Light Emitting Diode and its Manufacturing Method

Abstract

This invention provides a light-emitting diode (LED) and a method for manufacturing the same. The LED includes: a substrate; an epitaxial layer comprising a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer sequentially stacked on the substrate, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types; a transparent conductive layer located on a portion of the surface of the epitaxial layer, wherein the transparent conductive layer has opposite doping types to the contacting epitaxial layer; a reflective layer located on the transparent conductive layer; a current spreading layer covering the transparent conductive layer and the reflective layer and extending onto the epitaxial layer, wherein the current spreading layer has the same doping type as the contacting epitaxial layer; and a first electrode located on the current spreading layer above the reflective layer. The technical solution of this invention increases the lateral current spreading length while also improving light extraction efficiency and reliability.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a light-emitting diode and its manufacturing method. Background Technology

[0002] Uneven current density distribution in the active layer of a light-emitting diode (LED) not only leads to uneven luminous intensity distribution but also causes excessively high temperatures in localized areas, thus reducing the LED's reliability. To improve the photoelectric performance and reliability of LEDs, optimized LED design requires suppressing the current crowding effect, enhancing the lateral current spread performance, mitigating the quantum efficiency drop under high current injection conditions, and enabling the LED to withstand higher operating current densities.

[0003] For example Figure 1a Taking the light-emitting diode shown as an example, the epitaxial layer of the light-emitting diode includes a first semiconductor layer 12, a multiple quantum well layer 13, and a second semiconductor layer 14 formed from bottom to top on the front side of the substrate 11. The second semiconductor layer 14 has a flat surface, and the light emitted from the multiple quantum well layer 13 is emitted through the front side of the light-emitting diode (e.g., light emitted from the front side of the light-emitting diode). Figure 1a (The arrow in the image represents the light emitted from the front of the LED). The first electrode 15 is formed on a portion of the second semiconductor layer 14, and the second electrode 16 is formed on the back side of the substrate 11.

[0004] When the first semiconductor layer 12 is N-type and the second semiconductor layer 14 is P-type, because the hole mobility of the second semiconductor layer 14 is much smaller than the electron mobility of the first semiconductor layer 12, the conductivity of the second semiconductor layer 14 is much weaker than that of the first semiconductor layer 12 at a comparable carrier concentration. Therefore, the lateral current spread of the second semiconductor layer 14 is shorter. To improve the lateral current spread performance of the light-emitting diode, such as... Figure 1bAs shown, an ITO (indium tin oxide) transparent conductive layer 17 is typically deposited on the second semiconductor layer 14 using electron beam evaporation or ion beam sputtering. The first electrode 15 is formed on a portion of the ITO transparent conductive layer 17. To reduce the contact resistance between the ITO transparent conductive layer 17 and the second semiconductor layer 14 and to improve the visible light transmittance of the ITO transparent conductive layer 17, thermal annealing is generally performed after evaporation or ion beam sputtering. However, after annealing, the sheet resistance of the ITO transparent conductive layer 17 is greater than that of the first semiconductor layer 12, causing the injected current to concentrate near the first electrode 15, resulting in a relatively short lateral current spread. Furthermore, for high-power light-emitting diodes, the lateral current spread gradually decreases with increasing injected current density. Under high current density driving conditions, this current concentration phenomenon below the first electrode 15 becomes more severe, leading to a large concentration of photons generated by the active layer (i.e., the multi-quantum-well layer 13) below the first electrode 15.

[0005] Currently, in order to improve the current accumulation phenomenon near the first electrode 15 in the light-emitting diode, such as Figure 1c As shown, a SiO2 current blocking layer 18 is deposited in a portion of the region between the ITO transparent conductive layer 17 and the second semiconductor layer 14 below the first electrode 15. The SiO2 current blocking layer 18 can prevent the longitudinal transmission of current below the first electrode 15, forcing the current to spread laterally in the ITO transparent conductive layer 17, as shown. Figure 2 As indicated by the arrow, the current extends laterally from the ITO transparent conductive layer 17 above the SiO2 current blocking layer 18 to the transparent conductive layer 17 surrounding the SiO2 current blocking layer 18, and then travels vertically downwards. Therefore, the SiO2 current blocking layer 18 can increase the lateral current extension length, thereby mitigating the current concentration effect.

[0006] However, since the first electrode 15 is made of metal, it is opaque in the visible light band and strongly absorbs photons emitted by the multi-quantum well layer 13. This results in a loss of the area of ​​the multi-quantum well layer 13 in the light-emitting diode, leading to a decrease in the light extraction efficiency. Furthermore, most photons below the first electrode 15 are absorbed by the first electrode 15, causing an increase in temperature in the vicinity of the first electrode 15, which in turn reduces the reliability of the light-emitting diode. Additionally, the presence of the SiO2 current-blocking layer 18 results in a smaller longitudinal current transmission below the first electrode 15, leading to lower luminous intensity in the active layer region below the first electrode 15. Most of the luminous area is distributed around the periphery of the first electrode 15, resulting in a lower external quantum efficiency. Therefore, although the technique of adding the SiO2 current-blocking layer 18 increases the lateral current extension length, the problems of low light extraction efficiency and low reliability of the light-emitting diode still exist.

[0007] When the first semiconductor layer 12 is P-type and the second semiconductor layer 14 is N-type, the electron mobility of the second semiconductor layer 14 is also low at conventional doping concentrations. Increasing the doping concentration of the second semiconductor layer 14 can increase the lateral current spread length; however, as the doping concentration of the second semiconductor layer 14 increases, the semiconductor crystal quality decreases. Alternatively, increasing the thickness of the second semiconductor layer 14 can also increase the lateral current spread length and improve the uniformity of the current density distribution in the active layer; however, excessive thickness of the second semiconductor layer 14 can lead to thin film cracking. Therefore, all of the above methods for increasing the lateral current spread length have problems, and the improvement effect is very limited.

[0008] Furthermore, since the second semiconductor layer 14 has a flat surface, light will undergo total internal reflection at the surface of the second semiconductor layer 14. Even if an ITO transparent conductive layer 17 is formed on the second semiconductor layer 14, the refractive index of the second semiconductor layer 14 (for example, the refractive indices of the second semiconductor layer 14 when the material of the second semiconductor layer 14 is GaN, GaAs and SiC are 2.4, 3.57 and 2.65 respectively) is greater than the refractive index of the ITO transparent conductive layer 17 (the refractive index is 2.08). This causes total internal reflection to occur at the interface between the second semiconductor layer 14 and the ITO transparent conductive layer 17, which results in the light generated by the active layer not being effectively extracted.

[0009] Therefore, a light-emitting diode and its manufacturing method are provided to improve the light extraction efficiency and reliability of the light-emitting diode while increasing the lateral current extension length. Summary of the Invention

[0010] The purpose of this invention is to provide a light-emitting diode and its manufacturing method, which can improve light extraction efficiency and reliability while increasing the lateral extension length of the current.

[0011] To achieve the above objectives, the present invention provides a light-emitting diode, comprising:

[0012] Substrate;

[0013] The epitaxial layer includes a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer stacked sequentially on the substrate, wherein the doping types of the first semiconductor layer and the second semiconductor layer are opposite.

[0014] A transparent conductive layer is located on a portion of the surface of the epitaxial layer, and the doping type of the transparent conductive layer is opposite to that of the epitaxial layer in contact with it.

[0015] A reflective layer is located on the transparent conductive layer;

[0016] A current spreading layer covers the transparent conductive layer and the reflective layer and extends to the epitaxial layer, wherein the current spreading layer has the same doping type as the contacting epitaxial layer;

[0017] The first electrode is located on the current spreading layer above the reflective layer.

[0018] Optionally, the contact resistance between the transparent conductive layer and the contacting epitaxial layer is greater than the contact resistance between the current spreading layer and the contacting epitaxial layer.

[0019] Optionally, the transparent conductive layer is p-type doped, and the material of the transparent conductive layer is at least one of the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O.

[0020] Optionally, the transparent conductive layer is N-type doped, and the material of the transparent conductive layer is at least one of the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO.

[0021] Optionally, the thickness of the transparent conductive layer is

[0022] Optionally, the doping concentration of the transparent conductive layer is 1E16cm. -3 ~1E20cm -3 .

[0023] Optionally, the doping concentration of the transparent conductive layer is 1E19cm⁻¹. -3 ~1E20cm -3 .

[0024] Optionally, the thickness of the reflective layer is

[0025] Optionally, when the doping type of the epitaxial layer in contact with the current spreading layer is P-type, the work function of the current spreading layer is greater than the work function of the epitaxial layer in contact with the current spreading layer; when the doping type of the epitaxial layer in contact with the current spreading layer is N-type, the work function of the current spreading layer is less than the work function of the epitaxial layer in contact with the current spreading layer.

[0026] Optionally, the sheet resistance of the current spreading layer is less than the sheet resistance of the epitaxial layer in contact with the current spreading layer.

[0027] Optionally, the doping type of the current spreading layer is P-type, and the material of the current spreading layer is at least one selected from the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O.

[0028] Optionally, the doping type of the current spreading layer is N-type, and the material of the current spreading layer is at least one selected from the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO.

[0029] Optionally, the thickness of the current spreading layer is 1 nm to 1000 nm.

[0030] Optionally, the doping concentration of the current spreading layer is 1E11ions / cm². 3 ~1E20ions / cm 3 .

[0031] Optionally, when the first semiconductor layer is N-type doped and the second semiconductor layer is P-type doped, the first semiconductor layer is closer to the substrate than the second semiconductor layer, the transparent conductive layer is located on a portion of the surface of the second semiconductor layer, and the current spreading layer extends onto the second semiconductor layer; or, the second semiconductor layer is closer to the substrate than the first semiconductor layer, the transparent conductive layer is located on a portion of the surface of the first semiconductor layer, the current spreading layer extends onto the first semiconductor layer, and the second semiconductor layer is bonded to the substrate via a bonding layer.

[0032] Optionally, when the second semiconductor layer is closer to the substrate than the first semiconductor layer, a reflective layer is further included between the second semiconductor layer and the bonding layer.

[0033] Optionally, the light-emitting diode further includes:

[0034] The second electrode is located on the bottom surface of the substrate; or, if the first semiconductor layer is closer to the substrate than the second semiconductor layer, the second electrode is located on the first semiconductor layer, and if the second semiconductor layer is closer to the substrate than the first semiconductor layer, the second electrode is located on the second semiconductor layer.

[0035] Optionally, if the first semiconductor layer is closer to the substrate than the second semiconductor layer, the second electrode is spaced apart from the multi-quantum well layer.

[0036] Optionally, the current spreading layer is covered with an insulating layer, and the first electrode penetrates the insulating layer above the reflective layer to connect with the current spreading layer; if the first semiconductor layer is closer to the substrate than the second semiconductor layer, the insulating layer extends from the surface of the current spreading layer in contact with the second semiconductor layer to contact with the first semiconductor layer, and the second electrode penetrates the insulating layer in contact with the first semiconductor layer to connect with the first semiconductor layer; if the second semiconductor layer is closer to the substrate than the first semiconductor layer, the insulating layer extends from the surface of the current spreading layer in contact with the first semiconductor layer to contact with the second semiconductor layer, and the second electrode penetrates the insulating layer in contact with the second semiconductor layer to connect with the second semiconductor layer.

[0037] Optionally, when the multi-quantum-well layer emits light toward the front of the light-emitting diode, the epitaxial layer has a roughened surface, and / or the transparent conductive layer has a roughened surface, and / or the reflective layer has a roughened surface, and / or the current spreading layer has a roughened surface.

[0038] Optionally, the light-emitting diode further includes a protective layer located between the reflective layer and the current spreading layer.

[0039] Optionally, the protective layer is made of at least one of Cr, Pt, Pd, Mo, Al, Ni, W, Cr / Ni, Ti / Ni, TiN, and TiW.

