Nitride-based semiconductor light-emitting device

Abstract

To provide a nitride-based semiconductor light-emitting device capable of reducing an operation voltage and increasing a coefficient of light confinement into an active layer.SOLUTION: A nitride-based semiconductor light-emitting device 100 comprises a semiconductor laminate 100S. The semiconductor laminate 100S includes an N-type first clad layer 102, an N-side guide layer 104, an active layer 105, a P-side first guide layer 106, a P-side second guide layer 107, and a P-type clad layer 110. Band gap energy of the P-side second guide layer 107 is larger than band gap energy of the N-side guide layer 104, and band gap energy of the N-side guide layer 104 is equal to or more than band gap energy of the P-side first guide layer 106. When a film thickness of the P-side first guide layer 106 is defined as Tp1, a film thickness of the P-side second guide layer 107 is defined as Tp2 and a film thickness of the N-side guide layer 104 is defined as Tn1, a relation of Tn1<Tp1+Tp2 is satisfied.SELECTED DRAWING: Figure 11

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 Laid-Open No. 2014-131019 Summary of the Invention [Problem to be solved by the invention]

[0004] In nitride-based semiconductor light-emitting devices, reducing the thickness of the P-type cladding layer is an effective way to reduce the operating voltage. However, as the thickness of the P-type cladding layer is reduced, the peak of the light intensity distribution in the stacking direction (i.e., the growth direction of each semiconductor layer) shifts from the active layer to the N-type cladding layer. This reduces the optical confinement coefficient in the active layer, and as a result, the thermal saturation level of the optical output decreases. 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, wherein the semiconductor laminate includes an N-type first cladding layer, an N-side guide layer arranged above the N-type first cladding layer, an active layer arranged above the N-side guide layer and including a well layer and a barrier layer and having a quantum well structure, a P-side first guide layer arranged above the active layer, a P-side second guide layer arranged above the P-side first guide layer, and a P-type cladding layer arranged above the P-side second guide layer, wherein the band gap energy of the P-side second guide layer is larger than the band gap energy of the N-side guide layer and the band gap energy of the N-side guide layer is equal to or greater than the band gap energy of the P-side first guide layer, and wherein, when the thickness of the P-side first guide layer is Tp1, the thickness of the P-side second guide layer is Tp2, and the thickness of the N-side guide layer is Tn1, Tn1 <Tp1+Tp2 Satisfy the relationship.

[0007] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, the average refractive index of the P-side first guide layer and the P-side second guide layer may be smaller than the average refractive index of the N-side guide layer.

[0008] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, the p-side first guide layer is In Xp1 Ga 1-Xp1 N, and the N-side guide layer is In Xn1 Ga 1-Xn1 It consists of N, Xn1≦Xp1 may satisfy the relationship:

[0009] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting device according to the present disclosure, Xn1 <Xp1 may satisfy the relationship:

[0010] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, the p-side second guide layer is InXp2 Ga 1-Xp2 It consists of N, Xp2 <Xn1 may satisfy the relationship:

[0011] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, the barrier layer is formed of In Xb Ga 1-Xb It consists of N, Xp1 <Xb may satisfy the relationship:

[0012] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, the band gap energy of the N-side guide layer may be larger than the band gap energy of the P-side first guide layer.

[0013] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting device according to the present disclosure, Tp1 <Tp2 may satisfy the relationship:

[0014] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting device according to the present disclosure, Tp1 <Tn1 may satisfy the relationship:

[0015] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, a peak of the light intensity distribution in the stacking direction may be located in the active layer.

[0016] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, the impurity concentration at an end of the P-type cladding layer closer to the active layer may be lower than the impurity concentration at an end of the P-type cladding layer farther from the active layer.

[0017] Furthermore, one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure may include an electron barrier layer disposed between the P-side second guide layer and the P-type cladding layer, and the electron barrier layer may have an Al composition change region in which the Al composition ratio monotonically increases with increasing distance from the active layer.

[0018] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, the first N-type cladding layer and the P-type cladding layer contain Al, and when the Al composition ratios of the first N-type cladding layer and the P-type cladding layer are Ync and Ypc, respectively, Ync>Ypc may satisfy the relationship:

[0019] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, the P-type cladding layer may have a thickness of 460 nm or less.

[0020] Furthermore, one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure may include a light-transmitting conductive film disposed above the P-type cladding layer.

[0021] Furthermore, one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure may include an N-type second cladding layer disposed between the N-type first cladding layer and the N-side guide layer, and the bandgap energy of the N-type second cladding layer may be smaller than the bandgap energy of the N-type first cladding layer and larger than the bandgap energy of the P-side second guide layer.

[0022] Furthermore, one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure may have a plurality of light-emitting portions arranged in an array.

[0023] In one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure, the facet of the semiconductor laminate may have a reflectance of 0.1% or less. [Effects of the Invention]

[0024] 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]

[0025] [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 band gap energy distribution and light intensity distribution in the stacking direction in the portion below the ridge of the nitride-based semiconductor light-emitting device of the comparative example. [Figure 6] FIG. 6 is a schematic graph showing the band gap energy distribution and light intensity distribution in the stacking direction in the portion below the trench of the nitride-based semiconductor light-emitting device of the comparative example. [Figure 7] FIG. 7 is a graph showing the simulation results of the light intensity distribution and the refractive index distribution in the portion below the ridge of the nitride-based semiconductor light-emitting element of Comparative Example 1. In FIG. [Figure 8] FIG. 8 is a graph showing the simulation results of the light intensity distribution and the refractive index distribution in the portion below the ridge of the nitride-based semiconductor light-emitting element of Comparative Example 2. In FIG. [Figure 9] FIG. 9 is a graph showing the simulation results of the light intensity distribution and the refractive index distribution in the portion below the ridge of the nitride-based semiconductor light-emitting device of Comparative Example 3. [Figure 10] FIG. 10 is a graph showing the simulation results of the light intensity distribution and the refractive index distribution in the portion below the ridge of the nitride-based semiconductor light-emitting device of Comparative Example 4. [Figure 11] FIG. 11 is a schematic graph showing the band gap energy distribution and the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element according to the first embodiment. [Figure 12] FIG. 12 is a graph showing the simulation results of the light intensity distribution and the refractive index distribution of the nitride-based semiconductor light-emitting element according to the first embodiment. [Figure 13] FIG. 13 is a graph showing the results of a simulation of the relationship between the radiation angle and the light intensity of the nitride-based semiconductor light-emitting element according to the first embodiment. [Figure 14] FIG. 14 is a graph showing the simulation results of the IL characteristics of the nitride-based semiconductor light-emitting device according to the first embodiment. [Figure 15] FIG. 15 is a graph showing a simulation result of the relationship between the In composition ratio and film thickness of the p-side second guide layer and each parameter when the In composition ratio of each barrier layer of the nitride-based semiconductor light-emitting element according to the first embodiment is 4%. [Figure 16] FIG. 16 is a graph showing a simulation result of the relationship between the In composition ratio and film thickness of the p-side second guide layer and each parameter when the In composition ratio of each barrier layer of the nitride-based semiconductor light-emitting element according to the first embodiment is 0%. [Figure 17] FIG. 17 is a graph showing the relationship between the thickness of the P-side second guide layer, the thickness of the P-type cladding layer, and each parameter in the nitride-based semiconductor light-emitting element of the comparative example. [Figure 18] FIG. 18 is a graph showing the relationship between the thickness of the P-side second guide layer, the thickness of the P-type cladding layer, and each parameter of the nitride-based semiconductor light-emitting element according to the first embodiment. [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 cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the third embodiment. [Figure 21A] FIG. 21A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to the fourth embodiment. [Figure 21B] FIG. 21B is a cross-sectional view showing the configuration of an active layer included in the nitride-based semiconductor light-emitting device according to the fourth embodiment. [Figure 22]FIG. 22 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 23] FIG. 23 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

