JP2015124339A - Method of producing fluorescent body, and fluorescent body and light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a fluorescent body which is simple and easy in adjustment of color rendering property, color temperature and the like, and a fluorescent body and a light- emitting device.SOLUTION: A new level corresponding to a second wave length light is formed by changing a crystal structure under irradiation of the second wave length light having a wave length other than a first wave length light in a part of a fluorescent body which is doped with a donor impurity and an acceptor impurity and emits the first wave length light by a donor acceptor pair when excited with excitation light so that the part of the fluorescent body is formed as an auxiliary light emitting part which emits the second wave length light when excited with the excitation light to emit both of the first wave length light and the second wave length light when excited with the excitation light.

Description

  The present invention relates to a phosphor manufacturing method, a phosphor, and a light emitting device.

  As a light emitting element using a pn junction of a compound semiconductor, an LED (light emitting diode) has been widely put into practical use, and is mainly used for optical transmission, display, and special illumination applications. In recent years, white LEDs using nitride semiconductors and phosphors have been put into practical use, and in the future, they are highly expected to be used for general lighting applications. However, in white LEDs, energy conversion efficiency is insufficient as compared with existing fluorescent lamps, so that significant efficiency improvement is necessary for general lighting applications. Furthermore, many problems remain for realizing high color rendering properties, low cost, and high luminous flux LEDs. As a white LED currently on the market, a blue light emitting diode element mounted on a lead frame, a yellow phosphor layer made of YAG: Ce over the blue light emitting diode element, and a transparent material such as an epoxy resin covering them. What is equipped with the mold lens which becomes is known. In this white LED, when blue light is emitted from the blue light emitting diode element, part of the blue light is converted into yellow light when passing through the yellow phosphor. Since blue and yellow are complementary to each other, when blue light and yellow light are mixed, white light is obtained. The white LED is required to improve the performance of the blue light-emitting diode element in order to improve efficiency and improve color rendering.

  As a blue light-emitting diode element, on an n-type SiC substrate, a buffer layer made of AlGaN, an n-type GaN layer made of n-GaN, a multiple quantum well active layer made of GaInN / GaN, an electron block layer made of p-AlGaN, It is known that a p-type contact layer made of p-GaN is continuously laminated in this order from the SiC substrate side. Further, a p-side electrode is formed on the surface of the p-type contact layer, and an n-side electrode is formed on the back surface of the SiC substrate, and a current is applied by applying a voltage between the p-side electrode and the n-side electrode. Thus, blue light is emitted from the multiple quantum well active layer. In this blue light-emitting diode element, the SiC substrate is conductive, so unlike the blue light-emitting diode element using a sapphire substrate, electrodes can be arranged above and below, simplifying the manufacturing process, and in-plane uniformity of current In addition, it is possible to effectively use the light emitting area with respect to the chip area.

  Furthermore, a light-emitting diode element that independently generates white light without using a phosphor has been proposed (see, for example, Patent Document 1). In this light emitting diode element, a fluorescent SiC substrate having a first SiC layer doped with boron and nitrogen and a second SiC layer doped with aluminum and nitrogen is used instead of the n-type SiC substrate of the blue light emitting diode element described above. Near ultraviolet light is emitted from the multiple quantum well active layer. Near-ultraviolet light is absorbed by the first SiC layer and the second SiC layer, and is converted from green to red visible light by the first SiC layer, and from blue to red visible light by the second SiC layer. As a result, white light close to sunlight is emitted from the fluorescent SiC substrate.

  In addition, the inventors of the present application made a porous single crystal 6H type SiC doped with boron and nitrogen, and a light emitting diode element having a porous SiC portion that emits visible light when excited by light emitted from a semiconductor light emitting portion. Has been proposed (see, for example, Patent Document 2). According to this light emitting diode element, light emission on the shorter wavelength side than the emission wavelength region of the donor-acceptor pair in ordinary 6H type SiC can be obtained by making it porous.

Japanese Patent No. 4153455 Japanese Patent No. 5330880 JP 2012-243824 A

  Furthermore, the inventors of the present application have made extensive studies on changes in the emission wavelength of 6H-type SiC. In particular, if the emission wavelength of 6H-type SiC can be arbitrarily changed, the color rendering properties, the color temperature, etc. can be easily and easily adjusted.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a phosphor manufacturing method, a phosphor, and a light-emitting element that can easily adjust color rendering, color temperature, and the like. is there.

  In order to achieve the above object, according to the present invention, when a donor impurity and an acceptor impurity are doped and excited by excitation light, a part of the phosphor that emits light with the first wavelength light by the donor-acceptor pair is used. When the crystal structure is changed under irradiation of second wavelength light having a wavelength different from that of light to form a new level corresponding to the second wavelength light, and a part of the phosphor is excited by the excitation light A method of manufacturing a phosphor that emits both the first wavelength light and the second wavelength light when the auxiliary light emitting unit emits light with the second wavelength light and is excited by the excitation light is provided.

  In the phosphor manufacturing method, the crystal structure of a part of the phosphor may be changed by changing the surface shape.

  In the phosphor manufacturing method, the surface shape of the phosphor may be changed by anodic oxidation.

  In the phosphor manufacturing method, the crystal structure in a part of the phosphor may be changed by changing the distribution of impurities.

  In the phosphor manufacturing method, the change in the impurity distribution may be performed by annealing.

  In the phosphor manufacturing method, an additional impurity may be doped into a part of the phosphor before changing the crystal structure.

  In the phosphor manufacturing method, the additional impurity may have a diffusion coefficient larger than that of the donor impurity and the acceptor impurity.

  In the phosphor manufacturing method, the doping of the additional impurity into a part of the phosphor may be performed by ion implantation.

  In the phosphor manufacturing method, the phosphor may be made of 6H-type SiC, the donor impurity may be nitrogen, and the acceptor impurity may be at least one of boron and aluminum.

  Further, in the present invention, a donor-acceptor pair light-emitting unit that is manufactured by the phosphor manufacturing method and emits the first wavelength light when excited by excitation light, and the second when excited by the excitation light. There is provided a phosphor including an auxiliary light emitting unit that emits light of a wavelength.

