Nitride-based semiconductor light-emitting device

Abstract

A nitride-based semiconductor light-emitting device (100) emits light and comprises an N-type cladding layer (104), an N-side light guide layer (106), an active layer (107), an electron barrier layer (109), a P-type intermediate layer (110), a P-side light guide layer (111), and a P-type cladding layer (112). The average band gap energy of the electron barrier layer (109) is greater than the average band gap energy of the P-type cladding layer (112). The average band gap energy of the P-type intermediate layer (110) is greater than the average band gap energy of the P-side light guide layer (111), and less than the average band gap energy of the electron barrier layer (109). The average impurity concentration of the P-type intermediate layer (110) is lower than the average impurity concentration of the electron barrier layer (109) and higher than the average impurity concentration of the P-side light guide layer (111). The peak wavelength of the light emitted is less than 400 nm.

Description

Nitride-based semiconductor light-emitting device

[0001] The present disclosure relates to a nitride-based semiconductor light-emitting device.

[0002] Conventionally, nitride-based semiconductor light-emitting elements, such as nitride-based semiconductor laser elements, that emit light in the ultraviolet region have been known (see, for example, Patent Document 1). Light in the ultraviolet region has higher energy than visible light, and therefore light absorption is particularly significant in optical guide layers, which have relatively small band gap energy. For example, in the nitride-based semiconductor laser element described in Patent Document 1, the band gap energy is increased by increasing the Al composition ratio of each semiconductor layer, such as the optical guide layer and cladding layer. This is intended to suppress light absorption in each semiconductor layer.

[0003] JP 2010-258363 A

[0004] However, increasing the Al composition ratio of each semiconductor layer increases stress within the semiconductor stack due to lattice mismatch with the GaN substrate of the nitride-based semiconductor laser element. This makes the semiconductor stack more susceptible to breakage, cracks, defects, and the like. Furthermore, increasing the Al composition ratio of each semiconductor layer reduces the proportion of impurities that function as acceptors or donors among the impurities doped into each semiconductor layer. This increases the electrical resistance of each semiconductor layer, thereby increasing the operating voltage of the nitride-based semiconductor laser element.

[0005] The present disclosure is intended to solve such problems, and aims to suppress optical loss while reducing the Al composition ratio in each semiconductor layer in a nitride-based semiconductor light-emitting element that emits light in the ultraviolet region.

[0006] In order to solve the above problems, one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure is a nitride-based semiconductor light-emitting device that emits light, comprising: a substrate; an N-type cladding layer that is disposed above the substrate and contains Al; an N-side optical guide layer that is disposed above the N-type cladding layer and contains Al; an active layer that is disposed above the N-side optical guide layer and includes a well layer and a barrier layer that contains Al; an electron barrier layer that is disposed above the active layer and contains Al; a P-type intermediate layer that is disposed above the electron barrier layer and contains Al; a P-side optical guide layer that is disposed above the P-type intermediate layer and contains Al; and a P-type cladding layer containing Al and disposed above the electron barrier layer, wherein the average band gap energy of the electron barrier layer is greater than the average band gap energy of the P-type cladding layer, the average band gap energy of the P-type intermediate layer is greater than the average band gap energy of the P-side optical guiding layer and less than the average band gap energy of the electron barrier layer, the average impurity concentration of the P-type intermediate layer is lower than the average impurity concentration of the electron barrier layer and higher than the average impurity concentration of the P-side optical guiding layer, and the peak wavelength of the light is less than 400 nm.

[0007] In order to solve the above-described problems, another aspect of the nitride-based semiconductor light-emitting device according to the present disclosure is a nitride-based semiconductor light-emitting device that emits light, comprising: a substrate; an N-type cladding layer that is disposed above the substrate and contains Al; an N-type intermediate layer that is disposed above the N-type cladding layer and contains Al; an N-side optical guide layer that is disposed above the N-type intermediate layer and contains Al; an active layer that is disposed above the N-side optical guide layer and includes a well layer and a barrier layer that contains Al; a P-side optical guide layer that is disposed above the active layer and contains Al; and a P-type cladding layer that is disposed above the P-side optical guide layer and contains Al;

[0008] According to the present disclosure, in a nitride-based semiconductor light-emitting device that emits light in the ultraviolet region, it is possible to reduce the Al composition ratio in each semiconductor layer while suppressing optical loss.

[0009] 1 is a schematic plan view showing the overall configuration of a nitride-based semiconductor light-emitting device according to a first embodiment. FIG. 2 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the first embodiment. FIG. 3 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting device according to a comparative example 1. FIG. 4 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting device according to the first embodiment. FIG. 5 is a graph showing the extinction coefficient spectrum of an AlGaN layer. FIG. 6 is a schematic cross-sectional view showing the shape of a side surface of a ridge according to the first embodiment. FIG. 7 is a graph showing the relationship between the order of a transverse mode of laser light in a nitride-based semiconductor light-emitting device and waveguide loss. FIG. 8 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting device according to a second embodiment. FIG. 9 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to a third embodiment. FIG. 10 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting device according to a fourth embodiment. 13 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting element according to a fifth embodiment. FIG. 14 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting element according to a sixth embodiment. FIG. 15 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to a seventh embodiment. FIG. 16 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting element according to the seventh embodiment. FIG. 17 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting element according to an eighth embodiment. FIG. 18 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting element according to a ninth embodiment. FIG. 19 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of a nitride-based semiconductor light-emitting element according to a tenth embodiment. FIG. 19 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to an eleventh embodiment.13 is a schematic graph showing the distribution of bandgap energy and impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting element according to embodiment 11. FIG. 14 is a graph showing the relationship between the waveguide loss and the Al composition ratio of the lower P-side light guiding layer of Structural Example 1 of the nitride-based semiconductor light-emitting element according to embodiment 11. FIG. 15 is a graph showing the relationship between the operating current and the Al composition ratio of the lower P-side light guiding layer when power consumption is 0.5 W of Structural Example 1 of the nitride-based semiconductor light-emitting element according to embodiment 11. FIG. 16 is a graph showing the relationship between the operating voltage value and the Al composition ratio of the lower P-side light guiding layer when power consumption is 0.5 W of Structural Example 1 of the nitride-based semiconductor light-emitting element according to embodiment 11. FIG. 17 is a graph showing the relationship between the optical confinement factor and the Al composition ratio of the lower P-side light guiding layer of Structural Example 1 of the nitride-based semiconductor light-emitting element according to embodiment 11. FIG. 18 is a graph showing the relationship between the effective refractive index difference ΔN and the Al composition ratio of the lower P-side light guiding layer of Structural Example 1 of the nitride-based semiconductor light-emitting element according to embodiment 11. 13 is a graph showing the relationship between WPE and the Al composition ratio of the lower P-side light guiding layer when power consumption is 0.5 W in Structural Example 1 of the nitride-based semiconductor light-emitting device according to Embodiment 11. FIG. 14 is a diagram showing the configurations and characteristics of Examples 1 to 4 of the nitride-based semiconductor light-emitting device according to Embodiment 11. FIG. 15 is a graph showing the relationship between the waveguide loss and the In composition ratio of the lower P-side light guiding layer in Structural Example 2 of the nitride-based semiconductor light-emitting device according to Embodiment 11. FIG. 16 is a graph showing the relationship between the operating current and the In composition ratio of the lower P-side light guiding layer when power consumption is 0.5 W in Structural Example 2 of the nitride-based semiconductor light-emitting device according to Embodiment 11. FIG. 17 is a graph showing the relationship between the operating voltage and the In composition ratio of the lower P-side light guiding layer when power consumption is 0.5 W in Structural Example 2 of the nitride-based semiconductor light-emitting device according to Embodiment 11. FIG. 18 is a graph showing the relationship between the optical confinement factor and the In composition ratio of the lower P-side light guiding layer in Structural Example 2 of the nitride-based semiconductor light-emitting device according to Embodiment 11. FIG. 19 is a graph showing the relationship between the effective refractive index difference ΔN and the In composition ratio of the lower P-side light guiding layer in Structural Example 2 of the nitride-based semiconductor light-emitting device according to Embodiment 11. 13 is a graph showing the relationship between WPE and the In composition ratio of the lower P-side optical guide layer in Configuration Example 2 of the nitride-based semiconductor light-emitting device according to Embodiment 11 when the power consumption is 0.5 W. FIG. 14 is a diagram showing the configurations and characteristics of Examples 5 to 8 of the nitride-based semiconductor light-emitting device according to Embodiment 11.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, and the arrangement and connection of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0011] Furthermore, each figure is a schematic diagram and is not necessarily an exact representation. Therefore, the scales and the like do not necessarily match in each figure. In each figure, the same reference numerals are used to denote substantially the same components, and redundant explanations will be omitted or simplified.

[0012] Furthermore, in this specification, terms indicating the relationship between elements, such as "equal," terms indicating the shape of elements, such as "flat," "parallel," "vertical," "plate-shaped," and "curved," as well as numerical ranges, are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0013] In this specification, the terms "above" and "below" do not refer to vertically above and below in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. The terms "above" and "below" are used not only when two components are arranged with a gap between them and another component is present between them, but also when two components are arranged in contact with each other.

[0014] First Embodiment A nitride-based semiconductor light-emitting device according to a first embodiment will be described.

[0015] [1-1. Overall Configuration] First, the overall configuration of the nitride-based semiconductor light-emitting device according to this embodiment will be described with reference to FIGS. 1 and 2. FIGS. 1 and 2 are a schematic plan view and a cross-sectional view, respectively, showing the overall configuration of a nitride-based semiconductor light-emitting device 100 according to this embodiment. FIG. 2 shows a cross section taken along line II-II in FIG. 1. Note that each figure shows an X-axis, a Y-axis, and a Z-axis that are orthogonal to one another. The X-axis, the Y-axis, and the Z-axis form a right-handed Cartesian coordinate system. The stacking direction of the nitride-based semiconductor light-emitting device 100 is parallel to the Z-axis direction, and the main emission direction of light (laser light) is parallel to the Y-axis direction.

[0016] As shown in FIG. 2 , the nitride-based semiconductor light-emitting element 100 includes a semiconductor stack 100S including nitride-based semiconductor layers, and emits light from a facet 100F (see FIG. 1 ) perpendicular to the stacking direction (i.e., the Z-axis direction) of the semiconductor stack 100S. In this embodiment, the nitride-based semiconductor light-emitting element 100 is a semiconductor laser element having two facets 100F and 100R that form a cavity. The facet 100F is a front facet from which laser light is emitted, and the facet 100R is a rear facet having a higher reflectivity than the facet 100F. The nitride-based semiconductor light-emitting element 100 also has a waveguide formed between the facets 100F and 100R. The reflectivities of the facets 100F and 100R are not particularly limited, but are 16% and 95%, respectively, in this embodiment. The cavity length of the nitride-based semiconductor light-emitting element 100 according to this embodiment (i.e., the distance between the facet 100F and the facet 100R) is approximately 800 μm. The peak wavelength of the light emitted by the nitride-based semiconductor light-emitting element 100 is less than 400 nm. The nitride-based semiconductor light-emitting element 100 emits ultraviolet light having a peak wavelength in the 375 nm band, for example. Note that the nitride-based semiconductor light-emitting element 100 may also emit ultraviolet light having a peak wavelength in a band other than the 375 nm band.

[0017] 2 , the nitride-based semiconductor light-emitting element 100 includes a substrate 101, a semiconductor stack 100S, a current blocking layer 120, a P-side electrode 131, an adhesion layer 132, a pad electrode 133, and an N-side electrode 140. The semiconductor stack 100S includes an underlayer 102, a buffer layer 103, an N-type cladding layer 104, an N-side light guide layer 106, an active layer 107, an electron barrier layer 109, a P-type intermediate layer 110, a P-side light guide layer 111, a P-type cladding layer 112, and a contact layer 113. An isolation trench 10T is formed on the side surface (end surface in the X-axis direction) of the semiconductor stack 100S. The isolation trench 10T is a trench for separating the nitride-based semiconductor light-emitting element 100 into individual elements.

[0018] The substrate 101 is a plate-shaped member made of a nitride-based semiconductor that serves as a base for the nitride-based semiconductor light-emitting device 100. The substrate 101 has main surfaces 101a and 101b. In this embodiment, the substrate 101 is disposed below the N-type cladding layer 104 and is made of N-type GaN. More specifically, the substrate 101 has an average concentration of 1.4×10 １８ cm －３ The substrate is a GaN substrate doped with Si and having a thickness of 85 μm.

[0019] The underlayer 102 is an N-type nitride-based semiconductor layer disposed above the substrate 101. The underlayer 102 may have an average Al composition ratio smaller than that of the N-type cladding layer 104. In this embodiment, the underlayer 102 is disposed on the main surface 101a of the substrate 101 and has an average Al concentration of 1.0×10 １８ cm －３ Si-doped N-type Al film with a thickness of 1000 nm ０．０２ Ga ０．９８ This is the N layer.

