WO2011030789A1

WO2011030789A1 - Light-emitting device

Info

Publication number: WO2011030789A1
Application number: PCT/JP2010/065410
Authority: WO
Inventors: 章彦村井; 和幸山江; 博司福島
Original assignee: パナソニック電工株式会社
Priority date: 2009-09-09
Filing date: 2010-09-08
Publication date: 2011-03-17
Also published as: JP2011060966A

Abstract

Disclosed is a light-emitting device which has improved luminous efficiency by reducing light loss that is caused by multiple reflection, while having improved production yield. Specifically disclosed is a light-emitting device which comprises: an LED chip (10) that has a multilayer structure composed of a an n-type nitride semiconductor layer (n-type semiconductor layer) (12), a nitride light-emitting layer (light-emitting layer) (13) and a p-type nitride semiconductor layer (p-type semiconductor layer) (14); a pyramidal (hexagonal prismoid-shaped) transparent member (30) that is formed from a first transparent material (such as ZnO) and arranged on the LED chip (10) such that the bottom surface (31) thereof faces the light extraction surface of the LED chip (10); and an adhesive layer (20) that is formed from a second transparent material (such as a silicone resin) and joins the transparent member (30) and the LED chip (10) together by intervening between the transparent member (30) and the LED chip (10). The refractive index of the first transparent material is higher than the refractive index of the second transparent material, and the shortest distance (L) between the light extraction surface of the LED chip (10) and the transparent member (30) is set so that the light from the LED chip (10) seeps to the transparent member (30) as an evanescent wave.

Description

Light emitting device

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

Conventionally, research and development for improving the efficiency and output of a semiconductor light emitting device composed of an LED chip in which a light emitting layer is formed of a nitride semiconductor material (GaN, InGaN, AlGaInN, etc.) have been performed in various places. Further, the light emission of the semiconductor light emitting element is made by combining this type of semiconductor light emitting element and a phosphor that is a wavelength conversion material that is excited by light emitted from the semiconductor light emitting element and emits light having a longer wavelength than the semiconductor light emitting element. Research and development of light-emitting devices that emit mixed-color light with a color different from the color are being conducted in various places. As this type of light emitting device, for example, a white light emitting device (generally white light emitting device) that obtains white light (white light emission spectrum) by combining a semiconductor light emitting element that emits blue light or ultraviolet light and a phosphor. (Referred to as LED) has been commercialized.

By the way, in order to efficiently extract the light emitted from the light emitting layer to the outside for the purpose of increasing the light output of the semiconductor light emitting device described above, a large number of conical projections are provided on the light extraction surface side of the semiconductor light emitting device. Those having a fine concavo-convex structure have been proposed (see, for example, Patent Documents 1 and 2).

Further, as a light-emitting device including a semiconductor light-emitting element in which this kind of fine concavo-convex structure is formed, as shown in FIG. 7, an LED chip 10 that is a semiconductor light-emitting element, a mounting substrate 40 on which the LED chip 10 is mounted, A device including a lens-shaped sealing portion 60 formed of a light-transmitting sealing material (for example, a silicone resin) and sealing the LED chip 10 and the mounting substrate 40 has been proposed. In the example shown in FIG. 7, the mounting substrate 40 is mounted on the wiring substrate 70 as the submount.

Here, the LED chip 10 includes an n-type nitride semiconductor layer (for example, an n-type GaN layer) 12, a nitride light-emitting layer 13, and a p-type nitride on the first surface 11 a side of the translucent substrate 11 made of a GaN substrate. An anode electrode 17 is formed on the opposite side of the p-type nitride semiconductor layer 14 from the nitride light-emitting layer 13 side, and an n-type semiconductor layer (for example, a p-type GaN layer) 14 is formed. A cathode electrode 18 is formed on the nitride semiconductor light emitting layer 13 side of the nitride semiconductor layer 12. Further, in the LED chip 10, a fine uneven structure 15 is formed on the second surface 11 b side of the translucent substrate 11. The anode electrode 17 is made of a material having a high reflectance with respect to the light emitted from the nitride light emitting layer 13.

In recent years, for the purpose of improving light extraction efficiency, an LED thin film portion having an n-type GaN layer and a p-type GaN layer and a transparent and conductive n-type ZnO substrate are joined, and then the n-type ZnO substrate is formed. There has been proposed an LED chip (semiconductor light emitting device) processed into a hexagonal pyramid shape by crystal anisotropic etching utilizing the crystal orientation dependence of the etching rate (see, for example, Non-Patent Document 1). As shown in FIG. 8, this type of LED chip 110 includes an n-type nitride semiconductor layer (for example, an n-type GaN layer) 112, a nitride light emitting layer 113, and a p-type nitride semiconductor layer (p-type GaN layer) 114. And an hexagonal pyramidal n-type ZnO substrate 119 bonded to the LED thin film portion, and an anode electrode 117 is formed on the bottom surface of the hexagonal pyramidal n-type ZnO substrate 119. In addition, a cathode electrode 118 is formed on the opposite side of the n-type nitride semiconductor layer 112 of the LED thin film portion from the n-type ZnO substrate 119 side.