  Furthermore, the present invention provides a light emitting device comprising a substrate made of the above-described phosphor and a semiconductor stacked portion that is formed on the substrate and emits the excitation light.

  According to the present invention, adjustment of color rendering properties, color temperature, and the like can be easily and easily performed by combining light emission based on a newly formed level and donor-acceptor pair light emission.

FIG. 1 is a schematic cross-sectional view of a light-emitting diode element showing a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a SiC substrate on which an ohmic electrode is formed. FIG. 3 is an explanatory diagram of an anodizing apparatus for making a SiC substrate porous. FIG. 4 is a schematic cross-sectional view of a SiC substrate on which a second fluorescent SiC layer is formed. FIG. 5 is a schematic cross-sectional view of a SiC substrate in which electrodes are formed on a semiconductor layer according to a modification. FIG. 6 is a schematic cross-sectional view of a SiC substrate on which a second fluorescent SiC layer is formed according to a modification. FIG. 7 is a schematic cross-sectional view of a light emitting diode element showing a second embodiment. FIG. 8 is a schematic cross-sectional view of a SiC substrate on which an ion implantation region is formed. FIG. 9 is a schematic cross-sectional view of a SiC substrate on which an ohmic electrode is formed. FIG. 10 is a schematic cross-sectional view of a SiC substrate on which an ohmic electrode showing a state in which guided light is irradiated is formed. FIG. 11 is a schematic longitudinal sectional view of a light emitting device showing a third embodiment of the present invention. FIG. 12 is a schematic cross-sectional view of a light-emitting device showing a fourth embodiment of the present invention.

  1 to 4 show a first embodiment of the present invention, and FIG. 1 is a schematic cross-sectional view of a light-emitting diode element.

  As shown in FIG. 1, the light emitting diode element 100 includes a SiC substrate 102 and a nitride semiconductor layer formed on the SiC substrate 102. A nitride semiconductor layer as a semiconductor light emitting unit includes a buffer layer 104, an n-type layer 106, a multiple quantum well active layer 108, an electron block layer 110, a p-type cladding layer 112, and a p-type contact layer 114 from the SiC substrate 102 side. Have in order. A p-side electrode 116 is formed on the p-type contact layer 114, and an n-side electrode 118 is formed on the back side of the SiC substrate 102.

  The SiC substrate 102 is made of single crystal 6H type SiC, and includes a first fluorescent SiC layer 122 that emits light by a donor-acceptor pair, and a second fluorescent SiC layer 124 that emits light based on a newly formed level. Have. The first fluorescent SiC layer 122 serving as a donor-acceptor pair light-emitting portion is bulky and contains nitrogen as a donor impurity and boron as an acceptor impurity. The second fluorescent SiC layer 124 as the auxiliary light emitting portion is processed into a porous shape, and a fine shape described later is formed on the surface, and a level different from the crystal structure of the normal single crystal 6H type SiC is formed. ing. The term “bulk” as used herein refers to a state where there is no interface with another substance inside or a state where a change in physical property value can be ignored even if an interface exists. In addition, the porous shape here refers to a state in which a porous shape is formed and an interface with the atmosphere exists inside.

When excited by ultraviolet light, the first fluorescent SiC layer 122 emits approximately yellow to orange visible light by donor-acceptor pair emission. For example, the first fluorescent SiC layer 122 emits first wavelength light having a wavelength of 500 nm to 750 nm having a peak at 500 nm to 650 nm. In the present embodiment, the first fluorescent SiC layer 122 is adjusted to emit light having a peak wavelength of 580 nm. The boron and nitrogen doping concentrations in the first fluorescent SiC layer 122 are 10 ¹⁷ / cm ³ to 10 ¹⁹ / cm ³ , respectively. Here, the first fluorescent SiC layer 122 can be excited by light of 408 nm or less.

  When excited by ultraviolet light, second fluorescent SiC layer 124 emits approximately blue to green light by light emission based on a newly formed level. The second fluorescent SiC layer 124 emits second wavelength light having a wavelength of 380 nm to 700 nm having a peak at 400 nm to 500 nm, for example. In the present embodiment, the second fluorescent SiC layer 124 is adjusted to emit light having a peak wavelength of 450 nm. Here, the second fluorescent SiC layer 124 can be excited by light of 408 nm or less.

  The buffer layer 104 is formed on the SiC substrate 102 and is made of AlGaN. In the present embodiment, the buffer layer 104 is grown at a lower temperature than an n-type layer 106 described later. The n-type layer 106 is formed on the buffer layer 104 and is made of n-GaN.

The multiple quantum well active layer 108 is formed on the n-type layer 106, is made of GalnN / GaN, and emits excitation light, for example, by injection of electrons and holes. In the present embodiment, the multiple quantum well active layer 108 is made of Ga _0.95 ln _0.05 N / GaN, and the peak wavelength of light emission is 385 nm. The peak wavelength in the multiple quantum well active layer 108 can be arbitrarily changed.

  The electron blocking layer 110 is formed on the multiple quantum well active layer 108 and is made of p-AIGaN. The p-type cladding layer 112 is formed on the electron block layer 110 and is made of p-AlGaN. The p-type contact layer 114 is formed on the p-type cladding layer 112 and is made of p-GaN.

  The buffer layer 104 to the p-type contact layer 114 are formed by epitaxial growth of a group III nitride semiconductor. In addition, when a voltage is applied to the first conductive type layer and the second conductive type layer at least including the first conductive type layer, the active layer, and the second conductive type layer, the active layer is formed by recombination of electrons and holes. As long as light can be emitted, the layer structure of the nitride semiconductor layer is arbitrary.

  The p-side electrode 116 is formed on the p-type contact layer 114, is made of, for example, Ni / Au, and is formed by a vacuum deposition method, a sputtering method, a CVD (Chemical Vapor Deposition) method, or the like. The n-side electrode 118 is formed on the SiC substrate 102 and is made of, for example, Ti / Al / Ti / Au, and is formed by a vacuum deposition method, a sputtering method, a CVD (Chemical Vapor Deposition) method, or the like.

  Next, a method for manufacturing the light emitting diode element 100 will be described with reference to FIGS. FIG. 2 is a schematic cross-sectional view of a SiC substrate on which an ohmic electrode is formed.

