Nitride-based semiconductor light-emitting element

Abstract

To provide a nitride-based semiconductor light-emitting element with an excellent temperature characteristic.SOLUTION: A nitride-based semiconductor light-emitting element 100 includes: an N-type clad layer 102; an N-side guide layer 103 disposed over the N-type clad layer 102; an active layer 104 disposed over the N-side guide layer 103; a first P-side guide layer 105 disposed over the active layer 104; an electron barrier layer 106 disposed over the first P-side guide layer 105; a second P-side guide layer 107 disposed over the electron barrier layer 106; and a P-type clad layer 108 disposed over the second P-side guide layer 107. The average band gap energy of the second P-side guide layer 107 is larger than that of the first P-side guide layer 105. The average band gap energy of the P-type clad layer 108 is smaller than that of the electron barrier layer 106.SELECTED DRAWING: Figure 9

Description

[Technical Field]

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

[0002] Conventionally, nitride-based semiconductor light-emitting elements that emit blue light have been known, but there is a demand for high-output nitride-based semiconductor light-emitting elements that emit ultraviolet light with shorter wavelengths (see, for example, Patent Document 1). For example, if a watt-class ultraviolet laser light source can be realized using a nitride-based semiconductor light-emitting element, it can be used as a light source for exposure, processing, and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-131019 Summary of the Invention [Problem to be solved by the invention]

[0004] An active layer having a quantum well structure, for example, is used as the light-emitting layer of a nitride-based semiconductor light-emitting element that emits ultraviolet light. Such an active layer includes one or more well layers and multiple barrier layers. Because ultraviolet light has a shorter wavelength (i.e., higher energy) than visible light, the band gap energy of the well layer that emits ultraviolet light is greater than the band gap energy of the well layer that emits visible light. This reduces the difference between the conduction band potential energy of the barrier layer and the electron quantum level energy. In this case, electrons are more likely to leak from the well layer across the barrier layer to the P-side guide layer, increasing the operating carrier density in the well layer (i.e., the carrier density during operation of the nitride-based semiconductor light-emitting element).

[0005] For example, if a nitride-based semiconductor light-emitting device is a laser device with a ridge current injection region, the amplification gain in the current injection region of the well layer increases as the operating carrier density increases. Meanwhile, due to the relationship between the real and imaginary parts of the complex refractive index in the current injection region of the well layer (corresponding to the Kramers-Kronig relationship), the refractive index of the well layer decreases as the amplification gain in the well layer increases. Furthermore, as the carrier density in the current injection region of the well layer increases, the refractive index in the current injection region of the well layer decreases due to the plasma effect. Therefore, the refractive index of the current injection region of the well layer can be lower than the refractive index outside the current injection region of the well layer. In this case, the waveguide mechanism of the laser light propagating through the waveguide including the ridge of the laser device becomes a refractive index anti-guided gain waveguide mechanism. As a result, a larger proportion of the laser light propagates outside the current injection region of the well layer, resulting in increased absorption loss in the well layer. This increases the oscillation threshold current of the laser device and decreases the thermal saturation level. In other words, the temperature characteristics of the laser device deteriorate.

[0006] The present disclosure is intended to solve such problems, and has an object to provide a nitride-based semiconductor light-emitting device with excellent temperature characteristics. [Means for solving the problem]

[0007] In order to solve the above problems, one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure includes an N-type cladding layer, an N-side guide layer arranged above the N-type cladding layer, an active layer arranged above the N-side guide layer, a first P-side guide layer arranged above the active layer, an electron barrier layer arranged above the first P-side guide layer, a second P-side guide layer arranged above the electron barrier layer, and a P-type cladding layer arranged above the second P-side guide layer, wherein an average bandgap energy of the second P-side guide layer is larger than an average bandgap energy of the first P-side guide layer, and an average bandgap energy of the P-type cladding layer is smaller than an average bandgap energy of the electron barrier layer. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a nitride-based semiconductor light-emitting device with excellent temperature characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic plan view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the first embodiment. [Figure 2A] FIG. 2A is a schematic cross-sectional view showing the overall configuration of the nitride-based semiconductor light-emitting device according to the first embodiment. [Figure 2B] FIG. 2B is a schematic cross-sectional view showing the configuration of an active layer included in the nitride-based semiconductor light-emitting device according to the first embodiment. [Figure 3] FIG. 3 is a graph showing the distribution of band gap energy and refractive index in the stacking direction in the well layer and barrier layer of a 405 nm band semiconductor light emitting device. [Figure 4] FIG. 4 is a graph showing the distribution of band gap energy and refractive index in the stacking direction in the well layer and barrier layer of a 375 nm band semiconductor light emitting device. [Figure 5] FIG. 5 is a graph showing the distribution of the effective refractive index and gain in the horizontal direction of a semiconductor light emitting device in the 375 nm band. [Figure 6] FIG. 6 is a diagram showing a far-field pattern in the horizontal direction of a conventional ultraviolet semiconductor light-emitting element. [Figure 7] FIG. 7 is a graph schematically showing the band gap energy distribution and the light intensity distribution in the stacking direction of the semiconductor stack according to Comparative Example 1. In FIG. [Figure 8] FIG. 8 is a graph schematically showing the band gap energy distribution and the light intensity distribution in the stacking direction of the semiconductor stack according to Comparative Example 2. In FIG. [Figure 9] FIG. 9 is a graph schematically showing the band gap energy distribution and the light intensity distribution of the semiconductor laminate according to the first embodiment. [Figure 10]FIG. 10 is a diagram showing the main configurations of Examples E01 to E03 and Comparative Examples C01 to C06, and the results of characteristic calculations. [Figure 11] FIG. 11 is a diagram showing the main configurations and characteristic calculation results of Examples E04 to E06 and Comparative Examples C11 to C16. [Figure 12] FIG. 12 is a diagram showing the main configurations of Comparative Examples C02, C12, and C21 to C26, and the results of characteristic calculations. [Figure 13] FIG. 13 is a graph showing coordinates of positions in the stacking direction of the nitride-based semiconductor light-emitting element according to the first embodiment. [Figure 14] FIG. 14 is a graph showing the relationship between the operating voltage of the nitride-based semiconductor light-emitting device according to the first embodiment when operated at 200 mA and the film thickness of the first p-side guide layer. [Figure 15] FIG. 15 is a graph showing the relationship between the waveguide loss and the film thickness of the first p-side guide layer of the nitride-based semiconductor light-emitting element according to the first embodiment. [Figure 16] FIG. 16 is a graph showing the relationship between the effective refractive index difference ΔN of the nitride-based semiconductor light-emitting element according to the first embodiment and the film thickness of the first p-side guide layer. [Figure 17] FIG. 17 is a graph showing the relationship between the optical confinement coefficient of the nitride-based semiconductor light-emitting element according to the first embodiment and the film thickness of the first p-side guide layer. [Figure 18] FIG. 18 is a graph schematically showing the band gap energy distribution and the light intensity distribution in the stacking direction of the semiconductor stack of Example E02. [Figure 19] FIG. 19 is a graph schematically showing the band gap energy distribution and the light intensity distribution in the stacking direction of the semiconductor stack of Example E07. [Figure 20] FIG. 20 is a graph showing the relationship between the band gap energy in an AlxGa1-x-yInyN layer and the band gap energy in an AlzGa1-zN layer. [Figure 21]FIG. 21 is a schematic side view showing warpage of the substrate and the semiconductor stack that occurs when the semiconductor stack is stacked on the substrate according to the first embodiment. [Figure 22] FIG. 22 is a graph showing the relationship between the position in the stacking direction of the semiconductor stack of Example E11 and the band gap energy. [Figure 23] FIG. 23 is a graph showing the relationship between the position in the stacking direction of the semiconductor stack of Example E11 and the stress. [Figure 24] FIG. 24 is a graph showing the relationship between the integrated stress and the position in the stacking direction of the semiconductor stack of Example E11. [Figure 25] FIG. 25 is a graph showing the relationship between the position in the stacking direction of the semiconductor stack of Example E12 and the band gap energy. [Figure 26] FIG. 26 is a graph showing the relationship between the position in the stacking direction of the semiconductor stack of Example E12 and the stress. [Figure 27] FIG. 27 is a graph showing the relationship between the integrated stress and the position in the stacking direction of the semiconductor stack of Example E12. [Figure 28] FIG. 28 is a graph illustrating the composition required for the well layer of Example E13. [Figure 29] FIG. 29 is a graph showing the relationship between the In composition ratio of the well layer and the lattice mismatch with respect to GaN. [Figure 30] FIG. 30 is a graph schematically showing the band gap energy distribution in the stacking direction of the semiconductor stack of Example E14. [Figure 31] FIG. 31 is a graph schematically showing the band gap energy distribution in the stacking direction of the semiconductor stack of Example E15. [Figure 32] FIG. 32 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the second embodiment. [Figure 33] FIG. 33 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[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] In this specification, the terms "above" and "below" do not refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. Furthermore, the terms "above" and "below" are applied not only to cases where two components are arranged with a gap between them and another component exists between the two components, but also to cases where two components are arranged in contact with each other.

[0013] (Embodiment 1) A nitride-based semiconductor light-emitting device according to a first embodiment will be described.

[0014] [1-1. Overall structure] First, the overall configuration of a nitride-based semiconductor light-emitting device according to this embodiment will be described with reference to FIGS. 1, 2A, and 2B. FIGS. 1 and 2A 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. 2A shows a cross section taken along line II-II in FIG. 1. FIG. 2B is a schematic cross-sectional view showing the configuration of an active layer 104 included in the nitride-based semiconductor light-emitting device 100 according to this embodiment. Each drawing shows an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other. The X-axis, the Y-axis, and the Z-axis represent 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.

[0015] As shown in FIG. 2A, 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. In this embodiment, the reflectivities of the facets 100F and 100R are 16% and 95%, respectively. 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 1200 μm. The nitride-based semiconductor light-emitting element 100 emits ultraviolet light having a peak wavelength in the 375 nm band, for example. The nitride-based semiconductor light-emitting element 100 may emit ultraviolet light having a peak wavelength outside the 375 nm band, or may emit light having a peak wavelength in a wavelength band other than ultraviolet light.

[0016] 2A , the nitride-based semiconductor light-emitting element 100 includes a substrate 101, a semiconductor stack 100S, a current blocking layer 110, a P-side electrode 111, and an N-side electrode 112. The semiconductor stack 100S includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, a first P-side guide layer 105, an electron barrier layer 106, a second P-side guide layer 107, a P-type cladding layer 108, and a contact layer 109.

[0017] The substrate 101 is a plate-like member that serves as a base for the nitride-based semiconductor light-emitting device 100. In this embodiment, the substrate 101 is disposed below the N-type cladding layer 102 and is made of N-type GaN. More specifically, the substrate 101 is made of N-type GaN with a concentration of 1×10 18 cm -3 The Si-doped GaN substrate is 8500 nm thick.

[0018] The N-type cladding layer 102 is an N-type nitride-based semiconductor layer disposed above the substrate 101. The N-type cladding layer 102 has a smaller refractive index than the active layer 104 and a larger average band gap energy. In this embodiment, the N-type cladding layer 102 contains Al. The average Al composition ratio of the N-type cladding layer 102 is equal to or less than the average Al composition ratio of the P-type cladding layer 108. The N-type cladding layer 102 contains Al as an impurity at a concentration of 5×10 17 cm -3 It is doped with Si.

[0019] 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 position of the interface on the substrate side in the stacking direction of the layer to the position of the interface on the side farther from the substrate, and dividing the result by the film thickness of the layer (the distance between the interface on the substrate side and the interface on the side farther from the substrate).

[0020] 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 on the substrate side to the interface position on the side farther from the substrate, and divided by the film thickness of the layer (the distance between the interface on the substrate side and the interface on the side farther from the substrate).

[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 from the interface position on the substrate side in the stacking direction of the layer to the interface position on the side farther from the substrate, and dividing the result by the film thickness of the layer (the distance between the interface on the substrate side and the interface on the side farther from the substrate).

[0022] The average impurity concentration of a certain layer is the value of the impurity concentration at a certain position in the stacking direction of that layer, integrated in the stacking direction from the interface position on the substrate side to the interface position on the side farther from the substrate, and divided by the film thickness of that layer (the distance between the interface on the substrate side and the interface farther from the substrate). In an N-type semiconductor layer, impurities refer to impurities doped to obtain N-type conductivity, and in a P-type semiconductor layer, impurities doped to obtain P-type conductivity.

[0023] The N-side guide layer 103 is disposed above the N-type cladding layer 102 and is an optical guide layer made of a nitride-based semiconductor. The N-side guide layer 103 has a higher refractive index and a smaller band gap energy than the N-type cladding layer 102. In this embodiment, the average band gap energy of the N-side guide layer 103 is larger than the average band gap energy of the first P-side guide layer 105 and smaller than the average band gap energy of the second P-side guide layer 107. The N-side guide layer 103 contains Al. The N-side guide layer 103 is an undoped nitride-based semiconductor layer. In other words, the average N-type impurity concentration of the N-side guide layer 103 is 1×10 18 cm -3 In the following description, the N-type impurity concentration in each layer on the N side and the P-type impurity concentration in each layer on the P side will also be simply referred to as the impurity concentration.

