JP5627174B2 - Light emitting element - Google Patents

Description

  The present invention relates to a light emitting element.

Conventionally, various semiconductor light-emitting elements with improved light extraction efficiency have been proposed. For example, in the semiconductor light-emitting device described in Patent Document 1, by forming a concavo-convex shape on the light extraction surface, the light emitted from the light-emitting layer is more critical than the light extraction surface formed in a planar shape. The ratio of the light incident on the light extraction surface at an angle smaller than the angle is increased to improve the light extraction efficiency to the outside.
JP 2000-196152 A

  However, in the semiconductor light emitting device of Patent Document 1, it is not possible to effectively use the light emitted from the light emitting layer toward the side opposite to the light extraction surface, and increase the light extraction efficiency accordingly. There was a problem that could not.

  In addition, the semiconductor light emitting element of Patent Document 1 has a semiconductor crystal layer having a light emitting layer formed on a sapphire substrate, and the light extraction surface of the semiconductor crystal layer is disposed on the opposite side of the sapphire substrate. Therefore, when this semiconductor light emitting element is mounted on the mounting substrate, the sapphire substrate is disposed on the mounting substrate, and heat generated in the light emitting layer is dissipated through the sapphire substrate. For this reason, there is a problem in that the heat dissipation efficiency is poor, the semiconductor light emitting element becomes high temperature, and the internal quantum efficiency is lowered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a light-emitting element with improved heat extraction efficiency and good heat dissipation efficiency.

A light-emitting element according to the present invention is formed by laminating a light-transmitting substrate and a plurality of semiconductor layers on the substrate, and sequentially laminating n-type nitride-based semiconductor layers from the substrate side, A light-emitting portion having at least a light-emitting layer and a p-type nitride-based semiconductor layer; a conductive film which is provided on the p-type nitride-based semiconductor layer and diffuses current and has translucency; and A photonic crystal structure having a concavo-convex structure, a convex portion having a thickness larger than that of the conductive film, a light reflecting layer provided on the photonic crystal layer, and the n A first electrode connected to the nitride semiconductor layer of the type, and a second electrode connected to the conductive film
The conductive film is made of ITO, the photonic crystal layer, characterized in that it consists of ZrO _2.

In the light emitting device configured as described above, the conductive film is preferably made of ITO. The light emitting layer can be formed of InGaN. In addition, it is preferable that the second electrode is disposed only on a part of the conductive film .

In the present invention, the nitride semiconductor is B _x In _y Al _z Ga _(1-xyz) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1). A group III-V compound semiconductor represented by the composition formula is included, and the group V includes a mixed crystal containing phosphorus (P), arsenic (As), and the like in addition to N.

  According to the present invention, it is possible to provide a light-emitting element with improved light extraction efficiency and good heat dissipation efficiency.

  Hereinafter, an embodiment of a light emitting device according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the light emitting device according to this embodiment.

  As shown in FIG. 1, the light emitting element 1 according to this embodiment is mounted on a mounting substrate 3 by so-called flip chip connection. The light emitting element 1 includes a substrate 5, a light emitting unit 7 provided on the substrate 5, and a first electrode 9 and a second electrode 11 that supply current to the light emitting unit 7.

  The substrate 5 is made of a material capable of crystal growth of each semiconductor layer, which will be described later, forming the light emitting portion 7 and capable of transmitting light from the light emitting portion 7. The light absorption rate of the substrate 5 is preferably 20% or less, for example. The substrate 5 of the present embodiment is made of sapphire, has a thickness of 0.3 mm, and has an absorptance of about 6% for light emitted from the light emitting layer 17 described later.

  The light emitting unit 7 is formed of a plurality of semiconductor layers stacked on the substrate 5, and more specifically, the light emitting unit 7 of the present embodiment includes an n-type contact layer 13 sequentially stacked from the substrate 5 side, The n-type cladding layer 15, the light emitting layer 17, the p-type cladding layer 19, and the p-type contact layer 21 are configured. The n-type contact layer 13 and the n-type cladding layer 15 correspond to the n-type nitride semiconductor layer in the present invention, and the p-type cladding layer 19 and the p-type contact layer 21 in the present invention are p-type nitride. It corresponds to a semiconductor layer.

