JP2007258276A - Semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device which can improve light extraction efficiency from a desired light extraction surface. <P>SOLUTION: An anode electrode 5 located on the opposite side to a desired light extraction surface against a light emitting layer 3 is comprised of a first transparent conductive film 51 formed on a p-type semiconductor layer 4; a second transparent conductive film 52 formed on the first transparent conductive film 51; a plurality of multilayer reflection film layers 53 which are formed on the second transparent conductive film 52, and reflect a light radiated from the light emitting layer 3; a metal reflecting film 54 made of a metallic material which is formed in a manner that it may cover a region nor covered by the multilayer reflecting film layers 53 and the multilayer reflecting film layers 53 in the second transparent conductive film 52, and which has a high reflection factor to a light from the light emitting layer 3; a barrier metal film 55 formed on the metal reflecting film 54; and an external connection metal film 56 made of a metallic material which is formed on the barrier metal film 55. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device having an emission peak wavelength on the shorter wavelength side than red.

  Conventionally, in a semiconductor light emitting device such as an oxide-based compound semiconductor light-emitting device or a nitride-based compound semiconductor light-emitting device, a portion of light emitted from a light emitting layer in a direction other than the light extraction surface is emitted approximately isotropically. There is a problem that the light extraction efficiency is lowered due to the absorption of the portion by the electrode.

  Therefore, in order to solve this type of problem, a semiconductor light-emitting element has been proposed in which light extraction efficiency is improved by forming an electrode located on the side opposite to the light extraction surface side from a highly reflective metal material. (For example, Patent Documents 1 and 2).

  Here, as this type of semiconductor light-emitting element, for example, one having the configuration shown in FIG. 5 has been proposed. The semiconductor light emitting device having the configuration shown in FIG. 5 is a blue light emitting diode that employs a GaN-based compound semiconductor material as a material for the light emitting layer (active layer) 3 and the like, on one surface side of the base substrate 1 made of a sapphire substrate. N-type semiconductor layer 2 formed through buffer layer 10, the above-described light-emitting layer 3 formed on n-type semiconductor layer 2, p-type semiconductor layer 4 formed on light-emitting layer 3, and p-type An anode electrode 5 formed on the surface side of the semiconductor layer 4 and a cathode electrode 6 formed on the surface side opposite to the base substrate 1 side in the n-type semiconductor layer 2 are provided. An ohmic contact layer 61 made of a metal material capable of making ohmic contact with the layer 2 (for example, Ti), and an external connection metal layer 62 made of a metal material such as Au laminated on the ohmic contact layer 61. A reflective metal layer 58 made of a metal material (for example, Ag, silver white metal material, Al, etc.) having a high reflectivity with respect to the light emitted from the light emitting layer 3, and the anode electrode 5 also serving as a reflective layer; The external connection metal layer 59 made of a metal material such as Au laminated on the reflection metal layer 58 is formed. Here, Patent Document 1 describes that when Ag is used as the material of the reflective metal layer 58, the thickness of the reflective metal layer 58 is set to a value larger than 20 nm.

  In the semiconductor light emitting device having the configuration shown in FIG. 5, when a forward bias voltage is applied between the anode electrode 5 and the cathode electrode 6, a current flows from the anode electrode 5 toward the cathode electrode 6, and Light is emitted when the injected electrons and holes recombine. Here, the semiconductor light emitting device having the configuration shown in FIG. 5 is flip-chip mounted on a mounting substrate and the other surface of the base substrate 1 is used as a light extraction surface, from the light emitting layer 3 to the n-type semiconductor layer 2 side. The emitted light is emitted from the light extraction surface through the base substrate 1, and the light emitted to the p-type semiconductor layer 4 side is reflected by the reflective metal layer 58 and emitted from the light extraction surface ( The arrow C in FIG. 5 shows an example of a propagation path of light emitted from the light emitting layer 3 and reflected by the reflective metal layer 58), so that the light extraction efficiency can be increased.

In the semiconductor light emitting device having the configuration shown in FIG. 5 described above, a sapphire substrate, which is an insulating crystal growth substrate, is used as the base substrate 1, and the anode electrode 5 and the cathode electrode are formed on the one surface side of the base substrate 1. 6 is used as the base substrate 1, using a conductive crystal growth substrate (for example, a conductive single crystal substrate, a conductive compound semiconductor substrate, or the like) and the crystal growth substrate. Light emission comprising the n-type semiconductor layer 2, the light-emitting layer 3, and the p-type semiconductor layer 4 by providing a cathode electrode on the surface side, or removing a sapphire substrate after crystal growth and attaching a metal substrate that also serves as the cathode electrode. The electrode is provided with electrodes on both sides in the thickness direction, and one of the two electrodes is formed of a translucent material and the other electrode is a gold that reflects light from the light emitting layer 3 Even the semiconductor light emitting element formed of a material have been proposed, the semiconductor light-emitting device of this type, at least one electrode is connected packages and electrically conductive patterns through the bonding wires.
Japanese Patent Laid-Open No. 11-186598 JP 11-191641 A

  By the way, in the semiconductor light emitting device having the configuration shown in FIG. 5, a part of the light generated in the light emitting layer 3 is obtained by adopting Ag, silver white metal material, Al or the like as the metal material of the reflective metal layer 58. Since the light is reflected by the reflective metal layer 58 and emitted from the light extraction surface, the light extraction efficiency can be increased. However, the reflectance of the metal material is 95% or less, and the light emitting layer 3 is connected to the anode electrode. At least 5% of the light propagating toward 5 is absorbed by the anode electrode 5 and becomes a light absorption loss.

