JP2004356213A - Semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device which is capable of restraining a semiconductor light emitting element from deteriorating due to heat released from it when it emits light using light emitted from the element more effectively, manufactured at a low cost, and reduced in size. <P>SOLUTION: The semiconductor light emitting device is equipped with a semiconductor light emitting element which contains a GaN semiconductor as a component element and is positioned on the bottom of a cone-shaped hollow provided to a support substrate. A silicon substrate is used as the above support substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor light emitting device, and more particularly, to a semiconductor light emitting device incorporating a blue or ultraviolet light emitting element.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a semiconductor light emitting device, one having a configuration disclosed in Patent Document 1 or Patent Document 2, for example, is known. The devices disclosed in these patent documents are examples of a blue semiconductor light emitting device, and have a structure in which a semiconductor light emitting element is provided on an insulating circuit board.
[0003]
As an insulating substrate used in a conventional semiconductor light emitting device, a ceramic substrate such as alumina is generally used, but these ceramic substrates have low thermal conductivity. Therefore, the action of discharging the heat generated at the time of light emission is small, and this heat may cause a problem of deterioration of the semiconductor light emitting element.
[0004]
In the semiconductor light emitting device of Patent Document 2, a gap is provided between a resin sealing body for sealing the semiconductor light emitting element and the wiring board, and heat is radiated from the gap. In order to avoid the problem of heat generation at the time of light emission, it is necessary to adopt the special structure as described above.
[0005]
In a semiconductor light emitting device, a part of light generated from a semiconductor light emitting element usually leaks from a side surface of the element and is absorbed by constituent members of the device. For this reason, there is a problem that the ratio of light emitted from the semiconductor light emitting element that can be extracted to the outside of the semiconductor light emitting device and used effectively is reduced.
[0006]
[Patent Document 1]
JP-A-11-340517 [Patent Document 2]
JP 2002-208737 A
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress deterioration of a semiconductor light emitting device due to heat generated during light emission, and to more effectively utilize light emitted from the device. It is another object of the present invention to provide a semiconductor light emitting device that can achieve cost reduction and downsizing while being able to perform the operations.
[0008]
[Means for Solving the Problems]
The semiconductor light emitting device of the present invention is a semiconductor light emitting device having a semiconductor light emitting element including a GaN-based semiconductor as a component on a bottom surface of a concave portion of a support substrate having a mortar-shaped concave portion on the inner surface, wherein the support substrate is The feature is that it is a silicon substrate.
[0009]
In the semiconductor light emitting device of the present invention, since the supporting substrate is a silicon substrate having excellent heat conduction, heat generated during light emission can be effectively discharged through the silicon substrate, and thermal degradation of the semiconductor light emitting element can be suppressed. . In addition, the silicon substrate as the support substrate is inexpensive as compared with a conventional ceramic substrate, so that cost reduction can be achieved.
[0010]
Further, a driving circuit or the like for driving the semiconductor light emitting element can be provided on the supporting substrate, so that the size of the semiconductor light emitting device can be reduced.
[0011]
In addition, the light leaking from the side surface of the semiconductor light emitting element can be reflected on the inclined surface of the concave portion of the support substrate and taken out of the device. Therefore, of the light emitted from the semiconductor light emitting element, the ratio of light that can be extracted to the outside of the device and effectively used (hereinafter, may be referred to as “light extraction efficiency”) can be increased.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
<First embodiment>
FIG. 1 is a schematic plan view showing a first embodiment of the semiconductor light emitting device of the present invention, and FIG. 2 is a schematic diagram showing a cross section taken along line AA of FIG. 1 in more detail. In the semiconductor light emitting device 10a according to the first embodiment, a semiconductor light emitting element 102 is fixed to a bottom surface of a concave portion of a support substrate 101 which is a silicon substrate having a mortar-shaped concave portion on the inner surface. The semiconductor light emitting element 102 is sealed with a sealing resin 109.
[0013]
The semiconductor light-emitting element 102 includes a GaN-based semiconductor in which an n-layer 104, a light-emitting layer 105, and a p-layer 106 are sequentially stacked on a light-transmitting substrate 103 as a component, and further includes a p-type electrode 108 on the surface of the p-layer 106. And an exposed surface is formed so that a part of the n-layer 104 is exposed from the p-layer 106 side, and the n-type electrode 107 is provided on the exposed surface.
