WO2010125792A1 - Light emitting diode and method for producing the same, and light emitting diode lamp - Google Patents

Abstract

Disclosed is a light emitting diode of high brightness wherein the loss of light emitted from the LED chip in the package can be reduced and the efficiency of extraction of light from the package can also be improved. In a light emitting diode (1), a chemical compound semiconductor layer (2) and a transparent substrate (4) are connected through a connecting layer (3). A first reflective surface (3a) is provided between the bottom face of the chemical compound semiconductor layer (2) and the top face of the connecting layer (3). A second reflective surface (3b) is provided between the bottom face of the connecting layer (3) and the top face of the transparent substrate (4).

Description

LIGHT EMITTING DIODE, MANUFACTURING METHOD THEREOF, AND LIGHT EMITTING DIODE LAMP

The present invention relates to a light emitting diode, a manufacturing method thereof, and a light emitting diode lamp.
This application claims priority based on Japanese Patent Application No. 2009-112268 filed in Japan on May 1, 2009, the contents of which are incorporated herein by reference.

Conventionally, as a high-intensity light emitting diode (English abbreviation: LED) that emits red, orange, yellow or yellow-green visible light, aluminum phosphide, gallium indium (composition formula (Al _X Ga _1-X ) _Y In _{1- Y P; 0 ≦ X ≦ 1,0} < compound semiconductor LED having a light emitting layer composed of Y ≦ 1) is known. In such an LED, a light-emitting portion having a light-emitting layer made of (Al _X Ga _1-X ) _Y In _1-YP (0 ≦ X ≦ 1, 0 <Y ≦ 1) is generally formed from the light-emitting layer. It is formed on a substrate material such as gallium arsenide (GaAs) that is optically opaque to emitted light and that is not mechanically strong.

Therefore, recently, in order to obtain a brighter visible LED, and for the purpose of further improving the mechanical strength of the element, the substrate material opaque to the emitted light is removed, and then, Techniques are disclosed in which a bonded layer is formed by bonding a support layer (substrate) made of a material that transmits or reflects emitted light and is excellent in mechanical strength (for example, Patent Documents 1 to 7). reference).

Further, in the package technology using LEDs, LED lamp products in which a plurality of LED chips are put into the same package for high output and multicolor use are widespread.

JP 2001-339100 A JP-A-6-302857 JP 2002-246640 A Japanese Patent No. 2588849 JP 2001-57441 A JP 2007-81010 A JP 2006-32952 A

As described above, the development of substrate bonding technology has increased the degree of freedom of substrates that can be applied as a support layer, and proposals have been made for applications such as Si, Ge, metals, ceramics, and GaP substrates that have significant advantages such as cost and mechanical strength. Has been.

However, these substrates, particularly opaque substrates, have a problem that the improvement in light absorption is insufficient. Specifically, in a product in which a plurality of LED chips are mounted in the same package, light emission is lost by the substrate of adjacent chips, and the efficiency of extracting light out of the package is reduced. was there. In particular, in a full color or high output package, since a plurality of LED chips are arranged adjacent to each other, the substrate of the light emitting diode chip absorbs light emitted from the adjacent chip, and the entire package is reduced in luminous efficiency or taken out from the package. There was a problem that light emission became non-uniform.

The present invention has been made in view of the above circumstances, and is a high-intensity light-emitting diode capable of reducing loss of light emission from an LED chip in a package and improving light extraction efficiency from the package, and its It is an object to provide a manufacturing method and a light emitting diode lamp.

That is, the present invention relates to the following.
(1) A compound semiconductor layer including at least a light emitting part having a light emitting layer, a connection layer, and a transparent substrate, wherein the compound semiconductor layer and the transparent substrate are bonded via the connection layer, A first reflective surface is provided between the bottom surface of the compound semiconductor layer and the top surface of the connection layer, and a second reflective surface is provided between the bottom surface of the connection layer and the top surface of the transparent substrate. A light-emitting diode, which is provided.
(2) The light-emitting diode according to item 1 above, wherein a third reflecting surface is provided on the bottom surface of the transparent substrate.
(3) The first reflecting surface has a reflectance of 90% or more in the wavelength band of light emitted from the light emitting unit, and the second and third reflecting surfaces have a reflectance of 90% or more in the wavelength band of external light. 3. The light-emitting diode according to item 1 or 2 above.
(4) The first electrode is provided on the upper surface side of the compound semiconductor layer, the second electrode is provided on the bottom surface side of the transparent substrate, and the space between the bottom surface of the transparent substrate and the second electrode. 4. The light emitting diode according to claim 1, wherein the third reflecting surface is provided.
(5) The light-emitting diode according to any one of (1) to (4), wherein the connection layer is made of a metal including at least one of silver, gold, copper, and aluminum.
(6) The light-emitting diode according to (5), wherein the second electrode is made of a metal including at least one of silver, gold, copper, and aluminum.
(7) The light-emitting diode according to any one of (1) to (6), wherein the transparent substrate is a semiconductor.
(8) The light-emitting diode according to any one of (1) to (7), wherein the transparent substrate is GaP or SiC.
(9) The light-emitting diode according to any one of (1) to (8), wherein the light-emitting layer includes an AlGaInP or AlGaAs layer.
(10) The transparent conductive film is provided between the compound semiconductor layer and the connection layer, and the compound semiconductor layer and the transparent conductive film are in ohmic contact, The light emitting diode according to any one of the above.
(11) Any one of the preceding items 1 to 10, wherein a transparent conductive film is provided between the connection layer and the transparent substrate, and the transparent conductive film and the transparent substrate are in ohmic contact. The light emitting diode according to one item.
(12) The transparent conductive film is provided between the transparent substrate and the second electrode, and the transparent conductive film and the transparent substrate are in ohmic contact. The light emitting diode according to any one of the above.
(13) The light-emitting diode according to (10), wherein the transparent conductive film is indium tin oxide or indium zinc oxide.
(14) The light-emitting diode as described in (12) above, wherein the transparent conductive film is indium tin oxide or indium zinc oxide.
(15) The light-emitting diode according to any one of (1) to (13), wherein a thickness of the transparent substrate is 50 μm or more and 350 μm or less.
(16) A step of forming a compound semiconductor layer including a light emitting portion having a light emitting layer on a semiconductor substrate, a step of forming a first metal film on the growth surface of the compound semiconductor layer, and a surface of one of the transparent substrates A light emitting diode comprising: a step of forming a second metal film; a step of bonding the first and second metal films to form a connection layer; and a step of removing the semiconductor substrate. Manufacturing method.
(17) The light-emitting diode according to item 16 above, wherein a second metal film is formed on one surface of the transparent substrate and a third metal film is formed on the other surface of the transparent substrate. Production method.
(18) In the step of forming the first metal film on the growth surface of the compound semiconductor layer, the growth surface of the compound semiconductor layer is flattened to form a flat surface, and a transparent conductive film is formed on the flat surface. A step of forming a first metal film on the transparent conductive film after the heat treatment and the heat treatment; and forming a second and third metal film on one and the other surfaces of the transparent substrate. Then, one and the other surfaces of the transparent substrate are flattened to form a flat surface, a transparent conductive film is formed on the flat surface, heat treatment is performed, and a second heat treatment is performed on the transparent conductive film after the heat treatment. 18. The method for producing a light-emitting diode according to 17 above, wherein the method is a step of forming a third metal film and a third metal film, respectively.
(19) The first and second metal films are made of a metal containing at least one of silver, gold, copper, and aluminum, and a connection layer is formed by joining the first and second metal films. 19. The light-emitting diode according to any one of items 16 to 18, wherein the forming step is a room temperature metal bonding step of bonding the first and second metal films at a bonding temperature of less than 50 ° C. Production method.
(20) A light-emitting diode lamp having two or more light-emitting diodes mounted thereon, wherein at least one or more light-emitting diodes according to any one of items 1 to 14 are mounted.
(21) The light emitting diode lamp as described in (20) above, wherein the mounted light emitting diode is die-bonded by a metal layer.

