Light emitting diode with improved electrode reliability and preparation method thereof

Abstract

The invention provides a light emitting diode with improved electrode reliability and a preparation method thereof, and belongs to the technical field of photoelectron manufacturing. The light-emitting diode comprises an epitaxial layer and an electrode, wherein the electrode is positioned on the surface of the epitaxial layer; the side wall of the electrode comprises at least two sections of inclined planes, the at least two sections of inclined planes are sequentially connected in the direction away from the epitaxial layer, and the inclination angle of the inclined plane, close to the epitaxial layer, in the at least two sections of inclined planes is smaller than the inclination angle of the inclined plane, away from the epitaxial layer, in the at least two sections of inclined planes. According to the embodiment of the invention, the problem that metal atoms in the electrode migrate to form an intermetallic compound can be improved, and the reliability of the electrode is improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of optoelectronic manufacturing, and particularly relates to a light emitting diode with improved electrode reliability and a preparation method thereof. BACKGROUND

[0002] Light emitting diode (LED) is a new product with great influence in the optoelectronic industry. The light emitting diode includes an epitaxial layer and an electrode, and the electrode is located on the surface of the epitaxial layer and is electrically connected with the epitaxial layer.

[0003] In the related art, the electrode generally includes an Au layer and an Al layer. During the working process of the light emitting diode, metal atoms in the electrode will migrate, so that Au and Al form Au-Al intermetallic compounds, thereby reducing the reliability of the electrode. Therefore, a barrier metal is generally inserted between the Au layer and the Al layer of the electrode to avoid the formation of intermetallic compounds of Au and Al.

[0004] However, the coverage effect of each metal layer in the edge region of the electrode is poor, which causes the metal atoms to easily migrate in the edge region of the electrode, so that Au and Al form Au-Al intermetallic compounds, thereby affecting the reliability of the electrode. SUMMARY

[0005] The present disclosure provides a light emitting diode with improved electrode reliability and a preparation method thereof, which can improve the problem of metal atom migration in the electrode to form intermetallic compounds and improve the reliability of the electrode. The technical solution is as follows:

[0006] In one aspect, the present disclosure provides a light emitting diode, which includes an epitaxial layer and an electrode, and the electrode is located on the epitaxial layer. The sidewall of the electrode includes at least two inclined surfaces, and the at least two inclined surfaces are sequentially connected in a direction away from the epitaxial layer. The inclination angle of the inclined surface close to the epitaxial layer in the at least two inclined surfaces is smaller than the inclination angle of the inclined surface away from the epitaxial layer in the at least two inclined surfaces.

[0007] In one implementation manner of the present disclosure, the sidewall of the electrode includes a first inclined surface and a second inclined surface which are sequentially connected in a direction away from the epitaxial layer.

[0008] In another implementation manner of the present disclosure, the inclination angle of the first inclined surface is 30° to 40°, and the inclination angle of the second inclined surface is 40° to 70°.

[0009] In another implementation manner of the present disclosure, the electrode includes an Al layer and an Au layer, the Al layer is close to the epitaxial layer, and the Au layer is arranged on the side of the Al layer away from the epitaxial layer.

[0010] In another implementation manner of the present disclosure, the electrode further comprises a barrier layer, and the barrier layer is located between the Al layer and the Au layer.

[0011] In another implementation manner of the present disclosure, the thickness of the Al layer is 100 nm to 500 nm, the thickness of the Au layer is 50 nm to 200 nm, and the thickness of the barrier layer is 10 nm to 80 nm.

[0012] In another implementation manner of the present disclosure, the barrier layer has a first surface and a second surface, the first surface is close to the Al layer, and the second surface is away from the Al layer; and the junction of the first inclined surface and the second inclined surface is located between the first surface and the second surface.

[0013] The present disclosure provides a light emitting diode, which comprises an electrode, and the resistance change rate of the electrode after being exposed to an environment with a temperature of 85℃ and a relative humidity of 85% for at least 1000 hours is less than 5%.

[0014] Optionally, the electrode comprises an Al layer and an Au layer which are stacked in sequence.

[0015] Optionally, the electrode further comprises a barrier layer, and the barrier layer is located between the Al layer and the Au layer.

[0016] The technical scheme provided by the present disclosure has at least the following beneficial effects:

[0017] The light emitting diode provided by the present disclosure designs at least two inclined surfaces which are connected in sequence on the sidewall of the electrode, and the inclined surface close to the epitaxial layer has a smaller inclination angle, that is, the inclined surface close to the epitaxial layer is more gentle; and the inclined surface away from the epitaxial layer has a larger inclination angle, that is, the inclined surface away from the epitaxial layer is more steep.

