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

Abstract

A nitride semiconductor light emitting element is provided which can suppress the decrease of the light emission lifetime even when an electron blocking layer having an Al composition ratio of a certain size or more is provided. The nitride semiconductor light emitting element (1) comprises: a light emitting layer (40) comprising a well layer (44a-c) formed of AlGaN and emitting ultraviolet light; an electron blocking layer (51, 52) located on the light emitting layer (40) and formed of AlGaN having a first Al composition ratio greater than the Al composition ratio of the well layer (44a-c); and a p-type cladding layer (70) located on the electron blocking layer (51, 52) and formed of AlGaN having a second Al composition ratio greater than the Al composition ratio of the well layer (44a-c) and less than the first Al composition ratio and doped with a p-type dopant having a predetermined concentration, and an n-type dopant of a predetermined amount or more is doped at the interface between the electron blocking layer (51, 52) and the p-type cladding layer (70).

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] As a conventional nitride semiconductor light emitting element, there is a nitride semiconductor light emitting element including a light emitting layer formed of AlGaN and emitting deep ultraviolet light (see Patent Document 1), for example.

[0003] The nitride semiconductor light-emitting element described in Patent Document 1 has a stacked structure, which is formed by stacking an n-type semiconductor layer, a light-emitting layer having a quantum well structure including a well layer and a barrier layer containing AlGaN, an electron blocking layer having an Al composition larger than that of the barrier layer, a p-type cladding layer formed on the electron blocking layer, and a p-type contact layer formed on the p-type cladding layer.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6001756 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] However, according to the nitride semiconductor light-emitting element described in Patent Document 1, since an electron blocking layer with a large Al composition is provided, there is a large difference in Al composition between the electron blocking layer and the p-type cladding layer, which may shorten the light emission lifetime due to quality degradation caused by lattice mismatch.

[0009] Therefore, an object of the present invention is to provide a nitride semiconductor light emitting element and a method for manufacturing a nitride semiconductor light emitting element, which can suppress the reduction of the light emitting lifetime even in the case of having an electron blocking layer with an Al composition ratio of a certain size or more.

[0010] Solutions for solving problems

[0011] The present invention aims to solve the above-mentioned problems and provides a nitride semiconductor light-emitting element, comprising: a light-emitting layer, which includes a well layer formed of AlGaN and emits ultraviolet light; an electron blocking layer, which is located on the above-mentioned light-emitting layer and is formed of AlGaN having a first Al composition ratio larger than the Al composition ratio of the above-mentioned well layer; and a p-type cladding layer, which is located on the above-mentioned electron blocking layer and is formed of AlGaN having a second Al composition ratio larger than the above-mentioned Al composition ratio of the well layer and smaller than the above-mentioned first Al composition ratio, and is doped with a p-type dopant having a specified concentration, and an n-type dopant of a predetermined amount or more is doped at the interface between the above-mentioned electron blocking layer and the above-mentioned p-type cladding layer.

[0012] In addition, the present invention provides a method for manufacturing a nitride semiconductor light-emitting element, comprising: a process of forming a light-emitting layer, wherein the light-emitting layer includes a well layer formed of AlGaN and emits ultraviolet light; a process of forming an electron blocking layer on the light-emitting layer, wherein the electron blocking layer is formed of AlGaN having a first Al composition ratio greater than the Al composition ratio of the well layer; a process of intermittently supplying an n-type dopant and a p-type dopant to an upper surface of the electron blocking layer; and a process of forming a p-type cladding layer on the electron blocking layer, wherein the p-type cladding layer is formed of AlGaN having a second Al composition ratio greater than the Al composition ratio of the well layer and smaller than the first Al composition ratio, and is doped with a p-type dopant having a specified concentration.

[0013] Effects of the Invention

[0014] According to the present invention, a nitride semiconductor light emitting element and a method for manufacturing a nitride semiconductor light emitting element can be provided, which can suppress a decrease in light emission lifetime even when an electron blocking layer having an Al composition ratio of a certain size or more is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram schematically showing the structure of a nitride semiconductor light-emitting element according to one embodiment of the present invention.

[0016] Figure 2 1 and 2 are diagrams schematically showing an example of control of switching the supply of Si and Mg, wherein (a) is a timing chart and (b) is a diagram showing the position of the top of a growing layer corresponding to the timing shown in (a).

[0017] Figure 3 The figures compare and show the distribution curves of Si concentration and Mg concentration of the embodiment and the comparative example, (a) is a figure showing an example of the distribution curve of Si concentration, and (b) is a figure showing an example of the distribution curve of Mg concentration.

[0018] Figure 4Graphs comparing Si concentration and Mg concentration in the intermediate layer of the Example and the Comparative Example. (a) is a graph showing Si peak concentration, and (b) is a graph showing Mg concentration.

[0019] Figure 5 Graphs comparing Si concentration and Mg concentration in a p-type cladding layer of an example and a comparative example. (a) is a graph showing Si concentration, and (b) is a graph showing Mg concentration.

