Nitride semiconductor light-emitting element and method for manufacturing nitride semiconductor light-emitting element

Abstract

Provided is a nitride semiconductor light-emitting element that emits ultraviolet light and that has improved light-emitting efficiency. The light-emitting element includes an n-side semiconductor layer, a p-side semiconductor layer, and an active layer located between the n-side semiconductor layer and the p-side semiconductor layer, and an electron blocking layer is provided between the p-side semiconductor layer and the active layer. The active layer includes, in order from the n-side semiconductor layer side, a first barrier layer containing Al, a first well layer containing Al and emitting ultraviolet light, a second barrier layer containing Al, and a second well layer in contact with the electron blocking layer and emitting ultraviolet light, the Al composition ratio of the second well layer being greater than the Al composition ratio of the first well layer. A film thickness of the second well layer is smaller than a film thickness of the first well layer.

Description

Technical Field

[0001] The present invention relates to a nitride semiconductor light-emitting element and a method for manufacturing the nitride semiconductor light-emitting element. Background Art

[0002] In recent years, the development of nitride semiconductor light-emitting elements that emit ultraviolet light has been advanced. For example, Patent Document 1 discloses a light-emitting element having a light-emitting layer that emits ultraviolet light.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 9-153645 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Nitride semiconductor light-emitting elements that emit ultraviolet light have room for improvement in light-emitting efficiency compared to light-emitting elements that emit visible light.

[0008] Therefore, an object of the present invention is to provide a nitride semiconductor light-emitting element that emits ultraviolet light and has improved luminous efficiency, and a method for manufacturing the nitride semiconductor light-emitting element.

[0009] Technical solutions to solve problems

[0010] The present invention provides a nitride semiconductor light-emitting element, which comprises an n-side semiconductor layer, a p-side semiconductor layer, and an active layer located between the n-side semiconductor layer and the p-side semiconductor layer, and an electron blocking layer is provided between the p-side semiconductor layer and the active layer, wherein:

[0011] The active layer includes, in order from the n-side semiconductor layer side, a first barrier layer containing Al, a first well layer containing Al and emitting ultraviolet light, a second barrier layer containing Al, and a second well layer that is in contact with the electron blocking layer and contains Al and emits ultraviolet light,

[0012] The Al composition ratio of the second well layer is greater than the Al composition ratio of the first well layer,

[0013] The second well layer has a smaller thickness than the first well layer.

[0014] In addition, the present invention provides a method for manufacturing a nitride semiconductor light-emitting element, the method comprising:

[0015] A step of forming an n-side semiconductor layer;

[0016] forming an active layer on the n-side semiconductor layer;

[0017] forming a p-side semiconductor layer on the active layer,

[0018] The process of forming the active layer includes:

[0019] forming a first barrier layer containing Al on the n-side semiconductor layer;

[0020] forming a first well layer containing Al and emitting ultraviolet light on the first barrier layer;

[0021] forming a second barrier layer containing Al on the first well layer;

[0022] forming a second well layer on the second barrier layer, wherein the second well layer has a smaller film thickness than the first well layer, contains Al at a composition ratio higher than the Al composition ratio of the first well layer, and emits ultraviolet light,

[0023] The method includes forming an electron blocking layer in contact with the second well layer between the step of forming the active layer and the step of forming the p-side semiconductor layer.

[0024] Effects of the Invention

[0025] According to a nitride semiconductor light emitting element and a method for manufacturing the nitride semiconductor light emitting element according to an embodiment of the present invention, it is possible to provide a nitride semiconductor light emitting element emitting ultraviolet light with improved luminous efficiency and a method for manufacturing the nitride semiconductor light emitting element. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a cross-sectional view showing the structure of a nitride semiconductor light emitting element according to one embodiment of the present invention.

[0027] Figure 2 Yes means Figure 1 The diagram shows the structure of the active layer and electron blocking layer of the nitride semiconductor light-emitting element.

[0028] Figure 3 This is a cross-sectional view when a base layer is formed on the upper surface of a substrate in a method for manufacturing a light emitting element according to an embodiment of the present invention.

[0029] Figure 4 In a method for manufacturing a light emitting element according to an embodiment of the present invention, Figure 3 A cross-sectional view showing a superlattice layer formed on a base layer.

[0030] Figure 5 In a method for manufacturing a light emitting element according to an embodiment of the present invention, Figure 4 A cross-sectional view showing a state where an n-side semiconductor layer is formed on the superlattice layer.

[0031] Figure 6 In a method for manufacturing a light emitting element according to an embodiment of the present invention, Figure 5 A cross-sectional view showing a state where an active layer is formed on the n-side semiconductor layer.

[0032] Figure 7 In a method for manufacturing a light emitting element according to an embodiment of the present invention, Figure 6 A cross-sectional view showing a case where an electron blocking layer is formed on the active layer.

[0033] Figure 8 In a method for manufacturing a light emitting element according to an embodiment of the present invention, Figure 7 A cross-sectional view showing a case where a p-side semiconductor layer is formed on the electron blocking layer.

[0034] Description of Reference Numerals

[0035] 1 Nitride semiconductor light-emitting device

[0036] 10 substrates

[0037] 11. Basal layer

[0038] 12 superlattice layers

[0039] 20n-side semiconductor layer

[0040] 21 Undoped layer

[0041] 22n side contact layer

[0042] 30 active layers

[0043] 31First barrier layer

[0044] 31aFirst floor

[0045] 31b Second floor

[0046] 32First well layer

[0047] 33 Second barrier layer

[0048] 34 Second well layer

[0049] 40Electron blocking layer

[0050] 50p side semiconductor layer

[0051] 51 first p-side semiconductor layer

[0052] 52 second p-side semiconductor layer

[0053] 60 n electrode

[0054] 70 p electrode

[0055] 100Semiconductor structures DETAILED DESCRIPTION

[0056] Hereinafter, embodiments or examples for implementing the present invention will be described with reference to the accompanying drawings. It should be noted that the light emitting element and the method for manufacturing the light emitting element described below are used to embody the technical concept of the present invention, and the present invention is not limited to the following contents unless otherwise specified.

[0057] In each figure, the same figure mark is sometimes used to mark components with the same function. Considering the ease of description or understanding of the main points, they are sometimes divided into implementation methods or examples for convenience, but parts of the structures shown in different implementation methods or examples can be replaced or combined. In the implementation methods or examples described later, the description of matters common to the above is omitted, and only the different points are described. In particular, the same effects brought about by the same structure are not mentioned one by one for each implementation method or example. In order to make the description clear, the size or positional relationship of the components represented in each figure is sometimes expressed in an exaggerated manner. For example, the drawings attached to this specification are schematic diagrams that mainly represent stacked structures and do not necessarily accurately reflect the film thickness of each layer.

[0058] Implementation

[0059] Figure 1 It is a schematic cross-sectional view of a nitride semiconductor light emitting element 1 according to the embodiment. Figure 2 It is a cross-sectional schematic diagram showing an enlarged view of a part of the semiconductor structure 100 , namely, the active layer 30 and the electron blocking layer 40 .

[0060] like Figure 1 , 2 As shown, the nitride semiconductor 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 semiconductor layer 20, a p-side semiconductor layer 50, each formed of a nitride semiconductor, and an active layer 30 located between the n-side semiconductor layer 20 and the p-side semiconductor layer 50 and emitting ultraviolet light. In addition, the semiconductor structure 100 includes: a base layer 11 and a superlattice layer 12 located between the substrate 10 and the n-side semiconductor layer 20, and an electron blocking layer 40 located between the active layer 30 and the p-side semiconductor layer 50. The nitride semiconductor light emitting element 1 has an n-electrode 60 electrically connected to the n-side semiconductor layer 20, and a p-electrode 70 electrically connected to the p-side semiconductor layer 50.

