JP2006013381A - Luminous element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a luminous element that is capable of more increasing a substantial reflectance ratio with a metal layer and is superior in light extraction efficiency, in the luminous element in which the luminous layer is covered with the metal layer. <P>SOLUTION: For the luminous element 100, the first main surface of a compound semiconductor layer 50 having a luminous layer 24 is set as a light-extracting surface, and the metal layer 10, having a reflecting surface which reflects the light from the luminous layer 24 to the light-extracting surface PF side is formed on a second main surface side of the compound semiconductor layer 50. A reflection adjustment layer BG, comprising a compound semiconductor where the reflectance ratio to the peak luminous wavelength of the luminous layer 24 is smaller than that of the compound semiconductor contacting the first main surface side of the layer 24, is provided in the form that the layer 24 contacts the metal layer 10 between the metal layer 10 and the luminous layer 24. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

TECHNICAL FIELD OF THE INVENTION

  The present invention relates to a light emitting element.

JP-A-7-66455 JP 2001-339100 A Nikkei Electronics October 21, 2002, pages 124-132

  As a result of many years of progress in materials and element structures used in light-emitting elements such as light-emitting diodes and semiconductor lasers, the photoelectric conversion efficiency inside the elements 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 and a p-type AlGaInP cladding layer having a larger band gap. By adopting a sandwiched double hetero structure, a high-luminance element can be realized. Such an AlGaInP double heterostructure can be formed by epitaxially growing each layer of an AlGaInP mixed crystal on a GaAs single crystal substrate by utilizing the lattice matching of the AlGaInP mixed crystal with GaAs. When this is used as a light emitting element, a GaAs single crystal substrate is usually used as an element substrate as it is. However, since the AlGaInP mixed crystal constituting the light emitting layer has a larger band gap than GaAs, 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 (for example, Patent Document 1) in which a reflective layer made of a semiconductor multilayer film is inserted between a substrate and a light emitting element has also been proposed. Therefore, only light incident at a limited angle is reflected, and a significant improvement in light extraction efficiency cannot be expected in principle.

  Therefore, Patent Document 2 discloses a technique in which a growth GaAs substrate is peeled off while a reinforcing element substrate (having conductivity) is bonded to a peeled surface through a reflective Au layer. Yes. This Au layer has an advantage that the reflectivity is high and the dependency of the reflectivity on the incident angle is small. However, as is apparent from the fact that the Au layer appears to be colored yellow under white light, the Au layer has a large absorption with respect to light in a specific wavelength band, and the light emitting device has a peak wavelength set in the wavelength range. There is a problem in that the reflectance decreases due to absorption. Therefore, Non-Patent Document 1 discloses a light-emitting element in which the reflection intensity is increased by configuring the reflection layer with Al whose wavelength dependency of reflectance is smaller than that of Au.

  As a result of examination by the present inventor, the Al layer used in the configuration of Non-Patent Document 1 shows a good value of about 90% in the air with a reflectance in the visible light region. In contact with a compound semiconductor such as AlGaInP, the reflectance was greatly reduced to about 80%, and it was found that the light extraction efficiency was not necessarily improved. It was also found that such a decrease in reflectivity occurs more or less when the reflective surface is formed of a metal other than Al.

  An object of the present invention is to provide a light emitting device in which the substantial reflectance by the metal layer can be further increased in a light emitting device in which the light emitting layer portion is covered with a metal layer, and thus the light extraction efficiency is excellent.

Means for Solving the Problems and Effects of the Invention

  In order to solve the above-described problems, the light-emitting element of the present invention has a light-emitting surface as a first main surface of a compound semiconductor layer having a light-emitting layer portion, and a light-emitting layer on the second main surface side of the compound semiconductor layer. A metal layer having a reflection surface for reflecting light from the light-extraction surface side is formed, and between the metal layer and the light-emitting layer portion, the peak light emission of the light-emitting layer portion is in contact with the metal layer. A reflection adjusting layer made of a compound semiconductor having a refractive index with respect to a wavelength smaller than that of the compound semiconductor in contact with the first main surface side of the self is provided.

