JP2008130894A - Light emitting element and illumination apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that light extraction efficiency may be reduced in a configuration for extracting light through a transparent conductive layer formed on one main surface of a semiconductor layer because light reflection occurs owing to a large refractive index difference of an interference between the transparent conductive layer and air and the reflected light is returned and absorbed into the transparent conductive layer or the semiconductor layer. <P>SOLUTION: A light emitting element has a semiconductor layer 8 including a lamination body composed of an n-type gallium nitride-based compound semiconductor layer 8a, a light emitting layer 8b composed of a gallium nitride-based compound semiconductor and a p-type gallium nitride-based compound semiconductor layer 8c, a transparent conductive layer 10 and a transparent layer 13 are successively formed on one main surface of the semiconductor layer 8, and the refractive index of the transparent layer 13 is the refractive index of the transparent conductive layer 10 and more. <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 and an illumination device.

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 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 has an energy saving and long life. As it is considered promising as a product, its practical application has begun. 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 influenced by the crystallinity of the gallium nitride compound semiconductor forming the light emitting element. As a measure to improve internal quantum efficiency, a buffer layer 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 as a known technique (for example, the following method) for relaxing the lattice mismatch between the substrate and the gallium nitride compound semiconductor layer and improving the crystallinity of the gallium nitride compound semiconductor layer. (See Patent Document 1).

  On the other hand, various techniques for improving the light extraction efficiency have been disclosed, and there is a method of 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 and suppressing the total internal reflection. (For example, refer to Patent Document 2 and Non-Patent Document 1).

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 that is transparent to the emitted light is used, and the entire upper surface of the p-type gallium nitride compound semiconductor layer 2 c is used to uniformly diffuse the current in the p-type gallium nitride compound semiconductor layer 2 c. Formed. An n-type pad electrode 5 and a p-type pad electrode 6 are respectively provided in part of the n-type electrode 3 and the p-type electrode 4 in order to inject current from the outside. Connected. As the substrate 1 used for forming the gallium nitride compound semiconductor layer, a sapphire substrate is generally used.
Japanese Patent No. 3026087 JP-A-17-259970 Applied. Physics. Letters. 86.2211101 (2005) (APPLIED.PHYSICS.LETTERS.86.221101 (2005))

In the conventional light emitting device of FIG. 4, the refractive index of the sapphire substrate is about 1.78 when the wavelength of the light emitted from the light emitting layer 2b is 400 nm, whereas the refractive index of the gallium nitride compound semiconductor is It is as high as about 2.55. For this reason, of the light emitted from the light emitting layer 2b, light incident at an angle exceeding the critical angle θ _r of about 44 ° (θ _r = arcsin (1.78 / 2.55)) is incident on the sapphire substrate. The total reflection is repeated 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 boundary with the semiconductor layer 2 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 is further increased. Therefore, the light extraction efficiency is further deteriorated.

  In order to solve the above problems, in the case of improving the light extraction efficiency of the light emitting device using the method of Patent Document 2, the uneven structure formed on one main surface of the p-type gallium nitride compound semiconductor layer, 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 refractive index difference between the transparent conductive layer and air is large. The amount of light reflected at these interfaces is large, and the reflected light is again returned to and absorbed in the transparent conductive layer or semiconductor layer, so there is a limit to increasing the light extraction efficiency.

  Further, in the method of Non-Patent Document 1, by forming a concavo-convex structure on a transparent conductive layer as a p-type electrode, reflection at the interface between the transparent conductive layer and air is suppressed, and light extraction efficiency is improved. However, when forming a concavo-convex structure 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 is large before being taken out to the outside. There was a problem of becoming.

  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 capable of dramatically improving light extraction efficiency.

  The light-emitting element of the present invention includes an n-type gallium nitride-based compound semiconductor layer, a light-emitting layer made of a gallium nitride-based compound semiconductor, and a semiconductor layer including a laminate composed of a p-type gallium nitride-based compound semiconductor layer, A transparent conductive layer and a transparent layer are sequentially formed on one main surface of the layer, and the refractive index of the transparent layer is equal to or higher than the refractive index of the transparent conductive layer.

