Light emitting diode with improved brightness and preparation method thereof

Abstract

The invention provides a light emitting diode with improved brightness and a preparation method thereof, and belongs to the technical field of photoelectron manufacturing. The light-emitting diode comprises an epitaxial layer, a transparent conductive layer, a current blocking layer and a composite electrode, the transparent conducting layer and the current blocking layer are both located on the surface of the epitaxial layer, the transparent conducting layer covers the current blocking layer, and the transparent conducting layer is provided with a first through hole exposed out of the epitaxial layer; the composite electrode comprises a first metal layer and a second metal layer, the first metal layer is located in the first through hole and connected with the epitaxial layer, the second metal layer is located on the surface of the transparent conductive layer and in the first through hole, the second metal layer wraps the first metal layer, and the second metal layer is located on the surface of the transparent conductive layer and connected with the epitaxial layer. And the light reflectivity of the first metal layer is greater than that of the second metal layer. According to the embodiment of the invention, the problem that the light extraction efficiency of the light-emitting diode is affected due to light absorption of the electrode can be improved.

Description

Technical Field

[0001] The present disclosure relates to the field of optoelectronic manufacturing technologies, and particularly to a light-emitting diode for improving brightness and a preparation method thereof. Background Art

[0002] As a highly influential new product in the optoelectronic industry, a light-emitting diode (English: Light Emitting Diode, abbreviated as: LED) has the characteristics of small volume, long service life, rich and colorful colors, low energy consumption, etc., and is widely used in the fields of lighting, display screens, signal lights, backlights, toys, etc.

[0003] In related technologies, a light-emitting diode includes an epitaxial layer, a transparent conductive layer, and an electrode. The transparent conductive layer is located on the surface of the epitaxial layer, and the electrode is located on the surface of the transparent conductive layer away from the epitaxial layer.

[0004] However, the electrode usually absorbs part of the light energy, and the stronger the light emission of the active region below the electrode, the stronger the light absorption effect of the electrode, resulting in a reduction in the light extraction efficiency of the light-emitting diode. Summary of the Invention

[0005] Embodiments of the present disclosure provide a light-emitting diode for improving brightness and a preparation method thereof, which can solve the problem that the light extraction efficiency of the light-emitting diode is affected by light absorption of the electrode. The technical solutions are as follows:

[0006] On the one hand, embodiments of the present disclosure provide a light-emitting diode, which includes: an epitaxial layer, a transparent conductive layer, a current blocking layer, and a composite electrode; both the transparent conductive layer and the current blocking layer are located on the surface of the epitaxial layer, the transparent conductive layer covers the current blocking layer, and the transparent conductive layer has a first through hole exposing the epitaxial layer; the composite electrode includes: a first metal layer and a second metal layer, the first metal layer is located in the first through hole and is connected to the epitaxial layer, the second metal layer is located on the surface of the transparent conductive layer and in the first through hole, and the second metal layer wraps the first metal layer, and the light reflectivity of the first metal layer is greater than that of the second metal layer.

[0007] In another implementation manner of the present disclosure, the transparent conductive layer is further located on the inner wall of the first through hole, the first metal layer and the transparent conductive layer located in the first through hole are arranged at intervals, and the second metal layer located in the first through hole connects the first metal layer and the transparent conductive layer located in the first through hole; the adhesion between the first metal layer and the transparent conductive layer is higher than the adhesion between the second metal layer and the transparent conductive layer.

[0008] In another implementation of the present disclosure, the ratio of the area of the positive projection of the first metal layer on the surface of the epitaxial layer to the area of the positive projection of the first through hole on the surface of the epitaxial layer is greater than or equal to 0.3

[0009] In another implementation of the present disclosure, the first metal layer includes at least one metal block, and the shape of the positive projection of the metal block on the surface of the epitaxial layer includes: polygon, bow shape, circle, ellipse, and ring.

[0010] In another implementation of the present disclosure, the light-emitting diode further includes finger electrodes, the finger electrodes are located on the surface of the transparent conductive layer and outside the first through hole, and one end of the finger electrodes is connected to the composite electrode.

[0011] In another implementation of the present disclosure, the first metal layer includes at least one of an Ag layer and an Al layer.

[0012] In another implementation of the present disclosure, the second metal layer includes at least one of a Cr layer and a Ti layer.

[0013] In another implementation of the present disclosure, the thickness of the first metal layer is 300 angstroms to 3000 angstroms.

