JP2008159894A - Light emitting element and illuminator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element and an illuminator capable of remarkably improving light extraction efficiency. <P>SOLUTION: The light emitting element includes a semiconductor layer 7 including a light emitting layer 7b on a conductive substrate 10 as an n side electrode, a transparent conductive layer 8 with a plurality of openings 11 as a p side electrode is formed on the main surface on the opposite side of the conductive substrate 10 of the semiconductor layer 7, and the other part of the conductive substrate 10 is removed leaving the part facing the openings 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light emitting element such as a light emitting diode (LED) using a nitride gallium compound semiconductor.

In recent years, Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) is used as a light emitting element that emits light from the ultraviolet light region to blue light. A light emitting device using a gallium nitride compound semiconductor or a nitride semiconductor is attracting attention.

  A light-emitting element using such a gallium nitride-based compound semiconductor can emit white light when combined with a phosphor, and is energy-saving and has a long life. It is considered promising as an alternative and has been put into practical use. However, since the luminous efficiency of a light-emitting element using a gallium nitride-based compound semiconductor is lower than that of a fluorescent lamp, further improvement in efficiency has been demanded, and various studies have been conducted for that purpose.

  By the way, the external quantum efficiency, which is the light emission efficiency of the light emitting element, is the internal quantum efficiency indicating the rate at which electrical energy is converted into light energy in the light emitting layer, and the light extraction indicating the rate at which the converted light energy is emitted to the outside. Determined by product with efficiency.

  The internal quantum efficiency is greatly affected by the crystallinity of the gallium nitride compound semiconductor layer forming the light emitting element. As a method of improving internal quantum efficiency, a buffer layer made of amorphous or polycrystalline AlN-based or AlGaN-based material is formed on a substrate made of sapphire or the like, and a gallium nitride-based compound semiconductor layer is grown on the buffer layer. Is known to relax the lattice mismatch between the substrate and the gallium nitride compound semiconductor layer and improve the crystallinity of the gallium nitride compound semiconductor layer (for example, see Patent Document 1 below). reference).

  On the other hand, various techniques for improving the light extraction efficiency have been disclosed, and a method of reducing internal refractive index by reducing the difference in refractive index from the outside by forming a concavo-convex structure on the surface of the light emitting element or electrode ( For example, refer to Patent Documents 2 and 3, and a method of reducing light absorption at the electrodes by patterning the electrodes into a comb shape or forming a plurality of openings to form a mesh (for example, Patent Document 4). , 5).

  A cross-sectional view of an example of a conventional light emitting element is shown in FIG. An n-type gallium nitride compound semiconductor layer 2a, a light emitting layer 2b made of a gallium nitride compound semiconductor layer, and a semiconductor layer 2 made of a p-type gallium nitride compound semiconductor layer 2c are formed on the substrate 1, and n-type nitride An n-type electrode 3 and a p-type electrode 4 are formed on the gallium compound semiconductor layer 2a and the p-type gallium nitride compound semiconductor layer 2c, respectively.

  As the p-type electrode 4, a conductive layer transparent to the emitted light is used. The p-type electrode 4 is formed of p-type gallium nitride in order to uniformly diffuse current on the p-type gallium nitride compound semiconductor layer 2 c. It is formed on the entire upper surface of the system compound semiconductor layer 2c. An n-type pad electrode 5 and a p-type pad electrode 6 are provided in part of the n-type electrode 3 and the p-type electrode 4 in order to inject current from the outside, and are connected to the package by wire bonding. .