[0020] Figure 6 Graphs comparing initial output and residual output of an embodiment and a comparative example are shown. (a) is a graph showing the initial output, and (b) is a graph showing the residual output.

[0021] Description of Reference Numerals

[0022] 1… Nitride semiconductor light emitting element (light emitting element)

[0023] 10…Substrate

[0024] 20…Buffer layer

[0025] 30…n-type cladding layer

[0026] 30a…show your face

[0027] 40…luminescent layer

[0028] 42a, 42b, 42c…barrier layer

[0029] 44a, 44b, 44c ... well layer

[0030] 50…Electron blocking layer stack

[0031] 51…First electron blocking layer

[0032] 52…Second electron blocking layer

[0033] 60…Middle layer

[0034] 70…p-type cladding layer

[0035] 80…p-type contact layer

[0036] 90…n-side electrode

[0037] 92…p-side electrode DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described with reference to the accompanying drawings. In addition, the embodiments described below are given as preferred specific examples of implementing the present invention, and although there are also parts that specifically illustrate various technical matters that are technically preferred, the technical scope of the present invention is not limited to the specific scheme.

[0039] (Structure of Nitride Semiconductor Light Emitting Element)

[0040] Figure 1 1 is a diagram schematically showing the structure of a nitride semiconductor light emitting element according to one embodiment of the present invention. Figure 1 The size ratio of each component shown is not necessarily consistent with the size ratio of an actual nitride semiconductor light-emitting element. The nitride semiconductor light-emitting element 1 (hereinafter, also referred to as "light-emitting element 1") includes, for example, a laser diode or a light-emitting diode (LED). In this embodiment, a light-emitting diode (LED) that emits ultraviolet light (including deep ultraviolet light) with a central wavelength of 250 nm to 360 nm is used as an example for explanation.

[0041] like Figure 1 As shown, the light emitting element 1 is composed of a substrate 10, a buffer layer 20, an n-type cladding layer 30, a light emitting layer 40, an electron blocking layer stack 50, an intermediate layer 60, a p-type cladding layer 70, and a p-type contact layer 80 in this order. In addition, the light emitting element 1 further includes: a cathode side electrode (also referred to as "n-side electrode") 90, which is provided on the n-type cladding layer 30; and an anode side electrode (also referred to as "p-side electrode") 92, which is provided on the p-type contact layer 80. The following describes each component.

[0042] (1)Substrate 10

[0043] The substrate 10 is made of, for example, sapphire (Al 2 O 3 ) is a sapphire substrate formed of aluminum nitride (AlN). In addition, the substrate 10 may also be an AlN single crystal substrate formed of aluminum nitride (AlN).

[0044] (2) Buffer layer 20

[0045] The buffer layer 20 is a layer formed of AlN or AlGaN. In order to make the buffer layer 20 flat, the film thickness of the buffer layer 20 is preferably 1.5 μm or more and 4.5 μm or less. The buffer layer 20 may have a single layer structure or a multilayer structure. In addition, the buffer layer 20 may not necessarily be provided.

[0046] (3) n-type cladding layer 30

[0047] The n-type cladding layer 30 is a layer formed of n-type AlGaN, for example, an AlGaN layer doped with silicon (Si) as an n-type impurity (hereinafter also referred to as an "n-type dopant."). In addition, as an n-type dopant, oxygen (О), germanium (Ge), selenium (Se) or tellurium (Te) may also be used. The n-type cladding layer 30 has a film thickness of not less than 1 μm and not more than 4 μm, preferably a film thickness of not less than 2 μm and not more than 3 μm. The n-type cladding layer 30 may be a single-layer structure or a multi-layer structure.

[0048] (4) Light-emitting layer 40

[0049] The light emitting layer 40 is a layer formed by alternately stacking barrier layers 42a, 42b, 42c formed of AlGaN and well layers 44a, 44b, 44c formed of AlGaN having an Al composition ratio smaller than the Al composition ratio of AlGaN forming the barrier layers 42a, 42b, 42c from the side of the n-type cladding layer 30. The light emitting layer 40 is configured to have a band gap of 3.4 eV or more in order to emit deep ultraviolet light having a central wavelength of 360 nm or less.

[0050] In addition, in the present embodiment, a multiple quantum well structure is provided in which the barrier layers 42a, 42b, 42c and the well layers 44a, 44b, 44c are provided with three layers each, but the barrier layers 42a, 42b, 42c and the well layers 44a, 44b, 44c are not necessarily limited to three layers each, and may be two layers each, or may be four or more layers each. In addition, a single quantum well structure in which the barrier layers and the well layers are provided with one layer each may also be provided.

[0051] (5) Electron Blocking Layer 50

[0052] The electron blocking stack 50 has a structure in which a plurality of electron blocking layers 51 and 52 are stacked. The electron blocking stack 50 plays a role in suppressing the outflow of electrons to the intermediate layer 60 side. In the present embodiment, the electron blocking stack 50 has a structure in which a first electron blocking layer 51 located on the light emitting layer 40 side and a second electron blocking layer 52 located on the first electron blocking layer 51 are stacked. The second electron blocking layer 52 is an example of an “electron blocking layer”.

