JP5123221B2 - Light emitting device - Google Patents

Description

  The present invention relates to a light emitting device including an LED chip (light emitting diode chip).

  2. Description of the Related Art Conventionally, a light emitting device is known in which an LED chip using a GaN-based nitride semiconductor material (for example, GaN, InGaN, AlGaN, etc.) as a light emitting layer material is flip-chip mounted on a mounting substrate (for example, Patent Document 1).

  In Patent Document 1, as shown in FIG. 4, an n-type nitride semiconductor layer 14 made of an n-type GaN layer on one surface side of a transparent substrate 10a ′ transparent to light from the nitride light emitting layer 15 ′. LED chip 10 'having a laminated structure of', nitride light emitting layer 15 'and p-type nitride semiconductor layer 16' made of p-type GaN layer, and mounting substrate 20 'on which the LED chip 10' is flip-chip mounted A light-emitting device A ′ comprising:

  Here, the LED chip 10 ′ uses a sapphire substrate which is a crystal growth substrate as the transparent substrate 10a ′, and the buffer substrate 10b ′ and the light uniformizing layer 13 ′ are disposed on the one surface side of the transparent substrate 10a ′. An n-type nitride semiconductor layer 14 ′ is formed, and a nitride light emitting layer 15 ′ is formed on the opposite side of the n-type nitride semiconductor layer 14 ′ from the light homogenizing layer 13 ′ side. A p-type nitride semiconductor layer 16 ′ is formed on the opposite side to the n-type nitride semiconductor layer 14 ′ side, and on the opposite side of the p-type nitride semiconductor layer 16 ′ to the nitride light emitting layer 15 ′ side. An anode electrode 17 ′ is formed, and a cathode electrode 18 ′ is formed on the exposed surface of the n-type nitride semiconductor 14 ′ on the nitride light emitting layer 15 ′ side.

  Further, the mounting substrate 20 ′ has, for example, an anode electrode 17 ′ and a cathode electrode 18 ′ of the LED chip 10 ′ with bumps 37 ′ and 38 ′ on one surface side of a flat insulating substrate 20a ′ made of an aluminum nitride substrate. Conductor patterns (wiring patterns) 27 ′ and 28 ′ made of a metal layer electrically connected through the wirings are formed.

  Note that Patent Document 1 describes that a GaN substrate, a ZnO substrate, or the like may be used as the crystal growth substrate in addition to the sapphire substrate.

JP 2007-329463 A

  By the way, the light emitting device A ′ having the configuration shown in FIG. 4 is obtained by flip-chip mounting the LED chip 10 ′ on the mounting substrate 20 ′ so that the other surface of the transparent substrate 10a ′ becomes a light extraction surface. 17 ′ also serves as a reflection mirror that reflects light from the nitride light emitting layer 15 ′. However, since it is necessary to reduce the ohmic resistance between the anode electrode 17 ′ and the p-type nitride semiconductor layer 16 ′, the anode electrode 17 For example, Pt or Ni is adopted. For this reason, in the light emitting device A ′ configured as shown in FIG. 4, the anode electrode 17 ′ formed on the surface of the p-type nitride semiconductor layer 16 ′ having a larger area than the exposed surface of the n-type nitride semiconductor layer. (Pt and Ni have a reflectance with respect to light having a wavelength of 450 nm of 60% or less), resulting in a decrease in luminous efficiency. Further, in the light emitting device A ′ having the configuration shown in FIG. 4, the size of the anode electrode 17 ′ is reduced so that the plurality of anode electrodes 17 ′ are dispersedly arranged, and the insulating substrate 20a ′ in the mounting substrate is arranged as described above. A reflection film that reflects light from the LED chip 10 ′ toward the LED chip 10 ′ may be formed on one surface, but the specific resistance of the p-type nitride semiconductor layer 16 ′ composed of a p-type GaN layer is n. Since it is higher than the specific resistance of the n-type nitride semiconductor layer 14 ′ composed of the n-type GaN layer, the region where the current flows in the plane is limited (current diffusion becomes insufficient), and the light emission efficiency is lowered. In this type of light emitting device A ′, the anode electrode 17 ′ is generally formed in a square shape, whereas the bump 37 ′ is generally circular in cross section. Thus, the light reflected from the reflective film toward the LED chip 10 ′ side is absorbed by the exposed portion of the anode electrode.

