JP2004288788A - Light emitting element and method of manufacture the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element having a structure in which a metallurgical reaction of an element substrate and a metal layer at a laminating heat treatment time can be not only effectively prevented but also a fault hardly occurs due to a decrease in a laminating strength or a reflectivity due to the reaction, in the light emitting element having the structure in which a light emitting layer and the element substrate are laminated via the metal layer, and to provide a method of manufacturing the same. <P>SOLUTION: The light emitting element includes the first main surface of a compound semiconductor layer having a light emitting layer part 24 as a light retrieving surface, and an element substrate 7 coupled to the second main surface side of the compound semiconductor layer via a main metal layer 10 having a reflecting surface for reflecting the light from the light emitting layer part 24 to the light retrieving surface side to the second main surface side of the compound semiconductor layer. The light emitting element is characterised in that the part including at least the main surface of the main metal layer 10 side of the element substrate 7 is formed of a conductive material which contains an inorganic conductive phase made of a carbon or a silicon carbide as a main body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light emitting device and a method for manufacturing the same.
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-66455 [Patent Document 2]
JP 2001-339100 A
Materials and device structures used for light-emitting devices such as light-emitting diodes and semiconductor lasers have been developed over many years, and the photoelectric conversion efficiency inside the devices is gradually approaching the theoretical limit. Therefore, when an element with higher luminance is to be obtained, the light extraction efficiency from the element is extremely important. For example, in a light emitting device having a light emitting layer portion formed of AlGaInP mixed crystal, a thin AlGaInP (or GaInP) active layer is sandwiched between an n-type AlGaInP cladding layer having a larger band gap and a p-type AlGaInP cladding layer. By adopting the double hetero structure sandwiched therebetween, a high-luminance element can be realized. Such an AlGaInP double hetero structure can be formed by epitaxially growing each layer made of an AlGaInP mixed crystal on a GaAs single crystal substrate, utilizing the fact that the AlGaInP mixed crystal lattice-matches with GaAs. When this is used as a light emitting element, a GaAs single crystal substrate is often used as it is as an element substrate. However, the AlGaInP mixed crystal constituting the light emitting layer has a band gap larger than that of GaAs, so that the emitted light is absorbed by the GaAs substrate and it is difficult to obtain sufficient light extraction efficiency. In order to solve this problem, a method of inserting a reflective layer composed of a semiconductor multilayer film between the substrate and the light emitting layer portion has been proposed (for example, Patent Document 1). Since the difference is used, only the light incident at a limited angle is reflected, and a great improvement in light extraction efficiency cannot be expected in principle.
[0004]
Therefore, various publications including Patent Literature 2 disclose a GaAs substrate for growth while removing a conductive element substrate (made of semiconductor or metal) for reinforcement and Au for reflection. There is disclosed a technique of attaching a layer to a release surface via a layer. This Au layer has the advantage that the reflectance is high and the dependency of the reflectance on the incident angle is small.
[0005]
[Problems to be solved by the invention]
However, in the above-described method, problems such as peeling and a decrease in reflectance are likely to occur in the Au layer serving as the reflective layer at the time of bonding. In particular, when the element substrate is formed of a semiconductor, a metallurgical reaction such as eutectic tends to occur between the element substrate component such as Si and the Au layer component during the bonding heat treatment. Becomes even more noticeable.
[0006]
An object of the present invention is to effectively prevent a metallurgical reaction between an element substrate and a metal layer during a bonding heat treatment in a light emitting element having a structure in which a light emitting layer portion and an element substrate are bonded via a metal layer. Accordingly, it is an object of the present invention to provide a light emitting element having a structure which is less likely to cause a failure due to a decrease in bonding strength or reflectance due to the reaction, and a method for manufacturing the same.
