Nitride-based semiconductor light-emitting device

Abstract

To provide a nitride semiconductor light emitting element capable of reducing operating voltage and also capable of increasing an optical confinement factor in an active layer.SOLUTION: A nitride semiconductor light emitting element 100 includes a semiconductor multilayer body 100S. The semiconductor multilayer body 100S includes an N-type first cladding layer 102, an N-side guide layer 104, an active layer 105 that includes a well layer and a barrier layer, a P-side guide layer 106, and a P-type cladding layer 110. The band gap energy of the P-side guide layer 106 monotonically increases as it gets away from the active layer 105, and the average band gap energy of the P-side guide layer 106 is equal to or more than the average band gap energy of the N-side guide layer 104. The band gap energy of the barrier layer is equal to or less than the minimum values of the band gap energies of the N-side guide layer 104 and the P-side guide layer 106. The film thickness of the P-side guide layer 106 is larger than the film thickness of the N-side guide layer 104.SELECTED DRAWING: Figure 5

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 have been used as light sources for processing equipment and the like. Light sources for processing equipment are required to have even higher output and efficiency. To improve the efficiency of nitride-based semiconductor light-emitting elements, for example, a technique for reducing the operating voltage is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-50021 Summary of the Invention [Problem to be solved by the invention]

[0004] In addition to the technique described in Patent Document 1, reducing the thickness of the P-type cladding layer is also effective for reducing the operating voltage of nitride-based semiconductor light-emitting devices. However, reducing the thickness of the P-type cladding layer shifts the peak of the light intensity distribution in the stacking direction (i.e., the growth direction of each semiconductor layer) from the active layer toward the N-type cladding layer. This reduces the optical confinement coefficient in the active layer, and therefore reduces the thermal saturation level of the optical output. This makes it difficult to achieve high output from nitride-based semiconductor light-emitting devices.

[0005] The present disclosure is intended to solve such problems, and has an object to provide a nitride-based semiconductor light-emitting device that can reduce the operating voltage and increase the optical confinement coefficient in the active layer. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of a nitride-based semiconductor light-emitting device according to the present disclosure is a nitride-based semiconductor light-emitting device that includes a semiconductor laminate and emits light from an end face in a direction perpendicular to a stacking direction of the semiconductor laminate, the semiconductor laminate including an N-type first cladding layer, an N-side guide layer disposed above the N-type first cladding layer, an active layer disposed above the N-side guide layer and including a well layer and a barrier layer and having a quantum well structure, a P-side guide layer disposed above the active layer, and a P-type cladding layer disposed above the P-side guide layer, the band gap energy of the layers monotonically increases with increasing distance from the active layer, the P-side guide layer includes a portion whose band gap energy continuously increases with increasing distance from the active layer, the average band gap energy of the P-side guide layer is equal to or greater than the average band gap energy of the N-side guide layer, and the band gap energy of the barrier layer is equal to or less than the minimum value of the band gap energies of the N-side guide layer and the P-side guide layer, and when the thickness of the P-side guide layer is Tp and the thickness of the N-side guide layer is Tn, Tn <Tp Satisfy the relationship. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a nitride-based semiconductor light-emitting device that can reduce the operating voltage and increase the optical confinement coefficient in the active layer. [Brief explanation of the drawings]

[0008] [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 schematic diagram showing an outline of the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element according to the first embodiment. [Figure 4] FIG. 4 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 5] FIG. 5 is a schematic graph showing the distribution of band gap energy in the active layer and each layer in the vicinity thereof of the nitride-based semiconductor light-emitting device according to the first embodiment. [Figure 6] FIG. 6 is a graph showing the refractive index distribution and light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device according to the first embodiment. [Figure 7] FIG. 7 is a graph showing the simulation results of the distribution of valence electron charge potential and hole Fermi level in the stacking direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device according to Embodiment 1. [Figure 8] FIG. 8 is a graph showing simulation results of carrier concentration distribution in the stacking direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device according to the first embodiment. [Figure 9] FIG. 9 is a graph showing a simulation result of the relationship between the film thickness of the N-side guide layer and the optical confinement factor according to the first embodiment. [Figure 10] FIG. 10 is a graph showing a simulation result of the relationship between the film thickness of the N-side guide layer and the waveguide loss according to the first embodiment. [Figure 11] FIG. 11 is a graph showing a simulation result of the relationship between the film thickness of the N-side guide layer and the effective refractive index difference according to the first embodiment. [Figure 12] FIG. 12 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer and the position P1 according to the first embodiment. [Figure 13] FIG. 13 is a graph showing a simulation result of the relationship between the film thickness of the N-side guide layer and the difference ΔP according to the first embodiment. [Figure 14]FIG. 14 is a graph showing a simulation result of the relationship between the film thickness of the P-type cladding layer and the optical confinement factor according to the first embodiment. [Figure 15] FIG. 15 is a graph showing a simulation result of the relationship between the thickness of the P-type cladding layer and the waveguide loss according to the first embodiment. [Figure 16] FIG. 16 is a graph showing a simulation result of the relationship between the film thickness of the P-type cladding layer and the effective refractive index difference according to the first embodiment. [Figure 17] FIG. 17 is a graph showing the simulation results of the relationship between the film thickness of the P-type cladding layer and the position P1 according to the first embodiment. [Figure 18] FIG. 18 is a graph showing the simulation results of the relationship between the thickness of the P-type cladding layer according to the first embodiment and the difference ΔP. [Figure 19] FIG. 19 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the second embodiment. [Figure 20] FIG. 20 is a schematic graph showing the distribution of band gap energy in the active layer and each layer in the vicinity thereof of the nitride-based semiconductor light-emitting device according to the second embodiment. [Figure 21] FIG. 21 is a graph showing the simulation results of the distribution of valence electron charge potential and hole Fermi level in the stacking direction of the nitride-based semiconductor light-emitting element according to the second embodiment. [Figure 22] FIG. 22 is a graph showing the results of a simulation of the distribution of carrier concentration in the stacking direction of the nitride-based semiconductor light-emitting element according to the second embodiment. [Figure 23] FIG. 23 is a graph showing a simulation result of the relationship between the average In composition ratio in the p-side guide layer and the waveguide loss according to the second embodiment. [Figure 24] FIG. 24 is a graph showing a simulation result of the relationship between the average In composition ratio in the p-side guide layer and the optical confinement factor according to the second embodiment. [Figure 25] FIG. 25 is a graph showing a simulation result of the relationship between the film thickness of the N-side guide layer and the optical confinement factor according to the second embodiment. [Figure 26] FIG. 26 is a graph showing a simulation result of the relationship between the film thickness of the N-side guide layer and the waveguide loss according to the second embodiment. [Figure 27] FIG. 27 is a graph showing a simulation result of the relationship between the film thickness of the N-side guide layer and the effective refractive index difference according to the second embodiment. [Figure 28] FIG. 28 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer and the position P1 according to the second embodiment. [Figure 29] FIG. 29 is a graph showing a simulation result of the relationship between the film thickness of the N-side guide layer and the difference ΔP according to the second embodiment. [Figure 30] FIG. 30 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the third embodiment. [Figure 31] FIG. 31 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the fourth embodiment. [Figure 32A] FIG. 32A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the fifth embodiment. [Figure 32B] FIG. 32B is a cross-sectional view showing the configuration of an active layer included in the nitride-based semiconductor light-emitting device according to the fifth 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 sixth embodiment. [Figure 34] FIG. 34 is a schematic graph showing the distribution of band gap energy in the active layer and each layer in the vicinity thereof of the nitride-based semiconductor light-emitting device according to the sixth embodiment. [Figure 35] FIG. 35 is a graph showing a simulation result of the relationship between the average In composition ratio in the N-side guide layer and the optical confinement factor according to the sixth embodiment. [Figure 36] FIG. 36 is a graph showing a simulation result of the relationship between the average In composition ratio in the N-side guide layer and the operating voltage according to the sixth embodiment. [Figure 37]FIG. 37 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light-emitting element according to the first embodiment and the piezoelectric polarization charge density, the piezoelectric polarization electric field, and the conduction field potential. [Figure 38] FIG. 38 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light-emitting device according to the sixth embodiment and the piezoelectric polarization charge density, the piezoelectric polarization electric field, and the conduction field potential. [Figure 39] FIG. 39 is a graph showing a simulation result of the relationship between the average In composition ratio in the N-side guide layer of the nitride-based semiconductor light-emitting device according to the sixth embodiment and the optical confinement factor. [Figure 40] FIG. 40 is a graph showing the simulation results of the relationship between the average In composition ratio in the N-side guide layer of the nitride-based semiconductor light-emitting device according to the sixth embodiment and the waveguide loss. [Figure 41] FIG. 41 is a graph showing a simulation result of the relationship between the average In composition ratio in the N-side guide layer of the nitride-based semiconductor light-emitting device according to the sixth embodiment and the operating voltage. [Figure 42] FIG. 42 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the seventh embodiment. [Figure 43] FIG. 43 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the eighth embodiment. [Figure 44] FIG. 44 is a graph showing the distribution of the Al composition ratio in the stacking direction of the electron barrier layer according to the eighth embodiment. [Figure 45] FIG. 45 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Modification 1. As shown in FIG. [Figure 46] FIG. 46 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Modification 2. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] 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.

[0011] 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.

[0012] (Embodiment 1) A nitride-based semiconductor light-emitting device according to a first embodiment will be described.

[0013] [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 105 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.

[0014] As shown in FIG. 2A, the nitride-based semiconductor light-emitting device 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 device 100 is a semiconductor laser device 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. 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 device 100 according to this embodiment (i.e., the distance between the facet 100F and the facet 100R) is approximately 1200 μm.

[0015] 2A , the nitride-based semiconductor light-emitting element 100 includes a semiconductor stack 100S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor stack 100S includes a substrate 101, an N-type first cladding layer 102, an N-type second cladding layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 106, an intermediate layer 108, an electron barrier layer 109, a P-type cladding layer 110, and a contact layer 111.

[0016] 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 an N-type GaN substrate.

[0017] The N-type first cladding layer 102 is an example of an N-type cladding layer disposed above the substrate 101. The N-type first cladding layer 102 has a smaller refractive index than the active layer 105 and a larger band gap energy. In this embodiment, the N-type first cladding layer 102 is a layer having a thickness of 1200 nm and an N-type Al 0.026 Ga 0.974 The N-type first cladding layer 102 contains impurities at a concentration of 1×10 18 cm -3 It is doped with Si.

[0018] The N-type second cladding layer 103 is an example of an N-type cladding layer disposed above the substrate 101. In this embodiment, the N-type second cladding layer 103 is disposed above the N-type first cladding layer 102. The N-type second cladding layer 103 is a layer having a smaller refractive index than the active layer 105 and a larger band gap energy. In this embodiment, the N-type second cladding layer 103 is an N-type GaN layer having a film thickness of 100 nm. The N-type second cladding layer 103 contains impurities at a concentration of 1×10 18 cm -3 The band gap energy of the N-type second cladding layer 103 is smaller than the band gap energy of the N-type first cladding layer 102 and is equal to or larger than the maximum value of the band gap energy of the P-side guide layer 106.

[0019] The N-side guide layer 104 is an optical guide layer disposed above the N-type second cladding layer 103. The N-side guide layer 104 has a higher refractive index and a smaller band gap energy than the N-type first cladding layer 102 and the N-type second cladding layer 103. In this embodiment, the N-side guide layer 104 is an undoped InP layer with a thickness of 160 nm. 0.04 Ga 0.96 This is the N layer.

[0020] The active layer 105 is a light-emitting layer having a quantum well structure and is disposed above the N-side guide layer 104. In this embodiment, the active layer 105 includes well layers 105b and 105d and barrier layers 105a, 105c, and 105e, as shown in FIG.

[0021] The barrier layer 105a is disposed above the N-side guide layer 104 and functions as a barrier for the quantum well structure. In this embodiment, the barrier layer 105a is an undoped In layer having a thickness of 7 nm. 0.05 Ga 0.95 This is the N layer.

[0022] The well layer 105b is disposed above the barrier layer 105a and functions as a well of the quantum well structure. The well layer 105b is disposed between the barrier layer 105a and the barrier layer 105c. In this embodiment, the well layer 105b is a 3-nm-thick undoped In 0.18 Ga 0.82 This is the N layer.

[0023] The barrier layer 105c is disposed above the well layer 105b and functions as a barrier for the quantum well structure. In this embodiment, the barrier layer 105c is an undoped In layer having a thickness of 7 nm. 0.05 Ga 0.95 This is the N layer.

[0024] The well layer 105d is disposed above the barrier layer 105c and functions as a well of the quantum well structure. The well layer 105d is disposed between the barrier layer 105c and the barrier layer 105e. In this embodiment, the well layer 105d is a 3-nm-thick undoped In 0.18 Ga 0.82 This is the N layer.

[0025] The barrier layer 105e is disposed above the well layer 105d and functions as a barrier for the quantum well structure. In this embodiment, the barrier layer 105e is an undoped In layer having a thickness of 5 nm. 0.05 Ga 0.95 This is the N layer.

[0026] In this embodiment, the bandgap energy of each barrier layer is equal to or less than the minimum value of the bandgap energy of the N-side guide layer 104 and the P-side guide layer 106. In other words, the refractive index of each barrier layer is greater than the refractive index of the N-side guide layer 104 and the P-side guide layer 106. Therefore, the optical confinement coefficient in the active layer 105 can be increased.

[0027] The P-side guide layer 106 is an optical guide layer disposed above the active layer 105. The P-side guide layer 106 has a higher refractive index and a smaller bandgap energy than the P-type cladding layer 110. The bandgap energy of the P-side guide layer 106 increases monotonically with increasing distance from the active layer 105. Here, a configuration in which the bandgap energy increases monotonically also includes a configuration in which there is a region in which the bandgap energy is constant in the stacking direction. The P-side guide layer 106 includes a portion in which the bandgap energy increases continuously with increasing distance from the active layer 105. Here, a configuration in which the bandgap energy increases continuously does not include a configuration in which the bandgap energy changes discontinuously in the stacking direction. In the present disclosure, a configuration in which the bandgap energy increases continuously and monotonically means a configuration in which the discontinuous increase in the bandgap energy at a certain position in the stacking direction is less than 2% of the magnitude of the bandgap energy at that position. For example, a configuration in which the bandgap energy increases continuously does not include a configuration in which the bandgap energy increases stepwise by 2% or more in the stacking direction, but does include a configuration in which the bandgap energy increases stepwise by less than 2% in the stacking direction. In this embodiment, the bandgap energy increases continuously throughout the entire P-side guide layer 106 with increasing distance from the active layer 105, but the configuration of the P-side guide layer 106 is not limited to this. For example, the ratio of the film thickness of the portion in which the bandgap energy increases continuously with increasing distance from the active layer 105 to the entire film thickness of the P-side guide layer 106 may be 50% or more. Alternatively, this ratio may be 70% or more, or 90% or more.

