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WO2018012585A1 - Diode électroluminescente et dispositif électroluminescent - Google Patents

Diode électroluminescente et dispositif électroluminescent Download PDF

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WO2018012585A1
WO2018012585A1 PCT/JP2017/025534 JP2017025534W WO2018012585A1 WO 2018012585 A1 WO2018012585 A1 WO 2018012585A1 JP 2017025534 W JP2017025534 W JP 2017025534W WO 2018012585 A1 WO2018012585 A1 WO 2018012585A1
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layer
quantum well
light emitting
light
nitride semiconductor
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Japanese (ja)
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麻祐子 渡部
修 川崎
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Sharp Corp
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Sharp Corp
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80—Constructional details
    • H10H20/81—Bodies
    • H10H20/822—Materials of the light-emitting regions
    • H10H20/824—Materials of the light-emitting regions comprising only Group III-V materials, e.g. GaP
    • H10H20/825—Materials of the light-emitting regions comprising only Group III-V materials, e.g. GaP containing nitrogen, e.g. GaN
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80—Constructional details
    • H10H20/81—Bodies
    • H10H20/811—Bodies having quantum effect structures or superlattices, e.g. tunnel junctions
    • H10H20/812—Bodies having quantum effect structures or superlattices, e.g. tunnel junctions within the light-emitting regions, e.g. having quantum confinement structures
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80—Constructional details
    • H10H20/81—Bodies
    • H10H20/819—Bodies characterised by their shape, e.g. curved or truncated substrates
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80—Constructional details
    • H10H20/81—Bodies
    • H10H20/819—Bodies characterised by their shape, e.g. curved or truncated substrates
    • H10H20/821—Bodies characterised by their shape, e.g. curved or truncated substrates of the light-emitting regions, e.g. non-planar junctions
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80—Constructional details
    • H10H20/85—Packages
    • H10H20/851—Wavelength conversion means
    • H10H20/8511—Wavelength conversion means characterised by their material, e.g. binder
    • H10H20/8512—Wavelength conversion materials
    • H10H20/8513—Wavelength conversion materials having two or more wavelength conversion materials
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80—Constructional details
    • H10H20/81—Bodies
    • H10H20/811—Bodies having quantum effect structures or superlattices, e.g. tunnel junctions
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80—Constructional details
    • H10H20/81—Bodies
    • H10H20/8215—Bodies characterised by crystalline imperfections, e.g. dislocations; characterised by the distribution of dopants, e.g. delta-doping

Definitions

  • One embodiment of the present invention relates to a light-emitting diode and a light-emitting device. This application claims priority on July 13, 2016 based on Japanese Patent Application No. 2016-138783 for which it applied to Japan, and uses the content here.
  • the group III-V compound semiconductor material containing nitrogen (hereinafter referred to as “nitride semiconductor material”) has a band gap energy corresponding to the energy of light having a wavelength in the infrared region to the ultraviolet region.
  • nitride semiconductor material has a band gap energy corresponding to the energy of light having a wavelength in the infrared region to the ultraviolet region.
  • a light-emitting diode made of an AlGaInN-based nitride semiconductor material generates light with a short wavelength such as blue with high efficiency. Therefore, a light emitting device that emits white light can be obtained by combining this light emitting diode and a wavelength converting substance such as a phosphor.
  • (external) quantum efficiency is shown as one index for evaluating the efficiency of the light emitting diode.
  • the (external) quantum efficiency is represented by the number of photons emitted from the light emitting diode relative to the number of electrons injected into the light emitting diode.
  • light emission efficiency is shown as one index for evaluating the efficiency of the light emitting device.
  • the luminous efficiency (unit: lm / W) is represented by the luminous flux (unit: lm) emitted from the light emitting device with respect to the electric power (unit: W) input to the light emitting device.
  • the luminous efficiency of the light emitting device increases as the luminous flux increases and the driving power (electric power) decreases.
  • the luminous flux is a physical quantity that represents the brightness of light emitted from the light emitting device in consideration of the sensitivity (visual sensitivity) of the human eye. Visibility varies depending on the wavelength of light, and becomes maximum at 555 nm, and the luminous flux becomes maximum. That is, in a light emitting device that emits light containing a large amount of light at 555 nm, the luminous flux becomes large. Therefore, in order to increase the luminous flux, for example, it is conceivable to provide a phosphor having a main emission peak at 555 nm in the light emitting device.
  • light emitting devices that emit mainstream white light (pseudo white light) achieve high luminous efficiency by combining a blue light emitting diode and a yellow phosphor in consideration of visibility. Furthermore, the light emission efficiency of the light emitting device can be further increased by using a phosphor with high quantum efficiency.
  • Such a light emitting device is superior in luminous efficiency as compared with a fluorescent lamp, it is used more frequently as a backlight for an illuminating device or a liquid crystal display device in place of the fluorescent lamp.
  • a light emitting device that not only has excellent brightness and luminous efficiency, but also has excellent color reproducibility for lighting devices and excellent color reproducibility for backlights.
  • a light emitting device having an emission spectrum close to sunlight or a light emitting device having an emission spectrum change according to a human circadian rhythm is preferable.
  • a light emitting device having an emission spectrum with a narrow half-value width that overlaps the transmission wavelength band of the color filter is preferable.
  • a conventionally known light emitting device with excellent pseudo white light emission efficiency has a problem of low color rendering.
  • a light emitting device with improved color rendering using a phosphor that emits green light or red light has low visibility and may have lower luminous efficiency than a light emitting device that emits pseudo white light. It was.
  • these phosphors have different optimum excitation wavelengths for each emission color, depending on the type of phosphor, the quantum efficiency of the phosphor may be reduced depending on the type of phosphor, resulting in a light emitting device. In some cases, the luminous efficiency of the film was lowered. Therefore, a light emitting device that can achieve both high luminous efficiency and color rendering suitable for lighting applications has been desired.
  • each phosphor has an optimum wavelength.
  • the technology that can be excited by the is desired.
  • Patent Document 1 discloses a light emitting device including a light emitting diode and a phosphor that emit light having a main light emission peak from the near ultraviolet region to the blue region (300 to 490 nm).
  • the light emitting device of Patent Document 1 includes two or more types of phosphors having different direct transition type emission centers as phosphors.
  • Patent Document 2 discloses a light emitting device including a blue light emitting diode and a phosphor. Around the blue light emitting diode, a phosphor having emission peaks at 490 to 510 nm and 530 to 580 nm (green phosphor), and a phosphor having an emission peak at 610 to 660 nm (red phosphor) are formed on a transparent resin. It is provided in a mixed and dispersed state.
  • the peak intensity of the emission spectrum of the phosphor is A
  • the peak intensity of 490 to 510 nm is B
  • the peak intensity of 530 to 580 nm is B
  • the peak intensity of 610 to 660 nm is C / B.
  • A is 0.8 to 1.2
  • C / A is 0.5 to 1.2.
  • Patent Document 3 discloses a white light source having a light emitting diode and a covering made of a transparent material that at least partially surrounds the light emitting diode.