[0007]
Means for Solving the Problems and Functions / Effects of the Invention
In order to solve the above problems, the light emitting device of the present invention is
A first main surface of the compound semiconductor layer having a light emitting layer portion is a light extraction surface, and a reflection surface for reflecting light from the light emitting layer portion toward the light extraction surface on a second main surface side of the compound semiconductor layer. A light-emitting element having an element substrate bonded thereto via a main metal layer having
At least a portion of the element substrate including the main surface on the main metal layer side is made of a conductive material mainly composed of an inorganic conductive phase made of carbon or silicon carbide. In the present specification, “main component” means a component having the highest mass content, and “phase” means a uniform portion of a substance system that is distinguished from others by a physical boundary. In the present specification, the “main metal layer” is a metal layer located between the compound semiconductor layer and the element substrate, and has a role of forming a reflection surface and bonding the compound semiconductor layer and the element substrate. Refers to the metal layer that carries the Therefore, a bonding metal layer described later does not belong to the main metal layer.
[0008]
According to the light emitting element of the present invention, the element substrate has a contact surface with the main metal layer made of a conductive material mainly composed of an inorganic conductive phase made of carbon (C) or silicon carbide (SiC). Therefore, a metallurgical reaction with the main metal layer hardly occurs due to the strong covalent bond that carbon or silicon carbide has in the molecule. Therefore, it is possible to prevent a decrease in reflectance on the reflection surface.
[0009]
In the light-emitting element, in order to obtain light emission intensity, it is desirable to flow as large a current as possible through the light-emitting layer. Therefore, the element substrate is required to have conductivity that can withstand it, and furthermore, to have sufficient heat conductivity (role as a heat sink) capable of sufficiently dissipating heat generated by a large current. Since carbon or silicon carbide has excellent conductivity and thermal conductivity, such an element substrate can be realized by forming the entire element substrate from the above-described conductive material. Generally, carbon and silicon carbide have electrical and thermal conductivity close to metals. Note that silicon carbide is slightly inferior in conductivity to carbon and is classified as a semiconductor.
[0010]
The conductive material can be a composite of an inorganic conductive phase and a metal. Such composites have better electrical and thermal conductivity than the inorganic conductive phase (carbon or silicon carbide) alone. In addition, strength and workability are also excellent, and it can be suitably used as an element substrate.
[0011]
In addition, the composite material can have a structure in which a metal is dispersed in a substrate made of an inorganic conductive phase. By adopting such a structure, an element having uniform properties such as conductivity and heat conductivity can be obtained. A substrate can be obtained. Specifically, the composite material is characterized in that a porous substrate composed of an inorganic conductive phase is impregnated with a metal. This can be obtained, for example, by impregnating a porous substrate made of an inorganic conductive phase (carbon or silicon carbide) with a molten metal by a known melt forging method. Further, by using a porous substrate, a strong metal layer can be obtained by the anchor effect when a metal layer is formed on the surface of the composite material by means such as sputtering or vacuum deposition.
[0012]
Specifically, when the inorganic conductive phase is carbon, at least one metal selected from Al, Cu and Mg can be used as a main component of the metal contained in the composite material. When the phase is silicon carbide, the main component may be one or more metals selected from Al and Cu. As described above, a light-emitting element having an element substrate which is excellent in conductivity and heat conductivity, and which is excellent in strength and workability can be obtained.
[0013]
Next, in the light emitting element of the present invention, the main metal layer may have an Au-based coupling layer containing Au as a main component. With such a structure, the bonding strength between the compound semiconductor layer and the element substrate can be increased. Details will be described later.
[0014]
Further, in the light emitting element having the Au-based coupling layer, the reflection surface can be formed by the Au-based coupling layer. Since the Au-based bonding layer is chemically stable and hardly causes a deterioration in reflectance due to oxidation or the like, it is suitable as a material for forming the reflection surface. In the present invention, a metallurgical reaction between the element substrate and the Au-based bonding layer is extremely effectively performed by configuring the element substrate with a conductive material mainly composed of an inorganic conductive phase made of carbon or silicon carbide. Since it is possible to suppress the reflection, it is possible to form a reflection surface having a good reflectance by the Au-based coupling layer.
