Light emitting diode

Abstract

The embodiment of the utility model discloses a light emitting diode. The light emitting diode comprises a substrate, an epitaxial layer, a third semiconductor layer, a two-dimensional current expansion layer, a fourth semiconductor layer, a current guiding structure and a first electrode. The two-dimensional current expansion layer is formed between the third semiconductor layer and the fourth semiconductor layer and electrically connected with the first electrode, and current in the two-dimensional current expansion layer flows in the direction parallel to the surface of the epitaxial layer. The current guiding structure passes through first through holes in the third semiconductor layer, the two-dimensional current expansion layer and the fourth semiconductor layer to guide current in the two-dimensional current expansion layer to the epitaxial layer, so that the first electrode is electrically connected with the epitaxial layer through the two-dimensional current expansion layer and the current guiding structure. According to the embodiment of the utility model, the current guide structure and the two-dimensional current expansion layer are arranged, so that the current distribution is optimized, the working voltage of the light-emitting diode is reduced, and the light-emitting efficiency of the light-emitting diode is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductors, in particular to a light emitting diode. Background Art

[0002] Front-emitting LEDs usually use metal strip extension electrodes and thicker current extension layers to expand current, thereby obtaining better light distribution. However, the metal strip extension electrodes and thicker current extension layer materials have a significant absorption effect on light, which affects the light efficiency of the LED. Utility Model Content

[0003] In view of this, an object of the present invention is to provide a light emitting diode, which reduces the absorption of light by electrodes and current spreading layer materials and improves the light emitting efficiency of the light emitting diode.

[0004] The embodiment of the utility model provides a light-emitting diode, which includes: a substrate; an epitaxial layer, located on the substrate, the epitaxial layer includes a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence from bottom to top, and the first semiconductor layer and the second semiconductor layer have different doping types; a third semiconductor layer, located on the second semiconductor layer; a fourth semiconductor layer, located on the third semiconductor layer, the bandgap width of the third semiconductor layer is greater than the bandgap width of the fourth semiconductor layer; a two-dimensional current expansion layer, located between the third semiconductor layer and the fourth semiconductor layer, the current in the two-dimensional current expansion layer flows in a direction parallel to the surface of the second semiconductor layer, and a plurality of first through holes penetrate the third semiconductor layer, the two-dimensional current expansion layer and the fourth semiconductor layer; a plurality of current guiding structures, arranged in the first through holes, the current guiding structures electrically connecting the two-dimensional current expansion layer and the second semiconductor layer; a first electrode, electrically connected to the two-dimensional current expansion layer. Further, the third semiconductor layer is an impurity semiconductor, the doping type of the third semiconductor is the same as the doping type of the second semiconductor, and the fourth semiconductor layer is an intrinsic semiconductor.

[0005] Furthermore, the thickness of the third semiconductor layer is 50nm-200nm, and the thickness of the fourth semiconductor layer is 50nm-200nm.

[0006] Furthermore, the light-emitting diode also includes a roughening layer arranged on the two-dimensional current spreading layer, the roughening layer has a second through hole that penetrates the first through hole, the current guiding structure is located in the first through hole and the second through hole, and the first electrode penetrates the roughening layer and the fourth semiconductor layer and is electrically connected to the two-dimensional current spreading layer.

[0007] Furthermore, the light emitting diode further comprises a bonding layer and a reflective structure arranged between the substrate and the epitaxial layer, wherein the bonding layer is located between the substrate and the reflective structure, and the reflective structure comprises a metal reflective layer located on a side of the substrate close to the epitaxial layer.

[0008] Furthermore, the reflective structure also includes: a dielectric layer, located between the metal reflective layer and the epitaxial layer, the dielectric layer includes a conductive part and an insulating part, the insulating part covers the surface of the metal reflective layer close to the epitaxial layer and has a plurality of third through holes passing through the insulating part, the plurality of conductive parts are respectively arranged in the plurality of third through holes, and each conductive part electrically connects the epitaxial layer and the metal reflective layer.

[0009] Furthermore, the light-emitting diode includes a step structure, which is located on the four edges of the light-emitting diode. The step structure runs through the roughening layer, the fourth semiconductor layer, the two-dimensional current spreading layer, the third semiconductor layer and the epitaxial layer. The lower step surface of the step structure is the surface of the reflective structure, and the upper step surface of the step structure is the surface of the roughening layer.

[0010] Furthermore, the light emitting diode further comprises a passivation layer arranged on the step structure, the passivation layer covers the roughening layer, the side wall and the lower step surface of the step structure, and the passivation layer has an opening to expose the surface of the first electrode.

[0011] Furthermore, the light emitting diode further includes a second electrode arranged on a side of the substrate away from the epitaxial layer.

[0012] Furthermore, the shape of the current guiding structure includes a cylinder or a prism; the current guiding structure includes a current guiding structure of a transparent conductive oxide structure or a metal structure.

[0013] The embodiment of the utility model provides a light-emitting diode, and the embodiment of the utility model discloses a light-emitting diode, which includes a substrate, an epitaxial layer, a third semiconductor layer, a fourth semiconductor layer, a two-dimensional current expansion layer, a current guiding structure, and a first electrode. The two-dimensional current expansion layer is formed between the third semiconductor layer and the fourth semiconductor layer and is electrically connected to the first electrode, and the current in the two-dimensional current expansion layer flows in a direction parallel to the surface of the epitaxial layer. The current guiding structure passes through the first through hole in the third semiconductor layer, the two-dimensional current expansion layer, and the fourth semiconductor layer to guide the current in the two-dimensional current expansion layer longitudinally to the epitaxial layer, so that the first electrode and the epitaxial layer are electrically connected through the two-dimensional current expansion layer and the current guiding structure. The embodiment of the utility model optimizes the current distribution, reduces the operating voltage of the light-emitting diode, reduces the absorption of light, and improves the luminous efficiency of the light-emitting diode by setting the current guiding structure and the two-dimensional current expansion layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and other purposes, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0015] Figure 1 is a cross-sectional view of a light emitting diode provided by an embodiment of the utility model;

