JP2005187791A - Phosphor and light-emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor capable of being excited by a long-wavelength light source in an ultraviolet region or a visible region of a blue color to a violet color and capable of emitting light mainly in a visible region of the violet color through the blue color and a yellow color to a red color, and to provide a light-emitting diode capable of being easily mounted, excellent in color rendering properties, capable of being given at a low cost, and scarcely causing changes in coloration due to radiation angles. <P>SOLUTION: This phosphor made of SiC is excited by the external light source and emits the light, wherein the substance is doped by at least one kind of elements of B and Al, and further by N. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a SiC phosphor that emits light by being excited by an electromagnetic wave such as an electron beam, X-ray, ultraviolet light, or blue-violet visible light, a method for producing the same, and a semiconductor substrate and powder made of the phosphor. . The present invention also relates to a light-emitting diode including a group III nitride semiconductor, which is expected to spread in the future as a new solid-state lighting device.

  Development of PDP panels that excite phosphors by using vacuum ultraviolet rays emitted by rare gas discharge to emit light has been actively conducted. A PDP panel is formed by a number of display cells arranged in a matrix, and each display cell is provided with a discharge electrode. In addition, a phosphor is applied in the inside, and a rare gas such as He—Xe or Ne—Xe is enclosed. When a voltage is applied to the discharge electrode, vacuum ultraviolet rays are emitted, whereby the phosphor is excited and emits visible light.

  In the case of a fluorescent lamp, when discharge is started in a discharge tube in which a mixed gas of mercury and argon gas is sealed, electrons in the discharge space are accelerated by an electric field and drift toward the anode. During this time, electrons excite mercury atoms in the fluorescent lamp tube, and visible light is emitted by ultraviolet rays having a wavelength of 253.7 nm emitted from the excited mercury atoms.

  Phosphors that emit light when excited by ultraviolet rays (hereinafter referred to as “ultraviolet-excited phosphors”) are decorated with fluorescent lamps, high-pressure mercury lamps, fluorescent wall materials and fluorescent tiles used indoors and outdoors in addition to PDPs. Widely used in various applications. Fluorescent wall materials or tiles are excited by ultraviolet light having a long wavelength of about 365 nm, and emit light brightly in various colors.

  Devices that are excited by light emitted from a semiconductor are also known. In this device, the load on the semiconductor is reduced when the light from the semiconductor is as long as possible. Therefore, the wavelength of the excitation light is preferably 360 nm or more, more preferably 380 nm or more, and particularly preferably 400 nm or more.

Conventional phosphors excited by long-wavelength ultraviolet light include blue-emitting Eu-activated alkaline earth halophosphate phosphors, Eu-activated alkaline earth aluminate phosphors, Eu-activated LnO phosphors, and the like. Further, there is a green light emitting Zn ₂ GeO ₄ : Mn phosphor, a yellow light emitting YAG: Ce (cerium-doped yttrium, aluminum, garnet) phosphor, a red light emitting Y ₂ O ₂ S: Eu phosphor, and YVO. ₄ : Eu phosphors have been put into practical use.

  However, with the diversification and higher functionality of display, there are demands for multicolored and high luminance emission colors, improved durability, and improved weather resistance. Furthermore, research on phosphors using II-VI group semiconductors such as ZnSe and ZnO has been actively conducted (see Patent Document 1).

  On the other hand, a phosphor is known that emits infrared light of 900 nm or more by adding rare earth elements such as Yb and Er using SiC as a base material and exciting the rare earth elements themselves (see Patent Document 2). In this phosphor, the base material is SiC, but in principle, it is centered on the emission of rare earth elements and uses the same mechanism as the emission of light by adding rare earth elements based on oxides. is there. The SiC crystal can be produced by an improved Rayleigh method in which sublimation recrystallization is performed using an SiC single crystal as a seed crystal (see Non-Patent Document 1).

  In recent years, crystal growth methods for nitride semiconductors have rapidly progressed, and high-intensity blue and green light-emitting diodes using nitride semiconductors have been put into practical use. By combining the existing red light emitting diodes with these blue and green light emitting diodes, all three primary colors of light are aligned, and a full color display device can be realized. That is, when all three primary colors of light are mixed, white light can be obtained, and application to a white illumination device is also possible.

  Several configurations have been proposed as white light sources using light emitting diodes, and some have been put into practical use. FIG. 9 shows an example of a white light source using a light emitting diode. As shown in FIG. 9, this white light source is formed by forming light emitting diodes of three primary colors of a red light emitting diode 911, a green light emitting diode 912, and a blue light emitting diode 913 on a metal layer 903 of a conductive heat sink 902. The resin 908 is fixed on the stem 905.

  In this white light source, the lead wire connected to each light emitting diode is connected to an individual terminal, and the current flowing to each is controlled independently, so that not only white but also full color can be displayed. High conversion efficiency. On the other hand, the device and the drive circuit are complicated and the cost is high, so it is not suitable as a simple lighting device.

  Another example of a white light source using a light emitting diode is shown in FIG. In this white light source, as shown in FIG. 10, a blue light emitting diode 101 is formed on a metal layer 103 of a conductive heat sink 102, and a yellow phosphor layer 104 made of a YAG-based material is formed on the blue light emitting diode 101. It is formed and fixed on the stem 105 with an epoxy resin 108.

  In this white light source, a part of light having a peak wavelength of about 450 nm emitted from the blue light emitting diode 101 is absorbed by the YAG yellow phosphor layer 104 and converted into yellow fluorescence having a wavelength of about 570 nm. For this reason, both blue light transmitted through the YAG yellow phosphor layer 104 and yellow light emitted from the YAG yellow phosphor layer 104 are emitted to the outside of the element. Since yellow is complementary to blue, two types of light, yellow and blue, are mixed to obtain white light.

Since the white light source shown in FIG. 10 includes a single light emitting diode 101, it can be manufactured at a relatively low cost. Moreover, the highest luminous efficiency is currently achieved, and at the research level, a luminance efficiency of about 701 m / W has been achieved, which is almost the same as existing fluorescent lamps.
JP 2001-228809 A Japanese Patent Laid-Open No. 10-270807 YM Tairov and VF Tsvctkov, Journal of Crystal Growth, (1981) vol. 52 pp. 146-150

  A conventional phosphor that is excited by a light source having a long wavelength and uses an oxide as a base material has a lower fluorescence emission efficiency, particularly a red emission efficiency, as the excitation light has a longer wavelength. Since oxides generally have a very wide band gap, the excitation of the oxide itself cannot be used when excited by a long wavelength light source. Therefore, although the excitation of the rare earth element itself is used, the emission efficiency of the fluorescence when the material added with the rare earth element is excited at a long wavelength is very low, and the emission efficiency is not improved.

  Since phosphors using II-VI group semiconductors can easily form mixed crystals or solid solutions, techniques such as band engineering can be used, and the luminous efficiency is very high. However, since both group II and group VI have high electronegativity, the ionic bonding property of the II-VI group semiconductor crystal becomes high and is likely to change over time.

  The method of using infrared light emission by adding a rare earth element to SiC and exciting the rare earth element has a very small lattice constant of SiC, whereas the rare earth element has a large atomic radius. Addition causes the crystallinity of SiC to deteriorate significantly. Therefore, the amount of rare earth element added is limited, and the emission intensity cannot be increased.

  Further, light emission by a donor acceptor (hereinafter referred to as “DA”) pair in which N and B are simultaneously added to SiC and N functions as a donor and B functions as an acceptor has a peak at a wavelength of about 650 nm. However, since the emission intensity is extremely small, it cannot be used as a phosphor.

  On the other hand, for a white light source using a light emitting diode, for example, in the example shown in FIG. 9, the drive circuit and the device are complicated, so that mounting is difficult, the yield is low, and color unevenness occurs due to the light emission angle. There are various issues to be solved.