Here, in manufacturing the LED chip 110 having the configuration shown in FIG. 8, the n-type nitride semiconductor layer 112, the nitride light emitting layer 113, and the p-type are formed on the main surface side of the sapphire wafer whose main surface is the (0001) plane. A patterning process is performed in which an LED thin film portion having a laminated structure with the nitride semiconductor layer 114 is grown by a MOVPE method or the like, and then the LED thin film portion is patterned into a desired shape using a photolithography technique and an etching technique. Next, after performing the wafer bonding step of directly bonding the LED thin film portion on the main surface side of the sapphire wafer and the n-type ZnO wafer serving as the basis of the n-type ZnO substrate 119, the LED thin film portion and the sapphire Wafer lift-off process that removes the sapphire wafer from the LED thin film by irradiating the vicinity of the wafer interface with laser light (Laser lift-off process) is performed, and then an electrode forming process for forming the

electrodes

117 and 118 is performed. Then, a mask layer patterned in a predetermined shape is formed on the side opposite to the LED thin film portion side in the n-type ZnO wafer. The n-type ZnO wafer is formed by performing crystal anisotropic etching using the crystal orientation dependence of the etching rate using a hydrochloric acid-based etching solution (for example, hydrochloric acid aqueous solution). A processing step for forming a hexagonal pyramid-shaped n-type ZnO substrate 119 is performed, and then a mask layer removing step for removing the mask layer is performed.
JP 2005-150261 A JP 2005-181740 A "A new model of Matsushita Electric Works and UCSB, aiming for an external quantum efficiency of 80%", Nikkei Electronics, Nikkei BP, February 11, 2008, p. 16-17

However, in the light emitting device having the configuration shown in FIG. 7, there is a component in which light emitted from the spindle-shaped projections of the fine concavo-convex structure 15 reenters the adjacent spindle-shaped projections, and light extraction efficiency is caused by this component. The improvement is reduced. Further, in the light emitting device having the configuration shown in FIG. 7, light absorption and nitride at the anode electrode 17 and the cathode electrode 18 due to multiple reflection inside the LED chip 10 regardless of the presence or absence of the fine uneven structure 15. There is a problem that the light emission efficiency is low because light loss due to light absorption in the light emitting layer 13 and light absorption in the translucent substrate 11 increases.

In the LED chip 110 having the configuration shown in FIG. 8, the refractive index of the n-type ZnO substrate 119 is smaller than the refractive index of the p-type nitride semiconductor layer 114, and the n-type ZnO substrate out of the light generated in the LED thin film portion. Since light having a low incident angle with respect to the bonding surface between 119 and the p-type nitride semiconductor layer 114 is not introduced into the n-type ZnO substrate 119, light loss due to multiple reflection occurs, so that the luminous efficiency is improved. Further improvement was desired. Further, the LED chip 110 having the configuration shown in FIG. 8 requires the above-described wafer bonding process and wafer lift-off process at the time of manufacturing, and the manufacturing yield is low.

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 emitting efficiency by reducing the optical loss due to the multiple reflection and improving the manufacturing yield. .

According to the first aspect of the present invention, an LED chip having a stacked structure of an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer, and the LED chip is disposed so as to overlap the LED chip so that the light extraction surface side is the bottom surface side. A refractive index of the first transparent material, comprising: a weight-like transparent member made of a first transparent material; and an adhesive layer made of a second transparent material interposed between the transparent member and the LED chip. Is larger than the refractive index of the second transparent material, and the shortest distance between the light extraction surface of the LED chip and the transparent member is set so that light from the LED chip oozes out to the transparent member as an evanescent wave. It is characterized by that.

According to this invention, the light-transmitting surface side of the LED chip is the bottom surface side, and the weight-shaped transparent member made of the first transparent material disposed so as to overlap the LED chip is interposed between the transparent member and the LED chip. And an adhesive layer made of a second transparent material that interposes and bonds both, the refractive index of the first transparent material is larger than the refractive index of the second transparent material, and the light extraction surface of the LED chip and the transparent surface The shortest distance to the member is set so that the light from the LED chip oozes out to the transparent member as an evanescent wave, so that the light from the LED chip bleeds into the weight-like transparent member through the adhesive layer due to the evanescent effect Therefore, the light from the LED chip can be efficiently introduced into the transparent member, the light emission efficiency can be improved by reducing the light loss due to the multiple reflection, and the weight-like transparent member can be connected to the LED chip. Since the adhesive by the adhesive layer with respect to flop, the wafer bonding step and the wafer lift-off process during manufacture is not necessary, thereby improving the manufacturing yield.

The invention of claim 2 is characterized in that, in the invention of claim 1, the LED chip has a fine concavo-convex structure for changing the traveling direction of light on the light extraction surface side.

According to this invention, since the fine concavo-convex structure that changes the light traveling direction is formed on the light extraction surface side of the LED chip, the light generated by the LED chip can be introduced into the transparent member more efficiently. Thus, the light extraction efficiency is improved, and as a result, the light emission efficiency is improved.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the adhesive layer is excited by light emitted from the LED chip and emits light having a wavelength longer than the emission peak wavelength of the LED chip. It is characterized by containing a color conversion material.

According to this invention, the adhesive layer contains a color conversion material that is excited by light emitted from the LED chip and emits light having a wavelength longer than the emission peak wavelength of the LED chip. It is possible to obtain mixed color light of the light emitted from the LED chip and the light emitted from the color conversion material, and the light emitted from the color conversion material can be efficiently introduced into the transparent member.

The invention of claim 4 is characterized in that, in the invention of claim 3, the adhesive layer contains a light diffusing material.

According to this invention, since the adhesive layer contains a light diffusing material, uneven color can be reduced.

