JP2008072039A - Light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element with high reliability by preventing the occurrence of migration. <P>SOLUTION: The light emitting element 10 has a substrate 11, a semiconductor layer 12 including an n-layer 121, a light emitting layer 122 and a p-layer 123 that are laminated on the substrate 11, an n-electrode 13, and a p-electrode 14 having a reflective electrode 142. In the light emitting element 10, the p-electrode 14 is provided with: a p-contact electrode 141 provided with a plurality of recessed portions 141a and the reflective electrode 142 that is divided into each of a plurality of the recessed portions 141a; and a p-bonding electrode 143 that is formed in such a manner as to put a lid on the recessed portions 141a of the p-contact electrode 141. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light emitting device including a substrate, a semiconductor layer including a light emitting layer stacked on the substrate, and a p electrode including an n electrode and a reflective electrode as electrodes.

A conventional light emitting device having a reflective electrode is described in Patent Document 1. In the group III nitride compound semiconductor light emitting device described in Patent Document 1, an n + layer 103 is formed on a sapphire substrate, a light emitting layer is formed on the n + layer, and a p is formed on the light emitting layer. A mold layer is formed. Further, a first thin film metal layer and a positive electrode are laminated on the p-type layer, and a protective film made of a SiO ₂ film is formed on the top. This positive electrode is composed of a metal layer made of silver (Ag), rhodium (Rh), ruthenium (Ru), platinum (Pt), palladium (Pd), or an alloy containing at least one of these metals. It is what.
JP 2000-36619 A

Since the group III nitride compound semiconductor light emitting device described in Patent Document 1 includes a protective film formed of a SiO ₂ film so as to cover the positive electrode which is a reflective electrode, silver or a silver alloy is used. This protective film is considered to contribute in terms of preventing the influence of migration that is likely to occur in

  However, the protective film is a layer formed of an oxide film that is a semiconductor layer, and the interface between this protective film and the positive electrode that is a metal has a lower connection strength than the interface between metals, so a voltage is applied. When the light is emitted, the protective film may be peeled off due to growth of migration at the positive electrode. Then, the migration that has grown and leaked from the protective film may cause a short circuit with the light emitting layer or the n layer of the semiconductor layer, resulting in a light emission failure.

  Therefore, the light emitting element is desired to further improve the reliability by preventing the leakage of migration that causes the light emission failure.

  Therefore, an object of the present invention is to provide a light-emitting element with high reliability by preventing the occurrence of migration.

  The light-emitting element of the present invention is a light-emitting element including a substrate, a semiconductor layer including a light-emitting layer stacked on the substrate, an n-electrode, and a p-electrode having a reflective electrode, and the p-electrode is provided with a recess. And a first electrode provided with the reflective electrode in the recess, and a second electrode formed so as to cover the recess of the first electrode.

  In the light emitting device of the present invention, the reflection electrode is provided in the recess of the first electrode, and the second electrode is provided so as to cover the recess, so that short circuit and current leakage can be prevented. Even if it occurs, high reliability can be ensured.

  A first invention of the present application is a light-emitting element including a substrate, a semiconductor layer including a light-emitting layer stacked on the substrate, an n-electrode, and a p-electrode having a reflective electrode. The p-electrode has a recess. And a first electrode provided with a reflective electrode in the recess, and a second electrode formed so as to cover the recess of the first electrode.

  Since the reflective electrode using high reflectivity silver or silver alloy, which is likely to cause migration, is provided in the concave portion of the first electrode, and the second electrode is provided so as to cover the concave portion, Even if migration occurs, it is possible to prevent the growth of migration that progresses so as to spread out from between the interface between the first electrode and the second electrode beyond the peripheral wall of the recess of the first electrode. That is, it is possible to suppress short circuit and current leakage by suppressing migration from the reflective electrode from leaking out from the recess of the first electrode.

  The second invention of the present application is characterized in that the reflective electrode is formed at a position where the interface with the second electrode is lower than the opening surface of the recess.

  By forming the reflective electrode so that the interface between the reflective electrode and the second electrode is lower than the opening surface of the concave portion of the first electrode, even if migration occurs in the reflective electrode and grows, the opening surface of the concave portion is reached Therefore, it is possible to make it difficult for migration to exceed the peripheral wall of the recess. In addition, since a large connection area between the first electrode and the second electrode can be secured, the first electrode and the second electrode can be more firmly bonded to further prevent migration growth of the reflective electrode. .