[0016] Figure 2 is a cross-sectional view of another light emitting diode provided by an embodiment of the utility model;

[0017] Figure 3 It is a flow chart of a method for forming a light emitting diode provided by an embodiment of the utility model;

[0018] Figure 4-Figure 8 It is a schematic diagram of different stages of a light emitting diode provided by an embodiment of the utility model;

[0019] Fig. 9 It is a flow chart of another method for forming a light emitting diode provided by an embodiment of the utility model;

[0020] Fig.10 and 11 It is a schematic diagram of different stages of another light emitting diode provided by an embodiment of the utility model.

[0021] Description of reference numerals:

[0022] 110-temporary substrate; 120-substrate; 200-bonding layer;

[0023] 300-reflection structure; 310-metal reflection layer; 320-dielectric layer; 321-insulating part; 322-conductive part; 323-third through hole;

[0024] 400-epitaxial layer; 410-first semiconductor layer; 420-active layer; 430-second semiconductor layer;

[0025] 510 - two-dimensional current spreading layer; 520 - third semiconductor layer; 530 - fourth semiconductor layer; 540 - current guiding structure; 550 - first through hole;

[0026] 600-roughening layer; 610-second through hole;

[0027] 710-first electrode; 720-second electrode;

[0028] 800-passivation layer; 910-upper step surface; 920-lower step surface. DETAILED DESCRIPTION

[0029] The present application is described below based on embodiments, but the present application is not limited to these embodiments. In the detailed description of the present application below, some specific details are described in detail. It is possible for those skilled in the art to fully understand the present application without the description of these details. In order to avoid confusing the essence of the present application, known methods, processes, flows, components and circuits are not described in detail.

[0030] In addition, persons of ordinary skill in the art will appreciate that the drawings provided herein are for illustration purposes and are not necessarily drawn to scale.

[0031] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers.

[0032] For ease of explanation, spatially relative terms such as "inside", "outside", "below", "below", "lower", "above", "upper", etc. are used herein to describe the relationship of one element or feature illustrated in the figures to another element or feature. It will be understood that spatially relative terms may be intended to include different orientations of the device in use or operation other than the orientation depicted in the figures. For example, if the device in the figure is turned over, an element described as being "below" or "below" other elements or features will then be positioned as being "above" the other elements or features. Thus, the example term "below" can include both the orientations of above and below. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0033] Unless the context clearly requires otherwise, the words "include", "comprising" and similar words throughout the application should be interpreted as including rather than exclusive or exhaustive; that is, the meaning is "including but not limited to".

[0034] In the description of this application, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0035] Figure 1 is a cross-sectional view of a light emitting diode provided by an embodiment of the utility model, and the cross-sectional view corresponds to Figure 6The cross section at AA in the figure. The embodiment of the utility model provides a light-emitting diode, which includes a substrate 120, an epitaxial layer 400, a third semiconductor layer 520, a two-dimensional current spreading layer 510, a fourth semiconductor layer 530, a current guiding structure 540 and a first electrode 710. Among them, the epitaxial layer 400 includes a first semiconductor layer 410, an active layer 420 and a second semiconductor layer 430 stacked sequentially from bottom to top, and the first semiconductor layer 410 and the second semiconductor layer 430 have different doping types. The third semiconductor layer 520 and the fourth semiconductor layer 530 are sequentially arranged on the second semiconductor layer 430, the bandgap width of the third semiconductor layer 520 is greater than the bandgap width of the fourth semiconductor layer 530, and a two-dimensional current spreading layer 510 is formed between the third semiconductor layer 520 and the fourth semiconductor layer 530. The third semiconductor layer 520, the two-dimensional current spreading layer 510 and the fourth semiconductor layer 530 have a first through hole 550 exposing the second semiconductor layer 430, and the current guiding structure 540 is disposed in the first through hole 550, so that the current guiding structure 540 electrically connects the two-dimensional current spreading layer 510 and the second semiconductor layer 430. The electrons in the two-dimensional current spreading layer 510 are distributed in a two-dimensional direction parallel to the second semiconductor layer 430, and the current guiding structure 540 provides a longitudinal (vertical to the surface of the second semiconductor layer 430) barrier-free channel for the electrons that expand laterally (parallel to the surface direction of the second semiconductor layer 430) in the two-dimensional current spreading layer 510, and the electrons move from the two-dimensional current spreading layer 510 to the second semiconductor layer 430 through the current guiding structure 540, thereby achieving effective current expansion and reducing the operating voltage of the light-emitting diode.