[0018] Compared with the related art, the sidewall angle of the electrode is relatively steep, and the steep sidewall makes it difficult to form a continuous and dense covering layer at the edge when the metal is deposited, which causes the Au layer and the Al layer at the edge to be more likely to directly contact, and promotes the reaction of Au and Al to generate Au-Al alloy. The sidewall morphology designed in the present disclosure optimizes the metal coverage of the edge region of the electrode, and the gentle inclined surface close to the epitaxial layer can provide a longer transition path and a larger covering space for metal deposition, so that the barrier metal is more likely to uniformly and continuously wrap the underlying metal layer at the edge, thereby reducing the defects of thin coverage or no coverage in the edge region.

[0019] In addition, the abnormal diffusion of metal atoms generally tends to follow a relatively gentle and continuous path. The steep inclined surface away from the epitaxial layer changes the possible diffusion path of the metal atoms, and the steep angle makes it difficult for the metal atoms to form a continuous and smooth diffusion channel along the sidewall. Compared with a gentle surface, the steep surface increases the difficulty of metal atom diffusion, making it more difficult for metal atoms to gather and diffuse to the edge region.

[0020] Therefore, through the gentle edge sidewall and steep top sidewall structure, the problems of poor electrode edge coverage and easy formation of Au-Al intermetallic compounds in the edge region can be effectively solved, thereby improving the long-term reliability of the electrode and ensuring the electrical stability and optical performance of the light-emitting diode during operation. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art without creative labor.

[0022] Figure 1 is a structural schematic diagram of a light-emitting diode provided by an embodiment of the present disclosure;

[0023] Figure 2 is a scanning electron microscope (SEM) image of a light-emitting diode provided by an embodiment of the present disclosure;

[0024] Figure 3 is a structural schematic diagram of an electrode provided by an embodiment of the present disclosure;

[0025] Figure 4 is a flowchart of a preparation method of a light-emitting diode provided by an embodiment of the present disclosure.

[0026] The various signs in the drawings are explained as follows:

[0027] 10, epitaxial layer;

[0028] 20, electrode;

[0029] 21, first inclined surface; 22, second inclined surface;

[0030] 201, first Ni layer; 202, Al layer; 203, Cr layer; 204, second Ni layer; 205, Au layer; 206, GaN contact layer;

[0031] 30, insulating layer;

[0032] 40, pad. DETAILED DESCRIPTION

[0033] In order to make the objects, technical solutions and advantages of the present disclosure clearer, the following further describes the embodiments of the present disclosure in detail with reference to the drawings.

[0034] Unless otherwise defined, technical terms or scientific terms used herein should be understood as having the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms "first", "second", "third" and similar terms used in the description and claims of the present patent application do not denote any order, quantity or importance, but are used to distinguish different components. Similarly, the terms "one" or "a" or similar terms do not denote a quantity limitation, but mean that at least one exists. The terms "include" or "contain" or similar terms mean that the elements or objects appearing before the terms "include" or "contain" cover the elements or objects listed after the terms "include" or "contain" and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" or similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", "top", "bottom" and the like are used only to indicate relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships may also change accordingly.

[0035] Figure 1 is a structural schematic diagram of a light-emitting diode provided by an embodiment of the present disclosure. As shown in Figure 1 , the light-emitting diode comprises an epitaxial layer 10 and an electrode 20, and the electrode 20 is located on the epitaxial layer 10.

[0036] Figure 2 is a scanning electron microscope (SEM) image of a light-emitting diode provided by an embodiment of the present disclosure. As shown in Figure 1 , 2 the sidewall of the electrode 20 comprises at least two inclined surfaces, the at least two inclined surfaces are sequentially connected in a direction away from the epitaxial layer 10, the inclination angle a of the inclined surface close to the epitaxial layer 10 in the at least two inclined surfaces is smaller than the inclination angle β of the inclined surface away from the epitaxial layer 10 in the at least two inclined surfaces.

[0037] The light-emitting diode provided by the embodiment of the present disclosure designs at least two inclined surfaces sequentially connected on the sidewall of the electrode 20, and the inclination angle of the inclined surface close to the epitaxial layer 10 is smaller, i.e. the inclined surface close to the epitaxial layer 10 is more gentle; the inclination angle of the inclined surface away from the epitaxial layer 10 is larger, i.e. the inclined surface away from the epitaxial layer 10 is more steep.