  Further, as described above, electrodes are provided on both sides in the thickness direction of the light-emitting portion composed of the n-type semiconductor layer 2, the light-emitting layer 3, and the p-type semiconductor layer 4, and one of the two electrodes is made transparent. Even in a semiconductor light emitting device that is formed of a conductive material and the other electrode is formed of a metal material that reflects light from the light emitting layer 3, the same light loss occurs in the electrode formed of the metal material.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a semiconductor light emitting device capable of improving the light extraction efficiency from a desired light extraction surface.

  The invention of claim 1 has a laminated structure of an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer, and an anode electrode is formed on the opposite side of the p-type semiconductor layer from the light-emitting layer side. A cathode electrode is formed on the side of the semiconductor layer where the light emitting layer is laminated, and a plurality of types of dielectric films are periodically laminated on the side opposite to the desired light extraction surface side in the thickness direction of the light emitting layer. A multilayer reflection film layer that reflects light emitted from the light emitting layer is provided.

  According to the present invention, a plurality of types of dielectric films are periodically stacked on the side opposite to the desired light extraction surface side in the thickness direction of the light emitting layer and reflect light emitted from the light emitting layer. Since the multi-layer reflective film layer is provided, the light radiated from the light emitting layer to the side opposite to the desired light extraction surface side can be efficiently reflected as compared with a reflective metal layer made of a conventional metal material. Therefore, the light extraction efficiency from the desired light extraction surface can be improved, and the light emission efficiency can be increased.

  According to a second aspect of the present invention, in the first aspect of the invention, the multilayer reflective film layer is formed by alternately laminating two types of the dielectric films having different refractive indexes, and each dielectric film is oxidized. It consists of a film or a nitride film. Here, the two types of dielectric films having different refractive indexes may be a combination of an oxide film and a nitride film, a combination of two kinds of oxide films having different materials, or two kinds of materials having different materials. A combination of nitride films may be used.

  According to the present invention, by appropriately setting the film thickness of each of the two types of dielectric films, the reflected light can be strengthened and the reflectance can be increased due to the light interference effect, and the desired light extraction can be achieved. The light extraction efficiency from the surface can be increased, and the dielectric films can be easily formed by a general thin film forming technique such as ion beam evaporation or resistance heating evaporation.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the multilayer reflective film layer is laminated in the order in which the refractive index increases as the plurality of types of dielectric films move away from the side closer to the light emitting layer. It is characterized by.

  According to this invention, since the plurality of types of dielectric films have a smaller refractive index as the dielectric film is closer to the light emitting layer, the reflectance in the multilayer reflective film layer can be increased, and the light extraction efficiency can be improved.

  According to a fourth aspect of the present invention, in the first to third aspects of the invention, the multilayer reflective film layer has a reflectance higher than 95% with respect to light in a wavelength region of an emission peak wavelength ± 30 nm of the light emitting layer. It is formed so that it may become.

  According to this invention, light in the wavelength region of the emission spectrum of light generated in the light emitting layer can be efficiently reflected by the multilayer reflective film layer (that is, not only light having a light emission peak wavelength but also light emission peak wavelength). Nearby light can also be reflected efficiently), and the light extraction efficiency can be improved.

  According to a fifth aspect of the present invention, in the first to fourth aspects of the invention, the multilayer reflective film layer has a desired light in the thickness direction of the light emitting layer of the two electrodes of the anode electrode and the cathode electrode. It is provided on one electrode located on the side opposite to the extraction surface side, and is formed in a plurality of independent islands on a plane parallel to the light emitting layer.

  According to this invention, it is possible to suppress a decrease in conductivity of one electrode due to the multilayer reflective film layer, and it is possible to suppress an increase in operating voltage due to the multilayer reflective film layer. That is, according to the present invention, it is possible to improve the light extraction efficiency while suppressing an increase in operating voltage.

  According to a sixth aspect of the present invention, in the first to fifth aspects of the invention, the multilayer reflective film layer has a desired light in the thickness direction of the light emitting layer of the two electrodes of the anode electrode and the cathode electrode. Provided on one electrode located on the opposite side to the take-out surface side, formed in an independent island shape on each of a plurality of planes parallel to the light emitting layer, and provided on the respective planes. The electrode is characterized in that the position of the multilayer reflective film layer is shifted for each plane.