  The light emitting device of the present invention is preferably characterized in that an uneven structure is formed on the surface of the transparent layer.

  The light emitting device of the present invention is preferably characterized in that a concavo-convex structure is formed at the interface where the semiconductor layer and the transparent conductive layer are in contact.

  The light emitting device of the present invention is preferably characterized in that the semiconductor layer is epitaxially grown on a reflective layer formed on a substrate.

  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 includes a semiconductor layer including an n-type gallium nitride-based compound semiconductor layer, a light-emitting layer made of a gallium nitride-based compound semiconductor, and a stacked body composed of a p-type gallium nitride-based compound semiconductor layer. The transparent conductive layer and the transparent layer are sequentially formed on one main surface of the transparent layer, and the refractive index of the transparent layer is equal to or higher than the refractive index of the transparent conductive layer, thereby reflecting light at the interface between the transparent conductive layer and the transparent layer. Is significantly suppressed, and the light returning into the transparent conductive layer is reduced. As a result, the amount of light absorbed in the transparent conductive layer made of an ITO layer or the like having a relatively large light absorption coefficient can be reduced, and the light extraction efficiency can be greatly improved.

  The light emitting device of the present invention preferably has a concavo-convex structure formed on the surface of the transparent layer, so that the refractive index difference at the interface between the transparent layer and air is relaxed and the amount of reflected light is reduced. The light that has entered the transparent layer from the transparent conductive layer can be effectively extracted to the outside, and the light extraction efficiency can be further increased.

  In the light-emitting element of the present invention, preferably, a concavo-convex structure is formed at the interface where the semiconductor layer and the transparent conductive layer are in contact with each other, so that the difference in refractive index at the interface between the semiconductor layer and the transparent conductive layer is reduced. The amount of reflection decreases. Therefore, it becomes possible to increase the amount of light incident on the transparent conductive layer from the semiconductor layer, and the light extraction efficiency is further improved.

  In the light-emitting element of the present invention, preferably, the semiconductor layer is epitaxially grown on the reflective layer formed on the substrate, so that the light traveling toward the substrate side is directed to the transparent layer side where light is extracted by the reflective layer. Since it is reflected and light can be collected effectively in the light extraction direction, the light extraction efficiency is improved.

  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. Since the electric power is small and small, 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. 1 is a schematic cross-sectional view showing an example of an embodiment of a light emitting device of the present invention. In FIG. 1, 8 is a semiconductor layer (stacked body) formed by laminating a plurality of gallium nitride compound semiconductor layers, 8a is an n-type gallium nitride compound semiconductor layer, and 8b is a light emission composed of a gallium nitride compound semiconductor layer. A layer, 8c is a p-type gallium nitride compound semiconductor layer, 9 is an n-side electrode or an n-side conductive layer for forming an n-side electrode, and 10 is a p-side electrode or a p-side electrode This is a p-side conductive layer.

  The light-emitting element of the present invention has a semiconductor layer 8 including a laminate composed of an n-type gallium nitride compound semiconductor layer 8a, a light-emitting layer 8b made of a gallium nitride compound semiconductor, and a p-type gallium nitride compound semiconductor layer 8c. The transparent conductive layer 10 and the transparent layer 13 are sequentially formed on one main surface of the semiconductor layer 8 (the surface opposite to the substrate 7 in FIG. 1), and the refractive index of the transparent layer 13 is that of the transparent conductive layer 10. It is the structure which is more than a refractive index.

As the transparent conductive layer 10, metal oxides such as indium tin oxide (ITO), tin oxide (SnO ₂ ), and zinc oxide (ZnO) are used. Among these, indium tin oxide (ITO) is particularly used. ) Is suitable not only because it has high transmittance from ultraviolet light to blue light, but also because good ohmic contact can be obtained with the p-type gallium nitride compound semiconductor layer 8c.

