a side of the first current spreading layer away from the first electrode. The first current spreading layer includes a contact surface with the first cladding layer. The projection of the contact surface is located within the projection of the first cladding layer along the thickness of the micro-LED chip. The first electrode is disposed in contact with the first current spreading layer. Embodiments of the present invention can improve the luminous efficiency of the micro-LED chip.

Description

Technical Field

[0001] The embodiments of the present invention relate to display technology, and in particular to a micro light emitting diode chip, a manufacturing method thereof, and a display panel. Background Art

[0002] With the continuous development of micro-LED chip technology, the application of micro-LED display panels is becoming more and more extensive.

[0003] However, existing micro-LED chips have a large amount of non-radiative recombination during current recombination, which results in low luminous efficiency of the micro-LED chips and limits the further application of micro-LED display panels. Summary of the Invention

[0004] The present invention provides a micro-LED chip and a preparation method thereof, and a display panel, so as to reduce non-radiative recombination of current in the micro-LED chip and improve luminous efficiency.

[0005] In a first aspect, embodiments of the present invention provide a micro-LED chip comprising an epitaxial wafer and a first electrode. The epitaxial wafer comprises a first cladding layer and a first current spreading layer, the first cladding layer being located on a side of the first current spreading layer away from the first electrode. The first current spreading layer comprises a contact surface with the first cladding layer, the projection of the contact surface being located within the projection of the first cladding layer along the thickness of the micro-LED chip. The first electrode is disposed in contact with the first current spreading layer. This reduces the amount of current that undergoes non-radiative recombination at the sidewalls of the micro-LED chip, thereby significantly reducing non-radiative recombination and improving luminous efficiency.

[0006] Optionally, the first current spreading layer includes multiple block structures, with gaps between adjacent block structures. This facilitates separation of the micro-LED chip from the transfer head, thereby improving the yield rate of mass transfer, and also enhances the bonding strength between the micro-LED chip and the driver backplane.

[0007] Optionally, the first current spreading layer further includes a flat structure located between the plurality of block structures and the first cladding layer, which can reduce the resistance of current transmission, thereby lowering the turn-on voltage of the micro-LED chip, reducing the power consumption of the micro-LED chip, and further improving the luminous efficiency.

[0008] Optionally, the first cladding layer includes a plurality of raised structures on a side adjacent to the first current spreading layer; the raised structures correspond one-to-one with the plurality of block structures. This facilitates separation of the micro-LED chip from the transfer head, improving the yield rate of mass transfer, and significantly enhances the bonding strength between the micro-LED chip and the driver backplane.

[0009] Optionally, the plurality of block structures are evenly distributed, which can make the current distribution inside the active layer more even and improve the stability of the electrical connection between the micro-LED chip and the driving backplane.

[0010] Optionally, the shape of the first electrode matches the shape of the first current spreading layer. The first electrode has a larger contact area with the solder column, effectively reducing contact resistance, thereby reducing losses, and also increasing the stability of the electrical connection between the first electrode and the solder column, thereby improving the stability of the light-emitting display of the micro-LED chip.

[0011] Optionally, the epitaxial wafer includes a second cladding layer, an active layer, the first cladding layer, and the first current spreading layer, which are stacked together; the micro-LED chip further includes a second electrode, and the second electrode is arranged in contact with the second cladding layer;

[0012] Preferably, the first electrode is the anode of the micro light-emitting diode chip, and the second electrode is the cathode of the micro light-emitting diode chip;

[0013] Preferably, the second covering layer includes a plurality of protrusions, and the shape of the second electrode matches the shape of the protrusions, which can further improve the stability of the connection between the micro-LED chip and the driving backplane.

[0014] In a second aspect, an embodiment of the present invention further provides a method for preparing a micro-LED chip, the method comprising: forming an epitaxial wafer, wherein the epitaxial wafer comprises a first cladding layer and a first current spreading layer arranged in a stacked manner, the first cladding layer being located on a side of the first current spreading layer away from the first electrode; the first cladding layer being located on a side of the first current spreading layer away from the first electrode; the first current spreading layer comprising a contact surface in contact with the first cladding layer, the projection of the contact surface being located within the projection of the first cladding layer along the thickness direction of the micro-LED chip; and forming a first electrode in contact with the first current spreading layer.