[0053] The first electron blocking layer 51 and the second electron blocking layer 52 are layers formed of p-type AlGaN, for example, AlGaN layers doped with magnesium (Mg) as a p-type impurity (hereinafter also referred to as a "p-type dopant.") In addition, zinc (Zn), beryllium (Be), calcium (Ca), strontium (Sr), barium (Ba), or carbon (C) may also be used as a p-type dopant.

[0054] The Al composition ratio of AlGaN forming the first electron blocking layer 51 is greater than the Al composition ratio of AlGaN forming the second electron blocking layer 52. In addition, the Al composition ratio of AlGaN forming the second electron blocking layer 52 is greater than the Al composition ratio of AlGaN forming the well layers 44a, 44b, and 44c. The Al composition ratio of the second electron blocking layer 52 is an example of the “first Al composition ratio”.

[0055] In addition, the first electron blocking layer 51 and the second electron blocking layer 52 do not necessarily need to be formed of p-type AlGaN, and may also be formed of neutral AlGaN. In addition, the second electron blocking layer 52 does not necessarily need to be provided. Moreover, the electron blocking layer stack 50 may also include three or more electron blocking layers.

[0056] (6) Intermediate layer 60

[0057] The intermediate layer 60 functions as a dislocation suppression layer that suppresses the generation and growth of crystal defects such as dislocations and improves the crystal quality. The intermediate layer 60 is formed of p-type AlGaN doped with a predetermined amount or more of an n-type dopant. The intermediate layer 60 is an example of a "co-doped layer". The Al composition ratio forming the intermediate layer 60 takes a value between the Al composition ratio of the second electron blocking layer 52 and the Al composition ratio of the p-type cladding layer 70. In addition, the intermediate layer 60 does not necessarily have to be formed of p-type AlGaN, and can also be formed of n-type AlGaN or neutral AlGaN.

[0058] 〔n-type dopant〕

[0059] The n-type dopant included in the intermediate layer 60 is preferably Si. Alternatively, the n-type dopant included in the intermediate layer 60 may be oxygen, germanium, selenium, tellurium, or the like as described above.

[0060] In addition, the n-type dopant has a maximum value (hereinafter also referred to as a “concentration peak”) of the concentration distribution in the height direction of the light-emitting element 1 in the intermediate layer 60. In other words, the n-type dopant has a concentration peak in the height direction of the light-emitting element 1 between the second electron blocking layer 52 and the p-type cladding layer 70.

[0061] The value of the concentration peak of the n-type dopant (hereinafter also referred to as “concentration peak value” or “peak concentration”) is 4.0×10 18 cm -3 Above 1.0×10 20 cm -3 Below, preferably 5.0×10 18 cm -3 Above 5.0×10 19 cm -3 In addition, the unit of concentration is number cm -3 (atoms·cm-3 ), the string "atoms" is omitted and referred to as "cm -3 ”.

[0062] 〔p-type dopant〕

[0063] The p-type dopant contained in the intermediate layer 60 is preferably Mg. In addition, the p-type dopant contained in the intermediate layer 60 may also use the above-mentioned zinc, beryllium, calcium, strontium, barium or carbon. The concentration of the p-type dopant is 1.0×10 18 cm -3 Above 1.0×10 20 cm -3 The p-type dopant preferably has a concentration peak in the intermediate layer 60 . In other words, the p-type dopant has a concentration peak in the height direction of the light emitting element 1 between the second electron blocking layer 52 and the p-type cladding layer 70 .

[0064] (7) p-type cladding layer 70

[0065] The p-type cladding layer 70 is a layer formed of p-type AlGaN. The Al composition ratio of AlGaN forming the p-type cladding layer 70 is greater than the Al composition ratio of AlGaN forming the well layers 44a, 44b, and 44c. The Al composition ratio of AlGaN forming the p-type cladding layer 70 is an example of the “second Al composition ratio”.

[0066] The p-type cladding layer 70 has a film thickness of not less than 10 nm and not more than 1000 nm, preferably a film thickness of not less than 20 nm and not more than 800 nm. In addition, the p-type cladding layer 70 includes: the above-mentioned n-type dopant doped in the intermediate layer 60 diffuses from the intermediate layer 60 to a region from the top of the second electron blocking layer 52 side (i.e., the interface with the intermediate layer 60) to a predetermined position. In other words, the p-type cladding layer 70 includes a diffusion region formed by the diffusion of the n-type dopant from the intermediate layer 60. Here, the so-called "diffusion" refers to the movement of the n-type dopant doped in the intermediate layer 60 to the p-type cladding layer 70 with the heat applied when the p-type cladding layer 70 is crystal-grown as a driving force.

