TW202125847A - Light-emitting diode - Google Patents

Abstract

A light-emitting diode is provided, including an epitaxial stack and a reflective layer. The epitaxial stack has a first upper surface. The reflective layer has an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface. From a cross-sectional view of the light-emitting diode, the reflective layer includes a thicker area and a thinner area. The side surface of the reflective layer is inclined outward from the upper surface to the lower surface to form the thinner area. The reflective layer has a first thickness between the upper surface and the lower surface and a second thickness between the side surface and the lower surface. The second thickness is smaller than the first thickness.

Description

Light-emitting diode

The present invention relates to light-emitting diodes, in particular to light-emitting diodes with high reflectivity and/or high thermal stability.

In the existing light-emitting diode structure, the metal reflective layer used to reflect light is generally formed by coating. However, the thickness of the metal reflective layer in the light-emitting diode structure will vary in the same metal reflective layer due to the coating method. There are differences in thickness. Since the reflectivity of the metal reflective layer is related to its thickness, designing a metal reflective layer suitable for reflecting light from the light-emitting diode is one of the goals of research and development by those skilled in the art.

In view of the foregoing, the present invention proposes a light emitting diode to improve the light extraction efficiency of the light emitting diode.

An embodiment of the present invention provides a light emitting diode, which includes: an epitaxial stack having a first upper surface; and a reflective layer disposed on the epitaxial stack and including a thick region and a thin region. The reflective layer has an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, and the upper surface is a surface farther from the epitaxial stack than the lower surface. The thin area has a width. From a plan view, the first upper surface of the epitaxial stack has a first area, the upper surface of the thick region of the reflective layer has a second area, and the lower surface has a third area. Among them, the first area>the third area>the second area, and satisfies a range: 0.9 <(third area/first area)<0.999 and 0.001<((third area-second area)/third area) <0.006.

Another embodiment of the present invention provides a light emitting diode, which includes: an epitaxial stack, which is disposed on a substrate and has a first upper surface; and a reflective layer, which is disposed on the epitaxial stack and includes a thick region And a thin area. The reflective layer has an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, and the upper surface is farther from the first upper surface than the lower surface. Wherein, the upper surface and the lower surface have a first thickness to form a thick zone, and the side surface and the lower surface have a second thickness to form a thin zone, and the second thickness is smaller than the first thickness. The thin area has a width. Wherein, the thin area further has a critical interval, and the second thickness between the critical intervals has a critical reflectivity equal to or greater than 90%, and satisfies a range: 0<(critical interval/width)<0.5.

Hereinafter, referring to the drawings, the concept of the present invention is explained with exemplary embodiments. The drawings are drawn for ease of understanding, and the thickness and shape of each layer in the drawings are not the actual size or proportional relationship of the components. It should be noted that elements not shown in the drawings or described in the specification can be in the form known to those with ordinary knowledge in the technical field to which the invention belongs.

Please refer to Fig. 1, which is a schematic cross-sectional view of a light-emitting diode 1 according to an embodiment of the present invention; Fig. 2 is a schematic top view of a light-emitting diode 1; Fig. 3 is a light-emitting diode 1 shown in Fig. 1 An enlarged view of the local area 100. As shown in FIG. 1, the light emitting diode 1 of the present invention includes a substrate 106, an epitaxial stack 10, and a reflective layer 20 in this order. Among them, the epitaxial stack 10 includes a first semiconductor layer 102, a light emitting layer 103, and a second semiconductor layer 104, and includes a first upper surface 11. Preferably, there is a buffer layer 105 between the substrate 106 and the second semiconductor layer 104. The reflective layer 20 is located on the epitaxial stack 10 and includes an upper surface 21 away from the epitaxial stack 10, a lower surface 22 adjacent to the epitaxial stack 10, and a side surface 23 connecting the upper surface 21 and the lower surface 22. The lower surface 22 of the reflective layer 20 is in contact with the first upper surface 11 of the epitaxial stack 10. In another embodiment, the first protective layer 30 is located on the reflective layer 20 and covers the periphery of the reflective layer 20.

The substrate 106 includes an upper surface 106a. In one embodiment, the substrate 106 may be a growth substrate, including a gallium arsenide (GaAs) wafer used to epitaxially grow aluminum gallium indium phosphide (AlGaInP), or used to grow gallium nitride (GaN), nitride Indium gallium (InGaN) or aluminum gallium nitride (AlGaN) sapphire (Al ₂ O ₃ ) wafers, gallium nitride (GaN) wafers, silicon carbide (SiC) wafers, or aluminum nitride (AlN) wafers. In another embodiment, the substrate 106 may be a support substrate (such as the support substrates 62A and 54A in FIGS. 11 and 13), and the growth substrate originally used for epitaxial growth of the epitaxial stack 10 can be selected according to the needs of the application. The ground is removed, and then the epitaxial stack 10 is transferred to the aforementioned supporting substrate. In one embodiment, the growth substrate is used as a permanent substrate (such as the substrate 106 in FIG. 12).