  According to the light emitting device of the present invention, a compound having a lower refractive index than a compound semiconductor in contact with the first main surface side of the metal layer between the metal layer forming the reflecting surface and the light emitting layer portion in contact with the metal layer. A reflection adjustment layer made of a semiconductor was interposed. Thereby, when the compound semiconductor in contact with the first main surface side of the self forms a light emitting layer part, the reflectance by the metal layer is higher than that of the light emitting element having a structure in which the light emitting layer part is in direct contact with the metal layer. As a result, a light-emitting element superior in light extraction efficiency is realized. This effect is particularly remarkable when the reflective surface of the metal layer is formed of an Al-based metal containing Al as a main component. On the other hand, even when the reflective surface of the metal layer is formed of an Au-based metal containing Au as a main component or an Ag-based metal containing Ag as a main component, due to the arrangement of the reflection adjusting layer, the reflection surface is not as large as in the case of an Al-based metal. Although not, the effect of increasing the reflected light intensity is exhibited similarly. In order to make the above effect remarkable, the refractive index of the reflection adjusting layer is n, the peak emission wavelength in the air of the light emitting layer portion is λ, and the light emission light flux from the light emitting layer portion is within the reflection adjusting layer. It is desirable to adjust the optical film thickness of the reflection adjusting layer to λ ′ / 4 or more, with the wavelength λ ′ at λ / n.

According to Beer's law, when the incident light intensity is I ₀ and the reflected light intensity is I, the reflectance I / I ₀ is expressed by the following formula:
(I / I ₀ ) = exp (−αZ) (1)
α = 4πk / λ ′ (2)
Z: penetration depth of incident light, α: absorption coefficient, λ ′: wavelength, k: extinction coefficient In equation (1), the penetration depth of incident light is uniquely determined by the material constituting the reflecting surface. It can be seen that in order to improve the reflectance, it is necessary to make the absorption coefficient as small as possible. On the other hand, according to the equation (2), it can be seen that, in addition to the extinction coefficient k specific to the material, the wavelength λ ′ of the incident light also affects the value of the absorption coefficient α. Even in the light emitting layer portion having the same band gap energy, the wavelength of the emitted light beam varies depending on the refractive index of the medium through which the light propagates. If the wavelength in the atmosphere (in the case of visible light, approximately the same as the wavelength in vacuum) is λ and the refractive index of the medium is n, the wavelength λ ′ in the medium is expressed as λ / n. The wavelength becomes shorter as the refractive index n of the medium increases.

  Therefore, for example, if the light emitting layer portion having a high refractive index is in direct contact with the metal layer forming the reflecting surface, the wavelength λ ′ of the incident light is shortened by the equation (2), and the absorption coefficient α is increased (1 ), The reflectivity tends to decrease. Therefore, by making the layer in contact with the metal layer a reflection adjusting layer made of a compound semiconductor having a refractive index lower than that of the compound semiconductor forming the light emitting layer portion, the wavelength λ ′ of incident light can be increased and the reflectance can be improved. I understand.

  On the other hand, the extinction coefficient k, which is another factor governing the absorption coefficient α, varies depending on the wavelength of the incident light. However, when expressed by the relative ratio of Al: Ag: Au, the ratio of 13: 11: 8 and Al is approximately. highest. As apparent from the equation (1), the reflectance decreases exponentially with respect to the increase in the absorption coefficient α and hence the extinction coefficient k, so that the influence on the decrease in reflectance is particularly significant. This is considered to be one of the reasons that the effect of improving the reflectance by the arrangement of the reflection adjusting layer is particularly remarkable in the case of Al-based metal.

  Since the metal layer forms a part of the energization path to the light emitting layer portion, the reflection adjusting layer in contact with the metal layer needs to be composed of a compound semiconductor that can ensure conductivity. Further, since the reflection adjusting layer made of a compound semiconductor can be formed by epitaxial growth together with the light emitting layer portion, it goes without saying that it is advantageous in terms of process simplification. In this case, if the reflection adjustment layer is made of a compound semiconductor having a band gap energy larger than the photon energy corresponding to the peak emission wavelength of the light emitting layer portion, the addition of the reflection adjustment layer acts on absorption of the emitted light flux. Without this, the light extraction efficiency can be further improved.

