CN115295692A - Light emitting diode and method for manufacturing the same - Google Patents
Light emitting diode and method for manufacturing the same Download PDFInfo
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- CN115295692A CN115295692A CN202210927517.XA CN202210927517A CN115295692A CN 115295692 A CN115295692 A CN 115295692A CN 202210927517 A CN202210927517 A CN 202210927517A CN 115295692 A CN115295692 A CN 115295692A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/025—Physical imperfections, e.g. particular concentration or distribution of impurities
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
- H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/10—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a light reflecting structure, e.g. semiconductor Bragg reflector
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
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Abstract
The invention provides a light emitting diode and a manufacturing method thereof, wherein the light emitting diode comprises: a substrate; the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the substrate, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite; the transparent conducting layer is positioned on part of the surface of the epitaxial layer, and the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer; a reflective layer on the transparent conductive layer; the current extension layer covers the transparent conductive layer and the reflection layer and extends to the epitaxial layer, and the doping type of the current extension layer is the same as that of the epitaxial layer in contact with the current extension layer; a first electrode on the current spreading layer above the reflective layer. The technical scheme of the invention can improve the light extraction efficiency and reliability while increasing the transverse extension length of the current.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a light-emitting diode and a manufacturing method thereof.
Background
The uneven current density distribution of the active layer of the light emitting diode not only causes uneven light intensity distribution, but also causes overhigh temperature of the local area of the light emitting diode, thereby reducing the reliability of the light emitting diode. In order to improve the photoelectric performance and reliability of the light emitting diode, in the optimal design of the light emitting diode, it is necessary to suppress a Current steering Effect (Current steering Effect) in the light emitting diode, improve the Current lateral spreading performance of the light emitting diode, and alleviate the quantum Efficiency attenuation (Efficiency Droop) phenomenon of the light emitting diode under the condition of large Current injection, so that the light emitting diode can bear higher working Current density.
Taking the light emitting diode shown in fig. 1a as an example, the epitaxial layer in the light emitting diode includes a first semiconductor layer 12, a multiple quantum well layer 13 and a second semiconductor layer 14 formed on the front surface of a substrate 11 from the bottom to the top, the second semiconductor layer 14 has a flat surface, light emitted from the multiple quantum well layer 13 is emitted through the front surface of the light emitting diode (as the arrow in fig. 1a indicates light emitted from the front surface of the light emitting diode), a first electrode 15 is formed on a part of the second semiconductor layer 14, and a second electrode 16 is formed on the back surface of the substrate 11.
When the first semiconductor layer 12 is N-type and the second semiconductor layer 14 is P-type, the current spreading length of the second semiconductor layer 14 is short because the hole mobility of the second semiconductor layer 14 is much smaller than the electron mobility of the first semiconductor layer 12, and the conductivity of the second semiconductor layer 14 is much weaker than that of the first semiconductor layer 12 at a comparable carrier concentration. In order to improve the lateral current spreading performance of the led, as shown in fig. 1b, an ITO (indium tin oxide) transparent conductive layer 17 is deposited on the second semiconductor layer 14 by electron beam evaporation or ion beam sputtering, and the first electrode 15 is formed on a portion of the ITO transparent conductive layer 17. However, in order to reduce the contact resistance between the ITO transparent conductive layer 17 and the second semiconductor layer 14 and to improve the transmittance of the ITO transparent conductive layer 17 to visible light, thermal annealing is generally performed after evaporation or ion beam sputtering, but the sheet resistance of the ITO transparent conductive layer 17 after annealing is larger than that of the first semiconductor layer 12, so that the injected current is concentrated near the first electrode 15, and the lateral spread length of the current is still short. Moreover, for the high-power light emitting diode, as the density of the injected current increases, the lateral current expansion length gradually decreases, and under the driving condition of high current density, the current aggregation phenomenon below the first electrode 15 becomes more serious, so that a large number of photons generated by the active layer (i.e., the multiple quantum well layer 13) are aggregated below the first electrode 15.
At present, in order to improve the current concentration phenomenon near the first electrode 15 in the light emitting diode, as shown in fig. 1c, a layer of SiO is deposited on a partial region between the ITO transparent conductive layer 17 and the second semiconductor layer 14 under the first electrode 15 2 Current barrier layer 18, siO 2 The current blocking layer 18 can prevent the longitudinal transmission of current under the first electrode 15, forcing the current to spread laterally in the ITO transparent conductive layer 17, as indicated by the arrows in FIG. 2, from SiO 2 Into SiO in the ITO transparent conductive layer 17 over the current blocking layer 18 2 The transparent conductive layer 17 on the periphery of the current blocking layer 18 is laterally spread and then vertically transferred downward. Thus, siO 2 The current blocking layer 18 may increase the current lateral extension length, thereby mitigating the current crowding effect.
However, since the first electrode 15 is made of metal, it is opaque in the visible light band, and has a strong absorption effect on the photons emitted from the mqw layer 13, on one hand, the area of the mqw layer 13 of the led is lost, which results in a decrease in the light extraction efficiency of the led, and on the other hand, most of the photons below the first electrode 15 are absorbed by the first electrode 15, which results in an increase in the temperature of the region near the first electrode 15, which further results in a decrease in the reliability of the led; and, due to SiO 2 The presence of the current blocking layer 18 results in less current being transmitted longitudinally under the first electrode 15, the light emission intensity of the active layer region under the first electrode 15 is lower, and the light emission region is mostly distributed at the periphery of the first electrode 15, which in turn results in lower external quantum efficiency. Therefore, the use of SiO 2 2 Of current-blocking layers 18Technical solution although the lateral current spreading length is increased, there still exist problems of low light extraction efficiency and low reliability of the light emitting diode.
When the first semiconductor layer 12 is P-type and the second semiconductor layer 14 is N-type, since the electron mobility of the second semiconductor layer 14 is also low at a normal doping concentration, the current lateral expansion length can be increased by increasing the doping concentration of the second semiconductor layer 14, but the semiconductor crystal quality may be degraded as the doping concentration of the second semiconductor layer 14 is increased; alternatively, the current lateral spread length can also be increased and the current density distribution uniformity of the active layer can be improved by increasing the thickness of the second semiconductor layer 14, but the excessive thickness of the second semiconductor layer 14 may cause film cracking. Therefore, the above methods for increasing the lateral current spreading length have problems, and the improvement effect is limited.
In addition, since the second semiconductor layer 14 has a flat surface, total reflection of light occurs on the surface of the second semiconductor layer 14; even if the ITO transparent conductive layer 17 is formed on the second semiconductor layer 14, since the refractive index of the second semiconductor layer 14 (for example, the refractive indices of 2.4, 3.57, and 2.65 corresponding to the materials of GaN, gaAs, and SiC of the second semiconductor layer 14) is greater than the refractive index of the ITO transparent conductive layer 17 (the refractive index is 2.08), total reflection of light occurs at the interface between the second semiconductor layer 14 and the ITO transparent conductive layer 17, and thus light generated from the active layer cannot be efficiently extracted.
Therefore, a light emitting diode and a method for manufacturing the same are provided to increase the lateral current spreading length and also to improve the light extraction efficiency and reliability of the light emitting diode.
Disclosure of Invention
The invention aims to provide a light emitting diode and a manufacturing method thereof, which can improve the light extraction efficiency and reliability while increasing the transverse current extension length.
To achieve the above object, the present invention provides a light emitting diode, including:
a substrate;
the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the substrate, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite;
the transparent conducting layer is positioned on part of the surface of the epitaxial layer, and the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer;
a reflective layer on the transparent conductive layer;
the current extension layer covers the transparent conductive layer and the reflection layer and extends to the epitaxial layer, and the doping type of the current extension layer is the same as that of the epitaxial layer in contact with the current extension layer;
a first electrode on the current spreading layer above the reflective layer.
Optionally, a contact resistance between the transparent conductive layer and the epitaxial layer in contact with the transparent conductive layer is greater than a contact resistance between the current spreading layer and the epitaxial layer in contact with the current spreading layer.
Optionally, the doping type of the transparent conductive layer is P-type, and the transparent conductive layer is made of co-doped N and Ga ZnO or Mg-doped CuAlO 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 LaCuOS doped with Sr, laCuOS doped with Mg, laCuOSe doped with Mg and Sr doped with K 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO and Cu doped with Li 2 At least one of O.
Optionally, the doping type of the transparent conductive layer is N-type, and the material of the transparent conductive layer is In doped with Sn 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO.
Optionally, the thickness of the transparent conductive layer is
Optionally, the doping concentration of the transparent conductive layer is 1E16cm -3 ～1E20cm -3 。
Optionally, the doping concentration of the transparent conductive layer is 1E19cm -3 ～1E20cm -3 。
Optionally, the thickness of the reflecting layer is
Optionally, when the doping type of the epitaxial layer in contact with the current extension layer is P-type, the work function of the current extension layer is greater than that of the epitaxial layer in contact with the current extension layer; and when the doping type of the epitaxial layer in contact with the current expansion layer is N type, the work function of the current expansion layer is smaller than that of the epitaxial layer in contact with the current expansion layer.
Optionally, the sheet resistance of the current spreading layer is smaller than the sheet resistance of the epitaxial layer in contact with the current spreading layer.
Optionally, the doping type of the current spreading layer is P-type, and the material of the current spreading layer is co-doped N and Ga ZnO or Mg-doped CuAlO 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 Sr-doped LaCuOS, mg-doped LaCuOSe, K-doped Sr 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO doped with Li and Cu 2 In O toOne of them is used.
Optionally, the doping type of the current spreading layer is N-type, and the material of the current spreading layer is In doped with Sn 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO.
Optionally, the thickness of the current spreading layer is 1nm to 1000nm.
Optionally, the doping concentration of the current spreading layer is 1E11ions/cm 3 ～1E20ions/cm 3 。
Optionally, when the doping type of the first semiconductor layer is N-type and the doping type of the second semiconductor layer is P-type, the first semiconductor layer is closer to the substrate than the second semiconductor layer, the transparent conductive layer is located on a part 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 part 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 with the substrate through a bonding layer.
Optionally, when the second semiconductor layer is closer to the substrate than the first semiconductor layer, a mirror layer is further included between the second semiconductor layer and the bonding layer.
Optionally, the light emitting diode further includes:
a second electrode located on a 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.
Optionally, if the first semiconductor layer is closer to the substrate than the second semiconductor layer, the second electrode and the multiple quantum well layer are spaced apart from each other.