The n-type contact layer 13 is made of gallium nitride (GaN) doped with an n-type impurity and has a thickness of 10 to 1000 nm. An example of the n-type impurity is silicon (Si), and the doping concentration of the n-type contact layer 13 is 1 × 10 ^{17 to} 5 × 10 ¹⁸ atoms / cm ³ . As shown in FIG. 1, a part of the n-type contact layer 13 is exposed by selectively etching a part of the n-type cladding layer 15, the light emitting layer 17, the p-type cladding layer 19 and the p-type contact layer 21. The first electrode 9 is formed on the exposed portion.

The n-type cladding layer 15 is made of aluminum gallium nitride (AlGaN) doped with an n-type impurity, and has a thickness of 10 to 1000 nm. Examples of the n-type impurity include silicon (Si), and the doping concentration of the n-type cladding layer 15 is set to 1 × 10 ^{17 to} 5 × 10 ¹⁸ atoms / cm ³ .

  The light emitting layer 17 is made of non-doped indium gallium nitride (InGaN) and has a thickness of 10 to 100 nm.

The p-type cladding layer 19 is made of AlGaN doped with a p-type impurity and has a thickness of 10 to 100 nm. An example of the n-type impurity is magnesium (Mg), and the doping concentration of the p-type cladding layer 19 is 1 × 10 ¹⁷ to 1 × 10 ²⁰ atoms / cm ³ .

The p-type contact layer 21 is made of GaN doped with a p-type impurity and has a thickness of 10 to 100 nm. An example of the p-type impurity is magnesium (Mg), and the doping concentration of the p-type contact layer 21 is 1 × 10 ¹⁷ to 1 × 10 ²⁰ atoms / cm ³ .

  Each semiconductor layer constituting the light emitting unit 7 is formed by using, for example, the MOCVD (Metal-organic Chemical Vapor Deposition) method or the MBE (Molecular Beam Epitaxy) method to form the substrate 5. It is formed by epitaxial growth on it.

  The first electrode 9 has an ohmic junction 9a that is ohmic-bonded to the n-type contact layer 13, and a pad portion 9b that covers the ohmic junction 9a. The pad portion 9 b is bonded to the circuit wiring 23 formed on the mounting substrate 3 via the solder bump 25. The ohmic junction 9a is formed of, for example, an alloy made of titanium (Ti) and aluminum (Al). The pad portion 9b is made of, for example, gold (Au). The pad portion 9b and the ohmic junction portion 9a are formed, for example, by depositing and patterning respective metal films.

  On the p-type contact layer 21, there is provided a conductive film 27 that diffuses current supplied from the second electrode 11 and has translucency. The light absorption rate of the conductive film 27 is preferably 30% or less, for example. The conductive film 27 of the present embodiment is made of ITO (Indium Tin Oxide), has a thickness of 10 to 100 nm, and has an absorptance with respect to light emitted from the light emitting layer 17 of 0.13 to 1.3%. It is about. The conductive film 27 is formed by, for example, a sputtering method or an electron beam evaporation method.

  A second electrode 11 and a photonic crystal layer 29 described later are provided on the conductive film 27. The second electrode 11 is formed of, for example, gold (Au), and is joined to the circuit wiring 23 formed on the mounting substrate 3 via the solder bumps 25. Similar to the first electrode 9, the second electrode 11 is formed, for example, by depositing gold and patterning.

The photonic crystal layer 29 has a photonic crystal structure. The photonic crystal layer 29 of the present embodiment is formed by forming a crystal layer made of zirconium oxide (ZrO ₂ ) using a sputtering method, an electron beam evaporation method, or the like, and etching a periodic uneven structure in the crystal layer. Is formed. Further, the thickness of the photonic crystal layer 29 is set to 100 to 2000 nm, for example. Details of the uneven structure of the photonic crystal layer 29 will be described later.

  A light reflecting layer 31 is provided on the photonic crystal layer 29. The light reflecting layer 31 is made of a material layer having a reflectance of 80% or more with respect to the light from the light emitting layer 17 of the light emitting unit 7. The wavelength of light emitted from the light emitting layer 17 formed of InGaN of this embodiment is around 375 nm, and examples of materials having a reflectance of 80% or more in this wavelength region include, for example, aluminum (Al) or silver (Ag). Or an alloy containing at least one of them. The light reflecting layer 31 is formed by evaporating these materials on the photonic crystal layer 29, for example.

  In the light emitting device 1 configured as described above, a forward voltage is applied between the first electrode 9 and the second electrode 11, and a pn junction is formed by the p-type cladding layer 19 and the n-type cladding layer 15. When the current is supplied to the light emitting unit 7, the light emitting layer 17 emits light.