As the substrate 1 used for forming the gallium nitride compound semiconductor layer, conductive silicon carbide (SiC) or gallium nitride (GaN) is used in addition to a substrate made of insulating sapphire which is generally widely used. The board | substrate which consists of etc. is used. In the case of using a conductive substrate, the substrate 1 itself can be used as an n-type electrode instead of the n-type electrode 3.
JP-A-2-229476 JP 2005-259970 A JP 2006-128227 A JP 2003-133589 A Japanese Patent Laid-Open No. 2004-55646

In the conventional light emitting device of FIG. 1, the refractive index of the substrate 1 made of sapphire is about 1.78 when the wavelength of light emitted from the light emitting layer 2b is 400 nm, whereas the gallium nitride compound semiconductor. Has a high refractive index of about 2.55. Therefore, of the light emitted by the light-emitting layer 2b, incident at an angle incident angle to the substrate 1 made of sapphire in excess of about _{44 ° (θ r = arcsin (} 1.78 / 2.55)) of the critical angle theta _r The light to be repeated is totally reflected inside the semiconductor layer 2 formed by laminating each gallium nitride compound semiconductor layer. Therefore, most of the light is absorbed by the semiconductor layer 2 in the process of repeating total reflection at the semiconductor layer 2, and the remaining light is emitted from the end of the semiconductor layer 2 to the outside, so that the amount of light emission is reduced. There is a problem.

  Further, when the outside of the boundary between the semiconductor layer 2 and the outside is air (refractive index≈1), the refractive index difference between these media is further increased, and the amount of light reflected to the semiconductor layer 2 side at the boundary. Therefore, the light extraction efficiency is further deteriorated.

  In order to solve the above problem, when the light extraction efficiency of the light-emitting element is improved using the method of Patent Document 2, the uneven structure formed on one main surface of the p-type gallium nitride compound semiconductor layer causes p The light extraction efficiency is improved by suppressing reflection at the interface between the p-type gallium nitride compound semiconductor layer and the transparent conductive layer as the p-type electrode, but the difference in refractive index between the transparent conductive layer and air is large. The amount of light reflected at the interface increases. As a result, the reflected light returns to the transparent conductive layer or the semiconductor layer and is absorbed again, and there is a limit to increasing the light extraction efficiency.

  Moreover, in the method of patent document 3, the uneven | corrugated structure is formed on the transparent conductive layer as a p-type electrode, the reflection in the interface of a transparent conductive layer and air is suppressed, and the light extraction efficiency is improved. However, when a concavo-convex structure is formed in the transparent conductive layer, the thickness of the transparent conductive layer increases by the amount of forming the concavo-convex structure, so that the amount of light absorbed in the transparent conductive layer increases before being taken out to the outside. There is a problem.

  Further, in the methods of Patent Documents 4 and 5, the transparent conductive layer as a p-type electrode is subdivided into a branched shape or a mesh shape, thereby reducing the amount of light absorbed in the transparent conductive layer and extracting light. Although the efficiency is improved, the current injected from the transparent conductive layer into the semiconductor layer does not spread sufficiently over the entire surface of the semiconductor layer and concentrates directly under the transparent conductive layer. The light emission distribution has a light emission peak immediately below. Therefore, since most of the emitted light is absorbed by the transparent conductive layer directly above, there is a limit to the improvement of light extraction efficiency by the opening formed by subdividing the transparent conductive layer.

  Accordingly, the present invention has been completed in view of the above-described problems in the prior art, and an object of the present invention is to provide a light emitting element and a lighting device capable of dramatically improving light extraction efficiency. .

  The light-emitting element of the present invention includes a semiconductor layer including a light-emitting layer on a conductive substrate as one electrode, and a plurality of the other layers as the other electrode on the main surface of the semiconductor layer facing the conductive substrate. A transparent conductive layer having a plurality of openings is formed, and a portion of the conductive substrate other than a portion facing the openings is removed.

  In the light emitting device of the present invention, preferably, the semiconductor layer is a stacked body in which an n-type gallium nitride compound semiconductor layer, a light emitting layer made of a gallium nitride compound semiconductor, and a p-type gallium nitride compound semiconductor layer are stacked. It is characterized by including.

  The light emitting device of the present invention is preferably characterized in that a light reflecting layer is formed between the conductive substrate and the semiconductor layer.

  The light emitting device of the present invention is preferably characterized in that the semiconductor layer has a concavo-convex structure formed in a portion exposed from the opening of the main surface.

  The light emitting device of the present invention is preferably characterized in that an antireflection layer is formed on a portion of the semiconductor layer exposed from the opening of the main surface.