  First, a SiC substrate 102 made of bulk single crystal 6H-type SiC doped with boron and nitrogen is prepared by a sublimation method (fluorescent SiC preparation step). The SiC substrate 102 is a phosphor that emits visible light by donor-acceptor pair emission. The doping concentration of boron and nitrogen in the SiC crystal can be controlled by adding an impurity gas to the atmosphere gas during crystal growth and adding an impurity element or compound thereof to the raw material powder. Although the thickness of SiC substrate 102 is arbitrary, it is 250 micrometers, for example. The SiC substrate 102 is manufactured through steps such as peripheral grinding, slicing, surface grinding, and surface polishing by preparing a bulk crystal of about 30 mm by bulk growth by a sublimation method.

  Then, as shown in FIG. 2, an ohmic electrode 201 is formed on one surface of the SiC substrate 102 (electrode formation step). In the present embodiment, the ohmic electrode 201 is made of Ni, and is subjected to heat treatment after being deposited by sputtering. Although the thickness of the ohmic electrode 201 is arbitrary, it is 100 nm, for example, and is heat-treated at about 1000 ° C., for example. It is arbitrary whether the ohmic electrode 201 is formed on the Si surface or the C surface, but in this embodiment, the ohmic electrode 201 is formed on the Si surface. This is because, in the light emitting diode device 100 of the present embodiment, since the nitride semiconductor layer is stacked on the Si surface, it is desirable that the Si surface is not as rough as possible, and that the C surface is the Si surface. Since the speed of the oxidation reaction is faster than that of C, the C surface is easier to process by anodization described later.

FIG. 3 is an explanatory view of an anodizing apparatus.
As shown in FIG. 3, the anodizing apparatus 200 includes a stainless plate 202 on which the SiC substrate 102 is placed, and a container 206 having an opening 204 disposed above the stainless steel plate 202 and formed immediately above the SiC substrate 102. A platinum wire 208 disposed inside the container 206, and a DC power source 210 that applies a voltage to the SiC substrate 102 and the platinum wire 208. The container 206 is provided on the stainless steel plate 202 via the hydrofluoric acid resistant sheet 212, and the inside is filled with the solution 214. In addition, the container 206 is formed with an opening 216 through which light 218 and 220 can be incident.

  In the present embodiment, the solution 214 is a hydrofluoric acid aqueous solution obtained by diluting hydrofluoric acid with pure water, to which nitric acid as an oxidation aid is added. As a solvent for hydrofluoric acid, ethanol or the like can be used in addition to water. Further, whether or not nitric acid is added is arbitrary. Since nitric acid has a function of promoting a chemical oxidation reaction of the SiC crystal, the formation of the second fluorescent SiC layer 124 can be promoted by anodic oxidation. In addition to nitric acid, sulfuric acid, potassium persulfate, and the like can be used as an oxidation aid.

  In this anodizing apparatus 200, a voltage is applied to the ohmic electrode 201 by the DC power supply 210 in a state where the first fluorescent SiC layer 122 is in contact with the solution 214 with the SiC substrate 102 being in contact with the solution 214. Current is passed through. When the current starts to flow, the following chemical reaction proceeds from the surface of SiC substrate 102 toward the inside.

SiC + 6OH ⁻ → SiO ₂ + CO ₂ + 2H ₂ O + 2H ⁺ + 8e ⁻ (1)
SiO ₂ + 6F ⁻ + 2H ⁺ → H ₂ SiF ₆ + 2H ₂ O + 4e ⁻ (2)

Simultaneously with the voltage application, the ultraviolet light 218 and the guide light 220 are irradiated to the contact portion between the first fluorescent SiC layer 122 and the solution. The ultraviolet light 218 is irradiated to promote the electrochemical reaction of anodic oxidation. SiC changes to SiO ₂ and CO ₂ by an oxidation reaction, and SiO ₂ further changes to water-soluble H ₂ SiF ₆ by fluorine ions and melts into the solution. Since CO ₂ is a gas, it disappears as it is by vaporization. Thereby, the crystal | crystallization of the 2nd fluorescence SiC layer 124 becomes a fiber form.

  Thus, during anodization, the surface of SiC substrate 102 is in a changeable state, and the fine shape of the surface changes randomly. That is, the crystal structure of a part of SiC substrate 102 can be changed. As a result, a fine shape suitable for generating evanescent light based on the guide light 220 can be obtained. If a voltage is continuously applied when the fine shape is formed on the surface of the SiC substrate 102, evanescent light is generated in the fine shape. Since the evanescent light here includes the meaning of a virtual electromagnetic field, the formation of the virtual electromagnetic field is understood as meaning the generation of the evanescent light. According to Patent Document 3, it is said that a non-adiabatic process is caused by the generation of the evanescent light.

  According to Patent Document 3, the adiabatic process and the non-adiabatic process are described as follows. First, regarding the adiabatic process, since the wavelength of propagating light is generally much larger than the size of the molecule, it can be regarded as a spatially uniform electric field at the molecular level. That is, adjacent electrons are vibrated with the same amplitude and the same phase. Here, since the nucleus is heavy, it cannot follow the vibration of the electrons, and the molecular vibration hardly occurs in the propagating light. Thus, in propagating light, it can be ignored that molecular vibration is involved in the excitation process of electrons. This process is an adiabatic process.

  On the other hand, according to Patent Literature 3, the spatial electric field gradient of the evanescent light is very steep in the non-adiabatic process. That is, in evanescent light, different electrons are given to adjacent electrons, and heavy nuclei are also vibrated by the vibration of different electrons. The occurrence of molecular vibration in this way corresponds to energy taking the form of molecular vibration, and evanescent light enables an excitation process via vibration levels. In this way, the excitation process via the vibration level of the nucleus is a non-adiabatic process because the nucleus moves in response to the adiabatic process, which is a normal optical response.

  And it is thought that the electron density in the conduction band becomes higher than the hole density in the lower level by continuing to apply the voltage. Thereby, it is considered that an inversion distribution based on the difference in electron density is formed between the conduction band and the lower level. Due to the inversion distribution thus formed, electrons in the conduction band can be virtually transitioned to a vibration level located in the middle of the band gap based on a non-adiabatic process using evanescent light. This evanescent light is due to a fine shape generated at a certain probability by anodic oxidation. The electrons that have transitioned to the vibration level go back to the conduction band from the vibration level after passing through a virtual field virtually generated by the evanescent light.