  In the light emitting element 1, only a part of the light emitted from the light emitting layer 17 can be extracted and used outside the element. Light that cannot be extracted to the outside of the element is repeatedly reflected and scattered inside the element and gradually converted into heat energy or the like, so that it cannot be used effectively. One of the biggest reasons why this light cannot be extracted efficiently is the phenomenon of total reflection at the interface between the light emitting element and the outside.

Hereinafter, total reflection will be described. When light is incident on the medium having the refractive index n _{1 from} the medium having the refractive index n _{2 at} the incident angle θ ₁ and is emitted at the outgoing angle θ ₂ , the following equation (1) is obtained between the incident light and the outgoing light. A relationship is established.

Here, when n ₁ > n ₂ , that is, when light is incident on the interface from a medium having a high refractive index toward a medium having a low refractive index, the incident angle is equal to or greater than an incident angle given by sin θ ₁ = n ₂ / n ₁ Sometimes, θ ₂ that satisfies the formula (1) does not exist. In other words, the presence of a light wave that passes through the interface is not allowed, and is totally reflected at the interface. This phenomenon is called total reflection, and θ ₁ at this time is called a critical angle θ _C. In particular, since the optical semiconductor material has a large refractive index, the influence of total reflection becomes significant.

For example, the nitride-based semiconductor constituting each semiconductor layer of the light emitting unit 7 of the present embodiment has a refractive index of about 2.5 in the light emission wavelength region of the light emitting layer 17 of the present embodiment. = 1.0) is a critical angle θ _C of about 23 degrees. The critical angle θ _C at the interface between the nitride-based semiconductor and sapphire (refractive index = about 1.8) is about 46 degrees, and the critical angle θ _{C at} the interface between sapphire and air is about 34 degrees. It is. Here, assuming that the light intensity distribution emitted from the light emitting layer 17 is a Lambert distribution (I (φ) = I ₀ · cos (φ): I ₀ is the light emission intensity in the main line direction), the critical angle θ _C The light energy radiated at is (1−cos 2θ _C ) / 2 × 100 (%) with respect to the total radiant energy. Here, Fresnel reflection is not considered. Substituting the above critical angle θ _C , the light energy emitted within the critical angle θ _C at the interface between air and nitride semiconductor, the interface between sapphire and nitride semiconductor, and the interface between air and sapphire is respectively , About 15%, about 48%, about 31%. Of course, since the reflection loss due to Fresnel reflection is further added, this value is actually further reduced. Therefore, in order to improve the light extraction efficiency to the outside of the light emitting element, it is necessary to reduce this total reflection.

  The photonic crystal structure of the photonic crystal layer 29 has a periodic uneven structure as described above. The principle of reducing total reflection by this photonic crystal structure will be described. Here, in order to facilitate understanding, the one-dimensional diffraction phenomenon will be described. Consider a case where light is incident on a so-called reflection type diffraction grating in which a light reflection layer is formed on a crystal layer on which a one-dimensional periodic uneven structure (photonic crystal structure) is formed. When the period of the concavo-convex structure is sufficiently larger than the wavelength of incident light, the light path can be obtained by performing detailed ray tracing according to the law of reflection. However, when the period of the concavo-convex structure is on the order of the wavelength of the incident light, the light wave diffraction phenomenon appears remarkably. When light is incident on the reflective diffraction grating, the intensity distribution of the emitted light can be most easily obtained from the Fraunhofer diffraction image with respect to the periodic aperture. Specifically, the lightwave electric field amplitude after entering the aperture can be obtained by Fourier transform of the aperture function.

  The reflection type diffraction grating can be regarded as a phase diffraction grating in principle. That is, in the crystal layer in which the concavo-convex structure is formed, the optical path length difference between the convex portion and the concave portion when viewed from the light source is such that the refractive index of the crystal layer that is the light propagation portion is n and the height of the convex portion is d. 2nd. The reason why the numerical value “2” is added to the product (nd) of the refractive index of the light propagation part and the height of the convex part is that light propagating through the convex part is reflected by the light reflecting layer and reciprocates the convex part again. By propagating.

  Here, consider the simplest case where the aperture function u (x) of the diffraction grating having the period a and the phase difference φ = 4πnd / λ (λ: wavelength) is expressed by the following equation (2) of the trigonometric function.

The light wave electric field amplitudes of the fundamental light (0th order diffracted light) and the mth order diffracted light are each represented by a ratio of J _m (φ / 2), and the diffraction angle θ of each diffracted light is given by the following equation (3).