  The light emitting device of the present invention is preferably characterized in that the transparent conductive layer is an ITO layer.

In the light emitting device of the present invention, preferably, the conductive substrate is a diboride unit represented by a chemical formula XB ₂ (where X includes at least one of Zr, Ti, Mg, Al, and Hf). It consists of crystals.

  The illuminating device of the present invention includes the light emitting element of the present invention and at least one of a phosphor and a phosphor that emits light upon receiving light emitted from the light emitting element.

  The light-emitting element of the present invention has a semiconductor layer including a light-emitting layer on a conductive substrate as one electrode, and a plurality of openings as the other electrode on the main surface of the semiconductor layer facing the conductive substrate. Since the transparent conductive layer having a portion is formed, and the conductive substrate is removed except for the portion facing the opening, the following effects are obtained. That is, the current injected from the transparent conductive layer into the semiconductor layer has conventionally flowed almost immediately below the transparent conductive layer as shown in FIG. 2, whereas in the present invention, the transparent conductive layer As shown in FIG. 3, the current path from the conductive layer to the conductive substrate changes from the transparent conductive layer to the portion of the conductive substrate facing the opening. For example, as shown in FIG. 3, the current path in the longitudinal section is Y-shaped. As a result, the light emitting layer has a light emission distribution having a light emission peak in the vicinity immediately below the opening, so that light can be effectively extracted from the opening to the outside, and the light extraction efficiency can be dramatically improved. It becomes possible.

In the light-emitting element of the present invention, preferably, the semiconductor layer includes a stacked body in which an n-type gallium nitride compound semiconductor layer, a light-emitting layer made of a gallium nitride compound semiconductor, and a p-type gallium nitride compound semiconductor layer are stacked. Thus, by using a conductive substrate made of ZrB ₂ single crystal or the like and a gallium nitride compound semiconductor layer having good lattice matching, the crystallinity of the gallium nitride compound semiconductor layer is increased, and a light emitting device with high emission efficiency is obtained. Become.

  In the light-emitting element of the present invention, preferably, a light reflecting layer is formed between the conductive substrate and the semiconductor layer, so that light directed toward the conductive substrate out of the light emitted from the light-emitting layer is reflected. The light is reflected toward the transparent conductive layer having an opening in the layer, so that light can be effectively collected in the light extraction direction, and the light extraction efficiency can be further improved.

  In the light-emitting element of the present invention, preferably, the semiconductor layer has a concavo-convex structure formed in a portion exposed from the opening of the main surface, so that a difference in refractive index between the exposed semiconductor layer and the outside is reduced. Since the amount of reflection at these interfaces decreases, it becomes possible to more effectively extract light from the opening to the outside.

  In the light emitting device of the present invention, preferably, the semiconductor layer has an antireflection layer formed in a portion exposed from the opening on the main surface, so that the amount of reflection at the interface exposed from the opening and the outside is reflected. Therefore, light can be taken out from the opening more effectively.

  In the light-emitting device of the present invention, preferably, the transparent conductive layer is an ITO layer, so that the transmittance from the ultraviolet light region to the blue light region is increased, light absorption can be suppressed, and the nitride gallium compound. Good ohmic contact with the semiconductor can be formed.

In the light-emitting device of the present invention, preferably, the conductive substrate is a diboride represented by the chemical formula XB ₂ (where X includes at least one of Zr, Ti, Mg, Al, and Hf). By comprising a single crystal, the difference in lattice constant and thermal expansion coefficient between the gallium nitride compound semiconductor and the gallium nitride compound semiconductor formed on the conductive substrate is improved. As a result, not only a light-emitting element with high internal quantum efficiency can be configured, but also the conductive substrate can be easily removed by wet etching using hydrofluoric acid which is a mixed liquid of hydrofluoric acid and nitric acid.

  The illuminating device of the present invention includes the light emitting element of the present invention and at least one of a phosphor and a phosphor that emits light upon receiving light emitted from the light emitting element. The electric power is small and the size is reduced, so that the lighting device is small and has high brightness.

  Hereinafter, embodiments of a light emitting device of the present invention will be described in detail with reference to the drawings.