  In the present embodiment, a vibration level located between the conduction band and the lower level is formed according to the wavelength of the guide light 220. The electrons make a transition to this vibration level once, and then transition to a lower level by stimulated emission. The emission wavelength at this time depends on the band gap difference between the vibration level and the ground level. In the present embodiment, the wavelength of the guide light 220 is 450 nm, and the band gap difference between the vibration level and the ground level also corresponds to 450 nm.

  As a result of stimulated emission due to such a non-adiabatic process, the electron density in the conduction band decreases. As a result, the amount of electrons that move is reduced for a fine shape in which evanescent light is generated. That is, stimulated emission takes away energy of electrons and holes, the electrochemical reaction of anodic oxidation is suppressed, and the surface shape is fixed as it is.

  In addition, when evanescent light is emitted at a predetermined location on SiC substrate 102, the emitted light itself becomes guide light, and evanescent light with a fine shape is likely to be generated at other locations on SiC substrate 102. In this way, while moving the location on the surface of the SiC substrate 102, generation of evanescent light and fixation of the fine shape are repeated, and a vibration level located entirely between the conduction band and the lower level is formed. It will be. This is a phosphor that emits light having a wavelength corresponding to the guide light 220 when irradiated with light having a wavelength shorter than the absorption edge wavelength of the single crystal 6H type SiC.

FIG. 4 is a schematic cross-sectional view of a SiC substrate on which a second fluorescent SiC layer is formed.
As shown in FIG. 4, the second fluorescent SiC layer 124 is formed from the surface side of the first fluorescent SiC layer 122 by the above-described anodic oxidation reaction (auxiliary fluorescent layer forming step). FIG. 4 shows the SiC substrate 102 from which the ohmic electrode 201 is removed after the second fluorescent SiC layer 124 is formed. The thickness of the second fluorescent SiC layer 124 is proportional to the anodic oxidation time, and is 50 μm in this embodiment.

  Moreover, by adding nitric acid, the reaction of the above formula (1) is promoted, and the number of cavities in the second fluorescent SiC layer 124 can be increased. Thereby, the surface area of the 2nd fluorescence SiC layer 124 can be increased, and the area | region in which a specific fine shape is formed can be increased.

  In the present embodiment, after the second fluorescent SiC layer 124 is formed, the SiC substrate 102 is heat-treated (surface cleaning process). Specifically, C that is excessively deposited on the crystal surface of the second fluorescent SiC layer 124 is removed by performing a heat treatment at 850 ° C. or lower in a hydrogen atmosphere.

Furthermore, in the present embodiment, a protective film is formed after the surface cleaning process of the second fluorescent SiC layer 124 (protective film forming process). Specifically, by performing heat treatment at 850 ° C. or less in an atmosphere of hydrogen and ammonia, a protective film of Si ₃ N ₄ can be formed on the surface of the clean crystal, and the second fluorescent SiC layer 124 is formed. The surface level of can be stably reduced. In order to prevent C from precipitating on the crystal surface of the second fluorescent SiC layer 124, it is preferable that the surface cleaning process and the protective film forming process are continuously performed in the same container.

  In this way, SiC substrate 102 having second fluorescent SiC layer 124 as shown in FIG. 4 is manufactured. Thereafter, a group III nitride semiconductor is epitaxially grown on the SiC substrate 102. In the present embodiment, for example, after growing the buffer layer 104 made of AlGaN by an organic metal compound vapor phase growth method, the n-type layer 106 made of n-GaN, the multiple quantum well active layer 108, the electron block layer 110, p A mold cladding layer 112 and a p-type contact layer 114 are grown. After the nitride semiconductor layer is formed, the electrodes 116 and 118 are formed and divided into a plurality of light emitting diode elements 100 by dicing, whereby the light emitting diode element 100 is manufactured. Here, the SiC substrate 102 shown in FIG. 4 can be used as a fluorescent plate instead of the substrate of the light emitting diode element 100.

  In the light emitting diode element 100 configured as described above, when a voltage is applied to the p-side electrode 116 and the n-side electrode 118, ultraviolet light is emitted radially from the multiple quantum well active layer 108. Of the ultraviolet light emitted from the multiple quantum well active layer 108, most of the ultraviolet light directed to the p-side electrode 116 is reflected by the p-side electrode 116 and travels toward the SiC substrate 102. Therefore, most of the light emitted from the multiple quantum well active layer 108 goes to the SiC substrate 102.

  The ultraviolet light incident on the SiC substrate 102 is converted from blue to green first visible light by the second fluorescent SiC layer 124, and the rest is converted from yellow to orange second visible light by the first fluorescent SiC layer 122. Is done. As described above, by combining the light emission based on the newly formed level and the donor-acceptor pair light emission, the adjustment of the color rendering property, the color temperature, and the like can be easily performed. In the present embodiment, since the second fluorescent SiC layer 124 has a light emitting component on the short wavelength side and the first fluorescent SiC layer 122 has a light emitting component on the long wavelength side, white light with high color rendering can be obtained. it can. This light is emitted from the SiC substrate 102 to the outside as white light similar to sunlight.

  As described above, according to the light emitting diode element 100 of the present embodiment, the emission wavelength region of 6H-type SiC doped with boron and nitrogen based on the level newly formed in the second fluorescent SiC layer 124. The light emission on the shorter wavelength side can be obtained. In the present embodiment, the elements to be doped into the SiC substrate 102 are only boron and nitrogen, so that the SiC substrate 102 can be easily and easily manufactured. As a result, the manufacturing cost of the SiC substrate 102 and the manufacturing cost of the light emitting diode element 100 can be reduced. Can be reduced.

  In addition, according to the present embodiment, the surface shape of the SiC substrate 102 is easily changed by anodic oxidation, and the SiC substrate 102 is irradiated with the guide light 220, so that the surface shape suitable for evanescent light is relatively easy. Can get to. In addition, the emission wavelength of the second fluorescent SiC layer 124 can be adjusted by changing the wavelength of the guide light 220, and the color rendering properties and the color temperature can be easily adjusted.