As the transparent layer 13, since the refractive index of the transparent conductive layer 10 is about 2.0 with respect to ultraviolet light to blue light, it has a refractive index higher than this value and a small light absorption coefficient. It is preferable to use it. As such a material, zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), silicon carbide (SiC), and the like are good, and the refractive index thereof is 2.2 to 2.8.

  The difference between the refractive index of the transparent layer 13 and the refractive index of the transparent conductive layer 10 is preferably 0 to 1. When the difference in refractive index exceeds 1, the reflection of light at the interface between the transparent layer 13 and air increases, and the difference in refractive index increases, so that the effect of reducing the refractive index difference by the concavo-convex structure 14 is sufficiently obtained. I can't.

  The thickness of the transparent conductive layer 10 is preferably 250 nm to 500 nm. If it is less than 250 nm, there is a tendency that good ohmic contact cannot be formed with the p-type gallium nitride compound semiconductor 8c. If it exceeds 500 nm, the amount of light absorption in the transparent conductive layer 10 increases and the light extraction efficiency tends to decrease. .

  The thickness of the transparent layer 13 is preferably 500 nm to 5 μm. If it is less than 500 nm, the concavo-convex structure 14 having a sufficient height for improving the light transmittance tends to be unable to be formed. When the thickness exceeds 5 μm, not only the light absorption amount in the transparent layer 13 increases, but also depends on the material of the transparent layer 13 and the film forming method, but in the case of using a general film forming method such as an evaporation method or a sputtering method. The film formation time becomes very long and the productivity is lowered.

  It is preferable that the uneven structure 14 is formed on the surface of the transparent layer 13, that is, the uneven structure 14 is formed at the interface between the transparent layer 13 and air.

  Further, the concavo-convex structure 14 is formed at the interface between the semiconductor layer 8 and the transparent conductive layer 10, that is, the concavo-convex structure 14 is formed at the interface between the p-type gallium nitride compound semiconductor layer 8 c and the transparent conductive layer 10. It is preferable.

  Of course, as shown in FIG. 1, the concavo-convex structure 14 may be formed on the surface of the transparent layer 13, and the concavo-convex structure 14 may be formed at the interface between the semiconductor layer 8 and the transparent conductive layer 10.

  The size of the concavo-convex structure 14 is such that the average interval between the concavo-convex protrusions is equal to or less than the effective wavelength in the medium (transparent layer 13, p-type gallium nitride compound semiconductor layer 8c), and the height is also in the medium. It is preferable that the wavelength is equal to or greater than the effective wavelength. In this case, the refractive index difference between the upper and lower layers of the interface is further relaxed, light reflection is suppressed, and the effect of light scattering is obtained. As a result, in the case where there is no concavo-convex structure 14, the light that is totally reflected at the interface beyond the critical angle and confined inside the transparent layer or the semiconductor layer also changes the traveling direction of the light. The amount of light extraction is improved by increasing the ratio within the range.

  The concavo-convex structure 14 is formed by forming an n-type gallium nitride compound semiconductor layer 8a, a light emitting layer 8b, and a p-type gallium nitride compound semiconductor layer 8c on the substrate 7 in this order, and then forming a p-type gallium nitride compound semiconductor layer 8a. A mask made of a resist layer, a metal layer, or the like is formed on the surface, and a reactive ion etching (RIE: dry ion etching) method or the like is used to form the mask easily. The uneven structure 14 on the transparent layer 13 can also be formed by the same method.

  The semiconductor layer 8 of the present invention is preferably epitaxially grown on the reflective layer 15 formed on the substrate 7. Since the light directed toward the substrate 7 is reflected by the reflective layer 15 toward the transparent layer 13 that is the light extraction direction, the light can be effectively collected in the light extraction direction.

As the reflective layer 15, for example, by alternately stacking a plurality of high refractive index layers and low refractive index layers, the reflection of the high refractive index layer and the low refractive index layer is strengthened by Bragg reflection due to the light interference effect. It is preferable to use distributed Bragg reflectors (DBR). Specifically, by forming a DBR 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, an emission wavelength of 400 nm A reflection layer 15 having a very good reflectance with respect to light is obtained.

