JP6888651B2 - Semiconductor light emitting device - Google Patents

Description

The present invention relates to a semiconductor light emitting device.

Various studies have been conducted on light emitting devices using nitride semiconductors because they can emit light in the red region from near-ultraviolet rays due to their wide bandgap characteristics. As a general structure of a nitride semiconductor light emitting device, in a semiconductor laminated structure in which an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are laminated on a substrate, almost the entire surface of the p-type nitride semiconductor layer is covered. A structure in which an electrode is provided can be mentioned.

Further, a type of nitride semiconductor light emitting device in which an electrode provided on almost the entire surface of a p-type nitride semiconductor layer is a translucent electrode made of a metal oxide such as ITO, and light is emitted through the translucent electrode. There is also. The translucent electrode made of ITO or the like has a higher resistance than metal, and it is necessary to form the translucent electrode thicker in order to obtain sufficient current diffusivity, but the translucent electrode is thicker. Then, there is a concern that the light absorption by the translucent electrode will increase. In order to solve such a problem, Patent Document 1 describes current diffusion made of a metal material between the p-type nitride semiconductor layer and the translucent electrode in order to supplement the current diffusivity of the translucent electrode. It is disclosed that a layer is provided to reduce the thickness of the translucent electrode.

Japanese Unexamined Patent Publication No. 2006-156590

However, a translucent electrode made of a metal oxide such as ITO absorbs less light but exists to some extent. Therefore, it is required to further increase the output of the semiconductor light emitting device, and it is desired to suppress the absorption of light in the electrode.

Therefore, an object of the present invention is to provide a semiconductor light emitting device capable of suppressing the absorption of light in an electrode and realizing further high output.

In order to solve the above problems, the semiconductor light emitting device according to the embodiment of the present invention is
The first conductive type first semiconductor layer, the second conductive type second semiconductor layer, the light emitting region formed between the first semiconductor layer and the second semiconductor layer, and the first semiconductor layer are connected to each other. A semiconductor light emitting element including the first electrode and the second electrode connected to the second semiconductor layer.
The second electrode is
A connection electrode having translucency and in contact with the second semiconductor layer,
It has a semiconductor electrode having translucency and made of a semiconductor layer in contact with the connection electrode.

According to the embodiment of the present invention configured as described above, since the semiconductor electrode composed of the semiconductor layer is provided, the semiconductor light emitting device capable of suppressing the absorption of light in the electrode and realizing further high output is provided. be able to.

It is sectional drawing which shows the structure of the semiconductor light emitting element of Embodiment 1 which concerns on this invention. It is sectional drawing when the semiconductor electrode 23 is grown on the growth substrate 21 in the manufacturing method of the semiconductor light emitting element of Embodiment 1. FIG. 5 is a cross-sectional view when an adhesive layer 25 is formed on the upper surface of a semiconductor electrode 23 and a support substrate 27 is further bonded in the method for manufacturing a semiconductor light emitting device according to the first embodiment. In the method for manufacturing a semiconductor light emitting device of the first embodiment, when the growth substrate 21 is removed after the support substrate 27 is bonded and the second ohmic electrode 29 is formed on the surface of the semiconductor electrode 23 exposed by the removal of the growth substrate 21. It is a cross-sectional view of. FIG. 5 is a cross-sectional view when a first conductive semiconductor layer 3, a light emitting layer 5, and a second conductive semiconductor layer 7 are grown on the surface of a substrate 1 in the method for manufacturing a semiconductor light emitting device according to the first embodiment. In the method for manufacturing a semiconductor light emitting device of the first embodiment, after the first conductive semiconductor layer 3, the light emitting layer 5, and the second conductive semiconductor layer 7 are grown on the surface of the substrate 1, the second conductive semiconductor layer is formed. It is sectional drawing when the 1st ohmic electrode 9 is formed on the upper surface of 7. In the method for manufacturing a semiconductor light emitting device of the first embodiment, the first ohmic electrode 9 formed on the upper surface of the second conductive semiconductor layer 7 and the second ohmic electrode 29 formed on the surface of the semiconductor electrode 23 are joined. It is a cross-sectional view of the time. FIG. 5 is a cross-sectional view when the adhesive layer 25 and the support substrate 27 are removed in the method for manufacturing a semiconductor light emitting device according to the first embodiment. It is sectional drawing which shows the structure of the semiconductor light emitting element of the modification which concerns on this invention.