[0061] Here, the active layer 30 includes, in order from the n-side semiconductor layer 20 side: a first barrier layer 31 containing Al, a first well layer 32 containing Al and emitting ultraviolet light, a second barrier layer 33 containing Al, and a second well layer 34 containing Al and emitting ultraviolet light, and the second well layer 34 is connected to the electron blocking layer 40.

[0062] Furthermore, the Al composition ratio of the second well layer 34 is greater than the Al composition ratio of the first well layer 32 , and the film thickness of the second well layer 34 is smaller than the film thickness of the first well layer 32 .

[0063] According to the nitride semiconductor light emitting element of the embodiment formed as described above, it is possible to manufacture a nitride semiconductor light emitting element that emits ultraviolet light with improved light emission efficiency.

[0064] Hereinafter, the specific structures of the substrate 10 and each semiconductor layer will be described.

[0065] It should be noted that in the following description, after the structures other than the active layer 30 are described, the active layer 30 will be described in detail.

[0066] The material of the substrate 10 can be, for example, sapphire, silicon (Si), gallium nitride (GaN), aluminum nitride (AlN), etc. The substrate 10 formed of sapphire has high light transmittance with respect to the ultraviolet light from the active layer 30, and is therefore preferred. The semiconductor structure 100 can be configured, for example, on the c-plane of the sapphire substrate, preferably on a surface inclined in the range of 0.2° to 2° from the c-plane of the sapphire substrate to the a-axis direction or the m-axis direction of the sapphire substrate. The thickness of the substrate 10 can be set, for example, to be 150 μm to 800 μm. The nitride semiconductor light-emitting element 1 may not have a substrate 10.

[0067] The semiconductor structure 100 is a stacked body formed by stacking a plurality of semiconductor layers formed of nitride semiconductors. The nitride semiconductor includes a x Al y Ga 1-x-y Semiconductors of all compositions in which the composition ratios x and y are varied within respective ranges in a chemical formula formed by N (0≤x≤1, 0≤y≤1, x+y≤1).

[0068] In the base layer 11, for example, a layer formed of AlN can be used. The base layer 11 has a function of alleviating the lattice mismatch between the substrate 10 and the nitride semiconductor layer arranged on the base layer 11. The film thickness of the base layer 11 can be set to, for example, 0.5 μm to 4 μm, preferably 1.5 μm to 4 μm. The base layer 11 may include a buffer layer, which is located near the surface of the substrate 10. It should be noted that in this specification, the film thickness of each semiconductor layer refers to the thickness in the stacking direction of the semiconductor structure 100.

[0069] The superlattice layer 12 has a multilayer structure in which a first semiconductor layer and a second semiconductor layer having a lattice constant different from that of the first semiconductor layer are alternately stacked. The superlattice layer 12 has a function of alleviating stress generated in a semiconductor layer arranged above the superlattice layer 12. The superlattice layer 12 can be, for example, a multilayer structure in which an AlN layer and an aluminum gallium nitride (AlGaN) layer are alternately stacked. In the superlattice layer 12, the number of pairs of the first semiconductor layer and the second semiconductor layer can be set to be greater than 20 pairs and less than 50 pairs. When the first semiconductor layer is set to an AlGaN layer and the second semiconductor layer is set to an AlN layer, for example, the film thickness of the first semiconductor layer can be set to be greater than 5 nm and less than 30 nm, and the film thickness of the second semiconductor layer can be set to be greater than 5 nm and less than 30 nm.

[0070] The n-side semiconductor 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) or 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 18 / cm 3 Above 1×10 20 / cm 3 As follows. The n-side semiconductor layer 20 may include an undoped layer as long as it has the function of supplying electrons to the active layer 30. Here, the undoped layer refers to a layer that is not intentionally doped with n-type impurities or p-type impurities. In the case where the undoped layer is adjacent to a layer intentionally doped with n-type impurities and / or p-type impurities, n-type impurities and / or p-type impurities may be included in the undoped layer due to diffusion from the adjacent layer.

[0071] like Figure 1 As shown, the n-side semiconductor layer 20 includes, for example, an undoped layer 21 and an n-side contact layer 22. The undoped layer 21 is disposed between the superlattice layer 12 and the n-side contact layer 22. The n-side contact layer 22 is disposed between the undoped layer 21 and the active layer 30.

[0072] For example, an undoped AlGaN layer can be used as the undoped layer 21. When the undoped layer 21 is an AlGaN layer, the Al composition ratio of the AlGaN layer can be set to, for example, 25% to 70%.

[0073] The n-side contact layer 22 can be formed of, for example, AlGaN containing n-type impurities. When the n-side contact layer is an AlGaN layer, the Al composition ratio of the AlGaN layer can be set to, for example, 25% to 70%. It should be noted that, in this specification, for example, an AlGaN layer with an Al composition ratio of 50% refers to a layer formed of AlGaN. X Ga1-X N is AlGaN with a composition ratio x of 0.5 in the chemical formula. The n-type impurity concentration of the n-side contact layer 22 can be set to 5×10 18 / cm 3 Above 1×10 20 / cm 3 The thickness of the n-side contact layer 22 is preferably thicker than the thickness of the undoped layer 21. By making the thickness of the n-side contact layer 22 thicker than the thickness of the undoped layer 21, the rise in forward voltage can be reduced. The thickness of the n-side contact layer 22 can be set to, for example, 1.5 μm to 4 μm. The n-side contact layer 22 has an upper surface on which no other semiconductor layer is configured. An n-electrode 60 is configured on the upper surface of the n-side contact layer 22 on which no other semiconductor layer is configured.

[0074] The electron blocking layer 40 is a layer for reducing the overflow of electrons supplied from the n-side semiconductor layer 20. It is preferable to use a nitride semiconductor layer with a large band gap in the electron blocking layer 40. For example, as described later, when the second well layer 34 connected to the electron blocking layer 40 is formed of a nitride semiconductor layer containing Al, for example, a nitride semiconductor layer containing more Al than the second well layer 34 can be used in the electron blocking layer 40. The electron blocking layer 40 may also include a plurality of layers. For example, Figure 2 As shown, the electron blocking layer 40 can be set to a multilayer structure having a first electron blocking layer 41, a second electron blocking layer 42, and a third electron blocking layer 43 in order from the active layer 30 side. For example, the first electron blocking layer 41, the second electron blocking layer 42, and the third electron blocking layer 43 each contain Al. For example, the first electron blocking layer 41 can be set to an AlN layer, the second electron blocking layer 42 can be set to an AlGaN layer, and the third electron blocking layer 43 can be set to an AlGaN layer. In this specific example, the Al composition ratio of the second electron blocking layer 42 is lower than the Al composition ratio of the third electron blocking layer 43. In addition, the Al composition ratio of the second electron blocking layer 42 is higher than the Al composition ratio of the first well layer 32 and the second well layer 34. In the electron blocking layer 40 of this specific example, the Al composition ratio of the second electron blocking layer 42 and the Al composition ratio of the third electron blocking layer 43 are preferably higher than the Al composition ratio of the second barrier layer 33, for example. Thereby, the overflow of electrons can be reduced. For example, an undoped AlGaN layer, an undoped AlN layer, or the like can be used for the electron blocking layer 40. The total film thickness of the electron blocking layer 40 can be set to, for example, 4 nm or more and 15 nm or less.

