JP2004179347A - Semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element that can be manufactured comparatively easily while ohmic contact property and high reflectivity of an electrode are kept and wherein light emitting efficiency is improved. <P>SOLUTION: The semiconductor light emitting element is provided with an n-type semiconductor layer 2, a light emitting layer 3, and a p-type semiconductor layer 4 that are stacked in sequence on one surface of a supporting substrate 1. The p-type semiconductor layer 4 is provided with a p electrode 6, and then the n-type semiconductor layer 2 wherein a part of the n-type semiconductor layer 2, the light emitting layer 3 and the p-type semiconductor layer 4 is removed and they are exposed, is provided with an n electrode 5. Furthermore, the p electrode 6 and the n electrode 5 are formed by stacking transparent layers 51 and 61 made of indium oxide tin that is formed being in contact with almost entire surface of the p-type semiconductor layer 4 and the n-type semiconductor layer 2, and reflection layers 52 and 62 that are formed thereon and are at least equivalent in size to the transparent layers 51 and 61, and are made of at least one material among silver, aluminum and rhodium. <P>COPYRIGHT: (C)2004,JPO

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 having a structure in which electrodes for applying a voltage to a light emitting semiconductor layer are formed on the same surface side of a support substrate.
[0002]
[Prior art]
2. Description of the Related Art As a conventional semiconductor light emitting element, for example, there is one proposed in Japanese Patent Application Laid-Open No. 2000-294837 (Patent Document 1), which is shown in FIG. FIG. 2 is a side sectional view.
[0003]
In this device, a buffer layer 102 made of gallium nitride (GaN) is laminated on a support substrate 101 made of sapphire, and then a GaN layer 103 having an n-type conductivity and light emission made of undoped indium gallium nitride (InGaN) are used. It has a structure in which a layer 104, an aluminum gallium nitride (AlGaN) layer 105 having a p-type conductivity, and a GaN layer 106 having a p-type conductivity are sequentially stacked.
[0004]
Among them, the GaN layer 103 having the n-type conductivity is composed of the light emitting layer 104 made of non-doped indium gallium nitride (InGaN), the aluminum gallium nitride (AlGaN) layer 105 having the p-type conductivity, and the p-type conductivity. Is removed by etching to expose the surface. An n-electrode 107 is formed on the exposed portion 103a of the GaN layer 103 having the n-type conductivity. The n-electrode 107 is laminated by sequentially depositing titanium (Ti) and aluminum (Al), and has a thickness of 250 ° for Ti and 10,000 ° for Al.
[0005]
A p-electrode 108 is formed on almost the entire surface of the GaN layer 106 having a p-type conductivity. The p-electrode 108 is laminated by sequentially depositing nickel (Ni) and silver (Ag). Furthermore, by annealing Ni and Ag after vapor deposition of the entire semiconductor light emitting element, the p electrode 108 is alloyed to realize ohmic contact. Further, by setting the thickness of the Ni layer of the p-electrode 108 to 10 ° and the thickness of the Ag layer to 2500 °, the ratio of the light reflection component in the Ni layer is reduced, and at the same time, the reflection component of the light in the Ag layer is reduced. The proportion of the light is increased to reflect light efficiently.
[0006]
The n-electrode 107 and the p-electrode 108 are provided with a conductive material 109 made of, for example, solder. The external electrode terminal 111 formed on the base 110 and the conductive material 109 are used for flip-chip mounting. Have been.
[0007]
Therefore, according to this semiconductor light emitting device, light emitted from the base 110 can be extracted, and the support substrate 101 is placed on the base 110 and the light is extracted from the surface on which the n-electrode 107 and the p-electrode 108 are formed. Since the amount of light reflected by the p-electrode 108 increases as compared with the case of, the light extraction efficiency can be improved.
[0008]
[Patent Document 1]
JP 2000-294837 A
[Problems to be solved by the invention]
However, in such a semiconductor light emitting device, as described above, the thickness of the Ni layer is 10 °, and the reflectance for light having a peak wavelength of 470 nm is 70.9%. It is also said that if the thickness of the Ni layer exceeds 100 °, it is not practical. That is, in order to reduce the reflection and absorption of light in the Ni layer and improve the ratio of reflection in the Ag layer, it is necessary to form the Ni layer thinly. At around 100 °, the reflectance decreases to about 30%. Would.
[0010]
Furthermore, it is relatively difficult to accurately form a Ni layer having a thickness of about 10 °, and a slight variation in the film thickness is reflected in a decrease in reflectivity. It is difficult to relatively easily manufacture a semiconductor light emitting device with improved characteristics.