In the light-emitting diode of the present invention, a compound semiconductor layer and a transparent substrate with little light absorption are joined via a connection layer, and the first reflective surface is between the bottom surface of the compound semiconductor layer and the top surface of the connection layer. It has a provided configuration. Since the light emitted from the light emitting unit can be reflected by the first reflecting surface, loss of light emitted from the LED chip in the package can be reduced.

Further, the second reflecting surfaces provided on the top and bottom surfaces of the transparent substrate can reflect external light such as light emitted from adjacent LED chips in the package, so that light is absorbed in the transparent substrate. Can be reduced. Therefore, the light extraction efficiency from the package can be improved.
Furthermore, the configuration in which the third reflecting surface is provided on the bottom surface of the transparent substrate can further improve the light extraction efficiency from the package.

According to the light-emitting diode of the present invention, it is possible to provide a high-intensity light-emitting diode capable of reducing the loss of light emission from the LED chip in the package and improving the light extraction efficiency from the package.

According to the method of manufacturing a light emitting diode of the present invention, a compound semiconductor layer including a light emitting portion having a light emitting layer is formed on a semiconductor substrate, a first metal film is formed on a growth surface of the compound semiconductor layer, After the second metal film is formed on the other surface, the first and second metal films are joined to form a connection layer. By joining the first and second metal films to form a connection layer, the light emitting diode can be reliably and easily manufactured.
In addition, since the third metal film can be formed simultaneously with the formation of the second metal film, the light-emitting diode with high light extraction efficiency can be easily manufactured.

According to the light-emitting diode lamp of the present invention, the light-emitting diode lamp in which two or more light-emitting diodes are mounted has a configuration in which at least one light-emitting diode is mounted. Since the second and third reflecting surfaces provided in the light emitting diode reflect light emitted from the LED chips adjacent in the package, loss of light emitted from the LED chip in the package can be reduced. Therefore, it is possible to provide a light emitting diode lamp capable of improving the light extraction efficiency from the package.

It is a figure which shows the light emitting diode which is one Embodiment of this invention, Comprising: A top view is shown. 1B is a view showing a light emitting diode according to an embodiment of the present invention, and is a cross-sectional view taken along the line A-A ′ shown in FIG. 1A. FIG. It is a cross-sectional schematic diagram of the epiwafer used for the light emitting diode which is one Embodiment of this invention. It is a cross-sectional schematic diagram of the bonded wafer used for the light emitting diode which is one Embodiment of this invention. It is a figure for demonstrating the light emitting diode lamp which is one Embodiment of this invention, Comprising: The top view is shown. FIG. 4B is a diagram for explaining the light-emitting diode lamp according to the embodiment of the present invention, and is a cross-sectional view taken along line C-C ′ shown in FIG. 4A.

Hereinafter, a light-emitting diode and a light-emitting diode lamp according to an embodiment to which the present invention is applied will be described in detail with reference to the drawings. In the drawings used in the following description, in order to make the features easy to understand, the portions that become the features may be shown in an enlarged manner for convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

<Light emitting diode>
First, a configuration of a light emitting diode according to an embodiment to which the present invention is applied will be described.
As shown in FIGS. 1A and 1B, a light emitting diode (LED) 1 according to this embodiment includes a compound semiconductor layer 2, a connection layer 3, and a transparent substrate 4, and the compound semiconductor layer 2 and the transparent substrate 4 include It is schematically configured by being joined via a connection layer 3. The first electrode 5 is provided on the upper surface side of the compound semiconductor layer 2, and the second electrode 6 is provided on the bottom surface side of the transparent substrate 4.

The compound semiconductor layer 2 is not particularly limited as long as it includes the pn junction type light emitting portion 7. Specifically, for example, as shown in FIG. 1B, the compound semiconductor layer 2 includes a p-type GaP layer 8 doped with Mg and having a carrier concentration of 1 × 10 ¹⁸ to 8 × 10 ¹⁸ cm ⁻³ and a layer thickness of 1 to 15 μm. A light emitting unit 7 is laminated on the top. The p-type GaP layer 8 can be omitted or replaced with another transparent layer.

Specifically, the light emitting unit 7 is a stacked body of compound semiconductors in which, for example, a lower cladding layer 9, a light emitting layer 10, and an upper cladding layer 11 are sequentially stacked. As the light emitting section 7, for example, a compound semiconductor including a light emitting layer 10 made of (Al _X Ga _1-X ) _Y In _1-YP (0 ≦ X ≦ 1, 0 <Y ≦ 1) which is a red light source is used. Can be used. Further, a compound semiconductor including the light emitting layer 10 made of Al _x Ga _(1-x) As (0 ≦ X ≦ 1) which is a light source for red and infrared light emission can be used.