The support substrate may include conductive materials, such as silicon (Si), aluminum (Al), copper (Cu), tungsten (W), molybdenum (Mo), gold (Au), silver (Ag), silicon carbide (SiC) or the above Alloys of materials, or thermally conductive materials, such as diamond, graphite, or aluminum nitride. Also, although not shown in the figure, the surface of the substrate 106 that is connected to the epitaxial stack 10 may have a roughened surface, and the roughened surface may be a surface with an irregular shape or a surface with a regular shape, such as the above The surface 106a has a plurality of hemispherical surfaces protruding or recessed on the upper surface 106a, a conical surface having a plurality of protrusions or recesses on the upper surface 106a, or a surface having a plurality of protrusions or recesses on the upper surface 106a Polygonal cone-shaped surface.

In one embodiment of the present invention, metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor deposition (HVPE), physical vapor deposition (PVD) or ion An electroplating method is used to form an epitaxial laminate 10 with optoelectronic properties, such as a light-emitting laminate, on the substrate 106. The physical vapor deposition method may include sputtering or evaporation.

In one embodiment of the present invention, the buffer layer 105 is used to relieve the stress caused by the material lattice mismatch between the substrate 106 and the epitaxial stack 10, so as to reduce the misalignment and lattice defects, thereby improving the epitaxy quality. The buffer layer 105 may be a single layer or a structure including multiple layers. In one embodiment, PVD aluminum nitride (AlN) may be used as the buffer layer 105 to be formed between the epitaxial stack 10 and the substrate 106 to improve the epitaxial quality of the epitaxial stack 10. In one embodiment, the target material used to form PVD aluminum nitride (AlN) is composed of aluminum nitride. In another embodiment, a target made of aluminum is used, and aluminum nitride is formed reactively with the aluminum target in an environment of a nitrogen source.

By changing the physical and chemical composition of one or more layers in the epitaxial stack 10, the wavelength of the light emitted by the light-emitting diode 1 is adjusted. The material of the epitaxial stack 10 includes III-V group semiconductor materials, such as Al _x In _y Ga _(1-xy) N or Al _x In _y Ga _(1-xy) P, where 0≦x≦1, 0≦y ≦1 and (x+y)≦1. When the material of the epitaxial stack 10 is an AlInGaP series material, it can emit red light with a wavelength between 610 nm and 650 nm, or a green light with a wavelength between 530 nm and 570 nm. When the material of the epitaxial stack 10 is an InGaN series material, it can emit blue light with a wavelength between 400 nm and 490 nm. When the material of the epitaxial stack 10 is AlGaN series or AlInGaN series material, it can emit ultraviolet light with a wavelength between 250 nm and 400 nm.

The first semiconductor layer 102 and the second semiconductor layer 104 may be cladding layers, which have different conductivity types, electrical properties, polarities, or provide electrons or holes depending on doped elements, such as the first semiconductor layer 102 and the second semiconductor layer 104. One semiconductor layer 102 is an n-type electrical semiconductor, and the second semiconductor layer 104 is a p-type electrical semiconductor. The light-emitting layer 103 is formed between the first semiconductor layer 102 and the second semiconductor layer 104, and electrons and holes are recombined in the light-emitting layer 103 under the current drive to convert electrical energy into light energy to emit light. The structure of the light-emitting layer 103 includes a single heterostructure (SH), a double heterostructure (DH), a double-side double heterostructure (DDH), or a multi-layer quantum well structure (Multi- Quantum Well, MQW). The material of the light-emitting layer 103 can be a neutral, p-type or n-type semiconductor. The first semiconductor layer 102, the second semiconductor layer 104, or the light emitting layer 103 may be a single layer or a structure including multiple layers.

Referring to FIGS. 2 and 3, the reflective layer 20 includes a thick region H and a thin region T. The upper surface of the thick area H is the upper surface 21 of the reflective layer 20, and the lower surface of the thick area H and the thin area T on the same side constitutes the lower surface 22 of the reflective layer 20, so the lower surface 22 of the reflective layer 20 is formed The outer periphery of the upper surface 21 is larger than the outer periphery of the upper surface 21. The other surface of the thin region T extends from the outer periphery of the upper surface of the thick region H to the outer periphery of the lower surface 22 of the reflective layer 20, that is, the aforementioned other surface of the thin region T connects the upper surface 21 and the lower surface 22 of the reflective layer 20 That is to say, the side surface 23 of the reflective layer 20 is formed by the aforementioned other surface of the thin area T. From the top view, the first upper surface 11 of the epitaxial stack 10 of the light emitting diode 1 has a first area A, and the upper surface 21 (ie, the thick region H) of the reflective layer 20 has a second area B, and the reflection The lower surface 22 of the layer 20 has a third area C, where 0.9<C/A<0.999 and 0.001<(CB)/C<0.006.

