CN116469974A - Light-emitting element and method for manufacturing light-emitting element - Google Patents
Light-emitting element and method for manufacturing light-emitting element Download PDFInfo
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- CN116469974A CN116469974A CN202310075052.4A CN202310075052A CN116469974A CN 116469974 A CN116469974 A CN 116469974A CN 202310075052 A CN202310075052 A CN 202310075052A CN 116469974 A CN116469974 A CN 116469974A
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- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 26
- 239000000203 mixture Substances 0.000 claims abstract description 79
- 239000004065 semiconductor Substances 0.000 claims abstract description 75
- 230000004888 barrier function Effects 0.000 claims abstract description 41
- 150000004767 nitrides Chemical class 0.000 claims abstract description 18
- 239000012535 impurity Substances 0.000 claims description 76
- 229910002601 GaN Inorganic materials 0.000 claims description 14
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 claims description 8
- RNQKDQAVIXDKAG-UHFFFAOYSA-N aluminum gallium Chemical compound [Al].[Ga] RNQKDQAVIXDKAG-UHFFFAOYSA-N 0.000 claims description 7
- 238000000605 extraction Methods 0.000 abstract description 14
- 239000007789 gas Substances 0.000 description 117
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 35
- 239000002994 raw material Substances 0.000 description 31
- 230000000903 blocking effect Effects 0.000 description 29
- XCZXGTMEAKBVPV-UHFFFAOYSA-N trimethylgallium Chemical compound C[Ga](C)C XCZXGTMEAKBVPV-UHFFFAOYSA-N 0.000 description 23
- 239000000758 substrate Substances 0.000 description 20
- JLTRXTDYQLMHGR-UHFFFAOYSA-N trimethylaluminium Chemical compound C[Al](C)C JLTRXTDYQLMHGR-UHFFFAOYSA-N 0.000 description 19
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 14
- 239000012159 carrier gas Substances 0.000 description 13
- 230000031700 light absorption Effects 0.000 description 11
- 239000011777 magnesium Substances 0.000 description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 7
- 229910052594 sapphire Inorganic materials 0.000 description 7
- 239000010980 sapphire Substances 0.000 description 7
- 230000004048 modification Effects 0.000 description 6
- 238000012986 modification Methods 0.000 description 6
- 239000001257 hydrogen Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 229910001873 dinitrogen Inorganic materials 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- MHYQBXJRURFKIN-UHFFFAOYSA-N C1(C=CC=C1)[Mg] Chemical compound C1(C=CC=C1)[Mg] MHYQBXJRURFKIN-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- 230000002040 relaxant effect Effects 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 238000002834 transmittance Methods 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- PIGFYZPCRLYGLF-UHFFFAOYSA-N Aluminum nitride Chemical compound [Al]#N PIGFYZPCRLYGLF-UHFFFAOYSA-N 0.000 description 1
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
- H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
- H01L33/0062—Processes for devices with an active region comprising only III-V compounds
- H01L33/0075—Processes for devices with an active region comprising only III-V compounds comprising nitride compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
- H01L33/145—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure with a current-blocking structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/26—Materials of the light emitting region
- H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
- H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
- H01L33/325—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen characterised by the doping materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
- H01L33/38—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape
- H01L33/385—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape the electrode extending at least partially onto a side surface of the semiconductor body
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
- H01L33/40—Materials therefor
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Abstract
The invention provides a light-emitting element and a method for manufacturing the same, which have high light extraction efficiency. The light emitting element includes: a semiconductor structure including an n-side layer, a p-side layer, and an active layer which is formed of nitride semiconductor, is located between the n-side layer and the p-side layer, and emits ultraviolet light; an n-electrode electrically connected to the n-side layer; and a p-electrode electrically connected to the p-side layer. The active layer has: an Al-containing well layer, an Al-containing barrier layer, and a hole portion including a side surface of the well layer and a side surface of the barrier layer, wherein the p-side layer has: the first layer containing Al, the second layer containing Al and disposed on the first layer and contacting the side surface of the well layer, and the third layer disposed on the second layer, wherein the third layer has a thickness smaller than that of the first layer, the difference between the Al composition ratio of the second layer and the Al composition ratio of the well layer is 10% or less, the third layer is a layer having a lower Al composition ratio than that of the second layer, or is a layer containing no Al, and the p-electrode is disposed on the third layer.
Description
Technical Field
The present invention relates to a light-emitting element and a method for manufacturing the light-emitting element.
Background
In patent document 1, a light emitting element that has a layer formed of a plurality of nitride semiconductors and emits deep ultraviolet light has been disclosed. In the above light emitting element, it is desirable to improve light extraction efficiency.
Prior art literature
Patent literature
Patent document 1: japanese patent application laid-open No. 2019-54122
Disclosure of Invention
Technical problem to be solved by the invention
An object of one embodiment of the present invention is to provide a light-emitting element having high light extraction efficiency and a method for manufacturing the light-emitting element.
Technical scheme for solving technical problems
A light-emitting element according to an embodiment of the present invention includes: a semiconductor structure including an n-side layer, a p-side layer, and an active layer which is formed of nitride semiconductor, is located between the n-side layer and the p-side layer, and emits ultraviolet light;
an n-electrode electrically connected to the n-side layer;
a p-electrode electrically connected to the p-side layer;
the active layer has: an Al-containing well layer, an Al-containing barrier layer, and a hole portion including a side surface of the well layer and a side surface of the barrier layer, wherein the p-side layer includes: the semiconductor device includes a first layer containing Al, a second layer containing Al and disposed on the first layer so as to be in contact with the side surface of the well layer, and a third layer disposed on the second layer, wherein the third layer is thinner than the first layer, the difference between the Al composition ratio of the second layer and the Al composition ratio of the well layer is 10% or less, the third layer is a layer having a lower Al composition ratio than the second layer, or a layer containing no Al, and the p-electrode is disposed on the third layer.
The method for manufacturing a light-emitting element according to one embodiment of the present invention includes: forming an n-side layer formed of a nitride semiconductor; forming an active layer including a well layer containing Al, a barrier layer containing Al, and a hole portion including a side surface of the well layer and a side surface of the barrier layer, each formed of a nitride semiconductor, on the n-side layer, the active layer emitting ultraviolet light; forming a p-side layer including a first layer containing Al, a second layer containing Al and having a difference of 10% or less from the Al composition ratio of the well layer, and a third layer which is thinner than the first layer and has a lower Al composition ratio than the second layer, or a layer containing no Al, over the active layer; forming an n-electrode electrically connected to the n-side layer; and forming a p electrode electrically connected to the third layer of the p-side layer. The step of forming the p-side layer includes: the method includes a step of forming the first layer on the active layer, a step of forming the second layer in contact with the first layer and the side surface of the well layer, and a step of forming the third layer on the second layer.
ADVANTAGEOUS EFFECTS OF INVENTION
According to one embodiment of the present invention, a light-emitting element having high light extraction efficiency and a method for manufacturing the light-emitting element can be provided.
Drawings
Fig. 1 is a schematic cross-sectional view showing the structure of a light-emitting element according to an embodiment of the present invention.
Fig. 2 is a schematic cross-sectional view showing the structure of a light-emitting element according to an embodiment of the present invention.
Fig. 3 is a schematic cross-sectional view showing a structure of a light-emitting element according to a modification of one embodiment of the present invention.