  The third invention of the present application is characterized in that the concave portion of the first electrode is provided so as to divide the reflective electrode into a plurality of island shapes.

  Since the first electrode is a recess that divides the reflective electrode into a plurality of islands, the connection area between the first electrode and the second electrode can be increased, so the connection between the first electrode and the second electrode can be increased. Strength can be increased. In addition, in order for migration from the reflective electrode located at the center of the first electrode to leak out of the light emitting element, it must grow beyond the surrounding recess, thus preventing migration growth more reliably. can do. Furthermore, if the reflective electrode is formed of multiple layers, the stress generated from the difference in expansion and contraction of each layer when the reflective electrode is laminated can be reduced by dividing the reflective electrode to reduce the individual area. Can be made. Therefore, it is possible to prevent the respective layers from being peeled off when the multilayer reflective electrodes are stacked.

  The fourth invention of the present application is characterized in that the reflective electrode located on the outermost side among the plurality of reflective electrodes formed in an island shape is formed of a non-migration metal.

  For example, when a plurality of island-like reflective electrodes are formed of Ag or Ag alloy that is likely to undergo migration, when migration occurs in the outermost Ag reflective electrode, there are few portions that can become a barrier. By forming the outermost reflective electrode among the plurality of reflective electrodes formed in an island shape with a non-migration metal, a distance from the outermost reflective electrode to the p-layer end can be secured. Therefore, it is possible to prevent migration from growing and leaking from the side surface of the light emitting element, rather than simply forming the reflective electrode in a plurality of island shapes.

  The fifth invention of the present application is characterized in that the concave portion of the first electrode is formed so as to surround the entire periphery of the reflective electrode with its peripheral wall.

  A short circuit or leakage of current due to migration occurs when the migration propagates along the side surface of the semiconductor layer and grows across each semiconductor layer, or grows in contact with the n-electrode. Therefore, at least if short circuit and leakage of current can be prevented from leaking outside from the p electrode, short circuit and current leakage can be prevented. The light emitting device of the present invention can prevent leakage from the side surface of the p electrode by forming the concave portion of the first electrode so as to surround the entire periphery of the reflective electrode with the peripheral wall thereof, and Since the 1st electrode is formed so that it may surround, a reflective electrode is not parted and reduction of the reflective efficiency in a reflective electrode can be suppressed.

  In a sixth invention of the present application, the p layer of the semiconductor layer is formed of a p-type gallium nitride based semiconductor layer, the first electrode is a contact electrode in contact with the semiconductor layer, and Pt, Pd, In, Sn, Zn, It is characterized by being formed of Ni, or an alloy containing at least one of these, or a single layer or a multilayer film made of a conductive film.

  When the p layer of the semiconductor layer is formed of a p-type gallium nitride based semiconductor layer, the first electrode is used as a contact electrode in contact with the semiconductor layer, and Pt, Pd, In, Sn, Zn, Ni, or among these By forming the alloy including at least one kind, or a single layer or a multilayer film made of a conductive film, the p layer and the first electrode can be in ohmic contact.

  The seventh invention of the present application is characterized in that the second electrode is formed so as to cover a peripheral side surface of the first electrode.

  Even if the migration grows from the concave portion of the first electrode closest to the outermost side or exceeds the peripheral wall of the concave portion, since the second electrode covers the first electrode, the migration can be further prevented from leaking. it can.

  In an eighth invention of the present application, the second electrode is a bonding electrode, and Rh, Ti, Au, Mo, W, Pt, In, Sn, Zn, Pd, Cr, Al, or at least one of these It is characterized by being a single layer or a multilayer film made of an alloy containing a conductive film.

  The second electrode is a bonding electrode, and Rh, Ti, Au, Mo, W, Pt, In, Sn, Zn, Pd, Cr, Al, or an alloy containing at least one of these, or a single conductive film made of a conductive film. By forming with a layer or a multilayer film, the adhesion to the first electrode can be improved.

  The ninth invention of the present application is characterized in that the first electrode and the second electrode are formed of the same material.