As shown in FIG. 3, the thick region H of the reflective layer 20 has a first thickness h1, and the thin region T has a second thickness h2, and h1 is greater than h2. The thin area T has a width d, wherein the width d is between 0.01 μm and 2 μm, preferably between 0.05 μm and 1 μm, and more preferably between 0.1 μm and 1 μm.

In one embodiment, the reflective layer 20 is a metal layer, such as a silver layer, for reflecting the light generated from the active layer in the epitaxial stack 10 toward the light-emitting surface. The reflectivity of the reflective layer 20 is related to its thickness. As shown in FIG. 3, the first thickness h1 of the thick region H and the second thickness h2 of the thin region T of the reflective layer 20 have different reflectivities due to different thicknesses. When the second thickness h2 of the thin area T is greater than a critical thickness h2", a reflectivity value greater than a critical reflectivity can be obtained. Among them, the critical reflectivity can be determined according to the needs of the user, such as 90%~96%. If the thickness of the thin area T is too large and less than the critical thickness h2", that is, its light reflectivity is lower than the critical reflectivity, it will significantly reduce the overall luminous efficiency, resulting in the LED can not achieve the expected brightness . In one embodiment, the material of the reflective layer 20 is silver, as shown in FIG. 6 shows the corresponding relationship between the thickness of the reflective layer 20 and the trend of reflectivity. When the thickness of the reflective layer 20 is greater than 600 Å, the reflectivity can reach over 96%, the thickness at this time is set as the critical thickness, and the reflectivity is the critical reflectivity. If the thickness is greater than 2500 Å, it can have a reflectivity close to 99% or above. In one embodiment, the critical thickness h2" is between 400 Å and 700 Å. As shown in Figure 3, the second thickness h2 gradually becomes smaller as it moves away from the thick region H. Therefore, as mentioned above, the thickness becomes thinner. The second thickness h2 of the area T will cause the reflectivity to decrease as the thickness decreases. According to this embodiment, the first thickness h1 of the reflective layer 20 is selected to be 500-5000 Å, preferably 600-4000 Å, and more preferably 1000~3000Å. Among them, the thickness of the thin area T of the reflective layer 20 is within a critical distance d1 from the boundary of the thick area H (that is, the vertical distance between the boundary of the thick area H and the critical thickness h2"). It has a critical thickness h2" or more, that is, the reflectance can be greater than or equal to the critical reflectance, which satisfies a range: 0 <d1/d<0.5, preferably 0.1<d1/d<0.4. In one embodiment, The material of the reflective layer 20 may be a reflective material other than silver, such as a reflective aluminum material.

In the present invention, the side surface 23 of the thin area T includes a plane or curved surface, and the side surface 23 of the thin area T is connected from the outer periphery of the upper surface 21 of the thick area H to the outer periphery of the lower surface 22, and the second thickness is linear, Non-linear, continuous, and discontinuous ways of decreasing. The curved surface can also be a concave-convex surface, or an irregular curved surface. In one embodiment, the thickness change of the second thickness h2 in the critical interval d1 is not less than the critical thickness h2". In another embodiment, the thickness change of the second thickness h2 in the critical interval d1 is as follows: More than half of the thickness is not less than the critical thickness h2".

In one embodiment, as shown in FIGS. 3 and 4, the second thickness h2 in the thin region T generally becomes smaller gradually away from the thick region H, that is, gradually toward the outside of the light-emitting diode 1 Thinning. There is an angle θ between the side surface 23 of the reflective layer 20 and the lower surface 22, for example, as shown in the SEM image of FIG. 4, the angle θ in this embodiment is 44.6 degrees. FIG. 5 shows an SEM image of another embodiment, in which the angle θ of the reflective layer 20 is close to 90 degrees. When the angle θ between the side surface 23 of the reflective layer 20 and the lower surface 22 is larger, it means that the thin area T has a greater range of greater than the critical reflectivity, which means that the effective reflective area of the reflective layer 20 will increase. Improve the luminous efficiency of light-emitting diodes.

In the present invention, since the inclination angle of the side surface 23 of the reflective layer 20 is related to the subsequent coverage of the first protective layer 30, when the angle θ between the side surface 23 of the reflective layer 20 and the lower surface 22 is too large, the first A protective layer 30 has the disadvantage of poor coverage. Therefore, the angle θ of the reflective layer 20 that affects the coverage and the effective reflection area needs to be considered at the same time. In one embodiment, the angle θ may be 35 degrees to 90 degrees, preferably 40 degrees to 70 degrees, and more preferably 40 degrees to 50 degrees. The first protective layer 30 in this angle range can cover the reflective layer 20 well, and the reflective layer 20 can obtain the best effective reflection area.

