JP2008098486A - Light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain excellent light extraction efficiency by reducing the influence of light absorption in transparent conductive layers of a light emitting element in which the transparent conductive layers having the absorptivity of ultraviolet light and near-ultraviolet light are formed. <P>SOLUTION: In the light emitting element, an n-type gallium nitride group compound semiconductor layer 12, a light emitting layer 13 and a p-type gallium nitride group compound semiconductor layer 14 are formed on substrate 10. A p-type electrode 15 composed of laminating a plurality of transparent conductive layers 15a, 15b, 15c including phosphors for converting the wavelength of light generated from the light emitting layer 13 is formed on the surface of the p-type gallium nitride group compound semiconductor layer 14, the transparent conductive layer 15a most close to the light emitting layer 13 includes a phosphor 17a for converting light generated from the light emitting layer 13 into light of a first wavelength and the transparent conductive layers 15b, 15c including phosphors 17b, 17c for converting the light generated from the light emitting layer 13 into light of a wavelength shorter than the first wavelength are laminated according to separation from the light emitting layer 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention has the formula _{In x Al y Ga 1-x} -y N ( However, 0 ≦ x, y ≦ 1 , x + y ≦ 1) gallium nitride-based compound represented by such as a semiconductor (III-V nitride compound semiconductor) The present invention relates to a light emitting element in which is laminated.

Gallium nitride-based compound semiconductors represented by the chemical formula In _x Al _y Ga _1-xy N (0 ≦ x, y ≦ 1, x + y ≦ 1) are AlGaN, InGaN which are mixed crystals with AlN, InN, and the like. , InGaAlN, etc., by selecting the composition so as to be a material for light emitting diodes such as light emitting diodes (LEDs) and semiconductor lasers (LDs) that can emit light from the visible light region to the ultraviolet light region, Some are being put to practical use.

  Also, field effect transistors (FETs) such as MESFETs (Metal-Semiconductor Field Effect Transistors), MISFETs (Metal-Insulator-Semiconductor FETs), high electron mobility transistors (HEMTs), and Schottky barrier diodes (SBDs). ), Etc., and are being developed as electronic devices that handle high-output high-frequency waves.

  FIG. 2 is a schematic cross-sectional view of a light emitting device using a conventional gallium nitride compound semiconductor. In this light emitting device, for example, a sapphire substrate 1 is used as a substrate, and an n-type gallium nitride compound semiconductor layer 3, an active layer 4 serving as a light emitting layer, and a p-type gallium nitride system are provided on the sapphire substrate 1 via a buffer layer 2. The compound semiconductor layer 5 is formed, and a part of the p-type gallium nitride compound semiconductor layer 5 is etched to form a part of the n-type gallium nitride compound semiconductor layer 3 in order to form the n-type electrode 6. . The p-type electrode has a transparent electrode 7 formed on one surface of the p-type gallium nitride compound semiconductor layer 5 in order to extract light emitted from the active layer 4 to the p-type gallium nitride compound semiconductor layer 5 side. A pad electrode 8 for wire bonding or the like is formed on a part of the electrode 7 outside.

  As such a transparent electrode 7, a laminate of a nickel (Ni) layer and a gold (Au) layer is mainly used. For example, Patent Document 1 describes that a transparent electrode made of tin-doped indium oxide (ITO), which is a transparent conductive oxide, is used.

  Furthermore, as a configuration for obtaining a white light source using such a light emitting element, Patent Document 2 discloses a transparent resin including a phosphor that arranges a light emitting element (LED element) on a stem and performs wavelength conversion. Describes a configuration in which the periphery of the light emitting element is molded.

In addition, a method for manufacturing a light-emitting element that obtains white light by converting the wavelength of light generated from the light-emitting element using a phosphor in the mold resin requires a step of incorporating the phosphor into the mold resin, and emits monochromatic light. Compared with the manufacture of a light emitting device, the number of processes has increased. As the method of manufacturing the light emitting device to solve this problem, Patent Document 3, a method of manufacturing a light emitting diode comprising a light-emitting layer and the In ₂ O ₃ layer, an inorganic phosphor performs wavelength conversion to In ₂ O ₃ layer A production method is described which contains.
Japanese Utility Model Publication No. 6-38265 JP-A-5-152609 JP 2002-164576 A