[0028] The increase in the band gap energy of the P-side guide layer 106 in the stacking direction (ΔEgp) is preferably 100 meV or more. Here, the increase in the band gap energy of the P-side guide layer 106 in the stacking direction is defined, for example, as the difference between the band gap energy near the end face of the P-side guide layer 106 closer to the active layer 105 and the band gap energy near the end face closer to the P-type cladding layer 110. The magnitude of the continuously increasing band gap energy in ΔEgp may be 70% or more. This proportion may also be 80% or more, or 90% or more.

[0029] The P-side guide layer 106 is In Xp Ga 1-Xp When the p-side guide layer 106 is made of N, the In composition ratio Xp of the p-side guide layer 106 monotonically decreases with increasing distance from the active layer 105. As a result, the band gap energy of the p-side guide layer 106 monotonically increases with increasing distance from the active layer 105. Here, a configuration in which the In composition ratio Xp continuously and monotonically decreases includes a configuration in which there is a region in which the In composition ratio Xp is constant in the stacking direction. The p-side guide layer 106 includes a portion in which the In composition ratio Xp continuously decreases with increasing distance from the active layer 105. Here, a configuration in which the In composition ratio Xp continuously decreases does not include a configuration in which the In composition ratio Xp changes discontinuously in the stacking direction. In the present disclosure, a configuration in which the In composition ratio Xp continuously decreases means a configuration in which the discontinuous decrease in the In composition ratio Xp at a certain position in the p-side guide layer 106 in the stacking direction is less than 20% of the In composition ratio Xp at that position.

[0030] The average band gap energy of the P-side guide layer 106 is equal to or greater than the average band gap energy of the N-side guide layer 104. In other words, the average value of the In composition ratio of the N-side guide layer 104 is equal to or greater than the average value of the In composition ratio of the P-side guide layer 106. In this embodiment, the average value of the In composition ratio of the N-side guide layer 104 is greater than the average value of the In composition ratio of the P-side guide layer 106. Furthermore, assuming that the thickness of the P-side guide layer 106 is Tp and the thickness of the N-side guide layer 104 is Tn, Tn <Tp (1) Satisfy the relationship.

[0031] The maximum value of the In composition ratio in the p-side guide layer 106 is equal to or less than the In composition ratio of each barrier layer.

[0032] In this embodiment, the p-side guide layer 106 is an undoped In layer having a thickness of 280 nm. Xp Ga 1-Xp More specifically, the P-side guide layer 106 has an In layer near the interface on the side closer to the active layer 105. 0.04 Ga 0.96 The p-side guide layer 106 has a composition represented by N, and a composition represented by GaN near the interface far from the active layer 105. The In composition ratio Xp of the p-side guide layer 106 decreases at a constant rate as it moves away from the active layer 105.

[0033] The intermediate layer 108 is a layer disposed above the active layer 105. In this embodiment, the intermediate layer 108 is disposed between the P-side guide layer 106 and the electron barrier layer 109, and reduces stress caused by the difference in lattice constant between the P-side guide layer 106 and the electron barrier layer 109. This makes it possible to suppress the occurrence of crystal defects in the nitride-based semiconductor light-emitting element 100. In this embodiment, the intermediate layer 108 is an undoped GaN layer with a thickness of 20 nm.

[0034] The electron barrier layer 109 is disposed above the active layer 105 and is a nitride-based semiconductor layer containing at least Al. In this embodiment, the electron barrier layer 109 is disposed between the intermediate layer 108 and the P-type cladding layer 110. The electron barrier layer 109 is a 5-nm-thick P-type Al 0.36 Ga 0.64 The electron barrier layer 109 contains impurities at a concentration of 1×10 19 cm -3 The electron barrier layer 109 can prevent electrons from leaking from the active layer 105 to the P-type cladding layer 110.

[0035] The P-type cladding layer 110 is a P-type cladding layer disposed above the active layer 105. In this embodiment, the P-type cladding layer 110 is disposed between the electron barrier layer 109 and the contact layer 111. The P-type cladding layer 110 has a lower refractive index and a higher band gap energy than the active layer 105. The thickness of the P-type cladding layer 110 may be 460 nm or less. This reduces the electrical resistance of the nitride-based semiconductor light-emitting device 100. This reduces the operating voltage of the nitride-based semiconductor light-emitting device 100. Furthermore, this reduces self-heating during operation of the nitride-based semiconductor light-emitting device 100, thereby improving the temperature characteristics of the nitride-based semiconductor light-emitting device 100. This enables high-power operation of the nitride-based semiconductor light-emitting device 100. In the nitride-based semiconductor light-emitting device 100 according to this embodiment, the thickness of the P-type cladding layer 110 is required to be 200 nm or more in order for the P-type cladding layer 110 to fully function as a cladding layer. The thickness of the P-type cladding layer 110 may be 250 nm or more. In this embodiment, the P-type cladding layer 110 is a P-type Al layer having a thickness of 450 nm. 0.026 Ga 0.974 The P-type cladding layer 110 is an N layer. The P-type cladding layer 110 is doped with Mg as an impurity. The impurity concentration at the end of the P-type cladding layer 110 closer to the active layer 105 is lower than the impurity concentration at the end farther from the active layer 105. Specifically, the P-type cladding layer 110 has an impurity concentration of 2×10 18 cm -3 Mg-doped p-type Al with a thickness of 150 nm 0.026 Ga 0.974 N layer and a layer with a concentration of 1×10 19 cm -3 Mg-doped P-type Al with a thickness of 300 nm 0.026 Ga 0.974 It has N layers.

[0036] A ridge 110R is formed in the P-type cladding layer 110 of the nitride-based semiconductor light-emitting device 100. Two grooves 110T are formed in the P-type cladding layer 110, arranged along the ridge 110R 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 110R (i.e., the bottom of the groove 110T) and the active layer 105 is defined as dp. The film thickness of the P-type cladding layer 110 at the lower end of the ridge 110R (i.e., the distance between the lower end of the ridge 110R and the interface between the P-type cladding layer 110 and the electron barrier layer 109) is defined as dc.

[0037] The contact layer 111 is disposed above the P-type cladding layer 110 and is in ohmic contact with the P-side electrode 113. In this embodiment, the contact layer 111 is a P-type GaN layer with a thickness of 60 nm. The contact layer 111 contains impurities with a concentration of 1×10 20 cm -3 It is doped with Mg.

[0038] The current blocking layer 112 is disposed above the P-type cladding layer 110 and is an insulating layer that is transparent to light from the active layer 105. The current blocking layer 112 is disposed on the upper surface of the P-type cladding layer 110 except for the upper surface of the ridge 110R. In this embodiment, the current blocking layer 112 is a SiO2 layer.

[0039] The P-side electrode 113 is a conductive layer disposed above the contact layer 111. In this embodiment, the P-side electrode 113 is disposed above the contact layer 111 and the current blocking layer 112. The P-side electrode 113 is a single-layer film or a multi-layer film formed of at least one of Cr, Ti, Ni, Pd, Pt, and Au, for example.

[0040] The N-side electrode 114 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 first cladding layer 102 and the like are disposed). The N-side electrode 114 is a single-layer film or a multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt, and Au, for example.

[0041] 2A, the nitride-based semiconductor light-emitting device 100 has the above-described configuration, and therefore an effective refractive index difference ΔN occurs between the portion below the ridge 110R and the portion below the groove 110T. This allows light generated in the portion of the active layer 105 below the ridge 110R to be confined in the horizontal direction (i.e., the X-axis direction).

[0042] [1-2. Light intensity distribution and light output stability] Next, the light intensity distribution and stability of the light output of the nitride-based semiconductor light-emitting device 100 according to this embodiment will be described.

[0043] First, the light intensity distribution in the stacking direction (Z-axis direction in each drawing) of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be described with reference to Fig. 3. Fig. 3 is a schematic diagram showing an outline of the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Fig. 3 shows a schematic cross-sectional view of the nitride-based semiconductor light-emitting element 100 and a graph showing an outline of the light intensity distribution in the stacking direction at positions corresponding to the ridge 110R and the groove 110T.

[0044] Generally, in nitride-based semiconductor light-emitting devices, light is generated in the active layer. However, the light intensity distribution in the stacking direction depends on the stacking structure, and the peak of the light intensity distribution does not necessarily lie in the active layer. Furthermore, since the stacking structure of the nitride-based semiconductor light-emitting device 100 according to this embodiment differs between the portion below the ridge 110R and the portion below the groove 110T, the light intensity distribution also differs between the portion below the ridge 110R and the portion below the groove 110T. As shown in FIG. 3 , the peak position of the light intensity distribution in the stacking direction at the center in the horizontal direction (i.e., the X-axis direction) of the portion below the ridge 110R is designated P1. Furthermore, the peak position of the light intensity distribution in the stacking direction below the groove 110T is designated P2. Positions P1 and P2 will now be described with reference to FIG. 4 . FIG. 4 is a graph showing coordinates of positions in the stacking direction of the nitride-based semiconductor light-emitting device 100 according to this embodiment. 4, the coordinate of the position in the stacking direction of the N-side end face of the well layer 105b of the active layer 105, that is, the end face of the well layer 105b closer to the N-side guide layer 104, is set to zero, the downward direction (toward the N-side guide layer 104) is set to the negative direction of the coordinate, and the upward direction (toward the P-side guide layer 106) is set to the positive direction of the coordinate. The absolute value of the difference between positions P1 and P2 is set to the peak position difference ΔP.

[0045] The light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be described below with reference to Fig. 5. Fig. 5 is a schematic graph showing the distribution of band gap energy in the active layer 105 and each layer in the vicinity thereof of the nitride-based semiconductor light-emitting element 100 according to this embodiment.

[0046] In the nitride-based semiconductor light-emitting device 100 according to this embodiment, the thickness of the P-type cladding layer 110 is set to be relatively thin in order to reduce the operating voltage. Accordingly, the height of the ridge 110R (i.e., the height of the ridge 110R from the bottom surface of the groove 110T) is also set to be relatively low. In general, in a semiconductor light-emitting device having such a configuration, the peak position of the light intensity distribution in the stacking direction shifts from the active layer 105 toward the N-type second cladding layer 103. This reduces the optical confinement coefficient in the active layer, and accordingly reduces the thermal saturation level of the optical output. This makes it difficult for the semiconductor light-emitting device to operate at high output. In this embodiment, as shown in FIG. 5 , the average bandgap energy of the P-side guiding layer 106 is equal to or greater than the average bandgap energy of the N-side guiding layer 104. Meanwhile, the thickness Tp of the P-side guiding layer 106 is greater than the thickness Tn of the N-side guiding layer 104 (see inequality (1) above). In this way, by increasing the film thickness of the P-side guide layer 106, which has a refractive index higher than that of each cladding layer, it is possible to shift the light intensity distribution in a direction from the active layer 105 toward the P-side guide layer 106. Therefore, with the nitride-based semiconductor light-emitting element 100 according to this embodiment, it is possible to control the peak of the light intensity distribution in the stacking direction so that it is located in the active layer 105.

[0047] Furthermore, in this embodiment, the p-side guide layer 106 has a portion in which the bandgap energy increases continuously and monotonically with increasing distance from the active layer 105. In other words, the p-side guide layer 106 has a portion in which the refractive index increases continuously and monotonically with increasing distance from the active layer 105. Since the refractive index of the p-side guide layer 106 increases with increasing distance from the active layer 105, the peak of the light intensity distribution in the stacking direction can be brought closer to the active layer 105.

[0048] In this embodiment, the barrier layers 105a, 105c, and 105e of the active layer 105 are made of In. Xb Ga 1-Xb The In composition ratios Xb, Xn, and Xp of each barrier layer, the N-side guide layer 104, and the P-side guide layer 106 are: Xp≦Xb (2) Xn≦Xb (3) The relationship is satisfied. As a result, the band gap energy of each barrier layer is equal to or less than the minimum value of the band gap energy of the N-side guide layer 104 and the P-side guide layer 106. In other words, the refractive index of each barrier layer can be equal to or greater than the maximum value of the P-side guide layer 106 and the N-side guide layer 104. This makes it possible to bring the peak of the light intensity distribution in the stacking direction closer to the active layer 105. Furthermore, it is possible to prevent the light intensity distribution from moving too far in a direction approaching the P-type cladding layer 110 from the active layer 105. This effect can be further enhanced by making the refractive index of each barrier layer greater than the maximum value of the P-side guide layer 106 and the N-side guide layer 104.

[0049] With the above-described configuration, in this embodiment, the position P1 of the peak of the light intensity distribution in the stacking direction below the ridge 110R can be set to 1.3 nm. In other words, the peak of the light intensity distribution can be positioned in the well layer 105b of the active layer 105 (see FIG. 4). Also, ΔP can be suppressed to 5.6 nm. This allows the light confinement factor in the active layer 105 to be increased to approximately 1.49%.

[0050] As described above, according to the nitride-based semiconductor light-emitting device 100 of this embodiment, the peak of the light intensity distribution in the stacking direction can be positioned in the active layer 105. Note that, "the peak of the light intensity distribution in the stacking direction is positioned in the active layer 105" means that the peak of the light intensity distribution in the stacking direction is positioned in the active layer 105 at least one position in the horizontal direction of the nitride-based semiconductor light-emitting device 100, and is not limited to a state in which the peak of the light intensity distribution in the stacking direction is positioned in the active layer 105 at all positions in the horizontal direction.

[0051] When the peak of the light intensity distribution in the stacking direction is positioned in the active layer 105 as in this embodiment, the proportion of the portion of the light located in the P-type cladding layer 110 can be increased compared to when the peak of the light intensity distribution is positioned in the N-side guide layer 104. Here, since the P-type cladding layer 110 has a higher impurity concentration than the N-type first cladding layer 102 and the N-type second cladding layer 103, the increase in the proportion of the portion of the light located in the P-type cladding layer 110 raises concerns about an increase in free carrier loss in the P-type cladding layer 110. However, in this embodiment, the P-side guide layer 106 is an undoped layer, and the thickness Tp of the P-side guide layer 106 is relatively large, thereby increasing the proportion of the portion of the light intensity distribution located in the undoped layer. Therefore, an increase in free carrier loss can be suppressed. Specifically, in this embodiment, the waveguide loss is reduced to 3.2 cm. -1 It can be suppressed to a certain extent.