[0067] 〔p-type dopant〕

[0068] The p-type dopant contained in the p-type cladding layer 70 is preferably Mg. In addition, the p-type dopant contained in the p-type cladding layer 70 may also use the above-mentioned zinc, beryllium, calcium, strontium, barium or carbon. The concentration of the p-type dopant is 1.0×10 18 cm -3 Above 1.0×10 20 cm -3 the following.

[0069] 〔n-type dopant〕

[0070] The n-type dopant included in the p-type cladding layer 70 is preferably Si. In addition, the n-type dopant included in the p-type cladding layer 70 may also use the above-mentioned oxygen, germanium, selenium, or tellurium. It is believed that the n-type dopant combines with the inert p-type dopant (Mg in this case) that does not contribute to the p-type conversion of AlGaN, thereby playing the role of suppressing the decrease in the light output of the light-emitting element 1 that may occur due to the diffusion of the p-type dopant into the light-emitting layer 40 when the light-emitting element 1 is energized.

[0071] The concentration of the n-type dopant contained in the p-type cladding layer 70 is 1 / 2 or less, and preferably 1 / 80 to 1 / 4 of the concentration of the p-type dopant contained in the p-type cladding layer 70 .

[0072] (8) p-type contact layer 80

[0073] The p-type contact layer 80 is, for example, a p-type GaN layer doped with a p-type dopant such as Mg at a high concentration. Alternatively, the p-type contact layer 80 may be, for example, a layer formed of p-type AlGaN having an Al composition ratio of 10% or less.

[0074] (9) n-side electrode 90

[0075] The n-side electrode 90 is formed on a part of the n-type cladding layer 30. The n-side electrode 90 is formed of a multilayer film in which titanium (Ti) / aluminum (Al) / Ti / gold (Au) are stacked in this order on the n-type cladding layer 30, for example.

[0076] (10) P-side electrode 92

[0077] The p-side electrode 92 is formed on the p-type contact layer 80. The p-side electrode 92 is formed of, for example, a multilayer film of nickel (Ni) / gold sequentially stacked on the p-type contact layer 80. Alternatively, the p-side electrode 92 may be a reflective electrode formed of rhodium (Rh) or the like.

[0078] (Method for Manufacturing Light Emitting Element 1)

[0079] Next, a description will be given of a method for manufacturing the light emitting element 1. Here, two methods ("method 1" and "method 2") will be described as examples.

[0080] <Method 1>

[0081] First, the buffer layer 20, the n-type cladding layer 30, the light-emitting layer 40, the first electron blocking layer 51 and the electron blocking layer 52 are sequentially formed by high-temperature growth (hereinafter referred to as "film formation") on the substrate 10. The film formation of each layer is performed in a chamber.

[0082] The buffer layer 20, the n-type cladding layer 30, the light-emitting layer 40, the first electron blocking layer 51 and the second electron blocking layer 52 can be formed by using a well-known epitaxial growth method such as metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and hydride vapor phase epitaxy (HVPE). In addition, in order to supply AlGaN, trimethylaluminum (TMA) is used as an Al source, trimethylgallium (TMG) is used as a Ga source, and ammonia (NH 3 ) as the N source.

[0083] After the film is formed up to the second electron blocking layer 52, the substance in the state of being formed up to the second electron blocking layer 52 (hereinafter also referred to as the "intermediate") is temporarily taken out of the chamber into the atmosphere. Next, the intermediate taken out from the chamber is treated to be doped with Si and O, and then it is returned to the chamber again. The treatment described here may include, for example, a process for setting up an evaluation process by the PL (Photo Luminescence) method, etc., but the method is not limited as long as Si and O are doped. Next, the p-type cladding layer 70 is formed on the second electron blocking layer 52 using the above-mentioned epitaxial growth method. When the intermediate is taken out into the atmosphere, silicon and oxygen are introduced into the interface between the second electron blocking layer 52 and the p-type cladding layer 70. In this way, the intermediate layer 60 doped with both Si and O is formed between the second electron blocking layer 52 and the p-type cladding layer 70.

[0084] After the p-type cladding layer 70 is formed, the p-type contact layer 80 is further stacked on the p-type cladding layer 70 using the above-mentioned epitaxial growth method to form a circular plate-shaped nitride semiconductor stack (also called a "wafer" or "chip") having a specified diameter (for example, about 50 mm).

[0085] Next, a mask is formed on the p-type contact layer 80, and the exposed regions where the mask is not formed in a portion of the thickness direction of the n-type cladding layer 30, the light emitting layer 40, the electron blocking layer stack 50, the intermediate layer 60, the p-type cladding layer 70, and the p-type contact layer 80 are removed. Removal of these layers can be performed, for example, by plasma etching.

[0086] On the exposed surface 30a of the n-type cladding layer 30 (see Figure 1 ) is formed on the n-side electrode 90, and the p-side electrode 92 is formed on the p-type contact layer 80 from which the mask is removed. The n-side electrode 90 and the p-side electrode 92 can be formed by a well-known method such as electron beam evaporation method, sputtering method, etc. By cutting the wafer into a predetermined size, Figure 1 The light-emitting element 1 is shown.