[0015]
When the reflection surface is formed by the Au-based coupling layer, a bonding metal layer containing Au as a main component is disposed between the Au-based coupling layer and the compound semiconductor layer so as to be dispersed on the main surface of the Au-based coupling layer. can do. The Au-based coupling layer forms a part of a current supply path to the light emitting layer. However, when the Au-based coupling layer is directly joined to the light emitting layer portion made of a compound semiconductor, the contact resistance increases, the series resistance increases, and the luminous efficiency may decrease. The contact resistance can be reduced by joining the Au-based coupling layer to the light emitting layer portion via the Au-based junction metal layer. However, the Au-based bonding metal layer requires a relatively large amount of alloying components necessary for securing contacts, and the reflectivity is slightly inferior. Therefore, if the bonding metal layer is dispersedly formed on the main surface of the Au-based coupling layer, high reflectivity of the Au-based coupling layer can be secured in a region where the bonding metal layer is not formed.
[0016]
As the bonding metal layer, a compound semiconductor layer of n-type III-V compound semiconductor in contact with this (for example, the aforementioned _{(Al x Ga 1-x)} y In 1-y P ( However, 0 ≦ x ≦ 1, In the case of 0 ≦ y ≦ 1)), the effect of reducing the contact resistance is particularly enhanced by employing the AuGeNi junction metal layer. In this case, an AuGeNi bonding metal layer can be formed on the bonding-side main surface of the compound semiconductor layer, and an Au-based bonding layer (the first Au-based layer) can be formed so as to cover the AuGeNi bonding metal layer. In this case, by performing the alloying heat treatment of the AuGeNi junction metal layer and the compound semiconductor layer at, for example, 350 ° C. or more and 500 ° C. or less, the effect of reducing the contact resistance is enhanced.
[0017]
In order to sufficiently enhance the light extraction effect, the formation area ratio of the bonding metal layer to the Au-based bonding layer (a value obtained by dividing the formation area of the bonding metal layer by the total area of the Au-based bonding layer) is 1 % Or more and 25% or less. If the formation area ratio of the bonding metal layer is less than 1%, the effect of reducing the contact resistance will not be sufficient, and if it exceeds 25%, the reflection intensity will decrease. By setting the Au content of the Au-based bonding layer higher than that of the bonding metal layer, the reflectance of the Au-based bonding layer can be further increased in a region where the bonding metal layer is not formed.
[0018]
On the other hand, in the light emitting element having the Au-based coupling layer, the reflection surface may be formed by an Ag-based layer containing Ag as a main component interposed between the Au-based coupling layer and the compound semiconductor layer. The Ag-based layer is inexpensive as compared with the Au-based coupling layer, and exhibits a good reflectance over almost the entire visible light wavelength range (350 nm or more and 700 nm or less), so that the wavelength dependence of the reflectance is small. As a result, high light extraction efficiency can be realized regardless of the emission wavelength of the element. Also, as compared with a metal such as Al, a decrease in reflectance due to the formation of an oxide film or the like is less likely to occur.
[0019]
FIG. 6 shows the reflectivity of various mirror-polished metal surfaces. The plot point “■” represents the reflectivity of Ag, the plot point “△” represents the reflectivity of Au, and the plot point “◆” represents the reflectivity of Au. It is a reflectance (comparative example) of Al. The plot points “x” are for AgPdCu alloy. The reflectance of Ag is particularly good when the reflectance of Ag is 350 nm or more and 700 nm or less (and in the infrared region on the longer wavelength side), particularly, 380 nm or more and 700 nm or less.