[0052] Furthermore, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, in order to reduce the divergence angle of the emitted light in the horizontal direction (i.e., the X-axis direction), the effective refractive index difference ΔN between the portion below the ridge 110R and the portion below the groove 110T is set to be relatively small. Specifically, the effective refractive index difference ΔN is set by adjusting the distance dp (see FIG. 2A) between the current blocking layer 112 and the active layer 105. Here, the greater the distance dp, the smaller the effective refractive index difference ΔN. In this embodiment, the effective refractive index difference ΔN is 2.1×10 -3 Therefore, in this embodiment, the effective refractive index difference ΔN is about 2.1×10 -3When the ridge 110R is larger than the ridge 110R, the number of higher-order modes (i.e., higher-order transverse modes) that can propagate through the waveguide formed by the ridge 110R is smaller. Therefore, the proportion of each higher-order mode among all transverse modes included in the emitted light from the nitride-based semiconductor light-emitting element 100 is relatively large. Consequently, the increase or decrease in the number of modes and the change in the optical confinement factor in the active layer 105 due to inter-mode coupling are relatively large. Therefore, when the increase or decrease in the number of modes and inter-mode coupling occur in the nitride-based semiconductor light-emitting element 100, the linearity of the optical output characteristic with respect to the supplied current (the so-called IL characteristic) decreases. In other words, a non-linear portion (a so-called kink) appears in the graph showing the IL characteristic. This may result in a decrease in the stability of the optical output of the nitride-based semiconductor light-emitting element 100.

[0053] The above-mentioned decrease in stability of light output will be explained below. In the nitride-based semiconductor light-emitting element 100, the light intensity distribution in the portion below the ridge 110R is dominated by the fundamental mode (i.e., the zeroth-order mode), and the light intensity distribution in the portion below the groove 110T is dominated by a higher-order mode. Therefore, when the difference ΔP between the peak position P1 of the light intensity distribution in the stacking direction in the portion below the ridge 110R of the nitride-based semiconductor light-emitting element 100 and the peak position P2 of the light intensity distribution in the stacking direction in the portion below the groove 110T is large, an increase or decrease in the number of modes and inter-mode coupling occur, which causes a fluctuation in the light confinement coefficient in the active layer 105, thereby decreasing the stability of the light output.

[0054] For example, when the number of higher-order modes decreases, the peak of the light intensity distribution obtained by adding together the light intensity distributions below both the ridge 110R and the groove 110T moves to a position closer to position P1. Therefore, the larger the difference ΔP between positions P1 and P2, the greater the fluctuation in the light confinement factor in the active layer 105 when the number of modes changes. Therefore, the stability of the light output decreases.

[0055] The nitride-based semiconductor light-emitting device 100 according to this embodiment includes the N-side guide layer 104 and the P-side guide layer 106 having the above-described configurations, and therefore the peak of the light intensity distribution can be positioned in the active layer 105 both below the ridge 110R and below the trench 110T. That is, the difference ΔP between the positions P1 and P2 of the light intensity distribution peaks can be reduced. As a result, even if the number of modes increases or decreases and inter-mode coupling occurs, fluctuations in the stacking direction of the peak of the light intensity distribution obtained by adding the light intensity distributions below both the ridge 110R and the trench 110T can be suppressed. This can improve the stability of the light output.

[0056] As described above, the distance dp is set to a relatively large value in order to set the effective refractive index difference ΔN to a relatively small value. When the distance dp is set, if the lower end of the ridge 110R (i.e., the bottom of the trench 110T) is set to be lower than the electron barrier layer 109, holes injected from the contact layer 111 are likely to leak from the sidewall of the ridge 110R to the outside of the ridge 110R when passing through the electron barrier layer 109 because the electron barrier layer 109 has a large band gap energy. As a result, the holes flow downward into the trench 110T. Accordingly, the light distribution intensity in the active layer 105 below the trench 110T is low, so the probability of radiative recombination between electrons and holes injected into the active layer 105 decreases, and non-radiative recombination increases. Such an increase in non-radiative recombination makes the nitride-based semiconductor light-emitting element 100 more susceptible to degradation. To suppress such degradation, the lower end of the ridge 110R is set to be higher than the electron barrier layer 109. Furthermore, if the distance dc (see FIG. 2A) from the bottom end of the ridge 110R to the electron barrier layer 109 becomes too large, holes will flow from the ridge 110R into the gap between the groove 110T and the electron barrier layer 109, resulting in leakage current. To prevent this leakage current from increasing, the distance dc is set to the smallest possible value. The distance dc is, for example, 10 nm or more and 70 nm or less.

[0057] [1-3.Effects] [1-3-1. Each guide layer] The effects of each guide layer of the nitride-based semiconductor light-emitting element 100 according to the present embodiment will be described with reference to FIGS. 6 to 8, in comparison with nitride-based semiconductor light-emitting elements of comparative examples. FIG. 6 is a graph showing the refractive index distribution and light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting elements of Comparative Examples 1 to 3, and the nitride-based semiconductor light-emitting element 100 according to the present embodiment. Graphs (a) to (c) of FIG. 6 show the refractive index distribution and light intensity distribution of the nitride-based semiconductor light-emitting elements of Comparative Examples 1 to 3, respectively. Graph (d) of FIG. 6 shows the refractive index distribution and light intensity distribution of the nitride-based semiconductor light-emitting element 100 according to the present embodiment. In each graph of FIG. 6, the refractive index distribution is shown by a solid line, and the light intensity distribution is shown by a dashed line.

[0058] 7 is a graph showing the simulation results of the distribution of valence charge potential and hole Fermi level in the stacking direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device 100 according to this embodiment. Graphs (a) to (c) in FIG. 7 show the distribution of valence charge potential and hole Fermi level of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3, respectively. Graph (d) in FIG. 7 shows the distribution of valence charge potential and hole Fermi level of the nitride-based semiconductor light-emitting device 100 according to this embodiment. In each graph in FIG. 7, the valence charge potential is shown by a solid line, and the hole Fermi level is shown by a dashed line.

[0059] Fig. 8 is a graph showing simulation results of the carrier concentration distribution in the stacking direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device 100 according to this embodiment. Graphs (a) to (c) of Fig. 8 show the carrier concentration distribution of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3, respectively. Graph (d) of Fig. 8 shows the carrier concentration distribution of the nitride-based semiconductor light-emitting device 100 according to this embodiment. In each graph of Fig. 8, the electron concentration distribution is shown by a solid line, and the hole concentration distribution is shown by a dashed line.

[0060] The nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 differ from the nitride-based semiconductor light-emitting device 100 according to the present embodiment in the configurations of the N-side guide layer and the P-side guide layer. The nitride-based semiconductor light-emitting device of Comparative Example 1 shown in graph (a) of FIG. 6 has an undoped In 0.04 Ga 0.96 The N-side guide layer 1104 is made of an N layer, and the undoped In layer is made of a 160 nm thick 0.04 Ga 0.96 The nitride-based semiconductor light-emitting device of Comparative Example 2 shown in graph (b) of FIG. 6 has a 160 nm-thick undoped In layer. 0.04 Ga 0.96 The N-side guide layer 1204 is made of an N layer and an undoped In layer with a thickness of 280 nm. 0.04 Ga 0.96 The nitride-based semiconductor light-emitting device of Comparative Example 3 shown in graph (c) of FIG. 6 has a 160 nm-thick undoped In 0.04 Ga 0.96 The nitride-based semiconductor light-emitting device of Comparative Example 3 includes an N-side guide layer 1304 made of an N layer and a P-side guide layer 1306 having a thickness of 280 nm. The P-side guide layer 1306 of the nitride-based semiconductor light-emitting device of Comparative Example 3 is an undoped InP layer having a thickness of 140 nm and disposed above the active layer 105. 0.04 Ga 0.96 A P-side first guide layer 1306a made of an N layer and an undoped In layer with a thickness of 140 nm disposed above the P-side first guide layer 1306a. 0.02 Ga 0.98 and a P-side second guide layer 1306b consisting of N layers.

[0061] In the nitride-based semiconductor light-emitting device of Comparative Example 1, the N-side guide layer 1104 and the P-side guide layer 1106 have the same composition, and the N-side guide layer 1104 is thicker than the P-side guide layer 1106. Therefore, in the nitride-based semiconductor light-emitting device of Comparative Example 1, the peak of the light intensity distribution in the stacking direction is located in the N-side guide layer 1104, as shown in graph (a) of FIG. 6 . Therefore, the nitride-based semiconductor light-emitting device of Comparative Example 1 has a low optical confinement factor of 1.33%. Furthermore, as shown in graph (a) of FIG. 7 , in the P-side guide layer 1106, in order to conduct holes from the P-side guide layer 1106 to the active layer 105, the hole Fermi level increases from the interface of the P-side guide layer 1106 farther from the active layer 105 to the interface closer to the active layer 105. Meanwhile, the valence electron charge potential is substantially constant in the stacking direction of the P-side guide layer 1106. Therefore, the difference between the hole Fermi level and the valence electron charge potential in the P-side guide layer 1106 increases with increasing distance from the active layer 105. Therefore, as shown in graph (a) of FIG. 8, the concentration of holes and electrons in the stacking direction of the P-side guide layer 1106, i.e., the free carrier concentration, increases with increasing distance from the active layer 105. As described above, in the nitride-based semiconductor light-emitting device of Comparative Example 1, the free carrier concentration in the stacking direction of the P-side guide layer 1106 cannot be reduced, and therefore reductions in free carrier loss and non-radiative recombination probability cannot be achieved. In the nitride-based semiconductor light-emitting device of Comparative Example 1, the effective refractive index difference ΔN is 3.6×10 -3 The peak positions P1 and P2 of the light intensity distribution are −34.1 nm and −75.6 nm, respectively, and the difference ΔP is 41.5 nm. The waveguide loss is 4.5 cm -1 The free carrier loss in the N-side guide layer 1104 and the P-side guide layer 1106 (hereinafter also referred to as "guide layer free carrier loss") is 2.8 cm -1 is.

[0062] In the nitride-based semiconductor light-emitting device of Comparative Example 2, the thickness of the P-side guide layer 1206 is greater than the thickness of the N-side guide layer 1204. Therefore, as shown in graph (b) of FIG. 6, the peak of the light intensity distribution in the stacking direction is closer to the active layer 105 than in the nitride-based semiconductor light-emitting device of Comparative Example 1. Therefore, in the nitride-based semiconductor light-emitting device of Comparative Example 2, the optical confinement factor is 1.37%, which is slightly improved compared to the nitride-based semiconductor light-emitting device of Comparative Example 1. However, as shown in graph (b) of FIG. 7, similar to Comparative Example 1, the difference between the hole Fermi level and the valence electron charge potential in the P-side guide layer 1206 increases with increasing distance from the active layer 105. Therefore, as shown in graph (b) of FIG. 8, the concentration of holes and electrons in the stacking direction of the P-side guide layer 1206, i.e., the free carrier concentration, increases with increasing distance from the active layer 105. As described above, the free carrier concentration in the stacking direction of the p-side guide layer 1206 cannot be reduced, and therefore, the nitride-based semiconductor light-emitting device of Comparative Example 2 cannot achieve a reduction in free carrier loss or a reduction in the probability of non-radiative recombination. In the nitride-based semiconductor light-emitting device of Comparative Example 2, the effective refractive index difference ΔN is 3.3×10 -3 The peak positions P1 and P2 of the light intensity distribution are 31.3 nm and 10.8 nm, respectively, and the difference ΔP is 20.5 nm. The waveguide loss is 5.2 cm -1 and the free carrier loss in the guiding layer is 3.6 cm -1 is.

[0063] In the nitride-based semiconductor light-emitting device of Comparative Example 3, the refractive index of the P-side second guide layer 1306b, which is a region of the P-side guide layer 1306 far from the active layer 105, is smaller than the refractive index of the P-side first guide layer 1306a, which is a region close to the active layer 105. As a result, as shown in graph (c) of FIG. 6, the peak of the light intensity distribution in the stacking direction is closer to the active layer 105 than in the nitride-based semiconductor light-emitting device of Comparative Example 2. Therefore, in the nitride-based semiconductor light-emitting device of Comparative Example 3, the optical confinement factor is 1.47%, which is further improved than that of the nitride-based semiconductor light-emitting device of Comparative Example 2. However, at the heterobarrier at the interface between the P-side first guide layer 1306a and the P-side second guide layer 1306b, a spike-shaped region is generated in the distribution of valence electron charge potential due to piezoelectric polarization charges, as shown in graph (c) of FIG. 8, the electron concentration in the stacking direction of the p-side guide layer 1306 increases in a spike-like manner in the area where the valence electron charge potential changes discontinuously. Also, the hole concentration in the p-side guide layer 1306 also increases by 1×10 17 cm -3 In this way, since the free carrier concentration in the stacking direction of the p-side guide layer 1306 cannot be reduced, the nitride-based semiconductor light-emitting device of Comparative Example 3 cannot realize a reduction in free carrier loss and a reduction in the probability of non-radiative recombination. In the nitride-based semiconductor light-emitting device of Comparative Example 3, the effective refractive index difference ΔN is 2.5×10 -3 The peak positions P1 and P2 of the light intensity distribution are 10.7 nm and 4.4 nm, respectively, and the difference ΔP is 6.3 nm. The waveguide loss is 3.93 cm -1 and the free carrier loss in the guiding layer is 2.56 cm -1 is.

[0064] In the nitride-based semiconductor light-emitting device 100 according to this embodiment, as shown in graph (d) of FIG. 6 , the refractive index of the p-side guide layer 106 increases toward the active layer 105, so that the peak of the light intensity distribution in the stacking direction can be moved closer to the active layer 105. Therefore, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, the optical confinement factor is 1.49%, which is further improved compared to the nitride-based semiconductor light-emitting device of Comparative Example 3. Furthermore, since the bandgap energy of the p-side guide layer 106 increases continuously and monotonically with increasing distance from the active layer 105, the valence charge potential continuously decreases with increasing distance from the active layer 105, as shown in graph (d) of FIG. 7 . This makes it possible to maintain a substantially constant difference between the hole Fermi level and the valence charge potential in the p-side guide layer 106. Therefore, as shown in graph (d) of FIG. 8 , the hole and electron concentrations in the stacking direction of the p-side guide layer 106 can be reduced and maintained substantially constant. Here, if the increase in the band gap energy of the P-side guide layer 106 in the stacking direction (ΔEgp) is small, the effect will be small, so ΔEgp should be 100 meV or more. Conversely, if ΔEgp is made too large, the band gap energy of the P-side guide layer 106 at the end on the active layer 105 side may become small. In this case, the gradient of the valence electron charge potential of the P-side guide layer 106 becomes too large, causing a leakage current in which holes injected into the active layer 105 leak toward the N-side guide layer 104. For this reason, ΔEgp may be 400 meV or less.

[0065] In this way, since the free carrier concentration in the stacking direction of the p-side guide layer 106 can be reduced, the nitride-based semiconductor light-emitting device 100 according to this embodiment can realize a reduction in free carrier loss and a reduction in the probability of non-radiative recombination. In the nitride-based semiconductor light-emitting device 100 according to this embodiment, the effective refractive index difference ΔN is 2.1×10 -3The peak positions P1 and P2 of the light intensity distribution are 1.3 nm and -4.3 nm, respectively, and the difference ΔP is 5.6 nm. In this way, in this embodiment, the position P1 and the difference ΔP can be reduced, so that non-linear portions are less likely to occur in the graph showing the IL characteristics. In addition, the waveguide loss is 3.20 cm -1 and the free carrier loss in the guiding layer is 1.8cm -1 As described above, in this embodiment, the waveguide loss and the free carrier loss can be reduced compared to the comparative examples.

