JP4458870B2 - Fluorescent light emitting device, fluorescent light emitting element, and phosphor - Google Patents

Description

  The present invention relates to a light emitting device that emits light in a desired wavelength range, a light emitting element, and a phosphor.

  In recent years, multi-color light emission or white color using light-emitting elements made up of so-called LEDs (light-emitting diodes) for illumination light sources, display devices, and the like because they consume less power than incandescent and fluorescent lamps and have a longer life. Research and development for utilizing light emission have been actively conducted (for example, see Patent Document 1 and Patent Document 2).

On the other hand, group III nitrides InN, GaN, and AlN have direct transition band gaps of 1.9, 3.4, and 6.2 eV (all crystal structures are hexagonal), respectively. _{x in Y Ga 1-X-} Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1) is promising as a luminescent material for a wide range of wavelengths ranging from the visible light in the ultraviolet region, it to the light-emitting element in the same region Research and development for use have also been made (see, for example, Patent Document 3 and Patent Document 4).

JP-A-10-107325 Japanese Patent Laid-Open No. 9-167861 JP 2002-261324 A JP 2002-368267 A

  Patent Document 1 discloses a light emitting device in which an LED chip that emits blue light is coated with a fluorescent material that is excited by light emitted from the LED chip and emits yellow light. The light-emitting device is intended to obtain white light emission by mixing the blue light emission from the LED chip and the yellow light emission from the fluorescent material. However, under the white light obtained by such two-color mixing, red color is not emitted directly, so that the red color is poor and the full color cannot be fully recognized, and it is sufficient compared to fluorescent lamps. There is a problem that a high luminance is not obtained.

  Patent Document 2 discloses a multicolor light emitting element in which green, red, and blue LED chips having different emission wavelengths are arranged on a common substrate. In such a multicolor light emitting element, white light can be obtained by lighting all the LED chips of each color. In such an embodiment, the use of LED chips suitable for light emission of each color (with good light emission efficiency) increases the luminance and color mixing properties, but the cost for manufacturing the three color LED chips separately is high, and There is a problem that the implementation becomes complicated.

  Both Patent Document 3 and Patent Document 4 disclose a semiconductor light emitting device including a light emitting layer formed by adding a rare earth element, a transition metal element, or a transition metal element to a nitride that is a mixed crystal of InN, GaN, and AlN. ing. All of these semiconductor light emitting elements are configured by forming the light emitting layer as an active layer having a so-called double hetero structure. Light is obtained by exciting a rare earth or transition metal element added to the active layer by applying a voltage between electrodes provided on both sides via both clad layers of pn. In particular, in the semiconductor light emitting device disclosed in Patent Document 4, the luminous efficiency is improved by realizing the structure of the light emitting layer that further improves the carrier confinement effect by the nitride. However, in any semiconductor light emitting device, the light emission efficiency can be improved by increasing the amount of the additive element added. However, if the amount of the rare earth element or transition metal element increases, the light emission as the active layer is caused by the presence of the additive element. Since the electric field generated in the layer is weakened, and as a result, the light emission efficiency is deteriorated, the addition amount has a restriction from the viewpoint.

  The present invention has been made in view of the above problems, and can emit light in an arbitrary wavelength range with better luminous efficiency, and a light emitting device that emits desired light in which light of a plurality of wavelengths is mixed, and light emission An object is to provide an element and a phosphor.

The invention according to claim 1 includes a plurality of addition regions in which at least one rare earth element or transition metal element is added to a nitride containing at least one element of Al, In, Ga, and B, respectively. And regions where no rare earth or transition metal element is added are alternately arranged in layers, and the nitride composition of each of the added regions is adjacent to the adjacent rare earth or transition metal element. Unlike nitride composition without region and the than the band gap of the respective doped region, and the rare earth or the larger phosphor band gap of the region the transition metal element is not added, the first wavelength A light source emitting a first light having a range, and exciting the rare earth element or the transition metal element by the first light emitted from the light source. Accordingly, to emit light having a second light having a second wavelength range as a component, characterized in that.

A second aspect of the present invention is the fluorescent light emitting device according to the first aspect, wherein the added region is at least one type of nitride containing at least one element of Al, In, Ga, and B. It is a region formed by island-like crystals to which the rare earth or transition metal element is added.

The invention according to claim 3, a fluorescent light emitting device according to claim 1 or claim 2, wherein the phosphor has a plurality of fluorescent regions containing the added region respectively, the additive The kind of the at least one rare earth or transition metal element added to the region is different for each of the fluorescent regions.

The invention according to claim 4 is the fluorescent light emitting device according to claim 3 , wherein the light source emits blue light as the first light, and the phosphor is the at least one rare earth or transition. A first fluorescent region doped with a first rare earth or transition metal element that emits red light upon excitation as a metal element, and a first fluorescent region that emits green light upon excitation as the at least one rare earth or transition metal element. And a second fluorescent region to which two rare earth or transition metal elements are added, and the first and second rare earth or transition metal elements are excited by blue light emitted from the light source. The red light and the green light are emitted as the second light from the first and second fluorescent regions, respectively, thereby having the blue light and the second light as components. Emit, characterized in that.

Invention of Claim 5 is the fluorescence light-emitting device of Claim 3 , Comprising: The said light source is a light source which light-emits ultraviolet light as said 1st light, The said fluorescent substance is said at least 1 sort (s) of A first fluorescent region doped with a first rare earth or transition metal element that emits red light upon excitation as a rare earth or transition metal element, and green light upon excitation as the at least one rare earth or transition metal element. A second fluorescent region to which a second rare earth element or transition metal element that emits light is added, and a third rare earth element or transition metal element that emits blue light by excitation is added as the at least one rare earth element or transition metal element. A third fluorescent region, and the first, second and third rare earths or transitions by ultraviolet light emitted from the light source. The first exciting the metal element, thereby emitting the second and third, respectively from the fluorescent regions red, green, and blue light as the second light, and wherein the.

A sixth aspect of the present invention is the fluorescent light emitting device according to any one of the first to fifth aspects, wherein the light source is a light emitting diode.

A seventh aspect of the present invention is the fluorescent light emitting device according to any one of the first to sixth aspects, wherein the phosphor is formed epitaxially on a predetermined substrate. .

The invention according to claim 8 includes a plurality of addition regions in which at least one rare earth element or transition metal element is added to a nitride containing at least one element of Al, In, Ga, and B, respectively. And regions where no rare earth or transition metal element is added are alternately arranged in layers, and the nitride composition of each of the added regions is adjacent to the adjacent rare earth or transition metal element. Unlike nitride composition without region and the than the band gap of each doped region, the phosphor structure the larger the band gap of the rare earth or region transition metal element is not added, the phosphor A light emitter structure that is connected to the structure and emits first light having a first wavelength range, wherein the first light emitted from the light emitter structure is provided. Wherein by exciting a rare earth or transition metal element, to emit light having a second light having a second wavelength range as a component, characterized in that the.

The invention according to claim 9 is the fluorescent light-emitting device according to claim 8 , wherein the additive region is at least one kind of nitride containing at least one element of Al, In, Ga, and B. It is a region formed by island-like crystals to which the rare earth or transition metal element is added.

The invention according to claim 10 is the fluorescent light-emitting device according to claim 8 or claim 9 , wherein the phosphor structure has a plurality of fluorescent regions each including the additive region, The kind of the at least one rare earth or transition metal element added to the addition region is different for each of the fluorescent regions.

The invention according to claim 11 is the fluorescent light emitting device according to claim 10 , wherein the light emitting structure emits blue light as the first light, and the phosphor structure has the at least one kind of the light emitting structure. A first fluorescent region doped with a first rare earth or transition metal element that emits red light upon excitation as a rare earth or transition metal element, and green light upon excitation as the at least one rare earth or transition metal element. A second fluorescent region to which light is emitted and a second fluorescent region to which a transition metal element is added; and the first and second rare earths or transitions by blue light emitted from the light emitter structure. The blue light and the second light are emitted by exciting a metal element to emit red light and green light as the second light from the first and second fluorescent regions, respectively. The emit light having as a component, characterized in that.

The invention according to claim 12 is the fluorescent light-emitting device according to claim 10 , wherein the light-emitting structure emits ultraviolet light as the first light, and the phosphor structure has the at least one kind of light. A first fluorescent region doped with a first rare earth or transition metal element that emits red light upon excitation as a rare earth or transition metal element, and green light upon excitation as the at least one rare earth or transition metal element. A second fluorescent region to which a second rare earth element or transition metal element that emits light is added, and a third rare earth element or transition metal element that emits blue light by excitation is added as the at least one rare earth element or transition metal element. And three third fluorescent regions, and the first, second and third rare earth elements are formed by ultraviolet light emitted from the light emitter structure. There is a transition metal element to excite the first to emit the second and third, respectively from the fluorescent regions red, green, and blue light as the second light, and wherein the.

A thirteenth aspect of the present invention is the fluorescent light emitting device according to any one of the eighth to twelfth aspects, wherein the light emitter structure has a diode structure.

A fourteenth aspect of the present invention is the fluorescent light emitting device according to any one of the eighth to thirteenth aspects, wherein the phosphor structure and the light emitter structure are formed epitaxially on a predetermined substrate. It is characterized by being.

A fifteenth aspect of the present invention is the fluorescent light emitting element according to the fourteenth aspect , wherein the phosphor structure and the light emitting structure are laminated.

A sixteenth aspect of the present invention is the fluorescent light emitting device according to any one of the eighth to fifteenth aspects, wherein the luminous body structure is at least one element selected from the group consisting of Al, In, Ga, and B. It has a light emitting layer containing a nitride containing.

The invention according to claim 17 includes a plurality of addition regions in which at least one rare earth element or transition metal element is added to a nitride containing at least one element of Al, In, Ga, and B, respectively. And regions where no rare earth or transition metal element is added are alternately arranged in layers, and the nitride composition of each of the added regions is adjacent to the adjacent rare earth or transition metal element. The band gap of the region to which the rare earth or transition metal element is not added is larger than the band gap of each of the added regions , and is different from the nitride composition of the regions where no added light is emitted. Exciting the rare earth element or the transition metal element with the light of 1 has the second light having the second wavelength range as a component. Emit light, characterized in that.

The invention according to claim 18 is the phosphor according to claim 17 , wherein the addition region includes at least one kind of nitride containing at least one element of Al, In, Ga, and B. It is a region formed by island-like crystals to which a rare earth or transition metal element is added.

The invention according to claim 19 is the phosphor according to claim 17 or claim 18 , which has a plurality of fluorescent regions each including the added region, and is added to the added region. The kind of the at least one rare earth or transition metal element is different for each of the fluorescent regions.

The invention according to claim 20 is the phosphor according to claim 19 , wherein the at least one rare earth element or transition metal element is added with the first rare earth element or transition metal element that emits red light by excitation. And the second fluorescent region to which the second rare earth or transition metal element that emits green light by excitation is added as the at least one rare earth or transition metal element. The first and second rare earth elements or transition metal elements are excited by blue light emitted from a predetermined light source, and red light and green light are emitted from the first and second fluorescent areas, respectively. Is emitted as the second light to emit light having the blue light and the second light as components.