  In the example shown in FIG. 10, a part of the blue light emitted from the blue light emitting diode 101 is converted into yellow light by exciting the yellow phosphor layer 104, and both blue and yellow are emitted to the outside. To get white light. In this case, the hue changes unless the intensity ratio of blue light and yellow light is set appropriately. Therefore, it is necessary to adjust the film thickness and the phosphor concentration of the yellow phosphor layer 104 formed on the blue light emitting diode 101 appropriately and uniformly. For this reason, the technique of mixing yellow fluorescent substance powder uniformly in resin-made binders and apply | coating with a uniform film thickness is needed.

  Even if the phosphor layer 104 is uniform, the light emitted from the blue light emitting diode 101 has a different path length through the phosphor layer depending on the emission angle. For this reason, a change in white hue is inevitable depending on the emission angle. Furthermore, the combination of the blue light emitting diode 101 and the yellow phosphor layer 104 as shown in FIG. 10 has a very small red component, so that the color rendering property, which is important as an illumination light source, is inferior, and the red reproducibility is low. is there.

  An object of the present invention is to provide a phosphor that is excited by a long wavelength light source in the ultraviolet region or in the visible region of blue-purple and emits light mainly in the visible region of purple-blue-yellow-red. Also, to provide a phosphor that efficiently emits fluorescent light with good characteristics by primary light from a light source such as a mercury discharge tube, a high-pressure mercury lamp, or an LED (laser emitting diode), vacuum ultraviolet rays or electron beams generated by discharge of a PDP panel, etc. It is in.

  Another object of the present invention is to provide a low-cost light-emitting diode that is easy to mount and excellent in color rendering. It is another object of the present invention to provide a light emitting diode with little color change due to the radiation angle.

The SiC phosphor of the present invention emits light when excited by an external light source and is doped with N and one or more elements of B or Al. In such a phosphor, and doping concentration by any one or more elements of B or Al, any doping concentration by N, preferably embodiment is ^{10 15 / cm 3 ~10 20 /} cm 3, 10 16 / cm ³ to 10 embodiment and more preferably ²⁰ / cm ^3.

The phosphors made of SiC of the present invention include those that emit fluorescence with a wavelength of 500 nm to 750 nm and have a peak wavelength at 500 nm to 650 nm. Such SiC is doped with N and B, and the concentration of either N or B is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ^3. Those of ³ are preferred.

Further, the SiC phosphor of the present invention includes those that emit fluorescence with a wavelength of 400 nm to 750 nm and have a peak wavelength at 400 nm to 550 nm. Such SiC is doped with N and Al, and the concentration of either N or Al is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ , and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ^3. Those of ³ are preferred.

The manufacturing method of the SiC phosphor of the present invention is excited by an external light source, emits fluorescence with a wavelength of 500 nm to 750 nm, has a peak wavelength at 500 nm to 650 nm, is doped with N and B, and N or B A method for producing a phosphor made of SiC in which one of the concentrations is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ³ ,
According to the first aspect, LaB ₆ , B ₄ C, TaB ₂ , NbB ₂ , ZrB ₂ , HfB ₂ , BN, or carbon containing B is used as a B source to form a SiC crystal by sublimation recrystallization. It is characterized by doing.

Further, according to the second aspect, B alone, LaB ₆ , B ₄ C, TaB ₂ , NbB ₂ , ZrB ₂ , HfB ₂ or BN are used as the B source, and 1500 ° C. under vacuum or in an inert gas atmosphere. As described above, it is characterized by thermal diffusion into SiC.

  The semiconductor substrate of the present invention is a phosphor that emits light when excited by an external light source, and is made of a 6H-type SiC single crystal phosphor doped with one or more elements of B or Al and N. It is characterized by becoming. Such semiconductor substrates include those made of 6H-type SiC single crystal phosphor doped with N and B, emitting fluorescence with a wavelength of 500 nm to 750 nm, and having a peak wavelength at 500 nm to 650 nm. Further, a semiconductor substrate made of 6H-type SiC single crystal phosphor that is doped with N and Al, emits fluorescence with a wavelength of 400 nm to 750 nm, and has a peak wavelength at 400 nm to 550 nm is included.

The method for producing a semiconductor substrate of the present invention is excited by an external light source, emits fluorescence with a wavelength of 500 nm to 750 nm, has a peak wavelength at 500 nm to 650 nm, is doped with N and B, and either N or B In the method for producing a substrate made of a 6H-type SiC single crystal phosphor having one concentration of 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ and the other concentration of 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ³ There,
According to the first aspect, B alone, LaB ₆ , B ₄ C, TaB ₂ , NbB ₂ , ZrB ₂ , HfB ₂ or BN are used as a B source, at 1500 ° C. or higher in a vacuum or in an inert gas atmosphere. And a step of thermally diffusing into SiC and a step of removing the surface layer.

Further, according to the second aspect, the atmosphere gas during crystal growth includes 1% to 30% N ₂ gas in terms of gas partial pressure, and the raw material SiC includes 0.05 mol% to 15 mol% B source. The SiC crystal is formed by the sublimation recrystallization method characterized by the above.

  The semiconductor powder of the present invention is excited by an external light source, emits fluorescence with a wavelength of 500 nm to 750 nm, and consists of a 6H type SiC single crystal phosphor having a peak wavelength at 500 nm to 650 nm, and has a particle size of 2 μm to 10 μm. The center particle size is 3 μm to 6 μm.

  According to a first aspect, the light-emitting diode of the present invention includes a semiconductor substrate composed of a 6H-type SiC single crystal phosphor doped with one or more elements of B or Al and N, and a substrate. A light emitting element made of a nitride semiconductor is provided thereon.

  Further, according to the second aspect, one or more layers made of 6H-type SiC single crystal phosphor doped with one or more elements of B or Al and N are made of SiC. A light-emitting element made of a nitride semiconductor is provided on a semiconductor substrate and on a 6H-type SiC single crystal phosphor layer. In such a light emitting diode, a light emitting element made of a nitride semiconductor preferably has an emission wavelength of 408 nm or less.

In such a light emitting diode, in the 6H type SiC single crystal phosphor, the doping concentration by one or more elements of B or Al and the doping concentration by N are both 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ^3. Are preferable, and those having a density of 10 ¹⁷ / cm ³ to 10 ¹⁹ / cm ³ are more preferable.

  According to the present invention, the impurity concentration in SiC can be controlled and excited by a long wavelength light or an electron beam in the ultraviolet region or the blue-purple visible region, and the visible region of purple-blue-yellow-red Thus, a phosphor that emits light efficiently can be provided.

  In addition, according to the present invention, the color rendering properties can be easily adjusted, and since the light emitting diode is formed, a white light source that can be easily mounted can be provided at low cost. Since this white light source produces white light inside, the change in hue due to the radiation angle is so small that it can be ignored, and the light emission efficiency is excellent.

(SiC phosphor)
The SiC phosphor of the present invention is characterized in that it is doped with one or more elements of B or Al and N. Take it. The SiC phosphor is excited by an ultraviolet light source or an external light source such as an electron beam, and emits light mainly in the visible region of purple-blue-yellow-red.

  For example, a SiC phosphor doped with B and N is excited by an external light source, emits fluorescence having a wavelength of 500 nm to 750 nm, and has a peak wavelength at 500 nm to 650 nm. The SiC phosphor doped with Al and N emits fluorescence with a wavelength of 400 nm to 750 nm and has a peak wavelength at 400 nm to 550 nm. Furthermore, the SiC phosphor doped with Al, B, and N emits fluorescence of 400 nm to 750 nm and has a peak wavelength of 400 nm to 650 nm.

In order to increase the luminous efficiency of fluorescence, a state density of impurity levels sufficient to accept electron-hole pairs relaxed from the band edge of SiC is necessary. In this respect, it is preferable that the impurity concentration of any one or more elements of B or Al and the impurity concentration of N are both 10 ¹⁵ / cm ³ or more, and 10 ¹⁶ / cm ³ or more. Is more preferably 10 ¹⁸ / cm ³ or more. On the other hand, when the impurity concentration is too high, the light emission efficiency of fluorescence tends to decrease, and therefore it is preferably 10 ²⁰ / cm ³ or less.