  • the transparent material includes a conversion material that at least partially converts the wavelength of light emitted from the light emitting diode.
  • the light emitting diode has at least two light emitting regions. These light emitting regions are formed so that the maximum value of the emission spectrum is energetically different and has a wavelength shorter than the maximum value of the emission spectrum of the conversion substance. Further, these light emitting regions are arranged side by side in the main radiation direction of the light emitting diode, and the light energy of the light emission maximum value increases toward the main beam direction.
  • Patent Document 4 discloses a light emitting device including a light emitting diode and at least two types of fluorescent powders coated on the light emitting diode.
  • the light emitting diode includes at least two light emitting layers capable of emitting light of two different wavelengths ⁇ 1 and ⁇ 2.
  • the fluorescent powder absorbs light of one type of light emitted from the light emitting diode and generates light of two different types of wavelengths ⁇ 3 and ⁇ 4.
  • the relationship between these wavelengths is ⁇ 1 ⁇ 2 ⁇ 3 ⁇ 4, and white light can be obtained by mixing the three wavelengths ⁇ 2, ⁇ 3, and ⁇ 4.
  • Patent Document 1 and Patent Document 2 use only a phosphor that can be excited in a wavelength range of a single emission spectrum, color rendering properties are not always sufficient. Further, for example, when a plurality of phosphors having different emission spectra are contained in order to improve the color rendering, the resulting fluorescence is scattered by the phosphor, resulting in poor transmittance. Moreover, since the scattered fluorescence is reabsorbed by the phosphor, the light emission efficiency tends to decrease.
  • a well layer that emits light having a long wavelength is formed first, and a well layer that generates light having a short wavelength is formed thereon.
  • a method of increasing the In ratio in the nitride semiconductor or increasing the layer thickness is employed.
  • this method tends to deteriorate the crystal quality of the formed well layer.
  • the crystal quality tends to deteriorate and the quantum efficiency of the light-emitting diode tends to decrease.
  • One embodiment of the present invention has been made in view of the above points, and can improve light emission efficiency of a light-emitting device and can realize color rendering properties suitable for illumination applications and color reproducibility suitable for backlight applications.
  • a diode and a light emitting device including the light emitting diode are provided.
  • One embodiment of the present invention is a light-emitting diode including a transparent substrate and a nitride semiconductor multilayer film provided on a surface of the transparent substrate, the nitride semiconductor multilayer film including a first nitride semiconductor layer, Between the first nitride semiconductor layer, the second nitride semiconductor layer provided on the opposite side of the transparent substrate, the first nitride semiconductor layer, and the second nitride semiconductor layer with respect to the first nitride semiconductor layer
  • the transparent substrate has a convex portion on the surface facing the first nitride semiconductor layer, and the light emitting layer is sequentially from the first nitride semiconductor layer side, A plurality of quantum well layers from the first quantum well layer to the Nth quantum well layer (N ⁇ 2) are provided, and the plurality of quantum well layers emit two or more types of light having different main emission peak wavelengths 2.
  • Quantum having more than one kind of quantum well layer and having the longest main emission peak of two or more kinds of quantum well layers Toso, in the light emitting layer, to provide a light emitting diode that is located from the first nitride semiconductor layer side to the second and subsequent layers.
  • the light-emitting layer has a depression extending from the first nitride semiconductor layer to the second nitride semiconductor layer, and the depression is formed from the first quantum well layer to the Nth.
  • the quantum well layer may be provided over the quantum well layer, and the inside of the recess may be configured such that the quantum well layer is thinner than the outside of the recess.
  • the quantum well layer having the shortest wavelength main emission peak among the two or more types of quantum well layers may have a main emission peak in the range of 370 nm to 480 nm.
  • a structure having a main emission peak in the range of 430 nm to 550 nm may be used except for the quantum well layer having the shortest wavelength main emission peak among the two or more types of quantum well layers.
  • One embodiment of the present invention includes the light-emitting diode described above and a wavelength conversion material provided on an optical path of light emitted from the light-emitting diode, and the wavelength conversion material includes a plurality of lights emitted from the light-emitting layer.
  • a light emitting device that absorbs at least one kind of light and emits light having a wavelength different from that of light emitted from a light emitting layer.
  • the wavelength conversion material includes a first wavelength conversion material and a second wavelength conversion material, and the first wavelength conversion material absorbs light emitted from the quantum well layer. Then, light having a wavelength different from that emitted from the quantum well layer is emitted, and the second wavelength converting material is light emitted from the quantum well layer having a main emission peak having a wavelength longer than that of the quantum well layer. It is good also as a structure which injects light and inject
  • a light emitting diode capable of improving the light emission efficiency of a light emitting device and realizing color rendering properties suitable for illumination applications and color reproducibility suitable for backlight applications, and the light emitting diodes are provided.
  • a light emitting device is provided.
  • FIG. 1 is a cross-sectional view showing a light emitting diode 101 of the present embodiment.
  • the light emitting diode 101 includes a transparent substrate 3 and a nitride semiconductor multilayer film provided on the surface of the transparent substrate 3.
  • the light emitting diode 101 includes the substrate portion 7, the n-type nitride semiconductor layer 13, and the p-type nitride semiconductor layer 27.
  • the first nitride semiconductor layer in the claims is described as an n-type nitride semiconductor layer
  • the second nitride semiconductor layer is described as a p-type nitride semiconductor layer.
  • a functional layer 20 is provided between the n-type nitride semiconductor layer 13 and the p-type nitride semiconductor layer 27.
  • the substrate portion 7, the n-type nitride semiconductor layer 13, the functional layer 20, and the p-type nitride semiconductor layer 27 are stacked in this order in the + Z direction (height direction) in FIG.
  • a configuration in which the n-type nitride semiconductor layer 13, the functional layer 20, and the p-type nitride semiconductor layer 27 are combined is a nitride semiconductor multilayer film.
  • the substrate portion 7 and the n-type nitride semiconductor layer 13 are provided to have the same width, and the functional layer 20 has an area larger than that of the n-type nitride semiconductor layer 13. It is provided to be narrow.
  • the p-type nitride semiconductor layer 27 is provided so as to have the same area as the functional layer 20. That is, a part of the upper surface (surface on the functional layer 20 side) of the n-type nitride semiconductor layer 13 is exposed.
  • a p-side electrode 33 is provided on the surface of the p-type nitride semiconductor layer 27 via the transparent electrode 31.
  • an n-side electrode 29 is provided on the exposed portion of the n-type nitride semiconductor layer 13.
  • n-type nitride semiconductor layer 13 the functional layer 20, the p-type nitride semiconductor layer 27, the upper surface and / or the side surfaces of the transparent electrode 31, except for the exposed surfaces of the p-side electrode 33 and n-side electrode 29.
  • a transparent protective film 35 is provided.
  • the substrate unit 7 includes a transparent substrate 3 and a base layer 5.
  • a buffer layer 4 is provided between the transparent substrate 3 and the base layer 5.
  • the transparent substrate 3, the buffer layer 4, and the base layer 5 are laminated in this order in the + Z direction (height direction) in FIG.