According to a fifth aspect of the present invention, there is provided a mounting substrate on which the LED chip is mounted according to any of the first to fourth aspects of the invention, and the LED chip is on the opposite side of the p-type semiconductor layer from the light emitting layer side. An anode electrode is formed, and a cathode electrode is formed on the side of the n-type semiconductor layer where the light emitting layer is laminated. Each of the anode electrode and the cathode electrode is connected to a bump on the mounting substrate, and the anode electrode of the LED chip on the mounting substrate. And a conductor pattern associated with each of the cathode electrodes.

According to this invention, each of the anode electrode and the cathode electrode of the LED chip is bonded to the conductor pattern corresponding to each of the anode electrode and the cathode electrode of the LED chip on the mounting substrate. Compared with the case where an anode electrode or a cathode electrode is formed on the take-out surface side, the LED chip and the transparent member can be easily bonded, and the controllability of the thickness of the adhesive layer is improved.

The invention of claim 6 is characterized in that, in the invention of claim 1, the shortest distance is equal to or less than an emission peak wavelength of light emitted from the LED chip.

According to this invention, since the shortest distance between the light extraction surface of the LED chip and the transparent member is equal to or less than the emission peak wavelength of the light emitted from the LED chip, the light from the LED chip is It exudes to the weight-like transparent member through the layer by the evanescent effect. Therefore, the same effect as that of the invention of claim 1 can be obtained.

The invention of claim 7 is characterized in that, in the invention of claim 2, the fine concavo-convex structure is composed of a large number of conical protrusions (microcones).

According to the present invention, since the fine concavo-convex structure is composed of a large number of spindle-shaped protrusions, the fine concavo-convex structure can be easily formed using a method such as anisotropic etching. The fine concavo-convex structure allows the light generated by the LED chip to be introduced into the transparent member more efficiently, improving the light extraction efficiency and consequently improving the light emission efficiency.

The invention of claim 8 is characterized in that, in the invention of claim 2, the fine concavo-convex structure is composed of a number of prismatic protrusions.

According to the present invention, since the fine concavo-convex structure is composed of a large number of prismatic protrusions, the fine concavo-convex structure allows light generated in the LED chip to be more efficiently introduced into the transparent member. The light extraction efficiency is improved, and as a result, the light emission efficiency is improved.

The invention of claim 9 is the invention of claim 1, wherein the first transparent material is ZnO.

According to this invention, since the transparent member is made of ZnO, the transparent member can be formed in a weight shape by crystal anisotropic etching or the like. Therefore, the smoothness of the side surface of the transparent member is improved, and light scattering on the side surface of the transparent member can be prevented.

The invention of claim 1 is effective in improving the light emission efficiency by reducing the light loss caused by the multiple reflection and improving the production yield.

1 is a schematic cross-sectional view of a light emitting device according to Embodiment 1. FIG. It is characteristic explanatory drawing of a light-emitting device same as the above. It is characteristic explanatory drawing of a light-emitting device same as the above. 6 is a schematic cross-sectional view of a light emitting device according to Embodiment 2. FIG. 6 is a schematic cross-sectional view of a light emitting device according to Embodiment 3. FIG. 6 is a schematic cross-sectional view of a light emitting device according to Embodiment 4. FIG. It is a schematic sectional drawing of the light-emitting device of a prior art example. It is a schematic sectional drawing of the LED chip of another prior art example.

(Embodiment 1)
As shown in FIG. 1, the light emitting device of this embodiment includes an LED chip 10 having a stacked structure of an n-type nitride semiconductor layer 12, a nitride light emitting layer 13, and a p-type nitride semiconductor layer 14, and the LED chip 10. A transparent member 30 in the form of a weight (here, a hexagonal frustum) made of a first transparent material (for example, ZnO) disposed on the LED chip 10 in such a manner that the light extraction surface side is the bottom surface 31 side. And an adhesive layer 20 made of a second transparent material (for example, a silicone resin) that is interposed between the transparent member 30 and the LED chip 10 and adheres both. In this embodiment, the n-type nitride semiconductor layer constitutes an n-type semiconductor layer, the nitride light-emitting layer 13 constitutes a light-emitting layer, and the p-type nitride semiconductor layer constitutes a p-type semiconductor layer. .

In addition, the light emitting device of this embodiment includes a mounting substrate 40 on which the LED chip 10 is mounted.

Here, in the LED chip 10, an anode electrode 17 is formed on the side opposite to the nitride light emitting layer 13 side in the p-type nitride semiconductor layer 14, and the nitride light emitting layer 13 in the n-type nitride semiconductor layer 12 is formed. A cathode electrode 18 is formed on the laminated side, and the anode electrode 17 and the cathode electrode 18 are associated with the anode electrode 17 and the cathode electrode 18 of the LED chip 10 on the mounting substrate 40 via the

bumps

57 and 58, respectively. The

conductor patterns

47 and 48 are joined separately.

The mounting substrate 40 has bumps on each of the anode electrode 17 and the cathode electrode 18 of the LED chip 10 on the one surface 41a side of the flat insulating substrate 41 made of an aluminum nitride substrate having electrical insulation and high thermal conductivity. The above-described

conductor patterns

47 and 48 joined through 57 and 58 are formed. The mounting substrate 40 has a rectangular shape (in this embodiment, a square shape) in plan view, but is not limited to a square shape, and may be, for example, a rectangular shape, a circular shape, or a hexagonal shape.

The insulating substrate 41 of the mounting substrate 40 also serves as a heat transfer plate for transferring heat generated by 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

47 and 48 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.