[0066] Next, the effect of the relationship between the film thicknesses of the N-side guide layer 104 and the P-side guide layer 106 according to this embodiment will be described with reference to FIGS. 9 to 13. FIG. 9 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the optical confinement factor (Γv). FIG. 10 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the waveguide loss. FIG. 11 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the effective refractive index difference ΔN. FIG. 12 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the position P1. FIG. 13 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the difference ΔP. 9 to 13, the thicknesses of the N-side guide layer 104 and the P-side guide layer 106 are varied while the sum of their thicknesses is kept constant at 440 nm. The N-side guide layer 104 has an In composition ratio of 4%, and the P-side guide layer 106 has an In composition ratio of 4% near the interface closer to the active layer 105 and 0% near the interface farther from the active layer 105. The In composition ratio of the P-side guide layer 106 is varied at a constant rate in the stacking direction. Also shown in FIGS. 9 to 13 are dashed lines the simulation results of a comparative example in which the In composition ratio of the P-side guide layer is constant at 2%.

[0067] 9, by setting the thickness Tn of the N-side guide layer 104 to less than 220 nm, that is, by setting it to be smaller than the thickness Tp of the P-side guide layer 106, the optical confinement factor can be increased. The thickness Tn of the N-side guide layer 104 may be 100 nm or more. This prevents the optical intensity distribution from shifting too far in the direction from the active layer 105 to the P-side guide layer 106, which would otherwise be caused by the thickness Tn of the N-side guide layer 104 being too thin. Also, as shown in FIG. 9, even when the In composition ratio of the P-side guide layer 106 is constant at 2%, the optical confinement factor can be increased by setting the thickness of the N-side guide layer 104 to be smaller than the thickness of the P-side guide layer 106. However, the optical confinement factor can be further increased by continuously and monotonically decreasing the In composition ratio with increasing distance from the active layer 105, as in the P-side guide layer 106 according to this embodiment.

[0068] 10, when the In composition ratio is continuously and monotonically decreased with increasing distance from the active layer 105, as in the case of the P-side guide layer 106 according to this embodiment, the waveguide loss can be reduced more than when the In composition ratio is constant at 2%. Also, in this embodiment, even when the thickness of the N-side guide layer 104 is changed, the waveguide loss can be reduced to 3.5 cm. -1 can be made almost constant below this value.

[0069] 11, the effective refractive index difference ΔN can be reduced by setting the thickness Tn of the N-side guide layer 104 to less than 220 nm, that is, by setting it to be smaller than the thickness Tp of the P-side guide layer 106. Also, as shown in Fig. 11, the effective refractive index difference ΔN can be reduced more when the In composition ratio is continuously and monotonically decreased with increasing distance from the active layer 105, as in the P-side guide layer 106 according to this embodiment, than when the In composition ratio is constant at 2%.

[0070] 12, by setting the thickness Tn of the N-side guide layer 104 to less than 220 nm, that is, by setting it smaller than the thickness Tp of the P-side guide layer 106, the absolute value of the position P1 can be reduced. The thickness Tn of the N-side guide layer 104 may be 100 nm or more and 190 nm or less. In other words, the thickness of the N-side guide layer 104 may be 23% or more and 43% or less of the sum of the thicknesses of the N-side guide layer 104 and the P-side guide layer. This makes it possible to set the position P1 to -7 nm or more and 18 nm or less, that is, to position the peak of the light intensity distribution within the active layer 105. Furthermore, when the thickness of the N-side guide layer 104 is 23% or more and 43% or less of the sum of the thicknesses of the N-side guide layer 104 and the P-side guide layer and the distance dc is 40 nm, as shown in FIG. 11, the effective refractive index difference ΔN is 2×10 -3 Over 2.2 x 10 -3 It can be maintained within the following range:

[0071] 12, even when the In composition ratio of the P-side guide layer 106 is constant at 2%, the absolute value of the position P1 can be reduced by making the film thickness of the N-side guide layer 104 smaller than the film thickness of the P-side guide layer 106. However, when the film thickness of the N-side guide layer is 160 nm or more, the absolute value of the position P1 can be further reduced by continuously and monotonically decreasing the In composition ratio with increasing distance from the active layer 105, as in the P-side guide layer 106 according to the present embodiment.

[0072] 13, by setting the thickness Tn of the N-side guide layer 104 to less than 220 nm, that is, by setting it to be smaller than the thickness Tp of the P-side guide layer 106, the difference ΔP can be reduced. In particular, by setting the thickness of the N-side guide layer 104 to be 23% to 43% of the sum of the thicknesses of the N-side guide layer 104 and the P-side guide layer, the difference ΔP can be set to 20 nm or less. Also, as shown in FIG. 13, even when the In composition ratio of the P-side guide layer 106 is constant at 2%, the difference ΔP can be reduced by setting the thickness of the N-side guide layer to be smaller than the thickness of the P-side guide layer 106. However, when the thickness of the N-side guide layer is 160 nm or more, the difference ΔP can be further reduced by continuously and monotonically decreasing the In composition ratio with increasing distance from the active layer 105, as in the P-side guide layer 106 according to this embodiment.

[0073] [1-3-2. Each barrier layer] Next, the effect of the configuration of each barrier layer of the active layer 105 according to this embodiment will be described in comparison with a comparative example. In this embodiment, as described above, the bandgap energy of each barrier layer is equal to or less than the minimum value of the bandgap energy of the N-side guide layer 104 and the P-side guide layer 106. Here, as a comparative example, simulation results for a nitride-based semiconductor light-emitting device of Comparative Example 4, in which the composition of each barrier layer is undoped GaN, the bandgap energy of each barrier layer is equal to or greater than the minimum value of the bandgap energy of the N-side guide layer 104 and the P-side guide layer 106, and the other configuration is the same as that of the nitride-based semiconductor light-emitting device 100 according to this embodiment, are shown. The nitride-based semiconductor light-emitting device of Comparative Example 4 has an optical confinement coefficient of 1.39% and an effective refractive index difference ΔN of 2.3×10 -3 The peak positions P1 and P2 of the light intensity distribution are 0.35 nm and -21.9 nm, respectively, and the difference ΔP is 22.3 nm. The waveguide loss is 3.4 cm -1 The free carrier loss in the N-side and P-side guide layers is 1.84 cm -1As described above, in the nitride-based semiconductor light-emitting device of Comparative Example 4, the band gap energy of each barrier layer is large, that is, the refractive index of each barrier layer is small, so the optical confinement factor is smaller than that of nitride-based semiconductor light-emitting device 100 according to the present embodiment. Accordingly, the other evaluation indexes of the nitride-based semiconductor light-emitting device of Comparative Example 4 are also worse than those of nitride-based semiconductor light-emitting device 100 according to the present embodiment, except for position P1.

[0074] As described above, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, the optical confinement factor can be increased by setting the bandgap energy of each barrier layer to be equal to or less than the minimum value of the bandgap energy of the N-side guide layer 104 and the P-side guide layer 106. Accordingly, the difference ΔP can be reduced, and non-linear portions are less likely to occur in the graph showing the IL characteristics.

[0075] [1-3-3. P-type cladding layer] Next, the film thickness of the P-type cladding layer 110 according to this embodiment will be described with reference to FIGS. 14 to 18. FIG. 14 is a graph showing the simulation results of the relationship between the film thickness of the P-type cladding layer 110 according to this embodiment and the optical confinement factor (Γv). FIG. 15 is a graph showing the simulation results of the relationship between the film thickness of the P-type cladding layer 110 according to this embodiment and the waveguide loss. FIG. 16 is a graph showing the simulation results of the relationship between the film thickness of the P-type cladding layer 110 according to this embodiment and the effective refractive index difference ΔN. FIG. 17 is a graph showing the simulation results of the relationship between the film thickness of the P-type cladding layer 110 according to this embodiment and the position P1. FIG. 18 is a graph showing the simulation results of the relationship between the film thickness of the P-type cladding layer 110 according to this embodiment and the difference ΔP. In addition, FIGS. 14 to 18 also show the simulation results of two comparative examples in which the In composition ratios of the P-side guide layer are constant at 2% and 4%, respectively. 14 to 18 also show simulation results for a nitride-based semiconductor light-emitting device 400 according to a fourth embodiment, which will be described later.

[0076] 14, the nitride-based semiconductor light-emitting element 100 according to this embodiment can have a larger optical confinement coefficient than the nitride-based semiconductor light-emitting elements of the comparative examples. Furthermore, in this embodiment, due to the configurations of the guide layers and barrier layers described above, the optical confinement coefficient does not decrease even when the thickness of the P-type cladding layer 110 is reduced to 250 nm.

[0077] 15, the nitride-based semiconductor light-emitting element 100 according to this embodiment can reduce waveguide loss more than the nitride-based semiconductor light-emitting element of the comparative example. Furthermore, the nitride-based semiconductor light-emitting element 100 according to this embodiment can suppress a significant increase in waveguide loss even when the thickness of the P-type cladding layer 110 is reduced to approximately 300 nm.

[0078] As shown in FIG. 16, the nitride-based semiconductor light-emitting device 100 according to this embodiment can reduce the effective refractive index difference ΔN more than the nitride-based semiconductor light-emitting devices of the respective comparative examples.

[0079] As shown in FIGS. 17 and 18, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, the absolute value of the position P1 and the difference ΔP can be reduced more than in the nitride-based semiconductor light-emitting devices of the comparative examples.

[0080] As described above, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, it is possible to reduce the film thickness of the P-type cladding layer 110, and therefore the operating voltage can be reduced.

[0081] (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 the band gap energy distribution of the P-side guide layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below, focusing on the differences from the nitride-based semiconductor light-emitting device 100 according to embodiment 1.

[0082] [2-1. Overall composition] First, the overall configuration of the nitride-based semiconductor light-emitting device according to this embodiment will be described with reference to Figures 19 and 20. Figure 19 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 200 according to this embodiment. Figure 20 is a schematic graph showing the distribution of band gap energy in active layer 105 and each layer in the vicinity thereof of nitride-based semiconductor light-emitting device 200 according to this embodiment.

[0083] 19 , a nitride-based semiconductor light-emitting device 200 according to this embodiment includes a semiconductor laminate 200S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor laminate 200S includes a substrate 101, an N-type first cladding layer 102, an N-type second cladding layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 206, an intermediate layer 108, an electron barrier layer 109, a P-type cladding layer 110, and a contact layer 111.

[0084] In the P-side guide layer 206, similarly to the P-side guide layer 106 according to the first embodiment, the bandgap energy of the P-side guide layer 206 increases monotonically with increasing distance from the active layer 105. The P-side guide layer 206 also includes a portion in which the bandgap energy increases continuously with increasing distance from the active layer 105. In this embodiment, the P-side guide layer 206 is made of undoped In Xp Ga 1-Xp The average rate of change in the In composition ratio in the stacking direction in the region from the interface of the P-side guide layer 206 closer to the active layer 105 to the center of the P-side guide layer 206 in the stacking direction is greater than the average rate of change in the In composition ratio in the stacking direction in the region from the center to the interface of the P-side guide layer 206 closer to the P-type cladding layer 110. In other words, the curve showing the relationship between the position in the stacking direction of the P-side guide layer 206 and the In composition ratio has a downward convex shape. In further other words, the curve showing the relationship between the position in the stacking direction of the P-side guide layer 206 and the band gap energy has an upward convex shape (see FIG. 20).

[0085] In this embodiment, the P-side guide layer 206 includes a P-side first guide layer 206a and a P-side second guide layer 206b. The P-side first guide layer 206a is an undoped InP layer with a thickness of 140 nm. Xp Ga 1-Xp More specifically, the P-side first guide layer 206a is an In layer near the interface on the side closer to the active layer 105. Xp1 Ga 1-Xp1 N, and in the vicinity of the interface farther from the active layer 105 Xpm Ga 1-Xpm The P-side first guide layer 206a has a composition represented by the formula: In composition ratio Xp of the P-side first guide layer 206a decreases at a constant rate with increasing distance from the active layer 105. The P-side second guide layer 206b is an undoped In Xp Ga 1-Xp More specifically, the P-side second guide layer 206b is an In layer near the interface on the side closer to the active layer 105. Xpm Ga 1-Xpm N, and in the vicinity of the interface farther from the active layer 105 Xp2 Ga 1-Xp2 N. The In composition ratio Xp of the p-side second guide layer 206b decreases at a constant rate with increasing distance from the active layer 105. In this embodiment, Xp1=0.04, Xpm=0.02, and Xp2=0.

[0086] [2-2. Effects] [2-2-1. Free Carrier Losses] Next, the free carrier loss reduction effect of the nitride-based semiconductor light-emitting device 200 according to this embodiment will be described with reference to Fig. 21 and Fig. 22. Fig. 21 is a graph showing the simulation results of the distribution of valence electron charge potential and hole Fermi level in the stacking direction of the nitride-based semiconductor light-emitting device 200 according to this embodiment. Fig. 22 is a graph showing the simulation results of the distribution of carrier concentration in the stacking direction of the nitride-based semiconductor light-emitting device 200 according to this embodiment.

[0087] As shown in FIG. 21 , in the nitride-based semiconductor light-emitting device 200 according to this embodiment, the curve representing the valence charge potential in the P-side guide layer 206 can be made to have a downwardly convex shape. Here, the curve representing the hole Fermi level in the P-side guide layer 206 has a downwardly convex shape. Therefore, by making the curve representing the valence charge potential in the P-side guide layer 206 have a downwardly convex shape, the difference between the hole Fermi level and the valence charge potential in the P-side guide layer 206 can be made more uniform than in the P-side guide layer 106 according to the first embodiment. Therefore, as shown in FIG. 22 , the hole concentration in the P-side guide layer 206, particularly in the region close to the active layer 105, can be reduced. This further reduces the free carrier loss in the P-side guide layer 206. Specifically, in this embodiment, the guide layer free carrier loss is reduced to 1.7 cm -1 The waveguide loss can be reduced to 3.1cm -1 can be reduced to

[0088] In the nitride-based semiconductor light-emitting device 200 according to this embodiment, the effective refractive index difference ΔN is 1.9×10 -3 The peak positions P1 and P2 of the light intensity distribution are −3.8 nm and −15.8 nm, respectively, and the difference ΔP is 12 nm. In this way, in this embodiment, the position P1 and the difference ΔP can be reduced, so that non-linear portions are less likely to occur in the graph showing the IL characteristics.