[0038] Compared with the related art, the side wall angle of the electrode 20 is steeper, and the steep side wall makes it difficult to form a continuous and dense coverage layer at the edge during metal deposition, causing the Au layer 205 and the Al layer 202 at the edge to be more likely to directly contact each other, promoting the reaction of Au and Al to form an Au-Al alloy. The side wall morphology designed in the embodiment of the present disclosure optimizes the metal coverage of the edge region of the electrode 20. The gentle near-epitaxial layer 10 inclined surface can provide a longer transition path and more coverage space for metal deposition, so that the barrier metal is more likely to uniformly and continuously wrap the metal layer below at the edge, reducing the defects of thin coverage or no coverage in the edge region.

[0039] In addition, abnormal diffusion of metal atoms usually tends to follow a relatively gentle and continuous path. The steep inclined surface away from the epitaxial layer 10 changes the possible diffusion path of metal atoms, and the steep angle makes it difficult for metal atoms to form a continuous and smooth diffusion channel along the side wall. Compared with a gentle surface, a steep surface increases the difficulty of metal atom diffusion, making it more difficult for metal atoms to gather and diffuse to the edge region.

[0040] Therefore, through the gentle edge side wall and the steep top side wall structure, the problems of poor edge coverage of the electrode 20 and easy formation of Au-Al intermetallic compounds in the edge region can be effectively solved, thereby improving the long-term reliability of the electrode 20 and ensuring the electrical stability and optical performance of the light-emitting diode during operation.

[0041] Optionally, as shown in Figure 1 The side wall of the electrode 20 includes a first inclined surface 21 and a second inclined surface 22 connected in sequence in a direction away from the epitaxial layer 10.

[0042] As shown in Figure 1 The inclination angle α of the first inclined surface 21 is 30° to 40°. For example, the inclination angle of the first inclined surface 21 is 35°.

[0043] As shown in Figure 1 The inclination angle β of the second inclined surface 22 is 40° to 70°. For example, the inclination angle of the first inclined surface 21 is 60°.

[0044] The inclination angle of the first inclined surface 21 or the second inclined surface 22 refers to the included angle of the first inclined surface 21 or the second inclined surface 22 with the surface of the epitaxial layer 10.

[0045] In the above implementation, the first inclined surface 21 has a small inclination angle and belongs to a gentle transition structure. In the metal deposition process of the electrode 20, the gentle inclination angle provides a longer lateral diffusion path and a larger coverage space for metal atoms, so that the metal layer can uniformly and continuously wrap the edge of the epitaxial layer 10. The probability of direct contact between the Au layer 205 and the Al layer 202 at the edge is reduced from the source. In this way, by preferentially ensuring the complete coverage of the edge, the generation path of intermetallic compounds is directly cut off, and the reliability of the electrode 20 is improved.

[0046] Meanwhile, the second inclined surface 22 has a large inclination angle and belongs to a steep structure. On the one hand, the steep angle can reduce unnecessary material accumulation while ensuring the overall thickness of the metal layer, and avoid excessive metal layer caused by excessive gentleness; on the other hand, the steep inclined surface of the epitaxial layer 10 changes the path direction of metal atom diffusion, forming a diffusion barrier. When the metal atoms propagate from the epitaxial layer 10 upward, the steep interface increases the resistance of abnormal diffusion of the metal atoms to the edge, thereby further inhibiting the enrichment of Au or Al atoms to the edge region.

[0047] Optionally, the electrode 20 includes an Al layer 202 and an Au layer 205; the Al layer 202 is close to the epitaxial layer 10, and the Au layer 205 is arranged on a side of the Al layer 202 away from the epitaxial layer.

[0048] Optionally, the electrode 20 further includes a barrier layer, and the barrier layer is located between the Al layer 202 and the Au layer 205.

[0049] Illustratively, the barrier layer can include at least one of a Cr layer and a Ni layer.

[0050] Optionally, the thickness of the barrier layer can be 10 nm to 80 nm.

[0051] Optionally, the barrier layer has a first surface and a second surface; the first surface is close to the Al layer 202, and the second surface is away from the Al layer 202.

[0052] As an example, in the electrode 20 in the embodiment of the present disclosure, the electrode 20 can include a first Ni layer 201, an Al layer 202, a Cr layer 203, a second Ni layer 204 and an Au layer 205 which are sequentially stacked.