When doping with N and B, the concentration of either N or B is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ^{3. The} embodiment which is ³ is preferable. On the other hand, also when doping with N and Al, the concentration of either N or Al is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ^{3. The} embodiment which is ³ is preferable. In the present specification, the light emission is represented by a numerical value obtained by measuring the light emission when a light beam (purple) having a wavelength of 404.7 nm is incident, using a PHOTOLUMINOR-S manufactured by Horiba. Further, the concentration of N, Al or B is represented by a numerical value measured by SIMS (secondary ion mass spectrometer).

  The external light source that can be used in the present invention is a light source that emits visible light such as blue-purple, ultraviolet rays, X-rays, or an electron beam, and in particular, visible light such as blue-purple having a wavelength of 100 nm to 500 nm. And ultraviolet rays are preferred because they tend to emit fluorescence with high emission intensity. The SiC semiconductor has a wide forbidden band of about 3 eV, and various orders can be created in the band by adding impurities. In particular, 6H-type SiC has a band edge wavelength of 408 nm. By utilizing the band gap of SiC, it is possible to excite light with a wavelength shorter than the band edge wavelength, and excite relatively long wavelength light. Can be used as a source.

As a result of intensive studies, the present inventors have doped 6H-type polytype SiC crystals with N as a donor under the condition that B as an acceptor is sufficiently activated, and the concentration of DA pair is 10 ¹⁵ / It has been found that the emission intensity is sufficiently high when it is cm ³ to 10 ¹⁸ / cm ³ . The concentration of DA pair, in that the luminous intensity is improved, the lower limit is more preferably 5 × 10 ¹⁵ / cm ³ or more, particularly preferably 10 ¹⁶ / cm ³ or more, more preferably 2 × 10 ¹⁶ / cm ³ or more . On the other hand, the upper limit is more preferably 8 × 10 ¹⁷ / cm ³ or less in terms of increasing the emission intensity.

If the concentration of the DA pair is in such a range, the lower limit of the concentration of either B or N is more preferably 10 ¹⁶ / cm ³ or more in that good light emission can be obtained. 10 ¹⁶ / cm ³ or more is particularly preferable. On the other hand, the upper limit is more preferably 10 ¹⁹ / cm ³ or less, and particularly preferably 5 × 10 ¹⁸ / cm ³ or less, in that good light emission can be obtained.

  The light emission of the SiC phosphor having the B and N concentrations within such a range shows a broad spectrum as shown in FIG. 3, and emits good red-yellow fluorescence. That is, the SiC phosphor of the present invention emits fluorescence having a wavelength of 500 nm to 750 nm, and has a high emission intensity at a wavelength of 550 nm to 680 nm. Moreover, what has a peak wavelength in 500 nm-650 nm and has a peak wavelength in 570 nm-630 nm is preferable. The emission wavelength and its relative intensity vary depending on the doping concentrations of B and N in SiC.

In addition, the present inventors similarly found a concentration condition in which the emission intensity of the DA pair of Al and N becomes strong. That is, when a 6H-type polytype SiC crystal is doped with N as a donor under the condition that Al as an acceptor is sufficiently activated, and the DA pair concentration is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ Further, it has been found that the emission intensity is sufficiently high. The concentration of DA pair, in that the luminous intensity is improved, the lower limit is more preferably 5 × 10 ¹⁵ / cm ³ or more, particularly preferably 10 ¹⁶ / cm ³ or more, more preferably 2 × 10 ¹⁶ / cm ³ or more . On the other hand, the upper limit is more preferably 8 × 10 ¹⁷ / cm ³ or less in terms of increasing the emission intensity.

If the concentration of the DA pair is within such a range, the lower limit of the concentration of either Al or N is more preferably 10 ¹⁶ / cm ³ or more in that good light emission can be obtained. 10 ¹⁶ / cm ³ or more is particularly preferable. On the other hand, the upper limit is more preferably 10 ¹⁹ / cm ³ or less, and particularly preferably 5 × 10 ¹⁸ / cm ³ or less, in that good light emission can be obtained.

  The light emission of the SiC phosphor in which the concentrations of Al and N are within such a range shows a broad spectrum and emits a blue broad fluorescence as illustrated in FIG. That is, the SiC phosphor of the present invention emits fluorescence having a wavelength of 400 nm to 750 nm, and has a high emission intensity at a wavelength of 400 nm to 550 nm. Moreover, what has a peak wavelength in 400 nm-550 nm and has a peak wavelength in 410 nm-470 nm is preferable. The emission wavelength and its relative intensity vary depending on the doping concentrations of Al and N in SiC.

(Manufacturing method of SiC phosphor)
The manufacturing method of the SiC phosphor of the present invention uses LaB ₆ , B ₄ C, TaB ₂ , NbB ₂ , ZrB ₂ , HfB ₂ , BN, or B-containing carbon as a B source, and a sublimation recrystallization method. A SiC crystal is formed. By this method, SiC is doped with N and B, and either N or B has a concentration of 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ and the other concentration of 10 ¹⁶ / cm ³ to 10 ^19. The doping concentration can be adjusted to be / cm ^3, and an SiC phosphor having a peak wavelength in the range of 500 nm to 650 nm can be produced by exciting with an external light source to emit fluorescence having a wavelength of 500 nm to 750 nm.

  Such concentration adjustment can be achieved by positively adding N and B during SiC crystal growth. The SiC crystal can be produced by an improved Rayleigh method, but this method uses a seed crystal, so the nucleation process of the crystal can be controlled, and the atmosphere is set to about 100 Pa to 15 kPa with an inert gas. The crystal growth rate can be controlled with good reproducibility.

  In the improved Rayleigh method, as shown in FIG. 2, first, an SiC single crystal serving as a seed crystal 21 is attached to a lid 24 of a crucible 23, and SiC crystal powder as a raw material 22 for sublimation recrystallization is placed in a graphite crucible 23. In addition, it is heated to 133 Pa to 13.3 kPa and 2000 ° C. to 2400 ° C. in an atmosphere of an inert gas such as Ar. At the time of heating, as shown by the arrows in FIG. 2, the temperature gradient is set so that the SiC crystalline powder as the raw material 22 is slightly heated (H) and the seed crystal 21 is slightly cooled (L). After the sublimation, the raw material 22 is diffused in the direction of the seed crystal 21 and transported by the concentration gradient formed based on the temperature gradient. The growth of the SiC single crystal 20 is realized by recrystallizing the source gas arriving at the seed crystal 21 on the seed crystal.

The doping concentration of the SiC crystal can be controlled by adding an impurity gas to the atmospheric gas during crystal growth and adding an impurity element or compound thereof to the raw material powder. In particular, it is preferable to add N ₂ gas and perform sublimation recrystallization to easily control the N concentration of 5 × 10 ¹⁸ / cm ³ or more. In addition, in order to stabilize the concentration control of DA pairs of 1 × 10 ¹⁸ / cm ³ or less, improve reproducibility, and improve the emission intensity, N is set to be actively added, and B is stabilized. It is preferable to set the conditions so that they are added to the crystal.

For example, an SiC phosphor having an N concentration of 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ is manufactured by setting the partial pressure of N ₂ gas in the atmospheric gas during crystal growth to 1% to 30%. Can do. In this case, the partial pressure of N ₂ gas is preferably 5% to 10% in terms of increasing the fluorescence emission intensity.

B can be added by mixing B alone (metallic boron) with the raw material, but this method has a high B concentration in the initial stage of crystallization, and the B concentration decreases in the latter half of the crystallization, so that the B concentration is stable. There is a disadvantage of not. Therefore, when M is added as a B compound represented by MB ₂ as a metal containing at least one of Ta, Nb, Zr, or Hf, the B concentration is less likely to change during crystal growth. Is preferable. Further, it is preferable to add it as LaB ₆ or B ₄ C because the change in the B concentration can be similarly suppressed. By this method, B having a concentration of 10 ¹⁷ / cm ³ to 10 ¹⁸ / cm ³ can be easily added stably.