That is, it can be seen that part of the light incident on the light reflecting layer is reflected as diffracted light. Therefore, the total reflection at the interface can be reduced by making the diffracted light more incident on the interface with the outside of the light emitting element at an angle smaller than the critical angle. Here, J _m is an m-th order Bessel function, and by setting φ / 2 appropriately, it is possible to adjust the diffraction efficiency of a desired order although it is limited. Therefore, since light from an actual light emitting element is incident on the reflection type diffraction grating in a spherical wave, a comprehensive effective diffraction angle and each diffraction efficiency are calculated with respect to all incident wave directions, and the period and convexity of the concavo-convex structure are calculated. What is necessary is just to determine a part height.

  The phase difference of light propagating through a specific concavo-convex structure is not represented by a simple periodic function as shown in Equation (2), but as described above, the distribution of diffracted reflected light is an aperture function. Since it is obtained by Fourier transform, basically the same handling can be performed. Here, in order to facilitate understanding, the description is limited to the reflective diffraction grating having a one-dimensional concavo-convex structure. However, the basic concept is a reflective diffraction having a two-dimensional concavo-convex structure as in this embodiment. The grid can also be easily expanded. In the light emitting device 1 of the present embodiment, the photonic crystal layer 29 having a photonic crystal structure and the light reflecting layer 31 form a reflective diffraction grating having a two-dimensional uneven structure.

  In the case of a reflection type diffraction grating having a two-dimensional concavo-convex structure, the concavo-convex structure can have various geometric structures with a period a, for example, a square lattice, a triangular lattice, or the like can be considered. Furthermore, a structure in which a plurality of periods are superimposed is also possible.

  FIG. 2 is a partial plan view showing an embodiment of the photonic crystal structure formed in the photonic crystal layer 29 of the present embodiment. In this photonic crystal structure, concave portions 29a are arranged in a square lattice pattern on the surface of the photonic crystal layer 29 on the light reflecting layer 31 side. The recess 29a is formed by forming a resist mask by photolithography and removing a portion of the photonic crystal layer 29 where the resist mask is not formed by reactive ion etching (RIE). The shape of the recess 29a of the present embodiment is formed so as to be a circular shape in plan view, but may be formed, for example, to be a polygonal shape in plan view. It is preferable that the distance between the centers of the recesses 29a is, for example, 100 to 1000 nm, the depth of the recesses 29a is 10 to 200 nm, and the maximum dimension of the recesses 29a in plan view is 50 to 500 nm. Further, here, the concave portion 29a is formed in the photonic crystal layer 29, but a photonic crystal structure may be formed by forming a plurality of convex portions. The shape of this convex part may be, for example, a cylinder, a polygonal column, a cone, a polygonal guess, a truncated cone or a polygonal guess.

According to the light emitting device 1 of the present embodiment, the light emitted from the light emitting layer 17 to the substrate 5 side is transmitted through the substrate 5 because the substrate 5 has translucency. 1 is taken out. On the other hand, light emitted to the conductive film 27 side passes through the light-transmitting conductive film 27 and enters the photonic crystal layer 29. The light incident on the photonic crystal layer 29 is reflected at the boundary surface between the photonic crystal layer 29 and the light reflecting layer 31. More specifically, the photonic crystal structure of the photonic crystal layer 29 has a minute uneven shape as described above. For this reason, the reflected light interferes according to the period of the unevenness and the optical path difference due to the unevenness in the photonic crystal layer 29, whereby the traveling direction of the reflected light is changed in a predetermined direction. This reflected light reaches the substrate 5 from the photonic crystal layer 29 via the conductive film 27 and the light emitting unit 7. In this embodiment, the refractive index of the photonic crystal layer 29 made of ZrO ₂ is 2.1. Since the refractive index of the conductive film 27 made of ITO is about 2.1, total reflection hardly occurs at the interface between the photonic crystal layer 29 and the conductive film 27. Further, since the refractive index of the light emitting portion 7 made of a nitride-based semiconductor is about 2.5, total reflection does not occur at the interface between the conductive film 27 and the light emitting portion 7. On the other hand, since the refractive index of the substrate 5 made of sapphire is about 1.8, total reflection tends to occur at the interface between the light emitting unit 7 and the substrate 5. Therefore, in the present embodiment, a photonic crystal structure is appropriately formed, and most of the light reflected at the interface between the photonic crystal layer 29 and the light reflecting layer 31 is emitted from the light emitting unit 7 (more specifically, n-type). By controlling the direction of light so that it enters the interface between the contact layer 13) and the substrate 5 at an angle smaller than the critical angle, total reflection can be made difficult to occur. Therefore, more light can be transmitted through the substrate 5, and the light emitted from the light emitting layer 17 can be efficiently extracted from the substrate 5 side, which is the light extraction side of the light emitting element 1.