[0020] In the present disclosure, the average impurity concentration of each layer (i.e., average impurity concentration) refers to the value of the impurity concentration obtained by integrating the magnitude of the impurity concentration at a certain position in the stacking direction of the layer in the stacking direction from the position of the interface on the side closer to the substrate 101 in the stacking direction of the layer to the position of the interface on the side farther from the substrate 101, and dividing the result by the film thickness of the layer (the distance between the interface on the side closer to the substrate 101 and the interface on the side farther from the substrate 101). In an N-type semiconductor layer, the impurity refers to an impurity doped to obtain N-type conductivity, and in a P-type semiconductor layer, it refers to an impurity doped to obtain P-type conductivity.

[0021] The average Al composition ratio of a certain layer is the value of the Al composition ratio obtained by integrating the magnitude of the Al composition ratio at a certain position in the stacking direction of the layer in the stacking direction from the position of the interface closer to the substrate 101 in the stacking direction of the layer to the position of the interface farther from the substrate 101 in the stacking direction of the layer, and dividing the result by the film thickness of the layer.

[0022] The buffer layer 103 is an N-type nitride-based semiconductor layer disposed between the substrate 101 and the N-type cladding layer 104. In this embodiment, the buffer layer 103 is disposed on the underlayer 102. In this embodiment, the buffer layer 103 has an average concentration of 1.0×10 １８ cm －３ and an N-type GaN layer having a thickness of 10 nm and doped with Si of an average concentration of 1.0×10 １８ cm －３ Si-doped N-type In ０．０４ Ga ０．９６ N layer and a layer with an average density of 1.0×10 １８ cm －３ and a 10 nm thick N-type GaN layer doped with Si.

[0023] The N-type cladding layer 104 is disposed above the substrate 101 and is an N-type nitride-based semiconductor layer containing Al. In this embodiment, the N-type cladding layer 104 is disposed on the buffer layer 103. The N-type cladding layer 104 has a smaller average refractive index and a larger average band gap energy than the active layer 107. The N-type cladding layer 104 also has a smaller average refractive index and a larger average band gap energy than the N-side optical guide layer 106. The average Al composition ratio of the N-type cladding layer 104 is larger than the average Al composition ratio of the N-side optical guide layer 106. The average Al composition ratio of the N-type cladding layer 104 may be less than 10%. In this embodiment, the N-type cladding layer 104 has an average Al concentration of 1.0×10 １８ cm －３ Si-doped N-type Al film with a thickness of 900 nm ０．０６５ Ga ０．９３５ This is the N layer.

[0024] Here, in the present disclosure, the average band gap energy of a certain layer refers to the value of the band gap energy obtained by integrating the magnitude of the band gap energy at a certain position in the stacking direction of the layer in the stacking direction from the interface position on the side closer to the substrate 101 in the stacking direction of the layer to the interface position on the side farther from the substrate 101 in the stacking direction of the layer, and dividing the result by the film thickness of the layer.

[0025] The average refractive index of a layer is the refractive index at a certain position in the stacking direction of the layer, integrated in the stacking direction from the interface position closest to the substrate 101 in the stacking direction of the layer to the interface position farthest from the substrate 101, and divided by the film thickness of the layer.

[0026] The N-side optical guide layer 106 is disposed above the N-type cladding layer 104 and is a nitride-based semiconductor layer containing Al. The N-side optical guide layer 106 has a larger average refractive index and a smaller average band gap energy than the N-type cladding layer 104. The average Al composition ratio of the N-side optical guide layer 106 may be less than 10%. In this embodiment, the N-side optical guide layer 106 has an average concentration of 1.0×10 １８ cm －３ Si-doped N-type Al film with a thickness of 127 nm ０．０３ Ga ０．９７An N layer and an undoped Al layer with a thickness of 80 nm arranged above the N layer. ０．０３ Ga ０．９７ In the present disclosure, an undoped layer is an N layer having an impurity concentration of 1.0×10 １８ cm －３ It means a semiconductor layer that is less than

[0027] The active layer 107 is disposed above the N-side optical guide layer 106 and is a nitride-based semiconductor layer including a well layer 107b and barrier layers 107a and 107c containing Al. The well layer 107b is disposed between the barrier layer 107a and the barrier layer 107c. In this embodiment, the active layer 107 emits ultraviolet light. However, the configuration of the active layer 107 is not limited thereto. For example, the active layer 107 may have a multiple quantum well structure. Specifically, the active layer 107 may have three or more barrier layers and two or more well layers. That is, the active layer 107 includes one or more well layers and multiple barrier layers.

[0028] Each of the barrier layers 107a and 107c is a nitride-based semiconductor layer disposed above the N-side optical guide layer 106 and functions as a barrier for the quantum well structure. The barrier layer 107c is disposed above the barrier layer 107a. In this embodiment, the average band gap energy of each of the barrier layers 107a and 107c is larger than the average band gap energy of the well layer 107b. In this embodiment, the barrier layer 107a is a 14 nm-thick undoped Al ０．０４ Ga ０．９６ The barrier layer 107c is an undoped AlN layer with a thickness of 12 nm. ０．０４ Ga ０．９６ This is the N layer.

[0029] The well layer 107b is a nitride-based semiconductor layer disposed above the barrier layer 107a and functions as a well of the quantum well structure. In this embodiment, the well layer 107b is an undoped In layer having a thickness of 17.5 nm. ０．０１ Ga ０．９９ This is the N layer.

[0030] The electron barrier layer 109 is disposed above the active layer 107 and is a P-type nitride-based semiconductor layer containing Al. The average band gap energy of the electron barrier layer 109 is greater than the average band gap energy of the barrier layer 107c. This makes it possible to suppress leakage of electrons from the active layer 107 to the P-type cladding layer 112. In this embodiment, the average band gap energy of the electron barrier layer 109 is greater than the average band gap energy of each of the P-type intermediate layer 110 and the P-type cladding layer 112. The average impurity concentration of the electron barrier layer 109 is higher than the average impurity concentrations of the P-type intermediate layer 110 and the P-side optical guide layer 111. In this embodiment, the electron barrier layer 109 has an average concentration of 1.5×10 １９ cm －３ P-type Al doped with Mg having a thickness of 1.6 nm ０．３６ Ga ０．６４ This is the N layer.

[0031] The P-type intermediate layer 110 is disposed above the electron barrier layer 109 and is a P-type nitride-based semiconductor layer containing Al. The average impurity concentration of the P-type intermediate layer 110 is lower than the average impurity concentration of the electron barrier layer 109 and higher than the average impurity concentration of the P-side light guide layer 111. The average Al composition ratio of the P-type intermediate layer 110 may be less than 10%. The thickness of the P-type intermediate layer 110 may be larger than the thickness of the electron barrier layer 109. In this embodiment, the P-type intermediate layer 110 has an average Al concentration of 1.0×10 １９ cm －３ P-type Al doped with Mg having a thickness of 20 nm ０．０６５ Ga ０．９３５ This is the N layer.

[0032] The P-side optical guide layer 111 is disposed above the electron barrier layer 109 and is a nitride-based semiconductor layer containing Al. In this embodiment, the P-side optical guide layer 111 is disposed above the P-type intermediate layer 110. The P-side optical guide layer 111 has a larger average refractive index and a smaller average band gap energy than the P-type cladding layer 112. In this embodiment, the average band gap energy of the P-side optical guide layer 111 is smaller than the average band gap energies of the P-type intermediate layer 110 and the P-type cladding layer 112. The average Al composition ratio of the P-side optical guide layer 111 may be less than 10%. In this embodiment, the P-side optical guide layer 111 has an average Al concentration of 2.0×10 １８ cm －３ P-type Al doped with Mg having a thickness of 110 nm ０．０３ Ga ０．９７ This is the N layer.

[0033] The P-type cladding layer 112 is disposed above the P-side optical guide layer 111 and is a P-type nitride-based semiconductor layer containing Al. The P-type cladding layer 112 has a smaller average refractive index than the active layer 107 and a higher average bandgap energy. The average bandgap energy of the P-type cladding layer 112 is smaller than the average bandgap energy of the electron barrier layer 109. The average Al composition ratio of the P-type cladding layer 112 may be less than 10%. The impurity concentration at the end of the P-type cladding layer 112 closer to the active layer 107 may be lower than the impurity concentration at the end farther from the active layer 107. This reduces the impurity concentration in the region of high light intensity in the P-type cladding layer 112, thereby reducing free carrier loss of light due to impurities. In this embodiment, the P-type cladding layer 112 has an average Al concentration of 2.0×10 １８ cm －３ P-type Al doped with Mg having a thickness of 170 nm ０．０６５ Ga ０．９３５ N layers and an average density of 1.0×10 １９ cm －３ P-type Al doped with Mg having a thickness of 300 nm ０．０６５ Ga ０．９３５ N layers.

[0034] The contact layer 113 is a P-type nitride-based semiconductor layer disposed above the P-type cladding layer 112 and in ohmic contact with the P-side electrode 131. In this embodiment, the contact layer 113 has an average concentration of 2.0×10 １９ cm －３ A 50 nm thick P-type GaN layer doped with Mg of 2.0×10 ２０ cm －３ and a 10 nm thick P-type GaN layer doped with Mg.

[0035] A ridge 11R is formed in the contact layer 113 and the P-type cladding layer 112. In this embodiment, the ridge 11R is formed in the contact layer 113, the P-type cladding layer 112, and the P-side optical guide layer 111. Two grooves 11T are formed in the contact layer 113, the P-type cladding layer 112, and the P-side optical guide layer 111, and are arranged along the ridge 11R and extend in the Y-axis direction. In this embodiment, the ridge width W is approximately 15 μm. As shown in FIG. 2 , the distance between the lower end of the ridge 11R (i.e., the bottom of the groove 11T) and the electron barrier layer 109 is defined as dc. In this embodiment, the distance dc is 35 nm. In other words, the 20 nm thick P-type intermediate layer 110 and the lower 15 nm thick portion of the 110 nm thick P-side optical guide layer 111 are located between the lower end of the ridge 11R and the electron barrier layer 109, and the upper 95 nm thick portion of the P-side optical guide layer 111 is located on the ridge 11R.

[0036] The current blocking layer 120 is disposed above the P-type cladding layer 112 and is an insulating layer that is transparent to light from the active layer 107. The current blocking layer 120 is disposed in a region of the upper surface of the semiconductor laminate 100S other than the upper surface of the ridge 11R. The current blocking layer 120 may also be disposed in a partial region of the upper surface of the ridge 11R. For example, the current blocking layer 120 may be disposed in an edge region of the upper surface of the ridge 11R. In this embodiment, the current blocking layer 120 is a 300 nm-thick SiO ２ It is a layer.

[0037] The P-side electrode 131 is a conductive layer disposed above the contact layer 113. In this embodiment, the P-side electrode 131 is in contact with the contact layer 113. The P-side electrode 131 is, for example, a single-layer film or a multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt, Ag, and Au. Furthermore, by using Ag, which has a low refractive index for light in the 375 nm wavelength band, for at least a portion of the P-side electrode 131, it is possible to reduce the seepage of light propagating through the waveguide into the P-side electrode 131, thereby reducing the waveguide loss generated in the P-side electrode 131. Ag has a refractive index of 0.5 or less in the wavelength range of 325 nm to 1500 nm and a refractive index of 0.2 or less in the wavelength range of 360 nm to 950 nm. In this case, the P-side electrode 131 containing Ag can reduce optical loss in the P-side electrode 131 over a wide wavelength range from 325 nm to 950 nm. In this case, even if the thickness of the P-type cladding layer 112 is 400 nm or less, leakage of light propagating through the waveguide into the P-side electrode 131 can be reduced, thereby making it possible to suppress an increase in waveguide loss while reducing the series resistance of the nitride-based semiconductor light-emitting element 100. As a result, the operating voltage and operating current can be reduced. In this embodiment, the P-side electrode 131 has a 40-nm-thick Pd layer and a 100-nm-thick Pt layer disposed on the Pd layer.

[0038] The thickness of the P-type cladding layer 112 may be greater than the total thickness of the P-side optical guide layers (the thickness of the P-side optical guide layer 111 in this embodiment) and the total thickness of the N-side optical guide layers (the thickness of the N-side optical guide layer 106 in this embodiment). This allows the thickness of the P-type cladding layer 112 to be sufficient to confine light below the P-side electrode 131, thereby suppressing waveguide loss. Furthermore, when the P-side electrode 131 contains Ag, the thickness of the P-type cladding layer 112 may be, for example, 200 nm or more and 400 nm or less. This allows the operating voltage and operating current to be reduced while suppressing waveguide loss.

[0039] Furthermore, a layer with a high Al composition ratio, such as the P-type cladding layer 112, causes a large strain on the N-type GaN substrate 101. By reducing the film thickness of the P-type cladding layer 112, the total Al content in the P-type cladding layer 112 can be reduced, thereby reducing the strain on the substrate 101 in the P-type cladding layer 112. Therefore, cracking of the nitride-based semiconductor light-emitting element 100 caused by strain in the P-type cladding layer 112 can be suppressed.