In the present invention, the light emitting diode 1 may further include a metal barrier layer (not shown in the figure) on the reflective layer 20, which is composed of a single layer or a plurality of layers. In the present invention, the material of the metal barrier layer may include, but is not limited to: titanium, aluminum, chromium, platinum, nickel-titanium alloy, titanium-tungsten alloy or any combination thereof. In the present invention, it may further include a second protective layer (not shown in the figure) on the metal barrier layer, the second protective layer is from top to bottom, and is sequentially covered along the sides of the layers below .

In the present invention, the materials of the first protective layer and the second protective layer may include _{silicon dioxide (SiO 2} ), silicon nitride (SiN), or aluminum oxide (Al ₂ O ₃ ).

In the present invention, as shown in FIG. 7, which is a schematic cross-sectional view of a light emitting diode 2 according to another embodiment of the present invention. In this embodiment, the structure of the light-emitting diode 2 is similar to that shown in FIG. 1 above, but the difference between the two is that the light-emitting diode 3 of this embodiment further includes a transparent conductive layer 40. The transparent conductive layer 40 is located between the reflective layer 20 and the first protective layer 30 and covers the side portions of the reflective layer 20, and the first protective layer 30 covers and protects the side portions of the reflective layer 20 and the transparent conductive layer 40. Alternatively, in the present invention, the transparent conductive layer 40 may also be located between the reflective layer 20 and the epitaxial stack 10 (not shown in the figure). In another embodiment of the present invention, the transparent conductive layer 40 does not completely cover the reflective layer 20, and is only formed on a part of the upper surface of the reflective layer 20, that is, the width of the transparent conductive layer 40 is smaller than the width of the reflective layer 20. A protective layer 30 covers and protects the side surfaces of the reflective layer 20 and the transparent conductive layer 40.

In the present invention, the material of the transparent conductive layer 40 is, for example, but not limited to: indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), zinc oxide (ZnO), and the like. The thickness of the transparent conductive layer 40 may be 100-3000 Å.

In this article, the light-emitting diode described can be a wafer or a chip, and Figures 1 and 7 only show a part of the actual structure of the light-emitting diode, and other structures can be inventions. The technical field has any form known to the ordinary knowledgeable person.

Please refer to FIG. 8, which is a flowchart illustrating the manufacturing process of the light-emitting diode 2 according to an embodiment of the present invention. As shown in the figure, in the manufacturing process of the light-emitting diode of this embodiment, a reflective layer 20 is formed on the epitaxial laminate 10 (step S21), and a transparent conductive layer 40 is formed on the reflective layer 20 (step S22). The transparent conductive layer 40 is etched (step S23), the reflective layer 20 is etched (step S24), and then a first protective layer 30 is provided to cover the reflective layer 20 and the transparent conductive layer 40 (step S26). In one embodiment, after step S24, a heat treatment process (step S25) may be included. The heat treatment process referred to herein is, for example, but not limited to: annealing, tempering, quenching, or quenching, etc., or various heat treatment process techniques may be used. The temperature can be raised and lowered by machinery and equipment to control the temperature rise and fall to form the side surface 23 of the reflective layer 20 in the aforementioned different forms. In an embodiment of the present invention, an annealing process (step S25) is used, so that the reflective layer 20 is formed into a reflective layer having a thick region H and a thin region T such as the light emitting diode 1, wherein the thin region T has the aforementioned width d and the second thickness h2. In another embodiment of the present invention, the transparent conductive layer 40 does not completely cover the reflective layer 20 and is only formed on part of the upper surface of the reflective layer 20, that is, the width of the transparent conductive layer 40 is smaller than the width of the reflective layer 20. According to the above process, in another embodiment of the present invention, when the transparent conductive layer 40 is located between the reflective layer 20 and the epitaxial stack 10, the process step is to arrange the transparent conductive layer 40 on the epitaxial stack 10. The transparent conductive layer 40 is etched, the reflective layer 20 is then placed on the epitaxial stack 10, the reflective layer 20 is etched, and the first protective layer 30 is placed on the reflective layer 20, and a heat treatment process is performed.

In the present invention, as shown in FIG. 8, after step S26, a metal barrier layer may be further formed on the first protective layer 30. The first protective layer 30 has a pattern, exposing a part of the transparent conductive layer 40, and the metal barrier layer is formed on the patterned first protective layer 30 and is in contact with the exposed part of the transparent conductive layer 40. In the process of forming the metal barrier layer, because the metal barrier layer needs to be alloyed at a high temperature, the first protective layer 30 covers the sides or surroundings of the reflective layer 20 and the transparent conductive layer 40 to protect the reflective layer 20 from forming the metal. The yellow light process stage of the barrier layer avoids the precipitation of metal ions in the reflective layer during the photoresist removal process, such as silver ions, which may cause element yield problems.