[0040] Optionally, the projection of the protective layer in the direction perpendicular to the substrate is located within the projection of the transparent conductive layer in the direction perpendicular to the substrate or coincides with the projection of the transparent conductive layer in the direction perpendicular to the substrate; the projection of the reflective layer in the direction perpendicular to the substrate is located within the projection of the protective layer in the direction perpendicular to the substrate; the projection of the reflective layer in the direction perpendicular to the substrate coincides with the projection of the first electrode in the direction perpendicular to the substrate, or the projection of the reflective layer in the direction perpendicular to the substrate completely coincides with the projection of the first portion of the first electrode located in the insulating layer in the direction perpendicular to the substrate.

[0041] Optionally, the power of the light-emitting diode is ≥1W, and the operating current of the light-emitting diode is ≥1mA.

[0042] The present invention also provides a method for manufacturing a light-emitting diode, comprising:

[0043] Provide a first substrate;

[0044] An epitaxial layer is formed on the first substrate, the epitaxial layer comprising a first semiconductor layer, a multiple quantum well layer and a second semiconductor layer stacked sequentially from bottom to top on the first substrate, wherein the doping types of the first semiconductor layer and the second semiconductor layer are opposite.

[0045] A transparent conductive layer is formed on a portion of the surface of the epitaxial layer, wherein the doping type of the transparent conductive layer is opposite to that of the epitaxial layer in contact with it;

[0046] A reflective layer is formed on the transparent conductive layer;

[0047] A current spreading layer is formed, which covers the transparent conductive layer and the reflective layer and extends to the epitaxial layer, wherein the current spreading layer has the same doping type as the epitaxial layer in contact with it;

[0048] A first electrode is formed on a current spreading layer above the reflective layer.

[0049] Optionally, the contact resistance between the transparent conductive layer and the contacting epitaxial layer is greater than the contact resistance between the current spreading layer and the contacting epitaxial layer.

[0050] Optionally, the transparent conductive layer is p-type doped, and the material of the transparent conductive layer is at least one of the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O.

[0051] Optionally, the transparent conductive layer is N-type doped, and the material of the transparent conductive layer is at least one of the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO.

[0052] Optionally, the thickness of the transparent conductive layer is

[0053] Optionally, the doping concentration of the transparent conductive layer is 1E16cm. -3 ~1E20cm -3 .

[0054] Optionally, the doping concentration of the transparent conductive layer is 1E19cm⁻¹. -3 ~1E20cm -3 .

[0055] Optionally, the thickness of the reflective layer is

[0056] Optionally, when the doping type of the epitaxial layer in contact with the current spreading layer is P-type, the work function of the current spreading layer is greater than the work function of the epitaxial layer in contact with the current spreading layer; when the doping type of the epitaxial layer in contact with the current spreading layer is N-type, the work function of the current spreading layer is less than the work function of the epitaxial layer in contact with the current spreading layer.

[0057] Optionally, the sheet resistance of the current spreading layer is less than the sheet resistance of the epitaxial layer in contact with the current spreading layer.

[0058] Optionally, the doping type of the current spreading layer is P-type, and the material of the current spreading layer is at least one selected from the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O.

[0059] Optionally, the doping type of the current spreading layer is N-type, and the material of the current spreading layer is at least one selected from the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO.

[0060] Optionally, the thickness of the current spreading layer is 1 nm to 1000 nm.

[0061] Optionally, the doping concentration of the current spreading layer is 1E11ions / cm². 3 ~1E20ions / cm 3 .

[0062] Optionally, when the first semiconductor layer is N-type doped and the second semiconductor layer is P-type doped, the transparent conductive layer is formed on a portion of the surface of the second semiconductor layer, and the current spreading layer extends onto the second semiconductor layer; the method for manufacturing the light-emitting diode further includes:

[0063] A second electrode is formed on the bottom surface of the first substrate or on the first semiconductor layer.

[0064] Optionally, when the first semiconductor layer is N-type doped and the second semiconductor layer is P-type doped, the transparent conductive layer is formed on a portion of the surface of the first semiconductor layer, and the current spreading layer extends onto the first semiconductor layer; before forming the transparent conductive layer on a portion of the surface of the epitaxial layer, the method for manufacturing the light-emitting diode further includes:

[0065] Provide a second substrate;

[0066] The side of the epitaxial layer away from the first substrate is bonded to the second substrate by a bonding layer;

[0067] Remove the first substrate;

[0068] The method for manufacturing the light-emitting diode further includes:

[0069] A second electrode is formed on the bottom surface of the second substrate or on the second semiconductor layer.

[0070] Optionally, before bonding the side of the epitaxial layer away from the first substrate to the second substrate via the bonding layer, the method for manufacturing the light-emitting diode further includes:

[0071] A reflective layer is formed on the second semiconductor layer.

[0072] Optionally, if the second electrode is formed on the first semiconductor layer, the second electrode is spaced apart from the multi-quantum well layer.

[0073] Optionally, the steps of forming the first electrode on the current spreading layer above the reflective layer and forming the second electrode on the first semiconductor layer include:

[0074] A first via is formed that sequentially penetrates the current spreading layer, the second semiconductor layer, and the multiple quantum well layer in contact with the second semiconductor layer;

[0075] An insulating layer is formed over the current spreading layer, and the insulating layer fills the first through-hole;

[0076] The insulating layer is etched to form a second via that exposes a current spreading layer above the reflective layer, and a third via that exposes a portion of the first semiconductor layer at the bottom of the first via.

[0077] A first electrode is formed in the second via and a second electrode is formed in the third via, the first electrode being connected to the current spreading layer and the second electrode being connected to the first semiconductor layer;

[0078] Alternatively, the steps of forming the first electrode on the current spreading layer above the reflective layer and forming the second electrode on the second semiconductor layer include:

[0079] A first via is formed that sequentially penetrates the current spreading layer, the first semiconductor layer, and the multiple quantum well layer in contact with the first semiconductor layer;

[0080] An insulating layer is formed over the current spreading layer, and the insulating layer fills the first through-hole;

[0081] The insulating layer is etched to form a second via that exposes a current spreading layer above the reflective layer, and a third via that exposes a portion of a second semiconductor layer at the bottom of the first via.

[0082] A first electrode is formed in the second via and a second electrode is formed in the third via. The first electrode is connected to the current spreading layer and the second electrode is connected to the second semiconductor layer.

[0083] Optionally, when the multi-quantum-well layer emits light toward the front of the light-emitting diode, the epitaxial layer has a roughened surface, and / or the transparent conductive layer has a roughened surface, and / or the reflective layer has a roughened surface, and / or the current spreading layer has a roughened surface.

[0084] Optionally, after forming the reflective layer on the transparent conductive layer and before forming the current spreading layer, the method of manufacturing the light-emitting diode further includes forming a protective layer between the reflective layer and the current spreading layer.

[0085] Optionally, the protective layer is made of at least one of Cr, Pt, Pd, Mo, Al, Ni, W, Cr / Ni, Ti / Ni, TiN, and TiW.

[0086] Optionally, the projection of the protective layer in the direction perpendicular to the first substrate is located within the projection of the transparent conductive layer in the direction perpendicular to the first substrate or coincides with the projection of the transparent conductive layer in the direction perpendicular to the first substrate; the projection of the reflective layer in the direction perpendicular to the first substrate is located within the projection of the protective layer in the direction perpendicular to the first substrate; the projection of the reflective layer in the direction perpendicular to the first substrate coincides with the projection of the first electrode in the direction perpendicular to the first substrate, or the projection of the reflective layer in the direction perpendicular to the substrate completely coincides with the projection of the first portion of the first electrode located in the insulating layer in the direction perpendicular to the substrate.

[0087] Optionally, the power of the light-emitting diode is ≥1W, and the operating current of the light-emitting diode is ≥1mA.

[0088] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0089] 1. The light-emitting diode of the present invention comprises: an epitaxial layer including a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer sequentially stacked on a substrate, wherein the doping types of the first semiconductor layer and the second semiconductor layer are opposite; a transparent conductive layer located on a portion of the surface of the epitaxial layer, wherein the doping type of the transparent conductive layer is opposite to that of the epitaxial layer in contact with it; a reflective layer located on the transparent conductive layer; a current spreading layer covering the transparent conductive layer and the reflective layer and extending to the epitaxial layer, wherein the doping type of the current spreading layer is the same as that of the epitaxial layer in contact with it; and a first electrode located on the current spreading layer above the reflective layer; thereby increasing the lateral current spreading length while improving the light extraction efficiency and reliability of the light-emitting diode.

[0090] 2. The method for manufacturing a light-emitting diode according to the present invention includes: forming an epitaxial layer on a first substrate, the epitaxial layer comprising a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer stacked sequentially from bottom to top on the first substrate, wherein the doping types of the first semiconductor layer and the second semiconductor layer are opposite; forming a transparent conductive layer on a portion of the surface of the epitaxial layer, wherein the doping type of the transparent conductive layer is opposite to that of the epitaxial layer in contact with it; forming a reflective layer on the transparent conductive layer; forming a current spreading layer, the current spreading layer covering the transparent conductive layer and the reflective layer and extending to the epitaxial layer, wherein the doping type of the current spreading layer is the same as that of the epitaxial layer in contact with it; and forming a first electrode on the current spreading layer above the reflective layer; thereby increasing the lateral current spreading length while improving the light extraction efficiency and reliability of the light-emitting diode. Attached Figure Description

[0091] Figure 1a This is a schematic diagram of the structure of a light-emitting diode;

[0092] Figure 1b This is a schematic diagram of the structure of a light-emitting diode;

[0093] Figure 1c This is a schematic diagram of the structure of a light-emitting diode;

[0094] Figure 2 yes Figure 1c The diagram shows the current spread of the light-emitting diode.

[0095] Figure 3 This is a schematic diagram of the light-emitting diode structure according to Embodiment 1 of the present invention;

[0096] Figure 4 yes Figure 3 The diagram shows the current spread of the light-emitting diode.

[0097] Figure 5 This is a schematic diagram of the structure of the light-emitting diode according to Embodiment 2 of the present invention;

[0098] Figure 6 This is a schematic diagram of the structure of the light-emitting diode according to Embodiment 3 of the present invention;

[0099] Figure 7 This is a schematic diagram of the structure of the light-emitting diode according to Embodiment 4 of the present invention;

[0100] Figure 8 This is a schematic diagram of the structure of the light-emitting diode according to Embodiment 5 of the present invention;

[0101] Figure 9 This is a schematic diagram of the structure of the light-emitting diode according to Embodiment Six of the present invention;

[0102] Figure 10 This is a flowchart of a method for manufacturing a light-emitting diode according to an embodiment of the present invention;

[0103] Figures 11a to 11f yes Figure 10 A schematic diagram of the device used in the manufacturing method of the light-emitting diode shown.

[0104] Among them, the appendix Figures 1a to 11f The annotations in the attached figures are explained as follows:

[0105] 11-Substrate; 12-First semiconductor layer; 13-Multiple quantum well layer; 14-Second semiconductor layer; 15-First electrode; 16-Second electrode; 17-ITO transparent conductive layer; 20-Substrate; 201-Binding layer; 202-Mirror layer; 21-First semiconductor layer; 22-Multiple quantum well layer; 23-Second semiconductor layer; 24-Transparent conductive layer; 25-Reflective layer; 26-Protective layer; 27-Current spreading layer; 28-First electrode; 29-Second electrode; 291-Insulating layer; 200-First substrate. Detailed Implementation

[0106] To make the objectives, advantages, and features of the present invention clearer, the light-emitting diode and its manufacturing method proposed in this invention will be further described in detail below. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0107] An embodiment of the present invention provides a light-emitting diode, comprising: a substrate; an epitaxial layer including a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer sequentially stacked on the substrate, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types; a transparent conductive layer located on a portion of the surface of the epitaxial layer, wherein the transparent conductive layer has opposite doping types to the epitaxial layer it contacts; a reflective layer located on the transparent conductive layer; a current spreading layer covering the transparent conductive layer and the reflective layer and extending to the epitaxial layer, wherein the current spreading layer has the same doping type as the epitaxial layer it contacts; and a first electrode located on the current spreading layer above the reflective layer.

[0108] See below. Figures 3-9 A more detailed description of the light-emitting diode provided in this embodiment is provided below. Figures 3-9 This is also a schematic diagram of a longitudinal cross-section of a light-emitting diode.