  FIG. 4 is a schematic cross-sectional view showing an example of an embodiment of the light emitting device of the present invention. In FIG. 4, 7 is a semiconductor layer (stacked body) formed by laminating a plurality of gallium nitride compound semiconductor layers, 7a is an n-type gallium nitride compound semiconductor layer, and 7b is a light emission composed of a gallium nitride compound semiconductor layer. The layer 7c is a p-type gallium nitride compound semiconductor layer. In the same figure, the conductive substrate 10 is used as an n-side electrode or as an n-side conductive layer for forming an n-side electrode, and 8 is used as a p-side electrode or for forming a p-side electrode. Transparent conductive layer (p-side conductive layer).

  The light-emitting element of the present invention has a semiconductor layer 7 including a light-emitting layer 7b on a conductive substrate 10 as an n-side electrode, and a p-side electrode on a main surface opposite to the conductive substrate 10 of the semiconductor layer 7. The transparent conductive layer 8 having a plurality of openings 11 is formed, and the conductive substrate 10 has a configuration in which a portion other than the portion facing the openings 11 is removed.

  In addition, as shown in FIG. 8, when the transparent conductive layer 8 has a lattice shape, for example, the conductive substrate 10 has a portion other than the portion facing the opening 11 removed. In this configuration, rectangular parallelepiped blocks are arranged. Therefore, as shown in FIG. 4, in order to input a current to the conductive substrate 10 as the n-side electrode, it is made of a silver (Ag) paste or the like formed on the substrate 15 such as an external package substrate or a circuit substrate. This is performed by directly connecting the conductive substrate 10 to the n-side electrode 14. As a result, current injection into the conductive substrate 10 individually separated into blocks is performed in common.

  Moreover, the planar view shape of the opening 11 of the transparent conductive layer 8 can be a circular shape, an elliptical shape, a triangular shape, a pentagonal or higher polygonal shape, and in this case, the conductive substrate 10 has a cylindrical shape, an elliptical shape. It has a configuration in which blocks such as columnar, triangular, and polygonal columns are arranged.

In the light emitting device of the present invention, the semiconductor layer includes a stacked body including an n-type gallium nitride compound semiconductor layer 7a, a light emitting layer 7b made of a gallium nitride compound semiconductor, and a p-type gallium nitride compound semiconductor layer 7c. Is preferred. Since the gallium nitride compound semiconductor layer has good lattice matching with a conductive substrate made of a ZrB ₂ single crystal or the like, the crystallinity of the gallium nitride compound semiconductor layer is increased and a light emitting element with high emission efficiency is obtained.

The transparent conductive layer 8 is made of a metal oxide such as indium tin oxide (ITO), tin oxide (SnO ₂ ), or zinc oxide (ZnO). In particular, indium tin oxide (ITO) is ultraviolet. It is suitable not only because it has a high transmittance from light to blue light, but also because good ohmic contact can be made with the p-type gallium nitride compound semiconductor layer 7c.

The semiconductor layer 7 of the present invention is epitaxially grown on the light reflecting layer 13 formed on the conductive substrate 10. The light reflecting layer 13 reflects light directed toward the conductive substrate 10 toward the transparent conductive layer 8 side, which is the light extraction direction, so that light can be effectively collected in the light extraction direction. As the light reflecting layer 13, distributed Bragg reflection in which reflection is intensified in each of the high refractive index layer and the low refractive index layer by Bragg reflection due to light interference effect by stacking a plurality of high refractive index layers and low refractive index layers. A mirror (DBR: Distributed Bragg Reflectors) is used. For example, by forming a DBR having a periodic structure in which 20 pairs of a GaN layer having a thickness of 41.5 nm and an Al _0.52 Ga _0.48 N layer having a thickness of 38.5 nm are stacked, A light reflecting layer 13 having a very good reflectance is formed.