[0024] The active layer 104 is disposed above the N-side guide layer 103 and is a light-emitting layer made of a nitride-based semiconductor. In this embodiment, the active layer 104 has a quantum well structure and emits ultraviolet light. Specifically, as shown in FIG. 2B , the active layer 104 includes two barrier layers 104a and 104c and a well layer 104b disposed between the two barrier layers 104a and 104c. Note that the configuration of the active layer 104 is not limited thereto. For example, the active layer 104 may have a multiple quantum well structure. Specifically, the active layer 104 may include three or more barrier layers and two or more well layers.

[0025] Each of the barrier layers 104a and 104c is a nitride-based semiconductor layer disposed above the N-side guide layer 103 and functioning as a barrier of the quantum well structure. The barrier layer 104c is disposed above the barrier layer 104a. In this embodiment, the bandgap energy of each of the barrier layers 104a and 104c is larger than the bandgap energy of the well layer 104b, the average bandgap energy of the first P-side guide layer 105, and the average bandgap energy of the N-side guide layer 103, and is smaller than the average bandgap energy of the electron barrier layer 106.

[0026] The well layer 104b is a nitride-based semiconductor layer disposed above the barrier layer 104a and functions as a well of the quantum well structure.

[0027] The first P-side guide layer 105 is disposed above the active layer 104 and is an optical guide layer made of a nitride-based semiconductor. The first P-side guide layer 105 has a higher refractive index and a smaller band gap energy than the P-type cladding layer 108. In this embodiment, the first P-side guide layer 105 contains Al. The first P-side guide layer 105 is an undoped nitride-based semiconductor layer. In other words, the average impurity concentration of the first P-side guide layer 105 is 1×10 18 cm -3The first p-side guide layer 105 has a thickness greater than that of each of the two barrier layers 104a and 104c. The first p-side guide layer 105 has a thickness less than that of the second p-side guide layer 107. The first p-side guide layer 105 has an average band gap energy less than that of the barrier layers 104a and 104c.

[0028] The electron barrier layer 106 is a nitride-based semiconductor layer disposed above the first P-side guide layer 105. The band gap energy of the electron barrier layer 106 is larger than the band gap energy of the barrier layer 104c. This makes it possible to prevent electrons from leaking from the active layer 104 to the P-type cladding layer 108. In this embodiment, the band gap energy of the electron barrier layer 106 is larger than the band gap energy of the P-type cladding layer 108.

[0029] The second P-side guide layer 107 is disposed above the electron barrier layer 106 and is an optical guide layer made of a nitride-based semiconductor. The second P-side guide layer 107 has a higher refractive index and a smaller band gap energy than the P-type cladding layer 108. The average band gap energy of the second P-side guide layer 107 is larger than the band gap energy of the first P-side guide layer 105. In this embodiment, the second P-side guide layer 107 contains Al. The second P-side guide layer 107 is doped with an impurity. In other words, the average impurity concentration of the second P-side guide layer 107 is 1×10 18 cm -3 That's all.

[0030] The P-type cladding layer 108 is disposed above the second P-side guide layer 107 and is a cladding layer made of a P-type nitride-based semiconductor. The P-type cladding layer 108 has a lower refractive index than the active layer 104 and a higher average band gap energy. The average band gap energy of the P-type cladding layer 108 is lower than the average band gap energy of the electron barrier layer 106. In this embodiment, the P-type cladding layer 108 contains Al. The P-type cladding layer 108 is doped with Mg as an impurity. The impurity concentration at the end of the P-type cladding layer 108 closer to the active layer 104 is lower than the impurity concentration at the end farther from the active layer 104. Specifically, the P-type cladding layer 108 is an AlGaN layer with a thickness of 450 nm, and the P-type cladding layer 108 is an AlGaN layer with a concentration of 2×10 18 cm -3 a P-type AlGaN layer having a thickness of 150 nm and doped with Mg at a concentration of 1×10 19 cm -3 and a 300 nm thick P-type AlGaN layer doped with Mg.

[0031] A ridge 108R is formed in the P-type cladding layer 108. Two grooves 108T are formed in the P-type cladding layer 108, arranged along the ridge 108R and extending in the Y-axis direction. In this embodiment, the ridge width W is approximately 30 μm. As shown in FIG. 2A, the distance between the lower end of the ridge 108R (i.e., the bottom of the groove 108T) and the active layer 104 is defined as dp. The distance between the lower end of the ridge 108R and the electron barrier layer 106 is defined as dc.

[0032] The contact layer 109 is a nitride-based semiconductor layer disposed above the P-type cladding layer 108 and in ohmic contact with the P-side electrode 111. In this embodiment, the contact layer 109 is a P-type GaN layer with a thickness of 60 nm. The contact layer 109 contains impurities with a concentration of 1×10 20 cm -3 It is doped with Mg.

[0033] The current blocking layer 110 is disposed above the P-type cladding layer 108 and is an insulating layer that is transparent to light from the active layer 104. The current blocking layer 110 is disposed on the upper surfaces of the P-type cladding layer 108 and the contact layer 109 in a region other than the upper surface of the ridge 108R. The current blocking layer 110 may also be disposed on a portion of the upper surface of the ridge 108R. For example, the current blocking layer 110 may be disposed in an edge region of the upper surface of the ridge 108R. In this embodiment, the current blocking layer 110 is a SiO2 layer.

[0034] The P-side electrode 111 is a conductive layer disposed above the contact layer 109. In this embodiment, the P-side electrode 111 is disposed above the contact layer 109 and the current blocking layer 110. The P-side electrode 111 is a single-layer film or a multi-layer film formed of at least one of Cr, Ti, Ni, Pd, Pt, Ag, and Au, for example.

[0035] 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 111 on the contact layer 109, it is possible to reduce the leakage of light propagating through the waveguide into the P-side electrode 111, thereby reducing waveguide loss in the P-side electrode 111. 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, even if the thickness of the P-type cladding layer 108 is 0.4 μm or less, it is possible to reduce the leakage of light propagating through the waveguide into the P-side electrode 111, thereby reducing the series resistance of the nitride-based semiconductor light-emitting device 100 and suppressing an increase in waveguide loss. As a result, the operating voltage and operating current can be reduced.

[0036] To stably confine light propagating through the waveguide within the ridge 108R, a difference in effective refractive index (ΔN) must be created so that the effective refractive index of the inner region of the ridge 108R is greater than that of the outer region, as described below. Specifically, SiO2 with a refractive index lower than that of the P-type cladding layer 108 must be formed on the sidewalls of the ridge 108R to reduce the effective refractive index of the outer region of the ridge 108R. In this case, if the thickness of the P-type cladding layer 108 is too thin, the area in the thickness direction of the sidewalls of the ridge 108R where SiO2 is formed becomes smaller, thereby reducing the effect of reducing the effective refractive index of the outer region of the ridge 108R. For this reason, the thickness of the P-type cladding layer 108 needs to be 0.15 μm or more.

[0037] The N-side electrode 112 is a conductive layer disposed below the substrate 101 (i.e., on the principal surface of the substrate 101 opposite to the principal surface on which the N-type cladding layer 102 and the like are disposed). The N-side electrode 112 is a single-layer film or a multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt, and Au, for example.

[0038] 2A, the nitride-based semiconductor light-emitting element 100 has the above-described configuration, and therefore an effective refractive index difference ΔN occurs between the inner portion of the ridge 108R and the outer portion of the ridge 108R (the groove 108T portion), which allows light generated in the portion of the active layer 104 below the ridge 108R to be confined in the horizontal direction (i.e., the X-axis direction).

[0039] [1-2. Issues with ultraviolet semiconductor light-emitting devices] The problems that may arise in the ultraviolet semiconductor light-emitting device described in the "Problems to be Solved by the Invention" section of this disclosure will be described in detail with reference to FIGS. 3 to 6. Hereinafter, FIG. 3 is a graph showing the distribution of bandgap energy (Eg) and refractive index in the stacking direction in well layers and barrier layers of a semiconductor light-emitting device operating in the 405 nm band, which has a wavelength longer than that of ultraviolet light. FIG. 4 is a graph showing the distribution of bandgap energy (Eg) and refractive index in the stacking direction in well layers and barrier layers of a semiconductor light-emitting device operating in the 375 nm band, which is the ultraviolet range. FIG. 5 is a graph showing the distribution of effective refractive index and gain in the horizontal direction (corresponding to the X-axis direction in FIGS. 1 to 2B) of a 375 nm band semiconductor light-emitting device. FIG. 6 is a diagram showing the far-field pattern in the horizontal direction of a conventional ultraviolet semiconductor light-emitting device. The horizontal axis of FIG. 6 represents the radiation angle in the horizontal direction, and the vertical axis represents the light intensity.

[0040] 3, in a 405 nm band semiconductor light emitting device, the band gap energy of the well layer is relatively small, so the difference ΔEc between the conduction band potential energy of the barrier layer and the electron quantum level energy can be set to a relatively large value (198 meV). In this case, the Fermi energy Ef of electrons is sufficiently smaller than the conduction band potential energy of the barrier layer, so that leakage of electrons from the well layer, across the barrier layer, to the P-side semiconductor layer can be suppressed.

[0041] On the other hand, in an ultraviolet semiconductor light-emitting device, as shown in Figure 4, the band gap energy of the well layer is relatively large, so the difference ΔEc between the conduction band potential energy of the barrier layer and the electron quantum level energy is small (67 meV). In this case, the Fermi energy Ef of electrons can be larger than the conduction band potential energy of the barrier layer, making it easier for electrons to leak from the well layer, over the barrier layer, into the P-side semiconductor layer. As a result, more carriers cannot contribute to light emission in the well layer, and the operating carrier density in the well layer increases.

[0042] Increasing the operating carrier density in the well layer in this way increases the optical amplification gain in the well layer. Meanwhile, due to the relationship between the real and imaginary parts of the complex refractive index in the current injection region of the well layer, the refractive index of the well layer decreases as the amplification gain in the well layer increases. Furthermore, as the carrier density in the current injection region of the well layer increases, the refractive index in the current injection region of the well layer decreases due to the plasma effect. Therefore, the refractive index of the current injection region of the well layer can be lower than the refractive index outside the current injection region of the well layer. For example, if the semiconductor light-emitting device is a laser device with a ridge and current is injected into the ridge, the effective refractive index in the current injection region, i.e., the ridge, can be lower than the refractive index outside the current injection region, as shown in FIG. 5.

[0043] As a result, the waveguide mechanism of the laser light propagating through the waveguide corresponding to the ridge of the semiconductor light-emitting device becomes a refractive index anti-guiding gain waveguide mechanism. Therefore, a higher proportion of the laser light propagates outside the current injection region (the region below the ridge) in the well layer, resulting in a peak at the base of the far-field pattern of the semiconductor light-emitting device, as shown in FIG. 6. In this case, light is absorbed outside the current injection region in the well layer, increasing absorption loss in the well layer. This increases the oscillation threshold current of the semiconductor light-emitting device and reduces the thermal saturation level. This means that the temperature characteristics of the laser device deteriorate. Furthermore, a nonlinear bend (a kink) may occur in a graph showing the current-light output (IL) characteristics of the semiconductor light-emitting device. This means that the stability of the light output of the semiconductor light-emitting device deteriorates.

[0044] The nitride-based semiconductor light-emitting device 100 according to this embodiment solves such problems associated with ultraviolet semiconductor light-emitting devices.

[0045] [1-3.Light intensity distribution] The light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be described with reference to Figs. 7 to 9, in comparison with comparative examples. Figs. 7 and 8 are graphs schematically showing the bandgap energy distribution and light intensity distribution in the stacking direction of the semiconductor stacks according to comparative example 1 and comparative example 2, respectively. Fig. 9 is a graph schematically showing the bandgap energy distribution and light intensity distribution of the semiconductor stack 100S according to this embodiment. Figs. 8 and 9 also show the P-type impurity concentration distribution in the stacking direction of the semiconductor stacks according to comparative example 2 and this embodiment, respectively.

[0046] 7 includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, a P-side guide layer 915, an electron barrier layer 916, and a P-type cladding layer 108. The semiconductor stack of Comparative Example 1 differs from the semiconductor stack 100S of this embodiment in the configuration of the P-side guide layer 915. In the semiconductor stack of Comparative Example 1, the N-side guide layer 103 and the P-side guide layer 915 have the same composition and film thickness. The electron barrier layer 916 is disposed between the P-side guide layer 915 and the P-type cladding layer 108.