[0040] In order to stably confine the light propagating through the waveguide within the ridge 11R, it is necessary to create a difference in effective refractive index (ΔN) so that the effective refractive index of the inner region of the ridge 11R is greater than that of the outer region, as will be described later (see FIG. 2). Specifically, a SiO 2 layer having a refractive index lower than that of the P-type cladding layer 112 is formed on the sidewall of the ridge 11R. ２ In this case, if the thickness of the P-type cladding layer 112 becomes too thin, the SiO ２ Therefore, the effect of reducing the effective refractive index of the ridge in the outer region of the ridge 11R is reduced. Therefore, the thickness of the P-type cladding layer 112 needs to be 0.15 μm or more.

[0041] The adhesion layer 132 is a metal layer disposed between the current blocking layer 120 and the pad electrode 133. The adhesion layer 132 has a function of increasing the adhesion of the pad electrode 133. The adhesion layer 132 may be disposed on the P-side electrode 131. In this embodiment, the adhesion layer 132 has a Ti layer with a thickness of 10 nm disposed on the current blocking layer 120, and a Pt layer with a thickness of 100 nm disposed on the Ti layer.

[0042] The pad electrode 133 is a pad-shaped electrode disposed above the P-side electrode 131. In this embodiment, the pad electrode 133 is disposed above the P-side electrode 131 and the adhesion layer 132. In this embodiment, the pad electrode 133 is an Au layer with a film thickness of 2.0 μm.

[0043] The N-side electrode 140 is a conductive layer disposed below the substrate 101 (i.e., on the principal surface 101b of the substrate 101 opposite to the principal surface 101a on which the N-type cladding layer 104 and the like are disposed). The N-side electrode 140 is, for example, a single-layer film or a multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt, and Au. In this embodiment, the N-side electrode 140 has, stacked in this order from the substrate 101 side, a 10-nm-thick Ti layer, a 50-nm-thick Pt layer, and a 300-nm-thick Au film.

[0044] [1-2. Effects] The effects of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be described with reference to FIGS. 3 to 5, in comparison with the nitride-based semiconductor light-emitting element according to Comparative Example 1. FIGS. 3 and 4 are schematic graphs showing the distribution of band gap energy and impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting element according to Comparative Example 1 and this embodiment, respectively. Note that FIGS. 3 and 4 also show the intensity distribution of light propagating through the nitride-based semiconductor light-emitting element 100. FIG. 5 is a graph showing the extinction coefficient spectrum in an AlGaN layer. FIG. 5 shows the extinction coefficient spectrum of an undoped AlGaN layer. ０．０３ Ga ０．９７ N layer, and average density 1.0 × 10 １９ cm －３ of Mg-doped Al ０．０３ Ga ０．９７ The extinction coefficient spectra of the N layers are shown by the solid and dashed lines, respectively.

[0045] The nitride-based semiconductor light-emitting device according to Comparative Example 1 differs from the nitride-based semiconductor light-emitting device 100 according to the present embodiment in that it does not include the P-type intermediate layer 110, but is the same in other respects.

[0046] Each of the nitride-based semiconductor light-emitting devices according to Comparative Example 1 and the present embodiment includes an electron barrier layer 109 having a large bandgap energy. To reduce the electrical resistance of the electron barrier layer 109, the electron barrier layer 109 is doped with a high concentration of impurities (Mg). Accordingly, in the manufacturing process of each nitride-based semiconductor light-emitting device, layers deposited following the step of depositing the electron barrier layer 109 are doped with impurities remaining in the chamber used for the deposition. Therefore, as shown in FIG. 3 , in the nitride-based semiconductor light-emitting device of Comparative Example 1, the P-side light guide layer 111 deposited on the electron barrier layer 109 is doped with an impurity at a concentration higher than the design impurity concentration of the P-side light guide layer 111. The impurity concentration is particularly high in the region of the P-side light guide layer 111 near the electron barrier layer 109.

[0047] 5 , in an AlGaN layer such as the p-side optical guiding layer 111, the optical absorption edge (the long-wavelength end of the optical absorption wavelength band) is shifted to a lower energy level (i.e., shifted to a longer wavelength side) due to the influence of the impurity level. The amount of the lower energy shift increases as the impurity concentration increases. Therefore, in an AlGaN layer with a relatively small average Al composition ratio, such as the p-side optical guiding layer 111, the influence of optical absorption (i.e., optical loss) caused by the increase in impurity concentration becomes significant.

[0048] In contrast, the nitride-based semiconductor light-emitting element 100 according to this embodiment is provided with a P-type intermediate layer 110 on the electron barrier layer 109. The P-type intermediate layer 110 has an average bandgap energy smaller than that of the electron barrier layer 109 and larger than that of the P-side optical guide layer 111. The average impurity concentration of the P-type intermediate layer 110 is lower than that of the electron barrier layer 109 and higher than that of the P-side optical guide layer 111.

[0049] As described above, the nitride-based semiconductor light-emitting element 100 according to the present embodiment includes the P-type intermediate layer 110 having a larger average bandgap energy than the P-side optical guide layer 111 in the region where the impurity concentration is high on the electron barrier layer 109, and thereby the optical absorption edge in this region can be shifted to the higher energy side (shorter wavelength side) than in the nitride-based semiconductor light-emitting element 100 according to Comparative Example 1. Therefore, the nitride-based semiconductor light-emitting element 100 according to the present embodiment can suppress optical absorption in this region more than the nitride-based semiconductor light-emitting element 100 according to Comparative Example 1. As described above, the nitride-based semiconductor light-emitting element 100 according to the present embodiment can suppress optical loss while reducing the Al composition ratio of each layer, such as the P-side optical guide layer 111 and the P-type cladding layer 112.

[0050] In the nitride-based semiconductor light-emitting device 100 , the average bandgap energy of the P-type intermediate layer 110 may be equal to or greater than the average bandgap energy of the P-type cladding layer 112 .

[0051] This allows the optical absorption edge in the P-type intermediate layer 110 to be shifted further to the higher energy side, thereby further suppressing optical loss in the P-type intermediate layer 110 .

[0052] In the nitride-based semiconductor light-emitting device 100, the thickness of the P-type intermediate layer 110 may be 10 nm or more.

[0053] The influence of remaining impurities is reduced in a region that is spaced above the electron barrier layer 109 by a certain distance or more. For example, in a region that is spaced above the electron barrier layer 109 by 10 nm or more, the impurity concentration can be reduced by 20% or more compared to the impurity concentration at the interface above the electron barrier layer 109. Therefore, by making the film thickness of the P-type intermediate layer 110 10 nm or more, optical loss due to remaining impurities can be suppressed.

[0054] Furthermore, in a region spaced 20 nm or more above the electron barrier layer 109 , the impurity concentration can be reduced to half or less of the impurity concentration at the interface above the electron barrier layer 109 .

[0055] Therefore, when the thickness of the P-type intermediate layer 110 is 20 nm or more, the optical loss caused by the remaining impurities can be sufficiently suppressed.

[0056] In the nitride-based semiconductor light-emitting device 100, the P-type intermediate layer 110 is made of AlGaN. In other words, the composition of the P-type intermediate layer 110 is Al ｘ Ga １－ｘ N (0<x<1). The average Al composition ratio of the P-type intermediate layer 110 may be greater than 3%.

[0057] In this way, by using an AlGaN layer with an average Al composition ratio of 3% or more as the P-type intermediate layer 110, the average band gap energy can be increased to a degree that can sufficiently suppress absorption of light in the ultraviolet region.

[0058] In addition, in the nitride-based semiconductor light-emitting element 100, the average Al composition ratio of each of the N-type cladding layer 104, the N-side optical guide layer 706, the P-type intermediate layer 110, the P-side optical guide layer 111, and the P-type cladding layer 112 may be less than 10%.

[0059] This reduces stress throughout the nitride-based semiconductor light-emitting device 100 and internal stress caused by lattice mismatch. As a result, breakage and cracks in the wafer on which the semiconductor stack 100S is formed are reduced during the manufacturing process of the nitride-based semiconductor light-emitting device 100. Furthermore, defects generated inside the nitride-based semiconductor light-emitting device 700 are reduced. Therefore, the yield of the nitride-based semiconductor light-emitting device 700 can be improved.

[0060] The nitride-based semiconductor light-emitting device 100 may also have a ridge 11R extending in the light propagation direction (that is, in a direction parallel to the Y-axis direction in each drawing).

[0061] This allows the current supplied to the nitride-based semiconductor light-emitting element 100 to be confined within the ridge 11R, and also allows an optical waveguide to be formed along the ridge 11R.

[0062] Furthermore, in the nitride-based semiconductor light-emitting device 100, the side surface of the ridge 11R may be inclined with respect to the main surface 101a of the substrate 101. The effects of such a configuration of the ridge 11R will be described with reference to FIGS. 6 and 7 . FIG. 6 is a schematic cross-sectional view showing the shape of the side surface 11Rs of the ridge 11R according to this embodiment. FIG. 6 also shows the outline of the ridge 11R. FIG. 7 is a graph showing the relationship between the transverse mode order of laser light in a nitride-based semiconductor light-emitting device and the waveguide loss. FIG. 7 shows the results of a simulation of the waveguide loss in a nitride-based semiconductor light-emitting device having a waveguide structure substantially equivalent to that of the nitride-based semiconductor light-emitting device 100 according to this embodiment. Furthermore, FIG. 7 shows the waveguide loss when the inclination angle θr of the side surface 11Rs of the ridge 11R is set to 50 degrees, 60 degrees, 70 degrees, 80 degrees, and 90 degrees. Since no substantial difference was observed in the waveguide loss when the tilt angle θr was 80 degrees and 90 degrees, FIG. 7 shows the waveguide loss for angles from 80 degrees to 90 degrees.

[0063] 6, a tilt angle θr is defined for the side surface 11Rs of the ridge 11R (the end surface in the X-axis direction of the ridge 11R) with respect to the main surface 101a of the substrate 101. The XY plane shown in FIG.

[0064] As shown in FIG. 7 , the waveguide loss generally tends to increase as the order increases, and in low-order modes (e.g., the zeroth-order mode), the waveguide loss is the same regardless of the tilt angle θr. Below, the trend with respect to the tilt angle θr is shown. When the tilt angle θr is 80 degrees or greater, the waveguide loss does not change significantly with the mode order. When the tilt angle θr is less than 80 degrees, the waveguide loss of higher-order modes (e.g., 12th-order mode) is greater than when the tilt angle θr is 80 degrees or greater. In particular, when the tilt angle θr is 70 degrees, the waveguide loss of 12th-order mode light is greatest compared to other tilt angles. On the other hand, when the tilt angle θr is 50 degrees, the loss of intermediate-order modes such as 4th-order mode light and 7th-order mode light increases, resulting in greater waveguide loss than at other angles. When the average Al composition ratio of the N-type cladding layer 104 is small (for example, less than 10%) and / or the film thickness is relatively small, as in the nitride-based semiconductor light-emitting device 100 according to this embodiment, a substrate mode in which light propagates through the substrate 101 is likely to occur. Therefore, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, the waveguide loss as described above becomes significant.

[0065] Here, high-order mode light such as 12th-order mode light causes a nonlinear bending portion (a so-called kink) to occur in a graph showing the current-light output (IL) characteristics of the nitride-based semiconductor light-emitting element 100.

[0066] 7 , for example, by setting the tilt angle θr to be equal to or greater than 60 degrees and less than 80 degrees, the waveguide loss of higher-order mode light can be increased and the waveguide loss of intermediate-order mode light can be suppressed. In other words, by reducing the abundance ratio of higher-order mode light while suppressing the waveguide loss of lower-order mode light and intermediate-order mode light, the occurrence of kinks in the current-light output characteristics can be suppressed. Furthermore, by reducing the abundance ratio of higher-order mode light, the occurrence of substrate mode can be suppressed and anti-guided mode light leaking from the side surface 11Rs of the ridge 11R to the outside of the ridge 11R can be suppressed. Furthermore, by reducing the abundance ratio of higher-order mode light, the horizontal divergence angle (divergence angle in the XY plane) of the output light of the nitride-based semiconductor light-emitting element 100 can also be reduced.

[0067] The tilt angle θr may be equal to or greater than 60 degrees and equal to or less than 75 degrees, which can further reduce the abundance ratio of high-order mode light.

[0068] The ridge 11R having such an inclination angle θr can be realized by the following method.

[0069] Generally, nitride semiconductors can be etched using chlorine radicals and ions. Specifically, chlorine-containing gas is converted into plasma using the ISM (Inductively Super Magnetron) method or the ICP (Inductively Coupled Plasma) method, and the plasma is irradiated onto the nitride semiconductor. Etching using chlorine ions contained in the plasma is highly anisotropic. Therefore, etching using chlorine ions enables highly perpendicular etching. On the other hand, etching using chlorine radicals is highly isotropic. In the above method, the abundance ratio of chlorine ions and chlorine radicals and the kinetic energy of the chlorine ions can be controlled by changing the pressure and applied voltage. This allows the balance between anisotropic etching and isotropic etching to be controlled, thereby obtaining the desired tilt angle θr.