[0036] In this embodiment, the second semiconductor layer 430, the third semiconductor layer 520 and the fourth semiconductor layer 530 are arranged in parallel on their opposite surfaces. The third semiconductor layer 520 is an impurity semiconductor, and the fourth semiconductor layer 530 is an intrinsic semiconductor. Donor impurities are doped in the third semiconductor layer 520, and the doping type of the third semiconductor layer 520 is the same as that of the second semiconductor layer 430. When the second semiconductor layer 430 is N-type doped, the third semiconductor layer 520 is also N-type doped. The N-type dopant may include Si or Te, and the doping concentration is 5*10E17 / cm 3 -1*10E18 / cm 3. The bandgap width of the third semiconductor layer 520 is greater than the bandgap width of the fourth semiconductor layer 530. The third semiconductor layer 520 is made of a wide bandgap material, such as AlGaInP, AlGaN, and AlGaAs, and the fourth semiconductor layer 530 is made of a narrow bandgap material, such as GaAs and GaN. A triangular potential well is formed at the interface of semiconductors with different bandgap widths. When the third semiconductor layer 520 and the fourth semiconductor layer 530 are stacked, the electrons in the third semiconductor layer 520 with a higher Fermi energy level will be released to the fourth semiconductor layer 530 with a lower Fermi energy level, so that only positive charges are left in the third semiconductor layer 520. Due to the change in charge, an electrostatic potential is generated, which causes energy band bending. As the Fermi energy level at the interface between the third semiconductor layer 520 and the fourth semiconductor layer 530 matches, the Fermi energy levels of the third semiconductor layer 520 and the fourth semiconductor layer 530 tend to be consistent. The electrons are restricted to move in the narrow potential well of the fourth semiconductor layer 530, and a two-dimensional electron gas (2DEG) is formed on the interface between the third semiconductor layer 520 and the fourth semiconductor layer 530, that is, the two-dimensional current expansion layer 510. The two-dimensional current expansion layer 510 is located between the third semiconductor layer 520 and the fourth semiconductor layer 530. The movement of electrons in the two-dimensional current expansion layer 510 in a direction perpendicular to the surface of the second semiconductor layer 430 is restricted, and the electrons can only move freely in a two-dimensional space parallel to the surface of the second semiconductor layer 430, and have a higher migration efficiency in a direction parallel to the plane of the second semiconductor layer.

[0037] The two-dimensional current spreading layer 510 is located between the third semiconductor layer 520 and the fourth semiconductor layer 530. The thickness of the third semiconductor layer 520, the two-dimensional current spreading layer 510 and the fourth semiconductor layer 530 is thinner than that of a general current spreading layer, so that when the light emitting diode emits light, the third semiconductor layer 520, the two-dimensional current spreading layer 510 and the fourth semiconductor layer 530 absorb less light than a general current spreading layer, thereby improving the light emitting efficiency of the light emitting diode.

[0038] The two-dimensional current expansion layer 510 forms a barrier for the longitudinal conduction of electrons, and thus the propagation of electrons in the direction perpendicular to the surface of the second semiconductor layer 430 requires an additional voltage, resulting in an increase in the operating voltage of the light-emitting diode and a decrease in efficiency. The current guiding structure 540 forms an ohmic contact with the second semiconductor layer 430, and electrons are longitudinally conducted through the current guiding structure 540. Specifically, the first through hole 550 penetrates the fourth semiconductor layer 530, the two-dimensional current expansion layer 510 and the third semiconductor layer 520, and the current guiding structure 540 is arranged in the first through hole 550 and contacts the third semiconductor layer 520 and the fourth semiconductor layer 530 respectively. The current guiding structure 540 includes a transparent conductive oxide structure or a metal structure. The current guiding structure 540 is arranged one-to-one with the first through hole 550, and the current guiding structure 540 is electrically connected to the two-dimensional current expansion layer 510 and the second semiconductor layer 430. The first through hole 550 is a through hole in the shape of a cylinder, a prism or other columnar structure, the current guiding structure 540 is a cylinder, a prism or other columnar structure, and the cross-sectional shape of the current guiding structure 540 in the vertical axis direction matches the opening shape of the first through hole 550, that is, the current guiding structure 540 fills the first through hole 550. In this embodiment, the axis of the first through hole 550 is perpendicular to the surface of the second semiconductor layer 430, so that the current guiding structure 540 arranged in the first through hole 550 is perpendicular to the surface of the second semiconductor layer 430, and then the current guiding structure 540 provides electrons with a movement space perpendicular to the surface of the second semiconductor layer 430. After the electrons enter the two-dimensional current expansion layer 510 from the first electrode 710, they move in the lateral direction, and after entering the current guiding structure 540, they move in the longitudinal direction. It should be noted that the longitudinal direction here refers to the direction perpendicular to the second semiconductor layer 430, and the lateral direction is perpendicular to the longitudinal direction.

[0039] The light emitting diode may further include a roughening layer 600 disposed on the fourth semiconductor layer 530, and the side of the roughening layer 600 away from the fourth semiconductor layer 530 has a rough surface, thereby improving the light emitting efficiency of the light emitting diode. The roughening layer 600 has a second through hole 610 that penetrates the first through hole 550, and the current guiding structure 540 also fills the second through hole 610. That is, the current guiding structure 540 passes through the roughening layer 600, the fourth semiconductor layer 530, the two-dimensional current spreading layer 510, the third semiconductor layer 520, and is electrically connected to the second semiconductor layer 430. Figure 6 As shown, in this embodiment, the mutually interpenetrating first through holes 550 and second through holes 610 are arranged in an array avoiding the first electrode 710. In some embodiments, the mutually interpenetrating first through holes 550 and second through holes 610 are arranged in a certain order, and the specific arrangement form is selected according to the actual use scenario or needs, and is not limited here.

[0040] like Figure 1As shown, the light emitting diode is a light emitting diode of reverse polarity structure. In the present embodiment, the first semiconductor layer 410 is P-type doped, and the second semiconductor layer 430 is N-type doped. The reverse polarity light emitting diode also includes a reflective structure 300 and a bonding layer 200 arranged on the side of the epitaxial layer 400 away from the first electrode 710, and the bonding layer 200 bonds the substrate 120 and the reflective structure 300. Specifically, a temporary substrate 110 is first provided, and a roughening layer 600, a fourth semiconductor layer 530, a third semiconductor layer 520, an epitaxial layer 400 and a reflective structure 300 are sequentially formed on the temporary substrate 110, and then a substrate 120 is provided and the substrate 120 and the reflective structure 300 are bonded and connected using the bonding layer 200.