[0015] Optionally, the first current spreading layer includes a plurality of block structures, a gap exists between two adjacent block structures, and the first covering layer includes a plurality of protruding structures on a side close to the first current spreading layer; the plurality of protruding structures correspond one-to-one to the plurality of block structures; the block structures and the protruding structures are formed by a one-step etching process.

[0016] In a third aspect, an embodiment of the present invention further provides a display panel comprising a plurality of micro-LED chips and a driving backplane as described in the first aspect; the driving backplane comprises a first driving electrode, and the first driving electrode is bound to the first electrode.

[0017] In this embodiment, the micro-LED chip includes an epitaxial wafer and a first electrode. The epitaxial wafer includes a first cladding layer and a first current spreading layer, which are stacked together. The first cladding layer is located on the side of the first current spreading layer away from the first electrode. The first current spreading layer includes a contact surface with the first cladding layer. The projection of the contact surface along the thickness of the micro-LED chip is located within the projection of the first cladding layer. The first electrode is arranged in contact with the first current spreading layer. The amount of current reaching the sidewalls of the first cladding layer is extremely small, and thus the current flowing through the sidewalls of the micro-LED chip is extremely small. Correspondingly, the current that undergoes non-radiative recombination on the sidewalls of the micro-LED chip is also low, thereby significantly reducing non-radiative recombination and improving luminous efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of a micro light-emitting diode chip provided by an embodiment of the present invention;

[0019] Figure 2 A schematic diagram of the circuit structure of a pixel circuit provided by an embodiment of the present invention;

[0020] Figure 3 A schematic structural diagram of another micro-LED chip provided by an embodiment of the present invention;

[0021] Figure 4 for Figure 1 A partial enlarged view of

[0022] Figure 5 A schematic structural diagram of another micro-LED chip provided by an embodiment of the present invention;

[0023] Figure 6 for Figure 5 A partial enlarged view of

[0024] Figure 7 A schematic structural diagram of another micro-LED chip provided by an embodiment of the present invention;

[0025] Figure 8 A schematic structural diagram of another micro-LED chip provided by an embodiment of the present invention;

[0026] Figure 9 A flow chart of a method for preparing a micro light-emitting diode chip provided by the present invention;

[0027] Figure 10A schematic structural diagram of a display panel provided by an embodiment of the present invention;

[0028] Figure 11 A schematic structural diagram of a display device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0030] As mentioned in the background technology, the existing micro-LED chips have a large amount of non-radiative recombination and low luminous efficiency. After careful research, the inventors found that the reason for this technical problem is that the existing micro-LED chips generally include a current expansion layer and a cladding layer. The current expansion layer extends to the edge of the cladding. When the micro-LED chip emits light, the current expanded inside the current expansion layer will reach the side wall of the cladding. The side wall of the cladding is usually also the side wall of the micro-LED chip. The side wall of the micro-LED chip usually has large defects (for example, due to process reasons, the material of the current expansion layer remains on the side wall), which will cause the current to be transmitted along the side wall to produce non-radiative recombination, thereby making the luminous efficiency of the micro-LED chip low.

[0031] Based on the above technical problems, the present invention proposes the following solutions: Figure 1 A schematic diagram of the structure of a micro-LED chip provided by an embodiment of the present invention, referring to Figure 1 The micro-LED chip includes an epitaxial wafer and a first electrode 101. The epitaxial wafer includes a first cladding layer 103 and a first current spreading layer 102 that are stacked. The first cladding layer 103 is located on a side of the first current spreading layer 102 away from the first electrode 101. The first current spreading layer 102 includes a contact surface that contacts the first cladding layer 103. Along the thickness direction of the micro-LED chip, the projection of the contact surface is located inside the projection of the first cladding layer 103. The first electrode 101 is arranged in contact with the first current spreading layer 102.