Each of the

bumps

57 and 58 described above employs Au as a material, and is formed on the surface of each

conductor pattern

47 and 48 of the mounting substrate 40 by a stud bump method (also called a ball bump method). It is composed of bumps. Here, the number of bumps 57 bonded to the anode electrode 17 having a larger area than the cathode electrode 18 is not particularly limited. However, the number is larger from the viewpoint of efficiently dissipating the heat generated in the LED chip 10. preferable. The

bumps

57 and 58 are not limited to stud bumps, and may be bumps formed by plating (so-called plated bumps), for example.

As shown in FIG. 1, the LED chip 10 includes an n-type nitride semiconductor layer made of an n-type GaN layer on the first surface 11 a side (the lower surface side in FIG. 1) of a light-transmitting substrate 11 made of a GaN substrate. 12 is formed, a nitride light emitting layer 13 having a quantum well structure is formed on the n-type nitride semiconductor layer 12, and a p-type nitride semiconductor layer 14 made of a p-type GaN layer is formed on the nitride light emitting layer 13. Has been. In short, the LED chip 10 has a laminated structure of the n-type nitride semiconductor layer 12, the nitride light emitting layer 13, and the p-type nitride semiconductor layer 14 on the first surface 11 a side of the translucent substrate 11. . The n-type nitride semiconductor layer 12, the nitride light-emitting layer 13, and the p-type nitride semiconductor layer 14 are formed on the first surface 11a side of the translucent substrate 11 using an epitaxial growth technique such as MOVPE. Since the film is formed, a buffer layer may be provided as appropriate between the translucent substrate 11 and the n-type nitride semiconductor layer 12. Further, the crystal growth method of the n-type nitride semiconductor layer 12, the nitride light emitting layer 13, and the p-type nitride semiconductor layer 14 is not limited to the MOVPE method, and for example, a hydride vapor phase growth method (HVPE method). Alternatively, a molecular beam epitaxy method (MBE method) or the like may be employed. Moreover, the translucent substrate 11 should just be transparent with respect to the light radiated | emitted from the nitride light emitting layer 13, for example, may employ | adopt a sapphire substrate, a SiC substrate, a ZnO substrate etc.

Further, as described above, the LED chip 10 has the anode electrode 17 formed on the side opposite to the nitride light emitting layer 13 side in the p-type nitride semiconductor layer 14 and the nitride in the n-type nitride semiconductor layer 12. A cathode electrode 18 is formed on the laminated side of the light emitting layer 13. Here, the cathode electrode 18 is formed by sequentially growing the n-type nitride semiconductor layer 12, the nitride light-emitting layer 13, and the p-type nitride semiconductor layer 14 on the first surface 11a side of the translucent substrate 11, A predetermined region of the laminated film of the n-type nitride semiconductor layer 12, the nitride light emitting layer 13, and the p-type nitride semiconductor layer 14 extends from the surface side of the p-type nitride semiconductor layer 14 to the middle of the n-type nitride semiconductor layer 12. It is formed on the surface of n-type nitride semiconductor layer 12 exposed by etching.

Here, in the LED chip 10, 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 14, and the cathode electrode Electrons are injected from 18 into the n-type nitride semiconductor layer 12, and the electrons and holes injected into the nitride light-emitting layer 13 recombine to emit light.

The above-described n-type nitride semiconductor layer 12 is composed of an n-type GaN layer formed on the translucent substrate 11, but is not limited to a single layer structure, and may be a multi-layer structure, for example, a translucent substrate. When 11 is a sapphire substrate, an n-type AlGaN layer formed on the first surface 11a side of the translucent substrate 11 via a buffer layer made of an AlN layer, an AlGaN layer, or the like, and the n-type AlGaN layer The n-type GaN layer may be used.

The nitride light emitting layer 13 has a quantum well structure in which a well layer made of an InGaN layer is sandwiched by a barrier layer made of a GaN layer so that the emission peak wavelength of the nitride light emitting layer 13 is 450 nm. However, the emission wavelength (emission peak wavelength) is not particularly limited. The quantum well structure of the nitride light emitting layer 13 is not limited to a single quantum well structure, and may be a multiple quantum well structure. The nitride light emitting layer 13 does not necessarily have a quantum well structure, and may have a single layer structure. Further, the material of the nitride light emitting layer 13 may be a nitride semiconductor material, and for example, AlInGaN, AlInN, AlGaN, or the like may be appropriately employed according to a desired light emission wavelength.

The p-type nitride semiconductor layer 14 is composed of a p-type GaN layer formed on the nitride light-emitting layer 13, but is not limited to a single layer structure, and may have a multilayer structure, for example, a p-type AlGaN layer. You may comprise by the 1st p-type semiconductor layer which consists of, and the 2nd p-type semiconductor layer which consists of a p-type GaN layer formed on the 1st p-type semiconductor layer.

The anode electrode 17 has a stacked structure of a Pt layer on the p-type nitride semiconductor layer 14 and an Ag layer on the Pt layer, and has a reflectance of light emitted from the nitride light emitting layer 13. Since it is formed of high Ag or the like, the light emitted from the nitride light emitting layer 13 to the p-type nitride semiconductor layer 14 side can be efficiently reflected to the nitride light emitting layer 13 side. The anode electrode 17 is not limited to the above-described laminated structure, and has, for example, a laminated structure of an Au layer on the p-type nitride semiconductor layer 14, a Ti layer on the Au layer, and an Au layer on the Ti layer. It may be a single layer structure.

The cathode electrode 18 has a laminated structure of a Ti layer on the n-type nitride semiconductor layer 12 and an Au layer on the Ti layer. Here, the Ti layer on the n-type nitride semiconductor layer 12 is provided as an ohmic contact layer with respect to the n-type nitride semiconductor layer 12, but the material of the ohmic contact layer is, for example, Ti, V, Al, or these An alloy containing any one kind of metal may be employed.

