Light-emitting element and method for manufacturing a light-emitting element

Abstract

To provide a light-emitting device having a high light extraction efficiency, and a manufacturing method thereof.SOLUTION: A light-emitting device comprises: a semiconductor structure body including n-side and p-side layers each composed of a nitride semiconductor, and an active layer located between the n-side and p-side layers and emitting ultraviolet light; an n-electrode electrically connected to the n-side layer; and a p-electrode electrically connected to the p-side layer. In the light-emitting device, the active layer has an Al-containing well layer, an Al-containing barrier layer, and a hole part including a side face of the well layer and a side face of the barrier layer. The p-side layer has an Al-containing first layer, a second layer containing Al, disposed on the first layer in contact with the side face of the well layer, and a third layer disposed on the second layer. The third layer is smaller than the first layer in thickness. The difference between the second layer and the well layer in Al composition ratio is equal to or smaller than 10%. The third layer is composed of a layer smaller than the second layer in Al composition ratio, otherwise an Al-free layer. The p-electrode is disposed on the third layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light-emitting element and a method for manufacturing a light-emitting element. [Background technology]

[0002] Patent Document 1 discloses a light-emitting element that has layers made of multiple nitride semiconductors and emits deep ultraviolet light. In such a light-emitting element, it is desirable to improve the light extraction efficiency. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-54122 [Overview of the project] [Problems that the invention aims to solve]

[0004] One embodiment of the present invention aims to provide a light-emitting element having high light extraction efficiency and a method for manufacturing a light-emitting element. [Means for solving the problem]

[0005] A light-emitting element according to one embodiment of the present invention includes a semiconductor structure comprising an n-side layer, a p-side layer, and an active layer located between the n-side layer and the p-side layer that emits ultraviolet light, each made of a nitride semiconductor. An n electrode electrically connected to the n-side layer and a p electrode electrically connected to the p-side layer, wherein the active layer has a well layer containing Al, a barrier layer containing Al, and a hole portion including side surfaces of the well layer and 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 smaller 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 an Al composition ratio lower than the Al composition ratio of the second layer or a layer not containing Al; and the p electrode is disposed on the third layer.

[0006] A method of manufacturing a light-emitting device according to an embodiment of the present invention includes: forming an n-side layer made of a nitride semiconductor; forming, on the n-side layer, an active layer that emits ultraviolet light and has a well layer containing Al, a barrier layer containing Al, and a hole portion including side surfaces of the well layer and the barrier layer, each made of a nitride semiconductor; forming, on the active layer, a p-side layer having a first layer containing Al, a second layer containing Al and having a difference in Al composition ratio from the well layer of 10% or less, and a third layer that is thinner than the first layer and has an Al composition ratio lower than the Al composition ratio of the second layer or does not contain Al, each made of a nitride semiconductor; 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 forming the first layer on the active layer, forming the second layer in contact with the first layer and the side surface of the well layer, and forming the third layer on the second layer.

Advantages of the Invention

[0007] According to an embodiment of the present invention, a light-emitting device having high light extraction efficiency and a method of manufacturing the light-emitting device can be provided.

Brief Description of the Drawings

[0008] [Figure 1] It is a schematic cross-sectional view showing the configuration of a light-emitting element according to an embodiment of the present invention. [Figure 2] It is a schematic cross-sectional view showing the configuration of a light-emitting element according to an embodiment of the present invention. [Figure 3] It is a schematic cross-sectional view showing the configuration of a light-emitting element according to a modified example of an embodiment of the present invention. [Figure 4] It is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention. [Figure 5] It is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention. [Figure 6] It is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention. [Figure 7] It is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention. [Figure 8] It is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention. [Figure 9] It is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention. [Figure 10] It is a schematic cross-sectional view for explaining a method of manufacturing a light-emitting element according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of a light-emitting element according to the present invention will be described. Note that the drawings referred to in the following description schematically show the present invention, so the scale, interval, positional relationship, etc. of each member may be exaggerated, or illustration of a part of the member may be omitted. Also, in the following description, the same names and reference numerals generally indicate the same or similar members, and detailed descriptions will be omitted as appropriate.

[0010] Figure 1 is a schematic cross-sectional view of the light-emitting element 1. Figure 2 is a schematic cross-sectional view showing an enlarged portion of the semiconductor structure 100. As shown in Figures 1 and 2, the light-emitting element 1 has 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 emits ultraviolet light and is located between the n-side layer 20 and the p-side layer 50, each made of a nitride semiconductor. The semiconductor structure 100 also includes a buffer layer 11 and a superlattice layer 12 located between the substrate 10 and the n-side layer 20, and an electron blocking layer 40 located 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.

[0011] The substrate 10 can be made of, for example, sapphire, silicon (Si), gallium nitride (GaN), aluminum nitride (AlN), etc. A substrate 10 made of sapphire is preferred because it has high light transmittance to ultraviolet light from the active layer 30. The semiconductor structure 100 can be placed, for example, on the c-plane of the sapphire substrate, and is preferably placed on a plane that is inclined from the c-plane of the sapphire substrate in the a-axis direction or m-axis direction of the sapphire substrate by a range of 0.2° to 2°. The thickness of the substrate 10 can be, for example, 150 μm to 800 μm. The light-emitting element 1 does not need to have a substrate 10.

[0012] The semiconductor structure 100 is a laminate in which multiple semiconductor layers made of nitride semiconductors are stacked. Nitride semiconductors are In x Al y Ga 1-x-y This includes semiconductors of all compositions obtained by varying the composition ratios x and y within the respective ranges in the chemical formula N (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, x + y ≤ 1).

[0013] For example, the buffer layer 11 can be made of AlN. The buffer layer 11 has the function of mitigating lattice mismatch between the substrate 10 and the nitride semiconductor layer placed on the buffer layer 11. The thickness of the buffer layer 11 can be, for example, 0.5 μm or more and 4 μm or less, and is preferably 1.5 μm or more and 4 μm or less. In this specification, the thickness of each semiconductor layer refers to the thickness in the stacking direction of the semiconductor structure 100.

[0014] The superlattice layer 12 has a multilayer structure in which a first semiconductor layer and a second semiconductor layer having a different lattice constant from the first semiconductor layer are alternately stacked. The superlattice layer 12 has the function of relieving stress generated in the semiconductor layer placed above the superlattice layer 12. The superlattice layer 12 can be a multilayer structure in which, for example, AlN layers and aluminum gallium nitride (AlGaN) layers are alternately stacked. In the superlattice layer 12, the number of pairs of the first semiconductor layer and the second semiconductor layer can be 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 can be 5 nm or more and 30 nm or less, and the thickness of the second semiconductor layer can be 5 nm or more and 30 nm or less.