[0026] 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.

[0027] 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.

[0028] 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.

[0029] (Embodiment 1) A nitride-based semiconductor light-emitting device according to a first embodiment will be described.

[0030] [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 IIA-IIA 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, which 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.

[0031] 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.

[0032] 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 first guide layer 106, a P-side second guide layer 107, an intermediate layer 108, an electron barrier layer 109, a P-type cladding layer 110, and a contact layer 111.

[0033] 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.

[0034] 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 0.035 Ga 0.965 The N-type first cladding layer 102 contains impurities at a concentration of 1×10 18 cm -3 It is doped with Si.

[0035] 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 It is doped with Si.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The P-side first guide layer 106 is an optical guide layer disposed above the active layer 105. The P-side first guide layer 106 has a higher refractive index and a smaller band gap energy than the P-type cladding layer 110. In this embodiment, the P-side first guide layer 106 is an undoped InP layer with a thickness of 80 nm. 0.045Ga 0.955 This is the N layer.

[0044] The P-side second guide layer 107 is an optical guide layer disposed above the P-side first guide layer 106. The P-side second guide layer 107 has a higher refractive index and a smaller band gap energy than the P-type cladding layer 110. In this embodiment, the P-side second guide layer 107 is an undoped InP layer with a thickness of 195 nm. 0.01 Ga 0.99 This is the N layer.

[0045] 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 second guide layer 107 and the electron barrier layer 109, and reduces stress caused by the difference in lattice constant between the P-side second guide layer 107 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.

[0046] 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 P-type AlGaN layer with a thickness of 5 nm. The electron barrier layer 109 also has an Al composition ratio gradient 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 109 according to this embodiment, the entire electron barrier layer 109 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 109 has an Al composition ratio gradient 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 Ga0.64 The electron barrier layer 109 has a composition represented by the formula: N. The electron barrier layer 109 contains impurities at a concentration of 1×10 19 cm -3 It is doped with Mg.

[0047] The electron barrier layer 109 can prevent electrons from leaking from the active layer 105 to the P-type cladding layer 110. Furthermore, since the electron barrier layer 109 has an Al composition change region where the Al composition ratio monotonically increases, the potential barrier of the valence band of the electron barrier layer 109 can be reduced compared to when the Al composition ratio is uniform. Therefore, holes can flow more easily from the P-type cladding layer 110 to the active layer 105. Therefore, even when the combined thickness of the P-side first guide layer 106 and the P-side second guide layer 107, which are undoped layers, is large, as in this embodiment, an increase in the electrical resistance of the nitride-based semiconductor light-emitting element 100 can be prevented. This can reduce the operating voltage of the nitride-based semiconductor light-emitting element 100. Furthermore, self-heating of the nitride-based semiconductor light-emitting element 100 during operation can be reduced, thereby improving the temperature characteristics of the nitride-based semiconductor light-emitting element 100. Therefore, the nitride-based semiconductor light-emitting element 100 can operate at high power.

[0048] 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. 0.035 Ga 0.965 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 0.035 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.

[0049] 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.

[0050] 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 film thickness of 100 nm. The contact layer 111 contains impurities with a concentration of 1×10 20 cm -3 It is doped with Mg.

[0051] 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.

[0052] 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.

[0053] 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 components of the semiconductor stack 100S other than the substrate 101 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.

[0054] 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).

[0055] [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.

[0056] 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.

[0057] 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 PS1. Furthermore, the peak position of the light intensity distribution in the stacking direction below the groove 110T is designated PS2. Positions PS1 and PS2 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 first guide layer 106) is set to the positive direction of the coordinate. Also, the absolute value of the difference between positions PS1 and PS2 is set to the peak position difference ΔP.

[0058] 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. Generally, 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 toward the N-type cladding layer. 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, the bandgap energy of the P-side second guide layer 107 is larger than the bandgap energy of the N-side guide layer 104, and the bandgap energy of the N-side guide layer 104 is equal to or larger than the bandgap energy of the P-side first guide layer 106. Furthermore, if the thickness of the P-side first guide layer 106 is Tp1, the thickness of the P-side second guide layer 107 is Tp2, and the thickness of the N-side guide layer 104 is Tn1, then: Tn1 <Tp1+Tp2 (1) Satisfy the relationship.

[0059] Thus, in the nitride-based semiconductor light-emitting device 100, the band gap energy of the N-side guide layer 104 is equal to or greater than the band gap energy of the P-side first guide layer 106. Specifically, the P-side first guide layer 106 is made of In Xp1 Ga 1-Xp1 N, and the N-side guide layer 104 is made of In Xn1 Ga 1-Xn1 It consists of N, Xn1≦Xp1 (2) Therefore, the refractive index of the N-side guide layer 104 is equal to or less than the refractive index of the P-side first guide layer 106. This allows the light intensity distribution to shift from the active layer 105 toward the P-side first guide layer 106, compared to when the refractive index of the N-side guide layer 104 is higher than the refractive index of the P-side first guide layer 106, for example.

[0060] In this embodiment, the In composition ratios Xn1 and Xp1 of the N-side guide layer 104 and the P-side first guide layer 106 are as follows: Xn1 <Xp1 (3) More specifically, the N-side guide layer 104 is In 0.04 Ga 0.96 The P-side first guide layer 106 is an In 0.045 Ga 0.955 The N-side layer 104 is an N-layer. Here, in an InGaN layer, as the In composition ratio increases, the bandgap energy decreases and the refractive index increases. Therefore, the bandgap energy of the N-side guide layer 104 is greater than the bandgap energy of the P-side first guide layer 106. In other words, the refractive index of the N-side guide layer 104 is smaller than the refractive index of the P-side first guide layer 106. This allows the light intensity distribution to shift from the active layer 105 toward the P-side first guide layer 106, compared to when the refractive index of the N-side guide layer 104 is equal to or greater than the refractive index of the P-side first guide layer 106.