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

  The invention of claim 1 includes an LED chip and a mounting substrate on which the LED chip is mounted. The LED chip has a stacked structure of an n-type nitride semiconductor layer, a nitride light-emitting layer, and a p-type nitride semiconductor layer. An n-type ZnO substrate that is bonded to the p-type nitride semiconductor layer on the side opposite to the nitride light emitting layer side of the p-type nitride semiconductor layer and has a larger planar size than the p-type nitride semiconductor layer; A plurality of island-shaped cathode electrodes are formed in ohmic contact with the n-type nitride semiconductor layer on the surface of the n-type nitride semiconductor layer opposite to the nitride light-emitting layer side, The anode electrode is formed so as to be in ohmic contact with the n-type ZnO substrate on the p-type nitride semiconductor layer side of the n-type ZnO substrate, and the LED thin film portion is closer to the mounting substrate than the n-type ZnO substrate. substrate The mounting substrate is formed with a conductor pattern bonded to each of the cathode electrode and the anode electrode of the LED chip via bumps, and light emitted from the LED chip to the mounting substrate side is directed to the LED chip side. A reflecting film is formed, and the planar shape of each cathode electrode of the LED chip is formed in a circular shape whose diameter is equal to or smaller than the diameter of the circular joint surface with the conductor pattern in the bump.

  According to the present invention, the n-type nitride semiconductor layer is located on the side farther from the n-type ZnO substrate than the p-type nitride semiconductor layer, and the plurality of island-shaped cathode electrodes emit nitride light in the n-type nitride semiconductor layer. The surface opposite to the layer side is formed so as to be in ohmic contact with the n-type nitride semiconductor layer, and the anode electrode is formed on the n-type ZnO substrate on the p-type nitride semiconductor layer side of the n-type ZnO substrate. Since it is formed so as to be in ohmic contact, absorption loss due to the cathode electrode of light emitted from the nitride light emitting layer to the n-type nitride semiconductor layer side can be suppressed, and the mounting substrate can be connected to the LED chip. A reflective film that reflects the light emitted to the mounting substrate side to the LED chip side is formed, and the planar shape of each cathode electrode of the LED chip is a direct diameter of the circular joint surface with the conductor pattern in the bump. Because it is formed following a circular shape, it can suppress the light reflected from the reflective film to the LED chip side of the mounting substrate is absorbed to the cathode electrodes, thereby improving the luminous efficiency.

  According to a second aspect of the present invention, in the first aspect of the present invention, the LED chip is characterized in that the n-type ZnO substrate is formed in a hexagonal pyramid shape with the surface on the LED thin film portion side as a bottom surface. .

  According to the present invention, since the n-type ZnO substrate of the LED chip is formed in a hexagonal pyramid shape, the light extraction efficiency can be improved as compared with the case where the n-type ZnO substrate is formed in a flat plate shape. it can.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, each of the cathode electrodes is a virtual two-dimensional triangular lattice in which the unit lattice on the surface of the n-type nitride semiconductor layer is an equilateral triangle. It is arranged at each part corresponding to a lattice point.

  According to the present invention, the distance between the adjacent cathode electrodes can be made equal, the uniformity of the current density of the n-type nitride semiconductor layer can be improved, and the luminous efficiency can be further improved.

  According to the first aspect of the present invention, absorption loss due to the cathode electrode of light emitted from the nitride light emitting layer to the mounting substrate side can be suppressed, and light reflected from the reflective film of the mounting substrate to the LED chip side can be reduced. Can be prevented from being absorbed and the luminous efficiency can be improved.