The light emitting layer 10 is also composed of undoped, n-type or p-type conductivity type (Al _X Ga _1-X ) _Y In _1-YP (0 ≦ X ≦ 1, 0 <Y ≦ 1). be able to. The light emitting layer 10 may have a double hetero structure, a single quantum well (abbreviation: SQW) structure, or a multi quantum well (abbreviation: MQW) structure, but is monochromatic. In order to obtain excellent light emission, an MQW structure is preferable. Further, a barrier layer and a well layer having a quantum well (English abbreviation: QW) structure are formed (Al _X Ga _1-X ) _Y In _1-YP (0 ≦ X ≦ 1,0) The composition of Y ≦ 1) can be determined so that quantum levels resulting in the desired emission wavelength are formed in the well layer.

The light emitting unit 7 is a lower portion disposed opposite to the upper side and the upper side of the light emitting layer 10 in order to “confine” the light emitting layer 10, a carrier (carrier) that causes radiative recombination, and light emission in the light emitting layer 10. A so-called double hetero (English abbreviation: DH) structure including the clad layer 9 and the upper clad layer 11 is preferable for obtaining high-intensity light emission. The lower cladding layer 9 and the upper cladding layer 11 have a forbidden bandwidth larger than (Al _X Ga _1-X ) _Y In _1-YP (0 ≦ X ≦ 1, 0 <Y ≦ 1) constituting the light emitting layer 10. It is preferable to construct from a wide semiconductor material.

Further, an intermediate layer for gently changing the band discontinuity between both layers may be provided between the light emitting layer 10 and the lower cladding layer 9 and the upper cladding layer 11. In this case, the intermediate layer is preferably made of a semiconductor material having a band gap between the light emitting layer 10 and the lower and upper clad layers 9 and 11.

Further, above the light emitting portion 7, a contact layer for lowering the contact resistance of the ohmic electrode, a current diffusion layer for planarly diffusing the element driving current throughout the light emitting portion, and conversely, the element driving current. A known layer structure such as a current blocking layer or a current confinement layer for limiting the region through which the current flows may be provided. Further, the light emitting unit 7 may have either the p-type or n-type polarity on the upper surface side (and the bottom surface side).

The p-type GaP layer 8 is, for example, a semiconductor layer doped with Mg and having a carrier concentration of 1 × 10 ¹⁸ to 8 × 10 ¹⁸ cm ⁻³ and a layer thickness of 1 to 15 μm. The p-type GaP layer 8 is arranged on the connection layer 3 side in the compound semiconductor layer 2, and the bottom surface of the p-type GaP layer 8 is a connection surface with the upper surface of the connection layer 3. The bottom surface of the p-type GaP layer 8 is preferably a mirror-polished smooth surface. Specifically, the surface roughness is preferably in the range of 0.1 to 10 nm, for example.

As shown in FIG. 1B, the connection layer 3 is disposed between the compound semiconductor layer 2 and the transparent substrate 4, and on the first metal film 3A provided on the compound semiconductor layer 2 side and the transparent substrate 4 side. The provided second metal film 3B is joined to the second metal film 3B. The connection layer 3 has a function of bonding the compound semiconductor layer 2 and the transparent substrate 4 together. In addition, the connection layer 3 has a reflective structure with a high reflectivity for increasing the brightness, and has a function of reflecting light incident from the compound semiconductor layer 2 side and the transparent substrate 4 side. The material of the connection layer 3 is preferably a material having a low electrical resistance, and is preferably a material that can be connected at a low temperature in consideration of the stress of the light emitting portion.

The first metal film 3A reflects light (hereinafter referred to as internal light) emitted mainly from the light emitting portion 7 (light emitting layer 10) toward the transparent substrate 4 for the purpose of increasing the luminance of the light emitting diode 1. It is provided to efficiently take it out. The material of the first metal film 3A is not particularly limited, but a material having a reflectance of 90% or more in the wavelength band of internal light can be used. Among these, it is particularly preferable to use silver, aluminum, or an alloy thereof having a reflectance of 90% in the entire visible light region.

On the other hand, examples of the material having a reflectance of 90% or more in a part of the wavelength band of the visible light region include gold and copper. Here, gold has a high reflectance at a wavelength longer than about 550 nm, and the reflectance exceeds 90% at about 590 nm. Copper has a high reflectance at a wavelength longer than about 600 nm, and the reflectance exceeds 90% at about 610 nm. As described above, the material of the first metal film 3 </ b> A can be appropriately selected according to the wavelength band of light emitted from the light emitting unit 7.

When the light-emitting diode 1 of the present embodiment is used in a package such as a light-emitting diode lamp, the second metal film 3B is used for the purpose of increasing the brightness of the package and is adjacent to the light-emitting diode 1 in the package. When light emitted from the light emitting diode or the like (hereinafter referred to as external light) is incident on the inside of the transparent substrate 4, it is provided to reflect the external light and efficiently extract it to the outside of the transparent substrate 4. Yes.

The material of the second metal film 3B is not particularly limited, but a material having a reflectance of 90% or more in the wavelength band of external light can be used. Among these, it is particularly preferable to use silver, aluminum, or an alloy thereof having a reflectance of 90% in the entire visible light region.

On the other hand, examples of the material having a reflectance of 90% or more in a part of the wavelength band of the visible light region include gold and copper. Here, gold has a high reflectance at a wavelength longer than about 550 nm, and the reflectance exceeds 90% at about 590 nm. Copper has a high reflectance at a wavelength longer than about 600 nm, and the reflectance exceeds 90% at about 610 nm. Thus, the material of the second metal film 3B can be appropriately selected according to the wavelength band of the external light.

The materials of the first and second metal films 3A and 3B may be different from each other, but are preferably the same. In the case where the materials of the first and second metal films 3A and 3B are the same, the connection layer 3 is formed by connecting the first metal film 3A and the second metal film 3B to a room temperature metal bonding method (J. Vac. Sci. Technol. A-16 (4), Jul / Aug 1998-P2125 Metal-bonding-during-sputter-film-deposition-T.Shimatsu-et-al.).

On the other hand, when the materials of the first and second metal films 3A and 3B are different, the connection layer 3 is formed by bonding the first metal film 3A and the second metal film 3B with a eutectic metal such as AuSn or AuGe. Alternatively, it can be a structure joined by a known joining technique such as joining at high temperature and high pressure. In addition, when applying these joining techniques involving heating, titanium and titanium are prevented so that no diffusion or reaction occurs between the first and second metal films 3A and 3B, the compound semiconductor layer 2 and the transparent substrate 4. It is preferable to insert a known high melting point barrier metal layer (not shown) such as chromium, tungsten or the like.