  By forming the first electrode and the second electrode with the same material, the degree of adhesion can be further improved, so that even if migration occurs in the reflective electrode, it grows between the first electrode and the second electrode. Can be difficult.

(Embodiment 1)
A light-emitting element according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a light emitting device according to Embodiment 1 of the present invention. FIG. 2 is a plan view showing the light emitting element according to Embodiment 1 of the present invention.

  As shown in FIGS. 1 and 2, the light emitting element 10 includes a substrate 11, a semiconductor layer 12, an n electrode 13, and a p electrode 14.

  The substrate 11 is made of n-type GaN that is a nitride-based gallium semiconductor.

  The semiconductor layer 12 includes an n layer 121, a light emitting layer 122, and a p layer 123. The n layer 121 is an n-type semiconductor layer formed by stacking GaN, AlGaN or the like on the substrate 11. It is also possible to provide a buffer layer made of GaN, InGaN or the like between the n layer 121 and the substrate 11. The light emitting layer 122 is formed by laminating InGaN or the like on the n layer 121. The p layer 123 is a p-type semiconductor layer formed by stacking AlGaN on the light emitting layer 122.

  The n-electrode 13 is formed by laminating the light-emitting layer 122 and the p-layer 123 on the n-layer 121, and then removing the light-emitting layer 122, the p-layer 123, and a part of the n-layer 121 by dry etching. A region to be formed is exposed and formed on the exposed n layer 121. The n-electrode 13 has a two-layer structure, and includes an n-contact electrode 131 for good connection with the n-layer 121 and an n-bonding electrode 132 for bonding. The n-contact electrode 131 can be formed of any one of Ti, Al, In, Zn, and Cr as a contact electrode material, or an alloy or conductive film containing one or more of these metals. The n bonding electrode 132 is made of Au suitable for bonding.

  The p-electrode 14 has a three-layer structure, and includes a p-contact electrode (first electrode) 141, a reflective electrode 142, and a p-bonding electrode 143 (second electrode) from the p-layer 123 side. .

  The p-contact electrode 141 has a plurality of recesses 141a, and a reflective electrode 142 is provided in the recess 141a. Accordingly, the reflective electrode 142 is disposed in each concave portion 141a of the p-contact electrode 141 so as to be divided into a plurality of island shapes.

The p-contact electrode 141 is preferably formed from Pt, Pd, In, Sn, Zn, Ni, an alloy containing at least one of these, or a conductive film in view of contact with the semiconductor layer 12. In this embodiment mode, it is possible to form a thick film while maintaining high transmittance. Therefore, ITO is used as the p-contact electrode 141. The p-contact electrode 141 can be a single layer or a multilayer film. When the p-contact electrode 141 is a multilayer film, the first layer is a Pt layer having a film thickness of about 10 mm (0.001 μm), and the second layer is an ITO layer. Can be maintained. The recess 141a is masked by forming a protective film such as a resist or SiO _{2 on the} surface of the metal layer or conductive film to be the p-contact electrode 141 in addition to the position to be the recess 141a on the surface. It can be formed easily by etching to a predetermined depth and removing the protective film.

  The reflective electrode 142 can be made of Ag or Ag alloy having a high reflectivity in order to reflect the light from the light emitting layer 122 toward the substrate 11 side. The thickness of the reflective electrode 142 has such a thickness as to reflect light, and the film thickness is such that the interface between the reflective electrode 142 and the p-bonding electrode 143 is located in the concave portion 141a. It is sometimes desirable because the peripheral wall of the recess 141a becomes an obstacle and suppresses growth. In the present embodiment, the depth of the recess 141a is 0.4 μm, and the thickness of the reflective electrode 142 is 0.2 μm. By doing so, a margin of 0.2 μm can be secured from the reflective electrode 142 before leaking out from the recess 141a. The reflective electrode 142 is formed by forming a protective film on the upper surface of the p-contact electrode 141 in which the concave portion 141a is formed, forming an Ag layer or an Ag alloy layer, and then forming the formed Ag layer or Ag alloy layer together with the protective film. By removing, it can form only in the recessed part 141a.