  For example, when the light emitting layer portion is configured to have a double heterostructure of an AlGaInP compound lattice-matched with GaAs, the reflection adjustment layer can be composed of AlGaAs. AlGaAs has a small lattice constant difference from GaAs, and has an advantage that it can be epitaxially grown together with a light emitting layer portion made of an AlGaInP compound on a GaAs substrate. In this case, it is necessary to adjust the AlAs mixed crystal ratio so that the reflection adjusting layer made of the AlGaAs compound has a refractive index smaller than that of the AlGaInP compound forming the cladding layer of the light emitting layer portion. The refractive index of the AlGaAs compound decreases as the AlAs mixed crystal ratio increases. On the other hand, the lower limit value of the AlAs mixed crystal ratio x is such that the band gap energy is larger than that of the active layer included in the light emitting layer part (that is, the band gap energy larger than the photon energy corresponding to the peak emission wavelength). If it is set in advance, it is advantageous because it does not absorb the luminous flux.

In the present invention, “a compound semiconductor that lattice-matches with GaAs” is assumed to be a bulk crystal state in which no lattice displacement is caused by stress, and the lattice constant of the compound semiconductor is a1, and the lattice constant of GaAs is a0. , {| A1-a0 | / a0} × 100 (%) means a compound semiconductor in which the lattice mismatch rate is within 1%. Further, among the compounds represented by “composition formula (Al _{x ′} Ga _{1−x ′} ) _{y ′} In _{1−y ′} P (where 0 ≦ x ′ ≦ 1, 0 ≦ y ′ ≦ 1), GaAs The compound that is lattice-matched with “AlGaInP that is lattice-matched with GaAs” or the like is described.

  The light-emitting element of the present invention can be configured as an element substrate bonded to a compound semiconductor layer via a metal layer. On the other hand, it is also possible to adopt a configuration in which the element substrate is omitted and a metal layer also serving as an electrode is formed on the second main surface of the compound semiconductor layer.

  Hereinafter, an embodiment of a method for manufacturing a light emitting device according to the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a light emitting element to which the present invention is applied. The light emitting element 100 includes a light emitting layer portion on a first main surface of a silicon substrate 7 (in this embodiment, n-type but may be p-type) made of silicon single crystal as an element substrate via a metal layer 10. The compound semiconductor layer 50 containing 24 is bonded.

The light emitting layer portion 24 is made of AlGaInP lattice-matched with GaAs, and is non-doped (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 0.55, 0.45 ≦ y ≦ 0.55). the active layer 5 consisting of) mixed crystal, the first-conductivity-type cladding layer, p-type cladding made of p-type in this embodiment _{(Al z Ga 1-z)} y in 1-y P ( where, x <z ≦ 1) the layer 6, made of a different second conductive type clad layer, n-type in this embodiment _{(Al z Ga 1-z)} y in 1-y P ( where, x <z ≦ 1) and the first-conductivity-type cladding layer According to the composition of the active layer 5, the emission wavelength can be adjusted in the green to red region (the emission wavelength (peak emission wavelength) is not less than 550 nm and not more than 670 nm).

  A current diffusion layer 20 made of AlGaAs (AlInP or GaInP) is formed on the first main surface of the light emitting layer portion 24, and the compound semiconductor layer 50 is configured together with the light emitting layer portion 24. A light extraction surface side electrode 9 (for example, an Au electrode) for applying a light emission driving voltage to the light emitting layer portion 24 is formed substantially at the center of the first main surface of the current diffusion layer 20. Between the light extraction surface side electrode 9 and the current diffusion layer 20, an AuBe bonding alloyed layer 9a as a light extraction side bonding alloyed layer is disposed. A region around the light extraction surface side electrode 9 on the first main surface of the current diffusion layer 20 forms a light extraction region PF from the light emitting layer portion 24.