Optionally, the current spreading layer is covered with an insulating layer, and the first electrode penetrates through the insulating layer above the reflective layer to be connected 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 which is in contact with the second semiconductor layer to be in contact with the first semiconductor layer, and the second electrode penetrates through the insulating layer which is 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 be in contact with the second semiconductor layer, and the second electrode penetrates through the insulating layer in contact with the second semiconductor layer, so that the second electrode is connected with the second semiconductor layer.
Optionally, when the multiple quantum well layer emits light to the front surface 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.
Optionally, the light emitting diode further includes a protective layer, and the protective layer is located between the reflective layer and the current spreading layer.
Optionally, the material of the protective layer is at least one of Cr, pt, pd, mo, al, ni, W, cr/Ni, ti/Ni, tiN and TiW.
Optionally, a projection of the protective layer in the direction perpendicular to the substrate is located within a projection of the transparent conductive layer in the direction perpendicular to the substrate or coincides with a projection of the transparent conductive layer in the direction perpendicular to the substrate; the projection of the reflecting layer in the direction perpendicular to the substrate is positioned in the projection of the protective layer in the direction perpendicular to the substrate; the projection of the reflecting 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 reflecting layer in the direction perpendicular to the substrate coincides completely with the projection of the first portion of the first electrode in the insulating layer in the direction perpendicular to the substrate.
Optionally, the power of the light emitting diode is not less than 1W, and the working current of the light emitting diode is not less than 1mA.
The invention also provides a manufacturing method of the light-emitting diode, which comprises the following steps:
providing a first substrate;
forming an epitaxial layer on the first substrate, wherein the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the first substrate from bottom to top, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite;
forming a transparent conducting layer on a part of the surface of the epitaxial layer, wherein the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer;
forming a reflective layer on the transparent conductive layer;
forming a current spreading layer, wherein the current spreading layer covers the transparent conducting layer and the reflecting layer and extends to the epitaxial layer, and the doping type of the current spreading layer is the same as that of the epitaxial layer in contact with the current spreading layer;
forming a first electrode on the current spreading layer over the reflective layer.
Optionally, the contact resistance between the transparent conductive layer and the epitaxial layer in contact is greater than the contact resistance between the current spreading layer and the epitaxial layer in contact.
Optionally, the doping type of the transparent conductive layer is P-type, and the transparent conductive layer is made of co-doped N and Ga ZnO or Mg-doped CuAlO 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 Sr-doped LaCuOS, mg-doped LaCuOSe, K-doped Sr 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO doped with Li and Cu 2 At least one of O.
Optionally, the doping type of the transparent conductive layer is N type, and the material of the transparent conductive layer is Sn-doped In 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO.
Optionally, the thickness of the transparent conductive layer is
Optionally, the doping concentration of the transparent conductive layer is 1E16cm -3 ～1E20cm -3 。
Optionally, the doping concentration of the transparent conductive layer is 1E19cm -3 ～1E20cm -3 。
Optionally, the thickness of the reflecting layer is
Optionally, when the doping type of the epitaxial layer in contact with the current extension layer is P-type, the work function of the current extension layer is greater than that of the epitaxial layer in contact with the current extension layer; and when the doping type of the epitaxial layer in contact with the current expansion layer is N type, the work function of the current expansion layer is smaller than that of the epitaxial layer in contact with the current expansion layer.
Optionally, the sheet resistance of the current spreading layer is smaller than the sheet resistance of the epitaxial layer in contact with the current spreading layer.
Optionally, the doping type of the current spreading layer is PThe current expansion layer is made of ZnO co-doped with N and Ga or CuAlO doped with Mg 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 LaCuOS doped with Sr, laCuOS doped with Mg, laCuOSe doped with Mg and Sr doped with K 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO and Cu doped with Li 2 At least one of O.
Optionally, the doping type of the current spreading layer is N type, and the material of the current spreading layer is Sn-doped In 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO.
Optionally, the thickness of the current spreading layer is 1nm to 1000nm.
Optionally, the doping concentration of the current spreading layer is 1E11ions/cm 3 ～1E20ions/cm 3 。
Optionally, when the doping type of the first semiconductor layer is N-type and the doping type of the second semiconductor layer is P-type, the transparent conductive layer is formed on a part of the surface of the second semiconductor layer, and the current spreading layer extends to the second semiconductor layer; the method for manufacturing the light emitting diode further comprises the following steps:
and forming a second electrode on the bottom surface of the first substrate or the first semiconductor layer.
Optionally, when the doping type of the first semiconductor layer is N-type and the doping type of the second semiconductor layer is P-type, the transparent conductive layer is formed on a part of the surface of the first semiconductor layer, and the current spreading layer extends to the first semiconductor layer; before forming the transparent conductive layer on a part of the surface of the epitaxial layer, the method for manufacturing the light emitting diode further comprises:
providing a second substrate;
bonding one surface of the epitaxial layer, which is far away from the first substrate, on the second substrate through a bonding layer;
removing the first substrate;
the manufacturing method of the light emitting diode further comprises the following steps:
and forming a second electrode on the bottom surface of the second substrate or the second semiconductor layer.
Optionally, before bonding a side of the epitaxial layer away from the first substrate to the second substrate through the bonding layer, the method for manufacturing a light emitting diode further includes:
and forming a reflector layer on the second semiconductor layer.
Optionally, if the second electrode is formed on the first semiconductor layer, the second electrode and the mqw layer are spaced apart from each other.
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:
forming a first through hole which sequentially penetrates through the current spreading layer, the second semiconductor layer and the multiple quantum well layer which are in contact with the second semiconductor layer;
forming an insulating layer to cover the current expansion layer, wherein the insulating layer fills the first through hole;
etching the insulating layer to form a second through hole exposing the current expansion layer above the reflecting layer and a third through hole exposing a part of the first semiconductor layer on the bottom surface of the first through hole;
forming a first electrode in the second via and a second electrode in the third via, the first electrode being connected to the current spreading layer, the second electrode being connected to the first semiconductor layer;
alternatively, the step of forming the first electrode on the current spreading layer above the reflective layer and the step of forming the second electrode on the second semiconductor layer may include:
forming a first via hole sequentially penetrating through a current spreading layer in contact with the first semiconductor layer, and the multiple quantum well layer;
forming an insulating layer to cover the current expansion layer, wherein the insulating layer fills the first through hole;
etching the insulating layer to form a second through hole exposing the current expansion layer above the reflecting layer and a third through hole exposing a part of the second semiconductor layer on the bottom surface of the first through hole;
forming a first electrode in the second via and a second electrode in the third via, the first electrode being connected to the current spreading layer and the second electrode being connected to the second semiconductor layer.
Optionally, when the multiple quantum well layer emits light to the front surface 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.
Optionally, after forming the reflective layer on the transparent conductive layer and before forming the current spreading layer, the method for manufacturing a light emitting diode further includes: and forming a protective layer between the reflecting layer and the current spreading layer.
Optionally, the material of the protective layer is at least one of Cr, pt, pd, mo, al, ni, W, cr/Ni, ti/Ni, tiN and TiW.
Optionally, a projection of the protective layer in the direction perpendicular to the first substrate is located within a projection of the transparent conductive layer in the direction perpendicular to the first substrate or coincides with a projection of the transparent conductive layer in the direction perpendicular to the first substrate; the projection of the reflecting layer in the direction perpendicular to the first substrate is positioned in the projection of the protective layer in the direction perpendicular to the first substrate; the projection of the reflecting 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 reflecting layer in the direction perpendicular to the substrate coincides completely with the projection of the first portion of the first electrode in the insulating layer in the direction perpendicular to the substrate.
Optionally, the power of the light emitting diode is greater than or equal to 1W, and the working current of the light emitting diode is greater than or equal to 1mA.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. the light emitting diode of the present invention comprises: the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the substrate, wherein the doping types of the first semiconductor layer and the second semiconductor layer are opposite; the transparent conducting layer is positioned on part of the surface of the epitaxial layer, and the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer; a reflective layer on the transparent conductive layer; the current extension layer covers the transparent conductive layer and the reflection layer and extends to the epitaxial layer, and the doping type of the current extension layer is the same as that of the epitaxial layer in contact with the current extension layer; a first electrode on the current spreading layer above the reflective layer; the light extraction efficiency and reliability of the light emitting diode can be improved while the transverse current extension length is increased.
2. The manufacturing method of the light emitting diode of the invention comprises the following steps: forming an epitaxial layer on a first substrate, wherein the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the first substrate from bottom to top, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite; forming a transparent conducting layer on a part of the surface of the epitaxial layer, wherein the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer; forming a reflective layer on the transparent conductive layer; forming a current spreading layer, wherein the current spreading layer covers the transparent conducting layer and the reflecting layer and extends to the epitaxial layer, and the doping type of the current spreading layer is the same as that of the epitaxial layer in contact with the current spreading layer; forming a first electrode on the current spreading layer above the reflective layer; the light extraction efficiency and reliability of the light emitting diode can be improved while the transverse current extension length is increased.
Drawings
FIG. 1a is a schematic structural diagram of a light emitting diode;
FIG. 1b is a schematic diagram of a light emitting diode;
FIG. 1c is a schematic diagram of a light emitting diode;
FIG. 2 is a schematic current spreading diagram of the LED shown in FIG. 1 c;
fig. 3 is a schematic structural diagram of a light emitting diode according to a first embodiment of the invention;
FIG. 4 is a schematic current spreading diagram of the LED shown in FIG. 3;
fig. 5 is a schematic structural diagram of a light emitting diode according to a second embodiment of the invention;
fig. 6 is a schematic structural diagram of a light emitting diode according to a third embodiment of the present invention;
fig. 7 is a schematic structural diagram of a light emitting diode according to a fourth embodiment of the present invention;
fig. 8 is a schematic structural diagram of a light emitting diode according to a fifth embodiment of the present invention;
fig. 9 is a schematic structural diagram of a light emitting diode according to a sixth embodiment of the present invention;
FIG. 10 is a flow chart of a method of fabricating a light emitting diode according to an embodiment of the present invention;
fig. 11a to 11f are schematic views of devices in the method of manufacturing the light emitting diode shown in fig. 10.