  According to the present invention, it is possible to increase the area occupied by the multilayer reflective film layer in the projection region of the light emitting layer while suppressing a decrease in conductivity of one electrode on which the multilayer reflective film layer is provided, Light incident on one electrode can be reflected more efficiently.

  In the invention of claim 1, there is an effect that the light extraction efficiency from a desired light extraction surface can be improved.

(Embodiment 1)
Hereinafter, the semiconductor light emitting device of this embodiment will be described with reference to FIGS. 1 and 2.

The semiconductor light emitting device of this embodiment is a visible light emitting diode that emits visible light having a shorter wavelength than red, and as shown in FIG. 1, is one surface side of a base substrate 1 made of a sapphire substrate (FIG. 1 ( An n-type semiconductor layer 2 made of a gallium nitride-based compound semiconductor layer is formed on the upper surface side in b), and a light-emitting layer 3 made of a group III nitride semiconductor layer is formed on the n-type semiconductor layer 2. A p-type semiconductor layer 4 made of a gallium nitride compound semiconductor layer is formed. In short, the semiconductor light emitting device of this embodiment has a stacked structure of the n-type semiconductor layer 2, the light emitting layer 3, and the p-type semiconductor layer 4 on the one surface side of the base substrate 1. Note that the n-type semiconductor layer 2, the light emitting layer 3, and the p-type semiconductor layer 4 are formed on the one surface side of the base substrate 1 by using an epitaxial growth technique such as the MOVPE method. Needless to say, it is desirable to provide a buffer layer between the base substrate 1 and the n-type semiconductor layer 2 in order to reduce the threading dislocation of the n-type semiconductor layer 2 and the residual strain of the n-type semiconductor layer 2. In the example shown in FIG. 1, the outermost surface side of the one surface side of the base substrate 1 is exposed, but a protective film such as a SiO ₂ film or a Si ₃ N ₄ film may be formed on the outermost surface side. Good.

  In the semiconductor light emitting device of this embodiment, the anode electrode 5 is formed on the opposite side of the p-type semiconductor layer 4 to the light emitting layer 3 side, and the cathode electrode is formed on the stacked side of the light emitting layer 3 in the n-type semiconductor layer 2. 6 is formed. More specifically, the anode electrode 5 is formed on the p-type semiconductor layer 4, and the cathode electrode 6 has the n-type semiconductor layer 2, the light emitting layer 3, and the p-type semiconductor layer 4 on the one surface side of the base substrate 1. After sequentially growing, a predetermined region of the laminated film of the n-type semiconductor layer 2, the light emitting layer 3, and the p-type semiconductor layer 4 is etched from the surface side of the p-type semiconductor layer 4 to the middle of the n-type semiconductor layer 2. The n-type semiconductor layer 2 is exposed on the surface.

  Here, in the semiconductor light emitting device of this embodiment, the planar view shape of the base substrate 1 is rectangular, and the planar view shapes of the cathode electrode 6 and the anode electrode 5 are comb shapes as shown in FIG. The cathode electrode 6 and the anode electrode 5 are intertwined with each other in plan view.

  As the crystal material of the light emitting layer 3, for example, InGaN, AlInGaN, AlInN, AlGaN or the like may be adopted, or the composition ratio of the group 3 elements may be set as appropriate, or n-type such as Si, Ge, S, Se, or the like. By appropriately doping impurities and p-type impurities such as Zn and Mg, it is possible to set the emission color to a desired color in the visible light range shorter than red. Here, in the semiconductor light emitting device of this embodiment, by applying a forward bias voltage between the anode electrode 5 and the cathode electrode 6, a current flows from the anode electrode 5 toward the cathode electrode 6, and the light emitting layer 3. Light is emitted by recombination of electrons and holes injected into.

  The cathode electrode 6 electrically connected to the n-type semiconductor layer 2 includes an ohmic contact film 61 made of a metal material capable of making ohmic contact with the n-type semiconductor layer 2 and a metal material laminated on the ohmic contact film 61. It is comprised with the metal film 62 for external connection which consists of. Here, as the metal material of the ohmic contact film 61, for example, Ti, V, Al, or an alloy containing any one of these metals may be employed, and the metal material of the external connection metal film 62 may be used. Alternatively, Au that is chemically stable and easy to bond may be used.

