Nitride semiconductor light-emitting diodes

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] This disclosure relates to nitride-based semiconductor light-emitting devices. [Background technology]

[0002] Conventionally, nitride-based semiconductor light-emitting elements have been used as light sources in processing equipment and the like. In light sources for processing equipment, there is a demand for even higher output power and higher efficiency. To improve the efficiency of nitride-based semiconductor light-emitting elements, techniques such as reducing the operating voltage are known (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-131019 [Overview of the project] [Problems that the invention aims to solve]

[0004] In nitride-based semiconductor light-emitting devices, reducing the thickness of the P-type cladding layer is effective in lowering 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 toward the N-type cladding layer. As a result, the light confinement coefficient in the active layer decreases, and consequently, the thermal saturation level of the light output decreases. Therefore, achieving high output in nitride-based semiconductor light-emitting devices becomes difficult.

[0005] This disclosure aims to solve these problems by providing a nitride-based semiconductor light-emitting element that can reduce the operating voltage and increase the photoconfinement coefficient in the active layer. [Means for solving the problem]

[0006] To solve the above problems, one embodiment of a nitride-based semiconductor light-emitting element according to the present disclosure is a nitride-based semiconductor light-emitting element comprising a semiconductor stack, which emits light from an end face perpendicular to the stacking direction of the semiconductor stack, wherein the semiconductor stack comprises an N-type first cladding layer, an N-side guide layer disposed above the N-type first cladding layer, an active layer disposed above the N-side guide layer and including a well layer and a barrier layer, having a quantum well structure, 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, and a P-type cladding layer disposed above the P-side second guide layer, wherein the band gap energy of the P-side second guide layer is greater than the band gap energy of the N-side guide layer, the band gap energy of the N-side guide layer is greater than or equal to the band gap energy of the P-side first guide layer, and if the film thickness of the P-side first guide layer is Tp1, the film thickness of the P-side second guide layer is Tp2, and the film thickness of the N-side guide layer is Tn1, Tn1 <Tp1+Tp2 It satisfies the following relationship.

[0007] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element according to this 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] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure, the P-side first guide layer is In Xp1 Ga 1-Xp1 It consists of N, and the N-side guide layer is In Xn1 Ga 1-Xn1 It consists of N, Xn1≦Xp1 The relationship may be satisfied.

[0009] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element relating to this disclosure, Xn1 <Xp1 The relationship may be satisfied.

[0010] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure, the P-side second guide layer is InXp2 Ga 1-Xp2 It consists of N, XP2 <Xn1 The relationship may be satisfied.

[0011] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element relating to this disclosure, the barrier layer is In Xb Ga 1-Xb It consists of N, XP1 <Xb The relationship may be satisfied.

[0012] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure, the band gap energy of the N-side guide layer may be greater than the band gap energy of the P-side first guide layer.

[0013] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element relating to this disclosure, Tp1 <Tp2 The relationship may be satisfied.

[0014] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element relating to this disclosure, Tp1 <Tn1 The relationship may be satisfied.

[0015] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure, the peak of the light intensity distribution in the stacking direction may be located in the active layer.

[0016] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure, the impurity concentration at the end of the P-type cladding layer closer to the active layer may be lower than the impurity concentration at the end of the P-type cladding layer further from the active layer.

[0017] Furthermore, one embodiment of a nitride-based semiconductor light-emitting element according to the present disclosure includes an electron barrier layer disposed between the P-side second guide layer and the P-type cladding layer, wherein the electron barrier layer has an Al composition change region in which the Al composition ratio increases monotonically as it moves away from the active layer.

[0018] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure, the N-type first cladding layer and the P-type cladding layer contain Al, and the Al composition ratios of the N-type first cladding layer and the P-type cladding layer are Ync and Ypc, respectively. Ync>Ypc The relationship may be satisfied.

[0019] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure, the thickness of the P-type cladding layer may be 460 nm or less.

[0020] Furthermore, one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure may include a translucent conductive film disposed above the P-type cladding layer.

[0021] Furthermore, one embodiment of the nitride-based semiconductor light-emitting element according to the present disclosure comprises an N-type second cladding layer disposed between the N-type first cladding layer and the N-side guide layer, wherein the band gap energy of the N-type second cladding layer may be smaller than the band gap energy of the N-type first cladding layer and larger than the band gap energy of the P-side second guide layer.

[0022] Furthermore, one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure may have a plurality of light-emitting elements arranged in an array.

[0023] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element according to this disclosure, the reflectance of the end face of the semiconductor laminate may be 0.1% or less. [Effects of the Invention]

[0024] According to this disclosure, it is possible to provide a nitride-based semiconductor light-emitting element that can reduce the operating voltage and increase the photoconfinement coefficient to the active layer. [Brief explanation of the drawing]