  In the above embodiment, the semiconductor layer is stacked on the SiC substrate 102 after the second fluorescent SiC layer 124 of the SiC substrate 102 is formed. However, the semiconductor layer is stacked on the SiC substrate 102. The second fluorescent SiC layer 124 may be formed later. For example, as shown in FIG. 5, the SiC substrate 102 made of the first fluorescent SiC layer 122 is produced, and a group III nitride semiconductor is epitaxially grown on the SiC substrate 102 to form the p-side electrode 116. Then, the second fluorescent SiC layer 124 is formed on the SiC substrate 102 as shown in FIG. 6 by anodizing the SiC substrate 102 using the p-side electrode 116 instead of the ohmic electrode 201 of the embodiment. You may make it do. Thereafter, as shown in FIG. 1, if the n-side electrode 118 is formed on the second fluorescent SiC layer 124, the light emitting diode element 100 is obtained. Furthermore, the ohmic electrode 201 may not be formed on the SiC substrate 102, but a conductor substrate may be attached to perform anodization. A semiconductor layer may be formed on the conductor substrate to form a light emitting diode element.

  Moreover, in the said embodiment, although what obtained the SiC substrate 102 by sublimation recrystallization was shown, you may make it obtain the SiC substrate 102 by CVD method etc. FIG. Moreover, although what changed the surface shape of SiC by anodic oxidation was shown, the method of changing the surface shape is arbitrary as long as the light for promoting the reaction and the induced light are combined.

  Moreover, in the said embodiment, what used SiC fluorescent substance as a board | substrate of the light emitting diode element 100 was shown, However, It can also utilize as a fluorescent substance separate from a light source. This SiC phosphor may be used as a powder or as a fluorescent plate for wavelength conversion.

  Moreover, although the thing using nitrogen and boron was shown as a donor impurity and an acceptor impurity, of course, another element may be sufficient. For example, white light may be emitted even if the first fluorescent SiC layer emits blue to green visible light using nitrogen and aluminum as the donor impurity and acceptor impurity, and the second fluorescent SiC layer emits yellow to orange visible light. Can be obtained. Furthermore, other V group elements and III group elements such as P, As, Sb, Ga, and In can be used as donor impurities and acceptor impurities, and further, transition metals such as Ti and Cr, Be, and the like can be used. Group II elements can also be used, and the donor impurities and acceptor impurities can be appropriately changed as long as they can be used as donor impurities and acceptor impurities in the SiC crystal.

  FIGS. 7 to 10 show a second embodiment of the present invention, and FIG. 7 is a schematic cross-sectional view of a light-emitting diode element.

  As shown in FIG. 7, the light emitting diode element 400 includes a SiC substrate 402 and a nitride semiconductor layer formed on the SiC substrate 402. The nitride semiconductor layer as the semiconductor light emitting unit includes a buffer layer 404 made of AIGaN, a first contact layer 406 made of n-GaN, a first cladding layer 408 made of n-AIGaN, and GalnN. Multiple quantum well active layer 410 composed of / GaN, electron block layer 412 composed of p-AIGaN, second cladding layer 414 composed of p-AIGaN, and second composed of p-GaN. The contact layer 416 is continuously provided in this order from the SiC substrate 10 side. The GaN-based semiconductor layer 420 is stacked on the SiC substrate 410 by, for example, a metal organic compound vapor deposition method. A p-electrode 431 made of Ni / Au is formed on the surface of the second contact layer 416. Further, the first contact layer 406 is exposed by etching in a thickness direction from the second contact layer 416 to a predetermined position of the first contact layer 406, and the n electrode 432 made of Ti / Al / Ti / Au is exposed at this exposed portion. Is formed.

In the present embodiment, the multiple quantum well active layer 410 is made of Ga _0.95 ln _0.05 N / GaN, and the peak wavelength of light emission is 385 nm. The peak wavelength in the multiple quantum well active layer 410 can be arbitrarily changed. In addition, it includes at least a first conductivity type layer, an active layer, and a second conductivity type layer. When a voltage is applied to the first conductivity type layer and the second conductivity type layer, the active layer is formed by recombination of electrons and holes. As long as light can be emitted, the layer configuration of the GaN-based semiconductor layer 420 is arbitrary.

  The SiC substrate 402 is made of single crystal 6H type SiC, and includes a first fluorescent SiC layer 422 that emits light by a donor-acceptor pair, and a second fluorescent SiC that serves as an auxiliary light emitting unit that emits light based on a newly formed level. A layer 424. The first fluorescent SiC layer 422 is bulky and contains nitrogen as a donor impurity and boron as an acceptor impurity. The second fluorescent SiC layer 424 has a bulk shape, has a predetermined dopant distribution, which will be described later, and has a level different from the crystal structure of normal single crystal 6H-type SiC.

When excited by ultraviolet light, the first fluorescent SiC layer 422 emits approximately yellow to orange visible light by donor-acceptor pair emission. The first fluorescent SiC layer 422 emits light having a wavelength of 500 nm to 750 nm having a peak at 500 nm to 650 nm, for example. In the present embodiment, the first fluorescent SiC layer 422 is adjusted to emit light having a peak wavelength of 580 nm. The doping concentration of boron and nitrogen in the first fluorescent SiC layer 422 are each ^{10 17 / cm 3 ~10 19 /} cm 3. Here, the first fluorescent SiC layer 422 can be excited by light of 408 nm or less.

  When excited by ultraviolet light, second fluorescent SiC layer 424 emits approximately blue to green light by light emission based on a level newly formed by the distribution of additional impurities as will be described later. In this embodiment, beryllium is doped as an additional impurity. The second fluorescent SiC layer 424 emits light with a wavelength of 380 nm to 700 nm having a peak at 400 nm to 500 nm, for example. In the present embodiment, the second fluorescent SiC layer 424 is adjusted to emit light having a peak wavelength of 450 nm. Here, the second fluorescent SiC layer 424 can be excited by light of 408 nm or less.

  Next, a method for manufacturing the light emitting diode element 400 will be described with reference to FIGS. FIG. 8 is a schematic cross-sectional view of a SiC substrate on which an ion implantation region is formed.