[0053] Optionally, the first Ni layer 201 is used as an adhesion layer, and the first Ni layer 201 is in contact with the epitaxial layer 10, so as to solve the problem of poor adhesion between the Al layer 202 and the epitaxial material. Ni has good interface bonding force with most semiconductor materials, which ensures stable adhesion of subsequent metal layers and avoids falling off.

[0054] The Al layer 202 serves as an intermediate layer in direct contact with the epitaxial layer 10. The Al layer 202 mainly provides high reflectivity, efficiently reflects the light emitted by the epitaxial layer 10 back to the light-emitting surface, and improves the light extraction efficiency of the device. Meanwhile, Al has good electrical conductivity, which helps to transmit current to the epitaxial layer 10.

[0055] The Cr layer 203 and the second Ni layer 204 serve as a barrier layer between the Al layer 202 and the Au layer 205. The main role of Cr is to prevent Al atoms from diffusing and reacting with Au. During operation, high temperature or electric field can drive the migration of Al and Au atoms. If they are in direct contact, they will form a brittle Au-Al intermetallic compound, which will cause the contact resistance of the electrode 20 to rise and the interface to delaminate. Cr can form stable compounds with Al and Au, inhibiting the direct diffusion of Al and Au atoms through chemical bonding and lattice matching, thereby protecting the reflective function of the Al layer 202 and the electrical conductivity of the Au layer 205, and improving the long-term reliability of the electrode 20.

[0056] The second Ni layer 204 can further block the diffusion of possible metal atoms and enhance the adhesion to the Au layer 205, providing a more stable bonding basis for the surface Au layer 205.

[0057] The Au layer 205 is the outermost layer of the electrode 20. Au has good electrical conductivity and chemical stability, which can ensure low resistance connection between the electrode 20 and the external circuit, and at the same time resist oxidation or corrosion in the environment, prolonging the service life of the device.

[0058] Optionally, the thickness of the first Ni layer 201 is 5-20 nm.

[0059] The first Ni layer 201 with the above thickness ensures sufficient adhesion to the epitaxial layer 10. Excessive thickness will increase the cost and may introduce stress.

[0060] Illustratively, the thickness of the first Ni layer 201 is 10 nm.

[0061] Optionally, the thickness of the Al layer 202 is 100-500 nm.

[0062] The Al layer 202 with a larger thickness can provide high light reflection to improve light extraction efficiency while ensuring sufficient electrical conductivity.

[0063] Illustratively, the thickness of the Al layer 202 is 200 nm.

[0064] Optionally, the thickness of the Cr layer 203 is 10-30 nm.

[0065] The Cr layer 203 with the above thickness is sufficient to block the diffusion of Al / Au atoms, while an excessively thick Cr layer 203 will increase the resistance or stress.

[0066] Exemplarily, the thickness of the Cr layer 203 is 20 nm.

[0067] Optionally, the thickness of the second Ni layer 204 is 20 nm to 50 nm.

[0068] The second Ni layer 204 with the above thickness can enhance adhesion with the Au layer 205 and assist in diffusion barrier.

[0069] Exemplarily, the thickness of the second Ni layer 204 is 30 nm.

[0070] Optionally, the thickness of the Au layer 205 is 50 nm to 200 nm.

[0071] The Au layer 205 with the above thickness can ensure low resistance conduction and soldering reliability.

[0072] Exemplarily, the thickness of the Au layer 205 is 100 nm.

[0073] Optionally, the electrode 20 further comprises a GaN contact layer 206, the GaN layer is located on the surface of the epitaxial layer 10, and the first Ni layer 201, the Al layer 202, the Cr layer 203, the second Ni layer 204 and the Au layer 205 are sequentially stacked on the GaN layer.

[0074] In the above implementation, the GaN contact layer 206 serves as a transition layer between the metal electrode 20 and the epitaxial layer 10, which can effectively alleviate the lattice mismatch and band gap difference between the GaN semiconductor and the metal, improve the interface bonding quality, ensure the first Ni layer 201 to form a stable and low resistance ohmic contact with GaN, avoid interface defects or high contact resistance caused by direct contact, and thus ensure efficient charge injection into the active region.

[0075] At the same time, the GaN contact layer 206 provides a flat and uniform physical substrate for subsequent metal stacking, which helps to form a continuous and dense coverage during metal layer deposition, especially optimizes the metal wrapping effect in the edge area, reduces the risk of abnormal diffusion of metal atoms in the edge, indirectly suppresses the generation of Au-Al intermetallic compounds, and improves the long-term reliability of the electrode 20.