This embodiment is made by paying attention to the fact that the semiconductor layer has a higher resistivity than the electrode typified by metal, but the sheet resistance can be made equivalent to that of metal by increasing the film thickness.

1. 1. Theoretical Consideration The function as an electrode that diffuses current is shown in Table 1 below when comparing conventional ITO and Ag with n-type gallium nitride (n-GaN) in terms of resistivity.

As is clear from Table 1, the resistivity of n-type gallium nitride (n-GaN) is 1000 times or more higher than that of metals such as Ag, and 10 times higher than that of conventionally used transparent electrodes such as ITO. More than twice as large. However, since the resistivity can be lowered by increasing the film thickness of the n-GaN layer used as the electrode layer, it is possible to realize a sheet resistance comparable to that of a metal such as Ag or a metal oxide such as ITO. For example, the Ag electrode used as a translucent electrode is formed to have a film thickness of about 20 Å to ensure translucency and diffuse a current, but the sheet resistance equivalent to that of the Ag electrode having a film thickness of 20 Å is high. This can be achieved by using an n-GaN layer with a thickness of 6 μm (see Table 3 below). Since there is no problem in forming a nitride semiconductor layer having a thickness of several μm to several tens of μm as a component of the semiconductor light emitting device, a semiconductor layer such as an n-GaN layer can be sufficiently used as an electrode. It is possible.

Further, a comparison between conventional ITO and Ag and n-type gallium nitride (n-GaN) in terms of optical constants with the intention of using the semiconductor electrode as a translucent electrode is shown in Table 2 below. become.

In Table 2, n and k are the real part of the refractive index and the imaginary part of the refractive index in the complex refractive index N represented by the following formula (1). Here, the complex index of refraction N is defined by the ratio of the speed of light c in a vacuum to the speed of light v in a medium.
N = n-ik ... (1)
Here, i is an imaginary number, and it goes without saying that i ² = -1.
Further, the refractive index real number part n is usually simply referred to as a refractive index, and the refractive index imaginary part k is a value related to light absorption, and has a relationship given by the absorption coefficient α and the following equation (2).
α = 4πk / λ ... (2)
Here, α is the reciprocal of the propagation distance that reduces the intensity of the incident light to the intensity of 1 / e, and λ is the wavelength of the light.
Further, the transmittance T when traveling a distance d through the membrane, which is the absorption coefficient α, is given by the following equation (3).
T = exp (-αd) ... (3)

As is clear from the above, the light absorption rate of n-type gallium nitride (n-GaN) is extremely small as compared with the conventionally used transparent electrodes such as ITO, and the n-type gallium nitride (n-GaN) has a slightly smaller light absorption rate. It can be understood that an electrode having a sufficiently small light absorption rate can be realized even if the film thickness of the GaN) layer is increased.

Therefore, when each film thickness is set so as to have the same sheet resistance, the sheet resistivity and the light absorption are calculated and shown in Table 3 below.

As can be seen from Table 3, for example, instead of using an ITO electrode having a thickness of about 0.2 μm (1930 Å), an n-type gallium nitride semiconductor layer having a thickness of about 6 μm (60,000 Å) made of n-GaN is used as an electrode. It can be understood that a translucent electrode having almost the same sheet resistance as the ITO electrode and having an extremely small light absorption rate can be realized by using the electrode.

As described above, the semiconductor layer such as n-type gallium nitride (n-GaN) can be used as a semiconductor electrode by setting the film thickness so as to obtain a desired resistance value. ..
Further, by adopting a semiconductor electrode instead of using only a conventionally used transparent electrode such as ITO as an electrode, a translucent electrode having the same resistance as the conventional one and having extremely low light absorption than the conventional one is realized. it can.
The present invention has been made through the theoretical consideration as described above.
Hereinafter, the semiconductor light emitting device of the embodiment according to the present invention will be described with reference to the drawings.