[0014]
The semiconductor light-emitting element 102 is fixed to the support substrate 101 so that a light-transmitting substrate 103 is interposed between the n-layer 104 and the support substrate 101, and is electrically connected to the support substrate 101 by wire bonds 110. It is connected. A power source (stable power source 114) is connected to the support substrate 101. The connection to the support substrate by wire bonding may be at a position other than the above-described concave portion of the support substrate as shown in FIG. 2 or may be an inclined surface of the concave portion.
[0015]
When a forward bias is applied between the n-type electrode 107 and the p-type electrode 108 by the stable power supply 114 (that is, a positive voltage is applied to the p-type electrode), electrons and holes are combined in the light emitting layer 105. Then, blue or ultraviolet light (wavelength: 500 to 250 nm) is generated, and this light is extracted to the outside of the device through the sealing resin 109. At this time, light traveling toward the side surface of the semiconductor light emitting element 102 is reflected by the inclined surface 111 of the support substrate 101 toward the upper side of the device (outside of the device) (a1 in FIG. 2), so that the light is also extracted. Therefore, the efficiency of extracting light generated inside the element can be increased.
[0016]
The support substrate 101, that is, the concave portion of the silicon substrate can be formed by known anisotropic etching. Anisotropic etching is a technique for forming a microstructure based on the crystal plane by utilizing the characteristic of silicon that the etching rate varies depending on the direction of the crystal plane. The recess can be formed by etching the (100) plane of single-crystal silicon to expose the (111) plane using, for example, a KOH aqueous solution. The shape (for example, opening area and depth) of the concave portion can be adjusted by controlling the etching depth by adjusting the shape of the etching mask and the etching time.
[0017]
Next, the semiconductor light emitting device 102 will be described. Sapphire is generally used as a material of the light-transmitting substrate 103. The thickness of the translucent substrate is usually 30 to 500 μm.
[0018]
n layer 104 is a layer formed from n-type GaN-based compound semiconductor, _{specifically,} expressed by _{Al a In b Ga 1-a} -b N (0 ≦ a, 0 ≦ b, a + b ≦ 1) Consists of compounds. For example, a can or _Al a _{Ga 1-a} N is 0.5 or less, b is _{In b Ga 1-b} N is preferably 0.5 or less.
[0019]
Although the n-layer 104 is shown as a single layer in FIG. 2, the n-layer has a laminated structure in which an n-type contact layer and an n-type clad layer are laminated in this order from the support substrate side. Is also good. In this case, the exposed surface for forming the n-type electrode 107 is formed such that the n-type contact layer is exposed. As the n-type contact layer, GaN is generally used among the above compounds constituting the n-layer. In addition, as the n-type cladding layer, Al _0.3 Ga _0.7 N, AlN, GaN, or the like is generally used among the above-described compounds constituting the n-layer.
[0020]
It is desirable that the n-layer, the n-type contact layer, and the n-type clad layer having the single-layer structure be doped with an n-type impurity such as Si, Ge, or S because the carrier concentration can be increased.
[0021]
When the n-layer has a single-layer structure, the thickness of the n-layer is generally 0.5 to 10 μm. When the n-layer has a laminated structure of an n-type contact layer and an n-type clad layer, the thickness of the n-type contact layer is generally 0.2 to 10 μm, and the thickness of the n-type clad layer is particularly limited. However, it is usually 0.01 to 3 μm.
[0022]
Emitting layer 105 is a layer formed from GaN-based compound semiconductor, _{specifically,} the _{Al c In d Ga 1-c} -d N (0 ≦ c, 0 ≦ d, c + d ≦ 1) represented by compounds Be composed. In this light emitting layer, for example, by adjusting the composition ratio of In and Al of the above compound, the light emitting layer is doped with an n-type impurity such as Si, Ge, and S, or a p-type impurity such as Mg and Zn. By doing so, the wavelength of the generated light can be adjusted in the range from blue to ultraviolet.
[0023]
In FIG. 2, the light-emitting layer 105 is shown as a single layer; however, for example, the light-emitting layer has a stacked structure including a plurality of layers, and has a so-called multiple quantum well structure in which the composition of a compound forming each layer is changed. Is also preferred. The thickness of the light emitting layer is generally 0.001 to 0.5 μm in total thickness.
[0024]
The p layer 106 is a layer made of a p-type GaN-based compound semiconductor. Although the p-layer 106 is shown as a single layer in FIG. 2, it generally has a stacked structure in which a p-type cladding layer and a p-type contact layer are stacked in this order from the light emitting layer side.