  Carbon is easily impregnated with B simple substance (metallic boron) and has a feature of gradually releasing B even at a sublimation recrystallization temperature of 2000 ° C. or higher. Therefore, carbon containing B simple substance is used as a B source for sublimation. The recrystallization method is excellent as a method for forming a SiC crystal to which B is added. By adding carbon impregnated with B alone at a high temperature of 1500 ° C. or higher in advance to the raw material, it is advantageous that almost no change in the B concentration in the crystal can be eliminated.

By adding powdery or solid BN to the raw material of SiC and maintaining it at a relatively low temperature of about 2000 ° C. and sublimation recrystallization, both N and B can be simultaneously performed without adding N ₂ gas. It can be added in SiC. In this case, since the addition amount of B tends to be relatively lowered, it is preferable to add B in a positive manner in combination with any of the methods described above. By a sublimation recrystallization method using BN, a SiC phosphor having a DA pair concentration of 1 × 10 ¹⁸ / cm ³ to 8 × 10 ¹⁸ / cm ³ can be stably obtained.

  After sublimation recrystallization, it is preferable to apply a thermal annealing treatment at 1300 ° C. or higher for 1 hour or longer in that the intensity of fluorescence emission can be increased. It is considered that B and N mixed in an energetically inactive manner are fixed at the Si or C position by the heat treatment and activated, resulting in an increase in the DA pair concentration. .

Although the blending amount of the B source varies depending on other conditions such as the type of the B source, it is 10 ¹⁶ / cm by using a mixture of 0.05 mol% to 15 mol% with respect to the SiC powder. B having a concentration of ³ to 10 ¹⁹ / cm ³ can be easily and stably added to the SiC crystal. In this case, when a component other than B alone (metal boron) such as MB ₂ , BN or LaB ₆ is blended as the B source, the converted amount of B contained in the B source is defined as the blend amount. The blending amount of the B source is preferably 2.5 mol% to 5 mol% with respect to the SiC powder in terms of increasing the fluorescence emission intensity.

Another method for producing the SiC phosphor of the present invention is as follows: B alone, LaB ₆ , B ₄ C, TaB ₂ , NbB ₂ , ZrB ₂ , HfB ₂ or BN as a B source, under vacuum or in an inert gas atmosphere In this case, the thermal diffusion to SiC is performed at 1500 ° C. or higher. By this method, SiC is doped with N and B, and either N or B has a concentration of 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ and the other concentration of 10 ¹⁶ / cm ³ to 10 ^19. The doping concentration can be adjusted so as to be / cm ^3, and it is excited by an external light source to emit light, emit fluorescence with a wavelength of 500 nm to 750 nm, and produce a phosphor made of SiC having a peak wavelength at 500 nm to 650 nm. it can.

The concentration adjustment of B and N can also be achieved by controlling the thermal diffusion conditions. As SiC to be subjected to thermal diffusion, for example, N doped with about 10 ¹⁷ / cm ³ by a sublimation recrystallization method can be used. In addition, when the B source is brought into direct contact with the SiC crystal during thermal diffusion, the B source and the SiC crystal may react and the SiC crystal may be eroded. Therefore, the B source is separated from the SiC crystal by about 0.1 mm. Thus, it is preferable that the thermal diffusion be performed.

  In the thermal diffusion, an inert gas such as Ar gas can be used, and it is heated to 1500 ° C. or higher, preferably 1700 ° C. to 2000 ° C., and held for 3 hours to 5 hours. A diffusion layer made of B having a thickness of about 3 μm is formed. For example, when an ultraviolet ray having an output of 30 W and a wavelength of 250 nm is irradiated, fluorescence that can be confirmed with the naked eye is emitted.

Depending on the thermal diffusion conditions, a diffusion layer in which B is present at a high concentration of 10 ¹⁹ / cm ³ or more may be formed on the surface of the SiC crystal. Since the region that emits strong fluorescence is 2 μm to 4 μm from the surface of the SiC crystal, it is preferable to remove the high-concentration B layer on the surface by about 2 μm to increase the emission intensity. For example, after thermal diffusion, heating is performed at 1000 ° C. or higher, preferably 1200 ° C. to 1400 ° C. for 2 hours to 4 hours in an acidic atmosphere to form an oxide film, and then chemically treated with, for example, hydrofluoric acid. Thus, it is preferable to remove the surface of the oxide film. In addition, the removal of the surface layer can be preferably carried out by polishing or by reactive ion etching (RIE). Furthermore, as in the case of sublimation recrystallization, it is preferable to perform a thermal annealing treatment at 1300 ° C. or higher for 1 hour or longer after thermal diffusion because the intensity of fluorescence emission can be increased.

The above embodiment exemplifies a method for producing a SiC phosphor in which the concentration of N is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ and the concentration of B is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ^3. To do. However, according to the present invention, the pair concentration of B and N is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ , and the concentration of either B or N is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ³ . Since there is a remarkable effect in a certain phosphor made of SiC, the concentration of N is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ³ and the concentration of B is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ . A phosphor and a method for producing the same are also included in the present invention.

(Semiconductor substrate and powder)
The semiconductor substrate and powder of the present invention are phosphors that emit light when excited by an external light source, and are 6H-type SiC single crystal fluorescence doped with N and one or more elements of B or Al. It consists of a body.

  For example, a semiconductor substrate and powder composed of a 6H-type SiC single crystal phosphor doped with B and N are excited by an external light source to emit fluorescence having a wavelength of 500 nm to 750 nm and have a peak wavelength at 500 nm to 650 nm. The semiconductor substrate and powder made of 6H-type SiC single crystal phosphor doped with Al and N emit fluorescence having a wavelength of 400 nm to 750 nm and have a peak wavelength of 400 nm to 550 nm. Furthermore, the semiconductor substrate and powder made of 6H-type SiC single crystal phosphor doped with Al, B and N emit fluorescence of 400 nm to 750 nm and have a peak wavelength of 400 nm to 650 nm.

  When the SiC phosphor of the present invention is used for a substrate or powder used for a semiconductor such as a GaN-based compound semiconductor that emits light in the blue-ultraviolet region, the resulting light-emitting device is capable of emitting blue-ultraviolet light from the semiconductor. The primary light excites the 6H-type SiC single crystal phosphor to emit secondary light in the visible region of purple-blue-yellow-red, so that direct light from the semiconductor and secondary light from the SiC phosphor Excellent white light can be obtained by the mixed light or the secondary light.

A semiconductor substrate and powder composed of a 6H-type SiC single crystal phosphor doped with B and N have B as a B source, LaB ₆ , B ₄ C, TaB ₂ , NbB ₂ , ZrB ₂ , HfB ₂ or BN, It can be manufactured by a method comprising a step of thermally diffusing into SiC at 1500 ° C. or higher in a vacuum or an inert gas atmosphere and a step of removing the surface layer. As described above, the surface layer is removed by a method in which an oxide film is formed in an oxidizing atmosphere at 1000 ° C. or higher and the surface of the formed oxide film is removed with hydrofluoric acid or the like, or a method of removing by polishing or a reaction. A method of removing by reactive ion etching is preferable.

The semiconductor substrate and powder made of 6H-type SiC single crystal phosphor doped with B and N have an atmosphere gas during crystal growth containing N ₂ gas of 1% to 30% by gas partial pressure, and the raw material SiC is 0 It can also be produced by a sublimation recrystallization method characterized by containing 0.05 mol% to 15 mol% of a B source. In such an embodiment, it is preferable to perform thermal annealing at 1300 ° C. or higher after sublimation recrystallization or thermal diffusion.

In SiC powder containing N at a concentration of 10 ¹⁶ / cm ³ to 10 ¹⁷ / cm ³ , MB ₂ , BN, B ₄ C or LaB ₆ is encapsulated in a carbon capsule as a B source and mixed. Heat in a crucible made at 1300 ° C to 2000 ° C under vacuum and hold for 3-5 hours. Since the obtained SiC powder has a high concentration of B on the surface, the SiC powder is held at 1000 ° C. to 1400 ° C. for 2 hours to 4 hours in an oxidizing atmosphere, and then chemically treated with, for example, hydrofluoric acid. When the oxide film on the surface is removed, strong fluorescence can be observed.