The transparent substrate 4 is joined to the p-type GaP layer 8 side of the compound semiconductor layer 2 via the connection layer 3 as shown in FIG. 1B. The transparent substrate 4 has a sufficient strength to mechanically support the light emitting unit 7 and has a wide forbidden band width through which light emitted from the light emitting unit 7 can be transmitted. Preferably, it is made of a material. Examples of such a transparent substrate 4 include III-V group compound semiconductor crystal such as gallium phosphide (GaP), aluminum gallium arsenide (AlGaAs), and gallium nitride (GaN), zinc sulfide (ZnS), and selenide. A II-VI compound semiconductor crystal such as zinc (ZnSe), a IV group semiconductor crystal such as hexagonal or cubic silicon carbide (SiC), a glass substrate, a sapphire substrate, or the like can be used. In particular, SiC and GaP having characteristics of transparency, workability, mechanical strength, and low cost are the most suitable semiconductor materials. SiC is excellent in heat conduction and mechanical strength. GaP has an advantage that it is a semiconductor material that can be easily processed, although the wavelength that can be transmitted is longer than that of green. On the other hand, glass, sapphire substrates, and the like can be used, but are limited to low current applications because they are insulative and have better thermal conductivity than semiconductor materials.

Although the thickness of the transparent substrate 4 is desirably thin, it can be appropriately optimized according to the strength of the material so that cracking and warping during handling do not occur. Specifically, when using GaP which is the most suitable material for the transparent substrate 4, if it is thinner than 100 μm, it is not preferable because it tends to break. On the other hand, if it is thicker than 350 μm, it becomes difficult to cut, which is not preferable because it leads to an increase in cost. On the other hand, when SiC is used as the transparent substrate 4, 50 to 150 μm is a good range for the same reason.

The first electrode 5 is a low-resistance ohmic contact electrode provided on the upper surface side of the compound semiconductor layer 2. On the other hand, the second electrode 6 is a low-resistance ohmic contact electrode provided on the bottom side of the substrate 3. In the present embodiment, the case where the polarity of the first electrode 5 is n-type and the polarity of the second electrode 6 is p-type will be described. However, the polarity of the first electrode 5 is p-type and the second electrode 6 is The polarity may be n-type.

The first electrode 5 can be formed using, for example, AuGe, AuSi, or the like. Further, as the surface material of the first electrode 5, gold is generally used in order to cope with mounting by wire bonding. Note that it is preferable to devise the shape and arrangement of the first electrode 5 with respect to the light emitting unit 7 in order to uniformly diffuse the current to the light emitting unit 7. There is no restriction | limiting in particular about the shape and arrangement | positioning of the 1st electrode 5, A well-known technique is applicable.

The second electrode 6 (third metal film) is not particularly limited, but a material having a reflectance of 90% or more in the wavelength band of external light can be used. Among these, it is particularly preferable to use silver, aluminum, or an alloy thereof having a reflectance of 90% in the entire visible light region. On the other hand, examples of the material having a reflectance of 90% or more in a part of the wavelength band of the visible light region include gold and copper. Here, gold has a high reflectance at a wavelength longer than about 550 nm, and the reflectance exceeds 90% at about 590 nm. Copper has a high reflectance at a wavelength longer than about 600 nm, and the reflectance exceeds 90% at about 610 nm. Thus, the material of the second electrode 6 can be appropriately selected according to the wavelength band of the external light.

Further, the second electrode 6 may have a single layer structure or a laminated structure composed of a plurality of metal films composed of the above metals. Specific examples of the laminated structure include a three-layer structure composed of silver, tungsten (W), and a gold metal film from the transparent substrate 4 side. According to the second electrode 6 having the three-layer structure, silver having high reflectance can be disposed on the third reflecting surface 6a. By using tungsten for the intermediate layer, mutual diffusion between silver and gold can be prevented, and chemically stable gold can be disposed on the surface side.

In the light-emitting diode 1 of the present embodiment, a transparent conductive film 12 having a small light absorption is provided at the interface between the semiconductor layer and the metal layer. The transparent conductive film 12 prevents diffusion / reaction between the metal constituting the connection layer 3 and the second electrode 6 and the semiconductor substrate constituting the transparent substrate 4 when the transparent substrate 4 is a semiconductor substrate. be able to. Thereby, the fall of the reflectance of the 1st reflective surface 3a mentioned later, the 2nd reflective surface 3b, and the 3rd reflective surface 6a can be suppressed. As the transparent conductive film 12, for example, indium tin oxide (ITO), indium zinc oxide (IZO), or the like is preferably used.

When the transparent substrate 4 is a semiconductor substrate, the transparent conductive film 12 is in direct ohmic contact at the interface between the metal constituting the connection layer 3 and the second electrode 6 and the semiconductor substrate constituting the transparent substrate 4. It is preferable. Specifically, a transparent conductive film 12A is provided between the p-type GaP layer 8 constituting the compound semiconductor layer 2 and the first metal film 3A constituting the connection layer 3, and the compound semiconductor layer 2 and the transparent layer 12 are transparent. The conductive film 12A is in ohmic contact. Further, a transparent conductive film 12B is provided between the second metal film 3B constituting the connection layer 3 and the transparent substrate 4, and the transparent conductive film 12B and the transparent substrate 4 are in ohmic contact. Further, a transparent conductive film 12C is provided between the transparent substrate 4 and the second electrode 6, and the transparent conductive film 12C and the transparent substrate 4 are in ohmic contact.

The light-emitting diode 1 of the present embodiment has a reflective surface that reflects internal light for higher brightness, and when the light-emitting diode 1 is used in a package such as a light-emitting diode lamp, the brightness of the package is increased. And a reflective surface for reflecting external light. That is, between the bottom surface of the p-type GaP layer 8 constituting the compound semiconductor layer 2 and the top surface of the first metal film 3A constituting the connection layer 3, the first reflecting surface 3a for reflecting internal light. Is provided. Further, a second reflecting surface 3 b for reflecting external light is provided between the bottom surface of the second metal film 3 </ b> B constituting the connection layer 3 and the top surface of the transparent substrate 4. Further, a third reflecting surface 6 a for reflecting external light is provided between the bottom surface of the transparent substrate 4 and the second electrode 6.

More specifically, as shown in FIG. 1B, the first is an interface between the p-type GaP layer 8 (or the transparent conductive film 12A when the transparent conductive film 12A is provided) and the first metal film 3A. The upper surface of the metal film 3A is a first reflecting surface 3a. The bottom surface of the second metal film 3B, which is the interface between the second metal film 3B and the transparent substrate 4 (the transparent conductive film 12B when the transparent conductive film 12B is provided), is the second reflective surface 3b. It is said that. Further, the upper surface of the second electrode 6 that is an interface between the transparent substrate 4 (the transparent conductive film 12C when the transparent conductive film 12C is provided) and the second electrode 6 is defined as the third reflective surface 6a. ing.