Embodiment 1.
The semiconductor light emitting device of the first embodiment according to the present invention is a semiconductor light emitting device including a semiconductor electrode made of an n-type nitride semiconductor and emitting light through the semiconductor electrode.
Specifically, the semiconductor light emitting device of the first embodiment is as shown in FIG.
For example, a substrate 1 made of sapphire and
For example, a first conductive semiconductor layer 3 made of an n-type nitride semiconductor and provided on the substrate 1 and
For example, a light emitting layer 5 made of a nitride semiconductor containing In and provided on the first conductive semiconductor layer 3 and the like.
For example, a second conductive semiconductor layer 7 made of a p-type nitride semiconductor and provided on the light emitting layer 5 and the like.
It has a first electrode (first pad electrode) 41 connected to the first conductive semiconductor layer 3 and a second electrode 43 connected to the second conductive semiconductor layer 7.
Further, the second electrode 43 is
For example, a connection electrode 11 made of ITO and provided on almost the entire upper surface of the second conductive semiconductor layer 7 and the like.
For example, a semiconductor electrode 23 made of n-type GaN and
A second pad electrode 33 provided on the upper surface of the semiconductor electrode 23 is provided.
The connection electrode 11 in the first embodiment is composed of a junction of the first ohmic electrode 9 and the second ohmic electrode 29.

Specific materials that can be used for each component of the first embodiment are illustrated below.
First conductive semiconductor layer 3: n-GaN,
Light emitting layer 5: InGaN, InAlGaN,
Second conductive semiconductor layer 7: p-GaN,
First ohmic electrode 9: at least one of ITO, Ag, Ti, Ni Second ohmic electrode 29: at least one of ITO, Ag, Ti, Al Semiconductor electrode 23: at least one of n-GaN, n-AlGaN First 1-pad electrode 41 and 2nd pad electrode 33: Ti / Al / Ti / Pt / Au (laminate of Ti, Al, Ti, Pt, and Au)

Here, ITO, Ag, Ti, and Ni exemplified as the first ohmic electrode 9 are p-type when the second conductive semiconductor layer 7 is formed of, for example, a p-type nitride semiconductor layer such as p-GaN. It can be connected to the nitride semiconductor layer with low contact resistance by, for example, ohmic contact.
Further, ITO, Ag, Ti, and Al exemplified as the second ohmic electrode 29 are n-type nitride when the semiconductor electrode 23 is formed of an n-type nitride semiconductor layer such as n-GaN or n-AlGaN. It is possible to connect to a physical semiconductor layer with low contact resistance by, for example, ohmic contact.

The film thicknesses of the first ohmic electrode 9 and the second ohmic electrode 29 differ depending on the material constituting each ohmic electrode. For example, when the first ohmic electrode 9 or the second ohmic electrode is composed of a metal such as Ag, Ti, or Ni, it is 0.1 nm or more and 0.8 nm or less, preferably 0.1 nm or more and 0.4 nm or less, more preferably. Can be 0.1 nm or more and 0.2 nm or less. When a metal oxide such as ITO is used as the first ohmic electrode 9 or the second ohmic electrode 29, it can be 1 nm or more and 100 nm or less, preferably 1 nm or more and 50 nm or less, and more preferably 1 nm or more and 30 nm or less. Ohmic contact can be ensured by setting the film thickness to a certain level or higher, and light absorption in the first ohmic electrode 9 can be suppressed by setting the film thickness to a certain level or lower. The film thickness of the first ohmic electrode 9 and the second ohmic electrode 29 can be the same, but the first ohmic electrode 9 is preferably made thicker than the second ohmic electrode 29. Generally, since the surface of the p-type nitride semiconductor layer has many convex portions, the surface of the first ohmic electrode 9 is difficult to be flattened. However, by forming the first ohmic electrode 9 thickly, the first ohmic electrode 9 is formed. The surface of the can be flattened.