Fig. 4 is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention.
Fig. 5 is a schematic sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention.
Fig. 6 is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention.
Fig. 7 is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention.
Fig. 8 is a schematic sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention.
Fig. 9 is a schematic sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention.
Fig. 10 is a schematic sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention.
Detailed Description
Next, embodiments of the light-emitting element of the present invention will be described. In the following description, the present invention is generally described with reference to the drawings, and therefore, the proportions, intervals, positional relationships, and the like of the respective components are exaggerated, or some of the components may be omitted. In the following description, the same names and symbols are used to indicate the same or similar components, and detailed description thereof is omitted as appropriate.
Fig. 1 is a schematic sectional view of a light emitting element 1. Fig. 2 is a schematic sectional view showing a part of the semiconductor structure 100 in an enlarged manner. As shown in fig. 1 and 2, the light-emitting element 1 includes a substrate 10 and a semiconductor structure 100 disposed on the substrate 10. The semiconductor structure 100 includes an n-side layer 20, a p-side layer 50, and an active layer 30 that is formed of nitride semiconductors, respectively, and that is located between the n-side layer 20 and the p-side layer 50 and emits ultraviolet light. Further, the semiconductor structure 100 includes: a buffer layer 11 and a superlattice layer 12 between the substrate 10 and the n-side layer 20, and an electron blocking layer 40 between the active layer 30 and the p-side layer 50. The light-emitting element 1 has: an n-electrode 60 electrically connected to the n-side layer 20, and a p-electrode 70 electrically connected to the p-side layer 50.
As a material of the substrate 10, for example, sapphire, silicon (Si), gallium nitride (GaN), aluminum nitride (AlN), or the like can be used. The substrate 10 made of sapphire is preferable because it has high light transmittance to ultraviolet rays from the active layer 30. The semiconductor structure 100 may be disposed on the c-plane of the sapphire substrate, for example, and is preferably disposed on a plane inclined in a range of 0.2 ° or more and 2 ° or less from the c-plane of the sapphire substrate to the a-axis or m-axis of the sapphire substrate. The thickness of the substrate 10 may be, for example, 150 μm or more and 800 μm or less. The light emitting element 1 may not have the substrate 10.
The semiconductor structure 100 is a laminate in which a plurality of semiconductor layers formed of nitride semiconductors are laminated. The nitride semiconductor is composed of In x Al y Ga 1-x-y N (0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, x+y.ltoreq.1) and all the components of the semiconductor having the composition ratios x and y varying within the respective ranges.
For example, a layer formed of AlN may be used for the buffer layer 11. The buffer layer 11 has a function of relaxing lattice mismatch between the substrate 10 and the nitride semiconductor layer disposed on the buffer layer 11. The thickness of the buffer layer 11 may be, for example, 0.5 μm or more and 4 μm or less, and preferably 1.5 μm or more and 4 μm or less. In the present specification, the thickness of each semiconductor layer refers to the thickness in the lamination direction of the semiconductor structure 100.
The superlattice layer 12 has a multilayer structure in which first semiconductor layers and second semiconductor layers having lattice constants different from those of the first semiconductor layers are alternately laminated. The superlattice layer 12 has a function of relaxing stress generated in a semiconductor layer disposed above the superlattice layer 12. The superlattice layer 12 may be, for example, a multilayer structure in which AlN layers and aluminum gallium nitride (AlGaN) layers are alternately laminated. In the superlattice layer 12, the first semiconductor layer and the second semiconductor layer may have a pair number of 20 pairs or more and 50 pairs or less. When the first semiconductor layer is an AlGaN layer and the second semiconductor layer is an AlN layer, the thickness of the first semiconductor layer may be 5nm to 30nm, and the thickness of the second semiconductor layer may be 5nm to 30 nm.
The n-side layer 20 includes one or more n-type semiconductor layers. Examples of the n-type semiconductor layer include a semiconductor layer containing n-type impurities such as silicon (Si) and germanium (Ge). The N-type semiconductor layer is, for example, an AlGaN layer containing aluminum (Al), gallium (Ga), and nitrogen (N), and may contain indium (In). For example, the n-type impurity concentration of the n-type semiconductor layer containing Si as the n-type impurity is 5×10 18 /cm 3 Above, 1×10 20 /cm 3 The following is given. The n-side layer 20 may have a function of supplying electrons, and may include an undoped layer. Here, the undoped layer refers to a layer which is not intentionally doped with an n-type impurity or a p-type impurity. In the case where an undoped layer adjoins a layer intentionally doped with an n-type impurity and/or a p-type impurity, the undoped layer may contain the n-type impurity and/or the p-type impurity due to diffusion or the like from the adjoining layer.
As shown in fig. 1, the n-side layer 20 includes a base layer 21, and an n-contact layer 22. The base layer 21 is disposed between the superlattice layer 12 and the n-contact layer 22. The n-contact layer 22 is arranged between the base layer 21 and the active layer 30.
The underlayer 21 may be, for example, an undoped AlGaN layer. When the underlayer 21 is an AlGaN layer, the Al composition ratio of the AlGaN layer may be 50% or more, for example.
The n-contact layer 22 may be a layer formed of AlGaN containing an n-type impurity. When the n-contact layer is an AlGaN layer, the Al composition ratio of the AlGaN layer may be 50% or more, for example. In the present specification, for example, an AlGaN layer having an Al composition ratio of 50% means that the AlGaN layer is made of Al X Ga 1-X N is an AlGaN layer having a composition ratio x of 0.5. The n-type impurity concentration of the n-contact layer 22 may be, for example, 5×10 18 /cm 3 Above, 1×10 20 /cm 3 The following is given. The thickness of the n-contact layer 22 is thicker than the thickness of the base layer 21. The thickness of the n-contact layer 22 may be, for example, 1.5 μm or more and 4 μm or less. The n-contact layer 22 has an upper surface where no other semiconductor layer is arranged. An n-electrode 60 is disposed on the upper surface of the n-contact layer 22 where no other semiconductor layer is disposed.
The active layer 30 is disposed between the n-side layer 20 and the p-side layer 50. The active layer 30 emits ultraviolet rays. The peak wavelength of the ultraviolet light emitted from the active layer 30 is, for example, 220nm or more and 350nm or more.
The active layer 30 has: an Al-containing well layer 31, an Al-containing barrier layer 32, and a hole portion including a side surface of the well layer 31 and a side surface of the barrier layer 32. The hole portion of the active layer 30 is, for example, a V-shaped pit formed when the active layer 31 is formed. The hole of the active layer 30 may be, for example, a through hole penetrating the active layer 30, or a hole in which a part of the barrier layer 32 is a bottom. The active layer 30 has, for example, a multiple quantum well structure including a plurality of well layers 31 and a plurality of barrier layers 32. The Al composition ratio of the barrier layer 32 is larger than that of the well layer 31. That is, the band gap energy of the band gap energy well layer 31 of the barrier layer 32 is large. Light having an emission wavelength corresponding to the band gap energy of the well layer 31 is emitted from the Al-containing well layer 31. The active layer 30 is not limited to a multiple quantum well structure including a plurality of well layers 31, and may be a single quantum well structure. In fig. 2, the lowermost layer of the active layer 30 is the barrier layer 32, but the lowermost layer of the active layer 30 may be the well layer 31. Although the uppermost layer of the active layer 30 is used as the well layer 31, the uppermost layer of the active layer 30 may be used as the barrier layer 32.