[0076] Optionally, the connection between the first inclined surface 21 and the second inclined surface 22 is located between the first surface and the second surface of the barrier layer.

[0077] Figure 3 is a structural schematic diagram of an electrode provided by an embodiment of the present disclosure. As shown in Figure 3 The connection between the first inclined surface 21 and the second inclined surface 22 is located in the Cr layer 203 or the second Ni layer 204.

[0078] If the connection between the first inclined surface 21 and the second inclined surface 22 is located in the Au layer 205, the steep transition is prone to local cracking due to the high ductility but low hardness of the Au layer 205 under thermal stress or mechanical deformation. However, if it is placed in the Cr layer 203 or the second Ni layer 204, these intermediate layers have higher hardness and Young's modulus, which can effectively disperse stress and avoid metal layer fracture or delamination caused by stress concentration at the connection, thereby improving the overall mechanical stability of the electrode 20.

[0079] Furthermore, metal layer deposition typically employs sputtering or evaporation processes. The bottom layer (e.g., Al layer 202) closest to the epitaxial layer 10 must prioritize adhesion to the substrate, while the intermediate layers (Cr, second Ni layer 204) act as barrier or transition layers, and their deposition process is more sensitive to surface roughness. Placing the junctions in these intermediate layers leverages the stable adhesion interface already formed in the bottom layer and allows for a smooth transition through the subsequent Cr or second Ni layer 204, avoiding uneven deposition or poor step coverage caused by improper junction placement, thus ensuring the continuity of the metal layer on the inclined sidewalls.

[0080] For example, if the connection between the first inclined surface 21 and the second inclined surface 22 is located in the Cr layer 203, the steep transition can be further suppressed by the high stability of Cr and the formation of a stable interface with Al / Au, thus suppressing the abnormal diffusion of metal atoms in the connection region.

[0081] For example, if the connection between the first inclined surface 21 and the second inclined surface 22 is located in the second Ni layer 204, the diffusion path is reduced by the auxiliary blocking effect of the second Ni layer 204.

[0082] Optionally, such as Figure 1 As shown, the light-emitting diode also includes an insulating layer 30, which is located on the surface of the epitaxial layer 10 and covers the electrode 20.

[0083] For example, the insulating layer 30 includes a plurality of silicon oxide layers and a plurality of titanium oxide layers stacked alternately.

[0084] Among them, multiple periodically alternating SiO2 layers and TiO2 layers can form a distributed Bragg reflector layer.

[0085] For example, the number of cycles in a DBR layer can be between 20 and 50. For instance, the number of cycles in a DBR layer is 32.

[0086] The thickness of the SiO2 layer in the DBR layer can be from 800 angstroms to 1200 angstroms, and the thickness of the TiO2 layer can be from 500 angstroms to 900 angstroms.

[0087] In addition to its passivation function, the DBR layer also reflects light emitted from the multi-quantum-well layer to the DBR layer back to the light-emitting surface, thus improving the light emission effect.

[0088] Optionally, as shown in Figure 1 The light emitting diode further includes pads 40 on the surface of the insulating layer 30, and the insulating layer 30 has a through hole exposing the electrode 20, and the pads 40 are connected to the electrode 20 through the through hole.

[0089] The pads 40 can be rectangular blocks, which can increase the area and facilitate conduction. The two pads 40 are spaced apart on the surface of the insulating layer 30.

[0090] Exemplarily, the pad 40 can be a first Al layer 202, a first Ti layer, a second Al layer 202, a second Ti layer, and an Au layer 205 stacked in sequence.

[0091] The first Al layer 202 has a thickness of 8000 angstroms to 12000 angstroms, the first Ti layer has a thickness of 100 angstroms to 500 angstroms, the second Al layer 202 has a thickness of 8000 angstroms to 12000 angstroms, the second Ti layer has a thickness of 500 angstroms to 1500 angstroms, and the Au layer 205 has a thickness of 2000 angstroms to 5000 angstroms.

[0092] For example, the first Al layer 202 has a thickness of 10000 angstroms, the first Ti layer has a thickness of 200 angstroms, the second Al layer 202 has a thickness of 10000 angstroms, the second Ti layer has a thickness of 1000 angstroms, and the Au layer 205 has a thickness of 3000 angstroms.

[0093] Optionally, the epitaxial layer 10 includes a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer stacked in sequence.

[0094] The surface of the second semiconductor layer has a groove exposing the first semiconductor layer.