[0014] On the other hand, an embodiment of the present disclosure further provides a method for manufacturing a light-emitting diode, the manufacturing method including: forming an epitaxial layer; forming a current blocking layer and a transparent conductive layer on the surface of the epitaxial layer, the transparent conductive layer covering the current blocking layer, the transparent conductive layer having a first through hole exposing the epitaxial layer; forming a composite electrode on the surface of the transparent conductive layer and in the first through hole, the composite electrode including: a first metal layer and a second metal layer, the first metal layer being located in the first through hole and connected to the epitaxial layer, the second metal layer being located on the surface of the transparent conductive layer and in the first through hole, and the second metal layer wrapping the first metal layer, the light reflectivity of the first metal layer being greater than the light reflectivity of the second metal layer.

[0015] Optionally, forming a current blocking layer and a transparent conductive layer on the surface of the epitaxial layer includes: forming a current blocking layer on the surface of the epitaxial layer, and etching a first through hole exposing the epitaxial layer on the surface of the current blocking layer; forming a transparent conductive layer covering the current blocking layer on the surface of the epitaxial layer, the transparent conductive layer is located on the inner wall of the first through hole and is connected to the epitaxial layer exposed by the first through hole; forming a composite electrode on the surface of the transparent conductive layer and in the first through hole includes: forming the first metal layer in the first through hole, the first metal layer and the transparent conductive layer located in the first through hole are arranged at intervals; forming a second metal layer in the gap between the first metal layer and the transparent conductive layer and on the surface of the transparent conductive layer, and the adhesion between the first metal layer and the transparent conductive layer is higher than the adhesion between the second metal layer and the transparent conductive layer.

[0016] The beneficial effects brought by the technical solutions provided by the embodiments of the present disclosure at least include:

[0017] In the light-emitting diode provided by the embodiment of the present disclosure, a current blocking layer and a transparent conductive layer are sequentially stacked on the epitaxial layer, and the transparent conductive layer has a first through hole exposing the epitaxial layer. Among them, the first metal layer of the composite electrode is arranged in the first through hole and is connected to the epitaxial layer, the second metal layer is arranged on the surface of the transparent conductive layer and in the first through hole, and the second metal layer wraps the first metal layer. Since the first metal layer with a higher light reflectivity in the composite electrode is connected to the epitaxial layer and the first metal layer is opposite to the epitaxial layer. Therefore, most of the light rays emitted from the epitaxial layer to the composite electrode can be reflected at the interface between the first metal layer and the epitaxial layer, so that more light rays are reflected back to the light-emitting surface of the light-emitting diode to improve the light extraction efficiency of the light-emitting diode. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 is a schematic structural diagram of a light-emitting diode provided by the related art;

[0020] Figure 2 is a schematic structural diagram of a light-emitting diode provided by an embodiment of the present disclosure;

[0021] Figure 3 is Figure 2 a provided AA cross-sectional view;

[0022] Figure 4It is a flowchart of a method for manufacturing a light-emitting diode provided by an embodiment of the present disclosure;

[0023] Figure 5 It is a preparation state diagram of a light-emitting diode provided by an embodiment of the present disclosure;

[0024] Figure 6 It is a preparation state diagram of a light-emitting diode provided by an embodiment of the present disclosure;

[0025] Figure 7 It is a preparation state diagram of a light-emitting diode provided by an embodiment of the present disclosure.

[0026] The descriptions of each mark in the figure are as follows:

[0027] 10. Substrate;

[0028] 20. Epitaxial layer; 21. First semiconductor layer; 22. Multi-quantum well layer; 23. Second semiconductor layer;

[0029] 30. Transparent conductive layer;

[0030] 40. Current blocking layer;

[0031] 50. First through hole;

[0032] 60. Composite electrode; 61. First metal layer; 62. Second metal layer;

[0033] 70. Finger electrode. Detailed implementation manners

[0034] To make the objectives, technical solutions, and advantages of the present disclosure clearer, the following will further describe the embodiments of the present disclosure in detail with reference to the accompanying drawings.

[0035] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art to which this disclosure pertains. The terms "first", "second", "third" and similar terms used in the specification and claims of this patent application of the present disclosure do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, terms such as "a" or "an" do not denote a quantity limitation, but mean that there is at least one. Terms such as "comprising" or "including" mean that the elements or items appearing before "comprising" or "including" cover the elements or items listed after "comprising" or "including" and their equivalents, and do not exclude other elements or items. Terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper", "lower", "left", "right", "top", "bottom" are only used to indicate relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationships may also change accordingly.