  By the way, the semiconductor light emitting device of the present embodiment has the other surface of the base substrate 1 (of FIG. 1B) formed of a material transparent to light emitted from the light emitting layer 3 (sapphire in the present embodiment). The lower surface is a desired light extraction surface, and the anode electrode 5 is formed on the first transparent conductive film 51 and the first transparent conductive film 51 formed on the p-type semiconductor layer 4. The second transparent conductive film 52, the plurality of multilayer reflective film layers 53 that are formed on the second transparent conductive film 52 and reflect the light emitted from the light emitting layer 3, and the second transparent conductive film 52 has the multilayer reflection A metal reflective film 54 made of a metal material that is formed so as to cover a portion not covered with the film layer 53 and the multilayer reflective film layer 53 and has a high reflectance with respect to the light from the light emitting layer 3, and the metal reflective film 54 Barrier metal film 55 formed on the And an external connection metal layer 56 made of a metal material and formed on barrel film 55. In short, the semiconductor light emitting device of this embodiment includes the multilayer reflective film layer 53 that reflects the light emitted from the light emitting layer 3 on the side opposite to the desired light extraction surface side in the thickness direction of the light emitting layer 3. The light emitted from the light emitting layer 3 to the side opposite to the desired light extraction surface side and incident on the anode electrode 5 is reflected to the light extraction surface side by the multilayer reflection film layer 53 or the metal reflection film 54 ( In addition, the arrow C in FIG.1 (b) has shown an example of the propagation path of the light radiated | emitted from the light emitting layer 3, and reflected by the multilayer reflective film layer 53). In the semiconductor light emitting device of this embodiment, the plurality of multilayer reflective film layers 53 and the metal reflective film 54 constitute a reflective part that reflects light from the light emitting layer 3 toward the desired light extraction surface.

Since the film thickness of the first transparent conductive film 51 is set in the range of 2 to 10 nm, examples of the material of the first transparent conductive film 51 include Ni, Pd, Pt, Cr, and Mn. , Ta, Cu, Fe, or an alloy containing any one of them can be employed. Further, as the material of the second transparent conductive film 52, a material transparent to the light from the light emitting layer 3 may be employed. For example, ITO, IZO, ZnO, In ₂ O ₃ , SnO ₂ , Mg _x One material selected from the group consisting of Zn _1-x O (x ≦ 0.5), amorphous AlGaN, GaN, and SiON may be adopted. Further, although Ag is adopted as the material of the metal reflective film 54, it is not limited to Ag, and Al, Rh, or the like may be adopted. Further, as the metal material of the external connection metal film 56, Au or the like that is chemically stable and easy to bond is adopted, and as the material of the barrier metal film 55, Ti is adopted.

  Each of the multilayer reflective film layers 53 described above has a planar shape formed in a circular shape, and is distributed on the second transparent conductive film 52 (arranged in a two-dimensional array). More specifically, the multilayer reflective film layer 53 is disposed at each portion corresponding to each lattice point of a virtual two-dimensional square lattice having a square unit lattice. In short, the anode electrode 5 in the present embodiment is provided with a plurality of multilayer reflective film layers 53 formed in an independent island shape on a plane parallel to the light emitting layer 3.

Here, as shown in FIG. 2, the multilayer reflective film layer 53 is formed by periodically laminating two kinds of dielectric films 53a and 53b having insulating properties and different refractive indexes. Each of the dielectric films 53a and 53b may be formed of an oxide film or a nitride film. By forming the dielectric films 53a and 53b with an oxide film or a nitride film, each of the dielectric films 53a and 53b is formed by an ion beam evaporation method or a resistance heating evaporation method. It can be easily formed by a general thin film forming technique such as. For example, SiO ₂ , ZrO ₂ , TiO ₂ , Al ₂ O ₃ or the like is adopted as a material for this type of oxide film, and for example, Si ₃ N ₄ , AlN or the like is used as a material for this type of nitride film. Adopt it.

The multilayer reflective film layer 53 described above has a reflectivity (%) by appropriately setting the film thickness, refractive index, and number of layers of the dielectric films 53a and 53b in accordance with the light emission wavelength λ (nm) of the light emitting layer 3. ) And the stop bandwidth (nm) can be adjusted. Here, regarding the film thickness of each of the dielectric films 53a and 53b, if the film thickness of the single film is D (nm) and the refractive index of the single film is n, the film thickness D is
(D × n) / (2m−1) = λ / 4 (where m = 1, 2,...)
It is obtained from the relational expression. This relational expression is a surface parallel to the incident surface of light incident on the incident surface of the medium X1 having a refractive index n and parallel to the incident surface, and is an interface between the medium X1 and the medium X2 in contact with the medium X1. The phase of the light emitted from the medium X1 after being reflected and the light reflected on the incident surface out of the light incident on the incident surface of the medium X1 is the same, and the reflected light is reflected by the interference between the lights having the same phase. It means that the strength becomes stronger. However, here, the medium X1 is considered as one pair of the above-mentioned two single layer films (a pair of the dielectric film 53a and the dielectric film 53b). The design is such that the phase of the light is inverted as in the equation.