In forming the anode electrode 17 described above, for example, after forming a resist layer in which a region where the anode electrode 17 is to be formed is opened by using a photolithography technique, the anode electrode 17 is formed by an electron beam evaporation method or the like. Subsequently, the resist layer and the unnecessary film on the resist layer may be removed using an organic solvent (eg, acetone) (lifted off). Moreover, the formation method of the cathode electrode 18 can employ | adopt the formation method similar to the anode electrode 17. FIG.

Further, in the light emitting device of this embodiment, the fine uneven structure 15 that changes the traveling direction of light is formed on the light extraction surface side of the LED chip 10. In the light emitting device of this embodiment, a GaN substrate is used as the translucent substrate 11 as described above, and the fine concavo-convex structure 15 is formed on the second surface 11b side of the translucent substrate 11. Here, the translucent substrate 11 has a (0001) plane which is a Ga polar plane of the GaN substrate as a first surface 11a, and a (000-1) plane which is an N polar plane as a second surface 11b. The fine concavo-convex structure 15 is formed by chemical etching using an appropriate etching solution. Specifically, a KOH solution is used as an etching solution, and the light-transmitting substrate 11 made of a GaN substrate is crystal-anisotropically etched to form a fine concavo-convex structure 15 having a large number of conical protrusions (microcones). Forming. Here, the many spindle-shaped projections are arranged in a two-dimensional array. Here, the height of the spindle-shaped projections can be appropriately set within a range of 1 μm or less by appropriately setting the etching time, and the pitch of the spindle-shaped projections when the height of the spindle-shaped projections is 1 μm is approximately 1 μm. Become.

The method for forming the fine concavo-convex structure 15 is not limited to the chemical etching method. For example, after forming a transfer layer on the second surface 11b side of the translucent substrate 11 made of a GaN substrate, the fine concavo-convex structure 15 is formed. After the mold having a concavo-convex pattern designed according to the pattern is pressed against the transfer layer to transfer the concavo-convex pattern to the transfer layer, the transfer layer and the translucent substrate 11 are dry-etched by dry etching. The fine concavo-convex structure 15 may be formed on the second surface 11 b side of the substrate 11. In this case, the height and pitch of the spindle-shaped protrusions may be appropriately set to 1 μm or less, for example.

The hexagonal frustum-shaped transparent member 30 is formed using an n-type ZnO wafer, and the height (thickness) of the hexagonal frustum-shaped transparent member 30 is the thickness of the n-type ZnO wafer. In this embodiment, since the n-type ZnO wafer having a thickness of 500 μm is used, the transparent member 30 has a height of 500 μm, but the thickness of the n-type ZnO wafer is The thickness is not particularly limited. In addition, the inclination angle of each side surface 33 with respect to the bottom surface 31 of the hexagonal frustum-shaped transparent member 30 is defined by the crystal axis direction of the n-type ZnO wafer. In this embodiment, crystal anisotropic etching is performed on a ZnO wafer having a (0001) plane with a Zn polar plane on the LED thin film portion side and a (000-1) plane with an O polar plane on the opposite side to the LED thin film portion side. Since the transparent member 30 is formed by performing, each side surface 33 of the transparent member 30 is constituted by {10-1-1} surface, and the side surface 33 having an inclination angle of 60 ° is formed with good reproducibility. be able to. As can be seen from the above description, the transparent member 30 has a bottom surface 31 of a ZnO (0001) surface and a top surface 32 of a ZnO (000-1) surface.

Therefore, according to the light emitting device of the present embodiment, each side surface 33 of the transparent member 30 is formed by performing crystal anisotropic etching, so that the smoothness of each side surface 33 is good and the light on each side surface 33 is light. Can be prevented.

By the way, the light emitting device of the present embodiment is made of the first transparent material (for example, ZnO) disposed on the LED chip 10 so that the light extraction surface side of the LED chip 10 becomes the bottom surface 31 side as described above. A transparent member 30 having a pyramid shape (here, a hexagonal frustum shape), and an adhesive made of a second transparent material (for example, a silicone resin) that is interposed between the transparent member 30 and the LED chip 10 and adheres to both. Layer 20. Here, in this embodiment, the refractive index of the first transparent material of the transparent member 30 is larger than the refractive index of the second transparent material of the adhesive layer 20, and the light extraction surface of the LED chip 10 (here, The shortest distance (L in FIG. 1) between the surface of the fine concavo-convex structure 15 and the transparent member 30 is set to about the emission wavelength of the LED chip 10 so that the light from the LED chip 10 exudes to the transparent member 30 as an evanescent wave. It is set. The shortest distance L is about the emission wavelength of the LED chip 10 and is preferably equal to or less than the emission peak wavelength of the light emitted from the LED chip 10. In short, the light emitting device of the present embodiment has a refractive index of the first transparent material of n ₁ , a refractive index of the second transparent material of n ₂ , and an emission peak wavelength of the LED chip 10 of λ, where n ₁ > The above-mentioned conditions regarding the condition of n ₂ and the shortest distance L are satisfied. For example, when the emission peak wavelength λ of the LED chip 10 is 450 nm, ZnO having a refractive index n ₁ of 2.1 is adopted as the first transparent material, and the refractive index n ₂ is 1 as the second transparent material. When a silicone resin of .4 is used and the height and pitch of the spindle-shaped protrusions are each 1 μm, the evanescent effect can be obtained by setting the shortest distance L to 0.25 μm or less.