[0095] In the embodiments of the present disclosure, one of the first semiconductor layer and the second semiconductor layer is a p-type layer, and the other of the first semiconductor layer and the second semiconductor layer is an n-type layer.

[0096] Exemplarily, the first semiconductor layer is an n-type layer, and the second semiconductor layer is a p-type layer.

[0097] Optionally, the first semiconductor layer is a silicon-doped n-type GaN layer. The n-type GaN layer can have a thickness of 0.5 μm to 3 μm.

[0098] Optionally, the multiple quantum well layer includes InGaN quantum well layers and GaN quantum barrier layers alternately grown. The multiple quantum well layer can include 3 to 8 periods of InGaN quantum well layers and GaN quantum barrier layers alternately stacked.

[0099] As an example, in the embodiments of the present disclosure, the multiple quantum well layer includes 5 periods of InGaN quantum well layers and GaN quantum barrier layers alternately stacked.

[0100] Optionally, the thickness of the multi-quantum well layer is 150 nm to 200 nm.

[0101] Optionally, the second semiconductor layer is a magnesium-doped p-type GaN layer. The thickness of the p-type GaN layer is 0.5 μm to 3 μm.

[0102] Table 1 is a test data comparison table of electrode aging provided by the embodiment of the present disclosure.

[0103] Table 1

[0104]

[0105] In the embodiment of the present disclosure, the resistance change rate of the electrode after being exposed to an environment with a temperature of 85°C and a relative humidity of 85% for at least 1000 hours is less than 5%.

[0106] In the above table 1, IV% refers to the percentage change of forward voltage, ΔVf refers to the change amount of forward voltage, and ΔIr refers to the change amount of reverse leakage current.

[0107] The embodiment of the present disclosure provides a light-emitting diode, which comprises an electrode, and the resistance change rate of the electrode after being exposed to an environment with a temperature of 85°C and a relative humidity of 85% for at least 1000 hours is less than 5%.

[0108] According to Table 1, the light-emitting diode provided by the embodiment of the present disclosure is still qualified after being aged for 3000 hours in an environment with a temperature of 85°C and a relative humidity of 85%. It can be seen that the embodiment of the present disclosure can improve the reliability of the electrode and guarantee the electrical stability and optical performance of the light-emitting diode during the working process.

[0109] Optionally, the electrode comprises an Al layer and an Au layer which are stacked in sequence.

[0110] Optionally, the electrode further comprises a barrier layer, and the barrier layer is located between the Al layer and the Au layer.

[0111] Illustratively, the barrier layer can comprise at least one of a Cr layer and a Ni layer.

[0112] The thickness of the barrier layer can be 10 nm to 80 nm.

[0113] Optionally, the barrier layer has a first surface and a second surface; the first surface is close to the Al layer, and the second surface is away from the Al layer.

[0114] As an example, in the embodiment of the present disclosure, the electrode can comprise a first Ni layer, an Al layer, a Cr layer, a second Ni layer and an Au layer which are stacked in sequence.

[0115] Figure 4is a flowchart of a preparation method of a light emitting diode provided by the embodiments of the present disclosure. The method is used for preparing Figure 1 the light emitting diode as shown in the figure. As shown in the figure, Figure 4 the preparation method comprises:

[0116] S11: forming an epitaxial layer on a substrate.

[0117] S12: forming an electrode on the surface of the epitaxial layer.

[0118] wherein the sidewall of the electrode comprises at least two inclined surfaces, the at least two inclined surfaces are sequentially connected in a direction away from the epitaxial layer, and the inclination angle of the inclined surface close to the epitaxial layer among the at least two inclined surfaces is smaller than the inclination angle of the inclined surface away from the epitaxial layer among the at least two inclined surfaces.

[0119] The light emitting diode prepared by the preparation method is designed with at least two inclined surfaces sequentially connected on the sidewall of the electrode, and the inclination angle of the inclined surface close to the epitaxial layer is smaller, i.e. the inclined surface close to the epitaxial layer is more gentle; the inclination angle of the inclined surface away from the epitaxial layer is larger, i.e. the inclined surface away from the epitaxial layer is more steep. The sidewall morphology designed in the embodiments of the present disclosure optimizes the metal coverage of the edge region of the electrode, and the gentle inclined surface close to the epitaxial layer can provide a longer transition path and a larger coverage space for metal deposition, so that the blocking metal is more easily uniformly and continuously wrapped around the metal layer below at the edge, so as to reduce the defects of thin coverage or no coverage in the edge region.