[0070] Here, the nitride-based semiconductor light-emitting element 100 according to this embodiment additionally has the following effect. When the P-type intermediate layer 110, which has a refractive index smaller than that of the P-side optical guide layer 111, is disposed between the electron barrier layer 109 and the P-side optical guide layer 111, the light confinement function works even in a location closer to the active layer 107 than the P-type cladding layer 112. As a result, the center of the optical distribution shifts toward the N-side (i.e., toward the N-type cladding layer 104) and the effective refractive index difference ΔN decreases compared to a case where the P-type intermediate layer 110 is not present. Such a shift of the optical distribution toward the N-side reduces the effective gain, resulting in an increase in the threshold current. Furthermore, as the effective refractive index difference ΔN decreases, higher-order modes in the waveguide become unstable, causing kinks.

[0071] Therefore, in order to reduce the effect of the P-type intermediate layer 110 on the light distribution, the thickness of the P-type intermediate layer 110 may be made thinner when the Al composition ratio of the P-type cladding layer 112 is large, and the thickness of the P-type intermediate layer 110 may be made thicker when the Al composition ratio of the P-type cladding layer 112 is small. In the case where the Al composition ratio of the P-side optical guide layer 111 is 0.03 (i.e., 3%) and the Al composition ratio of the P-type cladding layer 112 is 0.065 (i.e., 6.5%) as in this embodiment, when the Al composition ratio of the P-type intermediate layer 110 is 0.050 or more and 0.080 or less (i.e., 5.0% or more and 8.0% or less), the film thickness of the P-type intermediate layer 110 may be 5 nm or more and 20 nm or less, and when the Al composition ratio of the P-type intermediate layer 110 is 0.030 or more and 0.050 or less (i.e., 3.0% or more and 5.0% or less), the film thickness of the P-type intermediate layer 110 may be 20 nm or more and 40 nm or less.

[0072] In particular, when the Al composition ratio of the P-type intermediate layer 110 is higher than the Al composition ratio of the P-type cladding layer 112 (i.e., when the Al composition ratio of the P-type intermediate layer 110 is 0.065 or more and 0.080 or less), the film thickness of the P-type intermediate layer 110 may be 5 nm or more and 10 nm or less.

[0073] (Embodiment 2) A nitride-based semiconductor light-emitting device according to embodiment 2 will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 100 according to embodiment 1 in the configuration of the P-type intermediate layer, but is the same in other configurations. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 8, focusing on the differences from nitride-based semiconductor light-emitting device 100 according to embodiment 1.

[0074] 8 is a schematic graph showing the distribution of the band gap energy and the impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting device according to this embodiment. As shown in FIG. 8, the nitride-based semiconductor light-emitting device according to this embodiment includes a P-type intermediate layer 210.

[0075] The P-type intermediate layer 210 differs from the P-type intermediate layer 110 according to the first embodiment in that the average band gap energy of the P-type intermediate layer 210 is smaller than the average band gap energy of the P-type cladding layer 112. In this embodiment, the P-type intermediate layer 210 has an average concentration of 1.0×10 １９ cm －３ P-type Al doped with Mg having a thickness of 20 nm ０．０５ Ga ０．９５ This is the N layer.

[0076] The nitride-based semiconductor light-emitting device according to this embodiment having the above-described configuration also exhibits the same effects as those of nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0077] In the nitride-based semiconductor light-emitting device according to this embodiment, the average bandgap energy of the P-type intermediate layer 210 is smaller than the average bandgap energy of the P-type cladding layer 112 .

[0078] This allows the average refractive index of the P-type intermediate layer 210 to be greater than the average refractive index of the P-type cladding layer 112. Therefore, in this embodiment, the P-type intermediate layer 210 can also function as an optical guide layer. This allows the optical loss in the nitride-based semiconductor light-emitting element 100 to be reduced without deteriorating the function of confining light in the active layer 107.

[0079] Furthermore, as in this embodiment, by increasing the average refractive index of the P-type intermediate layer 210, it is possible to suppress a decrease in the light confinement function in the active layer 107 that occurs with an increase in the film thickness of the P-type intermediate layer 210. Therefore, even when the region with a high impurity concentration is large, by increasing the film thickness of the P-type intermediate layer 210, it is possible to reduce optical loss while suppressing a decrease in the light confinement function.

[0080] (Embodiment 3) A nitride-based semiconductor light-emitting device according to embodiment 3 will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 100 according to embodiment 1 in the position of the lower end of the ridge and the relative position with respect to P-type intermediate layer 110, but is identical in other configurations. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 9, focusing on the differences from nitride-based semiconductor light-emitting device 100 according to embodiment 1.

[0081] 9 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 300 according to this embodiment, taken at the same position as in FIG.

[0082] As shown in FIG. 9 , the nitride-based semiconductor light-emitting element 300 according to this embodiment includes a substrate 101, a semiconductor stack 100S, a current blocking layer 120, a P-side electrode 131, an adhesion layer 132, a pad electrode 133, and an N-side electrode 140, similar to the nitride-based semiconductor light-emitting element 100 according to the first embodiment.

[0083] In this embodiment, a ridge 21R is formed in the contact layer 113, the P-type cladding layer 112, the P-side optical guide layer 111, and the P-type intermediate layer 110. Furthermore, two grooves 21T are formed in the contact layer 113, the P-type cladding layer 112, the P-side optical guide layer 111, and the P-type intermediate layer 110, and are arranged along the ridge 21R and extend in the Y-axis direction. As described above, in the nitride-based semiconductor light-emitting device 300 according to this embodiment, the lower end of the ridge 21R is located in the P-type intermediate layer 110. In other words, at least a portion of the P-type intermediate layer 110 is located on the ridge 21R. In this embodiment, the distance dc between the lower end of the ridge 21R and the electron barrier layer 109 is equal to or greater than 0 and less than 20 nm.

[0084] The nitride-based semiconductor light-emitting device 300 according to this embodiment having the above-described configuration also achieves the same effects as the nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0085] Furthermore, in this embodiment, at least a portion of the P-type intermediate layer 110 is disposed in the ridge 21R. As a result, the P-side optical guide layer 111 located above the P-type intermediate layer 110 is disposed within the ridge 21R. Therefore, the refractive index of the ridge 21R and the current blocking layer 120 located on the side surfaces of the ridge 21R is smaller than that of the ridge 21R, thereby improving the optical confinement function in the lateral direction (the X-axis direction in each figure). Therefore, stable multi-mode oscillation can be achieved in the nitride-based semiconductor light-emitting element 300.

[0086] Furthermore, in this embodiment, a surface state due to dangling bonds (unshared electrons) is formed on the surface of the P-type intermediate layer 110 corresponding to the bottom and side surfaces of the trench 21T formed by etching. This reduces the band gap of the P-type intermediate layer 110 in the region in contact with the bottom and side surfaces of the trench 21T. Furthermore, doping the P-type intermediate layer 110 with Mg shifts the absorption range in the absorption coefficient spectrum to longer wavelengths. To address absorption losses due to these factors, the P-type intermediate layer 110 having a larger Al composition ratio than the P-side optical guide layer 111 can be provided with a P-type intermediate layer 110 having a larger average band gap energy than the P-side optical guide layer 111, as in this embodiment. Therefore, even when the lower end of the ridge 21R is located within the P-type intermediate layer 110, absorption losses in the region of the P-type intermediate layer in contact with the trench 21T can be suppressed.

[0087] (Fourth Embodiment) A nitride-based semiconductor light-emitting device according to the fourth embodiment will be described. The nitride-based semiconductor light-emitting device according to the present embodiment differs from nitride-based semiconductor light-emitting device 100 according to the first embodiment in the configuration of the P-type intermediate layer, but is the same in other configurations. The nitride-based semiconductor light-emitting device according to the present embodiment will be described below with reference to FIG. 10 , focusing on the differences from nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0088] 10 is a schematic graph showing the distribution of the band gap energy and the impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting device according to this embodiment. As shown in FIG. 10, the nitride-based semiconductor light-emitting device according to this embodiment includes a P-type intermediate layer 410.

[0089] The P-type intermediate layer 410 includes a first P-type intermediate layer 410a and a second P-type intermediate layer 410b disposed above the first P-type intermediate layer 410a and having a smaller average bandgap energy than the first P-type intermediate layer 410a. The average Al composition ratio of the first P-type intermediate layer 410a is larger than the average Al composition ratio of the second P-type intermediate layer 410b.

[0090] In this embodiment, the average bandgap energy of the first P-type intermediate layer 410a is larger than the average bandgap energy of the P-type cladding layer 112, and the average bandgap energy of the P-type intermediate layer 410 is smaller than the average bandgap energy of the P-type cladding layer 112. In addition, the average impurity concentration (average Mg concentration) of the first P-type intermediate layer 410a is larger than the average impurity concentration of the second P-type intermediate layer 410b.

[0091] In this embodiment, the first P-type intermediate layer 410a has an average concentration of 1.3×10 １９ cm －３ P-type Al doped with Mg having a thickness of 5 nm ０．０８ Ga ０．９２ The second P-type intermediate layer 410b has an average concentration of 9.0×10 １８ cm －３ P-type Al doped with Mg having a thickness of 15 nm ０．０５ Ga ０．９５ This is the N layer.

[0092] The nitride-based semiconductor light-emitting device according to this embodiment having the above-described configuration also exhibits the same effects as those of nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0093] In addition, in this embodiment, the P-type intermediate layer 410 has a first P-type intermediate layer 410a and a second P-type intermediate layer 410b that is arranged above the first P-type intermediate layer 410a and has a smaller average band gap energy than the first P-type intermediate layer 410a.

[0094] Here, in the P-type intermediate layer 410, due to the influence of the residual impurities described above, the impurity concentration tends to increase toward the electron barrier layer 109. In an AlGaN layer such as the P-type intermediate layer 410, the higher the impurity concentration, the greater the light absorption. In this embodiment, by providing the first P-type intermediate layer 410a, which has a large average band gap energy, in a region close to the electron barrier layer 109 and with a high impurity concentration, the light loss in the P-type intermediate layer 410 can be further suppressed.

[0095] In addition, in this embodiment, the average bandgap energy of the first P-type intermediate layer 410a may be larger than the average bandgap energy of the P-type cladding layer 112, and the average bandgap energy of the P-type intermediate layer 410 may be smaller than the average bandgap energy of the P-type cladding layer 112.

[0096] In this way, by increasing the average bandgap energy of the first P-type intermediate layer 410a near the electron barrier layer 109, where the impurity concentration is particularly likely to be high, within the P-type intermediate layer 410, it is possible to suppress optical loss in the first P-type intermediate layer 410a. Furthermore, by making the average bandgap energy of the entire P-type intermediate layer 410 smaller than the average bandgap energy of the P-type cladding layer 112, it is possible to allow a portion of the P-type intermediate layer 410 to function as an optical guide layer, as in the second embodiment. Furthermore, by reducing the bandgap energy of the P-type intermediate layer 410, it is possible to reduce the average Al composition ratio of the entire P-type intermediate layer 410. This allows the proportion of impurities that function as acceptors among the impurities doped into the P-type intermediate layer 410 to be increased, thereby suppressing the electrical resistance of the P-type intermediate layer 410.

[0097] In the present embodiment, the P-type intermediate layer 410 has two layers, the first P-type intermediate layer 410a and the second P-type intermediate layer 410b, but the P-type intermediate layer 410 may have three or more layers. For example, the P-type intermediate layer 410 may further have a third P-type intermediate layer disposed above the second P-type intermediate layer 410b and having an average bandgap energy smaller than that of the second P-type intermediate layer 410b.

[0098] Fifth Embodiment A nitride-based semiconductor light-emitting device according to a fifth embodiment will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 100 according to the first embodiment in the configuration of the P-type intermediate layer, but is the same in other configurations. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 11 , focusing on the differences from nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0099] 11 is a schematic graph showing the distribution of the band gap energy and the impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting device according to this embodiment. As shown in FIG. 11, the nitride-based semiconductor light-emitting device according to this embodiment includes a P-type intermediate layer 510.

[0100] The P-type intermediate layer 510 has a P-type graded region in which the Al composition ratio decreases with increasing distance from the electron barrier layer 109. In this embodiment, the entire P-type intermediate layer 510 is a P-type graded region. The average band gap energy of the P-type intermediate layer 510 is smaller than the average band gap energy of the P-type cladding layer 112.

[0101] The P-type intermediate layer 510 also has an impurity concentration gradient region in which the impurity concentration decreases with increasing distance from the electron barrier layer 109. In this embodiment, the entire P-type intermediate layer 510 is an impurity concentration gradient region.

[0102] In this embodiment, the P-type intermediate layer 510 has an average concentration of 1.0×10 １９ cm －３ The composition of the P-type intermediate layer 510 at the interface with the electron barrier layer 109 is Al ０．０８ Ga ０．９２ N, and the composition at the interface of the P-type intermediate layer 510 with the P-side optical guide layer 111 is Al ０．０５ Ga ０．９５ The Al composition ratio of the P-type intermediate layer 510 decreases continuously with increasing distance from the electron barrier layer 109. The impurity concentration of the P-type intermediate layer 510 is 1.5×10 １９ cm －３ From 2.0 × 10 １８ cm －３continuously decreases until

[0103] The nitride-based semiconductor light-emitting device according to this embodiment having the above-described configuration also exhibits the same effects as those of nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0104] In this embodiment, the P-type intermediate layer 510 has a P-type gradient region in which the Al composition ratio decreases with increasing distance from the electron barrier layer 109 .