  However, in the light emitting device described in Patent Document 1, the light transmittance (light transmittance with respect to light having a wavelength of around 400 nm) of a normal laminate of a nickel layer and a gold layer is about 60%. The light transmittance of tin-added indium oxide (ITO) (light transmittance with respect to light having a wavelength near 400 nm) is as high as 80% to 90%. However, since ITO has a refractive index of about 2.1 and is close to 2.5 of gallium nitride, but significantly different from air 1, light generated in the light emitting layer is transferred from the p-type GaN layer to the ITO layer. Although reflection at the interface proceeds small, large reflection occurs at the interface between the ITO layer and air. Furthermore, the light that passes through the p-type GaN layer and the ITO layer by being repeatedly reflected at the interface between the ITO layer and air and the confined light are gradually absorbed by the p-type GaN layer and the ITO layer. It will be attenuated. Therefore, there is a limit to improving the light extraction efficiency of the light emitting element.

  Further, as described in Patent Document 2, when the periphery of the LED element is molded with a resin containing a phosphor capable of wavelength conversion, and white light is obtained, for example, a resin having a refractive index of about 1.5 is used. By molding, the reflection of light at the interface when passing from the ITO layer to the resin is suppressed more than in the case of air. However, when near-ultraviolet light having an emission wavelength of the LED element of around 400 nm is used, there are concerns such as deterioration of the resin due to long-term use and reduction of light transmittance due to deterioration of the resin due to heat generation of the LED element itself. Furthermore, for near-ultraviolet light having an emission wavelength of around 400 nm, the light transmittance of the ITO layer decreases near 380 nm to 390 nm, so that the influence of light absorption in the ITO layer becomes significant.

In addition, in the configuration in which wavelength conversion is performed by an inorganic phosphor contained in an In ₂ O ₃ layer to which impurities are added instead of the phosphor in the mold resin as described in Patent Document 3, the phosphor is used as the phosphor. It is difficult to disperse uniformly in the In ₂ O ₃ layer, and there is a concern that uneven emission color may occur.

Further, in the configuration in which the light emitted from the light emitting layer is blue light and the wavelength is converted into yellow light by the phosphor to obtain white light, since the phosphor used is one kind, the unevenness of the emission color is not significant. However, when the light emitted from the light emitting layer is ultraviolet light or near ultraviolet light, and white light is obtained by performing wavelength conversion using phosphors that convert red light, green light, and blue light, respectively, the phosphor is converted to In ₂ O _3. Since it is necessary to disperse uniformly in the layer, there is a concern that unevenness in emission color becomes remarkable.

Furthermore, in the case of an In ₂ O ₃ layer doped with impurities (ITO when the impurity is Sn) layer, the light generated in the light emitting layer passes through the ITO layer because of absorption of ultraviolet light and near ultraviolet light as described above. While some of the wavelength is converted by the phosphor while it travels, it is gradually absorbed and the rate of conversion on the upper part of the ITO layer on the side farther from the light emitting layer is reduced, resulting in poor efficiency.

  Accordingly, the present invention has been completed in view of the above problems in the prior art, and its purpose is to absorb light in a transparent conductive layer such as an ITO layer that absorbs ultraviolet light or near ultraviolet light. An object of the present invention is to provide a light-emitting element using a gallium nitride-based compound semiconductor having a smaller influence and excellent light extraction efficiency.

  The light emitting device of the present invention is a light emitting device in which an n-type gallium nitride compound semiconductor layer, a light emitting layer made of a gallium nitride compound semiconductor, and a p type gallium nitride compound semiconductor layer are formed on a substrate. The p-type gallium nitride compound semiconductor layer has a p-type electrode formed by laminating a plurality of transparent conductive layers each containing a phosphor that converts the wavelength of light generated by the light emitting layer, The plurality of transparent conductive layers include a phosphor that converts light generated by the light emitting layer into light having a first wavelength by the transparent conductive layer closest to the light emitting layer, and emits the light as the distance from the light emitting layer increases. The transparent conductive layer including a phosphor that converts light generated by the layer into light having a wavelength shorter than that of the light having the first wavelength is laminated.