  In the semiconductor layer 7 of the present invention, the uneven structure 12 is preferably formed in a portion exposed from the opening 11. The size of the concavo-convex structure 12 is such that the average distance between protrusions is about the same as or less than the effective wavelength in the medium (for example, the transparent conductive layer 8), and the height is about the same as or more than the effective wavelength. It is preferable. With this size, the refractive index difference between the semiconductor layer 7 and the outside (air) is relaxed to suppress the reflection of light, and the effect of light scattering can be obtained. Further, the light that is totally reflected beyond the critical angle and is confined inside the semiconductor layer 7 also changes the traveling direction of the light. The amount is improved.

The uneven structure 12 is formed as follows. First, the light reflecting layer 13, the n-type gallium nitride compound semiconductor layer 7a, the light emitting layer 7b, the p-type gallium nitride compound semiconductor layer 7c, and the transparent conductive layer 8 are formed in this order on the conductive substrate 10, and transparent When a mask made of a resist layer having the pattern of the opening 11 is formed on the surface of the conductive layer 8 to form, for example, an ITO layer as the transparent conductive layer 8, hydrochloric acid (HCl) and ferric chloride (FeCl _3). The plurality of openings 11 are formed by wet etching using a mixed solution. Next, a mask made of a resist layer, a metal layer, or the like is formed on a portion exposed by the opening 11 of the transparent conductive layer 8, and then reactive ion etching (RIE :) using a chlorine-based gas such as Cl ₂ or BCl _2. The concavo-convex structure 12 can be formed relatively easily by a dry etching method such as a Riactive Ion Etching method.

Further, instead of the concavo-convex structure 12, an antireflection layer may be formed in a portion exposed by the opening 11. In this case, a transparent layer having a refractive index intermediate between the refractive index of the semiconductor layer 7 and the refractive index of external air is used as the antireflection layer. As a material for such a transparent layer, SiO ₂ , MgO, HfO _{2 and the} like are suitable. Furthermore, it is also possible to suppress reflection more by superposing a plurality of transparent layers of these materials from those having a large refractive index to those having a small refractive index.

The semiconductor layer 7 of the present invention has a configuration in which the light emitting layer 7b is sandwiched between an n-type gallium nitride compound semiconductor layer 7a and a p-type gallium nitride compound semiconductor layer 7c. The layer 7a is formed of a stacked body of a GaN layer as a first n-type cladding layer, an In _0.02 Ga _0.98 N layer as a second n-type cladding layer, and the like. The n-type gallium nitride compound semiconductor layer 7a has a thickness of about 2 μm to 3 μm.

Further, for example, the p-type gallium nitride compound semiconductor layer 7c includes an Al _0.15 Ga _0.85 N layer as a first p-type cladding layer and an Al _0.2 Ga ₀ as a second p-type cladding layer. _{.8 It} consists of a laminate of an N layer, a GaN layer as a p-type contact layer, and the like. The p-type gallium nitride compound semiconductor layer 7c has a thickness of about 200 nm to 300 nm.

Further, for example, the light emitting layer 7b includes an In _0.01 Ga _0.99 N layer as a barrier layer having a wide forbidden band and an In _0.11 Ga _0.89 N layer as a well layer having a narrow forbidden band. Are composed of a multiple quantum well structure (MQW: Muliti Quantum Well) or the like that is alternately and regularly stacked three times. The thickness of the light emitting layer 7b is about 25 nm to 150 nm.

  The growth method of the semiconductor layer 7 including the n-type gallium nitride compound semiconductor layer 7a, the light emitting layer 7b, and the p-type gallium nitride compound semiconductor layer 7c of the present invention is a metal organic vapor phase epitaxy (MOVPE) method. Other examples include molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), and pulsed laser deposition (PLD).

  A p-side pad electrode 9 is provided on the p-side transparent conductive layer 8 to connect a conductive wire or the like for electrical connection with the outside. As the p-side pad electrode 9, for example, a titanium (Ti) layer, or a layer in which a titanium (Ti) layer is used as a base layer and a gold (Au) layer is stacked may be used.