  The p-bonding electrode 143 is an electrode for bonding in which a convex portion 143a that matches the concave portion 141a of the p-contact electrode 141 is formed, and is arranged so as to cover the concave portion 141a of the p-contact electrode 141. The p bonding electrode 143 is formed so as to surround the peripheral side surface of the p contact electrode 141. The p bonding electrode 143 may be Rh, Ti, Au, Mo, W, Pt, In, Sn, Zn, Pd, Cr, Al, an alloy containing at least one of these, or a conductive film. From the viewpoint of adhesion between the p-contact electrode 141 and the reflective electrode 142, the p-bonding electrode 143 can be a single layer or a multilayer film. In this embodiment, the p-bonding electrode 143 is a multilayer, and ITO is used for the first layer, Rh for the second layer, and Au for the third layer. Since the first layer of the bonding electrode is made of ITO, it is made of the same material as the contact electrode, so that the adhesion can be improved. ITO and Rh have good adhesion. The outermost layer is preferably Au from the viewpoint of bonding properties.

  As described above, the reflective electrode 142 using Ag or Ag alloy having high reflectivity that is likely to cause migration is provided in the concave portion 141a of the p-contact electrode 141, and the concave portion 141a is covered with the p-bonding electrode 143. Therefore, even if migration occurs in the reflective electrode 142, it extends beyond the peripheral wall of the concave portion 141 a of the p contact electrode 141 and spreads between the interface between the p contact electrode 141 and the p bonding electrode 143. It is possible to prevent migration from growing.

  Further, the reflective electrode 142 is formed so that the interface between the reflective electrode 142 and the p contact electrode 141 is positioned lower than the opening surface of the concave portion 141a of the p contact electrode 141, whereby the p contact electrode 141, the p bonding electrode 143, Therefore, the p contact electrode 141 and the p bonding electrode 143 can be bonded more firmly.

  Further, since the p bonding electrode 143 is formed so as to surround the peripheral side surface of the p contact electrode 141, only the upper surface of the p contact electrode 141 and the inside of the recess 141a are used as a connection surface between the p contact electrode 141 and the p bonding electrode 143. In addition, since the peripheral side surface of the p-contact electrode 141 can be secured, it is possible to bond more firmly.

(Embodiment 2)
A light-emitting element according to Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 3 is a cross-sectional view showing a light emitting element according to Embodiment 2 of the present invention. FIG. 4 is a plan view showing a light emitting element according to Embodiment 2 of the present invention.

  As shown in FIGS. 3 and 4, the light emitting element 20 includes an n electrode 22 on one surface side of a substrate 21 and a semiconductor layer 23 and a p electrode 24 on the other surface side. The substrate 21 is made of n-type GaN, which is a nitride-based gallium semiconductor. The n electrode 22 can be an n contact electrode 221 and an n bonding electrode 222 in the same manner as the n electrode 13 of the first embodiment. Similarly to the semiconductor layer 12 of Embodiment 1, the semiconductor layer 23 can be an n-layer 231, a light-emitting layer 232, and a p-layer 233, and can be formed by sequentially stacking layers.

  The p electrode 24 has a three-layer structure as in the first embodiment. From the p layer 233 side, the p contact electrode (first electrode) 241, the reflective electrode 242, and the p bonding electrode 243 (second electrode) are provided. Electrode). The same materials as those in the first embodiment can be used for the p contact electrode 241, the reflective electrode 242, and the p bonding electrode 243.

  As described above, in the second embodiment, the p-contact is formed as the light-emitting element 20 in which the n-electrode 22 is provided on one surface side of the substrate 21 and the semiconductor layer 23 and the p-electrode 24 are provided on the other surface side. By forming the recess 241 a in the electrode 241 and providing the reflective electrode 242 in the recess 241 a, it is possible to prevent migration from growing and leaking outside the p electrode 24.

(Embodiment 3)
A light-emitting element according to Embodiment 3 of the present invention will be described with reference to FIGS. FIG. 5 is a cross-sectional view showing a light-emitting element according to Embodiment 3 of the present invention. FIG. 6 is a plan view showing a light-emitting element according to Embodiment 3 of the present invention. 5 and FIG. 6, the same components as those in FIG. 1 and FIG.