[0015] The n-side layer 20 includes one or more n-type semiconductor layers. Examples of n-type semiconductor layers include semiconductor layers 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 also contain indium (In). For example, the n-type impurity concentration of an n-type semiconductor layer containing Si as an n-type impurity is 5 × 10⁻⁶. 18 / cm 3 The above 1 x 10 20 / cm 3The following applies. The n-side layer 20 only needs to have a function of supplying electrons and may include an undoped layer. Here, the undoped layer is a layer in which n-type impurities and p-type impurities are not intentionally doped. When the undoped layer is adjacent to a layer in which n-type impurities and / or p-type impurities are intentionally doped, the undoped layer may contain n-type impurities and / or p-type impurities due to diffusion from the adjacent layer or the like.

[0016] 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 disposed between the base layer 21 and the active layer 30.

[0017] For example, an undoped AlGaN layer can be used for the base layer 21. When the base layer 21 is an AlGaN layer, the Al composition ratio of the AlGaN layer can be, for example, 50% or more.

[0018] For example, a layer made of AlGaN containing n-type impurities can be used for the n-contact layer 22. When the n-contact layer is an AlGaN layer, the Al composition ratio of the AlGaN layer can be, for example, 50% or more. In this specification, for example, an AlGaN layer with an Al composition ratio of 50% means an AlGaN layer in which the composition ratio x is 0.5 in the chemical formula composed of Al X Ga 1-X N. The n-type impurity concentration of the n-contact layer 22 can be, for example, 5×10 18 / cm 3 or more and 1×10 20 / cm 3 or less. 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 can be, for example, 1.5 μm or more and 4 μm or less. The n-contact layer 22 has an upper surface on which no other semiconductor layer is disposed. An n-electrode 60 is disposed on the upper surface of the n-contact layer 22 on which no other semiconductor layer is disposed.

[0019] The active layer 30 is located between the n-side layer 20 and the p-side layer 50. The active layer 30 emits ultraviolet light. The emission peak wavelength of the ultraviolet light emitted by the active layer 30 is, for example, between 220 nm and 350 nm.

[0020] The active layer 30 includes an Al-containing well layer 31, an Al-containing barrier layer 32, and a pore portion including the side surface of the well layer 31 and the side surface of the barrier layer 32. The pore portion of the active layer 30 is, for example, a V-pit formed when the active layer 31 is formed. The pore portion of the active layer 30 may be, for example, a through hole penetrating the active layer 30, or a pore portion where a part of the barrier layer 32 forms the bottom. The active layer 30 has a multiple quantum well structure including, for example, a plurality of well layers 31 and a plurality of barrier layers 32. The Al composition ratio of the barrier layer 32 is greater than the Al composition ratio of the well layer 31. That is, the band gap energy of the barrier layer 32 is greater than the band gap energy of the well layer 31. Light with an emission wavelength corresponding to the band gap energy of the well layer 31 is emitted from the Al-containing well layer 31. Note that the active layer 30 is not limited to a multiple quantum well structure including a plurality of well layers 31, but may be a single quantum well structure. Furthermore, in Figure 2, the bottom layer of the active layer 30 is shown as the barrier layer 32, but the bottom layer of the active layer 30 may also be the well layer 31. Also, the top layer of the active layer 30 is shown as the well layer 31, but the top layer of the active layer 30 may also be the barrier layer 32.

[0021] For example, a layer made of AlGaN can be used for the well layer 31. For example, a layer made of AlGaN can be used for the barrier layer 32. The Al composition ratio of the well layer 31 can be, for example, 10% or more, more specifically 10% to 50%, and more specifically 30% to 50%. When the emission peak wavelength of light from the well layer 31 is about 280 nm, an AlGaN layer with an Al composition ratio of about 42% can be used for the well layer 31. The Al composition ratio of the barrier layer 32 can be, for example, 10% or more, more specifically 10% to 60%, and more specifically 30% to 60%.

[0022] The thickness of the well layer 31 can be, for example, 3 nm to 6 nm. The thickness of the barrier layer 32 can be, for example, 2 nm to 4 nm. From the viewpoint of increasing the volume of the semiconductor layer that contributes to light emission, it is preferable that the thickness of the well layer 31 be greater than the thickness of the barrier layer 32. The thickness of the well layer 31 can be 1.5 to 2 times the thickness of the barrier layer 32. At least a portion of the well layer 31 and the barrier layer 32 may contain n-type impurities and / or p-type impurities.

[0023] V-pits 33 are arranged continuously with the active layer 30, the electron blocking layer 40, and a portion of the p-side layer 50. In this embodiment, the V-pits 33 are defined by a surface including the side surface of the well layer 31, the side surface of the barrier layer 32, the side surface of the electron blocking layer 40, the side surface of the fourth layer 54, and the side surface of the first layer 51. The V-pits 33 are formed when the semiconductor structure 100 is grown, and recesses are formed on the surface of the semiconductor structure 100 corresponding to the portion where the V-pits 33 are formed. Multiple V-pits 33 are arranged in the semiconductor structure 100. In a top view, the shape of the V-pits 33 is, for example, circular, elliptical, or hexagonal. In a top view, the diameter of the V-pits 33 is, for example, 30 nm or more and 100 nm or less. A single V-pit 33 is, for example, a conical shape, elliptical cone shape, or polygonal pyramidal shape, with its diameter increasing from the n-side layer 20 towards the p-side layer 50. The V-pits 33 are formed, for example, when epitaxially growing a semiconductor structure 100 onto a substrate 10.

[0024] The electron blocking layer 40 is positioned to reduce electron overflow supplied from the n-side layer 20. The electron blocking layer 40 can be a multilayer structure having multiple semiconductor layers containing Al. For example, the electron blocking layer 40 can have a multilayer structure having, in order from the active layer 30 side, an AlN layer, a first AlGaN layer, and a second AlGaN layer. The Al composition ratio of the first AlGaN layer is lower than that of the second AlGaN layer and 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 reduces electron overflow. For example, the electron blocking layer 40 can use an undoped AlGaN layer, an undoped AlN layer, etc. The total thickness of the electron blocking layer 40 can be, for example, 5 nm or more and 15 nm or less.