  When BN is used as the B source, a predetermined doping is possible by using a BN crucible instead of a carbon crucible, putting raw SiC powder in the BN crucible, and heating and firing. . As long as the raw SiC powder has a purity of 98% or more, the production method is not limited, and it is not always necessary to use single crystal SiC.

  Moreover, since the layer which emits favorable fluorescence is 1 micrometer-4 micrometers from the surface on this diffusion condition, the minimum of the particle size of SiC powder is 2 micrometers, and 2.5 micrometers or more are preferable. In addition, the layer emitting good fluorescence is 1 μm to 4 μm from the surface, and the depth deeper than 4 μm from the surface weakens the emission intensity. Therefore, the upper limit of the particle size of the SiC powder is 10 μm, preferably 8 μm or less. For the same reason, the center particle size is preferably 3 μm to 6 μm, more preferably 4 μm to 5 μm.

(Light emitting diode)
The light-emitting diode of the present invention includes a semiconductor substrate composed of a 6H-type SiC single crystal phosphor doped with one or more elements of B or Al and N, and a light-emitting composed of a nitride semiconductor on the substrate. An element is provided.

  The SiC substrate emits fluorescence by using blue light-ultraviolet light emitted from the nitride semiconductor on the SiC substrate as excitation light, and can be mixed with the light from the nitride semiconductor to realize a solid white light source. . In addition, it is possible to provide a light source that does not require difficult mounting technology, has high color temperature reproducibility of white light, and is excellent in color rendering.

  For example, a light emitting diode having a GaN-based semiconductor that emits purple light having a wavelength of about 400 nm on a substrate made of 6H-type SiC single crystal phosphor doped with B and N is an excitation light source. Since the SiC substrate emits yellow fluorescence, white light with high reproducibility and good color rendering can be obtained by using yellow fluorescence from SiC and violet light from a GaN-based semiconductor.

  Further, the semiconductor substrate made of SiC has one or more layers made of 6H-type SiC single crystal phosphor doped with one or more elements of B or Al and N, A light-emitting diode having a light-emitting element made of a nitride semiconductor on a 6H-type SiC single crystal phosphor layer has one or more fluorescent lights on the SiC substrate using blue light or violet light from the nitride semiconductor as excitation light. Since the body layer emits fluorescence according to the added impurities, it is possible to provide an excellent solid white light source by mixing these fluorescences or by mixing light and fluorescence from the nitride semiconductor it can.

  For example, a first SiC layer doped with Al and N is formed on an n-SiC substrate doped with N, and a second SiC layer doped with B and N is formed on the first SiC layer. The light emitting diode having a GaN-based semiconductor that emits purple light having a wavelength of about 400 nm on the second SiC uses the purple light from the GaN-based semiconductor as an excitation light source, and the second SiC layer emits yellow fluorescence, Since the first SiC layer emits blue fluorescence, white light with high reproducibility and good color rendering can be obtained by utilizing the yellow and blue fluorescence from the SiC layer.

By using a 6H type single crystal as the SiC semiconductor substrate and doping with B, Al and N, the SiC substrate can be used as the phosphor of the present invention and white light can be obtained. On the other hand, good white light can be obtained by using the SiC phosphor layer and the nitride semiconductor layer formed on the substrate without using the SiC substrate as the phosphor. The doping concentration of one or more elements of B or Al and the doping concentration of N of the 6H-type SiC single crystal phosphor in the light-emitting diode of the present invention are increased in luminous efficiency. 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ³ is preferable, and 10 ¹⁷ / cm ³ to 10 ¹⁹ / cm ³ is more preferable.

  One typical structure of the light emitting diode of the present invention is illustrated in FIG. In this example, a first impurity-added SiC layer 402 to which Al and N are added and a second impurity-added SiC layer 403 to which B and N are added are epitaxially grown on the SiC substrate 401 by, for example, a CVD method. Further, epitaxial growth is performed on the SiC layer 403 by, for example, an organic metal compound vapor deposition method, and an AlGaN buffer layer 404, an n-GaN first contact layer 405, an n-AlGaN first cladding layer 406, a GaInN / GaN multiple quantum well. An active layer 407, a p-AlGaN electron blocking layer 408, a p-AlGaN second cladding layer 409, and a p-GaN second contact layer 410 are formed. Next, after forming a p-electrode 411 made of Ni / Au on the p-GaN second contact layer 410, etching is performed until the n-GaN first contact layer 405 is exposed, as shown in FIG. The light emitting diode of the present invention can be obtained by forming the n-electrode 412 on the GaN first contact layer 405. In this example, a light-emitting element made of a nitride semiconductor refers to each layer on the second impurity-added SiC layer 403.

  Excitation light from the nitride semiconductor is once absorbed at the absorption edge of SiC, and the electron-hole pairs are relaxed to the impurity level. Therefore, it is preferable that the SiC layer doped with impurities is disposed between the SiC substrate 401 and the AlGaN buffer layer 404. The nitride semiconductor can be appropriately selected from group III nitride semiconductors such as GaN, but the emission wavelength of the light emitting element that is the excitation wavelength is 408 nm or less, which is the absorption edge wavelength of 6H-type SiC. It is preferable to select a semiconductor.

  The SiC layer to which Al, B and N are added can be formed by epitaxial growth, but can also be formed by diffusion. For example, before epitaxially growing a nitride semiconductor, using a carbon sputtered on a SiC substrate doped with N as a mask, B or Al is locally diffused, and the yellow part and the blue part are partially separated in a single process. It is also possible to obtain a composite diode that can control color rendering. In addition to an embodiment in which two or more impurity-added layers are formed, the same effect can be obtained by simultaneously adding B, Al and N to one layer.

Example 1
As shown in FIG. 1, a SiC phosphor was prepared by an improved Rayleigh method. First, the substrate 1 made of a SiC single crystal as a seed crystal was attached to the inner surface of the lid 4 of the graphite crucible 3. In addition, the graphite crucible 3 was filled with a high-purity SiC powder (JIS particle size # 250) as a raw material 2 and a B source, and then filled.

Next, the graphite crucible 3 filled with the raw material 2 is closed with a lid 4 and placed inside the quartz tube 5 with a graphite support rod 6, and the surroundings of the graphite crucible 3 are covered with a heat shield 7 made of black bell. Covered. As the atmospheric gas, Ar gas and N ₂ gas were passed through the flow meter 10 into the quartz tube 5 through the introduction tube 9 (Ar gas flow rate 1 liter / min). Subsequently, a high-frequency current was passed through the work coil 8 to adjust the temperature of the raw material 2 to 2300 ° C. and the temperature of the substrate 1 to 2200 ° C.

Subsequently, while adjusting the flow rates of Ar gas and N ₂ gas, the inside of the quartz tube 5 was decompressed using the vacuum pump 11. The pressure was gradually reduced from atmospheric pressure to 133 Pa over 20 minutes, and the SiC crystal having a diameter of 55 mm and a thickness of 10 mm was obtained by holding at 133 Pa for 5 hours.

The partial pressure of N ₂ gas in the atmospheric gas during crystal growth was 1%. Further, carbon impregnated with 5 mol% of B simple substance (metal boron) was used as the B source, and the SiC powder was mixed with the SiC powder so that the B simple substance was 0.05 mol% to obtain a raw material powder.

When the B and N concentrations of the obtained SiC crystal were measured by SIMS, N was 5 × 10 ¹⁷ / cm ³ and B was 3 × 10 ¹⁶ / cm ³ . Further, after cutting out a crystal having a diameter of 55 mm and a thickness of 0.3 mm from the obtained SiC single crystal, one surface was polished and fluorescence was measured on a flat surface. As a result of the measurement, the peak wavelength was 620 nm, fluorescence with a wavelength of 500 nm to 750 nm was emitted, and a broad spectrum as shown in FIG. 3 was exhibited.