[0025] [Figure 1]Figure 1 is a schematic plan view showing the overall configuration of a nitride-based semiconductor light-emitting element according to Embodiment 1. [Figure 2A] Figure 2A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to Embodiment 1. [Figure 2B] Figure 2B is a schematic cross-sectional view showing the configuration of the active layer of the nitride-based semiconductor light-emitting element according to Embodiment 1. [Figure 3] Figure 3 is a schematic diagram showing an overview of the light intensity distribution in the stacking direction of a nitride-based semiconductor light-emitting element according to Embodiment 1. [Figure 4] Figure 4 is a graph showing the coordinates of the position in the stacking direction of the nitride-based semiconductor light-emitting element according to Embodiment 1. [Figure 5] Figure 5 is a schematic graph showing the bandgap energy distribution and light intensity distribution in the stacking direction in the lower part of the ridge of the nitride-based semiconductor light-emitting element of the comparative example. [Figure 6] Figure 6 is a schematic graph showing the bandgap energy distribution and light intensity distribution in the stacking direction in the lower part of the groove of the nitride-based semiconductor light-emitting element of the comparative example. [Figure 7] Figure 7 is a graph showing the simulation results of the light intensity distribution and refractive index distribution in the lower part of the ridge of the nitride-based semiconductor light-emitting element of Comparative Example 1. [Figure 8] Figure 8 is a graph showing the simulation results of the light intensity distribution and refractive index distribution in the lower part of the ridge of the nitride-based semiconductor light-emitting element of Comparative Example 2. [Figure 9] Figure 9 is a graph showing the simulation results of the light intensity distribution and refractive index distribution in the lower part of the ridge of the nitride-based semiconductor light-emitting element of Comparative Example 3. [Figure 10] Figure 10 is a graph showing the simulation results of the light intensity distribution and refractive index distribution in the lower part of the ridge of the nitride-based semiconductor light-emitting element of Comparative Example 4. [Figure 11] Figure 11 is a schematic graph showing the bandgap energy distribution and light intensity distribution in the stacking direction of a nitride-based semiconductor light-emitting element according to Embodiment 1. [Figure 12] Figure 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 according to Embodiment 1. [Figure 13] Figure 13 is a graph showing the simulation results of the relationship between the emission angle and light intensity of a nitride-based semiconductor light-emitting element according to Embodiment 1. [Figure 14] Figure 14 is a graph showing the simulation results of the IL characteristics of the nitride-based semiconductor light-emitting device according to Embodiment 1. [Figure 15] Figure 15 is a graph showing the simulation results 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 Embodiment 1 is 4%. [Figure 16] Figure 16 is a graph showing the simulation results 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 semiconductor light-emitting element according to Embodiment 1 is 0%. [Figure 17] Figure 17 is a graph showing the relationship between the film thickness of the P-side second guide layer, the film thickness of the P-type cladding layer, and each parameter in a comparative example of a nitride-based semiconductor light-emitting element. [Figure 18] Figure 18 is a graph showing the relationship between the film thickness of the P-side second guide layer, the film thickness of the P-type cladding layer, and each parameter of the nitride-based semiconductor light-emitting element according to Embodiment 1. [Figure 19] Figure 19 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to Embodiment 2. [Figure 20] Figure 20 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to Embodiment 3. [Figure 21A] Figure 21A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to Embodiment 4. [Figure 21B] Figure 21B is a cross-sectional view showing the configuration of the active layer of the nitride-based semiconductor light-emitting element according to Embodiment 4. [Figure 22]Figure 22 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to Modification 1. [Figure 23] Figure 23 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to Modification 2. [Modes for carrying out the invention]

[0026] The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are all specific examples of this disclosure. Therefore, the numerical values, shapes, materials, components, and their arrangement and connection configurations shown in the following embodiments are examples only and are not intended to limit this disclosure.

[0027] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Therefore, the scale and other aspects may not necessarily be consistent across all figures. In addition, the same reference numerals are used for substantially identical components in each figure, and redundant explanations are omitted or simplified.

[0028] Furthermore, in this specification, the terms "upper" and "lower" do not refer to the upward (vertically upward) and downward (vertically downward) directions in absolute spatial perception, but rather are used as terms defined by the relative positional relationship based on the stacking order in a stacked configuration. Moreover, the terms "upper" and "lower" apply not only when two components are spaced apart and another component exists between them, but also when two components are placed in contact with each other.

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

[0030] [1-1. Overall Structure] First, the overall configuration of the nitride-based semiconductor light-emitting element according to this embodiment will be described using Figures 1, 2A, and 2B. Figures 1 and 2A are schematic plan and cross-sectional views, respectively, showing the overall configuration of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Figure 2A shows a cross-section along the line IIA-IIA in Figure 1. Figure 2B is a schematic cross-sectional view showing the configuration of the active layer 105 provided in the nitride-based semiconductor light-emitting element 100 according to this embodiment. Note that each figure shows mutually orthogonal X, Y, and Z axes. The X, Y, and Z axes are in a right-handed orthogonal coordinate system. The stacking direction of the nitride-based semiconductor light-emitting element 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 Figure 2A, the nitride-based semiconductor light-emitting element 100 comprises a semiconductor stack 100S including a nitride-based semiconductor layer, and emits light from an end face 100F (see Figure 1) perpendicular to the stacking direction (i.e., the Z-axis direction) of the semiconductor stack 100S. In this embodiment, the nitride-based semiconductor light-emitting element 100 is a semiconductor laser element having two end faces 100F and 100R that form a resonator. End face 100F is the front end face from which laser light is emitted, and end face 100R is the rear end face with a higher reflectivity than end face 100F. In this embodiment, the reflectivity of end faces 100F and 100R is 16% and 95%, respectively. The resonator length of the nitride-based semiconductor light-emitting element 100 according to this embodiment (i.e., the distance between end face 100F and end face 100R) is approximately 1200 μm.

[0032] As shown in Figure 2A, the nitride-based semiconductor light-emitting element 100 comprises a semiconductor laminate 100S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor laminate 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 the base of the nitride-based semiconductor light-emitting device 100. In the present 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 is a layer having a refractive index smaller than that of the active layer 105 and a larger bandgap energy. In the present embodiment, the N-type first cladding layer 102 is an N-type Al 0.035 Ga 0.965 N layer with a thickness of 1200 nm. The N-type first cladding layer 102 is doped with Si at a concentration of 1×10 18 cm -3 as an impurity.

[0035] The N-type second cladding layer 103 is an example of an N-type cladding layer disposed above the substrate 101. In the present 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 refractive index smaller than that of the active layer 105 and a larger bandgap energy. In the present embodiment, the N-type second cladding layer 103 is an N-type GaN layer with a thickness of 100 nm. The N-type second cladding layer 103 is doped with Si at a concentration of 1×10 18 cm -3 as an impurity.

[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 refractive index larger than those of the N-type first cladding layer 102 and the N-type second cladding layer 103 and a smaller bandgap energy. In the present embodiment, the N-side guide layer 104 is an undoped In 0.04 Ga 0.96 N layer with a thickness of 160 nm.

[0037] The active layer 105 is a light-emitting layer disposed above the N-side guide layer 104 and having a quantum well structure. In the present embodiment, as shown in FIG. 2B, the active layer 105 has well layers 105b and 105d and barrier layers 105a, 105c, and 105e.

[0038] The barrier layer 105a is positioned above the N-side guide layer 104 and functions as a barrier to the quantum well structure. In this embodiment, the barrier layer 105a is an undoped In layer with a thickness of 7 nm. 0.05 Ga 0.95 It is an N-layer structure.