[0036] Figure 1 is a schematic structural diagram of a light-emitting diode provided by the related art. As Figure 1 shown, the light-emitting diode in the related art includes: an epitaxial layer 20, a transparent conductive layer 30, a current blocking layer 40 and an electrode. The current blocking layer 40 and the transparent conductive layer 30 are both located on the surface of the epitaxial layer 20, and the transparent conductive layer 30 covers the current blocking layer 40. The electrode is located on the surface of the transparent conductive layer 30 away from the epitaxial layer 20.

[0037] In the related art, the current blocking layer 40 is usually a silicon oxide layer. Since the silicon oxide layer is brittle and easily breaks under external force, when wire bonding is performed above the transparent conductive layer 30 to fabricate the electrode, it is easy to apply a relatively large pressure to the transparent conductive layer 30, which causes the silicon oxide layer below the transparent conductive layer 30 to be shattered, resulting in abnormal electrode preparation.

[0038] Moreover, the silicon oxide layer has a good reflectivity and can improve the brightness of the light-emitting diode to a certain extent. However, during the process of fabricating the electrode, the brittle fracture of the silicon oxide layer will also affect the brightness of the light-emitting diode. At the same time, the electrode usually absorbs part of the light energy, and the stronger the light emission of the active region below the electrode, the stronger the light absorption effect of the electrode, resulting in a reduction in the light extraction efficiency of the light-emitting diode.

[0039] Therefore, the embodiments of the present disclosure provide a light-emitting diode. Figure 2 is a schematic structural diagram of a light-emitting diode provided by an embodiment of the present disclosure. Figure 3 is Figure 2 a provided AA cross-sectional view. As Figure 2 、 3As shown, the light-emitting diode includes: an epitaxial layer 20, a transparent conductive layer 30, a current blocking layer 40, and a composite electrode 60.

[0040] As Figure 3 shown, both the transparent conductive layer 30 and the current blocking layer 40 are located on the surface of the epitaxial layer 20. The transparent conductive layer 30 covers the current blocking layer 40, and the transparent conductive layer 30 has a first through hole 50 exposing the epitaxial layer 20.

[0041] As Figure 3 shown, the composite electrode 60 includes: a first metal layer 61 and a second metal layer 62. The first metal layer 61 is located in the first through hole 50 and is connected to the epitaxial layer 20. The second metal layer 62 is located on the surface of the transparent conductive layer 30 and in the first through hole 50, and the second metal layer 62 wraps the first metal layer 61. The light reflectivity of the first metal layer 61 is greater than that of the second metal layer 62.

[0042] In the light-emitting diode provided by the embodiment of the present disclosure, the current blocking layer 40 and the transparent conductive layer 30 are sequentially stacked on the epitaxial layer 20, and the transparent conductive layer 30 has a first through hole 50 exposing the epitaxial layer 20. Among them, a partial area of the composite electrode 60 is located in the first through hole 50. In this way, when the composite electrode 60 is fabricated above the transparent conductive layer 30, even if the transparent conductive layer 30 is under pressure, since most of the area of the current blocking layer 40 is not opposite to the composite electrode 60, therefore, the current blocking layer 40 will not bear a large pressure and have a problem of brittle fracture.

[0043] Among them, the first metal layer 61 of the composite electrode 60 is disposed in the first through hole 50 and is connected to the epitaxial layer 20. The second metal layer 62 is disposed on the surface of the transparent conductive layer 30 and in the first through hole 50, and the second metal layer 62 wraps the first metal layer 61. Since the first metal layer 61 with a higher light reflectivity in the composite electrode 60 is connected to the epitaxial layer 20 and the first metal layer 61 is opposite to the epitaxial layer 20. Therefore, most of the light rays emitted from the epitaxial layer 20 to the composite electrode 60 can be reflected at the interface between the first metal layer 61 and the epitaxial layer 20, so that more light rays are reflected back to the light-emitting surface of the light-emitting diode, thereby improving the light extraction efficiency of the light-emitting diode.

[0044] Optionally, the first metal layer 61 includes at least one of an Ag layer and an Al layer.

[0045] As an example, in the embodiment of the present disclosure, the first metal layer 61 includes an Ag layer. The light reflectivity of metal Ag exceeds 90%. Using metal Ag as the first metal layer 61 can reflect most of the light rays emitted from the epitaxial layer 20 to the composite electrode 60 back to the light-emitting surface of the light-emitting diode, improving the light extraction efficiency of the light-emitting diode.

[0046] Optionally, the thickness of the first metal layer 61 is from 300 Å to 3000 Å.

[0047] Setting the thickness of the first metal layer 61 within the above range can avoid increasing the manufacturing cost of the composite electrode 60 due to an overly large thickness of the first metal layer 61, and can also avoid the situation where the thickness of the first metal layer 61 is too small to achieve the purpose of sufficiently reflecting light.