[0075] The p-side semiconductor layer 50 preferably has high light transmittance with respect to the light from the first well layer 32 and the second well layer 34. For example, it is preferred to include an AlGaN layer having an Al composition ratio higher than the Al composition ratio of the first well layer 32 and the second well layer 34. However, the AlGaN layer having a high Al composition ratio has a larger band gap than the GaN layer and the like. Therefore, if the AlGaN layer having a high Al composition ratio is used for the p-side semiconductor layer 50, it is easy to produce insufficient p-type conversion of the p-side semiconductor layer 50, or the contact resistance caused by the p-electrode 70 and the p-side semiconductor layer 50 becomes larger. Therefore, in a nitride semiconductor light-emitting element in which an AlGaN layer formed with a higher Al composition ratio is used as the first well layer 32 and the second well layer 34, it is necessary to take into account both high light extraction efficiency and low forward voltage. Therefore, in the present embodiment, by having the following p-side semiconductor layer 50, a nitride semiconductor light-emitting element 1 having high light extraction efficiency and low forward voltage can be made.

[0076] For example, in this embodiment, Figure 1 As shown, the p-side semiconductor layer 50 includes a first p-side semiconductor layer 51 and a second p-side semiconductor layer 52. Here, the first p-side semiconductor layer 51 is a layer containing p-type impurities such as magnesium (Mg) and having a large Al composition ratio, and the second p-side semiconductor layer 52 is a layer containing p-type impurities such as Mg and having a small Al composition ratio or a layer not containing Al (for example, a GaN layer). In this way, by including the first p-side semiconductor layer 51 and the second p-side semiconductor layer 52, a nitride semiconductor light-emitting element 1 with high light extraction efficiency and low forward voltage Vf can be manufactured.

[0077] Moreover, the first p-side semiconductor layer 51 and the second p-side semiconductor layer 52 may be a single layer or a layer including a plurality of layers. For example, the first p-side semiconductor layer 51 may include, in order from the active layer 30 side, a first layer formed of an AlGaN layer, a second layer formed of an AlGaN layer having a lower Al composition ratio than the first layer, and a third layer formed of an AlGaN layer having a lower Al composition ratio than the second layer. In this case, the third layer may also be a composition gradient layer in which the Al composition ratio is gradually reduced. The second p-side semiconductor layer 52 may also include, for example, a fourth layer formed of an AlGaN layer and a fifth layer formed of a GaN layer from the first p-side semiconductor layer 51 side. In this way, by including the first to fifth layers, a nitride semiconductor light-emitting element 1 having a higher light extraction efficiency and a lower forward voltage Vf can be made.

[0078] The n-electrode 60 is disposed on the n-side contact layer 22 and electrically connected to the n-side semiconductor layer 20 . The p-electrode 70 is disposed on the second p-side semiconductor layer 52 of the p-side semiconductor layer 50 and electrically connected to the p-side semiconductor layer 50 .

[0079] For example, metals such as Ag, Al, Ni, Au, Rh, Ti, Pt, Mo, Ta, W, and Ru, or alloys containing these metals as main components can be used for the n-electrode 60. For example, the n-electrode 60 can be a multilayer structure including a Ti layer, an Al alloy layer, a Ta layer, and a Ru layer in this order from the n-side contact layer 22 side.

[0080] In the p-electrode 70, for example, the same metal as the above-mentioned n-electrode 60 can be used. In the case of the p-electrode 70 having the function of reflecting the light from the active layer 30 toward the p-electrode 70 side toward the n-side semiconductor layer 20 side, it is preferable to set the metal layer in contact with the third layer 53 in the p-electrode 70 as a metal layer having a high reflectivity with respect to the light from the active layer 30. For example, it is preferable to use a metal layer having a reflectivity of 70% or more, preferably 80% or more with respect to the light from the active layer 30. As such a metal layer, for example, an Rh layer or a Ru layer is preferably used. The p-electrode 70 can be set as a multilayer structure including 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.

[0081] 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 semiconductor layer 50 and the n-side semiconductor layer 20 , and holes and electrons are supplied to the active layer 30 , whereby the active layer 30 emits light.

[0082] Hereinafter, the active layer 30 will be described in detail.

[0083] The active layer 30 is disposed between the n-side semiconductor layer 20 and the p-side semiconductor 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, 220 nm to 350 nm.

[0084] The active layer 30 includes, for example, a first barrier layer 31 containing Al, a first well layer 32 containing Al and emitting ultraviolet light, a second barrier layer 33 containing Al, and a second well layer 34 containing Al and emitting ultraviolet light in order from the n-side semiconductor layer 20 side.

[0085] In addition, the film thickness of the first well layer 32 can be set to, for example, 3 nm or more and 6 nm or less. The film thickness of the second well layer 34 can be set to, for example, 1 nm or more and 4 nm or less. The film thickness of the first layer 31a of the first barrier layer 31 is, for example, 10 nm or more and 60 nm or less, and the film thickness of the second layer 31b is, for example, 5 nm or more and 20 nm or less. The film thickness of the second barrier layer 33 is, for example, 1 nm or more and 5 nm or less.

[0086] Hereinafter, specific examples of the first well layer 32 , the second well layer 34 , the first barrier layer 31 , and the second barrier layer 33 will be described.

[0087] The first well layer 32 and the second well layer 34 can use a layer formed of AlGaN, for example. The first barrier layer 31 and the second barrier layer 33 can use a layer formed of AlGaN, for example. The Al composition ratio of the first well layer 32 and the second well layer 34 can be set to, for example, 10% or more, specifically, 10% or more and 50% or less, more specifically, 30% or more and 50% or less. When the emission peak wavelength of the light from the first well layer 32 and the second well layer 34 is set to about 280nm, an AlGaN layer with an Al composition ratio of about 42% can be used as the first well layer 32 and the second well layer 34. The Al composition ratio of the first barrier layer 32 and the second barrier layer 33 can be set to, for example, 10% or more, specifically, 10% or more and 70% or less, more specifically, 30% or more and 70% or less.

[0088] Furthermore, in the nitride semiconductor light emitting element 1, the Al composition ratio of the second well layer 34 is made greater than the Al composition ratio of the first well layer 32, and the film thickness of the second well layer 34 is made smaller than the film thickness of the first well layer 32. Thus, the light emission efficiency of the entire active layer including the first well layer 32 and the second well layer 34 can be improved.

[0089] In detail, in the second well layer 34 connected to the electron blocking layer 40, a deformation occurs in the band structure, and the probability of luminescent recombination is easily reduced. As a result, sometimes an offset occurs between the peak wavelength of luminescence of the second well layer 34 and the peak wavelength of luminescence of the first well layer 32. In the nitride semiconductor light-emitting element 1 of the present embodiment, the Al composition ratio of the second well layer 34 is made greater than the Al composition ratio of the first well layer 32. As a result, the difference between the band gap of the second well layer 34 and the band gap of the electron blocking layer 40 can be reduced, and the deformation generated in the band structure of the second well layer 34 can be reduced. As a result, the offset between the peak wavelength of luminescence of the second well layer 34 and the peak wavelength of luminescence of the first well layer 32 can be reduced, and therefore, the luminescent efficiency of the active layer as a whole can be improved.

[0090] In addition, by making the thickness of the second well layer 34 smaller than the thickness of the first well layer 32, the light emission in the second well layer 34 is reduced. As a result, the light with a peak wavelength shifted from the peak wavelength of the first well layer 32 emitted from the second well layer 34 can be reduced, thereby improving the light emission efficiency of the entire active layer.

[0091] In the nitride semiconductor light emitting element 1 of the present embodiment, the difference between the Al composition ratio of the second well layer 34 and the Al composition ratio of the first well layer 32, and the ratio of the film thickness of the second well layer 34 and the film thickness of the first well layer 32 are appropriately set in consideration of the luminous efficiency of the active layer 30 as a whole and the shift of the luminous wavelength.

[0092] For example, the film thickness of the second well layer 34 is not less than 30% and not more than 60% of the film thickness of the first well layer 32 .