[0039] The well layer 105b is positioned above the barrier layer 105a and functions as a well in the quantum well structure. The well layer 105b is positioned between the barrier layer 105a and the barrier layer 105c. In this embodiment, the well layer 105b is an undoped In 0.18 Ga 0.82 It is an N-layer structure.

[0040] The barrier layer 105c is positioned above the well layer 105b and functions as a barrier to the quantum well structure. In this embodiment, the barrier layer 105c is an undoped In layer with a thickness of 7 nm. 0.05 Ga 0.95 It is an N-layer structure.

[0041] The well layer 105d is positioned above the barrier layer 105c and functions as a well in the quantum well structure. The well layer 105d is positioned between the barrier layer 105c and the barrier layer 105e. In this embodiment, the well layer 105d is an undoped In 0.18 Ga 0.82 It is an N-layer structure.

[0042] The barrier layer 105e is positioned above the well layer 105d and functions as a barrier to the quantum well structure. In this embodiment, the barrier layer 105e is an undoped In layer with a thickness of 5 nm. 0.05 Ga 0.95 It is an N-layer structure.

[0043] The P-side first guide layer 106 is an optical guide layer positioned above the active layer 105. The P-side first guide layer 106 has a higher refractive index and a lower bandgap energy than the P-type cladding layer 110. In this embodiment, the P-side first guide layer 106 is an undoped In-type cladding layer with a film thickness of 80 nm. 0.045Ga 0.955 It is an N-layer structure.

[0044] The P-side second guide layer 107 is an optical guide layer positioned above the P-side first guide layer 106. The P-side second guide layer 107 has a higher refractive index and a lower bandgap energy than the P-type cladding layer 110. In this embodiment, the P-side second guide layer 107 is an undoped In-type cladding layer with a film thickness of 195 nm. 0.01 Ga 0.99 It is an N-layer structure.

[0045] The intermediate layer 108 is a layer positioned above the active layer 105. In this embodiment, the intermediate layer 108 is positioned between the P-side second guide layer 107 and the electron barrier layer 109, reducing stress caused by the difference in lattice constants between the P-side second guide layer 107 and the electron barrier layer 109. This suppresses the occurrence of crystal defects in the nitride 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 positioned 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 positioned 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 increases monotonically as it approaches the P-type cladding layer 110. Here, the configuration in which the Al composition ratio increases monotonically also includes a configuration in which the Al composition ratio is constant in the stacking direction. For example, the configuration in which the Al composition ratio increases monotonically also includes a configuration in which the Al composition ratio increases in a step-like manner. 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 of change in the stacking direction. Specifically, the electron barrier layer 109 has Al near the interface with the intermediate layer 108. 0.02 Ga 0.98 It has a composition represented by N, and as it approaches the P-type cladding layer 110, the Al composition ratio increases monotonically, and near the interface with the P-type cladding layer 110, Al 0.36 Ga0.64 It has a composition represented by N. The electron barrier layer 109 contains impurities at a concentration of 1 × 10⁻⁶. 19 cm -3 It is doped with magnesium.

[0047] The electron barrier layer 109 suppresses electron leakage from the active layer 105 to the P-type cladding layer 110. Furthermore, because the electron barrier layer 109 has an Al composition change region that increases monotonically with the Al composition ratio, the potential barrier of the valence band of the electron barrier layer 109 can be reduced compared to the case where the Al composition ratio is uniform. Consequently, holes can more easily flow from the P-type cladding layer 110 to the active layer 105. Therefore, as in this embodiment, even when the total film thickness of the undoped layers, the P-side first guide layer 106 and the P-side second guide layer 107, is large, the increase in the electrical resistance of the nitride semiconductor light-emitting element 100 can be suppressed. This allows for a reduction in the operating voltage of the nitride semiconductor light-emitting element 100. In addition, since self-heating during operation of the nitride semiconductor light-emitting element 100 can be reduced, the temperature characteristics of the nitride semiconductor light-emitting element 100 can be improved. Consequently, high-power operation of the nitride semiconductor light-emitting element 100 becomes possible.

[0048] The P-type cladding layer 110 is a P-type cladding layer positioned above the active layer 105. In this embodiment, the P-type cladding layer 110 is positioned 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 bandgap energy than the active layer 105. The thickness of the P-type cladding layer 110 may be 460 nm or less. This suppresses the electrical resistance of the nitride semiconductor light-emitting element 100. Therefore, the operating voltage of the nitride semiconductor light-emitting element 100 can be reduced. Furthermore, since self-heating during operation of the nitride semiconductor light-emitting element 100 can be reduced, the temperature characteristics of the nitride semiconductor light-emitting element 100 can be improved. Therefore, high-power operation of the nitride semiconductor light-emitting element 100 becomes possible. In the nitride semiconductor light-emitting element 100 according to this embodiment, in order for the P-type cladding layer 110 to fully exhibit its function as a cladding layer, the thickness of the P-type cladding layer 110 should be 200 nm or more. Furthermore, 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 made of P-type Al with a thickness of 450 nm. 0.035 Ga 0.965 This is an N layer. The P-type cladding layer 110 is doped with Mg as an impurity. Furthermore, 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 further away from the active layer 105. Specifically, the concentration of the P-type cladding layer 110 located closer to the active layer 105 is 2 × 10⁻¹⁰. 18 cm -3 P-type Al with Mg doped, 150 nm film thickness. 0.035 Ga 0.965 The N layer and the concentration 1 × 10 located on the side furthest from the active layer 105. 19 cm -3 P-type Al with Mg doped, 300 nm film thickness. 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 element 100. Two grooves 110T are also 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 Figure 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 positioned above the P-type cladding layer 110 and is a layer that makes ohmic contact with the P-side electrode 113. In this embodiment, the contact layer 111 is a P-type GaN layer with a thickness of 100 nm. The contact layer 111 contains impurities with a concentration of 1 × 10⁻⁶ 20 cm -3 It is doped with magnesium.

[0051] The current blocking layer 112 is positioned 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 positioned on the upper surface of the P-type cladding layer 110, in a region other than the upper surface of the ridge 110R. In this embodiment, the current blocking layer 112 is an SiO2 layer.

[0052] The P-side electrode 113 is a conductive layer positioned above the contact layer 111. In this embodiment, the P-side electrode 113 is positioned above the contact layer 111 and the current blocking layer 112. The P-side electrode 113 is, for example, a monolayer or multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt, and Au.