[0011]
The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor light emitting device with improved luminous efficiency which can be relatively easily manufactured while maintaining ohmic contact and high reflectivity of an electrode. Is to provide.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a semiconductor light emitting device according to the first aspect of the present invention includes a support substrate, an n-type semiconductor layer on one surface of the support substrate, a light-emitting layer, and a p-type semiconductor layer. A p-electrode is provided on the p-type semiconductor layer, and an n-electrode is provided on the n-type semiconductor layer which is exposed by removing a part of the n-type semiconductor layer, the light emitting layer and the p-type semiconductor layer. A semiconductor light emitting device provided, wherein the p-electrode and the n-electrode are each formed of a transparent layer made of indium tin oxide and in contact with substantially the entire surface of the p-type semiconductor layer and the n-type semiconductor layer. It is formed on a transparent layer and has a size at least equal to that of the transparent layer, and is formed by laminating a reflective layer made of at least one material of silver, aluminum and rhodium.
[0013]
In this configuration, indium tin oxide has a high light-transmitting property even when the film thickness is large, and for example, has a light-transmitting property of about 90% even if the thickness is about 100 times the thickness of the Ni layer. Therefore, as in the prior art, silver is used for the reflective layer, and even if the thickness of the transparent layer is about 100 times, the reflectivity of the n-electrode and the p-electrode is about 73%. A transparent layer having a good transmittance can be formed relatively easily without the need for, and a reduction rate of the light transmittance due to a variation in film thickness can be reduced. As a result, a reduction in the reflectance is suppressed. As a result, the luminous efficiency can be improved.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
A semiconductor light emitting device according to a first embodiment will be described with reference to FIG. FIG. 1 is a perspective view in which the vicinity of the center of the semiconductor light emitting device is cut.
[0015]
This semiconductor light-emitting element has a supporting substrate 1, an n-type semiconductor layer 2, a light-emitting layer 3, a p-type semiconductor layer 4, an n-electrode 5, and a p-electrode 6 as main components.
[0016]
The support substrate 1 serves as a base of the semiconductor light emitting element, and is formed of, for example, a translucent and insulating substrate such as sapphire. On one surface of the support substrate 1, an n-type semiconductor layer 2, a light-emitting layer 3, and a p-type semiconductor layer 4 are sequentially stacked.
[0017]
The n-type semiconductor layer 2 is formed on the supporting substrate 1 so as to have an n-type conductivity. More specifically, the semiconductor layer 2 having the first conductivity type is composed of a buffer layer 21, an n-type contact layer 22, and an n-type cladding layer 23. The buffer layer 21 is formed of, for example, GaN, and is provided to reduce lattice mismatch between the support substrate 1 and the n-type contact layer 22. The n-type cladding layer 23 is formed of, for example, a composition such as aluminum gallium nitride (AlGaN) having a larger band gap energy than the light emitting layer 3 described later. The n-type contact layer 22 is formed of, for example, GaN, and has a contact barrier (Schottky barrier) at a contact interface between the two, as compared with an n-electrode 5 described later provided directly on the n-type cladding layer 23. And ohmic contact is realized. Further, a part of the n-type contact layer 22 is exposed by removing the n-type cladding layer 23, the light emitting layer 3 and the p-type semiconductor layer 4 described later on the surface.
[0018]
The light emitting layer 3 is formed of, for example, a semiconductor made of indium gallium nitride (InGaN), and has a single quantum well or multiple quantum well structure. The light emitting layer 3 is a neutral InGaN layer without implanting impurities. Thereby, light emission with good color purity is obtained. In addition, the emission wavelength can be changed by adjusting the composition ratio of In and Ga or changing the band gap by changing the composition to n-type or p-type. In order to obtain an n-type conductivity, an impurity such as silicon (Si) or germanium (Ge) may be implanted as appropriate. Conversely, for obtaining a p-type conductivity, magnesium (Mg) or zinc (Zn) may be used. ) May be implanted.
[0019]
The p-type semiconductor layer 4 includes, for example, a p-type contact layer 41 and a p-type cladding layer 42, like the n-type semiconductor layer 2. The p-type contact layer 41 is formed of, for example, GaN, and has a smaller contact barrier (Schottky barrier) at the contact interface between the two than when a p-electrode 6 described later is directly provided on the p-type cladding layer 42. And realizes ohmic contact. Further, the p-type cladding layer 42 is formed of, for example, a composition such as AlGaN having a band gap energy larger than that of the light emitting layer 3.