The semiconductor layer 8 of the present invention has a configuration in which the light emitting layer 8b is sandwiched between an n-type gallium nitride compound semiconductor layer 8a and a p-type gallium nitride compound semiconductor layer 8c. The layer 8a 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 8a has a thickness of about 2 μm to 3 μm.

In addition, for example, the p-type gallium nitride compound semiconductor layer 8c 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 8c has a thickness of about 200 nm to 300 nm.

Further, for example, the light emitting layer 8b 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 8b is about 25 nm to 150 nm.

  The growth method of the semiconductor layer 8 including the n-type gallium nitride compound semiconductor layer 8a, the light emitting layer 8b, and the p-type gallium nitride compound semiconductor layer 8c 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).

  The material of the n-side conductive layer 9 is preferably a material that reflects the light generated by the light emitting layer 8b without loss and can have a good ohmic connection with the n-type gallium nitride compound semiconductor layer 8a.

Examples of such materials include aluminum (Al), titanium (Ti), nickel (Ni), chromium (Cr), indium (In), tin (Sn), molybdenum (Mo), silver (Ag), Gold (Au), Niobium (Nb), Tantalum (Ta), Vanadium (V), Platinum (Pt), Lead (Pb), Beryllium (Be), Indium oxide (In ₂ O ₃ ), Gold-silicon alloy (Au -Si alloy), gold-germanium alloy (Au-Ge alloy), gold-zinc alloy (Au-Zn alloy), gold-beryllium alloy (Au-Be alloy), or the like may be used. Among these, aluminum (Al) or silver (Ag) is preferable because it has a high reflectance with respect to blue light (wavelength 450 nm) to ultraviolet light (wavelength 350 nm) emitted from the light emitting layer 8b. Aluminum (Al) is also particularly suitable in terms of ohmic junction with the n-type gallium nitride compound semiconductor layer 8a. Further, a plurality of layers selected from the above materials may be stacked.

  Further, an n-side pad electrode 11 and a p-side pad electrode 12 are provided on the n-type electrode 9 and the p-side transparent conductive layer 10 for connecting a conductive wire or the like for electrical connection with the outside. . Both electrodes may be, for example, a titanium (Ti) layer or a layer in which a gold (Au) layer is stacked with a titanium (Ti) layer as a base layer.

The semiconductor layer 8 may be formed on the substrate 7 made of sapphire, SiC or the like through a buffer layer made of a gallium nitride compound semiconductor, and the chemical formula XB ₂ (where X is Zr, Ti and Hf). May be directly formed on the substrate 7 made of a diboride single crystal represented by the following formula.

By using the substrate 7 made of diboride single crystal represented by a chemical formula XB _2, the lattice constant difference between the gallium nitride compound semiconductor is 0.57%, the difference of thermal expansion coefficient of 2.7 × 10 ^-6 Since the substrate 7 is as small as / K, it becomes possible to form a gallium nitride compound semiconductor layer with a low dislocation density and a small residual strain.

A substrate 7 made of a diboride single crystal represented by the chemical formula XB ₂ is made of a ZrB ₂ single crystal, a TiB ₂ single crystal, an HfB ₂ single crystal, or the like, but has lattice matching and thermal expansion with a gallium nitride compound semiconductor. In view of excellent coefficient consistency, it is preferable to use a ZrB ₂ single crystal. 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 8 including the light emitting layer 8b, the light emitting layer 8b generates ultraviolet light to near ultraviolet light or violet light having a wavelength of about 350 to 400 nm, and the ultraviolet light to near ultraviolet light 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 element of the present invention, a computer simulation of light scattering and light extraction efficiency was performed using a finite difference time domain (FDTD) method and a ray tracing method.

  First, a light scattering simulation by the FDTD method was performed using a model having only a concavo-convex structure, and a scattering angle distribution of scattered light was obtained. Next, the distribution was applied as a boundary condition of the uneven structure in the ray tracing method, and a computer simulation of the light extraction efficiency in the light emitting element (LED element) of the present invention was performed.