[0093] In addition, for example, the difference between the Al composition ratio of the first well layer 32 and the Al composition ratio of the second well layer 34 is 2% or more and 10% or less.

[0094] Furthermore, for example, the difference between the Al composition ratio of the second well layer 34 and the Al composition ratio of the electron blocking layer 40 is smaller than the difference between the Al composition ratio of the first well layer 32 and the electron blocking layer 40 .

[0095] Hereinafter, preferred embodiments of the first barrier layer 31 and the second barrier layer 33 will be described.

[0096] The peak of the highest n-type impurity concentration in the first barrier layer 31 is preferably located on the p-side semiconductor layer 50 side. Thus, the light emission efficiency in the first well layer 32 can be improved. That is, in the first barrier layer 31, the difference between the band gap of the first barrier layer 31 and the band gap of the first well layer 32 in the valence band is further increased so that the peak of the n-type impurity concentration is located on the p-side semiconductor layer 50 side, and the hole confinement effect in the first well layer 32 is further improved. Thus, the light emission efficiency in the first well layer 32 can be further improved. In addition, if n-type impurities are added to the first barrier layer 31, the crystallinity of the first barrier layer 31 may be deteriorated. However, in this example, by making the peak of the highest n-type impurity concentration in the first barrier layer 31 located on the p-side semiconductor layer 50 side, the barrier at the boundary between the first well layer 32 and the first barrier layer 31 is improved, and the n-type impurity concentration in the first barrier layer 31 on the n-side semiconductor layer 20 side is reduced. Thus, the deterioration of the crystallinity of the entire first barrier layer 31 is reduced. Here, the value of the peak of the highest n-type impurity concentration in the first barrier layer 31 located on the p-side semiconductor layer 50 side is, for example, 1×10 19 / cm 3 Above 6×10 19 / cm 3 In addition, the position of the lowest n-type impurity concentration in the first barrier layer 31 is located closer to the n-side semiconductor layer 20 than the position of the peak of the highest n-type impurity concentration in the first barrier layer 31. For example, the value of the lowest n-type impurity concentration in the first barrier layer 31 is 1×10 17 / cm 3 Above 9×10 17 / cm 3 the following.

[0097] In addition, the Al composition ratio of the first barrier layer 31 is preferably higher than the Al composition ratio of the second barrier layer 33. Thus, the light emission efficiency in the first well layer 32 can be improved. That is, by making the Al composition ratio of the first barrier layer 31 higher than the Al composition ratio of the second barrier layer 33, the band gap of the second barrier layer 33 can be made smaller than the band gap of the first barrier layer 31, and the holes injected into the first well layer 32 can be increased. In addition, since the band gap of the first barrier layer 31 is larger than the band gap of the second barrier layer 33, the hole confinement effect in the first well layer 32 can be improved. Thus, the light emission efficiency in the first well layer 32 is improved. For example, the Al composition ratio of the first barrier layer 31 is larger than the Al composition ratio of the second barrier layer 33 in the range of 3% to 17%.

[0098] Hereinafter, specific structural examples and preferred examples of the barrier layer and the well layer according to the present embodiment will be described.

[0099] For example, Figure 2 As shown, the first barrier layer 31 includes a first layer 31a and a second layer 31b located on the p-side semiconductor layer 50 side relative to the first layer 31a. The n-type impurity concentration of the first layer 31a is different from the n-type impurity concentration of the second layer 31b. Specifically, the n-type impurity concentration of the first layer 31a is a concentration lower than the average value of the n-type impurity concentration in the entire first barrier layer 31, and the n-type impurity concentration of the second layer 31b is a concentration higher than the average value of the n-type impurity concentration in the entire first barrier layer 31. In this way, by having the first layer 31a and the second layer 31b having different n-type impurity concentrations, the highest peak of the n-type impurity concentration in the first barrier layer 31 can be located on the p-side semiconductor layer 50 side. The highest peak of the n-type impurity concentration in the first barrier layer 31 is located in the first layer 31a. In addition, the position of the lowest n-type impurity concentration in the first barrier layer 31 is located in the second layer 31b.

[0100] Here, the thickness of the second layer 31b is preferably smaller than the thickness of the first layer 31a. The n-type impurity concentration of the second layer 31b is a concentration higher than the average value of the n-type impurity concentration in the first barrier layer 31 as a whole. Therefore, by reducing the thickness of the second layer 31b having a higher n-type impurity concentration, the deterioration of the crystallinity of the first barrier layer 31 caused by the thickening of the layer having a high n-type impurity concentration can be reduced, and the luminous efficiency can be improved. For example, the thickness of the second layer 31b is preferably not less than 5% and not more than 30% of the thickness of the entire first barrier layer 31. As a result, the confinement effect of holes in the first well layer 32 can be improved, and the deterioration of the crystallinity of the first barrier layer 31 can be reduced.

[0101] In addition, the film thickness of the second barrier layer 33 is preferably smaller than the film thickness of the second layer 31 b . This can increase the supply of holes to the first well layer 32 .

[0102] The second barrier layer 33 may be undoped or may contain n-type impurities. When the second barrier layer 33 is undoped, the deterioration of the crystallinity of the active layer 30 can be reduced. In addition, when the second barrier layer 33 contains n-type impurities, the resistance of the second barrier layer 33 can be reduced and the forward voltage can be reduced. When the second barrier layer 33 contains n-type impurities, it is preferred that the n-type impurity concentration of the second barrier layer 33 is less than the n-type impurity concentration of the second layer 31b and greater than the n-type impurity concentration of the first layer 31a. Thus, the deterioration of the crystallinity of the second barrier layer 33 can be reduced and the forward voltage can be reduced.

[0103] In addition, the Al composition ratio of the first layer 31a and the Al composition ratio of the second layer 31b are preferably substantially the same. Thus, the difference in band gap caused by the difference in Al composition ratio of the first layer 31a and the Al composition ratio of the second layer 31b can be reduced, so that electrons can be efficiently supplied to the first well layer 32.

[0104] Furthermore, the first barrier layer 31 is in contact with the n-side semiconductor layer 20, and the Al composition ratio of the first barrier layer 31 is preferably substantially the same as the Al composition ratio of the n-side semiconductor layer 20. Thus, the difference in band gap caused by the difference in Al composition ratio of the n-side semiconductor layer 20 and the Al composition ratio of the first barrier layer 31 can be reduced, and thus, electrons can be efficiently supplied to the first well layer 32.

[0105] When the n-side semiconductor layer 20 includes the n-side contact layer 22 and the first barrier layer 31 is in contact with the n-side contact layer 22, it is preferred that the n-type impurity concentration of the n-side contact layer 22 is lower than the n-type impurity concentration of the second layer 31b and higher than the n-type impurity concentration of the first layer 31a. Thus, the deterioration of the crystallinity of the n-side contact layer 22 can be reduced, and the resistance of the n-side contact layer 22 can be reduced.

[0106] As described above, the film thickness of the second well layer 34 is preferably smaller than the film thickness of the first well layer 32. This can increase the supply of holes to the first well layer 32.

[0107] As described above, the Al composition ratio of the second well layer 34 is greater than that of the first well layer 32. The Al composition ratio of the second well layer 34 can be greater than that of the first well layer 32 within a range of 2% to 10%, for example.

[0108] In the above, the specific structural examples and preferred examples of the barrier layer and the well layer are described, but the film thickness, Al composition ratio, and doping amount of n-type impurities of the first layer 31a and the second layer 31b in the first barrier layer 31 and the second barrier layer 33 can be optimized based on the target emission wavelength and emission output, driving voltage and current, etc., taking into account the above specific structural examples and preferred examples. Similarly, the film thickness, Al composition ratio, and doping amount of the first well layer 32 and the second well layer 34 can also be optimized taking into account the above specific structural examples and preferred examples.