  Next, the crystal after measurement was held at 1850 ° C. for 4 hours and subjected to thermal annealing. As a result, the shape of the spectrum was almost the same, but the relative intensity of light emission was higher than that before thermal annealing. Improved more than twice.

Example 2
A SiC crystal was produced in the same manner as in Example 1 except that the partial pressure of N ₂ gas in the atmospheric gas during crystal growth was 5% and the concentration of B alone with respect to the SiC powder was 0.5 mol%. The N and B concentrations of the obtained SiC crystal were 3 × 10 ¹⁸ / cm ³ for N and 1 × 10 ¹⁷ / cm ³ for B. Further, the shape of the fluorescence spectrum was the same as in Example 1, but the relative intensity of light emission was improved almost three times as compared with the crystal before thermal annealing in Example 1.

Example 3
A SiC crystal was produced in the same manner as in Example 1 except that the partial pressure of N ₂ gas in the atmospheric gas during crystal growth was 10% and the concentration of B alone with respect to the SiC powder was 5 mol%. Regarding the N and B concentrations of the obtained SiC crystal, N was 8 × 10 ¹⁸ / cm ³ and B was 5 × 10 ¹⁷ / cm ³ . The shape of the fluorescence spectrum was the same as that of Example 1, but the relative intensity of light emission was improved approximately 5 times compared to the crystal before thermal annealing in Example 1.

Example 4
A SiC crystal was produced in the same manner as in Example 1 except that the partial pressure of N ₂ gas in the atmospheric gas during crystal growth was 30% and the concentration of B alone with respect to the SiC powder was 15 mol%. The N and B concentrations in the obtained SiC crystal were 1 × 10 ¹⁹ / cm ³ for N and 1 × 10 ¹⁸ / cm ³ for B. Further, the shape of the fluorescence spectrum was the same as that of Example 1, but the relative intensity of light emission was reduced to approximately 1/10 compared to the crystal before thermal annealing in Example 1.

From the results of Examples 1 to 4, by setting the partial pressure of N ₂ gas in the atmosphere gas during crystal growth to 1% to 30% and the concentration of B alone with respect to SiC powder to 0.05 mol% to 15 mol%, An SiC phosphor in which N is 5 × 10 ¹⁷ / cm ³ to 1 × 10 ¹⁹ / cm ³ and B is 3 × 10 ¹⁶ / cm ³ to 1 × 10 ¹⁸ / cm ³ is obtained. Was found to emit fluorescence having a wavelength of 500 nm to 750 nm and to have a peak wavelength at 500 nm to 650 nm.

Example 5
A SiC single crystal having a diameter of 55 mm and a thickness of 10 mm was obtained by the modified Rayleigh method in the same manner as in Example 1 except that the source B was not blended with the raw material powder. A crystal having a diameter of 55 mm and a thickness of 0.3 mm was cut out from the obtained SiC single crystal in the same manner as in Example 1, and then one surface was polished. Next, TaB ₂ was used as a B source, 3 mol% of TaB ₂ with respect to the SiC powder was mixed with the SiC powder, and then fixed to the jig. The above-mentioned polished SiC crystal was attached to this jig, and the jig was prepared so that the distance between the flat surface of the SiC crystal and TaB ₂ was 0.1 mm.

Subsequently, the jig was placed in a carbon crucible, heated to 1800 ° C. in an Ar gas atmosphere, and held for 4 hours. When the fluorescence of the obtained crystal was measured, as in Example 1, the peak wavelength was 620 nm, the fluorescence with a wavelength of 500 nm to 750 nm was emitted, and a broad spectrum as shown in FIG. 3 was exhibited. Moreover, when the density | concentration of B and N of the obtained SiC crystal is measured by SIMS, N is 5 * 10 < ¹⁷ > / cm < ³ >, B is 5 * 10 < ¹⁶ > / cm < ³ > -8 * 10 < ¹⁸ > / cm < ³ >. there were.

  Furthermore, when the thermal annealing treatment was performed at 1800 ° C. for 4 hours, the shape of the fluorescence spectrum was not changed, but the relative intensity of light emission was doubled. Next, when the surface of the crystal was scraped off by 2 μm by RIE, the shape of the fluorescence spectrum was the same, and the relative intensity of light emission was improved by a factor of 1.5 compared to that before scraping off.

Example 6
The SiC single crystal obtained in Example 5 was pulverized in a mortar and classified to obtain a powder having a particle size of 2 μm to 3 μm. This powder was placed in a crucible made of a white BN sintered body and heated and fired. Firing was performed under a reduced pressure of 300 Pa in an N ₂ gas atmosphere, and held at 1800 ° C. for 4 hours. After firing, the SiC powder was pulverized in a mortar and heated at 1200 ° C. for 3 hours in an air atmosphere (oxidizing atmosphere) to form an oxide film on the surface. The obtained sintered body was treated with 70% hydrofluoric acid, the surface was removed with a thickness of about 1 μm, and dried to obtain a powder.

When the fluorescence of the obtained powder was measured, the peak wavelength was 640 nm, the fluorescence with a wavelength of 500 nm to 750 nm was emitted, and the same broad spectrum as in Example 5 was exhibited. Moreover, when the density | concentration of B and N of the obtained powder was measured by SIMS, N was 7 * 10 < ¹⁷ > / cm < ³ > and B was 9 * 10 < ¹⁷ > / cm < ³ >.

Example 7
FIG. 4 shows the structure of the light-emitting diode of this example. A first impurity-added SiC layer 402 to which Al and N are added and a second impurity-added SiC layer 403 to which B and N are added are epitaxially grown and formed on the SiC substrate 401 by, for example, a CVD method. Further, an AlGaN buffer layer 404, an n-GaN first contact layer 405, an n-AlGaN first cladding layer 406, a GaInN / GaN multiple quantum well active layer 407 are formed on the SiC layer 403 by, for example, metal organic compound vapor deposition. The p-AlGaN electron block layer 408, the p-AlGaN second cladding layer 409, and the p-GaN second contact layer 410 were formed. Next, after forming a p-electrode 411 made of Ni / Au on the p-GaN second contact layer 410, etching is performed until the n-GaN first contact layer 405 is exposed, as shown in FIG. An n-electrode 412 was formed on the GaN first contact layer 405 to obtain a light emitting diode.

  Subsequently, as shown in FIG. 5, the light emitting diode 501 was mounted on the stem 505. Mounting was performed on the metal layers 503a and 503b of the insulating heat sink 502 formed on the stem 505 by an epicide down method via gold bumps 504. Thereafter, the metal layer 503a and the wiring lead 506 were connected by a gold wire 507a, and the gold wire 507b was connected to the metal layer 503b and fixed by an epoxy resin 508.

  When a voltage was applied to the light emitting diode 501 via the gold wires 507a and 507b, a current was injected into the light emitting diode. As a result, violet light having a wavelength of 400 nm was emitted from the GaInN / GaN multiple quantum well active layer 407 of FIG. Of this violet light, the light emitted in the direction of the SiC substrate 401 enters the second impurity-added SiC layer 403 and the first impurity-added SiC layer 402, and almost all is absorbed by these layers. Fluorescence was generated by the impurity level of each layer.

In the second impurity-added SiC layer 403, B and N are added at a concentration of about 10 ¹⁸ / cm ³ , and when excited with 400 nm violet light, fluorescence having a spectrum as shown in FIG. Released. As apparent from FIG. 3, this fluorescence has a wavelength of 500 nm to 750 nm, a peak wavelength of about 600 nm, and is yellow fluorescence, but also contains a relatively large amount of red component exceeding 600 nm. The thickness of the second impurity-added SiC layer 403 was 20 μm.