The invention according to claim 21 is the phosphor according to claim 19 , wherein the first rare earth or transition metal element that emits red light upon excitation is added as the at least one rare earth or transition metal element. The first fluorescent region, the second fluorescent region to which the second rare earth or transition metal element emitting green light by excitation is added as the at least one rare earth or transition metal element, and the at least one As a kind of rare earth or transition metal element, it has three fluorescent regions including a third fluorescent region added with a third rare earth or transition metal element that emits blue light by excitation, and emitted from a predetermined light source. The first, second, and third fluorescent regions are excited by the ultraviolet light to excite the first, second, and third rare earth elements or transition metal elements. Respectively emit red light, green light, and blue light as the second light, and wherein the.

The invention according to claim 22 is the phosphor according to any one of claims 17 to 21 , wherein the phosphor is formed epitaxially on a predetermined substrate.

According to the inventions of claims 1 to 22 , light emission of any color can be realized with high luminous efficiency by appropriately determining the composition of the nitride and the composition of the rare earth or transition metal element. Since light is emitted by photoexcitation, the composition of the phosphor is not electrically restricted. Therefore, rare earth elements or transition metal elements are dissolved in a solid solution with a higher solid solubility than a light emitting element that emits light by applying a voltage. By doing so, high luminous efficiency can be realized.

In particular, according to the inventions according to claims 1 to 22 , since the light superposed with the light emission from each of the addition regions is emitted, it is possible to realize an increase in the light emission intensity and a color mixture due to the light emission of a plurality of colors.

In particular, according to the invention of claims 1 to 22 , since the rare earth or transition metal element is added to the well layer portion of the quantum well structure, the light emission efficiency from the rare earth or transition metal element can be increased.

In particular, according to according to the invention of claims 1 to 22, and the well layer, since the stacked alternately and more band gap larger barrier layer, the effect of confining carriers in the well layer is further enhanced, as a result, Since the carrier recombination is efficiently performed, the light emission efficiency of the rare earth element or the transition metal element is further improved.

In particular, according to the inventions of claim 2 , claim 9 , and claim 18 , the island-like crystal acts as a quantum dot having a small band gap, thereby further enhancing the carrier confinement effect. Therefore, the light emission efficiency of the rare earth element or the transition metal element is further improved.

In particular, claims 3 to 5, claims 10 to 12, and according to the invention of claim 19 through claim 21, the light obtained by superimposing the light from the fluorescent region to emit different colors for each Since it emits light, it is possible to realize color mixing by light emission of a plurality of colors. Since each fluorescent region can be configured to have an optimal structure and composition for light emission of each color, the light emission efficiency can be further improved.

In particular, according to the inventions of claims 4 , 11 , and 20 , when blue light is used as an excitation light source and green light and red light are generated by excitation, ultraviolet light is used as the excitation light source. A light emitting device with three colors can be realized with a simpler configuration.

In particular, according to the inventions of claims 5 , 12 , and 21 , three colors are made equivalent by using ultraviolet light as an excitation light source and generating blue light, green light, and red light by excitation. Since white light can be obtained by generating, white light with less bias can be emitted.

According to the invention of claim 6 and claim 13 , since the light-emitting diode with low power consumption and long life is used as the light source, the light-emitting device or the light-emitting element can be manufactured at low cost and with high reliability. In addition, by appropriately determining the composition of the nitride and the type of rare earth or transition metal element, the use of a three-color LED chip allows the emission of white light by three-color mixing, which is superior to two-color mixing that emits light. It can be realized by a combination of one light emitting diode and one phosphor, which is less expensive.

In addition, according to the inventions of claims 7 , 14 , 15 , and 22, a phosphor having a good crystal quality can be formed, so that the luminous efficiency can be further improved.

In particular, according to the invention of claim 15 , since the device can be downsized and the excitation energy from the light source can be efficiently absorbed without being diffused, compared with the case where the light source is provided separately, the luminous efficiency is improved. It also leads to.

According to the invention of claim 16 , since the phosphor and the light source can be continuously formed using the same kind of material, the manufacturing process can be simplified and the cost can be reduced.

<First Embodiment>
FIG. 1 is a diagram schematically showing a light emitting device 1 according to a first embodiment of the present invention. The light emitting device 1 shown in FIG. 1 includes a phosphor 10 and an LED element 20.

The phosphor 10 may include an addition region in which at least one rare earth or transition metal is added to a nitride containing at least one element of Al, In, Ga, and B, and various formation methods are used. Can do. For example, it can be formed by sintering a raw material containing each constituent element or by dispersing the above-mentioned region powder in a resin. Also, it can be formed on the substrate by various thin film forming methods such as CVD (chemical vapor deposition), sputtering, MBE (molecular beam epitaxy). For example, a base layer 12 and a fluorescent layer 13 are formed in this order on a substrate 11 made of sapphire single crystal. The substrate 11 is not only a sapphire single crystal but also a ZnO single crystal, LiAlO ₂ single crystal, LiGaO ₂ single crystal, MgAl ₂ O ₄ single crystal, MgO single crystal or other oxide single crystal, Si single crystal, SiC single crystal, etc. Group IV or IV-IV single crystals, GaAs single crystals, AlN single crystals, GaN single crystals, III-V single crystals such as AlGaN single crystals, boride single crystals such as ZrB ₂ , alumina, AlN, etc. It can be composed of a known substrate material such as a bonded substrate or a glass substrate. The underlayer 12 and the fluorescent layer 13 are formed by adding a predetermined group III nitride or a predetermined additive element thereto. The specific composition of each layer depends on its purpose and function, It is set appropriately. In the phosphor 10, the underlayer 12 is formed by MOCVD (metal-organic chemical vapor deposition), and the fluorescent layer 13 is formed by MBE (molecular beam epitaxy). Although it is preferable from the viewpoint of realizing high crystal quality, all layers may be formed by the MOCVD method, or all layers may be formed by the MBE method. Further, the addition of the transition metal and the rare earth is not necessarily performed simultaneously with the formation of the nitride film which is the parent phase, and may be added separately by using an ion implantation method or the like.

  The underlayer 12 is made of, for example, GaN. However, when GaN is used for the underlayer 12, a low temperature buffer layer 14 of AlN or GaN is first formed on the substrate 11 at a low temperature of about 500 ° C., and then a GaN layer is further formed at a temperature of 1000 ° C. or higher. Thus, the underlayer 12 satisfying the crystal quality is formed. Thereby, the fluorescent layer 13 formed on the base layer 12 has good crystal quality. The thickness of the underlayer 12 is appropriately selected in consideration of the occurrence of cracks and the use. For example, it is about several μm.

  The fluorescent layer 13 is composed of two types of layers as shown in an enlarged view in FIG. One is a green fluorescent layer 13G that emits green (G) fluorescence by absorbing predetermined energy, and the other is red (R) fluorescence by absorbing predetermined energy. This is the red fluorescent layer 13R.

  In the green fluorescent layer 13G, the Group III nitride includes an additive layer 131 to which a rare earth element or a transition metal element that emits green light when excited is added, and a non-added layer 132 to which the additive is not added are several nanometers each. The layers are alternately stacked (preferably several tens of layers).

  In the red fluorescent layer 13R, a Group III nitride is added with an additive layer 133 to which a rare earth or transition metal element that emits red light when excited is added, and a non-added layer 134 without such addition is several nanometers each. It is a layer formed by alternately laminating a large number (preferably several tens to several hundreds).

  The additive layers 131 and 133 are formed of nitride having a composition different from that of the non-added layers 132 and 134, respectively. That is, in the green fluorescent layer 13G and the red fluorescent layer 13R, MQW (Multi Quantum Well) in which well layers and barrier layers having wider bands are alternately deposited by alternately changing the composition of nitrides. Quantum well) structure is realized.

  Here, the rare earth element or the transition metal element is added in order to obtain light having a desired wavelength while increasing the luminous efficiency. Rare earths or transition metal elements have their own emission wavelengths with respect to external excitation such as light or electron beams. By adding an appropriate amount of a plurality of rare earth elements or transition metal elements, light having an arbitrary color, for example, white light can be emitted. Further, the rare earth element or the transition metal element can be dissolved in the nitride without causing trouble in the light emission mechanism.

For example, in the case where the underlayer 12 is formed of GaN, the additive layer 131 in the green phosphor layer 13G is, for example, Ga _x In _y N (x + y = 1, x ≧ 0, y ≧ 0) with Tb or Ho. The non-added layer 132 is formed of GaN. In the red fluorescent layer 13R, the additive layer 133 is formed by adding Eu to Ga _x In _y N (x + y = 1, x ≧ 0, y ≧ 0), and the non-added layer 134 is formed of GaN. That is, in the present embodiment, both the green fluorescent layer 13G and the red fluorescent layer 13R are formed on the basis of GaN or Ga _x In _y N. Although it is possible to form the fluorescent layers of the respective colors with substances made of completely different kinds of elements, it is more costly to form a layer with a base substance in common as in this embodiment. Needless to say, this is also efficient in terms of production time.

  From the viewpoint of improving the luminous efficiency, as much of the rare earth element or transition metal element as possible within the range in which the crystallinity is not deteriorated in any of the additive layer 131 of the green phosphor layer 13G and the additive layer 133 of the red phosphor layer 13R. Is preferably added. In the present embodiment, since there is no electrical restriction, the composition is compared with that of the light emitting element that emits light by applying a voltage to the active layer as disclosed in Patent Document 3 and Patent Document 4. It can be said that there is a high degree of freedom. That is, more rare earth elements or transition metal elements can be added than a light emitting element by voltage application, and higher issuance efficiency can be obtained.

  The LED element 20 is a PN-type semiconductor light emitting element that emits blue light, a so-called blue light emitting diode. The LED element 20 includes an n-type conductive layer 21, a light emitting layer 22, a clad layer 23, and a p-type conductive layer 24 formed in this order on a substrate 27 made of, for example, sapphire. The clad layer may not be provided between the n-type conductive layer 21 and the light emitting layer 22, but may be provided. A p-type electrode 25 made of, for example, Al / Ni is formed on the p-type conductive layer 24. A part of the n-type conductive layer 21 is exposed, and an n-type electrode 26 made of, for example, Au / Ti is formed in the exposed part. For the substrate 27, a substrate material similar to that used for the phosphor 13 can be used. The n-type conductive layer 21, the light emitting layer 22, the clad layer 23, and the p-type conductive layer 24 are formed by adding a group III nitride having a predetermined composition or a predetermined additive element thereto. The specific composition is appropriately set according to the purpose and action. Each layer is formed by the MOCVD method, which is preferable from the viewpoint of realizing high crystal quality, but the MBE method may be used for forming some or all layers.

  In the present embodiment, blue light having a predetermined wavelength is emitted from the light emitting layer 22 by applying a predetermined voltage between the p-type electrode 25 and the n-type electrode 26 by a predetermined power source (not shown). In the present embodiment, the LED element 20 acts as a light emitting light source or an excitation light source as will be described later. However, the excitation light source may be other as long as it can excite the phosphor 10. For example, the excitation light source can be an electron beam gun or an electron emitter, and the rare earth or transition metal element of the fluorescent layer 13 can be excited by electrons.