In the semiconductor light emitting element of the first embodiment configured as described above, the connection electrode 11 is made of, for example, a metal oxide such as ITO or a metal such as Ag, and the second conductive semiconductor layer 7 and the semiconductor electrode 23 are formed. It is an electrode that joins and secures good conduction between the second conductive semiconductor layer 7 and the semiconductor electrode 23. That is, when the second conductive type semiconductor layer 7 and the semiconductor electrode 23 are directly bonded, good conduction cannot be ensured, for example, a PN junction or the like is formed. Therefore, in the present embodiment, for example, a connection electrode 11 that makes ohmic contact is provided on both the second conductive semiconductor layer 7 and the semiconductor electrode 23 to ensure good conduction between the second conductive semiconductor layer 7 and the semiconductor electrode 23. I have secured it. Further, in the semiconductor light emitting device of the first embodiment, since light is emitted through the semiconductor electrode 23 by utilizing the translucency of the semiconductor electrode 23, the connection electrode 11 is composed of, for example, a translucent electrode member such as ITO. To do.

Further, the connection electrode 11 is an electrode that joins the second conductive semiconductor layer 7 and the semiconductor electrode 23 and secures good conduction between the second conductive semiconductor layer 7 and the semiconductor electrode 23. The semiconductor electrode 23 is responsible for diffusing the current injected through the two-pad electrode 33. Therefore, the connection electrode 11 can be formed sufficiently thinner than the conventional electrode that is responsible for current diffusion. For example, in the semiconductor light emitting device of the first embodiment that emits light through the semiconductor electrode 23, the connection electrode 11 may be formed sufficiently thinner than the conventional translucent electrode such as ITO that is responsible for current diffusion. It is possible, and the absorption of light by the connecting electrode 11 can be made extremely small. Further, in the semiconductor light emitting device of the first embodiment, as described above, the semiconductor electrode 23 responsible for current diffusion has sufficiently small light absorption even if it is thickened so as to have a sheet resistance that effectively enables current diffusion. it can.
Therefore, in the semiconductor light emitting device of the first embodiment, by providing the semiconductor electrode 23 having translucency and responsible for current diffusion, an electrode structure having substantially no light absorption and low resistance can be realized, and light extraction can be realized. It is possible to provide a semiconductor light emitting device having high efficiency, high light emission efficiency, and low drive voltage.

The film thickness of the semiconductor electrode 23 can be 2 um or more and 200 um or less, preferably 3 um or more and 20 um or less, and more preferably 4 um or more and 10 um or less. As described above, when the film thickness is set to a certain level or higher, the resistance is lowered and the current can be efficiently passed. Further, as described above, by setting the film thickness to a certain level or less, the influence of warpage due to the difference in thermal expansion between the semiconductor electrode and the growth substrate at the time of producing the semiconductor electrode can be alleviated, so that the process yield is expected to be improved.

Next, a method of manufacturing the semiconductor light emitting device of the first embodiment will be described.
The method for manufacturing a semiconductor light emitting device according to the first embodiment includes a semiconductor electrode forming process, a semiconductor laminated structure forming process, and an electrode structure forming process. The semiconductor electrode forming process and the semiconductor laminated structure forming process can be performed in parallel, and the electrode structure forming process is performed after the semiconductor electrode forming process and the semiconductor laminated structure forming process.

(Semiconductor electrode formation process)
In this manufacturing method, as shown in FIG. 2A, first, a semiconductor electrode 23 made of a nitride semiconductor such as n-type GaN is grown on a growth substrate 21 made of sapphire, for example, via a buffer layer. ..
In the semiconductor light emitting device according to the first embodiment in which light is emitted through the semiconductor electrode 23, the semiconductor material constituting the semiconductor electrode 23 is a semiconductor material having a band gap larger than that of the semiconductor material constituting the light emitting layer. Is selected. When a multiple quantum well structure composed of a well layer and a barrier layer is applied as the light emitting layer, a semiconductor material having a bandgap larger than that of the well layer is selected. Further, a semiconductor material capable of achieving a low resistance value by adding impurities is selected. For example, in a nitride semiconductor light emitting device, when a nitride semiconductor containing In is used as an active layer, n-type GaN and n-type AlGaN added with Si or Ge as impurities are used as semiconductor materials constituting the semiconductor electrode 23. You can choose. In the case of n-type GaN, the impurity concentration is preferably increased to such an extent that the crystal does not deteriorate too much, and can be, for example, 1 × 10 ¹⁸ / cm ³ or more and 1 × 10 ¹⁹ / cm ³ or less. In the case of n-type AlGaN, the impurity concentration can be, for example, 1 × 10 ¹⁸ / cm ³ or more and 1 × 10 ¹⁹ / cm ³ or less. Since n-type GaN can be grown into a thick film with good crystallinity, it can be mentioned as a preferable material when forming a nitride semiconductor light emitting device that emits visible light such as blue, for example. Further, n-type AlGaN has a wider bandgap than GaN, and the absorption rate of ultraviolet rays can be reduced by increasing the ratio of Al, so that it is a preferable material when constructing a nitride semiconductor light emitting device that emits ultraviolet light. can give. The Al mixed crystal ratio of n-type AlGaN shall be 0.02 ≦ x ≦ 0.1, preferably 0.02 ≦ x ≦ 0.06 when AlxGa1-xN (1>x> 0). Can be done.