[0109] The light-emitting diode is Figures 3-6 In the vertical structure shown, the substrate 20 can be made of at least one semiconductor material such as silicon, germanium, silicon carbide, and gallium arsenide, and its electrical properties can be changed by doping the substrate 20; the light-emitting diode is... Figures 7-9 In the non-vertical structure shown, the substrate 20 can be made of at least one of sapphire, aluminum nitride, gallium nitride, gallium oxide, magnesium aluminate, lithium gallium oxide, and lithium aluminate. Furthermore, the light-emitting diode can be... Figure 7 The upright structure shown, or the light-emitting diode can also be... Figures 8-9 The inverted structure shown.

[0110] The epitaxial layer includes a first semiconductor layer 21, a multiple quantum well layer 22, and a second semiconductor layer 23 sequentially stacked on the substrate 20. The first semiconductor layer 21 and the second semiconductor layer 23 have opposite doping types. The multiple quantum well layer 22 serves as a light-emitting layer. Figures 3-7 In the illustrated embodiment, the multiple quantum well layer 22 emits light toward the front of the light-emitting diode, such as... Figure 3 Light L1 in; Figures 8-9 In the illustrated embodiment, the multiple quantum well layer 22 emits light toward the back side of the light-emitting diode, and the front and back sides of the light-emitting diode are opposite sides.

[0111] Preferably, the first semiconductor layer 21 is N-type doped and the second semiconductor layer 23 is P-type doped. In this case, as... Figures 3-5 as well as Figures 7-8As shown, the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, that is, the first semiconductor layer 21, the multiple quantum well layer 22, and the second semiconductor layer 23 are stacked sequentially on the substrate 20 from bottom to top; or, as shown... Figure 6 and Figure 9 As shown, the second semiconductor layer 23 is closer to the substrate 20 than the first semiconductor layer 21, that is, the first semiconductor layer 21, the multiple quantum well layer 22, and the second semiconductor layer 23 are stacked sequentially on the substrate 20 from top to bottom. It should be noted that, in other embodiments, the doping type of the first semiconductor layer 21 can be P-type, and the doping type of the second semiconductor layer 23 can be N-type.

[0112] Wherein, if the second semiconductor layer 23 is closer to the substrate 20 than the first semiconductor layer 21, such as Figure 9 As shown, the second semiconductor layer 23 is bonded to the substrate 20 via a bonding layer 201; as Figure 6 As shown, the second semiconductor layer 23 is bonded to the substrate 20 through the bonding layer 201, and a reflective mirror layer 202 is also included between the second semiconductor layer 23 and the bonding layer 201 to improve the front light emission efficiency.

[0113] When the multi-quantum-well layer 22 emits light towards the front of the light-emitting diode, it is preferable that the side of the epitaxial layer away from the substrate 20 has a roughened surface. Specifically, if the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, and the side of the epitaxial layer away from the substrate 20 is the second semiconductor layer 23, then it is preferable that the second semiconductor layer 23 has a roughened surface, i.e., its surface is uneven. If the second semiconductor layer 23 is closer to the substrate 20 than the first semiconductor layer 21, and the side of the epitaxial layer away from the substrate 20 is the first semiconductor layer 21, then it is preferable that the first semiconductor layer 21 has a roughened surface, i.e., its surface is uneven. The roughened surfaces are continuously distributed on the surfaces of the second semiconductor layer 23 and the first semiconductor layer 21. It should be noted that in other embodiments, the second semiconductor layer 23 and the first semiconductor layer 21 may have partially roughened surfaces (i.e., partially roughened and partially flat surfaces) or no roughened surfaces (i.e., completely flat surfaces).

[0114] The longitudinal section of the roughened surface can be at least one of the following: arc surface, circular arc surface, sawtooth surface, wavy surface, and irregular surface. For example... Figures 3-7 The longitudinal section of the roughened surface shown is a serrated surface. It should be noted that the longitudinal section of the roughened surface is not limited to the shape described above.

[0115] The first semiconductor layer 21 can be made of at least one of GaN, AlGaN, GaAs, and SiC; the second semiconductor layer 23 can be made of at least one of GaN, AlGaN, BAlN, GaAs, and SiC; and the multi-quantum well layer 22 can be made of at least one of AlN, GaN, AlGaN, InGaN, AlInGaN, GaAs, and SiC. It should be noted that the materials of the first semiconductor layer 21, the second semiconductor layer 23, and the multi-quantum well layer 22 are not limited to the types described above.

[0116] The transparent conductive layer 24 is located on a portion of the surface of the epitaxial layer, and the doping type of the transparent conductive layer 24 is opposite to that of the epitaxial layer it contacts. When the doping type of the epitaxial layer in contact with the transparent conductive layer 24 is P-type, the doping type of the transparent conductive layer 24 is N-type; when the doping type of the epitaxial layer in contact with the transparent conductive layer 24 is N-type, the doping type of the transparent conductive layer 24 is P-type.

[0117] When the multi-quantum well layer 22 emits light toward the front of the light-emitting diode, if the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, then the transparent conductive layer 24 is located on a portion of the surface of the second semiconductor layer 23. In this case, if the second semiconductor layer 23 has a roughened surface, it is preferable that the surface morphology of the second semiconductor layer 23 is transferred to the transparent conductive layer 24, that is, the transparent conductive layer 24 is conformal with the second semiconductor layer 23, so that the transparent conductive layer 24 also has a roughened surface. If the second semiconductor layer 23 is closer to the substrate 20 than the first semiconductor layer 21, then the transparent conductive layer 24 is located on a portion of the surface of the first semiconductor layer 21. In this case, if the first semiconductor layer 21 has a roughened surface, it is preferable that the surface morphology of the first semiconductor layer 21 is transferred to the transparent conductive layer 24, that is, the transparent conductive layer 24 is conformal with the first semiconductor layer 21, so that the transparent conductive layer 24 also has a roughened surface. It should be noted that, in other embodiments, the transparent conductive layer 24 may have a partially roughened surface (i.e., the surface is partially roughened and partially flat) or no roughened surface (i.e., the surface is completely flat).

[0118] When the doping type of the transparent conductive layer 24 is N-type, the material of the transparent conductive layer 24 can be at least one of the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO (IZO is indium zinc oxide). When the doping type of the transparent conductive layer 24 is P-type, the material of the transparent conductive layer 24 can be at least one selected from the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O. It should be noted that the material of the transparent conductive layer 24 is not limited to the types mentioned above.

[0119] The transparent conductive layer 24 is very thin; preferably, the thickness of the transparent conductive layer 24 is [thickness value missing].

[0120] The transparent conductive layer 24 has a very high doping concentration, for example, 1E16cm⁻¹. -3 ~1E20cm -3 Preferably, the doping concentration of the transparent conductive layer 24 is 1E19cm⁻¹. -3 ~1E20cm -3 .

[0121] The reflective layer 25 is located on the transparent conductive layer 24.

[0122] Furthermore, when the multi-quantum-well layer 22 emits light towards the front of the light-emitting diode, if the transparent conductive layer 24 has a roughened surface, it is preferable that the surface morphology of the transparent conductive layer 24 is transferred to the reflective layer 25, that is, the reflective layer 25 is conformal to the transparent conductive layer 24, so that the reflective layer 25 also has a roughened surface. It should be noted that, in other embodiments, the reflective layer 25 may have a partially roughened surface (i.e., the surface is partially roughened and partially flat) or no roughened surface (i.e., the surface is completely flat).

[0123] Preferably, the reflective layer 25 is made of a high-reflectivity material with a reflectivity greater than 95%, such as at least one of silver (Ag), copper (Cu), aluminum (Al), rhodium (Rh), and gold (Au). In other embodiments, the reflectivity of the reflective layer 25 may be less than or equal to 95%.

[0124] The thickness of the reflective layer 25 can be

[0125] Furthermore, since the adhesion between the metal material of the reflective layer 25 and the epitaxial layer is poor, the adhesion strength between the reflective layer 25 and the epitaxial layer is improved by forming the transparent conductive layer 24 between the reflective layer 25 and the epitaxial layer.

[0126] The current spreading layer 27 covers the transparent conductive layer 24 and the reflective layer 25 and extends onto the epitaxial layer. The current spreading layer 27 has the same doping type as the contacting epitaxial layer. The current spreading layer 27 extending onto the epitaxial layer may cover part or all of the epitaxial layer. The larger the area covered by the current spreading layer 27 on the surface of the epitaxial layer, the longer the lateral current spread.

[0127] When the doping type of the epitaxial layer in contact with the current spreading layer 27 is P-type, the doping type of the current spreading layer 27 is P-type; when the doping type of the epitaxial layer in contact with the current spreading layer 27 is N-type, the doping type of the current spreading layer 27 is N-type.

[0128] The thickness of the current spreading layer 27 can be from 1 nm to 1000 nm, and the doping concentration of the current spreading layer 27 can be 1 E11 ions / cm. 3 ~1E20ions / cm 3 .

[0129] When the multiple quantum well layer 22 emits light toward the front of the light-emitting diode, if the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, the current spreading layer 27 extends onto the second semiconductor layer 23. In this case, if the second semiconductor layer 23 has a roughened surface, it is preferable that the surface morphology of the second semiconductor layer 23 is transferred to the portion of the current spreading layer 27 located on the second semiconductor layer 23, that is, the portion of the current spreading layer 27 located on the second semiconductor layer 23 is conformal to the second semiconductor layer 23, such that the current spreading layer 27 is located on the second semiconductor layer 23. The portion of layer 3 also has a roughened surface; if the second semiconductor layer 23 is closer to the substrate 20 than the first semiconductor layer 21, then the current spreading layer 27 extends onto the first semiconductor layer 21. In this case, if the first semiconductor layer 21 has a roughened surface, it is preferable that the surface morphology of the first semiconductor layer 21 is transferred to the portion of the current spreading layer 27 located on the first semiconductor layer 21, that is, the portion of the current spreading layer 27 located on the first semiconductor layer 21 is conformal to the first semiconductor layer 21, so that the portion of the current spreading layer 27 located on the first semiconductor layer 21 also has a roughened surface. It should be noted that, in other embodiments, the portion of the current spreading layer 27 located on the second semiconductor layer 23 and the first semiconductor layer 21 may have a partially roughened surface (i.e., the surface is partially roughened and partially flat) or no roughened surface (i.e., the surface is completely flat).

[0130] Because a heterojunction is formed between the transparent conductive layer 24, which has opposite doping types, and the contacting epitaxial layer (e.g., ... Figure 4 The diode is formed between the transparent conductive layer 24 and the second semiconductor layer 23, and the current spreading layer 27 has the same doping type as the contact epitaxial layer, such that the contact resistance between the transparent conductive layer 24 and the contact epitaxial layer is greater than the contact resistance between the current spreading layer 27 and the contact epitaxial layer. A Schottky barrier exists between the transparent conductive layer 24 and the contact epitaxial layer, and the current spreading layer 27 forms an ohmic contact with the contact epitaxial layer.

[0131] exist Figure 1c and Figure 2 In the illustrated light-emitting diode, taking the ITO transparent conductive layer 17 as an N-type semiconductor material and the second semiconductor layer 14 as a P-type as an example, the ITO transparent conductive layer 17 acts as a resistor R in the circuit. A heterojunction with a depletion layer is formed between the N-type ITO transparent conductive layer 17 and the P-type second semiconductor layer 14 surrounding the SiO2 current blocking layer 18. Figure 2The Schottky barrier formed by the diode in the circuit increases the contact resistance, leading to a larger voltage drop under high current drive, which in turn results in a higher drive voltage and a poorer uniformity of the injected current spread. However, in embodiments of the present invention, although a heterojunction is also formed between the transparent conductive layer 24 and the contacting epitaxial layer (such as...), the... Figure 4 The diode formed between the transparent conductive layer 24 and the second semiconductor layer 23 is used. However, when the doping type of the epitaxial layer in contact with the current spreading layer 27 is P-type, the work function of the current spreading layer 27 is adjusted to be greater than the work function of the epitaxial layer in contact with the current spreading layer 27. Alternatively, when the doping type of the epitaxial layer in contact with the current spreading layer 27 is N-type, the work function of the current spreading layer 27 is adjusted to be less than the work function of the epitaxial layer in contact with the current spreading layer 27. This allows the current spreading layer 27 to form a good ohmic contact with the epitaxial layer in contact with it. Furthermore, by adjusting the sheet resistance of the current spreading layer 27 to be less than the sheet resistance of the epitaxial layer in contact with the current spreading layer 27, the lateral extension length of the current is increased, thereby making the current spread layer 27 and the epitaxial layer in contact with it more ohmic. Figure 1c and Figure 2 Compared to the previously shown LEDs, this invention significantly reduces the driving voltage of high-power LEDs and improves the lateral current spread distance and uniformity under high-current driving, thereby enhancing the luminous efficacy and reliability of high-power LEDs. In embodiments of this invention, since the Fermi level of a semiconductor changes with doping concentration, the work function can be adjusted by changing the doping concentration, and the sheet resistance can be adjusted by changing the annealing process.