Wherein the reference numerals of figures 1a to 11f are as follows:
11-a substrate; 12-a first semiconductor layer; 13-a multi-quantum well layer; 14-a second semiconductor layer; 15-a first electrode; 16-a second electrode; 17-an ITO transparent conductive layer; 20-a substrate; 201-a bonding layer; 202-a mirror layer; 21-a first semiconductor layer; 22-multiple quantum well layer; 23-a second semiconductor layer; 24-a transparent conductive layer; 25-a reflective layer; 26-a protective layer; 27-a current spreading layer; 28-a first electrode; 29-a second electrode; 291-an insulating layer; 200-first substrate.
Detailed Description
To make the objects, advantages and features of the present invention more apparent, the light emitting diode and the method for manufacturing the same proposed by the present invention are described in further detail below. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
An embodiment of the present invention provides a light emitting diode, including: a substrate; the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the substrate, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite; the transparent conducting layer is positioned on part of the surface of the epitaxial layer, and the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer; a reflective layer on the transparent conductive layer; the current expansion layer covers the transparent conducting layer and the reflecting layer and extends to the epitaxial layer, and the doping type of the current expansion layer and the doping type of the epitaxial layer which is contacted with the current expansion layer are the same; a first electrode on the current spreading layer above the reflective layer.
The light emitting diode provided in the present embodiment is described in more detail with reference to fig. 3 to 9, and fig. 3 to 9 are schematic longitudinal cross-sectional views of the light emitting diode.
When the light emitting diode has a vertical structure as shown in fig. 3 to 6, the substrate 20 may be made of at least one semiconductor material such as silicon, germanium, silicon carbide, or gallium arsenide, and electrical properties of the substrate 20 can be changed by doping; when the light emitting diode has a non-vertical structure as shown in fig. 7 to 9, the substrate 20 may be made of at least one material selected from sapphire, aluminum nitride, gallium oxide, magnesium aluminate, lithium gallate, lithium aluminate and the like. The light emitting diode may have a front-mount structure as shown in fig. 7, or may have a flip-chip structure as shown in fig. 8 to 9.
The epitaxial layer includes a first semiconductor layer 21, a multiple quantum well layer 22 and a second semiconductor layer 23 stacked on the substrate 20 in this order, and the doping type of the first semiconductor layer 21 is opposite to that of the second semiconductor layer 23. Wherein the mqw layer 22 serves as a light emitting layer, and in the embodiment shown in fig. 3 to 7, the mqw layer 22 emits light, such as light L1 in fig. 3, to the front surface of the light emitting diode; in the embodiments shown in fig. 8 to 9, the mqw layer 22 emits light to the back surface of the light emitting diode, and the front surface and the back surface of the light emitting diode are opposite surfaces.
Preferably, the doping type of the first semiconductor layer 21 is N-type, and the doping type of the second semiconductor layer 23 is P-type, in this case, as shown in fig. 3 to 5 and fig. 7 to 8, 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 mqw layer 22, and the second semiconductor layer 23 are stacked on the substrate 20 in this order from bottom to top; alternatively, as shown in fig. 6 and 9, 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 on the substrate 20 in this order from top to bottom. In other embodiments, the doping type of the first semiconductor layer 21 may be a P-type, and the doping type of the second semiconductor layer 23 may be an N-type.
If the second semiconductor layer 23 is closer to the substrate 20 than the first semiconductor layer 21 is, as shown in fig. 9, the second semiconductor layer 23 is bonded to the substrate 20 through a bonding layer 201; as shown in fig. 6, the second semiconductor layer 23 is bonded to the substrate 20 through a bonding layer 201, and a mirror layer 202 is further included between the second semiconductor layer 23 and the bonding layer 201 to improve front light extraction efficiency.
When the mqw layer 22 emits light to the front surface of the light emitting diode, the surface of the epitaxial layer away from the substrate 20 preferably has a roughened surface. If the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, and the surface of the epitaxial layer away from the substrate 20 is the second semiconductor layer 23, the second semiconductor layer 23 preferably has a roughened surface, that is, the surface of the second semiconductor layer 23 is uneven; if the second semiconductor layer 23 is closer to the substrate 20 than the first semiconductor layer 21, and a surface of the epitaxial layer away from the substrate 20 is the first semiconductor layer 21, the first semiconductor layer 21 preferably has a roughened surface, that is, the surface of the first semiconductor layer 21 is uneven. Wherein the roughened surface is 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 a partially roughened surface (i.e., the surface is partially roughened and partially flat) or have no roughened surface (i.e., the surface is entirely flat).
The longitudinal section of the coarsening surface can be at least one of a cambered surface, a circular arc surface, a sawtooth surface, a wavy surface and an irregular surface. The longitudinal section of the roughened surface as shown in fig. 3 to 7 is a serrated surface. The longitudinal section of the roughened surface is not limited to the above-described shape.
The material of the first semiconductor layer 21 may be at least one of GaN, alGaN, gaAs, siC, and the like; the material of the second semiconductor layer 23 may be at least one of GaN, alGaN, BAlN, gaAs, siC, and the like; the material of the mqw layer 22 may be at least one of AlN, gaN, alGaN, inGaN, alInGaN, gaAs, and SiC. The materials of the first semiconductor layer 21, the second semiconductor layer 23, and the mqw layer 22 are not limited to the above-described types.
The transparent conductive layer 24 is located on a part 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 in contact with the transparent conductive layer. When the doping type of the epitaxial layer in contact with the transparent conducting layer 24 is P-type, the doping type of the transparent conducting 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.
When the mqw layer 22 emits light to the front surface of the light emitting diode, if the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, the transparent conductive layer 24 is located on a part of the surface of the second semiconductor layer 23, and at this time, 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, the transparent conductive layer 24 is located on a portion of the surface of the first semiconductor layer 21, and in this case, if the first semiconductor layer 21 has a roughened surface, the surface topography of the first semiconductor layer 21 is preferably 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 entirely flat).
When the doping type of the transparent conductive layer 24 is N-type, the material of the transparent conductive layer 24 may be Sn-doped In 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO (IZO is indium zinc oxide). When the doping type of the transparent conductive layer 24 is P-type, the transparent conductive layer 24 may be made of ZnO co-doped with N and Ga, or CuAlO doped with Mg 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 LaCuOS doped with Sr, laCuOS doped with Mg, laCuOSe doped with Mg and Sr doped with K 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Doped with NiCr 2 O 3 Sr-doped LaCrO 3 NiO doped with Li and Cu 2 At least one of O. The material of the transparent conductive layer 24 is not limited to the above.
The thickness of the transparent conductive layer 24 is very thin, and preferably, the thickness of the transparent conductive layer 24 is
The doping concentration of the transparent conductive layer 24 is high, and the doping concentration of the transparent conductive layer 24 is 1E16cm -3 ～1E20cm -3 Preferably, the doping concentration of the transparent conductive layer 24 is 1E19cm -3 ～1E20cm -3 。
The reflective layer 25 is located on the transparent conductive layer 24.
When the mqw layer 22 emits light to the front surface of the light emitting diode, if the transparent conductive layer 24 has a roughened surface, the surface morphology of the transparent conductive layer 24 is preferably transferred to the reflective layer 25, that is, the reflective layer 25 conforms 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 may not have a roughened surface (i.e., the surface is entirely flat).
Preferably, the reflective layer 25 is made of a high-reflectivity material having a reflectivity of more than 95%, for example, 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%.
The thickness of the reflective layer 25 may be
In addition, since the adhesion between the metal material of the reflective layer 25 and the epitaxial layer is poor, the transparent conductive layer 24 is formed between the reflective layer 25 and the epitaxial layer, so that the adhesion strength between the reflective layer 25 and the epitaxial layer is improved.
The current spreading layer 27 covers the transparent conductive layer 24 and the reflective layer 25 and extends onto the epitaxial layer, and the doping type of the current spreading layer 27 is the same as that of the epitaxial layer in contact. The current spreading layer 27 extending to the epitaxial layer may cover part or all of the epitaxial layer, and the larger the area covered by the current spreading layer 27 on the surface of the epitaxial layer is, the longer the length of the current lateral spreading is.
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.
The thickness of the current spreading layer 27 may be 1nm to 1000nm, and the doping concentration of the current spreading layer 27 may be 1E11ions/cm 3 ～1E20ions/cm 3 。
When the mqw layer 22 emits light to the front surface 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, and at this time, 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 a portion of the current spreading layer 27 on the second semiconductor layer 23, that is, a portion of the current spreading layer 27 on the second semiconductor layer 23 is conformal with the second semiconductor layer 23, so that a portion of the current spreading layer 27 on the second semiconductor layer 23 also has a roughened surface; if the second semiconductor layer 23 is closer to the substrate 20 than the first semiconductor layer 21, the current spreading layer 27 extends onto the first semiconductor layer 21, and at this time, if the first semiconductor layer 21 has a roughened surface, the surface topography of the first semiconductor layer 21 is preferably transferred to the portion of the current spreading layer 27 on the first semiconductor layer 21, that is, the portion of the current spreading layer 27 on the first semiconductor layer 21 is conformal with the first semiconductor layer 21, so that the portion of the current spreading layer 27 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 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 does not have a roughened surface (i.e., the surface is entirely flat).
Since a heterojunction is formed between the transparent conductive layer 24 and the epitaxial layer in contact, which are opposite in doping type (such as a diode formed between the transparent conductive layer 24 and the second semiconductor layer 23 in fig. 4), and the current spreading layer 27 and the epitaxial layer in contact are the same in doping type, the contact resistance between the transparent conductive layer 24 and the epitaxial layer in contact is greater than the contact resistance between the current spreading layer 27 and the epitaxial layer in contact. The transparent conductive layer 24 and the epitaxial layer in contact form a schottky barrier, and the current spreading layer 27 and the epitaxial layer in contact form an ohmic contact.