The well layer 31 may be a layer formed of AlGaN, for example. The barrier layer 32 may be formed of AlGaN, for example. The Al composition ratio of the well layer 31 may be, for example, 10% or more, specifically, 10% or more and 50% or less, and more specifically, 30% or more and 50% or less. When the emission peak wavelength of light from the well layer 31 is about 280nm, an AlGaN layer having an Al composition ratio of about 42% can be used for the well layer 31. The Al composition ratio of the barrier layer 32 may be, for example, 10% or more, specifically 10% or more and 60% or less, and more specifically 30% or more and 60% or less.
The thickness of the well layer 31 may be, for example, 3nm to 6 nm. The thickness of the barrier layer 32 is, for example, 2nm to 4 nm. The thickness of the well layer 31 is preferably thicker than the thickness of the barrier layer 32 from the viewpoint of increasing the volume of the semiconductor layer contributing to light emission. The thickness of the well layer 31 may be 1.5 times or more and 2 times or less the thickness of the barrier layer 32. At least a part of the well layer 31 and the barrier layer 32 may contain an n-type impurity and/or a p-type impurity.
The V-shaped pits 33 are arranged continuously with a part of the active layer 30, the electron blocking layer 40, and the p-side layer 50. In the present embodiment, the V-shaped pits 33 are defined by a face including the side face of the well layer 31, the side face of the barrier layer 32, the side face of the electron blocking layer 40, the side face of the fourth layer 54, and the side face of the first layer 51. The V-shaped pits 33 are formed when the semiconductor structure 100 is grown, and recesses are formed in the surface of the semiconductor structure 100 corresponding to the portions where the V-shaped pits 33 are formed. A plurality of V-shaped pits 33 are arranged in the semiconductor structure 100. The V-shaped recess 33 has a circular shape, an elliptical shape, or a hexagonal shape in plan view, for example. The diameter of the V-shaped recess 33 is, for example, 30nm to 100nm in plan view. One V-shaped pit 33 is, for example, a conical shape, an elliptic conical shape, a polygonal pyramid shape, or the like, the diameter of which increases from the n-side layer 20 toward the p-side layer 50. The V-shaped pits 33 are formed, for example, when the semiconductor structure 100 is epitaxially grown on the substrate 10.
The electron blocking layer 40 is provided to reduce the overflow of electrons supplied from the n-side layer 20. The electron blocking layer 40 may have a multilayer structure having a plurality of semiconductor layers containing Al. The electron blocking layer 40 may have a multilayer structure including an AlN layer, a first AlGaN layer, and a second AlGaN layer in this order from the active layer 30 side. The Al composition ratio of the first AlGaN layer is lower than that of the second AlGaN layer, and is higher than that of the well layer 31. The electron blocking layer 40 uses a semiconductor layer having an Al composition ratio higher than that of the barrier layer 32. This can reduce the overflow of electrons. The electron blocking layer 40 may be, for example, an undoped AlGaN layer, an undoped AlN layer, or the like. The total thickness of the electron blocking layer 40 may be, for example, 5nm to 15 nm.
In general, in order to reduce absorption of light from the well layer 31 by the semiconductor layer and to improve light extraction efficiency, it is preferable to use a semiconductor layer having high light transmittance to light from the well layer 31 for the p-side layer 50. For example, by using an AlGaN layer having a higher Al composition ratio than that of the well layer 31 for the p-side layer 50, light from the well layer 31 can be made difficult to be absorbed by the p-side layer 50. However, alGaN layers having a high Al composition ratio have a larger band gap energy than GaN layers and the like. Therefore, when an AlGaN layer having a high Al composition ratio is used for the p-side layer 50, there is a possibility that the p-type of the p-side layer 50 is insufficient, or the contact resistance between the p-electrode 70 and the p-side layer 50 increases. From the above description, in a light-emitting element using an AlGaN layer formed with a relatively high Al composition ratio as the well layer 31, it is difficult to achieve both high light extraction efficiency and low forward voltage Vf. In the present embodiment, the light-emitting element 1 having high light extraction efficiency and low forward voltage Vf can be formed by having the following p-side layer 50.
The p-side layer 50 includes more than one p-type semiconductor layer. The p-type semiconductor layer may include a semiconductor layer containing a p-type impurity such as magnesium (Mg). As shown in fig. 2, the p-side layer 50 includes a first layer 51, a second layer 52, and a third layer 53 in this order from the active layer 30 side. The p-side layer 50 also has a fourth layer 54 disposed between the electron blocking layer 40 and the first layer 51. The first layer 51 contains Al. The second layer contains Al, is disposed on the first layer 51, and is disposed so as to be in contact with the side surface of the well layer 31. The third layer 53 is disposed on the second layer 52. The fourth layer 54 contains Al.
The difference between the Al composition ratio of the second layer 52 and the Al composition ratio of the well layer 31 is 10% or less. This reduces light absorption of the second layer 52, and allows light from the side surface of the well layer 31 located in the V-shaped pit 33 to propagate through the second layer 52 disposed in contact with the side surface of the well layer 31, thereby facilitating extraction toward the p-side layer 50. Therefore, the light emitting element 1 having high light extraction efficiency can be formed.
The thickness of the third layer 53 is thinner than the thickness of the first layer 51. The third layer 53 is a layer having a lower Al composition ratio than that of the second layer 52, or a layer containing no Al. The p-electrode 70 is disposed on the third layer 53. Thereby, light absorption of the third layer 53 can be reduced, and contact resistance between the p-electrode 70 and the third layer 53 can be reduced. Therefore, it is possible to reduce the deterioration of the light extraction efficiency and reduce the forward voltage Vf.
As described above, according to the present embodiment, the light emitting element 1 having high light extraction efficiency can be formed. In addition, the forward voltage Vf can be reduced.
The second layer 52 is disposed continuously with the upper surface of the first layer 51, the side surface of the fourth layer 54, the side surface of the electron blocking layer 40, the side surface of the well layer 31, and the side surface of the barrier layer 32. The side surfaces of the semiconductor layers located in the V-shaped recesses 33 are covered with the second layer 52, and recesses corresponding to the shape of the V-shaped recesses 33 are formed in the surface of the second layer 52. In order to make the surface state of the third layer 53 arranged on the second layer 52 nearly flat, the depth of the recess formed on the surface of the second layer 52 is preferably smaller than the depth of the V-shaped recess 33 in cross section. In the present embodiment, as shown in fig. 2, the upper surface of the second layer 52 is entirely covered with the third layer 53, but the present invention is not limited thereto. For example, a part of the upper surface of the second layer 52 may be exposed from the third layer 53 to such an extent that the contact resistance between the p-electrode 70 and the third layer 53 does not deteriorate.
The thickness of the third layer 53 is preferably equal to or less than the thickness of the second layer 52. For example, the thickness of the third layer 53 located above the first layer 51 is preferably equal to or less than the thickness of the second layer 52. This can reduce light absorption of the third layer 53. The thickness of the second layer 52 is preferably thinner than the thickness of the first layer 51. This can reduce the light absorption of the second layer 52.