[0061] As described above, the sum of the thickness Tp1 of the P-side first guide layer 106 and the thickness Tp2 of the P-side second guide layer 107 is greater than the thickness Tn1 of the N-side guide layer 104. By making the sum of the thicknesses of the P-side first guide layer 106 and the P-side second guide layer 107, which have relatively high refractive indices, greater than the thickness Tn1 of the N-side guide layer 104, the light intensity distribution can be shifted from the active layer 105 toward the P-side first guide layer 106, compared to when the sum of the thicknesses of the P-side first guide layer 106 and the P-side second guide layer 107 is equal to or less than the thickness Tn1 of the N-side guide layer 104. Therefore, the peak of the light intensity distribution in the stacking direction can be prevented from shifting in the direction from the active layer 105 toward the N-type second cladding layer 103. Here, the band gap energy of the P-side second guide layer 107 is greater than the band gap energy of the N-side guide layer 104. That is, the refractive index of the P-side second guide layer 107 is smaller than the refractive index of the N-side guide layer 104. This makes it possible to prevent the light intensity distribution from moving too far in the direction from the active layer 105 toward the P-type cladding layer 110.

[0062] As described above, the band gap energy of the P-side second guide layer 107 is larger than the band gap energy of the N-side guide layer 104. Specifically, the P-side second guide layer 107 is made of In Xp2 Ga 1-Xp2 The P-side second guide layer 107 is made of In, and the N-side guide layer 104 is made of In, and the In composition ratio Xp2 of the P-side second guide layer 107 and the In composition ratio Xn1 of the N-side guide layer 104 are Xp2 <Xn1 (4) More specifically, the N-side guide layer 104 is In 0.04 Ga 0.96 The P-side second guide layer 107 is an In 0.01 Ga 0.99 The N-side guide layer 104 is an N layer. Therefore, the refractive index of the N-side guide layer 104 is greater than the refractive index of the P-side second guide layer 107. This makes it possible to prevent the light intensity distribution from moving too far in the direction approaching the P-type cladding layer 110 from the active layer 105.

[0063] In this embodiment, the barrier layers 105a, 105c, and 105e of the active layer 105 are made of In. Xb Ga 1-Xb N, and the In composition ratios Xb and Xp1 of each barrier layer and the P-side first guide layer 106 are as follows: Xp1 <Xb (5) This satisfies the relationship shown below. As a result, the refractive index of each barrier layer can be made larger than those of the P-side first guide layer 106 and the N-side guide layer 104. This allows the peak of the light intensity distribution in the stacking direction to be positioned in the active layer 105. Furthermore, excessive movement of the light intensity distribution in a direction approaching the P-type cladding layer 110 from the active layer 105 can be suppressed.

[0064] In this embodiment, the average refractive index of the P-side first guide layer 106 and the P-side second guide layer 107 is smaller than the average refractive index of the N-side guide layer 104. This makes it possible to prevent the light intensity distribution from moving too far in the direction from the active layer 105 toward the P-type cladding layer 110.

[0065] In this embodiment, the thicknesses Tp1 and Tp2 of the P-side first guide layer 106 and the P-side second guide layer 107 are as follows: Tp1 <Tp2 (6) The following relationship is satisfied. In this way, by making the film thickness of the P-side first guide layer 106, which has a small band gap energy, i.e., a large refractive index, relatively small, it is possible to prevent the light intensity distribution from moving too far in the direction approaching the P-type cladding layer 110 from the active layer 105. Furthermore, by making the film thickness of the P-side first guide layer 106, which has a small In composition ratio, relatively small, it is possible to avoid arranging the P-side first guide layer 106, which has a small In composition ratio and a large film thickness, above and in the vicinity of the well layers 105b and 105d, which have the highest In composition ratio in the semiconductor laminate 100S. Therefore, it is possible to prevent the occurrence of lattice defects.

[0066] In this embodiment, the thicknesses Tp1 and Tn1 of the P-side first guide layer 106 and the N-side guide layer 104 are set as follows: Tp1 <Tn1 (7) In this way, by making the film thickness of the P-side first guide layer 106, which has a small band gap energy, that is, a large refractive index, smaller than the film thickness of the N-side guide layer 104, it is possible to prevent the light intensity distribution from moving too far in the direction approaching the P-type cladding layer 110 from the active layer 105.

[0067] In this embodiment, the band gap energy of the N-type second cladding layer 103 is smaller than that of the N-type first cladding layer 102 and larger than that of the P-side second guide layer 107. In this way, by disposing the N-type second cladding layer 103, which has a smaller band gap energy than the N-type first cladding layer 102, i.e., a larger refractive index, between the N-type first cladding layer 102 and the N-side guide layer 104, it is possible to prevent the light intensity distribution from moving too far in a direction from the active layer 105 toward the P-type cladding layer 110. Furthermore, by making the band gap energy of the N-type second cladding layer 103 larger than that of the P-side second guide layer 107, it is possible to prevent the light intensity distribution from moving too far from the active layer 105 toward the N-type second cladding layer 103.

[0068] With the above configuration, in this embodiment, the position PS1 of the peak of the light intensity distribution in the stacking direction below the ridge 110R can be set to 2.5 nm. In other words, the peak of the light intensity distribution can be positioned in the active layer 105. Furthermore, ΔP can be suppressed to 6.4 nm. This allows the light confinement factor in the active layer 105 to be increased to approximately 1.45%.

[0069] 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.

[0070] 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 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 proportion of the light located in the P-type cladding layer 110 increases, which raises concerns about an increase in free carrier loss in the P-type cladding layer 110. However, in this embodiment, the P-side first guide layer 106 and the P-side second guide layer 107 are undoped layers, and the sum of the film thickness Tp1 of the P-side first guide layer 106 and the film thickness Tp2 of the P-side second guide layer 107 is relatively large, thereby increasing the proportion of the light intensity distribution located in the undoped layers. Therefore, an increase in free carrier loss can be suppressed. Specifically, in this embodiment, the waveguide loss is reduced to 1.6 cm. -1 It can be suppressed to a certain extent.

[0071] Furthermore, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, 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 in order to reduce the divergence angle of the emitted light in the horizontal direction (i.e., the X-axis direction). 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 2.4×10 -3 Therefore, in this embodiment, the effective refractive index difference ΔN is about 2.4×10 -3 When 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.

[0072] The above-mentioned decrease in stability of light output will be explained below. In the nitride-based semiconductor light-emitting device 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 PS1 of the light intensity distribution in the stacking direction in the portion below the ridge 110R of the nitride-based semiconductor light-emitting device 100 and the peak position PS2 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.

[0073] 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 PS1. Therefore, the larger the difference ΔP between positions PS1 and PS2, 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.