[0048] Exemplarily, the thickness of the first metal layer 61 is less than the depth of the first through hole 50. This can avoid an overly large thickness of the first metal layer 61. When manufacturing the first metal layer 61, the first metal layer 61 adheres to the transparent conductive layer 30, which may affect the connection reliability between the composite electrode 60 and the transparent conductive layer 30.

[0049] As an example, in the embodiments of the present disclosure, the thickness of the first metal layer 61 is 2000 Å.

[0050] Optionally, as Figure 3 shown, the transparent conductive layer 30 also lies on the inner wall of the first through hole 50. The first metal layer 61 and the transparent conductive layer 30 located within the first through hole 50 are arranged at intervals, and the second metal layer 62 located within the first through hole 50 connects the first metal layer 61 and the transparent conductive layer 30 located within the first through hole 50.

[0051] Among them, the adhesion between the first metal layer 61 and the transparent conductive layer 30 is higher than the adhesion between the second metal layer 62 and the transparent conductive layer 30.

[0052] In the above implementation, the transparent conductive layer 30 extends into the first through hole 50 and adheres to the inner wall of the first through hole 50. This can avoid the connection between the second metal layer 62 and the current blocking layer 40, and make full use of the characteristic that the adhesion between the second metal layer 62 and the transparent conductive layer 30 is better, so that the composite electrode 60 is more firmly fixed on the epitaxial layer 20.

[0053] At the same time, the second metal layer 62 is also used to connect the first metal layer 61 and the transparent conductive layer 30 located within the first through hole 50, so that the composite electrode 60 can be more stably fixed within the first through hole 50, preventing the composite electrode 60 from becoming loose.

[0054] Optionally, the second metal layer 62 includes at least one of a Cr layer and a Ti layer.

[0055] As an example, in the embodiments of the present disclosure, the second metal layer 62 includes a Ti layer. Using metal Ti as the second metal layer 62 can also effectively improve the ohmic contact characteristics between the transparent conductive layer 30 and the second metal layer 62, enabling the current of the composite electrode 60 to spread to various regions of the epitaxial layer 20 through the transparent conductive layer 30.

[0056] Optionally, the ratio of the area of the positive projection of the first metal layer 61 on the surface of the epitaxial layer 20 to the area of the positive projection of the first via hole 50 on the surface of the epitaxial layer 20 is greater than or equal to 0.3.

[0057] Since the light reflectivity of the first metal layer 61 is stronger than that of the second metal layer 62, the area ratio of the first metal layer 61 in the first via hole 50 cannot be too small to ensure that a large enough area of the first metal layer 61 participates in the reflection.

[0058] Moreover, a part of the second metal layer 62 needs to be provided in the first via hole 50. By utilizing the characteristic that the adhesion between the second metal layer 62 and the epitaxial layer 20 is better, the composite electrode 60 is firmly fixed in the first via hole 50.

[0059] Exemplarily, the ratio of the area of the positive projection of the first metal layer 61 on the surface of the epitaxial layer 20 to the area of the positive projection of the first via hole 50 on the surface of the epitaxial layer 20 is greater than or equal to 0.6.

[0060] Optionally, the first metal layer 61 includes at least one metal block, and the shape of the positive projection of the metal block on the surface of the epitaxial layer 20 includes: polygon, bow shape, circle, ellipse, and ring.

[0061] Exemplarily, as Figure 2 shown, the first metal layer 61 includes one metal block, and the projection shape of the metal block is a ring.

[0062] By setting the shape of the first metal layer 61 as a ring, a film layer structure in which the second metal layer 62, the first metal layer 61, and the second metal layer 62 are alternately formed in the first via hole 50 is formed. In this way of sandwiching the first metal layer 61 with the second metal layer 62, the adhesion of the second metal layer 62 can be fully utilized to firmly fix the first metal layer 61 on the surface of the epitaxial layer 20 as well.

[0063] Exemplarily, the first metal layer 61 includes a plurality of metal blocks, and the plurality of metal blocks are circumferentially spaced apart around the center of the first via hole 50. For example, the projection shape of the metal block can be an ellipse, so that the plurality of metal blocks are combined to form a petal shape. In this arrangement of the first metal layer 61, the first metal layer 61 is also doped and arranged in the second metal layer 62. While ensuring the reflection effect, the connection reliability between the first metal layer 61 and the epitaxial layer 20 can also be improved.

[0064] Optionally, as Figure 2 shown, the light-emitting diode further includes a finger electrode 70. The finger electrode 70 is located on the surface of the transparent conductive layer 30, and the finger electrode 70 is located outside the first via hole 50. One end of the finger electrode 70 is connected to the composite electrode 60.