Next, as shown in FIG. 2B, an adhesive layer 25 made of, for example, an adhesive resin such as a thermosetting resin is formed on the upper surface of the semiconductor electrode 23, and a support substrate 27 made of, for example, sapphire is bonded.
Next, the growth substrate 21 is removed as shown in FIG. 2C by using a laser lift-off method or the like. Specifically, a laser beam having a wavelength that passes through the growth substrate 21 and is absorbed by the semiconductor material constituting the semiconductor electrode 23 is selected, and the laser beam is irradiated from the growth substrate 21 side to irradiate the growth substrate 21 and the semiconductor. The growth substrate 21 is removed by raising the temperature near the interface of the electrode 23 and ablating (decomposing) the adhesive layer.

After removing the growth substrate 21, the surface of the semiconductor electrode 23 is polished by a chemical mechanical polishing method or the like to smooth the surface of the semiconductor electrode 23, and as shown in FIG. 2C, the growth substrate 21 is removed and exposed. On the surface of the electrode 23, for example, a second ohmic electrode 29 made of a metal oxide such as ITO or a metal such as Ag is formed.

(Semiconductor laminated structure formation process)
In the semiconductor laminated structure forming process, first, for example, a substrate 1 made of sapphire or the like is prepared.
Next, as shown in FIG. 2D, the surface of the substrate 1 on which the semiconductor layer is grown is processed to form a convex portion. The step of processing the surface of the substrate 1 is not an indispensable step.
This surface treatment can be formed by setting the crystal form of the substrate, the surface orientation of the substrate surface on which the convex portion is formed, the mask shape and dimensions, and the etching conditions according to the target shape.

For example, when a circular mask is formed on the surface of the sapphire substrate consisting of the C surface and etched, the portion where the mask is not formed at the initial stage is removed by etching, and the mask shape is reflected almost as it is. The part is formed, but as the etching progresses, it is affected by the direction dependence of the etching rate due to the crystal morphology (the rate at which the etching proceeds differs depending on the direction), and the shape reflects the crystal morphology. To go. By forming the convex portion, it is possible to grow a semiconductor layer having excellent crystallinity, and it is possible to form a semiconductor layer having excellent light extraction efficiency.

Next, as shown in FIG. 2D, on the processed surface of the substrate 1, for example, a first conductive semiconductor layer 3 made of an n-type nitride semiconductor and a light emitting layer 5 made of a nitride semiconductor containing, for example, In, for example. A second conductive semiconductor layer 7 made of a p-type nitride semiconductor is grown to produce a semiconductor laminated structure.
Further, as shown in FIG. 2D, for example, a first ohmic electrode 9 made of ITO is formed on the entire upper surface of the second conductive semiconductor layer 7.

After forming the first ohmic electrode 9 made of ITO, the surface of the first ohmic electrode 9 may be flattened by a known method such as a CMP (Chemical Mechanical Polishing) method. That is, when the semiconductor layer is grown, the surface of the p-type nitride semiconductor layer may be uneven, and at this time, the surface of the first ohmic electrode 9 is also formed uneven, and the surface of the first ohmic electrode 9 is also uneven. Joining can be difficult. In such a case, flattening the surface of the first ohmic electrode 9 facilitates bonding with the second ohmic electrode 29.