The thickness of the first layer 51 may be, for example, 20nm to 40 nm. The thickness of the second layer 52 is, for example, preferably 3nm to 20nm, more preferably 3nm to 15 nm. By setting the thickness of the second layer 52 to 3nm or more, the V-shaped pits 33 can be easily buried. By setting the thickness of the second layer 52 to 20nm or less, light absorption of the second layer 52 can be reduced. The thickness of the third layer 53 is, for example, preferably 3nm to 20nm, and more preferably 3nm to 15 nm. By setting the thickness of the third layer 53 to 3nm or more, the effect of reducing the contact resistance between the p-electrode 70 and the third layer 53 can be easily obtained. By setting the thickness of the third layer 53 to 20nm or less, light absorption of the third layer 53 can be reduced.
The first layer 51, the second layer 52, and the third layer 53 contain p-type impurities. The p-type impurity concentration of the second layer 52 and the p-type impurity concentration of the third layer 53 are preferably higher than those of the first layer 51. By increasing the p-type impurity concentration around the third layer 53 where the p-electrode 70 is disposed, holes can be easily supplied from the p-side layer 50 to the active layer 30, and the light-emitting efficiency of the light-emitting element 1 can be improved.
The p-type impurity concentration of the third layer 53 is preferably higher than that of the second layer 52. By increasing the p-type impurity concentration of the third layer 53 where the p-electrode 70 is disposed, holes can be easily supplied from the p-side layer 50 to the active layer 30, and the light-emitting efficiency of the light-emitting element 1 can be improved. The p-type impurity concentration of the third layer 53 is higher than that of the fourth layer 54.
The p-type impurity concentration of the first layer 51, the second layer 52, the third layer 53, and the fourth layer 54 is, for example, 1×10 19 /cm 3 Above, 1×10 21 /cm 3 The following is given.
The Al composition ratio of the first layer 51 is preferably higher than that of the second layer 52. By making the Al composition ratio of the first layer 51 located closer to the active layer 30 than the second layer 52 higher than the Al composition ratio of the second layer 52, light absorption by the first layer 51 can be reduced, and light extraction efficiency can be improved.
The first layer 51 may be a composition inclined layer in which the Al composition ratio is reduced from the active layer 30 side to the second layer 52 side, for example. Thus, compared with the case where the first layer 51 is a semiconductor layer having a constant Al composition ratio, the forward voltage Vf can be reduced due to the reduction in the portion of the first layer 51 where the Al composition is relatively high. For example, the difference between the Al composition ratio of the portion of the first layer 51 on the active layer 30 side and the Al composition ratio of the portion of the first layer 51 on the second layer 52 side may be 20% or more and 60% or less. Specifically, the Al composition ratio of the portion of the composition inclined layer on the active layer 30 side may be set to 40% or more and 70% or less, and the Al composition ratio of the portion of the composition inclined layer on the second layer 52 side may be set to 0% or more and 20% or less. In addition, a part of the first layer 51 may be a composition gradient layer in which the Al composition ratio is reduced. Thus, compared with the case where the entire first layer 51 is a composition inclined layer, the portion where the Al composition ratio is reduced, so that the light absorption of the first layer 51 can be reduced. For example, only the portion of the first layer 51 located on the second layer 52 side may be a constituent oblique layer. The portion of the first layer 51 that constitutes the inclined layer may be, for example, 3% or more and 20% or less with respect to the thickness of the first layer 51. The portion of the first layer 51 that constitutes the inclined layer may be, for example, 1nm or more and 30nm or less.
The Al composition ratio of the second layer 52 is preferably higher than that of the well layer 31. This can further reduce the light absorption of the second layer 52, and light from the side surface of the well layer 31 can more easily propagate through the second layer 52, so that the light extraction efficiency can be improved.
The Al composition ratio of the first layer 51 is, for example, preferably 50% or more and 70% or less, and more preferably 50% or more and 60% or less. The Al composition ratio of the second layer 52 is preferably 30% or more and 60% or less, more preferably 35% or more and 55% or less, and still more preferably 40% or more and 55% or less. By setting the Al composition ratio of the second layer 52 to 30% or more, the light absorption of the second layer 52 can be reduced. By setting the Al composition ratio of the second layer 52 to 60% or less, the bulk resistance of the second layer 52 can be reduced, and deterioration of the forward voltage Vf can be reduced. The Al composition ratio of the third layer 53 is preferably 3% or less, for example. This promotes the p-type of the third layer 53, thereby improving the light emission efficiency.
The first layer 51 is formed of, for example, aluminum gallium nitride. The second layer 52 is formed of, for example, aluminum gallium nitride. The third layer 53 is formed of gallium nitride, or aluminum gallium nitride, for example. The fourth layer 54 is formed of, for example, aluminum gallium nitride. The first layer 51, the second layer 52, the third layer 53, and the fourth layer 54 may contain In.
The thickness of the fourth layer 54 is thicker than the thickness of the third layer 53. The thickness of the fourth layer 54 may be, for example, 60nm to 100 nm. The Al composition ratio of the fourth layer 54 is higher than that of the first layer 51, and lower than that of the semiconductor layer (second AlGaN layer) of the electron blocking layer 40 in contact with the fourth layer 54. Thus, holes from the p-electrode 70 side can be easily supplied to the active layer 30. The Al composition ratio of the fourth layer 54 is, for example, preferably 50% to 70%, more preferably 60% to 70%
The n-electrode 60 is disposed on the n-contact layer 22 and electrically connected to the n-side layer 20. The p-electrode 70 is disposed on the third layer 53 of the p-side layer 50 and electrically connected to the p-side layer 50.
For example, a metal such as Ag, al, ni, au, rh, ti, pt, mo, ta, W, ru or an alloy containing the above metal as a main component may be used for the n-electrode 60. The n-electrode 60 may have a multilayer structure including, for example, a Ti layer, an Al alloy layer, a Ta layer, and a Ru layer in this order from the n-contact layer 22 side.
The p-electrode 70 may be made of the same metal as the n-electrode 60 described above. In the case of the p-electrode 70 having a function of reflecting light from the active layer 30 to the p-electrode 70 side from the p-electrode 70 to the n-side layer 20 side, the metal layer in contact with the third layer 53 among the p-electrode 70 is preferably a metal layer having a high reflectance for light from the active layer 30. For example, a metal layer having a reflectance of 70% or more, preferably 80% or more with respect to light from the active layer 30 is preferably used. As the metal layer, for example, a Rh layer or a Ru layer is preferably used. The p-electrode 70 may be, for example, a multilayer structure including a Rh layer, an Au layer, a Ni layer, and a Ti layer, or a multilayer structure including a Ru layer, an Au layer, a Ni layer, and a Ti layer.
When a forward voltage is applied between the n-electrode 60 and the p-electrode 70, a forward voltage is applied between the p-side layer 50 and the n-side layer 20, and holes and electrons are supplied to the active layer 30, whereby the active layer 30 emits light.