[0032] Specifically, if Figure 1As shown, the epitaxial wafer may include a second current spreading layer 106, a second cladding layer 105, an active layer 104, a first cladding layer 103, and a first current spreading layer 102, which are sequentially stacked on a substrate 107. The substrate 107 may be a dielectric or a semiconductor. For example, the material of the substrate 107 may be sapphire (Al2O3), Si, SiC, GaAs, or a mixture thereof. For example, a substrate having a good lattice match with the second cladding layer 105 may be selected to facilitate the growth of the second cladding layer 105. The second cladding layer 105 and the first cladding layer 103 may be formed by metal organic chemical vapor deposition, liquid phase epitaxy, hydride vapor phase epitaxy, molecular beam epitaxy, or metal organic vapor phase epitaxy. The first cladding layer 103 and the second cladding layer 105 may be, for example, GaN or GaP. For example, when the micro-LED chip emits red light, the material of the first cladding layer 103 and the second cladding layer 105 is GaP. When the micro-LED chip emits blue light or green light, the material of the first cladding layer 103 and the second cladding layer 105 is GaN. The first cladding layer 103 and the second cladding layer 105 have opposite conductivity types. For example, the first cladding layer 103 may be a p-type cladding layer, which may be achieved by doping with Mg; the second cladding layer 105 may be an n-type cladding layer, which may be achieved by doping with Si.

[0033] The micro-LED chip's light-emitting principle is that holes and electrons generated in the first cladding layer 103 and the second cladding layer 105 recombine in the active layer 104 to emit light, a process known as radiative recombination. The emitted light can be visible light, thus enabling the micro-LED chip's luminescent display. The active layer can be a single quantum well or multiple quantum wells, and its properties can be adjusted, such as by using different materials or doping different materials, to enable the active layer to emit light of different wavelengths (e.g., red, green, or blue).

[0034] The first current spreading layer 102 and the second current spreading layer 106 have good conductivity. For example, the conductivity of the first current spreading layer 102 is superior to that of the first cladding layer 103. The first current spreading layer 102 and the first cladding layer 103 can have the same doping type, such as both being p-type doped. In this case, the doping concentration of the first current spreading layer 102 can be set to be greater than the doping concentration of the first cladding layer 103. The first cladding layer 103 can also be undoped. In other words, the first current spreading layer 102 has a higher conductivity, facilitating ohmic contact with the first electrode 101. The second current spreading layer 106 and the second cladding layer 105 can have the same doping type, such as both being n-type doped. In this case, the doping concentration of the second current spreading layer 106 can be set to be greater than the doping concentration of the second cladding layer 105. The second cladding layer 105 can also be undoped. In other words, the second current spreading layer 106 has a higher conductivity, facilitating ohmic contact with the corresponding electrode. The material of the first current spreading layer 102 can be indium tin oxide (ITO), GaP, or InGaN.

[0035] The first electrode 101 can be any conductive material or a combination of multiple conductive materials, for example, it can be one or more alloys of Cu, Ni, Ag, Al, Au, Ti, etc. The first electrode 101 is preferably the anode of the micro-LED chip. This embodiment takes the first electrode 101 as the anode of the micro-LED as an example for explanation. When it is the anode, it generally serves as a reflective surface, and the second current spreading layer 106 corresponds to the light-emitting surface of the micro-LED chip, that is, the light emitted by the active layer needs to pass through the second current spreading layer 106 before being emitted, and the light emitted by the active layer 104 can be reflected to the second current spreading layer 106 after reaching the first electrode 101 to improve the luminous efficiency. The first electrode 101 can be made of a reflective material, for example, it can be one or more alloys of Ag, Al, Pt, etc. Figure 2 A schematic diagram of the circuit structure of a pixel circuit provided in an embodiment of the present invention is provided, which can be used to drive the micro-LED chip provided in an embodiment of the present invention to emit light for display. This pixel circuit, also known as a 2T1C circuit, includes two transistors and a storage capacitor. When the corresponding scan signal line is selected, the switching transistor Tsw turns on, and the grayscale voltage on the data signal line is transmitted to the storage capacitor C. The storage capacitor C stores the grayscale voltage, enabling the driving transistor Tdrv to generate a stable driving current based on the grayscale voltage, thereby driving the micro-LED chip to emit light. It should be noted that in some other embodiments, the pixel circuit can also be a driving circuit with a threshold compensation function, such as a 7T1C pixel circuit, so that the generated driving current is independent of the threshold voltage of the driving transistor. Since the anode of the micro-LED chip receives the driving current of the driving transistor, and the cathode is generally a common ground electrode, the state of the current at the anode (the state within the first cladding layer) greatly affects the luminous efficiency of the micro-LED chip, while the state of the current at the cathode has less influence. Therefore, the first electrode in this embodiment can be set as the anode of the micro-LED chip.