[0053] The N-side electrode 114 is a conductive layer positioned below the substrate 101 (i.e., on the main surface of the substrate 101 opposite to the main surface of the semiconductor laminate 100S where the substrate 101 and other components are located). The N-side electrode 114 is, for example, a monolayer or multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt, and Au.

[0054] As a result of having the above configuration, the nitride-based semiconductor light-emitting element 100 generates an effective refractive index difference ΔN between the lower portion of the ridge 110R and the lower portion of the groove 110T, as shown in Figure 2A. This allows the light generated in the lower portion of the ridge 110R of the active layer 105 to be confined in the horizontal direction (i.e., in the X-axis direction).

[0055] [1-2. Light intensity distribution and stability of light output] Next, the light intensity distribution and light output stability of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be described.

[0056] First, the light intensity distribution in the stacking direction (Z-axis direction in each figure) of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be explained using Figure 3. Figure 3 is a schematic diagram showing the outline of the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Figure 3 shows a schematic cross-sectional view of the nitride-based semiconductor light-emitting element 100 and a graph showing the outline of the light intensity distribution in the stacking direction at positions corresponding to the ridge 110R and groove 110T, respectively.

[0057] In general, in nitride-based semiconductor light-emitting devices, light is generated in the active layer, but the light intensity distribution in the stacking direction depends on the stacking structure, and the peak of the light intensity distribution is not necessarily located in the active layer. Furthermore, in the nitride-based semiconductor light-emitting device 100 according to this embodiment, the stacking structure differs between the lower part of the ridge 110R and the lower part of the groove 110T, so the light intensity distribution also differs between the lower part of the ridge 110R and the lower part of the groove 110T. As shown in Figure 3, the peak position of the light intensity distribution in the stacking direction at the center of the horizontal direction (i.e., the X-axis direction) of the lower part of the ridge 110R is denoted as PS1. The peak position of the light intensity distribution in the stacking direction at the lower part of the groove 110T is denoted as PS2. Here, positions PS1 and PS2 will be explained using Figure 4. Figure 4 is a graph showing the coordinates of the positions in the stacking direction of the nitride-based semiconductor light-emitting device 100 according to this embodiment. As shown in Figure 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 (towards the N-side guide layer 104) is set to the negative direction of the coordinate, and the upward direction (towards the P-side first guide layer 106) is set to the positive direction of the coordinate. Furthermore, the absolute value of the difference between position PS1 and position PS2 is defined as the difference in peak positions ΔP.

[0058] In the nitride-based semiconductor light-emitting element 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 semiconductor light-emitting elements having such a configuration, the peak position of the light intensity distribution in the stacking direction shifts in the direction from the active layer towards the N-type cladding layer. As a result, the light confinement coefficient in the active layer decreases, and consequently, the thermal saturation level of the light output decreases. Therefore, it becomes difficult to operate the semiconductor light-emitting element at high power. In this embodiment, 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, and the band gap energy of the N-side guide layer 104 is greater than or equal to the band gap energy of the P-side first guide layer 106. Furthermore, if the film thickness of the P-side first guide layer 106 is Tp1, the film thickness of the P-side second guide layer 107 is Tp2, and the film thickness of the N-side guide layer 104 is Tn1, Tn1 <Tp1+Tp2 (1) It satisfies the following relationship.

[0059] Thus, in the nitride semiconductor light-emitting device 100, the band gap energy of the N-side guide layer 104 is greater than or equal to the band gap energy of the P-side first guide layer 106. Specifically, the P-side first guide layer 106 is In Xp1 Ga 1-Xp1 It consists of N, and the N-side guide layer 104 is In Xn1 Ga 1-Xn1 It consists of N, Xn1≦Xp1 (2) This satisfies the following relationship. Therefore, the refractive index of the N-side guide layer 104 is less than or equal to the refractive index of the P-side first guide layer 106. As a result, for example, compared to the case where the refractive index of the N-side guide layer 104 is greater than the refractive index of the P-side first guide layer 106, the light intensity distribution can be shifted in a direction closer to the P-side first guide layer 106 from the active layer 105.

[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 described above are as follows: Xn1 <Xp1 (3) The relationship is satisfied. More specifically, the N-side guide layer 104 is In 0.04 Ga 0.96 It is an N layer, and the P-side first guide layer 106 is In 0.045 Ga 0.955 This is an N-layer. In the 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 be shifted from the active layer 105 towards the P-side first guide layer 106, for example, compared to the case where the refractive index of the N-side guide layer 104 is greater than or equal to the refractive index of the P-side first guide layer 106.

[0061] Furthermore, as described above, 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 greater than the film thickness Tn1 of the N-side guide layer 104. In this way, by making the sum of the film 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 film thickness Tn1 of the N-side guide layer 104, the light intensity distribution can be shifted in a direction closer to the P-side first guide layer 106 from the active layer 105 compared to the case where the sum of the film thicknesses of the P-side first guide layer 106 and the P-side second guide layer 107 is less than or equal to the film thickness Tn1 of the N-side guide layer 104. Therefore, it is possible to suppress the shift of the peak of the light intensity distribution in the stacking direction toward the N-type second cladding layer 103 from the active layer 105. 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. In other words, 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 prevents the light intensity distribution from shifting too far in the direction of moving from the active layer 105 towards the P-type cladding layer 110.

[0062] Furthermore, as mentioned above, 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. Specifically, the P-side second guide layer 107 is In Xp2 Ga 1-Xp2 It consists of N, 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 as follows: XP2 <Xn1 (4) The relationship is satisfied. More specifically, the N-side guide layer 104 is In 0.04 Ga 0.96 It is an N layer, and the P-side second guide layer 107 is In 0.01 Ga 0.99 This 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 prevents the light intensity distribution from shifting too far in the direction of moving from the active layer 105 towards the P-type cladding layer 110.

[0063] Furthermore, in this embodiment, the barrier layers 105a, 105c, and 105e of the active layer 105 are In Xb Ga 1-Xb It consists of N, and the In composition ratios Xb and Xp1 of each barrier layer and the first guide layer 106 on the P side are as follows: XP1 <Xb (5) This satisfies the following relationship. As a result, the refractive index of each barrier layer can be made larger than that 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 located in the active layer 105. In addition, it is possible to suppress the light intensity distribution from shifting too far in the direction toward the P-type cladding layer 110 from the active layer 105.