[0065] Exemplarily, the finger electrode 70 may include at least one of a Ti layer, a Cr layer, and an Ag layer.

[0066] In an embodiment of the present disclosure, the composite electrode 60 is an electrode for connecting to an external power source. Meanwhile, a finger electrode 70 connected to the composite electrode 60 is further provided, which can transmit the current injected onto the composite electrode 60 to the finger electrode 70 and extend it to various regions of the epitaxial layer 20 through the finger electrode 70.

[0067] Optionally, as Figure 3 shown, the light-emitting diode includes a substrate 10, and an epitaxial layer 20 is located on the surface of the substrate 10.

[0068] Exemplarily, the substrate may be a sapphire substrate. The sapphire substrate has a relatively high light transmittance, that is, the substrate is a transparent substrate. Moreover, the sapphire material is relatively hard and has relatively stable chemical properties, enabling the light-emitting diode to have good light-emitting effects and stability.

[0069] Optionally, as Figure 3 shown, the epitaxial layer 20 includes a first semiconductor layer 21, a multi-quantum well layer 22, and a second semiconductor layer 23 that are sequentially stacked on the substrate 10.

[0070] One of the first semiconductor layer 21 and the second semiconductor layer 23 is a p-type layer, and the other of the first semiconductor layer 21 and the second semiconductor layer 23 is an n-type layer.

[0071] Exemplarily, the first semiconductor layer 21 is an n-type layer, and the second semiconductor layer 23 is a p-type layer.

[0072] Optionally, the first semiconductor layer 21 is an n-type GaN layer doped with silicon. The thickness of the n-type GaN layer may be 0.5 μm to 3 μm.

[0073] Optionally, the multi-quantum well layer 22 includes alternately grown InGaN quantum well layers and GaN quantum barrier layers. Among them, the multi-quantum well layer 22 may include 3 to 8 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0074] As an example, in an embodiment of the present disclosure, the multi-quantum well layer 22 includes 5 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0075] Optionally, the thickness of the multi-quantum well layer 22 may be 150 nm to 200 nm.

[0076] Optionally, the second semiconductor layer 23 is a p-type GaN layer doped with magnesium. The thickness of the p-type GaN layer may be 0.5 μm to 3 μm.

[0077] In an embodiment of the present disclosure, the surface of the second semiconductor layer 23 has a groove exposing the first semiconductor layer 21, and electrodes are provided both in the groove and on the surface of the second semiconductor layer 23.

[0078] Exemplarily, the first semiconductor layer 21 is an n-type layer, and the second semiconductor layer 23 is a p-type layer. Then, the electrode in the groove is an n electrode, and the electrode above the second semiconductor layer 23 is a p electrode.

[0079] Wherein, the n electrode and the p electrode may be a composite electrode 60, and the embodiment of the present disclosure does not limit this.

[0080] Optionally, the light-emitting diode further includes an AlN buffer layer and a u-type GaN layer. The AlN buffer layer and the u-type GaN layer are sequentially stacked on the substrate, and the epitaxial layer 20 is located on the u-type GaN layer.

[0081] Optionally, the transparent conductive layer 30 may be an indium tin oxide (ITO for short) layer. The indium tin oxide layer has good transmittance and low resistivity. Using the indium tin oxide layer as the transparent conductive layer 30 can allow more light to transmit through the transparent conductive layer 30, thus ensuring the light output effect; at the same time, due to the low resistivity, it is also convenient for carrier conduction and improves the injection efficiency.

[0082] Exemplarily, the transparent conductive layer 30 may be an indium zinc oxide (IZO for short) layer. The indium zinc oxide layer has good transmittance and low resistivity. Using the indium zinc oxide layer as the transparent conductive layer 30 can allow more light to transmit through the transparent conductive layer 30, thus ensuring the light output effect; at the same time, due to the low resistivity, it is also convenient for carrier conduction and improves the injection efficiency.

[0083] As an example, the thickness of the transparent conductive layer 30 may be from 200 Å to 5000 Å. For example, the thickness of the transparent conductive layer 30 is 2000 Å.

[0084] Optionally, the light-emitting diode further includes a passivation layer. The passivation layer is located on the surface of the epitaxial layer 20 and covers the composite electrode 60. The passivation layer has a through hole exposing the composite electrode 60 so that an external power supply can be connected to the composite electrode 60 through the through hole.

[0085] Exemplarily, the passivation layer may include at least one of a silicon oxide layer, an aluminum oxide layer, and a silicon nitride layer.