  In the light emitting device of the present invention, preferably, the plurality of transparent conductive layers include a transparent conductive layer including a phosphor that converts light generated by the light emitting layer into red light, and light generated by the light emitting layer is green. A transparent conductive layer containing a phosphor that converts light into light and a transparent conductive layer that contains a phosphor that converts light generated by the light emitting layer into blue light are sequentially stacked from the light emitting layer side. The generated light is emitted to the outside as white light.

  In the light-emitting device of the present invention, preferably, the n-type gallium nitride compound semiconductor layer has a plurality of transparent conductive layers each containing a phosphor that converts a wavelength of light generated by the light-emitting layer on an exposed surface. A plurality of transparent conductive layers are formed, and the transparent conductive layer closest to the light emitting layer is a phosphor that converts light generated by the light emitting layer into light having a first wavelength. And the transparent conductive layer including a phosphor that converts light generated by the light emitting layer into light having a shorter wavelength than the light having the first wavelength as the distance from the light emitting layer is increased. It is characterized by.

  In the light emitting device of the present invention, it is preferable that the plurality of transparent conductive layers have a thickness that decreases with distance from the light emitting layer.

  The light emitting device of the present invention is a light emitting device in which an n-type gallium nitride compound semiconductor layer, a light emitting layer made of a gallium nitride compound semiconductor, and a p type gallium nitride compound semiconductor layer are formed on a substrate. The p-type gallium nitride compound semiconductor layer has a p-type electrode formed by laminating a plurality of transparent conductive layers each containing a phosphor that converts the wavelength of light generated by the light emitting layer, and has a plurality of transparent The conductive layer includes a phosphor whose transparent conductive layer closest to the light emitting layer converts light generated by the light emitting layer into light having a first wavelength. A transparent conductive layer containing a phosphor that converts light having a shorter wavelength than light having a wavelength is laminated, and each transparent conductive layer contains a phosphor that converts light having a different wavelength. Color uniformity Well made.

For example, even if three types (three colors) of phosphors are dispersed together in a transparent conductive layer such as an In ₂ O ₃ layer, the three types of phosphors are uniformly distributed in all parts of the transparent conductive layer. The possibility of dispersion is low, and in an extreme case, phosphors of one color are partially collected due to aggregation or the like, and the mixing ratio tends to be non-uniform. Therefore, it is difficult for the finally synthesized light to have a uniform color. On the other hand, it is relatively easy to uniformly disperse one type (one color) of phosphor in a transparent conductive layer such as an In ₂ O ₃ layer, and by laminating them in a plurality of layers, Since the phosphor is uniformly converted into fluorescence, the color of the finally synthesized light is also uniform.

  Moreover, by converting the light having a longer wavelength in the transparent conductive layer closer to the light emitting layer, the influence of absorption can be reduced, and the light generated in the light emitting layer can be effectively wavelength converted. That is, the light generated in the light emitting layer passes through the transparent conductive layer, but at this time, part of the light is first converted to the first wavelength in the transparent conductive layer containing the phosphor that converts the light to the first wavelength, Since the first wavelength (for example, about 600 nm) is a wavelength at which light absorption by the transparent conductive layer such as the ITO layer is small, the light of the first wavelength is extracted outside with almost no absorption by the transparent conductive layer. Becomes higher. In addition, the light that has passed through the transparent conductive layer containing the phosphor that converts to the first wavelength reaches the transparent conductive layer that contains the phosphor that continuously converts to the second wavelength shorter than the first wavelength (for example, about 510 nm). Therefore, the second wavelength is converted to the second wavelength, but since the second wavelength is also a wavelength with small light absorption by the transparent conductive layer, the light of the second wavelength is extracted outside without being almost absorbed by the transparent conductive layer. The extraction efficiency is increased.

  In addition, when the light converted by the phosphor travels from the transparent conductive layer toward the outside air or the like, even when reflection occurs at the interface, the reflected light is less absorbed in the transparent conductive layer. Therefore, it will be taken out to the outside with little attenuation after all.

  Further, the transparent conductive layer on the outermost surface side includes a phosphor that converts to a third wavelength (for example, about 450 nm) having a shorter wavelength, and the converted light has a wavelength with the largest absorption, but is emitted to the outside. Therefore, even if the light absorption by the transparent conductive layer is relatively large, the light extraction efficiency is not greatly reduced.