[0074] The nitride-based semiconductor light-emitting device 100 according to this embodiment includes the N-side guide layer 104, the P-side first guide layer 106, and the P-side second guide layer 107 configured as described above, 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 groove 110T. That is, the difference ΔP between the positions PS1 and PS2 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 position 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 groove 110T can be suppressed. Therefore, the stability of the light output can be improved.

[0075] 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 groove 110T) is set to be lower than the electron barrier layer 109, the electron barrier layer 109 has a large band gap energy. Therefore, holes injected from the contact layer 111 tend to leak from the sidewall of the ridge 110R to the outside of the ridge 110R when passing through the electron barrier layer 109. As a result, the holes flow below the groove 110T. Accordingly, the light distribution intensity in the active layer 105 below the groove 110T is low, which reduces the probability of radiative recombination between electrons and holes injected into the active layer 105 and increases non-radiative recombination. This makes the nitride-based semiconductor light-emitting element 100 more susceptible to degradation. Therefore, 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 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 as small a value as possible.

[0076] [1-3.Effects] The effects of the nitride-based semiconductor light-emitting element 100 according to the present embodiment will be described with reference to FIGS. 5 to 12, in comparison with nitride-based semiconductor light-emitting elements of comparative examples. FIGS. 5 and 6 are schematic graphs showing the bandgap energy distribution and light intensity distribution in the stacking direction in the portion below the ridge 110R and the portion below the groove 110T of the nitride-based semiconductor light-emitting element of the comparative example, respectively. Graphs (a) to (c) of FIG. 5 show the bandgap energy distribution and light intensity distribution in the portion below the ridge 110R of the nitride-based semiconductor light-emitting elements of Comparative Examples 1 to 3, respectively. Graphs (a) to (c) of FIG. 6 show the bandgap energy distribution and light intensity distribution in the portion below the groove 110T of the nitride-based semiconductor light-emitting elements of Comparative Examples 1 to 3, respectively. FIGS. 7 to 10 are graphs showing the simulation results of the light intensity distribution and the refractive index distribution in the portion below the ridge 110R of the nitride-based semiconductor light-emitting elements of Comparative Examples 1 to 4, respectively. Fig. 11 is a schematic graph showing the bandgap energy distribution and light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Graphs (a) and (b) in Fig. 11 show the bandgap energy distribution and light intensity distribution in the portion below the ridge 110R and the portion below the groove 110T of the nitride-based semiconductor light-emitting element 100, respectively. Fig. 12 is a graph showing the simulation results of the light intensity distribution and refractive index distribution of the nitride-based semiconductor light-emitting element 100 according to this embodiment.

[0077] The horizontal axes in Figures 5, 6, and 11 indicate the stacking direction, and the vertical axes indicate band gap energy and light intensity. The horizontal axes in Figures 7 to 10 and 12 indicate position in the stacking direction, and the left and right vertical axes indicate light intensity and refractive index, respectively. In Figures 7 to 10 and 12, the light intensity distribution in the stacking direction below the groove 110T is also shown by a dotted line.

[0078] 5 to 9 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 P-side guide layer. The nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 have a single N-side guide layer 904 and a single P-side guide layer 906. The N-side guide layer 904 and the P-side guide layer 906 have the same bandgap energy.

[0079] In the nitride-based semiconductor light-emitting device of Comparative Example 1, the thickness Tn0 of the N-side guide layer 904 is larger than the thickness Tp0 of the P-side guide layer 906. Specifically, the N-side guide layer 904 is an In 0.03 Ga 0.97 The P-side guide layer 906 is an In layer with a thickness of 100 nm. 0.03 Ga 0.97 In the nitride-based semiconductor light-emitting device of Comparative Example 2, the thickness Tn0 of the N-side guide layer 904 is equal to the thickness Tp0 of the P-side guide layer 906. Specifically, both the N-side guide layer 904 and the P-side guide layer 906 are made of InN with a thickness of 220 nm. 0.03 Ga 0.97 In the nitride-based semiconductor light-emitting device of Comparative Example 3, the thickness Tn0 of the N-side guide layer 904 is smaller than the thickness Tp0 of the P-side guide layer 906. Specifically, the N-side guide layer 904 is an In layer having a thickness of 100 nm. 0.03 Ga 0.97 The P-side guide layer 906 is an In layer with a thickness of 340 nm. 0.03 Ga 0.97 This is the N layer.

[0080] 10 differs from the nitride-based semiconductor light-emitting device 100 according to the present embodiment in the configurations of the N-side guide layer and P-side guide layer. The nitride-based semiconductor light-emitting device of Comparative Example 4 has an N-side guide layer, a P-side first guide layer, and a P-side second guide layer, similar to the nitride-based semiconductor light-emitting device 100 according to the present embodiment. In the nitride-based semiconductor light-emitting device of Comparative Example 4, the band gap energy of the P-side second guide layer is larger than the band gap energy of the N-side first guide layer, and the band gap energy of the N-side first guide layer is equal to the band gap energy of the P-side first guide layer. With respect to the thickness Tp1 of the P-side first guide layer, the thickness Tp2 of the P-side second guide layer, and the thickness Tn1 of the N-side first guide layer, Tn1=Tp1+Tp2, (8) and, Tp1=Tp2 (9) Specifically, the N-side guide layer is an In layer with a thickness of 220 nm. 0.03 Ga 0.97 The N layer is the P-side first guide layer, and the In layer is 110 nm thick. 0.03 Ga 0.97 The N layer is the P-side second guide layer, which is an In layer with a thickness of 110 nm. 0.01 Ga 0.99 This is the N layer.

[0081] In the simulation, the Al composition ratio of the electron barrier layer 909 of Comparative Example 1-4 and the Al composition ratio of the electron barrier layer 109 according to this embodiment are set to be uniform. In other words, the Al composition ratio of each electron barrier layer is not graded in the stacking direction.

[0082] The device structures used in the simulations of the nitride-based semiconductor light-emitting devices according to Comparative Examples 1 to 4 and the present embodiment described above are shown in Table 1 below, and the numerical values ​​obtained in the simulations are shown in Table 2 below.

[0083] [Table 1]

[0084] [Table 2]

[0085] Table 2 shows the distance dc from the bottom end of the ridge 110R to the electron barrier layer 109, the optical confinement factor, the waveguide loss, the effective refractive index difference ΔN, the peak position PS1 of the light intensity distribution in the stacking direction at the horizontal center of the lower part of the ridge 110R, and the absolute value ΔP of the difference between the peak position PS1 and the peak position PS2 in the stacking direction of the limit mode for wave-guiding. Note that the distance dc is set when the effective refractive index difference is 2.8×10 -3 The distance is set to be such that the following can be achieved. The limiting mode for wave-guiding refers to the highest-order mode that can propagate in each nitride-based semiconductor light-emitting element. The peak position in the stacking direction of the limiting mode for wave-guiding corresponds to the peak position of the light intensity distribution in the portion below trench 110T where higher-order modes are dominant.