[0086] Optionally, the thickness of the passivation layer may be from 800 Å to 3000 Å. For example, the thickness of the passivation layer may be 1000 Å.

[0087] Figure 4 It is a flowchart of a method for manufacturing a light-emitting diode provided by an embodiment of the present disclosure. AsFigure 4 As shown in Figure 4 , the manufacturing method includes:

[0088] S11: Form an epitaxial layer 20.

[0089] Among them, the epitaxial layer 20 includes a first semiconductor layer 21, a multi-quantum well layer 22, and a second semiconductor layer 23 that are stacked in sequence.

[0090] S12: Form a current blocking layer 40 and a transparent conductive layer 30 on the surface of the epitaxial layer 20.

[0091] Among them, the transparent conductive layer 30 covers the current blocking layer 40, and the transparent conductive layer 30 has a first through hole 50 exposing the epitaxial layer 20.

[0092] S13: Form a composite electrode 60 on the surface of the transparent conductive layer 30 and within the first through hole 50.

[0093] Among them, the composite electrode 60 includes: a first metal layer 61 and a second metal layer 62. The first metal layer 61 is located within the first through hole 50 and is connected to the epitaxial layer 20. The second metal layer 62 is located on the surface of the transparent conductive layer 30 and within the first through hole 50, and the second metal layer 62 wraps the first metal layer 61. The light reflectivity of the first metal layer 61 is greater than that of the second metal layer 62.

[0094] In the light-emitting diode manufactured by this manufacturing method, the current blocking layer 40 and the transparent conductive layer 30 are stacked in sequence on the epitaxial layer 20, and the transparent conductive layer 30 has a first through hole 50 exposing the epitaxial layer 20. Among them, the first metal layer 61 of the composite electrode 60 is disposed within the first through hole 50 and is connected to the epitaxial layer 20, and the second metal layer 62 is disposed on the surface of the transparent conductive layer 30 and within the first through hole 50, and the second metal layer 62 wraps the first metal layer 61. Since the first metal layer 61 with a higher light reflectivity in the composite electrode 60 is connected to the epitaxial layer 20 and the first metal layer 61 faces the epitaxial layer 20. Therefore, most of the light rays emitted from the epitaxial layer 20 towards the composite electrode 60 can be reflected at the interface between the first metal layer 61 and the epitaxial layer 20, so that more light rays are reflected back to the light-emitting surface of the light-emitting diode to improve the light extraction efficiency of the light-emitting diode.

[0095] The epitaxial layer 20 formed in step S11 is located on a substrate.

[0096] Among them, 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.

[0097] As an example, in the embodiments of the present disclosure, the substrate is a sapphire substrate. The sapphire substrate is a commonly used substrate with mature technology and low cost. Specifically, it can be a patterned sapphire substrate or a sapphire flat substrate.

[0098] Among them, the sapphire substrate can be pre-treated by placing the sapphire substrate in a MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber and baking the sapphire substrate for 12 to 18 minutes. As an example, in the embodiments of the present disclosure, the sapphire substrate is baked for 15 minutes.

[0099] Specifically, the baking temperature can be 1000°C to 1200°C, and the pressure in the MOCVD reaction chamber during baking can be 100 mbar to 200 mbar.

[0100] Before step S11, it may include: sequentially forming an AlN buffer layer and a u-shaped GaN layer on the sapphire substrate by MOCVD technology.

[0101] Such as Figure 5 As shown, growing the epitaxial layer 20 on the substrate in step S11 may include: sequentially forming a first semiconductor layer 21, a multi-quantum well layer 22, and a second semiconductor layer 23 on the sapphire substrate by MOCVD technology.

[0102] Exemplarily, the epitaxial layer 20 includes an n-type GaN layer, a multi-quantum well layer 22, and an n-type GaN layer stacked in sequence.

[0103] Optionally, the thickness of the n-type GaN layer can be 0.5 μm to 3 μm.

[0104] The growth temperature of the n-type GaN layer can be 1000°C to 1100°C, and the growth pressure of the n-type GaN layer can be 100 torr to 300 torr.

[0105] Optionally, the multi-quantum well layer 22 includes alternately grown InGaN quantum well layers and GaN quantum barrier layers. Among them, the multi-quantum well layer 22 may include 3 to 8 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0106] When growing the multi-quantum well layer 22, 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°C to 780°C. When growing the GaN quantum barrier layer, the reaction chamber temperature is 860°C to 890°C.

[0107] As an example, in the embodiments of the present disclosure, the multi-quantum well layer 22 includes 5 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0108] Optionally, the thickness of the multi-quantum well layer 22 can be 150 nm to 200 nm.