1A is a schematic cross-sectional view of a light-emitting device, FIG. 2B is a schematic bottom view of an LED chip, and FIG. It is characteristic explanatory drawing by simulation of a light-emitting device same as the above and a comparative example. It is a schematic bottom view which shows the other structural example of an LED chip same as the above. It is a schematic sectional drawing of the light-emitting device which shows a prior art example.

  As shown in FIG. 1A, the light emitting device A of the present embodiment includes an LED chip 10 and a mounting substrate 20 on which the LED chip 10 is mounted.

  The LED chip 10 is a GaN-based blue LED chip that emits blue light, and includes an n-type nitride semiconductor layer 14, a nitride light-emitting layer 15, and a p-type nitride semiconductor layer 16 each formed of a nitride semiconductor material. The LED thin film portion 12 having the laminated structure of FIG. 5 and the p-type nitride semiconductor layer 16 which is bonded to the p-type nitride semiconductor layer 16 on the side opposite to the nitride light emitting layer 15 side and is more planar than the p-type nitride semiconductor layer 16. And an n-type ZnO substrate 11 having a large size.

  In addition, the LED chip 10 is formed such that the shape of the LED thin film portion 12 in plan view is slightly smaller than the one surface 11a that is the surface of the n-type ZnO substrate 11 on the LED thin film portion 12 side. The cathode electrode 18 is formed so as to be in ohmic contact with the n-type nitride semiconductor layer 14 on the surface of the n-type nitride semiconductor layer 14 opposite to the nitride light emitting layer 15 side, and has a plurality of island shapes. The anode electrode 17 is formed to be in ohmic contact with the n-type ZnO substrate 11 at a portion where the p-type nitride semiconductor layer 16 is not bonded to the p-type nitride semiconductor layer 16 side of the n-type ZnO substrate 11. ing. Thus, in the LED chip 10, the n-type nitride semiconductor layer 14, the nitride light emitting layer 15, and the p-type nitride semiconductor layer 16 can have the same planar size. The LED thin film portion 12 is a sapphire wafer whose one surface is a (0001) surface before bonding the n-type ZnO wafer serving as the basis of the n-type ZnO substrate 11 to the LED thin film portion 12 as described later. A film is formed on one surface side using an epitaxial growth technique such as metal organic chemical vapor deposition (MOVPE). Here, the epitaxial growth method of the LED thin film portion 12 is not limited to the MOVPE method, and for example, a hydride vapor phase growth method (HVPE method), a molecular beam epitaxy method (MBE method), or the like may be employed.

  In the LED thin film portion 12 of the LED chip 10 described above, the n-type nitride semiconductor layer 14 is composed of an n-type GaN layer, the nitride light-emitting layer 15 is composed of an InGaN layer, and the p-type nitride semiconductor layer 16 is nitrided. The p-type AlGaN layer on the light emitting layer 15 side and the p-type GaN layer on the opposite side to the nitride light emitting layer 15 side in the p-type AlGaN layer are configured, but the stacked structure of the LED thin film portion 12 is particularly limited. The nitride light emitting layer 15 is not limited to a single layer structure, and may be a multiple quantum well structure or a single quantum well structure.

  In the LED chip 10, the n-type ZnO substrate 11 is formed in a hexagonal pyramid shape with the one surface 11 a on the LED thin film portion 12 side as a bottom surface, and the LED thin film portion 12 is formed of the n-type ZnO substrate 11. It is formed in a regular hexagonal shape that is slightly smaller than the one surface 11a. The n-type ZnO substrate 11 may be of an n-type conductivity type due to oxygen vacancies or zinc interstitial defects instead of doping, but the conductivity type is changed to n-type by doping and the conductivity is increased. A controlled substrate, for example, a Ga-doped ZnO substrate (GZO substrate) or an Al-doped ZnO substrate (AZO substrate) is more preferable in terms of reducing the ohmic contact resistance with the anode electrode 5.