[0086] In the nitride-based semiconductor light-emitting device of Comparative Example 1, as shown in graphs (a) of FIGS. 5 and 6 and in FIG. 7, the thickness of the N-side guide layer 904 is greater than the thickness of the P-side guide layer 906, so the peak of the light intensity distribution is located within the N-side guide layer 904. This results in a low optical confinement coefficient in the active layer 105 and a low thermal saturation level of the optical output. Furthermore, the small thickness of the P-side guide layer 906 reduces the distance dp between the bottom end of the ridge 110R and the active layer 105. This increases the effective refractive index difference ΔN, resulting in a large horizontal divergence angle of the emitted light. Furthermore, to reduce the effective refractive index difference ΔN, the distance dc from the bottom end of the ridge 110R to the electron barrier layer 909 needs to be relatively large, at 80 nm. This increases the leakage current described above, thereby increasing the oscillation threshold current of the nitride-based semiconductor light-emitting device.

[0087] Furthermore, in the nitride-based semiconductor light-emitting device of Comparative Example 1, the film thickness of the p-side guide layer 906 is relatively small, which has a relatively large effect on the light intensity distribution of the current blocking layer 112 arranged in the groove 110T. As a result, the difference ΔP between the peak position of the light intensity distribution in the stacking direction below the ridge 110R and the peak position of the light intensity distribution in the stacking direction below the groove 110T is relatively large (see FIG. 7 in particular). As a result, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting device of Comparative Example 1 is low.

[0088] In the nitride-based semiconductor light-emitting device of Comparative Example 2, as shown in graphs (b) of FIGS. 5 and 6 and FIG. 8 , the film thickness of the N-side guide layer 904 is equal to the film thickness of the P-side guide layer 906, and therefore the peak of the light intensity distribution is located in the active layer 105 below the ridge 110R. Therefore, the light confinement coefficient to the active layer 105 is high below the ridge 110R. However, in the nitride-based semiconductor light-emitting device of Comparative Example 2, the film thickness of the P-side guide layer 906 is not large, and therefore is affected by the light intensity distribution of the current blocking layer 112 disposed in the groove 110T. The peak of the light intensity distribution in the stacking direction below the groove 110T is located in the N-side guide layer 904, and therefore the light confinement coefficient is low below the groove 110T. Furthermore, the difference ΔP between the peak position of the light intensity distribution in the stacking direction below the ridge 110R and the peak position of the light intensity distribution in the stacking direction below the groove 110T is relatively large. Therefore, the nitride-based semiconductor light-emitting element of Comparative Example 2 has low linearity in the IL characteristics.

[0089] 5 and 6, and also as shown in Fig. 9, in the nitride-based semiconductor light-emitting device of Comparative Example 3, the film thickness of the N-side guide layer 904 is smaller than the film thickness of the P-side guide layer 906, and therefore the peak of the light intensity distribution is located in the P-side guide layer 906. As a result, the optical confinement coefficient in the active layer 105 is low, and the thermal saturation level of the optical output is low.

[0090] Furthermore, in the nitride-based semiconductor light-emitting device of Comparative Example 3, the peak of the light intensity distribution is located in the P-side guide layer 906, so the current blocking layer 112 has a relatively large effect on the light intensity distribution. As a result, the difference ΔP between the peak position of the light intensity distribution in the stacking direction below the ridge 110R and the peak position of the light intensity distribution in the stacking direction below the groove 110T is relatively large (see FIG. 9 in particular). Therefore, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting device of Comparative Example 3 is low.

[0091] In the nitride-based semiconductor light-emitting device of Comparative Example 4, the film thickness of the P-side second guide layer is smaller than that of the nitride-based semiconductor light-emitting device 100 according to the present embodiment, and therefore the influence of the current blocking layer 112 on the light intensity distribution is relatively large, as shown in Fig. 10. Therefore, the difference ΔP between the peak position of the light intensity distribution in the stacking direction below the ridge 110R and the peak position of the light intensity distribution in the stacking direction below the groove 110T is relatively large. Therefore, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting device of Comparative Example 4 is low.

[0092] In contrast to the above comparative examples, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, the sum of the thickness Tp1 of the P-side first guide layer 106 and the thickness Tp2 of the P-side second guide layer 107 is larger than the thickness Tn1 of the N-side guide layer 104, so the effective refractive index difference ΔN can be reduced. Therefore, the horizontal divergence angle of the emitted light can be reduced. Furthermore, the distance dc from the bottom end of the ridge 110R to the electron barrier layer 109 can be set to 40 nm, which is significantly smaller than the distance dc in the comparative examples. Therefore, the leakage current flowing between the bottom end of the ridge 110R and the electron barrier layer 109 can be suppressed, and the oscillation threshold current can be reduced.

[0093] 11 and 12, in this embodiment, the peak of the light intensity distribution in the stacking direction can be positioned in the active layer 105 in both the portion below the ridge 110R and the portion below the groove 110T. Therefore, the optical confinement factor can be increased compared to the comparative examples. Furthermore, since the difference ΔP in the peak positions can be reduced, the linearity of the IL characteristics can be improved.

[0094] Furthermore, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, the peak of the light intensity distribution in the stacking direction is positioned in the active layer 105, and therefore the light intensity in the P-type cladding layer 110 is higher than when the peak of the light intensity distribution is positioned in the N-side guide layer, as in Comparative Example 1. This raises concerns about increased free carrier loss in the P-type cladding layer 110, which has a higher impurity concentration than the N-type first cladding layer 102 and the N-type second cladding layer 103. However, in this embodiment, the P-side first guide layer 106 and the P-side second guide layer 107 are undoped layers, and the sum of the film thickness Tp1 of the P-side first guide layer 106 and the film thickness Tp2 of the P-side second guide layer 107 is relatively large, thereby increasing the proportion of the portion of the light intensity distribution located in the undoped layers. This suppresses an increase in free carrier loss. Furthermore, in this embodiment, 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, so that free carrier loss at the end of the P-type cladding layer 110 closer to the active layer 105, where the light intensity is relatively high, can be suppressed.

[0095] Here, the output characteristics of the nitride-based semiconductor light-emitting device 100 according to this embodiment will be described with reference to Figs. 13 and 14. Fig. 13 is a graph showing the results of a simulation of the relationship between the radiation angle and light intensity of the nitride-based semiconductor light-emitting device 100 according to this embodiment. Fig. 13 also shows a graph of the output characteristics of a nitride-based semiconductor light-emitting device having an effective refractive index difference ΔN of 7×10 -3 14 is a graph showing the results of a simulation of the IL characteristics of the nitride-based semiconductor light-emitting device 100 according to the present embodiment. The IL characteristics of the nitride-based semiconductor light-emitting device of Comparative Example 2 are also shown in FIG.