In the present embodiment, as shown in fig. 2, the second layer 52 is in contact with the side surfaces of the two well layers 31, but the present invention is not limited thereto. Fig. 3 is a schematic cross-sectional view showing a modification of the present embodiment. As shown in fig. 3, in the case where the active layer 30 includes a plurality of well layers 31, the second layer 52 may be at least contiguous with a side of the well layer 31 located closest to the p-side layer 50 among the plurality of well layers 31. As shown in fig. 3, the side surface of the well layer 31 on the n-side layer 20 side among the side surfaces of the plurality of well layers 31 is exposed from the second layer 52. The well layer 31 located closest to the p-side layer 50 among the plurality of well layers 31 easily emits light more strongly than the other well layers 31. Therefore, by disposing the second layer 52 in contact with at least the side surface of the well layer 31 located closest to the p-side layer 50 among the plurality of well layers 31, the above-described effect of improving the light extraction efficiency can be effectively obtained.
Next, a method for manufacturing a light-emitting element according to the present embodiment will be described with reference to fig. 4 to 10.
The method for manufacturing a light-emitting element according to the present embodiment includes: a process of forming an n-side layer 20 formed of a nitride semiconductor, a process of forming an active layer 30 on the n-side layer 20, a process of forming a p-side layer 50 on the active layer 30, a process of forming an n-electrode 60 electrically connected to the n-side layer 20, and a process of forming a p-electrode 70 electrically connected to the p-side layer 50. The step of forming the p-side layer 50 includes: a step of forming a first layer 51 on the active layer 30, a step of forming a second layer 52 on the first layer 51 and on the side surface of the well layer 31, and a step of forming a third layer 53 on the second layer 52.
First, as shown in fig. 4, for example, a process of forming a buffer layer 11 made of AlN on the c-plane of a substrate 10 made of sapphire is performed. The buffer layer 11 is formed by, for example, a Metal Organic Chemical Vapor Deposition (MOCVD) method or the like. The semiconductor layers described later may be formed by epitaxial growth by the MOCVD method, for example.
Next, as shown in fig. 5, a step of forming the superlattice layer 12 on the buffer layer 11 is performed. The superlattice layer 12 is formed by alternately growing a first semiconductor layer and a second semiconductor layer having a lattice constant different from that of the first semiconductor layer. The first semiconductor layer uses, for example, trimethylaluminum (TMA) gas, ammonia gas, and mainly hydrogen (H) gas as a carrier gas 2 ) To grow the AlN layer. The second semiconductor layer is formed by growing an AlGaN layer using TMA gas, trimethylgallium (TMG) gas, ammonia gas, and mainly hydrogen gas as a carrier gas, for example. The layers of the superlattice layer 12 may be formed at a temperature of 1000 ℃ or more and 1250 ℃ or less, for example.
Next, as shown in fig. 6, a step of forming an n-side layer 20 including a base layer 21 and an n-contact layer 22 on the superlattice layer 12 is performed. The underlayer 21 is formed by growing an AlGaN layer using TMA gas, TMG gas, ammonia gas, and mainly hydrogen gas as a carrier gas as raw material gases. The n-contact layer 22 uses TMA gas, TMG gas, ammonia gas, and monosilane (SiH) as n-type impurity gas as raw material gases 4 ) The gas and the carrier gas are mainly hydrogen gas, and are formed by growing an AlGaN layer containing n-type impurities. Each layer of the n-side layer 20 may be formed at a temperature of 1000 ℃ or more and 1250 ℃ or less, for example.
Next, as shown in fig. 7, a process of forming an active layer 30 including a well layer 31 and a barrier layer 32 on the n-side layer 20 is performed. The well layer 31 uses TMA by a source gas, for exampleThe AlGaN layer is grown mainly using nitrogen as a carrier gas, which is a gas, TMG gas, ammonia gas, or the like. The barrier layer 32 is formed by growing an AlGaN layer using TMA gas, TMG gas, ammonia gas, and mainly nitrogen gas as carrier gases, for example, as raw material gases. For example, by alternately growing the well layers 31 and the barrier layers 32, the active layer 30 including a plurality of well layers 31 and a plurality of barrier layers 32 is formed. In the step of forming the barrier layer 32, siH is used 4 The gas may contain n-type impurities as n-type impurity gas. Each layer of the active layer 30 may be formed at a temperature of, for example, 850 ℃ to 1050 ℃.
As shown in fig. 7, a hole including the side surfaces of the plurality of well layers 31 and the side surfaces of the plurality of barrier layers 32 is formed in the active layer 30 by the step of forming the active layer. In the step of forming the active layer 30, a carrier gas that does not substantially contain hydrogen is preferably used. Thus, the hole is hard to fill, and the active layer 30 is easily formed in a state where the side surface of the well layer 31 is exposed.
Next, as shown in fig. 8, a step of forming an electron blocking layer 40 on the active layer 30 is performed. The electron blocking layer 40 includes an AlN layer, a first AlGaN layer, and a second AlGaN layer. The AlN layer of the electron blocking layer 40 is formed by using TMA gas, ammonia gas, and mainly nitrogen gas as carrier gases, for example, as raw material gases. The first AlGaN layer of the electron blocking layer 40 is formed using TMA gas, TMG gas, ammonia gas, and mainly nitrogen gas as a carrier gas, for example, as a raw material gas. The second AlGaN layer of the electron blocking layer 40 is formed using TMA gas, TMG gas, ammonia gas, and mainly nitrogen gas as a carrier gas, for example, as a raw material gas. For example, in the step of forming the second AlGaN layer, the flow rate ratio of TMA gas, which is the source gas of Al, is set to be larger than the flow rate ratio of TMA gas in the step of forming the first AlGaN layer. Thus, the Al composition ratio of the second AlGaN layer is made higher than that of the first AlGaN layer. Each layer of the electron blocking layer 40 may be formed at a temperature of, for example, 750 ℃ to 950 ℃.
As shown in fig. 8, the electron blocking layer 40 is formed so as not to be formed in the hole portion of the active layer 30, and thus is formed on the active layer 30 in which the hole portion of the active layer 30 is not formed. In the step of forming the electron blocking layer 40, a carrier gas that does not substantially contain hydrogen is preferably used. Thus, the hole portion of the active layer 30 is hard to be buried, and the electron blocking layer 40 is easily formed in a state where the side surface of the well layer 31 is exposed from the electron blocking layer 40.
Next, as shown in fig. 9 and 10, a step of forming a p-side layer 50 on the electron blocking layer 40 is performed. The p-side layer 50 is formed by growing a fourth layer 54, a first layer 51, a second layer 52, and a third layer 53 in this order from the active layer 30 side. For example, TMA gas, TMG gas, ammonia gas, and cyclopentadienyl magnesium (Cp) as p-type impurity gas are used as raw material gases 2 Mg) gas to grow an AlGaN layer containing Mg as a p-type impurity, thereby forming a first layer 51, a second layer 52, a third layer 53, and a fourth layer 54, respectively. Each layer of the p-side layer 50 may be formed at a temperature of, for example, 750 ℃ to 950 ℃.
As shown in fig. 9, the fourth layer 54 is formed so as not to be formed in the hole portion of the active layer 30, and is thereby formed on the electron blocking layer 40 in which the hole portion of the active layer 30 is not formed. In the step of forming the fourth layer 54, a carrier gas that does not substantially contain hydrogen is preferably used. Thus, the hole portion of the active layer 30 is hard to fill, and the fourth layer 54 is easily formed in a state where the side surface of the well layer 31 is exposed from the electron blocking layer 40.