  Further, the anode electrode 17 and the cathode electrode 18 described above are constituted by a laminated film of a Ti film, an Al film, and an Au film, and the outermost surface side of each is constituted by an Au film. Here, the anode electrode 17 and the cathode electrode 18 are set such that the film thickness of the Ti film is 10 nm, the film thickness of the Al film is 50 nm, and the film thickness of the Au film is 500 nm. There is no particular limitation. In any case, in the LED chip 10 in this embodiment, the anode electrode 17 and the cathode electrode 18 are formed of the same metal material and have the same electrode structure. In the laminated film to be formed, the adhesion between the films overlapping in the thickness direction can be enhanced, and the adhesion to the n-type ZnO substrate 11 and the n-type nitride semiconductor layer 14 can be enhanced. Here, in this embodiment, the anode electrode 17 and the cathode electrode 18 are simultaneously formed by the electron beam evaporation method (EB evaporation method).

  By the way, in the LED chip 10 in this embodiment, the laminated film of Ti film, Al film, and Au film is used as the anode electrode 17 and the cathode electrode 18 as described above, so that the n-type ZnO substrate 11, n Good ohmic contact (low ohmic resistance ohmic contact) can be obtained with respect to the nitride semiconductor layer 14, but not limited to the above laminated film, a laminated film of a Ti film and an Au film, an Al film and an Au film Or a single laminated film selected from the group of laminated films of a Ti film, an Al film, a Ni film, and an Au film. Since the outermost surface side is an Au film, oxidation of the anode electrode 17 and the cathode electrode 18 can be prevented, and a bump 37 made of Au bumps on the mounting substrate 20. 38 can improve the reliability of the bonding between the bumps 37 and 38 when mounting utilized. In the LED chip 10 according to the present embodiment, a fine concavo-convex structure for changing the light traveling direction that changes the light traveling direction is formed on the surface of the n-type nitride semiconductor layer 14 opposite to the nitride light emitting layer 15 side. The total reflection at the interface between the n-type ZnO substrate 11 and the p-type nitride semiconductor layer 16 can be suppressed, and the light generated in the nitride light emitting layer 15 can be efficiently introduced into the ZnO substrate. The extraction efficiency is improved, and as a result, the light emission efficiency is improved. Here, the fine concavo-convex structure is formed on the surface of the n-type nitride semiconductor layer 22 at a part other than the part where the cathode electrode 18 is formed.

  In manufacturing the LED chip 10 described above, the LED thin film portion 12 having the laminated structure is grown on the one surface side of the sapphire wafer whose one surface is the (0001) plane by an epitaxial growth method (for example, MOVPE method). Thereafter, the LED thin film portion 12 is patterned into a regular hexagonal shape, and then the LED thin film portion 12 is bonded to the n-type ZnO wafer serving as the basis of the n-type ZnO substrate 11, and the sapphire wafer is so-called laser lift-off. Then, a fine concavo-convex structure forming step for forming the fine concavo-convex structure on the surface of the n-type nitride semiconductor layer 14 is performed, and thereafter an anode electrode 17 and a cathode electrode 18 are formed. Utilizing the crystal orientation dependence of the etching rate using a hydrochloric acid-based etching solution (for example, hydrochloric acid aqueous solution) Forming a n-type ZnO substrate 11 of hexagonal Tsumujo consisting part of n-type ZnO wafer by performing anisotropic etching. In addition, as an n-type ZnO wafer, what was manufactured using the hydrothermal synthesis method is used. The height of the hexagonal pyramidal n-type Zn substrate 11 can be defined by the thickness of the n-type ZnO wafer. In this embodiment, the n-type ZnO wafer having a thickness of 500 μm is used. Although the height of the n-type ZnO substrate 11 is 500 μm, the thickness of the n-type ZnO wafer is not particularly limited. The inclination angle of each inclined surface 11b with respect to the one surface 11a of the hexagonal pyramidal n-type ZnO substrate 11 is defined by the crystal axis direction of the n-type ZnO wafer. An appropriately patterned mask is provided on the (000-1) plane which is the O polar plane opposite to the (0001) plane which is the Zn polar plane to be the one surface 11a, so that the n-type ZnO wafer is different from the O polar plane side. Since the hexagonal pyramidal n-type ZnO substrate 11 is formed by isotropic etching, the inclination angle of each inclined surface 11b with respect to the one surface 11a is 60 °.