[0096] As shown in FIG. 13, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, the effective refractive index difference ΔN is 2.8×10 -313, the beam divergence angle in the horizontal direction can be reduced to 1 / e 2 The total beam width at which the intensity is achieved can be reduced to approximately 9.3°.

[0097] 14, the nitride-based semiconductor light-emitting device 100 according to this embodiment can obtain IL characteristics with higher linearity than the nitride-based semiconductor light-emitting device of the comparative example, and can also obtain a higher slope efficiency (about 1.9 W / A) than the comparative example.

[0098] Next, the relationship between the configuration and effects of the P-side second guide layer 107 according to this embodiment will be described in detail with reference to FIGS. 15 and 16. FIG. 15 is a graph showing the results of a simulation of the relationship between the In composition ratio Xp2 and film thickness Tp2 of the P-side second guide layer 107 and each parameter when the In composition ratio of each barrier layer of the nitride-based semiconductor light-emitting element 100 according to this embodiment is 4%. FIG. 16 is a graph showing the results of a simulation of the relationship between the In composition ratio Xp2 and film thickness Tp2 of the P-side second guide layer 107 and each parameter when the In composition ratio of each barrier layer of the nitride-based semiconductor light-emitting element 100 according to this embodiment is 0%. Graphs (a) to (f) in FIGS. 15 and 16 respectively show the film thickness Tp2 of the P-side second guide layer, the waveguide loss, the optical confinement factor Γv, and the effective refractive index difference ΔN(×10 -3 ), position PS1, position PS2, and ΔP. Each graph shows the relationship between the In composition ratio Xp2 of the P-side second guide layer 107 and the In composition ratio Xp2 of the P-side second guide layer 107, which are 0%, 0.5%, 1%, 2%, 3%, and 4%. In the simulation, the In composition ratio Xn1 of the N-side guide layer 104 is set to 4% and the film thickness is set to 160 nm. The In composition ratio Xp1 of the P-side first guide layer 106 is set to 4.5%, and the film thickness is set to 80 nm.

[0099] 15 and 16, for all In composition ratios Xp2, the waveguide loss decreases as the film thickness Tp2 of the p-side second guide layer 107 increases. Also, the waveguide loss decreases as the In composition ratio Xp2 decreases.

[0100] 15 and 16, for all In composition ratios Xp2, the optical confinement factor Γv is maximum when the thickness Tp2 of the p-side second guide layer 107 is in the range of about 0 to 100 nm, and as the thickness Tp2 exceeds 100 nm, the optical confinement factor Γv decreases. Furthermore, when the thickness Tp2 is 100 nm or more, the optical confinement factor Γv increases as the In composition ratio Xp2 decreases.

[0101] 15 and 16, for all In composition ratios Xp2, the effective refractive index difference ΔN decreases as the film thickness Tp2 of the p-side second guide layer 107 increases. Also, the effective refractive index difference ΔN generally tends to decrease as the In composition ratio Xp2 decreases.

[0102] 15 and 16, for all In composition ratios Xp2, the positions PS1 and PS2 increase as the thickness Tp2 of the p-side second guide layer 107 increases. Furthermore, the positions PS1 and PS2 tend to generally decrease as the In composition ratio Xp2 decreases. Note that graphs (d) and (e) in FIGS. 15 and 16 show a range in which the positions PS1 and PS2 are greater than or equal to -5 nm and less than or equal to 18 nm as an example of the range in which the positions PS1 and PS2 can increase the optical confinement factor. Within this range, the range in which the positions PS1 and PS2 are greater than or equal to 0 nm and less than or equal to 13 nm corresponds to the case in which the positions PS1 and PS2 are in any of the well layer 105b, the barrier layer 105c, and the well layer 105d of the active layer 105. Furthermore, the range of positions PS1 and PS2 equal to or greater than −5 nm and less than 0 corresponds to a distance range of 5 nm from the well layer 105b closest to the N-type second cladding layer 103 of the active layer 105 toward the N-type second cladding layer 103. Furthermore, the range of positions PS1 and PS2 equal to or greater than 13 nm and equal to or less than 18 nm corresponds to a distance range of 5 nm from the well layer 105d closest to the P-type cladding layer 110 of the active layer 105 toward the P-type cladding layer 110. Therefore, by positioning the peak of the light intensity distribution at such a position equal to or greater than −5 nm and equal to or less than 18 nm, the optical confinement factor Γv can be increased.

[0103] 15 and 16, except for the case where the In composition ratio Xp1 of the P-side first guide layer 106 and the In composition ratio of the P-side second guide layer 107 are equal (that is, a case different from the present embodiment), ΔP generally tends to decrease as the film thickness Tp2 of the P-side second guide layer 107 increases. Note that, in the graphs (f) of Fig. 15 and 16, a range of ΔP between 0 and 20 nm is shown as an example of the range of ΔP that can improve the linearity of the IL characteristics.

[0104] 15 and 16, by setting the thickness Tp2 of the p-side second guide layer 107 to 100 nm or more, it is possible to simultaneously reduce the waveguide loss, increase the optical confinement factor Γv, and reduce the effective refractive index difference ΔN. To further increase the optical confinement factor Γv, the thickness Tp2 may be 250 nm or less. To position the positions PS1 and PS2 near the well layers 105b and 105d of the active layer 105, the In composition ratio Xp2 of the p-side second guide layer 107 may be 0.5% or more.

[0105] Next, the relationship between the thickness Tp2 of the P-side second guide layer 107 and the thickness of the P-type cladding layer 110 of the nitride-based semiconductor light-emitting element 100 according to this embodiment and each parameter will be described with reference to FIGS. 17 and 18, while comparing with a comparative example. FIG. 17 is a graph showing the relationship between the thickness of the P-side second guide layer and the thickness of the P-type cladding layer of the nitride-based semiconductor light-emitting element of the comparative example and each parameter. FIG. 18 is a graph showing the relationship between the thickness of the P-side second guide layer 107 and the thickness of the P-type cladding layer 110 of the nitride-based semiconductor light-emitting element 100 according to this embodiment and each parameter. In FIGS. 17 and 18, the relationship between each thickness and the waveguide loss α i 17 includes a single N-side guide layer and a single P-side guide layer having the same film thickness and In composition ratio as the nitride-based semiconductor light-emitting device of Comparative Example 2 described above.

[0106] 17, the region where the positions PS1 and PS2 are both −5 nm or more and 18 nm or less and ΔP is 20 nm or less in the nitride-based semiconductor light-emitting device of the comparative example is hatched. However, in this region, the effective refractive index difference ΔN is 4×10 -3 Since the angle of divergence of the emitted light in the horizontal direction becomes larger than the reference angle, it is not possible to suppress the angle of divergence of the emitted light in the horizontal direction. Moreover, in this region, it is not possible to make ΔP 10 nm or less. Note that, even in the nitride-based semiconductor light-emitting element of the comparative example, by setting the distance dc to about 80 nm, the effective refractive index difference ΔN can be reduced to 3×10 -3However, in this case, as described above, leakage current occurs between the electron barrier layer 109 and the groove 110T, which increases the oscillation threshold current and leads to a deterioration in the temperature characteristics of the nitride-based semiconductor light-emitting device. Thus, the nitride-based semiconductor light-emitting device of the comparative example cannot solve the problem of the present disclosure.