[0105] Here, in the P-type intermediate layer 510, due to the influence of the residual impurities described above, the impurity concentration tends to decrease with increasing distance from the electron barrier layer 109. Furthermore, in an AlGaN layer such as the P-type intermediate layer 510, the higher the impurity concentration, the greater the light absorption. In this embodiment, by providing a P-type graded region in which the Al composition ratio decreases with increasing distance from the electron barrier layer 109, it is possible to decrease the bandgap energy with increasing distance from the electron barrier layer 109. This makes it possible to reduce the Al composition ratio while suppressing light loss in the P-type intermediate layer 510.

[0106] In this embodiment, the average bandgap energy of the P-type intermediate layer 510 may be smaller than the average bandgap energy of the P-type cladding layer 112 .

[0107] This allows a portion of the P-type intermediate layer 510 to function as a light guide layer, as in the second embodiment. Furthermore, by reducing the band gap energy of the P-type intermediate layer 510, the average Al composition ratio of the entire P-type intermediate layer 510 can be reduced. Therefore, the proportion of impurities that function as acceptors among the impurities doped into the P-type intermediate layer 410 can be increased, thereby suppressing the electrical resistance in the P-type intermediate layer 410.

[0108] Sixth Embodiment A nitride-based semiconductor light-emitting device according to the sixth embodiment will be described. The nitride-based semiconductor light-emitting device according to the sixth embodiment differs from nitride-based semiconductor light-emitting device 100 according to the first embodiment in the configuration of the P-type intermediate layer, but is identical in other configurations. The nitride-based semiconductor light-emitting device according to the present embodiment will be described below with reference to FIG. 12 , focusing on the differences from nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0109] 12 is a schematic graph showing the distribution of the band gap energy and the impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting device according to this embodiment. As shown in FIG. 12, the nitride-based semiconductor light-emitting device according to this embodiment includes a P-type intermediate layer 610.

[0110] The P-type intermediate layer 610 includes a first P-type intermediate layer 610a having an average bandgap energy smaller than that of the P-type cladding layer 112, and a second P-type intermediate layer 610b disposed above the first P-type intermediate layer 610a and having an average bandgap energy larger than that of the first P-type intermediate layer 610a. In this embodiment, the second P-type intermediate layer 610b has an average bandgap energy smaller than that of the P-type cladding layer 112. The average Al composition ratio of the first P-type intermediate layer 610a is smaller than that of the second P-type intermediate layer 610b.

[0111] Furthermore, the average impurity concentration (average Mg concentration) of the first P-type intermediate layer 610a is lower than the average impurity concentration of the second P-type intermediate layer 610b.

[0112] In this embodiment, the first P-type intermediate layer 610a has an average concentration of 5.0×10 １８ cm －３ P-type Al doped with Mg having a thickness of 10 nm ０．０４ Ga ０．９６ The second P-type intermediate layer 610b has an average concentration of 1.0×10 １９ cm －３ P-type Al doped with Mg having a thickness of 15 nm ０．０５ Ga ０．９５ This is the N layer.

[0113] In the nitride-based semiconductor light-emitting element according to the present embodiment having the above-described configuration, the Mg concentration is low in the region of P-type intermediate layer 610 that is closer to active layer 107, i.e., in the region where the light intensity is higher, and therefore the effect of suppressing optical loss is greater than that of nitride-based semiconductor light-emitting element 100 according to the first embodiment.

[0114] In addition, in this embodiment, the P-type intermediate layer 610 has a first P-type intermediate layer 610a having an average bandgap energy smaller than that of the P-type cladding layer 112, and a second P-type intermediate layer 610b arranged above the first P-type intermediate layer 610a and having an average bandgap energy larger than that of the first P-type intermediate layer 610a.

[0115] As described above, the residual impurities tend to increase the impurity concentration in the layers stacked on the electron barrier layer 109. This effect can occur over a film thickness of approximately 80 nm to 100 nm. By disposing a P-type intermediate layer in most of this region where the impurity concentration tends to increase, optical loss can be suppressed. However, if the refractive index of the P-type intermediate layer is high and the film thickness of the P-type intermediate layer is large, the optical confinement function in the active layer 107 may be significantly reduced.

[0116] In this embodiment, the average bandgap energy of the first P-type intermediate layer 610a is made smaller than the average bandgap energy of the P-type cladding layer 112, thereby making the average refractive index of the first P-type intermediate layer 610a larger than the average refractive index of the P-type cladding layer 112. As a result, the first P-type intermediate layer 610a, which functions as a light guide layer, is disposed in a region of the P-type intermediate layer 610 that is close to the active layer 107. Therefore, it is possible to suppress a decrease in the light confinement function in the active layer 107 in the nitride-based semiconductor light-emitting device according to this embodiment.

[0117] Furthermore, the average impurity concentration in the first P-type intermediate layer 610 a may be lower than the average impurity concentration in the second P-type intermediate layer 610 b, which can suppress a shift of the optical absorption edge to the long wavelength side caused by impurities in the first P-type intermediate layer 610 a, thereby suppressing optical loss in the first P-type intermediate layer 610 a.

[0118] The thickness of the first P-type intermediate layer 610a may be less than 15 nm, which can suppress optical loss in the first P-type intermediate layer 610a.

[0119] In this embodiment, the P-type intermediate layer 610 has two layers, a first P-type intermediate layer 610a and a second P-type intermediate layer 610b, but the P-type intermediate layer 610 may have three or more layers. For example, the P-type intermediate layer 610 may further have a third P-type intermediate layer disposed above the second P-type intermediate layer 610b and having an average bandgap energy smaller than that of the second P-type intermediate layer 610b.

[0120] Seventh Embodiment A nitride-based semiconductor light-emitting device according to a seventh embodiment will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 100 according to the first embodiment in that it includes an N-type intermediate layer, but is the same in other respects. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIGS. 13 and 14, focusing on the differences from nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0121] Fig. 13 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element 700 according to this embodiment. Fig. 13 shows a cross section of the nitride-based semiconductor light-emitting element 700 taken at the same position as in Fig. 2. Fig. 14 is a schematic graph showing the distribution of the band gap energy and impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting element 700 according to this embodiment.

[0122] As shown in FIG. 13 , the nitride-based semiconductor light-emitting element 700 according to this embodiment includes a substrate 101, a semiconductor stack 700S, a current blocking layer 120, a P-side electrode 131, an adhesion layer 132, a pad electrode 133, and an N-side electrode 140.

[0123] The semiconductor laminate 700S has an underlayer 102, a buffer layer 103, an N-type cladding layer 104, an N-type intermediate layer 705, an N-side optical guide layer 706, an active layer 107, an electron barrier layer 109, a P-type intermediate layer 110, a P-side optical guide layer 111, a P-type cladding layer 112, and a contact layer 113.

[0124] The N-type intermediate layer 705 is disposed above the N-type cladding layer 104 and is a nitride-based semiconductor layer containing Al. The average band gap energy of the N-type intermediate layer 705 is larger than the average band gap energy of the N-side optical guide layer 706 and smaller than the average band gap energy of the N-type cladding layer 104. The average Al composition ratio of the N-type intermediate layer 705 may be less than 10%. The average impurity concentration of the N-type intermediate layer 705 is equal to or smaller than the average impurity concentration of the N-type cladding layer 104 and is higher than the average impurity concentration of the N-side optical guide layer 706. In this embodiment, the N-type intermediate layer 705 has an average concentration of 1.0×10 １８ cm －３ Si-doped N-type Al film with a thickness of 20 nm ０．０５ Ga ０．９５ This is the N layer.

[0125] The N-side optical guide layer 706 is disposed above the N-type intermediate layer 705 and is a nitride-based semiconductor layer containing Al. The N-side optical guide layer 706 has a larger average refractive index and a smaller average band gap energy than the N-type cladding layer 104 and the N-type intermediate layer 705. In this embodiment, the N-side optical guide layer 706 is an undoped Al layer having a thickness of 187 nm. ０．０３ Ga ０．９７ The N-type intermediate layer 705 has a thickness of 20 nm or more.

[0126] The effects of the nitride-based semiconductor light-emitting device 700 according to this embodiment will be described below.

[0127] Even when the N-side optical guiding layer 706, which is an undoped AlGaN layer, is directly stacked on the N-type cladding layer 104, which is an AlGaN layer doped with Si as an N-type impurity, the influence of residual impurities may still be present, although the influence is smaller than that of residual P-type impurities. Therefore, the impurity concentration in the N-side optical guiding layer 706, particularly in the region near the N-type cladding layer 104, may be higher than the design value. Furthermore, in the N-type AlGaN layer, as in the P-type AlGaN layer, a shift of the optical absorption edge to the long wavelength side may occur depending on the impurity concentration. Therefore, the optical loss in the N-side optical guiding layer 706 may increase.

[0128] The nitride-based semiconductor light-emitting element 700 according to this embodiment is provided with the N-type intermediate layer 705, which has a larger average bandgap energy than the N-side optical guide layer 706, in a region on the N-type cladding layer 104 where the impurity concentration is likely to be high, and thereby can suppress light absorption in the same way as the P-type intermediate layer 110. In this way, the nitride-based semiconductor light-emitting element 700 according to this embodiment can suppress optical loss while reducing the Al composition ratio of each layer, such as the N-side optical guide layer 706 and the N-type cladding layer 104.

[0129] In the nitride-based semiconductor light-emitting device 700, the film thickness of the N-type intermediate layer 705 may be 20 nm or more.

[0130] The influence of remaining impurities is reduced in a region that is 20 nm or more above the N-type cladding layer 104. For example, in a region that is 20 nm or more above the N-type cladding layer 104, the impurity concentration can be reduced to half or less of the impurity concentration at the interface above the N-type cladding layer 104. Therefore, by making the film thickness of the N-type intermediate layer 705 20 nm or more, optical loss due to remaining impurities can be sufficiently suppressed.

[0131] In the nitride-based semiconductor light-emitting device 700, the N-type intermediate layer 705 is made of AlGaN. In other words, the composition of the N-type intermediate layer 705 is Al ｙ Ga １－ｙ N (0<y<1). The average Al composition ratio of the N-type intermediate layer 705 may be greater than 3%.

[0132] In this way, by using an AlGaN layer with an average Al composition ratio of 3% or more as the N-type intermediate layer 705, the average band gap energy can be increased to a degree that can sufficiently suppress absorption of light in the ultraviolet region.

[0133] In the nitride-based semiconductor light-emitting element 700, the average Al composition ratio of each of the N-type cladding layer 104, the N-side optical guide layer 706, the N-type intermediate layer 705, the P-side optical guide layer 111, and the P-type cladding layer 112 may be less than 10%.

[0134] This reduces stress throughout the nitride-based semiconductor light-emitting device 700 and internal stress caused by lattice mismatch. Accordingly, breakage and cracks in the wafer on which the semiconductor stack 700S is formed are reduced during the manufacturing process of the nitride-based semiconductor light-emitting device 700. Furthermore, defects generated inside the nitride-based semiconductor light-emitting device 700 are reduced. Therefore, the yield of the nitride-based semiconductor light-emitting device 700 can be improved.

[0135] Eighth Embodiment A nitride-based semiconductor light-emitting device according to the eighth embodiment will be described. The nitride-based semiconductor light-emitting device according to the present embodiment differs from nitride-based semiconductor light-emitting device 700 according to the seventh embodiment in the configuration of the N-type intermediate layer, but is the same in other configurations. The nitride-based semiconductor light-emitting device according to the present embodiment will be described below with reference to FIG. 15 , focusing on the differences from nitride-based semiconductor light-emitting device 700 according to the seventh embodiment.

[0136] 15 is a schematic graph showing the distribution of band gap energy and impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting device according to this embodiment. As shown in FIG. 15, the nitride-based semiconductor light-emitting device according to this embodiment includes an N-type intermediate layer 805.

[0137] The N-type intermediate layer 805 includes a first N-type intermediate layer 805 a and a second N-type intermediate layer 805 b disposed above the first N-type intermediate layer 805 a and having an average band gap energy smaller than that of the first N-type intermediate layer 805 a. The average Al composition ratio of the first N-type intermediate layer 805 a is larger than that of the second N-type intermediate layer 805 b.

[0138] In this embodiment, the average impurity concentration (average Si concentration) of the first N-type intermediate layer 805a is higher than the average impurity concentration of the second N-type intermediate layer 805b.

[0139] In this embodiment, the first N-type intermediate layer 805a has an average concentration of 1.0×10 １８ cm －３ Si-doped N-type Al film with a thickness of 10 nm ０．０６ Ga ０．９４ The second N-type intermediate layer 805b has an average concentration of 8.0×10 １７ cm －３Si-doped N-type Al film with a thickness of 10 nm ０．０５ Ga ０．９５ This is the N layer.