For example, if the emission peak wavelength of the emission layer 3 is 470 nm, in the above equation, as m = 1, when the material of one of the dielectric film 53a and SiO _2, the thickness of one of the dielectric film 53a above may be designed to substantially 82nm refractive index of SiO ₂ as 1.43, when the material of the other of the dielectric film 53b and ZrO _2, the thickness of the other dielectric film 53b, the refractive index of the ZrO ₂ Is 1.89 and is approximately 62 nm. Here, in designing the multilayer reflective film layer 53, the laminated film of the dielectric film 53 a made of SiO ₂ and the dielectric film 53 _{b made} of ZrO _{2 is} regarded as one pair, and the relationship between the number of pairs of the laminated film and the reflectance. As a result of simulation, it was confirmed that the reflectance was higher than 95% for light having a wavelength λ of 470 nm by setting the number of pairs to at least 8, and the wavelength of the reflectance when the number of pairs was 8 was confirmed. When the dependence was simulated, it was confirmed that the reflectance was higher than 95% in the wavelength region of ± 30 nm with reference to the emission peak wavelength of the light emitting layer 3 (the stop bandwidth was confirmed to be 60 nm). ). In addition, although the above-mentioned simulation result is a value when the light from the light emitting layer 3 is perpendicularly incident on the multilayer reflective film layer 53, the unevenness of the interface between the light extraction surface of the semiconductor light emitting element and air or the sealing material, Due to the influence of the escape cone caused by the difference in refractive index, the angle formed between the incident surface and the incident surface is inclined from an angle of 90 degrees relative to the light intensity perpendicularly incident on the multilayer reflective film layer 53. A situation can occur where the incident light intensity is stronger. In such a case, it is a matter of course that the thickness of each of the dielectric films 53a and 53b may be designed according to the incident angle at which the light intensity is maximized. In short, the optical path difference between the light reflected by the incident surface of the medium X1 and the light that has entered the medium X1 and then exited from the medium X1 after being reflected at the interface between the medium X1 and the medium X2 The calculation may be performed at an incident angle at which the light intensity incident on the multilayer reflective film layer 53 is maximized.

  In the semiconductor light emitting device of the present embodiment described above, two types of dielectric films 53a and 53b are periodically stacked on the side opposite to the desired light extraction surface side in the thickness direction of the light emitting layer 3. Since the reflective portion is constituted by the plurality of multilayer reflective film layers 53 that reflect the light emitted from the light emitting layer 3 and the metal reflective film 54, the light emitting layer 3 is directed to the side opposite to the desired light extraction surface side. The emitted light can be reflected more efficiently than the reflective metal layer 58 (see FIG. 5) made of a conventional metal material, the light extraction efficiency from the desired light extraction surface can be improved, and the light emission efficiency Can be increased. In the semiconductor light emitting device of this embodiment, the multilayer reflective film layer 53 is formed by alternately stacking two types of dielectric films 53a and 53b having different refractive indexes as described above. By appropriately setting the film thickness of each of the body films 53a and 53b, the reflected light can be strengthened by the light interference effect and the reflectance can be increased, and the light extraction efficiency from the desired light extraction surface can be increased. Can do. Here, if each multilayer reflective film layer 53 is designed so that each multilayer reflective film layer 53 has a reflectance higher than 95% in a wavelength region of ± 30 nm with reference to the emission peak wavelength of the light emitting layer 3, the multilayer reflective film layer 53 is designed. In the film layer 53, light in the wavelength region of the emission spectrum of light generated in the light emitting layer 3 having a full width at half maximum of the emission spectrum of about 40 nm can be efficiently reflected by the multilayer reflective film layer 53 (that is, the emission peak wavelength). Light in the vicinity of the emission peak wavelength can be efficiently reflected), and the light extraction efficiency can be improved.

  Further, in the semiconductor light emitting device of this embodiment, the multilayer reflective film layer 53 is on the opposite side to the desired light extraction surface side in the thickness direction of the light emitting layer 3 of the two electrodes of the anode electrode 5 and the cathode electrode 6. Provided in the anode electrode 5 that is one of the electrodes positioned and formed in a plurality of independent islands on a plane parallel to the light emitting layer 3, the anode electrode 5 resulting from the multilayer reflective film layer 53 is provided. Since the decrease in conductivity can be suppressed and the increase in operating voltage due to the multilayer reflective film layer 53 can be suppressed, the light extraction efficiency can be improved while suppressing the increase in operating voltage.

  By the way, in the above-described embodiment, the multilayer reflective film layer 53 has a configuration in which two types of dielectric films 53a and 53b are periodically stacked. However, the configuration is not limited to two types, but a plurality of types (for example, three types). ) Dielectric films may be periodically laminated. In any case, the multilayer reflective film layer 53 has a structure in which a plurality of types of dielectric films are stacked in the order in which the refractive index increases as the distance from the side closer to the light emitting layer 3 increases. Light scattering at the interface with the second transparent conductive film 52 that is the base layer of the reflective film layer 53 can be prevented, the reflectance in the multilayer reflective film layer 53 can be increased, and the light extraction efficiency can be improved.