[0107] 18, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, the region where the positions PS1 and PS2 are both not less than -5 nm and not more than 18 nm, and where ΔP is not more than 20 nm, is indicated by hatching with diagonal lines and dots. Furthermore, within this range, the region where ΔP is not more than 5 nm is indicated by hatching with dots, and the region where ΔP is more than 5 nm and not more than 10 nm is indicated by hatching with diagonal lines. As shown in FIG. 18, in the hatched region, the effective refractive index difference ΔN is 2.8×10 -3 Therefore, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, even if the distance dc is about 40 nm, the above conditions can be satisfied.

[0108] (Embodiment 2) A nitride-based semiconductor light-emitting device according to embodiment 2 will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 100 according to embodiment 1 in the relationship between the Al composition ratios of the N-type first cladding layer and the P-type cladding layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 19, focusing on the differences from nitride-based semiconductor light-emitting device 100 according to embodiment 1.

[0109] 19 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 200 according to this embodiment. As shown in FIG. 19, the 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 202, an N-type second cladding layer 103, an N-side guide layer 104, an active layer 105, a P-side first guide layer 106, a P-side second guide layer 107, an intermediate layer 108, an electron barrier layer 109, a P-type cladding layer 210, and a contact layer 111.

[0110] The N-type first cladding layer 202 according to this embodiment is made of N-type Al 1N with a thickness of 1200 nm. 0.036 Ga 0.964 The N-type first cladding layer 202 contains impurities at a concentration of 1×10 18 cm -3 It is doped with Si.

[0111] The P-type cladding layer 210 according to this embodiment is a P-type Al layer having a thickness of 450 nm. 0.026 Ga 0.974 The P-type cladding layer 210 is an N layer. The P-type cladding layer 210 is doped with Mg as an impurity. The impurity concentration at the end of the P-type cladding layer 210 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 210 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.

[0112] The P-type cladding layer 210 also has a ridge 210R formed therein, similar to the P-type cladding layer 110 according to embodiment 1. The P-type cladding layer 210 also has two grooves 210T formed therein, which are arranged along the ridge 210R and extend in the Y-axis direction.

[0113] The nitride-based semiconductor light-emitting device 200 according to this embodiment also provides the same effects as those of the nitride-based semiconductor light-emitting device 100 according to the first embodiment.

[0114] Furthermore, in this embodiment, the N-type first cladding layer 202 and the P-type cladding layer 210 contain Al. If the Al composition ratios of the N-type first cladding layer 202 and the P-type cladding layer 210 are Ync and Ypc, respectively, then: Ync>Ypc (10) Satisfy the relationship.

[0115] Here, when at least one of the N-type first cladding layer 202 and the P-type cladding layer 210 has a superlattice structure, the composition ratios Ync and Ypc indicate average Al composition ratios. For example, when the N-type first cladding layer 202 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 202. When the P-type cladding layer 210 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 210.

[0116] This allows the refractive index of the N-type first cladding layer 202 to be lower than the refractive index of the P-type cladding layer 210. Therefore, even if the film thickness of the P-type cladding layer 210 is reduced to reduce the operating voltage of the nitride-based semiconductor light-emitting device 200, the refractive index of the N-type first cladding layer 202 is lower than the refractive index of the P-type cladding layer 210, and therefore it is possible to prevent the peak of the light intensity distribution in the stacking direction from shifting in a direction approaching the N-type first cladding layer 202 from the active layer 105.

[0117] According to this embodiment, the effective refractive index difference ΔN is 2.5×10 -3 The peak position PS1 of the light intensity distribution in the stacking direction in the portion below the ridge 210R is 2.5 nm, ΔP is 6.4 nm, the light confinement coefficient in the active layer 105 is 1.45%, and the waveguide loss is 1.9 cm -1 It is possible to realize a nitride-based semiconductor light-emitting device 200 having the above structure.

[0118] (Embodiment 3) A nitride-based semiconductor light-emitting device according to embodiment 3 will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from nitride-based semiconductor light-emitting device 200 according to embodiment 2 in that a translucent conductive film is provided on contact layer 111 of ridge 210R. The nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIG. 20, focusing on the differences from nitride-based semiconductor light-emitting device 200 according to embodiment 2.

[0119] 20 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 300 according to this embodiment. As shown in FIG. 20, the nitride-based semiconductor light-emitting device 300 according to this embodiment includes a semiconductor stack 200S, a current blocking layer 112, a P-side electrode 113, an N-side electrode 114, and a translucent conductive film 320.

[0120] The translucent conductive film 320 according to this embodiment is disposed above the P-type cladding layer 210, and is a conductive film that transmits at least a portion of the light generated by the nitride-based semiconductor light-emitting element 300. As the translucent conductive film 320, 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.

[0121] The nitride-based semiconductor light-emitting device 300 according to this embodiment also provides the same effects as those of the nitride-based semiconductor light-emitting device 200 according to the second embodiment.

[0122] Furthermore, in this embodiment, since the light-transmitting conductive film 320 is provided above the P-type cladding layer 210, it is possible to reduce the loss of light propagating above the P-type cladding layer 210. In addition, it is possible to further reduce the film thickness of the P-type cladding layer 210, which further reduces the electrical resistance of the nitride-based semiconductor light-emitting element 300. As a result, it is possible to increase the slope efficiency of the nitride-based semiconductor light-emitting element 300 and reduce the operating voltage.

[0123] According to this embodiment, the effective refractive index difference ΔN is 2.1×10 -3 The peak position PS1 of the light intensity distribution in the stacking direction in the portion below the ridge 210R is 2.0 nm, ΔP is 5.7 nm, the light confinement coefficient in the active layer 105 is 1.47%, and the waveguide loss is 1.9 cm -1 It is possible to realize a nitride-based semiconductor light-emitting device 300 having the above structure.

[0124] (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 200 according to embodiment 2 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. 21A and 21B, focusing on the differences from nitride-based semiconductor light-emitting device 200 according to embodiment 2.

[0125] Fig. 21A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 400 according to this embodiment. Fig. 21B is a cross-sectional view showing the configuration of an active layer 405 included in the nitride-based semiconductor light-emitting device 400 according to this embodiment.

[0126] 21A , a 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, and an N-side electrode 114. The semiconductor stack 400S includes a substrate 101, an N-type first cladding layer 202, an N-type second cladding layer 103, an N-side guide layer 104, an active layer 405, a P-side first guide layer 106, a P-side second guide layer 107, an intermediate layer 108, an electron barrier layer 109, a P-type cladding layer 210, and a contact layer 111.