The thicknesses of the n-type cladding layer 4 and the p-cladding layer 6 are, for example, 0.8 μm or more and 4 μm, respectively.
The thickness of the active layer 5 is, for example, not less than 0.4 μm and not more than 2 μm (desirably not less than 0.4 μm and not more than 1 μm). The total thickness of the light emitting layer portion 24 is, for example, 2 μm to 10 μm (desirably 2 μm to 5 μm). Furthermore, the thickness of the current spreading layer 20 is, for example, 5 μm or more and 28 μm or less (desirably 8 μm or more and 15 μm or less). Therefore, the thickness of the compound semiconductor layer 50 is, for example, 7 μm or more and 30 μm or less (desirably 5 μm or more and 15 μm or less). In the present embodiment, the p-type cladding layer 6 is a laminated form in which the light-extracting surface is located, but the n-type clad layer 4 may be in a laminated form in which it is located on the light-extracting side (in this case, current diffusion). The layer 20 must be n-type, and the bonded alloying layer 9a is made of AuGeNi or the like).

On the other hand, a reflection adjustment layer BG made of AlGaAs is formed on the second main surface of the light emitting layer portion 24. The AlAs mixed crystal ratio x is adjusted with Al _x Ga _1-x As so that the reflection adjusting layer BG has a refractive index smaller than that of AlGaInP forming the cladding layer 4 of the light emitting layer portion 24.

Specific composition setting examples of each layer in the case of red light emission are shown below:
p-type cladding layer 6: (Al _0.85 Ga _0.15 ) _0.5 In _0.5 P
Active layer 5: (Al _0.04 Ga _0.96 ) _0.5 In _0.5 P
n-type cladding layer 4: (Al _0.85 Ga _0.15 ) _0.5 In _0.5 P
Reflection adjustment layer BG: Al _0.9 Ga _0.1 As
The band gap energy of the active layer 5 is 1.94 eV, and the peak emission wavelength λ (in the atmosphere) is 639 nm. Further, the refractive index of the n-type cladding layer 4 with respect to the wavelength is 3.27, and the refractive index of the reflection adjusting layer BG is 3.22.

Moreover, specific composition setting examples of each layer in the case of yellow light emission are shown below:
p-type cladding layer 6: (Al _0.85 Ga _0.15 ) _0.5 In _0.5 P
Active layer 5: (Al _0.3 Ga _0.7 ) _0.5 In _0.5 P
n-type cladding layer 4: (Al _0.85 Ga _0.15 ) _0.5 In _0.5 P
Reflection adjustment layer BG: Al _0.9 Ga _0.1 As
The band gap energy of the active layer 5 is 2.06 eV, and the peak emission wavelength λ (in the atmosphere) is 602 nm. Further, the refractive index of the n-type cladding layer 4 with respect to the wavelength is 3.26, and the refractive index of the reflection adjusting layer BG is 3.21.

  The optical thickness of the reflection adjustment layer BG is λ / 4 or more. Further, the upper limit value of the optical thickness of the reflection adjustment layer BG is appropriately adjusted within a range of, for example, 1 μm or less so that an excessive increase in the element thickness and the influence of light absorption by the reflection adjustment layer BG are not significant.

  Next, the metal layer 10 includes a reflection metal layer 10r disposed in contact with the reflection adjustment layer BG to form a reflection surface, and a bonding metal layer 10a for bonding the reflection metal layer 10r and the silicon substrate 7 to each other. 10b, and a reflection metal layer side diffusion blocking layer 10f interposed between the reflection metal layer 10r and the coupling metal layers 10a and 10b (therefore, contact metal layers 31 and 32 described later are formed on the metal layer 10). Shall not belong). In this embodiment, the reflective metal layer 10r is an Al-based metal layer (Al layer), and the coupling metal layers 10a and 10b are Au-based metal layers (for example, an Au layer). Further, the reflection metal layer side diffusion blocking layer 10f is a Ti-based metal layer (for example, a Ti layer), and has a thickness of 1 nm to 10 μm (200 nm in this embodiment). The reflective metal layer side diffusion blocking layer 10f may be a Ni-based metal layer (for example, a Ni layer), a Cr-based metal layer (for example, a Cr layer), or a W-based metal layer (for example, a W layer) instead of the Ti-based metal layer.