The semiconductor layer 7 may be formed on the conductive substrate 10 made of SiC or the like via a buffer layer made of a gallium nitride compound semiconductor, and the chemical formula XB ₂ (where X is Zr, Ti, Mg) , Including at least one of Al and Hf.) May be directly formed on the conductive substrate 10 made of a diboride single crystal represented by:

Often use a conductive substrate 10 made of diboride single crystal represented by a chemical formula XB _2, in which case, 0.57% is difference in lattice constant between the GaN-based compound semiconductor, the thermal expansion coefficient difference even 2 Since the conductive substrate 10 is as small as 0.7 × 10 ⁻⁶ / K, it is possible to obtain a gallium nitride compound semiconductor layer having a low dislocation density and a small residual strain.

A substrate made of a diboride single crystal represented by the chemical formula XB ₂ (where X includes at least one of Zr, Ti, Mg, Al, and Hf) is a ZrB ₂ single crystal or a TiB ₂ single crystal. , HfB ₂ single crystal, etc., but considering that it is excellent in terms of lattice matching and thermal expansion coefficient matching with gallium nitride compound semiconductor, it is possible to use a ZrB ₂ single crystal. preferable. In the ZrB ₂ single crystal, a part of Zr may be substituted with Ti or Hf. Further, the ZrB ₂ single crystal may contain Ti, Hf, Mg, Al, etc. as impurities to such an extent that the crystallinity and lattice constant do not change greatly.

  Note that a light-emitting element to which the gallium nitride compound semiconductor of the present invention is applied can be used as a light-emitting diode (LED).

  Moreover, said light emitting element (LED) of this invention operate | moves as follows. That is, by applying a bias current to the semiconductor layer 7 including the light emitting layer 7b, ultraviolet light to near ultraviolet light or purple light having a wavelength of about 350 to 400 nm is generated in the light emitting layer 7b, and the ultraviolet light to near ultraviolet light is generated outside the light emitting element. Operates to extract light and purple light.

  The light-emitting element of the present invention can be applied to a lighting device, and the lighting device includes the light-emitting element of the present invention and at least one of a phosphor and a phosphor that emit light by receiving light emitted from the light-emitting element. It is the structure which has. With this configuration, a lighting device with high luminance and illuminance can be obtained. The lighting device may be configured such that the light-emitting element of the present invention is covered or encapsulated with a transparent resin or the like, and a phosphor or phosphor is mixed in the transparent resin or the like. The ultraviolet light to near ultraviolet light can be converted into white light or the like. In addition, a light reflecting member such as a concave mirror can be provided in a transparent resin or the like in order to improve the light collecting property. Such an illuminating device consumes less power than a conventional fluorescent lamp or the like, and is small in size. Therefore, the illuminating device is effective as a small and high-luminance lighting device.

  Examples of the light emitting device of the present invention will be described below. In order to confirm the effect of the light emitting device of the present invention, a computer simulation of light extraction efficiency was performed using a ray tracing method.

  5 and 6 show a cross-sectional view of a simulation model in an example of a conventional light-emitting element and a cross-sectional view of a simulation model in an example of a light-emitting element of the present invention. 5 and 6, a transparent conductive layer 8 as a p-side electrode having a plurality of openings 11 is formed on the upper surface of a p-type gallium nitride compound semiconductor layer 7c. Further, a light reflecting layer 13 is provided between the conductive substrate 10 and the n-type gallium nitride compound semiconductor layer 7a. In the conductive substrate 10 as the n-side electrode, only the model of FIG. 6 is left with a portion facing the opening 11 and the other portions are removed.

  In the conventional light emitting device of FIG. 5, the current injected from the transparent conductive layer 8 is concentrated almost directly below the transparent conductive layer 8 without spreading, so that the light source is directly below the transparent conductive layer 8 as shown in FIG. It was supposed to be located.

  On the other hand, in the light emitting device of the present invention shown in FIG. 6, the current path changes to the conductive substrate 10 facing the opening 11, and the light emitting layer 7 b has a light emission distribution having a light emission peak immediately below the opening 11. Therefore, as shown in FIG. 8, the light source is assumed to be located immediately below the opening 11.