  As shown in FIGS. 5 and 6, the light emitting element 30 is formed by forming the outermost reflective electrode 142 a among the plurality of reflective electrodes 142 formed in an island shape with a non-migration metal. In the present embodiment, Rh or Pt can be used as the non-migration metal. For example, a material such as Ag or Ag alloy that causes migration but has a high reflectance is disposed on the inner reflective electrode 142b, and is a non-migration metal such as Rh or Pt that does not cause migration, but Ag or Ag. The one having a lower reflectance than the alloy is arranged on the outermost side. By doing so, since no migration occurs in the outer reflective electrode 142a closest to the end of the p layer 123, higher reliability can be maintained than using a material that may cause migration. Moreover, it is possible to maintain a high reflectance by making the inner reflective electrode 142b Ag or an Ag alloy.

(Embodiment 4)
A light-emitting element according to Embodiment 4 of the present invention will be described with reference to FIGS. FIG. 7 is a cross-sectional view showing a light-emitting element according to Embodiment 4 of the present invention. FIG. 8 is a plan view showing a light-emitting element according to Embodiment 4 of the present invention. 7 and FIG. 8, the same components as those in FIG. 3 and FIG.

  As shown in FIG. 7 and FIG. 8, the light emitting element 40 includes an n electrode 22 on one surface side of the substrate 21 and a semiconductor layer 23 and a p electrode 24 on the other surface side. Further, an n layer 231, a light emitting layer 232, and a p layer 233 are sequentially stacked as the semiconductor layer 23. In the light emitting element 40 according to the fourth embodiment, as in the third embodiment, the outermost reflective electrode 242a among the plurality of reflective electrodes 242 formed in an island shape is a non-migration metal. The reflective electrode 242b formed of Rh and positioned inside the reflective electrode 242a is formed of Ag or an Ag alloy that has high reflectivity but may cause migration. By forming the reflective electrode 242 in this manner, migration is prevented from growing and leaking from the side surface of the light emitting element 40, as in the third embodiment, rather than simply forming the reflective electrode in a plurality of island shapes. can do.

(Embodiment 5)
A light-emitting element according to Embodiment 5 of the present invention will be described with reference to FIGS. FIG. 9 is a cross-sectional view showing a light-emitting element according to Embodiment 5 of the present invention. FIG. 10 is a plan view showing a light-emitting element according to Embodiment 5 of the present invention. 9 and FIG. 10, the same components as those in FIG. 1 and FIG.

  As shown in FIGS. 9 and 10, the light emitting element 50 includes a p-contact electrode 511 formed as a p-electrode 51 so as to surround the entire reflective electrode 512 with a peripheral wall 511 b of the recess 511 a. By forming the p electrode 51 in this way, even if migration occurs in the reflective electrode 512 and grows, the peripheral wall of the p contact electrode 511 becomes an obstacle to growth. Growth that propagates along the side surface of the layer 12 can be prevented. The area of the reflective electrode 512 is reduced by reducing the area of the peripheral wall 511b of the p-contact electrode 511 and the area of the connection between the p-bonding electrode 513 and the p-layer 123. Therefore, the reduction in reflection efficiency can be minimized.

(Embodiment 6)
A light-emitting element according to Embodiment 4 of the present invention will be described with reference to FIGS. FIG. 11 is a cross-sectional view showing a light-emitting element according to Embodiment 6 of the present invention. FIG. 12 is a plan view showing a light-emitting element according to Embodiment 6 of the present invention. 11 and 12, the same components as those in FIGS. 3 and 4 are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIGS. 11 and 12, the light emitting element 60 is provided with an n electrode 22 on one surface side of the substrate 21 and a semiconductor layer 23 and a p electrode 61 on the other surface side. In the light emitting element 60, a recess 611a is formed in the p-contact electrode 611 as in the third embodiment, the entire reflection electrode 612 is surrounded by the peripheral wall 611b of the recess 611a, and the p-bonding electrode 613 covers the recess 611a. In addition, since it is formed so as to surround the periphery of the p-contact electrode 611, it is possible to prevent migration from growing and leaking outside the p-electrode 61.

  As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments. For example, in Embodiments 1 and 2, the reflective electrodes are arranged in a matrix. It is also possible to arrange the reflective electrodes concentrically or radially. In that case, it is possible to change the position of the mask when forming the concave portion of the p-contact electrode, thereby forming the concave portion at a desired position, and forming the reflective electrode in the concave portion.