[0041] The reverse polarity light emitting diode has a reflective structure 300, and the reflective structure 300 includes a metal reflective layer 310 and a dielectric layer 320 stacked in sequence. The metal reflective layer 310 is located on the bonding layer 200. The dielectric layer 320 is located between the metal reflective layer 310 and the epitaxial layer 400. The dielectric layer 320 includes a conductive portion 322 and an insulating portion 321, the insulating portion 321 covers the surface of the metal reflective layer 310 close to the first semiconductor layer 410 and has a plurality of third through holes 323 penetrating the insulating portion 321, and a plurality of conductive portions 322 are respectively arranged in the plurality of third through holes 323 and conduct the metal reflective layer 310 and the epitaxial layer 400. In this embodiment, the plurality of third through holes 323 are arranged in an array, and the conductive portions 322 are filled in the third through holes 323. In some embodiments, the conductive portions 322 cover the sidewalls of the third through holes 323 and the surface of the epitaxial layer 400 exposed by the third through holes 323. In other embodiments, the conductive portion 322 may also cover the surface of the insulating portion 321 close to the metal reflective layer 310 to increase the adhesion between the insulating portion 321 and the metal reflective layer 310 and improve the reliability of the light emitting diode.

[0042] The insulating part 321 is made of an inorganic non-metallic material with a low refractive index, and the conductive part 322 is a transparent conductive oxide, thereby forming an ohmic contact with the epitaxial layer 400. Preferably, the insulating part 321 is formed of a material with a lower refractive index than the first semiconductor layer 410, and a material with a transmittance of more than 90% for visible light waves is selected to form the insulating part 321, thereby improving the reflective ability of the reflective structure 300. The metal reflective layer 310 and the dielectric layer 320 form an ODR (omni-directional reflector). When the light-emitting diode is turned on, the active layer 420 emits light, and the light toward the substrate 120 is reflected by the reflective structure 300 and emitted from the side away from the substrate 120, thereby improving the light intensity of the light-emitting diode and ensuring that the light-emitting diode emits light from the front (i.e., emitted from the side away from the substrate 120).

[0043] In some embodiments, the reflective structure 300 is a metal reflector and only includes a metal reflective layer 310 , which is located between the bonding layer 200 and the epitaxial layer 400 .

[0044] Furthermore, the light emitting diode includes a step structure, which is located at the edges of the light emitting diode, and the step structure penetrates the roughening layer 600, the fourth semiconductor layer 530, the two-dimensional current spreading layer 510, the third semiconductor layer 520 and the epitaxial layer 400, and the lower step surface 920 of the step structure is the surface of the dielectric layer 320, and the upper step surface 910 of the step structure is the surface of the roughening layer 600. Figure 6 As shown, since the side of the roughened layer 600 away from the substrate 120 has a rough surface, the upper step surface 910 has a rough surface.

[0045] The light emitting diode further includes a passivation layer 800 disposed on the step structure and the roughening layer 600 . The passivation layer 800 covers the roughening layer 600 , the sidewall of the step structure and the dielectric layer 320 of the lower step surface 920 . The passivation layer 800 has an opening to expose the surface of the first electrode 710 .

[0046] In this embodiment, the first electrode 710 is disposed on a side of the roughening layer 600 away from the substrate 120, and the first electrode 710 passes through the passivation layer 800, the roughening layer 600, and the fourth semiconductor layer 530 to connect with the two-dimensional current spreading layer 510, that is, the passivation layer 800, the roughening layer 600, and the fourth semiconductor layer 530 wrap part of the side wall of the first electrode 710, and the first electrode 710 does not penetrate the two-dimensional current spreading layer 510. The first electrode 710 injects electrons into the two-dimensional current spreading layer 510. The first electrode 710 is made of metal, and preferably, the first electrode 710 is Au, AuGe alloy, etc., which is convenient for subsequent welding connection with bonding wires. Figure 6 and Figure 7 As shown, the first electrode 710 is a columnar structure, such as a cylinder or a prism. The cross-sectional shape of the first electrode 710 perpendicular to the axis is set according to actual use scenarios or needs.

[0047] The light emitting diode further includes a second electrode 720 disposed opposite to the first electrode 710 . The second electrode 720 is disposed on a side of the substrate 120 away from the bonding layer 200 . That is, the second electrode 720 is a sheet structure covering a side of the substrate 120 away from the bonding layer 200 .

[0048] In some embodiments, the light emitting diode is only provided with the first electrode 710 , and the first electrode 710 is provided on both sides of the light emitting diode opposite to the substrate 120 , and the light emitting diode directly uses the substrate 120 as the second electrode.

[0049] When the first electrode 710 and the substrate 120 are connected, or the first electrode 710 and the second electrode 720 are connected, the electrons move from the first electrode 710 to the two-dimensional current expansion layer 510, and the electrons expand laterally from the two-dimensional current expansion layer 510 into the current guiding structure 540 and cross the electron potential barrier of longitudinal propagation, and guide the electrons to the epitaxial layer 400. The current guiding structure 540 and the two-dimensional current expansion layer 510 together make the electrons uniformly expand and transmit to the second semiconductor layer 430, the active layer 420, the first semiconductor layer 410 and the substrate 120. The embodiment of the utility model controls the distribution of the current guiding structure 540 so that the epitaxial layer 400 emits light uniformly, thereby improving the working efficiency of the light-emitting diode.

[0050] Figure 3 1 is a flow chart of a method for forming a light emitting diode provided by an embodiment of the present utility model. The method for forming a light emitting diode comprises the following steps:

[0051] Step S100: providing a temporary substrate, and forming a roughening layer, a fourth semiconductor layer, a third semiconductor layer, an epitaxial layer and a reflective structure on the temporary substrate.

[0052] Step S200: providing a substrate, bonding the substrate and the reflective structure, and removing the temporary substrate.