[0132] When the doping type of the current spreading layer 27 is P-type, the material of the current spreading layer 27 can be at least one of the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O. When the doping type of the current spreading layer 27 is N-type, the material of the current spreading layer 27 is at least one selected from the following: Sn-doped In₂O₃, Al-doped In₂O₃, F-doped SnO₂, Sb-doped SnO₂, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO₂, and Ga-doped IZO. It should be noted that the material of the current spreading layer 27 is not limited to the types mentioned above.

[0133] The light-emitting diode also includes a protective layer 26, which is located between the reflective layer 25 and the current spreading layer 27, and the current spreading layer 27 also covers the protective layer 26.

[0134] Furthermore, when the multiple quantum well layer 22 emits light towards the front of the light-emitting diode, preferably, as follows: Figures 3-4 , Figures 6-7 As shown, the protective layer 26 is thick enough to completely block the upward migration of metal in the reflective layer 25. In this case, the protective layer 26 does not have a roughened surface, and therefore, the portion of the current spreading layer 27 located on the protective layer 26 also does not have a roughened surface. Alternatively, in Figure 5 In the embodiment shown, the thickness of the protective layer 26 can also be relatively thin. In this case, if the reflective layer 25 has a roughened surface, the surface morphology of the reflective layer 25 is transferred to the protective layer 26, that is, the protective layer 26 is conformal with the reflective layer 25, so that the protective layer 26 also has a roughened surface. Then, the portion of the current spreading layer 27 located on the protective layer 26 also has a roughened surface.

[0135] The protective layer 26 can be made of at least one of the following: Cr, Platinum (Pt), Palladium (Pd), Mo, Aluminum (Al), Nickel (Ni), Tungsten (W), Cr / Ni, Ti / Ni, TiN, and TiW. It should be noted that the material of the protective layer 26 is not limited to the types mentioned above.

[0136] Furthermore, when the multiple quantum well layer 22 emits light toward the back of the light-emitting diode, preferably, as follows: Figures 8-9 As shown, the side of the epitaxial layer away from the substrate 20, the transparent conductive layer 24, the reflective layer 25, the protective layer 26, and the current spreading layer 27 all have flat surfaces.

[0137] The first electrode 28 is located on the current spreading layer 27 above the reflective layer 25. Wherein, as... Figures 3-5 as well as Figures 7-9 As shown, the number of the first electrode 28 can be one; or, the number of the first electrode 28 can be at least two, such as... Figure 6 As shown, there are two first electrodes 28. Increasing the number of first electrodes 28 per unit area of ​​the light-emitting diode can improve light extraction efficiency.

[0138] And, as Figure 6 As shown, when there are at least two first electrodes 28, the protective layer 26, the reflective layer 25 and the transparent conductive layer 24 under different first electrodes 28 are all disconnected, the current spreading layer 27 under different first electrodes 28 are connected to each other, and different first electrodes 28 can be connected in series through a conductive structure (not shown).

[0139] The light-emitting diode also includes a second electrode 29.

[0140] like Figures 3-6 As shown, the second electrode 29 can be located on the bottom surface of the substrate 20 (i.e., the back surface of the light-emitting diode). In this case, the first electrode 28 and the second electrode 29 are located on different sides of the light-emitting diode. Figures 3-5 As shown, the multiple quantum well layer 22 and the second semiconductor layer 23 are located on the entire surface of the first semiconductor layer 21; as Figure 6 As shown, the multi-quantum well layer 22 and the first semiconductor layer 21 are located on the entire surface of the second semiconductor layer 23.

[0141] Or, such as Figures 7-9 As shown, the first electrode 28 and the second electrode 29 are located on the same side of the light-emitting diode. Specifically, when the light-emitting diode is in a front-mounted structure, if the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, the multiple quantum well layer 22 and the second semiconductor layer 23 are only located on a portion of the surface of the first semiconductor layer 21, and the second electrode 29 is located on the surface of the first semiconductor layer 21 where the multiple quantum well layer 22 is not formed. Figure 7As shown; at this time, the second electrode 29 is spaced apart from the multi-quantum well layer 22, and the side of the second electrode 29 away from the substrate 20 can be lower than the side of the first electrode 28 away from the substrate 20 or flush with the side of the first electrode 28 away from the substrate 20.

[0142] When the light-emitting diode is a flip-chip structure, such as Figures 8-9 As shown, an insulating layer 291 covers the current spreading layer 27, and the first electrode 28 penetrates the insulating layer 291 above the reflective layer 25, so that the first electrode 28 is connected to the current spreading layer 27; and, as Figure 8 As shown, if the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, the insulating layer 291 extends from the surface of the current spreading layer 27 in contact with the second semiconductor layer 23, sequentially through the second semiconductor layer 23 and the multiple quantum well layer 22, to contact the first semiconductor layer 21. The second electrode 29 penetrates the insulating layer 291 in contact with the first semiconductor layer 21, so that the second electrode 29 is connected to the first semiconductor layer 21. The second electrode 29 is insulated from the current spreading layer 27, the second semiconductor layer 23, and the multiple quantum well layer 22. Figure 9 As shown, if the second semiconductor layer 23 is closer to the substrate 20 than the first semiconductor layer 21, the insulating layer 291 extends from the surface of the current spreading layer 27 in contact with the first semiconductor layer 21, sequentially through the first semiconductor layer 21 and the multiple quantum well layer 22, to contact the second semiconductor layer 23. The second electrode 29 penetrates the insulating layer 291 in contact with the second semiconductor layer 23, so that the second electrode 29 is connected to the second semiconductor layer 23. The second electrode 29 is insulated from the current spreading layer 27, the first semiconductor layer 21, and the multiple quantum well layer 22. At this time, both the first electrode 28 and the second electrode 29 extend onto the insulating layer 291. That is, both the first electrode 28 and the second electrode 29 include a first portion located in the insulating layer 291 and a second portion extending onto the insulating layer 291. The side of the first electrode 28 away from the substrate 20 is flush with the side of the second electrode 29 away from the substrate 20. It should be noted that the first portion of the first electrode 28 and the second electrode 29 located in the insulating layer 291 can each be composed of at least one conductive plug.

[0143] When the multiple quantum well layer 22 emits light towards the front of the light-emitting diode, taking the first semiconductor layer 21 being closer to the substrate 20 than the second semiconductor layer 23 as an example, compared to... Figures 1a to 1c and Figure 2Compared to the structure of the light-emitting diode shown (where the second semiconductor layer 14 has a flat surface), if the second semiconductor layer 23 of the present invention has a roughened surface, it is possible to prevent total internal reflection at certain angles when light emitted from the multiple quantum well layer 22 reaches the surface of the second semiconductor layer 23. That is, the amount of light that undergoes total internal reflection at the surface of the second semiconductor layer 23 is reduced, thereby improving the light extraction efficiency from the front of the light-emitting diode. Furthermore, the light emitted from the multiple quantum well layer 22 is scattered at the surface of the second semiconductor layer 23, allowing some of the light emitted from the multiple quantum well layer 22 below the first electrode 28 to be emitted from the side and / or front of the light-emitting diode. This reduces the amount of light absorbed by the first electrode 28, further improving the light extraction efficiency of the light-emitting diode and lowering the temperature in the region near the first electrode 28.

[0144] Furthermore, when the light scattered from the surface of the second semiconductor layer 23 reaches the reflective layer 25 after passing through the transparent conductive layer 24, if both the transparent conductive layer 24 and the reflective layer 25 have roughened surfaces, the scattered light at different angles will be reflected by the reflective layer 25 and emitted from the side of the light-emitting diode (e.g., Figure 3 The light source absorbs light (L2) from the first electrode 28, thereby reducing the amount of light absorbed by the first electrode 28 and further improving the light extraction efficiency of the light-emitting diode. In addition, it can effectively reduce the temperature in the area near the first electrode 28 and improve the reliability of the light-emitting diode.

[0145] In addition, such as Figures 3-9 As shown, preferably, the projection of the protective layer 26 in the direction perpendicular to the substrate 20 lies within the projection of the transparent conductive layer 24 in the direction perpendicular to the substrate 20 or completely coincides with the projection of the transparent conductive layer 24 in the direction perpendicular to the substrate 20, so as to increase the lateral current spread length; and, as Figures 3-9 As shown, preferably, the projection of the reflective layer 25 in the direction perpendicular to the substrate 20 lies within the projection of the protective layer 26 in the direction perpendicular to the substrate 20, so that the protective layer 26 can block the upward migration of metal in the reflective layer 25 and the transparent conductive layer 24 can block the downward migration of metal in the reflective layer 25, thereby avoiding reliability problems such as leakage; and, as Figures 3-7As shown, preferably, the projection of the reflective layer 25 in the direction perpendicular to the substrate 20 completely coincides with the projection of the first electrode 28 in the direction perpendicular to the substrate 20, so that all light emitted by the multi-quantum well layer 22 towards the region where the first electrode 28 is located can be reflected by the reflective layer 25. This greatly reduces the amount of light absorbed by the first electrode 28 while also preventing the reflective layer 25 from being too large and affecting the front light emission efficiency of the light-emitting diode. Furthermore, as... Figures 8-9 As shown, preferably, the projection of the reflective layer 25 in the direction perpendicular to the substrate 20 completely coincides with the projection of the first portion of the first electrode 28 located in the insulating layer 291 in the direction perpendicular to the substrate 20, so that the projection of the first portion of the first electrode 28 located in the insulating layer 291 in the direction perpendicular to the substrate 20 is located within the projection of the transparent conductive layer 24 in the direction perpendicular to the substrate 20, thereby reducing the accumulation of current below the first portion of the first electrode 28 and alleviating the current accumulation effect.

[0146] Furthermore, because the contact resistance between the transparent conductive layer 24 and the contacting epitaxial layer is greater than the contact resistance between the current spreading layer 27 and the contacting epitaxial layer, the transparent conductive layer 24 acts as a current blocking layer, preventing large current flows longitudinally below the first electrode 28 and forcing most of the current to spread laterally within the current spreading layer 27. Figure 4 As indicated by the arrow, most of the current extends laterally from the current extension layer 27 above the transparent conductive layer 24 to the current extension layer 27 surrounding the transparent conductive layer 24, and then is transmitted vertically downwards. Only a small portion of the current is transmitted directly vertically downwards from the transparent conductive layer 24.

[0147] Furthermore, because the transparent conductive layer 24 is very thin and has a high doping concentration, the PN junction barrier layer formed by the transparent conductive layer 24 and the contacting epitaxial layer is very thin. When a small voltage is applied to the first electrode 28, the electric field strength inside the barrier layer can reach a very high value. This strong electric field strength can directly pull the valence electrons of the neutral atoms in the barrier layer out of the covalent bonds and become free electrons, while generating holes. This process is called field excitation. Field excitation generates a large number of charge carriers, causing the reverse current of the PN junction to increase dramatically. From a band structure perspective, taking the example where the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, and the first semiconductor layer 21 is N-type doped while the second semiconductor layer 23 is P-type doped, the reverse bias causes the bottom of the conduction band of the N-type transparent conductive layer 24 to be lower than the top of the valence band of the P-type second semiconductor layer 23. In this case, quantum effects allow electrons in the valence band of the P-type second semiconductor layer 23 to tunnel directly into the conduction band of the N-type transparent conductive layer 24, forming a current. Under the influence of an electric field, charge carriers can more easily pass through the thin and highly doped transparent conductive layer 24. Therefore, a small current flow can be transmitted from below the first electrode 28, resulting in a uniform distribution of the injected current in the multi-quantum-well layer 22 of the light-emitting diode, improving luminous efficiency and reliability.