The n-type conductive layer 21 is formed by adding a predetermined n-type dopant to a group III nitride. As the group III nitride, for example, a nitride having a Ga content with respect to all group III elements of 50 at% or more, preferably 70 atomic% or more, more preferably GaN is used. Al and In may be included as group III elements other than Ga. For example, Si is used as the dopant. In addition, B, Ge, or the like can be used. The n-type conductive layer 21 is formed to a thickness of about several μm. The n-type conductive layer 21 is configured to have a high crystal quality such that a dislocation density is 1 × 10 ⁹ / cm ² or less and a half-value width in an X-ray rocking curve on the (002) plane is 300 seconds or less.

The composition of the group III nitride used for the light emitting layer 22 is determined according to the wavelength of light to be emitted. This is because the band gap of the light emitting layer 22 changes according to the composition. For example, when the light emitting layer 22 is formed with Ga _x In _y N (x + y = 1, x ≧ 0, y ≧ 0), the band gap, that is, the emission wavelength is adjusted in the range of emitting blue light by the ratio of In. It is possible.

The p-type conductive layer 24 is formed by adding a predetermined p-type dopant to a group III nitride. As the group III nitride, for example, a nitride having a Ga content with respect to all group III elements of 50 at% or more, preferably 70 atomic% or more, more preferably GaN is used. Al and In may be included as group III elements other than Ga. As the dopant, for example, Mg is used. In addition, Zn, Be, or the like can be used. The p-type conductive layer 24 is formed to a thickness of about several hundred nm. The p-type conductive layer 24 is configured to have a high crystal quality such that a dislocation density is 1 × 10 ⁹ / cm ² or less and a half-value width in an X-ray rocking curve on the (002) plane is 300 seconds or less. The carrier density needs to be 1 × 10 ¹⁶ / cm ³ or more, and more preferably 1 × 10 ¹⁷ / cm ³ or more. Thereby, a voltage drop in the p-type conductive layer 24 can be suppressed, and a voltage can be efficiently applied to the light emitting layer 22 to improve the light emission efficiency.

  The clad layer 23 is provided to enhance the confinement effect of injected electrons. For example, it is formed of a group III nitride having a composition in which a part of Ga of the p-type conductive layer 24 is replaced with Al.

  In the light emitting device 1 according to the present embodiment, when a predetermined voltage is applied and the LED element 20 emits blue light (B), a part thereof is absorbed by the phosphor 10, and the energy is excited energy. As a result, the rare earth or transition metal element added to the additive layers 131 and 133 is excited, and light emission having a specific wavelength occurs. In addition to this, the energy generated by the recombination of carriers such as electrons or holes confined in the additive layers 131 and 133 which are well layers of the MQW structure described above by obtaining energy from blue light (B) is also rare earth. Alternatively, since the transition metal element is excited, light emission is similarly generated by such a process. As a result, green light (G) and red light (R) are emitted with high luminous efficiency from the green fluorescent layer 13G and the red fluorescent layer 13R, respectively. The blue light emitted from the LED element 20 and the green light and red light emitted from the phosphor 10 are mixed to realize white light emission.

  As a result, light emission of white light by three-color mixing, which has better color developability than two-color mixing, is realized by a combination of one LED chip and one phosphor that is less expensive than using three-color LED chips. And high brightness white light can be obtained.

  In addition, by using other rare earth elements or transition metal elements as elements to be added to the fluorescent layer, or by using LED elements 20 that emit different colors, the color combination is different, so that only white light is emitted. It is also possible to realize light emission of any color. Alternatively, the fluorescent layer 13 may be formed of a layer that emits three or more colors.

  In addition, unlike a light emitting element that directly applies a voltage to the phosphor 10, there is no electrical restriction on the amount of rare earth or transition metal element added, and there is little adverse effect due to the presence of dislocations. Become wider. Therefore, it is easy to increase the size of one element.

<Second Embodiment>
In the first embodiment, the light emitting light source that emits blue light and the fluorescent layer that emits fluorescence of green light and red light are separated, but blue light is used as an excitation light source. In obtaining white light by emitting green light and red light, it is not an essential requirement that they are separate. In the present embodiment, a mode in which both are integrated will be described.

  FIG. 2 is a diagram schematically showing the light emitting device 101 according to the second embodiment. The light emitting device 101 according to the present embodiment is formed on the phosphor structure 110 corresponding to the phosphor 10 according to the first embodiment and on the layer above the substrate of the LED element 20 according to the first embodiment. It can be said that the corresponding diode structure 120 is formed. In other words, the light emitting device 101 functions as a light emitting element in which the phosphor structure 110 is used as a substrate and the diode structure 120 is formed thereon.

  More specifically, the light-emitting device 101 includes, for example, a low-temperature buffer layer 114, a base layer 112, a fluorescent layer 113, an n-type conductive layer 121, a light-emitting layer 122 on a substrate 111 made of sapphire single crystal. A clad layer 123 and a p-type conductive layer 124 are sequentially formed. These are the same as the substrate 11, the low-temperature buffer layer 14, the underlayer 12, the fluorescent layer 13, the n-type conductive layer 21, the light-emitting layer 22, the cladding layer 123, and the p-type conductive layer 24 according to the first embodiment, respectively. Therefore, detailed description thereof is omitted. Note that the low temperature buffer layer 114 is provided when necessary to ensure the crystallinity of the base layer 112. Similarly, a p-type electrode 125 is formed on the p-type conductive layer 124, a part of the n-type conductive layer 121 is exposed, and an n-type electrode 126 is formed on the exposed part. It is.

  In the light emitting device 101, it is preferable to form the base layer 112 by the MOCVD method and the other layers by the MBE method from the viewpoint of realizing high crystal quality, but all the layers are formed by the MOCVD method. Alternatively, all layers may be formed by the MBE method.

  Also in the present embodiment, when blue light is emitted from the light emitting layer 122 by applying a voltage between the p-type electrode 125 and the n-type electrode 126 of the diode structure 120, a part of the light is emitted from the phosphor structure. The rare earth element or the transition metal element added to the green fluorescent layer 113G and the red fluorescent layer 113R having the MQW structure as in the fluorescent layer 13 of the first embodiment is absorbed by 110 and the energy becomes excitation energy. Each is excited directly or by energy generated by recombination of carriers existing in the well layer. Thereby, fluorescence of green light (G) and red light (R) is emitted from the green fluorescent layer 113G and the red fluorescent layer 113R, respectively. The blue light emitted from the diode structure 120, the green light emitted from the phosphor structure 110, and the red light are mixed to realize white light emission.

  In addition, although a voltage is applied to the portion of the diode structure 120, but no voltage is applied to the portion of the light emitter structure 110 therebelow, there is no electrical restriction on its composition. It is the same as the form.

  Therefore, also in the light emitting device according to the present embodiment, high-luminance white light can be obtained at a low cost, as in the first embodiment. In addition, since the diode structure 120 is formed directly on the phosphor 110, a light emitting device that is smaller than the first embodiment and has high luminous efficiency can be obtained.

  In the present embodiment, a group III nitride having a blue emission efficiency is used as the light emitting layer 122 of the diode structure 120, and a substance composed of the same kind of element as the group III nitride is added to the fluorescent layer 113. By using it for the layer, a high confinement effect can be obtained. Therefore, for example, when the light emitting device is formed only by the MOCVD apparatus or only by the MBE apparatus, the phosphor structure 110 and the diode structure 120 can be continuously formed using the same kind of nitride. This is a preferable aspect in terms of simplification of the manufacturing process and cost reduction.

<Third Embodiment>
In both the first and second embodiments, blue light is used as an excitation light source and white light is obtained by obtaining fluorescence of green light and red light. However, white light is utilized using fluorescence. The mode of obtaining is not limited to these. In the present embodiment, an aspect of obtaining white light with a different configuration will be described.

  FIG. 3 is a diagram schematically showing a light emitting device 201 according to the third embodiment. A light emitting device 201 illustrated in FIG. 3 includes a phosphor 210 and an LED element 220.

The phosphor 210 has a base layer 212 and a phosphor layer 213 formed in this order on a substrate 211 made of, for example, sapphire single crystal. The substrate 211 is not only a sapphire single crystal but also a ZnO single crystal, a LiAlO ₂ single crystal, a LiGaO ₂ single crystal, a MgAl ₂ O ₄ single crystal, a MgO single crystal or other oxide single crystal, a Si single crystal, a SiC single crystal, or the like. Known substrate materials such as Group IV or IV-IV single crystals, GaAs single crystals, AlN single crystals, GaN single crystals, III-V single crystals such as AlGaN single crystals, and boride single crystals such as ZrB ₂ Can be configured. In addition, the underlayer 212 and the fluorescent layer 213 are formed by adding a predetermined group III nitride or a predetermined additive element thereto, and the specific composition of each layer depends on the purpose and function thereof. It is set appropriately. In the phosphor 210, it is preferable from the viewpoint of realizing high crystal quality that the underlayer 212 is formed by the MOCVD method and the fluorescent layer 213 is formed by the MBE method, but all layers are formed by the MOCVD method. Or all layers may be formed by the MBE method.

The underlayer 212 is a group III nitride such as AlGaN, for example. In particular, the underlayer 212 is desirably configured to have a high crystal quality such that the dislocation density is 1 × 10 ¹¹ / cm ² or less and the half-value width in the X-ray rocking curve on the (002) plane is 200 seconds or less. The thickness of the foundation layer 212 is appropriately selected in consideration of the occurrence of cracks and the use. For example, it is about several μm. In addition, since the band gap of the foundation layer 212 can be increased by using a group III nitride material containing Al, ultraviolet light emitted from the LED element 220 can be transmitted. Therefore, particularly when ultraviolet light is used as excitation light, it is desirable that the underlayer contains Al so that the band gap is equal to or greater than the band gap corresponding to the wavelength of ultraviolet light, and AlN is particularly desirable.

  The fluorescent layer 213 is composed of three types of layers as shown in an enlarged view in FIG. One is a blue fluorescent layer 213B that emits blue (B) fluorescence by absorbing predetermined energy, and the other is green (G) fluorescence by absorbing predetermined energy. The green fluorescent layer 213G is a red fluorescent layer 213R that emits red (R) fluorescence by absorbing predetermined energy.

  The blue fluorescent layer 213B is a group III nitride in which fine island-shaped crystals I1 made of rare earth or transition metal group III nitride are discretely formed and the thickness is about several nm so as to cover the island-shaped crystal I1. The structure that the cap layer C1 is formed is repeated many times (preferably several tens of times). The island-like crystal I1 is formed in a fine size such that a quantum effect appears. In other words, the blue fluorescent layer 213B has a structure in which multiple quantum dot structures in which the island-like crystals I1 act as quantum dots are stacked. The island-shaped crystal I1 and the cap layer C1 are formed of nitrides having different compositions. Specifically, an island-like crystal having a smaller band gap is formed in the cap layer C1. With such a structure, carriers are effectively confined in the island-like crystal I1. The island-shaped crystal I1 is made of, for example, GaN, InN, or GaInN, and the cap layer C1 is formed of AlN. The island-like crystal I1 has a larger lattice constant of the group III nitride constituting the island-like crystal I1 than the lattice constant of AlN constituting the base layer 212 or the cap layer C1, and the interfacial energy between the two is larger. It is formed using the big thing. Further, the island-like crystal I1 is doped with a rare earth or transition metal element that emits blue light when excited. For example, Tm is added. From another viewpoint, the blue fluorescent layer 213B has a multilayer structure in which an additive layer 2131 to which a rare earth or transition metal element is added and a non-added layer 2132 to which no additive is added are stacked. It can also be taken as.