[0053] Step S300: forming a first electrode and a current guiding structure.

[0054] Step S400: forming a step structure.

[0055] Step S500: forming a passivation layer.

[0056] Figure 4-Figure 8 Schematic diagram of different stages of a light emitting diode provided by an embodiment of the utility model. Figure 7 and Figure 8 The top view and the cross-sectional view correspond to each other.

[0057] In step S100, a temporary substrate 110 is provided, and a roughened layer 600, a fourth semiconductor layer 530, a third semiconductor layer 520, an epitaxial layer 400 and a reflective structure 300 are formed on the temporary substrate 110. Figure 5 Specifically, step S100 includes:

[0058] Step S110: providing a temporary substrate.

[0059] The temporary substrate 110 provides temporary assistance and support for the semiconductor structure to be formed subsequently. The temporary substrate 110 can be made of GaAs or other materials.

[0060] Step S120: forming a roughening layer, a fourth semiconductor layer, a third semiconductor layer and an epitaxial layer on the temporary substrate, such as Figure 4 shown.

[0061] The roughened layer 600 is Al x Ga 1-x As (x ranges from 0.2 to 0.4), AlGaInP and other materials, but not limited to the above materials. Preferably, the roughening layer 600 is lightly doped. In this embodiment, the thickness of the roughening layer 600 is 1 μm-3 μm, but not limited to this thickness range. The user can set the material and thickness of the roughening layer 600 according to the actual use scenario or needs.

[0062] The fourth semiconductor layer 530 is made of GaAs, GaN and other materials, and the third semiconductor layer 520 is made of AlGaInP, AlGaN, AlGaAs and other materials. The material of the third semiconductor layer 520 is selected according to the light emitting wavelength of the light emitting diode. The third semiconductor layer 520 is doped with N-type dopants, such as Si or Te, and the fourth semiconductor layer 530 is not doped. In this embodiment, the thickness of the third semiconductor layer 520 is 50nm-200nm, and the thickness of the fourth semiconductor layer 530 is 50nm-200nm.

[0063] When the fourth semiconductor layer 530 and the third semiconductor layer 520 are sequentially stacked on the roughening layer 600, the electrons in the wide bandgap third semiconductor layer 520 move to the narrow bandgap fourth semiconductor layer 530 so that the Fermi levels of the two can reach the same level. All electrons are confined to move in the narrow potential well of the fourth semiconductor layer 530, and a two-dimensional current expansion layer 510 is formed on the interface between the third semiconductor layer 520 and the fourth semiconductor layer 530.

[0064] The epitaxial layer 400 includes a second semiconductor layer 430, an active layer 420, and a first semiconductor layer 410 stacked sequentially from bottom to top on the third semiconductor layer 520, and the first semiconductor layer 410 and the second semiconductor layer 430 have different doping types. In this embodiment, the first semiconductor layer 410 is P-type doped, and the second semiconductor layer 430 is N-type doped. The active layer 420 can be a single quantum well or a multiple quantum well.

[0065] When the reflective structure 300 includes a metal reflective layer 310 and a dielectric layer 320 stacked in sequence, the following steps are performed after step S120:

[0066] Step S130: evaporating insulating material.

[0067] The insulating material is an inorganic non-metallic material with a low refractive index, such as one or a combination of silicon dioxide (SiO2), magnesium fluoride (MgF2), gallium fluoride (GaF2), silicon nitride (Si3N4), aluminum oxide (Al2O3), zinc oxide (ZnO) or gallium oxide (Ga2O3), but is not limited to the above materials. Preferably, the insulating material has a light transmittance of more than 90% in the visible light band, and the refractive index of the insulating material is lower than the refractive index of the first semiconductor layer 410. The insulating material can be formed by any deposition technology known to those skilled in the art. Preferably, an evaporation process is used.

[0068] Step S140: etching the insulating material.

[0069] A photoresist is coated on the insulating material, and then the photoresist in a specific area is cured through a series of steps such as exposure and development to form a patterned first mask layer. An etching technique is used to etch part of the insulating material to form an insulating portion 321 having a third through hole 323. Preferably, a plurality of third through holes 323 are arranged in an array in the insulating portion 321. After the etching is completed, the first mask layer is removed.

[0070] Step S150: forming a conductive portion.

[0071] The material of the conductive portion 322 may be a transparent conductive oxide, such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc tin oxide (AZO), but is not limited to the above materials. The conductive portion 322 is filled in the third through hole 323 and forms an ohmic contact with the first semiconductor layer 410. Alternatively, the conductive portion 322 covers the sidewall and bottom of the third through hole 323 and forms an ohmic contact with the first semiconductor layer 410. In some embodiments, part of the conductive portion 322 extends and covers the surface of the insulating portion 321, that is, part of the conductive portion 322 is disposed between the insulating portion 321 and the subsequently disposed metal reflective layer 310.

[0072] Step S160: forming a metal reflective layer, such as Figure 5 shown.

[0073] The metal reflective layer 310 may include but is not limited to silver (Ag), aluminum (Al), gold (Au), preferably silver (Ag). The metal reflective layer 310 may be formed by any technique known to those skilled in the art. Preferably, physical vapor deposition (PVD) is used, and magnetron sputtering (Sputter), electron beam evaporation (E-beam), etc. may also be used. The metal reflective layer 310 covers the dielectric layer 320 and the conductive portion 322. When the conductive portion 322 does not completely fill the third through hole 323, the metal reflective layer 310 fills the third through hole 323.

[0074] When the reflective structure 300 is a metal reflector, step S100 does not include the above steps S130 to S160, but is performed after step S120:

[0075] Step S131 : depositing a reflective structure.

[0076] The reflective structure 300 can be formed by any technique known to those skilled in the art. The reflective structure 300 can include but is not limited to metal materials such as Ag, Al, Au, etc. The reflective structure 300 is directly disposed on the surface of the epitaxial layer 400 away from the roughened layer 600.