[0025] Generally, to reduce the absorption of light from the well layer 31 by the semiconductor layer and improve light extraction efficiency, it is preferable to use a semiconductor layer with high light transmittance to light from the well layer 31 for the p-side layer 50. For example, by using an AlGaN layer with 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 less likely to be absorbed by the p-side layer 50. However, an AlGaN layer with a high Al composition ratio has a larger band gap energy compared to a GaN layer, etc. Therefore, when an AlGaN layer with a high Al composition ratio is used for the p-side layer 50, it is likely that the p-type formation of the p-side layer 50 will be insufficient, or the contact resistance between the p-electrode 70 and the p-side layer 50 will increase. For these reasons, it is difficult to achieve both high light extraction efficiency and a low forward voltage Vf in a light-emitting element that uses an AlGaN layer with a relatively high Al composition ratio as the well layer 31. In this embodiment, by having the following p-side layer 50, a light-emitting element 1 with high light extraction efficiency and a low forward voltage Vf can be obtained.

[0026] The p-side layer 50 includes one or more p-type semiconductor layers. Examples of p-type semiconductor layers include semiconductor layers containing p-type impurities such as magnesium (Mg). As shown in Figure 2, the p-side layer 50 has, in order from the active layer 30 side, a first layer 51, a second layer 52, and a third layer 53. The p-side layer 50 further has a fourth layer 54 disposed between the electron block 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 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.

[0027] 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 by the second layer 52, while allowing light from the side of the well layer 31 located in the V-pit 33 to propagate through the second layer 52, which is positioned in contact with the side of the well layer 31, and to be easily extracted to the p-side layer 50. As a result, a light-emitting element 1 with high light extraction efficiency can be obtained. The thickness of the third layer 53 is thinner than the thickness of the first layer 51. Furthermore, the third layer 53 is a layer with an Al composition ratio lower than that of the second layer 52, or a layer that does not contain Al. The p electrode 70 is placed on the third layer 53. This reduces light absorption by the third layer 53 while also reducing the contact resistance between the p electrode 70 and the third layer 53. As a result, the forward voltage Vf can be lowered while reducing the deterioration of light extraction efficiency. As described above, according to this embodiment, a light-emitting element 1 with high light extraction efficiency can be obtained. Furthermore, the forward voltage Vf can be lowered.

[0028] The second layer 52 is arranged continuously with respect to the top surface of the first layer 51, the side surface of the fourth layer 54, the side surface of the electron block layer 40, the side surface of the well layer 31, and the side surface of the barrier layer 32. The side surfaces of each semiconductor layer located in the V-pit 33 are covered by the second layer 52, and recesses corresponding to the shape of the V-pit 33 are formed on the surface of the second layer 52. In order to make the surface state of the third layer 53, which is arranged on the second layer 52, as flat as possible, it is preferable that the depth of the recesses formed on the surface of the second layer 52 is smaller than the depth of the V-pit 33 in a cross-sectional view. In this embodiment, as shown in Figure 2, the entire top surface of the second layer 52 is covered by the third layer 53, but this is not limited to this. For example, a part of the top surface of the second layer 52 may be exposed from the third layer 53 to the extent that the contact resistance between the p electrode 70 and the third layer 53 does not deteriorate.

[0029] The thickness of the third layer 53 is preferably less than or equal to the thickness of the second layer 52. For example, the thickness of the third layer 53 located above the first layer 51 is preferably less than or equal to the thickness of the second layer 52. This reduces light absorption by the third layer 53. The thickness of the second layer 52 is preferably thinner than the thickness of the first layer 51. This reduces light absorption by the second layer 52.

[0030] The thickness of the first layer 51 can be, for example, 20 nm to 40 nm. The thickness of the second layer 52 is preferably, for example, 3 nm to 20 nm, and more preferably, 3 nm to 15 nm. By making the thickness of the second layer 52 3 nm or more, it is possible to easily embed the V-pit 33. By making the thickness of the second layer 52 20 nm or less, it is possible to reduce light absorption by the second layer 52. The thickness of the third layer 53 is preferably, for example, 3 nm to 20 nm, and more preferably, 3 nm to 15 nm. By making the thickness of the third layer 53 3 nm or more, it is possible to easily obtain the effect of reducing the contact resistance between the p electrode 70 and the third layer 53. By making the thickness of the third layer 53 20 nm or less, it is possible to reduce light absorption by the third layer 53.

[0031] The first layer 51, the second layer 52, and the third layer 53 contain p-type impurities. Preferably, the p-type impurity concentrations in the second layer 52 and the third layer 53 are higher than those in the first layer 51. By increasing the p-type impurity concentration around the third layer 53 where the p-electrode 70 is located, it is possible to facilitate the supply of holes from the p-side layer 50 to the active layer 30, thereby improving the luminescence efficiency of the light-emitting element 1.

[0032] The p-type impurity concentration in the third layer 53 is preferably higher than that of the second layer 52. By increasing the p-type impurity concentration in the third layer 53 where the p-electrode 70 is located, it is easier to supply holes from the p-side layer 50 to the active layer 30, thereby increasing the luminescence efficiency of the light-emitting element 1. The p-type impurity concentration in the third layer 53 is higher than that of the fourth layer 54.

[0033] The p-type impurity concentrations in the first layer 51, the second layer 52, the third layer 53, and the fourth layer 54 are, for example, 1 × 10⁻⁶ 19 / cm 3 The above 1 x 10 21 / cm 3 The following applies:

[0034] 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, which is located closer to the active layer 30 than the second layer 52, higher than that of the second layer 52, light absorption by the first layer 51 can be reduced, thereby improving the light extraction efficiency.

[0035] The first layer 51 may be a composition gradient layer in which the Al composition ratio decreases from the active layer 30 side to the second layer 52 side. This reduces the forward voltage Vf compared to the case where the first layer 51 is a semiconductor layer with a constant Al composition ratio, by reducing the portion of the first layer 51 with a high Al composition ratio. For example, the difference between the Al composition ratio of the portion of the first layer 51 located on the active layer 30 side and the Al composition ratio of the portion of the first layer 51 located on the second layer 52 side can be 20% to 60%. Specifically, the Al composition ratio of the portion of the composition gradient layer located on the active layer 30 side can be 40% to 70%, and the Al composition ratio of the portion of the composition gradient layer located on the second layer 52 side can be 0% to 20%. Alternatively, a portion of the first layer 51 may be a composition gradient layer with a reduced Al composition ratio. This reduces the portion with a low Al composition ratio compared to the case where the entire first layer 51 is a composition gradient layer, thereby reducing light absorption by the first layer 51. For example, only the portion of the first layer 51 located on the side of the second layer 52 can be made into a compositionally graded layer. The portion of the first layer 51 that is made into a compositionally graded layer can be, for example, 3% to 20% of the thickness of the first layer 51. The portion of the first layer 51 that is made into a compositionally graded layer can be, for example, 1 nm to 30 nm.