On the other hand, in the first impurity-added SiC layer 402, Al and N are added at a concentration of about 10 ¹⁸ / cm ³ , and when excited with light of 400 nm, fluorescence having a spectrum as shown in FIG. Released. As apparent from FIG. 6, this fluorescence was blue light having a wavelength of 400 nm to 750 nm and a peak wavelength of around 460 nm. The thickness of the first impurity-added SiC layer 402 was 20 μm.

  By mixing the fluorescence of the two impurity-added SiC layers 402 and 403, white light with excellent color rendering was obtained. The mixing ratio could be adjusted by changing the aforementioned doping concentration and the film thickness of the SiC layers 402 and 403. From this, it was found that the color temperature of white light can be easily adjusted. Further, since white light is generated inside the light emitting diode, the angle dependence of the hue of the emitted white light is so small that it can be ignored.

Example 8
FIG. 7 shows the structure of the light-emitting diode of this example. As shown in FIG. 7, the light-emitting diode includes a first impurity-added SiC layer 702 to which Al and N are added and a second impurity-added to which B and N are added on an N-doped n-SiC substrate 701. The SiC layer 703 was epitaxially grown by the CVD method. Further, an n-AlGaN buffer layer 704, an n-GaN first contact layer 705, an n-AlGaN first cladding layer 706, a GaInN / GaN multiple quantum well active layer are formed on the SiC layer 703 by metal organic compound vapor deposition. 707, a p-AlGaN electron blocking layer 708, a p-AlGaN second cladding layer 709, and a p-GaN second contact layer 710 were stacked. Next, a p-electrode 711 made of Ni / Au was formed on the surface of the p-GaN second contact layer 710, and an n-electrode 712 was partially formed on the surface of the SiC substrate 701 to obtain a light emitting diode. .

  Subsequently, as shown in FIG. 8, the light emitting diode 801 was mounted on the stem 805. Mounting was performed on the metal layer 803 of the insulating heat sink 802 formed on the stem 805 by the epicide down method. Thereafter, the metal layer 803 and the wiring lead 806 were connected with a gold wire 807 and fixed with an epoxy resin 808.

  When voltage was applied to the light emitting diode 801, current was injected into the light emitting diode. As a result, violet light having a wavelength of 400 nm was emitted from the GaInN / GaN multiple quantum well active layer 707 of FIG. Of this violet light, light emitted in the direction of the SiC substrate 701 enters the second impurity-added SiC layer 703 and the first impurity-added SiC layer 702, and almost all is absorbed by these two layers. At the same time, fluorescence was emitted by the impurity level of each SiC layer.

In the second impurity-added SiC layer 703, B and N are added at a concentration of about 10 ¹⁸ / cm ³ , and when excited with light of 400 nm, fluorescence having a spectrum as shown in FIG. 3 is emitted. did. As apparent from FIG. 3, this fluorescence has a wavelength of 500 nm to 750 nm, a peak wavelength of about 600 nm, and is yellow fluorescence, but also contains a relatively large amount of red component exceeding 600 nm. The thickness of the second impurity-added SiC layer 703 was 30 μm.

On the other hand, in the first impurity-added SiC layer 702, Al and N are added at a concentration of about 10 ¹⁸ / cm ³ , and when excited with light of 400 nm, fluorescence having a spectrum as shown in FIG. Released. As apparent from FIG. 6, this fluorescence was blue light having a wavelength of 400 nm to 750 nm and a peak wavelength of around 460 nm. The thickness of the first impurity-added SiC layer 702 was 30 μm.

  By mixing the fluorescence of the two impurity-added SiC layers 702 and 703, white light with excellent color rendering was obtained. The mixing ratio can be adjusted by changing the impurity concentration to be doped and the film thicknesses of the SiC layers 702 and 703. From this, it was found that it is easy to adjust the hue of white light. Further, since white light is generated inside the light emitting diode, the angle dependence of the hue of the emitted white light is so small that it can be ignored.

Example 9
In this example, white light was synthesized by combining a conventional nitride semiconductor light emitting diode having an emission wavelength of 440 nm to 480 nm and the light emitting diode of the present invention. The light emitting diode of the present invention is a light emitting diode that emits yellow fluorescence using violet light from a nitride semiconductor as excitation light.

  The first impurity-added SiC layer doped with Al and N was not formed, but only the second impurity-added SiC layer doped with B and N was formed as the impurity-added SiC layer. A light emitting diode was manufactured and mounted in the same manner as in Example 8 as shown in FIG.

  When current is injected into the light emitting diode, violet light having a wavelength of 400 nm is emitted in the GaInN / GaN multiple quantum well active layer, and the violet light emitted toward the SiC substrate enters the impurity-added SiC layer, and the impurity-added SiC layer. Almost all was absorbed by the layer and fluoresced.

The impurity-added SiC layer is doped with both B and N at a concentration of about 10 ¹⁸ / cm ^3, and emits yellow fluorescence having a spectrum as shown in FIG. 3 when excited with 400 nm light. did. As apparent from FIG. 3, this yellow fluorescence has a wavelength of 500 nm to 750 nm, a peak wavelength of about 600 nm, and a relatively large amount of red component exceeding 600 nm. The thickness of the impurity-added SiC layer was 30 μm.

  This yellow light emitting diode is disposed in combination with a conventional light emitting diode (not shown) made of a nitride semiconductor having an emission wavelength of 440 nm to 480 nm, and the emitted light from the yellow light emitting diode and the conventional diode The white light excellent in color rendering could be synthesized by mixing 3: 1 with the emitted light from the light.

  As a diode emitting yellow light, a quaternary high-intensity diode made of AlGaInP has been put into practical use, but the light-emitting diode manufactured in this example exhibits a broad spectrum as shown in FIG. It was found that white with high color rendering can be obtained more easily by combining with a diode.

Example 10
Instead of the B source at the time of crystal growth, a SiC crystal is grown in the same manner as in Example 1 except that Al alone is mixed with the SiC powder so as to be 0.1 mol% with respect to the SiC powder to obtain a raw material powder. did. Regarding the concentration of Al and N in the obtained SiC crystal, N was 5 × 10 ¹⁷ / cm ³ and Al was 2 × 10 ¹⁶ / cm ³ . Further, the fluorescence spectrum had a peak wavelength of 430 nm, emitted fluorescence having a wavelength of 400 nm to 750 nm, and exhibited a broad spectrum as shown in FIG.

  Next, the crystal after measurement was held at 1850 ° C. for 4 hours and subjected to thermal annealing. As a result, the shape of the spectrum was almost the same, but the relative intensity of light emission was higher than that before thermal annealing. Improved more than twice.

Example 11
An SiC crystal was produced in the same manner as in Example 10 except that the partial pressure of N ₂ gas in the atmospheric gas during crystal growth was 5% and the concentration of Al alone with respect to the SiC powder was 1 mol%. The N and Al concentrations of the obtained SiC crystal were 5 × 10 ¹⁸ / cm ³ for N and 1 × 10 ¹⁷ / cm ³ for Al. The shape of the fluorescence spectrum was the same as in Example 10, but the relative intensity of light emission was improved almost twice as compared with the crystal before thermal annealing in Example 10.

Example 12
A SiC crystal was produced in the same manner as in Example 10 except that the partial pressure of N ₂ gas in the atmospheric gas during crystal growth was 10% and the concentration of Al alone with respect to the SiC powder was 10 mol%. The N and Al concentrations of the obtained SiC crystal were 8 × 10 ¹⁸ / cm ³ for N and 4 × 10 ¹⁷ / cm ³ for Al. The shape of the fluorescence spectrum was the same as in Example 10, but the relative intensity of light emission was improved almost three times compared to the crystal before thermal annealing in Example 10.