[0077] In some embodiments, between step S110 and step S120, the following steps are further included:

[0078] Step S101: forming a buffer layer and / or an etching stop layer on a temporary substrate.

[0079] The material of the buffer layer can be GaAs or other materials. The buffer layer is arranged on the temporary substrate 110 to reduce the stress caused by lattice mismatch and improve the crystal quality of the semiconductor structure grown subsequently. The corrosion cutoff layer can prevent the roughening layer 600 and other structures from being corroded when the temporary bottom 110 is removed. The user can also form other structures between the temporary substrate 110 and the roughening layer 600 according to the actual use scenario or needs to improve the performance of the light-emitting diode.

[0080] Step S200: provide a substrate, bond the substrate to the reflective structure, and remove the temporary substrate. Figure 6 Specifically, step S200 includes:

[0081] Step S210: providing a substrate.

[0082] The substrate 120 is made of a conductive material, preferably a conductive material with high thermal conductivity. The substrate 120 may be a heavily doped semiconductor material or a metal material. Specifically, the heavily doped semiconductor may be a combination of one or more of a Si substrate and a Ge substrate, and the metal may be a combination of one or more of a Cu substrate and a Mo substrate. The material of the substrate 120 may be selected according to the actual use scenario or needs. The thickness of the substrate 120 may be 100 μm-500 μm, but is not limited to the above thickness.

[0083] Step S220: forming a bonding layer on the substrate.

[0084] The bonding layer 200 can be formed by any technique known to those skilled in the art. The bonding layer 200 is used to bond the reflective structure 300 and the substrate 120 .

[0085] Step S230: removing the temporary substrate, such as Figure 6 shown.

[0086] The temporary substrate 110 is removed using any technique known to those skilled in the art, such as wet etching or dry etching.

[0087] Step S300: forming a first electrode and a current guiding structure. Specifically, step S300 includes:

[0088] Step S310: etching the roughening layer and the fourth semiconductor layer to form an opening.

[0089] A photoresist is coated on the roughening layer 600, and then the photoresist in a specific area is cured through a series of steps such as exposure and development to form a patterned second mask layer. The roughening layer 600 and the fourth semiconductor layer 530 are etched using an etching process.

[0090] Step S320: forming a first electrode.

[0091] The first electrode 710 may be Au or AuGe alloy, but is not limited thereto. The first electrode 710 may be formed by any technique known to those skilled in the art. The first electrode 710 is evaporated in the opening and electrically connected to the two-dimensional current spreading layer 510 exposed from the opening.

[0092] Specifically, a metal layer is evaporated on the second mask layer, and then the second mask layer and the metal layer on the second mask layer are removed by a metal lift-off technique to form an opening and a first electrode 710 disposed in the opening.

[0093] Step S330 , etching the roughening layer, the fourth semiconductor layer, the two-dimensional current spreading layer, and the third semiconductor layer to form a first through hole and a second through hole.

[0094] A photoresist is coated on the roughening layer 600 and the first electrode 710, and then the photoresist in a specific area is cured through a series of steps such as exposure and development to form a patterned third mask layer. The roughening layer 600, the fourth semiconductor layer 530, the two-dimensional current spreading layer 510 and the third semiconductor layer 520 are etched by an etching process. After the etching is completed, the third mask layer is removed to form a first through hole 550 and a second through hole 610 exposing the second semiconductor layer 430.

[0095] Step S340: forming a current guiding structure. Figure 7 and Figure 8 shown.

[0096] The current guiding structure 540 includes a transparent conductive oxide structure or a metal structure, and the transparent conductive oxide is such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc tin oxide (AZO), but is not limited to the above materials. The use of transparent conductive oxide can reduce the absorption of light, which is beneficial to improve the luminous efficiency of the light-emitting diode. The current guiding structure 540 can be formed by any technology known to those skilled in the art, and is preferably set by sputtering. The current guiding structure 540 is arranged in the first through hole 550 and the second through hole 610, and the current guiding structure 540 is electrically connected to the second semiconductor layer 430 and the two-dimensional current expansion layer 510 exposed from the first through hole 550 and the second through hole 610.

[0097] In this embodiment, step S310 and step S320 are performed first, and then step S330 and step S340 are performed. In some embodiments, step S330 and step S340 may be performed first, and then step S310 and step S320. That is, the formation order of the first electrode 710 and the current guiding structure 540 may be set according to the actual scene or need.

[0098] Step S350, roughening the surface of the roughening layer.

[0099] A photoresist is coated on the first electrode 710 and the current guiding structure 540, and then a series of steps such as exposure and development are performed to cure the photoresist in a specific area to form a patterned fourth mask layer. The exposed surface of the roughening layer 600 is roughened by any technique known to those skilled in the art, preferably by wet roughening. After the roughening is completed, the fourth mask layer is removed.

[0100] Step S400: forming a step structure.

[0101] Specifically, a photoresist is coated on the front side of the light-emitting diode (the surface of the roughening layer 600 and the first electrode 710), and then the photoresist in a specific area is cured through a series of steps such as exposure and development to form a patterned fifth mask layer. The roughening layer 600, the fourth semiconductor layer 530, the two-dimensional current spreading layer 510, the third semiconductor layer 520, the second semiconductor layer 430, the active layer 420 and the first semiconductor layer 410 are etched by an etching process to expose the surface of the dielectric layer 320. After the etching is completed, the remaining fifth mask layer is removed to form a cutting path. After the wafer is subsequently separated into a plurality of light-emitting diode dies along the cutting path, the edges of the four sides of the die of each light-emitting diode have a step structure, and the lower step surface 920 located on the surface of the dielectric layer 320 and the upper step surface 910 located on the surface of the roughening layer 600 constitute a step structure.