[0036] The Al composition ratio of the second layer 52 is preferably higher than that of the well layer 31. This further reduces light absorption by the second layer 52, allowing light from the side of the well layer 31 to propagate more easily through the second layer 52, thereby improving the light extraction efficiency.

[0037] The Al composition ratio of the first layer 51 is preferably, for example, 50% to 70%, and more preferably 50% to 60%. The Al composition ratio of the second layer 52 is preferably, for example, 30% to 60%, more preferably 35% to 55%, and even more preferably 40% to 55%. By setting the Al composition ratio of the second layer 52 to 30% or more, light absorption by 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 by the second layer 52 can be reduced, and the deterioration of the forward voltage Vf can be reduced. The Al composition ratio of the third layer 53 is preferably, for example, 3% or less. This promotes p-type formation in the third layer 53 and improves luminescence efficiency.

[0038] The first layer 51 is made of, for example, aluminum gallium nitride. The second layer 52 is made of, for example, aluminum gallium nitride. The third layer 53 is made of, for example, gallium nitride or aluminum gallium nitride. The fourth layer 54 is made of, for example, aluminum gallium nitride. The first layer 51, the second layer 52, the third layer 53, and the fourth layer 54 may also contain in.

[0039] The thickness of the fourth layer 54 is greater than the thickness of the third layer 53. The thickness of the fourth layer 54 can be, for example, 60 nm to 100 nm. The Al composition ratio of the fourth layer 54 is high, as is the Al composition ratio of the first layer 51, and lower than the Al composition ratio of the semiconductor layer (second AlGaN layer) of the electron blocking layer 40 that is in contact with the fourth layer 54. This makes it easier to supply holes from the p electrode 70 side to the active layer 30. The Al composition ratio of the fourth layer 54 is preferably, for example, 50% to 70%, and more preferably 60% to 70%.

[0040] The n electrode 60 is placed on the n contact layer 22 and electrically connected to the n side layer 20. The p electrode 70 is placed on the third layer 53 of the p side layer 50 and electrically connected to the p side layer 50.

[0041] For example, the n electrode 60 can be made of metals such as Ag, Al, Ni, Au, Rh, Ti, Pt, Mo, Ta, W, Ru, or alloys mainly composed of these metals. The n electrode 60 can have a multilayer structure, for example, containing a Ti layer, an Al alloy layer, a Ta layer, and a Ru layer in that order from the n contact layer 22 side.

[0042] For example, the same metal as the n electrode 60 described above can be used for the p electrode 70. If the p electrode 70 has the function of reflecting light directed from the active layer 30 toward the p electrode 70 toward the n side layer 20, it is preferable that the metal layer of the p electrode 70 that is in contact with the third layer 53 is a metal layer that has a high reflectivity to light from the active layer 30. For example, it is preferable to use a metal layer that has a reflectivity of 70% or more, preferably 80% or more, toward light from the active layer 30. For example, it is preferable to use an Rh layer or a Ru layer as such a metal layer. The p electrode 70 can be a multilayer structure including, for example, an 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.

[0043] 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, supplying holes and electrons to the active layer 30, causing the active layer 30 to emit light.

[0044] In this embodiment, as shown in Figure 2, the second layer 52 is in contact with the sides of the two well layers 31, but is not limited to this. Figure 3 is a schematic cross-sectional view showing a modified example of this embodiment. As shown in Figure 3, when the active layer 30 includes a plurality of well layers 31, the second layer 52 only needs to be in contact with at least the side of the well layer 31 that is closest to the p-side layer 50 among the plurality of well layers 31. As shown in Figure 3, the side of the well layer 31 located on the n-side layer 20 side among the plurality of well layers 31 is exposed from the second layer 52. The well layer 31 that is closest to the p-side layer 50 among the plurality of well layers 31 tends to emit light more strongly than the other well layers 31. Therefore, by arranging the second layer 52 in contact with at least the side of the well layer 31 that is closest to the p-side layer 50 among the plurality of well layers 31, the effect of improving the light extraction efficiency described above can be efficiently obtained.

[0045] The method for manufacturing a light-emitting element according to this embodiment will be described below with reference to Figures 4 to 10.

[0046] The method for manufacturing a light-emitting element of this embodiment includes the steps of: forming an n-side layer 20 made of a nitride semiconductor; forming an active layer 30 on the n-side layer 20; forming a p-side layer 50 on the active layer 30; forming an n-electrode 60 electrically connected to the n-side layer 20; and forming a p-electrode 70 electrically connected to the p-side layer 50. The step of forming the p-side layer 50 includes the steps of: forming a first layer 51 on the active layer 30; forming a second layer 52 so as to be in contact with the first layer 51 and the side surface of the well layer 31; and forming a third layer 53 on the second layer 52.

[0047] First, as shown in Figure 4, a buffer layer 11 made of AlN is formed on the c-plane of a substrate 10 made of sapphire. The buffer layer 11 is formed by, for example, metal-organic vapor deposition (MOCVD). The semiconductor layers described later can be formed by, for example, epitaxial growth by the MOCVD method.

[0048] Next, as shown in Figure 5, a step is performed to form a superlattice layer 12 on the buffer layer 11. The superlattice layer 12 is formed by alternately growing a first semiconductor layer and a second semiconductor layer having a different lattice constant from the first semiconductor layer. The first semiconductor layer is formed, for example, by growing an AlN layer using trimethylaluminum (TMA) gas and ammonia gas as source gases and mainly hydrogen (H2) gas as the carrier gas. The second semiconductor layer is formed, for example, by growing an AlGaN layer using TMA gas, trimethylgallium (TMG) gas and ammonia gas as source gases and mainly hydrogen gas as the carrier gas. Each layer of the superlattice layer 12 can be formed, for example, at a temperature of 1000°C to 1250°C.