  Regarding the green fluorescent layer 213G and the red fluorescent layer 213R, the rare earth element or transition metal element added emits red light when excited by the rare earth element or transition metal element that emits green light when excited. Each has a quantum dot structure similar to that of the blue fluorescent layer 213B, although there is a difference between rare earth elements and transition metal elements. That is, the green fluorescent layer 213G includes the island-shaped crystals I2 and the cap layer C2, and the red fluorescent layer 213R includes the island-shaped crystals I3 and the cap layer C3. The island-like crystal I2 is made of, for example, Tb or Ho added to GaN, the island-like crystal I3 is made of, for example, Eu added to GaN, and the cap layers C2 and C3 are both made of AlN. The green fluorescent layer 213G can also be regarded as a structure in which an additive layer 2133 to which a rare earth element or a transition metal element is added and a non-added layer 2134 to which no additive is added are laminated. The red fluorescent layer 213R Can also be regarded as a structure in which an additive layer 2135 to which a rare earth element or a transition metal element is added and a non-added layer 2136 to which no additive is added are laminated.

  Note that light of a desired color, for example, white light, can be emitted with high efficiency by adjusting the kind, concentration, density of island crystals, the number of layers including island crystals, and the like of the rare earth element or transition metal element to be added. It is possible.

  From the viewpoint of improving the light emission efficiency, both the island-like crystals C1 of the green phosphor layer 213G and the island-like crystals C2 of the red phosphor layer 213R have as many rare earths or transitions as possible without degrading the crystallinity. It is preferable to add a metal element. In this embodiment, since there are no electrical restrictions, the composition is less than that of the light emitting element that emits light by applying a voltage to the active layer as disclosed in Patent Document 3 and Patent Document 4. It can be said that the degree of freedom is high. That is, more rare earth elements or transition metal elements can be added than a light emitting element by voltage application, and higher issuance efficiency can be obtained.

  The LED element 220 is a PN-type semiconductor light-emitting element that emits ultraviolet light, a so-called ultraviolet light-emitting diode. The LED element 220 includes a base layer 228, an n-type conductive layer 221, a cladding layer 222, a light-emitting layer 223, and a p-type conductive layer 224 formed in this order on a substrate 227 made of, for example, sapphire. On the p-type conductive layer 224, a p-type electrode 225 made of, for example, Al / Ni is formed. A part of the n-type conductive layer 221 is exposed, and an n-type electrode 226 made of, for example, Au / Ti is formed in the exposed part. Note that as the substrate 227, a substrate material similar to that used for the phosphor 213 can be used. The underlayer 228, the n-type conductive layer 221, the cladding layer 222, the light emitting layer 223, and the p-type conductive layer 224 are formed by adding a group III nitride having a predetermined composition or a predetermined additive element thereto. However, the specific composition of each layer is appropriately set depending on the purpose and action. Each layer is formed by the MOCVD method, which is preferable from the viewpoint of realizing high crystal quality, but the MBE method may be used for forming some or all layers.

  In the present embodiment, ultraviolet light having a predetermined wavelength is emitted from the light emitting layer 223 by applying a predetermined voltage between the p-type electrode 225 and the n-type electrode 226 by a predetermined power source (not shown). In the present embodiment, the LED element 220 acts as a light emitting light source or an excitation light source as will be described later. However, the excitation light source may be other as long as the phosphor 210 can be excited. For example, the excitation light source can be an electron beam gun or an electron emitter, and the rare earth or transition metal element of the fluorescent layer 213 can be excited by electrons.

The underlayer 228 is made of, for example, AlN. In particular, the base layer 228 is desirably formed so as to have a high crystal quality such that the dislocation density is 1 × 10 ¹¹ / cm ² or less and the half-value width in the X-ray rocking curve on the (002) plane is 200 seconds or less. The thickness of the underlayer 12 is appropriately selected in consideration of the occurrence of cracks and the use. For example, it is about several μm.

The n-type conductive layer 221 is formed by adding a predetermined n-type dopant to a group III nitride. As described above, when the underlayer 228 is AlN, as the group III nitride, for example, a nitride in which the Al content with respect to all the group III elements is lower than the underlayer 228 is used. Ga and In may be included as group III elements other than Al. For example, Si is used as the dopant. In addition, B, Ge, or the like can be used. The n-type conductive layer 221 is configured to have a high crystal quality such that a dislocation density is 1 × 10 ¹¹ / cm ² or less and a half width in an X-ray rocking curve on the (002) plane is 200 seconds or less.

  For example, when the base layer 228 is AlN as described above, the cladding layer 222 is formed by adding Si to a group III nitride having a composition in which a part of Ga of the n-type conductive layer 221 is replaced with Al. Is done.

The light emitting layer 223 is formed by adding a predetermined additive element serving as an acceptor of the light emission center to the group III nitride. In the present embodiment, the light emitting layer 223 is formed by laminating several layers of first composition layers 2231 and second composition layers 2232 alternately by several nanometers, as shown in an enlarged view in FIG. . For example, the first composition layer 2231 is formed by adding Si to Al _x Ga _y In _z N (x + y + z = 1, x ≧ 0, y ≧ 0, z ≧ 0), and the second composition layer 2232 is formed of Al _x It is formed by adding Si to Ga _y N (x + y = 1, x ≧ 0, y ≧ 0). In such a case, the emission efficiency of ultraviolet light is improved by realizing an MQW structure in which the portion corresponding to the well is the first composition layer 2231 containing In.

The p-type conductive layer 224 is formed by adding a predetermined p-type dopant to a group III nitride. As the group III nitride, for example, a group III nitride having a Ga content of 50 at% or more with respect to all group III elements is used. Al and In may be included as group III elements other than Ga. As the dopant, for example, Mg is used. In addition, Zn, Be, or the like can be used. The p-type conductive layer 224 is formed with a thickness of about several hundred nm. The p-type conductive layer 224 is configured to have a high crystal quality such that the dislocation density is 1 × 10 ¹¹ / cm ² or less and the half width in the X-ray rocking curve on the (002) plane is 200 seconds or less. The carrier density needs to be 1 × 10 ¹⁶ / cm ³ or more, and more preferably 1 × 10 ¹⁷ / cm ³ or more. Thereby, a voltage drop in the p-type conductive layer 224 can be suppressed, and a voltage can be efficiently applied to the light emitting layer 223 to improve light emission efficiency.

  In the light emitting device 201 according to the present embodiment, when a predetermined voltage is applied and the LED element 220 emits ultraviolet light (UV), a part thereof is absorbed by the phosphor 210, and the energy is excited energy. Thus, the rare earth or transition metal element added to the island-like crystals C1, C2 and C3 is respectively excited, and light emission having a specific wavelength occurs. In addition to this, the energy generated by the recombination of carriers such as electrons or holes confined in the island-like crystals C1, C2 and C3, which are quantum dots, by obtaining energy by ultraviolet light (UV) is also rare earth or transition. Since the metal element is excited, light emission is caused by such a process as well. As a result, the fluorescence of blue light (B), green light (G), and red light (R) is high emission from the rare earth or transition metal blue fluorescent layer 213B, green fluorescent layer 213G, and red fluorescent layer 213R, respectively. It will be emitted with efficiency. The blue light, green light, and red light emitted from the phosphors 210 are mixed to realize white light emission.

  As a result, light emission of white light by three-color mixing, which has better color developability than two-color mixing, is realized by a combination of one LED chip and one phosphor that is less expensive than using three-color LED chips. And high brightness white light can be obtained.

  In addition, by using other rare earth elements or transition metal elements as elements to be added to the fluorescent layer, or by using the LED elements 220 that emit different colors, the color combination is different, so that only white light is emitted. It is also possible to realize light emission of any color. Alternatively, the fluorescent layer 213 may be formed of a layer that emits four or more colors.

  In addition, unlike a light emitting element that directly applies a voltage to the phosphor 210, there is no electrical restriction on the amount of rare earth or transition metal element added, and there is little adverse effect due to the presence of dislocations. Become wider. Therefore, it is easy to increase the size of one element.

<Fourth embodiment>
In the third embodiment, the emission light source that emits ultraviolet light and the fluorescent layer that emits blue, green, and red fluorescence are separated, but the ultraviolet light is excited. In order to obtain white light by emitting blue light, green light, and red light as light sources, it is not an essential requirement that they are separate. In the present embodiment, a mode in which both are integrated will be described.

  FIG. 4 is a diagram schematically showing a light emitting device 301 according to the fourth embodiment. The light emitting device 301 according to the present embodiment is formed on the phosphor structure 310 corresponding to the phosphor 210 according to the second embodiment, and on a layer above the substrate of the LED element 220 according to the second embodiment. It can be said that the corresponding diode structure 320 is formed. In other words, the light emitting device 301 functions as a light emitting element in which the phosphor structure 310 is used as a substrate and the diode structure 320 is formed thereon.

  More specifically, the light emitting device 301 includes, for example, a base layer 312, a fluorescent layer 313, an n-type conductive layer 321, a cladding layer 322, a light emitting layer 323, p on a substrate 311 made of sapphire single crystal. A type conductive layer 324 is sequentially formed. These have the same composition and structure as the substrate 211, the base layer 212, the fluorescent layer 213, the n-type conductive layer 221, the cladding layer 222, the light-emitting layer 223, and the p-type conductive layer 224 according to the third embodiment, respectively. Therefore, detailed description thereof is omitted. Similarly, a p-type electrode 325 is formed on the p-type conductive layer 324, a part of the n-type conductive layer 321 is exposed, and an n-type electrode 326 is formed on the exposed part. It is.

  In the light emitting device 301, it is preferable to form the base layer 312 by the MOCVD method and the other layers by the MBE method from the viewpoint of realizing high crystal quality, but all the layers are formed by the MOCVD method. Alternatively, all layers may be formed by the MBE method.

  Also in the present embodiment, when a voltage is applied between the p-type electrode 325 and the n-type electrode 326 of the diode structure 320 and ultraviolet light is emitted from the light emitting layer 323, a part of the phosphor structure is formed. The energy is absorbed by 310, and the energy becomes excitation energy, and is added to the blue fluorescent layer 313B, the green fluorescent layer 313G, and the red fluorescent layer 313R having the quantum dot structure similarly to the fluorescent layer 213 of the third embodiment. The rare earth element or transition metal element is excited directly or by energy generated by recombination of carriers existing in the well layer. Thereby, fluorescence of blue light (B), green light (G), and red light (R) is emitted from the blue fluorescent layer 313B, the green fluorescent layer 313G, and the red fluorescent layer 313R, respectively. The ultraviolet light emitted from the diode structure 320 and the blue light, the green light, and the red light emitted from the phosphor structure 310 are mixed to realize white light emission.

  In addition, although a voltage is applied to the portion of the diode structure 320, but no voltage is applied to the portion of the light emitter structure 310 below it, there is no electrical restriction on its composition. It is the same as the form.

  Therefore, also in the light emitting device according to the present embodiment, high-luminance white light can be obtained at low cost, as in the third embodiment. In addition, since the light emitting diode is formed directly on the phosphor, a light emitting device that is smaller than the third embodiment and has high luminous efficiency can be obtained.