[0102] Step S500: forming a passivation layer, such as Figure 1 shown.

[0103] An evaporation process is performed to cover the surface of the roughening layer 600, the step structure and the first electrode 710 with a passivation layer 800. Then, a photoresist is coated on the surface of the passivation layer 800, and then the photoresist in a specific area is cured through a series of steps such as exposure and development to form a patterned sixth mask layer. The passivation layer 800 is etched by an etching process to form an opening, and the sixth mask layer is removed after the etching is completed, so that the first electrode 710 is exposed from the opening of the passivation layer 800. Finally, the wafer is separated into a plurality of light-emitting diode dies along the cutting path.

[0104] When the light emitting diode needs to be provided with a second electrode 720, before "dividing the wafer into a plurality of light emitting diode dies along the dicing road", the following steps are also included:

[0105] Step S600: forming a second electrode.

[0106] The second electrode 720 can be formed by any technique known to those skilled in the art. The second electrode 720 covers the side of the substrate 120 away from the bonding layer 200 .

[0107] Figure 2 FIG. 1 is a cross-sectional view of another light emitting diode provided by an embodiment of the utility model. In this embodiment, the light emitting diode has a positive polarity structure. Figure 2 As shown, the positive polarity light emitting diode has the same third semiconductor layer 520, two-dimensional current spreading layer 510, fourth semiconductor layer 530, current guiding structure 540, roughening layer 600 and first electrode as the reverse polarity light emitting diode. The positive polarity light emitting diode is not provided with a reflective structure 300 and a bonding layer 200. In the positive polarity light emitting diode, the first semiconductor layer 410 disposed close to the substrate 120 has an N-type doping, and the second semiconductor layer 430 disposed away from the substrate 120 has a P-type doping. Therefore, the fourth semiconductor disposed on one side of the second semiconductor layer 430 also has a P-type doping. In addition, the positive polarity light emitting diode does not have a step structure, and the passivation layer 800 only covers the surface of the roughening layer 600 on the side away from the substrate 120. In the process of manufacturing the positive polarity light emitting diode, there is no need to form a temporary substrate 100, but directly provide a substrate 120 and sequentially form structures such as an epitaxial layer 400, a third semiconductor layer 520, and a fourth semiconductor layer 530 on the substrate 120.

[0108] Fig. 9 1 is a flow chart of another method for forming a light emitting diode provided by an embodiment of the present invention. The method for forming a light emitting diode comprises the following steps:

[0109] Step S100a: providing a substrate, and forming an epitaxial layer, a third semiconductor layer, a fourth semiconductor layer and a roughening layer on the substrate.

[0110] Step S200a: forming a first electrode and a current guiding structure.

[0111] Step S300a: forming a passivation layer.

[0112] Fig.10 and Fig.11 It is a schematic diagram of different stages of another light emitting diode provided by an embodiment of the utility model.

[0113] Step S100a, providing a substrate, and forming an epitaxial layer, a third semiconductor layer, a fourth semiconductor layer and a roughening layer on the substrate. Fig.10 shown.

[0114] Specifically, step S100a includes:

[0115] Step S110a: providing a substrate.

[0116] The substrate 120 is made of a conductive material, preferably a conductive material with high thermal conductivity. The substrate 120 may be a heavily doped semiconductor material or a metal material. Specifically, the heavily doped semiconductor may be a combination of one or more of a Si substrate and a Ge substrate, and the metal may be a combination of one or more of a Cu substrate and a Mo substrate. The material of the substrate 120 may be selected according to the actual use scenario or needs. The thickness of the substrate 120 may be 100 μm-500 μm, but is not limited to the above thickness.

[0117] Step S120a, forming an epitaxial layer.

[0118] The epitaxial layer 400 includes a first semiconductor layer 410, an active layer 420, and a second semiconductor layer 430 stacked sequentially from bottom to top on the substrate 120, and the first semiconductor layer 410 and the second semiconductor layer 430 have different doping types. In this embodiment, the first semiconductor layer 410 is N-type doped, and the second semiconductor layer 430 is P-type doped. The active layer 420 can be a single quantum well or a multiple quantum well.

[0119] Step S130a: forming a third semiconductor layer and a fourth semiconductor layer.

[0120] A third semiconductor layer 520 and a fourth semiconductor layer 530 are sequentially formed on the epitaxial layer 400. A two-dimensional current spreading layer 510 is formed between the third semiconductor layer 520 and the fourth semiconductor layer 530.

[0121] The fourth semiconductor layer 530 is made of materials such as GaAs and GaN, and the third semiconductor layer 520 is made of materials such as AlGaInP, AlGaN, and AlGaAs. The material of the third semiconductor layer 520 is selected according to the light emitting wavelength of the light emitting diode. The third semiconductor layer 520 is doped with P-type dopants, and the fourth semiconductor layer 530 is not doped. In this embodiment, the thickness of the third semiconductor layer 520 is 50nm-200nm, and the thickness of the fourth semiconductor layer 530 is 50nm-200nm.

[0122] When the fourth semiconductor layer 530 and the third semiconductor layer 520 are sequentially stacked on the roughening layer 600, the electrons in the wide bandgap third semiconductor layer 520 move to the narrow bandgap fourth semiconductor layer 530 so that the Fermi levels of the two can reach the same level. All electrons are confined to move in the narrow potential well of the fourth semiconductor layer 530, and a two-dimensional current expansion layer 510 is formed on the interface between the third semiconductor layer 520 and the fourth semiconductor layer 530.

[0123] Step S140a, forming a roughening layer, such as Fig.10 shown.