  On the other hand, an AuGeNi contact metal layer 31 (for example, Ge: 15% by mass, Ni: 10% by mass) is formed as a light emitting layer unit side contact metal layer between the light emitting layer unit 24 and the reflective metal layer 10r. This contributes to reducing the series resistance of the element. The AuGeNi contact metal layer 31 is dispersedly formed on the main surface of the reflective metal layer 10r, and the formation area ratio thereof is 1% or more and 25% or less. Further, instead of the AuGeNi contact metal layer 31, an AlGeNi contact metal layer may be used.

  The silicon substrate 7 is manufactured by slicing and polishing a Si single crystal ingot, and the thickness thereof is, for example, 100 μm or more and 500 μm or less. Between the Si single crystal substrate 7 and the metal layer 10, an AuSb contact metal layer 32 (for example, Sb: 5% by mass) as a substrate side contact metal layer is formed in contact with the main surface of the Si single crystal substrate 7. Has been. In place of the AuSb contact metal layer 32, an AuSn contact metal layer may be used.

  The entire surface of the AuSb contact metal layer 32 is covered with a substrate side diffusion blocking layer 10c made of a Ti-based metal layer (for example, a Ti layer). The thickness of the substrate side diffusion blocking layer 10c is 1 nm or more and 10 μm or less (200 nm in this embodiment). The substrate-side diffusion blocking layer 10c may be a Ni-based metal layer (for example, a Ni layer), a Cr-based metal layer (for example, a Cr layer), or a W-based metal layer (for example, a W layer) instead of the Ti-based metal layer. In addition, bonding metal layers 10a and 10b made of Au-based metal are disposed so as to cover the entire surface of the substrate-side diffusion blocking layer 10c so as to be in contact therewith. On the other hand, a back surface electrode (for example, an Au electrode) 15 is formed on the back surface of the silicon substrate 7 so as to cover the whole. An AuSb bonding alloyed layer 16 is interposed between the back electrode 15 and the silicon substrate 7 as a substrate side bonding alloyed layer. Instead of the AuSb bonding alloyed layer 16, an AuSn bonding alloyed layer may be used as the substrate side bonding alloyed layer.

  The light from the light emitting layer portion 24 is extracted in a form in which the light reflected directly from the light extraction surface is superimposed on the light reflected by the reflective metal layer 10r. The thickness of the reflective metal layer 10r is desirably 80 nm or more in order to ensure a sufficient reflection effect. Moreover, although there is no restriction | limiting in particular in the upper limit of thickness, since a reflective effect is saturated, it determines suitably (for example, about 1 micrometer) by balance with cost. Further, the thickness of the coupling metal layer 10a + 10b is set to 200 nm to 10 μm. When the reflective metal layer 10r made of Al layer is in direct contact with the light emitting layer portion 24, the reflectance is remarkably lowered. However, by inserting the reflection adjustment layer BG made of AlGaAs, the incident light becomes longer in wavelength, and the absorption coefficient. Therefore, the reflectance can be increased and the light extraction efficiency can be improved.

Hereinafter, a specific example of the method for manufacturing the light emitting device 100 will be described.
First, as shown in Step 1 of FIG. 2, an n-type GaAs buffer layer 2 is 0.5 μm, for example, and a release layer 3 made of AlAs is 0.5 μm, for example, on the main surface of a GaAs single crystal substrate 1 that is a growth substrate. Then, epitaxial growth is performed in this order. Thereafter, the reflection adjustment layer BG made of AlGaAs is epitaxially grown, for example, by 100 nm, and then the light emitting layer portion 24 is epitaxially grown. The total thickness of the light emitting layer portion 24 is 2.6 μm. Further, a current diffusion layer 20 made of p-type AlGaAs is epitaxially grown by 5 μm, for example. Epitaxial growth of each of these layers can be performed by a known MOVPE method. The following can be used as a source gas that is a component source of Al, Ga, In, P, and As;
Al source gas; trimethylaluminum (TMAl), triethylaluminum (TEAl), etc .;
Ga source gas; trimethylgallium (TMGa), triethylgallium (TEGa), etc .;
In source gas; trimethylindium (TMIn), triethylindium (TEIn), etc.
P source gas; tertiary butyl phosphine (TBP), phosphine (PH ₃ ), etc.
As source gas; tertiary butyl arsine (TBA), arsine (AsH ₃ ), etc.