[0025]
The p-type cladding layer is made of, for example, a compound represented by Al _e Ga _1-e N (0 <e ≦ 1), and further doped with a p-type impurity. e is preferably 0.05 or more. The p-type contact layer is made of, for example, p-type GaN doped with a p-type impurity. Examples of p-type impurities doped into the p-type cladding layer and the p-type contact layer include Mg, Zn, and the like. The thickness of the p-type cladding layer is usually 0.001 to 1.5 μm, and the thickness of the p-type contact layer is generally 0.01 to 2 μm.
[0026]
The material of the n-type electrode 107 and the p-type electrode 108 of the semiconductor light emitting device 102 is not particularly limited as long as it can be electrically connected to the n-layer and the p-layer, respectively. A laminated structure of an Au layer (the Au layer is the outermost layer) is generally used. In this case, the thickness of each layer is usually 0.1 to 0.5 μm for the V layer and 1 to 3 μm for the Au layer. The p-type electrode generally has, for example, a laminated structure of a Ni layer and an Au layer (Au is the outermost layer). In this case, the thickness of each layer is usually 0.1 to 0.5 μm for the Ni layer and 1 to 3 μm for the Au layer.
[0027]
In forming the n-layer 102, the light-emitting layer 103, and the p-layer 104, a known film forming method such as a vapor phase growth method [metalorganic vapor phase epitaxy (MOCVD) or the like] can be employed. The doping of the n-type impurity into the n-layer and the doping of the p-type impurity into the p-layer are performed when these layers are formed (vapor phase growth).
[0028]
Although not shown in FIG. 2, when the supporting substrate is a sapphire substrate, it is difficult to form the n-layer directly, so that a buffer layer is preferably provided between the n-layer and the supporting substrate. Such a buffer layer has an effect of alleviating lattice mismatch between the supporting substrate and the n-layer. Due to the presence of the buffer layer, the formation of the n-layer (growth of the n-type GaN-based compound semiconductor crystal) can be improved. It is possible to proceed. Examples of the buffer layer include GaN, AlN, GaAlN, and ZnO. By the way, when forming an n-layer by vapor phase growth using GaN, a two-step growth method is adopted in which a buffer layer is formed by first forming a film under low-temperature conditions, and then the temperature is increased to form an n-layer. By doing so, the buffer layer and the n layer can be formed more easily. The thickness of the buffer layer is usually 0.001 to 1 μm.
[0029]
The exposed surface of the n-layer for forming the n-type electrode can be formed by an etching method using a photoresist or the like. Further, the p-type electrode and the n-type electrode may be formed by a known evaporation method or the like.
[0030]
The method for fixing the semiconductor light emitting element 102 to the support substrate 101 is not particularly limited. However, as shown in FIGS. 1 and 2, when the semiconductor light emitting element is electrically connected to the support substrate by wire bonding, a known die is used. A bonding method or the like can be adopted. Further, the semiconductor light emitting element may be fixed to the support substrate and electrically connected by so-called flip chip bonding.
[0031]
As shown in FIGS. 1 and 2, by providing a metal film 112 that can function as a reflective film on a part or the entirety of the inclined surface 111, the reflection efficiency of light toward the upper part of the device can be further increased. Can be.
[0032]
The material forming the metal film 112 preferably has a reflectance of 60% or more of light generated from the semiconductor light emitting element, and examples thereof include Al, Ag, and Rh. The metal film 112 can be formed by a known evaporation method or the like.
[0033]
Further, it is preferable that a rough surface structure 113 is formed around the formation portion of the semiconductor light emitting element 102 on the bottom surface of the concave portion. Due to the rough surface structure 113, light generated from the semiconductor light emitting element 102 and traveling toward the support substrate 101 is irregularly reflected and directed toward the top of the device (a2 in FIG. 2) or toward the inclined surface 111 (metal film 112). The light can be further reflected toward the upper side of the device by the inclined surface 111 (metal film 112), so that the light extraction efficiency can be further increased.
[0034]
The shape and configuration of the rough surface structure 113 are not particularly limited, as long as the rough surface structure 113 can diffusely reflect light traveling toward the support substrate 101 side. For example, a configuration in which a plurality of protrusions having the shapes shown in FIGS. 1 and 2 may be present. The protrusions have a shape like a continuous wall and are formed so as to surround the periphery of the formation portion of the semiconductor light emitting element. It may be a configuration. However, in order to more effectively diffuse the light traveling toward the support substrate side, it is preferable that a plurality of protrusions having the shapes shown in FIGS. 1 and 2 exist.