[0124] The roughened layer 600 is Al x Ga 1-x As (x ranges from 0.2 to 0.4), AlGaInP and other materials, but not limited to the above materials. Preferably, the roughening layer 600 is lightly doped. In this embodiment, the thickness of the roughening layer 600 is 1 μm-3 μm, but not limited to this thickness range. The user can set the material and thickness of the roughening layer 600 according to the actual use scenario or needs.

[0125] Step S200a, forming a first electrode and a current guiding structure, such as Fig.11 shown.

[0126] Step S200a is the same as the aforementioned step S300.

[0127] Step S300a, forming a passivation layer, such as Figure 2 shown.

[0128] Step S300a is similar to the aforementioned step S500 , and the passivation layer formed in step S300a only needs to cover the surface of the roughening layer 600 away from the surface having the roughening structure. That is, the passivation layer 800 only covers the surface of the roughening layer 600 away from the substrate 120 .

[0129] When the light emitting diode needs to be provided with a second electrode 720, it also includes:

[0130] Step S400a: forming a second electrode.

[0131] The second electrode 720 can be formed by any technique known to those skilled in the art. The second electrode 720 covers the side of the substrate 120 away from the epitaxial layer 400 .

[0132] The utility model embodiment discloses a light-emitting diode, which includes a substrate, an epitaxial layer, a third semiconductor layer, a fourth semiconductor layer, a two-dimensional current expansion layer, a current guiding structure and a first electrode. The two-dimensional current expansion layer is formed between the third semiconductor layer and the fourth semiconductor layer and is electrically connected to the first electrode, and the current in the two-dimensional current expansion layer flows in a direction parallel to the surface of the epitaxial layer. The current guiding structure passes through the first through hole in the third semiconductor layer, the two-dimensional current expansion layer and the fourth semiconductor layer to guide the current in the two-dimensional current expansion layer longitudinally to the epitaxial layer, so that the first electrode and the epitaxial layer are electrically connected through the two-dimensional current expansion layer and the current guiding structure. The utility model embodiment optimizes the current distribution, reduces the operating voltage of the light-emitting diode, reduces the absorption of light, and improves the luminous efficiency of the light-emitting diode by setting the current guiding structure and the two-dimensional current expansion layer.

[0133] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A light emitting diode, characterized in that: The light emitting diode comprises: substrate; an epitaxial layer, located on the substrate, the epitaxial layer comprising a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence from bottom to top, the first semiconductor layer and the second semiconductor layer having different doping types; a third semiconductor layer, located on the second semiconductor layer; a fourth semiconductor layer, located on the third semiconductor layer, wherein the bandgap width of the third semiconductor layer is greater than the bandgap width of the fourth semiconductor layer; a two-dimensional current spreading layer, located between the third semiconductor layer and the fourth semiconductor layer, wherein the current in the two-dimensional current spreading layer flows in a direction parallel to the surface of the second semiconductor layer, and a plurality of first through holes penetrate the third semiconductor layer, the two-dimensional current spreading layer and the fourth semiconductor layer; a plurality of current guiding structures, disposed in the first through hole, the current guiding structures electrically connecting the two-dimensional current spreading layer and the second semiconductor layer; The first electrode is electrically connected to the two-dimensional current spreading layer.

2. The light emitting diode according to claim 1, characterized in that: The third semiconductor layer is an impurity semiconductor, the doping type of the third semiconductor is the same as the doping type of the second semiconductor, and the fourth semiconductor layer is an intrinsic semiconductor.

3. The light emitting diode according to claim 2, characterized in that: The thickness of the third semiconductor layer is 50nm-200nm, and the thickness of the fourth semiconductor layer is 50nm-200nm.

4. The light emitting diode according to claim 1, characterized in that: The light-emitting diode also includes a roughening layer arranged on the two-dimensional current spreading layer, the roughening layer has a second through hole that penetrates the first through hole, the current guiding structure is located in the first through hole and the second through hole, and the first electrode penetrates the roughening layer and the fourth semiconductor layer and is electrically connected to the two-dimensional current spreading layer.

5. The light emitting diode according to claim 4, characterized in that: The light emitting diode further comprises a bonding layer and a reflective structure arranged between the substrate and the epitaxial layer. The bonding layer is located between the substrate and the reflective structure. The reflective structure comprises a metal reflective layer located on a side of the substrate close to the epitaxial layer.

6. The light emitting diode according to claim 5, characterized in that: The reflective structure further comprises: A dielectric layer is located between the metal reflective layer and the epitaxial layer, the dielectric layer includes a conductive portion and an insulating portion, the insulating portion covers the surface of the metal reflective layer close to the epitaxial layer and has a plurality of third through holes penetrating the insulating portion, the plurality of conductive portions are respectively arranged in the plurality of third through holes, and each of the conductive portions electrically connects the epitaxial layer and the metal reflective layer.

7. The light emitting diode according to claim 5 or 6, characterized in that: The light-emitting diode includes a step structure, which is located at the edges of the light-emitting diode. The step structure runs through the roughening layer, the fourth semiconductor layer, the two-dimensional current spreading layer, the third semiconductor layer and the epitaxial layer. The lower step surface of the step structure is the surface of the reflective structure, and the upper step surface of the step structure is the surface of the roughening layer.

8. The light emitting diode according to claim 7, characterized in that: The light emitting diode further comprises a passivation layer disposed on the step structure, the passivation layer covers the roughening layer, the sidewall of the step structure and the lower step surface, and the passivation layer has an opening to expose the surface of the first electrode.

9. The light emitting diode according to claim 1, characterized in that: The light emitting diode further includes a second electrode disposed on a side of the substrate away from the epitaxial layer.

10. The light emitting diode according to claim 1, characterized in that: The shape of the current guiding structure includes a cylinder or a prism; the current guiding structure includes a current guiding structure of a transparent conductive oxide structure or a metal structure.

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