  • the n-type nitride semiconductor layer 13 includes a first n-type nitride semiconductor layer 9 and a second n-type nitride semiconductor layer 11.
  • the first n-type nitride semiconductor layer 9 and the second n-type nitride semiconductor layer 11 are stacked in this order in the + Z direction (height direction) in FIG.
  • the functional layer 20 includes a V pit generation layer 14, a superlattice layer 15, a light emitting layer 17, and an undoped layer 19.
  • the V pit generation layer 14, the superlattice layer 15, the light emitting layer 17, and the undoped layer 19 are laminated in this order in the + Z direction (height direction) in FIG.
  • the p-type nitride semiconductor layer 27 includes a first p-type nitride semiconductor layer 21, a second p-type nitride semiconductor layer 23, and a third p-type nitride semiconductor layer 25.
  • the first p-type nitride semiconductor layer 21, the second p-type nitride semiconductor layer 23, and the third p-type nitride semiconductor layer 25 are illustrated in this order. 1 are stacked in the + Z direction (height direction).
  • the configuration of the light emitting diode 101 will be described in detail with reference to FIG. In FIG. 1, the n-type dopant and the p-type dopant are omitted.
  • the substrate portion 7 is provided at the lowermost portion of the light emitting diode 101.
  • the substrate unit 7 includes a transparent substrate 3, a buffer layer 4, and a base layer 5.
  • the transparent substrate 3 shown in FIG. 1 has a function of transmitting light emitted from the light emitting layer 17 described later. Therefore, it is preferable that the transparent substrate 3 is transparent to light having a wavelength from the visible region to the ultraviolet region.
  • the transparent substrate 3 include an insulating substrate such as a sapphire substrate and a conductive substrate such as a GaN substrate, SiC substrate, or ZnO substrate.
  • the thickness of the transparent substrate 3 is preferably 60 ⁇ m or more and 300 ⁇ m or less. If the thickness of the transparent substrate 3 is smaller than 60 ⁇ m, it is difficult to handle at the manufacturing stage and the yield tends to be poor. On the other hand, when the thickness of the transparent substrate 3 is larger than 300 ⁇ m, processing such as cutting is difficult, and the yield tends to deteriorate.
  • the transparent substrate 3 preferably has a convex portion 3 a on the surface facing the n-type nitride semiconductor layer 13.
  • the transparent substrate 3 having a low refractive index from the n-type nitride semiconductor layer 13 having a high refractive index
  • at least part of the light is projected to the n-type nitride semiconductor layer 13 and the transparent substrate 3.
  • It has a function to suppress reflection at the interface.
  • since a part of the short wavelength light is absorbed by the light emitting layer 17, in order to improve the quantum efficiency and color rendering of the light emitting diode 101, it is preferable to reduce the reflection of the short wavelength light as much as possible. Therefore, light can be efficiently extracted from the end face of the transparent substrate 3 by the convex portions 3a, and quantum efficiency and color rendering can be improved.
  • the buffer layer 4 shown in FIG. 1 functions to suppress dislocation caused by the convex portions 3a when a plurality of layers having different lattice constants are formed on the transparent substrate 3.
  • the light emitting layer 17 is composed of layers that emit two or more types of light having different emission wavelength regions, dislocations are likely to occur, but by having the buffer layer 4, the dislocation of the light emitting layer 17 can be suppressed, Good quality crystals can be obtained.
  • AlN crystal or AlON crystals more preferably AlN crystal or AlON crystals, AlON Crystals are more preferred.
  • oxygen atoms for example, when the buffer layer 4 is formed by sputtering, the normal direction of the growth surface of the transparent substrate 3 Since the AlON crystal grows toward the surface, and the buffer layer 4 is obtained as an aggregate of columnar crystals having substantially the same crystal grain size, it is particularly preferable.
  • the thickness of the buffer layer 4 is preferably 5 nm to 100 nm, and more preferably 10 nm to 50 nm.
  • the underlayer 5 shown in FIG. 1 has a function of flattening the surface facing the lower surface of the n-type nitride semiconductor layer 13 and a function of reducing the dislocation density of the surface facing the lower surface of the n-type nitride semiconductor layer 13. Have.
  • the underlayer 5 has a function of suppressing threading dislocations.
  • the underlayer 5 preferably has a three-layer structure. That is, it is preferable that the first underlayer, the second underlayer, and the third underlayer are stacked in this order in the + Z direction in FIG. 1 on the upper surface of the buffer layer 4 (not shown).
  • the mechanism in which the three-layer structure of the underlayer 5 suppresses the through potential will be described in detail.
  • the second underlayer When forming the second underlayer on the upper surface of the first underlayer, if the temperature of the transparent substrate 3 is lowered, the second underlayer grows in a three-dimensional direction and a facet surface is formed (illustrated). None). Further, when the temperature of the transparent substrate 3 is increased when forming the third underlayer on the upper surface of the second underlayer, the third underlayer grows in the lateral direction, and the upper surface of the third underlayer is increased. That is, the upper surface of the underlayer 5 becomes flat.
  • the dislocations are bent at the facet surface formed in the second underlayer, so that threading dislocations can be suppressed.
  • the three-layer structure of the underlayer 5 can suppress the penetration potential, but when the first to third underlayers are formed by the above-described method, the first to third underlayers are n It is preferred that no type dopant is included.
  • the underlayer 5 can be obtained as a layer having a narrow X-ray half width and a uniform crystal axis when used in combination with the buffer layer 4 described above.
  • the thickness of the underlayer 5 is preferably 1 ⁇ m or more and 12 ⁇ m or less.
  • the n-type nitride semiconductor layer 13 is provided above the substrate portion 7.
  • the n-type nitride semiconductor layer 13 has a function of injecting electrons into the light emitting layer 17.
  • a crystal is preferable, and a crystal in which Al a2 Ga 1-a2 N (0 ⁇ a2 ⁇ 1) is doped with an n-type dopant is more preferable, and Al a2 Ga 1-a2 N (0 ⁇ a2 ⁇ 0.5) is n-type.
  • a crystal doped with a dopant is more preferred, and a crystal obtained by doping Al a2 Ga 1-a2 N (0 ⁇ a2 ⁇ 0.1) with an n-type dopant is particularly preferred.
  • n-type dopant for example, silicon, phosphorus, arsenic, antimony, or the like is preferable, and silicon is more preferable.
  • the n-type dopant concentration in the n-type nitride semiconductor layer 13 may vary, and is preferably 1 ⁇ 10 18 cm ⁇ 3 or more and 2 ⁇ 10 19 cm ⁇ 3 or less on average. When the n-type dopant concentration is 1 ⁇ 10 18 cm ⁇ 3 or more, the resistance is maintained and an increase in driving voltage is suppressed.
  • the n-type dopant concentration is 2 ⁇ 10 19 cm ⁇ 3 or less, the surface of the n-type nitride semiconductor layer 13 becomes flat, and the light emission provided on the n-type nitride semiconductor layer 13 Since the surface of the layer 17 is also flat, a decrease in quantum efficiency of the light emitting diode 101 is suppressed.