Moreover, as a dopant gas, the following can be used;
(P-type dopant)
Mg source: biscyclopentadienyl magnesium (Cp ₂ Mg), etc.
Zn source: dimethyl zinc (DMZn), diethyl zinc (DEZn), etc.
(N-type dopant)
Si source: silicon hydride such as monosilane.

  As a result, the compound semiconductor layer 50 including the reflection adjustment layer BG, the light emitting layer portion 24, and the current diffusion layer 20 is formed on the GaAs single crystal substrate 1. The thickness of the compound semiconductor layer 50 is 7.7 μm, and when the GaAs single crystal substrate 1 is removed, it is practically impossible to handle it alone. At this stage, the AuBe bonding metal layer 9a '(light extraction surface side bonding alloyed layer) and the light extraction surface side electrode 9 covering the same are patterned on the first main surface of the compound semiconductor layer 50. Subsequently, the light extraction side alloying heat treatment may be performed to make the AuBe bonding metal layer 9a ′ as the bonding alloying layer 9a. However, in this embodiment, the light extraction side alloying heat treatment is performed as a first bonded metal described later. This is also used for the bonding side alloying heat treatment when forming the AuGeNi bonding alloyed layer 31 on the layer 12a side.

  Next, as shown in step 2, the polymer material bonding layer 111 is applied and formed on the first main surface of the compound semiconductor layer 50 so as to cover the light extraction surface side electrode 9, and as shown in step 3, In a state where the polymer material bonding layer 111 is heated and softened, a separately prepared temporary support substrate 110 is superposed and adhered, and then cooled to cure the polymer material bonding layer 111, whereby the compound semiconductor layer 50 and A temporary support bonded body 120 is prepared by bonding the temporary support substrate 110 to the polymer material bonding layer 111 (step 3). At this time, the GaAs single crystal substrate 1 as a growth substrate is attached to the second main surface side of the compound semiconductor layer 50.

  The material of the temporary support substrate 110 is made of a material that maintains rigidity even during an alloying heat treatment described later and that generates less gas. Specifically, it can be composed of a Si substrate, a ceramic plate (for example, an alumina plate), a metal plate, or the like. The thickness is, for example, 100 μm or more and 500 μm or less, but may be thicker. On the other hand, as the polymer material bonding layer 111, a hot-melt adhesive or wax can be used.

  Next, as shown in step 4 of FIG. 3, the GaAs single crystal substrate 1 as a growth substrate attached to the temporary support bonded body 120 is removed. For this removal, for example, the temporary support bonded body 120 (see step 3) is immersed in an etching solution (for example, a 10% aqueous hydrofluoric acid solution) together with the GaAs single crystal substrate 1 and formed between the buffer layer 2 and the light emitting layer portion 24. The GaAs single crystal substrate 1 can be peeled from the temporary support bonded body 120 by selectively etching the AlAs release layer 3 thus formed. It should be noted that an etch stop layer made of AlInP is formed in place of the AlAs release layer 3, and a GaAs single crystal is used by using a first etching solution (for example, ammonia / hydrogen peroxide mixed solution) having selective etching properties with respect to GaAs. Etch and remove the substrate 1 together with the GaAs buffer layer 2 and then etch stop using a second etchant that has selective etching properties with respect to AlInP (for example, hydrochloric acid: hydrofluoric acid may be added to remove the Al oxide layer) A step of etching away the layer can also be employed. In addition, it is desirable to use the polymer material bonding layer 111 having a corrosion resistance to the above etching solution, and the above-mentioned commercially available products can be suitably employed in the present invention from the viewpoint of the corrosion resistance. .

  In this way, the compound semiconductor layer 50 from which the GaAs single crystal substrate 1 has been removed is bonded to the temporary support substrate 110 via the polymer material bonding layer 111 to form a temporary support bonded body 120. Therefore, even though the compound semiconductor layer 50 is very thin, it is difficult to cause a problem of being destroyed by an impact such as bubbles when the GaAs single crystal substrate 1 is removed by etching, and temporary support sticking is performed even after the GaAs single crystal substrate 1 is removed. Since it is reinforced in the form of the mating body 120, it is possible to easily handle when it is used in the subsequent steps.