(Embodiment 2)
The semiconductor light emitting device of this embodiment is a visible light emitting diode that emits visible light having a wavelength shorter than that of red, as in the first embodiment, and is a base substrate made of an n-type SiC substrate as shown in FIG. 1 is formed with an n-type semiconductor layer 2 made of a gallium nitride-based compound semiconductor layer on one surface side (the upper surface side in FIG. 3B), and a light emitting layer made of a group 3 nitride semiconductor layer on the n-type semiconductor layer 2 3 is formed, and a p-type semiconductor layer 4 made of a gallium nitride-based compound semiconductor layer is formed on the light emitting layer 3. In short, the semiconductor light emitting device of this embodiment also has a stacked structure of the n-type semiconductor layer 2, the light emitting layer 3, and the p-type semiconductor layer 4 on the one surface side of the base substrate 1 as in the first embodiment. Yes. Here, since the n-type semiconductor layer 2, the light emitting layer 3, and the p-type semiconductor layer 4 are formed on the one surface side of the base substrate 1 using an epitaxial growth technique such as the MOVPE method, the n-type semiconductor layer is formed. Of course, it is desirable to provide a buffer layer between the base substrate 1 and the n-type semiconductor layer 2 in order to reduce the threading dislocation of 2 and the residual strain of the n-type semiconductor layer 2. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  In the first embodiment, an insulating sapphire substrate is used as the base substrate 1, whereas in this embodiment, a conductive n-type SiC substrate is used, and light emission in the p-type semiconductor layer 4 occurs. An anode electrode 5 is formed on the side opposite to the layer 3 side, and a cathode electrode 6 is formed on the side of the n-type semiconductor layer 2 opposite to the light emitting layer 3 side. However, the cathode electrode 6 is formed on the other surface of the base substrate 1 (the lower surface in FIG. 3B). Therefore, it is not necessary to employ a structure in which a part of the p-type semiconductor layer 4 is etched as in the first embodiment.

  In the present embodiment, the anode electrode 5 side of the two electrodes of the cathode electrode 6 and the anode electrode 5 is the light extraction surface side, and the light emission layer 3 is on the side opposite to the desired light extraction surface side. A plurality of multilayer reflective film layers 64 and a plurality of multilayer reflective film layers 66 described later are provided on the cathode electrode 6 positioned.

The anode electrode 5 in this embodiment includes a transparent conductive film 151 formed on the p-type semiconductor layer 4, three metal films 154 formed in an island shape on the transparent conductive film 151, and the metal films 154. The three barrier metal films 55 are formed, and three external connection metal films 56 are formed on the respective barrier metal films 55. In short, the anode electrode 5 is provided with three external connection metal films 56 capable of wire bonding, and the metal film 154 and the barrier metal film 55 are interposed between the transparent conductive film 151 and each external connection metal film 56. The laminated film is interposed, and the exposed surface of the transparent conductive film 151 is a desired light extraction surface. Here, in this embodiment, the transparent conductive film 151 is composed of a ZnO thin film doped with Mg, and the film thickness of the transparent conductive film 151 may be set in the range of 2 to 10 nm, for example. In the present embodiment, Ni is used as the material of the metal film 154, the film thickness of the metal film 154 is set to 50 nm, Ti is used as the material of the barrier metal film 55, and the film thickness of the barrier metal film 55 is increased. The thickness is set to 50 nm, Au is adopted as the material of the external connection metal film 56, and the thickness of the external connection metal film 56 is set to 500 nm. However, these materials and film thickness are not particularly limited. .
The cathode electrode 6 includes a first transparent conductive film 63 stacked on the other surface side of the base substrate 1 and a plurality of island shapes formed on the opposite side of the first transparent conductive film 63 from the base substrate 1 side. Of the first transparent conductive film 63 on the side opposite to the base substrate 1 side of the first transparent conductive film 63 and the multilayer reflective film. A second transparent conductive film 65 formed so as to cover the layer 64, and a plurality of island-like multilayer reflective film layers 66 formed on the opposite side of the second transparent conductive film 65 from the base substrate 1 side; The second transparent conductive film 65 is formed on the opposite side of the second transparent conductive film 65 from the base substrate 1 side so as to cover the portion of the second transparent conductive film 65 where the multilayer reflective film layer 66 is not laminated and each multilayer reflective film layer 66. Barrier metal film 67 and laminated on barrier metal film 67 And an external connection metal layer 62. Here, in the present embodiment, the first transparent conductive film 63 and the second transparent conductive film 65 are made of an ITO thin film, and the film thickness of the transparent conductive films 63 and 65 is set in a range of 2 to 10 nm, for example. do it. In the present embodiment, Ti is used as the material of the barrier metal film 67, the film thickness of the barrier metal film 67 is set to 50 nm, and Au is used as the material of the metal film 62 for external connection. Although the film thickness of the film 62 is set to 500 nm, these materials and film thicknesses are not particularly limited. Further, each of the multilayer reflective film layers 64 and 66 may have a configuration in which a plurality of types of dielectric films having different refractive indexes are alternately stacked as in the multilayer reflective film layer 53 of the first embodiment.