  In the LED chip 10 described above, by applying a forward bias voltage between the anode electrode 17 and the cathode electrode 18, holes are injected from the anode electrode 17 into the p-type nitride semiconductor layer 16 by tunnel current injection. At the same time, electrons are injected from the cathode electrode 18 into the n-type nitride semiconductor layer 14, and the electrons and holes injected into the nitride light-emitting layer 15 recombine to emit light, and each inclined surface 11 b of the n-type ZnO substrate 11. And light is radiated | emitted from the said surface on the opposite side to the n-type ZnO board | substrate 11 side of the n-type nitride semiconductor layer 14 in the LED thin film part 12. FIG. Note that the refractive index of ZnO for light having a wavelength of 450 nm is 2.1, and the refractive index of GaN is 2.4.

  By the way, the LED chip 10 described above is mounted on the mounting substrate 20 such that the LED thin film portion 12 is closer to the mounting substrate 20 than the n-type ZnO substrate 11.

  Here, the mounting substrate 20 has an anode electrode 17 and a cathode electrode 18 of the LED chip 10 on one surface side of a flat insulating substrate 20a made of an aluminum nitride substrate having electrical insulation and high thermal conductivity, respectively. And the conductive patterns 27 and 28 joined via the bumps 37 and 38 are formed, and the reflection film 25 that reflects the light emitted from the LED chip 10 to the mounting substrate 20 side to the LED chip 10 side is formed. Has been. In addition, although the planar view shape of the mounting board | substrate 20 is a rectangular shape (this embodiment square shape), it is not restricted to a square shape, For example, a rectangular shape, circular shape, and hexagon shape may be sufficient.

  The insulating substrate 20a of the mounting substrate 20 also serves as a heat transfer plate for transferring heat generated in the LED chip 10, and has a higher thermal conductivity than an organic substrate such as a glass epoxy resin substrate. The substrate is not limited to the aluminum nitride substrate, and for example, an alumina substrate, a hollow substrate, a silicon substrate having a silicon oxide film formed on the surface, or the like may be employed.

  The conductor patterns 27 and 28 are composed of a laminated film of a Cu film, a Ni film, and an Au film, and the uppermost layer is an Au film. The light reflecting film 25 is composed of a laminated film of a Ni film and an Ag film, but may be composed of a laminated film of a Ni film and an Al film, for example. Here, the light reflecting film 25 may be made of Ag, Al, or the like, which is a material having a reflectance higher than that of Au at least on the outermost side portion of the light emitted from the LED chip 10.

  The bumps 37 and 38 described above employ Au as a material, and are formed on the surfaces of the conductor patterns 27 and 28 of the mounting substrate 20 by a stud bump method (also called a ball bump method). It is composed of a stud bump.

  Here, as shown in FIGS. 1B and 1C, the planar shape of each cathode electrode 18 of the LED chip 10 is such that the diameter L2 is a diameter L1 of a circular joint surface with the conductor pattern 28 in the bump 38 (for example, , About 70 to 100 μm). Here, the diameter L2 of each cathode electrode 18 may be equal to or smaller than the diameter L1 of the circular joint surface. When the LED chip 10 is mounted, it is aligned with an alignment accuracy of about ± 5 μm and a load is applied with ultrasonic waves. However, when a stud bump is employed as the bump 38 as described above, The diameter of the circular bonding surface is smaller than the diameter L1 of the circular bonding surface with the conductor pattern 28. Further, the planar shape of the anode electrode 17 may be the same circular shape as that of the cathode electrode 18. Further, the number of each of the anode electrode 17 and the cathode electrode 18 is not particularly limited, but a larger number is preferable from the viewpoint of efficiently dissipating heat generated in the LED chip 10. The bumps 37 and 38 may be bumps formed by plating (so-called plating bumps).