[0109] Optionally, the thickness of the p-type GaN layer may be from 0.5 μm to 3 μm.

[0110] When growing the p-type GaN layer, the growth pressure of the p-type GaN layer may be from 200 Torr to 600 Torr, and the growth temperature of the p-type GaN layer may be from 800 °C to 1000 °C.

[0111] Steps S12 to S13 may include the following steps:

[0112] First, a current blocking layer 40 is formed on the surface of the epitaxial layer 20, and a first through hole 50 exposing the epitaxial layer 20 is etched on the surface of the current blocking layer 40.

[0113] As Figure 6 shown, a current blocking layer 40 is formed on the surface of the second semiconductor layer 23, and a first through hole 50 exposing the second semiconductor layer 23 is formed on the surface of the current blocking layer 40 by etching.

[0114] Exemplarily, the current blocking layer 40 is a silicon oxide layer. And the thickness of the silicon oxide layer is from 500 Å to 3000 Å.

[0115] Second, a transparent conductive layer 30 covering the current blocking layer 40 is formed on the surface of the epitaxial layer 20.

[0116] Among them, as Figure 7 shown, the transparent conductive layer 30 is located on the inner wall of the first through hole 50, and the transparent conductive layer 30 is connected to the epitaxial layer 20 exposed by the first through hole 50.

[0117] When preparing the transparent conductive layer 30, a layer of transparent conductive layer 30 may be first formed on the surface of the second semiconductor layer 23, and then a mask plate is set, and part of the transparent conductive layer 30 is removed by etching, so that the transparent conductive layer 30 located in the first through hole 50 only adheres to the inner wall of the first through hole 50.

[0118] Exemplarily, the transparent conductive layer 30 may be an ITO layer or an IZO layer.

[0119] As an example, the thickness of the transparent conductive layer 30 may be from 200 Å to 5000 Å. For example, the thickness of the transparent conductive layer 30 is 2000 Å.

[0120] Third, a first metal layer 61 is formed in the first through hole 50.

[0121] Among them, as Figure 3 shown, the first metal layer 61 and the transparent conductive layer 30 located in the first through hole 50 are arranged at intervals.

[0122] Optionally, the first metal layer 61 includes at least one of an Ag layer and an Al layer. As an example, in an embodiment of the present disclosure, the first metal layer 61 includes an Ag layer.

[0123] Optionally, the thickness of the first metal layer 61 is from 300 Å to 3000 Å. As an example, in an embodiment of the present disclosure, the thickness of the first metal layer 61 is 2000 Å.

[0124] Optionally, the first metal layer 61 includes at least one metal block, and the shape of the orthographic projection of the metal block on the surface of the epitaxial layer 20 includes: polygon, bow, circle, ellipse, and ring.

[0125] Exemplarily, as Figure 2 shown, the first metal layer 61 includes one metal block, and the projection shape of the metal block is a ring.

[0126] Fourthly, a second metal layer 62 is formed in the gap between the first metal layer 61 and the transparent conductive layer 30 and on the surface of the transparent conductive layer 30.

[0127] Wherein, the adhesion between the first metal layer 61 and the transparent conductive layer 30 is higher than the adhesion between the second metal layer 62 and the transparent conductive layer 30.

[0128] Optionally, the second metal layer 62 includes at least one of a Cr layer and a Ti layer. As an example, in an embodiment of the present disclosure, the second metal layer 62 includes a Ti layer.

[0129] After step S13, it may further include: forming a passivation layer on the surface of the second semiconductor layer 23 away from the first semiconductor layer 21 and in the groove.

[0130] Specifically, it may include: forming a passivation layer on the surface of the p-type GaN layer, the surface of the transparent conductive layer 30, and in the groove.

[0131] Exemplarily, the passivation layer may be a silicon oxide layer, and the thickness of the passivation layer may be from 800 Å to 3000 Å.

[0132] Optionally, the part of the passivation layer located in the first through hole 50 of the transparent conductive layer 30 and at least part of the passivation layer located in the groove are barrier layers.

[0133] Optionally, the part of the passivation layer laminated on the surface of the transparent conductive layer 30 and the part on the groove wall are insulating layers.

[0134] Finally, the sapphire substrate can be invisibly cut and cleaved, and the invisible cutting and cleaving can preferably reduce the loss of brightness. Then, a light-emitting diode is obtained by testing.