  • the n-type dopant concentration in part of the n-type nitride semiconductor layer 13 may be lower than 1 ⁇ 10 18 cm ⁇ 3 , and may be higher than 2 ⁇ 10 19 cm ⁇ 3 in other parts.
  • the average value of the n-type dopant concentration is preferably 1 ⁇ 10 18 cm ⁇ 3 or more and 2 ⁇ 10 19 cm ⁇ 3 or less.
  • the thickness of the n-type nitride semiconductor layer 13 is preferably, for example, not less than 0.5 ⁇ m and not more than 10 ⁇ m. High resistance can be suppressed when the thickness of the n-type nitride semiconductor layer 13 is 0.5 ⁇ m or more. Moreover, when the thickness of the n-type nitride semiconductor layer 13 is 10 ⁇ m or less, the warp of the light emitting diode 101 tends to be suppressed and the yield tends to be improved.
  • the n-type nitride semiconductor layer 13 may be a single layer, or may have a plurality of layers having different thicknesses, n-type dopant concentrations, or both.
  • an n-type nitride semiconductor layer 13 includes a first n-type nitride semiconductor layer 9 and a second n-type nitride semiconductor layer 11 stacked in this order in the + Z direction (height direction) in FIG. Has a structured.
  • the second n-type nitride semiconductor layer 11 can suppress electrostatic breakdown of the light-emitting diode 101 when the n-type dopant is more doped than the first n-type nitride semiconductor layer 9. Therefore, it is preferable.
  • the functional layer 20 is provided between an n-type nitride semiconductor layer 13 and a p-type nitride semiconductor layer 27.
  • the functional layer 20 includes a V pit generation layer 14, a superlattice layer 15, a light emitting layer 17, and an undoped layer 19.
  • V pit generation layer The V pit generation layer 14 shown in FIG. 1 is for forming V pits 18 in the light emitting layer 17 using dislocations together with a superlattice layer 15 described later.
  • the function and generation conditions (growth temperature, carrier gas) of the V pit 18 will be described in detail later.
  • the thickness of the V pit generation layer 14 is preferably 10 nm or more and 300 nm or less.
  • the V pit 18 having a desired size can be formed in the light emitting layer 17.
  • the thickness of the V pit generation layer 14 is 300 nm or less, it is possible to suppress a decrease in the growth rate of the V pit 18, a prolonged growth time, and an increase in manufacturing cost.
  • the V pit generation layer 14 is distinguishable from other adjacent layers. However, as long as the function of the V pit generation layer 14 is not impaired, the V pit generation layer 14 may be indistinguishable from other adjacent layers in a later step.
  • the superlattice layer 15 shown in FIG. 1 functions as a buffer layer for relaxing crystal defects caused by the difference in lattice constant. Since the base layer 5 and the n-type nitride semiconductor layer 13 described above have greatly different lattice constants from the light-emitting layer 17 described later, crystal defects are introduced when the light-emitting layer 17 is formed on the surface of the n-type nitride semiconductor layer 13. Easy to be. Therefore, the introduction of crystal defects is suppressed by providing the superlattice layer 15 on the lower surface of the light emitting layer 17. Note that “superlattice” included in the name “superlattice layer” means a crystal lattice in which a plurality of layers having different crystal lattices are overlapped to make the periodic structure longer than the basic unit lattice.
  • the thickness of the superlattice layer 15 is preferably 30 nm or more and 500 nm or less.
  • V pits 18 having a desired size and surface density can be formed.
  • the V pit 18 does not become too large. Therefore, the light emitting layer 17 tends to be flat, and the light emitted from the light emitting diode 101 increases.
  • FIG. 3 is a schematic diagram showing an energy band of the light emitting diode of the present embodiment.
  • the superlattice layer 15 is a stacked body in which the first superlattice layer 15A and the second superlattice layer 15B are alternately provided, and the periodic structure thereof is the first superlattice layer. It is longer than the basic unit cell of 15A and the basic unit cell of the second superlattice layer 15B.
  • a crystal obtained by doping GaN with an n-type dopant is more preferable.
  • the first superlattice layer 15 ⁇ / b> A is doped with a higher concentration of n-type dopant than the n-type nitride semiconductor layer 13 at a temperature lower than the growth temperature of the n-type nitride semiconductor layer 13.
  • the n-type dopant concentration in the first superlattice layer 15A is preferably 1 ⁇ 10 18 cm ⁇ 3 or more and 5 ⁇ 10 19 cm ⁇ 3 or less.
  • the thickness of the first superlattice layer 15A is preferably not less than 0.5 nm and not more than 50 nm, for example. Since the thickness of the first superlattice layer 15A is 0.5 nm or more, the thickness is equal to or greater than the thickness of one atomic layer of the first superlattice layer 15A. Therefore, the first superlattice layer having a uniform thickness is used. 15A can be formed. Therefore, the crystal quality of the light emitting layer 17 can be improved, and the quantum efficiency of the light emitting diode 101 can be increased. Further, when the thickness of the first superlattice layer 15A is 50 nm or less, the first superlattice layer 15A tends to be flat. Therefore, the crystal quality of the light emitting layer 17 can be improved, and the quantum efficiency of the light emitting diode 101 can be increased.
  • the second superlattice layer 15B preferably has a larger band gap energy than the first superlattice layer 15A.
  • the second superlattice layer 15B may contain an n-type dopant in the above-described crystal.
  • the thickness of the second superlattice layer 15B is preferably not less than 0.5 nm and not more than 50 nm, for example. Since the thickness of the second superlattice layer 15B is 0.5 nm or more, the thickness is equal to or greater than the thickness of one atomic layer of the second superlattice layer 15B. Therefore, the second superlattice layer having a uniform thickness is used. 15B can be formed. Therefore, the crystal quality of the light emitting layer 17 can be improved, and the quantum efficiency of the light emitting diode 101 can be increased. Since the time required for the growth of the second superlattice layer 15B is not too long because the thickness of the second superlattice layer 15B is 50 nm or less, the productivity of the light emitting diode 101 can be maintained.
  • the total thickness of one first superlattice layer 15A and one second superlattice layer 15B is preferably, for example, 1 nm or more and 60 nm or less. It is preferable to determine the number of layers of the first superlattice layer 15A and the second superlattice layer 15B so that the thickness of the superlattice layer 15 satisfies the above range.
  • the superlattice layer 15 may include a semiconductor layer different from the first superlattice layer 15A and the second superlattice layer 15B.
  • the light emitting layer 17 shown in FIG. 1 has a function of emitting light having a plurality of wavelengths having different main emission peak wavelengths.
  • the light emitting layer 17 has a plurality of quantum well layers 1 and a plurality of barrier layers 2.
  • the light emitting layer 17 is a stacked body in which the quantum well layers 1 and the barrier layers 2 are alternately provided, and one quantum well layer 1 is provided between the two barrier layers 2. .
  • Such a structure is called a multiple quantum well structure.