[0047] In the semiconductor stack according to Comparative Example 1, when the N-type cladding layer 102 and the P-type cladding layer 108 are made of AlGaN and have the same Al composition ratio, the P-type cladding layer 108 has a higher refractive index than the N-type cladding layer 102. This is thought to be because the ionization energy of the P-type impurity, Mg, is greater than the ionization energy of the N-type impurity, Si, so the P-type impurity concentration must be set higher than the N-type impurity concentration. This results in greater light absorption and a higher refractive index in the P-type layer, which forms a relatively deep energy level. Therefore, as shown in FIG. 7 , the peak position of the light intensity distribution is biased toward the P-type cladding layer 108 from the active layer 104. As a result, in the semiconductor stack according to Comparative Example 1, the optical confinement coefficient of the active layer 104 decreases, and the operating carrier density increases. This results in a decrease in the refractive index of the well layer 104b.

[0048] 2A , the effective refractive index difference ΔN in the semiconductor stack according to Comparative Example 1 also depends on the distance dp from the lower end of the ridge 108R to the active layer 104. Because the semiconductor stack according to Comparative Example 1 does not include the second P-side guide layer 107, in order to position the peak position of the vertical light intensity distribution near the active layer 104, it is necessary to increase the film thickness of the P-side guide layer 915, which has a higher refractive index than the P-type cladding layer 108. Therefore, the distance dp in the semiconductor stack according to Comparative Example 1 is greater than the distance dp in the present embodiment. Therefore, the effective refractive index difference ΔN in the semiconductor stack according to Comparative Example 1 is smaller than the effective refractive index difference ΔN in the present embodiment. As a result, the stability of the transverse mode of the laser light during operation is reduced in the semiconductor stack according to Comparative Example 1.

[0049] 8 includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, an electron barrier layer 926, a P-side guide layer 925, and a P-type cladding layer 108. The semiconductor stack of Comparative Example 2 differs from the semiconductor stack of Comparative Example 1 in the arrangement of the electron barrier layer 926 and the P-side guide layer 925. As shown in Fig. 8, in the semiconductor stack of Comparative Example 2, the positions of the electron barrier layer 926 and the P-side guide layer 925 in the stacking direction are swapped with the positions of the electron barrier layer 916 and the P-side guide layer 915 in the semiconductor stack of Comparative Example 1 in the stacking direction.

[0050] In the semiconductor stack according to Comparative Example 2, the electron barrier layer 926 is closer to the active layer 104 than in Comparative Example 1, so the distance dp from the lower end of the ridge 108R to the active layer 104 is smaller than the distance dp in Comparative Example 1. Therefore, the effective refractive index difference ΔN of the semiconductor stack according to Comparative Example 2 is larger than the effective refractive index difference ΔN in Comparative Example 1. As a result, the stability of the transverse mode of the laser light during operation in the semiconductor stack according to Comparative Example 2 is higher than in Comparative Example 1. However, in the semiconductor stack according to Comparative Example 2, the electron barrier layer 926 with a high concentration of P-type impurities is adjacent to the active layer 104, so the light intensity in the electron barrier layer 926 is high. Since free carrier loss is large in the electron barrier layer 926 with a high concentration of P-type impurities, the semiconductor stack according to Comparative Example 2 has a higher waveguide loss than Comparative Example 1.

[0051] 9, the semiconductor laminate 100S according to this embodiment includes a first P-side guide layer 105 having a small band gap energy (i.e., a large refractive index) between the active layer 104 and the electron barrier layer 106. Furthermore, the average band gap energy of the first P-side guide layer 105 is smaller than that of the second P-side guide layer 107, and the average refractive index of the first P-side guide layer 105 is larger than that of the second P-side guide layer 107. As a result, in the semiconductor laminate 100S according to this embodiment, the peak position of the light intensity distribution can be brought closer to the active layer 104 than in the semiconductor laminates according to Comparative Example 1 and Comparative Example 2. In addition, the average impurity concentration of the first P-side guide layer 105 is 1×10 18 cm -3 Less than, specifically 7 x 10 17 cm -3Since the first p-side guide layer 105 is a nitride-based semiconductor layer (see FIG. 9 ), free carrier loss in the first p-side guide layer 105 can be reduced. Therefore, in the present embodiment, in the light intensity distribution in the stacking direction, the proportion of light present in the undoped region near the active layer 104 and in the first p-side guide layer 105 with a low impurity concentration increases, thereby reducing free carrier loss and waveguide loss. This reduces the oscillation threshold current value and thermal saturation level. In other words, a nitride-based semiconductor light-emitting element 100 with excellent temperature characteristics and high slope efficiency can be realized. This enables high-temperature, high-output operation in the nitride-based semiconductor light-emitting element 100. Although FIG. 9 shows a case where the impurity concentration of the first p-side guide layer 105 is constant in the stacking direction, the impurity concentration may monotonically increase with increasing distance from the active layer 104 in the stacking direction. In this case, the impurity concentration in the first P-side guide layer 105 in the region close to the active layer 104 where the light intensity is high can be made lower relative to the impurity concentration in the region far from the active layer 104, so that it is possible to reduce free carrier loss while suppressing an increase in the series resistance of the nitride-based semiconductor light-emitting element 100.

[0052] The second P-side guide layer 107 of the semiconductor laminate 100S according to this embodiment is doped with an impurity. This reduces the electrical resistance of the semiconductor laminate 100S, thereby reducing the operating voltage of the nitride-based semiconductor light-emitting element 100. Furthermore, since the second P-side guide layer 107 is farther from the active layer 104 than the first P-side guide layer 105, the light distribution intensity in the vertical direction is reduced, and free carrier loss in the second P-side guide layer 107 can be suppressed even if the average impurity concentration of the second P-side guide layer 107 is higher than the average impurity concentration of the first P-side guide layer 105.

[0053] Furthermore, in this embodiment, the thickness of the first P-side guide layer 105 is made thinner than the thickness of the second P-side guide layer 107, thereby reducing the distance dp. Therefore, in this embodiment, the effective refractive index difference ΔN can be increased. Therefore, the optical confinement factor in the waveguide of the nitride-based semiconductor light-emitting device 100 can be increased. As a result, in the nitride-based semiconductor light-emitting device 100, the horizontal transverse mode of laser light can be stably confined in the waveguide, thereby suppressing the occurrence of kinks in the current-light output characteristics. Furthermore, in this embodiment, the total thickness of the first P-side guide layer 105 and the second P-side guide layer 107 is equal to or greater than the thickness of the N-side guide layer 103. This allows the distance dc to be further increased, thereby further increasing the effective refractive index difference ΔN and the optical confinement factor.

[0054] Furthermore, in this embodiment, the average Al composition ratio of the second P-side guide layer 107 is made larger than the average Al composition ratio of the first P-side guide layer 105, thereby making the average bandgap energy of the second P-side guide layer 107 larger than the average bandgap energy of the first P-side guide layer 105. This allows the average refractive index of the first P-side guide layer 105 to be larger than that of the second P-side guide layer 107, and therefore the peak position of the light intensity distribution can be brought even closer to the active layer 104. Therefore, in this embodiment, the waveguide loss of the nitride-based semiconductor light-emitting device 100 can be reduced.

[0055] [1-4. Example] Examples of the nitride-based semiconductor light-emitting device 100 according to this embodiment will be described in comparison with comparative examples using FIGS. 10 to 13 and the like. FIG. 10 is a diagram showing the main configurations and characteristic calculation results of Examples E01 to E03 and Comparative Examples C01 to C06. FIG. 11 is a diagram showing the main configurations and characteristic calculation results of Examples E04 to E06 and Comparative Examples C11 to C16. FIG. 12 is a diagram showing the main configurations and characteristic calculation results of Comparative Examples C02, C12, and C21 to C26. Note that in FIGS. 10 to 12, data for the same comparative example is shown in multiple places (e.g., Comparative Example C02) to facilitate comparison between parameters and characteristics. FIG. 13 is a graph showing coordinates of positions in the stacking direction of the nitride-based semiconductor light-emitting device 100 according to this embodiment. As shown in FIG. 13, the coordinate of the position in the stacking direction of the N-side end face of the well layer 104b of the active layer 104, i.e., the end face of the well layer 104b closer to the N-side guide layer 103, is set to zero, the downward direction (toward the N-side guide layer 103) is set to the negative direction of the coordinate, and the upward direction (toward the first P-side guide layer 105) is set to the positive direction of the coordinate.

[0056] [1-4-1. Example E01] Example E01 will be described. The nitride-based semiconductor light-emitting device 100 of Example E01 has the following configuration (see FIG. 10). The N-type cladding layer 102 has a concentration of 5×10 17 cm -3 Si-doped N-type Al with a thickness of 800 nm 0.065 Ga 0.935 The N-side guide layer 103 is an undoped Al layer with a thickness of 180 nm. 0.03 Ga 0.97 Each of the barrier layers 104a and 104c is an undoped AlN layer with a thickness of 10 nm. 0.04 Ga 0.96 The well layer 104b is an undoped In layer having a thickness of 17.5 nm. 0.01 Ga 0.99 The first P-side guide layer 105 is an undoped AlN layer with a thickness of 56 nm. 0.02 Ga 0.98 The electron barrier layer 106 is an N layer. 19cm -3 P-type AlGaN layer with a thickness of 5 nm doped with Mg 0.36 Ga 0.64 This is the N layer. The second P-side guide layer 107 is a P-type AlGaN layer with a thickness of 124 nm doped with Mg at a concentration of 1×10 18 cm -3 P-type AlGaN layer with a thickness of 124 nm doped with Mg 0.04 Ga 0.96 This is the N layer. The P-type cladding layer 108 is a P-type AlGaN layer with a thickness of 450 nm 0.065 Ga 0.935 This is the N layer. The P-type cladding layer 108 is a P-type AlGaN layer 0.04 Ga 0.96 This is the N layer. The P-type cladding layer 108 is arranged on the side closer to the active layer 104 and is a P-type AlGaN layer with a thickness of 150 nm doped with Mg at a concentration of 2×10 18 cm -3 P-type AlGaN layer with a thickness of 150 nm doped with Mg 0.065 Ga 0.935 This is the N layer. It has a P-type AlGaN layer with a thickness of 300 nm doped with Mg at a concentration of 1×10 19 cm -3 P-type AlGaN layer with a thickness of 300 nm doped with Mg 0.065 Ga 0.935 This is the N layer. The contact layer 109 is a P-type GaN layer with a thickness of 100 nm doped with Mg at a concentration of 20 20 cm -3 This is the N layer. The contact layer 109 is a P-type GaN layer with a thickness of 100 nm doped with Mg at a concentration of 1×10

[0057] Note that the configurations not shown in Fig. 10 among the configurations of Comparative Examples C01 to C06 are the same as those of Example E01. For example, the nitride semiconductor light-emitting devices of Comparative Examples C02 and C06 differ from Example E01 in the Al composition ratio (Xpg1) of the first P-side guide layer and the Al composition ratio (Xpg2) of the second P-side guide layer, and are the same in other configurations. In Comparative Example C02, since the compositions of the first P-side guide layer and the second P-side guide layer are the same, the average bandgap energy of the second P-side guide layer is equal to the average bandgap energy of the first P-side guide layer. Also, in the nitride semiconductor light-emitting device of Comparative Example C06, since the Al composition ratio of the second P-side guide layer is smaller than the Al composition ratio of the first P-side guide layer, the average bandgap energy of the second P-side guide layer is smaller than the average bandgap energy of the first P-side guide layer.

[0058] On the other hand, in the nitride-based semiconductor light-emitting device 100 according to Example E01, the Al composition ratio of the second P-side guide layer 107 is higher than that of the first P-side guide layer 105, and therefore the average bandgap energy of the second P-side guide layer is higher than that of the first P-side guide layer. Comparing the characteristic calculation results of Example E01 with those of Comparative Examples C02 and C06 shown in Fig. 10 , it is found that in Example E01, the average bandgap energy of the second P-side guide layer 107 is higher than that of the first P-side guide layer 105 (that is, the refractive index of the first P-side guide layer 105 is higher than the refractive index of the second P-side guide layer 107), and therefore the proportion of light present in the undoped region near the active layer 104 and in the low-impurity-concentration first P-side guide layer 105 increases in the light distribution in the stacking direction, thereby increasing the optical confinement factor and reducing waveguide loss.