[0109] It should be noted that, in this embodiment, Figure 2 Although the specific example of including two barrier layers and two well layers is described, the present invention is not limited thereto. For example, one or more barrier layers and two or more well layers may be included between the first well layer 32 and the second well layer 34 .

[0110] Below, refer to Figure 3 to Figure 8 , a method for manufacturing the nitride semiconductor light-emitting element of this embodiment is described.

[0111] The method for manufacturing a nitride semiconductor light emitting device of this embodiment includes:

[0112] (S1) a step of forming an n-side semiconductor layer;

[0113] (S2) a step of forming an active layer on the n-side semiconductor layer;

[0114] (S3) a step of forming a p-side semiconductor layer on the active layer,

[0115] (S2) The step of forming an active layer includes:

[0116] (S2-1) forming a first barrier layer containing Al on the n-side semiconductor layer;

[0117] (S2-2) forming a first well layer containing Al and emitting ultraviolet light on the first barrier layer;

[0118] (S2-3) forming a second barrier layer including Al on the first well layer;

[0119] (S2-4) forming a second well layer on the second barrier layer, wherein the second well layer has a smaller film thickness than the first well layer, contains Al at a composition ratio higher than the Al composition ratio of the first well layer, and emits ultraviolet light,

[0120] (S4) A step of forming an electron blocking layer in contact with the second well layer is included between the step of forming the active layer and the step of forming the p-side semiconductor layer.

[0121] Here, the step (S2-1) of forming a first barrier layer on the n-side semiconductor layer may also include:

[0122] (S2-1-1) forming a first layer including Al and n-type impurities on the n-side semiconductor layer;

[0123] (S2-1-2) A step of forming a second layer containing Al and containing n-type impurities at a higher concentration than that of the first layer on the first layer.

[0124] In addition, when the process of forming a first barrier layer (S2-1) includes the process of forming a first layer and a second layer, the process of forming a second barrier layer (S2-3) is preferably a process of forming a second barrier layer including Al and n-type impurities and having an Al composition ratio lower than the Al composition ratio of the first layer and the Al composition ratio of the second layer, respectively.

[0125] In the following description, the above-mentioned preferred examples are included and described, but the preferred examples are arbitrary and not essential in the present embodiment.

[0126] First, if Figure 3 As shown, for example, a base layer 11 formed of AlN is formed on the c-plane of a substrate 10 formed of sapphire. The base layer 11 is formed by, for example, an organic metal vapor deposition (MOCVD) method or a sputtering method. Here, the process of forming the base layer 11 may also include a process of forming the base layer 11 including a buffer layer. For example, after a buffer layer formed of AlN is formed by a sputtering method, an AlN layer is formed on the buffer layer by, for example, an organic metal vapor deposition (MOCVD) method, thereby forming the base layer 11 including the buffer layer.

[0127] It should be noted that each semiconductor layer described below can be formed by epitaxial growth using, for example, the MOCVD method.

[0128] Then, if Figure 4 As shown, a superlattice layer 12 is formed on the base layer 11. 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 is formed, for example, by growing an AlN layer using trimethylaluminum (TMA) gas and ammonia gas as raw material gases, and mainly using hydrogen (H2) gas as a 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 raw material gases, and mainly using hydrogen gas as a carrier gas. Each layer of the superlattice layer 12 can be formed, for example, by setting the temperature to be above 1000°C and below 1250°C.

[0129] Then, if Figure 5As shown, an n-side semiconductor layer 20 including an undoped layer 21 and an n-side contact layer 22 is formed on the superlattice layer 12. The undoped 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 using hydrogen as a carrier gas. The n-side 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, and using monosilane (SiH4) gas as the n-type impurity gas, and mainly using hydrogen as a carrier gas. Each layer of the n-side semiconductor layer 20 can be formed, for example, by setting the temperature to be above 1000°C and below 1250°C.

[0130] Then, if Figure 6 As shown, an active layer 30 is formed on the n-side contact layer 22 .

[0131] Specifically, first, a first barrier layer 31 containing Al is formed on the n-side contact layer 22. The first barrier layer 31 is formed by, for example, using TMA gas, TEG gas, and ammonia gas as raw material gases, using monosilane (SiH4) gas as an n-type impurity gas as needed, and mainly using nitrogen gas as a carrier gas to grow a Si or undoped AlGaN layer containing n-type impurities.

[0132] Next, a first well layer 32 containing Al and emitting ultraviolet light is formed on the first barrier layer 31. The first well layer 32 is formed by growing an AlGaN layer using, for example, TMA gas, TEG gas, and ammonia gas as raw material gases and mainly nitrogen gas as a carrier gas.

[0133] Next, a second barrier layer 33 containing Al is formed on the first well layer 32. The second barrier layer 33 is formed similarly to the first barrier layer 31, for example, by growing a layer containing Si as an n-type impurity or an undoped AlGaN layer using TMA gas, TEG gas, and ammonia gas as raw material gases, monosilane (SiH4) gas as an n-type impurity gas as needed, and mainly using nitrogen gas as a carrier gas.

[0134] Next, a second well layer 34 is formed on the second barrier layer 33 . The second well layer 34 has a smaller film thickness than the first well layer 32 , contains Al at a higher composition ratio than the first well layer 32 , and emits ultraviolet light.

[0135] The second well layer 34 can be formed by using the same raw material gas and carrier gas as the first well layer 32, for example, by increasing the ratio of TMA gas in the raw material gas, and growing in a shorter time than the first well layer 32. Thus, the second well layer 34 can be formed, the film thickness of the second well layer 34 being smaller than that of the first well layer 32 and containing Al at a composition ratio higher than that of the first well layer 32.

[0136] In the case where the first barrier layer 31 is formed to include the first layer 31 a and the second layer 31 b including the n-type impurity at a higher concentration than the first layer 31 a , the first barrier layer 31 is formed, for example, as follows.

[0137] First, for example, TMA gas, TEG gas, ammonia gas are used as raw material gases, monosilane (SiH4) gas is used as n-type impurity gas, and nitrogen gas is mainly used as a carrier gas to form a first layer containing Al and n-type impurities on the n-side semiconductor layer.

[0138] Next, the flow rate of monosilane (SiH 4 ) gas is increased to form a second layer containing Al and n-type impurities at a higher concentration than that of the first layer on the first layer.

[0139] Then, if Figure 7 As shown, an electron blocking layer 40 is formed on the active layer 30, which is in contact with the second well layer 34 and has a larger band gap than the first well layer 32 and the second well layer 34. The electron blocking layer 40 is formed in a manner including a first electron blocking layer 41 as an AlN layer, a second electron blocking layer 42 as a first AlGaN layer, and a third electron blocking layer 43 as a second AlGaN layer. The first electron blocking layer 41 is formed, for example, by using TMA gas and ammonia gas in the raw material gas, and mainly using nitrogen as a carrier gas. The second electron blocking layer 42 is formed, for example, by using TMA gas, TEG gas, and ammonia gas in the raw material gas, and using nitrogen as a carrier gas. The third electron blocking layer 43 is formed, for example, by using TMA gas, TEG gas, and ammonia gas in the raw material gas, and mainly using nitrogen as a carrier gas. For example, in the process of forming the third electron blocking layer 43, the flow ratio of the TMA gas as the raw material gas of Al is made greater than the flow ratio of the TMA gas in the process of forming the second electron blocking layer 42. Thus, the Al composition ratio of the third electron blocking layer 43 is formed to be higher than the Al composition ratio of the second electron blocking layer 42. Each layer of the electron blocking layer 40 can be formed at a temperature of, for example, 750° C. to 950° C. inclusive.