  In this embodiment mode, a group III nitride having a high ultraviolet emission efficiency is used as the light emitting layer 323 of the diode structure 320, and a substance composed of the same kind of element as the group III nitride is added to the fluorescent layer 313. By using it for the layer, a high confinement effect can be obtained. Therefore, for example, when the light emitting device is formed only by the MOCVD apparatus or only by the MBE apparatus, the phosphor structure 310 and the diode structure 320 can be continuously formed using the same kind of nitride. This is a preferable aspect in terms of simplification of the manufacturing process and cost reduction.

<Fifth embodiment>
In the third and fourth embodiments, white light is obtained using ultraviolet light as an excitation light source. However, in order to realize such an aspect, it is an essential requirement that each color fluorescent layer has a quantum dot structure. In addition, white light can be obtained in the same manner even in the aspect having the MQW structure as in the first and second embodiments. In this embodiment, such an aspect will be described, and a diode structure different from the above embodiment will be described together.

  FIG. 5 is a diagram schematically showing a light emitting device 401 according to the fourth embodiment. It can be said that the light emitting device 401 according to the present embodiment is obtained by forming the diode structure 420 on the phosphor structure 410 as in the fourth embodiment. In other words, the light emitting device 401 functions as a light emitting element in which the phosphor structure 410 is used as a substrate and the diode structure 420 is formed thereon.

  More specifically, the light emitting device 401 includes, for example, a base layer 412, a fluorescent layer 413, an n-type conductive layer 421, a cladding layer 422, a light emitting layer 423, and a p on a substrate 411 made of sapphire single crystal. A type conductive layer 424 is sequentially formed. The specific composition of each layer is appropriately set depending on the purpose and action. Since the substrate 411 and the base layer 412 have the same composition and structure as the substrate 211 and the base layer 212 according to the third embodiment, detailed description thereof is omitted. Similarly, a p-type electrode 425 is formed on the p-type conductive layer 424, a part of the n-type conductive layer 421 is exposed, and an n-type electrode 426 is formed in the exposed part. It is.

  In the light emitting device 401, it is preferable from the viewpoint of realizing high crystal quality that the base layer 412 is formed by the MOCVD method and the other layers are formed by the MBE method, but all layers are formed by the MOCVD method. Alternatively, all layers may be formed by the MBE method.

  The fluorescent layer 413 is composed of three types of layers as shown in an enlarged view in FIG. One is a blue fluorescent layer 413B that emits blue (B) fluorescence by absorbing predetermined energy, and the other is green (G) fluorescence by absorbing predetermined energy. The green fluorescent layer 413G is a red fluorescent layer 413R that emits red (R) fluorescence by absorbing predetermined energy.

  The blue fluorescent layer 413B is composed of an added layer 4131 to which a rare earth or transition metal element that emits green light when excited by a group III nitride is added, and a non-added layer 4132 to which such an addition is not made are several nanometers each. The layers are alternately stacked (preferably several tens of layers).

  In the green fluorescent layer 413G, an additive layer 4133 in which a rare earth or transition metal element that emits green light when excited by a group III nitride is added, and a non-added layer 4134 to which such an additive is not added are several nanometers each. The layers are alternately stacked (preferably several tens of layers).

  In the red fluorescent layer 413R, a Group III nitride is added with an additive layer 4135 to which a rare earth element or a transition metal element that emits red light when excited is added, and a non-added layer 4136 without such addition is several nanometers each. The layers are alternately stacked (preferably several tens of layers).

  The additive layers 4131, 4133, and 4135 are formed of a nitride having a composition different from that of the non-additive layers 4132, 4134, and 4136, respectively. That is, in the green fluorescent layer 413G and the red fluorescent layer 413R, MQW (Multi Quantum Well) in which well layers and barrier layers having wider bands are alternately deposited by alternately changing the composition of nitrides. Quantum well) structure is realized.

  Here, the rare earth element or the transition metal element is added in order to obtain light having a desired wavelength while increasing the luminous efficiency. Rare earths or transition metal elements have their own emission wavelengths with respect to external excitation such as light or electron beams. By adding an appropriate amount of a plurality of rare earth elements or transition metal elements, light having an arbitrary color, for example, white light can be emitted. Further, the rare earth element or the transition metal element can be dissolved in the nitride without causing trouble in the light emission mechanism.

In the case where the base layer 411 is formed of AlN, the additive layer 4131 in the blue fluorescent layer 413B is, for example, added Tm to Al _x Ga _y N (x + y = 1, x ≧ 0, y ≧ 0). The non-added layer 4132 is formed of AlN. In the green fluorescent layer 413G, the additive layer 4133 is formed, for example, by adding Tb or Ho to Al _x Ga _y N (x + y = 1, x ≧ 0, y ≧ 0), and the non-added layer 4132 is made of AlN. It is formed. In the red fluorescent layer 413R, the addition layer 4133 is formed by adding Eu to Al _x Ga _y N (x + y = 1, x ≧ 0, y ≧ 0), and the non-addition layer 4134 is formed of AlN. That is, in the present embodiment, all of the blue fluorescent layer 413B, the green fluorescent layer 413G, and the red fluorescent layer 413R are formed on the basis of AlN or Al _x Ga _y N. Although it is possible to form the fluorescent layers of the respective colors with substances made of completely different kinds of elements, it is more costly to form a layer with a base substance in common as in this embodiment. Needless to say, this is also efficient in terms of production time. In the case of the present embodiment, the luminous efficiency is expected to be improved by including Al in the fluorescent layer 413.

  The n-type conductive layer 421 is formed by adding a predetermined n-type dopant to a group III nitride. As the group III nitride, for example, a group III nitride having an Al content of about 50 at% with respect to all group III elements is used. Ga and In may be included as group III elements other than Al. For example, Si is used as the dopant. In addition, B, Ge, or the like can be used.

  The cladding layer 422 is formed, for example, by adding Si to a group III nitride having a composition in which a part of Ga of the n-type conductive layer 421 is replaced with Al.

The light-emitting layer 423 is formed by adding a predetermined additive element that serves as an acceptor of a light emission center to a group III nitride. In this embodiment mode, the light emitting layer 423 is formed by laminating several layers of first composition layers 4231 and second composition layers 4232 alternately by several nanometers, as shown in an enlarged manner in FIG. . For example, the first composition layer 4231 is formed by adding Si to Al _x Ga _y In _z N (x + y + z = 1, x ≧ 0, y ≧ 0, z ≧ 0), and the second composition layer 4232 is formed of Al _x It is formed by adding Si to Ga _y N (x + y = 1, x ≧ 0, y ≧ 0). In such a case, the emission efficiency of ultraviolet light is improved by realizing an MQW structure in which the portion corresponding to the well is the first composition layer 4231 containing In.

  In the p-type conductive layer 424, a large number (preferably, an addition layer 4241 in which a predetermined p-type dopant is added to a group III nitride and a non-addition layer 4242 to which such addition is not performed are alternately arranged by several nm. Is a layer formed by stacking several tens of layers. That is, in the light emitting device 401 according to this embodiment, the p-type conductive layer 424 has such a stacked structure, thereby realizing an MQW structure in which the additive layer 4231 is a well layer.

  As the additive layer 4241, for example, a group III nitride having an Al content of 50 at% or more with respect to all group III elements is used. Ga and In may be included as group III elements other than Al. As the dopant, for example, Mg is used. In addition, Zn, Be, or the like can be used. As the non-addition layer 4242, a group III nitride having a lower Al ratio than the addition layer 4241 is used.

  Note that forming the p-type conductive layer 424 in the MQW structure has a higher resistance value of the p-type electrode 424 when forming a group III nitride semiconductor containing much Al than when forming a simple single-layer film. This is effective in that it can be reduced.

  Also in the present embodiment, when a voltage is applied between the p-type electrode 425 and the n-type electrode 426 of the diode structure 420 and ultraviolet light is emitted from the light emitting layer 423, a part of the phosphor structure is formed. The energy is absorbed by 410, and the energy becomes excitation energy to excite the rare earth or transition metal element added to the additive layers 4131, 4133, and 4135, respectively, and light emission having a specific wavelength occurs. In addition to this, energy generated by recombination of carriers such as electrons or holes confined in the additive layers 4131, 4133, and 4135, which are well layers having the MQW structure described above, by obtaining energy by ultraviolet light (UV). However, since the rare earth element or the transition metal element is excited, light emission is similarly generated by such a process. As a result, blue light (B), green light (G), and red light (R) are emitted from the rare earth or transition metal blue fluorescent layer 413B, the green fluorescent layer 413G, and the red fluorescent layer 413R, respectively. The ultraviolet light emitted from the diode structure 420 and the blue light, the green light, and the red light emitted from the phosphor structure 410 are mixed to realize white light emission.

  Therefore, also in the light emitting device according to this embodiment, high-intensity white light can be obtained at low cost.

<Sixth Embodiment>
Even if it is not a phosphor (structure) having an MQW structure or a quantum dot structure as described in the above embodiment, light emission of multicolor light is realized. In the present embodiment, a mode in which, for example, white light is obtained as multicolor light with a simpler structure will be described.

  FIG. 6 is a diagram schematically showing a light emitting device 1001 according to the sixth embodiment. The light emitting device 1001 according to the present embodiment has a structure similar to the light emitting device 101 according to the second embodiment. That is, the diode structure 1020 is formed on the phosphor structure 1110.

  More specifically, the light-emitting device 1001 includes, for example, a low-temperature buffer layer 1014, an underlayer 1012, a fluorescent layer 1013, an n-type conductive layer 1021, a light-emitting layer 1022, and a substrate 1011 made of sapphire single crystal. A clad layer 1023 and a p-type conductive layer 1024 are sequentially formed. These layers, except for the fluorescent layer 1013, are the substrate 111, the low-temperature buffer layer 114, the base layer 112, the n-type conductive layer 121, the light emitting layer 12223, the cladding layer 12322, and the p-type conductive layer 124, respectively, according to the second embodiment. Therefore, the detailed description thereof is omitted. Note that the low-temperature buffer layer 1014 is provided when necessary to ensure the crystallinity of the base layer 1012. Similarly, a p-type electrode 1025 is formed on the p-type conductive layer 1024, a part of the n-type conductive layer 1021 is exposed, and an n-type electrode 1026 is formed on the exposed part. It is.

The fluorescent layer 1013 includes a rare earth or transition metal element that emits green (G) fluorescence when excited by a nitride, and a rare earth or transition metal element that emits red (R) fluorescence when excited by the nitride. It is added. Preferably, each rare earth element or transition metal element is added so as to be dispersed finely and uniformly. The fluorescent layer 1013 is formed of, for example, Tb or Ho as a rare earth element or a transition metal element that emits green (G) fluorescence in Ga _x In _y N (x + y = 1, x ≧ 0, y ≧ 0), and red (R). It is formed by adding Eu as a rare earth or transition metal element that emits fluorescence.

  In the light emitting device 1001, it is preferable to form the base layer 1012 by the MOCVD method and the other layers by the MBE method from the viewpoint of realizing high crystal quality, but all the layers are formed by the MOCVD method. Alternatively, all layers may be formed by the MBE method.