[0020]
The n-electrode 5 is provided so as to cover substantially the entire exposed surface of the n-type contact layer 22. This has a two-layer structure in which a transparent layer 51 made of indium tin oxide (ITO) and a reflective layer 52 made of Ag are laminated. The n-contact layer 22, the transparent layer 51, and the reflective layer 52 are laminated in this order. I have. Further, this is alloyed by annealing after lamination to realize ohmic contact with the n-type contact layer 22. Further, in the present embodiment, the thickness of the transparent layer 51 is set to about 1000 °, and even at this thickness, ITO, which is a material of the transparent layer 51, has a good light transmittance and a light transmittance of about 90%. . The thickness of the reflective layer 52 is about 10000 °. The height of the n-electrode 5 is such that its upper surface (upward direction in FIG. 1) is closer to the support substrate 1 than the upper surface of a p-electrode 6 described later. (Not shown) when flip-chip mounted horizontally, the distance between the n-electrode 5 and the lead frame is larger than the distance between the p-electrode 6 and the lead frame.
[0021]
The p-electrode 6 is provided so as to cover substantially the entire surface of the p-type contact layer 41. This is composed of a transparent layer 61 made of indium tin oxide (ITO) and a reflective layer 62 made of Ag as in the case of the n-electrode 5, and a p-type contact layer 41, a transparent layer 61, and a reflective layer 62 in this order. Laminated. Further, this is alloyed by annealing after lamination, and realizes ohmic contact with the p-type contact layer 41. In the present embodiment, the thickness of the transparent layer 61 is set to about 1000 °. Even at this thickness, ITO, which is a material of the transparent layer 61, has good light transmittance and the light transmittance is about 90%. . The thickness of the reflective layer 62 is about 10000 °.
[0022]
According to the semiconductor light emitting device of the first embodiment described above, the n-electrode 5 and the p-electrode 6 are composed of two layers of the transparent layers 51 and 61 and the reflection layers 52 and 62, and the transparent layers 51 and 61 are formed of a film of 1000 °. By forming the reflective layers 52 and 62 from Ag having a thickness of 10000 °, ohmic contact is realized and the reflection layers 52 and 62 are reflected at the boundary surfaces between the transparent layers 51 and 61 and the reflective layers 52 and 62. Since the reflectance of the light to be emitted is about 73%, it is possible to relatively easily form a transparent layer having a high transmittance without requiring a highly accurate control of the film thickness for forming a thin film. The rate of decrease in light transmittance due to the variation in film thickness is reduced, the decrease in reflectance is suppressed, and the luminous efficiency can be improved.
[0023]
The thicknesses of the transparent layers 51 and 61 and the reflection layers 52 and 62 are not limited to the above thicknesses.
[0024]
【The invention's effect】
The semiconductor light-emitting device according to the first aspect of the present invention includes a support substrate, an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer sequentially stacked on one surface of the support substrate, and a p-type semiconductor layer. A semiconductor light emitting device comprising: a semiconductor layer provided with a p-electrode; and an n-type semiconductor layer, a light-emitting layer, and an n-type semiconductor layer provided by removing a part of the p-type semiconductor layer and exposing the n-type semiconductor layer. The p-electrode and the n-electrode are formed on a transparent layer of indium tin oxide formed in contact with substantially the entire surface of the p-type semiconductor layer and the n-type semiconductor layer, respectively; A transparent layer having good ohmic contact and transmittance can be formed as a high-precision film by making the size at least equivalent to the transparent layer and laminating a reflective layer made of at least one material of silver, aluminum and rhodium. Relatively compact without the need for thickness control Can be formed on, it can be reduced translucency reduction rate due to variations in thickness. In addition, since a material having a high reflectance is used on the transparent layer, a decrease in the reflectance can be suppressed, and the luminous efficiency of the semiconductor light emitting element can be improved.
[Brief description of the drawings]
FIG. 1 is a perspective view in which the vicinity of the center of a semiconductor light emitting device according to a first embodiment of the present invention is cut.
FIG. 2 is a side sectional view of a conventional semiconductor light emitting device.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 support substrate 2 n-type semiconductor layer 3 light-emitting layer 4 p-type semiconductor layer 5 n-electrode 51 transparent layer (n-electrode side)
52 reflection layer (n-electrode side)
6 p-electrode 61 transparent layer (p-electrode side)
62 Reflective layer (p electrode side)

Claims (1)

A support substrate, an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer are sequentially stacked on one surface of the support substrate, and a p-electrode is provided on the p-type semiconductor layer, and an n-type semiconductor layer is provided. A semiconductor light-emitting device in which an n-electrode is provided on an n-type semiconductor layer in which a semiconductor layer, a light-emitting layer, and a part of a p-type semiconductor layer are removed and exposed, wherein the p-electrode and the n-electrode are respectively A transparent layer made of indium tin oxide formed in contact with almost the entire surface of the n-type semiconductor layer and the n-type semiconductor layer, formed on the transparent layer to have a size at least equivalent to the transparent layer, silver, A semiconductor light-emitting device comprising: a stack of a reflection layer made of at least one of aluminum and rhodium.

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