As shown in fig. 9, the first layer 51 is formed so as not to be formed in the hole portion of the active layer 30, and is thereby formed on the fourth layer 54 in which the hole portion of the active layer 30 is not formed. In the step of forming the first layer 51, as in the step of forming the fourth layer 54, a carrier gas that does not substantially contain hydrogen is preferably used. Thus, the hole portion of the active layer 30 is hard to fill, and the first layer 51 is easily formed in a state where the side surface of the well layer 31 is exposed from the fourth layer 54.
As shown in fig. 10, in the step of forming the second layer 52, the second layer 52 is formed in contact with the side surface of the well layer 31, and the V-shaped pit 33 is buried in the second layer 52. The growth rate when forming the second layer 52 is preferably slower than the growth rate when forming the first layer 51. For example, by making the flow rate ratio of the ammonia gas, which is the raw material gas when the second layer 52 is formed, lower than the flow rate ratio of the ammonia gas, which is the raw material gas when the first layer 51 is formed, the growth rate can be slowed down. Accordingly, the V-shaped pits 33 are easily buried in the second layer 52, and therefore the second layer 52 can be easily formed so as to be in contact with the side surface of the well layer 31. In addition, since the surface state of the upper surface of the second layer 52 on which the third layer 53 is formed can be made nearly flat, crystallinity of the third layer 53 can be improved.
The growth rate when forming the third layer 53 is preferably slower than that when forming the first layer 51. For example, by making the flow rate ratio of the ammonia gas, which is the raw material gas when the third layer 53 is formed, lower than the flow rate ratio of the ammonia gas, which is the raw material gas when the first layer 51 is formed, the growth rate can be slowed down. Thereby, the surface state of the upper surface of the third layer 53 can be made closer to a flat surface state than the upper surface of the second layer 52. As a result, the third layer 53 and the p-electrode 70 are easily electrically connected, and therefore the forward voltage Vf can be reduced.
The flow rate ratio of the p-type impurity gas in the step of forming the second layer 52 is preferably higher than the flow rate ratio of the p-type impurity gas in the step of forming the first layer 51. Thus, the V-shaped pits 33 are easily buried in the second layer 52, and therefore the second layer 52 can be easily formed so as to be in contact with the side surface of the well layer 31.
The flow rate ratio of the p-type impurity gas in the step of forming the third layer 53 is preferably higher than the flow rate ratio of the p-type impurity gas in the step of forming the first layer 51. Thereby, the surface state of the upper surface of the third layer 53 can be made closer to a flat surface state than the upper surface of the second layer 52.
After each semiconductor layer is grown and formed, heat treatment is performed in a reaction vessel in a nitrogen atmosphere, for example, at a temperature in the range of 400 ℃ or more to 550 ℃.
After the heat treatment, a part of the p-side layer 50, a part of the electron blocking layer 40, and a part of the active layer 30 are removed to expose a part of the n-contact layer 22.
Then, as shown in fig. 1, an n-electrode 60 is formed on the exposed n-contact layer 22, and a p-electrode 70 is formed on the third layer 53 of the p-side layer 50.
By performing the steps described above, the light-emitting element of the present embodiment can be manufactured.
Next, the light-emitting elements of the first and second embodiments and the light-emitting element of the reference example will be described.
< first embodiment >
As the substrate 10, a substrate formed of sapphire having a C-plane as a main surface is used. The buffer layer 11 formed of AlN was formed to a thickness of 2 μm on the substrate 10.
Next, the temperature was set to 1175℃and the raw material gases were TMA gas, TMG gas and ammonia gas, and Al was deposited on the buffer layer 11 0.60 Ga 0.40 The N layer is formed to a thickness of about 21 nm. Next, the temperature was set to 1175℃and TMA gas and ammonia gas were used as raw material gases to form an AlN layer to a thickness of about 10 nm. The superlattice layer 12 is formed by forming 30 pairs of the laminated body of the AlGaN layer and the AlN layer thus formed.
Next, the temperature was set to 1175 ℃, and TMA gas, TMG gas, and ammonia gas were used as raw material gases to deposit Al on the superlattice layer 12 0.60 Ga 0.40 The N layer is formed to a thickness of about 0.5 μm, thereby forming the base layer 21. Next, the temperature was set to 1175℃and TMA gas, TMG gas, ammonia gas and SiH gas were used as the raw material gas 4 A gas containing Al having n-type impurities 0.60 Ga 0.40 The N layer is formed to a thickness of about 2.2 μm, thereby forming the N contact layer 22. An n-side layer 20 including the base layer 21 and the n-contact layer 22 is formed. In addition, the n-type impurity concentration of the n-contact layer 22 is about 9.5X10 18 /cm 3 。
Next, the temperature was set to 950℃and TMA gas, TMG gas, ammonia gas and SiH gas were used as the raw material gas 4 A gas for forming Al containing n-type impurities on the n-side layer 20 0.52 Ga 0.48 The N layer is formed to a thickness of about 50nm, thereby forming the barrier layer 32. Next, the temperature was set to 950℃and TMA gas, TMG gas and ammonia gas were used as raw material gases to prepare Al 0.42 Ga 0.58 The N layer is formed to a thickness of about 4.4nm, thereby forming the well layer 31. Next, the temperature was set to 950℃and TMA gas, TMG gas, ammonia gas and SiH gas were used as the raw material gas 4 A gas containing Al having n-type impurities 0.52 Ga 0.48 The N layer is formed to a thickness of about 2.5nm, thereby forming the barrier layer 32. Next, the temperature is raisedThe temperature is 950 ℃, TMA gas, TMG gas and ammonia gas are used as raw material gas, al is added 0.42 Ga 0.58 The N layer is formed to a thickness of about 4.4nm, thereby forming the well layer 31. An active layer 30 including the two well layers 31 and the two barrier layers 32 is formed.
Next, the temperature was set to 870 ℃, and TMA gas and ammonia gas were used as raw material gases to form an AlN layer on the active layer 30 to a thickness of about 1 nm. Next, the temperature was set to 870℃and TMA gas, TMG gas and ammonia gas were used as raw material gases to convert Al 0.55 Ga 0.45 The N layer is formed to a thickness of about 1nm, thereby forming a first AlGaN layer. Next, the temperature was set to 870℃and TMA gas, TMG gas and ammonia gas were used as raw material gases to convert Al 0.78 Ga 0.22 N is formed to a thickness of about 4nm, thereby forming a second AlGaN layer. An electron blocking layer 40 including the above AlN layer and two AlGaN layers is formed.
Next, the temperature was set to 870℃and TMA gas, TMG gas, ammonia gas and Cp were used as the raw material gas 2 Mg gas, al containing p-type impurities on the electron blocking layer 40 0.63 Ga 0.37 The N layer is formed to a thickness of about 78nm, thereby forming the fourth layer 54. Next, the temperature was set to 870℃and TMA gas, TMG gas, ammonia gas and Cp were used as the raw material gas 2 Mg gas to be P-type impurity-containing Al 0.53 Ga 0.47 The N layer is formed to a thickness of about 30nm, thereby forming the first layer 51. Next, the temperature was set to 900℃and TMA gas, TMG gas, ammonia gas and Cp were used as the raw material gas 2 Mg gas to be P-type impurity-containing Al 0.40 Ga 0.60 The N layer is formed to a thickness of about 10nm, thereby forming the second layer 52. Next, the temperature was set to 900 ℃, and TMA gas, TMG gas, and ammonia gas were used as raw material gases to form a GaN layer containing p-type impurities to a thickness of about 10nm, thereby forming the third layer 53. A p-side layer 50 including the above-described first layer 51, second layer 52, third layer 53, and fourth layer 54 is formed. The flow ratio of ammonia in the raw material gas at the time of forming the second layer 52 and the third layer 53 is made lower than the flow ratio of ammonia in the raw material gas at the time of forming the first layer 51. In addition, cp in the source gas is set to be the same when the second layer 52 and the third layer 53 are formed 2 Flow ratio of Mg gas to Cp in the raw material gas for the formation of the first layer 51 2 The flow rate of Mg gas is high.