  Therefore, the light converted by the phosphor is gradually converted from a long wavelength to a short wavelength from the side closer to the light emitting layer, so that light absorption in the transparent conductive layer can be suppressed as much as possible, and the converted light of each wavelength is extracted. High efficiency.

  In addition, when a transparent resin is molded around the light-emitting element in order to increase the extraction efficiency from the transparent conductive layer to the outside air, the resin is converted to each wavelength by the phosphor instead of the light generated in the light-emitting layer. Since the emitted light reaches and passes, the deterioration of the resin is reduced. That is, when the wavelength of light emitted from the light emitting layer made of a gallium nitride compound semiconductor is in the wavelength region of ultraviolet light or near ultraviolet light, the light having the first wavelength (long wavelength due to the fluorescent material) Red light or the like) or light having a wavelength shorter than the first wavelength (green light or blue light) is emitted and radiated to the outside, so that deterioration of the resin is reduced.

  In addition, unlike a case where a plurality of phosphors that convert to different wavelengths are dispersed in one transparent conductive layer, light that has been converted to light having a shorter wavelength is reconverted by a phosphor that converts to a longer wavelength again. Since there is almost nothing, the conversion efficiency is improved.

  In the light emitting device of the present invention, preferably, the plurality of transparent conductive layers include a transparent conductive layer including a phosphor that converts light generated by the light emitting layer into red light, and converts light generated by the light emitting layer into green light. A transparent conductive layer containing a fluorescent material and a transparent conductive layer containing a phosphor that converts light generated by the light emitting layer into blue light are sequentially laminated from the light emitting layer side, and the light generated in the light emitting layer is converted into white light. Therefore, when the light emitted from the light emitting layer is in the wavelength region of ultraviolet light or near ultraviolet light, white light with high light extraction efficiency, that is, white light with high light emission efficiency can be obtained.

  That is, ultraviolet light or near ultraviolet light generated in the light emitting layer is first converted into red light, and the converted red light is extracted outside with almost no absorption by the transparent conductive layer. In addition, the remaining ultraviolet light or near ultraviolet light partially converted into red light is converted into green light when passing through a transparent conductive layer containing a phosphor that converts to green light, and the green light is also converted into a transparent conductive layer. It is taken out to the outside with almost no attenuation. Further, the remaining ultraviolet light or near ultraviolet light is converted into blue light by the transparent conductive layer containing a phosphor that is finally converted into blue light, and is almost taken out to the outside as it is. In this way, red light, green light, and blue light that are sequentially converted while passing through the plurality of transparent conductive layers are extracted outside without being absorbed by the transparent conductive layer. White light can be efficiently obtained by mixing blue light.

  Furthermore, since ultraviolet light and near ultraviolet light hardly come out of the transparent conductive layer, even if the periphery of the light emitting element is molded with a transparent resin to further improve the light extraction efficiency, ultraviolet light or near ultraviolet light There is no deterioration of the resin by light, and the light emitting element emits white light with a long lifetime.

  In the light emitting device of the present invention, preferably, the n-type gallium nitride compound semiconductor layer is formed by laminating a plurality of transparent conductive layers each containing a phosphor for converting the wavelength of light generated by the light emitting layer on the exposed surface. And a plurality of transparent conductive layers are phosphors that convert light generated by the light emitting layer into light of a first wavelength from the transparent conductive layer closest to the n-type gallium nitride compound semiconductor layer. And a transparent conductive layer containing a phosphor that converts light generated by the light emitting layer into light having a shorter wavelength than the light having the first wavelength as the distance from the n-type gallium nitride compound semiconductor layer increases. Yes. That is, the n-type electrode has the same configuration as the p-type electrode. With this configuration, the same effect as described above can be obtained.

  Further, in the light emitting device of the present invention, preferably, the plurality of transparent conductive layers are thinned as they are separated from the light emitting layer, so that the thickness is increased in ascending order of light absorption, thereby further suppressing light absorption. it can.