[0049] Next, as shown in Figure 6, a step is performed to form an n-side layer 20 on the superlattice layer 12, which includes a base layer 21 and an n-contact layer 22. The base layer 21 is formed, for example, by growing an AlGaN layer using TMA gas, TMG gas, and ammonia gas as the raw material gas and mainly hydrogen gas as the carrier gas. The n-contact layer 22 is formed, for example, by growing an AlGaN layer containing n-type impurities using TMA gas, TMG gas, and ammonia gas as the raw material gas, monosilane (SiH4) gas as the n-type impurity gas and mainly hydrogen gas as the carrier gas. Each layer of the n-side layer 20 can be formed, for example, at a temperature of 1000°C to 1250°C.

[0050] Next, as shown in Figure 7, a step is performed to form an active layer 30 on the n-side layer 20, which includes a well layer 31 and a barrier layer 32. The well layer 31 is formed, for example, by growing an AlGaN layer using TMA gas, TMG gas, or ammonia gas as the raw material gas and mainly nitrogen gas as the carrier gas. The barrier layer 32 is formed, for example, by growing an AlGaN layer using TMA gas, TMG gas, or ammonia gas as the raw material gas and mainly nitrogen gas as the carrier gas. For example, by alternately growing the well layer 31 and the barrier layer 32, an active layer 30 including multiple well layers 31 and multiple barrier layers 32 is formed. In the step of forming the barrier layer 32, SiH4 gas may be used as the n-type impurity gas to include n-type impurities. Each layer of the active layer 30 can be formed, for example, at a temperature of 850°C to 1050°C.

[0051] As shown in Figure 7, the process of forming the active layer creates pores in the active layer 30 that include the sides of multiple well layers 31 and the sides of multiple barrier layers 32. In the process of forming the active layer 30, it is preferable to use a carrier gas that is substantially free of hydrogen gas. This makes it less likely for the pores to become clogged and makes it easier to form the active layer 30 with the sides of the well layers 31 exposed.

[0052] Next, as shown in Figure 8, a step is performed to form an electron blocking layer 40 on the active layer 30. The electron blocking layer 40 is formed to include an AlN layer, a first AlGaN layer, and a second AlGaN layer. The AlN layer of the electron blocking layer 40 is formed, for example, by using TMA gas and ammonia gas as the raw material gas and mainly nitrogen gas as the carrier gas. The first AlGaN layer of the electron blocking layer 40 is formed, for example, by using TMA gas, TMG gas, and ammonia gas as the raw material gas and mainly nitrogen gas as the carrier gas. The second AlGaN layer of the electron blocking layer 40 is formed, for example, by using TMA gas, TMG gas, and ammonia gas as the raw material gas and mainly nitrogen gas as the carrier gas. For example, in the step of forming the second AlGaN layer, the flow rate ratio of TMA gas, which is the raw material gas for Al, is made larger than the flow rate ratio of TMA gas in the step of forming the first AlGaN layer. As a result, the Al composition ratio of the second AlGaN layer is formed to be higher than the Al composition ratio of the first AlGaN layer. Each layer of the electron block layer 40 can be formed, for example, at a temperature of 750°C to 950°C.

[0053] As shown in Figure 8, the electron blocking layer 40 is formed so as not to form within the pores of the active layer 30, and is formed on the active layer 30 where no pores are formed. In the process of forming the electron blocking layer 40, it is preferable to use a carrier gas that is substantially free of hydrogen gas. This makes it less likely for the pores of the active layer 30 to be filled, and makes it easier to form the electron blocking layer 40 with the sides of the well layer 31 exposed from the electron blocking layer 40.

[0054] Next, as shown in Figures 9 and 10, a step is performed to form a p-side layer 50 on the electron block layer 40. The p-side layer 50 is formed by growing the fourth layer 54, the first layer 51, the second layer 52, and the third layer 53 in order from the active layer 30 side. The first layer 51, the second layer 52, the third layer 53, and the fourth layer 54 are formed, for example, by using TMA gas, TMG gas, or ammonia gas as the raw material gas, cyclopentadienylmagnesium (Cp2Mg) gas as the p-type impurity gas, and growing an AlGaN layer containing Mg as the p-type impurity. Each layer of the p-side layer 50 can be formed, for example, at a temperature of 750°C to 950°C.

[0055] As shown in Figure 9, the fourth layer 54 is formed so as not to form within the pores of the active layer 30, and is formed on the electron block layer 40 where the pores of the active layer 30 are not formed. In the process of forming the fourth layer 54, it is preferable to use a carrier gas that is substantially free of hydrogen gas. This makes it less likely for the pores of the active layer 30 to be filled, and makes it easier to form the fourth layer 54 with the sides of the well layer 31 exposed from the electron block layer 40.

[0056] As shown in Figure 9, the first layer 51 is formed so as not to form within the pores of the active layer 30, and is formed on the fourth layer 54 where the pores of the active layer 30 are not formed. In the process of forming the fourth layer 54, it is preferable to use a carrier gas that is substantially free of hydrogen gas, similar to the process of forming the fourth layer 54. This makes it less likely for the pores of the active layer 30 to be filled, and makes it easier to form the fourth layer 54 with the sides of the well layer 31 exposed from the fourth layer 54.

[0057] As shown in Figure 10, in the process of forming the second layer 52, the second layer 52 is formed so as to be in contact with the side surface of the well layer 31, and the V-pit 33 is filled by the second layer 52. It is preferable that the growth rate when forming the second layer 52 be slower than the growth rate when forming the first layer 51. For example, the growth rate can be slowed by lowering the flow rate ratio of the ammonia gas, which is the raw material gas when forming the second layer 52, compared to the flow rate ratio of the ammonia gas, which is the raw material gas when forming the first layer 51. This makes it easier for the V-pit 33 to be filled by the second layer 52, thus making it easier to form the second layer 52 so as to be in contact with the side surface of the well layer 31. In addition, the surface condition of the upper surface of the second layer 52 on which the third layer 53 is formed can be made closer to flat, thereby improving the crystallinity of the third layer 53.

[0058] It is preferable that the growth rate when forming the third layer 53 be slower than the growth rate when forming the first layer 51. For example, the growth rate can be slowed by lowering the flow rate ratio of the ammonia gas used as the raw material when forming the third layer 53 compared to the flow rate ratio of the ammonia gas used as the raw material when forming the first layer 51. This makes it possible to make the surface state of the upper surface of the third layer 53 flatter than the surface state of the upper surface of the second layer 52. As a result, the third layer 53 and the p electrode 70 are more easily electrically connected, and the forward voltage Vf can be reduced.