The first reflective surface 3a is made of a material having a reflectance of 90% or more in the wavelength band of internal light because the material of the first metal film 3A is 90% or more in the wavelength band of internal light. Yes. Further, the second reflecting surface 3b is made of a material having a reflectance of 90% or more in the wavelength band of external light because the material of the second metal film 3B is 90% or more in the wavelength band of external light. Has been. Furthermore, since the third electrode 6 (third metal film) is made of a material having a reflectivity of 90% or more in the external light wavelength band, the third reflective surface 6a is in the external light wavelength band. The reflectance is 90% or more.

According to the light-emitting diode 1 of the present embodiment, as shown in FIG. 1B, since the first reflecting surface 3a is provided, the light is emitted mainly from the light-emitting portion 7 (light-emitting layer 10) to the transparent substrate 4 side. The internal light can be reflected and taken out efficiently. Thereby, high brightness of the light emitting diode 1 can be achieved.

Further, according to the light emitting diode 1 of the present embodiment, the second reflecting surface 3b and the third reflecting surface 6a are provided on the upper surface and the bottom surface of the transparent substrate 4, respectively. For this reason, when external light other than the internal light emitted mainly from the light emitting unit 7 is incident on the inside of the transparent substrate 4, the external light is transmitted by the second reflective surface 3b and the third reflective surface 6a. It can be taken out of the transparent substrate 4 efficiently. Thereby, when the light-emitting diode 1 of the present embodiment is used in a package such as a light-emitting diode lamp, the brightness of the package can be increased.

As shown in FIG. 1B, the connection layer 13 is provided on the bottom surface side of the second electrode 6 in order to connect (die bond) the light emitting diode 1 and the p-type terminal 24. As the material of the connection layer 13, a known metal material can be used. Specifically, for example, an Ag paste can be used. The connection layer 13 can be made of a material having a low electrical resistance and capable of being connected at a low temperature, that is, a metal having a low melting point. As the low melting point metal, In, Sn metal and a known solder material can be applied, but it is preferable to use an Au-based eutectic metal material which is chemically stable and has a low melting point. Examples of the Au-based eutectic metal material include AuSn, AuGe, and AuSi. When an Au-based eutectic metal material is used as the low melting point metal, it is preferable to form an Au layer before and after the low melting point metal. By forming the Au layer in this way, the melting point is increased by changing the composition after melting, and the heat resistance in the mounting process can be improved.

<Method for manufacturing light-emitting diode>
Next, the manufacturing method of the light emitting diode 1 of this embodiment is demonstrated. The method for manufacturing the light-emitting diode 1 of the present embodiment includes a step of forming a compound semiconductor layer including a light-emitting portion having a light-emitting layer on a semiconductor substrate, and a step of forming a first metal film on a growth surface of the compound semiconductor layer. A step of forming second and third metal films on one and other surfaces of the transparent substrate, a step of bonding the first and second metal films to form a connection layer, and a step of removing the semiconductor substrate And.

First, as shown in FIG. 2, a compound semiconductor layer 2 is produced. The compound semiconductor layer 2 is composed of, for example, a buffer layer 16 made of n-type GaAs doped with Si, an etching stop layer (not shown), and an n-type AlGaInP doped with Si on a semiconductor substrate 15 made of GaAs single crystal or the like. The contact layer 17, the n-type upper clad layer 11, the light emitting layer 10, the p-type lower clad layer 9, and the Mg-doped p-type GaP layer 8 are sequentially laminated. Here, the buffer layer 16 is provided to alleviate a lattice mismatch between the semiconductor substrate 15 and the constituent layers of the light emitting unit 7. The etching stop layer is provided for use in selective etching.

Specifically, the layers constituting the compound semiconductor layer 2 are, for example, trimethylaluminum ((CH ₃ ) ₃ Al), trimethylgallium ((CH ₃ ) ₃ Ga), and trimethylindium ((CH ₃ ) ₃ In ) Can be epitaxially grown on the GaAs substrate 15 by a low pressure metalorganic chemical vapor deposition method (MOCVD method) using a group III constituent element as a raw material. As the Mg doping material, for example, biscyclopentadienyl magnesium (bis- (C ₅ H ₅ ) ₂ Mg) or the like can be used. As a Si doping material, for example, disilane (Si ₂ H ₆ ) or the like can be used. Further, phosphine (PH ₃ ), arsine (AsH ₃ ), or the like can be used as a raw material for the group V constituent element. As the growth temperature of each layer, 750 ° C. can be applied to the p-type GaP layer 8, and 730 ° C. can be applied to the other layers. Furthermore, the carrier concentration and layer thickness of each layer can be selected as appropriate.

Next, the epitaxial growth surface of the compound semiconductor layer 2 is flattened to form a flat surface. Specifically, a region extending from the surface of the p-type GaP layer 8 to a depth of, for example, about 1 μm is polished and processed into a mirror surface having a surface roughness of about 0.1 to 10 nm. Next, on the formed flat surface, for example, an ITO film is formed as the transparent conductive film 12A, and then heat treatment is performed at about 400 to 650 ° C. to form an ohmic contact. In addition, an ohmic contact electrode made of an alloy can be partially formed instead of the transparent conductive film, but the optical properties are inferior to the structure of the transparent conductive film because the electrode portion has a low reflectance.

Next, one and the other surfaces of the transparent substrate 4 are flattened to form a flat surface. Next, after forming the transparent conductive films 12B and 12C on the flat surface, heat treatment is performed to form ohmic contacts.

Next, the compound semiconductor layer 2 and the transparent substrate 4 are joined. Specifically, the first metal film 3A is formed on the transparent conductive film 12A formed on the compound semiconductor layer 2, and the second metal film is formed on the transparent conductive film 12B formed on one surface of the transparent substrate 4. The metal film 3B is formed. Then, these first and second metal films 3A and 3B are bonded to room temperature metal bonding method (J.Vac.Sci.Technol.A 16 (4), Jul / Aug 1998 P2125 Metal bonding during sputter film deposition T.Shimatsu et al.) to form the connection layer 3. Thereby, as shown in FIG. 3, the compound semiconductor layer 2 and the transparent substrate 4 can be joined.