[0036] Along the thickness direction of the micro LED chip (such as Figure 1 The first current spreading layer 102 includes a contact surface in contact with the first cladding layer 103, and the projection of the contact surface is located inside the projection of the first cladding layer 103, which means that the projection area of ​​the contact surface is smaller than the projection area of ​​the first cladding layer 103, and the projection of the first cladding layer 103 completely covers the projection of the contact surface. Figure 1As shown, along the thickness direction of the micro-LED chip, the part where the projection of the micro-LED chip completely overlaps with the projection of the contact surface can be understood as the main current recombination area Ia, and the remaining part can be understood as the secondary current recombination area Ib. The current is concentrated in the main current recombination area Ia. The conductivity of the first cladding layer 103 is lower than that of the first current spreading layer 102. The current mainly spreads in the first current spreading layer 102, while in the first cladding layer 103, the current is mainly transmitted along the thickness direction X of the micro-LED chip, and the longitudinal direction (such as Figure 1 The amount of current expansion in the Y direction in the micro-LED chip is small, that is, the current is mainly located in the portion of the first cladding layer 103 located in the current main recombination area Ia, and the amount of current reaching the side wall of the first cladding layer 103 is extremely small, that is, the current on the side wall of the micro-LED chip is extremely small, and correspondingly, the current that undergoes non-radiative recombination on the side wall of the micro-LED chip is also small, thereby greatly reducing the non-radiative recombination of the current and improving the luminous efficiency.

[0037] In this embodiment, the shape of the first current spreading layer 102 is not specifically limited, and the area of ​​the side away from the first cladding layer 103 may also be larger than the area of ​​the first cladding layer 103, such as Figure 3 As shown, Figure 3 This is a schematic structural diagram of another micro-LED chip provided in an embodiment of the present invention. Although the projected area of ​​the surface of the first current spreading layer 102 away from the first cladding layer 103 along the thickness direction X of the micro-LED chip is greater than or equal to the projected area of ​​the first cladding layer 103, because the projection of the contact surface is still located within the projection of the first cladding layer 103, the corresponding current is still mainly concentrated in the main current recombination area Ia. In other words, the current of non-radiative recombination occurring on the sidewall of the micro-LED chip can still be reduced, thereby improving the luminous efficiency. Figure 3 The structure shown in can be formed, for example, by anisotropic etching or the like.

[0038] In this embodiment, the micro-LED chip used includes an epitaxial wafer and a first electrode. The epitaxial wafer includes a first cladding layer and a first current spreading layer that are stacked. The first cladding layer is located on a side of the first current spreading layer away from the first electrode. The first current spreading layer includes a contact surface in contact with the first cladding. Along the thickness direction of the micro-LED chip, the projection of the contact surface is located inside the projection of the first cladding. The first electrode is arranged in contact with the first current spreading layer. The first electrode can be the anode of the micro-LED chip. This arrangement ensures that the amount of current reaching the side wall of the first cladding is extremely small, that is, the current on the side wall of the micro-LED chip is extremely small. Correspondingly, the current that undergoes non-radiative recombination on the side wall of the micro-LED chip is also relatively small, thereby greatly reducing the non-radiative recombination of the current and improving the luminous efficiency.