[0035]
The rough surface structure 113 can be formed by adjusting the etching conditions when the concave portion is formed by performing the above-described anisotropic etching on the support substrate 101.
[0036]
Although not shown in FIGS. 1 and 2, it is also preferable to provide the above-mentioned metal film (reflection film) on the bottom surface of the concave portion. In this case, light traveling toward the support substrate is more effectively transmitted to the upper portion of the device. Can be reflected to the side. Such a metal film can also be formed by a known vapor deposition method or the like.
[0037]
<Second embodiment>
FIG. 3 is a schematic plan view showing a second embodiment of the semiconductor light emitting device of the present invention, and FIG. 4 is a schematic diagram showing a cross section along line BB of FIG. 1 in more detail. Portions having the same functions as those in the first embodiment are denoted by the same reference numerals, and redundant description will be avoided. The second embodiment has the following features.
[0038]
In the semiconductor light emitting device 10b of the second embodiment, a drive circuit for driving the semiconductor light emitting element 102 is provided in the drive circuit forming section 116 of the support substrate 101. Thus, when the drive circuit is provided in the semiconductor light emitting device, it is not necessary to provide the drive circuit outside the support substrate 101, and the semiconductor light emitting device can be reduced in size.
[0039]
When a pattern for forming a drive circuit is provided on the inclined surface 111 of the concave portion of the support substrate 101, if a metal film (reflection layer) is directly formed on the inclined surface, current leaks. Since light emission of the semiconductor light emitting element may be hindered, an insulating film 115 such as a SiO ₂ film is preferably provided between the inclined surface 111 and the metal film 112 as shown in FIG.
[0040]
Further, a driving circuit provided in the supporting substrate 101 is not particularly limited, and examples thereof include a circuit including a resistor for reducing a current value as needed. In the case where an AC power supply is employed, a circuit in which an AC / DC conversion circuit is combined with the above circuit can be used.
[0041]
FIG. 5 shows an example of an equivalent circuit of the semiconductor light emitting device of the present invention including the semiconductor light emitting element 102 and the driving circuit 117. In the semiconductor light emitting device of the present invention, in any of the first embodiment, the second embodiment, and the third embodiment described below, as shown in FIG. Are preferably connected in parallel. By employing such a configuration, it is possible to prevent the semiconductor light emitting element 102 from being damaged when an overvoltage is applied.
[0042]
<Third embodiment>
FIG. 6 is a schematic sectional view showing a third embodiment of the semiconductor light emitting device of the present invention. In the semiconductor light emitting device 10c of the third embodiment, the bottom surface of the recess of the support substrate 101 formed with the recess by anisotropic etching described above, SiC or _{Al X In Y Ga 1-X} -Y N (0 ≦ X .Ltoreq.1,0.ltoreq.Y.ltoreq.1,0.ltoreq.1-XY.ltoreq.1) A semiconductor light emitting device in which an n-layer 104, a light-emitting layer 105, a p-layer 106, and a p-type electrode 108 are sequentially formed via a thin film 119. 102 are provided.
[0043]
n-type electrode 107 is provided on the supporting substrate 101, diffusion layer 120, and SiC or _{Al X In Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ 1- XY ≦ 1) It is electrically connected to the n-layer 106 via the thin film 119. The diffusion layer 120 of the supporting substrate 101 has impurities diffused therein, and thus has lower electric resistance than other portions, so that current can flow. The diffusion layer 120 can be formed by a method in which an impurity such as boron is ion-implanted and then heat treatment is performed. The depth of the diffusion layer is usually about 0.5 μm or less.
[0044]
Although not shown in FIG. 6, a part of the support substrate 101 and the semiconductor light emitting element 102 are sealed with a sealing resin as in the first embodiment and the second embodiment.
[0045]
The configuration, material, thickness, and forming method of the n-layer 104, the light-emitting layer 105, the p-layer 106, the n-type electrode 107, and the p-type electrode 108 according to the semiconductor light emitting device 102 are the same as those in the first embodiment. In the semiconductor light emitting device 10c of the third embodiment, the components of the semiconductor light emitting element 102 can be formed directly on the support substrate 101. Therefore, the step of fixing the semiconductor light emitting element 102 to the support substrate 101 by the above-described die bonding method or the like can be omitted.