  Next, as shown in step 5, in the state of the temporary support bonded body 120, an AuGeNi bonding metal layer is dispersedly formed on the second main surface of the compound semiconductor layer 50 exposed by removing the GaAs single crystal substrate 1, Further, a bonding-side alloying heat treatment is performed so that the AuGeNi bonded metal layer becomes the AuGeNi bonded alloyed layer 31. At this time, the AuBe bonding metal layer 9a 'can be alloyed with the light extraction surface side electrode 9 at the same time (that is, also used for light extraction side alloying heat treatment).

The AuGeNi bonding metal layer is formed by sputtering or vacuum deposition in a vacuum atmosphere. The alloying heat treatment is performed in an inert gas atmosphere at a temperature of 300 ° C. or higher and 450 ° C. or lower. Specifically, the alloying heat treatment can be performed in an inert gas atmosphere such as N _{2 at the} same level as atmospheric pressure. . In addition, since the said temperature of alloying heat processing is higher than the glass transition temperature (about 80-90 degreeC) of the polymeric material coupling layer 111, the polymeric material coupling layer 111 softens during a process. Therefore, in order to prevent slipping during the alloying heat treatment, the temporary support bonded body 120 is placed so that the compound semiconductor layer 50 side is on the upper side and the temporary support substrate 110 side is on the lower side (that is, step 5 in FIG. It is desirable to place them horizontally, and to place a load applying body such as a ceramic substrate or Si substrate.

  Next, the process proceeds to Step 6, and in the state of the temporary support bonded body 120, the reflective metal layer 10r made of Al-based metal is formed on the second main surface of the compound semiconductor layer 50 by vapor deposition, and then the reflective made of Ti-based metal. A metal layer side diffusion blocking layer 10f is formed by vapor deposition, and a bonding metal layer 10a made of Au-based metal is formed by vapor deposition. On the other hand, an AuSb bonding alloyed layer 32 is prepared by separately preparing a silicon substrate 7, forming AuSb bonding metal layers on both main surfaces, and further performing alloying heat treatment in a temperature range of 250 ° C. or higher and 360 ° C. or lower. , 16. Then, a substrate-side diffusion blocking layer 10c made of a Ti-based metal layer (for example, a Ti layer) is formed by vapor deposition so as to cover the bonding alloyed layer 32, and a bonding metal layer 10b made of Au-based metal is further formed. The alloying heat treatment may be performed after forming the bonding metal layer 10b.

  Next, as shown in Step 7 of FIG. 4, the Au-based metal layer 10a formed on the compound semiconductor layer 50 side is overlaid and pressed on the Au-based metal layer 10b formed on the silicon substrate 7 side, and 180 Bonding heat treatment is performed at a temperature of not lower than 360 ° C. and not higher than 360 ° C. (lower temperature than the above alloying heat treatment), for example, 250 ° C. Thereby, the Au-based metal layer 10a and the Au-based metal layer 10b are bonded together with sufficient strength. Further, the compound semiconductor layer 50 and the silicon substrate 7 are bonded together via the metal layer 10 to form a bonded bonded body 130. Since the Au-based metal layers 10a and 10b are mainly composed of Au that is not easily oxidized, the bonding heat treatment can be performed without any problem even in the air, for example.

  When the bonding heat treatment is completed, a temporary support substrate separation step is performed. In the temporary support substrate separation step, as shown in Step 8 of FIG. 4, the polymer material bonding layer 111 is heated and softened, and the temporary support substrate 110 is separated and removed. Note that this separation can be performed simultaneously with the bonding heat treatment in step 7. Thereafter, as shown in Step 9, the polymer material bonding layer 111 remaining on the first main surface of the compound semiconductor layer 50 is dissolved and removed using an organic solvent.

  In the above, for the purpose of facilitating understanding, the process of forming the bonded assembly 130 has been described in the form of a single element stack, but in practice, a plurality of element chips are arranged in a matrix. A bonded wafer formed in a lump is created. Then, the bonded wafer is diced by an ordinary method to form an element chip, which is fixed to a support and subjected to wire bonding of a lead wire, etc., and then sealed with a resin to obtain a final light emitting element. can get.