[0089] [2-2-2.In composition ratio distribution] Next, the effect of the In composition ratio distribution in the p-side guiding layer 206 of the nitride-based semiconductor light-emitting device 200 according to this embodiment will be described with reference to FIGS. 23 and 24. FIGS. 23 and 24 are graphs showing simulation results of the relationship between the average In composition ratio in the p-side guiding layer 206 according to this embodiment and the waveguide loss and the optical confinement factor (Γv). FIGS. 23 and 24 show the waveguide loss and the optical confinement factor when the In composition ratio Xp1 near the interface of the p-side guiding layer 206 closer to the active layer 105 is set to 4% and the In composition ratio Xp2 near the interface farther from the active layer 105 is set to 0%, and the In composition ratio is continuously and monotonically decreased with increasing distance from the active layer 105. More specifically, FIGS. 23 and 24 show the waveguide loss and the optical confinement factor when the average In composition ratio in the p-side guiding layer 206 is changed by changing the In composition ratio Xpm at the center of the p-side guiding layer 206 in the stacking direction. 23 and 24, when the average In composition ratio is less than 2%, the curve showing the relationship between the position in the stacking direction of the p-side guide layer 206 and the In composition ratio has a downwardly convex shape. For example, the case where the average In composition ratio is 1.5% corresponds to the nitride-based semiconductor light-emitting device 200 according to this embodiment, and the case where the average In composition ratio is 2% corresponds to the nitride-based semiconductor light-emitting device 100 according to the first embodiment. 23 and 24 also show, by dashed lines, simulation results for the case where the In composition ratio in the p-side guide layer is uniform.

[0090] 23 and 24, the waveguide loss can be reduced and the optical confinement factor can be increased when the In composition ratio in the P-side guiding layer 206 continuously and monotonically decreases with increasing distance from the active layer 105, compared to when the In composition ratio is uniform in the P-side guiding layer 206. Furthermore, when the average In composition ratio is less than 2%, the waveguide loss can be further reduced and the optical confinement factor can be further increased.

[0091] [2-2-3. Relationship between film thickness of each guide layer] Next, the effect of the relationship between the film thicknesses of the N-side guide layer 104 and the P-side guide layer 206 according to this embodiment will be described with reference to FIGS. 25 to 29. FIG. 25 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the optical confinement factor (Γv). FIG. 26 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the waveguide loss. FIG. 27 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the effective refractive index difference ΔN. FIG. 28 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the position P1. FIG. 29 is a graph showing the simulation results of the relationship between the film thickness of the N-side guide layer 104 according to this embodiment and the difference ΔP. 25 to 29, the thicknesses of the N-side guide layer 104 and the P-side guide layer 206 are varied while the sum of the thicknesses of the N-side guide layer 104 and the P-side guide layer 206 is kept constant at 440 nm. The N-side guide layer 104 has an In composition ratio of 4%, and the P-side guide layer 106 has an In composition ratio of 4% near the interface closer to the active layer 105, 0% near the interface farther from the active layer 105, and 1% at the center of the P-side guide layer 206 in the stacking direction. Also shown in FIGS. 25 to 29 are dashed lines the simulation results of a comparative example in which the In composition ratio of the P-side guide layer is constant at 1.5%.

[0092] 25 , by setting the thickness Tn of the N-side guide layer 104 to less than 220 nm, that is, by setting it to be smaller than the thickness Tp of the P-side guide layer 206, the optical confinement factor can be increased. The thickness Tn of the N-side guide layer 104 may be 100 nm or more. This prevents the optical intensity distribution from shifting too far in the direction from the active layer 105 toward the P-side guide layer 206, which would otherwise be caused by the thickness Tn of the N-side guide layer 104 being too thin. Also, as shown in FIG. 25 , even when the In composition ratio of the P-side guide layer 206 is constant at 1.5%, the optical confinement factor can be increased by setting the thickness of the N-side guide layer 104 to be smaller than the thickness of the P-side guide layer. However, the optical confinement factor can be further increased by continuously and monotonically decreasing the In composition ratio with increasing distance from the active layer 105, as in the P-side guide layer 206 according to this embodiment.

[0093] 26, when the In composition ratio is continuously and monotonically decreased with increasing distance from the active layer 105, as in the P-side guide layer 206 according to this embodiment, the waveguide loss can be reduced more than when the In composition ratio is constant at 1.5%. Also, in this embodiment, even when the film thickness of the N-side guide layer 104 is changed, the waveguide loss can be reduced to 3.2 cm. -1 can be made almost constant below this value.

[0094] 27, the effective refractive index difference ΔN can be reduced by setting the thickness Tn of the N-side guide layer 104 to less than 220 nm, that is, by setting it to be smaller than the thickness Tp of the P-side guide layer 206. Also, as shown in Fig. 27, when the In composition ratio is continuously and monotonically decreased with increasing distance from the active layer 105, as in the P-side guide layer 206 according to this embodiment, the effective refractive index difference ΔN can be reduced more than when the In composition ratio is constant at 1.5%.

[0095] 28, by setting the thickness Tn of the N-side guide layer 104 to less than 220 nm, that is, by setting it smaller than the thickness Tp of the P-side guide layer 206, the absolute value of the position P1 can be reduced. The thickness Tn of the N-side guide layer 104 may be 100 nm or more and 165 nm or less. In other words, the thickness of the N-side guide layer 104 may be 23% or more and 38% or less of the sum of the thicknesses of the N-side guide layer 104 and the P-side guide layer. This makes it possible to set the position P1 to -7 nm or more and 18 nm or less, that is, to position the peak of the light intensity distribution within the active layer 105. Furthermore, when the thickness of the N-side guide layer 104 is 23% or more and 38% or less of the sum of the thicknesses of the N-side guide layer 104 and the P-side guide layer and the distance dc is 40 nm, as shown in FIG. 27, the effective refractive index difference ΔN is 1.85×10 -3 Over 2.0 x 10 -3 It can be maintained within the following range:

[0096] 28, even when the In composition ratio of the P-side guide layer 206 is constant at 1.5%, the absolute value of the position P1 can be reduced by making the film thickness of the N-side guide layer 104 smaller than the film thickness of the P-side guide layer 206. However, when the film thickness of the N-side guide layer is 160 nm or more, the absolute value of the position P1 can be further reduced by continuously and monotonically decreasing the In composition ratio with increasing distance from the active layer 105, as in the P-side guide layer 106 according to the present embodiment.

[0097] 29 , by setting the thickness Tn of the N-side guide layer 104 to less than 220 nm, that is, by setting it to be smaller than the thickness Tp of the P-side guide layer 206, the difference ΔP can be reduced. In particular, by setting the thickness of the N-side guide layer 104 to be 23% to 38% of the sum of the thicknesses of the N-side guide layer 104 and the P-side guide layer, the difference ΔP can be set to 13 nm or less. Also, as shown in FIG. 29 , even when the In composition ratio of the P-side guide layer 206 is constant at 1.5%, the difference ΔP can be reduced by setting the thickness of the N-side guide layer to be smaller than the thickness of the P-side guide layer 206. However, the difference ΔP can be further reduced by continuously and monotonically decreasing the In composition ratio with increasing distance from the active layer 105, as in the P-side guide layer 206 according to the present embodiment.

[0098] [2-2-4. Barrier layer] Next, the effect of the configuration of each barrier layer of the active layer 105 according to this embodiment will be described in comparison with a comparative example. In this embodiment, the bandgap energy of each barrier layer is equal to or less than the minimum value of the bandgap energy of the N-side guide layer 104 and the P-side guide layer 206. Here, as a comparative example, simulation results for a nitride-based semiconductor light-emitting device of Comparative Example 5 are shown, in which the composition of each barrier layer is undoped GaN, the bandgap energy of each barrier layer is equal to or greater than the minimum value of the bandgap energy of the N-side guide layer 104 and the P-side guide layer 206, and the other configuration is the same as that of the nitride-based semiconductor light-emitting device 100 according to this embodiment. The nitride-based semiconductor light-emitting device of Comparative Example 5 has an optical confinement coefficient of 1.37% and an effective refractive index difference ΔN of 2.7×10 -3 The peak positions P1 and P2 of the light intensity distribution are 28.1 nm and 9.2 nm, respectively, and the difference ΔP is 18.9 nm. The waveguide loss is 4 cm -1 The free carrier loss in the N-side and P-side guide layers is 2.5 cm -1As described above, in the nitride-based semiconductor light-emitting device of Comparative Example 5, the band gap energy of each barrier layer is large, that is, the refractive index of each barrier layer is small, so the optical confinement factor is smaller than that of nitride-based semiconductor light-emitting device 200 according to the present embodiment. Accordingly, the other evaluation indexes of the nitride-based semiconductor light-emitting device of Comparative Example 5 are also worse than those of nitride-based semiconductor light-emitting device 200 according to the present embodiment, except for position P2.

[0099] As described above, in the nitride-based semiconductor light-emitting device 200 according to this embodiment, the optical confinement factor can be increased by setting the bandgap energy of each barrier layer to be equal to or less than the minimum value of the bandgap energy of the N-side guide layer 104 and the P-side guide layer 206. Accordingly, the difference ΔP can be reduced, and non-linear portions are less likely to occur in the graph showing the IL characteristics.

[0100] (Embodiment 3) A nitride-based semiconductor light-emitting device according to embodiment 3 will now be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 100 according to embodiment 1 in the relationship between the Al composition ratios of the N-type first cladding layer and the P-type cladding layer, and in the configuration of the electron barrier layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 30, focusing on the differences from nitride-based semiconductor light-emitting device 100 according to embodiment 1.

[0101] FIG. 30 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 300 according to this embodiment.

[0102] 30 , a nitride-based semiconductor light-emitting device 300 according to this embodiment includes a semiconductor stack 300S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor stack 300S includes a substrate 101, an N-type first cladding layer 302, an N-type second cladding layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 106, an intermediate layer 108, an electron barrier layer 309, a P-type cladding layer 110, and a contact layer 111.

[0103] The N-type first cladding layer 302 according to this embodiment is made of N-type Al 0.036 Ga 0.964 The N-type first cladding layer 302 contains impurities at a concentration of 1×10 18 cm -3 It is doped with Si.

[0104] As described above, the P-type cladding layer 110 according to this embodiment is a P-type Al layer having a thickness of 450 nm. 0.026 Ga 0.974 This is the N layer.

[0105] In this embodiment, the N-type first cladding layer 302 and the P-type cladding layer 110 contain Al. If the Al composition ratios of the N-type first cladding layer 302 and the P-type cladding layer 110 are Ync and Ypc, respectively, then: Ync>Ypc (4) Satisfy the relationship.

[0106] Here, when at least one of the N-type first cladding layer 302 and the P-type cladding layer 110 has a superlattice structure, the composition ratios Ync and Ypc indicate average Al composition ratios. For example, when the N-type first cladding layer 302 includes multiple 2-nm-thick GaN layers and multiple 2-nm-thick AlGaN layers with an Al composition ratio of 0.07, and the multiple GaN layers and multiple AlGaN layers are alternately stacked, Ync is 0.035, which is the average Al composition ratio of the entire N-type first cladding layer 302. When the P-type cladding layer 110 includes multiple 2-nm-thick GaN layers and multiple 2-nm-thick AlGaN layers with an Al composition ratio of 0.07, and the multiple GaN layers and multiple AlGaN layers are alternately stacked, Ypc is 0.035, which is the average Al composition ratio of the entire P-type cladding layer 110.

[0107] This allows the refractive index of the N-type first cladding layer 302 to be lower than the refractive index of the P-type cladding layer 110. Therefore, even if the film thickness of the P-type cladding layer 110 is reduced to reduce the operating voltage of the nitride-based semiconductor light-emitting device 300, the refractive index of the N-type first cladding layer 302 is lower than the refractive index of the P-type cladding layer 110, and therefore it is possible to prevent the peak of the light intensity distribution in the stacking direction from shifting in a direction approaching from the active layer 105 toward the N-type first cladding layer 302.

[0108] The electron barrier layer 309 is disposed above the active layer 105 and is a nitride-based semiconductor layer containing at least Al. In this embodiment, the electron barrier layer 309 is disposed between the intermediate layer 108 and the P-type cladding layer 110. The electron barrier layer 309 is a P-type AlGaN layer with a thickness of 5 nm. The electron barrier layer 309 also has an Al composition ratio increasing region in which the Al composition ratio monotonically increases toward the P-type cladding layer 110. Here, the configuration in which the Al composition ratio monotonically increases also includes a configuration including a region in which the Al composition ratio is constant in the stacking direction. For example, the configuration in which the Al composition ratio monotonically increases also includes a configuration in which the Al composition ratio increases stepwise. In the electron barrier layer 309 according to this embodiment, the entire electron barrier layer 309 is an Al composition ratio increasing region, and the Al composition ratio increases at a constant rate in the stacking direction. Specifically, the electron barrier layer 309 has an Al composition ratio increasing region near the interface with the intermediate layer 108. 0.02 Ga 0.98 The Al composition ratio monotonically increases as the layer approaches the P-type cladding layer 110, and the Al composition ratio is 0.36 Ga 0.64 The electron barrier layer 309 has a composition represented by the formula: N. The electron barrier layer 309 contains impurities at a concentration of 1×10 19 cm -3 It is doped with Mg.

[0109] The electron barrier layer 309 can prevent electrons from leaking from the active layer 105 to the P-type cladding layer 110. Furthermore, since the electron barrier layer 309 has an Al composition ratio increasing region where the Al composition ratio monotonically increases, the potential barrier of the valence band of the electron barrier layer 309 can be reduced compared to when the Al composition ratio is uniform. This facilitates the flow of holes from the P-type cladding layer 110 to the active layer 105. Therefore, even when the P-side guide layer 106, which is an undoped layer, is thick, as in this embodiment, an increase in the electrical resistance of the nitride-based semiconductor light-emitting element 300 can be suppressed. This allows the operating voltage of the nitride-based semiconductor light-emitting element 300 to be reduced. Furthermore, self-heating during operation of the nitride-based semiconductor light-emitting element 300 can be reduced, thereby improving the temperature characteristics of the nitride-based semiconductor light-emitting element 300. Therefore, the nitride-based semiconductor light-emitting element 300 can operate at a high output power.

[0110] According to this embodiment, the effective refractive index difference ΔN is 1.9×10 -3 The position P1 is 5.3 nm, the difference ΔP is 4.2 nm, the optical confinement coefficient in the active layer 105 is 1.55%, and the waveguide loss is 3.6 cm -1 and the free carrier loss in the guiding layer is 2.4 cm -1 It is possible to realize a nitride-based semiconductor light-emitting device 300 having the above structure.

[0111] (Fourth embodiment) A nitride-based semiconductor light-emitting device according to embodiment 4 will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 300 according to embodiment 3 mainly in that a translucent conductive film is provided on the contact layer in the ridge. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 31 , focusing on the differences from nitride-based semiconductor light-emitting device 300 according to embodiment 3.