Example 13
A SiC crystal was produced in the same manner as in Example 10 except that the partial pressure of N ₂ gas in the atmospheric gas during crystal growth was 30% and the concentration of Al alone with respect to the SiC powder was 20 mol%. The N and Al concentrations of the obtained SiC crystal were 1 × 10 ¹⁹ / cm ³ for N and 1 × 10 ¹⁸ / cm ³ for Al. Further, the shape of the fluorescence spectrum was the same as that in Example 10, but the relative intensity of light emission was reduced to almost 1/3 or less as compared with the crystal before thermal annealing in Example 10.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The SiC phosphor of the present invention obtains a mixed color of excitation light and fluorescence in order to emit efficient fluorescence even when blue-violet light having a relatively long wavelength is used as primary light. Thus, it is possible to manufacture a light emitting diode using a relatively long wavelength excitation light emitted from a semiconductor element or the like. This light emitting diode is excellent in color rendering properties, low in cost, and useful as a white light source with high light emission efficiency. Further, SiC is a material having high covalent bonding properties, hardly changes in quality, and has conductivity, so that it can withstand strong electron beams and can be used for a discharge tube or PDP.

It is a schematic diagram which shows an example of the single crystal growth apparatus used for the manufacturing method of the fluorescent substance made from SiC of this invention. It is a schematic diagram explaining the principle of the improved Rayleigh method used in the manufacturing method of this invention. It is a figure which shows the light emission characteristic of the fluorescent substance made from SiC of this invention. It is a schematic diagram which shows the structure of the light emitting diode of this invention. It is a schematic diagram which shows the state which mounted the light emitting diode of this invention. It is a figure which shows the light emission characteristic of the fluorescent substance made from SiC of this invention. It is a schematic diagram which shows the structure of the light emitting diode of this invention. It is a schematic diagram which shows the state which mounted the light emitting diode of this invention. It is a schematic diagram which shows the state which mounted the conventional light emitting diode. It is a schematic diagram which shows the state which mounted the conventional light emitting diode.

Explanation of symbols

  1 substrate 2 raw material 3 crucible 4 lid 5 quartz tube 6 support rod 7 heat shield 8 work coil 9 introduction tube 401 SiC substrate 402 first impurity doped SiC layer 403 second impurity Added SiC layer, 404 AlGaN buffer layer, 405 n-GaN first contact layer, 406 n-AlGaN first cladding layer, 407 GaInN / GaN multiple quantum well active layer, 408 p-AlGaN electron blocking layer, 409 p-AlGaN first 2 clad layers, 410 p-GaN second contact layer, 411 p electrode, 412 n electrode.

Claims (23)

  A SiC phosphor, which is a phosphor that emits light when excited by an external light source and is doped with N and one or more elements of B or Al. 2. The SiC according to claim 1, wherein the doping concentration by one or more elements of B or Al and the doping concentration by N are both 10 ¹⁵ / cm ³ to 10 ²⁰ / cm ^3. Made phosphor. ^3. The SiC according to claim 2, wherein the doping concentration by one or more elements of B or Al and the doping concentration by N are both 10 ¹⁶ / cm ³ to 10 ²⁰ / cm ^3. Made phosphor.   The phosphor made of SiC according to claim 1 or 2, which emits fluorescence having a wavelength of 500 nm to 750 nm and has a peak wavelength of 500 nm to 650 nm. SiC is doped with N and B, and the concentration of either N or B is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ^3. The SiC phosphor according to claim 4, wherein:   3. The SiC phosphor according to claim 1 or 2, which emits fluorescence having a wavelength of 400 nm to 750 nm and has a peak wavelength of 400 nm to 550 nm. SiC is doped with N and Al, and the concentration of either N or Al is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ , and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ^3. The SiC phosphor according to claim 6, wherein: Excited by an external light source, emits fluorescence with a wavelength of 500 nm to 750 nm, has a peak wavelength at 500 nm to 650 nm, is doped with N and B, and the concentration of either N or B is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ , and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ³ .
Made of SiC, characterized in that LaB ₆ , B ₄ C, TaB ₂ , NbB ₂ , ZrB ₂ , HfB ₂ , BN, or carbon containing B is used as a B source and SiC crystals are formed by sublimation recrystallization. A method for producing a phosphor. Excited by an external light source, emits fluorescence with a wavelength of 500 nm to 750 nm, has a peak wavelength at 500 nm to 650 nm, is doped with N and B, and the concentration of either N or B is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ , and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ³ .
It is possible to thermally diffuse into SiC at 1500 ° C. or higher in vacuum or in an inert gas atmosphere using B alone, LaB ₆ , B ₄ C, TaB ₂ , NbB ₂ , ZrB ₂ , HfB ₂ or BN as a B source. A method for producing a SiC phosphor.   The method for producing a SiC phosphor according to claim 9, wherein the surface layer is removed after the thermal diffusion.   The method for producing a SiC phosphor according to claim 8 or 9, wherein a thermal annealing treatment is performed at 1300 ° C or higher for 1 hour or longer after sublimation recrystallization or thermal diffusion.   A phosphor that emits light when excited by an external light source, and is made of a 6H-type SiC single crystal phosphor doped with one or more elements of B or Al and N substrate.   13. The semiconductor substrate according to claim 12, comprising a 6H-type SiC single crystal phosphor that is doped with N and B, emits fluorescence having a wavelength of 500 nm to 750 nm, and has a peak wavelength of 500 nm to 650 nm.   13. The semiconductor substrate according to claim 12, comprising a 6H-type SiC single crystal phosphor that is doped with N and Al, emits fluorescence having a wavelength of 400 nm to 750 nm, and has a peak wavelength of 400 nm to 550 nm. Excited by an external light source, emits fluorescence with a wavelength of 500 nm to 750 nm, has a peak wavelength at 500 nm to 650 nm, is doped with N and B, and the concentration of either N or B is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ , and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ³ .
A process of thermally diffusing into SiC at 1500 ° C. or higher in a vacuum or in an inert gas atmosphere using B alone, LaB ₆ , B ₄ C, TaB ₂ , NbB ₂ , ZrB ₂ , HfB ₂ or BN as a B source; ,
And a step of removing the surface layer. A method for manufacturing a semiconductor substrate, comprising: Excited by an external light source, emits fluorescence with a wavelength of 500 nm to 750 nm, has a peak wavelength at 500 nm to 650 nm, is doped with N and B, and the concentration of either N or B is 10 ¹⁵ / cm ³ to 10 ¹⁸ / cm ³ , and the other concentration is 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ³ .
The sublimation recrystallization method is characterized in that the atmosphere gas at the time of crystal growth contains 1% to 30% N ₂ gas by gas partial pressure, and the raw material SiC contains 0.05 mol% to 15 mol% B source. A method for manufacturing a semiconductor substrate for forming a SiC crystal.   The method for manufacturing a semiconductor substrate according to claim 15 or 16, wherein a thermal annealing treatment is performed at 1300 ° C or higher after sublimation recrystallization or thermal diffusion.   Excited by an external light source, emits fluorescence with a wavelength of 500 nm to 750 nm, and consists of a 6H-type SiC single crystal phosphor having a peak wavelength at 500 nm to 650 nm, a particle size of 2 μm to 10 μm, and a central particle size of 3 μm to 6 μm A powder for semiconductor, characterized in that   A semiconductor substrate made of a 6H-type SiC single crystal phosphor doped with one or more elements of B or Al and N, and a light emitting element made of a nitride semiconductor on the substrate. A light emitting diode.   One or two or more layers made of 6H-type SiC single crystal phosphor doped with one or more elements of B or Al and N are provided on a SiC semiconductor substrate, and the 6H A light emitting diode comprising a light emitting element made of a nitride semiconductor on a type SiC single crystal phosphor layer.   21. The light emitting diode according to claim 19 or 20, wherein a light emission wavelength of the light emitting element made of a nitride semiconductor is 408 nm or less. In the 6H-type SiC single crystal phosphor, both the doping concentration by one or more elements of B and Al and the doping concentration by N are 10 ¹⁶ / cm ³ to 10 ¹⁹ / cm ^3. The light-emitting diode according to claim 19 or 20, characterized in that In the 6H-type SiC single crystal phosphor, both the doping concentration by one or more elements of B and Al and the doping concentration by N are 10 ¹⁷ / cm ³ to 10 ¹⁹ / cm ^3. 23. A light emitting diode according to claim 22 characterized in that:

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