[0087] <Method 2>

[0088] Next, method 2 is described. Detailed description of the same contents as those of method 1 is sometimes omitted. The buffer layer 20, n-type cladding layer 30, light emitting layer 40, first electron blocking layer 51 and electron blocking layer 52 are sequentially formed on substrate 10 by high temperature growth.

[0089] Next, a predetermined amount or more of n-type dopant is supplied to the upper surface of the second electron blocking layer 52 to form the intermediate layer 60 at the interface between the second electron blocking layer 52 and the p-type cladding layer 70. Figure 2 Let me explain in detail.

[0090] Figure 2 This is a diagram schematically showing an example of control of switching the supply of Si, which is an example of an n-type dopant, and Mg, which is an example of a p-type dopant. Figure 2 In (a), the horizontal axis is the time axis, and the vertical axis represents the presence or absence of supply of Si and Mg ("ON", "OFF"). Figure 2 (b) is shown with Figure 2 (a) is a schematic diagram showing the position of the top of the growing layer at the time indicated by the numbers in the brackets. Figure 2 In (b), dopants intentionally added during the formation of each layer are described, and the state after diffusion is not shown. For example, TMSi (tetramethylsilane) is used as a Si supply source, and Cp2Mg (biscyclopentadienyl magnesium) is used as a Mg supply source.

[0091] like Figure 2 As shown in the figures, after the second electron blocking layer 52 is grown (refer to Figure 2 ), intermittently supplying n-type dopants and p-type dopants. Specifically, the supply of Mg used for the growth of the second electron blocking layer 52 is stopped ("ON"→"OFF"), and the supply of Si to the upper surface of the second electron blocking layer 52 is started ("OFF"→"ON"). The supply of Si is continued for a certain period (also referred to as "supply time") Δt. The supply time Δt is preferably not less than 5 seconds and not more than 18 seconds.

[0092] Next, after the supply time Δt has passed, the supply of Si is stopped (“ON”→“OFF”), and the supply of Mg is restarted (“OFF”→“ON”). In the above manner, the intermediate layer 60 containing both Si and Mg is formed.

[0093] After forming the intermediate layer 60 (refer to Figure 2), using the above-mentioned epitaxial growth method, a p-type cladding layer 70 is formed on the intermediate layer 60 (refer to Figure 2 At this time, Si also diffuses into the p-type cladding layer 70 .

[0094] The following is the same as the above-mentioned method 1. That is, a p-type contact layer 80 is further stacked on the p-type cladding layer 70, a mask is formed on the p-type contact layer 80, and a portion of the thickness direction of the n-type cladding layer 30, the light-emitting layer 40, the electron blocking layer stack 50, the intermediate layer 60, the p-type cladding layer 70, and the p-type contact layer 80, where the exposed regions are not masked, are removed, and the exposed surface 30a (refer to Figure 1 ), an n-side electrode 90 is formed on the wafer, a p-side electrode 92 is formed on the p-type contact layer 80 from which the mask has been removed, and the wafer is cut into pieces of a predetermined size to form the light-emitting element 1.

[0095] (Example)

[0096] Reference Figures 3 to 5 Hereinafter, the examples of the above-mentioned embodiments will be described. Hereinafter, regarding the examples of the above-mentioned embodiments, four light-emitting elements 1 of Examples 1 to 4 and one light-emitting element of the comparative example are listed and compared with each other for description. The light-emitting element 1 of Example 1 is manufactured by the above-mentioned method 1, and the light-emitting elements 1 of Examples 2 to 4 are respectively manufactured by the method 2. In contrast, the comparative example is configured not to have the above-mentioned intermediate layer 60. The dopants used in each example are summarized in the following Table 1.

[0097]

Table 1

[0098] Table 1: Types of dopants

[0099]

[0100] Table 2 summarizes the Al composition ratios of AlGaN forming the respective layers of Examples 1 to 4.

[0101]

Table 2

[0102] Table 2: Al composition ratio of each layer

[0103]

[0104] The Al composition ratio of the layers other than the p-type contact layer 80 and the first electron blocking layer 51 is a value calculated from the wavelength of photoluminescence (PL) measurement by thickening each layer to a single layer.

[0105] Figure 3The figures compare and show the distribution curves of Si concentration and Mg concentration of the light-emitting element 1 of Examples 1 to 4 and the comparative example, (a) is a figure showing an example of the distribution curve of Si concentration, and (b) is a figure showing an example of the distribution curve of Mg concentration. Figure 3 (a) shows the Si concentration and Figure 3 The distribution curves of Mg concentration shown in (b) are calculated based on the Al secondary ion intensity (not shown) measured by SIMS (Secondary Ion Mass Spectrometry). Figure 3 In the diagram, the position of the upper surface of the p-type contact layer 80 is set as the starting point of the depth measurement (ie, the measurement depth=0), and the direction of the substrate 10 side is set as the positive direction.