[0120] In addition, the abnormal diffusion of metal atoms usually tends to follow a relatively gentle and continuous path. The steep inclined surface away from the epitaxial layer changes the possible diffusion path of the metal atoms, and the steep angle makes it difficult for the metal atoms to form a continuous and smooth diffusion channel along the sidewall. Compared with the gentle surface, the steep surface increases the difficulty of metal atom diffusion, making it more difficult for metal atoms to gather and diffuse to the edge region.

[0121] Therefore, through the gentle edge sidewall and the steep top sidewall structure, the problems of poor electrode edge coverage and easy formation of Au-Al intermetallic compounds in the edge region can be effectively solved, thereby improving the long-term reliability of the electrode and ensuring the electrical stability and optical performance of the light emitting diode in the working process.

[0122] The detailed process of preparing the light emitting diode in the embodiments of the present disclosure can comprise the following steps:

[0123] First, growing an epitaxial layer on a substrate.

[0124] wherein the substrate is a sapphire substrate, a silicon substrate or a silicon carbide substrate. The substrate can be a flat substrate or a patterned substrate.

[0125] As an example, in the embodiments of the present disclosure, the substrate is a sapphire substrate. The sapphire substrate is a commonly used substrate, which is mature in technology and low in cost. Specifically, the sapphire substrate can be a patterned sapphire substrate or a sapphire wafer substrate.

[0126] In the embodiments of the present disclosure, the sapphire substrate can be pre-processed, and the sapphire substrate is placed in a MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber for baking treatment for 12 to 18 minutes. As an example, in the embodiments of the present disclosure, the sapphire substrate is baked for 15 minutes.

[0127] Specifically, the baking temperature can be 1000 to 1200 degrees Celsius, and the pressure in the MOCVD reaction chamber during baking can be 100 to 200 mbar.

[0128] The growing of the epitaxial layer on the substrate can include sequentially forming a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer on the sapphire substrate by MOCVD technology.

[0129] Specifically, the first semiconductor layer is an n-type layer, and the second semiconductor layer is a p-type layer.

[0130] Optionally, the first semiconductor layer is an n-type Si-doped GaN layer. The thickness of the n-type GaN layer can be 0.5 to 3 microns.

[0131] The growth temperature of the n-type GaN layer can be 1000 to 1100 degrees Celsius, and the growth pressure of the n-type GaN layer can be 100 to 300 torr.

[0132] Optionally, the multi-quantum well layer includes alternately grown InGaN quantum well layers and GaN quantum barrier layers. Specifically, the multi-quantum well layer can include 3 to 8 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0133] When growing the multi-quantum well layer, the pressure in the MOCVD reaction chamber is controlled at 200 torr. When growing the InGaN quantum well layer, the reaction chamber temperature is 760 to 780 degrees Celsius. When growing the GaN quantum barrier layer, the reaction chamber temperature is 860 to 890 degrees Celsius.

[0134] As an example, in the embodiments of the present disclosure, the multi-quantum well layer includes 5 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0135] Optionally, the thickness of the multi-quantum well layer can be 150 to 200 nanometers.

[0136] Optionally, the second semiconductor layer is a p-type Mg-doped GaN layer. The thickness of the p-type GaN layer can be 0.5-3 μm.

[0137] When growing the p-type GaN layer, the growth pressure of the p-type GaN layer can be 200-600 Torr, and the growth temperature of the p-type GaN layer can be 800-1000 °C.

[0138] After forming the epitaxial layer, the method further comprises etching the second semiconductor layer to form a recess exposing the first semiconductor layer.

[0139] In the second step, an electrode is evaporated on the surface of the second semiconductor layer and in the recess.

[0140] Specifically, the method can comprise sequentially stacking a plurality of metal layers on the surface of the epitaxial layer to form the electrode.

[0141] In the method, the plurality of metal layers comprises sequentially forming a first Ni layer, an Al layer, a Cr layer, a second Ni layer and an Au layer on the surface of the epitaxial layer.

[0142] Specifically, the thickness of the first Ni layer can be 5-20 nm, the thickness of the Al layer can be 100-500 nm, the thickness of the Cr layer can be 10-30 nm, the thickness of the second Ni layer can be 20-50 nm, and the thickness of the Au layer can be 50-200 nm.

[0143] Optionally, the electrode further comprises a GaN contact layer on the surface of the epitaxial layer, and the first Ni layer, the Al layer, the Cr layer, the second Ni layer and the Au layer are sequentially stacked on the GaN layer.