[0135] The above are only optional embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A light emitting diode, characterized in that: The light-emitting diode comprises: an epitaxial layer (20), a transparent conductive layer (30), a current blocking layer (40) and a composite electrode (60); The transparent conductive layer (30) and the current blocking layer (40) are both located on the surface of the epitaxial layer (20), the transparent conductive layer (30) covers the current blocking layer (40), and the transparent conductive layer (30) has a first through hole (50) exposing the epitaxial layer (20); The composite electrode (60) comprises: a first metal layer (61) and a second metal layer (62), wherein the first metal layer (61) is located in the first through hole (50) and connected to the epitaxial layer (20), and the second metal layer (62) is located on the surface of the transparent conductive layer (30) and in the first through hole (50), and the second metal layer (62) wraps the first metal layer (61), and the light reflectivity of the first metal layer (61) is greater than the light reflectivity of the second metal layer (62).

2. The light emitting diode according to claim 1, characterized in that: The transparent conductive layer (30) is also located on the inner wall of the first through hole (50), the first metal layer (61) and the transparent conductive layer (30) located in the first through hole (50) are arranged in a spaced relationship, and the second metal layer (62) located in the first through hole (50) connects the first metal layer (61) and the transparent conductive layer (30) located in the first through hole (50); The adhesion between the first metal layer (61) and the transparent conductive layer (30) is higher than the adhesion between the second metal layer (62) and the transparent conductive layer (30).

3. The light emitting diode according to claim 1, characterized in that: The ratio of the area of ​​the orthographic projection of the first metal layer (61) on the surface of the epitaxial layer (20) to the area of ​​the orthographic projection of the first through hole (50) on the surface of the epitaxial layer (20) is greater than or equal to 0.

3.

4. The light emitting diode according to claim 3, characterized in that: The first metal layer (61) comprises at least one metal block, and the shape of the orthographic projection of the metal block on the surface of the epitaxial layer (20) comprises: a polygon, an arc, a circle, an ellipse and a ring.

5. The light emitting diode according to claim 1, characterized in that: The light-emitting diode further comprises a finger electrode (70), wherein the finger electrode (70) is located on the surface of the transparent conductive layer (30) and outside the first through hole (50), and one end of the finger electrode (70) is connected to the composite electrode (60).

6. The light emitting diode according to any one of claims 1 to 5, characterized in that: The first metal layer (61) includes at least one of an Ag layer and an Al layer.

7. The light emitting diode according to any one of claims 1 to 5, characterized in that: The second metal layer (62) includes at least one of a Cr layer and a Ti layer.

8. The light emitting diode according to any one of claims 1 to 5, characterized in that: The thickness of the first metal layer (61) is 300 angstroms to 3000 angstroms.

9. A method for preparing a light emitting diode, characterized in that: The preparation method comprises: forming an epitaxial layer (20); A current blocking layer (40) and a transparent conductive layer (30) are formed on the surface of the epitaxial layer (20), wherein the transparent conductive layer (30) covers the current blocking layer (40), and the transparent conductive layer (30) has a first through hole (50) exposing the epitaxial layer (20); A composite electrode (60) is formed on the surface of the transparent conductive layer (30) and in the first through hole (50), the composite electrode (60) comprising: a first metal layer (61) and a second metal layer (62), the first metal layer (61) being located in the first through hole (50) and connected to the epitaxial layer (20), the second metal layer (62) being located on the surface of the transparent conductive layer (30) and in the first through hole (50), and the second metal layer (62) wraps the first metal layer (61), and the light reflectivity of the first metal layer (61) is greater than the light reflectivity of the second metal layer (62).

10. The light emitting diode according to any one of claims 1 to 5, characterized in that: Forming a current blocking layer (40) and a transparent conductive layer (30) on the surface of the epitaxial layer (20) comprises: forming a current blocking layer (40) on the surface of the epitaxial layer (20), and etching the surface of the current blocking layer (40) to form a first through hole (50) exposing the epitaxial layer (20); A transparent conductive layer (30) covering the current blocking layer (40) is formed on the surface of the epitaxial layer (20), wherein the transparent conductive layer (30) is located on the inner wall of the first through hole (50) and is connected to the epitaxial layer (20) exposed by the first through hole (50); Forming a composite electrode (60) on the surface of the transparent conductive layer (30) and in the first through hole (50) comprises: forming the first metal layer (61) in the first through hole (50), wherein the first metal layer (61) and the transparent conductive layer (30) located in the first through hole (50) are arranged in a spaced relationship; A second metal layer (62) is formed in the gap between the first metal layer (61) and the transparent conductive layer (30) and on the surface of the transparent conductive layer (30), and the adhesion between the first metal layer (61) and the transparent conductive layer (30) is higher than the adhesion between the second metal layer (62) and the transparent conductive layer (30).

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