[0046]
Note that, even if an n-layer is directly formed on a silicon substrate as a supporting substrate by the above-described vapor deposition method or the like, an n-layer forming component diffuses into the silicon substrate, and it is difficult to form a layer. Therefore, protection of the SiC or _{Al X In Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ 1-X-Y ≦ 1) thin film 119, for n layer 104 formed It is provided on the supporting substrate 101 as a layer. Preferable specific examples of _{Al X In Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ 1-X-Y ≦ 1) thin film, GaN, AlN and the like .
[0047]
The SiC or _{Al X In Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ 1-X-Y ≦ 1) thin film, similar to the like n-layer, the above-described air It can be formed by a phase growth method (such as a MOCVD method). The thickness of such a thin film is preferably 10 μm or less, more preferably 0.1 to 3 μm or less.
[0048]
Further, similarly to the first embodiment, a metal film is provided on the inclined surface of the concave portion of the support substrate 101, or a rough surface structure or a metal film is formed around the formation portion of the semiconductor light emitting element 102 on the bottom surface of the concave portion. It is also preferable from the viewpoint that the light extraction efficiency can be increased. Further, as in the second embodiment, it is also recommended to provide a drive circuit for driving the semiconductor light emitting element 102 on the support substrate 101, because the size of the semiconductor light emitting device can be reduced.
[0049]
【The invention's effect】
In the semiconductor light emitting device of the present invention, since the supporting substrate is a silicon substrate having excellent heat conduction, heat generated during light emission can be effectively discharged through the silicon substrate, and thermal degradation of the semiconductor light emitting element is suppressed. obtain. In addition, the silicon substrate as the support substrate is inexpensive as compared with a conventional ceramic substrate, so that cost reduction can be achieved.
[0050]
Further, a driving circuit or the like for driving the semiconductor light emitting element can be provided on the supporting substrate, so that the size of the semiconductor light emitting device can be reduced.
[0051]
In addition, since the light leaking from the side surface of the semiconductor light emitting element can be reflected and taken out of the device on the inclined surface of the concave portion of the support substrate, the light emitted from the element can be more effectively utilized. Can be.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a first embodiment of a semiconductor light emitting device of the present invention.
FIG. 2 is a schematic cross-sectional view taken along line AA of FIG.
FIG. 3 is a schematic plan view showing a second embodiment of the semiconductor light emitting device of the present invention.
FIG. 4 is a schematic sectional view taken along line BB of FIG. 2;
FIG. 5 is a diagram showing an example of an equivalent circuit of the semiconductor issuing device of the present invention.
FIG. 6 is a schematic sectional view showing a third embodiment of the semiconductor light emitting device of the present invention.
[Explanation of symbols]
10a 10b 10c Semiconductor light emitting device 101 Support substrate 102 Semiconductor light emitting element 103 Translucent substrate 104 N layer 105 Light emitting layer 106 P layer 107 N type electrode 108 P type electrode 109 Sealing resin 110 Wire bond 111 Inclined surface 112 Metal film 113 Rough foliation 114 stable power supply 115 insulating film 116 driver circuit formation section 117 drive circuit 118 diode 119 SiC or _{Al X In Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ 1-X −Y ≦ 1) Thin film 120 Diffusion layer a1 Path a2 of light reflected to the upper side of device by metal film Path a2 of light reflected to the upper side of device by rough surface structure

Claims (8)

A semiconductor light-emitting device having a semiconductor light-emitting element including a GaN-based semiconductor as a component on a bottom surface of a concave portion of a support substrate having a mortar-shaped concave portion on an inner surface,
The semiconductor light emitting device according to claim 1, wherein the support substrate is a silicon substrate. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting element has a light transmitting substrate between the n layer and the support substrate. The semiconductor light emitting device, SiC or _{Al X In Y Ga 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ 1-X-Y ≦ 1) through the thin film, the n layer 2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is formed sequentially. The semiconductor light emitting device according to any one of claims 1 to 3, wherein the semiconductor light emitting device has a rough surface structure around a formation portion of the semiconductor light emitting element on the bottom surface. The semiconductor light emitting device according to claim 1, wherein the inclined surface of the concave portion has a metal film having a reflectance of at least 60% for light generated from the semiconductor light emitting element. The semiconductor light emitting device according to claim 5, wherein the metal film is made of Al, Ag, or Rh. The semiconductor light emitting device according to any one of claims 1 to 6, wherein a drive circuit for driving the light emitting element electrically connected to the semiconductor light emitting element is provided on the support substrate. The semiconductor light emitting device according to claim 1, further comprising a diode connected in parallel with the semiconductor light emitting element.

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