  In the light emitting element of the present invention, the entire metal layer 10 including the reflective surface forming portion can be composed of an Au-based metal as in the light emitting element 200 of FIG. Common parts are given the same reference numbers). The metal layer 10 is obtained by bonding Au-based metal layers 10a and 10b together. Alternatively, the Au-based metal layers 10a and 10b may be replaced with Ag-based metal layers, and the Ag-based metal layers may be bonded to each other. In this case, the entire metal layer including the reflective surface forming portion is made of an Ag-based metal. Even in these configurations, although not as much as the light emitting device 100 of FIG. 1 using the Al-based reflective metal layer 10r, the reflectance can be improved by forming the reflection adjustment layer BG. Further, in the light emitting device 300 of FIG. 6, a GaP substrate (n-type) 70 that is a transparent conductive semiconductor substrate is bonded to the second main surface of the light emitting layer portion 24, and AlGaAs is bonded to the second main surface of the GaP substrate 70. A reflection adjustment layer BG made of (n-type) is formed. Then, a joining alloyed layer 16 ′ using an AuGeNi alloy is dispersedly formed on the second main surface of the reflection adjusting layer BG, and is covered with any of Al-based metal, Ag-based metal, or Au-based metal so as to cover it. A back electrode 15 that also serves as a reflective metal layer is formed. Although it is GaP that contacts the first main surface of the reflection adjustment layer BG, AlGaAs that forms the reflection adjustment layer BG has a lower refractive index than GaP, and contributes to the improvement of the reflectance by the back electrode 15.

1 is a schematic cross-sectional view illustrating a first example of a light-emitting element of the present invention. Process explanatory drawing which shows an example of the manufacturing method of the light emitting element of FIG. Process explanatory drawing following FIG. Process explanatory drawing following FIG. The cross-sectional schematic diagram which shows the 2nd example of the light emitting element of this invention. The cross-sectional schematic diagram which shows the 3rd example of the light emitting element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Metal layer 10r Reflective metal layer 24 Light emitting layer part BG Reflection adjustment layer 50 Compound semiconductor layer 100,200,300 Light emitting element

Claims (6)

The first main surface of the compound semiconductor layer having the light emitting layer portion is used as a light extraction surface, and the second main surface side of the compound semiconductor layer is a reflecting surface that reflects light from the light emitting layer portion to the light extraction surface side. In addition, the refractive index with respect to the peak emission wavelength of the light emitting layer portion is the first main layer of the light emitting layer portion in contact with the metal layer between the metal layer and the light emitting layer portion. A light-emitting element comprising a reflection adjusting layer made of a compound semiconductor smaller than a compound semiconductor in contact with the surface side. The refractive index of the reflection adjustment layer is n, the peak emission wavelength in the atmosphere of the light emitting layer portion is λ, and the wavelength λ ′ of the emitted light beam from the light emitting layer portion in the reflection adjustment layer is λ / n. The light emitting device according to claim 1, wherein an optical film thickness of the reflection adjusting layer is adjusted to λ ′ / 4 or more. The light emitting device according to claim 1, wherein the reflective surface of the metal layer is formed of an Al-based metal containing Al as a main component. 3. The light emitting device according to claim 1, wherein the reflective surface of the metal layer is formed of an Au-based metal containing Au as a main component or an Ag-based metal containing Ag as a main component. . The said reflection adjustment layer consists of a compound semiconductor which has a larger band gap energy than the photon energy corresponding to the peak light emission wavelength of the said light emitting layer part, The Claim 1 thru | or 4 characterized by the above-mentioned. Light emitting element. The light emitting layer portion is configured to have an AlGaInP compound double heterostructure lattice-matched with GaAs, and an AlAs mixed crystal ratio is set so that the refractive index is smaller than that of the AlGaInP compound forming the cladding layer of the light emitting layer portion. The light emitting device according to any one of claims 1 to 5, wherein the reflection adjustment layer is formed of adjusted AlGaAs.

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