  In the present embodiment, not only the reflection of light by the photonic crystal layer 29 but also the light is reflected by the light reflection layer 31. Therefore, leakage of light from the photonic crystal layer 29 to the mounting substrate 3 side can be suppressed, and the light extraction efficiency from the substrate 5 side of the light-emitting element 1 can also be improved.

  Further, since the p-type nitride semiconductor layer (in this embodiment, the p-type contact layer 21 made of GaN) generally has a large electric resistance, it is difficult for current to diffuse in the semiconductor layer. Here, in this embodiment, the case where the conductive film 27 does not exist on the p-type contact layer 21 is considered. In this case, in order to increase the light emitting region in the light emitting layer 17 by diffusing current throughout the p type contact layer 21, for example, instead of the conductive film 27, the surface of the p type contact layer 21 is entirely formed. It is conceivable to bring the second electrode 11 into contact. However, since the second electrode 11 blocks light from the light emitting layer 17, the light cannot reach the photonic crystal layer 29. On the other hand, in the present embodiment, current is diffused and supplied to the p-type contact layer 21 through the conductive film 27, and the conductive film 27 is translucent. Even if it is provided on the entire surface of the contact layer 21, the light from the light emitting portion 7 can be transmitted to the photonic crystal layer 29. Furthermore, since the conductive film 27 can be provided entirely on the surface of the p-type contact layer 21 as described above, the contact resistance between the p-type contact layer 21 and the conductive film 27 can be reduced, and the light emitting device 1 driving voltage can be reduced.

  Further, according to the present embodiment, the light emitted from the light emitting layer 17 is reflected by the photonic crystal layer 29 and the light reflecting layer 31, and the light is extracted from the substrate 5 side. Therefore, when the light emitting element 1 is mounted on the mounting substrate 3, the light reflection layer 31 side opposite to the substrate 5 is disposed on the mounting substrate 3 side as shown in FIG. The electrode 11 can be connected to the circuit wiring 23 of the mounting substrate 3. By doing so, the heat generated in the light emitting unit 7 is radiated to the mounting substrate 3 through the first electrode 9 and the second electrode 11 without passing through the substrate 5, so that the heat radiation efficiency can be improved. In addition, a decrease in internal quantum efficiency due to the heat of the light emitting element 1 can be suppressed.

  In the present embodiment, since the light emitting portion 7 is formed of a nitride semiconductor and the conductive film 27 is formed of ITO, the light extraction efficiency to the outside of the light emitting element 1 can be improved. That is, as described above, the refractive index of the nitride-based semiconductor is about 2.5, and the refractive index of ITO is about 2.1. The ratio of total reflection at the interface between the p-type contact layer 21) and the conductive film 27 is small. Therefore, a lot of light passes through this boundary surface and enters the conductive film 27. Therefore, the amount of light that can be incident on the photonic crystal layer 29 is increased, and as a result, the amount of light reflected by the photonic crystal layer 29 and the light reflecting layer 31 and extracted outside the light emitting element 1 can be increased. .

In the present embodiment, since the light emitting layer 17 is made of InGaN, light having a wavelength in the vicinity of 375 nm is emitted. However, when the conductive film 27 is made of ITO, the transmittance with respect to light having a wavelength of about 450 nm or less. Becomes smaller. Therefore, in this embodiment, it becomes a subject to make the electrically conductive film 27 as thin as possible. Here, for example, in this embodiment, instead of forming the photonic crystal structure in the photonic crystal layer 29, it may be possible to form the photonic crystal structure in the conductive film 27 without providing the photonic crystal layer 29. However, in this case, in order to form a photonic crystal structure, the conductive film 27 must be formed to be thick to some extent. On the other hand, according to the present embodiment, since the photonic crystal layer 29 that forms the photonic crystal structure is provided separately from the conductive film 27, the conductive film 27 can be formed thin, and the transmittance decreases. Can be supplemented.

In this embodiment, since the photonic crystal layer 29 is made of ZrO ₂ and has a refractive index of about 2.1, the refractive index of the conductive film 27 made of ITO is the same as or substantially equal to the value. ing. Therefore, the ratio of total reflection occurring at the boundary surface between the conductive film 27 and the photonic crystal layer 29 is small, and most of the light incident on the conductive film 27 can be incident on the photonic crystal layer 29. Therefore, coupled with the increase in the amount of light incident on the conductive film 27 from the light emitting section 7, the amount of light reflected by the photonic crystal layer 29 and the light reflecting layer 31 and extracted outside the light emitting element 1 is further increased. Can be increased.