  FIG. 2 is a cross-sectional view of a simulation model of an example of a conventional light emitting device, and has an uneven structure at the interface between the p-type gallium nitride compound semiconductor layer 2c and the transparent conductive layer 4 and the interface between the transparent conductive layer 4 and air. 14 is formed. In FIG. 2, 2 is a semiconductor layer, 2a is an n-type gallium nitride compound semiconductor layer, 2b is a light emitting layer made of a gallium nitride compound semiconductor, 3 is an n-side conductive layer, and 15 is a reflective layer.

  On the other hand, FIG. 3 is a cross-sectional view of a simulation model of an example of the light-emitting element of the present invention. The transparent model is formed on the interface between the p-type gallium nitride compound semiconductor layer 8c and the transparent conductive layer 10 and on the transparent conductive layer 10. An uneven structure 14 is formed at the interface between the layer 13 and air.

  In both models, light directed toward the reflective layer 15 is almost completely reflected by the reflective layer 15 or partially transmitted and absorbed and does not reach the substrate. Therefore, the substrate is not included in the simulation model.

  Further, assuming that the emission wavelength is 400 nm, light is emitted from the light emitting layer isotropically.

  Further, the refractive index of the semiconductor layers 2 and 8 having a thickness of 3.2 μm composed of the n-type gallium nitride compound semiconductor layers 2a and 8a, the light emitting layers 2b and 8b, and the p-type gallium nitride compound semiconductor layers 2c and 8c is 2.5. It was. At this time, the n-type gallium nitride compound semiconductor layers 2a and 8a, the light emitting layers 2b and 8b, and the p-type gallium nitride compound semiconductor layers 2c and 8c have almost no change in the refractive index, and thus all have the same refractive index.

  Further, the refractive index of the transparent conductive layers 4 and 10 made of indium tin oxide (ITO) having a thickness of 0.5 μm is 2.06, the refraction of the n-type electrode 3 made of aluminum (Al) and the reflective layer 15 having a thickness of 0.5 μm. The rate was 0.49.

  The size of the concavo-convex structure 14 is such that the interval between the concavo-convex protrusions is 320 nm and the protrusion height is 960 nm.

  FIG. 5 is a graph showing the result of calculating the light extraction efficiency by computer simulation when the refractive index of the transparent layer 13 having a thickness of 1 μm is changed from 1.5 to 3. As a result, when the refractive index of the transparent layer 13 is 2.06 or more of the transparent conductive layer 10 made of indium tin oxide (ITO), the light extraction efficiency (dotted line portion) is greatly improved. It can be seen that the effectiveness of the present invention is clearly shown.

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 about an example of the conventional light emitting element. It is sectional drawing which shows the simulation model about an example of the light emitting element of this invention. It is sectional drawing which shows an example of the conventional light emitting element. It is the 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: Substrate 8: Semiconductor layer 8a: n-type gallium nitride compound semiconductor layer 8b: light emitting layer 8c: p-type gallium nitride compound semiconductor layer 9: n-side conductive layer 10: p-side transparent conductive layer 11: n-side pad electrode 12: p-side pad electrode 13: transparent layer 14: uneven structure 15: reflective layer

Claims (5)

  An n-type gallium nitride-based compound semiconductor layer, a light-emitting layer made of a gallium nitride-based compound semiconductor, and a semiconductor layer including a laminate composed of a p-type gallium nitride-based compound semiconductor layer, and transparent on one main surface of the semiconductor layer A light emitting device, wherein a conductive layer and a transparent layer are sequentially formed, and a refractive index of the transparent layer is equal to or higher than a refractive index of the transparent conductive layer.   The light emitting device according to claim 1, wherein an uneven structure is formed on a surface of the transparent layer.   The light emitting device according to claim 1, wherein an uneven structure is formed at an interface where the semiconductor layer and the transparent conductive layer are in contact with each other.   4. The light emitting device according to claim 1, wherein the semiconductor layer is epitaxially grown on a reflective layer formed on a substrate.   An illumination device comprising: the light-emitting element according to claim 1; and at least one of a phosphor and a phosphor that emit light upon receiving light emitted from the light-emitting element.

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