In the light emitting diode shown in fig. 1c and 2, the ITO transparent conductive layer 17 is used as the resistor R, siO in the circuit, taking the material of the ITO transparent conductive layer 17 as the N-type semiconductor material and the second semiconductor layer 14 as the P-type as an example 2 A heterojunction having a depletion layer (e.g., a diode in fig. 2) is formed between the N-type ITO transparent conductive layer 17 and the P-type second semiconductor layer 14 at the periphery of the current blocking layer 18, and a schottky barrier is formed to increase a specific contact resistance and increase a voltage drop under a large current driving, thereby increasing a driving voltage and deteriorating uniformity of spreading of an injected current. In the embodiment of the present invention, although a heterojunction is also formed between the transparent conductive layer 24 and the epitaxial layer in contact with the transparent conductive layer (such as a diode formed between the transparent conductive layer 24 and the second semiconductor layer 23 in fig. 4), 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 larger than that of the epitaxial layer in contact with the current spreading layer 27, or when the doping type of the epitaxial layer in contact with the current spreading layer 27 is N-type, the doping type of the epitaxial layer is adjusted to be larger than that of the current spreading layer 27The work function of the current spreading layer 27 is adjusted to be smaller than that of the epitaxial layer in contact with the current spreading layer 27, so that the current spreading layer 27 and the epitaxial layer in contact with the current spreading layer can form good ohmic contact, and the transverse spreading length of the current is increased by adjusting the square resistance of the current spreading layer 27 to be smaller than that of the epitaxial layer in contact with the current spreading layer 27, so that compared with the light emitting diode shown in fig. 1c and 2, the light emitting diode greatly reduces the driving voltage of the high-power light emitting diode, improves the transverse spreading distance and uniformity of the current under the drive of large-flow current, and improves the light efficiency and reliability of the high-power light emitting diode. In the embodiment of the present invention, since the fermi level of the semiconductor changes with the change of the doping concentration, the work function can be adjusted by adjusting the doping concentration, and the sheet resistance can be adjusted by adjusting the annealing process.
When the doping type of the current spreading layer 27 is P-type, the current spreading layer 27 may be made of ZnO co-doped with N and Ga, or CuAlO doped with Mg 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 Sr-doped LaCuOS, mg-doped LaCuOSe, K-doped Sr 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO and Cu doped with Li 2 At least one of O. When the doping type of the current spreading layer 27 is N-type, the material of the current spreading layer 27 is Sn-doped In 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZOAt least one of (1). The material of the current spreading layer 27 is not limited to the above.
The light emitting diode further comprises a protective layer 26, the protective layer 26 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.
Further, when the mqw layer 22 emits light to the front surface of the light emitting diode, it is preferable that, as shown in fig. 3 to 4 and 6 to 7, the protective layer 26 has a thickness enough to completely block upward migration of the metal in the reflective layer 25, and at this time, the protective layer 26 does not have a roughened surface, and then, the portion of the current spreading layer 27 located on the protective layer 26 does not have a roughened surface. Alternatively, in the embodiment shown in fig. 5, the thickness of the protection layer 26 may also be relatively thin, in this case, if the reflection layer 25 has a roughened surface, the surface topography of the reflection layer 25 is transferred to the protection layer 26, that is, the protection layer 26 is conformal with the reflection layer 25, so that the protection layer 26 also has a roughened surface, and then the portion of the current spreading layer 27 located on the protection layer 26 also has a roughened surface.
The material of the protection layer 26 may be at least one of (Cr), platinum (Pt), palladium (Pd), molybdenum (Mo), aluminum (Al), nickel (Ni), tungsten (W), cr/Ni, ti/Ni, tiN, and TiW. The material of the protective layer 26 is not limited to the above.
In addition, when the mqw layer 22 emits light to the rear surface of the light emitting diode, it is preferable that, as shown in fig. 8 to 9, the surface of the epitaxial layer remote from the substrate 20, the transparent conductive layer 24, the reflective layer 25, the protective layer 26, and the current spreading layer 27 each have a flat surface.
The first electrode 28 is located on the current spreading layer 27 above the reflective layer 25. As shown in fig. 3 to 5 and 7 to 9, the number of the first electrodes 28 may be one; alternatively, the number of the first electrodes 28 is at least two, and as shown in fig. 6, the number of the first electrodes 28 is two. Wherein the light extraction efficiency can be improved by increasing the number of the first electrodes 28 of the light emitting diode per unit area.
Further, as shown in fig. 6, when the number of the first electrodes 28 is at least two, the protective layer 26, the reflective layer 25 and the transparent conductive layer 24 under different first electrodes 28 are disconnected, the current spreading layers 27 under different first electrodes 28 are connected to each other, and the different first electrodes 28 may be connected in series through a conductive structure (not shown).
The light emitting diode further comprises a second electrode 29.
As shown in fig. 3 to 6, the second electrode 29 may be located on a bottom surface of the substrate 20 (i.e., a back surface of the light emitting diode), in which case the first electrode 28 and the second electrode 29 are located on different sides of the light emitting diode. As shown in fig. 3 to 5, 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 shown in fig. 6, the mqw layer 22 and the first semiconductor layer 21 are located on the entire surface of the second semiconductor layer 23.
Alternatively, as shown in fig. 7 to 9, the first electrode 28 and the second electrode 29 are located on the same side of the light emitting diode. When the light emitting diode is in a forward mounting structure, if the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, the mqw layer 22 and the second semiconductor layer 23 are only located on a part 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 mqw layer 22 is not formed, as shown in fig. 7; at this time, the second electrode 29 is disposed at an interval from the mqw layer 22, and a surface of the second electrode 29 away from the substrate 20 may be lower than a surface of the first electrode 28 away from the substrate 20 or flush with a surface of the first electrode 28 away from the substrate 20.
When the light emitting diode is in a flip-chip structure, as shown in fig. 8 to 9, the current spreading layer 27 is covered with an insulating layer 291, and the first electrode 28 penetrates through the insulating layer 291 above the reflective layer 25, so that the first electrode 28 is connected to the current spreading layer 27; as shown in fig. 8, when 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 to be in contact with the first semiconductor layer 21 through the second semiconductor layer 23 and the mqw layer 22 in this order, the second electrode 29 penetrates through 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, and the second electrode 29 is insulated from the current spreading layer 27, the second semiconductor layer 23, and the mqw layer 22; as shown in fig. 9, 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 to be in contact with the second semiconductor layer 23 through the first semiconductor layer 21 and the mqw layer 22 in this order, the second electrode 29 penetrates through 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, and the second electrode 29 is insulated from the current spreading layer 27, the first semiconductor layer 21, and the mqw layer 22; at this time, the first electrode 28 and the second electrode 29 both extend onto the insulating layer 291, that is, the first electrode 28 and the second electrode 29 both include a first portion located in the insulating layer 291 and a second portion extending onto the insulating layer 291, and a surface of the first electrode 28 away from the substrate 20 is flush with a surface of the second electrode 29 away from the substrate 20. It should be noted that the first portions of the first electrode 28 and the second electrode 29 in the insulating layer 291 may be each composed of at least one conductive plug.
When the mqw layer 22 emits light to the front surface of the light emitting diode, taking the first semiconductor layer 21 as an example to be closer to the substrate 20 than the second semiconductor layer 23, compared with the structure of the light emitting diode shown in fig. 1a to 1c and fig. 2 (the second semiconductor layer 14 has a flat surface), if the second semiconductor layer 23 of the present invention has a roughened surface, when the light emitted from the mqw layer 22 reaches the surface of the second semiconductor layer 23, a part of angles are not totally reflected, that is, the amount of light totally reflected on the surface of the second semiconductor layer 23 is reduced, so that the light extraction efficiency of light emitted from the front surface of the light emitting diode is improved; furthermore, the light emitted from the mqw layer 22 is scattered on the surface of the second semiconductor layer 23, and further, part of the light emitted from the mqw layer 22 under the first electrode 28 can be emitted from the side and/or front of the light emitting diode, so that the amount of light absorbed by the first electrode 28 is reduced, the light extraction efficiency of the light emitting diode is further improved, and the temperature of the region near the first electrode 28 is reduced.
Moreover, when the light scattered on the surface of the second semiconductor layer 23 reaches the reflective layer 25 through the transparent conductive layer 24, if the transparent conductive layer 24 and the reflective layer 25 also have roughened surfaces, the light scattered at different angles is reflected by the reflective layer 25 and then emitted from the side surface of the light emitting diode (such as light L2 in fig. 3), so that the amount of light absorbed by the first electrode 28 is further reduced, the light extraction efficiency of the light emitting diode is further improved, the temperature of the region near the first electrode 28 can be effectively reduced, and the reliability of the light emitting diode is improved.
In addition, as shown in fig. 3 to 9, preferably, a projection of the protective layer 26 in a direction perpendicular to the substrate 20 is located within a projection of the transparent conductive layer 24 in a direction perpendicular to the substrate 20 or completely coincides with a projection of the transparent conductive layer 24 in a direction perpendicular to the substrate 20, so as to increase a current lateral expansion length; as shown in fig. 3 to 9, preferably, a projection of the reflective layer 25 in a direction perpendicular to the substrate 20 is located within a projection of the protective layer 26 in a direction perpendicular to the substrate 20, so that the protective layer 26 can block upward migration of the metal in the reflective layer 25 and the transparent conductive layer 24 can block downward migration of the metal in the reflective layer 25, thereby avoiding reliability problems such as electrical leakage; as shown in fig. 3 to 7, preferably, a projection of the reflective layer 25 in the direction perpendicular to the substrate 20 completely overlaps with a projection of the first electrode 28 in the direction perpendicular to the substrate 20, so that light emitted from the mqw layer 22 to the region where the first electrode 28 is located can be reflected by the reflective layer 25, and further, while the amount of light absorbed by the first electrode 28 is greatly reduced, the influence of too large area of the reflective layer 25 on the front light-emitting efficiency of the light-emitting diode can be avoided; furthermore, as shown in fig. 8 to 9, preferably, a projection of the reflective layer 25 in a direction perpendicular to the substrate 20 completely coincides with a 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 a projection of the transparent conductive layer 24 in the direction perpendicular to the substrate 20, and thus, current collection under the first portion of the first electrode 28 can be reduced, and a current collection effect can be alleviated.
Moreover, 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 functions as a current blocking layer, which can block a large amount of current from being transmitted longitudinally below the first electrode 28, and force a large portion of current to spread laterally in the current spreading layer 27, as indicated by the arrow in fig. 4, a large portion of current is spread laterally from the current spreading layer 27 above the transparent conductive layer 24 to the current spreading layer 27 at the periphery of the transparent conductive layer 24, and then transmitted longitudinally downward, and only a small portion of current is transmitted longitudinally downward directly from the transparent conductive layer 24.