Also refer to Figures 9 and 10, which are scanning electron microscope (Scanning Electron Microscope, SEM) photos of a light-emitting diode according to an embodiment of the present invention. Figures 9 and 10 respectively show the unimplemented The front exposure heat treatment process and the reflective structure formed after the front exposure heat treatment process is implemented. It can be seen from the figure that if the reflective layer (ie, Ag layer) of the present invention is only etched without further heat treatment process, the profile curve of the resulting reflective layer will be too steep and even have undercuts (No. 9) The occurrence of (the arrow in the figure) causes poor coverage of the film stack in the subsequent process, which in turn leads to electrical problems. Comparing Fig. 10, it can be seen that the boundary profile of the reflective layer of the light-emitting diode obtained by the heat treatment process is arc trapezoid, and the extension of the thin area (that is, the width d of the aforementioned thin area T) is greater than that of the reflective layer. The thickness from the upper surface to the lower surface of the thick region (that is, the aforementioned first thickness h1) is small.

In the present invention, if the transparent conductive layer 40 is arranged between the epitaxial stack 10 and the reflective layer 20 or between the reflective layer 20 and the first protective layer 30, it will help to improve the thermal stability and current of the light-emitting diode. Uniform dispersion. For example, in one example, the structure (a) is that the reflective layer 20 is directly disposed on the epitaxial stack 10, but there is no transparent conductive layer 40 disposed between the reflective layer 20 and the first protective layer 30. Polar body 1; (b) the structure is a light-emitting diode (not shown) in which the transparent conductive layer 40 is disposed between the epitaxial stack 10 and the reflective layer 20; and (c) the structure is that the transparent conductive layer 40 is disposed in In an experiment in which the forward voltage (Vf) of the light-emitting diode 2 between the reflective layer 20 and the first protective layer 30 was measured at different temperatures and times, the results showed: (a) The light-emitting diode 1 is in the environment The forward voltage (Vf) of the burning test at a temperature of 280~300℃ for 5 minutes has an increase of 5.6%~10.5%, and the light-emitting diode 1 has a local brightness decrease, and the brightness is attenuated by 5.1%~15.4%; (b) ) After the light-emitting diode with the transparent conductive layer 40 arranged between the epitaxial layer 10 and the reflective layer 20 is burned, its forward voltage (Vf) has an increase of 0.95%~1.08%, and the brightness is uniform without local darkening The situation; and (c) the transparent conductive layer 40 is arranged between the reflective layer 20 and the first protective layer 30. The forward voltage (Vf) of the light-emitting diode 2 is only 0.48%~0.68% increase after burning test , And the brightness is uniform without local darkening. It can be seen that the light-emitting diode 2 further forms a transparent conductive layer 40 between the reflective layer 20 and the first protective layer 30, which can improve the thermal stability and current uniformity of the light-emitting diode, thereby improving the light-emitting diode The brightness and life span.

Hereinafter, please refer to FIGS. 11 to 13, which are examples of the application of the embodiments of the foregoing FIGS. 1, 7 and/or 14.

As shown in FIG. 11, it is an embodiment of the light emitting diode LED1 of the present invention. The light emitting diode LED1 includes the aforementioned epitaxial laminate 10 structure, namely, a first semiconductor layer 102, a light emitting layer 103, and a second semiconductor layer 104, and the epitaxial laminate 10 is bonded and disposed on the supporting substrate 62A by a bonding layer 80 Above. In the epitaxial stack 10 structure, a reflective structure 101 is formed on one surface of the first semiconductor layer 102. The reflective structure 101 is composed of the reflective layer 20 (not shown in the figure) of any of the foregoing embodiments and may be added as required. The first protective layer 30 and/or the transparent conductive layer 40 (not shown in the figure) are formed. In the light-emitting diode LED2 shown in FIG. 13, from top to bottom, the second electrode 52, such as the n-electrode, is electrically connected to the second semiconductor layer 104, and the bottom of the second semiconductor layer 104 is sequentially connected to emit light. The layer 103, the first semiconductor layer 102, the reflective structure 101 and the supporting substrate 62A. The supporting substrate 62A may include a first electrode, such as a p-electrode (not shown in the figure), and the first electrode and the first semiconductor layer 102 are electrically connected through the reflective structure 101. The second electrode 52 and the first electrode are respectively located on opposite sides of the light emitting diode LED1, and form a vertical current path in the light emitting diode LED1.