  • the barrier layer 2 is provided on the surface in contact with the upper surface of the superlattice layer 15 and the surface in contact with the upper surface of the undoped layer 19. In other words, the barrier layer 2 is provided on the uppermost surface and the lowermost surface of the light emitting layer 17.
  • the light emitting layer 17 includes a plurality of quantum well layers 1 from the first quantum well layer to the Nth quantum well layer (N ⁇ 2) in order from the n-type nitride semiconductor layer 13 side. Further, the plurality of quantum well layers 1 have two or more types of quantum well layers that emit two or more types of light having different main emission peak wavelengths. Among the two or more types of quantum well layers, the quantum well layer having the longest wavelength main emission peak is located in the second and subsequent layers from the n-type nitride semiconductor layer 13 side in the light emitting layer 17.
  • the quantum well layer having the longest wavelength main emission peak is expressed as a quantum well layer 1B
  • the Nth quantum well layer from the first quantum well layer excluding the quantum well layer is expressed as a quantum well layer 1A.
  • the term “a plurality of quantum well layers 1” represents both the quantum well layer 1A and the quantum well layer 1B.
  • the stacked body in which the quantum well layers 1A and adjacent barrier layers 2A (described later) are alternately provided is caused by a difference in lattice constant as compared with the superlattice layer 15 described above with respect to the quantum well layer 1B. It functions as a buffer layer for alleviating crystal defects. Therefore, the crystal quality of the quantum well layer 1B can be improved and the emission intensity can be improved.
  • the injected electrons and holes are recombined, and light corresponding to the band gap is emitted.
  • the quantum well layer having the main emission peak with the shortest wavelength has the main emission peak in the range of 370 nm to 480 nm.
  • the main emission peak is in the range of 430 nm to 550 nm.
  • the light emitting diode 101 can emit two or more types of light having different main emission peak wavelengths.
  • the light emitting diode 101 when applied to a light emitting device, it can be excited with an excitation wavelength suitable for a plurality of wavelength converting substances (described later), and as a result, the color reproducibility of the light emitting device can be improved.
  • the thickness of the quantum well layer 1 is preferably 2 nm or more and 15 nm or less, for example.
  • the thickness of the quantum well layer 1 is within the above-described range, not only the quantum efficiency of the light-emitting diode 101 can be improved, but also an increase in driving voltage can be suppressed.
  • the thickness and composition of the quantum well layer 1 are determined in accordance with a desired emission wavelength.
  • the thicknesses of the quantum well layers 1A may be the same or different from each other.
  • the thicknesses of the quantum well layers 1B may be the same or different.
  • the number of quantum well layers 1 is, for example, preferably 2 or more, and more preferably 4 or more.
  • the number of quantum well layers 1B is preferably smaller than the number of quantum well layers 1A. Since the number of layers of the quantum well layer 1B is smaller than the number of layers of the quantum well layer 1A, the crystal quality of the layer provided on the quantum well layer 1B is improved, so that the quantum efficiency of the light emitting diode 101 is improved and driven. There is a tendency to suppress an increase in voltage.
  • the quantum well layer 1B is formed on at least one quantum well layer 1A. Since the quantum well layer 1A is thinner than the quantum well layer 1B and the In concentration contained in the crystal is low, it is easy to obtain a high-quality crystal. Therefore, by forming the quantum well layer 1B on the quantum well layer 1A, the crystal quality of the quantum well layer 1B can be improved, and a decrease in emission intensity can be suppressed.
  • the barrier layer 2 has a function of confining injected electrons and holes in the quantum well layer 1 described above.
  • the barrier layer adjacent to the quantum well layer 1A is referred to as “barrier layer 2A”, and the layers other than the barrier layer 2A are referred to as barrier layers 2B. That is, the barrier layer 2 includes a barrier layer 2A and a barrier layer 2B. When simply referred to as the barrier layer 2, it refers to both the barrier layer 2A and the barrier layer 2B.
  • the barrier layer 2 Al y Ga z In ( 1-yz) N (0 ⁇ y ⁇ 1,0 ⁇ z ⁇ 1) crystal are preferred.
  • the barrier layer 2 may be doped with an n-type dopant or a p-type dopant as long as it has a larger band gap energy than the quantum well layer 1.
  • the thickness of the barrier layer 2 is, for example, preferably from 1.5 nm to 50 nm, and more preferably from 1.5 nm to 20 nm.
  • the thickness of the barrier layer is 1.5 nm or more, the barrier layer 2 tends to be a flat and high-quality crystal, and the quantum efficiency of the light-emitting diode 101 tends to be improved.
  • the thickness of the barrier layer 2 is 50 nm or less, carriers injected into the light emitting layer 17 are diffused in the light emitting layer 17, so that not only the quantum efficiency of the light emitting diode 101 is improved, but also the driving voltage. Can be suppressed.
  • the thickness of the barrier layer 2 may be the same or different.
  • V pit The light emitting layer 17 shown in FIG. 1 preferably has a recess (hereinafter referred to as “V pit”) 18 extending in the direction from the n-type nitride semiconductor layer 13 to the p-type nitride semiconductor layer 27.
  • V pit a recess
  • 4A to 4C are schematic first to third sectional views showing the function of the V pit 18. As shown in FIG. 4A, the quantum well layer 1 and the barrier layer 2 are bent at the position of the V pit 18, and the quantum well layer 1 and the barrier layer 2 are laminated inside the V pit 18 thinner than the outside of the V pit 18. Has been.
  • the inside of the V pit 18 in which the quantum well layer 1 and the barrier layer 2 are thinly stacked is referred to as a region I
  • the outside of the V pit 18 in which the quantum well layer 1 and the barrier layer 2 are stacked thicker than the region I is referred to as a region II.
  • the “outside” of the V pit 18 refers to a peripheral portion of the V pit 18 in which the quantum well layer 1 and the barrier layer 2 are stacked substantially in parallel with other adjacent layers.
  • the “inside” of the V pit 18 refers to a portion that is lower than the peripheral portion of the V pit 18 described above.
  • V pit 18 Since electrons have a small effective mass and a high mobility, electrons can easily move between the layers constituting the quantum well layer 1 in the region I and the region II. On the other hand, since the hole has a large effective mass and low mobility, the region II can move only to the vicinity of the quantum well layer 1B on the p-type nitride semiconductor layer 27 side, and the quantum on the n-type nitride semiconductor layer 13 side. In some cases, sufficient light emission cannot be obtained from the well layer 1A.
  • the influence of the difference in driving current density of the light emitting diode 101 on the light emission characteristics can be suppressed.
  • the drive current density of the light emitting diode 101 is set between 5 A / cm 2 and 50 A / cm 2 and the emission spectrum is measured, the maximum value and the minimum of the main emission peaks of a plurality of lights emitted from the light emitting layer 17 are measured.
  • the value ratio can be kept within 10%.
  • the size of the V pit 18 varies depending on the thickness of the light emitting layer 17. For example, as shown in FIG. 4C, when the V pit 18 is not formed in a part of the layer constituting the quantum well layer 1, holes are not easily injected into the layer, and the emission intensity tends to decrease. . Therefore, the V pit 18 is preferably provided from the first quantum well layer constituting the quantum well layer 1 to the Nth quantum well layer.