Moreover, since the thickness of the transparent conductive layer 24 is very thin and the doping concentration of the transparent conductive layer 24 is very high, the PN junction barrier layer formed by the transparent conductive layer 24 and the epitaxial layer in contact with the transparent conductive 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, and this very high electric field strength can pull the valence electrons of the neutral atoms in the barrier layer directly from the covalent bonds to become free electrons and generate holes at the same time, which is called field excitation, and the field excitation generates a large number of carriers, so that the reverse current of the PN junction is increased dramatically. In terms of band theory, taking the case that the first semiconductor layer 21 is closer to the substrate 20 than the second semiconductor layer 23, and the doping type of the first semiconductor layer 21 is N-type and the doping type of the second semiconductor layer 23 is P-type, since the reverse bias voltage makes the bottom of the conduction band of the N-type transparent conductive layer 24 lower than the top of the valence band of the P-type second semiconductor layer 23, at this time, the quantum effect can make the electrons in the valence band of the P-type second semiconductor layer 23 directly tunnel into the conduction band of the N-type transparent conductive layer 24, forming a current. Under the action of the electric field, carriers can easily penetrate through the transparent conductive layer 24 with very thin physical thickness and high doping concentration, so that small-flow current can be transmitted from the lower part of the first electrode 28, the injection current is uniformly distributed in the MQW layer 22 of the light emitting diode, and the light emitting efficiency and the reliability are improved.
The invention is suitable for the light-emitting diode with high power, for example, the power of the light-emitting diode is more than or equal to 1W, and the working current of the light-emitting diode is more than or equal to 1mA.
As can be seen from the above, the light emitting diode of the present invention includes: a substrate; the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the substrate, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite; the transparent conducting layer is positioned on part of the surface of the epitaxial layer, and the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer; a reflective layer on the transparent conductive layer; the current extension layer covers the transparent conductive layer and the reflection layer and extends to the epitaxial layer, and the doping type of the current extension layer is the same as that of the epitaxial layer in contact with the current extension layer; a first electrode on the current spreading layer above the reflective layer. The light-emitting diode can increase the transverse current extension length and improve the light extraction efficiency and reliability of the light-emitting diode.
Referring to fig. 10, fig. 10 is a flowchart illustrating a method for manufacturing a light emitting diode according to an embodiment of the present invention, where the method for manufacturing a light emitting diode includes:
step S1, providing a first substrate;
s2, forming an epitaxial layer on the first substrate, wherein the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the first substrate from bottom to top, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite;
s3, forming a transparent conducting layer on part of the surface of the epitaxial layer, wherein the doping type of the transparent conducting layer is opposite to that of the epitaxial layer in contact with the transparent conducting layer;
s4, forming a reflecting layer on the transparent conducting layer;
s5, forming a current expansion layer, wherein the current expansion layer covers the transparent conducting layer and the reflecting layer and extends to the epitaxial layer, and the doping type of the current expansion layer is the same as that of the epitaxial layer in contact with the current expansion layer;
and S6, forming a first electrode on the current expansion layer above the reflecting layer.
The method for manufacturing the light emitting diode according to the present embodiment is described in more detail with reference to fig. 3 to 9 and fig. 11a to 11f, fig. 3 to 9 and fig. 11a to 11f are schematic longitudinal cross-sectional views of the light emitting diode, and fig. 11a to 11f illustrate steps for manufacturing the light emitting diode shown in fig. 3 to 4.
According to step S1, referring to fig. 11a, a first substrate 200 is provided.
If the light emitting diode shown in fig. 3 to 5 and 7 to 8 is manufactured, the first substrate 200 is the substrate 20 in fig. 3 to 5 and 7 to 8; if the light emitting diode shown in fig. 6 and 9 is manufactured, the first substrate 200 is replaced with a second substrate (not shown), which is the substrate 20 in fig. 6 and 9.
When the light emitting diode shown in fig. 3 to 6 is manufactured, the first substrate 200 and the second substrate may be made of at least one semiconductor material such as silicon, germanium, silicon carbide, or gallium arsenide, and electrical properties may be changed by doping the first substrate 200 and the second substrate; when the light emitting diode shown in fig. 7 to 9 is manufactured, the material of the first substrate 200 and the second substrate may be at least one of sapphire, aluminum nitride, gallium oxide, magnesium aluminate, lithium gallate, lithium aluminate and the like.
The light emitting diode may have a forward mounting structure as shown in fig. 7, or the light emitting diode may have a flip-chip structure as shown in fig. 8 to 9.
According to step S2, referring to fig. 11a, an epitaxial layer is formed on the first substrate 200, the epitaxial layer includes a first semiconductor layer 21, a mqw layer 22 and a second semiconductor layer 23 stacked on the first substrate 200 in sequence from bottom to top, and the doping types of the first semiconductor layer 21 and the second semiconductor layer 23 are opposite. Wherein the mqw layer 22 serves as a light emitting layer, and in the embodiment shown in fig. 3 to 7, the mqw layer 22 emits light, such as light L1 in fig. 3, to the front surface of the light emitting diode; in the embodiments shown in fig. 8 to 9, the mqw layer 22 emits light toward the back surface of the light emitting diode, and the front surface and the back surface of the light emitting diode are opposite surfaces.
Preferably, the doping type of the first semiconductor layer 21 is N-type, and the doping type of the second semiconductor layer 23 is P-type. In other embodiments, the doping type of the first semiconductor layer 21 may be a P type, and the doping type of the second semiconductor layer 23 is an N type.
When the doping type of the first semiconductor layer 21 is N-type and the doping type of the second semiconductor layer 23 is P-type, the surface of the epitaxial layer away from the first substrate 200 is the second semiconductor layer 23, and if the multiple quantum well layer 22 emits light to the front surface of the light emitting diode, preferably, the surface of the second semiconductor layer 23 may be roughened by using a chemical etching process, a plasma etching process, an epitaxial growth process, or the like, so that the surface of the second semiconductor layer 23 is uneven. Wherein the roughened surface is continuously distributed on the surface of the second semiconductor layer 23. In other embodiments, the surface of the second semiconductor layer 23 may be partially roughened (i.e., the surface is partially roughened and partially flat) or not roughened (i.e., the surface is entirely flat).
Alternatively, before the transparent conductive layer 24 is formed on a part of the surface of the epitaxial layer, the method for manufacturing a light emitting diode further includes: firstly, providing a second substrate; then, bonding one surface of the epitaxial layer, which is far away from the first substrate 200, on the second substrate through a bonding layer 201; then, the first substrate is removed, and at this time, the first substrate 200 is replaced with a second substrate, 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 on the second substrate in this order from bottom to top, and the first semiconductor layer 21 is formed on one surface of the epitaxial layer away from the second substrate, as shown in fig. 6 and 9. In addition, if the mqw layer 22 emits light to the front surface of the light emitting diode, the method for manufacturing the light emitting diode preferably further includes: the surface of the first semiconductor layer 21 is processed by using processes such as chemical etching, plasma etching or epitaxial growth, so that the first semiconductor layer 21 has a roughened surface (as shown in fig. 6), that is, 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 no roughened surface (i.e., the surface is entirely flat).
Before the side of the epitaxial layer away from the first substrate 200 is bonded to the second substrate through the bonding layer 201, the method for manufacturing the light emitting diode may further include: a mirror layer 202 is formed on the second semiconductor layer 23, as shown in fig. 6, to improve the front light extraction efficiency.
The longitudinal section of the coarsening surface can be at least one of a cambered surface, a circular arc surface, a sawtooth surface, a wavy surface and an irregular surface. The roughened surface has a serrated surface in a longitudinal section as shown in fig. 11a and 3 to 7. The longitudinal section of the roughened surface is not limited to the above-described shape.
In addition, when the light emitting diode is manufactured in a forward mounting structure, if the first semiconductor layer 21 is closer to the first substrate 200 than the second semiconductor layer 23, the method for manufacturing a light emitting diode further includes: portions of the second semiconductor layer 23 and portions of the multiple quantum well layer 22 are sequentially etched away to expose portions of the first semiconductor layer 21, as shown in fig. 7, and the multiple quantum well layer 22 and the second semiconductor layer 23 are formed only on portions of the surface of the first semiconductor layer 21.
The material of the first semiconductor layer 21 may be at least one of GaN, alGaN, gaAs, siC, and the like; the material of the second semiconductor layer 23 may be at least one of GaN, alGaN, BAlN, gaAs, siC, and the like; the material of the mqw layer 22 may be at least one of AlN, gaN, alGaN, inGaN, alInGaN, gaAs, and SiC. The materials of the first semiconductor layer 21, the second semiconductor layer 23, and the mqw layer 22 are not limited to the above-described types.
According to step S3, referring to fig. 11b, a transparent conductive layer 24 is formed on a portion of the surface of the epitaxial layer 23, where the doping type of the transparent conductive layer 24 is opposite to that of the epitaxial layer in contact. 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.
The material of the transparent conductive layer 24 may be formed on the surface of the epitaxial layer by methods such as atomic layer deposition, magnetron sputtering, or evaporation, and the transparent conductive layer 24 may be formed by photolithography and etching processes.
When the mqw layer 22 emits light to the front surface 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 part of the surface of the second semiconductor layer 23, and in this case, if the second semiconductor layer 23 has a roughened surface, it is preferable that, when the transparent conductive layer 24 is formed, 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, and further, the transparent conductive layer 24 also has 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, and if the first semiconductor layer 21 has a roughened surface, the surface topography of the first semiconductor layer 21 is preferably 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 entirely flat).
When the doping type of the transparent conductive layer 24 is N-type, the transparent conductive layer 24 may be Sn-doped In 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO. When the doping type of the transparent conductive layer 24 is P-type, the transparent conductive layer 24 may be made of co-doped N and Ga ZnO or Mg-doped CuAlO 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 LaCuOS doped with Sr, laCuOS doped with Mg, laCuOSe doped with Mg and Sr doped with K 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO and Cu doped with Li 2 At least one of O. The material of the transparent conductive layer 24 is not limited to the above.
The thickness of the transparent conductive layer 24 is very thin, and preferably, the thickness of the transparent conductive layer 24 is
The doping concentration of the transparent conductive layer 24 is high, and the doping concentration of the transparent conductive layer 24 is 1E16cm -3 ～1E20cm -3 Preferably, the doping concentration of the transparent conductive layer 24 is 1E19cm -3 ～1E20cm -3 。
According to step S4, referring to fig. 11c, a reflective layer 25 is formed on the transparent conductive layer 24.
The material of the reflective layer 25 may be formed on the transparent conductive layer 24 and the epitaxial layer by methods such as atomic layer deposition, magnetron sputtering, or evaporation, and the reflective layer 25 is formed by photolithography and etching processes.