[0059] Next, the film thickness (Tpg1) of the first P-side guide layer 105 and the impurity concentration (Ppg2) in the second P-side guide layer 107 will be described with reference to FIGS. 14 to 17. FIGS. 14 and 15 are graphs respectively showing the relationship between the operating voltage and waveguide loss of the nitride-based semiconductor light-emitting device 100 according to this embodiment at 200 mA operation and the film thickness of the first P-side guide layer 105. FIGS. 14 and 15 respectively show the operating voltage and waveguide loss when the total film thickness of the first P-side guide layer 105 and the second P-side guide layer 107 of the nitride-based semiconductor light-emitting device 100 according to Comparative Example C01 is set to 140 nm and the film thickness of the first P-side guide layer 105 is changed. Also, FIGS. 14 and 15 each show the relationship between the average impurity concentration (average Mg concentration) in the second P-side guide layer 107 and the film thickness of the first P-side guide layer 105 when the total film thickness of the first P-side guide layer 105 and the second P-side guide layer 107 is set to 140 nm. 17 cm -3 From 5 x 10 18 cm -3 16 and 17 are graphs showing the relationship between the effective refractive index difference ΔN and the optical confinement factor of the nitride-based semiconductor light-emitting element 100 according to this embodiment and the film thickness of the first p-side guide layer 105, respectively.

[0060] As shown in FIG. 14, the average impurity concentration of the second P-side guide layer 107 is set to 5×10 17 cm -3 15, when the average impurity concentration of the second P-side guide layer 107 is set to 2×10 18 cm -3 Therefore, the average impurity concentration of the second p-side guide layer 107 is set to 5×10 or less, thereby reducing the waveguide loss. 17 cm -3 Over 2×10 18 cm -3 Furthermore, by setting the average impurity concentration of the second P-side guide layer 107 to 1×10 or less, both the operating voltage and the waveguide loss can be reduced. 18 cm -3 By setting the above, the waveguide loss can be further reduced.

[0061] 14 and 17, as the thickness of the first P-side guide layer 105 increases, the operating voltage decreases and the optical confinement factor increases. On the other hand, as shown in Fig. 16, as the thickness of the first P-side guide layer 105 decreases (i.e., as the thickness (Tpg2) of the second P-side guide layer 107 increases), the effective refractive index difference ΔN increases. However, when the thickness of the first P-side guide layer 105 is decreased, the electron barrier layer 106, which has a high Al composition and a low refractive index, moves closer to the active layer 104, thereby decreasing the optical confinement factor.

[0062] Therefore, as shown in Example E01, it is possible to increase the optical confinement factor by setting the Al composition ratio of the first P-side guide layer 105 lower than the Al composition ratio of the second P-side guide layer 107, that is, by making the refractive index of the first P-side guide layer 105 relatively higher than that of the second P-side guide layer 107. By adopting such a configuration, the optical confinement factor of the structure of Example E01 can be increased to 5.65%, while the optical confinement factor of the structure of Comparative Example C01 was 4.86%.

[0063] In the structure of Example E01, as shown in FIG. 14, the average impurity concentration of the second p-side guide layer 107 was set to 5×10 17 cm -3 15, the average impurity concentration of the second P-side guide layer 107 is set to 2×10 18 cm -3 Therefore, the average impurity concentration of the second p-side guide layer 107 is set to 5×10 or less, thereby reducing the waveguide loss. 17 cm -3 Over 2×10 18 cm -3 By setting the average impurity concentration of the second P-side guide layer 107 to 1×10 or less, it is possible to obtain the effect of reducing both the operating voltage and the waveguide loss. 18 cm -3 By setting the waveguide loss to 4.91cm or less, -1 can be further reduced.

[0064] From the above, as in Example E01, the film thickness of the second p-side guide layer 107 is set to be thicker than the film thickness of the first p-side guide layer 105, and the average impurity concentration of the second p-side guide layer 107 is set to be 5×10 17 cm -3 Over 2×10 18 cm -3 By setting the above, it is possible to realize an increase in the effective refractive index difference ΔN, a reduction in the operating voltage, and a reduction in the waveguide loss.

[0065] In the structure according to Example E01, 17.67 × 10 -3 That is 1×10 -2 This also solves the problem of conventional ultraviolet semiconductor laser devices, where a refractive index anti-guiding type gain guide mechanism is likely to occur due to a decrease in the refractive index of the well layer caused by an increase in the operating carrier density. In the absence of current injection, ΔN, which is determined by the waveguide structure, is 1×10 -2If the refractive index difference is 1×10 or more, even if the effective refractive index difference ΔN decreases during laser oscillation due to a decrease in the refractive index of the well layer caused by an increase in the operating carrier density of the well layer during laser oscillation, the effective refractive index difference ΔN does not become negative, and a stable refractive index guided mechanism can be maintained. -2 The reason why such a high effective refractive index difference ΔN can be obtained is that the electron barrier layer 106 is formed between the first P-side guide layer 105 and the second P-side guide layer 107 in the semiconductor laminate 100S according to this embodiment, and as a result, the distance dp between the electron barrier layer 106 and the active layer 104 can be reduced.

[0066] [1-4-2. Example E02] Example E02 will be described. The nitride-based semiconductor light-emitting device 100 of Example E02 differs from the nitride-based semiconductor light-emitting device 100 of Example E01 in the film thicknesses of the N-side guide layer 103, the first P-side guide layer 105, and the second P-side guide layer 107 (see FIG. 10). Specifically, in Example E02, the film thickness (Tng) of the N-side guide layer 103 is 140 nm, the film thickness (Tpg1) of the first P-side guide layer 105 is 72 nm, and the film thickness (Tpg2) of the second P-side guide layer 107 is 148 nm. Thus, in Example E02, the total film thickness of the first P-side guide layer 105 and the second P-side guide layer 107 is greater than the film thickness of the N-side guide layer 103. The effects of this configuration will be described using Comparative Examples C01 to C03. 10, in the nitride-based semiconductor light-emitting device of Comparative Example C01, the total thickness of the first P-side guide layer and the second P-side guide layer is thinner than the thickness (Tng) of the N-side guide layer. In the nitride-based semiconductor light-emitting device of Comparative Example C02, the total thickness of the first P-side guide layer and the second P-side guide layer is equal to the thickness of the N-side guide layer. In the nitride-based semiconductor light-emitting device of Comparative Example C03, the total thickness of the first P-side guide layer and the second P-side guide layer is thicker than the thickness of the N-side guide layer. As can be seen from the characteristic calculation results of Comparative Examples C01 to C03 shown in FIG. 10, as the total thickness of the first P-side guide layer and the second P-side guide layer increases compared to the thickness of the N-side guide layer, the effective refractive index difference ΔN increases. As in Comparative Example C03, in the nitride-based semiconductor light-emitting device 100 of Example E02, the total thickness of the first P-side guide layer 105 and the second P-side guide layer 107 is thicker than the thickness of the N-side guide layer 103, and therefore the effective refractive index difference ΔN can be increased.

[0067] An example of the distribution of the P-type impurity (Mg) concentration in the stacking direction of the nitride-based semiconductor light-emitting device 100 of Example E02 will now be described with reference to Fig. 18. Fig. 18 is a graph schematically showing the bandgap energy distribution and light intensity distribution in the stacking direction of the semiconductor stack 100S of Example E02. Fig. 18 also shows an example of the P-type impurity concentration distribution in the stacking direction of the semiconductor stack 100S of Example E02.

[0068] As described above, the average impurity (Mg) concentration of the first p-side guide layer 105 is 1.0×10 18 cm -3 18 , the impurity concentration of the first P-side guide layer 105 may increase with increasing distance from the active layer 104. This allows the impurity concentration to be reduced in a region of the first P-side guide layer 105 close to the active layer 104, i.e., a region where the light intensity is high, and the impurity concentration to be increased in a region of the first P-side guide layer 105 far from the active layer 104, i.e., a region where the light intensity is low. Therefore, it is possible to achieve both a reduction in the waveguide loss and a reduction in the operating voltage of the nitride-based semiconductor light-emitting element 100. In this case, the average impurity concentration of the first P-side guide layer 105 is 1.0×10 17 cm -3 Over 1.0 x 10 18 cm -3 It may be less than.

[0069] As described above, the average impurity concentration of the second p-side guide layer 107 is 1.0×10 18 cm -3 This is the end. As a result, the operating voltage of the nitride-based semiconductor light-emitting element 100 can be reduced. The impurity concentration of the second P-side guide layer 107 may increase with increasing distance from the active layer 104. This allows the impurity concentration to be reduced in a region of the second P-side guide layer 107 close to the active layer 104, i.e., a region where the light intensity is high, and the impurity concentration to be increased in a region of the second P-side guide layer 107 far from the active layer 104, i.e., a region where the light intensity is low. This allows both reduction in waveguide loss and reduction in operating voltage of the nitride-based semiconductor light-emitting element 100 to be achieved. More specifically, the average impurity concentration in the region of the second P-side guide layer 107 close to the active layer 104, i.e., the region of the second P-side guide layer 107 from the interface on the side close to the active layer 104 to the center in the stacking direction, is 1.0×10 18 cm -3 Over 3.0 x 10 18 cm -3The average impurity concentration in the region of the second p-side guide layer 107 from the center in the stacking direction to the interface farther from the active layer 104 is 1.0×10 19 cm -3 Over 1.0 x 10 20 cm -3 It may be the following:

[0070] Furthermore, in the electron barrier layer 106 with a large Al composition ratio, the activation rate of the impurity Mg is low, and therefore the impurity concentration needs to be increased in order to reduce the electrical resistance of the electron barrier layer 106. As the electron barrier layer 106 is doped with high-concentration Mg, Mg diffuses into the second P-side guide layer 107, and as shown in Fig. 18 , the impurity concentration becomes high at the interface between the second P-side guide layer 107 and the electron barrier layer 106, and decreases as the impurity concentration approaches the position (Px1 or Px2) where the impurity concentration is minimum from the interface.

[0071] 18 (solid line and dashed line), there may be a position (Px1 or Px2) where the impurity concentration is minimum within a distance of 0.2 μm in the stacking direction from the electron barrier layer 106 toward the P-type cladding layer 108 (i.e., upward), and the impurity concentration may increase monotonically upward from this position. This reduces the impurity concentration in regions of the second P-side guide layer 107 and the P-type cladding layer 108 that are close to the active layer 104, thereby suppressing an increase in waveguide loss. The position where the impurity concentration is minimum may be located in the second P-side guide layer 107 or in the P-type cladding layer 108.

[0072] In the ultraviolet region at 375 nm wavelength, the smaller the Al composition ratio in an AlGaN layer with an Al composition ratio of 6% or less, the greater the effect of optical absorption loss between the impurity level of Mg used as a P-type impurity and the conduction band. Therefore, by keeping the Mg concentration as low as possible in an AlGaN layer with an Al composition ratio of 6% or less, the effect of free carrier loss and optical absorption loss via the Mg impurity level can be reduced.

[0073] Therefore, it is preferable that the second p-side guide layer 107 has a region in which the Mg concentration decreases with increasing distance from the active layer 104. This can reduce the effects of free carrier loss due to Mg doping and light absorption loss via Mg impurity levels.

[0074] [1-4-3. Example E03] Example E03 will now be described. The nitride-based semiconductor light-emitting device 100 of Example E03 differs from the nitride-based semiconductor light-emitting device 100 of Example E02 in the Al composition ratio (Xnc) of the N-type cladding layer 102 (see FIG. 10 ). Specifically, the Al composition ratio of the N-type cladding layer 102 of Example E03 is 4.5%. Thus, in Example E03, the average Al composition ratio of the N-type cladding layer 102 is smaller than the average Al composition ratio of the P-type cladding layer 108.

[0075] The effects of this configuration will be described using Comparative Examples C04, C02, and C05. As shown in FIG. 10, in the nitride-based semiconductor light-emitting device of Comparative Example C04, the average Al composition ratio of the N-type cladding layer is smaller than the average Al composition ratio of the P-type cladding layer. In the nitride-based semiconductor light-emitting device of Comparative Example C02, the average Al composition ratio of the N-type cladding layer is equal to the average Al composition ratio of the P-type cladding layer. In the nitride-based semiconductor light-emitting device of Comparative Example C05, the average Al composition ratio of the N-type cladding layer is larger than the average Al composition ratio of the P-type cladding layer.

[0076] As the average Al composition ratio of the N-type cladding layer becomes smaller compared to the average Al composition ratio of the P-type cladding layer, the average refractive index of the N-type cladding layer can be increased. Therefore, the peak position of the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting device (i.e., the vertical light distribution peak position shown in FIG. 10) can be prevented from being excessively biased in the direction from the active layer to the P-type cladding layer. As a result, as shown in the characteristic calculation results of Comparative Examples C04, C02, and C05 in FIG. 10, as the average Al composition ratio of the N-type cladding layer becomes smaller compared to the average Al composition ratio of the P-type cladding layer, the waveguide loss can be reduced.

[0077] As in Comparative Example C04, in the nitride-based semiconductor light-emitting device 100 of Example E03, the average Al composition ratio of the N-type cladding layer 102 is smaller than the average Al composition ratio of the P-type cladding layer 108, so that the waveguide loss can be reduced.