As shown in FIGS. 12 and 13, the concept of the present invention can also be applied to the implementation of the light-emitting diode LED2 and the light-emitting diode LED3.

As shown in Figure 12, the light-emitting diode LED2 is a flip chip type (Flip Chip Type) LED, which basically includes the aforementioned epitaxial stack 10 structure, including a first semiconductor layer 102, a light emitting layer 103, and a second semiconductor layer 102. Semiconductor layer 104; on the surface of the first semiconductor layer 102 away from the substrate 106 is formed a reflective structure 101 comprising the reflective layer 20 of any of the foregoing embodiments, wherein the reflective structure 101 is composed of the reflective layer 20 (not shown in the figure) It is composed of a first protective layer 30 and/or a transparent conductive layer 40 (not shown in the figure) which may be increased as required; preferably, the reflective structure 101 further includes a metal barrier layer (not shown in the figure). The light emitting diode LED2 further has a second electrode 52 and a first electrode 62 electrically connected to the second conductive layer 104 and the first semiconductor layer 102, respectively, and corresponding second electrode pads 50 and first electrode pads 60, wherein The two electrodes 52 and the second electrode pad 50, as well as the first electrode 62 and the first electrode pad 60 are located on the same side of the light emitting diode LED2. Preferably, a protective layer 70 is located between the first electrode pad 60/first electrode 62c and the second electrode pad 50/second electrode 52. The protective layer 70 is interposed between the first electrode 62 and the second electrode 52 to achieve electrical insulation. The current flows in the direction of the first semiconductor layer 102 through the first electrode pad 60 and the first electrode 62, passes through the light-emitting layer 103 and the second semiconductor layer 104, and then flows out through the second electrode 52 and the second electrode pad 50 to form a current The path, wherein the columnar portion of the second electrode 52 located in the via holes 90 of the epitaxial stack 10 is covered by the protective layer 70 (30C) to be insulated from the first semiconductor layer 102 and the light-emitting layer 103. The reflective structure 101 indirectly forms a current path between the first electrode 62 and the first semiconductor layer 102.

The light emitting diode LED3 that emits light from the front as shown in FIG. 13 also includes the aforementioned epitaxial stack 10 structure, that is, the first semiconductor layer 102, the light emitting layer 103, and the second semiconductor layer 104, and the epitaxial stack The layer 10 is bonded and disposed on the supporting substrate 54A by the bonding layer 80. The second electrode 52 is located on the supporting substrate 54A and between the epitaxial stack 10 and the supporting substrate 54A, and the reflective structure 101 is between the epitaxial stack 10 and the second electrode 52. Preferably, a protective layer 70 is located under the reflective structure 101, and the protective layer 70 is interposed between the first electrode 62 and the second electrode 52 to achieve electrical insulation. The first electrode 62 is located above the reflective structure 101 outside the epitaxial stack 10, the first electrode 62 is electrically connected to the first semiconductor layer 102 through the reflective structure 101, and the second electrode 52 is electrically connected to the second semiconductor layer 104. The columnar portion of the second electrode 52 located in the via hole 90 in the epitaxial stack 10 is covered by the protective layer 70 (30C) to be insulated from the first semiconductor layer 102 and the light-emitting layer 103. The current flows from the first electrode 62 through the reflective structure 101 to the light-emitting layer 103 and the second semiconductor layer 104, and then flows to the second electrode 52 to form a current path.

As shown in Figures 12 to 13, the two types of light-emitting diodes LED2, LED3 and the light-emitting diode LED1 shown in Figure 11 basically include the aforementioned epitaxial laminate 10 structure. The difference is that the second electrode 52 of the light-emitting diodes LED2 and LED3 is electrically connected to the second semiconductor layer 104 after passing through the reflective structure 101, the first semiconductor layer 102 and the light-emitting layer 103 through the design of the through hole 90 Wherein, the periphery of the second electrode 52 in the via 90 is isolated from the first semiconductor layer 102 and the light-emitting layer 103 by the protective layer 70 (30C).

In an embodiment of the present invention, the first protective layer 30 is used to protect the boundary of the reflective layer 20, which can prevent the reflective layer 20 from being etched by organic solutions such as photoresist liquids or acid-base solvents during subsequent manufacturing processes. In an embodiment of the present invention, the first protective layer 30 facilitates the uniform diffusion of current. In the above embodiment, the first protective layer 30 only covers the periphery of the reflective layer 20, that is, as shown in FIG. Alternatively, in another embodiment, as shown in FIG. 14, the first protective layer 30 of the light-emitting diode 3 includes an island 30A and a frame 30B, which are formed to cover at least the reflective layer 20 and the epitaxy The surrounding area of the crystal laminate 10 and part of the upper surface of the reflective layer 20.