  In this embodiment mode, when blue light is emitted from the light emitting layer 1022 by applying a voltage between the p-type electrode 1025 and the n-type electrode 1026 of the diode structure 1020, a part of the light is emitted from the phosphor structure. Absorbed by 1010, the energy becomes excitation energy, and the rare earth element or transition metal element added to the fluorescent layer 1013 is excited directly or by energy generated by recombination of carriers existing in the well layer. Thereby, the fluorescent layer 113 emits fluorescence of green light (G) and red light (R). However, since the rare earth elements or transition metal elements emitting the respective colors are finely and uniformly dispersed, apparently yellow light that is mixed light of both is emitted. The blue light emitted from the diode structure 1020 and the yellow light composed of the green light and the red light emitted from the phosphor structure 1010 are mixed to realize white light emission.

  A voltage is applied to the diode structure 1020, but no voltage is applied to the light emitter structure 1010 below, so that there is no electrical restriction on the composition of the second embodiment. It is the same as the form.

  Therefore, in the light emitting device according to this embodiment, white light with high luminance can be obtained with a simpler structure. Of course, by using other rare earth elements or transition metal elements as elements to be added to the fluorescent layer 1013, or by forming a diode structure 1020 that emits different colors, the color combinations can be made different. Not only light but also light emission of any color can be realized. Needless to say, when only one rare earth or transition metal element is added, light emission specific to the rare earth or transition metal element occurs. Further, a mode in which a corresponding type of rare earth or transition metal element is added so as to emit three or more colors from the fluorescent layer 1013 may be used.

Example 1
In this example, the light emitting device 1 shown in FIG. 1 was produced. First, in producing the phosphor 10, a C-plane sapphire single crystal having a diameter of 2 inches and a thickness of 500 μm was used as the substrate 11, and this was placed in a reaction vessel of a predetermined MOCVD apparatus. In the MOCVD apparatus, at least H ₂ , N ₂ , TMG (trimethyl gallium) and NH ₃ can be supplied into the reaction tube as a reaction gas or a carrier gas. After setting the pressure in the reaction tube to 100 Torr, the substrate 11 was heated to 1100 ° C. while H ₂ was flowed at an average flow rate of 1 m / sec.

Then, after raising the temperature to 500 ° C. once, TMA and NH ₃ are supplied, and after forming the low temperature buffer layer 14 of AlN to a thickness of 20 nm, the temperature is raised again to 1100 ° C., and TMG, NH ₃ and And a 2 μm-thick GaN layer was formed as the underlayer 12. At this time, the supply amounts of TMA and NH ₃ were set so that the film formation rate was 0.3 μm / hr. The dislocation density in the GaN layer was observed by TEM (transmission electron microscope) and found to be 1 × 10 ¹⁰ / cm ² . Further, when the X-ray rocking curve of the (002) plane of GaN was measured, the half-value width was 60 seconds, and the surface roughness (Ra) obtained by AFM (atomic force microscope) was 1.5 mm or less. It was. That is, it was confirmed that the underlayer 12 made of GaN has good crystal quality.

Subsequently, in order to protect the grown GaN layer, TMG and NH ₃ were flowed at an average flow rate of 10 m / sec to grow a GaN film with a thickness of 10 nm.

  After the growth was completed, the film-formed substrate was taken out and placed in a predetermined MBE apparatus. The MBE apparatus used 7N Ga, 7N In, and 6N Al as solid sources. Further, atomic nitrogen generated by a predetermined high-frequency plasma apparatus was used as the nitrogen source. A solid source of 3N Tb and Eu was provided for addition to form the fluorescent layer, respectively.

First, after heating the substrate to 900 ° C., the GaN film that was the protective layer was removed by flowing H ₂ .

Subsequently, Ga _0.75 In _0.25 N was formed to a thickness of 2 nm at 600 ° C. on the GaN foundation layer 12 to form the additive layer 131 of the green fluorescent layer 13G. At that time, Tb was doped at the same time. Further, as the non-added layer 132, GaN was formed to a thickness of 2 nm. The formation of the additive layer 131 and the non-added layer 132 was repeated alternately so that there were 30 layers each.

Similarly, Ga _0.75 In _0.25 N was formed to a thickness of 2 nm at 600 ° C. in order to form the additive layer 133 of the red fluorescent layer 13R. At that time, Eu was simultaneously doped. Further, as the non-added layer 134, GaN was formed to a thickness of 2 nm. The formation of the additive layer 133 and the non-added layer 134 was repeated alternately so that there were 20 layers each.

On the other hand, in the production of the LED element 20, a C-plane sapphire single crystal having a diameter of 2 inches and a thickness of 500 μm was used as the substrate 27, and this was placed in a reaction vessel of a predetermined MOCVD apparatus. The MOCVD apparatus can supply at least H ₂ , N ₂ , TMA (trimethylaluminum), TMG, TMI (trimethylindium), Cp ₂ Mg, NH ₃ , and SiH ₄ as reaction gas or carrier gas into the reaction tube. Has been. After setting the pressure in the reaction tube to 100 Torr, the substrate 27 was heated to 1100 ° C. while H ₂ was allowed to flow at an average flow rate of 1 m / sec.

Thereafter, TMG, NH ₃ and SiH ₄ were supplied to form a Si-doped GaN layer with a thickness of 2 μm as the n-type conductive layer 21. At this time, the supply amounts of TMG and NH ₃ were set so that the film formation rate was 0.3 μm / hr. When the dislocation density in the GaN layer was observed by TEM, it was 1 × 10 ¹⁰ / cm ² . Further, when the X-ray rocking curve of the (002) plane of GaN was measured, the half width was 60 seconds, and the surface roughness (Ra) determined by AFM was 1.5 mm or less. That is, it was confirmed that the n-type conductive layer 21 has good crystal quality.

Next, TMG, TMI, and NH ₃ were supplied to form Ga _0.8 In _0.2 N with a thickness of 2.5 μm as the light emitting layer 22.

Further, TMG, TMA, NH _3, and Cp ₂ Mg were supplied to form an Mg _0.1- doped Al _0.1 Ga _0.9 N layer with a thickness of 30 nm as the cladding layer 23.

Subsequently, TMG, NH _3, and Cp ₂ Mg were supplied, and a Mg-doped GaN layer was formed to a thickness of 0.2 μm as the p-type conductive layer 24. Next, N ₂ gas was introduced and maintained at 750 ° C. for 1 hour, and the p-type conductive layer 24 was activated.

  Thereafter, the light emitting layer 22, the clad layer 23, and the p-type conductive layer 24 are partially etched away by a predetermined etching process to expose a part of the Si-doped GaN layer constituting the n-type conductive layer 21, An n-type electrode 26 made of Al / Ti was formed on the exposed portion. A p-type electrode 25 made of Au / Ni was formed on the Mg-doped GaN layer constituting the p-type conductive layer 24.

  When a voltage was applied to the obtained LED element 20 between the Au / Ni electrode and the Al / Ti electrode, the LED element 20 was confirmed to emit blue light.

  Then, when such blue light was incident on the phosphor 10, emission of green light and red light was confirmed. Moreover, after arrange | positioning the fluorescent substance 10 and the LED element 20 in the predetermined arrangement | positioning relationship, light emission of white light was confirmed by applying a voltage between an Au / Ni electrode and an Al / Ti electrode.

(Example 2)
In this example, the light emitting device 101 shown in FIG. 2 was manufactured. First, the phosphor structure 110 was produced in the same manner as the phosphor 10 of Example 1 using an MOCVD apparatus and an MBE apparatus.

  Subsequently, the diode structure 120 was fabricated on the phosphor structure 110 in the MBE apparatus. In this embodiment, in addition to the solid source necessary for manufacturing the phosphor structure 110, the MBE apparatus includes a solid source of Si and Mg as dopant sources as a solid source necessary for manufacturing the diode structure 120. Prepared.

  The diode structure 120 was formed by first forming a Si-doped GaN layer as an n-type conductive layer 121 on the phosphor layer 113 at 600 ° C. to a thickness of 2 μm. Next, the light emitting layer 122 was formed to a thickness of 2.5 μm at 600 ° C. Further, an Al0.1Ga0.9N layer doped with Mg was formed to a thickness of 30 nm as the cladding layer 123 at 600 ° C. Subsequently, a GaN layer doped with Mg was formed to a thickness of 0.2 μm as the p-type conductive layer 124 at 600 ° C.

  Thereafter, a part of the Si-doped GaN layer constituting the n-type conductive layer 121 is exposed by partially removing the light emitting layer 122, the cladding layer 123, and the p-type conductive layer 124 by a predetermined etching process. An n-type electrode 126 made of Al / Ti was formed on the exposed portion. A p-type electrode 125 made of Au / Ni was formed on the Mg-doped GaN layer constituting the p-type conductive layer 124.

  When a voltage was applied to the obtained light emitting device 101 between the Au / Ni electrode and the Al / Ti electrode, white light emission was confirmed.

(Example 3)
In this example, the light emitting device 201 shown in FIG. 3 was manufactured. First, in manufacturing the phosphor 210, a C-plane sapphire single crystal having a diameter of 2 inches and a thickness of 500 μm was used as the substrate 211, and this was placed in a reaction vessel of a predetermined MOCVD apparatus. The MOCVD apparatus can supply at least H ₂ , N ₂ , TMA, TMG, and NH ₃ as reaction gas or carrier gas into the reaction tube. After setting the pressure in the reaction tube to 100 Torr, the temperature of the substrate 211 was raised to 1100 ° C. while flowing H 2 at an average flow rate of 1 m / sec.

Thereafter, TMA and NH 3 were supplied to form an AlN layer having a thickness of 1 μm as the base layer 212. At this time, the supply amounts of TMA and NH 3 were set so that the film formation rate was 0.3 μm / hr. When the dislocation density in the AlN layer was observed by TEM, it was 1 × 10 ¹⁰ / cm ² . Further, when the X-ray rocking curve of the (002) plane of GaN was measured, the half width was 60 seconds, and the surface roughness (Ra) determined by AFM was 1.5 mm or less. That is, it was confirmed that the base layer 212 made of AlN has good crystal quality.

Subsequently, in order to protect the grown AlN layer, TMG and NH ₃ were flowed at an average flow rate of 10 m / sec to grow a GaN film with a thickness of 10 nm.

  After the growth was completed, the film-formed substrate was taken out and placed in a predetermined MBE apparatus. The MBE apparatus used 7N Ga, 7N In, and 6N Al as solid sources. Further, atomic nitrogen generated by a predetermined high-frequency plasma apparatus was used as the nitrogen source. Solid sources of 3N Tm, Tb, and Eu were provided for addition to form the fluorescent layer, respectively.

  First, the substrate was heated to 900 ° C., and then the GaN film serving as the protective layer was removed by flowing H 2.

  Subsequently, an island-like crystal I1 formed by doping Tm with GaN at 600 ° C. was formed on the AlN underlayer 212 at a thickness of 2 nm and a horizontal diameter of 20 nm. Further, AlN was formed to a thickness of 3 nm as the cap layer C1 so as to embed the island crystal I1. This corresponds to the formation of the addition layer 2131 having a thickness of 2 nm and the non-addition layer 2132 having a thickness of 1 nm. The formation of the island crystal I1 and the cap layer C1 was repeated 40 times.