In the bonding of the compound semiconductor layer 2 and the transparent substrate 4 by the room temperature metal bonding method, first, the compound semiconductor layer 2 and the transparent substrate 4 are carried into the bonding apparatus, and the apparatus is evacuated to 3 × 10 ⁻⁵ Pa. . Next, silver having a reflectivity of 98% is formed on each bonding surface of the transparent conductive film 12A formed on the compound semiconductor layer 2 and the transparent conductive film 12B formed on the transparent substrate 4 as the first and second metal films 3A and 3B. Is formed with a thickness of about 0.2 μm by sputtering or the like, and is bonded at room temperature as it is. At this time, the first and second metal films 3A and 3B are preferably bonded at a bonding temperature of less than 100 ° C., desirably less than 50 ° C.

In the method of manufacturing a light emitting diode according to this embodiment, it is particularly preferable to use a room temperature metal bonding method as a bonding technique between the compound semiconductor layer 2 and the transparent substrate 4. Stress caused by heating in a simple process by joining the first and second metal films 3A, 3B constituting the first and second reflecting surfaces 3a, 3b at room temperature using a mirror material having high reflectivity. In addition, bonding can be performed without being restricted by a reduction in reflectance. Note that, as described above, room temperature metal bonding is a technique in which metal is sputtered in vacuum and bonded by bonding a clean surface, but in the present invention, the surface of the compound semiconductor has been successfully planarized. The present inventors have also found a condition that enables metal bonding even with high reflectance silver, aluminum, and gold.

In addition, the connection method of the compound semiconductor layer 2 and the transparent substrate 4 is not limited to the room temperature metal bonding method using the connection layer 3 described above, and known techniques such as diffusion bonding, adhesive, eutectic metal bonding, and the like. And a structure suitable for the joining method can be selected as appropriate.

Next, the semiconductor substrate 15 made of GaAs and the buffer layer 16 are selectively removed from the compound semiconductor layer 2 bonded to the transparent substrate 4 with an ammonia-based etchant.

Next, the first electrode 5 is formed. The first electrode 5 is formed by forming an n-type ohmic electrode on the exposed surface of the contact layer 17. Specifically, for example, AuGe, Ni alloy / Pt / Au are laminated by a vacuum deposition method so as to have an arbitrary thickness, and then patterned by a general photolithography means to arbitrarily form the first electrode 5. The shape is formed.

Next, the second electrode 6 is formed. The second electrode 6 is formed by forming a third metal film on the transparent conductive film 12 </ b> C that is an ohmic contact formed on the other surface of the transparent substrate 4. Specifically, for example, silver is formed as the third metal film with a thickness of 0.1 μm by sputtering. Thereafter, tungsten (W) is formed to a thickness of 0.1 μm and gold is formed to a thickness of 0.5 μm to form a second electrode 6 having a three-layer structure.

Next, the light emitting diode 1 is cut into chips. Specifically, first, before cutting into chips, the light emitting portion 7 in the cut region is removed by etching. As described above, the light-emitting diode 1 of the present embodiment can be manufactured.

<Light emitting diode lamp>
Next, a configuration of a light emitting diode lamp which is an embodiment to which the present invention is applied will be described. As shown in FIGS. 4A and 4B, the light-emitting diode lamp (LED lamp) 21 of this embodiment is schematically configured by mounting three light-emitting diodes 1, 21, 31 on the surface of a mount substrate 22. More specifically, the light emitting diode 1 is a red light emitting diode having the AlGaInP light emitting layer 10 using a GaAs substrate as described above. The light emitting diodes 21 and 31 may be the same red light emitting diode as the light emitting diode 1. Thereby, it can be set as a monochromatic LED lamp. On the other hand, by using blue and green light emitting diodes having a GaInN light emitting layer using a sapphire substrate as the light emitting diodes 21 and 31, a full color LED lamp can be obtained.

A plurality of n-electrode terminals 23 and p-electrode terminals 24 are provided on the surface of the mount substrate 22, and the light-emitting diode 1 has a silver (Ag) paste (metal layer) on the p-electrode terminals 24 of the mount substrate 22. ) Are fixed and supported (die-bonded), and the second electrode 6 and the p-electrode terminal 24 are connected. The first electrode 5 of the light emitting diode 1 and the n electrode terminal 23 of the mount substrate 22 are connected using a gold wire 25 (wire bonding). Similarly, the light emitting diodes 21 and 31 are fixed and supported (mounted) by silver (Ag) paste on the p electrode terminal 24, and the first and second electrodes (not shown) are the n electrode terminal 23 and the p electrode. Each is connected to a terminal 24. A reflection wall 26 is provided on the surface of the mount substrate 22 so as to cover the periphery of the light-emitting diodes 1, 21 and 31, and the space inside the reflection wall 26 is generally made of epoxy resin or the like. The sealing material 27 is sealed. Thus, the light emitting diode lamp 21 of the present embodiment has a configuration in which three red light emitting diodes are incorporated in the same package.

The case where the light emitting diodes 1, 21 and 31 are caused to emit light simultaneously with respect to the light emitting diode lamp 21 having the above configuration will be described.
As shown in FIGS. 4A and 4B, the upward light emission from the light emitting portion of each of the light emitting diodes 1, 21 and 31 is light emission from the main light extraction surface. Therefore, it can be taken out directly to the outside of the light emitting diode lamp 21. Further, light emitted downward from the light emitting portion of each of the light emitting diodes 1, 21, 31 cannot be taken out directly to the outside of the light emitting diode lamp 21. Here, in the light emitting diodes 1, 21, and 31, the first reflecting surface 3 a is provided between the bottom surface of the compound semiconductor layer 2 and the top surface of the bonding layer 3. For this reason, since the 1st reflective surface 3a reflects the internal light of the light emitting diode 1 to the light extraction surface side, the light emission from the light emission part 7 can be efficiently taken out of the light emitting diode lamp 21 outside. Therefore, the high-intensity light-emitting diode 1 and light-emitting diode lamp 21 can be provided.

Further, the light emission in the circumferential direction from the light emitting portions of the respective light emitting diodes 1, 21, 31 cannot be taken out directly to the outside of the light emitting diode lamp 21. Here, the light emitting diode lamp 21 is provided with a reflection wall 26 on the surface of the mount substrate 22. For this reason, light emitted from each light emitting diode in the circumferential direction can be reflected upward by the reflecting wall 26. Therefore, the light extraction efficiency of the light emitting diode lamp 21 can be improved.