[0039] It is understandable that a passivation layer 108 may be further included between the first electrode 101 and the first current spreading layer 102. The passivation layer 108 may be formed to cover the entire surface. The formation method may be, for example, a growth method. The material may be an oxide or a nitride, such as one or a mixture of AlO, SiO, SiN, etc., and an opening is provided on the passivation layer 108 to expose a portion of the surface of the first current spreading layer 102.

[0040] It should be noted that the shape of the micro LED chip can be prism-shaped, cylindrical or other irregular columnar structures, and the shape of the first current spreading layer 102 can also be ring-shaped, prism-shaped or columnar.

[0041] The size of the micro LED chip of this embodiment can be set differently according to different application scenarios. For example, the size of a display used for lighting can be several millimeters, while the size of a micro LED chip used for display can be tens of microns.

[0042] Optionally, the first current spreading layer 102 includes a plurality of block structures, and a gap exists between two adjacent block structures.

[0043] Specifically, if Figure 4 for Figure 1 A partial enlarged view, combined with Figure 1 and Figure 4 The first current spreading layer 102 includes a plurality of block structures 1021 (the number of the block structures is greater than or equal to 2). Gaps are formed between the block structures 1021. During the mass transfer process of the micro-LED chip, the solder columns on the driver backplane can fully fill the gaps when the micro-LED chip is pressed down, thereby fully wrapping the plurality of block structures 1021. On the one hand, this makes it easier to separate the micro-LED chip from the transfer head, thereby improving the yield of the mass transfer. On the other hand, it can also improve the binding strength between the micro-LED chip and the driver backplane.

[0044] Optionally, continue combining Figure 1 and Figure 4 The first current spreading layer 102 further includes a planar structure 1022 located between the plurality of block structures 1021 and the first cladding layer 103 .

[0045] In this embodiment, the block structures 1021 can be understood as multiple protrusions formed by the first current spreading layer 102 on the surface of the flat structure 1022. Along the thickness direction X of the micro-LED chip, the projected area of ​​the flat structure 1022 is larger than the projected area of ​​the multiple block structures 1021, and the projection of each block structure 1021 is located inside the flat structure 1022. After the first current spreading layer 102 is grown, etching can be performed to form the multiple block structures 1021 and the flat structure 1022. The etching method can be, for example, dry etching or wet etching. The flat structure 1022 contacts the first cladding layer 103. Compared with the contact between the multiple block structures 1021 and the first cladding layer 103, the contact surface area is larger, that is, the main current recombination area Ia is larger, which can reduce the resistance of current transmission, thereby reducing the turn-on voltage of the micro-LED chip, reducing the power consumption of the micro-LED chip, and further improving the luminous efficiency.

[0046] When the micro-LED chip emits red light, the thickness of the first current spreading layer 102 is relatively thick. Accordingly, a plurality of block structures 1021 and flat structures 1022 with a certain thickness can be formed on the first current spreading layer 102. When the micro-LED chip emits light of other colors, the first current spreading layer 102 is relatively thin, and the block structures 1021 formed are also relatively thin. The bonding strength between the micro-LED chip and the driver backplane is not significantly improved. Figure 5 and Figure 6 , Figure 5 This is a schematic structural diagram of another micro-LED chip provided by an embodiment of the present invention. Figure 6 for Figure 5 , the first cladding layer 103 includes a plurality of protruding structures 1031 on one side close to the first current spreading layer 102 ; the plurality of protruding structures 1031 correspond one to one to the plurality of block structures 1021 .

[0047] With this arrangement, the thickness of the first cladding layer 103 is typically relatively thick, and the thickness of the raised portion formed by the combination of the raised structure 1031 and the corresponding block structure 1021 can be relatively thick. For example, the sum of the thickness of the raised structure 1031 and the corresponding block structure 1021 (i.e., the thickness of the raised portion) is greater than 0.3 μm. This, on the one hand, makes it easier to separate the micro-LED chip from the transfer head, improving the yield rate of mass transfer, and on the other hand, significantly improves the bonding strength between the micro-LED chip and the driver backplane. The raised structure 1031 and the block structure 1021 can be formed by a one-step etching process. After etching to form multiple block structures 1021, further etching can be performed to form multiple raised structures 1031. Along the thickness direction of the micro-LED chip, the projection of the first current spreading layer 102 completely overlaps with the projection of the multiple raised structures 1031, which can reduce the number of etching steps and save process costs. In this embodiment, for example, the etching depth can be adjusted by adjusting the etching time.