In the present invention, the material of the first protection layer 30 may include, but is not limited to: _{silicon dioxide (SiO 2} ), silicon nitride (SiN), or aluminum oxide (Al ₂ O ₃ ).

In an embodiment of the present invention, FIG. 15 is a schematic top view of the light emitting diodes LED1 and LED3 of FIG. 11 and FIG. 13 with the design of the protective layer 30 having the island portion 30A as shown in FIG. 14. From the top view, the embodiment in FIG. 15 is a state with 4 via holes. Since the current distribution is mainly concentrated on the periphery of the four via holes and the periphery of the light emitting diode, the frame portion 30B and the via hole portion 30C of the first protective layer 30 can be increased by adding the periphery of the light emitting diode and the periphery of the via hole. The area of the first protective layer 30, combined with the design of the different island-shaped portions 30A of the first protective layer 30, can make the current spreading effect better, thereby improving the luminous efficiency of the light-emitting diode. The first protection layer 30 can be patterned according to requirements and can achieve the effect of uniform current dispersion. As shown in FIG. 15, the width of the frame portion 30B and/or the via portion 30C of the first protective layer 30 is changed; or the distribution and arrangement of the island-shaped portion 30A of the first protective layer 30 are changed and matched Both have the effect of optimizing current diffusion. As long as the island portion 30A, the frame portion 30B, and/or the via hole portion 30C are formed above the reflective layer 20, the aforementioned current spreading effect can be achieved. Therefore, the aspects disclosed in the present invention only disclose preferred implementation aspects, but The graphical design is not limited to the aspect disclosed in this embodiment.

In the present invention, the electrode material of the light-emitting diode 1 may include metal materials, such as aluminum (Al), indium (In), tin (Sn), nickel (Ni), chromium (Cr), titanium (Ti), Metals such as tungsten (W) and platinum (Pt) or metal alloys or metal laminates of the above materials, but not limited to this.

It should be noted that the foregoing embodiments of the present invention are only used to illustrate the present invention, but not to limit the scope of the present invention. Various modifications and changes made to the invention by those with ordinary knowledge in the technical field to which the invention belongs do not depart from the spirit and scope of the invention. The same or similar components in different embodiments, or components denoted by the same symbol in different embodiments, have the same physical or chemical characteristics. In addition, under appropriate circumstances, the above-mentioned embodiments of the present invention can be combined or replaced with each other, and are not limited to the specific embodiments described above. The connection relationship between the specific component and other components described in one embodiment can also be applied to other embodiments, and they all fall within the scope of the present invention as attached.

1, 2, 3, LED1, LED2, LED3: light-emitting diode 10: epitaxial stack 11: The first upper surface 100: local area 101: reflective structure 102: The first semiconductor layer 103: luminescent layer 104: second semiconductor layer 105: buffer layer 106: substrate 20: reflective layer 21: upper surface 22: lower surface 23: side 30: The first protective layer 30A: Island 30B: Frame part 30C: Via hole 40: Transparent conductive layer 50: The second electrode pad 52: second electrode 54A: Support substrate 60: The first electrode pad 62: first electrode 62A: Support substrate 70: protective layer 80: Bonding layer 90: Via A: The first area B: second area C: third area h1: first thickness h2: second thickness h2”: critical thickness d: predetermined distance d1: critical distance H: Thick area T: thin area θ: Angle S21~S26: steps

The drawings described here are used to provide a further understanding of the application and constitute a part of the application. The exemplary embodiments and descriptions of the application are used to explain the application, and do not constitute an improper limitation of the application. In the scheme:

Figure 1 is a schematic cross-sectional view of a light emitting diode according to an embodiment of the invention.

Figure 2 is a top view of the light emitting diode shown in Figure 1.

Fig. 3 is an enlarged view of a partial area 100 of the light emitting diode shown in Fig. 1.

Figure 4 is an SEM image of a light-emitting diode according to an embodiment of the present invention.

Figure 5 is an SEM image of a light-emitting diode according to an embodiment of the present invention.

Figure 6 is a graph showing the relationship between the thickness of the reflective layer (silver) of the light-emitting diode according to the present invention and the reflectivity (%).

FIG. 7 is a schematic cross-sectional view of a light emitting diode according to an embodiment of the invention.

FIG. 8 is a flow chart of the manufacturing process of a light emitting diode according to an embodiment of the present invention.

FIG. 9 is an SEM image of a reflective layer structure of a light emitting diode without a heat treatment process according to an embodiment of the present invention.

FIG. 10 is an SEM image of a reflective layer structure of a light emitting diode subjected to a heat treatment process according to an embodiment of the present invention.

FIG. 11 is a schematic cross-sectional view of a light-emitting diode according to an embodiment of the invention.

FIG. 12 is a schematic cross-sectional view of a light emitting diode according to an embodiment of the invention.