[0059] The flow rate ratio of the p-type impurity gas in the process of forming the second layer 52 is preferably higher than the flow rate ratio of the p-type impurity gas in the process of forming the first layer 51. This makes it easier for the V-pit 33 to be filled by the second layer 52, and thus makes it easier to form the second layer 52 in contact with the side surface of the well layer 31.

[0060] In the process of forming the third layer 53, the flow rate ratio of the p-type impurity gas is preferably higher than that of the p-type impurity gas in the process of forming the first layer 51. This makes it possible to make the surface state of the upper surface of the third layer 53 flatter than that of the upper surface of the second layer 52.

[0061] After growing and forming each semiconductor layer, heat treatment is performed in a reaction vessel under a nitrogen atmosphere at a temperature in the range of, for example, 400°C to 550°C.

[0062] After heat treatment, a portion of the p-side layer 50, a portion of the electron blocking layer 40, and a portion of the active layer 30 are removed to expose a portion of the n-contact layer 22.

[0063] Then, as shown in Figure 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.

[0064] By performing the above steps, the light-emitting element of this embodiment can be manufactured.

[0065] The following describes the light-emitting elements related to Examples 1 and 2, and the light-emitting elements related to the Reference Example.

[0066] <Example 1> A substrate 10 made of sapphire with the chamfered plane as the main surface was used. A buffer layer 11 made of AlN was formed on the substrate 10 to a thickness of 2 μm.

[0067] Next, the temperature is raised to 1175°C, and TMA gas, TMG gas, and ammonia gas are used as the raw material gases, and Al is placed on the buffer layer 11. 0.60 Ga 0.40 An N layer was formed to a thickness of approximately 21 nm. Subsequently, at a temperature of 1175°C, an AlN layer was formed to a thickness of approximately 10 nm using TMA gas and ammonia gas as source gases. A superlattice layer 12 was formed by creating 30 pairs of laminates of the AlGaN layer and AlN layer formed in this manner.

[0068] Next, the temperature is raised to 1175°C, and TMA gas, TMG gas, and ammonia gas are used as the raw material gases, and Al is placed on the superlattice layer 12. 0.60 Ga 0.40The base layer 21 was formed by creating an N layer with a thickness of approximately 0.5 μm. Subsequently, the temperature was raised to 1175°C, and TMA gas, TMG gas, ammonia gas, and SiH4 gas were used as raw material gases, and Al containing n-type impurities was formed. 0.60 Ga 0.40 An n-contact layer 22 was formed by creating an N-layer with a thickness of approximately 2.2 μm. An n-side layer 20 was then formed, including the underlying layer 21 and the n-contact layer 22. The n-type impurity concentration of the n-contact layer 22 was approximately 9.5 × 10⁻⁶. 18 / cm 3 That's what I decided.

[0069] Next, the temperature is raised to 950°C, and TMA gas, TMG gas, ammonia gas, and SiH4 gas are used as the raw material gases, and Al containing n-type impurities is placed on the n-side layer 20. 0.52 Ga 0.48 A barrier layer 32 was formed by creating an N layer with a thickness of approximately 50 nm. Subsequently, the temperature was raised to 950°C, and TMA gas, TMG gas, and ammonia gas were used as raw material gases, and Al 0.42 Ga 0.58 The well layer 31 was formed by creating an N layer with a thickness of approximately 4.4 nm. Subsequently, the temperature was raised to 950°C, and TMA gas, TMG gas, ammonia gas, and SiH4 gas were used as raw material gases, and Al containing n-type impurities was formed. 0.52 Ga 0.48 A barrier layer 32 was formed by creating an N layer with a thickness of approximately 2.5 nm. Subsequently, the temperature was raised to 950°C, and TMA gas, TMG gas, and ammonia gas were used as raw material gases, and Al 0.42 Ga 0.58 A well layer 31 was formed by creating an N layer with a thickness of approximately 4.4 nm. An active layer 30 was then formed, which included two such well layers 31 and two barrier layers 32.

[0070] Next, the temperature was raised to 870°C, and TMA gas and ammonia gas were used as raw material gases to form an AlN layer approximately 1 nm thick on the active layer 30. Subsequently, the temperature was raised to 870°C, and TMA gas, TMG gas, and ammonia gas were used as raw material gases, Al 0.55 Ga 0.45The first AlGaN layer was formed by creating an N layer with a thickness of approximately 1 nm. Subsequently, the temperature was raised to 870°C, and TMA gas, TMG gas, and ammonia gas were used as source gases, and Al 0.78 Ga 0.22 A second AlGaN layer was formed by creating a layer of N with a thickness of approximately 4 nm. An electron blocking layer 40 was then formed, containing this AlN layer and the two AlGaN layers.

[0071] Next, the temperature is raised to 870°C, and TMA gas, TMG gas, ammonia gas, and Cp2Mg gas are used as the source gases, and Al containing p-type impurities is placed on the electron blocking layer 40. 0.63 Ga 0.37 The fourth layer 54 was formed by creating an N layer with a thickness of approximately 78 nm. Subsequently, the temperature was raised to 870°C, and TMA gas, TMG gas, ammonia gas, and Cp2Mg gas were used as raw material gases, and Al containing p-type impurities was formed. 0.53 Ga 0.47 The first layer 51 was formed by creating an N layer with a thickness of approximately 30 nm. Subsequently, the temperature was raised to 900°C, and TMA gas, TMG gas, ammonia gas, and Cp2Mg gas were used as raw material gases, and Al containing p-type impurities was formed. 0.40 Ga 0.60 A second layer 52 was formed by creating an N layer to a thickness of approximately 10 nm. Subsequently, a third layer 53 was formed by raising the temperature to 900°C and using TMA gas, TMG gas, and ammonia gas as the raw material gas to create a GaN layer containing p-type impurities to a thickness of approximately 10 nm. Thus, a p-side layer 50 was formed, including the first layer 51, second layer 52, third layer 53, and fourth layer 54. The flow rate ratio of ammonia gas in the raw material gas when forming the second layer 52 and third layer 53 was lower than the flow rate ratio of ammonia gas in the raw material gas when forming the first layer 51. Furthermore, the flow rate ratio of Cp2Mg gas in the raw material gas when forming the second layer 52 and third layer 53 was higher than the flow rate ratio of Cp2Mg gas in the raw material gas when forming the first layer 51.