  Similarly, at 600 ° C., the formation of the island-like crystal I2 in which GaN is doped with Tb and the cap layer C2 of AlN is repeated 30 times for the green fluorescent layer 213G, and the red fluorescent layer 213R is formed of the GaN The formation of the island-like crystal I3 doped with Eu and the cap layer C2 of AlN was repeated 20 times.

On the other hand, in manufacturing the LED element 220, a C-plane sapphire single crystal having a diameter of 2 inches and a thickness of 500 μm was used as the substrate 227, and this was placed in a reaction vessel of a predetermined MOCVD apparatus. The MOCVD apparatus can supply at least H ₂ , N ₂ , TMA, TMG, TMI, Cp ₂ Mg, NH ₃ , and SiH ₄ as reaction gas or carrier gas into the reaction tube. After setting the pressure in the reaction tube to 100 Torr, the substrate 11 was heated to 1100 ° C. while H ₂ was flowed at an average flow rate of 1 m / sec.

First, an AlN layer having a thickness of 1 μm was formed as the base layer 228. At this time, the supply amounts of TMA and NH ₃ were set so that the film formation rate was 0.3 μm / hr.

Thereafter, TMA, TMG, NH _3, and SiH ₄ were supplied to form an Si _0.3- doped Al _0.3 Ga _0.7 N layer having a thickness of 2 μm as the n-type conductive layer 221.

Subsequently, an Al _0.4 Ga _0.6 N layer doped with Si was formed to a thickness of 20 nm as the cladding layer 22.

Next, in order to form the first composition layer 2231, a Si-doped Al _0.2 Ga _0.78 In _0.02 N layer was formed to a thickness of 2.5 nm. Further, an Al _0.25 Ga _0.75 N layer doped with Si was formed to a thickness of 2.5 nm as the second composition layer 2232. The formation of the first composition layer 2231 and the second composition layer 2232 was repeated alternately so that there were five layers each.

Subsequently, TMA, TMG, NH ₃ and Cp ₂ Mg were supplied to form an Mg _0.3- doped Al _0.3 Ga _0.7 N layer with a thickness of 0.1 μm as the p-type conductive layer 224. . Next, N 2 gas was introduced and maintained at 750 ° C. for 1 hour, and the p-type conductive layer 224 was activated.

  Thereafter, the cladding layer 222, the light emitting layer 223, and the p-type conductive layer 224 are partially etched away by a predetermined etching process to expose a part of the n-type conductive layer 221, and Al is exposed to the exposed portion. An n-type electrode 226 made of / Ti was formed. A p-type electrode 225 made of Au / Ni was formed on the p-type conductive layer 224.

  When a voltage was applied to the obtained LED element 220 between the Au / Ni electrode and the Al / Ti electrode, the LED element 220 was confirmed to emit blue light.

  Then, when such blue light was made incident on the phosphor 210, emission of green light and red light was confirmed. Moreover, after arrange | positioning the fluorescent substance 210 and the LED element 220 in the predetermined arrangement | positioning relationship, the light emission of white light was confirmed by applying a voltage between an Au / Ni electrode and an Al / Ti electrode.

Example 4
In this example, a light emitting device 301 shown in FIG. 4 was manufactured. First, the phosphor structure 310 was produced in the same manner as the phosphor 210 of Example 3 using an MOCVD apparatus and an MBE apparatus.

  Subsequently, a diode structure 320 was formed on the phosphor structure 310 in the MBE apparatus. In this embodiment, the MBE apparatus includes a solid source necessary for manufacturing the phosphor structure 310, a solid source necessary for manufacturing the diode structure 320, and a solid source of In, Si, and Mg as a dopant source. Prepared the source.

The diode structure 320 was formed by first forming a Si-doped Al _0.3 Ga _0.7 N layer having a thickness of 2 μm as an n-type conductive layer 321 on the fluorescent layer 313 at 600 ° C. Subsequently, an Al _0.4 Ga _0.6 N layer doped with Si was formed to a thickness of 20 nm as a clad layer 322 at 600 ° C.

Next, an Si _0.2 doped Al _0.2 Ga _0.78 In _0.02 N layer was formed to a thickness of 2.5 nm at 600 ° C. to form the first composition layer 3231 of the light emitting layer 323. Further, an Al _0.25 Ga _0.75 N layer doped with Si was formed to a thickness of 2.5 nm as the second composition layer 3232. The formation of the first composition layer 3231 and the second composition layer 3232 was repeated alternately so that there were five layers each.

Subsequently, an Al _0.3 Ga _0.7 N layer doped with Mg was formed to a thickness of 0.1 μm as the p-type conductive layer 324 at 600 ° C.

  Thereafter, the light emitting layer 322, the cladding layer 323, and the p-type conductive layer 324 are partially etched away by a predetermined etching process to expose a part of the n-type conductive layer 321 and Al is exposed to the exposed portion. An n-type electrode 326 made of / Ti was formed. A p-type electrode 325 made of Au / Ni was formed on the p-type conductive layer 324.

  When a voltage was applied to the obtained light emitting device 301 between the Au / Ni electrode and the Al / Ti electrode, emission of white light was confirmed.

(Example 5)
In this example, a light emitting device 401 shown in FIG. 5 was manufactured. First, a 2-inch diameter C-plane sapphire single crystal having a diameter of 2 inches was used as the substrate 411, and this was placed in a reaction vessel of a predetermined MOCVD apparatus. The MOCVD apparatus can supply at least H ₂ , N ₂ , TMA, TMG, and NH ₃ as reaction gas or carrier gas into the reaction tube. After setting the pressure in the reaction tube to 100 Torr, the temperature of the substrate 411 was raised to 1100 ° C. while flowing H 2 at an average flow rate of 1 m / sec.

Thereafter, TMA and NH ₃ were supplied to form an AlN layer having a thickness of 1 μm as the base layer 412. At this time, the supply amounts of TMA and NH ₃ were set so that the film formation rate was 0.3 μm / hr. When the dislocation density in the AlN layer was observed by TEM, it was 1 × 10 ¹⁰ / cm ² . Further, when the X-ray rocking curve of the (002) plane of GaN was measured, the half width was 60 seconds, and the surface roughness (Ra) determined by AFM was 1.5 mm or less. That is, it was confirmed that the underlayer 412 made of AlN has a good crystal quality.

Subsequently, in order to protect the grown AlN layer, TMG and NH ₃ were flowed at an average flow rate of 10 m / sec to grow a GaN film with a thickness of 10 nm.

  After the growth was completed, the film-formed substrate was taken out and placed in a predetermined MBE apparatus. The MBE apparatus used 7N Ga, 7N In, and 6N Al as solid sources. Further, atomic nitrogen generated by a predetermined high-frequency plasma apparatus was used as the nitrogen source. Solid sources of 3N Tm, Tb, and Eu were provided for addition to form the fluorescent layer, respectively. Furthermore, a solid source of Si and Mg was provided as a dopant source.

  First, the substrate was heated to 900 ° C., and then the GaN film serving as the protective layer was removed by flowing H 2.

Subsequently, Al _0.3 Ga _0.7 N was formed to a thickness of 3 nm at 600 ° C. on the AlN base layer 412 to form the additive layer 4131 of the blue fluorescent layer 413B. At that time, Tm was doped at the same time. Further, AlN was formed to a thickness of 3 nm as the non-added layer 4132. The additive layer 4131 and the non-added layer 4132 were formed alternately and repeatedly so that there were 40 layers each.

Similarly, Al _0.3 Ga _0.7 N was formed to a thickness of 3 nm at 600 ° C. in order to form the additive layer 4133 of the green fluorescent layer 413G. At that time, Tb was doped at the same time. Further, AlN was formed to a thickness of 3 nm as the non-added layer 4134. The formation of the additive layer 4133 and the non-added layer 4134 was repeated alternately so that there were 30 layers each.

Similarly, Al _0.3 Ga _0.7 N was formed to a thickness of 3 nm at 600 ° C. in order to form the additive layer 4135 of the red fluorescent layer 413R. At that time, Eu was simultaneously doped. Further, AlN was formed to a thickness of 3 nm as the non-added layer 4135. The formation of the additive layer 4135 and the non-added layer 4136 was repeated alternately so that there were 20 layers each.

Furthermore, an Al _0.5 Ga _0.5 layer doped with Si was formed to a thickness of 2 μm as the n-type conductive layer 421 at 600 ° C. Subsequently, an Al _0.48 Ga _0.52 N layer doped with Si was formed to a thickness of 20 nm as the cladding layer 422 at 600 ° C.

Next, an Al _0.4 Ga _0.58 In _0.02 N layer doped with Si was formed to a thickness of 2.5 nm at 600 ° C. to form the first composition layer 4231 of the light emitting layer 423. Further, an Al _0.45 Ga _0.55 N layer doped with Si was formed to a thickness of 2.5 nm as the second composition layer 4232 at 600 ° C. The formation of the first composition layer 4231 and the second composition layer 4232 was repeated alternately so that there were 10 layers each. Note that the light-emitting layer 423 having such a composition emits ultraviolet light having a shorter wavelength than the light-emitting layer 323 having the composition illustrated in Example 4.

Subsequently, to form the p-type conductive layer 424, an Al _0.5 Ga _0.5 N layer doped with Mg is formed to a thickness of 2.5 nm as the additive layer 4241 at 600 ° C., and then the non-added layer As 4242, an Al _0.48 Ga _0.52 N layer was formed to a thickness of 2.5 nm at 600 ° C. The formation of the additive layer 4241 and the non-added layer 4242 was repeated so that there were 100 layers each.

  Thereafter, the cladding layer 422, the light emitting layer 423, and the p-type conductive layer 424 are partially etched away by a predetermined etching process to expose a part of the n-type conductive layer 221, and the exposed portion is exposed to Al. An n-type electrode 426 made of / Ti was formed. A p-type electrode 425 made of Au / Ni was formed on the p-type conductive layer 224.

  When a voltage was applied to the obtained light emitting device 401 between the Au / Ni electrode and the Al / Ti electrode, emission of white light was confirmed.

(Example 6)
In this example, a light emitting device 1001 shown in FIG. 6 was manufactured. First, with respect to the phosphor structure 1010, a buffer layer 1014 made of AlN and an underlayer 1012 made of GaN were produced using the MOCVD apparatus in the same manner as the phosphor 10 of Example 1. Subsequently, in order to protect the grown GaN layer, TMG and NH3 were flowed at an average flow rate of 10 m / sec to grow a GaN film to a thickness of 10 nm.

  After the growth was completed, the film-formed substrate was taken out and placed in a predetermined MBE apparatus. The MBE apparatus used 7N Ga, 7N In, and 6N Al as solid sources. Further, atomic nitrogen generated by a predetermined high-frequency plasma apparatus was used as the nitrogen source. A solid source of 3N Tb and Eu was provided for addition to form the fluorescent layer, respectively.

  First, the substrate was heated to 900 ° C., and then the GaN film serving as the protective layer was removed by flowing H 2.

Subsequently, Ga _0.75 In _0.25 N having a thickness of 2 nm was formed on the GaN base layer 1012 at 600 ° C. to form the fluorescent layer 1013. At that time, Tb and Eu were doped at the same time.

  Subsequently, in the MBE apparatus, the diode structure 1020 was manufactured on the phosphor structure 1010 in the same manner as the diode structure 120 of Example 2.