[0020]
On the other hand, Au is a colored metal, and as is clear from the reflectance shown in FIG. 6, it absorbs in the visible light region having a wavelength of 570 nm or less (especially 550 nm or less), and the peak emission wavelength of the light emitting layer portion becomes 570 nm or less. If present, the reflectivity decreases. As a result, the emission intensity tends to decrease, and the spectrum of the extracted light becomes different from the original emission spectrum due to absorption, and the emission color tone tends to change. However, Ag has a very good reflectance even in the visible light region having a wavelength of 570 nm or less. In other words, when the peak emission wavelength of the light emitting layer is 570 nm or less (especially 550 nm or less, furthermore, 500 nm or less), the reflection surface of the Ag-based layer can realize higher light extraction efficiency than the Au-based metal.
[0021]
On the other hand, as shown in FIG. 6, although Al does not produce an absorption peak in reflectance, it does not. However, the reflectance in the visible light range is slightly lower (for example, 85 -92%). However, since an Ag-based metal does not easily form an oxide film, a higher reflectance than that of Al can be secured in the visible light region. Specifically, it can be seen that at a wavelength of 400 nm or more (especially 450 nm or more), the reflectance is better than that of Al.
[0022]
The reflectivity of Al in FIG. 6 was measured on a mirror-finished Al surface in a state where the formation of a surface oxide film was suppressed by mechanical polishing and chemical polishing. Accordingly, there is a possibility that the reflectance is further reduced as compared with the data shown in FIG. In the case of Ag, in FIG. 6, the reflectance is inferior to Al in a short wavelength region of 350 nm or more and 400 nm or less, but an oxide film is much less likely to be formed than Al. Therefore, when a reflective metal layer is actually formed on the light emitting element, the use of an Ag-based layer makes it possible to achieve a reflectance higher than that of Al even in this wavelength region. Also in this wavelength range, the reflectivity of Ag is higher than that of Au.
[0023]
In summary, the Ag-based layer has a light extraction efficiency of about 350 nm or more and 700 nm or less (preferably 400 nm or more and 570 nm or less, more preferably 450 nm or more and 550 nm or less) in the light emitting layer portion having a peak emission wavelength. It can be said that the improvement effect is particularly remarkable. Emitting layer portion having a peak emission wavelength as described above, for example, _{(Al x Ga 1-x)} y In 1-y P ( However, 0 ≦ x ≦ 1,0 ≦ y ≦ 1) or _In x _Ga y Al _{According to 1-} xyN (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, x + y ≦ 1), a double where a first conductivity type clad layer, an active layer and a second conductivity type clad layer are laminated in this order. It can be configured as having a heterostructure.
[0024]
When the Ag-based layer is used for forming the reflection surface, an Ag-based bonding metal layer containing Ag as a main component is disposed between the Ag-based layer and the compound semiconductor layer so as to be dispersed on the main surface of the Ag-based layer. be able to. The Ag-based junction metal layer is formed such that the compound semiconductor layer in contact with the Ag-based junction metal layer is an n-type III-V group compound semiconductor (for example, (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1). , 0 ≦ y ≦ 1)), the effect of reducing the contact resistance is particularly enhanced by employing the AgGeNi bonding metal layer. It is desirable that the formation area ratio of the Ag-based bonding metal layer to the Ag-based layer be 1% or more and 25% or less as in the case of the above-mentioned Au-based bonding metal layer.
[0025]
Next, the method for manufacturing a light-emitting device of the present invention having the above Au-based coupling layer includes:
The main surface on the side opposite to the light extraction surface of the compound semiconductor layer is defined as a bonding-side main surface, and the first Au to be an Au-based bonding layer containing Au as a main component is formed on the bonding-side main surface. Place the system layer,
The main surface of the element substrate, which is supposed to be located on the light-emitting layer portion side, is used as a bonding-side main surface, and on the bonding-side main surface, a Au-based bonding layer to be an Au-based coupling layer is formed. Arrange two Au-based layers,
It is characterized in that the first Au-based layer and the second Au-based layer are adhered and adhered to each other.
[0026]
When the element substrate and the compound semiconductor layer are bonded to each other, it is preferable that the element substrate and the compound semiconductor layer be overlapped with each other via an Au-based bonding layer, and the bonding heat treatment be performed in this state.