[0064] Furthermore, 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 suppresses excessive shift in the light intensity distribution from the active layer 105 towards the P-type cladding layer 110.

[0065] Furthermore, in this embodiment, the film 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) This satisfies the following relationship. In this way, by making the thickness of the P-side first guide layer 106, which has a small bandgap energy, i.e., a large refractive index, relatively small, it is possible to suppress the light intensity distribution from shifting too far in the direction toward the P-type cladding layer 110 from the active layer 105. Furthermore, by making the thickness of the P-side first guide layer 106, which has a small In composition ratio, relatively small, it is possible to avoid placing the P-side first guide layer 106, which has a small In composition ratio and a large thickness, near the well layers 105b and 105d, which have the largest In composition ratio in the semiconductor laminate 100S. Therefore, the occurrence of lattice defects can be suppressed.

[0066] Furthermore, in this embodiment, the film thicknesses Tp1 and Tn1 of the P-side first guide layer 106 and the N-side guide layer 104 are as follows: Tp1 <Tn1 (7) This satisfies the following relationship. In this way, by making the 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 thickness of the N-side guide layer 104, it is possible to suppress the light intensity distribution from shifting too far in the direction of moving from the active layer 105 towards the P-type cladding layer 110.

[0067] Furthermore, in this embodiment, the bandgap energy of the N-type second cladding layer 103 is smaller than the bandgap energy of the N-type first cladding layer 102, but larger than the bandgap energy of the P-side second guide layer 107. By placing the N-type second cladding layer 103, which has a smaller bandgap energy than the N-type first cladding layer 102, that is, a larger refractive index, between the N-type first cladding layer 102 and the N-side guide layer 104, it is possible to suppress the light intensity distribution from shifting too far towards the P-type cladding layer 110 from the active layer 105. Additionally, by making the bandgap energy of the N-type second cladding layer 103 larger than the bandgap energy of the P-side second guide layer 107, it is possible to suppress the light intensity distribution from shifting too far towards the N-type second cladding layer 103 from the active layer 105.

[0068] With the above configuration, in this embodiment, the position PS1 of the peak of the light intensity distribution in the stacking direction in the lower part of 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. As a result, the light confinement coefficient in the active layer 105 can be increased to about 1.45%.

[0069] As described above, the nitride-based semiconductor light-emitting element 100 according to this embodiment allows the peak of the light intensity distribution in the stacking direction to be located in the active layer 105. Note that the statement that the peak of the light intensity distribution in the stacking direction is located in the active layer 105 means that at least one position in the horizontal direction of the nitride-based semiconductor light-emitting element 100 has the peak of the light intensity distribution in the stacking direction located in the active layer 105, and is not limited to the state where the peak of the light intensity distribution in the stacking direction is located in the active layer 105 at all positions in the horizontal direction.

[0070] As in this embodiment, if the peak of the light intensity distribution in the stacking direction is located in the active layer 105, the proportion of light located in the P-type cladding layer 110 may increase compared to when the peak of the light intensity distribution is located 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, there is a concern that the proportion of light located in the P-type cladding layer 110 will increase as the proportion of light located in the P-type cladding layer 110 increases. However, in this embodiment, the P-side first guide layer 106 and the P-side second guide layer 107 are undoped, 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 made relatively large, thereby increasing the proportion of the light intensity distribution located in the undoped layer. Therefore, the increase in free carrier loss can be suppressed. Specifically, in this embodiment, the waveguide loss is 1.6 cm -1 It can be suppressed to a certain extent.

[0071] Furthermore, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, in order to reduce the divergence angle of the emitted light in the horizontal direction (i.e., the X-axis direction), the effective refractive index difference ΔN between the lower part of the ridge 110R and the lower part of the groove 110T is set to be relatively small. Specifically, the effective refractive index difference ΔN is set by adjusting the distance dp (see Figure 2A) between the current blocking layer 112 and the active layer 105. Here, the larger the distance dp, the smaller the effective refractive index difference ΔN becomes. In this embodiment, the effective refractive index difference ΔN is 2.4 × 10⁻⁶. -3 It is approximately such that, therefore, in this embodiment, the effective refractive index difference ΔN is 2.4 × 10 -3 In cases where the ridge is larger, 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 contained in the light emitted from the nitride semiconductor light-emitting element 100 is relatively large. Consequently, the change in the number of modes and the change in the optical confinement coefficient to the active layer 105 due to intermode coupling are relatively large. Therefore, when the number of modes increases or decreases and intermode coupling occurs in the nitride semiconductor light-emitting element 100, the linearity of the optical output characteristics with respect to the supplied current (so-called IL characteristics) decreases. In other words, a non-linear portion (so-called kink) occurs in the graph showing the IL characteristics. Consequently, the stability of the optical output of the nitride semiconductor light-emitting element 100 may decrease.

[0072] The decrease in optical output stability described above will be explained below. In the nitride semiconductor light-emitting element 100, the optical intensity distribution in the lower part of the ridge 110R is dominated by the fundamental mode (i.e., the 0th-order mode), while the optical intensity distribution in the lower part of the groove 110T is dominated by higher-order modes. Therefore, when the difference ΔP between the peak position PS1 of the optical intensity distribution in the stacking direction in the lower part of the ridge 110R of the nitride semiconductor light-emitting element 100 and the peak position PS2 of the optical intensity distribution in the stacking direction in the lower part of the groove 110T is large, the number of modes increases or decreases, and intermode coupling occurs, causing the optical confinement coefficient in the active layer 105 to fluctuate, thus reducing the stability of the optical output.

[0073] For example, if higher-order modes decrease, the peak of the light intensity distribution, which is the sum of the light intensity distributions in the lower parts of both the ridge 110R and the groove 110T, shifts to a position closer to position PS1. Therefore, the larger the difference ΔP between position PS1 and position PS2, the greater the fluctuation in the light confinement coefficient in the active layer 105 when the number of modes changes. Consequently, the stability of the light output decreases.