[0078] [1-4-4. Example E04] Example E04 will be described. The nitride-based semiconductor light-emitting device 100 of Example E04 differs from Example E01 in the Al composition ratio of each layer, but is otherwise identical in configuration. Specifically, as shown in Fig. 11, the Al composition ratios of the N-type cladding layer 102, N-side guide layer 103, each barrier layer, first P-side guide layer 105, second P-side guide layer 107, and P-type cladding layer 108 of Example E04 are 10%, 5%, 7%, 4%, 6%, and 10%, respectively.

[0079] Note that, among the configurations of Comparative Examples C11 to C16, the configurations not shown in FIG. 11 are the same as those of Example E04. The nitride semiconductor light-emitting devices of Comparative Example C12 and Comparative Example C16 differ from Example E04 in the Al composition ratio of the first P-side guide layer and the Al composition ratio of the second P-side guide layer, and match in other configurations. In Comparative Example C12, since the compositions of the first P-side guide layer and the second P-side guide layer are the same, the average bandgap energy of the second P-side guide layer is equal to the average bandgap energy of the first P-side guide layer. Further, in the nitride semiconductor light-emitting device of Comparative Example C16, since the Al composition ratio of the second P-side guide layer is smaller than the Al composition ratio of the first P-side guide layer, the average bandgap energy of the second P-side guide layer is smaller than the average bandgap energy of the first P-side guide layer.

[0080] On the other hand, in the nitride semiconductor light-emitting device 100 according to Example E04, since the Al composition ratio of the second P-side guide layer 107 is larger than the Al composition ratio of the first P-side guide layer 105, the average bandgap energy of the second P-side guide layer is larger than the average bandgap energy of the first P-side guide layer. Comparing the characteristic calculation results of Example E04 shown in FIG. 11 with Comparative Example C12 and Comparative Example C16, in Example E04, since the average bandgap energy of the second P-side guide layer 107 is larger than the average bandgap energy of the first P-side guide layer 105 (that is, since the refractive index of the first P-side guide layer 105 is higher than the refractive index of the second P-side guide layer 107), in the light distribution in the stacking direction, the ratio of the light present in the undoped region near the active layer 104 and the first P-side guide layer 105 with a low impurity concentration increases, so that it can be seen that the light confinement coefficient can be increased and the waveguide loss can be reduced.

[0081] Here, the relationship between the Al composition ratios of each layer will be explained with reference to FIG. 12. The nitride-based semiconductor light-emitting devices of Comparative Examples C21 to C23 shown in FIG. 12 differ from Comparative Example C02 in the Al composition ratios (Xng, Xpg1, and Xpg2) of each guide layer, but are identical in other configurations. In Comparative Examples C21, C22, and C23, the Al composition ratios of each guide layer are 2%, 4%, and 5%, respectively. The nitride-based semiconductor light-emitting devices of Comparative Examples C24 to C26 shown in FIG. 12 differ from Comparative Example C12 in the Al composition ratios (Xng, Xpg1, and Xpg2) of each guide layer, but are identical in other configurations. In Comparative Examples C24, C25, and C26, the Al composition ratios of each guide layer are 4%, 6%, and 7%, respectively.

[0082] As shown in the characteristic calculation results of Comparative Examples C21 to C23 and C02 in Fig. 12, when the Al composition ratio of each cladding layer is 6.5% and the Al composition ratio of each guide layer is 4% or more, the bias of the vertical light distribution peak position in the direction from the active layer to the P-type cladding layer increases, resulting in an increase in waveguide loss.Also, as shown in the characteristic calculation results of Comparative Examples C24 to C26 and C12 in Fig. 12, when the Al composition ratio of each cladding layer is 10% and the Al composition ratio of each guide layer is 6% or more, the bias of the vertical light distribution peak position in the direction from the active layer to the P-type cladding layer increases, resulting in an increase in waveguide loss.

[0083] Therefore, in the nitride-based semiconductor light-emitting device 100, the average Al composition ratio of the N-side guide layer 103, the average Al composition ratio of the first P-side guide layer 105, and the average Al composition ratio of the second P-side guide layer 107 may be 60% or less of the average Al composition ratio of the P-type cladding layer 108. This allows the vertical light distribution peak position to approach the center of the active layer 104 in the stacking direction, thereby reducing waveguide loss. Furthermore, the average Al composition ratio of each guide layer may be 50% or less of the average Al composition ratio of the P-type cladding layer 108. This further reduces waveguide loss. However, if the average Al composition ratio of the N-side guide layer 103, the average Al composition ratio of the first P-side guide layer 105, and the average Al composition ratio of the second P-side guide layer 107 are made too small, the difference between the Fermi energy and the conduction field potential of electrons in these three layers during laser oscillation operation becomes small, increasing the electron concentration and free carrier loss. To suppress this, the average Al composition ratio of the N-side guide layer 103, the average Al composition ratio of the first P-side guide layer 105, and the average Al composition ratio of the second P-side guide layer 107 should each be 1.5% or more.

[0084] In each of the comparative examples shown in FIG. 12, the Al composition ratio of each guide layer is set to the same value. However, by determining the Al composition ratio of each guide layer so as to satisfy Xpg1 < Xng < Xpg2, the vertical light distribution peak position can be made closer to the center in the stacking direction of the active layer. Therefore, waveguide loss can be further reduced. Thus, in the nitride semiconductor light-emitting device 100, when the Al composition ratios of the respective guide layers are different from each other, the average value of the average Al composition ratios of the N-side guide layer 103, the first P-side guide layer 105, and the second P-side guide layer 107 (that is, the average value of Xng, Xpg1, and Xpg2) may be 60% or less or 50% or less of the average Al composition ratio of the P-type clad layer 108. Thereby, waveguide loss can be further reduced. However, if the average Al composition ratio of the N-side guide layer 103, the average Al composition ratio of the first P-side guide layer 105, and the average Al composition ratio of the second P-side guide layer 107 are made too small, the difference between the Fermi energy and the conduction band potential of electrons in the above three layers during laser oscillation operation becomes small, the electron concentration increases, and free carrier loss increases. In order to suppress this, the average Al composition ratio of the N-side guide layer 103, the average Al composition ratio of the first P-side guide layer 105, and the average Al composition of the second P-side guide layer 107 may each be 1.5% or more.

[0085] Furthermore, in the nitride-based semiconductor light-emitting device 100, when the N-type cladding layer 102 and the P-type cladding layer 108 have different average Al composition ratios, the average value of the average Al composition ratios of the N-side guide layer 103, the first P-side guide layer 105, and the second P-side guide layer 107 (i.e., the average value of Xng, Xpg1, and Xpg2) may be 60% or less or 50% or less of the average value of the average Al composition ratios of the N-type cladding layer 102 and the P-type cladding layer 108 (i.e., the average value of Xnc and Xpc). However, if the average Al composition ratio of the N-side guide layer 103, the average Al composition ratio of the first P-side guide layer 105, and the average Al composition ratio of the second P-side guide layer 107 are made too small, the difference between the Fermi energy and the conduction band potential of electrons in these three layers during laser oscillation operation becomes small, resulting in an increase in electron concentration and free carrier loss. To suppress this, the average Al composition ratio of the N-side guide layer 103, the average Al composition ratio of the first P-side guide layer 105, and the average Al composition ratio of the second P-side guide layer 107 should each be 1.5% or more.

[0086] [1-4-5. Example E05] Example E05 will be described. The nitride-based semiconductor light-emitting device 100 of Example E05 differs from the nitride-based semiconductor light-emitting device 100 of Example E04 in the film thicknesses of the N-side guide layer 103, the first P-side guide layer 105, and the second P-side guide layer 107 (see FIG. 11). Specifically, in Example E05, the N-side guide layer 103 has a film thickness of 140 nm, the first P-side guide layer 105 has a film thickness of 72 nm, and the second P-side guide layer 107 has a film thickness of 148 nm. Thus, in Example E05, the total film thickness of the first P-side guide layer 105 and the second P-side guide layer 107 is greater than the film thickness of the N-side guide layer. The effects of this configuration will be described using Comparative Examples C11 to C13. As shown in FIG. 11, in the nitride-based semiconductor light-emitting device of Comparative Example C11, the total film thickness of the first P-side guide layer and the second P-side guide layer is less than the film thickness of the N-side guide layer. In the nitride-based semiconductor light-emitting device of Comparative Example C12, the total thickness of the first P-side guide layer and the second P-side guide layer is equal to the thickness of the N-side guide layer. In the nitride-based semiconductor light-emitting device of Comparative Example C13, the total thickness of the first P-side guide layer and the second P-side guide layer is thicker than the thickness of the N-side guide layer. As can be seen from the characteristic calculation results of Comparative Examples C11 to C13 shown in FIG. 11, the effective refractive index difference ΔN increases as the total thickness of the first P-side guide layer and the second P-side guide layer increases compared to the thickness of the N-side guide layer. As in Comparative Example C13, in the nitride-based semiconductor light-emitting device 100 of Example E05, the total thickness of the first P-side guide layer 105 and the second P-side guide layer 107 is thicker than the thickness of the N-side guide layer 103, so that the effective refractive index difference ΔN can be increased.

[0087] [1-4-6. Example E06] Example E06 will be described. The nitride-based semiconductor light-emitting device 100 of Example E06 differs from the nitride-based semiconductor light-emitting device 100 of Example E05 in the Al composition ratio of the N-type cladding layer 102 (see FIG. 11). Specifically, the Al composition ratio of the N-type cladding layer 102 of Example E06 is 8%. Thus, in Example E06, the average Al composition ratio of the N-type cladding layer 102 is smaller than the average Al composition ratio of the P-type cladding layer 108.

[0088] The effects of this configuration will be described using Comparative Examples C14, C12, and C15. As shown in FIG. 11 , in the nitride-based semiconductor light-emitting device of Comparative Example C14, the average Al composition ratio of the N-type cladding layer is smaller than the average Al composition ratio of the P-type cladding layer. In the nitride-based semiconductor light-emitting device of Comparative Example C12, the average Al composition ratio of the N-type cladding layer is equal to the average Al composition ratio of the P-type cladding layer. In the nitride-based semiconductor light-emitting device of Comparative Example C15, the average Al composition ratio of the N-type cladding layer is larger than the average Al composition ratio of the P-type cladding layer.

[0089] As the average Al composition ratio of the N-type cladding layer becomes smaller compared to the average Al composition ratio of the P-type cladding layer, the average refractive index of the N-type cladding layer can be increased. Therefore, the peak position of the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting device (vertical light distribution peak position) can be prevented from being excessively biased in the direction from the active layer to the P-type cladding layer. As a result, as shown in the characteristic calculation results of Comparative Examples C14, C12, and C15 in Figure 11, as the average Al composition ratio of the N-type cladding layer becomes smaller compared to the average Al composition ratio of the P-type cladding layer, the waveguide loss can be reduced.

[0090] As in Comparative Example C14, in the nitride-based semiconductor light-emitting device 100 of Example E06, the average Al composition ratio of the N-type cladding layer 102 is smaller than the average Al composition ratio of the P-type cladding layer 108, and therefore the waveguide loss can be reduced.

[0091] [1-4-7. Example E07] Example E07 will be described with reference to FIG. 19. FIG. 19 is a graph schematically illustrating the bandgap energy distribution and light intensity distribution in the stacking direction of the semiconductor stack 100S of Example E07. As shown in FIG. 19, Example E07 differs from Example E01 in that it includes a region in which the Al composition ratios of the first P-side guide layer 105 and the second P-side guide layer 107 monotonically increase with increasing distance from the active layer 104, but is otherwise identical to Example E01. In other words, in Example E07, the first P-side guide layer 105 and the second P-side guide layer 107 include a bandgap gradient region in which the bandgap energy increases with increasing distance from the active layer 104. Here, the monotonically increasing Al composition ratio includes a configuration in which there is a region in which the Al composition ratio is constant in the stacking direction. For example, it also includes a configuration in which the Al composition ratio increases stepwise. In Example E07, the Al composition ratios of the first p-side guide layer 105 and the second p-side guide layer 107 are represented by Xpg1 and Xpg2, respectively. For example, the Al composition ratios Xpg1 near the interface closer to and farther from the active layer 104 of the first p-side guide layer 105 are 1.5% and 2.5%, respectively. The Al composition ratios Xpg2 near the interface closer to and farther from the active layer 104 of the second p-side guide layer 107 are 3.5% and 4.5%, respectively.

[0092] In this way, by monotonically increasing the Al composition ratio in the first P-side guide layer 105 and the second P-side guide layer 107 with increasing distance from the active layer 104, the refractive index of each layer can be increased with increasing distance from the active layer 104. Therefore, the refractive index of the regions of the first P-side guide layer 105 and the second P-side guide layer 107 that are close to the active layer 104 can be increased, which prevents the peak position of the light intensity distribution in the stacking direction from being excessively biased in the direction from the active layer 104 toward the P-type cladding layer 108. This reduces waveguide loss.

[0093] According to Example E07, the optical confinement coefficient is 5.52%, and the effective refractive index difference ΔN is 20.9×10 -3 and the waveguide loss is 4.71 cm-1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 15.1 nm.