FIG. 13 is a schematic cross-sectional view of a light emitting diode according to an embodiment of the invention.

FIG. 14 is a schematic cross-sectional view of a light emitting diode according to an embodiment of the invention.

FIG. 15 is a schematic diagram of different implementations of the first protective layer in the light-emitting diode of the present invention.

1: Light-emitting diode

10: epitaxial stack

100: local area

102: The first semiconductor layer

103: luminescent layer

104: second semiconductor layer

105: buffer layer

106: substrate

20: reflective layer

21: upper surface

22: lower surface

23: side

30: The first protective layer

Claims (22)

A light-emitting diode, which comprises: An epitaxial stack having a first upper surface; and A reflective layer is disposed on the epitaxial stack and includes a thick region and a thin region, wherein the reflective layer has an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, and the upper surface The surface is the surface farther from the epitaxial stack than the lower surface; Wherein, the thin area has a width; Wherein, in a top view, the first upper surface of the epitaxial layer has a first area, the upper surface of the reflective layer has a second area, and the lower surface has a third area; Wherein, the first area>the third area>the second area, and satisfies a range: 0.9<(the third area/the first area)<0.999 and 0.001<((the third area-the second area) Area)/The third area)<0.006. A light-emitting diode, which comprises: An epitaxial stack is disposed on the substrate and has a first upper surface; and A reflective layer is disposed on the epitaxial stack and includes a thick region and a thin region, wherein the reflective layer has an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, and the upper surface The surface is farther from the first upper surface than the lower surface; Wherein, a first thickness is formed between the upper surface and the lower surface to form the thick region; a second thickness is formed between the side surface and the lower surface to form the thin region; and the second thickness is smaller than the first thickness; Wherein, the thin area has a width; Wherein, the thin area further has a critical interval, and the second thickness between the critical intervals has a critical reflectivity equal to or greater than 90%, and satisfies a range: 0 ＜(the critical interval/the width)＜ 0.5. In the light-emitting diode described in item 2 of the scope of patent application, the second thickness corresponding to the critical distance is 400-700 Å. The light-emitting diode described in item 2 of the scope of patent application, wherein the first thickness of the reflective layer is 500-5000 Å. In the light-emitting diode described in item 2 of the scope of patent application, the second thickness gradually becomes smaller as it gets away from the edge of the upper surface of the reflective layer. Such as the light-emitting diode described in item 1 or item 2 of the scope of patent application, wherein the width is 0.01~2 μm. Such as the light-emitting diode described in item 1 or item 2 of the scope of patent application, wherein the width is 0.01~1 μm. For the light-emitting diode described in item 1 or item 2 of the scope of patent application, the side surface of the reflective layer is substantially flat or curved. According to the light-emitting diode described in item 1 or item 2 of the scope of patent application, there is an angle θ between the side surface of the reflective layer and the lower surface, and the angle is 35 to 70 degrees. The light-emitting diode described in item 9 of the scope of patent application, wherein the angle is 40-50 degrees. The light-emitting diode described in item 1 or item 2 of the scope of patent application, wherein the material of the reflective layer includes metal. The light-emitting diode described in item 1 or item 2 of the scope of patent application, wherein the reflective layer is directly disposed on the epitaxial stack. The light-emitting diode described in item 1 or item 2 of the scope of patent application, wherein the reflective layer has a first protective layer on it. The light-emitting diode described in claim 13 further includes a transparent conductive layer disposed between the reflective layer and the first protective layer, or between the epitaxial stack and the reflective layer between. The light-emitting diode described in item 14 of the scope of patent application, wherein the thickness of the transparent conductive layer is 100-3000 Å. The light-emitting diode described in item 14 of the scope of patent application, wherein the transparent conductive layer covers the periphery of the reflective layer. The light-emitting diode described in item 14 of the scope of patent application, wherein the material of the transparent conductive layer includes indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO) or zinc oxide (ZnO). According to the light-emitting diode described in item 14 of the scope of patent application, as seen from the cross-sectional view of the light-emitting diode, the width of the transparent conductive layer is smaller than the width of the reflective layer. The light-emitting diode described in item 14 of the scope of patent application, wherein the first protective layer further covers the periphery of the transparent conductive layer. The light-emitting diode described in item 13 of the scope of patent application, wherein the first protective layer at least covers the periphery of the reflective layer. According to the light-emitting diode described in item 20 of the scope of patent application, the first protective layer includes a plurality of island-shaped portions arranged and distributed on the reflective layer. According to the light-emitting diode described in item 13 of the scope of patent application, the material of the first protective layer includes _{silicon dioxide (SiO 2} ), silicon nitride (SiN) or aluminum oxide (Al ₂ O ₃ ).

Images