[0127] 21B, active layer 405 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.

[0128] The nitride-based semiconductor light-emitting device 400 according to this embodiment has the same effects as the nitride-based semiconductor light-emitting device 200 according to the second embodiment. In particular, in the nitride-based semiconductor light-emitting device 400 having the above-described single quantum well structure, the active layer 405 has a single well layer 105b. Thus, even in the nitride-based semiconductor light-emitting device 400 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 405 by the configuration of the N-side guide layer 104, the P-side first guide layer 106, the P-side second guide layer 107, etc. Therefore, the optical confinement factor can be increased.

[0129] According to this embodiment, the effective refractive index difference ΔN is 2.5×10 -3The peak position PS1 of the light intensity distribution in the stacking direction in the portion below the ridge 210R is 2.1 nm, ΔP is 6.3 nm, the light confinement coefficient in the active layer 405 is 0.72%, and the waveguide loss is 1.8 cm -1 It is possible to realize a nitride-based semiconductor light-emitting device 400 having the above structure. In this embodiment, the total film thickness of the active layer 405 is 8 nm smaller than that of the active layer 105 according to the second embodiment, and therefore the optical confinement factor is smaller than that of the second embodiment.

[0130] (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.

[0131] For example, in each of the above-described embodiments, the nitride-based semiconductor light-emitting element is a semiconductor laser element, but the nitride-based semiconductor light-emitting element is not limited to a semiconductor laser element. For example, the nitride-based semiconductor light-emitting element may be a superluminescent diode. In this case, the reflectance of the end face of the semiconductor stack included in the nitride-based semiconductor light-emitting element with respect to light emitted from the semiconductor stack may be 0.1% or less. Such a reflectance can be achieved, for example, by forming an anti-reflection film made of a dielectric multilayer film or the like on the end face. Alternatively, by using an inclined stripe structure in which the ridge serving as the waveguide intersects with the front end face at an angle of 5° or more from the normal direction of the front end face, the proportion of the component of the guided light reflected at the front end face that recouples with the waveguide and becomes guided light can be reduced to a small value of 0.1% or less.

[0132] Furthermore, in the first to third embodiments, the nitride-based semiconductor light-emitting device has a structure including two well layers as the active layer 105, but it may have a structure including only a single well layer. Even when the active layer includes only one high-refractive-index well layer, the use of the N-side guide layer 104, P-side first guide layer 106, and P-side second guide layer 107 of the present disclosure can improve 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.

[0133] 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. 22 . FIG. 22 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element 500 according to Modification 1. As shown in FIG. 22 , the nitride-based semiconductor light-emitting element 500 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. 22 , the nitride-based semiconductor light-emitting element 500 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 500 is not limited to three. The number of nitride-based semiconductor light-emitting elements 100 included in the nitride-based semiconductor light-emitting element 500 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 element 500 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 element 500, thereby realizing a high-output nitride-based semiconductor light-emitting element 500. Note that, although the nitride-based semiconductor light-emitting element 500 according to the first modification includes a plurality of nitride-based semiconductor light-emitting elements 100, the plurality of nitride-based semiconductor light-emitting elements included in the nitride-based semiconductor light-emitting element 500 is not limited thereto and may be nitride-based semiconductor light-emitting elements according to other embodiments.

[0134] 23, 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.

[0135] Furthermore, since the nitride-based semiconductor light-emitting element of the present invention has a small ΔN and can reduce the horizontal spread angle, even if the distance between the centers of the light-emitting portions 100E shown in Figures 22 and 23 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, this distance is 225 µm.

[0136] 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.

[0137] 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.

[0138] 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]

[0139] 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]

[0140] 100, 200, 300, 400, 500, 500a Nitride-based semiconductor light-emitting device 100E Light output part 100F, 100R end face 100T separation groove 100S, 200S, 400S Semiconductor laminate 101 Substrate 102, 202 N-type first cladding layer 103 N-type second cladding layer 104, 904 N-side guide layer 105, 405 active layer 106 P-side first guide layer 107 P-side second guide layer 108 Middle Class 109, 909 Electron barrier layer 110, 210 P-type cladding layer 110R, 210R Ridge 110T, 210T groove 111 Contact layer 112 Current Blocking Layer 113 P side electrode 114 N side electrode 320 Transparent conductive film 906 P side guide layer

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 disposed above the N-side guide layer; a P-side first guide layer disposed above the active layer; a P-side second guide layer disposed above the P-side first guide layer; a P-type clad layer disposed above the P-side second guide layer, the band gap energy of the P-side second guide layer is larger than the band gap energy of the N-side guide layer, the band gap energy of the N-side guide layer is equal to or greater than the band gap energy of the P-side first guide layer, When the thickness of the P-side first guide layer is Tp1, the thickness of the P-side second guide layer is Tp2, and the thickness of the N-side guide layer is Tn1, Tn1<Tp1+Tp2 Satisfy the relationship Nitride-based semiconductor light-emitting device.

2. The average refractive index of the P-side first guide layer and the P-side second guide layer is smaller than the average refractive index of the N-side guide layer. The nitride-based semiconductor light-emitting device according to claim 1 .

3. The P-side first guide layer is In Ｘｐ１ Ga １－Ｘｐ１ It consists of N, The N-side guide layer is In Ｘｎ１ Ga １－Ｘｎ１ It consists of N, Xn1≦Xp1 Satisfy the relationship The nitride-based semiconductor light-emitting device according to claim 1 or 2.

4. Xn1<Xp1 Satisfy the relationship The nitride-based semiconductor light-emitting device according to claim 3 .

5. The P-side second guide layer is In Ｘｐ２ Ga １－Ｘｐ２ It consists of N, Xp2<Xn1 Satisfy the relationship 5. The nitride-based semiconductor light-emitting device according to claim 3 or 4.

6. The barrier layer is made of In Ｘｂ Ga １－Ｘｂ It consists of N, Xp1<Xb Satisfy the relationship 6. The nitride-based semiconductor light-emitting device according to claim 3.

7. The band gap energy of the N-side guide layer is larger than the band gap energy of the P-side first guide layer.

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

8. Tp1<Tp2 Satisfy the relationship 8. The nitride-based semiconductor light-emitting device according to claim 1.

9. Tp1<Tn1 Satisfy the relationship 9. The nitride-based semiconductor light-emitting device according to claim 1.

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

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

11. 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. The nitride-based semiconductor light-emitting device according to any one of claims 1 to 10.

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

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

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

14. 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 13.

15. a transparent conductive film disposed above the P-type clad layer; The nitride-based semiconductor light-emitting device according to any one of claims 1 to 14.

16. 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 is larger than the band gap energy of the P-side second guide layer. The nitride-based semiconductor light-emitting device according to any one of claims 1 to 15.

17. 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 16.

18. 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 17.

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