[0094] [1-4-8. Example E08] Example E08 will be described. Example E08 differs from Example E04 in that it includes a region in which the Al composition ratios of the first p-side guide layer 105 and the second p-side guide layer 107 monotonically increase with increasing distance from the active layer 104, but is otherwise identical in configuration. In other words, in Example E08, the first p-side guide layer 105 and the second p-side guide layer 107 include a bandgap gradient region in which the bandgap energy increases with increasing distance from the active layer 104. In Example E08, as in Example E07, the Al composition ratios of the first p-side guide layer 105 and the second p-side guide layer 107 are represented by Xpg1 and Xpg2, respectively. For example, the Al composition ratios Xpg1 near the interface of the first p-side guide layer 105 closer to and farther from the active layer 104 are 3.5% and 4.5%, respectively. The Al composition ratios Xpg2 near the interface closer to and farther from the active layer 104 of the second p-side guide layer 107 are 5.5% and 6.5%, respectively.

[0095] Thus, in Example E08, as in Example E07, by monotonically increasing the Al composition ratio in the first P-side guide layer 105 and the second P-side guide layer 107 with increasing distance from the active layer 104, it is possible to prevent the peak position of the light intensity distribution in the stacking direction from being excessively biased in the direction from the active layer 104 toward the P-type cladding layer 108. This makes it possible to reduce waveguide loss.

[0096] In Examples E07 and E08, both the first p-side guide layer 105 and the second p-side guide layer 107 included a band gap gradient region, but at least one of the first p-side guide layer 105 and the second p-side guide layer 107 may include a band gap gradient region. Even with such a configuration, the same effect is achieved.

[0097] According to Example E08, the optical confinement coefficient is 6.06%, and the effective refractive index difference ΔN is 22.1×10 -3 and the waveguide loss is 4.37 cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 13.2 nm.

[0098] [1-4-9. Example E09] Example E09 will be described. Example E09 differs from Example E02 in that the first p-side guide layer 105 contains Al and In, but is the same in other configurations. In Example E09, the composition of the first p-side guide layer 105 is Al 0.04 Ga 0.9516 In 0.0084 N. In this way, when the first P-side guide layer 105 contains Al and In, it becomes possible to control the band gap energy and lattice constant of the first P-side guide layer 105 independently.

[0099] Here, Al x Ga 1-x-y In y Band gap energy in the N layer and Al z Ga 1-z The relationship between the band gap energy in the N layer (0≦z<1) will be explained using FIG. 20. x Ga 1-x-y In y Band gap energy in the N layer and Al z Ga 1-z 20 is a graph showing the relationship between the band gap energy in the N layer and the Al x Ga 1-x-y In y The vertical axis shows the In composition ratio y in the N layer, and the vertical axis shows the Al x Ga 1-x-y In y The Al composition ratio x in the N layer is shown in Fig. 20. x Ga 1-x-y In y In the N layer, Al z Ga 1-zThe relationship between the In composition ratio y and the Al composition ratio x to obtain the same band gap energy as the N layer is shown. z Ga 1-z The relationship is shown for each of the cases where the Al composition ratio z of the N layer is 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40. x Ga 1-x-y In y The relationship between the In composition ratio y and the Al composition ratio x to make the lattice constant of the N layer equal to that of the GaN layer is shown by the dashed line. Therefore, the region above (or to the left of) the dashed line in the graph of FIG. x Ga 1-x-y In y The lattice constant of the N layer is smaller than that of the GaN layer. The region below (or to the right of) the dashed line is Al x Ga 1-x-y In y The lattice constant of the N layer is larger than that of the GaN layer. In calculating the lattice constant, 0.311 nm, 0.3182 nm, and 0.354 nm were used as the lattice constants of AlN, GaN, and InN, respectively.

[0100] Al x Ga 1-x-y In y Al in the N layer z Ga 1-z In order to obtain the same band gap energy as the N layer, the following formula (1) must be satisfied, as shown in FIG.

[0101] x=(-0.1727z+2.595)y+z (1)

[0102] In this way, the first p-side guide layer 105 made of an AlGaN layer in each of the above-described embodiments can be replaced with the first p-side guide layer 105 made of an AlGaInN layer without changing the band gap energy.

[0103] Furthermore, for example, in the semiconductor laminate 100S of Example E02, the tensile strain on the substrate 101 is relatively large, which may cause warpage in the nitride-based semiconductor light-emitting element 100. Here, warpage in the nitride-based semiconductor light-emitting element 100 will be described with reference to Fig. 21. Fig. 21 is a schematic side view showing warpage of the substrate 101 and the semiconductor laminate 100S that occurs when the semiconductor laminate 100S is laminated on the substrate 101 according to this embodiment.

[0104] As shown in FIG. 21 , when the semiconductor laminate 100S is stacked on the substrate 101 (i.e., crystal growth is performed), tensile strain on the substrate 101 caused by the AlGaN layer in the semiconductor laminate 100S causes warpage in the substrate 101 and the semiconductor laminate 100S. For example, in Example E02, tensile strain on the substrate 101 caused by the AlGaN layer causes warpage in a direction that makes the top surface of the semiconductor laminate 100S concave. Here, the amount of warpage when the top surface of the semiconductor laminate 100S becomes concave (i.e., the depth ΔR of the concave portion indicated by the arrow in FIG. 21 ) is expressed as a negative numerical value. On the other hand, the amount of warpage when the top surface of the semiconductor laminate 100S becomes convex (i.e., the height of the convex portion) is expressed as a positive numerical value.

[0105] In Example E09, by adjusting the In composition ratio y and the Al composition ratio x of the first P-side guide layer 105, the lattice constant of the first P-side guide layer 105 can be adjusted independently of the band gap energy, thereby reducing the tensile strain of the first P-side guide layer 105 relative to the substrate 101. This reduces warpage of the nitride-based semiconductor light-emitting element 100. This makes it possible to suppress breakage of the wafer and the occurrence of cracks in the wafer when the semiconductor stack 100S is stacked on a GaN wafer, which is the base material of the substrate 101, and then processed.

[0106] According to Example E09, the optical confinement coefficient is 5.62%, and the effective refractive index difference ΔN is 19.6×10 -3 and the waveguide loss is 4.90 cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 14.3 nm.

[0107] In Example E09, only the first P-side guide layer 105 contained Al and In, but the N-side guide layer 103, the second P-side guide layer 107, and the P-type cladding layer 108 may also contain Al and In. In this configuration, as in Example E01, the relationships of the following formulas (2) and (3) can be established among the bandgap energy Eng of the N-side guide layer 103, the bandgap energy Epg1 of the first P-side guide layer 105, the bandgap energy Epg2 of the second P-side guide layer 107, and the bandgap energy Epc of the P-type cladding layer 108.

[0108] Epg1 <Epg2<Epc (2)

[0109] Epg1 <Eng<Epg2 (3)

[0110] This will be explained below using equation (1). When equation (1) is transformed, the following equation (4) is obtained.

[0111] z=(x-2.595y) / (1.0-0.1727y) (4)

[0112] Here, Al z Ga 1-z As the Al composition ratio z in the N layer increases, the band gap energy increases. Therefore, when the following formula (5) is satisfied, z Ga 1-z The band gap energy of the N layer is Al x Ga 1-x-y In y It becomes larger than the band gap energy of the N layer.

[0113] z>(x-2.595y) / (1.0-0.1727y) (5)

[0114] From this, it can be seen that the first p-side guide layer 105 is Al Xpg1 Ga 1-Xpg1-Ypg1 In Ypg1 N, and the second P-side guide layer 107 is AlXpg2 Ga 1-Xpg2-Ypg2 In Ypg2 When the first P-side guide layer 105 is made of N, the band gap energy Epg1 of the first P-side guide layer 105 can be made smaller than the band gap energy Epg2 of the second P-side guide layer 107 by satisfying the following formula (6).

[0115] (Xpg1-2.595Ypg1) / (1.0-0.1727Ypg1) <(Xpg2-2.595Ypg2) / (1.0-0.1727Ypg2) (6)

[0116] Furthermore, the P-type cladding layer 108 is Al Xpc Ga 1-Xpc-Ypc In Ypc N, the following equation (7) is satisfied, and thus equation (2) holds.

[0117] (Xpg1-2.595Ypg1) / (1.0-0.1727Ypg1) <(Xpg2-2.595Ypg2) / (1.0-0.1727Ypg2) <(Xpc-2.595Ypc) / (1.0-0.1727Ypc) (7)

[0118] As a result, the refractive index of the first P-side guide layer 105 can be made the largest among the first P-side guide layer 105, the second P-side guide layer 107, and the P-type cladding layer 108, and the position of the vertical light distribution peak can be made closer to the center of the active layer 104 in the stacking direction.

[0119] In addition, the N-side guide layer 103 is Al Xng Ga 1-Xng-Yng In Yng N, the following equation (8) is satisfied, and thus equation (3) holds.

[0120] (Xpg1-2.595Ypg1) / (1.0-0.1727Ypg1) <(Xng-2.595Yng) / (1.0-0.1727Yng) <(Xpg2-2.595Ypg2) / (1.0-0.1727Ypg2) (8)

[0121] This allows the refractive index of the first P-side guide layer 105 to be greater than the refractive indexes of the N-side guide layer 103 and the second P-side guide layer 107, and the position of the vertical light distribution peak can be brought closer to the center of the active layer 104 in the stacking direction.

[0122] [1-4-10. Example E10] Example E10 will be described. Example E10 differs from Example E05 in that the first p-side guide layer 105 contains Al and In, but is the same in other configurations. In Example E10, the composition of the first p-side guide layer 105 is Al 0.04 Ga 0.9516 In 0.0084 N. In this way, the first p-side guide layer 105 contains Al and In, and therefore, in Example E10, the same effects as in Example E09 are achieved.

[0123] According to Example E10, the optical confinement coefficient is 6.12%, and the effective refractive index difference ΔN is 22.3×10 -3 and the waveguide loss is 4.02 cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 14.0 nm.

[0124] [1-4-11. Example E11] Example E11 will be described. Example E11 differs from Example E02 in that the N-type cladding layer 102 contains Al and In, but is the same in other configurations. In Example E11, the composition of the N-type cladding layer 102 is Al 0.065 Ga 0.925 In 0.01The effect of the N-type cladding layer 102 containing Al and In will be described with reference to Figs. 22 to 24. Fig. 22 is a graph showing the relationship between the position in the stacking direction of the semiconductor laminate 100S of Example E11 and the band gap energy. Fig. 23 is a graph showing the relationship between the position in the stacking direction of the semiconductor laminate 100S of Example E11 and the stress. The stress shown in Fig. 23 is the stress on the substrate 101, and a positive stress value means that the stress is compressive, and a negative stress value means that the stress is tensile. Note that Fig. 23 shows the case where the N-type cladding layer 102 contains Al as in Example E02. 0.065 Ga 0.935 The stress when the N-type cladding layer 102 is made of Al is also shown by a dotted line. Figure 24 is a graph showing the relationship between the position in the stacking direction of the semiconductor laminate 100S of Example E11 and the integrated stress. Here, the integrated stress means the value obtained by integrating the stress at each position in the stacking direction of the semiconductor laminate 100S from the interface between the N-type cladding layer 102 and the substrate 101 in the semiconductor laminate 100S upward in the stacking direction. In other words, the integrated stress means the value obtained by integrating the stress shown in Figure 23 from position zero to each position in the stacking direction. Note that Figure 24 shows the case where the N-type cladding layer 102 is made of Al as in Example E02. 0.065 Ga 0.935 The integral stress for the case consisting of N is also shown by the dotted line.

[0125] 22, in Example E11, the band gap energy of the N-type cladding layer 102 can be reduced more than in Example E02. That is, in Example E11, the refractive index of the N-type cladding layer 102 can be increased more than in Example E02. Therefore, it is possible to prevent the peak position of the light intensity distribution in the stacking direction from being excessively biased in the direction from the active layer 104 toward the P-type cladding layer 108.

[0126] 23 and 24, Example E11 can reduce the tensile stress (strain) in the N-type cladding layer 102 more than Example E02. For example, when the semiconductor laminate 100S of Example E02 is laminated on a GaN substrate measuring 5 cm square and 85 μm thick, the integrated stress is −725.8 Pa·m, and the wafer warpage (see FIG. 21) is 553.6 μm. On the other hand, when the semiconductor laminate 100S of Example E11 is laminated on a GaN substrate measuring 5 cm square and 85 μm thick, the integrated stress is −436.4 Pa·m, and the wafer warpage is 335.0 μm. Thus, Example E11 can reduce wafer warpage, thereby suppressing wafer breakage and cracking.

[0127] According to Example E11, the optical confinement coefficient is 4.95%, and the effective refractive index difference ΔN is 9.29×10 -3 and the waveguide loss is 4.23 cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 8.2 nm.