[0140] Then, if Figure 8As shown, a p-side semiconductor layer 50 is formed on the electron blocking layer 40. The p-side semiconductor layer 50 is formed by growing a first p-side semiconductor layer 51 and a second p-side semiconductor layer 52 in sequence from the active layer 30 side. The first p-side semiconductor layer 51 is generated, for example, by using TMA gas, TEG gas, and ammonia gas as raw material gases, and using cyclopentadienyl magnesium (Cp2Mg) gas as a p-type impurity gas to grow an AlGaN layer containing Mg as a p-type impurity. The second p-side semiconductor layer 52 is formed, for example, by using TMA gas, TMG gas, and ammonia gas as raw material gases, and using cyclopentadienyl magnesium (Cp2Mg) gas as a p-type impurity gas to grow an AlGaN layer containing Mg as a p-type impurity, or, for example, by using TMG gas and ammonia gas as raw material gases instead of TMA gas, and using cyclopentadienyl magnesium (Cp2Mg) gas as a p-type impurity gas to grow a GaN layer containing Mg as a p-type impurity.

[0141] Each layer of the p-side semiconductor layer 50 can be formed at a temperature of, for example, 750° C. or higher and 950° C. or lower.

[0142] After the p-side semiconductor layer 50 is formed, a portion of the p-side semiconductor 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-side contact layer 22 .

[0143] Moreover, if Figure 1 As shown, an n-electrode 60 is formed on the exposed n-side contact layer 22 , and a p-electrode 70 is formed on the third layer 53 of the p-side semiconductor layer 50 .

[0144] By performing the above steps, the nitride semiconductor light emitting element of this embodiment can be manufactured.

[0145] Hereinafter, the nitride semiconductor light emitting element of the example will be described.

[0146] <Example>

[0147] A substrate made of sapphire having a C-plane as a major surface was used as the substrate 10. On the substrate 10, a base layer 11 made of AlN including a buffer layer was formed to a thickness of 2.1 μm.

[0148] Next, the temperature was set to 1175° C., and TMA gas, TMG gas, and ammonia gas were used as raw material gases to form an Al film with a thickness of about 21 nm on the base layer 11. 0.60 Ga 0.40 Next, the temperature was set to 1175° C., and TMA gas and ammonia gas were used as raw material gases to form an AlN layer with a film thickness of about 10 nm. By forming 30 pairs of stacked bodies of the AlGaN layer and the AlN layer formed in this way, the superlattice layer 12 was formed.

[0149] Next, the temperature was set to 1175° C., and TMA gas, TMG gas, and ammonia gas were used as raw material gases to form an Al film with a thickness of about 0.5 μm on the superlattice layer 12. 0.60 Ga 0.40 N layer, thereby forming the undoped layer 21. Next, the temperature was set to 1175°C, and TMA gas, TMG gas, ammonia gas, and SiH4 gas were used as raw material gases to mix Al containing n-type impurities. 0.60 Ga 0.40 The N layer is formed to a thickness of about 2.2 μm, thereby forming an n-side contact layer 22. The n-side semiconductor layer 20 including the undoped layer 21 and the n-side contact layer 22 is formed. The n-type impurity concentration of the n-side contact layer 22 is set to about 9.5×10 18 / cm 3 .

[0150] Next, the temperature was set to 950° C., and TMA gas, TMG gas, ammonia gas, and SiH 4 gas were used as raw material gases to form an Al film containing n-type impurities with a thickness of about 40 nm on the n-side semiconductor layer 20. 0.60 Ga 0.40 Next, the temperature was set to 950° C., TMA gas, TMG gas, ammonia gas, and SiH 4 gas were used as raw material gases, and Al containing n-type impurities was added. 0.60 Ga 0.40 The N layer is formed to a film thickness of about 10 nm, thereby forming the second layer 31b. Here, the flow rate of the raw material gas when forming the first layer 31a is set to 16 sccm of TMA gas, 45 sccm of TEG gas, 10 slm of ammonia gas, and 0.5 sccm of SiH4 gas, and the flow rate of the raw material gas when forming the second layer 31b is set to 16 sccm of TMA gas, 45 sccm of TEG gas, 10 slm of ammonia gas, and 16 sccm of SiH4 gas.

[0151] As described above, the first barrier layer 31 including the first layer 31 a including the n-type impurity and the second layer 31 b including a larger amount of the n-type impurity than the first layer 31 a is formed.

[0152] In addition, the film thickness of the first layer 31a and the film thickness of the second layer 31b mentioned here are the thicknesses during the manufacturing process, and the film thickness of the first layer 31a having a specific concentration lower than the average value of the n-type impurity concentration in the first barrier layer 31 as a whole and the film thickness of the second layer 31b having an n-type impurity concentration higher than the average value of the n-type impurity concentration in the first barrier layer 31 as a whole in the manufactured product may not be the same.

[0153] Next, the temperature was set to 950° C., TMA gas, TEG gas, and ammonia gas were used as raw material gases, and Al 0.43 Ga0.57 The N layer is formed to a thickness of about 4.4 nm, thereby forming the first well layer 32 .

[0154] Next, the temperature was set to 950° C., TMA gas, TEG gas, and ammonia gas were used as raw material gases, and Al 0.53 Ga 0.47 The N layer was formed to a thickness of about 2.5 nm, thereby forming the second barrier layer 33. Next, the temperature was set to 950° C., and TMA gas, TEG gas, and ammonia gas were used as raw material gases. 0.47 Ga 0.53 The N layer is formed to a film thickness of about 2.2 nm to form the second well layer 34. In this way, the active layer 30 including two well layers and two barrier layers is formed.

[0155] Next, the temperature was set to 870°C, TMA gas and ammonia gas were used as raw material gases, and the first electron blocking layer 41 as an AlN layer was formed on the active layer 30 with a thickness of about 1.3 nm. Next, the temperature was set to 870°C, TMA gas, TEG gas and ammonia gas were used as raw material gases, and the Al 0.55 Ga 0.45 The N layer was formed to a thickness of about 1.2 nm, thereby forming the second electron blocking layer 42 as the first AlGaN layer. Next, the temperature was set to 870° C., and TMA gas, TEG gas, and ammonia gas were used as raw material gases to form Al 0.78 Ga 0.22 N is formed to a film thickness of about 4 nm, thereby forming the third electron blocking layer 43 as the second AlGaN layer. In this way, the electron blocking layer 40 including the AlN layer and two AlGaN layers is formed.

[0156] Next, the temperature was set to 870° C., and TMA gas, TEG gas, ammonia gas, and Cp2Mg gas were used as raw material gases to form an Al2O3 film containing p-type impurities on the electron blocking layer 40 with a film thickness of about 75 nm. 0.63 Ga 0.37 Next, the temperature was set to 870°C, and TMA gas, TEG gas, ammonia gas, and Cp2Mg gas were used as raw material gases to form Al containing p-type impurities. 0.53 Ga 0.47 The N layer is formed to a thickness of about 27 nm. Next, the temperature is set to 870°C, and TMA gas, TEG gas, ammonia gas, and Cp2Mg gas are used as raw material gases. The TMA gas is gradually reduced, thereby forming a layer containing p-type impurities and Al 0.53 Ga 0.47 The composition gradient layer formed by gradually reducing N and Al and finally making the Al composition ratio 0 was formed to a thickness of 3 nm. As described above, the first p-side semiconductor layer 51 was formed.

[0157] Next, the temperature was set to 900°C, and TMA gas, TMG gas, ammonia gas, and Cp2Mg gas were used as raw material gases to mix Al containing p-type impurities. 0.40 Ga 0.60 The N layer is formed to a thickness of about 10 nm. Next, the temperature is set to 900°C, and TMA gas, TMG gas, and ammonia gas are used as raw material gases to form a GaN layer containing p-type impurities to a thickness of about 10 nm. 0.40 Ga 0.60 N layer and a second p-side semiconductor layer 52 of a GaN layer containing p-type impurities.