  • the V pit 18 having a desired size can be formed by changing the growth conditions, thickness, and composition of the superlattice layer 15 described above.
  • the growth temperature of the superlattice layer 15 is preferably lower than the growth temperature of the underlayer 5 by 100 ° C. or more.
  • nitrogen is preferably used as a carrier gas (a gas that is a raw material carrying gas and does not become a constituent element of a nitride semiconductor).
  • the size of the V pit 18 can be changed by changing the ratio of the thicknesses of the first superlattice layer 15A and the second superlattice layer 15B.
  • the V pit 18 is filled with a p-type nitride semiconductor layer 27 described later.
  • a p-type nitride semiconductor layer 27 described later.
  • the threading dislocation hardly propagates to a layer above the V pit 18 (layer formed in the + Z direction in FIG. 1). Therefore, the penetration potential exposed to the surface of the p-type nitride semiconductor layer 27 that finally forms the electrode can be reduced, and the reliability of the light emitting diode 101 can be improved.
  • the undoped layer 19 shown in FIG. 1 is provided between the light emitting layer 17 and the p-type nitride semiconductor layer 27. Specifically, as shown in FIG. 3, the barrier layer 2 ⁇ / b> B and the p-type nitride semiconductor layer 27 are provided in contact with each other.
  • the undoped layer 19 has a function of suppressing the overflow of injected electrons and suppressing the diffusion of the p-type dopant to improve the temperature characteristics of the light emitting diode 101. Therefore, the undoped layer 19 has a larger band gap energy than the adjacent barrier layer 2B.
  • the ratio of Al contained in the undoped layer 19 is in the above-described range, both the effect of suppressing the diffusion of the p-type dopant and the effect of suppressing the increase in drive voltage can be obtained.
  • the undoped layer 19 means a layer not intentionally doped with an n-type dopant and a p-type dopant, but an n-type dopant or a p-type dopant is unintentionally contained in the undoped layer 19 by diffusion. Also good.
  • the thickness of the undoped layer 19 is limited by the p-type dopant concentration in the p-type nitride semiconductor layer 27 provided on the upper surface of the undoped layer 19, and is preferably 1 nm or more and 50 nm or less, and more preferably 2 nm or more and 30 nm or less.
  • the thickness of the undoped layer 19 is 1 nm or more, the diffusion distance of the p-type dopant is shortened and diffusion can be suppressed, so that the temperature characteristics of the light emitting diode 101 can be improved. Therefore, it is possible to suppress the influence of the temperature increase in the vicinity of the light emitting layer 17 on the light emission characteristics of the light emitting diode 101.
  • the decrease in peak intensity with respect to a plurality of lights emitted from the light emitting layer 17 can be suppressed to within 10%.
  • the thickness of the undoped layer 19 is 50 nm or less, an increase in the driving voltage of the light emitting diode 101 can be suppressed.
  • the p-type nitride semiconductor layer 27 is provided on the side opposite to the substrate portion 7 with respect to the n-type nitride semiconductor layer 13.
  • the p-type nitride semiconductor layer 27 has a function of injecting holes into the light emitting layer 17.
  • a crystal in which Al x Ga y In z N (0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, x + y + z 1) is doped with a p-type dopant.
  • a crystal in which Al x Ga 1-x N (0 ⁇ x ⁇ 0.4) is doped with a p-type dopant is more preferable.
  • the p-type dopant for example, magnesium is preferable.
  • the p-type dopant concentration in the p-type nitride semiconductor layer 27 is preferably 1 ⁇ 10 18 cm ⁇ 3 or more and 2 ⁇ 10 20 cm ⁇ 3 or less.
  • the p-type dopant is magnesium, the growth rate of the slope of the V pit 18 described above can be increased, and the V pit 18 can be easily embedded.
  • the thickness of the p-type nitride semiconductor layer 27 is preferably 30 nm or more. When the thickness of the p-type nitride semiconductor layer 27 is 30 nm or more, the V pit 18 described above can be embedded, and the surface of the p-type nitride semiconductor layer 27 can be flattened.
  • the p-type nitride semiconductor layer 27 preferably has a three-layer structure in which at least one of thickness, p-type dopant concentration and composition in the p-type nitride semiconductor layer 27 is different. That is, the p-type semiconductor layer includes the first p-type nitride semiconductor layer 21, the second p-type nitride semiconductor layer 23, and the third p-type nitride semiconductor layer 25 in this order in the + Z direction (high It is preferable that the structure is stacked in the vertical direction.
  • first p-type nitride semiconductor layer 21, the second p-type nitride semiconductor layer 23, and the third p-type nitride semiconductor layer 25 of this embodiment will be described with specific examples.
  • the first p-type nitride semiconductor layer 21 is preferably a crystal in which the material used for the p-type nitride semiconductor layer 27 described above is doped with a p-type dopant, and Al a5 Ga 1-a5 N (0 ⁇ a5 ⁇ 0.4, more preferably 0.1 ⁇ a5 ⁇ 0.3), a crystal doped with a p-type dopant is more preferable. At this time, it is preferable that 8 ⁇ 10 18 cm ⁇ 3 or more and 1 ⁇ 10 20 cm ⁇ 3 or less of magnesium is contained in the first p-type nitride semiconductor layer 21 as a p-type dopant.
  • the thickness of the first p-type nitride semiconductor layer 21 is preferably 3 nm to 200 nm, and preferably 5 nm to 30 nm.
  • the second p-type nitride semiconductor layer 23 provided so as to be in contact with the upper surface of the first p-type nitride semiconductor layer 21 is a p-type material used for the p-type nitride semiconductor layer 27 described above.
  • a crystal doped with a dopant is preferred, and a crystal obtained by doping GaN with a p-type dopant is more preferred.
  • the thickness of the second p-type nitride semiconductor layer 23 is preferably 3 nm or more and 200 nm or less. Since the first p-type nitride semiconductor layer 21 and the second p-type nitride semiconductor layer 23 are configured as described above, the number of holes injected into the light-emitting layer 17 can be increased. The quantum efficiency of 101 can be further increased.
  • the material used for the p-type nitride semiconductor layer 27 described above is p-type.
  • a crystal doped with a dopant is preferred, and a crystal obtained by doping GaN with a p-type dopant is more preferred.
  • magnesium as a p-type dopant is contained in the third p-type nitride semiconductor layer 25 more than the second p-type nitride semiconductor layer 23.
  • the thickness of the third p-type nitride semiconductor layer 25 is preferably 3 nm or more and 200 nm or less. Since the second p-type nitride semiconductor layer 23 and the third p-type nitride semiconductor layer 25 are configured as described above, the third p-type nitride semiconductor layer 25 and the third p-type nitride semiconductor layer 25 The contact resistance with the p-side electrode 33 in contact with the upper surface of the physical semiconductor layer 25 can be suppressed. In addition, the p-type dopant can be prevented from diffusing into the light emitting layer 17.
  • the transparent electrode 31 shown in FIG. 1 is preferably made of, for example, ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide).