[0048] Optionally, the plurality of block structures 1021 are evenly distributed.

[0049] Exemplarily, multiple block structures 1021 can be arranged in an array form, for example, can be evenly distributed on the surface of the first cladding layer 103. On the one hand, during light-emitting display, the current distribution inside the active layer 104 is also relatively uniform, so that the light emission is more uniform; on the other hand, when the micro-LED chip is bound to the driving backplane, since the distribution of the protrusions is also uniform, after the solder column fills the gap between the protrusions, the various parts of the solder column are subjected to more uniform force when the transfer head is separated, preventing a certain part from being damaged due to excessive force, thereby ensuring the stability of the electrical connection between the micro-LED chip and the driving backplane.

[0050] Optionally, the shape of the first electrode 101 matches the shape of the first current spreading layer 102 .

[0051] Specifically, the first electrode 101 may be disposed along the surface of the first current spreading layer 102. Figure 1 When the first current spreading layer 102 is a plurality of block structures, the first cladding layer 103 includes a plurality of protruding structures, the first electrode 101 may be disposed along the protruding portion, ie, as shown Figure 5 When the micro-LED chip is bonded to the driver backplane, the first electrode 101 has a larger contact area with the solder column, effectively reducing contact resistance and thus loss. It can also increase the stability of the electrical connection between the first electrode 101 and the solder column, thereby improving the stability of the light-emitting display of the micro-LED chip.

[0052] Optionally, along the thickness direction of the micro LED chip, the projection area of ​​the first electrode 101 is smaller than the projection area of ​​the second cladding layer 103 , and the projection of the first electrode 101 is located within the projection of the second cladding layer 103 .

[0053] Specifically, the edge of the first electrode 101 is at a certain distance from the edge of the first cladding layer 103, that is, the edge of the first electrode 101 is at a certain distance from the side wall of the micro-LED chip. The current in the first electrode 101 will not be transmitted to the side wall of the micro-LED chip, thereby causing non-radiative recombination on the side wall, thereby further improving the luminous efficiency of the micro-LED chip.

[0054] The micro LED chip of this embodiment can be a vertical structure chip or a flip chip chip, such as Figure 7 As shown, Figure 7 This is a structural diagram of another micro-LED chip provided by an embodiment of the present invention. A second electrode 201 can be provided on the surface of the second cover layer 105. The second electrode 201 can serve as the cathode of the micro-LED chip, and its material can be any conductive material.

[0055] Alternatively, as Figure 8 As shown, Figure 8 This is a schematic structural diagram of another micro-LED chip provided in an embodiment of the present invention. A plurality of second cladding protrusions 1051 may also be provided on the portion of the second cladding layer 105 corresponding to the second electrode 201. Corresponding portions may also include a plurality of second current spreading layer block structures 1061. The shape of the second electrode 201 matches the shape of the protrusions 1051. For example, the second electrode 201 is provided along the second cladding protrusions 1051 and the second current spreading layer block structures 1061. This can increase the stability of the electrical connection between the second electrode 201 and the solder column on the driver backplane and reduce contact resistance, thereby reducing power consumption.

[0056] Figure 9 This is a flow chart of a method for preparing a micro-light-emitting diode chip provided by the present invention, with reference to Figure 9 , the preparation method of the micro light emitting diode chip includes:

[0057] Step S901, forming an epitaxial wafer, wherein the epitaxial wafer includes a first cladding layer and a first current spreading layer that are stacked, the first cladding layer being located on a side of the first current spreading layer away from the first electrode; the first current spreading layer including a contact surface in contact with the first cladding layer, wherein a projection of the contact surface is located within a projection of the first cladding layer along a thickness direction of the micro-LED chip;

[0058] Step S902 : forming a first electrode in contact with the first current spreading layer.