[0144] Optionally, the sidewall of the electrode comprises a first inclined surface and a second inclined surface sequentially connected in a direction away from the epitaxial layer.

[0145] Specifically, the first inclined surface can have an angle of 30-40°, and the second inclined surface can have an angle of 40-70°.

[0146] Optionally, the junction of the first inclined surface and the second inclined surface is located on the Al layer, the Cr layer or the second Ni layer.

[0147] In the third step, an insulating layer is formed on the surface of the epitaxial layer to cover the electrode.

[0148] Specifically, the insulating layer can comprise a DBR layer.

[0149] In the DBR layer, the thickness of the SiO2 layer can be 800-1200 angstroms, and the thickness of the TiO2 layer can be 500-900 angstroms.

[0150] Specifically, the insulating layer on the sidewall of the epitaxial layer forms a cavity.

[0151] In the fourth step, a via hole is etched on the surface of the insulating layer to expose the electrode.

[0152] In the fifth step, a pad is evaporated on the surface of the insulating layer, so that the pad is connected to the electrode through the via hole.

[0153] Exemplarily, the pad can be a first Al layer, a first Ti layer, a second Al layer, a second Ti layer and an Au layer which are stacked in sequence.

[0154] The thickness of the first Al layer is 8000-12000 angstroms, the thickness of the first Ti layer is 100-500 angstroms, the thickness of the second Al layer is 8000-12000 angstroms, the thickness of the second Ti layer is 500-1500 angstroms, and the thickness of the Au layer is 2000-5000 angstroms.

[0155] For example, the thickness of the first Al layer is 10000 angstroms, the thickness of the first Ti layer is 200 angstroms, the thickness of the second Al layer is 10000 angstroms, the thickness of the second Ti layer is 1000 angstroms, and the thickness of the Au layer is 3000 angstroms.

[0156] Finally, the sapphire substrate can be inaudibly cut and cracked, which can better reduce the loss of brightness. Then, the light-emitting diode is tested.

[0157] The above description is only optional embodiments of the present disclosure, and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A light-emitting diode, characterized in that, The light-emitting diode includes an epitaxial layer (10) and an electrode (20), wherein the electrode (20) is located on the epitaxial layer (10); The sidewall of the electrode (20) includes at least two inclined surfaces, which are connected sequentially in a direction away from the epitaxial layer (10). The tilt angle of the inclined surface closer to the epitaxial layer (10) is smaller than the tilt angle of the inclined surface away from the epitaxial layer (10).

2. The light-emitting diode according to claim 1, characterized in that, The sidewall of the electrode (20) includes a first inclined surface (21) and a second inclined surface (22) connected sequentially in a direction away from the epitaxial layer (10).

3. The light-emitting diode according to claim 2, characterized in that, The first inclined surface (21) has an inclination angle of 30° to 40°, and the second inclined surface (22) has an inclination angle of 40° to 70°.

4. The light-emitting diode according to claim 2 or 3, characterized in that, The electrode (20) includes an Al layer (202) and an Au layer (205); the Al layer (202) is close to the epitaxial layer (10), and the Au layer (205) is disposed on the side of the Al layer (202) away from the epitaxial layer.

5. The light-emitting diode according to claim 4, characterized in that, The electrode (20) further includes a barrier layer located between the Al layer (202) and the Au layer (205).

6. The light-emitting diode according to claim 5, characterized in that, The thickness of the Al layer (202) is 100 nm to 500 nm, the thickness of the Au layer (205) is 50 nm to 200 nm, and the thickness of the barrier layer is 10 nm to 80 nm.

7. The light-emitting diode according to claim 5 or 6, characterized in that, The barrier layer has a first surface and a second surface; the first surface is close to the Al layer (202), and the second surface is away from the Al layer (202); the connection between the first inclined surface (21) and the second inclined surface (22) is located between the first surface and the second surface.

8. A light-emitting diode, characterized in that, The light-emitting diode includes an electrode (20), and the resistance change rate of the electrode (20) after being exposed to an environment of 85°C and 85% relative humidity for at least 1000 hours is less than 5%.

9. The light-emitting diode according to claim 8, characterized in that, The electrode (20) comprises an Al layer (202) and an Au layer (205) stacked sequentially.

10. The light-emitting diode according to claim 9, characterized in that, The electrode (20) further includes a barrier layer located between the Al layer (202) and the Au layer (205).

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