[0074] In the nitride-based semiconductor light-emitting element 100 according to this embodiment, since it includes an N-side guide layer 104 having the configuration described above, a P-side first guide layer 106, and a P-side second guide layer 107, the peak of the light intensity distribution can be positioned in the active layer 105 in both the lower portion of the ridge 110R and the lower portion of the groove 110T. In other words, the difference ΔP between the positions PS1 and PS2 of the light intensity distribution peak can be reduced. As a result, even if the number of modes increases or decreases, or intermode coupling occurs, fluctuations in the position of the peak of the light intensity distribution, which is the sum of the light intensity distributions in the lower portions of both the ridge 110R and the groove 110T, in the stacking direction are suppressed. Therefore, the stability of the light output can be improved.

[0075] As mentioned above, in order to set the effective refractive index difference ΔN to a relatively small value, the distance dp is set to a relatively large value. When setting the distance dp, if the lower end of the ridge 110R (i.e., the bottom of the groove 110T) is positioned below the electron barrier layer 109, the electron barrier layer 109 has a large bandgap energy, so holes injected from the contact layer 111 are more likely to leak out of the ridge 110R from the sidewall when passing through the electron barrier layer 109. As a result, the holes flow downwards to the groove 110T. Consequently, the light distribution intensity in the active layer 105 below the groove 110T is small, which reduces the probability of luminescent recombination between electrons and holes injected into the active layer 105, and increases non-luminescent recombination. Consequently, the nitride semiconductor light-emitting element 100 is more likely to degrade. For this reason, the lower end of the ridge 110R is set to be positioned above the electron barrier layer 109. Furthermore, if the distance dc (see Figure 2A) from the lower end of the ridge 110R to the electron barrier layer 109 becomes too large, holes will flow from the ridge 110R into the space between the groove 110T and the electron barrier layer 109, resulting in leakage current. To suppress this increase in leakage current, the distance dc is set to the smallest possible value.

[0076] [1-3. Effects] The effects of the nitride-based semiconductor light-emitting element 100 according to the above-described embodiment will be explained using Figures 5 to 12, in comparison with the nitride-based semiconductor light-emitting elements of comparative examples. Figures 5 and 6 are schematic graphs showing the bandgap energy distribution and light intensity distribution in the stacking direction in the lower portion of the ridge 110R and the lower portion of the groove 110T of the nitride-based semiconductor light-emitting elements of comparative examples, respectively. Graphs (a) to (c) in Figure 5 show the bandgap energy distribution and light intensity distribution in the lower portion of the ridge 110R of the nitride-based semiconductor light-emitting elements of comparative examples 1 to 3, respectively. Graphs (a) to (c) in Figure 6 show the bandgap energy distribution and light intensity distribution in the lower portion of the groove 110T of the nitride-based semiconductor light-emitting elements of comparative examples 1 to 3, respectively. Figures 7 to 10 are graphs showing the simulation results of the light intensity distribution and refractive index distribution in the lower portion of the ridge 110R of the nitride-based semiconductor light-emitting elements of comparative examples 1 to 4, respectively. Figure 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) of Figure 11 show the bandgap energy distribution and light intensity distribution in the lower portion of the ridge 110R and the lower portion of the groove 110T of the nitride-based semiconductor light-emitting element 100, respectively. Figure 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] In Figures 5, 6, and 11, the horizontal axis indicates the stacking direction, and the vertical axis indicates the bandgap energy and light intensity. In Figures 7-10 and 12, the horizontal axis indicates the position in the stacking direction, and the left and right vertical axes indicate light intensity and refractive index, respectively. In Figures 7-10 and 12, the light intensity distribution in the stacking direction in the lower part of groove 110T is also shown by a dotted line.

[0078] The nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3, shown in Figures 5 to 9, differ from the nitride-based semiconductor light-emitting device 100 according to this embodiment in the configuration of the N-side guide layer and the 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 semiconductor light-emitting element of Comparative Example 1, the film thickness Tn0 of the N-side guide layer 904 is greater than the film thickness Tp0 of the P-side guide layer 906. Specifically, the N-side guide layer 904 has a film thickness of 340 nm. 0.03 Ga 0.97 It is an N layer, and the P-side guide layer 906 is made of In with a film thickness of 100 nm. 0.03 Ga 0.97 It is an N layer. In the nitride semiconductor light-emitting element of Comparative Example 2, the film thickness Tn0 of the N-side guide layer 904 is equal to the film 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 In 0.03 Ga 0.97 It is an N layer. In the nitride semiconductor light-emitting element of Comparative Example 3, the film thickness Tn0 of the N-side guide layer 904 is smaller than the film thickness Tp0 of the P-side guide layer 906. Specifically, the N-side guide layer 904 has a film thickness of 100 nm. 0.03 Ga 0.97 It is an N layer, and the P-side guide layer 906 is made of In with a film thickness of 340 nm. 0.03 Ga 0.97 It is an N-layer structure.

[0080] The nitride-based semiconductor light-emitting element of Comparative Example 4 shown in Figure 10 differs from the nitride-based semiconductor light-emitting element 100 according to this embodiment in the configuration of the N-side guide layer and the P-side guide layer. The nitride-based semiconductor light-emitting element 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 element 100 according to this embodiment. In the nitride-based semiconductor light-emitting element of Comparative Example 4, the band gap energy of the P-side second guide layer is greater 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. The film thickness Tp1 of the P-side first guide layer, the film thickness Tp2 of the P-side second guide layer and the film thickness Tn1 of the N-side first guide layer are as follows: Tn1 = Tp1 + Tp2, (8) And, Tp1 = Tp2 (9) This holds true. Specifically, the N-side guide layer is made of In film with a thickness of 220 nm. 0.03 Ga 0.97 It is an N layer, and the first guide layer on the P side is an In layer with a film thickness of 110 nm. 0.03 Ga 0.97 It is an N layer, and the second guide layer on the P side is an In layer with a thickness of 110 nm. 0.01 Ga 0.99 It is an N-layer structure.

[0081] Furthermore, in the simulation, the Al composition ratio of the electron barrier layer 909 in Comparative Examples 1-4 and the electron barrier layer 109 in this embodiment are assumed 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 Comparative Examples 1 to 4 and each nitride-based semiconductor light-emitting device according to this embodiment are shown in Table 1 below, and the numerical values ​​obtained from the simulations are shown in Table 2 below.