  First, a SiC substrate 402 made of bulk single crystal 6H-type SiC doped with boron and nitrogen is prepared by a sublimation method (fluorescent SiC preparation step). The SiC substrate 402 is a phosphor that emits visible light by donor-acceptor pair emission. The doping concentration of boron and nitrogen in the SiC crystal can be controlled by adding an impurity gas to the atmosphere gas during crystal growth and adding an impurity element or compound thereof to the raw material powder. Although the thickness of SiC substrate 402 is arbitrary, it is 250 micrometers, for example. The SiC substrate 402 is manufactured through steps such as peripheral grinding, slicing, surface grinding, and surface polishing by preparing a bulk crystal of about 30 mm by bulk growth by a sublimation method.

The SiC substrate 402 is further doped with an impurity by an ion implantation method to form an ion implantation region 426. As the additional impurity, an element having a larger diffusion coefficient than the donor impurity and the acceptor impurity is preferable. In this embodiment, beryllium having a larger diffusion coefficient than boron and nitrogen is doped as an additional impurity by an ion implantation method. In this embodiment, the beryllium concentration is 10 ¹⁹ / cm ³ to 10 ²⁰ / cm ^{3 in the} vicinity of 700 nm from the surface. It is arbitrary whether the ion implantation region 426 is formed on the Si surface or the C surface, but in this embodiment, the ion implantation region 426 is formed on the C surface. This is because, in the light emitting diode device 100 of the present embodiment, since the nitride semiconductor layer is stacked on the Si surface, it is desirable that the Si surface be as rough as possible.

  Then, as shown in FIG. 9, ohmic electrodes 501 and 502 are formed on both surfaces of the SiC substrate 402 (electrode forming step). In the present embodiment, the ohmic electrodes 501 and 502 are made of Ni and deposited by a sputtering method and then subjected to heat treatment. Although the thickness of each ohmic electrode 501 and 502 is arbitrary, it is 100 nm, for example, and it heat-processes at about 1000 degreeC, for example.

  Thereafter, as shown in FIG. 10, a voltage is applied to the ohmic electrodes 501 and 502, and at the same time, the guide light 520 is irradiated to the ion implantation region 426. Here, since the crystal quality is deteriorated by ion implantation, the ion implantation region 426 has a higher resistance value than other regions and generates heat when a voltage is applied. As a result of heat generation in the ion implantation region 426, the fluidity of the ion implantation region 426 increases. That is, the crystal structure of a part of SiC substrate 402 can be changed.

  In this manner, the dopant distribution changes randomly as the fluidity of the ion implantation region 426 increases. As a result, a dopant distribution suitable for generating evanescent light based on the guide light 520 can be obtained. If a voltage is continuously applied when the dopant distribution is formed in the ion implantation region 426, evanescent light is generated in the dopant distribution.

  Further, it is considered that the electron density in the conduction band becomes higher than the hole density in the lower level by continuing to apply the voltage. Thereby, it is considered that an inversion distribution based on the difference in electron density is formed between the conduction band and the lower level. Due to the inversion distribution thus formed, electrons in the conduction band can be virtually transitioned to a vibration level located in the middle of the band gap based on a non-adiabatic process using evanescent light. This evanescent light is due to a dopant distribution generated with a certain probability due to heat generation in the ion implantation region 426. The electrons that have transitioned to the vibration level go back to the conduction band from the vibration level after passing through a virtual field virtually generated by the evanescent light.

  In the present embodiment, a vibration level positioned between the conduction band and the lower level is formed according to the wavelength of the guide light 520. The electrons make a transition to this vibration level once, and then transition to a lower level by stimulated emission. The emission wavelength at this time depends on the band gap difference between the vibration level and the ground level. In this embodiment, the wavelength of the guide light 520 is 450 nm, and the band gap difference between the vibration level and the ground level also corresponds to 450 nm.

  As a result of stimulated emission due to such a non-adiabatic process, the electron density in the conduction band decreases. As a result, the amount of moving electrons is reduced in the region where the dopant distribution in which evanescent light is generated is formed. That is, stimulated emission takes away energy of electrons and holes, heat generation is suppressed, and the dopant distribution is fixed without change.

  Further, when evanescent light is emitted at a predetermined location on SiC substrate 102, the emitted light itself becomes induced light, and evanescent light due to dopant distribution is likely to be generated at other locations on SiC substrate 102. In this way, generation of evanescent light and fixation of the dopant distribution are repeated while moving the location within the ion implantation region 426, and a vibration level located entirely between the conduction band and the lower level is formed. become. This is a phosphor that emits light having a wavelength corresponding to the guide light 520 when irradiated with light having a wavelength shorter than the absorption edge wavelength of the single crystal 6H-type SiC.

  The light emitting diode element 400 configured as described above emits ultraviolet light radially from the multiple quantum well active layer 410 when a voltage is applied to the p-side electrode 431 and the n-side electrode 432. Of the ultraviolet light emitted from the multiple quantum well active layer 410, most of the ultraviolet light directed to the p-side electrode 431 and the n-side electrode 432 is reflected by the electrodes 431 and 432 and travels toward the SiC substrate 402. Therefore, most of the light emitted from the multiple quantum well active layer 410 is directed to the SiC substrate 402.

  The ultraviolet light incident on the SiC substrate 402 is converted from blue to green first visible light by the second fluorescent SiC layer 424, and the rest is converted from yellow to orange second visible light by the first fluorescent SiC layer 422. Is done. Thus, since the second fluorescent SiC layer 424 has a light emitting component on the short wavelength side and the first fluorescent SiC layer 422 has a light emitting component on the long wavelength side, white light with high color rendering can be obtained. This light is emitted from the SiC substrate 402 to the outside as white light similar to sunlight.

  Thus, according to the light-emitting diode element 400 of the present embodiment, the emission wavelength region of 6H-type SiC doped with boron and nitrogen based on the newly formed level in the second fluorescent SiC layer 424. The light emission on the shorter wavelength side can be obtained.