[0072] After forming each semiconductor layer, heat treatment was performed on each semiconductor layer in a reaction vessel. The heat treatment was carried out in a nitrogen atmosphere at a temperature of approximately 475°C.

[0073] After heat treatment, a portion of the p-side layer 50 and a portion of the active layer 30 were removed, exposing a portion of the n-side contact layer 22 from the p-side layer 50 and the active layer 30.

[0074] Next, an n electrode 60 was formed on the n contact layer 22, and a p electrode 70 was formed on the third layer 53 of the p side layer 50. For the n electrode 60, a multilayer electrode was used in which a Ti layer, an AlSi layer, a Ta layer, a Ru layer, and a Ti layer were stacked in that order from the n contact layer 22 side. For the p electrode 70, a multilayer electrode was used in which a Ti layer, a Ru layer, and a Ti layer were stacked in that order from the third layer 53 side.

[0075] Subsequently, the substrate 10 was fragmented into multiple light-emitting elements. The outer shape of the substrate 10 for each fragmented light-emitting element was a square with sides of 1000 μm in a plan view. The thickness of the substrate 10 for each light-emitting element was 700 μm.

[0076] The light-emitting element of Example 1, fabricated as described above, had a forward voltage Vf of 5.86V and an output power Po of 182mW. In Examples 1 and 2, and the Reference Example, the forward voltage Vf and output power Po are the values ​​obtained when a current of 350mA is applied.

[0077] <Example 2> The light-emitting element in Example 2 was manufactured in the same manner as in Example 1, except that the structure of the first layer 51 was different.

[0078] In the light-emitting element according to Example 2, the first layer 51 is made of Al containing p-type impurities and having a thickness of approximately 27 nm. 0.53 Ga 0.47 The structure was formed by an N layer and a composition gradient layer containing p-type impurities and having a thickness of approximately 3 nm. The composition gradient layer was formed so that it was located on the side of the second layer 52 within the first layer 51. The composition gradient layer was formed so that the Al composition ratio decreased from the active layer 30 side to the second layer 52 side by reducing the flow rate ratio of the TMA gas. The composition gradient layer was formed so that the Al composition ratio decreased from approximately 53% to 0% from the active layer 30 side to the second layer 52 side.

[0079] The light-emitting element of Example 2, fabricated as described above, had a forward voltage Vf of 5.13V and an output power Po of 161mW.

[0080] <Reference example> The light-emitting element in the reference example was manufactured in the same manner as in Example 1, except that some parts of the structure of the p-side layer 50 and some parts of the structure of the p-electrode 70 were different.

[0081] In the reference example of the light-emitting element, the second layer 52 was formed using a GaN layer containing p-type impurities and having a thickness of approximately 350 nm, at a temperature of 870°C, using TMG gas, ammonia gas, and Cp2Mg gas as raw material gases. The third layer 53 was also formed using a GaN layer containing p-type impurities and having a thickness of approximately 20 nm, at a temperature of 870°C, using TMG gas, ammonia gas, and Cp2Mg gas as raw material gases. For the p electrode 70, a multilayer electrode structure was used, in which a Ti layer, an Rh layer, and a Ti layer were stacked in that order from the third layer 53 side.

[0082] In the reference example light-emitting element fabricated as described above, the forward voltage Vf was 7.08V and the output power Po was 103mW.

[0083] From the above, it can be seen that the light-emitting elements according to Examples 1 and 2 can achieve a higher output Po than the light-emitting element according to the Reference Example, and the forward voltage Vf can also be reduced. This is thought to be because the V-pit 33 is filled by the second layer 52, making it easier to extract light from the side of the well layer 31. The light-emitting element according to Example 2 has an output Po that is 21mW lower than the light-emitting element according to Example 1, but the forward voltage Vf is 0.73V lower. This is thought to be because, although the forward voltage Vf can be reduced by making a portion of the first layer 51 a composition gradient layer with a lower Al composition ratio, the portion of the first layer 51 with a low Al composition ratio increases, causing light absorption by the first layer 51, which reduces the output Po.

[0084] The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. All forms that a person skilled in the art can implement by appropriately modifying the design based on the above-described embodiments of the present invention also fall within the scope of the present invention, insofar as they encompass the gist of the present invention. Furthermore, within the scope of the idea of ​​the present invention, a person skilled in the art can conceive of various modifications and alterations, and these modifications and alterations also fall within the scope of the present invention.

[0085] This embodiment includes the following forms.