[0106] like Figure 3 As shown in (a), in the light-emitting elements 1 of Examples 1 to 4, the distribution local maximum of Si concentration exists in the intermediate layer 60. In contrast, in the light-emitting element of the comparative example, the distribution local maximum of Si concentration does not exist at the position corresponding to the depth of the intermediate layer 60 of Examples 1 to 4. Figure 3 As shown in (b) of FIG. 1 , in the light-emitting element 1 of Example 4 among Examples 1 to 4, a local maximum value of the Mg concentration distribution exists in the intermediate layer 60 .

[0107] The Si concentration peak, O concentration peak, n-type dopant concentration peak, and Mg concentration of the intermediate layer 60, and the Si concentration, O concentration, and Mg concentration of the p-type cladding layer 70 are summarized in the following Table 3. In addition, the Mg concentration of the intermediate layer 60 is set to the average value of the Mg concentration in the depth direction of the intermediate layer 60, and the Si concentration, O concentration, and Mg concentration of the p-type cladding layer 70 are set to the average value of the Si concentration, the average value of the O concentration, and the average value of the Mg concentration in the depth direction of the p-type cladding layer 70, respectively. In Example 1, the "n-type dopant peak concentration" is set to the total value of the "Si peak concentration" and the "O peak concentration", and the "n-type dopant concentration" is set to the total value of the "Si concentration" and the "O concentration".

[0108]

Table 3

[0109] Table 3: Dopants of the intermediate layer 60 and the p-type cladding layer 70

[0110]

[0111] In addition, as described above, the light-emitting element of the comparative example does not have a layer equivalent to the intermediate layer 60 of the light-emitting element 1 of Examples 1 to 4. Therefore, the "Si peak concentration" of the comparative example shows the average value within the depth range corresponding to the intermediate layer 60 of the light-emitting element 1 of Examples 1 to 4.

[0112] Figure 4 (a) is a graph comparing the Si peak concentration of the intermediate layer 60 shown in Table 3 between Examples 1 to 4 and the comparative example, and (b) is a graph comparing the Mg concentration of the intermediate layer 60 shown in Table 3 between Examples 1 to 4 and the comparative example. Figure 4 As shown in (a), the Si peak concentrations of Examples 1 to 4 are greater than the Si peak concentration of the comparative example (i.e., the average value of the Si concentration within the depth range corresponding to the intermediate layer 60 of the light emitting element 1 of Examples 1 to 4). In addition, as shown in Table 3, in Examples 1 to 4, the peak concentration of Si in the intermediate layer 60 is 3.08×10 18 cm -3 Above 2.13×10 19 cm -3 In Examples 1 to 4, the Mg concentration of the intermediate layer 60 is in the range of 7.72×10 18 cm -3 Above 1.38×10 19 cm -3 the following.

[0113] Figure 5 (a) is a graph comparing the Si concentration of the p-type cladding layer 70 shown in Table 3 between Examples 1 to 4 and the comparative example, and (b) is a graph comparing the Mg concentration of the p-type cladding layer 70 shown in Table 3 between the comparative example and Examples 1 to 4. Figure 5 As shown in (a), the Si concentration of Examples 1 to 4 is greater than that of the Comparative Example. In addition, as shown in Table 3, in Examples 1 to 4, it is 8.29×10 16 cm -3 Above 1.86×10 18 cm -3 In Examples 1 to 4, the Mg concentration of the p-type cladding layer 70 is in the range of 1.07×10 19 cm -3 Above 1.64×10 19 cm -3 the following.

[0114] In Examples 1 to 4, the ratio of the n-type dopant (Si concentration + O concentration) to the p-type dopant (Mg concentration) in the p-type cladding layer 70 was 1.73×10 -2 , 1.20×10 -2 , 5.91×10 -2 and 1.14×10 -1 , which ranges from 1.20×10 -2 Above 1.14×10-1 That is, in Examples 1 to 4, the Si concentration of the p-type cladding layer 70 is 1.20×10 -2 times more than 1.14×10 -1 That is, in Examples 1 to 4, the Si concentration of the p-type cladding layer 70 is 1 / 2 or less of the Mg concentration of the p-type cladding layer 70 .

[0115] In particular, in Examples 1, 3, and 4, the ratio of the Si concentration to the Mg concentration of the p-type cladding layer 70 (1.73×10 -2 , 5.91×10 -2 and 1.14×10 -1 ) is a value within the above-mentioned range of not less than 1 / 80 and not more than 1 / 4.