After each semiconductor layer is formed, each semiconductor layer is heat-treated in a reaction vessel. The heat treatment was performed in a nitrogen atmosphere at a temperature of about 475 ℃.
After the heat treatment, a part of the p-side layer 50 and a part of the active layer 30 are removed, and a part of the n-side contact layer 22 is exposed from the p-side layer 50 and the active layer 30.
Next, an n-electrode 60 is formed on the n-contact layer 22, and a p-electrode 70 is formed on the third layer 53 of the p-side layer 50. The n-electrode 60 has a multilayer structure in which a Ti layer, alSi layer, ta layer, ru layer, and Ti layer are laminated in this order from the n-contact layer 22 side. The p-electrode 70 has a multilayer structure in which a Ti layer, a Ru layer, and a Ti layer are laminated in this order from the third layer 53 side.
Thereafter, the substrate 10 is singulated into a plurality of light emitting elements. The substrate 10 of the singulated light emitting element has a square shape with a side length of 1000 μm in plan view. The thickness of the substrate 10 of the light-emitting element was 700. Mu.m.
The forward voltage Vf of the light-emitting element of the first embodiment manufactured as described above was 5.86V, and the output Po was 182mW. In the first, second and reference examples, the forward voltage Vf and the output Po are values when a current of 350mA is applied.
< second embodiment >
The light-emitting element of the second embodiment is fabricated in the same manner as the first embodiment, except that the structure of the first layer 51 is different.
In the light-emitting element of the second embodiment, the light-emitting element is composed of Al containing p-type impurities and having a thickness of about 27nm 0.53 Ga 0.47 The N layer, and the compositionally tilted layer containing p-type impurities and having a thickness of about 3nm form the first layer 51. The composition inclined layer is formed so as to be located on the second layer 52 side among the first layers 51. The composition gradient layer is formed by decreasing the flow rate ratio of TMA gas and decreasing the Al composition ratio from the active layer 30 side to the second layer 52 side. The composition gradient layer is formed so that the Al composition ratio is from the active layer 30 side to the second layer 52 sideAbout 53% to 0%.
The forward voltage Vf of the light-emitting element of the second embodiment manufactured as described above was 5.13V, and the output Po was 161mW.
Reference example
The light-emitting element of the reference example was fabricated in the same manner as in the first embodiment, except that a part of the structure of the p-side layer 50 and a part of the structure of the p-electrode 70 were different.
In the light-emitting element of the reference example, TMG gas, ammonia gas, and Cp were used as the raw material gas at 870 ℃ 2 The Mg gas forms the second layer 52 from a GaN layer containing p-type impurities and having a thickness of about 350 nm. The temperature was set to 870℃and TMG gas, ammonia gas and Cp were used as the raw material gas 2 The Mg gas forms the third layer 53 from a GaN layer containing p-type impurities and having a thickness of about 20 nm. The p-electrode 70 has a multilayer structure in which a Ti layer, an Rh layer, and a Ti layer are laminated in this order from the third layer 53 side.
In the light-emitting element of the reference example fabricated as described above, the forward voltage Vf was 7.08V, and the output Po was 103mW.
As is clear from the above description, the light-emitting elements according to the first and second embodiments can form the output Po higher than that of the light-emitting element according to the reference example, and can reduce the forward voltage Vf. This is considered to be because light from the side surface of the well layer 31 is easily extracted by embedding the V-shaped pits 33 in the second layer 52. The light emitting element of the second embodiment has an output Po lower than that of the light emitting element of the first embodiment by 21mW, but has a forward voltage Vf lower than 0.73V. This is considered to be that, although the forward voltage Vf can be reduced by making a part of the first layer 51 a composition inclined layer with a reduced Al composition ratio, the output Po decreases because the part of the first layer 51 with a relatively low Al composition increases and the first layer 51 absorbs light.
The embodiments of the present invention are described above with reference to specific examples. However, the present invention is not limited to the specific examples described above. All modes which can be implemented by appropriately changing the design of the present invention based on the above-described embodiments of the present invention are within the scope of the present invention as long as they include the gist of the present invention. In addition, various modifications and modifications are conceivable to those skilled in the art within the scope of the present invention, and the modifications and modifications are also within the scope of the present invention.
The present embodiment includes the following modes.
Additional note 1
A light emitting element comprising:
a semiconductor structure including an n-side layer, a p-side layer, and an active layer which is formed of nitride semiconductor, is located between the n-side layer and the p-side layer, and emits ultraviolet light;
an n-electrode electrically connected to the n-side layer;
a p-electrode electrically connected to the p-side layer;
the active layer has: an Al-containing well layer, an Al-containing barrier layer, and a hole portion including a side surface of the well layer and a side surface of the barrier layer,
the p-side layer has: a first layer containing Al, a second layer containing Al and disposed on the first layer and in contact with the side surface of the well layer, and a third layer disposed on the second layer,
the thickness of the third layer is thinner than the thickness of the first layer,
the difference between the Al composition ratio of the second layer and the Al composition ratio of the well layer is 10% or less,
the third layer is a layer having a lower Al composition ratio than that of the second layer, or a layer containing no Al,
the p-electrode is disposed on the third layer.
Additional note 2
The light-emitting element as described in supplementary note 1,
the thickness of the third layer is equal to or less than the thickness of the second layer.
Additional note 3
The light-emitting element described in supplementary note 1 or 2,
the first layer, the second layer, and the third layer contain p-type impurities,
the second layer has a p-type impurity concentration higher than the first layer.
Additional note 4
The light-emitting element according to the annex 3,
the third layer has a p-type impurity concentration higher than that of the second layer.
Additional note 5
The light-emitting element described in supplementary notes 3 or 4,
the second layer has a p-type impurity concentration of 1×10 19 /cm 3 Above, 1×10 21 /cm 3 The following is given.
Additional note 6
The light-emitting element according to any one of supplementary notes 1 to 5,
the Al composition ratio of the first layer is higher than the Al composition ratio of the second layer.
Additional note 7
The light-emitting element according to any one of supplementary notes 1 to 6,
the Al composition ratio of the second layer is higher than that of the well layer.
Additional note 8
The light-emitting element according to any one of supplementary notes 1 to 7,
the Al composition ratio of the well layer is more than 10%.
Additional note 9
The light-emitting element according to any one of supplementary notes 1 to 8,
the thickness of the second layer is 3nm to 20 nm.
Additional note 10
The light-emitting element according to any one of supplementary notes 1 to 9,
the first layer and the second layer are formed of aluminum gallium nitride,
The third layer is formed of gallium nitride.