[0086] Note 1 A semiconductor structure comprising an n-side layer, a p-side layer, and an active layer located between the n-side layer and the p-side layer that emits ultraviolet light, each made of a nitride semiconductor, The n electrode is electrically connected to the n side layer, The p-electrode is electrically connected to the p-side layer, The active layer comprises an Al-containing well layer, an Al-containing barrier layer, and a pore including the side surface of the well layer and the side surface of the barrier layer. The p-side layer comprises a first layer containing Al, a second layer containing Al, 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 with an Al composition ratio lower than that of the second layer, or a layer that does not contain Al. The p electrode is a light-emitting element disposed on the third layer. Note 2 The light-emitting element according to Appendix 1, wherein the thickness of the third layer is less than or equal to the thickness of the second layer. Note 3 The first layer, the second layer, and the third layer contain p-type impurities. The light-emitting element according to Appendix 1 or 2, wherein the p-type impurity concentration of the second layer and the p-type impurity concentration of the third layer are higher than the p-type impurity concentration of the first layer. Note 4 The light-emitting element described in Appendix 3, wherein the p-type impurity concentration of the third layer is higher than that of the p-type impurity concentration of the second layer. Note 5 The p-type impurity concentration in the second layer is 1 × 10⁻⁶ 19 / cm 3 The above 1 x 10 21 / cm 3 The following light-emitting element as described in Appendix 3 or 4. Note 6 The light-emitting element according to any one of the appendices 1 to 5, wherein the Al composition ratio of the first layer is higher than that of the second layer. Appendix 7 The light-emitting element according to any one of the appendices 1 to 6, wherein the Al composition ratio of the second layer is higher than the Al composition ratio of the well layer. Note 8 The light-emitting element according to any one of the appendices 1 to 7, wherein the Al composition ratio of the well layer is 10% or more. Note 9 The light-emitting element according to any one of the appendices 1 to 8, wherein the thickness of the second layer is 3 nm or more and 20 nm or less. Note 10 The first and second layers are made of aluminum gallium nitride. The third layer is a light-emitting element according to any one of appendices 1 to 9, wherein the third layer is made of gallium nitride. Note 11 A process for forming an n-side layer made of a nitride semiconductor, A step of forming an active layer on the n-side layer, having an Al-containing well layer, an Al-containing barrier layer, and a pore portion including the side surface of the well layer and the side surface of the barrier layer, which emits ultraviolet light. A step of forming a p-side layer on the active layer, each consisting of a first layer containing Al, each made of a nitride semiconductor; a second layer containing Al, the difference in Al composition ratio with the well layer being 10% or less; and a third layer that is thinner than the thickness of the first layer and has an Al composition ratio lower than that of the second layer, or is a layer that does not contain Al. A step of forming an n electrode that is electrically connected to the n side layer, The process includes forming a p electrode that is electrically connected to the third layer of the p side layer, The step of forming the p-side layer is, The step of forming the first layer on the active layer, A step of forming the second layer so as to be in contact with the first layer and the side surface of the well layer, A method for manufacturing a light-emitting element, comprising the step of forming the third layer on the second layer. Note 12 The method for manufacturing a light-emitting element according to Appendix 11, wherein the growth rate when forming the second layer is slower than the growth rate when forming the first layer. Note 13 The method for manufacturing a light-emitting element according to Appendix 11 or 12, wherein the growth rate when forming the third layer is slower than the growth rate when forming the first layer. Note 14 In the process of forming the first layer, a p-type impurity gas is used to form the first layer containing p-type impurities. In the process of forming the second layer, a p-type impurity gas is used to form the second layer containing p-type impurities. A method for manufacturing a light-emitting element according to any one of the appendices 11 to 13, wherein 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. Note 15 In the process of forming the first layer, a p-type impurity gas is used to form the first layer containing p-type impurities. In the process of forming the third layer, a p-type impurity gas is used to form the third layer containing p-type impurities. A method for manufacturing a light-emitting element according to any one of the appendices 11 to 14, wherein 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. [Explanation of symbols]

[0087] 1 Light-emitting element 10 circuit boards 11 Buffer Layer 12 superlattice layer 20 n-side layer 21 Base layer 22 n contact layer 30 Active layer 31 Well layer 32 Barrier Layer 33 V-Pit 40 Electron Block Layer 50p side layer 51 1st layer 52 2nd layer 53 3rd layer 54 4th layer 60n electrode 70p electrode 100 Semiconductor Structures

Claims

1. A semiconductor structure comprising an n-side layer, a p-side layer, and an active layer located between the n-side layer and the p-side layer that emits ultraviolet light, each made of a nitride semiconductor, The n electrode is electrically connected to the n side layer, The p electrode is electrically connected to the p side layer, The active layer comprises an Al-containing well layer, an Al-containing barrier layer, and a pore including the side surface of the well layer and the side surface of the barrier layer. The p-side layer comprises a first layer containing Al, a second layer containing Al and positioned on the first layer and in contact with the side surface of the well layer, and a third layer positioned 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 with an Al composition ratio lower than that of the second layer, or a layer that does not contain Al. The p electrode is a light-emitting element disposed on the third layer.

2. The light-emitting element according to claim 1, wherein the thickness of the third layer is less than or equal to the thickness of the second layer.

3. The first layer, the second layer, and the third layer contain p-type impurities. The light-emitting element according to claim 1, wherein the p-type impurity concentration of the second layer and the p-type impurity concentration of the third layer are higher than the p-type impurity concentration of the first layer.

4. The light-emitting element according to claim 3, wherein the p-type impurity concentration of the third layer is higher than the p-type impurity concentration of the second layer.

5. The p-type impurity concentration in the second layer is 1 × 10⁻⁶ １９ / cm ３ The above 1 x 10 ２１ / cm ３ The following is the light-emitting element according to claim 3.

6. The light-emitting element according to any one of claims 1 to 5, wherein the Al composition ratio of the first layer is higher than the Al composition ratio of the second layer.

7. The light-emitting element according to any one of claims 1 to 5, wherein the Al composition ratio of the second layer is higher than the Al composition ratio of the well layer.

8. The light-emitting element according to any one of claims 1 to 5, wherein the Al composition ratio of the well layer is 10% or more.

9. The light-emitting element according to any one of claims 1 to 5, wherein the thickness of the second layer is 3 nm or more and 20 nm or less.

10. The first and second layers are made of aluminum gallium nitride. The light-emitting element according to any one of claims 1 to 5, wherein the third layer is made of gallium nitride.

11. A process of forming an n-layer made of a nitride semiconductor, The process of forming an active layer on the n-side layer, having an Al-containing well layer, an Al-containing barrier layer, and a pore portion including the side surface of the well layer and the side surface of the barrier layer, which emits ultraviolet light, A step of forming a p-side layer on the active layer, each consisting of a first layer containing Al, each made of a nitride semiconductor; a second layer containing Al, the difference in Al composition ratio with the well layer being 10% or less; and a third layer that is thinner than the thickness of the first layer and has an Al composition ratio lower than that of the second layer, or is a layer that does not contain Al. The process of forming an n electrode that is electrically connected to the n side layer, The process includes forming a p electrode that is electrically connected to the third layer of the p-side layer, The step of forming the p-side layer is, The step of forming the first layer on the active layer, A step of forming the second layer so as to be in contact with the first layer and the side surface of the well layer, A method for manufacturing a light-emitting element, comprising the step of forming the third layer on the second layer.

12. The method for manufacturing an light-emitting element according to claim 11, wherein the growth rate when forming the second layer is slower than the growth rate when forming the first layer.

13. The method for manufacturing an light-emitting element according to claim 12, wherein the growth rate when forming the third layer is slower than the growth rate when forming the first layer.

14. In the process of forming the first layer, a p-type impurity gas is used to form the first layer containing p-type impurities. In the process of forming the second layer, a p-type impurity gas is used to form the second layer containing p-type impurities. The method for manufacturing a light-emitting element according to any one of claims 11 to 13, wherein 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. In the process of forming the first layer, a p-type impurity gas is used to form the first layer containing p-type impurities. In the process of forming the third layer, a p-type impurity gas is used to form the third layer containing p-type impurities. A method for manufacturing a light-emitting element according to any one of claims 11 to 13, wherein 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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