  Hereinafter, embodiments of the light emitting device of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an example of a light-emitting element according to the present invention. A gallium nitride compound semiconductor is formed on a substrate 10 via a buffer layer 11 by MOCVD, and further a transparent conductive material containing a phosphor thereon. A layer is formed. In the gallium nitride compound semiconductor having a multilayer structure, a light emitting layer 13 made of a gallium nitride compound semiconductor and a p-type gallium nitride compound semiconductor layer 14 are sequentially stacked on an n-type gallium nitride compound semiconductor layer 12. a p-type electrode 15 formed by laminating a plurality of transparent conductive layers 15a, 15b, 15c and 16a, 16b, 16c on the n-type gallium nitride compound semiconductor layer 12 and the p-type gallium nitride compound semiconductor layer 14; An n-type electrode 16 is formed.

  In the light emitting device of the present invention, an n-type gallium nitride compound semiconductor layer 12, a light emitting layer 13 made of a gallium nitride compound semiconductor, and a p-type gallium nitride compound semiconductor layer 14 are formed on a substrate 10. In the light-emitting element, the p-type gallium nitride compound semiconductor layer 14 is a p-type electrode formed by laminating a plurality of transparent conductive layers 15a, 15b, and 15c each containing a phosphor that converts the wavelength of light generated by the light-emitting layer 13. 15 is formed on the surface, and the plurality of transparent conductive layers 15a, 15b, and 15c are phosphors that convert light generated by the light emitting layer 13 into light having the first wavelength by the transparent conductive layer 15a closest to the light emitting layer 13. 17a, and includes phosphors 17b and 17c that convert light generated by the light emitting layer 13 into light having a shorter wavelength than light having the first wavelength as the distance from the light emitting layer 13 increases. Conductive layer 15b, is configured to 15c are stacked.

In the light emitting device of the present invention, the substrate 10 may be a sapphire (Al ₂ O ₃ ) substrate which is a transparent substrate, but as other transparent substrates, silicon carbide (SiC), zinc oxide (ZnO), gallium nitride ( GaN) or the like may be used.

Further, a substrate made of zirconium diboride (ZrB ₂ ) or the like can be used as the substrate that does not transmit light. More specifically, a substrate made of a diboride single crystal represented by the chemical formula XB ₂ (where X includes at least one of Ti, Mg, Al, Hf, and Zr) is used as the substrate 10. May be. In that case, considering that the substrate 10 is excellent in terms of lattice matching with the gallium nitride compound semiconductor and thermal expansion coefficient matching, it is preferable to use a substrate made of a ZrB ₂ single crystal. In the ZrB ₂ single crystal, a part of Zr may be substituted with Ti, Mg, Al, Hf, or the like. Further, the ZrB ₂ single crystal may contain Ti, Mg, Al, Hf, etc. as impurities to such an extent that its crystallinity and lattice constant do not change greatly.

  In the present invention, the n-type gallium nitride compound semiconductor layer 12 has a plurality of transparent conductive layers 16a to 16c each including phosphors 17a to 17c that convert the wavelength of light generated by the light emitting layer 14 on the exposed surface. A laminated n-type electrode is formed, and the plurality of transparent conductive layers 16 a to 16 c are configured to emit light generated by the light emitting layer from the transparent conductive layer 16 a closest to the n-type gallium nitride compound semiconductor layer 12 at the first wavelength. A phosphor that converts light generated by the light-emitting layer 14 into light having a shorter wavelength than the light having the first wavelength as the distance from the n-type gallium nitride compound semiconductor layer 12 increases. A transparent conductive layer 16a including 17a is laminated. That is, the n-type electrode has the same configuration as the p-type electrode. With this configuration, the same effect as in the case of the p-type electrode can be obtained.

  In the n-type gallium nitride compound semiconductor layer 12, the n-type electrode is formed by etching away a part of the light emitting layer 13 and the p-type gallium nitride compound semiconductor layer 14 as shown in FIG. It may be a portion where a part of the gallium nitride compound semiconductor layer 12 is exposed.

  Further, when the substrate 10 is conductive, the n-type electrode 16 formed on the n-type gallium nitride compound semiconductor layer 12 is not necessary, and the n-type electrode 16 is formed directly on the back surface (lower surface) of the substrate 10. It becomes possible.

  In addition, when the substrate 10 is removed, an n-type electrode can be formed on the surface of the n-type gallium nitride compound semiconductor layer 12 from which the substrate 10 is removed.