Here, the emission peak wavelength λ of the LED chip 10 is 450 nm, and the transparent member 30 made of the first transparent material (n ₁ = 2.1 ZnO) is disposed on the light extraction surface side of the LED chip 10 via the adhesive layer 20. Regarding the arranged structure, when light of all incident angle components is incident on the light emitted from the nitride light emitting layer 13 of the LED chip 10 toward the transparent member 30 and incident on the transparent member 30, the light is incident on the transparent member 30 once. FIG. 2 shows the result of simulating the relationship between the transmittance and the thickness of the adhesive layer 20, where the transmittance (the ratio of being introduced) is the transmittance. Here, “A” in FIG. 2 indicates that the fine protrusions 15 are provided, the height of the weight projections is 1 μm, the pitch of the weight projections is 1 μm, and the refractive index of the second transparent material of the adhesive layer 20 is 1. 4, “B” in FIG. 6 indicates that the fine projections and depressions 15 are present, the height of the weight-like projections is 1 μm, the pitch of the weight-like projections is 1 μm, and the refractive index of the second transparent material of the adhesive layer 20 is In the case of 1.8, “C” in the figure is the case where the refractive index of the second transparent material of the adhesive layer 20 without the fine uneven structure 15 is 1.4. FIG. 2 shows a refractive index of the conventional light-emitting device shown in FIG. 7 without being reflected once in the light emitted from the nitride light-emitting layer 13 of the LED chip 10 to the fine relief structure 15 side. The result of simulating the ratio of the light emitted from the sealing part 60 made of silicone resin of 1.4 as the light emission rate is shown in “D”, and the simulation result of the light emission rate without the fine uneven structure 15 is shown in “D”. This is indicated by “E”. In each of “A”, “B”, and “C” in FIG. 2, the transmittance increases as the thickness of the adhesive layer 20 approaches 0 in the region of the light emission wavelength of the LED chip. This is the evanescent effect. Is due to.

Incidentally, “A”, “B”, and “C” in FIG. 2 are transmittances, and “D” and “E” are light output rates, but “A”, “B”, and “C” are transparent members. If the Fresnel reflection component at the interface between the air 30 and the air is ignored, the transmittance and the light emission rate can be regarded as the same (in practice, the Fresnel reflection caused by the refractive index difference between the transparent member 30 and the air). Because there are components, it is estimated that a value of transmittance × 0.98 is the light output rate). Here, when the refractive index of the second transparent material of the adhesive layer 20 is 1.4 with the fine concavo-convex structure 15, when comparing “A” and “D”, the thickness of the adhesive layer 20 is 0. It can be seen that the light emission rate of “A” is higher than the light emission rate of “D” by setting the thickness to 1 μm. Further, when “A” and “B” are compared with the fine concavo-convex structure 15, “B” in which the refractive index of the second transparent material of the adhesive layer 20 is larger has higher transmittance and higher light emission rate. I understand that Further, in the case where the refractive index of the second transparent material of the adhesive layer 20 without the fine uneven structure 15 is 1.4, when comparing “C” and “E”, the thickness of the adhesive layer 20 is 0.2 μm. Thus, it can be seen that the light emission rate of “C” is higher than the light emission rate of “E”.

Further, assuming that the emission peak wavelength λ of the LED chip 10 is 450 nm, the height of the weight-like protrusions of the fine uneven structure 15 is 1 μm, and the pitch of the weight-like protrusions is 1 μm, the fine uneven structure 15 on the light extraction surface side of the LED chip 10 The second transparent material of the adhesive layer 20 is filled between the spindle-shaped protrusions, and the transparent member 30 made of the first transparent material (n ₁ = 2.1 ZnO) is disposed on the light extraction surface side of the LED chip 10. In this example (in this example, L = 0), when the refractive index n ₂ of the second transparent material is variously changed in the range of 1 to 2.1, the nitride light emitting layer 13 of the LED chip 10 is transparent. The simulation result with the ratio of the light transmitted through the transparent member 30 at one time (the ratio of being introduced) when the light of all the incident angle components is incident on the light emitted to the member 30 side and incident on the transparent member 30 as a transmittance The figure It is shown in "A". Further, in the conventional light emitting device shown in FIG. 7 as a comparative example, the refractive index is 1 without being reflected once even in the light emitted from the nitride light emitting layer 13 of the LED chip 10 to the fine relief structure 15 side. The result of simulating the ratio of the light emitted from the sealing portion 60 made of .4 silicone resin as the light emission rate is shown in “B” of FIG. In short, “B” in FIG. 3 indicates the light emission rate of the light emitting device in which the sealing portion 60 having the same refractive index as the material of the adhesive layer 20 is provided instead of the adhesive layer 20 and the transparent member 30.

By the way, “A” in FIG. 3 is the transmittance, and “B” is the light emission rate. As for “A”, if the Fresnel reflection component at the interface between the transparent member 30 and the air is ignored, as described above. The transmittance and the light output rate can be regarded as the same. Here, when the refractive index of the second transparent material of the adhesive layer 20 is 1.4, when comparing “A” as an example and “B” as a comparative example, the light emission rate of the example 44% and the emission rate of the comparative example is 28%. It can be seen that the light emission rate of the example can be significantly improved compared to the comparative example. Here, when the number of reflections inside the LED chip 10 increases, absorption loss in the translucent substrate 11, loss in the anode electrode 17 and cathode electrode 18, absorption loss in the nitride light emitting layer 13 and the like increase. The higher the light emission rate, which is the ratio of the light emitted from the nitride light emitting layer 13 and emitted to the outside without being reflected, the higher the light extraction efficiency. Therefore, according to the light emitting device of the present embodiment, the light emission rate is higher and the light extraction efficiency is higher than the light emitting device having the configuration shown in FIG.