(Electrode structure formation process)
Here, the first ohmic electrode 9 (see FIG. 2E) formed on the entire upper surface of the second conductive semiconductor layer 7 having the semiconductor laminated structure and the surface of the semiconductor electrode 23 supported by the support substrate 27 were formed. The second ohmic electrode 29 (see FIG. 2C) is joined by normal temperature bonding (see FIG. 2F). In this embodiment, a surface activation bonding method is used as the room temperature bonding. The surface-activated bonding method is a method in which each member is directly bonded after activating the bonding interface by applying an ion beam, plasma, or the like to the bonding interface. According to the surface-activated bonding method, the materials can be bonded purely to each other. In the present embodiment, the connection electrode 11 which is a junction of the first ohmic electrode 9 and the second ohmic electrode 29 is composed of ITO.

In this embodiment, the surface activation bonding method is used as the room temperature bonding, but the bonding can also be performed by the atomic diffusion bonding method. It can also be joined by thermocompression bonding or the like.

The atomic diffusion bonding method is a method in which thin films made of metal films are superposed on each other to cause atomic diffusion at the bonding interface and grain boundaries, resulting in strong bonding between the two. In addition, the atomic diffusion bonding method includes not only bonding between the same materials such as bonding between metals, but also bonding between metals and semiconductors, metal oxides and semiconductors, or dissimilar materials between metals and metal oxides. It is also possible.
Further, when joining by the atomic diffusion joining method, the first ohmic electrode 9 and the second ohmic electrode 29 may have a thickness of, for example, 20 nm or less. Therefore, the thickness of the connection electrode 11 can be made extremely thin, and the absorption of light by the connection electrode 11 can be suppressed.
When bonding by the atomic diffusion bonding method, an atomic diffusion layer may be further formed between the first ohmic electrode 9 and the second ohmic electrode 29. If an atomic diffusion layer is provided, highly uniform bonding can be easily realized. The atomic diffusion layer of the first ohmic electrode 9 and the second ohmic electrode 29 is made of metal, for example, Au or Ti. At this time, the atomic diffusion layer has a thin film thickness so as not to absorb light. Although it depends on the material used for the atomic diffusion layer, for example, when Au is used, it is formed at 0.1 μm to 0.4 μm.

Further, in the first embodiment, a semiconductor electrode 23 grown on the growth substrate 21 bonded to the support substrate 27 is used in the electrode structure forming process. In the manufacturing process, the semiconductor electrode may be warped so as to be convex toward the semiconductor electrode due to the difference in thermal expansion between the semiconductor electrode and the growth substrate. Since warpage can be reduced by joining to the support substrate 27, a second ohmic electrode 29 provided on the semiconductor electrode and a second conductive semiconductor layer 7 having a semiconductor laminated structure are formed on the entire upper surface of the upper surface. 1 It becomes easy to join with the ohmic electrode 9. Needless to say, the step of joining to the support substrate 27 is not an indispensable step, and the semiconductor electrode 23 grown on the growth substrate 21 can be used in the electrode structure forming process. In this case, after forming the semiconductor electrode 23, the surface of the semiconductor electrode 23 is polished. By doing so, the step of sticking to the support substrate 27 is eliminated, so that the productivity can be improved.

Next, as shown in FIG. 2G, the adhesive layer 25 and the support substrate 27 are removed. Specifically, a laser beam having a wavelength that passes through the support substrate 27 and is absorbed by the semiconductor material constituting the semiconductor electrode 23 is selected, and the laser beam is irradiated from the support substrate 27 side to adhere to the support substrate 27. The support substrate 27 is removed by raising the temperature near the interface of the layer 25 and ablating (decomposing) the adhesive layer 25. After that, the adhesive layer 25 is removed by ashing with oxygen, a chemical solution such as sulfuric acid, or the like. In particular, a chemical solution such as sulfuric acid does not damage the semiconductor electrode 23.

After removing the adhesive layer 25 and the support substrate 27, the semiconductor electrode 23 and the second conductive semiconductor are placed on the electrode forming surface in order to expose a part (electrode forming surface) of the first conductive semiconductor layer 3. A part of the layer 7 and the light emitting layer 5 is removed.
Next, the first electrode 41 is formed on the electrode forming surface of the first conductive semiconductor layer 3, and the second pad electrode 33 is formed on a part of the surface of the semiconductor electrode 23. For example, the first electrode 41 and the second pad electrode 33 can be formed of a laminated body of Ti, Al, Ti, Pt and Au having the same configuration, and may be collectively produced at the same time.