  According to the light emitting device A of the present embodiment described above, the n-type nitride semiconductor layer 14 is located on the side farther from the n-type ZnO substrate 11 than the p-type nitride semiconductor layer 16, and a plurality of island-shaped cathode electrodes 18 is formed in ohmic contact with the n-type nitride semiconductor layer 14 on the surface of the n-type nitride semiconductor layer 14 opposite to the nitride light-emitting layer 15 side, and the anode 17 Since the n-type ZnO substrate 11 is formed to be in ohmic contact with the n-type ZnO substrate 11 on the p-type nitride semiconductor layer 16 side of the n-type ZnO substrate 11, radiation is emitted from the nitride light emitting layer 15 to the n-type nitride semiconductor layer 14 side. The reflective film 25 that can suppress the absorption loss of the emitted light by the cathode electrode 18 and reflects the light emitted from the LED chip 10 to the mounting substrate 20 side toward the mounting substrate 20 on the LED chip 10 side. The planar shape of each cathode electrode 18 of the LED chip 10 is formed in a circular shape having a diameter L2 that is equal to or smaller than the diameter L1 of the circular bonding surface with the conductor pattern 28 in the bump 38. Light reflected from the film 25 to the LED chip 10 side can be suppressed from being absorbed by each cathode electrode 17, and light emission efficiency can be improved. In addition, the arrow in Fig.1 (a) has shown the advancing path | route of the light radiated | emitted from the LED chip 10 to the mounting substrate 20 side.

  Here, in the light emitting device of the embodiment having the configuration shown in FIG. 1, the mounting substrate 20 has the diameter L2 = the diameter L1 and the reflectance of the side surface of the bump 37 is 40%, and the reflectance of the cathode electrode 18 is 90%. FIG. 2A shows the result of a simulation of the light extraction efficiency when the reflectance of the surface of the substrate is variously changed. The cathode electrode 18 of the light emitting device of the example is nitride-emitted in the n-type nitride semiconductor layer 14. In the light emitting device of Comparative Example 1 in which the cathode electrode 18 is formed on the entire surface on the opposite side to the layer 15 side, the simulation result of the light extraction efficiency when the reflectance of the cathode electrode 18 is variously changed is shown. In the light emitting device of Comparative Example 2 shown in “B” of FIG. 2, an LED thin film portion similar to the LED thin film portion 12 of the above example is bonded to one surface side of the Si substrate. Shows the result of simulation of the light extraction efficiency in the case where the reflectance was varied in the bonding film interposed between the LED thin film portion and the Si substrate to "C" in FIG. 2. Here, it is impossible to set the reflectance to 100%. Since the reflectance of the cathode electrode 18 in the light emitting device of the example is about 90%, the example and the comparative examples 1 and 2 have the same 90%. Comparing by reflectance, it can be seen that the light extraction efficiency can be significantly improved in the example compared to Comparative Examples 1 and 2.

  Further, according to the light emitting device A of the present embodiment, since the n-type ZnO substrate 11 of the LED chip 10 is formed in a hexagonal pyramid shape, compared to the case where the n-type ZnO substrate 11 is formed in a flat plate shape. Light extraction efficiency can be increased. However, the n-type ZnO substrate 11 may have a flat plate shape.

  Note that an underfill portion made of a translucent resin (for example, a silicone resin, an epoxy resin, etc.) may be provided in the gap between the LED chip 10 and the mounting substrate 20, and in this case, the anode of the LED chip 10 The connection reliability between the electrode 17 and the cathode electrode 18 and the conductor patterns 27 and 28 of the mounting substrate 20 can be improved.