[0112] 31 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 400 according to this embodiment. As shown in Fig. 31, the nitride-based semiconductor light-emitting device 400 according to this embodiment includes a semiconductor stack 400S, a current blocking layer 112, a P-side electrode 113, an N-side electrode 114, and a light-transmitting conductive film 420. The semiconductor stack 400S includes a substrate 101, an N-type first cladding layer 302, an N-type second cladding layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 106, an intermediate layer 108, an electron barrier layer 309, a P-type cladding layer 410, and a contact layer 411.

[0113] The P-type cladding layer 410 according to this embodiment is disposed between the electron barrier layer 309 and the contact layer 411. The P-type cladding layer 410 has a lower refractive index than the active layer 105 and a higher band gap energy. In this embodiment, the P-type cladding layer 410 is a P-type Al 330 nm thick layer. 0.026 Ga 0.974 The P-type cladding layer 410 is an N layer. The P-type cladding layer 410 is doped with Mg as an impurity. The impurity concentration at the end of the P-type cladding layer 410 closer to the active layer 105 is lower than the impurity concentration at the end farther from the active layer 105. Specifically, the P-type cladding layer 410 has an impurity concentration of 2×10 18 cm -3 Mg-doped p-type Al with a thickness of 150 nm 0.026 Ga 0.974 N layer and a layer with a concentration of 1×10 19 cm -3 P-type Al doped with Mg and 180 nm thick 0.026 Ga 0.974 It has N layers.

[0114] A ridge 410R is formed in the P-type cladding layer 410, similar to the nitride-based semiconductor light-emitting device 300 according to embodiment 3. Two grooves 410T are formed in the P-type cladding layer 410, arranged along the ridge 410R and extending in the Y-axis direction.

[0115] The contact layer 411 is disposed above the P-type cladding layer 410 and is in ohmic contact with the P-side electrode 113. In this embodiment, the contact layer 411 is a P-type GaN layer with a film thickness of 10 nm. The contact layer 411 contains impurities with a concentration of 1×10 20 cm -3 It is doped with Mg.

[0116] The translucent conductive film 420 according to this embodiment is disposed above the P-type cladding layer 410, and is a conductive film that transmits at least a portion of the light generated in the nitride-based semiconductor light-emitting element 400. As the translucent conductive film 420, an oxide film that is transmissive to visible light and exhibits low-resistance electrical conductivity, such as tin-doped indium oxide (ITO), Ga-doped zinc oxide, Al-doped zinc oxide, or In- and Ga-doped zinc oxide, can be used.

[0117] The transparent conductive film 420 only needs to be formed above at least the P-type cladding layer 410 , and may be formed between the current blocking layer 112 and the P-side electrode 113 .

[0118] The nitride-based semiconductor light-emitting device 400 according to this embodiment also achieves the same effects as the nitride-based semiconductor light-emitting device 100 according to the first embodiment, as shown in FIGS.

[0119] Furthermore, in this embodiment, since the light-transmitting conductive film 420 disposed above the P-type cladding layer 410 is provided, the loss of light propagating above the P-type cladding layer 410 can be reduced. As shown in FIG. 15, this effect is particularly remarkable when the thickness of the P-type cladding layer 410 is thin. Even when the thickness of the P-type cladding layer 410 is thinned to 0.32 μm, a significant increase in waveguide loss can be suppressed. Furthermore, even when the thickness of the P-type cladding layer 410 is thinned to 0.25 μm, the increase in waveguide loss is suppressed to 0.8 cm compared to when the thickness of the P-type cladding layer 410 is 0.6 μm. -1It can be seen that this increase can be suppressed to less than half of the increase in the nitride-based semiconductor light-emitting element 100 according to the first embodiment, which does not use the translucent conductive film 420. Furthermore, since it is possible to further reduce the film thickness of the P-type cladding layer 410, the electrical resistance of the nitride-based semiconductor light-emitting element 400 can be further reduced. As a result, the slope efficiency of the nitride-based semiconductor light-emitting element 400 can be increased, and the operating voltage can be reduced.

[0120] According to this embodiment, the effective refractive index difference ΔN is 2.0×10 -3 The position P1 is 1.4 nm, the difference ΔP is 4.0 nm, the optical confinement coefficient in the active layer 105 is 1.51%, and the waveguide loss is 3.8 cm -1 and the free carrier loss in the guiding layer is 1.9 cm -1 It is possible to realize a nitride-based semiconductor light-emitting device 400 having the above structure.

[0121] (Embodiment 5) A nitride-based semiconductor light-emitting device according to embodiment 5 will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 300 according to embodiment 3 in the configuration of the active layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIGS. 32A and 32B, focusing on the differences from nitride-based semiconductor light-emitting device 300 according to embodiment 3.

[0122] Fig. 32A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 500 according to this embodiment. Fig. 32B is a cross-sectional view showing the configuration of an active layer 505 included in the nitride-based semiconductor light-emitting device 500 according to this embodiment.

[0123] 32A , a nitride-based semiconductor light-emitting device 500 according to this embodiment includes a semiconductor stack 500S, a current blocking layer 112, a P-side electrode 113, an N-side electrode 114, and a light-transmitting conductive film 420. The semiconductor stack 500S includes a substrate 101, an N-type first cladding layer 302, an N-type second cladding layer 103, an N-side guide layer 104, an active layer 505, a P-side guide layer 106, an intermediate layer 108, an electron barrier layer 309, a P-type cladding layer 110, and a contact layer 111.

[0124] 32B, active layer 505 according to the present embodiment has a single quantum well structure, including a single well layer 105b and barrier layers 105a and 105c sandwiching well layer 105b. Well layer 105b has a similar structure to well layer 105b according to the first embodiment, and barrier layers 105a and 105c have a similar structure to barrier layers 105a and 105c according to the first embodiment.

[0125] The nitride-based semiconductor light-emitting device 500 according to this embodiment has the same effects as the nitride-based semiconductor light-emitting device 300 according to the third embodiment. In particular, in the nitride-based semiconductor light-emitting device 500 having the above-described single quantum well structure, the active layer 505 has a single well layer 105b. Thus, even in the nitride-based semiconductor light-emitting device 500 having a small number of well layers 105b with a high refractive index, the peak of the light intensity distribution in the stacking direction can be positioned in or near the active layer 505 by the configuration of the N-side guide layer 104, the P-side guide layer 106, etc. Therefore, the optical confinement factor can be increased.

[0126] According to this embodiment, the effective refractive index difference ΔN is 2.1×10 -3 The position P1 is 1.1 nm, the difference ΔP is 6.0 nm, the optical confinement coefficient in the active layer 505 is 0.75%, and the waveguide loss is 3.8 cm -1 and the free carrier loss in the guiding layer is 2.4 cm -1It is possible to realize a nitride-based semiconductor light-emitting device 500 having the above structure. In this embodiment, the total film thickness of the active layer 505 is 8 nm smaller than that of the active layer 105 according to the third embodiment, and therefore the optical confinement factor is smaller than that of the third embodiment.

[0127] (Embodiment 6) A nitride-based semiconductor light-emitting device according to embodiment 6 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 mainly in the configuration of the N-side guide layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below, focusing on the differences from the nitride-based semiconductor light-emitting device 100 according to embodiment 1.

[0128] [6-1. Overall composition] First, the overall configuration of the nitride-based semiconductor light-emitting device according to this embodiment will be described with reference to Figures 33 and 34. Figure 33 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 600 according to this embodiment. Figure 34 is a schematic graph showing the distribution of band gap energy in active layer 105 and each layer in the vicinity thereof of nitride-based semiconductor light-emitting device 600 according to this embodiment.

[0129] 33 , a nitride-based semiconductor light-emitting device 600 according to this embodiment includes a semiconductor stack 600S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor stack 600S includes a substrate 101, an N-type first cladding layer 602, an N-type second cladding layer 103, an N-side guide layer 604, an active layer 105, a P-side guide layer 106, an intermediate layer 108, an electron barrier layer 109, a P-type cladding layer 610, and a contact layer 111.

[0130] The N-type first cladding layer 602 according to this embodiment is made of N-type Al 0.035 Ga 0.965 The N-type first cladding layer 602 contains impurities at a concentration of 1×10 18 cm -3 It is doped with Si.

[0131] The P-type cladding layer 610 according to this embodiment is disposed between the electron barrier layer 109 and the contact layer 111. The P-type cladding layer 610 has a lower refractive index than the active layer 105 and a higher band gap energy. In this embodiment, the P-type cladding layer 610 is a P-type Al 104 with a thickness of 450 nm. 0.035 Ga 0.965 The P-type cladding layer 610 is an N layer. The P-type cladding layer 610 is doped with Mg as an impurity. The impurity concentration at the end of the P-type cladding layer 610 closer to the active layer 105 is lower than the impurity concentration at the end farther from the active layer 105. Specifically, the P-type cladding layer 610 has an impurity concentration of 2×10 18 cm -3 Mg-doped p-type Al with a thickness of 150 nm 0.035 Ga 0.965 N layer and a layer with a concentration of 1×10 19 cm -3 Mg-doped P-type Al with a thickness of 300 nm 0.035 Ga 0.965 It has N layers.

[0132] A ridge 610R is formed in the P-type cladding layer 610, similar to the nitride-based semiconductor light-emitting element 100 according to embodiment 1. Two grooves 610T are formed in the P-type cladding layer 610, arranged along the ridge 610R and extending in the Y-axis direction.

[0133] The N-side guide layer 604 according to this embodiment is an optical guide layer disposed above the N-type second cladding layer 103. The N-side guide layer 604 has a higher refractive index and a smaller bandgap energy than the N-type first cladding layer 602 and the N-type second cladding layer 103. As shown in Fig. 34, the bandgap energy of the N-side guide layer 604 increases continuously and monotonically with increasing distance from the active layer 105.

[0134] The N-side guide layer 604 is In Xn Ga 1-XnWhen the N-side guide layer 604 is made of N, the In composition ratio Xn of the N-side guide layer 604 continuously and monotonically decreases with increasing distance from the active layer 105. As a result, the band gap energy of the N-side guide layer 604 continuously and monotonically increases with increasing distance from the active layer 105.

[0135] The N-side guide layer 604 is an N-type In layer having a thickness of 160 nm. Xn Ga 1-Xn More specifically, the N-side guide layer 604 is an In layer near the interface on the side closer to the active layer 105. Xn1 Ga 1-Xn1 N, and in the vicinity of the interface farther from the active layer 105 Xn2 Ga 1-Xn2 N. In this embodiment, the In composition ratio Xn1 near the interface of the N-side guide layer 604 closer to the active layer 105 is 4%, and the In composition ratio Xn2 near the interface farther from the active layer 105 is 0%. The In composition ratio Xn of the N-side guide layer 604 decreases at a constant rate with increasing distance from the active layer 105.

[0136] [6-2.Effects] [6-2-1.In composition ratio distribution] Next, the effect of the In composition ratio distribution in the N-side guide layer 604 of the nitride-based semiconductor light-emitting device 600 according to this embodiment will be described with reference to Fig. 35 and Fig. 36. Fig. 35 and Fig. 36 are graphs showing simulation results of the relationship between the average In composition ratio in the N-side guide layer 604 according to this embodiment and the optical confinement factor (Γv) and the operating voltage, respectively.

[0137] 35 and 36 show the optical confinement factor and operating voltage when the In composition ratio Xn1 near the interface of the N-side guide layer 604 closer to the active layer 105 is 4%, and the In composition ratio Xn2 near the interface farther from the active layer 105 is 0%, 1%, 2%, 3%, and 4%, and the In composition ratio is decreased at a constant rate with increasing distance from the active layer 105. Each figure shows the operating voltage when a supply current of 3 A is used as the operating voltage. Also, in FIGS. 35 and 36, the dashed lines also show the simulation results when the In composition ratio in the N-side guide layer is uniform.

[0138] 35 and 36, when the In composition ratio in the N-side guide layer 604 continuously and monotonically decreases with increasing distance from the active layer 105, the high refractive index region of the N-side guide layer 604 can be brought closer to the active layer 105 than when the In composition ratio in the N-side guide layer is uniform, which makes it possible to increase the optical confinement factor and reduce the operating voltage. Furthermore, when the average In composition ratio is less than 2%, it is possible to further reduce the waveguide loss and increase the optical confinement factor.

[0139] Next, the operating voltage reduction effect of the nitride-based semiconductor light-emitting device 600 according to this embodiment will be described with reference to FIGS. 37 and 38 , in comparison with the nitride-based semiconductor light-emitting device 100 according to the first embodiment. FIG. 37 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light-emitting device 100 according to the first embodiment and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction field potential. FIG. 38 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light-emitting device 600 according to this embodiment and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction field potential. Graphs (a), (b), and (c) in FIGS. 37 and 38 respectively show the relationship between the position in the stacking direction of each nitride-based semiconductor light-emitting device and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction field potential. Note that graph (c) in FIGS. 37 and 38 also shows the hole Fermi level with a dashed line.

[0140] 37(a), the piezoelectric polarization charge density of the N-side guide layer 104 of the nitride-based semiconductor light-emitting element 100 according to the first embodiment is constant in the stacking direction. Therefore, there is a large gap in the piezoelectric polarization charge density at each interface between the N-side guide layer 104 and the N-type second cladding layer 103 and the active layer 105. Accordingly, piezoelectric polarization charges are locally formed at each interface between the N-side guide layer 104 and the N-type second cladding layer 103 and the active layer 105. This generates a large piezoelectric polarization electric field. Therefore, as shown in graph (b) of FIG. 37(b), a spike-shaped piezoelectric polarization electric field is generated at each interface between the N-side guide layer 104 and the N-type second cladding layer 103 and the active layer 105. As a result, holes are attracted to the vicinity of each interface between the N-side guide layer 104 and the N-type second cladding layer 103 and the active layer 105, and the conduction field potential at the interface increases (see ΔE1 shown in graph (c) of Figure 37).

[0141] 38(a), the polarization charge density of the N-side guide layer 604 of the nitride-based semiconductor light-emitting device 600 according to this embodiment monotonically decreases from the interface closer to the active layer 105 to the interface farther from it. This reduces the gap in the piezoelectric polarization charge density at each interface between the N-side guide layer 604 and the N-type second cladding layer 103 and the active layer 105. This allows the piezoelectric polarization charges to be dispersed in the stacking direction of the N-side guide layer 604. This reduces the piezoelectric polarization electric field at each interface between the N-side guide layer 604 and the N-type second cladding layer 103 and the active layer 105, as shown in graph (b) of FIG. 38, it is possible to suppress an increase in the conduction band potential (ΔE1 shown in graph (c) of FIG. 38) due to the attraction of holes in the vicinity of each interface between the N-side guide layer 604 and the N-type second cladding layer 103 and the active layer 105. As a result, in the nitride-based semiconductor light-emitting device 600 according to this embodiment, it is possible to improve the conductivity of electrons flowing from the N-type second cladding layer 103 toward the active layer 105, thereby reducing the operating voltage.