  Further, even when the n-type electrode 16 is formed on the n-type gallium nitride compound semiconductor layer 12, the n-type electrode 16 does not necessarily need to be composed of the transparent conductive layers 16a, 16b, and 16c. That is, light generated from the light emitting layer 13 travels toward the substrate 10 or the p-type gallium nitride compound semiconductor layer 14, and little light reaches the n-type electrode 16 on the n-type gallium nitride compound semiconductor layer 12. It is. Therefore, in this case, the n-type electrode 16 is formed of a known metal electrode that is not a transparent conductive layer such as titanium (Ti) layer / aluminum (Al) layer / nickel (Ni) layer / gold (Au) layer. Also good. However, in order to improve the light extraction efficiency, the n-type electrode 16 made of the transparent conductive layer of the present invention is preferable.

  In addition, regardless of the configuration of the n-type electrode 16, in order to extract light from the side opposite to the substrate 10, a reflective layer made of metal between the substrate 10 and the light emitting layer 13, gallium aluminum nitride (AlGaN ) And gallium nitride (GaN) or the like, a Bragg reflective layer (DBR: Distributed Bragg Reflector) or the like can be provided.

  The buffer layer 11 is not necessarily formed when the lattice constant or thermal expansion coefficient of the gallium nitride-based compound semiconductor is close to the lattice constant or thermal expansion coefficient of the substrate 10, but when the buffer layer 11 is formed, nitriding is performed. One made of gallium (GaN), aluminum nitride (AlN), or a mixed crystal thereof, gallium aluminum nitride (AlGaN), can be formed. The temperature of the substrate 10 when forming the buffer layer 11 is about 400 ° C. to 800 ° C.

  After the formation of the buffer layer 11, the temperature of the substrate 10 is raised to about 1000 ° C. to 1200 ° C., and the n-type gallium nitride compound semiconductor layer 12 is subsequently formed. The n-type gallium nitride compound semiconductor layer 12 is, for example, a GaN layer, but may be an AlGaN layer, an InGaN layer, or the like having a mixed crystal composition of AlN and indium nitride (InN). In addition to the MOCVD method, a method for forming a gallium nitride compound semiconductor such as the n-type gallium nitride compound semiconductor layer 12 includes a molecular beam epitaxy (MBE) method, a hydride vapor phase epitaxy (HVPE) method, and pulsed laser deposition. (PLD) method etc. are mentioned.

  The light emitting layer 13 has, for example, a quantum well structure (MQW: Multi Quantum Well) composed of a barrier layer and a well layer made of an InGaN layer, a GaN layer, an AlGaN layer, or the like. For example, a GaN layer can be used as the barrier layer, and an InGaN layer can be used as the well layer. The emission wavelength is determined by the In composition of the barrier layer and the well layer, the film thickness, and the number of repetitions of the quantum well structure.

After the p-type gallium nitride compound semiconductor layer 14 having a composition such as Al _x Ga _1-x N (0 ≦ x ≦ 1) is formed, the p-type electrode 15 including the phosphor 17 is formed. The transparent conductive layers 15a to 15c constituting the p-type electrode 15 are made of a conductive oxide or the like, for example, an ITO (Sn-added In ₂ O ₃ ) layer, a tin oxide film (SnO ₂ ) layer, an indium oxide film (In _2). O ₃ ) layer, gallium oxide (Ga ₂ O ₃ ) layer, germanium oxide (Ge ₂ O ₃ , GeO) layer, zinc oxide (ZnO) layer, CuMO ₂ (M: Al, Ga, In, Sc, Y, La) Or a SrCu ₂ O ₂ layer, or an impurity added to these layers. In particular, an ITO layer is preferable from the viewpoint of light transmittance and contact resistance between the p-type gallium nitride compound semiconductor layer.

  The p-type electrode 15 and the n-type electrode 16 may be the same or different. For example, an ITO layer is formed on the p-type gallium nitride compound semiconductor layer, and a zinc oxide (ZnO) layer is formed on the n-type gallium nitride compound semiconductor layer.