[0059] The epitaxial wafer may include, for example, a second current spreading layer, a second cladding layer, an active layer, a first cladding layer, and a first current spreading layer, which are sequentially stacked and grown on a substrate. Figure 1 As shown, along the thickness direction of the micro-LED chip, the part where the projection of the micro-LED chip completely overlaps with the projection of the contact surface can be understood as the main current recombination area Ia, and the remaining part can be understood as the secondary current recombination area Ib. The current is concentrated in the main current recombination area Ia. The conductivity of the first cladding layer 103 is lower than that of the first current spreading layer 102. The current mainly spreads in the first current spreading layer 102, while in the first cladding layer 103, the current is mainly transmitted along the thickness direction X of the micro-LED chip, and the longitudinal direction (such as Figure 1 The amount of current expansion in the Y direction in the micro-LED chip is small, that is, the current is mainly located in the portion of the first cladding layer 103 located in the current main recombination area Ia, and the amount of current reaching the side wall of the first cladding layer 103 is extremely small, that is, the current on the side wall of the micro-LED chip is extremely small, and correspondingly, the current that undergoes non-radiative recombination on the side wall of the micro-LED chip is also small, thereby greatly reducing the non-radiative recombination of the current and improving the luminous efficiency.

[0060] Optionally, the first current spreading layer includes multiple block structures, with gaps between adjacent block structures. The first cladding layer includes multiple raised structures on a side adjacent to the first current spreading layer. The multiple raised structures correspond one-to-one with the multiple block structures. The block structures and the raised structures are formed by a one-step etching process. The raised structures and the block structures can be formed by a one-step etching process. After etching to form the multiple block structures, further overetching can be performed to form multiple raised structures. Along the thickness direction of the micro-LED chip, the projection of the first current spreading layer completely overlaps with the projection of the multiple raised structures, thereby reducing etching steps and saving process costs.

[0061] Figure 10 A schematic diagram of the structure of a display panel provided by an embodiment of the present invention, referring to Figure 10 The display panel includes multiple micro-LED chips MicroLED and a driving backplane 301; the micro-LED chip MicroLED includes an epitaxial wafer and a first electrode, the epitaxial wafer includes a first cladding layer and a first current spreading layer arranged in contact with each other, the first cladding layer is located on a side of the first current spreading layer away from the first electrode; the first current spreading layer includes a contact surface in contact with the first cladding layer, and along the thickness direction of the micro-LED chip, the projection of the contact surface is located inside the projection of the first cladding layer; the first electrode is in contact with the first current spreading layer, and the first electrode can be the anode of the micro-LED chip; the driving backplane 301 includes a first driving electrode 401, and the first driving electrode 401 is bound to the first electrode.

[0062] Specifically, the driver backplane 301 may be a TFT backplane or a CMOS backplane, which may include pixel circuits. The first driver electrode 401 of the pixel circuit is bonded to the first electrode via a soldering post 502. The soldering post 502 may be made of, for example, In, Sn, an alloy, or a conductive polymer. In this embodiment, after the micro-LED chip is pressed and bonded to the driver backplane 301, a planarization layer 501 may be filled in the gap between the micro-LED chip and the driver backplane 301. The material of the planarization layer 501 may be, for example, an organic material. In other embodiments, the planarization layer 501 may be first formed on the driver backplane 301, and then the micro-LED chip and the driver backplane 301 are aligned and pressed. After alignment and pressing, the substrate of the micro-LED chip may be removed. If the substrate is SiC, this can be removed by mechanical thinning or chemical etching; if the substrate is sapphire, this can be removed by laser ablation or other methods. After removing the substrate, a second electrode 503 (i.e., a common electrode) can be formed on the entire surface of the exposed second current spreading layer. The second electrode 503 is electrically connected to the second drive electrode 402 on the drive backplane 301 to form a complete current loop. The material of the second electrode 503 is preferably a transparent or translucent conductive material, such as a magnesium-silver alloy, and can be formed by evaporation or the like. Before forming the second electrode 503, the surface of the second current spreading layer can also be roughened to increase the angle of the emitted light and increase the viewing angle of the display panel. After forming the second electrode 503, quantum dot materials can also be made at the corresponding positions of the micro-LED chips. The light emitted by the micro-LED chips becomes light of different colors after passing through different quantum dot materials, thereby enabling the display panel to achieve full-color display. The display panel provided in this embodiment includes the micro-LED chips provided in any embodiment of the present invention, and therefore has the same beneficial effects, which will not be described in detail here.