[0116] (Luminescence lifetime)

[0117] Next, the measurement results of the luminescence lifetime of the light-emitting element 1 of the above-mentioned Examples 1 to 4 are described. The luminescence lifetime is evaluated using the initial luminescence output (hereinafter, also referred to as the "initial output") and the ratio of the luminescence output measured after the power is turned on for a specified time (hereinafter, also referred to as the "residual output"). Here, the initial output is set to the light output obtained from the light-emitting element during manufacturing. In addition, the power-on time is set to 192 hours. In addition, the luminescence output can be measured by various well-known methods, but in this measurement, as an example, a certain current (for example, 350 mA) is passed between the above-mentioned n-side electrode 90 and the p-side electrode 92, and the measurement is performed by a photodetector arranged on the lower side of the light-emitting element 1.

[0118] The measurement results of the initial output and the residual output are summarized in Table 4 below.

[0119]

Table 4

[0120] Table 4: Results of determination of initial output and residual output

[0121]

[0122] (※ 1 ) is the initial light output measured when the light emitting element is manufactured. The current value is set to 350 mA.

[0123] (※ 2 ) is the light output measured after the light emitting element was energized for 192 hours. The current value was set to 350 mA.

[0124] (※ 3 ) is the residual output divided by the initial output (dimensionless units).

[0125] Figure 6 The initial output and residual output of the embodiment and the comparative example are compared and shown in the coordinate graph, (a) is a coordinate graph showing the initial output, and (b) is a coordinate graph showing the residual output. As shown in Table 4 and Figure 6 As shown in the figure, the residual ratio decreased to 46% in the comparative example, but decreased to 60% in Example 1, 53% in Example 2, 67% in Example 3, and 85% in Example 4. As shown in the measurement results, it was confirmed that the residual ratio of the light-emitting element 1 of Examples 1 to 4 was greater than that of the light-emitting element of the comparative example.

[0126] A large residual ratio means that the decrease in luminous output after 192 hours of power-on is small relative to the initial output, that is, the luminous lifetime is improved. Therefore, based on the above measurement results, it is confirmed that the luminous lifetime of the light-emitting element 1 of Examples 1 to 4 is improved compared with the light-emitting element of the comparative example.

[0127] <Modification>

[0128] The light emitting element 1 only needs to be doped with a predetermined amount or more of n-type dopant at the interface between the second electron blocking layer 52 and the p-type cladding layer 70, and it is not necessary to have a layer-like intermediate layer 60 as in the above-mentioned embodiment and its examples. For example, the intermediate layer 60 having a layer-like form may not be provided, and the n-type dopant may be doped in a specific region formed from the interface with the second electron blocking layer 52 to a predetermined position in the p-type cladding layer 70.

[0129] In addition, in the above-mentioned embodiment, for the sake of convenience, the intermediate layer 60 is described as a layer different from the p-type cladding layer 70, but the structure in which the p-type cladding layer 70 has the intermediate layer 60 on the second electron blocking layer 52 side therein is also within the technical scope of the light-emitting element 1 of the present invention.

[0130] (Summary of Implementation Methods)

[0131] Next, the technical ideas grasped from the above-described embodiments are described using the reference numerals in the embodiments. However, the reference numerals in the following description do not limit the constituent elements in the claims to the members specifically shown in the embodiments.

[0132] [1] A nitride semiconductor light-emitting element (1) comprises: a light-emitting layer (40) comprising a well layer (44a, 44b, 44c) formed of AlGaN, emitting ultraviolet light; an electron blocking layer, located on the light-emitting layer (40), formed of AlGaN having a first Al composition ratio greater than the Al composition ratio of the well layer (44a, 44b, 44c); and a p-type cladding layer (70), located on the electron blocking layer, formed of AlGaN having a second Al composition ratio greater than the Al composition ratio of the well layer (44a, 44b, 44c) and less than the first Al composition ratio, and doped with a p-type dopant having a specified concentration, wherein an n-type dopant greater than a predetermined amount is doped at an interface between the electron blocking layer and the p-type cladding layer (70).

[0133] [2] According to the nitride semiconductor light-emitting element (1) described in [1] above, the p-type cladding layer (70) includes a diffusion region formed by diffusing the n-type dopant from the top of the electron blocking layer side toward a predetermined position.

[0134] [3] The nitride semiconductor light-emitting element (1) according to [2] above, wherein the concentration of the n-type dopant contained in the diffusion region is less than 1 / 2 of the concentration of the p-type dopant.

[0135] [4] The nitride semiconductor light-emitting element (1) according to [2] or [3] above, wherein the concentration of the n-type dopant contained in the diffusion region is greater than 1 / 80 and less than 1 / 4 of the concentration of the p-type dopant.

[0136] [5] The nitride semiconductor light-emitting device (1) according to any one of [1] to [4], wherein the concentration of the p-type dopant in the p-type cladding layer is 1.0×10 18 atoms·cm -3 Above 1.0×10 20 atoms·cm -3 the following.

[0137] [6] A nitride semiconductor light-emitting element (1) according to any one of [2] to [5] above, wherein in the diffusion region, there exists a maximum value of the distribution of the concentration of the n-type dopant in the thickness direction of the nitride semiconductor light-emitting element (1).