When the mqw layer 22 emits light to the front surface of the light emitting diode, if the transparent conductive layer 24 has a roughened surface, it is preferable that when the reflective layer 25 is formed, the surface morphology of the transparent conductive layer 24 is transferred to the reflective layer 25, that is, the reflective layer 25 conforms 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 may not have a roughened surface (i.e., the surface is entirely flat).
Preferably, the reflective layer 25 is made of a high-reflectivity material having a reflectivity of more than 95%, for example, 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%.
The thickness of the reflective layer 25 may be
In addition, since the adhesion between the metal material of the reflective layer 25 and the epitaxial layer is poor, the transparent conductive layer 24 is formed between the reflective layer 25 and the epitaxial layer, so that the adhesion strength between the reflective layer 25 and the epitaxial layer is improved.
Referring to fig. 11d, after forming the reflective layer 25 on the transparent conductive layer 24 and before forming the current spreading layer 27, the method for manufacturing the light emitting diode further includes: a protection layer 26 is formed between the reflective layer 25 and the current spreading layer 27.
The protective layer 26 may be formed on the reflective layer 25 and the epitaxial layer by atomic layer deposition, magnetron sputtering, evaporation, or the like, and then the protective layer 26 is formed by photolithography and etching.
When the mqw layer 22 emits light to the front surface of the light emitting diode, it is preferable that the protective layer 26 has a thickness enough to completely block upward migration of the metal in the reflective layer 25 as shown in fig. 3 to 4, 6 to 7, and 11d, and in this case, the protective layer 26 does not have a roughened surface; alternatively, in the embodiment shown in fig. 5, the thickness of the protection layer 26 may also be relatively thin, and at this time, if the reflection layer 25 has a roughened surface, the surface topography of the reflection layer 25 is transferred to the protection layer 26, that is, the protection layer 26 is conformal with the reflection layer 25, so that the protection layer 26 also has a roughened surface.
The material of the protection layer 26 may be at least one of (Cr), platinum (Pt), palladium (Pd), molybdenum (Mo), aluminum (Al), nickel (Ni), tungsten (W), cr/Ni, ti/Ni, tiN, and TiW. The material of the protective layer 26 is not limited to the above.
According to step S5, referring to fig. 11e, a current spreading layer 27 is formed, where the current spreading layer 27 covers the transparent conductive layer 24 and the reflective layer 25 and extends onto the epitaxial layer, and the doping type of the current spreading layer 27 is the same as that of the epitaxial layer in contact. 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.
The current spreading layer 27 extending to the epitaxial layer may cover a part or all of the epitaxial layer, and the larger the area covered by the current spreading layer 27 on the surface of the epitaxial layer is, the longer the length of the lateral current spreading is.
The thickness of the current spreading layer 27 may be 1nm to 1000nm, and the doping concentration of the current spreading layer 27 may be 1E11ions/cm 3 ～1E20ions/cm 3 。
The current spreading layer 27 may be formed by atomic layer deposition, magnetron sputtering, evaporation, or the like.
When the mqw layer 22 emits light to the front surface 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, and at this time, 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 a portion of the current spreading layer 27 on the second semiconductor layer 23, that is, a portion of the current spreading layer 27 on the second semiconductor layer 23 is conformal with the second semiconductor layer 23, so that a portion of the current spreading layer 27 on the second semiconductor 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, and at this time, if the first semiconductor layer 21 has a roughened surface, it is preferable that the surface topography of the first semiconductor layer 21 is transferred to the portion of the current spreading layer 27 on the first semiconductor layer 21, that is, the portion of the current spreading layer 27 on the first semiconductor layer 21 is conformal with the first semiconductor layer 21, so that the portion of the current spreading layer 27 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 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 have no roughened surface (i.e., the surface is entirely flat).
The current spreading layer 27 also covers the protective layer 26, and if the protective layer 26 does not have a roughened surface when the mqw layer 22 emits light to the front surface of the light emitting diode, as shown in fig. 3 to 4, 6 to 7, and 11e, the portion of the current spreading layer 27 on the protective layer 26 does not have a roughened surface; if the protection layer 26 has a roughened surface, as shown in fig. 5, the part of the current spreading layer 27 on the protection layer 26 also has a roughened surface.
In addition, when the mqw layer 22 emits light to the back surface of the light emitting diode, it is preferable that, as shown in fig. 8 to 9, the surface of the epitaxial layer (i.e., the surface of the epitaxial layer away from the first substrate 200 or the surface 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 each have a flat surface.
Since a heterojunction is formed between the transparent conductive layer 24 and the epitaxial layer in contact, which are opposite in doping type (such as a diode formed between the transparent conductive layer 24 and the second semiconductor layer 23 in fig. 4), and the current spreading layer 27 and the epitaxial layer in contact are of the same doping type, the contact resistance between the transparent conductive layer 24 and the epitaxial layer in contact is greater than the contact resistance between the current spreading layer 27 and the epitaxial layer in contact. The transparent conductive layer 24 and the epitaxial layer in contact form a schottky barrier, and the current spreading layer 27 and the epitaxial layer in contact form an ohmic contact.
Light emitting diode shown in FIG. 1c and FIG. 2In the tube, taking the example that the material of the ITO transparent conductive layer 17 is N-type semiconductor material and the doping type of the second semiconductor layer 14 is P-type, the ITO transparent conductive layer 17 is used as the resistor R, siO in the circuit 2 A heterojunction (such as a diode in fig. 2) having a depletion layer is formed between the N-type ITO transparent conductive layer 17 and the P-type second semiconductor layer 14 at the periphery of the current blocking layer 18, and a schottky barrier is formed to increase a specific contact resistance and a voltage drop is increased under a large current driving, so that a driving voltage becomes high and uniformity of spreading of an injection current becomes poor. In the embodiment of the present invention, although a heterojunction is also formed between the transparent conductive layer 24 and the epitaxial layer in contact with the current spreading layer (e.g., a diode formed between the transparent conductive layer 24 and the second semiconductor layer 23 in fig. 4), 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 that of the epitaxial layer in contact with the current spreading layer 27, or 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 smaller than that of the epitaxial layer in contact with the current spreading layer 27, so that the current spreading length in the lateral direction is increased, thereby greatly reducing the work function of the light emitting diode compared with the light emitting diode shown in fig. 1c and fig. 2, and further increasing the lateral current spreading reliability and the light emitting efficiency under the condition of the large current, and improving the light emitting efficiency and light emitting diode efficiency. In the embodiment of the present invention, since the fermi level of the semiconductor changes with the change of the doping concentration, the work function can be adjusted by adjusting the doping concentration, and the sheet resistance can be adjusted by adjusting the annealing process.
When the doping type of the current spreading layer 27 is P-type, the current spreading layer 27 may be co-dopedZnO of N and Ga, cuAlO doped with Mg 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 Sr-doped LaCuOS, mg-doped LaCuOSe, K-doped Sr 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO doped with Li and Cu 2 At least one of O. When the doping type of the current spreading layer 27 is N-type, the material of the current spreading layer 27 is In doped with Sn 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO. The material of the current spreading layer 27 is not limited to the above.
According to step S6, referring to fig. 11f, a first electrode 28 is formed on the current spreading layer 27 above the reflective layer 25.
The first electrode 28 may be formed by atomic layer deposition, magnetron sputtering, or evaporation. As shown in fig. 3 to 5, 7 to 9, and 11f, the number of the first electrodes 28 may be one; alternatively, the number of the first electrodes 28 is at least two, and as shown in fig. 6, the number of the first electrodes 28 is two. Wherein the light extraction efficiency can be improved by increasing the number of the first electrodes 28 of the light emitting diode per unit area.
Also, as shown in fig. 6, when the number of the first electrodes 28 is at least two, the protective layer 26, the reflective layer 25 and the transparent conductive layer 24 under different first electrodes 28 are disconnected from each other, the current spreading layers 27 under different first electrodes 28 are connected to each other, and the different first electrodes 28 may be connected in series through a conductive structure (not shown).
If the first semiconductor layer 21 is closer to the first substrate 200 than the second semiconductor layer 23, the method for manufacturing a light emitting diode further includes: a second electrode 29 is formed on the bottom surface of the first substrate 200 (i.e., the back surface of the light emitting diode) or the first semiconductor layer 21.
If the second semiconductor layer 23 is closer to the second substrate than the first semiconductor layer 21, the method for manufacturing a light emitting diode further includes: a second electrode 29 is formed on the bottom surface of the second substrate or the second semiconductor layer 23.
The second electrode 29 may be formed by atomic layer deposition, magnetron sputtering, evaporation, or the like.
As shown in fig. 3 to 6 and 11f, if the second electrode 29 is formed on the bottom surface of the first substrate 200 (i.e., the substrate 20 in fig. 3 to 5 and 11 f) or the second substrate (i.e., the substrate 20 in fig. 6), the first electrode 28 and the second electrode 29 are located on different sides of the light emitting diode. Also, as shown in fig. 3 to 5 and 11f, 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 shown in fig. 6, the mqw layer 22 and the first semiconductor layer 21 are formed on the entire surface of the second semiconductor layer 23.
Alternatively, the first electrode 28 and the second electrode 29 are located on the same side of the light emitting diode. When the light emitting diode is of a forward-mounted structure, if the mqw layer 22 and the second semiconductor layer 23 are only formed on a part 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 mqw layer 22 is not formed, as shown in fig. 7, in this case, the second electrode 29 is disposed at a distance from the mqw layer 22, and a surface of the second electrode 29 away from the first substrate 200 may be lower than a surface of the first electrode 28 away from the first substrate 200 or flush with a surface of the first electrode 28 away from the first substrate 200.
When the led is in the flip-chip structure shown in fig. 8, the first semiconductor layer 21 is closer to the first substrate 200 (i.e. the substrate 20) than the second semiconductor layer 23, and 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, a first via hole (not shown) is formed to penetrate the current spreading layer 27, the second semiconductor layer 23, and the mqw layer 22 in contact with the second semiconductor layer 23 in this order to expose a part of the first semiconductor layer 21; then, forming an insulating layer 291 to cover the current spreading layer 27, wherein the insulating layer 291 fills the first through hole; then, the insulating layer 291 is etched to form a second via (not shown) exposing a portion of the current spreading layer 27 above the reflective layer 25, and a third via (not shown) exposing a portion of the first semiconductor layer 21 at a bottom surface of the first via, the third via extending from the insulating layer 291 in the first via to a top surface of the insulating layer 291; then, filling a conductive material in the second through hole and the third through hole and on the insulating layer 291 by using methods such as atomic layer deposition, magnetron sputtering, or evaporation, and removing a portion of the conductive material on the insulating layer 291 by using a lift-off process, so as to form a first electrode 28 in the second through hole and a second electrode 29 in the third through hole, where the first electrode 28 and the second electrode 29 further extend onto a portion of the insulating layer 291, the first electrode 28 is connected with the current spreading layer 27, the second electrode 29 is connected with the first semiconductor layer 21, and a surface of the first electrode 28 away from the first substrate 200 is flush with a surface of the second electrode 29 away from the first substrate 200.