[0158] After forming each semiconductor layer, each semiconductor layer is heat-treated in a reaction container. The heat treatment is performed at a temperature of about 475° C. in a nitrogen atmosphere.

[0159] After the heat treatment, a portion of the p-side semiconductor layer 50 and a portion of the active layer 30 are removed, so that a portion of the n-side contact layer 22 is exposed from the p-side semiconductor layer 50 and the active layer 30 .

[0160] Next, an n-electrode 60 is formed on the n-side contact layer 22, and a p-electrode 70 is formed on the p-side semiconductor layer 50. The n-electrode 60 has a multilayer structure in which a Ti layer, an AlSi layer, a Ta layer, a Ru layer, and a Ti layer are stacked in this order from the n-side 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 stacked in this order from the third layer 53 side.

[0161] The nitride semiconductor light emitting device of the example fabricated as described above had a forward voltage of 5.16 V and a light output Po of 172 mW. It should be noted that the forward voltage and light output Po shown here are values ​​when a current of 350 mA is applied.

[0162] The peak with the highest n-type impurity concentration in the first barrier layer 31 is located in the second layer 31 b. The peak with the highest n-type impurity concentration in the first barrier layer 31 has a value of about 3×10 19 / cm 3 .

[0163] The nitride semiconductor light emitting element according to the embodiment of the present disclosure includes the following aspects, for example.

[0164] [Item 1]

[0165] A nitride semiconductor light emitting element comprises an n-side semiconductor layer, a p-side semiconductor layer, and an active layer located between the n-side semiconductor layer and the p-side semiconductor layer, and an electron blocking layer is provided between the p-side semiconductor layer and the active layer, wherein:

[0166] The active layer includes, in order from the n-side semiconductor layer side, a first barrier layer containing Al, a first well layer containing Al and emitting ultraviolet light, a second barrier layer containing Al, and a second well layer containing Al and emitting ultraviolet light, which is in contact with the electron blocking layer.

[0167] The Al composition ratio of the second well layer is greater than the Al composition ratio of the first well layer.

[0168] The film thickness of the second well layer is smaller than the film thickness of the first well layer.

[0169] [Item 2]

[0170] The nitride semiconductor light emitting element according to item 1, wherein the film thickness of the second well layer is not less than 30% and not more than 60% of the film thickness of the first well layer.

[0171] [Item 3]

[0172] The nitride semiconductor light emitting device according to item 1 or 2, wherein

[0173] A difference between an Al composition ratio of the first well layer and an Al composition ratio of the second well layer is 2% or more and 10% or less.

[0174] [Item 4]

[0175] The nitride semiconductor light emitting device according to any one of items 1 to 3, wherein

[0176] The first barrier layer contains n-type impurities.

[0177] The highest peak of the n-type impurity concentration in the first barrier layer is located on the p-side semiconductor layer side.

[0178] [Item 5]

[0179] The nitride semiconductor light emitting device according to any one of items 1 to 4, wherein

[0180] The first barrier layer includes a first layer and a second layer, the first layer contains n-type impurities at a concentration lower than an average value of the n-type impurity concentration in the entire first barrier layer, and the second layer is located closer to the p-side semiconductor layer than the first layer, and contains n-type impurities at a concentration higher than the average value.

[0181] [Item 6]

[0182] The nitride semiconductor light emitting device according to any one of items 1 to 5, wherein

[0183] The Al composition ratio of the first barrier layer is greater than the Al composition ratio of the second barrier layer.

[0184] [Item 7]

[0185] The nitride semiconductor light emitting device according to item 5 or item 6 referring to item 5, wherein:

[0186] The film thickness of the first layer is greater than the film thickness of the second layer.

[0187] [Item 8]

[0188] The nitride semiconductor light emitting device according to item 5 or item 6 referring to item 5, wherein:

[0189] The film thickness of the second layer is not less than 5% and not more than 30% of the film thickness of the first barrier layer.

[0190] [Item 9]

[0191] The nitride semiconductor light emitting device according to any one of item 5 or item 6 to item 8 referring to item 5, wherein

[0192] The second barrier layer has a film thickness smaller than that of the second layer.

[0193] [Item 10]

[0194] The nitride semiconductor light emitting device according to any one of item 5 or items 6 to 9 referring to item 5, wherein:

[0195] The second barrier layer includes n-type impurities, and a concentration of the n-type impurities in the second barrier layer is lower than a concentration of the n-type impurities in the second layer and higher than a concentration of the n-type impurities in the first layer.

[0196] [Item 11]

[0197] The nitride semiconductor light emitting device according to any one of items 1 to 10, wherein

[0198] The Al composition ratio of the first barrier layer is substantially the same as the Al composition ratio of the n-side semiconductor layer.

[0199] [Item 12]

[0200] The nitride semiconductor light emitting device according to any one of item 5 or item 6 to item 11 referring to item 5, wherein

[0201] The n-type impurity concentration of the n-side semiconductor layer is lower than the n-type impurity concentration of the second layer, and higher than the n-type impurity concentration of the first layer.

[0202] [Item 13]

[0203] A method for manufacturing a nitride semiconductor light-emitting element, the method comprising:

[0204] A step of forming an n-side semiconductor layer;

[0205] forming an active layer on the n-side semiconductor layer;

[0206] forming a p-side semiconductor layer on the active layer,

[0207] The process of forming the active layer includes:

[0208] forming a first barrier layer containing Al on the n-side semiconductor layer;

[0209] forming a first well layer containing Al and emitting ultraviolet light on the first barrier layer;

[0210] forming a second barrier layer containing Al on the first well layer;

[0211] forming a second well layer on the second barrier layer, wherein the second well layer has a smaller film thickness than the first well layer, contains Al at a higher composition ratio than the Al composition ratio of the first well layer, and emits ultraviolet light,

[0212] Between the step of forming the active layer and the step of forming the p-side semiconductor layer, there is included a step of forming an electron blocking layer having an Al composition ratio in contact with the second well layer and having a larger band gap than the first well layer and the second well layer.

[0213] [Item 14]

[0214] The method for manufacturing a nitride semiconductor light-emitting element according to item 13, wherein:

[0215] In the step of forming the second well layer, the second well layer is formed to have a film thickness that is not less than 30% and not more than 60% of a film thickness of the first well layer.

[0216] [Item 15]

[0217] The method for manufacturing a nitride semiconductor light-emitting element according to item 13 or 14, wherein:

[0218] In the step of forming the second well layer, the second well layer is formed to have an Al composition ratio whose difference from the Al composition ratio of the first well layer is 2% or more and 10% or less.

[0219] [Item 16]

[0220] The method for producing a nitride semiconductor light-emitting device according to any one of items 13 to 15, wherein:

[0221] The first barrier layer contains n-type impurities.

[0222] The first barrier layer is formed so that a peak of the highest n-type impurity concentration in the first barrier layer is located on the p-side semiconductor layer side.

[0223] [Item 17]

[0224] The method for producing a nitride semiconductor light-emitting device according to any one of items 13 to 16, wherein:

[0225] The step of forming the first barrier layer comprises:

[0226] forming a first layer including n-type impurities;

[0227] A step of forming a second layer located closer to the p-side semiconductor layer than the first layer and containing an n-type impurity at a higher concentration than the first layer.

[0228] [Item 18]

[0229] The method for producing a nitride semiconductor light-emitting device according to any one of items 13 to 17, wherein:

[0230] In the step of forming the first barrier layer, the first barrier layer is formed to include Al.

[0231] In the step of forming the second barrier layer, the second barrier layer is formed to include Al at a composition ratio lower than the Al composition ratio of the first barrier layer.