[0083] [Table 1]

[0084] [Table 2]

[0085] Table 2 shows the distance dc from the lower end of ridge 110R to the electron barrier layer 109, the optical confinement coefficient, waveguide loss, effective refractive index difference ΔN, the peak position PS1 of the optical intensity distribution in the stacking direction at the horizontal center of the lower part of ridge 110R, and the absolute value ΔP of the difference between peak position PS1 and peak position PS2 in the stacking direction of the waveguide limit mode. Note that the distance dc is calculated by multiplying the effective refractive index difference by 2.8 × 10⁻⁶. -3 The following distances are set. Furthermore, the waveguide limit mode refers to the highest-order mode that can propagate in each nitride-based semiconductor light-emitting element. The peak position of the waveguide limit mode in the stacking direction is a numerical value that corresponds to the peak position of the light intensity distribution in the lower part of groove 110T where higher-order modes are dominant.

[0086] In the nitride-based semiconductor light-emitting element of Comparative Example 1, as shown in graphs (a) of Figures 5 and 6, and in Figure 7, the thickness of the N-side guide layer 904 is greater than that of the P-side guide layer 906, so the peak of the light intensity distribution is located within the N-side guide layer 904. Therefore, the light confinement coefficient to the active layer 105 is low, and the thermal saturation level of the light output is low. Also, because the thickness of the P-side guide layer 906 is small, the distance dp between the lower end of the ridge 110R and the active layer 105 becomes small. Consequently, the effective refractive index difference ΔN becomes large, and the horizontal divergence angle of the emitted light becomes large. Furthermore, in order to reduce the effective refractive index difference ΔN, the distance dc from the lower end of the ridge 110R to the electron barrier layer 909 needs to be relatively large at 80 nm. Therefore, the leakage current mentioned above increases, and the oscillation threshold current of the nitride-based semiconductor light-emitting element increases.

[0087] Furthermore, in the nitride-based semiconductor light-emitting element of Comparative Example 1, the thickness of the P-side guide layer 906 is relatively small, so the influence on the light intensity distribution of the current blocking layer 112 placed in the groove 110T is relatively large. For this reason, the difference ΔP between the peak position of the light intensity distribution in the stacking direction in the lower part of the ridge 110R and the peak position of the light intensity distribution in the stacking direction in the lower part of the groove 110T is relatively large (see Figure 7 in particular). For this reason, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting element of Comparative Example 1 is low.

[0088] In the nitride-based semiconductor light-emitting element of Comparative Example 2, as shown in graphs (b) of Figures 5 and 6, and in Figure 8, the thickness of the N-side guide layer 904 is equal to the thickness of the P-side guide layer 906. Therefore, in the lower part of the ridge 110R, the peak of the light intensity distribution is located within the active layer 105. Consequently, the light confinement coefficient to the active layer 105 is high in the lower part of the ridge 110R. However, in the nitride-based semiconductor light-emitting element of Comparative Example 2, the thickness of the P-side guide layer 906 is not large, so it is affected by the light intensity distribution of the current blocking layer 112 located in the groove 110T. In the lower part of the groove 110T, the peak of the light intensity distribution in the stacking direction is located in the N-side guide layer 904, resulting in a low light confinement coefficient in the lower part of the groove 110T. Furthermore, the difference ΔP between the peak position of the light intensity distribution in the stacking direction in the lower part of the ridge 110R and the peak position of the light intensity distribution in the stacking direction in the lower part of the groove 110T is relatively large. Therefore, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting element in Comparative Example 2 is low.

[0089] In the nitride-based semiconductor light-emitting element of Comparative Example 3, as shown in the graphs (c) of Figures 5 and 6, and in Figure 9, the thickness of the N-side guide layer 904 is smaller than the thickness of the P-side guide layer 906, so the peak of the light intensity distribution is located within the P-side guide layer 906. As a result, the light confinement coefficient to the active layer 105 is low, and the thermal saturation level of the light output is low.

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

[0091] In the nitride-based semiconductor light-emitting element of Comparative Example 4, the thickness of the P-side second guide layer is smaller compared to the nitride-based semiconductor light-emitting element 100 according to this embodiment. As a result, as shown in Figure 10, the influence of the current blocking layer 112 on the light intensity distribution is relatively large. Therefore, the difference ΔP between the peak position of the light intensity distribution in the stacking direction in the portion below the ridge 110R and the peak position of the light intensity distribution in the stacking direction in the portion below the groove 110T is relatively large. Consequently, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting element of Comparative Example 4 is low.

[0092] Compared to the comparative examples described above, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, 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 greater than the film thickness Tn1 of the N-side guide layer 104, thus reducing the effective refractive index difference ΔN. Therefore, the horizontal divergence angle of the emitted light can be reduced. In addition, the distance dc from the lower 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 of each comparative example. Therefore, the leakage current flowing between the lower end of the ridge 110R and the electron barrier layer 109 can be suppressed, thus reducing the oscillation threshold current.

[0093] Furthermore, in this embodiment, as shown in Figures 11 and 12, the peak of the light intensity distribution in the stacking direction can be positioned in the active layer 105 in both the lower portion of the ridge 110R and the lower portion of the groove 110T. Therefore, the light confinement coefficient can be increased compared to the comparative examples. In addition, the difference ΔP in peak position can be reduced, thereby improving the linearity of the IL characteristics.

[0094] Furthermore, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, since the peak of the light intensity distribution in the stacking direction is located in the active layer 105, the light intensity in the P-type cladding layer 110 is greater than in the case where the peak of the light intensity distribution is located in the N-side guide layer, as in Comparative Example 1. Therefore, there is a concern that the 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, will increase. 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 made relatively large, thereby increasing the proportion of the light intensity distribution located in the undoped layer. Therefore, the increase in free carrier loss can be suppressed. 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 further away from the active layer 105. Therefore, 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 element 100 according to this embodiment will be explained using Figures 13 and 14. Figure 13 is a graph showing the simulation results of the relationship between the radiation angle and light intensity of the nitride-based semiconductor light-emitting element 100 according to this embodiment. As a comparative example, Figure 13 shows an effective refractive index difference ΔN of 7 × 10 -3 The relationship between the emission angle and light intensity of the nitride-based semiconductor light-emitting element of the comparative example is also shown. Figure 14 is a graph showing the simulation results of the IL characteristics of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Figure 14 also shows the IL characteristics of the nitride-based semiconductor light-emitting element of comparative example 2.