According to the light emitting device of the present embodiment described above, the weight-like transparent member 30 made of the first transparent material is disposed so as to overlap the LED chip 10 such that the light extraction surface side of the LED chip 10 is the bottom surface 31 side. And an adhesive layer 20 made of a second transparent material that is interposed between the transparent member 30 and the LED chip 10 and adheres them, and the refractive index of the first transparent material is the refractive index of the second transparent material. And the shortest distance L between the light extraction surface of the LED chip 10 and the transparent member 30 is set so that light from the LED chip 10 oozes out to the transparent member 30 as an evanescent wave. Since the light from 10 oozes out into the weight-like transparent member 30 through the adhesive layer 20 by the evanescent effect, the light from the LED chip 10 can be efficiently introduced into the transparent member 30. Thereby improving the luminous efficiency by reducing light loss due to multiple reflection of light within the LED chip 10. Further, in the light emitting device of the present embodiment, the weight-like transparent member 30 is bonded to the LED chip 10 by the adhesive layer 20, so that the above-described wafer bonding step and wafer lift-off step are not necessary at the time of manufacture. Yield can be improved.

Further, in the light emitting device of the present embodiment, since the fine uneven structure 15 that changes the light traveling direction is formed on the light extraction surface side of the LED chip 10, the light generated by the LED chip 10 is more efficiently transmitted to the transparent member 30. Thus, the light extraction efficiency is improved, and as a result, the light emission efficiency is improved. Note that the shape of the transparent member 30 is not limited to a hexagonal frustum shape, and may be, for example, a hexagonal frustum shape, a square frustum shape, a quadrangular frustum shape, a truncated cone shape, or a conical shape.

In the light emitting device of this embodiment, as described above, the anode electrode 17 and the cathode electrode 18 of the LED chip 10 are associated with the anode electrode 17 and the cathode electrode 18 of the LED chip 10 on the mounting substrate 40, respectively. Since the

conductive patterns

47 and 48 are joined and electrically connected, the LED chip 10 and the transparent member 30 are compared with the case where the anode electrode 17 and the cathode electrode 18 are formed on the light extraction surface side of the LED chip 10. Can be easily adhered, and the controllability of the thickness of the adhesive layer 20 is improved. Note that the second transparent material of the adhesive layer 20 is not limited to a silicone resin having a refractive index of 1.4, but may be a silicone resin having a refractive index satisfying the above condition of n ₁ > n ₂ . Further, not limited to the silicone resin, for example, an epoxy resin, an acrylic resin, or the like, or an inorganic / organic hybrid material in which Si-based material SOG (spin on glass), Ti nanoparticles or the like are mixed may be used.

By the way, the adhesive layer 20 described above contains a color conversion material (for example, phosphor particles) that is excited by light emitted from the LED chip 10 and emits light having a wavelength longer than the emission peak wavelength of the LED chip 10. In this case, mixed light of the light emitted from the LED chip 10 and the light emitted from the color conversion material can be obtained, and the light emitted from the color conversion material is transmitted to the transparent member. 30 can be efficiently introduced. Here, when the blue LED chip that emits blue light is used as the LED chip 10 and the yellow phosphor particles are used as the phosphor particles, white light can be obtained. As the phosphor particles, the red phosphor particles and the green phosphor are used. If body particles are used, white light with higher color rendering can be obtained. Further, by using an ultraviolet LED chip that emits ultraviolet light as the LED chip 10 and using red phosphor particles, green phosphor particles, and blue phosphor particles as a color conversion material, white light with high color rendering properties can be obtained. Can be obtained. Further, when the adhesive layer 20 contains a color conversion material, color unevenness can be reduced by further containing a light diffusing material (eg, glass particles).

(Embodiment 2)
The basic configuration of the light emitting device of the present embodiment is substantially the same as that of the first embodiment, and only the shape of the fine concavo-convex structure 15 is different as shown in FIG. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

In the first embodiment, the fine concavo-convex structure 15 has a large number of spindle-shaped protrusions, whereas the fine concavo-convex structure 15 in the light-emitting device of the present embodiment has a large number of prismatic protrusions (here, quadrangular columnar protrusions, For example, a square columnar projection having a square bottom surface is arranged in a two-dimensional array.

The fine concavo-convex structure 15 in the light emitting device of the present embodiment is formed on the second surface 11b side of the translucent substrate 11 made of a GaN substrate using a photolithography technique and a dry etching technique. Here, the height of the prismatic protrusions depends on the light emission peak wavelength of the nitride light emitting layer 13 of the LED chip 10, but when the light emission peak wavelength is set to 450 nm, for example, the height is appropriately set to 2 μm or less, for example. That's fine. As a dry etching apparatus for forming the fine concavo-convex structure 15, for example, a reactive ion etching apparatus may be used.

Also in the light emitting device of the present embodiment described above, similarly to the first embodiment, light from the LED chip 10 can be efficiently introduced into the transparent member 30, and light loss due to multiple reflection of light inside the LED chip 10 is achieved. Therefore, the luminous efficiency can be improved.