  In this embodiment, the photonic crystal structure is formed in the photonic crystal layer 29. For example, the photonic crystal structure is formed directly on the p-type contact layer 21 without providing the photonic crystal layer 29. It is also possible. However, in this case, in order to form a photonic crystal structure, the p-type contact layer 21 must be formed to be somewhat thick. Since the p-type contact layer 21 is made of p-type GaN (nitride-based semiconductor) and has a large electric resistance as described above, the increase in the electric resistance becomes remarkable when the thickness is increased in this way, and the driving voltage is also increased. As a result, there is a problem that it must be enlarged. In addition, when a p-type nitride semiconductor layer is etched to form a photonic crystal structure, the semiconductor layer is damaged, and the internal quantum efficiency is reduced due to generation of non-light emitting levels, the surface contact resistance is increased, etc. May occur. On the other hand, according to the present embodiment, since the photonic crystal structure 29 is formed separately from the p-type nitride semiconductor layer to form the photonic crystal structure, the p-type nitride semiconductor layer There is an advantage that the above-described problems due to thickening and etching do not occur.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the meaning. In the above embodiment, an n-type nitride-based semiconductor layer is formed by the n-type contact layer 13 and the n-type cladding layer 15, and a p-type nitride-based semiconductor layer is formed by the p-type cladding layer 19 and the p-type contact layer 21. Although it is formed, it is not limited to this as long as the light emitting layer 17 can emit light. For example, a layer structure in which the n-type cladding layer 15 and the p-type cladding layer 19 are not formed may be used. . Further, the light emitting unit 7 may include other semiconductor crystal layers as long as it has at least an n-type nitride-based semiconductor layer, a light-emitting layer, and a p-type nitride-based semiconductor layer that are sequentially stacked from the substrate 5 side. A buffer layer or the like may be formed between the substrate 5 and the n-type contact layer 13.

  In the above embodiment, the n-type and p-type contact layers 13 and 21 are formed of GaN, and the n-type and p-type cladding layers 15 and 19 are formed of AlGaN. However, the n-type and p-type contact layers 13 and 21 are formed of a nitride-based semiconductor. As long as it is, it is not limited to this. Moreover, in the said embodiment, although the light emitting layer 17 is formed with InGaN, it is not limited to this, It can form with the semiconductor which has a band gap corresponding to a desired light emission wavelength.

Further, in the above embodiment, to form a photonic crystal layer 29 in ZrO _2, but is not limited thereto. The photonic crystal layer 29 preferably has a refractive index relatively close to the refractive index of the conductive film 27. When the conductive film 27 is made of ITO as in the above embodiment, for example, TiO ₂ (refractive index = about 1). .8), ZnO (refractive index = about 2.2) or ZnS (refractive index = about 2.2).

It is sectional drawing which shows one Embodiment of the light emitting element which concerns on this invention. It is a partial top view which shows one Embodiment of a photonic crystal structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emitting element 5 Board | substrate 7 Light emission part 9 1st electrode 11 2nd electrode 13 n-type contact layer 15 n-type clad layer 17 Light-emitting layer 19 p-type clad layer 21 p-type contact layer 27 Conductive film 29 Photonic crystal layer 31 Reflective layer

Claims (3)

A substrate having translucency;
A light-emitting part that is formed by laminating a plurality of semiconductor layers on the substrate and has at least an n-type nitride-based semiconductor layer, a light-emitting layer, and a p-type nitride-based semiconductor layer sequentially stacked from the substrate side When,
A conductive film which is provided on the p-type nitride-based semiconductor layer and diffuses current and has translucency;
A photonic crystal layer provided on the conductive film , having a photonic crystal structure having a concavo-convex structure, and having a convex thickness larger than the conductive film;
A light reflecting layer provided on the photonic crystal layer;
A first electrode connected to the n-type nitride-based semiconductor layer;
A second electrode connected to the conductive film;
Equipped with a,
The conductive film is made of ITO,
The photonic crystal layer is characterized in that it consists of ZrO _2, the light emitting element.   The light emitting device according to claim 2, wherein the light emitting layer is made of InGaN.   The light emitting device according to claim 1, wherein the second electrode is disposed only on a part of the conductive film.

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