As described above, the semiconductor light emitting device of the first embodiment shown in FIG. 1 is manufactured.

The semiconductor light emitting device of the first embodiment is configured to emit light through the semiconductor electrode 23, but the present invention is not limited to this, and the semiconductor electrode is covered with a dielectric multilayer film or the like. The light reflecting layer may be provided so as to emit light from the substrate 1 side having translucency such as sapphire. Even when light is emitted from the substrate 1 side, the light is absorbed by the electrode when the light directed toward the electrode side is reflected and taken out, so that the luminous efficiency can be improved by suppressing the absorption.

Further, in the semiconductor light emitting device of the first embodiment, the first ohmic electrode 9 formed on the second conductive nitride semiconductor layer and the second ohmic electrode 29 formed on the semiconductor electrode 23 are joined. I made it.
However, the present invention is not limited to this, and a connection electrode is formed on either one of the second conductive type nitride semiconductor layer and the semiconductor electrode 23, and the connection electrode and the second conductive type nitride semiconductor layer are formed. And the other of the semiconductor electrode 23 may be directly bonded (see FIG. 3).
Further, after forming the connection electrode on the second conductive nitride semiconductor layer, the semiconductor electrode 23 may be directly formed on the connection electrode by using a sputtering method (for example, an ECR (Electron Cyclotron Resonance) sputtering method).

1 Substrate 3 1st conductive type semiconductor layer 5 Light emitting layer 7 2nd conductive type semiconductor layer 43 2nd electrode 9, 11, 29 Connection electrode 21 Growth substrate 23 Semiconductor electrode 41 1st electrode (1st pad electrode)
33 Second pad electrode

Claims (12)

The first conductive type first semiconductor layer, the second conductive type second semiconductor layer, the light emitting region formed between the first semiconductor layer and the second semiconductor layer, and the first semiconductor layer are connected to each other. With the first electrode
A semiconductor light emitting device including a second electrode connected to the second semiconductor layer.
The second electrode is
A connection electrode having translucency and in contact with the second semiconductor layer,
It has a semiconductor electrode having a translucent property and made of a semiconductor layer in contact with the connection electrode.
The connection electrode is an ohmic electrode.
A first ohmic electrode that makes ohmic contact with the second semiconductor layer,
It has a second ohmic electrode that makes ohmic contact with the semiconductor electrode.
A semiconductor light emitting device characterized in that the film thickness of the first ohmic electrode is thicker than the film thickness of the second ohmic electrode. The semiconductor light emitting device according to claim 1, wherein the ohmic electrode includes one selected from the group consisting of Ag, Ti, Al, Ni, Au and ITO. The semiconductor light emitting device according to claim 1 or 2, wherein the first ohmic electrode and the second ohmic electrode are made of the same material, respectively. The semiconductor light emitting device according to any one of claims 1 to 3, wherein the first ohmic electrode includes one selected from the group consisting of Ag, Ti, Ni and ITO. The semiconductor light emitting device according to claim 3 or 4, wherein the second ohmic electrode includes one selected from the group consisting of Ag, Ti, Al and ITO. The semiconductor light emitting device according to any one of claims 1 to 5, wherein the first semiconductor layer, the second semiconductor layer, and the semiconductor electrode are each made of a nitride semiconductor. The semiconductor light emitting device according to claim 6, wherein the semiconductor electrode is made of GaN or AlGaN. The semiconductor light emitting device according to claim 7, wherein the semiconductor electrode is made of GaN containing n-type impurities. The semiconductor light emitting device according to any one of claims 1 to 8, wherein the second ohmic electrode is a metal. The semiconductor light emitting device according to claim 9, wherein the film thickness of the second ohmic electrode is 0.1 nm or more and 0.8 nm or less. The first ohmic electrode is a metal and
The semiconductor light emitting device according to any one of claims 1 to 10, wherein the film thickness of the first ohmic electrode is 0.1 nm or more and 0.8 nm or less. The first ohmic electrode is a metal oxide,
The semiconductor light emitting device according to any one of claims 1 to 10, wherein the film thickness of the first ohmic electrode is 1 nm or more and 100 nm or less.

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