[0140] The nitride-based semiconductor light-emitting device according to this embodiment having the above-described configuration also exhibits the same effects as those of the nitride-based semiconductor light-emitting device 700 according to the seventh embodiment.

[0141] In addition, in this embodiment, the N-type intermediate layer 805 has a first N-type intermediate layer 805a and a second N-type intermediate layer 805b that is arranged above the first N-type intermediate layer 805a and has a smaller average band gap energy than the first N-type intermediate layer 805a.

[0142] Here, in the N-type intermediate layer 805, due to the influence of the residual impurities described above, the impurity concentration tends to increase toward the N-type cladding layer 104. In an AlGaN layer such as the N-type intermediate layer 805, the higher the impurity concentration, the greater the light absorption. In this embodiment, by providing the first N-type intermediate layer 805a, which has a large average bandgap energy, in a region close to the N-type cladding layer 104 and with a high impurity concentration, the light loss in the N-type intermediate layer 805 can be further suppressed.

[0143] In this embodiment, N-type intermediate layer 805 has two layers, first N-type intermediate layer 805a and second N-type intermediate layer 805b, but N-type intermediate layer 805 may have three or more layers. For example, N-type intermediate layer 805 may further have a third N-type intermediate layer disposed above second N-type intermediate layer 805b and having an average band gap energy smaller than that of second N-type intermediate layer 805b.

[0144] Ninth Embodiment A nitride-based semiconductor light-emitting device according to a ninth embodiment will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 700 according to the seventh embodiment in the configuration of the N-type intermediate layer, but is the same in other configurations. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 16 , focusing on the differences from nitride-based semiconductor light-emitting device 700 according to the seventh embodiment.

[0145] 16 is a schematic graph showing the distribution of the band gap energy and the impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting device according to this embodiment. As shown in FIG. 16, the nitride-based semiconductor light-emitting device according to this embodiment includes an N-type intermediate layer 905.

[0146] The N-type intermediate layer 905 has an N-type gradient region in which the Al composition ratio decreases with increasing distance from the N-type cladding layer 104. In this embodiment, the entire N-type intermediate layer 905 is an N-type gradient region. The average band gap energy of the N-type intermediate layer 905 is smaller than the average band gap energy of the N-type cladding layer 104.

[0147] The N-type intermediate layer 905 also has an impurity concentration gradient region in which the impurity concentration decreases with increasing distance from the N-type cladding layer 104. In this embodiment, the entire N-type intermediate layer 905 is an impurity concentration gradient region.

[0148] In this embodiment, the N-type intermediate layer 905 has an average concentration of 8.0×10 １７ cm －３ The composition of the N-type intermediate layer 905 at the interface with the N-type cladding layer 104 is Al ０．０６５ Ga ０．９３５ The composition of the N-type intermediate layer 905 at the interface with the N-side optical guide layer 706 is Al ０．０５ Ga ０．９５ The Al composition ratio of the N-type intermediate layer 905 continuously decreases with increasing distance from the N-type cladding layer 104. The impurity concentration of the N-type intermediate layer 905 also continuously decreases with increasing distance from the N-type cladding layer 104.

[0149] The nitride-based semiconductor light-emitting device according to this embodiment having the above-described configuration also exhibits the same effects as those of the nitride-based semiconductor light-emitting device 700 according to the seventh embodiment.

[0150] In this embodiment, the N-type intermediate layer 905 has an N-type gradient region in which the Al composition ratio decreases with increasing distance from the N-type cladding layer 104 .

[0151] Here, in the N-type intermediate layer 905, due to the influence of the residual impurities described above, the impurity concentration tends to decrease with increasing distance from the N-type cladding layer 104. Furthermore, in an AlGaN layer such as the N-type intermediate layer 905, the higher the impurity concentration, the greater the optical absorption. In this embodiment, by providing an N-type gradient region in which the Al composition ratio decreases with increasing distance from the N-type cladding layer 104, it is possible to decrease the bandgap energy with increasing distance from the N-type cladding layer 104. This makes it possible to reduce the Al composition ratio while suppressing optical loss in the N-type intermediate layer 905.

[0152] Tenth Embodiment A nitride-based semiconductor light-emitting device according to a tenth embodiment will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 700 according to seventh embodiment in the configuration of the N-type intermediate layer, but is the same in other configurations. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 17 , focusing on the differences from nitride-based semiconductor light-emitting device 700 according to seventh embodiment.

[0153] 17 is a schematic graph showing the distribution of band gap energy and impurity concentration in the stacking direction of the nitride-based semiconductor light-emitting device according to this embodiment. As shown in FIG. 17, the nitride-based semiconductor light-emitting device according to this embodiment includes an N-type intermediate layer 1005.

[0154] The N-type intermediate layer 1005 includes a first N-type intermediate layer 1005a having an average bandgap energy smaller than that of the N-type cladding layer 104, and a second N-type intermediate layer 1005b disposed above the first N-type intermediate layer 1005a and having an average bandgap energy larger than that of the first N-type intermediate layer 1005a. In this embodiment, the second N-type intermediate layer 1005b has an average bandgap energy smaller than that of the N-type cladding layer 104. The average Al composition ratio of the first N-type intermediate layer 1005a is smaller than that of the second N-type intermediate layer 1005b.

[0155] Furthermore, the average impurity concentration (average Si concentration) of the first N-type intermediate layer 1005a is lower than the average impurity concentration of the second N-type intermediate layer 1005b.

[0156] In this embodiment, the first N-type intermediate layer 1005a has an average concentration of 8.0×10 １７ cm －３ Si-doped N-type Al film with a thickness of 10 nm ０．０５ Ga ０．９５ The second N-type intermediate layer 1005b has an average concentration of 1.0×10 １８ cm －３ Si-doped N-type Al film with a thickness of 10 nm ０．０６ Ga ０．９４ This is the N layer.

[0157] The nitride-based semiconductor light-emitting device according to this embodiment having the above-described configuration also exhibits the same effects as those of the nitride-based semiconductor light-emitting device 700 according to the seventh embodiment.

[0158] In addition, in this embodiment, the N-type intermediate layer 1005 has a first N-type intermediate layer 1005a having an average band gap energy smaller than that of the N-type cladding layer 104, and a second N-type intermediate layer 1005b arranged above the first N-type intermediate layer 1005a and having an average band gap energy larger than that of the first N-type intermediate layer 1005a.

[0159] As described above, the residual impurities tend to increase the impurity concentration in the layers stacked on the N-type cladding layer 104. This effect can occur over a film thickness of approximately 20 nm or more. By disposing an N-type intermediate layer in most of this region where the impurity concentration is likely to be high, optical loss can be suppressed. However, if the refractive index of the N-type intermediate layer is high and the film thickness of the N-type intermediate layer is large, the optical confinement function in the active layer 107 may be significantly reduced.

[0160] In this embodiment, the average bandgap energy of the first N-type intermediate layer 1005a is made smaller than the average bandgap energy of the N-type cladding layer 104, thereby making the average refractive index of the first N-type intermediate layer 1005a larger than the average refractive index of the N-type cladding layer 104. As a result, the first N-type intermediate layer 1005a, which functions as a light guide layer, is disposed in the N-type intermediate layer 1005. Therefore, it is possible to suppress a decrease in the light confinement function in the active layer 107 in the nitride-based semiconductor light-emitting device according to this embodiment.

[0161] Furthermore, the average impurity concentration in the first N-type intermediate layer 1005 a may be lower than the average impurity concentration in the second N-type intermediate layer 1005 b, which can suppress a shift of the optical absorption edge to the long wavelength side caused by impurities in the first N-type intermediate layer 1005 a, thereby suppressing optical loss in the first N-type intermediate layer 1005 a.

[0162] The thickness of the first N-type intermediate layer 1005a may be less than 15 nm, which can suppress optical loss in the first N-type intermediate layer 1005a.

[0163] In this embodiment, N-type intermediate layer 1005 has two layers, first N-type intermediate layer 1005a and second N-type intermediate layer 1005b, but N-type intermediate layer 1005 may have three or more layers. For example, N-type intermediate layer 1005 may further have a third N-type intermediate layer disposed above second N-type intermediate layer 1005b and having an average band gap energy smaller than that of second N-type intermediate layer 1005b.

[0164] Eleventh Embodiment A nitride-based semiconductor light-emitting device according to an eleventh embodiment will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 100 according to the first embodiment mainly in the layer structure between the active layer and the electron barrier layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below, focusing on the differences from nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0165] [11-1. Overall Configuration] The overall configuration of the nitride-based semiconductor light-emitting device according to this embodiment will be described with reference to Fig. 18 and Fig. 19. Fig. 18 is a schematic cross-sectional view showing the overall configuration of nitride-based semiconductor light-emitting device 1100 according to this embodiment. Fig. 18 shows a cross-section of nitride-based semiconductor light-emitting device 1100 at the same position as in Fig. 2. Fig. 19 is a schematic graph showing the distribution of band gap energy and impurity concentration in the stacking direction of nitride-based semiconductor light-emitting device 1100 according to this embodiment.

[0166] As shown in FIG. 18 , the nitride-based semiconductor light-emitting element 1100 according to this embodiment includes a substrate 101, a semiconductor laminate 1100S, a current blocking layer 120, a P-side electrode 131, an adhesion layer 132, a pad electrode 133, and an N-side electrode 140.

[0167] The semiconductor laminate 1100S has an underlayer 102, a buffer layer 103, an N-type cladding layer 1104, an N-side optical guide layer 106, an active layer 1107, a lower P-side optical guide layer 1111a, a lower P-side intermediate layer 1110a, an electron barrier layer 109, a P-type intermediate layer 1110, a P-side optical guide layer 111, a P-type cladding layer 112, and a contact layer 113.

[0168] The N-type cladding layer 1104 is disposed above the substrate 101 and is an N-type nitride-based semiconductor layer containing Al. In this embodiment, the N-type cladding layer 1104 has an average concentration of 1.0×10 １８ cm －３ Si-doped N-type Al film with a thickness of 1500 nm ０．０６５ Ga ０．９３５ This is the N layer.

[0169] The active layer 1107 is disposed above the N-side optical guide layer 106 and is a nitride-based semiconductor layer including a well layer 107b and barrier layers 107a and 1107c containing Al. The well layer 107b is disposed between the barrier layer 107a and the barrier layer 1107c.

[0170] The barrier layer 1107c is a nitride-based semiconductor layer disposed above the N-side optical guide layer 106 and functions as a barrier for the quantum well structure. The barrier layer 1107c is disposed above the barrier layer 107a. In this embodiment, the average band gap energy of the barrier layer 1107c is larger than the average band gap energy of the well layer 107b. In this embodiment, the barrier layer 1107c is a 10 nm-thick undoped Al ０．０４ Ga ０．９６ This is the N layer.

[0171] The lower P-side light guide layer 1111a is a nitride-based semiconductor layer containing Al and is disposed between the active layer 1107 and the electron barrier layer 109. In this embodiment, the lower P-side light guide layer 1111a is disposed below the lower P-side intermediate layer 1110a. The lower P-side light guide layer 1111a has a higher average refractive index and a lower average bandgap energy than the P-type cladding layer 112. The average bandgap energy of the lower P-side light guide layer 1111a is also lower than the average bandgap energy of the P-type intermediate layer 1110 and the average bandgap energy of the uppermost barrier layer 1107c (i.e., closest to the electron barrier layer 109) of the multiple barrier layers in the active layer 1107. This facilitates electrical conduction of holes from the P-type cladding layer 112 through the electron barrier layer 109 to the active layer 1107. This allows the operating voltage of the nitride-based semiconductor light emitting device 1100 to be reduced.

[0172] In this embodiment, the average bandgap energy of the lower P-side optical guiding layer 1111a is smaller than that of the lower P-side intermediate layer 1110a. The lower P-side optical guiding layer 1111a may be, for example, an AlGaN layer or an AlGaInN layer. A detailed configuration example of the lower P-side optical guiding layer 1111a will be described later.

[0173] The lower P-side intermediate layer 1110a is a nitride-based semiconductor layer containing Al, and is disposed between the lower P-side optical guide layer 1111a and the electron barrier layer 109. The average band gap energy of the lower P-side intermediate layer 1110a is larger than that of the lower P-side optical guide layer 1111a and smaller than that of the electron barrier layer 109. The lower P-side intermediate layer 1110a has an average concentration of, for example, 2.0×10 １８ cm －３ The lower P-side intermediate layer 1110a may be doped with the following P-type impurities (the lower P-side intermediate layer 1110a may be undoped). The average concentration of the P-type impurities in the lower P-side intermediate layer 1110a may be lower than the average concentration of the P-type impurities in the P-type intermediate layer 1110. In this way, the average concentration of the P-type impurities in the lower P-side intermediate layer 1110a may be set to 2.0×10 １８ cm －３In this embodiment, the lower P-side intermediate layer 1110a is made of Al 3 nm thick. ０．０４ Ga ０．９６ The N layer is thin and undoped, which reduces free carrier loss and suppresses voltage increases.