  • the thickness of the transparent electrode 31 is preferably 50 nm or more and 500 nm or less.
  • a reflective electrode made of aluminum, silver, or the like may be provided.
  • the n-side electrode 29 and the p-side electrode 33 shown in FIG. 1 preferably have a structure in which a nickel layer, a platinum layer, and a gold layer are laminated in this order in the + Z direction (height direction) in FIG. (Not shown).
  • the thickness of the n-side electrode 29 and the p-side electrode 33 is preferably 300 nm or more and 3000 nm or less.
  • Transparent protective film 35 is preferably made of SiO 2. Moreover, it is preferable that the thickness of the transparent protective film 35 is 50 nm or more and 1000 nm or less.
  • a light emitting diode capable of improving the light emission efficiency of the light emitting device and realizing color rendering properties suitable for illumination applications and color reproducibility suitable for backlight applications.
  • FIG. 2 is a cross-sectional view showing the light emitting device 100 of the present embodiment.
  • the light emitting device 100 includes a light emitting diode 101 having the above-described configuration, a wavelength conversion material 102 provided on an optical path of light emitted from the light emitting diode, and a medium provided around the light emitting diode 101 and the wavelength conversion material 102. 103.
  • An anode 104 and a cathode 105 are connected to the light emitting diode 101 via gold wires 107, respectively.
  • a ceramic package 106 is provided so as to cover the whole of the light emitting diode 101, the wavelength converting substance 102, the medium 103, and the gold wire 107 and part of the anode 104 and the cathode 105.
  • [Wavelength conversion material] 2 absorbs at least one of a plurality of lights emitted from the light emitting layer 17 of the light emitting diode 101 and has a wavelength different from that of the light emitted from the light emitting layer 17. Can be emitted at least in the light emission direction.
  • the wavelength converting material 102 preferably includes a first wavelength converting material 102A and a second wavelength converting material 102B.
  • the first wavelength conversion material 102A preferably absorbs light emitted from the quantum well layer 1A and emits light having a wavelength different from that of light emitted from the quantum well layer 1A.
  • the second wavelength conversion material 102B preferably absorbs light emitted from the quantum well layer 1B and emits light having a wavelength different from that of light emitted from the quantum well layer 1B.
  • the wavelength conversion substance 102 described above contains a phosphor.
  • the excitation wavelength region of the phosphor may be an ultraviolet region or a visible region.
  • Examples of the phosphor contained in the wavelength conversion material 102 include Sr 2 P 2 O 7 : Sn 4+ , Sr 4 Al 14 O 25 : Eu 2+ , BaMgAl 10 O 17 : Eu 2+ , and SrGa 2 S 4 : Ce.
  • the wavelength conversion substance 102 may contain a single phosphor, or may contain a plurality of phosphors that emit fluorescence having different wavelengths.
  • a light emitting device that has high luminous efficiency and can realize color rendering properties suitable for illumination applications and color reproducibility suitable for backlight applications.
  • a plurality of phosphors may be used as the wavelength conversion substance for the purpose of improving the color rendering properties of the light emitting device.
  • a plurality of phosphors having an emission spectrum with a narrow half-value width may be used in combination in order to improve color reproducibility.
  • the light-emitting diode of the light-emitting device according to the embodiment of the present invention emits light having a plurality of wavelengths. Therefore, in the light emitting device of the embodiment of the present invention, the wavelength at which the phosphor is excited is not limited, and a plurality of phosphors can be freely combined, and the quantum efficiency is excellent. In addition, since the light emitting diode of the embodiment of the present invention can extract light having a wavelength in the visible region, it can be used not only to excite the phosphor but also as one of the elements included in the white light. From the above, the light emitting device according to the embodiment of the present invention not only exhibits color rendering properties suitable for illumination applications and color reproducibility suitable for backlight applications, but also has excellent luminous efficiency.
  • the medium 103 provided in the light emitting device 100 is provided in contact with the light emitting diode 101 is illustrated, but the medium 103 is not in contact with the light emitting diode 101 but provided separately. It may be done.
  • the wavelength conversion substance 102 provided in the light emitting device 100 is provided inside the medium 103. There may be provided apart.
  • the emission spectrum was measured using an integrating sphere and a spectroscope under the condition of a current value of 0.1 mA to 1 A.
  • the intensity (unit: lm) of the total luminous flux was obtained using an integrating sphere, and the luminous efficiency (unit: lm / W) was calculated from the following equation.
  • the input power (unit: W) is a value obtained from the voltage value and current value at the time of measurement.
  • Luminous efficiency (lm / W) total luminous flux intensity (lm) / input power (W)
  • An underlayer 5 was formed on the surface of the buffer layer 4 so as to have a thickness of 3 ⁇ m.
  • a GaN crystal was grown at 1000 ° C. to a thickness of 100 nm, and a first underlayer was formed.
  • the temperature was lowered to 900 ° C., and a GaN crystal was grown in a three-dimensional direction so as to fill the gap between the convex portions, thereby forming a second underlayer.
  • the temperature was raised to 1100 ° C., and a GaN crystal was grown in the lateral direction to form a third underlayer having a flat surface.
  • an n-type GaN crystal having a silicon doping concentration of 1 ⁇ 10 19 cm ⁇ 3 is grown at 1100 ° C. so that the thickness becomes 3.5 ⁇ m, and the n-type nitride semiconductor layer 13 is formed. Formed. Subsequently, the surface of the n-type nitride semiconductor layer 13 was doped with silicon so that the thickness was reduced to 750 ° C. so that the thickness was 60 nm, and the nitrogen concentration in the carrier gas was 50% or more. An n-type GaN crystal was grown to form a V pit generation layer 14.
  • An In 0.02 Ga 0.98 N crystal having a silicon doping concentration of 7 ⁇ 10 18 cm ⁇ 3 was grown on the surface of the V pit generation layer 14 so as to have a thickness of 12 nm, thereby forming the first superlattice layer 15A.
  • a GaN crystal having a silicon doping concentration of 7 ⁇ 10 18 cm ⁇ 3 was grown on the surface of the first superlattice layer 15A so as to have a thickness of 30 nm, thereby forming the second superlattice layer 15B.
  • the first superlattice layer 15A and the second superlattice layer 15B as described above were laminated on the surface of the V pit generation layer 14 for one period for five periods.
  • an InGaN crystal was grown at 770 ° C. so as to have a thickness of 3.3 nm, thereby forming a quantum well layer 1A.
  • a GaN crystal was grown at 870 ° C. so as to have a thickness of 12 nm, thereby forming a barrier layer 2A.
  • Such a quantum well layer 1A and the barrier layer 2A were laminated in a period of seven periods on the surface of the second superlattice layer 15B.
  • an InGaN crystal was grown at 730 ° C. on the surface of the barrier layer 2A so as to have a thickness of 4.1 nm, thereby forming a quantum well layer 1B.
  • a GaN crystal was grown at 870 ° C. so as to have a thickness of 11 nm, the barrier layer 2B was formed, and the light emitting layer 17 was formed.
  • hydrogen was not intentionally used as a carrier gas when forming the light emitting layer 17.