[0063] The embodiment of the present invention further provides a display device, such as Figure 11 As shown, Figure 11 This is a schematic diagram of the structure of a display device provided in an embodiment of the present invention. The display device includes a display panel provided in any embodiment of the present invention and has the same beneficial effects as the display panel provided in the embodiment of the present invention. The details are not repeated here. The display device can be a mobile phone, tablet, computer, monitor, smartwatch, or other wearable device.

[0064] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A micro light-emitting diode chip, characterized in that: The micro-LED chip includes an epitaxial wafer and a first electrode. The epitaxial wafer includes a first cladding layer and a first current spreading layer that are stacked. The first cladding layer is located on a side of the first current spreading layer away from the first electrode. The first current spreading layer includes a contact surface that contacts the first cladding layer. Along the thickness direction of the micro-LED chip, the projection of the contact surface is located inside the projection of the first cladding layer. The first electrode is arranged in contact with the first current spreading layer; The first current spreading layer includes a plurality of block structures, and there is a gap between two adjacent block structures; The shape of the first electrode matches the shape of the first current spreading layer; the first electrode covers each block structure of the first current spreading layer and is arranged in contact with each block structure of the first current spreading layer; During the transfer process of the micro-LED chip, the soldering columns on the driving backplane are used to fill the gap when the micro-LED chip is pressed down.

2. The micro-LED chip according to claim 1, characterized in that: The first current spreading layer further includes a planar structure located between the plurality of block structures and the first cladding layer.

3. The micro-LED chip according to claim 1, characterized in that: A side of the first cladding layer close to the first current spreading layer includes a plurality of protruding structures; the plurality of protruding structures correspond one-to-one to the plurality of block structures.

4. The micro-LED chip according to claim 1, characterized in that: The plurality of block structures are evenly distributed.

5. The micro-LED chip according to claim 1, characterized in that: The epitaxial wafer includes a second cladding layer, an active layer, the first cladding layer and the first current spreading layer which are stacked. The micro-LED chip also includes a second electrode which is in contact with the second cladding layer.

6. The micro-LED chip according to claim 5, characterized in that: The first electrode is the anode of the micro light emitting diode chip, and the second electrode is the cathode of the micro light emitting diode chip.

7. The micro-LED chip according to claim 5, characterized in that: The second coating layer includes a plurality of protrusions, and a shape of the second electrode matches a shape of the protrusions.

8. A method for preparing a micro light-emitting diode chip, characterized in that: The method comprises: forming an epitaxial wafer, wherein the epitaxial wafer includes a first cladding layer and a first current spreading layer that are stacked, the first cladding layer being located on a side of the first current spreading layer away from the first electrode; the first current spreading layer including a contact surface in contact with the first cladding layer, wherein a projection of the contact surface is located within a projection of the first cladding layer along a thickness direction of the micro-LED chip; forming a first electrode in contact with the first current spreading layer; The first current spreading layer includes a plurality of block structures, and there is a gap between two adjacent block structures; The shape of the first electrode matches the shape of the first current spreading layer; the first electrode covers each block structure of the first current spreading layer and is arranged in contact with each block structure of the first current spreading layer; During the transfer process of the micro-LED chip, the soldering columns on the driving backplane are used to fill the gap when the micro-LED chip is pressed down.

9. The method according to claim 8, characterized in that The first cladding layer includes a plurality of protruding structures on a side close to the first current spreading layer; the plurality of protruding structures correspond one to one to the plurality of block structures; The block structure and the protruding structure are formed by a one-step etching process.

10. A display panel, characterized in that: comprising a plurality of micro light-emitting diode chips and a driving backplane as claimed in any one of claims 1 to 7; The driving backplane includes a first driving electrode, and the first driving electrode is bound to the first electrode.

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