  The p-type electrode 15 includes a transparent conductive layer 15a including a phosphor 17a that converts light (basic light) generated in the light emitting layer 13 into light having a first wavelength (red light), and a phosphor that converts basic light into green light. The transparent conductive layer 15b containing 17b, and 15c containing the fluorescent substance 17c which converts basic light into blue light. The transparent conductive layers 15a to 15c containing the phosphor are respectively applied to the p-type gallium nitride compound semiconductor layer 14 after mixing the particles of the phosphors 17a to 17c in a solvent when formed by, for example, a sol-gel method. Then, it can be formed by drying and baking. Further, it can be formed in the same manner by a spray method or the like. The particles of the phosphors 17a to 17c are dispersed by dispersing the particles of the phosphors 17a to 17c in a solvent, spray coating, drying, and firing. The transparent conductive layers 15a to 15c thus obtained can be obtained.

  In order to form the p-type electrode 15 having a multilayer structure, after forming a transparent conductive layer 15a containing a phosphor that converts basic light into red light, calcining is performed at, for example, about 200 to 400 ° C. for 30 minutes, and then basic light is formed. A solvent containing a phosphor that converts green light into green light is applied and calcined in the same manner to form the transparent conductive layer 15b. Finally, after applying a solvent containing a phosphor that converts basic light into blue light and calcining to form the transparent conductive layer 15c, heating is continued at a higher temperature (about 500 ° C. to 800 ° C.). Can be formed. The transparent conductive layers 16a to 16c constituting the n-type electrode 16 can be formed in the same manner.

As the phosphors 17a to 17c to be contained in the transparent conductive layer 15, known phosphors can be used. For example, Y ₂ O ₂ S: Eu, Ba ₃ MgSi ₂ O ₈ : Eu, Mn and the like can be cited as phosphors capable of converting basic light such as ultraviolet light and near ultraviolet light into red light. Examples of the phosphor that can convert basic light into green light include ZnS: Cu, Al, (Ba, Mg) Al ₁₀ O ₁₇ : Eu, Mn, (Ba, Sr) ₂ SiO ₄ : Eu, and the like. . Examples of phosphors that can convert basic light into blue light include (Sr, Ca, Ba, Ba) ₁₀ (PO ₄ ) ₆ C ₁₂ : Eu, (Ba, Mg) Al ₁₀ O ₁₇ : Eu, and the like. be able to.

  The above-mentioned formula of A: B indicates B dope A (A in which a small amount of B is mixed).

  The average particle size of each phosphor is preferably less than 1 μm because if the average particle size is too large, the thickness of the transparent conductive layers 15a to 15c is determined by the particle size of the phosphor and becomes thick.

  The content of the phosphors 17a to 17c in each of the transparent conductive layers 15a to 15c is preferably 20% by weight to 80% by weight. If it is less than 20% by weight, the amount of light that is transmitted without being converted into fluorescence increases, and if it exceeds 80% by weight, the amount of basic light that is transmitted to the next layer decreases, so that the fluorescence generated in the next layer is reduced.

  Further, the content of the phosphors 17a to 17c in each layer may be different in each layer. The content of each layer varies depending on the efficiency of the phosphor used, etc., and cannot be determined unconditionally, but can be adjusted while looking at the chromaticity.

  The thickness of each of the transparent conductive layers 15a to 15c is preferably 10 μm or less, and more preferably 2 μm or less because light absorption occurs in the transparent conductive layers 15a to 15c if the thickness is too large. Further, the thicknesses of the respective layers do not have to be the same and may be different from each other, but from the viewpoint of light absorption, the thickness can be increased in ascending order of light absorption. That is, the transparent conductive layer 15a including the phosphor 17a that converts basic light into red light is the thickest, the transparent conductive layer 15b including the phosphor 17b that converts basic light into green light, and the fluorescence that converts basic light into blue light. The transparent conductive layer 15c including the body 17c is preferably thicker in that order. As described above, since the plurality of transparent conductive layers 15a to 15c become thinner as they move away from the light emitting layer 13, the thickness is increased in ascending order of light absorption, and light absorption can be further suppressed.

  The outermost transparent conductive layer 15c may have a concavo-convex structure on the surface. In that case, the refractive index difference between the transparent conductive layer and the surrounding air or resin can be apparently changed in an inclined manner, and the light extraction efficiency can be further improved.

  Furthermore, a pad electrode may be provided on the p-type electrode 15 and the n-type electrode 16 in order to perform wire bonding or prober measurement. As the pad electrode, for example, a two-layer structure of Ti layer / Au layer can be used.