[0148] This invention applies to high-power light-emitting diodes, such as those with a power ≥ 1W and an operating current ≥ 1mA.

[0149] As described above, the light-emitting diode of the present invention comprises: a substrate; an epitaxial layer comprising a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer sequentially stacked on the substrate, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types; a transparent conductive layer located on a portion of the surface of the epitaxial layer, wherein the transparent conductive layer has opposite doping types to the epitaxial layer it contacts; a reflective layer located on the transparent conductive layer; a current spreading layer covering the transparent conductive layer and the reflective layer and extending onto the epitaxial layer, wherein the current spreading layer has the same doping type as the epitaxial layer it contacts; and a first electrode located on the current spreading layer above the reflective layer. The light-emitting diode of the present invention increases the lateral current spreading length while also improving the light extraction efficiency and reliability of the light-emitting diode.

[0150] One embodiment of the present invention provides a method for manufacturing a light-emitting diode, see below. Figure 10 , Figure 10 This is a flowchart of a method for manufacturing a light-emitting diode according to an embodiment of the present invention. The method for manufacturing a light-emitting diode includes:

[0151] Step S1, providing a first substrate;

[0152] Step S2, forming an epitaxial layer on the first substrate, the epitaxial layer comprising a first semiconductor layer, a multiple quantum well layer and a second semiconductor layer stacked sequentially from bottom to top on the first substrate, the doping types of the first semiconductor layer and the second semiconductor layer being opposite;

[0153] Step S3: A transparent conductive layer is formed on a portion of the surface of the epitaxial layer, wherein the doping type of the transparent conductive layer is opposite to that of the epitaxial layer in contact with it.

[0154] Step S4: Form a reflective layer on the transparent conductive layer;

[0155] Step S5: Form a current spreading layer, which covers the transparent conductive layer and the reflective layer and extends to the epitaxial layer. The current spreading layer has the same doping type as the epitaxial layer in contact with it.

[0156] Step S6: Form a first electrode on the current spreading layer above the reflective layer.

[0157] See below. Figures 3-9 as well as Figures 11a to 11f This embodiment provides a more detailed description of the manufacturing method of the light-emitting diode. Figures 3-9 as well as Figures 11a to 11f This is also a schematic diagram of a longitudinal cross-section of a light-emitting diode, and... Figures 11a to 11f The image shown is for manufacturing. Figures 3-4 The steps for creating a light-emitting diode are shown.

[0158] Follow step S1, refer to Figure 11a Provide a first substrate 200.

[0159] If the manufactured is Figures 3-5 as well as Figures 7-8 When the light-emitting diode is shown, the first substrate 200 is... Figures 3-5 as well as Figures 7-8 Substrate 20 in; if manufactured as Figure 6 and Figure 9 The light-emitting diode shown can be subsequently replaced by a second substrate (not shown), which is the second substrate. Figure 6 and Figure 9 Substrate 20 in the middle.

[0160] If manufacturing Figures 3-6 When manufacturing the light-emitting diode shown, the first substrate 200 and the second substrate can be made of at least one of semiconductor materials such as silicon, germanium, silicon carbide, and gallium arsenide, and their electrical properties can be changed by doping the first substrate 200 and the second substrate; if manufacturing Figures 7-9When the light-emitting diode shown is used, the materials of the first substrate 200 and the second substrate can be at least one of sapphire, aluminum nitride, gallium nitride, gallium oxide, magnesium aluminate, lithium gallium oxide, and lithium aluminate.

[0161] The light-emitting diode can be Figure 7 The upright structure shown, or the light-emitting diode can also be... Figures 8-9 The inverted structure shown.

[0162] Follow step S2, see Figure 11a An epitaxial layer is formed on the first substrate 200. The epitaxial layer includes a first semiconductor layer 21, a multiple quantum well layer 22, and a second semiconductor layer 23 stacked sequentially from bottom to top on the first substrate 200. The doping types of the first semiconductor layer 21 and the second semiconductor layer 23 are opposite. The multiple quantum well layer 22 serves as a light-emitting layer. Figures 3-7 In the illustrated embodiment, the multiple quantum well layer 22 emits light toward the front of the light-emitting diode, such as... Figure 3 Light L1 in; Figures 8-9 In the illustrated embodiment, the multiple quantum well layer 22 emits light toward the back side of the light-emitting diode, and the front and back sides of the light-emitting diode are opposite sides.

[0163] Preferably, the first semiconductor layer 21 is N-type doped and the second semiconductor layer 23 is P-type doped. It should be noted that in other embodiments, the first semiconductor layer 21 may be P-type doped and the second semiconductor layer 23 may be N-type doped.

[0164] Where the first semiconductor layer 21 is N-type doped and the second semiconductor layer 23 is P-type doped, the side of the epitaxial layer away from the first substrate 200 is the second semiconductor layer 23. If the multiple quantum well layer 22 emits light towards the front of the light-emitting diode, preferably, a roughened surface can be formed on the surface of the second semiconductor layer 23 by using processes such as chemical etching, plasma etching, or epitaxial growth, i.e., the surface of the second semiconductor layer 23 is uneven. The roughened surface is continuously distributed on the surface of the second semiconductor layer 23. It should be noted that in other embodiments, the surface of the second semiconductor layer 23 may have a partially roughened surface (i.e., partially roughened and partially flat) or no roughened surface (i.e., the entire surface is flat).

[0165] Alternatively, before the transparent conductive layer 24 is subsequently formed on a portion of the surface of the epitaxial layer, the method for manufacturing the light-emitting diode further includes: first, providing a second substrate; then, bonding the side of the epitaxial layer away from the first substrate 200 to the second substrate via a bonding layer 201; then, removing the first substrate, at which point the first substrate 200 is replaced by the second substrate, and the second semiconductor layer 23 is closer to the second substrate than the first semiconductor layer 21, that is, the second semiconductor layer 23, the multiple quantum well layer 22, and the first semiconductor layer 21 are stacked sequentially from bottom to top on the second substrate, and the side of the epitaxial layer away from the second substrate is the first semiconductor layer 21, such as... Figure 6 and Figure 9 As shown. Preferably, if the multiple quantum well layer 22 emits light towards the front of the light-emitting diode, the manufacturing method of the light-emitting diode further includes: treating the surface of the first semiconductor layer 21 using processes such as chemical etching, plasma etching, or epitaxial growth to give the first semiconductor layer 21 a roughened surface (e.g., ...). Figure 6 As shown in the diagram, the surface of the first semiconductor layer 21 is uneven, and the roughened surface is continuously distributed on the surface of the first semiconductor layer 21. It should be noted that in other embodiments, the first semiconductor layer 21 may have a partially roughened surface (i.e., the surface is partially roughened and partially flat) or may not have a roughened surface (i.e., the surface is completely flat).

[0166] Furthermore, before bonding the side of the epitaxial layer away from the first substrate 200 to the second substrate via the bonding layer 201, the method for manufacturing the light-emitting diode may further include: forming a reflective layer 202 on the second semiconductor layer 23, such as... Figure 6 As shown, this is to improve the light output efficiency from the front.

[0167] The longitudinal section of the roughened surface can be at least one of the following: arc surface, circular arc surface, sawtooth surface, wavy surface, and irregular surface. For example... Figure 11a as well as Figures 3-7 The longitudinal section of the roughened surface shown is a serrated surface. It should be noted that the longitudinal section of the roughened surface is not limited to the shape described above.

[0168] Furthermore, when the manufactured light-emitting diode is a front-mounted structure, if the first semiconductor layer 21 is closer to the first substrate 200 than the second semiconductor layer 23, the manufacturing method of the light-emitting diode further includes: sequentially etching away a portion of the second semiconductor layer 23 and a portion of the multiple quantum well layer 22 to expose a portion of the first semiconductor layer 21, such as... Figure 7 As shown, the multi-quantum well layer 22 and the second semiconductor layer 23 are formed only on a portion of the surface of the first semiconductor layer 21.

[0169] The first semiconductor layer 21 can be made of at least one of GaN, AlGaN, GaAs, and SiC; the second semiconductor layer 23 can be made of at least one of GaN, AlGaN, BAlN, GaAs, and SiC; and the multi-quantum well layer 22 can be made of at least one of AlN, GaN, AlGaN, InGaN, AlInGaN, GaAs, and SiC. It should be noted that the materials of the first semiconductor layer 21, the second semiconductor layer 23, and the multi-quantum well layer 22 are not limited to the types described above.

[0170] Follow step S3, see [link / reference] Figure 11b A transparent conductive layer 24 is formed on a portion of the surface of the epitaxial layer 23. The doping type of the transparent conductive layer 24 is opposite to that of the epitaxial layer it contacts. When the doping type of the epitaxial layer in contact with the transparent conductive layer 24 is P-type, the doping type of the transparent conductive layer 24 is N-type; when the doping type of the epitaxial layer in contact with the transparent conductive layer 24 is N-type, the doping type of the transparent conductive layer 24 is P-type.

[0171] The transparent conductive layer 24 can be formed on the surface of the epitaxial layer by methods such as atomic layer deposition, magnetron sputtering or evaporation, and then the transparent conductive layer 24 can be formed by photolithography and etching processes.

[0172] When the multi-quantum-well layer 22 emits light toward the front of the light-emitting diode, if the first semiconductor layer 21 is closer to the first substrate 200 than the second semiconductor layer 23, the transparent conductive layer 24 is formed on a portion of the surface of the second semiconductor layer 23. In this case, if the second semiconductor layer 23 has a roughened surface, it is preferable that the surface morphology of the second semiconductor layer 23 is transferred to the transparent conductive layer 24 when the transparent conductive layer 24 is formed, that is, the transparent conductive layer 24 is conformal with the second semiconductor layer 23, thereby making the transparent conductive layer 24 also have a roughened surface. If the second semiconductor layer 23 is closer to the second substrate than the first semiconductor layer 21, the transparent conductive layer 24 is formed on a portion of the surface of the first semiconductor layer 21. In this case, if the first semiconductor layer 21 has a roughened surface, it is preferable that the surface morphology of the first semiconductor layer 21 is transferred to the transparent conductive layer 24, that is, the transparent conductive layer 24 is conformal with the first semiconductor layer 21, thereby making the transparent conductive layer 24 also have a roughened surface. It should be noted that, in other embodiments, the transparent conductive layer 24 may have a partially roughened surface (i.e., the surface is partially roughened and partially flat) or no roughened surface (i.e., the surface is completely flat).

[0173] When the doping type of the transparent conductive layer 24 is N-type, the material of the transparent conductive layer 24 can be at least one of the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO. When the doping type of the transparent conductive layer 24 is P-type, the material of the transparent conductive layer 24 can be at least one selected from the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O. It should be noted that the material of the transparent conductive layer 24 is not limited to the types mentioned above.

[0174] The transparent conductive layer 24 is very thin; preferably, the thickness of the transparent conductive layer 24 is [thickness value missing].

[0175] The transparent conductive layer 24 has a very high doping concentration, for example, 1E16cm⁻¹. -3 ~1E20cm -3 Preferably, the doping concentration of the transparent conductive layer 24 is 1E19cm⁻¹. -3 ~1E20cm -3 .

[0176] Follow step S4, see Figure 11c A reflective layer 25 is formed on the transparent conductive layer 24.

[0177] The material of the reflective layer 25 can be formed on the transparent conductive layer 24 and the epitaxial layer by methods such as atomic layer deposition, magnetron sputtering or evaporation, and then the reflective layer 25 is formed by photolithography and etching processes.

[0178] When the multi-quantum-well layer 22 emits light toward the front of the light-emitting diode, if the transparent conductive layer 24 has a roughened surface, it is preferable that the surface morphology of the transparent conductive layer 24 is transferred to the reflective layer 25 during the formation of the reflective layer 25, that is, the reflective layer 25 is conformal to the transparent conductive layer 24, thereby making the reflective layer 25 also have a roughened surface. It should be noted that in other embodiments, the reflective layer 25 may have a partially roughened surface (i.e., the surface is partially roughened and partially flat) or no roughened surface (i.e., the surface is completely flat).