  Since the present invention can secure high reliability by suppressing the occurrence of migration, a substrate, a semiconductor layer including a light emitting layer stacked on the substrate, and a p including an n electrode and a reflective electrode as electrodes. It is suitable for a light emitting element provided with an electrode.

Sectional drawing which shows the light emitting element which concerns on Embodiment 1 of this invention. The top view which shows the light emitting element which concerns on Embodiment 1 of this invention. Sectional drawing which shows the light emitting element which concerns on Embodiment 2 of this invention. The top view which shows the light emitting element which concerns on Embodiment 2 of this invention. Sectional drawing which shows the light emitting element which concerns on Embodiment 3 of this invention. The top view which shows the light emitting element which concerns on Embodiment 3 of this invention. Sectional drawing which shows the light emitting element which concerns on Embodiment 4 of this invention. FIG. 7 is a plan view showing a light-emitting element according to Embodiment 4 of the present invention. Sectional drawing which shows the light emitting element which concerns on Embodiment 5 of this invention. FIG. 7 is a plan view showing a light emitting element according to Embodiment 5 of the present invention. Sectional drawing which shows the light emitting element which concerns on Embodiment 6 of this invention. FIG. 7 is a plan view showing a light-emitting element according to Embodiment 6 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light emitting element 11 Substrate 12 Semiconductor layer 13 N electrode 14 P electrode 20 Light emitting element 21 Substrate 22 N electrode 23 Semiconductor layer 24 P electrode 30, 40, 50 Light emitting element 51 P electrode 60 Light emitting element 61 P electrode 121 N layer 122 Light emitting layer 123 p layer 131 n contact electrode 132 n bonding electrode 141 p contact electrode 141a recess 142, 142a, 142b reflective electrode 143 p bonding electrode 221 n contact electrode 222 n bonding electrode 231 n layer 232 light emitting layer 233 p layer 241 p contact electrode 241a Recesses 242, 242 a, 242 b Reflective electrode 243 p bonding electrode 511 p contact electrode 511 a Recessed part 511 b peripheral wall 512 reflective electrode 513 p bonding electrode 611 p contact electrode 611 a Part 611b peripheral wall 612 reflective electrode 613 p bonding electrodes

Claims (9)

In a light-emitting element having a substrate, a semiconductor layer including a light-emitting layer stacked on the substrate, an n-electrode, and a p-electrode having a reflective electrode,
The p electrode includes a first electrode in which a concave portion is provided, the reflective electrode is provided in the concave portion, and a second electrode formed so as to cover the concave portion of the first electrode. A light emitting element characterized by the above. The light emitting device according to claim 1, wherein the reflective electrode is formed at a position where an interface with the second electrode is lower than an opening surface of the recess. The light emitting device according to claim 1 or 2, wherein the concave portion of the first electrode is provided so as to divide the reflective electrode into a plurality of island shapes. 4. The light emitting device according to claim 3, wherein an outermost reflective electrode among the plurality of reflective electrodes formed in an island shape is formed of a non-migration metal. 3. The light emitting device according to claim 1, wherein the concave portion of the first electrode is formed so as to surround the entire periphery of the reflective electrode with a peripheral wall thereof. The p layer of the semiconductor layer is formed of a p-type gallium nitride based semiconductor layer,
The first electrode is a contact electrode in contact with the semiconductor layer, and is a single layer or multilayer made of Pt, Pd, In, Sn, Zn, Ni, an alloy containing at least one of these, or a conductive film. 6. The light emitting device according to claim 1, wherein the light emitting device is formed of a film. The light emitting device according to any one of claims 1 to 6, wherein the second electrode is formed so as to cover a peripheral side surface of the first electrode. The second electrode is a bonding electrode, and Rh, Ti, Au, Mo, W, Pt, In, Sn, Zn, Pd, Cr, Al, or an alloy containing at least one of these, a conductive film The light-emitting element according to claim 1, wherein the light-emitting element is a single layer or a multilayer film. The light emitting device according to any one of claims 1 to 8, wherein the first electrode and the second electrode are formed of the same material.

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