  Further, according to the present embodiment, since the additional impurity is doped by ion implantation, the crystallinity of the ion implantation region 426 is impaired, and the reconfiguration of the crystal of the ion implantation region 426 is facilitated. Further, since the crystallinity is impaired, the resistance of the ion implantation region 426 becomes relatively high, and heat can be generated accurately in the ion implantation region 426 when a voltage is applied.

  Further, according to the present embodiment, since the additional impurity doped in the ion implantation region 426 has a diffusion coefficient larger than that of the donor impurity and the acceptor impurity, the additional impurity easily moves in the SiC, which is suitable for evanescent light. The dopant distribution can be obtained relatively easily. In addition to this, even if the additional impurity is doped by the ion implantation method, the additional impurity becomes interstitial atoms, so that it can easily move in SiC, and a dopant distribution suitable for evanescent light can be easily obtained. In addition, the emission wavelength of the second fluorescent SiC layer 424 can be adjusted by changing the wavelength of the guide light 520, and the color rendering properties and the color temperature can be easily adjusted.

  In the above embodiment, the ion implantation region 426 is annealed by current annealing. However, it is needless to say that annealing may be performed by other methods such as laser irradiation annealing. Moreover, although the thing which doped the additional impurity by the ion implantation method was shown, it is also possible to diffuse an impurity by thermal annealing in the state which put the impurity raw material on the surface of SiC, for example.

  In the above-described embodiment, the ion implantation region 426 is doped with an impurity different from the donor impurity and the acceptor impurity as an additional impurity. However, it is needless to say that the same impurity may be doped. In addition, although the impurity is diffused by annealing, it may be diffused by other methods.

FIG. 11 is a schematic longitudinal sectional view of a light emitting device showing a third embodiment of the present invention.
As shown in FIG. 11, the light emitting device 601 is formed at a cylindrical housing 602 having an opening 602a formed at one end, a SiC fluorescent plate 603 that closes the opening 602a, and the other end of the housing 602. Terminal portion 604. In the present embodiment, the case 602 will be described with one end side as an upward direction and the other end side as a downward direction. The housing 602 accommodates a plurality of types of LED elements to which power is supplied from the terminal portion 604, and the SiC fluorescent plate 603 is excited by ultraviolet light emitted from the LED elements to emit light. The blue light, green light, and red light emitted from the LED element pass through the SiC fluorescent plate 603 without being wavelength-converted.

  The housing 602 is made of an inorganic material, the lower end is closed, and the closed portion forms the bottom 602b. The housing 602 is made of ceramic and is AlN in this embodiment. A mounting substrate 610 on which the ultraviolet LED element 611, the blue LED element 612, the green LED element 613, and the red LED element 614 are mounted is fixed to the bottom portion 602b. Although the mounting substrate 610 can be fixed by any method, in this embodiment, the mounting substrate 610 is fixed by a screw 605 that is screwed into the bottom portion 602b. The portion of the opening 602a of the housing 602 is formed in a step shape, and the SiC fluorescent plate 603 is fixed to the step portion. The housing 602 has a flange 602c that protrudes downward from the bottom 602b. In this embodiment, the flange 602c is formed over the circumferential direction.

  The terminal portion 604 is made of an inorganic material and is configured to be screwable with a predetermined socket that supplies power. The terminal portion 604 includes a cylindrical portion 604a that is fixed to the inner peripheral surface of the flange 602c of the housing 602, an inclined portion 604b that is formed continuously with the lower end of the cylindrical portion 604a and narrows downward, and the inclined portion 604b. A first electrode 604c provided at the lower end and having an external thread formed on the outer surface, an insulating portion 604d formed continuously with the lower end of the first electrode 604c and extending radially inward, and a radially inner side of the insulating portion 604d closed. Two electrodes 604e. The cylindrical portion 604a, the inclined portion 604b, and the insulating portion 604d are made of an insulating ceramic, and the first electrode 604c and the second electrode 604e are made of a conductive metal. The cylindrical portion 604a, the inclined portion 604b, and the insulating portion 604d are preferably made of the same material as the housing 602. The first electrode 604 c and the second electrode 604 e are electrically connected to the screw 605 by an internal conductor 606. In this embodiment, the screw 605 is made of a conductive metal, and is electrically connected to the wiring pattern of the mounting substrate 610 when screwed with the mounting substrate 610.

  The SiC fluorescent plate 603 is made of 6H-type SiC crystal and is formed in a plate shape. The SiC fluorescent plate 603 is made of single crystal 6H-type SiC, and includes a first fluorescent SiC layer 603a that emits light by a donor-acceptor pair, and a second fluorescent SiC that serves as an auxiliary light emitting unit that emits light based on a newly formed level. A layer 603b. The first fluorescent SiC layer 603a is bulky and contains nitrogen as a donor impurity and boron as an acceptor impurity. The second fluorescent SiC layer 603 is processed into a porous shape, has a fine shape formed on the surface, and has a level different from the crystal structure of normal single crystal 6H-type SiC. The first fluorescent SiC layer 603a emits approximately yellow to orange visible light by donor-acceptor pair emission when excited by ultraviolet light, and the second fluorescent SiC layer 603b is newly formed when excited by ultraviolet light. It emits roughly blue to green light by light emission based on the level.

  In the light emitting device 601 configured as described above, the terminal portion 604 is screwed into an external socket, and thus power can be supplied to the LED elements 611, 612, 613, and 614. When a voltage is applied to each LED element 611, 612, 613, 614, light of a predetermined wavelength is emitted from each LED element 611, 612, 613, 614.

  The ultraviolet light emitted from the ultraviolet LED element 611 enters the SiC fluorescent plate 603, is absorbed by the SiC fluorescent plate 603 and converted into white, and then exits from the SiC fluorescent plate 603 to the outside of the apparatus. Further, visible light (in this embodiment, blue light, green light, and red light) emitted from the LED elements 612, 613, and 614 except the ultraviolet LED element 611 is incident on the SiC fluorescent plate 603, and then wavelength-converted. The light is emitted from the SiC fluorescent plate 603 to the outside of the apparatus without being processed.