[0027]
According to the manufacturing method of the present invention, the first and second Au-based bonding layers are separately formed on the compound semiconductor layer side and the element substrate side, and are adhered to each other in close contact with each other. Since the Au-based bonding layers are easily integrated even at a relatively low temperature, sufficient bonding strength can be obtained even at a low heat treatment temperature for bonding.
[0028]
In the present invention, as a specific method for forming the metal layer, in addition to a vapor phase film forming method such as vacuum evaporation or sputtering, it is also possible to employ an electrochemical film forming method such as electroless plating or electrolytic plating. it can.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram showing a light emitting device 100 according to one embodiment of the present invention. The light emitting device 100 has a structure in which a light emitting layer portion 24 is bonded via a main metal layer 10 on a first main surface of a metal-impregnated carbon substrate 7 serving as an element substrate.
[0030]
Emitting layer 24, a non-doped _{(Al x Ga 1-x)} y In 1-y P ( However, 0 ≦ x ≦ 0.55,0.45 ≦ y ≦ 0.55) active layer 5 consisting of a mixed crystal , the first-conductivity-type cladding layer, in this embodiment the p-type cladding layer 6 made of p-type _{(Al z Ga 1-z)} y in 1-y P ( except x <z ≦ 1), wherein the first conductivity type the second-conductivity-type cladding layer different from the clad layer, in this embodiment interposed by an n-type _{(Al z Ga 1-z)} y in 1-y P ( except x <z ≦ 1) n-type cladding layer 4 made of It has a concave structure, and the emission wavelength can be adjusted in the range from green to red (the emission wavelength (peak emission wavelength) is 550 nm or more and 670 nm or less) according to the composition of the active layer 5. In the light emitting device 100, the p-type AlGaInP cladding layer 6 is disposed on the metal electrode 9 side, and the n-type AlGaInP cladding layer 4 is disposed on the main metal layer 10 side. Therefore, the polarity of the conduction is positive on the metal electrode 9 side. The term “non-doped” as used herein means “do not actively add a dopant”, and contains a dopant component that is unavoidably mixed in a normal manufacturing process (for example, 10 ¹³ to 10 ¹⁶ / cm 3). ^The upper limit of about ³ ) is not excluded.
[0031]
A current diffusion layer 20 made of AlGaAs is formed on the main surface of the light emitting layer portion 24 on the side opposite to the surface facing the substrate 7, and the light emitting layer portion 24 has a light emission layer substantially at the center of the main surface. A metal electrode (for example, an Au electrode) 9 for applying a driving voltage is formed so as to cover a part of the main surface. The area around the metal electrode 9 on the main surface of the current diffusion layer 20 forms a light extraction area from the light emitting layer section 24. On the back surface of the metal-impregnated carbon substrate 7, a metal electrode (back surface electrode: for example, an Au electrode) 15 is formed so as to cover the entire surface.
[0032]
The metal-impregnated carbon substrate 7 is manufactured by impregnating porous metal (C) with a molten metal (for example, Al or the like) by a known molten metal forging method, and has a thickness of, for example, 100 μm or more and 500 μm or less. . Note that, instead of the metal-impregnated carbon substrate 7, a metal-impregnated silicon carbide substrate manufactured using porous silicon carbide (SiC) in the same manner as described above can be used as the element substrate.
[0033]
Then, the metal-impregnated carbon substrate 7 is bonded to the light emitting layer portion 24 with the main metal layer 10 interposed therebetween. The main metal layer 10 is entirely configured as an Au-based coupling layer. In the present embodiment, the Au-based bonding layer is made of pure Au or an Au alloy having an Au content of 95% by mass or more.