  When voltage was applied to the obtained light emitting device 1001 between the Au / Ni electrode and the Al / Ti electrode, emission of white light was confirmed.

<Modification>
If a nitride containing at least one kind of Al, In, Ga, B, that is, Al _x In _Y Ga _1- XYN (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1) is used as a phosphor. Of course, it is possible to use the nitride itself in various forms such as a single crystal, an epitaxial film, a polycrystal or a powder as well as an aspect of epitaxial growth on a single crystal substrate as described above. An embodiment in which a rare earth element or a transition metal element is added to these elements is also possible.

  As the rare earth or transition metal element, as described above, Eu can be used for red light emission, Tm for green light emission, green light emission Tb or Ho, and Er can be used for infrared light emission. However, it is not necessarily limited to these elements.

  Further, in the above-described embodiment, an aspect in which an additive layer to which a rare earth element or a transition metal element is added and an unadded layer to which an additive is not added is alternately arranged is realized. It may be an embodiment in which layers to which rare earth elements or transition metal elements are added are alternately arranged.

It is a figure which shows typically the light-emitting device 1 which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the light-emitting device 101 which concerns on the 2nd Embodiment of this invention. It is a figure which shows typically the light-emitting device 201 which concerns on the 3rd Embodiment of this invention. It is a figure which shows typically the light-emitting device 301 which concerns on the 4th Embodiment of this invention. It is a figure which shows typically the light-emitting device 401 which concerns on the 5th Embodiment of this invention. It is a figure which shows typically the light-emitting device 1001 which concerns on the 6th Embodiment of this invention.

Explanation of symbols

1, 101, 201, 301, 401, 1001 Light-emitting device 10, 210 Phosphor 110, 310, 410, 1010 Phosphor structure 11, 111, 211, 311, 411, 1011 (of phosphor (structure)) 12 1122, 212, 312, 412, 1012 (phosphor (structure)) underlayer 13, 113, 213, 313, 413, 1013 fluorescent layer 13G, 113G, 213G, 313G, 413G green fluorescent layer 13R, 113R, 213R 313R, 413R Red fluorescent layer 14, 114, 1014 Low temperature buffer layer 20, 229 LED element 120, 320, 420, 1020 Diode structure 21, 121, 221, 321, 421, 1021 n-type conductive layer 22, 122, 223, 323, 423, 1022 Light emitting layer 23, 123, 2 2, 322, 422, 1022 Clad layer 24, 124, 224, 324, 424, 1024 p-type conductive layer 25, 125, 225, 325, 425, 1025 p-type electrode 26, 126, 226, 326, 426, 1026 n Type electrode 213b, 313b, 413b Blue fluorescent layer 27, 227 (LED element) substrate C1-C3 Cap layer I1-I3 Island-like crystal

Claims (22)

An additive region in which at least one rare earth element or transition metal element is added to a nitride containing at least one element of Al, In, Ga, and B;
Each of the added regions and the region to which the rare earth or transition metal element is not added are alternately arranged in layers, and the nitride composition of each of the added regions is adjacent to the adjacent rare earth or transition metal Unlike nitride composition of the area element is not added, and the than the band gap of the respective doped region, and the rare earth or the larger phosphor band gap of the region the transition metal element is not added ,
A light source emitting a first light having a first wavelength range;
With
Exciting the rare earth element or the transition metal element with the first light emitted from the light source to emit light having a second light component having a second wavelength range as a component;
A fluorescent light emitting device characterized by that. The fluorescent light-emitting device according to claim 1,
The added region is a region formed by island-like crystals in which at least one rare earth element or transition metal element is added to a nitride containing at least one element selected from Al, In, Ga, and B. A fluorescent light emitting device characterized by the above. The fluorescent light-emitting device according to claim 1 or 2 ,
The phosphor is
Each has a plurality of fluorescent regions including the added region,
The kind of the at least one rare earth or transition metal element added to the added region is different for each of the fluorescent regions,
A fluorescent light emitting device characterized by that. The fluorescent light-emitting device according to claim 3 ,
The light source emits blue light as the first light;
The phosphor is
A first fluorescent region doped with a first rare earth or transition metal element that emits red light by excitation as the at least one rare earth or transition metal element;
A second fluorescent region to which a second rare earth or transition metal element that emits green light by excitation is added as the at least one rare earth or transition metal element;
With two fluorescent regions
The blue light emitted from the light source excites the first and second rare earth elements or the transition metal element to emit red light and green light as the second light from the first and second fluorescent regions, respectively. To emit light having the blue light and the second light as components.
A fluorescent light emitting device characterized by that. The fluorescent light-emitting device according to claim 3 ,
The light source is a light source that emits ultraviolet light as the first light;
The phosphor is
A first fluorescent region doped with a first rare earth or transition metal element that emits red light by excitation as the at least one rare earth or transition metal element;
A second fluorescent region to which a second rare earth or transition metal element that emits green light by excitation is added as the at least one rare earth or transition metal element;
A third fluorescent region to which a third rare earth or transition metal element that emits blue light by excitation is added as the at least one rare earth or transition metal element;
With three fluorescent regions
The first , second, and third rare earth or transition metal elements are excited by ultraviolet light emitted from the light source , and red light, green light, and blue light are emitted from the first , second, and third fluorescent regions, respectively. And as the second light ,
A fluorescent light emitting device characterized by that. The fluorescent light-emitting device according to any one of claims 1 to 5 ,
The fluorescent light-emitting device , wherein the light source is a light-emitting diode . The fluorescent light-emitting device according to any one of claims 1 to 6,
A fluorescent light-emitting device, wherein the phosphor is formed by epitaxially forming on a predetermined substrate . An additive region in which at least one rare earth element or transition metal element is added to a nitride containing at least one element of Al, In, Ga, and B;
Each of the added regions and the region to which the rare earth or transition metal element is not added are alternately arranged in layers, and the nitride composition of each of the added regions is adjacent to the adjacent rare earth or transition metal A phosphor structure that is different from the nitride composition in a region to which no element is added, and has a larger band gap in a region to which the rare earth or transition metal element is not added than the band gap in each of the added regions; ,
A phosphor structure that is connected to the phosphor structure and emits a first light having a first wavelength range;
With
Exciting the rare earth element or the transition metal element with the first light emitted from the light emitter structure, thereby emitting light having a second light component having a second wavelength range as a component;
A fluorescent light emitting device characterized by the above. The fluorescent light-emitting device according to claim 8,
The added region is a region formed by island-like crystals in which at least one rare earth or transition metal element is added to a nitride containing at least one element of Al, In, Ga, and B. A fluorescent light emitting device characterized by the above. The fluorescent light-emitting device according to claim 8 or 9,
The phosphor structure is
Each has a plurality of fluorescent regions including the added region,
The kind of the at least one rare earth or transition metal element added to the added region is different for each of the fluorescent regions,
A fluorescent light emitting device characterized by the above. The fluorescent light-emitting device according to claim 10 ,
The light emitter structure emits blue light as the first light;
The phosphor structure is
A first fluorescent region doped with a first rare earth or transition metal element that emits red light by excitation as the at least one rare earth or transition metal element;
A second fluorescent region to which a second rare earth or transition metal element that emits green light by excitation is added as the at least one rare earth or transition metal element;
With two fluorescent regions
The first and second rare earth elements or transition metal elements are excited by blue light emitted from the light emitter structure, and red light and green light are respectively emitted from the first and second fluorescent regions to the second light. To emit light having the blue light and the second light as components.
A fluorescent light emitting device characterized by the above. The fluorescent light-emitting device according to claim 10 ,
The phosphor structure emits ultraviolet light as the first light;
The phosphor structure is
A first fluorescent region doped with a first rare earth or transition metal element that emits red light by excitation as the at least one rare earth or transition metal element;
A second fluorescent region to which a second rare earth or transition metal element that emits green light by excitation is added as the at least one rare earth or transition metal element;
A third fluorescent region to which a third rare earth or transition metal element emitting blue light by excitation is added as the at least one rare earth or transition metal element;
With three fluorescent regions
The first, second, and third rare earth or transition metal elements are excited by ultraviolet light emitted from the phosphor structure, and red light and green light are respectively emitted from the first, second, and third fluorescent regions. Emitting blue light as the second light,
A fluorescent light emitting device characterized by the above. The fluorescent light-emitting device according to any one of claims 8 to 12,
The fluorescent light-emitting element, wherein the light-emitting structure has a diode structure . The fluorescent light-emitting device according to any one of claims 8 to 13 ,
A fluorescent light emitting device, wherein the phosphor structure and the light emitting structure are formed epitaxially on a predetermined substrate . The fluorescent light-emitting device according to claim 14 ,
A fluorescent light emitting device comprising the phosphor structure and the light emitting structure laminated . The fluorescent light-emitting device according to any one of claims 8 to 15,
The fluorescent light emitting device , wherein the light emitting structure has a light emitting layer containing a nitride containing at least one element of Al, In, Ga, and B. An additive region in which at least one rare earth element or transition metal element is added to a nitride containing at least one element of Al, In, Ga, and B;
Each of the added regions and the region to which the rare earth or transition metal element is not added are alternately arranged in layers, and the nitride composition of each of the added regions is adjacent to the adjacent rare earth or transition metal Unlike the nitride composition of the region where no element is added, and the band gap of the region where the rare earth or transition metal element is not added is larger than the band gap of the respective added region,
  Exciting the rare earth element or the transition metal element with the first light emitted from a predetermined light source to emit light having the second light having the second wavelength range as a component;
A phosphor characterized by that. The phosphor according to claim 17,
The added region is a region formed by island-like crystals in which at least one rare earth or transition metal element is added to a nitride containing at least one element of Al, In, Ga, and B. A phosphor characterized by. The phosphor according to claim 17 or 18,
Each has a plurality of fluorescent regions including the added region,
The kind of the at least one rare earth or transition metal element added to the added region is different for each of the fluorescent regions,
A phosphor characterized by that. The phosphor according to claim 19, wherein
A first fluorescent region doped with a first rare earth or transition metal element that emits red light by excitation as the at least one rare earth or transition metal element;
A second fluorescent region to which a second rare earth or transition metal element that emits green light by excitation is added as the at least one rare earth or transition metal element;
With two fluorescent regions
The first and second rare earth elements or transition metal elements are excited by blue light emitted from a predetermined light source, so that red light and green light are respectively emitted from the first and second fluorescent regions. To emit light having the blue light and the second light as components.
A phosphor characterized by that. The phosphor according to claim 19, wherein
A first fluorescent region doped with a first rare earth or transition metal element that emits red light by excitation as the at least one rare earth or transition metal element;
A second fluorescent region to which a second rare earth or transition metal element that emits green light by excitation is added as the at least one rare earth or transition metal element;
A third fluorescent region to which a third rare earth or transition metal element emitting blue light by excitation is added as the at least one rare earth or transition metal element;
With three fluorescent regions
The first, second, and third rare earth or transition metal elements are excited by ultraviolet light emitted from a predetermined light source, whereby red light and green light are respectively emitted from the first, second, and third fluorescent regions. And blue light as the second light,
A phosphor characterized by that. The phosphor according to any one of claims 17 to 21,
A phosphor formed by epitaxial formation on a predetermined substrate .

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