[0179] Preferably, the reflective layer 25 is made of a high-reflectivity material with a reflectivity greater than 95%, such as at least one of silver (Ag), copper (Cu), aluminum (Al), rhodium (Rh), and gold (Au). In other embodiments, the reflectivity of the reflective layer 25 may be less than or equal to 95%.

[0180] The thickness of the reflective layer 25 can be

[0181] Furthermore, since the adhesion between the metal material of the reflective layer 25 and the epitaxial layer is poor, the adhesion strength between the reflective layer 25 and the epitaxial layer is improved by forming the transparent conductive layer 24 between the reflective layer 25 and the epitaxial layer.

[0182] See Figure 11d After the reflective layer 25 is formed on the transparent conductive layer 24 and before the current spreading layer 27 is subsequently formed, the method of manufacturing the light-emitting diode further includes forming a protective layer 26 between the reflective layer 25 and the current spreading layer 27.

[0183] The protective layer 26 can be formed on the reflective layer 25 and the epitaxial layer by methods such as atomic layer deposition, magnetron sputtering or evaporation, and then the protective layer 26 can be formed by photolithography and etching processes.

[0184] Furthermore, when the multiple quantum well layer 22 emits light towards the front of the light-emitting diode, preferably, as follows: Figures 3-4 , Figures 6-7 Figure and Figure 11d As shown, the protective layer 26 is thick enough to completely block the upward migration of metal in the reflective layer 25; in this case, the protective layer 26 does not have a roughened surface; or, in Figure 5 In the embodiment shown, the thickness of the protective layer 26 can also be relatively thin. In this case, if the reflective layer 25 has a roughened surface, the surface morphology of the reflective layer 25 is transferred to the protective layer 26, that is, the protective layer 26 is conformal with the reflective layer 25, so that the protective layer 26 also has a roughened surface.

[0185] The protective layer 26 can be made of at least one of the following: Cr, Platinum (Pt), Palladium (Pd), Mo, Aluminum (Al), Nickel (Ni), Tungsten (W), Cr / Ni, Ti / Ni, TiN, and TiW. It should be noted that the material of the protective layer 26 is not limited to the types mentioned above.

[0186] Follow step S5, see [link / reference] Figure 11e A current spreading layer 27 is formed, which covers the transparent conductive layer 24 and the reflective layer 25 and extends onto the epitaxial layer. The doping type of the current spreading layer 27 is the same as that of the epitaxial layer it contacts. When the doping type of the epitaxial layer contacting the current spreading layer 27 is P-type, the doping type of the current spreading layer 27 is P-type; when the doping type of the epitaxial layer contacting the current spreading layer 27 is N-type, the doping type of the current spreading layer 27 is N-type.

[0187] The current spreading layer 27 extending onto the epitaxial layer can cover part or all of the epitaxial layer. The larger the area covered by the current spreading layer 27 on the surface of the epitaxial layer, the longer the length of the lateral current spread.

[0188] The thickness of the current spreading layer 27 can be from 1 nm to 1000 nm, and the doping concentration of the current spreading layer 27 can be 1 E11 ions / cm. 3 ~1E20ions / cm 3 .

[0189] The current spreading layer 27 can be formed by methods such as atomic layer deposition, magnetron sputtering, or evaporation.

[0190] When the multiple quantum well layer 22 emits light toward the front of the light-emitting diode, if the first semiconductor layer 21 is closer to the first substrate 200 than the second semiconductor layer 23, the current spreading layer 27 extends onto the second semiconductor layer 23. In this case, if the second semiconductor layer 23 has a roughened surface, it is preferable that the surface morphology of the second semiconductor layer 23 is transferred to the portion of the current spreading layer 27 located on the second semiconductor layer 23. That is, the portion of the current spreading layer 27 located on the second semiconductor layer 23 is conformal to the second semiconductor layer 23, such that the current spreading layer 27 is located on the second semiconductor layer 23. A portion of layer 23 also has a roughened surface. If the second semiconductor layer 23 is closer to the second substrate than the first semiconductor layer 21, the current spreading layer 27 extends onto the first semiconductor layer 21. In this case, if the first semiconductor layer 21 has a roughened surface, it is preferable that the surface morphology of the first semiconductor layer 21 is transferred to the portion of the current spreading layer 27 located on the first semiconductor layer 21, that is, the portion of the current spreading layer 27 located on the first semiconductor layer 21 is conformal to the first semiconductor layer 21, so that the portion of the current spreading layer 27 located on the first semiconductor layer 21 also has a roughened surface. It should be noted that, in other embodiments, the portion of the current spreading layer 27 located on the second semiconductor layer 23 and the first semiconductor layer 21 may have a partially roughened surface (i.e., the surface is partially roughened and partially flat) or no roughened surface (i.e., the surface is completely flat).

[0191] Furthermore, the current spreading layer 27 also covers the protective layer 26. When the multiple quantum well layer 22 emits light towards the front of the light-emitting diode, if the protective layer 26 does not have a roughened surface, then... Figures 3-4 , Figures 6-7 Figure and Figure 11e As shown, the portion of the current spreading layer 27 located on the protective layer 26 also does not have a roughened surface; if the protective layer 26 had a roughened surface, then, as Figure 5 As shown, the portion of the current spreading layer 27 located on the protective layer 26 also has a roughened surface.

[0192] Furthermore, when the multiple quantum well layer 22 emits light toward the back of the light-emitting diode, preferably, as follows: Figures 8-9 As shown, the surface of the epitaxial layer (i.e., the side of the epitaxial layer away from the first substrate 200 or the side of the epitaxial layer away from the second substrate), the transparent conductive layer 24, the reflective layer 25, the protective layer 26, and the current spreading layer 27 all have flat surfaces.

[0193] Because a heterojunction is formed between the transparent conductive layer 24, which has opposite doping types, and the contacting epitaxial layer (e.g., ... Figure 4 The diode is formed between the transparent conductive layer 24 and the second semiconductor layer 23, and the current spreading layer 27 has the same doping type as the contact epitaxial layer, such that the contact resistance between the transparent conductive layer 24 and the contact epitaxial layer is greater than the contact resistance between the current spreading layer 27 and the contact epitaxial layer. A Schottky barrier exists between the transparent conductive layer 24 and the contact epitaxial layer, and the current spreading layer 27 forms an ohmic contact with the contact epitaxial layer.

[0194] exist Figure 1c and Figure 2 In the illustrated light-emitting diode, taking the ITO transparent conductive layer 17 as an example where the material is an N-type semiconductor and the doping type of the second semiconductor layer 14 is P-type, the ITO transparent conductive layer 17 acts as a resistor R in the circuit. A heterojunction with a depletion layer is formed between the N-type ITO transparent conductive layer 17 and the P-type second semiconductor layer 14 surrounding the SiO2 current blocking layer 18 (e.g., Figure 2 The Schottky barrier formed by the diode in the circuit increases the contact resistance, leading to a larger voltage drop under high current drive, which in turn results in a higher drive voltage and a poorer uniformity of the injected current spread. However, in embodiments of the present invention, although a heterojunction is also formed between the transparent conductive layer 24 and the contacting epitaxial layer (such as...), the... Figure 4 The diode formed between the transparent conductive layer 24 and the second semiconductor layer 23 is used. However, when the doping type of the epitaxial layer in contact with the current spreading layer 27 is P-type, the work function of the current spreading layer 27 is adjusted to be greater than the work function of the epitaxial layer in contact with the current spreading layer 27. Alternatively, when the doping type of the epitaxial layer in contact with the current spreading layer 27 is N-type, the work function of the current spreading layer 27 is adjusted to be less than the work function of the epitaxial layer in contact with the current spreading layer 27. This allows the current spreading layer 27 to form a good ohmic contact with the epitaxial layer in contact with it. Furthermore, by adjusting the sheet resistance of the current spreading layer 27 to be less than the sheet resistance of the epitaxial layer in contact with the current spreading layer 27, the lateral extension length of the current is increased, thereby making the current spread layer 27 and the epitaxial layer in contact with it more ohmic. Figure 1c and Figure 2 Compared to the previously shown LEDs, this invention significantly reduces the driving voltage of high-power LEDs and improves the lateral current spread distance and uniformity under high-current driving, thereby enhancing the luminous efficacy and reliability of high-power LEDs. In embodiments of this invention, since the Fermi level of a semiconductor changes with doping concentration, the work function can be adjusted by changing the doping concentration, and the sheet resistance can be adjusted by changing the annealing process.

[0195] When the doping type of the current spreading layer 27 is P-type, the material of the current spreading layer 27 can be at least one of the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O. When the doping type of the current spreading layer 27 is N-type, the material of the current spreading layer 27 is at least one selected from the following: Sn-doped In₂O₃, Al-doped In₂O₃, F-doped SnO₂, Sb-doped SnO₂, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO₂, and Ga-doped IZO. It should be noted that the material of the current spreading layer 27 is not limited to the types mentioned above.

[0196] Follow step S6, see Figure 11f A first electrode 28 is formed on the current spreading layer 27 above the reflective layer 25.

[0197] The first electrode 28 can be formed using methods such as atomic layer deposition, magnetron sputtering, or evaporation. For example... Figures 3-5 , Figures 7-9 as well as Figure 11f As shown, the number of the first electrode 28 can be one; or, the number of the first electrode 28 can be at least two, such as... Figure 6 As shown, there are two first electrodes 28. Increasing the number of first electrodes 28 per unit area of ​​the light-emitting diode can improve light extraction efficiency.

[0198] And, as Figure 6 As shown, when there are at least two first electrodes 28, the protective layer 26, the reflective layer 25 and the transparent conductive layer 24 under different first electrodes 28 are all disconnected, the current spreading layer 27 under different first electrodes 28 are connected to each other, and different first electrodes 28 can be connected in series through a conductive structure (not shown).

[0199] If the first semiconductor layer 21 is closer to the first substrate 200 than the second semiconductor layer 23, the method of manufacturing the light-emitting diode further includes: forming a second electrode 29 on the bottom surface of the first substrate 200 (i.e., the back surface of the light-emitting diode) or on the first semiconductor layer 21.

[0200] If the second semiconductor layer 23 is closer to the second substrate than the first semiconductor layer 21, the method of manufacturing the light-emitting diode further includes: forming a second electrode 29 on the bottom surface of the second substrate or on the second semiconductor layer 23.

[0201] The second electrode 29 can be formed by methods such as atomic layer deposition, magnetron sputtering, or vapor deposition.

[0202] And, as Figures 3-6 and Figure 11f As shown, if the second electrode 29 is formed on the first substrate 200 (i.e., ... Figures 3-5 and Figure 11f The substrate 20) or the second substrate (i.e., the substrate 20) Figure 6 If the substrate 20) is located on the bottom surface of the light-emitting diode, then the first electrode 28 and the second electrode 29 are located on different sides of the light-emitting diode. Furthermore, as... Figures 3-5 and Figure 11f As shown, the multiple quantum well layer 22 and the second semiconductor layer 23 are formed on the entire surface of the first semiconductor layer 21; as Figure 6 As shown, the multi-quantum well layer 22 and the first semiconductor layer 21 are formed on the entire surface of the second semiconductor layer 23.

[0203] Alternatively, the first electrode 28 and the second electrode 29 are located on the same side of the light-emitting diode. Specifically, when the light-emitting diode is in a front-mounted structure, if the multiple quantum well layer 22 and the second semiconductor layer 23 are formed only on a portion of the surface of the first semiconductor layer 21, and the second electrode 29 is formed on the surface of the first semiconductor layer 21 where the multiple quantum well layer 22 is not formed, such as... Figure 7 As shown, at this time, the second electrode 29 is spaced apart from the multi-quantum well layer 22, and the side of the second electrode 29 away from the first substrate 200 can be lower than the side of the first electrode 28 away from the first substrate 200 or flush with the side of the first electrode 28 away from the first substrate 200.