[0142] [6-2-2. Impurities in the N-side guide layer] Next, the effect of the impurity in the N-side guide layer 604 according to this embodiment will be described with reference to Figs. 39 to 41. Figs. 39, 40, and 41 are graphs showing simulation results of the relationship between the average In composition ratio in the N-side guide layer 604 of the nitride-based semiconductor light-emitting device 600 according to this embodiment and the optical confinement factor (Γv), waveguide loss, and operating voltage. Graphs (a), (b), (c), and (d) in Figs. 39 to 41 show the results of simulations of the relationship between the average In composition ratio in the N-side guide layer 604 of the nitride-based semiconductor light-emitting device 600 according to this embodiment and the optical confinement factor (Γv), waveguide loss, and operating voltage, respectively. 17 cm -3 , 6×10 17 cm -3 , 1×10 18 cm -3 41 shows the simulation results when the amount of supplied current is 3 A. In addition, in FIG.

[0143] 39 to 41 show the optical confinement factor and operating voltage when the In composition ratio Xn1 near the interface of the N-side guide layer 604 closer to the active layer 105 is 4%, and the In composition ratio Xn2 near the interface farther from the active layer 105 is 0%, 1%, 2%, 3%, and 4%, and the In composition ratio is decreased at a constant rate of change with increasing distance from the active layer 105. 39 to 41 also show, by dashed lines, the simulation results when the In composition ratio in the N-side guide layer is uniform.

[0144] 39, the nitride-based semiconductor light-emitting device 600 according to this embodiment has a higher optical confinement factor than the nitride-based semiconductor light-emitting device of the comparative example in which the In composition ratio of the N-side guide layer is uniform. Furthermore, it can be seen from FIG. 39 that the optical confinement factor of the nitride-based semiconductor light-emitting device 600 according to this embodiment is almost independent of the impurity concentration.

[0145] 40, in the nitride-based semiconductor light-emitting device 600 according to this embodiment, except for the case where no impurities are added, the waveguide loss can be reduced compared to the nitride-based semiconductor light-emitting device of the comparative example in which the In composition ratio of the N-side guide layer is uniform. This is thought to be because the electron concentration increases by adding impurities, but the hole concentration decreases due to the energy band gap distribution in the stacking direction of the N-side guide layer 604.

[0146] 41, the nitride-based semiconductor light-emitting device 600 according to this embodiment can reduce the operating voltage compared to the nitride-based semiconductor light-emitting device of the comparative example in which the N-side guide layer has a uniform In composition ratio. Furthermore, by increasing the concentration of impurities added to the nitride-based semiconductor light-emitting device 600, the electron concentration in the N-side guide layer 604 can be increased, thereby further reducing the operating voltage.

[0147] 40 and 41, in the nitride-based semiconductor light-emitting device 600 according to this embodiment, the impurity concentration in the N-side guide layer 604 is set to 1×10 17 cm -3 6×10 or more 17 cm -3 By setting the above, it is possible to reduce the operating voltage while suppressing a significant increase in waveguide loss.

[0148] As described above, according to this embodiment, the effective refractive index difference ΔN is 2.9×10 -3 The position P1 is 15.9 nm, the difference ΔP is 6.2 nm, the optical confinement coefficient in the active layer 105 is 1.44%, and the waveguide loss is 3.4 cm -1 and the free carrier loss in the guiding layer is 1.45 cm -1 It is possible to realize a nitride-based semiconductor light-emitting device 600 having the above structure.

[0149] (Embodiment 7) A nitride-based semiconductor light-emitting device according to embodiment 7 will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 100 according to embodiment 1 mainly in the configuration of the P-type cladding layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 42, focusing on the differences from nitride-based semiconductor light-emitting device 100 according to embodiment 1.

[0150] 42 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 700 according to this embodiment. As shown in Fig. 42, the nitride-based semiconductor light-emitting device 700 according to this embodiment includes a semiconductor laminate 700S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor laminate 700S includes a substrate 101, an N-type first cladding layer 102, an N-type second cladding layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 106, an intermediate layer 108, an electron barrier layer 709, a P-type cladding layer 710, and a contact layer 111.

[0151] The electron barrier layer 709 according to this embodiment is a P-type Al layer having a thickness of 1.6 nm. 0.36 Ga 0.64 The electron barrier layer 709 contains an impurity of 1.5×10 19 cm -3 It is doped with Mg.

[0152] The P-type cladding layer 710 according to this embodiment is disposed between the electron barrier layer 709 and the contact layer 111. The P-type cladding layer 710 has a lower refractive index than the active layer 105 and a higher band gap energy. A ridge 710R is formed in the P-type cladding layer 710, similar to the P-type cladding layer 110 according to the first embodiment. Furthermore, two grooves 710T are formed in the P-type cladding layer 710, arranged along the ridge 710R and extending in the Y-axis direction.

[0153] The P-type cladding layer 710 is a P-type Al 0.026 Ga 0.974The P-type cladding layer 710 is an N layer. The P-type cladding layer 710 is doped with Mg as an impurity. In this embodiment, the impurity concentration at the end of the P-type cladding layer 710 closer to the active layer 105 is lower than the impurity concentration at the end farther from the active layer 105. The P-type cladding layer 710 has a region in which the impurity concentration monotonically increases with increasing distance from the active layer 105. Here, the configuration in which the impurity concentration monotonically increases also includes a configuration in which there is a region in which the impurity concentration is constant in the stacking direction. Specifically, the P-type cladding layer 710 has a region in which the impurity concentration is 2×10 18 cm -3 Mg-doped p-type Al with a thickness of 150 nm 0.026 Ga 0.974 N layer and a concentration of 1×10 19 cm -3 P-type Al doped with Mg and 180 nm thick 0.026 Ga 0.974 N layer and a concentration of 1.3 × 10 19 cm -3 P-type Al doped with Mg and 120 nm thick 0.026 Ga 0.974 In this manner, in the present embodiment, the P-type cladding layer 710 has a first layer closest to the active layer 105, a second layer having a higher impurity concentration than the first layer, and a third layer having a higher impurity concentration than the second layer.

[0154] In this embodiment, the thickness of the P-side guide layer 106 is greater than the thickness of the N-side guide layer 104. In this case, the peak of the light intensity distribution in the stacking direction is located in the region near the active layer 105, thereby suppressing the spread of light into the P-type cladding layer 710. Therefore, the light intensity in the P-type cladding layer 710 is weak. Therefore, even if the Mg concentration in the region of the P-type cladding layer 710 close to the contact layer 111 is increased, an increase in waveguide loss can be suppressed. Furthermore, by increasing the Mg concentration, it is possible to reduce the series resistance of the nitride-based semiconductor light-emitting device 700 (i.e., the resistance between the P-side electrode 113 and the N-side electrode 114).

[0155] For example, when the thickness of the P-side guide layer 106 is 200 nm or more, the Mg concentration is set to 1.3×10 in the region within 0.15 μm from the interface between the P-type cladding layer 710 and the contact layer 111. 19 cm -3 Even if the Mg concentration is increased above this level, the optical intensity is sufficiently low to prevent an increase in waveguide loss. Increasing the Mg concentration in the P-type cladding layer 710 in this way makes it possible to reduce the series resistance of the nitride-based semiconductor light-emitting device 700. The Mg concentration in the P-type cladding layer 710 is 1.6×10 19 cm -3 This can suppress a decrease in carrier mobility caused by an excessively high Mg concentration, thereby suppressing an increase in series resistance.

[0156] When the thickness of the P-side guide layer 106 is 250 nm or more, the light intensity in the P-type cladding layer 710 becomes even weaker, so even if the thickness of the low-concentration region in the P-type cladding layer 710 where the Mg concentration is lowest is set to 20 nm or less, an increase in waveguide loss can be suppressed.

[0157] Furthermore, in the P-type cladding layer 710, the Mg concentration does not need to be changed stepwise in the stacking direction, but may be changed continuously. For example, the Mg concentration in the P-type cladding layer 710 may have the following structure: At the interface of the P-type cladding layer 710 closer to the active layer 105, the Mg concentration is 1.5×10 5 in the electron barrier layer 709. 19 cm -3 In the region of the P-type cladding layer 710 within 100 nm from the interface, the Mg concentration is approximately equal to 1×10 18 cm -3 From 3 x 10 18 cm -3The Mg concentration may monotonically decrease with increasing distance from the interface so as to reach the range below. In this way, the P-type cladding layer 710 may have a concentration decreasing region in the region closest to the active layer 105, in which the impurity concentration monotonically decreases with increasing distance from the active layer 105. Furthermore, the P-type cladding layer 710 may have a low concentration region disposed above the concentration decreasing region, in which the change in Mg concentration in the stacking direction is small and in which the Mg concentration is the lowest in the P-type cladding layer 710. In the low concentration region, the Mg concentration is, for example, 1×10 18 cm -3 3x10 or more 18 cm -3 Furthermore, the P-type cladding layer 710 may have a concentration increasing region disposed above the low concentration region, in which the Mg concentration monotonically increases with increasing distance from the active layer 105. In the concentration increasing region, the Mg concentration is, for example, 1×10 18 cm -3 3x10 or more 18 cm -3 From the following range, 1.3 x 10 19 cm -3 increases monotonically until

[0158] The concentration increasing region may have a high increasing rate region located closer to the active layer 105 and a low increasing rate region located above the high increasing rate region. The rate of change in the Mg concentration in the stacking direction in the high increasing rate region is greater than the rate of change in the Mg concentration in the low increasing rate region in the stacking direction.

[0159] According to this embodiment, the effective refractive index difference ΔN is 1.9×10 -3 The position P1 is 3.6 nm, the difference ΔP is 2.8 nm, the optical confinement coefficient in the active layer 105 is 1.54%, and the waveguide loss is 3.6 cm -1 and the free carrier loss in the guiding layer is 2.4 cm -1 A nitride-based semiconductor light-emitting device 700 having the above structure can be realized.

[0160] (Embodiment 8) A nitride-based semiconductor light-emitting device according to embodiment 8 will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 700 according to embodiment 7 in the configuration of the electron barrier layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIGS. 43 and 44, focusing on the differences from nitride-based semiconductor light-emitting device 700 according to embodiment 7.

[0161] Fig. 43 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 800 according to this embodiment. Fig. 44 is a graph showing the distribution of the Al composition ratio in the stacking direction of an electron barrier layer 809 according to this embodiment. The horizontal axis of the graph shown in Fig. 44 represents the position x in the stacking direction, and the vertical axis represents the Al composition ratio. Fig. 44 also shows the distribution of the Al composition ratio in the intermediate layer 108 and a part of the P-type cladding layer 710, along with the electron barrier layer 709.

[0162] 43 , a nitride-based semiconductor light-emitting device 800 according to this embodiment includes a semiconductor laminate 800S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor laminate 800S includes a substrate 101, an N-type first cladding layer 102, an N-type second cladding layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 106, an intermediate layer 108, an electron barrier layer 809, a P-type cladding layer 710, and a contact layer 111.

[0163] The electron barrier layer 809 according to this embodiment is a P-type AlGaN layer. The electron barrier layer 809 contains impurities at a concentration of 1.5×10 19 cm -3The electron barrier layer 809 is doped with Mg. The electron barrier layer 809 has an Al composition ratio increasing region in which the Al composition ratio monotonically increases toward the P-type cladding layer 110, and an Al composition ratio decreasing region located above the Al composition ratio increasing region in which the Al composition ratio monotonically decreases toward the P-type cladding layer 710. Here, the configuration in which the Al composition ratio monotonically decreases includes a configuration including a region in which the Al composition ratio is constant in the stacking direction. For example, the configuration in which the Al composition ratio monotonically decreases includes a configuration in which the Al composition ratio decreases stepwise. In the graph shown in FIG. 44, position x=Xs indicates the interface of the electron barrier layer 809 with the intermediate layer 108, and position x=Xe indicates the interface of the electron barrier layer 809 with the P-type cladding layer 710. Note that position x=Xs may be defined as the end of the region in which the Al composition ratio increases toward the P-type cladding layer 710. The position x=Xe may be defined as the end of a region where the Al composition ratio decreases toward the P-type cladding layer 710, in other words, the end of a region where the Al composition ratio is constant in the stacking direction. The position x=Xm is the position where the Al composition ratio is maximum in the electron barrier layer 809. The region from position x=Xs to position x=Xm is the Al composition ratio increasing region, and the region from position x=Xm to position x=Xe is the Al composition ratio decreasing region.

[0164] The thickness of the electron barrier layer 809 is 5 nm or less. The thickness of the Al composition ratio increasing region is 2 nm or less. The thickness of the Al composition ratio decreasing region is greater than the thickness of the Al composition ratio increasing region. The thickness of the region in the electron barrier layer 809 where the Al composition ratio is maximum is 0.5 nm or less. Here, the region where the Al composition ratio is maximum means a region where the Al composition ratio is 95% or more of the maximum value of the Al composition ratio in the electron barrier layer 809.

[0165] In the graph shown in FIG. 44, a straight line g(x) and a straight line h(x) are shown together with a curve f(x) indicating the distribution of the Al composition ratio with respect to the position in the stacking direction of the electron barrier layer 809. The straight line g(x) is a straight line passing through the point at the position x = Xs of the curve f(x) and the point at the position x = Xm. The straight line h(x) is a straight line passing through the point at the position x = Xm of the curve f(x) and the point at the position x = Xe. As shown in FIG. 44, the curve f(x) is a downwardly convex curve in the range from the position x = Xs to the position x = Xm. Also, the curve f(x) is a downwardly convex curve in the range from the position x = Xm to the position x = Xe. In other words, at the position x = Xd1 corresponding to the midpoint between the position x = Xs and the position x = Xm, f(Xd1) < g(Xd1). Also, at the position x = Xd2 corresponding to the midpoint between the position x = Xm and the position x = Xe, f(Xd2) < h(Xd2).

[0166] As described above, by inclining the Al composition ratio on the side closer to the active layer 105 of the electron barrier layer 809, the positive piezopolarization charges formed at the interface with the intermediate layer 108 of the electron barrier layer 809 can be dispersed in the Al composition ratio increasing region. Along with this, at the interface between the electron barrier layer 809 and the intermediate layer 108, the electron concentration attracted by the positive piezopolarization charges is reduced. As a result, a decrease in the potential energy of the valence band at the interface between the electron barrier layer 809 and the intermediate layer 108 can be suppressed. Thereby, the potential barrier for holes flowing from the P-type clad layer 710 to the active layer 105 becomes smaller and the operating voltage is reduced.

[0167] Also, by setting the film thickness of the region where the Al composition ratio is maximum to 0.5 nm or less, the potential barrier in the valence band for holes can be made smaller and the operating voltage can be reduced.