By the way, in the conventional light emitting diode, the reflective surface was not provided in the upper surface and bottom face of the opaque substrate or transparent substrate connected with the compound semiconductor layer. For this reason, light emitted from the light emitting portion of each light emitting diode in the circumferential direction is emitted when the side surface of the substrate of the adjacent light emitting diode is irradiated in addition to the light reflected by the reflecting wall 26 provided on the mount substrate 22. In some cases, the substrate was absorbed. Therefore, there is a problem that the luminous efficiency of the entire package is lowered.

In contrast, the light-emitting diode lamp 21 of the present embodiment has two or more light-emitting diodes mounted thereon, and the light-emitting diodes in which the second and third reflecting surfaces 3b and 6a are provided on the top and bottom surfaces of the transparent substrate 4. 1 has a configuration in which at least one is mounted. For this reason, even if the light emitted in the circumferential direction from the adjacent light emitting diode is irradiated from the side surface of the transparent substrate 4 of the light emitting diode 1, it is reflected by the second and third reflecting surfaces 3b and 6a. It will be. Thus, since the light emitting diode 1 having the second and third reflecting surfaces 3b and 6a provided on the upper surface and the bottom surface of the transparent substrate 4 is included in the package, the loss of light emission from the LED chip in the package. Can be reduced. Therefore, it is possible to provide the high-intensity light-emitting diode lamp 21 capable of improving the light extraction efficiency from the package.

In the light emitting diode lamp 21 of the present embodiment, the light emitting wavelengths of the mounted light emitting diodes have the same configuration, but the light emitting wavelengths of the mounted light emitting diodes may all be different. Moreover, in the light emitting diode lamp 21 of this embodiment, the chip | tip height of the mounted light emitting diode has the same structure, However, All the chip heights of the mounted light emitting diode may differ.

Hereinafter, the effects of the present invention will be described in detail with reference to examples. The present invention is not limited to these examples.

An example in which a light-emitting diode and a light-emitting diode lamp according to the present invention are manufactured will be specifically described. In addition, the light emitting diode manufactured in this example is a red light emitting diode having an AlGaInP light emitting portion.

(Production of light emitting diode)
The red light-emitting diodes of Example 1 and Comparative Example 1 are semiconductor layers sequentially stacked on a semiconductor substrate made of GaAs single crystal having a surface inclined by 15 ° from an n-type (100) surface doped with Si. It produced using the epitaxial wafer provided with. The laminated semiconductor layer includes a buffer layer made of n-type GaAs doped with Si, a layer made of n-type (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P doped with Si (contact An upper cladding layer made of n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P doped with Si, undoped (Al _0.2 Ga _0.8 ) _{0. 5} In _0.5 P / Al _0.7 Ga _0.3 ) Light-emitting layer composed of 20 pairs of _0.5 In _0.5 P, and Mg-doped p-type (Al _0.7 Ga _0.3 ) _A lower clad layer made of _0.5 In _0.5 P, a thin film (Al _0.5 Ga _0.5 ), an intermediate layer made of _0.5 In _0.5 P, and a Mg-doped p-type GaP layer.

Each of the semiconductor layers described above used trimethylaluminum ((CH ₃ ) ₃ Al), trimethylgallium ((CH ₃ ) ₃ Ga), and trimethylindium ((CH ₃ ) ₃ In) as a group III constituent element material. An epitaxial wafer was formed by stacking on a GaAs substrate by a low pressure metalorganic chemical vapor deposition method (MOCVD method). Biscyclopentadienyl magnesium (bis- (C ₅ H ₅ ) ₂ Mg) was used as a Mg doping material. Disilane (Si ₂ H ₆ ) was used as a Si doping material. Further, phosphine (PH ₃ ) or arsine (AsH ₃ ) was used as a group V constituent element material. The GaP layer was grown at 750 ° C., and the other semiconductor layers were grown at 730 ° C.

The carrier concentration of the GaAs buffer layer was about 2 × 10 ¹⁸ cm ⁻³ and the layer thickness was about 0.2 μm. The layer made of (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P had a carrier concentration of about 2 × 10 ¹⁸ cm ⁻³ and a layer thickness of about 1.5 μm. The carrier concentration of the upper cladding layer was about 8 × 10 ¹⁷ cm ⁻³ and the layer thickness was about 1 μm. The light emitting layer was undoped 0.8 μm. The carrier concentration of the lower cladding layer was about 2 × 10 ¹⁷ cm ⁻³ and the layer thickness was 1 μm. The carrier concentration of the p-type GaP layer was about 3 × 10 ¹⁸ cm ⁻³ and the layer thickness was 3 μm.

Next, a region from the surface of the p-type GaP layer to a depth of 1 μm was polished and mirror-finished. The surface roughness after polishing was 0.18 nm. Next, an ITO film was formed on the mirror-polished surface of the p-type GaP layer, and then heat treatment was performed at 550 ° C. to form an ohmic contact.

Next, as the transparent substrate for pasting, single crystal p-type GaP having a thermal expansion coefficient equivalent to that of the light emitting part was used. After forming an ITO film on the front and back surfaces of this transparent substrate, heat treatment was performed to form ohmic contacts.

Next, the epitaxial wafer and the transparent substrate were carried into the bonding apparatus, and the inside of the apparatus was evacuated to 3 × 10 ⁻⁵ Pa. Then, 0.2 μm of silver having a reflectance of 98% was formed by sputtering on each bonding surface of the epitaxial wafer and the transparent substrate, and room temperature bonding was performed as it was.

Next, the GaAs semiconductor substrate for epitaxial lamination and the buffer layer were selectively removed with an ammonia-based etchant.

Next, as a first electrode, a vacuum is applied to the surface of the contact layer so that the AuGe (Ge mass ratio 12%) alloy has a thickness of 0.15 μm, the Ni alloy has a thickness of 0.05 μm, and Au has a thickness of 1 μm. An n-type ohmic electrode was formed by vapor deposition. After that, patterning was performed using a general photolithography means, and heat treatment was performed at 450 ° C. for 3 minutes to form an n-type ohmic electrode.

Next, the second electrode is formed on the ITO film on the back surface of the transparent substrate by vapor deposition so that the silver is 0.2 μm, the tungsten film is 0.1 μm, Au is 0.5 μm, and AuSn is 1 μm. Thus, a second electrode and a die bonding connection layer were formed.

Next, before cutting into chips, the light emitting part in the cut area was removed by etching. Thereafter, the substrate was cut with a dicing saw at a pitch of 0.3 mm. A red light emitting diode chip (hereinafter referred to as an LED chip) used in Example 1 was produced. The Ag reflective film had a reflectivity of 95% or more with respect to visible light (blue, green, red).

In contrast, for the red LED chip used in Comparative Example 1, a silicon (Si) substrate was used instead of the transparent substrate.