  • hydrogen obtained by decomposing the raw material is excluded because it is considered that it does not affect the formation of the V pit 18.
  • the temperature was raised to 980 ° C. so as to have a thickness of 15 nm, and an AlGaN crystal (however, containing 12% of aluminum in the crystal) was grown to form an undoped layer 19. Subsequently, an AlGaN crystal doped with magnesium (however, containing 20% of aluminum in the crystal) is grown on the surface of the undoped layer 19 by raising the temperature to 1050 ° C. so that the thickness becomes 22 nm. 1 p-type nitride semiconductor layer 21 was formed.
  • a GaN crystal doped with magnesium was grown on the surface of the first p-type nitride semiconductor layer 21 so as to have a thickness of 40 nm, and the second p-type nitride semiconductor layer 23 was formed.
  • a GaN crystal doped with magnesium was grown on the surface of the second p-type nitride semiconductor layer 23 so as to have a thickness of 12 nm, and a third p-type nitride semiconductor layer 25 was formed.
  • the magnesium concentration of the first to third p-type nitride semiconductor layers is 1 ⁇ 10 19 cm ⁇ from the first p-type nitride semiconductor layer 21 toward the third p-type nitride semiconductor layer 25.
  • Magnesium was doped so as to gradually increase from 3 to 2 ⁇ 10 19 cm ⁇ 3 . Note that the processes from the formation of the base layer 5 to the formation of the third p-type nitride semiconductor layer 25 were manufactured using the MOCVD method.
  • the ITO crystal was grown on the surface of the third p-type nitride semiconductor layer 25 using a sputtering method so as to have a thickness of 80 nm, and the transparent electrode 31 was formed. Subsequently, a bonding electrode composed of a nickel layer, a platinum layer and a gold layer was provided on the surface of the transparent electrode 31 to form a p-side electrode 33.
  • n-side electrode 29 was formed on the exposed surface of the n-type nitride semiconductor layer 13.
  • a transparent protective film 35 made of SiO 2 was formed by sputtering so as to mainly cover the transparent electrode 31 and the side surfaces of each layer exposed by the etching.
  • the light emitting diode of Production Example 1 was produced.
  • a drive current of 180 mA was applied to the p-side electrode 33 and the n-side electrode 29, and an emission spectrum was measured. It was found that light of 380 nm was emitted from the quantum well layer 1A, and light of 450 nm was emitted from the quantum well layer 1B.
  • the light emitting devices of Examples 1 to 3 were manufactured using the light emitting diodes and wavelength converting substances shown in Table 1.
  • FIG. 5A shows an emission spectrum of the light-emitting device manufactured in Example 1.
  • the Y 2 SiO 5 Ce, Tb phosphor absorbed 380 nm light emitted from the quantum well layer 1A of Example 1 and emitted green light.
  • the K 2 SiF 6 Mn phosphor absorbed 450 nm light emitted from the quantum well layer 1B of Example 1 and emitted red light.
  • a part of the 450 nm light was transmitted as it was and emitted outside the light emitting diode.
  • the light emitted from the two types of wavelength converting materials and the light emitting diode was mixed, and white light was emitted. Therefore, according to Example 1, a light-emitting device having high luminous efficiency and excellent color reproducibility when used in combination with a color filter was provided.
  • FIG. 5B shows an example of a transmission spectrum of a color filter used for a backlight of a liquid crystal display device.
  • Most of the white light of the light emitting device of Example 1 can pass through the color filter shown in FIG. 5B. Therefore, such a light emitting device can be used for a backlight of a liquid crystal display device.
  • FIG. 6 shows an emission spectrum of the light-emitting device manufactured in Example 2.
  • the BaMgAl 10 O 17 (hereinafter referred to as “BAM”): Eu phosphor absorbed 380 nm light emitted from the quantum well layer 1A of Example 2 and emitted blue light.
  • the Y 3 Al 5 O 12 (hereinafter, YAG): Ce phosphor absorbed 475 nm light emitted from the quantum well layer 1B of Example 2 and emitted yellow light.
  • the CaAlSiN 3 (hereinafter CASN): Eu phosphor is not only 475 nm light emitted from the quantum well layer 1B of Example 2, but also 380 nm light emitted from the quantum well layer 1A, BAM: Eu fluorescence. Blue light emitted from the body and part of yellow light emitted from the YAG: Ce phosphor were absorbed and emitted red. Light emitted from the above-described three types of wavelength converting substances was mixed, and white light was emitted. Therefore, according to Example 2, the light-emitting device excellent in color rendering was provided. Such a light-emitting device can be used for a lighting device.
  • the luminous efficiency was improved by about 3% compared to Example 1.
  • the drive current density of the light emitting diode C was set between 5 A / cm 2 and 50 A / cm 2 and the emission spectrum was measured, the ratio between the maximum value and the minimum value of the main light emission peak was higher than that in Example 1. About 2%.
  • the quantum well layer having the longest main emission peak is the n-type nitride semiconductor layer 13 in the light emitting layer 17.
  • the other quantum well layers having two types of main emission peaks are included in the quantum well layer 1A from the first quantum well layer to the Nth quantum well layer excluding the quantum well layer 1B.
  • the arrangement of the three types of quantum well layers from the first quantum well layer to the Nth quantum well layer is other than that the quantum well layer 1B is located in the second and subsequent layers from the n-type nitride semiconductor layer 13 side. Is not particularly limited. Even in such a case, it was confirmed that the effect of one embodiment of the present invention was obtained.
  • One embodiment of the present invention is a light-emitting diode that is required to improve the light-emitting efficiency of a light-emitting device, and to achieve color rendering properties suitable for illumination applications and color reproducibility suitable for backlight applications.
  • the present invention can be applied to a light emitting device provided.

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Abstract

L'invention concerne une diode électroluminescente dans laquelle un film multicouche à semi-conducteur de nitrure comprend une première couche semi-conductrice de nitrure, une seconde couche semi-conductrice de nitrure et une couche électroluminescente disposée entre la première couche semi-conductrice de nitrure et la seconde couche semi-conductrice de nitrure, un substrat transparent comporte une saillie sur une surface faisant face à la première couche semi-conductrice de nitrure, la couche électroluminescente comprenant, dans l'ordre à partir du côté de la première couche de semi-conducteur de nitrure, une pluralité de N couches de puits quantiques (N ≥2) à partir d'une première couche de puits quantique, la pluralité de couches de puits quantiques comportant au moins deux types de couche de puits quantiques pour émettre au moins deux types de lumière ayant des longueurs d'onde de pic électroluminescente principale différentes et, parmi les deux ou plus de deux types de couche de puits quantiques, la couche de puits quantiques ayant la plus grande longueur d'onde de pic électroluminescente principale est située, dans la couche électroluminescente, au niveau de la seconde couche à partir du côté de la première couche semi-conductrice de nitrure ou au-delà.
PCT/JP2017/025534 2016-07-13 2017-07-13 Diode électroluminescente et dispositif électroluminescent Ceased WO2018012585A1 (fr)

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