[0174] The P-type intermediate layer 1110 is disposed above the electron barrier layer 109 and is a P-type nitride-based semiconductor layer containing Al. In this embodiment, the P-type intermediate layer 1110 has an average concentration of 1.0×10 １９ cm －３ P-type Al doped with Mg having a thickness of 56 nm ０．０５ Ga ０．９５ In this embodiment, the lower end of the ridge 21R is located in the P-type intermediate layer 1110, and the distance dc between the lower end of the ridge 21R and the electron barrier layer 109 is 55 nm. The lower end of the ridge 21R may also be located in the P-side optical guide layer 111 above the P-type intermediate layer 1110. For example, the distance dc between the lower end of the ridge 21R and the electron barrier layer 109 may be 58 nm.

[0175] [11-2. Operating Characteristics of Structural Example 1] The operating characteristics of Structural Example 1 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment will be described. In Structural Example 1 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment, the lower P-side light-guiding layer 1111a is an AlGaN layer. The operating characteristics of Structural Example 1 of the nitride-based semiconductor light-emitting device 1100 will be described below with reference to FIGS. 20 to 25. FIG. 20 is a graph showing the relationship between the waveguide loss and the Al composition ratio of the lower P-side light-guiding layer 1111a of Structural Example 1 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment. FIG. 21 is a graph showing the relationship between the operating current and the Al composition ratio of the lower P-side light-guiding layer 1111a of Structural Example 1 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment when power consumption is 0.5 W. FIG. 22 is a graph showing the relationship between the operating voltage and the Al composition ratio of the lower P-side light-guiding layer 1111a of Structural Example 1 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment when power consumption is 0.5 W. 23 is a graph showing the relationship between the optical confinement factor and the Al composition ratio of the lower P-side light guide layer 1111a of Structural Example 1 of the nitride-based semiconductor light-emitting device 1100 according to the present embodiment. FIG. 24 is a graph showing the relationship between the effective refractive index difference ΔN and the Al composition ratio of the lower P-side light guide layer 1111a of Structural Example 1 of the nitride-based semiconductor light-emitting device 1100 according to the present embodiment. FIG. 25 is a graph showing the relationship between the WPE (Wall-Plug Efficiency) and the Al composition ratio of the lower P-side light guide layer 1111a when the power consumption is 0.5 W of Structural Example 1 of the nitride-based semiconductor light-emitting device 1100 according to the present embodiment. FIGS. 20 to 25 show the relationships when the film thickness T1 of the lower P-side light guide layer 1111a is 9 nm, 20 nm, 40 nm, and 60 nm.

[0176] 21 to 25, it can be seen that as the Al composition ratio of the lower P-side optical guiding layer 1111a, which is an AlGaN layer, decreases, the operating voltage and operating current decrease, and the optical confinement factor, effective refractive index difference ΔN, and WPE increase. Based on FIG. 21 to 25, the Al composition ratio of the lower P-side optical guiding layer 1111a may be set to 4% or less.

[0177] 21 to 23 and 25, it can be seen that as the thickness T1 of the lower P-side optical guide layer 1111a increases, the operating voltage and operating current decrease, and the optical confinement factor and WPE increase. Based on FIGS. 21 to 23 and 25, the thickness T1 of the lower P-side optical guide layer 1111a may be set to 9 nm or more. On the other hand, it can be seen from FIG. 24 that when the Al composition ratio of the lower P-side optical guide layer 1111a is 1% or more, the effective refractive index difference ΔN decreases as the thickness T1 increases, and the effective refractive index difference ΔN decreases as the Al composition ratio of the lower P-side optical guide layer 1111a increases. Based on FIG. 24, it can be seen that, when the Al composition ratio of the lower P-side optical guide layer 1111a is 1%, the effective refractive index difference ΔN decreases as the thickness T1 increases. －３ In order to obtain an effective refractive index difference ΔN of about 100 nm or more, the thickness T1 of the lower p-side optical guide layer 1111a may be set to 60 nm or less.

[0178] 20 , the waveguide loss is almost independent of the Al composition ratio of the lower P-side optical guiding layer 1111a, but the Al composition ratio of the lower P-side optical guiding layer 1111a may be greater than 0 to reduce optical absorption loss in the lower P-side optical guiding layer 1111a. This allows the bandgap energy of the lower P-side optical guiding layer 1111a to be greater than the bandgap energy of GaN, thereby reducing optical absorption loss in the lower P-side optical guiding layer 1111a. Furthermore, to further reduce optical absorption loss in the lower P-side optical guiding layer 1111a, the Al composition ratio of the lower P-side optical guiding layer 1111a may be 1% or more.

[0179] From the viewpoint of increasing the refractive index of the lower p-side optical guide layer 1111a and improving electrical conductivity, the band gap energy of the lower p-side optical guide layer 1111a may be equal to or lower than the band gap energy of the adjacent barrier layer 1107c. For example, in this embodiment, the barrier layer 1107c is made of Al ０．０４ Ga ０．９６ Since the lower P-side optical guide layer 1111a is an N layer, the Al composition ratio of the lower P-side optical guide layer 1111a may be 4% or less in order to make the band gap energy of the lower P-side optical guide layer 1111a equal to or less than the band gap energy of the barrier layer 1107c.

[0180] The Al composition ratio of the lower P-side light guide layer 1111a may be equal to or less than the Al composition ratio of the P-side light guide layer 111. For example, in this embodiment, since the Al composition ratio of the P-side light guide layer 111 is 3%, the Al composition ratio of the lower P-side light guide layer 1111a may be 3% or less. This allows the refractive index of the lower P-side light guide layer 1111a to be equal to or greater than the refractive index of the P-side light guide layer 111, thereby reducing the operating voltage and operating current and increasing the optical confinement factor, effective refractive index difference ΔN, and WPE.

[0181] The lower p-side optical guide layer 1111a may be an undoped AlGaN layer, which can suppress the light absorption caused by the increase in impurity concentration described above.

[0182] An example of configuration example 1 of nitride-based semiconductor light-emitting element 1100 according to the present embodiment will be described with reference to Fig. 26. Fig. 26 is a diagram showing the configurations and characteristics of examples 1 to 4 of nitride-based semiconductor light-emitting element 1100 according to the present embodiment. Fig. 26 also shows the configuration and characteristics of a nitride-based semiconductor light-emitting element according to comparative example 2. The nitride-based semiconductor light-emitting element according to comparative example 2 differs from nitride-based semiconductor light-emitting element 1100 according to the present embodiment in that it does not include lower P-side light guide layer 1111a, but is the same in other respects.

[0183] As shown in FIG. 26 , in Example 1, the Al composition ratio of the lower P-side light guide layer 1111a is 1.0%, and the film thickness T1 is 9.0 nm; in Example 2, the Al composition ratio of the lower P-side light guide layer 1111a is 2.0%, and the film thickness T1 is 20.0 nm; in Example 3, the Al composition ratio of the lower P-side light guide layer 1111a is 3.0%, and the film thickness T1 is 40.0 nm; and in Example 4, the Al composition ratio of the lower P-side light guide layer 1111a is 1.0%, and the film thickness T1 is 60.0 nm.

[0184] 26, in Examples 1 to 4, the operating voltage and operating current are reduced, and the optical confinement factor and WPE are increased, compared to Comparative Example 2, which does not include the lower P-side optical guide layer 1111a. －３Thus, in Examples 1 to 4, by providing the lower P-side optical guide layer 1111a, the effective refractive index difference ΔN of 10×10 －３ While realizing the above effective refractive index difference ΔN, the operating voltage and operating current can be reduced, and the optical confinement factor and WPE can be increased.

[0185] [11-3. Operating Characteristics of Structural Example 2] The operating characteristics of Structural Example 2 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment will be described. In Structural Example 2 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment, the lower P-side light-guiding layer 1111a is an AlGaInN layer. The operating characteristics of Structural Example 2 of the nitride-based semiconductor light-emitting device 1100 will be described below with reference to FIGS. 27 to 32. FIG. 27 is a graph showing the relationship between the waveguide loss and the In composition ratio of the lower P-side light-guiding layer 1111a of Structural Example 2 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment. FIG. 28 is a graph showing the relationship between the operating current and the In composition ratio of the lower P-side light-guiding layer 1111a of Structural Example 2 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment when power consumption is 0.5 W. FIG. 29 is a graph showing the relationship between the operating voltage and the In composition ratio of the lower P-side light-guiding layer 1111a of Structural Example 2 of the nitride-based semiconductor light-emitting device 1100 according to this embodiment when power consumption is 0.5 W. FIG. 30 is a graph showing the relationship between the optical confinement factor and the In composition ratio of the lower P-side light guide layer 1111a in Structural Example 2 of the nitride-based semiconductor light-emitting element 1100 according to this embodiment. FIG. 31 is a graph showing the relationship between the effective refractive index difference ΔN and the In composition ratio of the lower P-side light guide layer 1111a in Structural Example 2 of the nitride-based semiconductor light-emitting element 1100 according to this embodiment. FIG. 32 is a graph showing the relationship between the WPE and the In composition ratio of the lower P-side light guide layer 1111a when the power consumption is 0.5 W in Structural Example 2 of the nitride-based semiconductor light-emitting element 1100 according to this embodiment. FIGS. 27 to 32 show the relationship when the thickness T1 of the lower P-side light guide layer 1111a is 9 nm, 20 nm, 40 nm, and 60 nm. The Al composition ratio of the lower P-side light guide layer 1111a is 4.0% in all cases.

[0186] 28 to 32, it can be seen that as the In composition ratio of the lower P-side optical guiding layer 1111a, which is an AlGaInN layer, increases, the operating voltage and operating current decrease, and the optical confinement factor, effective refractive index difference ΔN, and WPE increase. Based on FIG. 28 to 32, the In composition ratio of the lower P-side optical guiding layer 1111a may be set to a value greater than 0%.

[0187] 28 to 30 and 32, it can be seen that as the thickness T1 of the lower P-side optical guiding layer 1111a increases, the operating voltage and operating current decrease, and the optical confinement factor and WPE increase. Based on FIGS. 28 to 30 and 32, the thickness T1 of the lower P-side optical guiding layer 1111a may be set to 9 nm or more. On the other hand, it can be seen from FIG. 31 that when the In composition ratio of the lower P-side optical guiding layer 1111a is 1% or more, the effective refractive index difference ΔN decreases as the thickness T1 increases, and the effective refractive index difference ΔN increases as the In composition ratio of the lower P-side optical guiding layer 1111a increases. Based on FIG. 31, it can be seen that, when the In composition ratio of the lower P-side optical guiding layer 1111a is 1%, the effective refractive index difference ΔN decreases as the thickness T1 increases, and the effective refractive index difference ΔN increases as the In composition ratio of the lower P-side optical guiding layer 1111a increases. －３ In order to obtain an effective refractive index difference ΔN of about 100 nm or more, the thickness T1 of the lower p-side optical guide layer 1111a may be set to 60 nm or less.

[0188] 27 , the waveguide loss is almost independent of the In composition ratio of the lower p-side optical guiding layer 1111a. However, to reduce optical absorption loss in the lower p-side optical guiding layer 1111a, the composition of the lower p-side optical guiding layer 1111a may be set so that the bandgap energy of the lower p-side optical guiding layer 1111a is greater than the bandgap energy of GaN. The Al composition ratio of the lower p-side optical guiding layer 1111a may be 3% or more and 6% or less, and the In composition ratio may be greater than 0% and 2% or less. Within such ranges of the Al composition ratio and In composition ratio of the lower p-side optical guiding layer 1111a, from the viewpoints of increasing the refractive index and improving the electrical conductivity of the lower p-side optical guiding layer 1111a, the Al composition ratio and In composition ratio may be set so that the bandgap energy of the lower p-side optical guiding layer 1111a is equal to or less than the bandgap energy of the adjacent barrier layer 1107c.

[0189] The bandgap energy of the lower P-side light guide layer 1111a may be equal to or lower than the bandgap energy of the P-side light guide layer 111. This allows the refractive index of the lower P-side light guide layer 1111a to be equal to or higher than the refractive index of the P-side light guide layer 111, thereby reducing the operating voltage and operating current and increasing the optical confinement factor, the effective refractive index difference ΔN, and the WPE.

[0190] The lower p-side optical guide layer 1111a may be an undoped AlGaInN layer, which can suppress the light absorption caused by the increase in impurity concentration described above.

[0191] By using an AlGaInN layer as the lower P-side optical guide layer 1111a, the AlGaInN layer, which is a compressive strained layer with respect to the substrate 101, can be disposed below and near the ridge 21R. This reduces the shear stress at the bottom end of the ridge 21R caused by the AlGaN layer, which is a tensile strained layer with respect to the substrate 101. Furthermore, warping of the wafer, which is the base material used in manufacturing the nitride-based semiconductor light-emitting element 1100, can be suppressed, and the occurrence of wafer cracking in the subsequent process of laminating the lower P-side optical guide layer 1111a can be suppressed.