(Production of light-emitting diode lamp)
Using the red LED chips used in Example 1 and Comparative Example 1 manufactured as described above, a high output LED lamp (light emitting diode lamp) on which three red LED chips as shown in FIG. 4A are mounted. Were respectively assembled (LED lamps of Example 1 and Comparative Example 1).

(Evaluation results of light emission characteristics)
In the LED lamps of Example 1 and Comparative Example 1, three LEDs were caused to emit light simultaneously, and the light emission characteristics were evaluated. Table 1 shows the evaluation results of the light emission characteristics.

As shown in Table 1, in the LED lamp of Comparative Example 1 in which the LED chip manufactured using the Si substrate that is an opaque substrate is used instead of the GaP substrate that is a transparent substrate, the dominant wavelength is 625 nm and the luminous efficiency is 65 lm. / W.
On the other hand, in the LED lamp of Example 1, the dominant wavelength was 625 nm and the luminous efficiency was 70 lm / W, and it was confirmed that high luminous efficiency was obtained.

The light emitting diode of the present invention is a light emitting diode with high brightness and high efficiency that reduces light absorption in the package, and can be used for various display lamps, lighting fixtures, and the like.

1, 2, 32 ... Light-emitting diodes 2 ... Compound semiconductor layer 3 ... Connection layer 3A ... First metal film 3B ... Second metal film 3a ... First reflecting surface 3b ... 2nd reflective surface 4 ... Transparent substrate 5 ... 1st electrode 6 ... 2nd electrode (3rd metal film)
6a ... 3rd reflective surface 7 ... Light emission part 8 ... p-type GaP layer 9 ... Lower clad layer 10 ... Light emitting layer 11 ... Upper clad layer 12, 12A, 12B, 12C ... Transparent conductive film 13 ... Connection layer 15 ... Semiconductor substrate 16 ... Buffer layer 17 ... Contact layer 21 ... Light emitting diode lamp 22 ... Mount substrate 23 ... n electrode terminal 24 ... P electrode terminal 25 ... Gold wire 26 ... Reflection wall 27 ... Sealing material

Claims (21)

1. A compound semiconductor layer including at least a light emitting portion having a light emitting layer, a connection layer, and a transparent substrate;
   The compound semiconductor layer and the transparent substrate are bonded via the connection layer,
   A first reflective surface is provided between the bottom surface of the compound semiconductor layer and the top surface of the connection layer,
   A light emitting diode, wherein a second reflective surface is provided between the bottom surface of the connection layer and the top surface of the transparent substrate.
2. The light emitting diode according to claim 1, wherein a third reflecting surface is provided on a bottom surface of the transparent substrate.
3. The first reflective surface has a reflectance of 90% or more in the wavelength band of light emitted from the light emitting unit,
   The light emitting diode according to claim 1 or 2, wherein the second and third reflecting surfaces have a reflectance of 90% or more in a wavelength band of external light.
4. A first electrode is provided on the upper surface side of the compound semiconductor layer;
   A second electrode is provided on the bottom side of the transparent substrate;
   The light emitting diode according to claim 1, wherein the third reflecting surface is provided between a bottom surface of the transparent substrate and the second electrode.
5. 3. The light emitting diode according to claim 1, wherein the connection layer is made of a metal including at least one of silver, gold, copper, and aluminum.
6. The light emitting diode according to claim 4, wherein the second electrode is made of a metal including at least one of silver, gold, copper, and aluminum.
7. 3. The light emitting diode according to claim 1, wherein the transparent substrate is a semiconductor.
8. The light-emitting diode according to claim 7, wherein the transparent substrate is GaP or SiC.
9. The light emitting diode according to claim 1 or 2, wherein the light emitting layer includes an AlGaInP or AlGaAs layer.
10. A transparent conductive film is provided between the compound semiconductor layer and the connection layer,
    The light emitting diode according to claim 1, wherein the compound semiconductor layer and the transparent conductive film are in ohmic contact.
11. A transparent conductive film is provided between the connection layer and the transparent substrate,
    The light emitting diode according to claim 1, wherein the transparent conductive film and the transparent substrate are in ohmic contact.
12. A transparent conductive film is provided between the transparent substrate and the second electrode;
    The light emitting diode according to claim 4, wherein the transparent conductive film and the transparent substrate are in ohmic contact.
13. The light-emitting diode according to claim 10, wherein the transparent conductive film is indium tin oxide or indium zinc oxide.
14. 13. The light emitting diode according to claim 12, wherein the transparent conductive film is indium tin oxide or indium zinc oxide.
15. 3. The light-emitting diode according to claim 1, wherein the transparent substrate has a thickness of 50 μm or more and 350 μm or less.
16. Forming a compound semiconductor layer including a light emitting portion having a light emitting layer on a semiconductor substrate;
    Forming a first metal film on a growth surface of the compound semiconductor layer;
    Forming a second metal film on one surface of the transparent substrate;
    Bonding the first and second metal films to form a connection layer;
    And a step of removing the semiconductor substrate.
17. 17. The method of manufacturing a light emitting diode according to claim 16, wherein a second metal film is formed on one surface of the transparent substrate and a third metal film is formed on the other surface of the transparent substrate. .
18. The step of forming the first metal film on the growth surface of the compound semiconductor layer includes planarizing the growth surface of the compound semiconductor layer to form a flat surface, and forming a transparent conductive film on the flat surface, and then performing a heat treatment. And forming a first metal film on the transparent conductive film after the heat treatment,
    The step of forming the second and third metal films on one and other surfaces of the transparent substrate planarizes one and the other surfaces of the transparent substrate to form a flat surface, and the transparent conductive film is formed on the flat surface. 18. The light emitting diode manufacturing method according to claim 17, wherein a heat treatment is performed after each of the first and second metal films is formed, and a second metal film and a third metal film are formed on the transparent conductive film after the heat treatment. Method.
19. The first and second metal films are made of a metal containing at least one of silver, gold, copper, and aluminum;
    The step of bonding the first and second metal films to form a connection layer is a room temperature metal bonding step of bonding the first and second metal films at a bonding temperature of less than 50 ° C. The method for manufacturing a light emitting diode according to any one of claims 16 to 18.
20. A light emitting diode lamp having two or more light emitting diodes mounted thereon,
    3. A light-emitting diode lamp comprising at least one light-emitting diode according to claim 1 mounted thereon.
21. 21. The light emitting diode lamp according to claim 20, wherein the mounted light emitting diode is die-bonded by a metal layer.

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