Additional note 11
A method of manufacturing a light emitting element, comprising:
forming an n-side layer formed of a nitride semiconductor;
forming an active layer that emits ultraviolet light on the n-side layer, the active layer including a well layer containing Al, a barrier layer containing Al, and a hole portion including a side surface of the well layer and a side surface of the barrier layer, each formed of a nitride semiconductor;
a step of forming a p-side layer on the active layer, wherein the p-side layer includes a first layer containing Al, a second layer containing Al and having a difference of 10% or less from the Al composition ratio of the well layer, and a layer having a smaller thickness than the first layer and a lower Al composition ratio than the second layer, or a third layer containing no Al, each formed of a nitride semiconductor;
forming an n-electrode electrically connected to the n-side layer;
forming a p-electrode electrically connected to the third layer of the p-side layer;
the step of forming the p-side layer includes:
forming the first layer on the active layer;
forming the second layer on the first layer and in contact with the side surface of the well layer;
And forming the third layer on the second layer.
Additional note 12
The method for manufacturing a light-emitting element according to supplementary note 11,
the growth rate when the second layer is formed is slower than the growth rate when the first layer is formed.
Supplementary note 13
The method for manufacturing a light-emitting element according to any one of supplementary notes 11 or 12,
the growth rate when the third layer is formed is slower than the growth rate when the first layer is formed.
Additional note 14
The method for manufacturing a light-emitting element according to any one of supplementary notes 11 to 13,
in the step of forming the first layer, the first layer containing p-type impurities is formed using a p-type impurity gas,
in the step of forming the second layer, the second layer containing p-type impurities is formed using p-type impurity gas,
the flow rate ratio of the p-type impurity gas in the step of forming the second layer is higher than the flow rate ratio of the p-type impurity gas in the step of forming the first layer.
Additional note 15
The method for manufacturing a light-emitting element according to any one of supplementary notes 11 to 14,
in the step of forming the first layer, the first layer containing p-type impurities is formed using a p-type impurity gas,
in the step of forming the third layer, the third layer containing p-type impurities is formed using p-type impurity gas,
The flow rate ratio of the p-type impurity gas in the step of forming the third layer is higher than the flow rate ratio of the p-type impurity gas in the step of forming the first layer.
Description of the reference numerals
1 a light emitting element; 10 a substrate; 11 a buffer layer; 12 superlattice layers; a 20n side layer; a base layer 21; a 22n contact layer; 30 active layer; 31 well layers; a 32 barrier layer; 33V-shaped pits; 40 electron blocking layer; a 50p side layer; 51 a first layer; 52 a second layer; 53 a third layer; 54 a fourth layer; a 60n electrode; a 70p electrode; 100 semiconductor structure.
Claims (15)
1. A light-emitting element, comprising:
a semiconductor structure including an n-side layer, a p-side layer, and an active layer which is formed of nitride semiconductor, is located between the n-side layer and the p-side layer, and emits ultraviolet light;
an n-electrode electrically connected to the n-side layer;
a p-electrode electrically connected to the p-side layer;
the active layer has: an Al-containing well layer, an Al-containing barrier layer, and a hole portion including a side surface of the well layer and a side surface of the barrier layer,
the p-side layer has: a first layer containing Al, a second layer containing Al and disposed on the first layer and in contact with the side surface of the well layer, and a third layer disposed on the second layer,
The thickness of the third layer is thinner than the thickness of the first layer,
the difference between the Al composition ratio of the second layer and the Al composition ratio of the well layer is 10% or less,
the third layer is a layer having a lower Al composition ratio than that of the second layer, or a layer containing no Al,
the p-electrode is disposed on the third layer.
2. A light-emitting element according to claim 1, wherein,
the thickness of the third layer is equal to or less than the thickness of the second layer.
3. A light-emitting element according to claim 1, wherein,
the first layer, the second layer, and the third layer contain p-type impurities,
the second layer has a p-type impurity concentration higher than the first layer.
4. A light-emitting element according to claim 3, wherein,
the third layer has a p-type impurity concentration higher than that of the second layer.
5. A light-emitting element according to claim 3, wherein,
the second layer has a p-type impurity concentration of 1×10 19 /cm 3 Above, 1×10 21 /cm 3 The following is given.
6. A light-emitting element according to any one of claim 1 to 5,
the Al composition ratio of the first layer is higher than the Al composition ratio of the second layer.
7. A light-emitting element according to any one of claim 1 to 5,
the Al composition ratio of the second layer is higher than that of the well layer.
8. A light-emitting element according to any one of claim 1 to 5,
the Al composition ratio of the well layer is more than 10%.
9. A light-emitting element according to any one of claim 1 to 5,
the thickness of the second layer is 3nm to 20 nm.
10. A light-emitting element according to any one of claim 1 to 5,
the first layer and the second layer are formed of aluminum gallium nitride,
the third layer is formed of gallium nitride.
11. A method for manufacturing a light-emitting element, comprising:
forming an n-side layer formed of a nitride semiconductor;
forming an active layer that emits ultraviolet light on the n-side layer, the active layer including a well layer containing Al, a barrier layer containing Al, and a hole portion including a side surface of the well layer and a side surface of the barrier layer, each formed of a nitride semiconductor;
a step of forming a p-side layer on the active layer, wherein the p-side layer includes a first layer containing Al, a second layer containing Al and having a difference between the Al composition ratio and the Al composition ratio of the well layer of 10% or less, and a layer having a smaller thickness than the first layer and a lower Al composition ratio than the second layer, or a third layer containing no Al, each formed of a nitride semiconductor;
Forming an n-electrode electrically connected to the n-side layer;
forming a p-electrode electrically connected to the third layer of the p-side layer;
the step of forming the p-side layer includes:
forming the first layer on the active layer;
forming the second layer on the first layer and in contact with the side surface of the well layer;
and forming the third layer on the second layer.
12. The method for manufacturing a light-emitting element according to claim 11, wherein,
the growth rate when the second layer is formed is slower than the growth rate when the first layer is formed.
13. The method for manufacturing a light-emitting element according to claim 12, wherein,
the growth rate when the third layer is formed is slower than the growth rate when the first layer is formed.
14. The method for manufacturing a light-emitting element according to any one of claims 11 to 13, wherein,
in the step of forming the first layer, the first layer containing p-type impurities is formed using a p-type impurity gas,
in the step of forming the second layer, the second layer containing p-type impurities is formed using p-type impurity gas,
the flow rate ratio of the p-type impurity gas in the step of forming the second layer is higher than the flow rate ratio of the p-type impurity gas in the step of forming the first layer.
15. The method for manufacturing a light-emitting element according to any one of claims 11 to 13, wherein,
in the step of forming the first layer, the first layer containing p-type impurities is formed using a p-type impurity gas,
in the step of forming the third layer, the third layer containing p-type impurities is formed using p-type impurity gas,
the flow rate ratio of the p-type impurity gas in the step of forming the third layer is higher than the flow rate ratio of the p-type impurity gas in the step of forming the first layer.
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| Application Number | Priority Date | Filing Date | Title |
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| JP2022-006580 | 2022-01-19 | ||
| JP2022147283A JP2023105782A (en) | 2022-01-19 | 2022-09-15 | Light-emitting device and method for manufacturing light-emitting device |
| JP2022-147283 | 2022-09-15 |
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| CN116469974A true CN116469974A (en) | 2023-07-21 |
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