[0128] [1-4-12. Example E12] Example E12 will be described. Example E12 differs from Example E05 in that the N-type cladding layer 102 contains Al and In, but is the same in other configurations. In Example E12, the composition of the N-type cladding layer 102 is Al 0.10 Ga 0.89 In 0.01 The effect of the N-type cladding layer 102 containing Al and In will be described with reference to Figs. 25 to 27. Fig. 25 is a graph showing the relationship between the position in the stacking direction of the semiconductor laminate 100S of Example E12 and the band gap energy. Fig. 26 is a graph showing the relationship between the position in the stacking direction of the semiconductor laminate 100S of Example E12 and the stress. Note that Fig. 26 shows the relationship between the position in the stacking direction of the semiconductor laminate 100S of Example E12 and the stress. 0.10 Ga 0.90The stress when the N-type cladding layer 102 is made of Al is also shown by a dotted line. Fig. 27 is a graph showing the relationship between the position in the stacking direction of the semiconductor laminate 100S of Example E12 and the integrated stress. Note that Fig. 27 also shows the case where the N-type cladding layer 102 is made of Al as in Example E05. 0.10 Ga 0.90 The integral stress for the case consisting of N is also shown by the dotted line.

[0129] When the semiconductor laminate 100S of Example E12 is laminated on a GaN substrate having a size of 5 cm square and a thickness of 85 μm, the integrated stress is −835.5 Pa·m, and the warpage of the wafer (see FIG. 21) is 639.4 μm. On the other hand, when the N-type cladding layer 102 is made of Al as in Example E05, 0.10 Ga 0.90 When the semiconductor laminate 100S made of N is laminated on a GaN substrate that is 5 cm square and 85 μm thick, the integrated stress is −1126.4 Pa m and the warpage of the wafer is 858.9 μm. As shown in Figures 25 to 27, when the N-type cladding layer 102 contains Al and In, Example E12 also achieves the same effects as Example E11.

[0130] According to Example E12, the optical confinement coefficient is 5.87%, and the effective refractive index difference ΔN is 10.9×10 -3 and the waveguide loss is 3.5cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 11.0 nm.

[0131] [1-4-13. Example E13] Example E13 will be described. Example E13 differs from Example E02 in that the well layer 104b contains Al and In, but is the same in other configurations. In Example E13, the composition of the well layer 104b is Al 0.071 Ga 0.889 In 0.04 It's N.

[0132] In order for the nitride-based semiconductor light-emitting element 100 to emit light having a wavelength of 375 nm or more and 380 nm or less, In0.01 Ga 0.99 It is necessary to use a well layer 104b having a bandgap energy equal to or greater than the bandgap energy of N and equal to or less than the bandgap energy of GaN. The composition of the well layer 104b will be described below with reference to FIG. 28. FIG. 28 is a graph illustrating the composition required for the well layer 104b of Example E13. The horizontal axis of FIG. 28 represents the In composition ratio y, and the vertical axis represents the Al composition ratio x.

[0133] The composition of the well layer 104b is Al x Ga 1-x-y In y When N is used, the band gap energy of the well layer 104b is set to In 0.01 Ga 0.99 In order to make the band gap energy equal to or greater than that of N and equal to or less than that of GaN, the following formula (9) should be satisfied.

[0134] 2.34y≧x≧2.34y-0.234 (9)

[0135] That is, if the Al composition ratio x and In composition ratio y of the well layer 104b have values ​​corresponding to the region between the solid line and the dashed line shown in FIG. 28, light of 375 nm or more and 380 nm or less can be emitted.

[0136] Here, the lattice mismatch of the well layer 104b with respect to GaN will be described with reference to Fig. 29. Fig. 29 is a graph showing the relationship between the In composition ratio of the well layer 104b and the lattice mismatch with respect to GaN.

[0137] For example, In 0.01 Ga 0.99 Since N has a compressive lattice mismatch of 0.11% with respect to GaN, the composition of the well layer 104b is changed to In. 0.01 Ga 0.99 In contrast, when the composition of the well layer 104b is set to Al, the Al composition ratio x and the In composition ratio y satisfy the formula (9). x Ga 1-x-y Iny The case where the In composition ratio y is set to N will be described. In this case, if the In composition ratio y is set to 0.04, for example, as shown in FIG. 29, the compressive lattice mismatch occurring in the well layer 104b is 0.23% or more and 0.28% or less. In this way, the well layer 104b containing Al and In can increase the compressive lattice mismatch occurring in the well layer 104b. Therefore, the tensile strain in the active layer 104 and its surrounding region can be reduced. If the In composition ratio in the well layer 104b is set to 0.06, for example, the compressive lattice mismatch in the well layer 104b can be increased to 0.34% or more and 0.38% or less, as shown in FIG. 29, thereby further reducing the tensile strain in the active layer 104 and its surrounding region.

[0138] Furthermore, increasing the compressive strain of the well layer 104b increases the difference in ground level energy between heavy holes and light holes formed in the well layer 104b. As a result, when the nitride-based semiconductor light-emitting device 100 is operated by supplying current, the number of heavy holes in the ground level can be increased, thereby reducing the oscillation threshold current value. Therefore, the operating carrier density can be reduced, which can suppress changes in the refractive index of the current injection region in the well layer 104b and a decrease in the refractive index due to the plasma effect. As a result, a decrease in the effective refractive index difference ΔN can be suppressed, thereby stabilizing the horizontal-transverse mode of the laser light.

[0139] According to Example E13, the optical confinement coefficient is 5.69%, and the effective refractive index difference ΔN is 18.79×10 -3 and the waveguide loss is 4.96 cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 12.84 nm.

[0140] [1-4-14. Example E14] Example E14 will be described. Example E14 is different from Example E01 in the configuration of the N-side guide layer 103 and is the same in other configurations. Hereinafter, the configuration of the semiconductor laminate 100S of Example E14 will be described with reference to FIG. 30. FIG. 30 is a graph schematically showing the bandgap energy distribution in the stacking direction of the semiconductor laminate 100S of Example E14.

[0141] As shown in FIG. 30, the N-side guide layer 103 of Example 14 has a first N-side guide layer 103a and a second N-side guide layer 103b disposed above the first N-side guide layer 103a. The bandgap energy of the first N-side guide layer 103a is larger than the bandgap energy of the second N-side guide layer 103b. Also, the Al composition ratio Xng1 of the first N-side guide layer 103a is larger than the Al composition ratio Xng of the second N-side guide layer 103b. Specifically, the first N-side guide layer 103a is an undoped Al 0.04 Ga 0.96 N layer with a thickness of 90 nm. That is, the Al composition ratio Xng1 of the first N-side guide layer 103a is 4.0%. On the other hand, the second N-side guide layer 103b is an undoped Al 0.02 Ga 0.98 N layer with a thickness of 90 nm. That is, the Al composition ratio Xng2 of the second N-side guide layer 103b is 2.0%.

[0142] In Example E14, the average Al composition ratio Xng of the N-side guide layer 103 is 3.0%, satisfying Xpg1 < Xng < Xpg2.

[0143] The average Al composition ratio of the N-side guide layer 103 is an average Al composition ratio that takes into account the Al composition ratio distribution in the two layers, the first N-side guide layer 103 a and the second N-side guide layer 103 b. More specifically, the average Al composition ratio of the N-side guide layer 103 is an Al composition ratio value obtained by integrating the magnitude of the Al composition ratio at a certain position including the two layers, the first N-side guide layer 103 a and the second N-side guide layer 103 b, in the stacking direction from the interface of the first N-side guide layer 103 a on the substrate 101 side to the interface of the second N-side guide layer 103 b on the active layer 104 side, and dividing the result by the total film thickness of the first N-side guide layer 103 a and the second N-side guide layer 103 b.

[0144] By satisfying the above inequality regarding the average Al composition ratio of the N-side guide layer 103, the average refractive index of the first P-side guide layer 105 is larger than the average refractive index of the N-side guide layer 103, and the average refractive index of the N-side guide layer 103 is larger than the average refractive index of the second P-side guide layer 107.

[0145] Here, the average refractive index of the N-side guide layer 103 refers to the average refractive index taking into consideration the refractive index distribution in the two layers, the first N-side guide layer 103 a and the second N-side guide layer 103 b. More specifically, the average refractive index of the N-side guide layer 103 refers to the refractive index value obtained by integrating the magnitude of the refractive index at a certain position including the two layers, the first N-side guide layer 103 a and the second N-side guide layer 103 b, in the stacking direction from the interface of the first N-side guide layer 103 a on the substrate 101 side to the interface of the second N-side guide layer 103 b on the active layer 104 side, and dividing the result by the total film thickness of the first N-side guide layer 103 a and the second N-side guide layer 103 b.

[0146] To explain the effects of Example E14, a comparison will be made with the semiconductor laminate of Comparative Example C30. The semiconductor laminate 100S of Comparative Example C30 is an example of the semiconductor laminate 100S according to the first embodiment, and differs from Example E14 in that the band gap energy of the first N-side guide layer 103a is smaller than the band gap energy of the second N-side guide layer 103b, but is otherwise identical in configuration. The first N-side guide layer 103a of Comparative Example C30 is a 90-nm-thick undoped Al 0.02Ga 0.98 The second N-side guide layer 103b is an undoped Al layer with a thickness of 90 nm. 0.04 Ga 0.96 As described above, in Comparative Example C30, the average Al composition of the N-side guide layer 103 is the same as in Examples E01 and E14, the Al composition of the first N-side guide layer 103a, which is a region of the N-side guide layer 103 far from the active layer 104, is 2%, and the Al composition of the second N-side guide layer 103b, which is a region of the N-side guide layer 103 close to the active layer 104, is 4%.

[0147] In the nitride-based semiconductor light-emitting device including the semiconductor laminate of Comparative Example C30, the optical confinement coefficient was 5.1% and the effective refractive index difference ΔN was 16.8×10 -3 and the waveguide loss is 6.1 cm -1 and the vertical light distribution peak position is 11.6 nm. As described above, the nitride-based semiconductor light-emitting device including the semiconductor laminate of Comparative Example C30 does not have as good characteristics as Example E01.

[0148] On the other hand, when the Al composition ratio (Xng2) of the region of the N-side guide layer 103 close to the active layer 104 is reduced as in Example E14, the refractive index of the region of the N-side guide layer 103 close to the active layer 104 becomes higher than the refractive index of the region of the N-side guide layer 103 far from the active layer 104. This increases the proportion of light located in the undoped first N-side guide layer 103a, second N-side guide layer 103b, and first P-side guide layer 105 near the active layer 104. Therefore, in the nitride-based semiconductor light-emitting device 100 including the semiconductor laminate 100S of Example E14, the waveguide loss is further reduced and the optical confinement coefficient to the active layer 104 is further increased compared to the nitride-based semiconductor light-emitting device 100 including the semiconductor laminate 100S of Example E01.

[0149] Specifically, according to Example E14, the optical confinement coefficient is 6.2%, and the effective refractive index difference ΔN is 17.4×10 -3 and the waveguide loss is 3.6 cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 5.6 nm.

[0150] Thus, according to Example E14, while the vertical light distribution peak position is located in the well layer 104b region of the active layer 104, 10×10 -3 or more effective refractive index difference ΔN can be realized, and waveguide loss can be reduced and the optical confinement factor can be increased.

[0151] [1-4-15. Example E15] Example E15 will be described. In Example E15, the configuration of the N-side guide layer 103 is different from that of Example E01, and the other configurations are the same. Hereinafter, the configuration of the semiconductor laminate 100S of Example E15 will be described using FIG. 31. FIG. 31 is a graph schematically showing the bandgap energy distribution in the stacking direction of the semiconductor laminate 100S of Example E15.

[0152] As shown in FIG. 31, the N-side guide layer 103 of Example E15 is different from the N-side guide layer 103 of Example E01 in that it includes a region where the Al composition ratio monotonically increases as it moves away from the active layer 104. In other words, in Example E15, the N-side guide layer 103 includes a bandgap gradient region where the bandgap energy increases as it moves away from the active layer 104. The Al composition ratios Xng near the interface closer to the active layer 104 and near the interface farther away of the N-side guide layer 103 are 2.0% and 4.0% respectively.

[0153] In Example E15, the average Al composition ratio Xng of the N-side guide layer 103 is 3.0%, and Xpg1 < Xng < Xpg2 is satisfied.

[0154] By satisfying the above inequality with respect to the average Al composition ratio of the N-side guide layer 103, the average refractive index of the first P-side guide layer 105 is larger than the average refractive index of the N-side guide layer 103, and the average refractive index of the N-side guide layer 103 is larger than the average refractive index of the second P-side guide layer 107.