  By the way, as shown in FIG. 1B, each cathode electrode 18 of the LED chip 10 is placed at each lattice point of a virtual two-dimensional square lattice in which the unit lattice on the surface of the n-type nitride semiconductor layer 14 is a square. As shown in FIG. 3, the unit cell on the surface of the n-type nitride semiconductor layer 14 is an equilateral triangular virtual two-dimensional triangular lattice (the one-dot chain line in FIG. 3). The distance between adjacent cathode electrodes 18 can be made equal, and the current density of the n-type nitride semiconductor layer 14 is uniform. The light emission efficiency can be further improved.

  In the above-described embodiment, the light emission color of the LED chip 10 is blue light, but the light emission color of the LED chip 10 is not limited to blue light, and may be green light, red light, purple light, ultraviolet light, or the like.

Further, in the light emitting device A described above, the light emitting device A is formed of a translucent material containing a phosphor that is excited by light emitted from the LED chip 10 and emits light having a longer wavelength than the LED chip 10. A dome-shaped color conversion member (not shown) that is fixed to the mounting substrate 20 so as to surround the LED chip 10 may be provided therebetween. As a translucent material used as the material of the color conversion member in this case, for example, a silicone resin may be used, but not limited to a silicone resin, for example, an acrylic resin, glass, an organic component and an inorganic component are on the nm level or Organic / inorganic hybrid materials mixed and bonded at the molecular level may be used. If glass is used, the thermal conductivity of the color conversion member will be improved compared to the case of using a silicone resin. , it is possible to improve the luminous flux can more suppress the temperature rise of the phosphor, moreover, with improved gas barrier properties and moisture impermeability against water vapor and NO _x, can suppress moisture absorption deterioration of the phosphor, the reliability and Durability is improved. In addition, a yellow phosphor is adopted as a phosphor to be mixed with a light-transmitting material used as the material of the color conversion member. However, the phosphor is not limited to the yellow phosphor, and for example, a red phosphor and a green phosphor are mixed. Even white light can be obtained.

DESCRIPTION OF SYMBOLS 10 LED chip 11 n-type ZnO substrate 12 LED thin film part 14 n-type nitride semiconductor layer 15 Nitride light emitting layer 16 p-type nitride semiconductor layer 17 Anode electrode 18 Cathode electrode 20 Mounting substrate 25 Reflective film 27 Conductive pattern 28 Conductive pattern 37 Bump 38 Bump A Light emitting device L1 diameter L2 diameter

Claims (3)

  An LED chip, and a mounting substrate on which the LED chip is mounted. The LED chip includes an LED thin film portion having a stacked structure of an n-type nitride semiconductor layer, a nitride light-emitting layer, and a p-type nitride semiconductor layer; a p-type nitride semiconductor layer having an n-type ZnO substrate which is bonded to the p-type nitride semiconductor layer on the side opposite to the nitride light-emitting layer side and has a larger planar size than the p-type nitride semiconductor layer; The cathode electrode of the n-type nitride semiconductor layer is formed to be in ohmic contact with the n-type nitride semiconductor layer on the surface of the n-type nitride semiconductor layer opposite to the nitride light emitting layer side, and the anode electrode is an n-type ZnO substrate Is formed to be in ohmic contact with the n-type ZnO substrate on the p-type nitride semiconductor layer side, and the LED thin film portion is mounted on the mounting substrate closer to the mounting substrate than the n-type ZnO substrate, The mounting substrate is formed with a conductive pattern bonded to the cathode and anode electrodes of the LED chip via bumps, and a reflection film that reflects light emitted from the LED chip to the mounting substrate side to the LED chip side. The light emitting device is characterized in that the planar shape of each cathode electrode of the LED chip is formed in a circular shape whose diameter is equal to or smaller than the diameter of the circular joint surface with the conductor pattern in the bump.   2. The light emitting device according to claim 1, wherein the LED chip has the n-type ZnO substrate formed in a hexagonal pyramid shape with a surface on the LED thin film portion side as a bottom surface.   Each of the cathode electrodes is arranged at a portion corresponding to each lattice point of a virtual two-dimensional triangular lattice in which the unit lattice on the surface of the n-type nitride semiconductor layer is an equilateral triangle. Item 3. The light emitting device according to item 1 or 2.

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