Alternatively, when the light emitting diode is in a flip-chip structure as shown in fig. 9, the second semiconductor layer 23 is closer to the second substrate (i.e. the substrate 20) than the first semiconductor layer 21, and 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, a first via hole (not shown) is formed to penetrate the current spreading layer 27, the first semiconductor layer 21, and the multiple quantum well layer 22 in order in contact with the first semiconductor layer 21 to expose a portion of the second semiconductor layer 23; then, an insulating layer 291 is formed to cover the current spreading layer 27, and the insulating layer 291 fills the first through hole; then, the insulating layer 291 is etched to form a second via hole (not shown) exposing the current spreading layer 27 above the reflective layer 25, and a third via hole (not shown) exposing a portion of the second semiconductor layer 23 at the bottom of the first via hole, the third via hole extending from the insulating layer 291 in the first via hole to the top surface of the insulating layer 291; then, filling a conductive material in the second through hole and the third through hole and on the insulating layer 291 by using methods such as atomic layer deposition, magnetron sputtering, or evaporation, and removing a portion of the conductive material on the insulating layer 291 by using a lift-off process, so as to form a first electrode 28 in the second through hole and a second electrode 29 in the third through hole, where the first electrode 28 and the second electrode 29 further extend onto a portion of the insulating layer 291, the first electrode 28 is connected with the current spreading layer 27, the second electrode 29 is connected with the second semiconductor layer 23, and a surface of the first electrode 28 away from the second substrate is flush with a surface of the second electrode 29 away from the second substrate.
It should be noted that, in the embodiment shown in fig. 8 and 9, both 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 may be composed of at least one conductive plug.
When the mqw layer 22 emits light to the front surface of the light emitting diode, taking the first semiconductor layer 21 as an example that the second semiconductor layer 23 is closer to the first substrate 200 than the first semiconductor layer 21, compared with the structure of the light emitting diode shown in fig. 1a to 1c and fig. 2 (the second semiconductor layer 14 has a flat surface), if the second semiconductor layer 23 of the present invention has a roughened surface, when the light emitted from the mqw layer 22 reaches the surface of the second semiconductor layer 23, total reflection does not occur at a part of the angles, that is, the amount of light totally reflected at the surface of the second semiconductor layer 23 is reduced, and thus the light extraction efficiency of light emitted from the front surface of the light emitting diode is improved; furthermore, the light emitted from the mqw layer 22 is scattered on the surface of the second semiconductor layer 23, and thus part of the light emitted from the mqw layer 22 under the first electrode 28 can be emitted from the side and/or front surface of the light emitting diode, so that the amount of light absorbed by the first electrode 28 is reduced, the light extraction efficiency of the light emitting diode is further improved, and the temperature of the region near the first electrode 28 is reduced.
Moreover, when the light scattered on the surface of the second semiconductor layer 23 reaches the reflective layer 25 through the transparent conductive layer 24, if the transparent conductive layer 24 and the reflective layer 25 also have roughened surfaces, the light scattered at different angles is reflected by the reflective layer 25 and then emitted from the side surface of the light emitting diode (such as light L2 in fig. 3), so that the amount of light absorbed by the first electrode 28 is further reduced, the light extraction efficiency of the light emitting diode is further improved, the temperature of the region near the first electrode 28 can be effectively reduced, and the reliability of the light emitting diode is improved.
In addition, as shown in fig. 3 to 9, preferably, a projection of the protective layer 26 in a direction perpendicular to the substrate 20 (i.e., the first substrate 200 or the second substrate) is located within a projection of the transparent conductive layer 24 in a direction perpendicular to the substrate 20 or completely coincides with a projection of the transparent conductive layer 24 in a direction perpendicular to the substrate 20, so as to increase a current lateral expansion length; as shown in fig. 3 to 9, preferably, a projection of the reflective layer 25 in a direction perpendicular to the substrate 20 is located in a projection of the protective layer 26 in a direction perpendicular to the substrate 20, so that the protective layer 26 can block upward migration of the metal in the reflective layer 25 and the transparent conductive layer 24 can block downward migration of the metal in the reflective layer 25, thereby avoiding reliability problems such as leakage current; as shown in fig. 3 to 7, preferably, a projection of the reflective layer 25 in a direction perpendicular to the substrate 20 completely overlaps a projection of the first electrode 28 in a direction perpendicular to the substrate 20, so that light emitted from the mqw layer 22 to a region where the first electrode 28 is located can be reflected by the reflective layer 25, and further, while the amount of light absorbed by the first electrode 28 is greatly reduced, the area of the reflective layer 25 can be prevented from being too large to affect the front light extraction efficiency of the light emitting diode; furthermore, as shown in fig. 8 to 9, preferably, a projection of the reflective layer 25 in a direction perpendicular to the substrate 20 completely coincides with a projection of the 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 portion of the first electrode 28 located in the insulating layer 291 in the direction perpendicular to the substrate 20 is located within a projection of the transparent conductive layer 24 in the direction perpendicular to the substrate 20, and thus, current collection under the portion of the first electrode 28 located in the insulating layer 291 can be reduced, and a current collection effect can be alleviated. Moreover, 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 functions as a current blocking layer, and can block a large amount of current from being transmitted longitudinally below the first electrode 28, so that most of the current is forced to be spread laterally in the current spreading layer 27, as indicated by the arrows in fig. 4, and most of the current is transmitted laterally from the current spreading layer 27 above the transparent conductive layer 24 to the current spreading layer 27 at the periphery of the transparent conductive layer 24, and then transmitted longitudinally downward, and only a small part of the current is transmitted longitudinally from the transparent conductive layer 24 directly downward.
Moreover, since the thickness of the transparent conductive layer 24 is very thin and the doping concentration of the transparent conductive layer 24 is very high, the PN junction barrier layer formed by the transparent conductive layer 24 and the epitaxial layer in contact with the transparent conductive 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, and this very high electric field strength can pull the valence electrons of the neutral atoms in the barrier layer directly from the covalent bonds to become free electrons and generate holes at the same time, which is called field excitation, and the field excitation generates a large number of carriers, so that the reverse current of the PN junction is increased dramatically. In terms of band theory, taking the first semiconductor layer 21 closer to the first substrate 200 than the second semiconductor layer 23 and the doping type of the first semiconductor layer 21 is N-type and the doping type of the second semiconductor layer 23 is P-type as an example, the bottom of the conduction band of the N-type transparent conductive layer 24 is lower than the top of the valence band of the P-type second semiconductor layer 23 due to reverse bias, and at this time, the quantum effect can cause 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, so as to form a current. Under the action of the electric field, carriers can easily penetrate through the transparent conductive layer 24 with very thin physical thickness and high doping concentration, so that small-flow current can be transmitted from the lower part of the first electrode 28, the injection current is uniformly distributed in the MQW layer 22 of the light emitting diode, and the light emitting efficiency and the reliability are improved.
The invention is suitable for the light-emitting diode with high power, for example, the power of the light-emitting diode is more than or equal to 1W, and the working current of the light-emitting diode is more than or equal to 1mA.
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, wherein the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the first substrate from bottom to top, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite; forming a transparent conducting layer on a part of the surface of the epitaxial layer, wherein the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer; forming a reflective layer on the transparent conductive layer; forming a current spreading layer, wherein the current spreading layer covers the transparent conducting layer and the reflecting layer and extends to the epitaxial layer, and the doping type of the current spreading layer is the same as that of the epitaxial layer in contact with the current spreading layer; forming a first electrode on the current spreading layer above the reflective layer. The manufacturing method of the light-emitting diode can improve the light extraction efficiency and reliability of the light-emitting diode while increasing the transverse current extension length.
The above description is only for the purpose of describing the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are intended to fall within the scope of the appended claims.
Claims (48)
1. A light emitting diode, comprising:
a substrate;
the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the substrate, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite;
the transparent conducting layer is positioned on part of the surface of the epitaxial layer, and the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer;
a reflective layer on the transparent conductive layer;
the current expansion layer covers the transparent conducting layer and the reflecting layer and extends to the epitaxial layer, and the doping type of the current expansion layer and the doping type of the epitaxial layer which is contacted with the current expansion layer are the same;
a first electrode on the current spreading layer above the reflective layer.
2. The light-emitting diode according to claim 1, wherein a contact resistance of the transparent conductive layer with the epitaxial layer in contact is greater than a contact resistance of the current spreading layer with the epitaxial layer in contact.
3. The light-emitting diode according to claim 1, wherein the doping type of the transparent conductive layer is P-type, and the transparent conductive layer is made of ZnO co-doped with N and Ga, or CuAlO doped with Mg 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 Sr-doped LaCuOS, mg-doped LaCuOSe, K-doped Sr 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO doped with Li and Cu 2 At least one of O.
4. The led of claim 1, wherein the doping type of the transparent conductive layer is N-type, and the material of the transparent conductive layer is In doped with Sn 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO.
5. The light-emitting diode according to claim 1, wherein the transparent conductive layer has a thickness of
6. The light-emitting diode according to claim 1, wherein the doping concentration of the transparent conductive layer is 1E16cm -3 ～1E20cm -3 。
7. The light-emitting diode according to claim 6, wherein the doping concentration of the transparent conductive layer is 1E19cm -3 ～1E20cm -3 。
8. The light-emitting diode according to claim 1, wherein the reflective layer has a thickness of
9. The light-emitting diode according to claim 1, wherein when the doping type of the epitaxial layer in contact with the current spreading layer is P-type, a work function of the current spreading layer is larger than a work function of the epitaxial layer in contact with the current spreading layer; and when the doping type of the epitaxial layer in contact with the current expansion layer is N type, the work function of the current expansion layer is smaller than that of the epitaxial layer in contact with the current expansion layer.
10. The light emitting diode of claim 1, wherein the current spreading layer has a sheet resistance less than a sheet resistance of the epitaxial layer in contact with the current spreading layer.