[0204] When the light-emitting diode is Figure 8In the flip-chip structure shown, the first semiconductor layer 21 is closer to the first substrate 200 (i.e., the substrate 20) than the second semiconductor layer 23. The steps of forming the first electrode 28 on the current spreading layer 27 above the reflective layer 25 and forming the second electrode 29 on the first semiconductor layer 21 include: First, forming a first via (not shown) that sequentially penetrates the current spreading layer 27, the second semiconductor layer 23, and the multiple quantum well layer 22 in contact with the second semiconductor layer 23 to expose a portion of the first semiconductor layer 21; then, forming an insulating layer 291 covering the current spreading layer 27, the insulating layer 291 filling the first via; then, etching the insulating layer 291 to form a second via (not shown) exposing a portion of the current spreading layer 27 above the reflective layer 25, and to form a via exposing the bottom of the first via. A third via (not shown) is formed in a portion of the first semiconductor layer 21. The third via extends from the insulating layer 291 in the first via to the top surface of the insulating layer 291. Then, conductive material is filled in the second via and the third via and on the insulating layer 291 by methods such as atomic layer deposition, magnetron sputtering or evaporation. A partial conductive material on the insulating layer 291 is removed by a stripping process to form a first electrode 28 in the second via and a second electrode 29 in the third via. The first electrode 28 and the second electrode 29 also extend to a portion of the insulating layer 291. The first electrode 28 is connected to the current spreading layer 27, and the second electrode 29 is connected to the first semiconductor layer 21. The side of the first electrode 28 away from the first substrate 200 is flush with the side of the second electrode 29 away from the first substrate 200.

[0205] Or, when the light-emitting diode is Figure 9In the flip-chip structure shown, the second semiconductor layer 23 is closer to the second substrate (i.e., the substrate 20) than the first semiconductor layer 21. The steps of forming the first electrode 28 on the current spreading layer 27 above the reflective layer 25 and forming the second electrode 29 on the second semiconductor layer 23 include: First, forming a first via (not shown) that sequentially penetrates the current spreading layer 27, the first semiconductor layer 21, and the multiple quantum well layer 22 in contact with the first semiconductor layer 21 to expose a portion of the second semiconductor layer 23; then, forming an insulating layer 291 covering the current spreading layer 27, the insulating layer 291 filling the first via; then, etching the insulating layer 291 to form a second via (not shown) exposing the current spreading layer 27 above the reflective layer 25, and to form the first via exposing the first via. A third via (not shown) is formed in a portion of the second semiconductor layer 23 on the bottom surface. The third via extends from the insulating layer 291 in the first via to the top surface of the insulating layer 291. Then, conductive material is filled in the second via and the third via and on the insulating layer 291 by methods such as atomic layer deposition, magnetron sputtering or evaporation. A partial conductive material on the insulating layer 291 is removed by a stripping process to form a first electrode 28 in the second via and a second electrode 29 in the third via. The first electrode 28 and the second electrode 29 also extend to a portion of the insulating layer 291. The first electrode 28 is connected to the current spreading layer 27, and the second electrode 29 is connected to the second semiconductor layer 23. The side of the first electrode 28 away from the second substrate is flush with the side of the second electrode 29 away from the second substrate.

[0206] It should be noted that, in Figure 8 and Figure 9 In the illustrated embodiment, the portion of the first electrode 28 located in the second through hole and the portion of the second electrode 29 located in the third through hole can both be composed of at least one conductive plug.

[0207] When the multiple quantum well layer 22 emits light towards the front of the light-emitting diode, taking the first semiconductor layer 21 being closer to the first substrate 200 than the second semiconductor layer 23 as an example, compared to... Figures 1a to 1c and Figure 2Compared to the structure of the light-emitting diode shown (where the second semiconductor layer 14 has a flat surface), if the second semiconductor layer 23 of the present invention has a roughened surface, it is possible to prevent total internal reflection at certain angles when light emitted from the multiple quantum well layer 22 reaches the surface of the second semiconductor layer 23. That is, the amount of light that undergoes total internal reflection at the surface of the second semiconductor layer 23 is reduced, thereby improving the light extraction efficiency from the front of the light-emitting diode. Furthermore, the light emitted from the multiple quantum well layer 22 is scattered at the surface of the second semiconductor layer 23, allowing some of the light emitted from the multiple quantum well layer 22 below the first electrode 28 to be emitted from the side and / or front of the light-emitting diode. This reduces the amount of light absorbed by the first electrode 28, further improving the light extraction efficiency of the light-emitting diode and lowering the temperature in the region near the first electrode 28.

[0208] Furthermore, when the light scattered from the surface of the second semiconductor layer 23 reaches the reflective layer 25 after passing through the transparent conductive layer 24, if both the transparent conductive layer 24 and the reflective layer 25 have roughened surfaces, the scattered light at different angles will be reflected by the reflective layer 25 and emitted from the side of the light-emitting diode (e.g., Figure 3 The light source absorbs light (L2) from the first electrode 28, thereby reducing the amount of light absorbed by the first electrode 28 and further improving the light extraction efficiency of the light-emitting diode. In addition, it can effectively reduce the temperature in the area near the first electrode 28 and improve the reliability of the light-emitting diode.

[0209] In addition, such as Figures 3-9 As shown, preferably, the projection of the protective layer 26 in the direction perpendicular to the substrate 20 (i.e., the first substrate 200 or the second substrate) lies within the projection of the transparent conductive layer 24 in the direction perpendicular to the substrate 20 or completely coincides with the projection of the transparent conductive layer 24 in the direction perpendicular to the substrate 20, so as to increase the lateral current spread length; and, as Figures 3-9 As shown, preferably, the projection of the reflective layer 25 in the direction perpendicular to the substrate 20 lies within the projection of the protective layer 26 in the direction perpendicular to the substrate 20, so that the protective layer 26 can block the upward migration of metal in the reflective layer 25 and the transparent conductive layer 24 can block the downward migration of metal in the reflective layer 25, thereby avoiding reliability problems such as leakage; and, as Figures 3-7As shown, preferably, the projection of the reflective layer 25 in the direction perpendicular to the substrate 20 completely coincides with the projection of the first electrode 28 in the direction perpendicular to the substrate 20, so that all light emitted by the multi-quantum well layer 22 towards the region where the first electrode 28 is located can be reflected by the reflective layer 25. This greatly reduces the amount of light absorbed by the first electrode 28 while also preventing the reflective layer 25 from being too large and affecting the front light emission efficiency of the light-emitting diode. Furthermore, as... Figures 8-9 As shown, preferably, the projection of the reflective layer 25 in the direction perpendicular to the substrate 20 completely coincides with the projection of the portion of the first electrode 28 located in the insulating layer 291 in the direction perpendicular to the substrate 20. This ensures that the projection of the portion of the first electrode 28 located in the insulating layer 291 in the direction perpendicular to the substrate 20 lies within the projection of the transparent conductive layer 24 in the direction perpendicular to the substrate 20. This reduces current accumulation below the portion of the first electrode 28 located in the insulating layer 291, mitigating the current accumulation effect. Furthermore, since the contact resistance between the transparent conductive layer 24 and the contacting epitaxial layer is greater than the contact resistance between the current spreading layer 27 and the contacting epitaxial layer, the transparent conductive layer 24 acts as a current blocking layer, preventing large current flows longitudinally below the first electrode 28 and forcing most of the current to spread laterally in the current spreading layer 27. Figure 4 As indicated by the arrow, most of the current extends laterally from the current extension layer 27 above the transparent conductive layer 24 to the current extension layer 27 surrounding the transparent conductive layer 24, and then is transmitted vertically downwards. Only a small portion of the current is transmitted directly vertically downwards from the transparent conductive layer 24.

[0210] Furthermore, because the transparent conductive layer 24 is very thin and has a high doping concentration, the PN junction barrier layer formed by the transparent conductive layer 24 and the contacting epitaxial layer is very thin. When a small voltage is applied to the first electrode 28, the electric field strength inside the barrier layer can reach a very high value. This strong electric field strength can directly pull the valence electrons of the neutral atoms in the barrier layer out of the covalent bonds and become free electrons, while generating holes. This process is called field excitation. Field excitation generates a large number of charge carriers, causing the reverse current of the PN junction to increase dramatically. From a band structure theory perspective, taking the example where the first semiconductor layer 21 is closer to the first substrate 200 than the second semiconductor layer 23, and the first semiconductor layer 21 is N-type doped while the second semiconductor layer 23 is P-type doped, the reverse bias causes the bottom of the conduction band of the N-type transparent conductive layer 24 to be lower than the top of the valence band of the P-type second semiconductor layer 23. In this case, quantum effects allow electrons in the valence band of the P-type second semiconductor layer 23 to tunnel directly into the conduction band of the N-type transparent conductive layer 24, forming a current. Under the influence of an electric field, charge carriers can more easily pass through the thin and highly doped transparent conductive layer 24. Therefore, a small current flow can be transmitted from below the first electrode 28, resulting in a uniform distribution of the injected current in the multi-quantum-well layer 22 of the light-emitting diode, improving luminous efficiency and reliability.

[0211] This invention applies to high-power light-emitting diodes, such as those with a power ≥ 1W and an operating current ≥ 1mA.

[0212] As can be seen from the above, the method for manufacturing a light-emitting diode according to the present invention includes: providing a first substrate; forming an epitaxial layer on the first substrate, the epitaxial layer including a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer stacked sequentially from bottom to top on the first substrate, wherein the doping types of the first semiconductor layer and the second semiconductor layer are opposite; forming a transparent conductive layer on a portion of the surface of the epitaxial layer, wherein the doping type of the transparent conductive layer is opposite to that of the epitaxial layer in contact with it; forming a reflective layer on the transparent conductive layer; forming a current spreading layer, the current spreading layer covering the transparent conductive layer and the reflective layer and extending to the epitaxial layer, wherein the doping type of the current spreading layer is the same as that of the epitaxial layer in contact with it; and forming a first electrode on the current spreading layer above the reflective layer. The method for manufacturing a light-emitting diode according to the present invention increases the lateral current spreading length while also improving the light extraction efficiency and reliability of the light-emitting diode.

[0213] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A light-emitting diode, characterized in that, include: Substrate; The epitaxial layer includes a first semiconductor layer, a multiple quantum well layer, and a second semiconductor layer stacked sequentially on the substrate, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types. A transparent conductive layer is located on a portion of the surface of the epitaxial layer. The transparent conductive layer has a doping type opposite to that of the epitaxial layer it contacts, thereby forming a PN junction barrier layer between the transparent conductive layer and the epitaxial layer it contacts. A reflective layer is located on the transparent conductive layer; A current spreading layer covers the transparent conductive layer and the reflective layer and extends to the epitaxial layer, wherein the current spreading layer has the same doping type as the contacting epitaxial layer; The first electrode is located on the current spreading layer above the reflective layer; Wherein, the contact resistance between the transparent conductive layer and the contacting epitaxial layer is greater than the contact resistance between the current spreading layer and the contacting epitaxial layer; When the doping type of the epitaxial layer in contact with the current spreading layer is P-type, the work function of the current spreading layer is greater than the work function of the epitaxial layer in contact with the current spreading layer; when the doping type of the epitaxial layer in contact with the current spreading layer is N-type, the work function of the current spreading layer is less than the work function of the epitaxial layer in contact with the current spreading layer; the sheet resistance of the current spreading layer is less than the sheet resistance of the epitaxial layer in contact with the current spreading layer.

2. The light-emitting diode as described in claim 1, characterized in that, The transparent conductive layer is p-type doped, and the material of the transparent conductive layer is at least one of the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O.

3. The light-emitting diode as described in claim 1, characterized in that, The transparent conductive layer is N-type doped, and the material of the transparent conductive layer is at least one of the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO.

4. The light-emitting diode as described in claim 1, characterized in that, The thickness of the transparent conductive layer is 5. The light-emitting diode as described in claim 1, characterized in that, The doping concentration of the transparent conductive layer is 1E16cm⁻¹ -3 ~1E20cm -3 .

6. The light-emitting diode as described in claim 5, characterized in that, The doping concentration of the transparent conductive layer is 1E19cm⁻¹. -3 ~1E20cm -3 .

7. The light-emitting diode as described in claim 1, characterized in that, The thickness of the reflective layer is 8. The light-emitting diode as described in claim 1, characterized in that, The current spreading layer is p-type doped, and the material of the current spreading layer is at least one of the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O.