  As described above, when the LED elements 611, 612, 613, and 614 are energized, the mixed light of the white light generated by the fluorescence of the SiC fluorescent plate 603 and the blue light, green light, and red light transmitted through the SiC fluorescent plate 603 is transmitted to the outside. Released. Therefore, in addition to the pure white fluorescence of the SiC fluorescent plate 603, the blue component, the green component, and the red component can be supplemented by the blue LED element 612, the green LED element 613, and the red LED element 614, and the white having extremely high color rendering properties. Light can be obtained.

  Further, according to the light emitting device 601 of the present embodiment, the second fluorescent SiC layer 603b is shorter than the emission wavelength region of 6H-type SiC doped with boron and nitrogen by a method other than donor-acceptor pair emission. Light emission on the wavelength side can be obtained. In addition, the emission wavelength of the second fluorescent SiC layer 603b can be adjusted by changing the wavelength of the guide light, and the color rendering properties and the color temperature can be easily adjusted.

  For example, as shown in FIG. 12, the mounting substrate 610 can be a SiC fluorescent substrate 710. FIG. 12 is a schematic cross-sectional view of a light-emitting device showing a fourth embodiment of the present invention. In the light emitting device 701 of FIG. 12, the opening 602 a of the housing 602 is closed by a transparent lens 703 instead of the SiC fluorescent plate 603.

  The SiC fluorescent substrate 710 is made of single crystal 6H-type SiC, and includes a first fluorescent SiC layer 710a that emits light by a donor-acceptor pair, and a second fluorescent light serving as an auxiliary light emitting unit that emits light based on a newly formed level. SiC layer 710b. The first fluorescent SiC layer 710a is bulky and contains nitrogen as a donor impurity and boron as an acceptor impurity. Second fluorescent SiC layer 710b is processed into a porous shape, has a fine shape on the surface, and has a level different from the crystal structure of normal single crystal 6H-type SiC. The first fluorescent SiC layer 710a emits approximately yellow to orange visible light by donor-acceptor pair emission when excited by ultraviolet light, and the second fluorescent SiC layer 710b is newly formed when excited by ultraviolet light. It emits roughly blue to green light by light emission based on the level.

The lens 703 is made of glass and condenses light emitted from the housing 602 with an emission surface having a convex shape upward. Here, when ultraviolet light is contained in the transmitted light, the glass cuts, for example, 70% or more of ultraviolet light alone. In the present embodiment, a multilayer reflective film (DBR film) made of an inorganic material that reflects light emitted from the ultraviolet LED element 611 is formed on the inner surface of the housing 602 of the lens 703. The multilayer reflective film can be made of SiO ₂ / TiO ₂ , for example. In addition, instead of the multilayer reflective film, an inorganic material having a higher reflectance than glass for ultraviolet light may be applied to the inner surface of the glass of the lens 703.

  In the light emitting device 701 configured as described above, when the LED elements 611, 612, 613, and 614 are energized, white light generated by the fluorescence of the SiC fluorescent substrate 710 and blue light emitted from the LED elements 612, 613, and 614. Mixed light of light, green light and red light is emitted to the outside. Therefore, in addition to the pure white fluorescence of the SiC fluorescent substrate 710, the blue component, the green component, and the red component can be supplemented by the blue LED element 612, the green LED element 613, and the red LED element 614, and the color rendering property is extremely high. White light can be obtained.

  Further, according to the light emitting device 701 of the present embodiment, the second fluorescent SiC layer 710b is shorter than the emission wavelength region of 6H type SiC doped with boron and nitrogen by a method other than donor-acceptor pair emission. Light emission on the wavelength side can be obtained. Further, the emission wavelength of the second fluorescent SiC layer 710b can be adjusted by changing the wavelength of the guide light, and the color rendering properties and the color temperature can be easily adjusted.

DESCRIPTION OF SYMBOLS 100 Light emitting diode element 102 SiC substrate 122 1st fluorescence SiC layer 124 2nd fluorescence SiC layer 220 Guide light 400 Light emitting diode element 402 SiC substrate 422 1st fluorescence SiC layer 424 2nd fluorescence SiC layer 520 Guide light 601 Light-emitting device 603 SiC phosphor plate 603a First fluorescent SiC layer 603b Second fluorescent SiC layer 701 Light emitting device 710 SiC fluorescent substrate 710a First fluorescent SiC layer 710b Second fluorescent SiC layer

Claims (11)

When a donor impurity and an acceptor impurity are doped and excited by excitation light, a part of the phosphor that emits light with the first wavelength light by the donor-acceptor pair is irradiated with the second wavelength light having a wavelength different from that of the first wavelength light. An auxiliary light emitting unit that changes the crystal structure below to form a new level corresponding to the second wavelength light and emits the phosphor with the second wavelength light when excited by the excitation light. age,
A method of manufacturing a phosphor that emits both the first wavelength light and the second wavelength light when excited by the excitation light.   The method for producing a phosphor according to claim 1, wherein the change in crystal structure in a part of the phosphor is performed by changing a surface shape.   The method for manufacturing a phosphor according to claim 2, wherein the change in the surface shape of the phosphor is performed by anodization.   The method for manufacturing a phosphor according to claim 1, wherein the change in crystal structure in a part of the phosphor is performed by changing the distribution of impurities.   The method for manufacturing a phosphor according to claim 4, wherein the change in the distribution of impurities is performed by annealing.   The method for manufacturing a phosphor according to claim 5, wherein a part of the phosphor is doped with an additional impurity before the crystal structure is changed.   The method of manufacturing a phosphor according to claim 6, wherein the additional impurity has a diffusion coefficient larger than that of the donor impurity and the acceptor impurity.   The method of manufacturing a phosphor according to claim 6 or 7, wherein the doping of the additional impurity into a part of the phosphor is performed by ion implantation. The phosphor is made of 6H SiC.
The donor impurity is nitrogen;
The method for manufacturing a phosphor according to claim 1, wherein the acceptor impurity is at least one of boron and aluminum. It is manufactured by the method for manufacturing a phosphor according to any one of claims 1 to 9,
A donor-acceptor pair light-emitting unit that emits the first wavelength light when excited by excitation light;
A phosphor comprising: an auxiliary light emitting unit that emits the second wavelength light when excited by the excitation light. A substrate comprising the phosphor according to claim 10;
A light emitting element comprising: a semiconductor stacked portion that is formed on the substrate and emits the excitation light.

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