[0232] [Item 19]

[0233] The method for manufacturing a nitride semiconductor light-emitting element according to item 17 or item 18 referring to item 17, wherein:

[0234] In the step of forming the second layer, the second layer is formed to have a film thickness smaller than a film thickness of the first layer.

[0235] [Item 20]

[0236] The method for manufacturing a nitride semiconductor light-emitting element according to item 17 or item 18 or item 19 referring to item 17, wherein:

[0237] In the step of forming the second layer, the second layer is formed to have a film thickness of not less than 5% and not more than 30% of a film thickness of the first barrier layer.

[0238] [Item 21]

[0239] The method for manufacturing a nitride semiconductor light-emitting device according to any one of item 17 or items 18 to 20 referring to item 17, wherein:

[0240] In the step of forming the second layer, the second barrier layer is formed to have a film thickness smaller than a film thickness of the second layer.

[0241] [Item 22]

[0242] The method for producing a nitride semiconductor light-emitting device according to any one of items 13 to 21, wherein:

[0243] In the step of forming the first barrier layer, the first barrier layer is formed so that an Al composition ratio is substantially the same as an Al composition ratio of the n-side semiconductor layer.

[0244] [Item 23]

[0245] The method for manufacturing a nitride semiconductor light-emitting device according to any one of item 17 or items 18 to 22 referring to item 17, wherein:

[0246] In the step of forming the first barrier layer, the first layer is formed to have a lower n-type impurity concentration than the n-side semiconductor layer, and the second layer is formed to have a higher n-type impurity concentration than the n-side semiconductor layer.

Claims

1. A nitride semiconductor light emitting element, comprising: an n-side semiconductor layer, a p-side semiconductor layer, and an active layer located between the n-side semiconductor layer and the p-side semiconductor layer, and an electron blocking layer is provided between the p-side semiconductor layer and the active layer, wherein: The active layer includes, in order from the n-side semiconductor layer side, a first barrier layer containing Al, a first well layer containing Al and emitting ultraviolet light, a second barrier layer containing Al, and a second well layer that is in contact with the electron blocking layer and contains Al and emits ultraviolet light, The Al composition ratio of the second well layer is greater than the Al composition ratio of the first well layer, The second well layer has a smaller thickness than the first well layer.

2. The nitride semiconductor light emitting element according to claim 1, wherein: The film thickness of the second well layer is not less than 30% and not more than 60% of the film thickness of the first well layer.

3. The nitride semiconductor light emitting element according to claim 1 or 2, wherein: A difference between an Al composition ratio of the first well layer and an Al composition ratio of the second well layer is greater than or equal to 2% and less than or equal to 10%.

4. The nitride semiconductor light emitting element according to claim 1 or 2, wherein: The first barrier layer contains n-type impurities, The highest peak of the n-type impurity concentration in the first barrier layer is located on the p-side semiconductor layer side.

5. The nitride semiconductor light emitting element according to claim 1 or 2, wherein: The first barrier layer includes a first layer and a second layer, the first layer containing n-type impurities at a concentration lower than an average value of the n-type impurity concentration in the entire first barrier layer, and the second layer is located closer to the p-side semiconductor layer than the first layer and contains n-type impurities at a concentration higher than the average value.

6. The nitride semiconductor light emitting element according to claim 1 or 2, wherein: An Al composition ratio of the first barrier layer is greater than an Al composition ratio of the second barrier layer.

7. The nitride semiconductor light emitting element according to claim 5, wherein: The film thickness of the first layer is greater than the film thickness of the second layer.

8. The nitride semiconductor light emitting device according to claim 5, wherein: The film thickness of the second layer is not less than 5% and not more than 30% of the film thickness of the first barrier layer.

9. The nitride semiconductor light emitting element according to claim 5, wherein: The film thickness of the second barrier layer is smaller than the film thickness of the second layer.

10. The nitride semiconductor light emitting element according to claim 5, wherein: The second barrier layer includes n-type impurities, and a concentration of the n-type impurities in the second barrier layer is lower than a concentration of the n-type impurities in the second layer and higher than a concentration of the n-type impurities in the first layer.

11. The nitride semiconductor light emitting element according to claim 1 or 2, wherein: An Al composition ratio of the first barrier layer and an Al composition ratio of the n-side semiconductor layer are substantially the same.

12. The nitride semiconductor light emitting element according to claim 5, wherein: The n-type impurity concentration of the n-side semiconductor layer is lower than the n-type impurity concentration of the second layer, and higher than the n-type impurity concentration of the first layer.

13. A method for manufacturing a nitride semiconductor light-emitting element, the method comprising: A step of forming an n-side semiconductor layer; forming an active layer on the n-side semiconductor layer; forming a p-side semiconductor layer on the active layer, The process of forming the active layer includes: forming a first barrier layer containing Al on the n-side semiconductor layer; forming a first well layer containing Al and emitting ultraviolet light on the first barrier layer; forming a second barrier layer containing Al on the first well layer; forming a second well layer on the second barrier layer, wherein the second well layer has a smaller film thickness than the first well layer, contains Al at a composition ratio higher than the Al composition ratio of the first well layer, and emits ultraviolet light, The method includes forming an electron blocking layer in contact with the second well layer between the step of forming the active layer and the step of forming the p-side semiconductor layer.

14. The method for manufacturing a nitride semiconductor light emitting element according to claim 13, wherein: In the step of forming the second well layer, the second well layer is formed to have a film thickness that is not less than 30% and not more than 60% of a film thickness of the first well layer.

15. The method for manufacturing a nitride semiconductor light emitting element according to claim 13 or 14, wherein: In the step of forming the second well layer, the second well layer is formed to have an Al composition ratio that is different from the Al composition ratio of the first well layer by 2% or more and 10% or less.

16. The method for manufacturing a nitride semiconductor light emitting element according to claim 13 or 14, wherein: The first barrier layer contains n-type impurities, The first barrier layer is formed so that the highest peak of the n-type impurity concentration in the first barrier layer is located on the p-side semiconductor layer side.

17. The method for manufacturing a nitride semiconductor light emitting element according to claim 13 or 14, wherein: The process of forming the first barrier layer includes: forming a first layer including n-type impurities; A step of forming a second layer located closer to the p-side semiconductor layer than the first layer and containing an n-type impurity at a higher concentration than the first layer.

18. The method for manufacturing a nitride semiconductor light emitting element according to claim 13 or 14, wherein: In the step of forming the first barrier layer, the first barrier layer including Al is formed. In the step of forming the second barrier layer, the second barrier layer containing Al at a composition ratio lower than the Al composition ratio of the first barrier layer is formed.

19. The method for manufacturing a nitride semiconductor light emitting element according to claim 17, wherein: In the step of forming the second layer, the second layer is formed to have a film thickness smaller than a film thickness of the first layer.

20. The method for manufacturing a nitride semiconductor light emitting element according to claim 17, wherein: In the step of forming the second layer, the second layer is formed to have a film thickness of not less than 5% and not more than 30% of a film thickness of the first barrier layer.

21. The method for manufacturing a nitride semiconductor light emitting element according to claim 17, wherein: In the step of forming the second barrier layer, the second barrier layer is formed to have a film thickness smaller than a film thickness of the second layer.

22. The method for manufacturing a nitride semiconductor light emitting element according to claim 13 or 14, wherein: In the step of forming the first barrier layer, the first barrier layer is formed so that the Al composition ratio is substantially the same as the Al composition ratio of the n-side semiconductor layer.

23. The method for manufacturing a nitride semiconductor light emitting element according to claim 17, wherein: In the step of forming the first barrier layer, the first layer is formed to have a lower n-type impurity concentration than the n-side semiconductor layer, and the second layer is formed to have a higher n-type impurity concentration than the n-side semiconductor layer.

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