  Then, dicing or scribing is performed on the mother substrate on which a large number of light emitting element regions are formed, and each light emitting element is separated into chips, whereby the light emitting element shown in FIG. 1 is obtained.

  The light emitting element is accommodated in, for example, a ceramic package, and the pad electrode is pulled out by wire bonding or the like, and then the light emitting element is covered with a transparent resin and mounted. Even if the resin does not contain a phosphor, white light can be obtained sufficiently, but in order to further improve efficiency, in order to convert light that was not converted in the transparent conductive layer in the resin, The resin may contain a phosphor. Even in this case, the number of manufacturing processes does not increase, and the amount of leaking ultraviolet light and near ultraviolet light is extremely smaller than that of the light emitting element having the conventional structure, so that the deterioration of the resin is smaller than that of the conventional structure.

  Such a light emitting device operates as follows. That is, a bias current is applied to the gallium nitride compound semiconductor including the light emitting layer 13 to generate ultraviolet light to near ultraviolet light having a wavelength of about 350 to 400 nm in the light emitting layer 13, and the ultraviolet light to near ultraviolet light outside the light emitting element. Operates to extract light.

  The light-emitting element of the present invention is configured as described above, and converts light generated in the light-emitting layer from light from the transparent conductive layer closer to the light-emitting layer to light having a longer wavelength. Absorption and attenuation can be suppressed, and a white light emitting element with high light extraction efficiency and excellent light emission efficiency can be obtained. Further, in a white light emitting element, a light reflecting member such as a concave mirror can be provided in a transparent resin or the like in order to improve the light collecting property. Such an illuminating device consumes less power than a conventional fluorescent lamp or the like, and is small in size. Therefore, the illuminating device is effective as a small and high-luminance lighting device.

  In addition, this invention is not limited to said embodiment, A various change can be given in the range which does not deviate from the summary of this invention.

It is sectional drawing which shows the example of embodiment about the light emitting element of this invention. It is sectional drawing of the conventional light emitting element.

Explanation of symbols

10: substrate 11: buffer layer 12: n-type gallium nitride compound semiconductor layer 13: light emitting layer 14: p-type gallium nitride compound semiconductor layer 15: p-type electrode 16: n-type electrode 17: phosphors 17a, 17b, 17c : Phosphor

Claims (4)

  In a light emitting device in which an n-type gallium nitride compound semiconductor layer, a light emitting layer made of a gallium nitride compound semiconductor, and a p type gallium nitride compound semiconductor layer are formed on a substrate, the p type gallium nitride compound The semiconductor layer has a p-type electrode formed by laminating a plurality of transparent conductive layers each containing a phosphor that converts the wavelength of light generated by the light emitting layer, and the plurality of transparent conductive layers are: The transparent conductive layer closest to the light emitting layer includes a phosphor that converts light generated by the light emitting layer into light having a first wavelength, and the light generated by the light emitting layer as the distance from the light emitting layer increases. A light-emitting element, wherein the transparent conductive layer including a phosphor that converts light having a shorter wavelength than light having a first wavelength is laminated.   The plurality of transparent conductive layers include a transparent conductive layer including a phosphor that converts light generated by the light emitting layer into red light, and a transparent conductive layer that includes a phosphor that converts light generated by the light emitting layer into green light. And a transparent conductive layer containing a phosphor that converts light generated by the light emitting layer into blue light are sequentially laminated from the light emitting layer side, and the light generated in the light emitting layer is emitted as white light to the outside. The light-emitting element according to claim 1.   The n-type gallium nitride compound semiconductor layer has an n-type electrode formed by laminating a plurality of transparent conductive layers each containing a phosphor that converts the wavelength of light generated by the light-emitting layer on the exposed surface. The plurality of transparent conductive layers include a phosphor that converts light generated by the light emitting layer into light having a first wavelength by the transparent conductive layer closest to the n-type gallium nitride compound semiconductor layer. The transparent conductive layer including a phosphor that converts light generated by the light emitting layer into light having a shorter wavelength than the light having the first wavelength as the distance from the n-type gallium nitride compound semiconductor layer is increased. The light-emitting element according to claim 1 or 2.   4. The light-emitting element according to claim 1, wherein the plurality of transparent conductive layers have a thickness that decreases with distance from the light-emitting layer. 5.

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