11. The light-emitting diode according to claim 1, wherein the doping type of the current spreading layer is P-type, and the current spreading layer is made of ZnO co-doped with N and Ga, or CuAlO doped with Mg 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 LaCuOS doped with Sr, laCuOS doped with Mg, laCuOSe doped with Mg and Sr doped with K 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO doped with Li and Cu 2 At least one of O.
12. The led of claim 1, wherein the doping type of the current spreading layer is N-type, and the material of the current spreading layer is In doped with Sn 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Doped with AlZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO.
13. The light-emitting diode according to claim 1, wherein the current spreading layer has a thickness of 1nm to 1000nm.
14. The light-emitting diode according to claim 1, wherein the current spreading layer has a doping concentration of 1E11ions/cm 3 ～1E20ions/cm 3 。
15. The light-emitting diode according to claim 1, wherein the doping type of the first semiconductor layer is N-type, and when the doping type of the second semiconductor layer is P-type, 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 part 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 with the substrate through a bonding layer.
16. The light-emitting diode according to claim 15, wherein when the second semiconductor layer is closer to the substrate than the first semiconductor layer, a mirror layer is further included between the second semiconductor layer and the bonding layer.
17. The light-emitting diode according to claim 15, further comprising:
a second electrode located on a 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.
18. The light-emitting diode according to claim 17, wherein the second electrode is spaced apart from the mqw layer if the first semiconductor layer is closer to the substrate than the second semiconductor layer.
19. The light-emitting diode according to claim 17, wherein the current spreading layer is covered with an insulating layer, and the first electrode penetrates the insulating layer above the reflective layer to be connected to 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 be in contact with the first semiconductor layer, and the second electrode penetrates through 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 be in contact with the second semiconductor layer, and the second electrode penetrates through the insulating layer in contact with the second semiconductor layer, so that the second electrode is connected with the second semiconductor layer.
20. The light emitting diode according to claim 1, wherein when the mqw layer emits light to the front surface 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.
21. The light-emitting diode of claim 19, further comprising a protective layer between the reflective layer and the current spreading layer.
22. The led of claim 21, wherein the protective layer comprises at least one of Cr, pt, pd, mo, al, ni, W, cr/Ni, ti/Ni, tiN, and TiW.
23. The light-emitting diode according to claim 21, wherein a projection of the protective layer in a direction perpendicular to the substrate is located within or coincides with a projection of the transparent conductive layer in a direction perpendicular to the substrate; the projection of the reflecting layer in the direction perpendicular to the substrate is positioned in the projection of the protective layer in the direction perpendicular to the substrate; the projection of the reflecting layer in the direction perpendicular to the substrate is coincident with the projection of the first electrode in the direction perpendicular to the substrate, or the projection of the reflecting layer in the direction perpendicular to the substrate is completely coincident with the projection of the first part of the first electrode in the insulating layer in the direction perpendicular to the substrate.
24. The LED of claim 1, wherein the power of the LED is greater than or equal to 1W, and the operating current of the LED is greater than or equal to 1mA.
25. A method of manufacturing a light emitting diode, comprising:
providing a first substrate;
forming an epitaxial layer on the first substrate, wherein the epitaxial layer comprises a first semiconductor layer, a multi-quantum well layer and a second semiconductor layer which are sequentially stacked on the first substrate from bottom to top, and the doping types of the first semiconductor layer and the second semiconductor layer are opposite;
forming a transparent conducting layer on a part of the surface of the epitaxial layer, wherein the doping type of the transparent conducting layer is opposite to that of the contacted epitaxial layer;
forming a reflective layer on the transparent conductive layer;
forming a current spreading layer, wherein the current spreading layer covers the transparent conducting layer and the reflecting layer and extends to the epitaxial layer, and the doping type of the current spreading layer is the same as that of the epitaxial layer in contact with the current spreading layer;
forming a first electrode on the current spreading layer above the reflective layer.
26. The method of claim 25, wherein the transparent conductive layer has a contact resistance with the epitaxial layer in contact that is greater than a contact resistance of the current spreading layer with the epitaxial layer in contact.
27. The method of claim 25, wherein the transparent conductive layer is P-type, and is made of ZnO co-doped with N and Ga, or CuAlO doped with Mg 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 Sr-doped LaCuOS, mg-doped LaCuOSe, K-doped Sr 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO doped with Li and Cu 2 At least one of O.
28. The method according to claim 25, wherein the doping type of the transparent conductive layer is N-type, and the material of the transparent conductive layer is In doped with Sn 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO.
29. The method of claim 25, wherein the transparent conductive layer has a thickness of
30. The method of claim 25, wherein the transparent conductive layer has a doping concentration of 1E16cm -3 ～1E20cm -3 。
31. The method of claim 30, wherein the doping concentration of the transparent conductive layer is 1E19cm -3 ～1E20cm -3 。
32. The method of claim 25, wherein the reflective layer has a thickness of
33. The method according to claim 25, wherein 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 larger than that of the epitaxial layer in contact with the current spreading layer; and when the doping type of the epitaxial layer in contact with the current expansion layer is N type, the work function of the current expansion layer is smaller than that of the epitaxial layer in contact with the current expansion layer.
34. The method of claim 25, wherein the current spreading layer has a sheet resistance less than a sheet resistance of the epitaxial layer in contact with the current spreading layer.
35. The method of claim 25, wherein the current spreading layer is P-type doped, and the current spreading layer is made of ZnO co-doped with N and Ga, or CuAlO doped with Mg 2 Mg-doped CuCrO 2 Ca-doped CuScO 2 Ca-doped CuInO 2 Ca-doped CuYO 2 K-doped SrCu 2 O 2 LaCuOS doped with Sr, laCuOS doped with Mg, laCuOSe doped with Mg and Sr doped with K 3 Cu 2 Sc 2 O 5 S 2 Sr doped with Mg 3 Cu 2 Sc 2 O 5 S 2 Li-doped Cr 2 O 3 Mg-doped Cr 2 O 3 Ni-doped Cr 2 O 3 Sr-doped LaCrO 3 NiO and Cu doped with Li 2 At least one of O.
36. The method of claim 25, wherein the current spreading layer is N-type doped, and the current spreading layer is In doped with Sn 2 O 3 In doped with Al 2 O 3 F-doped SnO 2 Sb-doped SnO 2 Al-doped ZnO, ga-doped ZnO, mg-doped ZnO, B-doped ZnO, in-doped ZnO, sn-doped CuInO 2 And Ga-doped IZO.
37. The method of claim 25, wherein the current spreading layer has a thickness of 1nm to 1000nm.
38. The method of claim 25, wherein the current spreading layer has a doping concentration of 1E11ions/cm 3 ～1E20ions/cm 3 。
39. The method according to claim 25, wherein when the doping type of the first semiconductor layer is N-type and the doping type of the second semiconductor layer is P-type, 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 manufacturing method of the light emitting diode further comprises the following steps:
and forming a second electrode on the bottom surface of the first substrate or the first semiconductor layer.
40. The method according to claim 25, wherein when the doping type of the first semiconductor layer is N-type and the doping type of the second semiconductor layer is P-type, the transparent conductive layer is formed on a portion of the surface of the first semiconductor layer, and the current spreading layer extends over the first semiconductor layer; before forming the transparent conductive layer on a portion of the surface of the epitaxial layer, the method for manufacturing a light emitting diode further includes:
providing a second substrate;
bonding one surface of the epitaxial layer, which is far away from the first substrate, on the second substrate through a bonding layer;
removing the first substrate;
the manufacturing method of the light emitting diode further comprises the following steps:
and forming a second electrode on the bottom surface of the second substrate or the second semiconductor layer.
41. The method of claim 40, wherein before bonding the side of the epitaxial layer remote from the first substrate to the second substrate via the bonding layer, the method further comprises:
and forming a reflector layer on the second semiconductor layer.
42. The method according to claim 39, wherein if the second electrode is formed on the first semiconductor layer, the second electrode is provided apart from the MQW layer.
43. The method according to claim 39 or 40, wherein the step of forming the first electrode on the current spreading layer over the reflective layer and the second electrode on the first semiconductor layer comprises:
forming a first through hole which sequentially penetrates through the current spreading layer, the second semiconductor layer and the multiple quantum well layer which are in contact with the second semiconductor layer;
forming an insulating layer to cover the current expansion layer, wherein the insulating layer fills the first through hole;
etching the insulating layer to form a second through hole exposing the current expansion layer above the reflecting layer and a third through hole exposing a part of the first semiconductor layer on the bottom surface of the first through hole;
forming a first electrode in the second via and a second electrode in the third via, the first electrode being connected to the current spreading layer, the second electrode being connected to the first semiconductor layer;
alternatively, the step of forming the first electrode on the current spreading layer above the reflective layer and the step of forming the second electrode on the second semiconductor layer may include:
forming a first via hole sequentially penetrating through a current spreading layer in contact with the first semiconductor layer, and the multiple quantum well layer;
forming an insulating layer to cover the current expansion layer, wherein the insulating layer fills the first through hole;
etching the insulating layer to form a second through hole exposing the current expansion layer above the reflecting layer and a third through hole exposing a part of the second semiconductor layer on the bottom surface of the first through hole;
forming a first electrode in the second via and a second electrode in the third via, the first electrode being connected to the current spreading layer and the second electrode being connected to the second semiconductor layer.
44. The method of claim 25, wherein when the MQW layer emits light to the front surface 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.
45. The method of claim 43, wherein after forming the reflective layer on the transparent conductive layer and before forming the current spreading layer, the method further comprises: and forming a protective layer between the reflecting layer and the current spreading layer.
46. The method of claim 45, wherein the protective layer is at least one of Cr, pt, pd, mo, al, ni, W, cr/Ni, ti/Ni, tiN, and TiW.
47. The method according to claim 45, wherein a projection of the protective layer in the direction perpendicular to the first substrate is within or coincides with a projection of the transparent conductive layer in the direction perpendicular to the first substrate; the projection of the reflecting layer in the direction perpendicular to the first substrate is positioned in the projection of the protective layer in the direction perpendicular to the first substrate; the projection of the reflecting 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 reflecting layer in the direction perpendicular to the substrate coincides completely with the projection of the first portion of the first electrode in the insulating layer in the direction perpendicular to the substrate.
48. The method of claim 25, wherein the power of the LED is greater than or equal to 1W, and the operating current of the LED is greater than or equal to 1mA.
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