  Incidentally, as can be seen from the above description, the plurality of multilayer reflective film layers 64 and the plurality of multilayer reflective film layers 66 are formed in independent island shapes on two planes parallel to the light emitting layer 3, respectively. The positions of the multilayer reflective film layer 64 on one plane and the multilayer reflective film layer 66 on the other plane are shifted, and the plurality of multilayer reflective film layers 64 and the plurality of multilayer reflective film layers 66 are arranged on the other surface of the base substrate 1. The planar shapes of the multilayer reflective film layers 64 and 66 are rectangular so as to cover substantially the entire projection area. Therefore, the area occupied by the multilayer reflective film layers 64 and 66 in the projection region of the light emitting layer 3 is increased while suppressing a decrease in conductivity of the cathode electrode 6 which is one of the electrodes provided with the multilayer reflective film layers 64 and 66. Therefore, the light incident on the cathode electrode 6 can be reflected more efficiently.

  In the semiconductor light emitting device of the present embodiment described above, a plurality of types of dielectric films are periodically stacked on the side opposite to the desired light extraction surface side in the thickness direction of the light emitting layer 3. Since the plurality of multilayer reflective film layers 64 and the plurality of multilayer reflective film layers 66 that reflect the light emitted from the light emitting layer 3 are formed, the light emitted from the light emitting layer 3 to the side opposite to the desired light extraction surface side Can be efficiently reflected as compared with a reflective metal layer made of a conventional metal material, the light extraction efficiency from a desired light extraction surface can be improved, and the light emission efficiency can be increased. Note that an arrow C in FIG. 3B shows an example of a propagation path of light emitted from the light emitting layer 3 and reflected by the multilayer reflective film layer 66.

  Incidentally, the cathode electrode 6 in the above-described embodiment is provided with a plurality of multilayer reflective film layers 64 and 66 on two planes parallel to the light emitting layer 3, but three or more planes parallel to the light emitting layer 3 are provided. A plurality of multilayer reflective film layers may be provided on each of them, and the position of the multilayer reflective film layer may be shifted for each plane.

(Embodiment 3)
The semiconductor light emitting device of this embodiment is a visible light emitting diode that emits visible light having a wavelength shorter than that of red, as in the first embodiment. As shown in FIG. An n-type semiconductor layer 2 made of a gallium nitride compound semiconductor layer is formed on one surface side (upper surface side in FIG. 4B), and a light-emitting layer 3 made of a group 3 nitride semiconductor layer is formed on the n-type semiconductor layer 2. A p-type semiconductor layer 4 made of a gallium nitride compound semiconductor layer is formed on the light emitting layer 3. In short, the semiconductor light emitting device of this embodiment also has a stacked structure of the n-type semiconductor layer 2, the light emitting layer 3, and the p-type semiconductor layer 4 on the one surface side of the base substrate 1 as in the first embodiment. Yes. Here, since the n-type semiconductor layer 2, the light emitting layer 3, and the p-type semiconductor layer 4 are formed on the one surface side of the base substrate 1 using an epitaxial growth technique such as the MOVPE method, the n-type semiconductor layer is formed. Of course, it is desirable to provide a buffer layer between the base substrate 1 and the n-type semiconductor layer 2 in order to reduce the threading dislocation of 2 and the residual strain of the n-type semiconductor layer 2. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  As in the first embodiment, the semiconductor light emitting device of this embodiment has an anode electrode 5 formed on the opposite side of the p-type semiconductor layer 4 to the light emitting layer 3 side, and the light emitting layer 3 of the n-type semiconductor layer 2 The cathode electrode 6 is formed on the laminated side. In the first embodiment, the multilayer reflection film layer 53 is provided on the anode electrode 5 with the other surface of the base substrate 1 as the light extraction surface. The difference lies in that a part of the surface of the anode electrode 5 is a desired light extraction surface. In short, when the semiconductor light emitting device of the first embodiment is mounted on a package, it is mounted face down (flip chip mounting), whereas when the semiconductor light emitting device of this embodiment is mounted on a package, it is face up. After mounting, the anode electrode 5 and the cathode electrode 6 are electrically connected to each wiring pattern of the package through bonding wires.

Also in the present embodiment, as in the first embodiment, the planar shape of the anode electrode 5 and the cathode electrode 6 is formed in a comb shape, and the cathode electrode 6 and the anode electrode 5 are intertwined in the planar view, In the present embodiment, only the transparent conductive films 51 and 52 are formed in a comb shape in the anode electrode 5, and the laminated film of the barrier metal film 55 and the external connection metal film 56 is island-shaped on the second transparent conductive film 52. And is provided at two locations on the portion corresponding to the comb portion of the comb-shaped second transparent conductive film 52. Therefore, in the semiconductor light emitting device of this embodiment, the exposed surface of the second transparent conductive film 52 in the anode electrode 5 can be a desired light extraction surface. In addition, the cathode electrode 6 in the present embodiment has a plurality of islands formed on the surface side of the portion corresponding to the comb bone portion of the comb-shaped transparent conductive film 68 and the comb-shaped transparent conductive film 68 in a plan view. (In the example shown in the figure, it is composed of three external connection metal films 62 and barrier metal films 161 interposed between the respective external connection metal films 62 and the transparent conductive film 68). In short, the laminated film of the barrier metal film 161 and the external connection metal film 62 is formed in an island shape on the transparent conductive film 68, and is formed at three positions on the portion corresponding to the comb bone portion of the comb-shaped transparent conductive film 68. Is provided. Here, as a material of the transparent conductive film 68, any one of ITO, ZnO, In ₂ O ₃ , and SnO ₂ may be adopted. Further, as the material of the barrier metal film 161, for example, Ti may be adopted.