[0168] Furthermore, by setting the film thickness of the electron barrier layer 809 to 5 nm or less, it is possible to narrow the width (i.e., thickness) of the potential barrier of the valence band formed by the electron barrier layer 809. As a result, it is possible to reduce the electrical conduction barrier for holes from the P-type cladding layer 710 to the active layer 105, thereby reducing the operating voltage. Here, if the film thickness of the electron barrier layer 809 is thinner than 2 nm, the number of electrons that flow from the active layer 105 to the P-type cladding layer 710 over the electron barrier layer 809 increases, so the film thickness of the electron barrier layer 809 needs to be 2 nm or more.

[0169] Furthermore, when the thickness of the Al composition ratio increasing region is 2 nm or less, by setting the thickness of the electron barrier layer 809 to 5 nm or less and making the thickness of the Al composition ratio decreasing region of the electron barrier layer 809 larger than the thickness of the Al composition ratio increasing region, it is possible to suppress the generation of electrons that flow from the active layer 105 to the P-type cladding layer 710 across the electron barrier layer 809.

[0170] Furthermore, the positive piezoelectric polarization charge formed near the interface of the electron barrier layer 809 with the intermediate layer 108 is greater in the region where the rate of change in the Al composition ratio is relatively large than in the region close to the intermediate layer 108 where the rate of change in the Al composition ratio is relatively small. By making the shape of the curve f(x) in the region of increasing Al composition ratio of the electron barrier layer 809 convex downward, the rate of change in the Al composition ratio near the interface of the electron barrier layer 809 with the intermediate layer 108 can be reduced, thereby reducing the positive piezoelectric polarization charge at the interface. Therefore, the concentration of electrons attracted by the positive piezoelectric polarization charge at the interface decreases. Accordingly, the potential barrier of the valence band for holes at the interface of the electron barrier layer 809 with the intermediate layer 108 can be reduced.

[0171] Furthermore, by making the shape of the curve f(x) in the region of decreasing Al composition ratio of the electron barrier layer 809 convex downward, it is possible to reduce the film thickness of the region of high Al composition ratio near the position x=Xm, and further narrow the width of the potential barrier of the valence band formed by the electron barrier layer 809. As a result, it is possible to reduce the electrical conduction barrier of holes from the P-type cladding layer 710 to the active layer 105, and the operating voltage is reduced.

[0172] The Mg concentration in the electron barrier layer 809 according to this embodiment is 1.5×10 19 cm -3 Since the Al composition is graded in the region of the electron barrier layer 809 closer to the active layer 105 (i.e., the region with an increased Al composition ratio), the Mg concentration may be 1.5×10 19 cm -3 Even if the Al composition ratio of the electron barrier layer 809 is increased to 30% or more, the potential barrier against holes in the electron barrier layer 809 can be reduced. This makes it possible to suppress an increase in the operating voltage even if the Al composition ratio of the electron barrier layer 809 is increased to 30% or more.

[0173] Furthermore, by making the shape of the curve f(x) in the region of the electron barrier layer 809 closer to the active layer 105 (i.e., the region where the Al composition ratio is increased) convex downward, the effect of suppressing the formation of a potential barrier in the valence band is enhanced, and the Mg concentration is increased to 1×10 19 cm -3 It is possible to reduce the Mg concentration to 0.7×10 18 cm -3 This can prevent the potential of the valence band of the electron barrier layer 809 from decreasing too much.

[0174] In this embodiment, the electron barrier layer 809 is made of Al 0.02 Ga 0.98 The electron barrier layer 809 has a composition represented by the formula: N, and the Al composition ratio of the electron barrier layer 809 increases monotonically as it approaches the P-type cladding layer 710. At a position x=Xm, which is 1 nm away from the interface of the electron barrier layer 809 with the intermediate layer 108, the electron barrier layer 809 has a composition represented by the formula: 0.36 Ga 0.64 The electron barrier layer 809 has a composition represented by the formula: AlN. As it approaches the P-type cladding layer 710 from the position x=Xm, the Al composition ratio of the electron barrier layer 809 decreases monotonically. The electron barrier layer 809 has a composition represented by the formula: AlN. 0.026 Ga 0.974 It has a composition represented by N.

[0175] According to this embodiment, the effective refractive index difference ΔN is 1.9×10 -3The position P1 is 3.6 nm, the difference ΔP is 2.8 nm, the optical confinement coefficient in the active layer 105 is 1.54%, and the waveguide loss is 3.6 cm -1 and the free carrier loss in the guiding layer is 2.4 cm -1 A nitride-based semiconductor light-emitting device 800 having the above structure can be realized.

[0176] (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.

[0177] For example, in the above-described embodiments, the nitride-based semiconductor light-emitting element is a semiconductor laser element. However, the nitride-based semiconductor light-emitting element is not limited to a semiconductor laser element. For example, the nitride-based semiconductor light-emitting element may be a superluminescent diode. In this case, the reflectance of the end face of the semiconductor stack included in the nitride-based semiconductor light-emitting element with respect to the 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 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 guided light reflected at the front end face and recoupled with the waveguide to become guided light can be reduced to a small value of 0.1% or less. In particular, when the wavelength of the emitted light is in the 430 nm to 455 nm band, the film thickness of the well layers 105b and 105d of the active layer 105 is 35 Å or less. In this case, optical amplification gain can be ensured even with reduced facet reflectance due to the low waveguide loss effect of the nitride-based semiconductor light-emitting device according to the present disclosure and the effect of increasing the optical confinement factor of active layer 105. Furthermore, when such a nitride-based semiconductor light-emitting device is disposed in an external resonator including a wavelength-selecting element, self-heating of the nitride-based semiconductor light-emitting device can be reduced and wavelength fluctuations of the emitted light can be suppressed, making it easier to achieve oscillation at a desired selected wavelength.

[0178] Furthermore, in the above-described first to fourth and sixth embodiments, the nitride-based semiconductor light-emitting device has a structure including two well layers as the structure of the active layer 105, but it may have a structure including only a single well layer. Thus, even when the active layer includes only one high-refractive-index well layer, the use of the N-side guide layer and P-side guide layer of the present disclosure can improve the controllability of the position of the vertical light distribution, thereby positioning the peak of the vertical light distribution near the well layer. Therefore, a nitride-based semiconductor light-emitting device having a low lasing threshold, low waveguide loss, a high optical confinement factor, and excellent linearity in current-light output (IL) characteristics can be realized.

[0179] Furthermore, in the above-described embodiments, the nitride-based semiconductor light-emitting element has a single ridge, but the nitride-based semiconductor light-emitting element may have multiple ridges. Such a nitride-based semiconductor light-emitting element will be described with reference to FIG. 45 . FIG. 45 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element 900 according to Modification 1. As shown in FIG. 45 , the nitride-based semiconductor light-emitting element 900 according to Modification 1 has a configuration in which a plurality of nitride-based semiconductor light-emitting elements 100 according to Embodiment 1 are horizontally arranged in an array. In FIG. 45 , the nitride-based semiconductor light-emitting element 900 has a configuration in which three nitride-based semiconductor light-emitting elements 100 are integrally arranged, but the number of nitride-based semiconductor light-emitting elements 100 included in the nitride-based semiconductor light-emitting element 900 is not limited to three. The number of nitride-based semiconductor light-emitting elements 100 included in the nitride-based semiconductor light-emitting element 900 may be two or more. Each nitride-based semiconductor light-emitting element 100 has a light-emitting portion 100E that emits light. The light-emitting portion 100E is a portion of the active layer 105 that emits light, and corresponds to a portion of the active layer 105 that is located below the ridge 110R. In this way, the nitride-based semiconductor light-emitting device 900 according to the first modification has a plurality of light-emitting portions 100E arranged in an array. This makes it possible to obtain a plurality of emitted lights from one nitride-based semiconductor light-emitting device 900, thereby realizing a high-output nitride-based semiconductor light-emitting device 900. Note that, although the nitride-based semiconductor light-emitting device 900 according to the first modification includes a plurality of nitride-based semiconductor light-emitting devices 100, the plurality of nitride-based semiconductor light-emitting devices included in the nitride-based semiconductor light-emitting device 900 is not limited thereto and may be nitride-based semiconductor light-emitting devices according to other embodiments.

[0180] 46, the individual light emitting portions 100E may be separated by separation grooves 100T having a width (dimension in the X-axis direction) of 8 μm to 20 μm and a depth (dimension in the Z-axis direction) of 1.0 μm to 1.5 μm. By employing such a structure, even if the spacing between adjacent light emitting portions 100E is narrowed to 300 μm or less, it is possible to reduce thermal interference due to self-heating of the individual light emitting portions 100E during operation.

[0181] Furthermore, since the semiconductor laser device of the present disclosure has a small ΔN and can reduce the horizontal divergence angle, even if the distance between the centers of the light emitting portions 100E shown in Figures 45 and 46 is narrowed, the light emitted from each light emitting portion 100E is less likely to interfere with each other, and the distance between the centers of the light emitting portions 100E can be narrowed to 250 μm or less. In Modification 2, the distance is 225 μm.

[0182] Furthermore, although the nitride-based semiconductor light-emitting device according to each of the above embodiments includes the N-type second cladding layer 103, the intermediate layer 108, the electron barrier layer 109, and the current blocking layer 112, these layers do not necessarily have to be included.

[0183] Although the P-type cladding layers 110, 410, and 610 are layers with a uniform Al composition ratio, the configuration of each P-type cladding layer is not limited to this. For example, each P-type cladding layer may have a superlattice structure in which multiple AlGaN layers and multiple GaN layers are alternately stacked. Specifically, each P-type cladding layer may have a superlattice structure in which, for example, 1.85-nm-thick AlGaN layers with an Al composition ratio of 0.052 (5.2%) and 1.85-nm-thick GaN layers are alternately stacked. In this case, the Al composition ratio of each P-type cladding layer is defined as the average Al composition ratio of 0.026 (2.6%) in the superlattice structure.

[0184] 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.

[0185] For example, the configuration of each cladding layer according to the first embodiment may be applied to each of the nitride-based semiconductor light-emitting devices according to the third and fourth embodiments. Also, the light-transmitting conductive film according to the third embodiment may be applied to each of the nitride-based semiconductor light-emitting devices according to the first and fourth embodiments. [Industrial Applicability]

[0186] 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 a processing machine. [Explanation of symbols]

[0187] 100, 200, 300, 400, 500, 600, 700, 800, 900, 900a Nitride-based semiconductor light-emitting device 100E Light output part 100F, 100R end face 100T separation groove 100S, 200S, 300S, 400S, 500S, 600S, 700S, 800S Semiconductor laminate 101 Substrate 102, 302, 602 N-type first cladding layer 103 N-type second cladding layer 104, 604, 1104, 1204, 1304 N-side guide layer 105, 505 active layer 105a, 105c, 105e Barrier layers 105b, 105d well layer 106, 206, 1106, 1206, 1306 P-side guide layer 108 Middle Class 109, 309, 709, 809 Electron barrier layer 110, 410, 610, 710 P-type cladding layer 110R, 410R, 610R, 710R Ridge 110T, 410T, 610T, 710T groove 111, 411 Contact layer 112 Current Blocking Layer 113 P side electrode 114 N side electrode 206a, 1306a P-side first guide layer 206b, 1306b P-side second guide layer 420 Transparent conductive film

Claims

1. A nitride-based semiconductor light-emitting element comprising a semiconductor laminate and emitting light from an end face in a direction perpendicular to a lamination direction of the semiconductor laminate, The semiconductor laminate is an N-type first cladding layer; an N-side guide layer disposed above the N-type first cladding layer; an active layer having a quantum well structure, the active layer including a well layer and a barrier layer, and the active layer being disposed above the N-side guide layer; a P-side guide layer disposed above the active layer; a P-type clad layer disposed above the P-side guide layer, the band gap energy of the P-side guide layer increases continuously and monotonically with increasing distance from the active layer, the average band gap energy of the P-side guide layer is equal to or greater than the average band gap energy of the N-side guide layer; the band gap energy of the barrier layer is equal to or less than the minimum value of the band gap energy of the N-side guide layer and the P-side guide layer, When the thickness of the P-side guide layer is Tp and the thickness of the N-side guide layer is Tn, Tn<Tp Satisfy the relationship Nitride-based semiconductor light-emitting device.

2. The P-side guide layer is In Ｘｐ Ga １－Ｘｐ It consists of N, The N-side guide layer is In Ｘｎ Ga １－Ｘｎ It consists of N, the In composition ratio of the P-side guide layer monotonically decreases with increasing distance from the active layer, The average value of the In composition ratio of the N-side guide layer is equal to or greater than the average value of the In composition ratio of the P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 1 .

3. The average value of the In composition ratio of the N-side guide layer is larger than the average value of the In composition ratio of the P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 2 .

4. The average rate of change in the In composition ratio in the stacking direction in a region from the interface of the P-side guide layer closer to the active layer to the center of the P-side guide layer in the stacking direction is larger than the average rate of change in the In composition ratio in the stacking direction in a region from the center to the interface of the P-side guide layer closer to the P-type cladding layer The nitride-based semiconductor light-emitting device according to claim 2 or 3.

5. The barrier layer is made of In Ｘｂ Ga １－Ｘｂ It consists of N, The maximum value of the In composition ratio in the P-side guide layer is equal to or less than the In composition ratio in the barrier layer.

5. The nitride-based semiconductor light-emitting device according to claim 2.

6. The peak of the light intensity distribution in the stacking direction is located in the active layer.

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

7. The impurity concentration at the end of the P-type cladding layer closer to the active layer is lower than the impurity concentration at the end farther from the active layer.

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

8. an electron barrier layer disposed between the P-side guide layer and the P-type cladding layer; The electron barrier layer has an Al composition ratio increasing region in which the Al composition ratio monotonically increases with increasing distance from the active layer.

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

9. an electron barrier layer disposed between the P-side guide layer and the P-type cladding layer; A ridge is formed in the P-type cladding layer, and the distance between the bottom end of the ridge and the electron barrier layer is 10 nm or more and 70 nm or less.

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

10. the N-type first cladding layer and the P-type cladding layer contain Al; When the Al composition ratios of the N-type first cladding layer and the P-type cladding layer are Ync and Ypc, respectively, Ync>Ypc Satisfy the relationship 10. The nitride-based semiconductor light-emitting device according to claim 1.

11. The thickness of the P-type cladding layer is 460 nm or less. The nitride-based semiconductor light-emitting device according to any one of claims 1 to 10.

12. a transparent conductive film disposed above the P-type clad layer; 12. The nitride-based semiconductor light-emitting device according to claim 1.

13. an N-type second cladding layer disposed between the N-type first cladding layer and the N-side guide layer; The band gap energy of the N-type second cladding layer is smaller than the band gap energy of the N-type first cladding layer, and the band gap energy of the P-side guide layer is is greater than or equal to the maximum value 13. The nitride-based semiconductor light-emitting device according to claim 1.

14. It has a plurality of light emitting parts arranged in an array. The nitride-based semiconductor light-emitting device according to any one of claims 1 to 13.

15. The reflectance of the end face of the semiconductor laminate is 0.1% or less. The nitride-based semiconductor light-emitting device according to any one of claims 1 to 14.

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