[0034]
An AuGeNi bonding metal layer 32 (for example, Ge: 15% by mass, Ni: 10% by mass) is formed as a bonding metal layer between the light emitting layer portion 24 and the main metal layer 10, which reduces the series resistance of the element. Have contributed. The AuGeNi bonding metal layer 32 is dispersedly formed on the main surface of the main metal layer 10, and the formation area ratio is 1% or more and 25% or less.
[0035]
The light from the light emitting layer portion 24 is extracted in such a manner that the light reflected directly by the main metal layer 10 is superimposed on the light emitted directly to the light extraction surface side. The thickness of the main metal layer 10 is desirably 80 nm or more in order to ensure a sufficient reflection effect. The upper limit of the thickness is not particularly limited, but is determined appropriately in consideration of the cost (for example, 1 μm or less) because the reflection effect is saturated.
[0036]
Hereinafter, a method for manufacturing the light emitting device 100 of FIG. 1 will be described.
First, as shown in Step 1 of FIG. 2, a p-type GaAs buffer layer 2 of, for example, 0.5 μm, AlAs is formed on a main surface of a GaAs single crystal substrate 1 which is a semiconductor single crystal substrate forming a light emitting layer growth substrate. The release layer 3 is epitaxially grown, for example, 0.5 μm, and the current diffusion layer 20 made of p-type AlGaAs, for example, 5 μm, in this order. Thereafter, a 1 μm p-type AlGaInP cladding layer 6, a 0.6 μm AlGaInP active layer (non-doped) 5, and a 1 μm n-type AlGaInP cladding layer 4 are epitaxially grown in this order.
[0037]
Next, as shown in Step 2, the AuGeNi bonding metal layer 32 is dispersedly formed on the main surface of the light emitting layer section 24. After the formation of the AuGeNi bonding metal layer 32, an alloying heat treatment is performed in a temperature range of 350 ° C. or more and 500 ° C. or less. After that, the first Au-based layer 10a is formed so as to cover the AuGeNi junction metal layer 32. An alloyed layer is formed between the light emitting layer portion 24 and the AuGeNi bonding metal layer 32 by the alloying heat treatment, and the series resistance is significantly reduced. On the other hand, as shown in step 3, a separately prepared metal-impregnated carbon substrate 7 has a second Au-based layer 10b formed on one main surface, and a back electrode layer 15 (for example, Au-based layer) formed on the other main surface. (Made of metal). In the above steps, each metal layer can be formed by using sputtering or vacuum evaporation.
[0038]
Then, as shown in Step 4, the second Au-based layer 10b on the side of the metal-impregnated carbon substrate 7 is overlaid and pressed on the first Au-based layer 10a formed on the light emitting layer section 24, for example, at 200 ° C. By performing a heat treatment for bonding, a substrate bonded body 50 is produced. The metal-impregnated carbon substrate 7 is bonded to the light emitting layer section 24 via the first Au-based layer 10a and the second Au-based layer 10b. Further, the first Au-based layer 10a and the second Au-based layer 10b are integrated into the main metal layer 10 by the bonding heat treatment. Since both the first Au-based layer 10a and the second Au-based layer 10b are mainly composed of Au which is hardly oxidized, the above-mentioned bonding heat treatment can be performed without any problem, for example, even in the air.
[0039]
In the present embodiment, since the element substrate is constituted by the metal-impregnated carbon substrate 7 mainly composed of carbon having a strong covalent bond, the metal-impregnated carbon substrate 7 in contact with the main metal layer 10 (Au-based bonding layer) There is no metallurgical reaction between them. Therefore, the reflection surface of the finally obtained main metal layer 10 (Au-based coupling layer) can realize good reflectance.