[0138] [7] The nitride semiconductor light-emitting device (1) according to [6], wherein the maximum value of the n-type dopant is 4.0×10 18 atoms·cm -3 Above 1.0×10 20 atoms·cm-3 the following.

[0139] [8] The nitride semiconductor light-emitting device (1) according to any one of [1] to [7], wherein the concentration of the p-type dopant at the interface between the electron blocking layer and the p-type cladding layer (70) is 1.0×10 18 atoms·cm -3 Above 1.0×10 20 atoms·cm -3 the following.

[0140] [9] The nitride semiconductor light-emitting element (1) according to [8] above, wherein, at the interface, there exists a maximum value of the distribution of the concentration of the p-type dopant in the thickness direction of the nitride semiconductor light-emitting element (1).

[0141]

[10] A method for manufacturing a nitride semiconductor light-emitting element (1), comprising: a step of forming a light-emitting layer (40), wherein the light-emitting layer (40) includes a well layer (44a, 44b, 44c) formed of AlGaN and emits ultraviolet light; a step of forming an electron blocking layer on the light-emitting layer (40), wherein the electron blocking layer is formed of AlGaN having a first Al composition ratio greater than the Al composition ratio of the well layer (44a, 44b, 44c); a step of intermittently supplying an n-type dopant and a p-type dopant to an upper surface of the electron blocking layer; and a step of forming a p-type cladding layer (70) on the electron blocking layer, wherein the p-type cladding layer (70) is formed of AlGaN having a second Al composition ratio greater than the Al composition ratio of the well layer (44a, 44b, 44c) and less than the first Al composition ratio, and is doped with a p-type dopant having a specified concentration.

Claims

1. A nitride semiconductor light emitting element, characterized in that: have: a light emitting layer including a well layer formed of AlGaN and emitting ultraviolet light; an electron blocking layer, which is located on the light emitting layer and is formed of AlGaN having a first Al composition ratio greater than the Al composition ratio of the well layer; and a p-type cladding layer located on the electron blocking layer, formed of AlGaN having a second Al composition ratio greater than the Al composition ratio of the well layer and smaller than the first Al composition ratio, and doped with a p-type dopant having a predetermined concentration, The p-type cladding layer includes a diffusion region formed by diffusion of an n-type dopant from an interface between the electron blocking layer and the p-type cladding layer toward a predetermined position. The concentration of the p-type dopant in the p-type cladding layer is 1.0×10 18 atoms·cm -3 Above 1.0×10 20 atoms·cm -3 the following, The concentration of the n-type dopant contained in the diffusion region is less than 1 / 2 of the concentration of the p-type dopant. The interface between the electron blocking layer and the p-type cladding layer is doped with a predetermined amount or more of the n-type dopant.

2. The nitride semiconductor light emitting element according to claim 1, wherein: The concentration of the n-type dopant included in the diffusion region is not less than 1 / 80 and not more than 1 / 4 of the concentration of the p-type dopant.

3. The nitride semiconductor light emitting element according to claim 1, wherein: In the diffusion region, there is a local maximum value of the distribution of the concentration of the n-type dopant in the thickness direction of the nitride semiconductor light emitting element.

4. The nitride semiconductor light emitting element according to claim 3, wherein: The above-mentioned maximum value of the above-mentioned n-type dopant is 4.0×10 18 atoms·cm -3 Above 1.0×10 20 atoms·cm -3 the following.

5. The nitride semiconductor light emitting device according to claim 1, wherein: The concentration of the p-type dopant in the above interface is 1.0×10 18 atoms·cm -3 Above 1.0×10 20 atoms·cm -3 the following.

6. The nitride semiconductor light emitting element according to claim 5, wherein: At the interface, there is a local maximum value of the distribution of the concentration of the p-type dopant in the thickness direction of the nitride semiconductor light-emitting element.

7. A method for manufacturing a nitride semiconductor light-emitting element, characterized in that: Include: A step of forming a light-emitting layer, wherein the light-emitting layer includes a well layer formed of AlGaN and emits ultraviolet light; forming an electron blocking layer on the light emitting layer, wherein the electron blocking layer is formed of AlGaN having a first Al composition ratio greater than the Al composition ratio of the well layer; A step of intermittently supplying an n-type dopant and a p-type dopant to the upper surface of the electron blocking layer; and forming a p-type cladding layer on the electron blocking layer, wherein the p-type cladding layer is made of AlGaN having a second Al composition ratio greater than that of the well layer and smaller than the first Al composition ratio, and is doped with a p-type dopant having a predetermined concentration, The p-type cladding layer includes a diffusion region in which the n-type dopant diffuses from an interface between the electron blocking layer and the p-type cladding layer toward a predetermined position. The concentration of the p-type dopant in the p-type cladding layer is 1.0×10 18 atoms·cm -3 Above 1.0×10 20 atoms·cm -3 the following, The concentration of the n-type dopant included in the diffusion region is less than or equal to 1 / 2 of the concentration of the p-type dopant.

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