  Also, in areas other than the light source, both models have almost the same current spread, and it can be assumed that they have the same light emission distribution, so they are not included in this simulation model, and there is a clear difference in the light emission position in both models. A focused analysis was conducted.

  In addition, the size of the light emitting element is a square having a side of 350 μm in a plan view, the light emission wavelength is 400 nm, and light rays are emitted isotropically from the respective light sources arranged in the light emitting layer 7b. The aperture ratio (ratio of the area of the opening 11 in the light emitting element area in plan view) was 50%.

Further, the refractive index of the semiconductor layer 7 (thickness: 3.2 μm) composed of the n-type gallium nitride compound semiconductor layer 7a, the light emitting layer 7b, and the p-type gallium nitride compound semiconductor layer 7c is 2.5 (n-type gallium nitride compound). The semiconductor layer 7a, the light emitting layer 7b, and the p-type gallium nitride compound semiconductor layer 7c have almost the same refractive index because there is almost no change in refractive index), and a transparent conductive layer 8 made of an indium tin oxide (ITO) layer ( Conductive substrate 10 (thickness: 250 μm) having a refractive index of 2.06 (thickness: 0.25 μm), a refractive index of light reflection layer 13 (thickness: 0.5 μm) made of aluminum (Al) is 0.49, and ZrB ₂ single crystal ) Was calculated with a refractive index of 1.93.

  FIG. 9 shows a graph of the result of calculating the light extraction efficiency by computer simulation. From FIG. 9, the light extraction efficiency of the light emitting device of the embodiment of the present invention is improved about 1.3 times compared with the conventional light emitting device, and the effectiveness of the present invention is clearly shown. I understand.

It is sectional drawing which shows an example of the conventional light emitting element. It is a typical sectional view of current distribution in an example of the conventional light emitting element. It is typical sectional drawing of the current distribution in an example of the light emitting element of this invention. It is sectional drawing which shows an example of embodiment about the light emitting element of this invention. It is sectional drawing which shows the simulation model in an example of the conventional light emitting element. It is sectional drawing which shows the simulation model in an example of the light emitting element of this invention. It is a top view which shows the light source position in the simulation model in an example of the conventional light emitting element. It is a top view which shows the light source position in the simulation model in an example of the light emitting element of this invention. It is a graph of the result of having calculated | required light extraction efficiency by computer simulation about the light emitting element of the Example of this invention, and the conventional light emitting element.

Explanation of symbols

7: Semiconductor layer 7a: n-type gallium nitride compound semiconductor layer 7b: light emitting layer 7c: p-type gallium nitride compound semiconductor layer 8: transparent conductive layer 9: p-side pad electrode 10: conductive substrate 11: opening 12: Uneven structure 13: light reflecting layer

Claims (8)

  Transparent conductive having a semiconductor layer including a light emitting layer on a conductive substrate as one electrode, and having a plurality of openings as the other electrode on the main surface of the semiconductor layer facing the conductive substrate A layer is formed, and a portion of the conductive substrate other than a portion facing the opening is removed.   2. The semiconductor layer according to claim 1, wherein the semiconductor layer includes a stacked body in which an n-type gallium nitride compound semiconductor layer, a light emitting layer made of a gallium nitride compound semiconductor, and a p-type gallium nitride compound semiconductor layer are stacked. Light emitting element.   The light emitting element according to claim 1, wherein a light reflection layer is formed between the conductive substrate and the semiconductor layer.   4. The light emitting device according to claim 1, wherein the semiconductor layer has a concavo-convex structure formed in a portion exposed from the opening of the main surface.   5. The light emitting device according to claim 1, wherein an antireflection layer is formed on a portion of the semiconductor layer exposed from the opening on the main surface.   The light-emitting element according to claim 1, wherein the transparent conductive layer is an ITO layer. The conductive substrate is made of a diboride single crystal represented by a chemical formula XB ₂ (where X includes at least one of Zr, Ti, Mg, Al, and Hf). Item 7. The light emitting device according to any one of Items 1 to 6.   An illumination device comprising: the light-emitting element according to claim 1; and at least one of a phosphor and a phosphor that emits light upon receiving light emitted from the light-emitting element.

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