[0155] As described above, when the Al composition ratio in the region of the N-side guide layer 103 close to the active layer 104 is reduced, the refractive index in the region of the N-side guide layer 103 close to the active layer 104 becomes higher than the refractive index in the region of the N-side guide layer 103 far from the active layer 104. This increases the proportion of light located in the undoped N-side guide layer 103 and the first P-side guide layer 105 near the active layer 104. Therefore, in the nitride-based semiconductor light-emitting device 100 including the semiconductor laminate 100S of Example E15, the waveguide loss is further reduced and the optical confinement coefficient in the active layer 104 is further increased compared to the nitride-based semiconductor light-emitting device 100 including the semiconductor laminate 100S of Example E01.

[0156] Specifically, according to Example E15, the optical confinement coefficient is 5.9%, and the effective refractive index difference ΔN is 17.4×10 -3 and the waveguide loss is 4.1 cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 6.5 nm.

[0157] Thus, according to Example E15, the vertical light distribution peak position was positioned in the well layer 104b region of the active layer 104, and the -3 The above effective refractive index difference ΔN can be realized, and the waveguide loss can be reduced and the optical confinement factor can be increased.

[0158] (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 the nitride-based semiconductor light-emitting device 100 according to embodiment 1 in that it includes a buffer layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 32, focusing on the differences from the nitride-based semiconductor light-emitting device 100 according to embodiment 1. FIG. 32 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 200 according to this embodiment.

[0159] 32, a nitride-based semiconductor light-emitting device 200 according to this embodiment includes a substrate 101, a semiconductor stack 200S, a current blocking layer 110, a P-side electrode 111, and an N-side electrode 112. The semiconductor stack 200S according to this embodiment differs from the semiconductor stack 100S according to the first embodiment in that it includes a buffer layer 221, but is the same in other respects.

[0160] The buffer layer 221 is disposed between the substrate 101 and the N-type cladding layer 102 and is an example of a first buffer layer made of InGaN. In this embodiment, the buffer layer 221 has a concentration of 5×10 17 cm -3 150 nm thick N-type In doped with Si 0.05 Ga 0.95 This is the N layer.

[0161] The nitride-based semiconductor light-emitting device 200 according to this embodiment includes the buffer layer 221, which allows compressive strain to be applied to the semiconductor laminate 200S. This reduces tensile strain in the semiconductor laminate 200S, thereby preventing breakage of the wafer and the occurrence of cracks in the wafer when the semiconductor laminate 200S is laminated on the GaN wafer and processed. For example, when the semiconductor laminate 200S is laminated on a GaN substrate that is 5 cm square and 85 μm thick, the integrated stress is −173.4 Pa·m, and the warpage of the wafer is 138.1 μm.

[0162] Furthermore, when a GaN substrate is used as the substrate 101, when light reaches the substrate 101, the refractive index of the substrate 101 is higher than the effective refractive index of the semiconductor laminate 200S for the waveguide mode, causing the light to diffuse throughout the substrate 101. In this case, the optical confinement factor of the waveguide mode in the active layer 104 decreases, increasing waveguide loss and resulting in an increase in the oscillation threshold current. As a result, the operating carrier density in the well layer 104b increases, and the refractive index of the current injection region in the well layer 104b decreases, reducing the effective refractive index difference ΔN. As a result, the waveguide mechanism for light propagating through the waveguide including the ridge 108R becomes an index-inverse waveguide mechanism. This destabilizes the horizontal transverse mode, making it more likely that a kink will occur in the current-light output characteristics.

[0163] On the other hand, by providing the buffer layer 221 made of InGaN having a band gap energy smaller than the energy corresponding to ultraviolet light, as in the nitride-based semiconductor light-emitting device 200 according to the present embodiment, the light is absorbed in the buffer layer 221, and therefore, it is possible to prevent the light from reaching the substrate 101.

[0164] According to this embodiment, the optical confinement coefficient is 5.69%, and the effective refractive index difference ΔN is 18.79×10 -3 and the waveguide loss is 4.96 cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 12.84 nm.

[0165] (Embodiment 3) A nitride-based semiconductor light-emitting device according to the third embodiment will be described. The nitride-based semiconductor light-emitting device according to the present embodiment differs from the nitride-based semiconductor light-emitting device 200 according to the second embodiment in that it includes two buffer layers. The nitride-based semiconductor light-emitting device according to the present embodiment will be described below with reference to FIG. 33, focusing on the differences from the nitride-based semiconductor light-emitting device 200 according to the second embodiment. FIG. 33 is a schematic cross-sectional view showing the overall configuration of the nitride-based semiconductor light-emitting device 300 according to the present embodiment.

[0166] 33, a nitride-based semiconductor light-emitting device 300 according to this embodiment includes a substrate 101, a semiconductor stack 300S, a current blocking layer 110, a P-side electrode 111, and an N-side electrode 112. The semiconductor stack 300S according to this embodiment differs from the semiconductor stack 200S according to the second embodiment in that it includes a buffer layer 321, but is the same in other respects.

[0167] The buffer layer 321 is disposed between the substrate 101 and the N-type cladding layer 102, and is an example of a second buffer layer made of AlGaN. In this embodiment, the buffer layer 321 is disposed between the substrate 101 and the buffer layer 221. The buffer layer 321 has a concentration of 5×10 17 cm -3 Si-doped N-type Al with a thickness of 1000 nm 0.007 Ga 0.993 This is the N layer.

[0168] The nitride-based semiconductor light-emitting device 300 according to this embodiment also achieves the same effects as the nitride-based semiconductor light-emitting device 200 according to embodiment 2. For example, when the semiconductor laminate 300S is laminated on a GaN substrate having a size of 5 cm square and a thickness of 85 μm, the integrated stress is −227.5 Pa m, and the warpage of the wafer is 173.8 μm.

[0169] According to this embodiment, the optical confinement coefficient is 5.69%, and the effective refractive index difference ΔN is 18.79×10 -3 and the waveguide loss is 4.96 cm -1 Thus, a nitride-based semiconductor light-emitting device 100 can be realized in which the vertical light distribution peak position is 12.84 nm.

[0170] (Variations, 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.

[0171] For example, in each of the above-described embodiments, the nitride-based semiconductor light-emitting element is a semiconductor laser element, but 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 light emitted 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.

[0172] Furthermore, although the P-type cladding layer 108 has been described as a layer having a uniform Al composition ratio, the configuration of the P-type cladding layer 108 is not limited to this. For example, the P-type cladding layer 108 may have a superlattice structure in which a plurality of AlGaN layers and a plurality of GaN layers are alternately stacked.

[0173] 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.

[0174] For example, the buffer layers according to the second and third embodiments may be applied to the examples of the nitride-based semiconductor light-emitting device 100 according to the first embodiment. [Industrial Applicability]

[0175] 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. [Explanation of symbols]

[0176] 100, 200, 300 Nitride-based semiconductor light-emitting device 100F, 100R end face 100S, 200S, 300S Semiconductor laminate 101 Substrate 102 N-type cladding layer 103 N-side guide layer 103a First N-side guide layer 103b Second N-side guide layer 104 Active layer 104a, 104c Barrier layer 104b Well layer 105 First P-side guide layer 106, 916, 926 Electron barrier layer 107 Second P-side guide layer 108 P-type cladding layer 108R Ridge 108T groove 109 Contact Layer 110 Current Blocking Layer 111 P side electrode 112 N side electrode 221, 321 buffer layer 915, 925 P side guide layer

Claims

1. An N-type cladding layer; an N-side guide layer disposed above the N-type cladding layer; an active layer disposed above the N-side guide layer; a first P-side guide layer disposed above the active layer; an electron barrier layer disposed above the first P-side guide layer; a second P-side guide layer disposed above the electron barrier layer; a P-type clad layer disposed above the second P-side guide layer, the average band gap energy of the second P-side guide layer is larger than the average band gap energy of the first P-side guide layer, the average band gap energy of the P-type cladding layer is smaller than the average band gap energy of the electron barrier layer; the average band gap energy of the N-side guide layer is greater than the average band gap energy of the first P-side guide layer; The average band gap energy of the N-side guide layer is smaller than the average band gap energy of the second P-side guide layer. Nitride-based semiconductor light-emitting element.

2. An N-type cladding layer; an N-side guide layer disposed above the N-type cladding layer; an active layer disposed above the N-side guide layer; a first P-side guide layer disposed above the active layer; an electron barrier layer disposed above the first P-side guide layer; a second P-side guide layer disposed above the electron barrier layer; a P-type clad layer disposed above the second P-side guide layer, the average band gap energy of the second P-side guide layer is larger than the average band gap energy of the first P-side guide layer, the average band gap energy of the P-type cladding layer is smaller than the average band gap energy of the electron barrier layer; The second P-side guide layer has a thickness larger than that of the first P-side guide layer, The second P-side guide layer has a ridge formed therein. Nitride-based semiconductor light-emitting element.

3. An N-type cladding layer; an N-side guide layer disposed above the N-type cladding layer; an active layer disposed above the N-side guide layer; a first P-side guide layer disposed above the active layer; an electron barrier layer disposed above the first P-side guide layer; a second P-side guide layer disposed above the electron barrier layer; a P-type clad layer disposed above the second P-side guide layer, the average band gap energy of the second P-side guide layer is larger than the average band gap energy of the first P-side guide layer, an impurity concentration at an end of the P-type cladding layer closer to the active layer is lower than an impurity concentration at an end of the P-type cladding layer farther from the active layer; The average band gap energy of the P-type cladding layer is smaller than the average band gap energy of the electron barrier layer. Nitride-based semiconductor light-emitting element.

4. The impurity concentration of the second P-side guide layer is lower than the impurity concentration of the electron barrier layer.

4. The nitride-based semiconductor light-emitting device according to claim 1.

5. Further comprising a buffer layer disposed below the N-type cladding layer, the N-type cladding layer is made of AlGaN; the electron barrier layer is made of AlGaN; the N-side guide layer, the first P-side guide layer, the second P-side guide layer, and the P-type cladding layer are made of AlGaN or AlInGaN, The buffer layer has a band gap energy smaller than the energy corresponding to ultraviolet light.

5. The nitride-based semiconductor light-emitting device according to claim 1.

6. The active layer is Two barrier layers; a well layer disposed between the two barrier layers.

6. The nitride-based semiconductor light-emitting device according to claim 1.

7. The band gap energy of each of the two barrier layers is greater than the average band gap energy of the first P-side guide layer and the average band gap energy of the N-side 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 6 .

8. The well layer contains Al and In. The nitride-based semiconductor light-emitting device according to claim 6 or 7.

9. The thickness of the first P-side guide layer is greater than the thickness of each of the two barrier layers.

9. The nitride-based semiconductor light-emitting device according to claim 6, wherein the nitride semiconductor light-emitting device is a nitride-based semiconductor light-emitting device.

10. The average band gap energy of the N-side guide layer is greater than the average band gap energy of the first P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 2 or 3.

11. At least one of the first P-side guide layer and the second P-side guide layer includes a band gap gradient region in which the band gap energy increases with increasing distance from the active layer. The nitride-based semiconductor light-emitting device according to claim 1 .

12. The average band gap energy of the N-side guide layer is smaller than the average band gap energy of the second P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 2 , 3 or 10 .

13. The total thickness of the first P-side guide layer and the second P-side guide layer is greater than the thickness of the N-side guide layer. The nitride-based semiconductor light-emitting device according to claim 1 , 10 , or 11 .

14. The average impurity concentration of the first P-side guide layer is 1×10 １８ cm －３ is less than The nitride-based semiconductor light-emitting device according to any one of claims 1 to 13.

15. The average impurity concentration of the second P-side guide layer is 1×10 １８ cm －３ That's all.

15. The nitride-based semiconductor light-emitting device according to claim 1.

16. the N-type cladding layer and the P-type cladding layer contain Al; The average Al composition ratio of the N-type cladding layer is equal to or lower than the average Al composition ratio of the P-type cladding layer. The nitride-based semiconductor light-emitting device according to any one of claims 1 to 15.

17. the N-side guide layer, the first P-side guide layer, and the second P-side guide layer contain Al, The average Al composition ratio of the N-side guide layer, the average Al composition ratio of the first P-side guide layer, and the average Al composition ratio of the second P-side guide layer are 60% or less of the average Al composition ratio of the P-type cladding layer. The nitride-based semiconductor light-emitting device according to claim 16 .

18. The N-type cladding layer contains Al and In.

14. The nitride-based semiconductor light-emitting device according to claim 1, wherein the nitride semiconductor light-emitting device is a nitride-based semiconductor light-emitting device.

19. The first P-side guide layer contains Al and In. The nitride-based semiconductor light-emitting device according to any one of claims 1 to 18.

20. a substrate made of GaN and disposed below the N-type cladding layer; a buffer layer made of InGaN and disposed between the substrate and the N-type cladding layer.

19. The nitride-based semiconductor light-emitting device according to claim 1, wherein the nitride semiconductor light-emitting device is a nitride-based semiconductor light-emitting device.

21. The active layer emits ultraviolet light. The nitride-based semiconductor light-emitting device according to any one of claims 1 to 20.

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