[0040]
Next, proceeding to step 5, the substrate bonded body 50 is immersed in an etching solution composed of, for example, a 10% hydrofluoric acid aqueous solution, and the AlAs release layer 3 formed between the buffer layer 2 and the light emitting layer portion 24 is selected. By etching, the GaAs single crystal substrate 1 (opaque to light from the light emitting layer portion 24) is removed from the laminate 50a of the light emitting layer portion 24 and the metal-impregnated carbon substrate 7 bonded thereto. . Note that an etch stop layer made of AlInP is formed instead of the AlAs peeling layer 3, and a GaAs single crystal is formed using a first etching solution (for example, a mixed solution of ammonia / hydrogen peroxide) having a selective etching property for GaAs. The substrate 1 is removed by etching together with the GaAs buffer layer 2, and then an etch stop is performed using a second etching solution having a selective etching property for AlInP (for example, hydrochloric acid: hydrofluoric acid may be added for removing the Al oxide layer). A step of etching away the layer may be employed.
[0041]
Then, as shown in step 6, an electrode 9 for wire bonding (bonding pad: FIG. 1) is formed so as to cover a part of the main surface of the current diffusion layer 20 exposed by removing the GaAs single crystal substrate 1. . Thereafter, a semiconductor chip is diced by a usual method, and the semiconductor chip is fixed to a support, wire-bonded to lead wires, and the like, and then sealed with a resin to obtain a final light-emitting element.
[0042]
In the above-described embodiment, the first Au-based layer 10a forms the reflection surface, but the Ag-based layer 10c is provided between the first Au-based layer 10a and the light emitting layer unit 24 as in the light emitting device 200 of FIG. Can also be inserted. In this case, instead of the Au-based joining metal layer, an Ag-based joining metal layer 132 made of AgGeNi (for example, Ge: 15% by mass, Ni: 10% by mass) is dispersed and formed. The other parts are the same as those of the light emitting device 100 of FIG. FIG. 4 shows an example of the manufacturing process. The difference from the manufacturing process of FIG. 2 is that in step 2, an Ag-based bonding metal layer 132 is dispersedly formed instead of the Au-based bonding metal layer 32, and an alloying heat treatment is performed in a temperature range of 350 ° C. or more and 660 ° C. Thereafter, the point is that the Ag-based layer 10c and the first Au-based layer 10a are formed in this order. Other than this, it is basically the same as FIG.
[0043]
When the Ag-based layer 10c is likely to be corroded by the etchant when removing the light emitting layer growth substrate by etching, the following may be performed. That is, as shown in Step 3, the first Au-based layer 10a that is in contact with the Ag-based layer 10c is positioned such that the outer peripheral edge of the Ag-based layer 10c is located inside the outer peripheral edge of the first Au-based layer 10a. It is formed with a larger area than the Ag-based layer 10c. As a result, the Ag-based layer 10c is surrounded by the first Au-based layer 10a, and the outer peripheral surface of the Ag-based layer 10c is protected by the outer peripheral edge 10e of the highly corrosion-resistant first Au-based layer 10a. In 5, even if the substrate for growing a light emitting layer (GaAs single crystal substrate 1) is etched, the effect is less likely to reach the Ag-based layer 10 c. When the GaAs single crystal substrate 1 is used as a substrate for growing a light emitting layer and dissolved and removed using a mixed solution of ammonia and hydrogen peroxide as an etchant, Ag is particularly susceptible to corrosion by the etchant. Is adopted, the GaAs single crystal substrate 1 can be dissolved and removed without any problem.
[0044]
Further, each layer of the light emitting layer section 24 can also be formed of AlGaInN mixed crystal. As the light emitting layer growth substrate for growing the light emitting layer portion 24, for example, a sapphire substrate (insulator) or a SiC single crystal substrate is used instead of the GaAs single crystal substrate. Further, in the above embodiment, the layers of the light emitting layer portion 24 are arranged in the order of the n-type cladding layer 4, the active layer 5, and the p-type cladding layer 6 from the substrate side. The cladding, the active layer, and the n-type cladding layer may be formed in this order.
[0045]
Further, as shown in FIG. 5 (Step 3), the main metal layer 10 is formed on one side of the metal-impregnated carbon substrate (element substrate) 7 and the light emitting layer portion (compound semiconductor layer) 24 (in FIG. (The part 24 side) and may be bonded. In this case, the bonding heat treatment temperature (step 4) has to be set slightly higher than 200 ° C. to 700 ° C. as compared with FIG.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a first embodiment of a light-emitting element to which the present invention is applied in a laminated structure.