  Further, in the semiconductor light emitting device of this embodiment, a multilayer reflective film layer 7 that reflects light emitted from the light emitting layer 3 is formed on the entire other surface of the base substrate 1 (FIG. 4B). The arrow C in the middle shows an example of a propagation path of light emitted from the light emitting layer 3 and reflected by the multilayer reflective film layer 7). In short, the semiconductor light emitting device of the present embodiment is a multilayer that reflects light emitted from the light emitting layer 3 on the entire other surface of the base substrate 1 on the side opposite to the desired light extraction surface side in the thickness direction of the light emitting layer 3. A reflective film layer 7 is formed. Here, the multilayer reflective film layer 7 has a structure in which a plurality of types of dielectric films having different refractive indexes are alternately laminated, like the multilayer reflective film layer 53 of the first embodiment.

  Thus, in the semiconductor light emitting device of this embodiment, a plurality of types of dielectric films are periodically stacked on the side opposite to the desired light extraction surface side in the thickness direction of the light emitting layer 3. Since the multilayer reflective film layer 7 that reflects the light emitted from the light emitting layer 3 is formed, the light emitted from the light emitting layer 3 to the side opposite to the desired light extraction surface side is reflected by a conventional metal material. The light can be reflected more efficiently than the metal layer, the light extraction efficiency from the desired light extraction surface can be improved, and the light emission efficiency can be increased. In the semiconductor light emitting device of this embodiment, a part of the light emitted from the light emitting layer 3 toward the desired light extraction surface and reflected by the multilayer reflective film layer 7 toward the cathode electrode 6 The light is emitted to the outside through the transparent conductive film 68.

1A and 1B show a semiconductor light emitting device of Embodiment 1, in which FIG. 1A is a schematic plan view, and FIG. It is explanatory drawing of the multilayer reflecting film layer of a semiconductor light emitting element same as the above. The semiconductor light-emitting device of Embodiment 2 is shown, (a) is a schematic plan view, (b) is a schematic sectional drawing of (a). The semiconductor light-emitting device of Embodiment 3 is shown, (a) is a schematic plan view, (b) is a schematic sectional drawing of (a). It is a schematic sectional drawing of the semiconductor light-emitting device which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base substrate 2 N-type semiconductor layer 3 Light emitting layer 4 P-type semiconductor layer 5 Anode electrode 6 Cathode electrode 51 First transparent conductive film 52 Second transparent conductive film 53 Multilayer reflective film layer 54 Metal reflective film 55 Barrier metal film 56 Metal film for external connection

Claims (6)

  An n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer are stacked, an anode electrode is formed on the opposite side of the p-type semiconductor layer from the light-emitting layer side, and the light-emitting layer is stacked on the n-type semiconductor layer. The cathode electrode is formed on the side, and a plurality of types of dielectric films are periodically stacked on the side opposite to the desired light extraction surface side in the thickness direction of the light emitting layer, and light emitted from the light emitting layer A semiconductor light emitting device comprising a multilayer reflective film layer that reflects light.   2. The multilayer reflective film layer is formed by alternately laminating two types of dielectric films having different refractive indexes, and each dielectric film is made of an oxide film or a nitride film, respectively. The semiconductor light emitting element as described.   3. The semiconductor light emitting device according to claim 1, wherein the multilayer reflective film layer is formed by laminating a plurality of types of dielectric films in order of increasing refractive index as the distance from the side closer to the light emitting layer increases. element.   The multilayer reflective film layer is formed so that a reflectance is higher than 95% with respect to light in a wavelength region of an emission peak wavelength ± 30 nm of the light emitting layer. 4. The semiconductor light emitting device according to any one of 3.   The multilayer reflective film layer is provided on one electrode located on a side opposite to a desired light extraction surface side in the thickness direction of the light emitting layer among the two electrodes of the anode electrode and the cathode electrode, 5. The semiconductor light emitting device according to claim 1, wherein a plurality of the light emitting layers are formed in an independent island shape on a plane parallel to the light emitting layer.   The multilayer reflective film layer is provided on one electrode located on a side opposite to a desired light extraction surface side in the thickness direction of the light emitting layer among the two electrodes of the anode electrode and the cathode electrode, Each of the plurality of planes parallel to the light emitting layer is formed in an independent island shape and provided on each plane, and the one electrode shifts the position of the multilayer reflective film layer for each plane. The semiconductor light-emitting device according to claim 1, wherein the semiconductor light-emitting device is provided.

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