(Embodiment 3)
The basic configuration of the light emitting device of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 5, the transparent conductive film 16 is interposed between the anode electrode 17 and the p-type nitride semiconductor layer 14 in the LED chip 10. The point which is intervening is different. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

In the present embodiment, GZO (Ga-doped ZnO) is adopted as the material of the transparent conductive film 16, but the material of the transparent conductive film 16 is, for example, GZO, AZO (Al-doped ZnO), IZO ( Any material selected from the group of InO-doped ZnO) and ITO may be used. By using a material selected from the group, contact between the transparent conductive film 16 and the p-type nitride semiconductor layer 14 can be achieved. It can be ohmic contact. Here, when the transparent conductive film 16 is composed of a GZO film, an AZO film, an IZO film, an ITO film, etc., in forming the transparent conductive film 16, the film is formed by O ₂ gas-assisted electron beam evaporation. Annealing may be performed in a mixed gas of N ₂ gas and O ₂ gas. By adopting such a forming method, the extinction coefficient of the transparent conductive film 16 can be set to about 0.001. .

Further, in the light emitting device of this embodiment, the planar shape of the anode electrode 17 is circular, and a plurality of anode electrodes 17 are provided on the transparent conductive film 16 in a two-dimensional array. A light reflecting film 49 that reflects light emitted to the outside of the LED chip 10 through the transparent conductive film 16 of the LED chip 10 is formed on the one surface 41 a side of 41. Note that the planar shape of the anode electrode 17 is not limited to a circular shape, and may be a hexagonal shape or a rectangular shape, for example.

Also in the light emitting device of this embodiment, light from the LED chip 10 can be efficiently introduced into the transparent member 30 as in the first embodiment, and light loss due to multiple reflection of light inside the LED chip 10 can be reduced. Therefore, the luminous efficiency can be improved. Note that the transparent conductive film 16 may be interposed between the anode electrode 17 and the p-type nitride semiconductor layer 14 in the LED chip 10 in the light emitting device of another embodiment, as in the present embodiment.

(Embodiment 4)
The basic configuration of the light emitting device of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 6, a sapphire substrate is used as the light transmissive substrate 11, and the first surface 11a side of the light transmissive substrate 11 is used. A fine relief structure 15 is formed (on the n-type nitride semiconductor layer 12 side), and the second surface 11b side of the translucent substrate 11 is a flat light extraction surface, a translucent sealing material (for example, A difference is that a lens-shaped sealing portion 60 formed of a silicone resin or the like and sealing the transparent member 30, the LED chip 10, and the mounting substrate 40 is provided. In the light emitting device of this embodiment, the mounting substrate 40 is mounted on the wiring substrate 70 with the mounting substrate 40 as a submount. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

Also in the light emitting device of this embodiment, light from the LED chip 10 can be efficiently introduced into the transparent member 30 as in the first embodiment, and light loss due to multiple reflection of light inside the LED chip 10 can be reduced. Therefore, the luminous efficiency can be improved. In other embodiments, the sealing portion 60 and the wiring board 70 similar to those of the present embodiment may be provided.

By the way, in each above-mentioned embodiment, although the blue LED chip or the ultraviolet LED chip is used as the LED chip 10, it is not limited thereto, and for example, a purple LED chip, a green LED chip, a red LED chip, or the like may be used. . However, it is preferable to determine the second transparent material of the adhesive layer 20 in consideration of the emission color of the LED chip 10. In each of the above-described embodiments, a nitride LED chip is employed as the LED chip 10. However, the present invention is not limited to this, and an InGaAsP LED chip, a GaP LED chip, or the like may be employed. The materials of the layer, the light emitting layer, and the p-type semiconductor layer are not limited to nitride semiconductors.

Claims

An LED chip having a stacked structure of an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer, and a first transparent material disposed on the LED chip so that the light extraction surface side of the LED chip is the bottom surface side A weight-like transparent member, and an adhesive layer made of a second transparent material that is interposed between the transparent member and the LED chip, and has a refractive index of the second transparent material. A light emitting device having a refractive index larger than a refractive index and a minimum distance between the light extraction surface of the LED chip and the transparent member set so that light from the LED chip oozes out to the transparent member as an evanescent wave .
2. The light emitting device according to claim 1, wherein the LED chip has a fine concavo-convex structure for changing a traveling direction of light on a light extraction surface side of the LED chip.
2. The color conversion material which is excited by the light radiated | emitted from the said LED chip, and radiates | emits the light longer than the light emission peak wavelength of the said LED chip is contained in the said contact bonding layer or Claim 1 characterized by the above-mentioned. The light emitting device according to claim 2.
The light emitting device according to claim 3, wherein the adhesive layer contains a light diffusing material.
The LED chip includes a mounting substrate on which the anode chip is formed on the side opposite to the light emitting layer side of the p-type semiconductor layer, and the light emitting layer of the n-type semiconductor layer is formed on the LED chip. A cathode electrode is formed on the laminated side, and each of the anode electrode and the cathode electrode is bonded to a conductor pattern corresponding to each of the anode electrode and the cathode electrode of the LED chip on the mounting substrate via a bump. The light emitting device according to any one of claims 1 to 4, wherein the light emitting device is characterized in that:
The light emitting device according to claim 1, wherein the shortest distance is equal to or less than an emission peak wavelength of light emitted from the LED chip.
3. The light emitting device according to claim 2, wherein the fine concavo-convex structure is composed of a large number of conical protrusions (microcones).
3. The light emitting device according to claim 2, wherein the fine concavo-convex structure is composed of a large number of prismatic protrusions.
The light emitting device according to claim 1, wherein the first transparent material is ZnO.