[0192] The Al composition ratio of the lower p-side light guide layer 1111a may be equal to the Al composition ratio of the adjacent barrier layer 1107c. In this case, when the barrier layer 1107c and the lower p-side light guide layer 1111a are successively formed, only the In composition ratio needs to be changed in the formation process of the lower p-side light guide layer 1111a compared to the formation process of the barrier layer 1107c. This improves controllability of the atomic composition in the formation process of the lower p-side light guide layer 1111a, thereby making the in-plane distribution of the composition of the lower p-side light guide layer 1111a (distribution in a plane perpendicular to the stacking direction) uniform. This allows, for example, uniform characteristics of each nitride-based semiconductor light-emitting element 1100 formed on a wafer. The In composition ratio of the lower p-side light guide layer 1111a may also vary depending on the position in the stacking direction. For example, the In composition ratio in the lower P-side optical guiding layer 1111a in a region close to the active layer 1107 may be higher than the In composition ratio in a region far from the active layer 1107. This reduces the band gap energy in the region of the lower P-side optical guiding layer 1111a close to the active layer 1107, thereby increasing the hole conductivity in that region. Therefore, the operating voltage of the nitride-based semiconductor light-emitting device 1100 can be further reduced.

[0193] An example of Configuration Example 2 of nitride-based semiconductor light-emitting device 1100 according to the present embodiment will be described with reference to Fig. 33. Fig. 33 is a diagram showing the configurations and characteristics of Examples 5 to 8 of nitride-based semiconductor light-emitting device 1100 according to the present embodiment. Fig. 33 also shows the configuration and characteristics of a nitride-based semiconductor light-emitting device according to Comparative Example 2.

[0194] 33, the Al composition ratio of the lower P-side optical guide layer 1111a is 4.0% and the In composition ratio is 1.3% in Examples 5 to 8. In Example 5, the film thickness T1 is 9.0 nm, in Example 6, the film thickness T1 is 20.0 nm, in Example 7, the film thickness T1 is 40.0 nm, and in Example 8, the film thickness T1 is 60.0 nm.

[0195] 33, in Examples 5 to 8, the operating voltage and operating current are reduced, and the optical confinement factor and WPE are increased, compared to Comparative Example 2, which does not include the lower P-side optical guide layer 1111a. －３ Thus, in Examples 5 to 8, by providing the lower P-side optical guide layer 1111a, an effective refractive index difference ΔN of 10×10 －３ While realizing the above effective refractive index difference ΔN, the operating voltage and operating current can be reduced, and the optical confinement factor and WPE can be increased.

[0196] (Modifications, etc.) Although the nitride-based semiconductor light-emitting device according to the present disclosure has been described above based on the respective embodiments, the present disclosure is not limited to the above-described respective embodiments.

[0197] For example, in the above-described embodiments, examples have been described in which the nitride-based semiconductor light-emitting element is a semiconductor laser element. However, the nitride-based semiconductor light-emitting element is not limited to a semiconductor laser element. For example, the nitride-based semiconductor light-emitting element may be a superluminescent diode. In this case, the reflectance of the end face of the semiconductor stack included in the nitride-based semiconductor light-emitting element with respect to the output light from the semiconductor stack may be 0.1% or less. Such a reflectance can be achieved, for example, by forming an anti-reflection film made of a dielectric multilayer film or the like on the end face. Alternatively, by using an inclined stripe structure in which the ridge serving as the waveguide intersects with the front end face at an angle of 5° or more from the normal direction of the front end face, the proportion of the component of the guided light reflected at the front end face that recouples with the waveguide and becomes guided light can be reduced to a small value of 0.1% or less.

[0198] In addition, in embodiments 1 to 5, the impurity concentration in the P-type intermediate layer decreases with increasing distance from the electron barrier layer 109, but the impurity concentration may increase with increasing distance from the electron barrier layer 109 in at least a portion of the P-type intermediate layer.

[0199] Furthermore, although the nitride-based semiconductor light-emitting devices according to the seventh to ninth embodiments each include a P-type intermediate layer, the P-type intermediate layer may not be included.

[0200] Furthermore, although the P-type cladding layer 112 has a uniform Al composition ratio, the configuration of the P-type cladding layer 112 is not limited to this. For example, the P-type cladding layer 112 may have a superlattice structure in which a plurality of AlGaN layers and a plurality of GaN layers are alternately stacked.

[0201] Although the first embodiment has been described above with reference to a configuration in which the p-side electrode 131 contains Ag, the other embodiments may also include the p-side electrode 131. As a result, the same effects as those achieved by the p-side electrode 131 containing Ag in the first embodiment can also be achieved in the other embodiments.

[0202] This disclosure also includes forms obtained by applying various modifications to the above-mentioned embodiments that a person skilled in the art would conceive, and forms realized by arbitrarily combining the components and functions of the above-mentioned embodiments within the scope of the present disclosure.

[0203] For example, each of the configurations according to the second to sixth embodiments may be combined with each of the configurations according to the seventh to ninth embodiments.

[0204] Furthermore, the P-type graded region according to the fourth embodiment may be included in the P-type intermediate layer according to the other embodiments.

[0205] Furthermore, the N-type graded region according to the ninth embodiment may be included in the N-type intermediate layer according to the seventh or eighth embodiment.

[0206] The nitride-based semiconductor light-emitting element of the present disclosure can be applied, for example, as a high-output, highly efficient light source for exposure devices and processing machines.

[0207] 10T Element isolation trench 11R, 21R Ridge 11Rs Side surface 11T, 21T Groove 100, 300, 700, 1100 Nitride-based semiconductor light-emitting device 100F, 100R End surface 100S, 700S, 1100S Semiconductor laminate 101 Substrate 102 Underlayer 103 Buffer layer 104, 1104 N-type cladding layer 106, 706 N-side optical guide layer 107, 1107 Active layer 107a, 107c, 1107c Barrier layer 107b Well layer 109 Electron barrier layer 110, 210, 410, 510, 610, 1110 P-type intermediate layer 111 P-side optical guide layer 112 P-type cladding layer 113 Contact layer 120 Current blocking layer 131 P-side electrode 132 Adhesion layer 133 Pad electrode 140 N-side electrode 410a, 610a First P-type intermediate layer 410b, 610b Second P-type intermediate layer 705, 805, 905, 1005 N-type intermediate layer 805a, 1005a First N-type intermediate layer 805b, 1005b Second N-type intermediate layer 1110a Lower P-side intermediate layer 1111a Lower P-side optical guide layer

Claims

1. A nitride-based semiconductor light-emitting element that emits light, A substrate; an N-type cladding layer including Al disposed above the substrate; an N-side optical guide layer including Al, the N-side optical guide layer being disposed above the N-type cladding layer; an active layer disposed above the N-side optical guide layer and including one or more well layers and a plurality of barrier layers including Al; an electron barrier layer including Al, the electron barrier layer being disposed above the active layer; a P-type intermediate layer including Al and disposed above the electron barrier layer; a P-side optical guide layer including Al, the P-side optical guide layer being disposed above the P-type intermediate layer; a P-type cladding layer including Al and disposed above the P-side optical guide layer; the average band gap energy of the electron barrier layer is greater than the average band gap energy of the P-type cladding layer; the average band gap energy of the P-type intermediate layer is greater than the average band gap energy of the P-side optical guiding layer and less than the average band gap energy of the electron barrier layer; an average impurity concentration of the P-type intermediate layer is lower than an average impurity concentration of the electron barrier layer and higher than an average impurity concentration of the P-side optical guide layer; the P-type intermediate layer has an impurity concentration gradient region in which the impurity concentration decreases with increasing distance from the electron barrier layer, The peak wavelength of the light is less than 400 nm. Nitride-based semiconductor light-emitting element.

2. The average band gap energy of the P-type intermediate layer is smaller than the average band gap energy of the P-type cladding layer. The nitride-based semiconductor light-emitting device according to claim 1 .

3. The thickness of the P-type intermediate layer is 10 nm or more. The nitride-based semiconductor light-emitting device according to claim 1 .

4. The thickness of the P-type intermediate layer is 20 nm or more. The nitride-based semiconductor light-emitting device according to claim 3 .

5. the P-type intermediate layer is AlGaN; The average Al composition ratio of the P-type intermediate layer is greater than 3%. The nitride-based semiconductor light-emitting device according to claim 1 .

6. The average Al composition ratio of each of the N-type cladding layer, the N-side optical guide layer, the P-type intermediate layer, the P-side optical guide layer, and the P-type cladding layer is less than 10%. The nitride-based semiconductor light-emitting device according to claim 1 .

7. The P-type intermediate layer is A first P-type intermediate layer; a second P-type intermediate layer disposed above the first P-type intermediate layer and having an average band gap energy smaller than that of the first P-type intermediate layer; The nitride-based semiconductor light-emitting device according to claim 1 .

8. the first P-type intermediate layer has an average band gap energy greater than the average band gap energy of the P-type cladding layer; The average band gap energy of the P-type intermediate layer is smaller than the average band gap energy of the P-type cladding layer. The nitride-based semiconductor light-emitting device according to claim 7 .

9. The P-type intermediate layer is a first P-type intermediate layer having an average band gap energy smaller than that of the P-type cladding layer; a second P-type intermediate layer disposed above the first P-type intermediate layer and having an average band gap energy greater than that of the first P-type intermediate layer; The nitride-based semiconductor light-emitting device according to claim 1 .

10. the P-type intermediate layer has a P-type gradient region in which the Al composition ratio decreases with increasing distance from the electron barrier layer, The average band gap energy of the P-type intermediate layer is smaller than the average band gap energy of the P-type cladding layer. The nitride-based semiconductor light-emitting device according to claim 1 .

11. the nitride semiconductor light emitting element has a ridge extending in the propagation direction of the light, At least a portion of the P-type intermediate layer is disposed on the ridge. The nitride-based semiconductor light-emitting device according to claim 1 .

12. the nitride semiconductor light emitting element has a ridge extending in the propagation direction of the light, The inclination angle of the side surface of the ridge with respect to the main surface of the substrate is equal to or greater than 60 degrees and less than 80 degrees. The nitride-based semiconductor light-emitting device according to claim 1 .

13. a lower P-side optical guiding layer disposed between the active layer and the electron barrier layer, the lower P-side optical guiding layer comprising Al; The average band gap energy of the lower P-side optical guide layer is smaller than the average band gap energy of the P-type intermediate layer and the average band gap energy of the uppermost barrier layer among the plurality of barrier layers. The nitride-based semiconductor light-emitting device according to claim 1 .

14. a lower P-side intermediate layer including Al and disposed between the lower P-side optical guiding layer and the electron barrier layer; The average band gap energy of the lower P-side intermediate layer is greater than the average band gap energy of the lower P-side optical guide layer and is smaller than the average band gap energy of the electron barrier layer. The nitride-based semiconductor light-emitting device according to claim 13 .

15. The lower P-side optical guiding layer is an AlGaN layer. The nitride-based semiconductor light-emitting device according to claim 13 .

16. The lower P-side optical guiding layer is an AlGaInN layer. The nitride-based semiconductor light-emitting device according to claim 13 .

17. A nitride-based semiconductor light-emitting element that emits light, A substrate; an N-type cladding layer including Al disposed above the substrate; an N-type intermediate layer including Al, the N-type intermediate layer being disposed above the N-type cladding layer; an N-side optical guide layer including Al, the N-side optical guide layer being disposed above the N-type intermediate layer; an active layer disposed above the N-side optical guide layer and including one or more well layers and a plurality of barrier layers including Al; a P-side optical guide layer including Al and disposed above the active layer; a P-type cladding layer including Al and disposed above the P-side optical guide layer; the average band gap energy of the N-type intermediate layer is larger than the average band gap energy of the N-side optical guide layer and smaller than the average band gap energy of the N-type cladding layer; an average impurity concentration of the N-type intermediate layer is equal to or lower than an average impurity concentration of the N-type cladding layer and is higher than an average impurity concentration of the N-side optical guide layer; the N-type intermediate layer has an impurity concentration gradient region in which the impurity concentration decreases with increasing distance from the N-type cladding layer, The peak wavelength of the light is less than 400 nm. Nitride-based semiconductor light-emitting element.

18. The thickness of the N-type intermediate layer is 20 nm or more. The nitride-based semiconductor light-emitting device according to claim 17 .

19. the N-type intermediate layer is AlGaN; The average Al composition ratio of the N-type intermediate layer is greater than 3%.

19. The nitride-based semiconductor light-emitting device according to claim 17 or 18.

20. The average Al composition ratio of each of the N-type cladding layer, the N-side optical guide layer, the N-type intermediate layer, the P-side optical guide layer, and the P-type cladding layer is less than 10%.

19. The nitride-based semiconductor light-emitting device according to claim 17 or 18.

21. The N-type intermediate layer is A first N-type intermediate layer; a second N-type intermediate layer disposed above the first N-type intermediate layer and having an average band gap energy smaller than that of the first N-type intermediate layer; 19. The nitride-based semiconductor light-emitting device according to claim 17 or 18.

22. The N-type intermediate layer has an N-type gradient region in which the Al composition ratio increases with increasing distance from the N-side optical guide layer.

19. The nitride-based semiconductor light-emitting device according to claim 17 or 18.