FIG. 2 is an explanatory view showing an example of a manufacturing process of the light emitting device of FIG.
FIG. 3 is a schematic diagram showing a second embodiment of a light emitting element to which the present invention is applied in a laminated structure.
FIG. 4 is an explanatory view showing an example of a manufacturing process of the light emitting device of FIG.
FIG. 5 is an explanatory view showing another example of the manufacturing process of the light emitting device of FIG. 1;
FIG. 6 is a graph showing reflectance of various metals.
[Explanation of symbols]
1 GaAs single crystal substrate (substrate for light emitting layer growth)
4 n-type cladding layer (second conductivity type cladding layer)
5 Active layer 6 p-type cladding layer (first conductivity type cladding layer)
7 Metal-impregnated carbon substrate (element substrate)
Reference Signs List 9 metal electrode 10 main metal layer 10a first Au-based layer 10b second Au-based layer 10c Ag-based layer 24 light-emitting layer 32 AuGeNi junction metal layer 132 AgGeNi junction metal layer 100, 200 light-emitting element

Claims (12)

A first main surface of the compound semiconductor layer having a light emitting layer portion is a light extraction surface, and a reflection surface for reflecting light from the light emitting layer portion toward the light extraction surface on a second main surface side of the compound semiconductor layer. A light-emitting element having an element substrate bonded thereto via a main metal layer having
A light-emitting element, wherein at least a portion of the element substrate including a main surface on the main metal layer side is made of a conductive material mainly composed of an inorganic conductive phase made of carbon or silicon carbide. The light emitting device according to claim 1, wherein the element substrate is entirely made of the conductive material. The light emitting device according to claim 1, wherein the conductive material is a composite material of the inorganic conductive phase and a metal. 4. The light emitting device according to claim 3, wherein the metal is dispersed in a substrate made of the inorganic conductive phase. The light emitting device according to claim 4, wherein the composite material is formed by impregnating a porous substrate made of the inorganic conductive phase with the metal. The method according to any one of claims 3 to 5, wherein the inorganic conductive phase is carbon, and the metal is mainly composed of at least one metal selected from Al, Cu and Mg. The light-emitting element according to any one of the preceding claims. The said inorganic conductive phase is a silicon carbide, and the said metal is a thing which has one or more types of metals selected from Al and Cu as a main component, The Claims 3-5 characterized by the above-mentioned. Light emitting element. The light emitting device according to any one of claims 1 to 7, wherein the main metal layer includes an Au-based coupling layer containing Au as a main component. The light emitting device according to claim 8, wherein the Au-based coupling layer forms the reflection surface. 9. The light emitting device according to claim 8, wherein an Ag-based layer containing Ag as a main component and interposed between the Au-based coupling layer and the compound semiconductor layer forms the reflection surface. A method for manufacturing a light emitting device according to any one of claims 8 to 10, wherein
The main surface on the side opposite to the light extraction surface of the compound semiconductor layer is used as a bonding-side main surface, and on the bonding-side main surface, Au is used as a main component, and the Au-based bonding layer to be the Au-based bonding layer is formed. Arrange one Au-based layer,
The element substrate has a main surface scheduled to be located on the light-emitting layer portion side as a bonding-side main surface, and on the bonding-side main surface, the Au-based bonding layer containing Au as a main component. Arrange the second Au-based layer to be formed,
A method for manufacturing a light-emitting element, wherein the first Au-based layer and the second Au-based layer are closely adhered and bonded. The element substrate and the compound semiconductor layer are attached to each other by laminating the element substrate and the compound semiconductor layer via the Au-based bonding layer and performing a bonding heat treatment in that state. Item 12. The method for manufacturing a light emitting device according to item 11.

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