9. The light-emitting diode as described in claim 1, characterized in that, The current spreading layer is N-type doped, and the material of the current spreading layer is at least one of the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO.

10. The light-emitting diode as claimed in claim 1, characterized in that, The thickness of the current spreading layer is 1 nm to 1000 nm.

11. The light-emitting diode as claimed in claim 1, characterized in that, The doping concentration of the current spreading layer is 1E11ions / cm² 3 ~1E20 ions / cm 3 .

12. The light-emitting diode as claimed in claim 1, characterized in that, When the first semiconductor layer is N-type doped and the second semiconductor layer is P-type doped, the first semiconductor layer is closer to the substrate than the second semiconductor layer, the transparent conductive layer is located on a portion of the surface of the second semiconductor layer, and the current spreading layer extends onto the second semiconductor layer. Alternatively, the second semiconductor layer is closer to the substrate than the first semiconductor layer, the transparent conductive layer is located on a portion of the surface of the first semiconductor layer, the current spreading layer extends onto the first semiconductor layer, and the second semiconductor layer is bonded to the substrate via a bonding layer.

13. The light-emitting diode as described in claim 12, characterized in that, When the second semiconductor layer is closer to the substrate than the first semiconductor layer, a reflective layer is also included between the second semiconductor layer and the bonding layer.

14. The light-emitting diode as described in claim 12, characterized in that, The light-emitting diode also includes: The second electrode is located on the bottom surface of the substrate; or, if the first semiconductor layer is closer to the substrate than the second semiconductor layer, the second electrode is located on the first semiconductor layer, and if the second semiconductor layer is closer to the substrate than the first semiconductor layer, the second electrode is located on the second semiconductor layer.

15. The light-emitting diode as described in claim 14, characterized in that, If the first semiconductor layer is closer to the substrate than the second semiconductor layer, the second electrode is spaced apart from the multi-quantum well layer.

16. The light-emitting diode as claimed in claim 14, characterized in that, An insulating layer is covered on the current spreading layer, and the first electrode penetrates the insulating layer above the reflective layer to connect with the current spreading layer; if the first semiconductor layer is closer to the substrate than the second semiconductor layer, the insulating layer extends from the surface of the current spreading layer in contact with the second semiconductor layer to contact with the first semiconductor layer, and the second electrode penetrates the insulating layer in contact with the first semiconductor layer so that the second electrode is connected with the first semiconductor layer. If the second semiconductor layer is closer to the substrate than the first semiconductor layer, the insulating layer extends from the surface of the current spreading layer in contact with the first semiconductor layer to the surface in contact with the second semiconductor layer, and the second electrode penetrates the insulating layer in contact with the second semiconductor layer, so that the second electrode is connected to the second semiconductor layer.

17. The light-emitting diode as claimed in claim 1, characterized in that, When the multiple quantum well layer emits light toward the front of the light-emitting diode, the epitaxial layer has a roughened surface, and / or the transparent conductive layer has a roughened surface, and / or the reflective layer has a roughened surface, and / or the current spreading layer has a roughened surface.

18. The light-emitting diode as claimed in claim 16, characterized in that, The light-emitting diode further includes a protective layer located between the reflective layer and the current spreading layer.

19. The light-emitting diode as claimed in claim 18, characterized in that, The protective layer is made of at least one of Cr, Pt, Pd, Mo, Al, Ni, W, Cr / Ni, Ti / Ni, TiN, and TiW.

20. The light-emitting diode as claimed in claim 18, characterized in that, The projection of the protective layer in the direction perpendicular to the substrate is located within the projection of the transparent conductive layer in the direction perpendicular to the substrate or coincides with the projection of the transparent conductive layer in the direction perpendicular to the substrate; the projection of the reflective layer in the direction perpendicular to the substrate is located within the projection of the protective layer in the direction perpendicular to the substrate; the projection of the reflective layer in the direction perpendicular to the substrate coincides with the projection of the first electrode in the direction perpendicular to the substrate, or the projection of the reflective layer in the direction perpendicular to the substrate completely coincides with the projection of the first portion of the first electrode located in the insulating layer in the direction perpendicular to the substrate.

21. The light-emitting diode as claimed in claim 1, characterized in that, The power of the light-emitting diode is ≥1W, and the operating current of the light-emitting diode is ≥1mA.

22. A method for manufacturing a light-emitting diode, characterized in that, include: Provide a first substrate; An epitaxial layer is formed on the first substrate, the epitaxial layer comprising a first semiconductor layer, a multiple quantum well layer and a second semiconductor layer stacked sequentially from bottom to top on the first substrate, wherein the doping types of the first semiconductor layer and the second semiconductor layer are opposite. A transparent conductive layer is formed on a portion of the surface of the epitaxial layer, wherein the doping type of the transparent conductive layer is opposite to that of the epitaxial layer in contact with it, thereby forming a PN junction barrier layer between the transparent conductive layer and the epitaxial layer in contact with it. A reflective layer is formed on the transparent conductive layer; A current spreading layer is formed, which covers the transparent conductive layer and the reflective layer and extends to the epitaxial layer, wherein the current spreading layer has the same doping type as the epitaxial layer in contact with it; A first electrode is formed on a current spreading layer above the reflective layer; Wherein, the contact resistance between the transparent conductive layer and the contacting epitaxial layer is greater than the contact resistance between the current spreading layer and the contacting epitaxial layer; When the doping type of the epitaxial layer in contact with the current spreading layer is P-type, the work function of the current spreading layer is greater than the work function of the epitaxial layer in contact with the current spreading layer; when the doping type of the epitaxial layer in contact with the current spreading layer is N-type, the work function of the current spreading layer is less than the work function of the epitaxial layer in contact with the current spreading layer; the sheet resistance of the current spreading layer is less than the sheet resistance of the epitaxial layer in contact with the current spreading layer.

23. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The transparent conductive layer is p-type doped, and the material of the transparent conductive layer is at least one of the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O.

24. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The transparent conductive layer is N-type doped, and the material of the transparent conductive layer is at least one of the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO.

25. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The thickness of the transparent conductive layer is 26. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The doping concentration of the transparent conductive layer is 1E16cm⁻¹ -3 ~1E20cm -3 .

27. The method for manufacturing a light-emitting diode as described in claim 26, characterized in that, The doping concentration of the transparent conductive layer is 1E19cm⁻¹. -3 ~1E20cm -3 .

28. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The thickness of the reflective layer is 29. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The current spreading layer is p-type doped, and the material of the current spreading layer is at least one of the following: ZnO co-doped with N and Ga, CuAlO2 doped with Mg, CuCrO2 doped with Mg, CuScO2 doped with Ca, CuInO2 doped with Ca, CuYO2 doped with Ca, SrCu2O2 doped with K, LaCuOS doped with Sr, LaCuOS doped with Mg, LaCuOSe doped with Mg, Sr3Cu2Sc2O5S2 doped with K, Sr3Cu2Sc2O5S2 doped with Mg, Cr2O3 doped with Li, Cr2O3 doped with Mg, Cr2O3 doped with Ni, LaCrO3 doped with Sr, NiO doped with Li, and Cu2O.

30. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The current spreading layer is N-type doped, and the material of the current spreading layer is at least one of the following: Sn-doped In2O3, Al-doped In2O3, F-doped SnO2, Sb-doped SnO2, Al-doped ZnO, Ga-doped ZnO, Mg-doped ZnO, B-doped ZnO, In-doped ZnO, Sn-doped CuInO2, and Ga-doped IZO.

31. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The thickness of the current spreading layer is 1 nm to 1000 nm.

32. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The doping concentration of the current spreading layer is 1E11 ions / cm 3 ~1E20 ions / cm 3 .

33. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, When the first semiconductor layer is N-type doped and the second semiconductor layer is P-type doped, the transparent conductive layer is formed on a portion of the surface of the second semiconductor layer, and the current spreading layer extends onto the second semiconductor layer. The method for manufacturing the light-emitting diode further includes: A second electrode is formed on the bottom surface of the first substrate or on the first semiconductor layer.

34. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, When the first semiconductor layer is N-type doped and the second semiconductor layer is P-type doped, the transparent conductive layer is formed on a portion of the surface of the first semiconductor layer, and the current spreading layer extends onto the first semiconductor layer. Before forming the transparent conductive layer on a portion of the surface of the epitaxial layer, the method for manufacturing the light-emitting diode further includes: Provide a second substrate; The side of the epitaxial layer away from the first substrate is bonded to the second substrate by a bonding layer; Remove the first substrate; The method for manufacturing the light-emitting diode further includes: A second electrode is formed on the bottom surface of the second substrate or on the second semiconductor layer.

35. The method for manufacturing a light-emitting diode as described in claim 34, characterized in that, Before bonding the side of the epitaxial layer away from the first substrate to the second substrate via the bonding layer, the method for manufacturing the light-emitting diode further includes: A reflective layer is formed on the second semiconductor layer.

36. The method for manufacturing a light-emitting diode as described in claim 33, characterized in that, If the second electrode is formed on the first semiconductor layer, the second electrode is spaced apart from the multiple quantum well layer.

37. The method for manufacturing a light-emitting diode as described in claim 33 or 34, characterized in that, The steps of forming the first electrode on the current spreading layer above the reflective layer and forming the second electrode on the first semiconductor layer include: A first via is formed that sequentially penetrates the current spreading layer, the second semiconductor layer, and the multiple quantum well layer in contact with the second semiconductor layer; An insulating layer is formed over the current spreading layer, and the insulating layer fills the first through-hole; The insulating layer is etched to form a second via that exposes a current spreading layer above the reflective layer, and a third via that exposes a portion of the first semiconductor layer at the bottom of the first via. A first electrode is formed in the second via and a second electrode is formed in the third via, the first electrode being connected to the current spreading layer and the second electrode being connected to the first semiconductor layer; Alternatively, the steps of forming the first electrode on the current spreading layer above the reflective layer and forming the second electrode on the second semiconductor layer include: A first via is formed that sequentially penetrates the current spreading layer, the first semiconductor layer, and the multiple quantum well layer in contact with the first semiconductor layer; An insulating layer is formed over the current spreading layer, and the insulating layer fills the first through-hole; The insulating layer is etched to form a second via that exposes a current spreading layer above the reflective layer, and a third via that exposes a portion of a second semiconductor layer at the bottom of the first via. A first electrode is formed in the second via and a second electrode is formed in the third via. The first electrode is connected to the current spreading layer and the second electrode is connected to the second semiconductor layer.

38. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, When the multiple quantum well layer emits light toward the front of the light-emitting diode, the epitaxial layer has a roughened surface, and / or the transparent conductive layer has a roughened surface, and / or the reflective layer has a roughened surface, and / or the current spreading layer has a roughened surface.

39. The method for manufacturing a light-emitting diode as described in claim 37, characterized in that, After forming the reflective layer on the transparent conductive layer and before forming the current spreading layer, the method of manufacturing the light-emitting diode further includes forming a protective layer between the reflective layer and the current spreading layer.

40. The method for manufacturing a light-emitting diode as described in claim 39, characterized in that, The protective layer is made of at least one of Cr, Pt, Pd, Mo, Al, Ni, W, Cr / Ni, Ti / Ni, TiN, and TiW.

41. The method for manufacturing a light-emitting diode as described in claim 39, characterized in that, The projection of the protective layer in the direction perpendicular to the first substrate is located within the projection of the transparent conductive layer in the direction perpendicular to the first substrate or coincides with the projection of the transparent conductive layer in the direction perpendicular to the first substrate; the projection of the reflective layer in the direction perpendicular to the first substrate is located within the projection of the protective layer in the direction perpendicular to the first substrate; the projection of the reflective layer in the direction perpendicular to the first substrate coincides with the projection of the first electrode in the direction perpendicular to the first substrate, or the projection of the reflective layer in the direction perpendicular to the substrate completely coincides with the projection of the first portion of the first electrode located in the insulating layer in the direction perpendicular to the substrate.

42. The method for manufacturing a light-emitting diode as described in claim 22, characterized in that, The power of the light-emitting diode is ≥1W, and the operating current of the light-emitting diode is ≥1mA.

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