[0096] As shown in Figure 13, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, the effective refractive index difference ΔN is 2.8 × 10 -3Therefore, the beam divergence angle in the horizontal direction can be reduced compared to the nitride-based semiconductor light-emitting element of the comparative example. In the example shown in Figure 13, the peak is 1 / e 2 The overall beam width required for this intensity can be reduced to approximately 9.3°.

[0097] As shown in Figure 14, the nitride-based semiconductor light-emitting element 100 according to this embodiment can obtain IL characteristics that are more linear than those of the nitride-based semiconductor light-emitting element of the comparative example. In addition, a higher slope efficiency (approximately 1.9 W / A) can be obtained than that of 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 explained in detail using Figures 15 and 16. Figure 15 is a graph showing the simulation results 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 semiconductor light-emitting element 100 according to this embodiment is 4%. Figure 16 is a graph showing the simulation results 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 semiconductor light-emitting element 100 according to this embodiment is 0%. Graphs (a) to (f) in Figures 15 and 16 show the relationship between the film thickness Tp2 of the P-side second guide layer, waveguide loss, optical confinement coefficient Γv, and effective refractive index difference ΔN(×10), respectively. -3 The relationship between position PS1, position PS2, and ΔP is shown. In addition, each graph shows the case where the In composition ratio Xp2 of the P-side second guide layer 107 is 0%, 0.5%, 1%, 2%, 3%, and 4%. Furthermore, 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. Also, 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] As shown in graph (a) of Figures 15 and 16, waveguide loss decreases as the film thickness Tp2 of the P-side second guide layer 107 increases for all In composition ratios Xp2. Furthermore, waveguide loss decreases as the In composition ratio Xp2 decreases.

[0100] As shown in graph (b) of Figures 15 and 16, for all In composition ratios Xp2, the optical confinement coefficient Γv is maximized when the film thickness Tp2 of the P-side second guide layer 107 is in the range of zero to approximately 100 nm, and decreases as the film thickness Tp2 increases beyond 100 nm. Furthermore, when the film thickness Tp2 is 100 nm or greater, the optical confinement coefficient Γv increases as the In composition ratio Xp2 decreases.

[0101] As shown in graph (c) of Figures 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. Furthermore, the effective refractive index difference ΔN tends to decrease as the In composition ratio Xp2 decreases.

[0102] As shown in graphs (d) and (e) of Figures 15 and 16, for all In composition ratios Xp2, positions PS1 and PS2 increase as the film thickness Tp2 of the P-side second guide layer 107 increases. Also, positions PS1 and PS2 tend to decrease as the In composition ratio Xp2 decreases. Note that graphs (d) and (e) of Figures 15 and 16 show an example of the range in which the photoconfinement coefficient can be increased for positions PS1 and PS2, where positions PS1 and PS2 are between -5 nm and 18 nm. Within this range, the range in which positions PS1 and PS2 are between 0 and 13 nm corresponds to the case where they are in one of the well layer 105b, barrier layer 105c, or well layer 105d of the active layer 105. Furthermore, the range where positions PS1 and PS2 are greater than -5 nm and less than 0 corresponds to a distance of within 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. Also, the range where positions PS1 and PS2 are greater than 13 nm and 18 nm or less corresponds to a distance of within 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 in such a range of -5 nm and 18 nm or less, the light confinement coefficient Γv can be increased.

[0103] As shown in graph (f) of Figures 15 and 16, except when 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 (i.e., different from this embodiment), ΔP tends to decrease as the film thickness Tp2 of the P-side second guide layer 107 increases. Note that graph (f) of Figures 15 and 16 shows an example of a range of ΔP in which the linearity of the IL characteristics can be improved, specifically the range where ΔP is between 0 and 20 nm.

[0104] From each of the graphs in FIGS. 15 and 16, by setting the film thickness Tp2 of the P-side second guide layer 107 to 100 nm or more, it is possible to simultaneously achieve reduction of waveguide loss, increase of the optical confinement factor Γv, and reduction of the effective refractive index difference ΔN. Also, in order to further increase the optical confinement factor Γv, the film thickness Tp2 may be 250 nm or less. Further, in order to position PS1 and PS2 in the vicinity of 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, regarding the relationship between the film thickness Tp2 of the P-side second guide layer 107 of the nitride semiconductor light-emitting device 100 according to the present embodiment, the film thickness of the P-type clad layer 110, and each parameter, FIGS. 17 and 18 will be used for explanation while comparing with a comparative example. FIG. 17 is a graph showing the relationship between the film thickness of the P-side second guide layer of the nitride semiconductor light-emitting device of the comparative example, the film thickness of the P-type clad layer, and each parameter. FIG. 18 is a graph showing the relationship between the film thickness of the P-side second guide layer 107 of the nitride semiconductor light-emitting device 100 according to the present embodiment, the film thickness of the P-type clad layer 110, and each parameter. In FIGS. 17 and 18, the relationship between each film thickness and the waveguide loss α i the optical confinement factor Γv, and the effective refractive index difference ΔN is shown by contour lines. The comparative example shown in FIG. 17 includes a single N-side guide layer and a single P-side guide layer having the same film thickness and In composition ratio, similar to the nitride semiconductor light-emitting device of Comparative Example 2 described above.

[0106] In FIG. 17, in the nitride semiconductor light-emitting device of the comparative example, a region where both position PS1 and position PS2 are -5 nm or more and 18 nm or less and ΔP is 20 nm or less is indicated by hatching. However, in this region, since the effective refractive index difference ΔN becomes larger than 4×10 -3 the divergence angle of the emitted light in the horizontal direction cannot be suppressed. Also, in this region, ΔP cannot be made 10 nm or less. In the nitride semiconductor light-emitting device of the comparative example as well, by setting the distance dc to about 80 nm, the effective refractive index difference ΔN is 3×10 -3The following configuration is possible, but 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 decrease in the temperature characteristics of the nitride semiconductor light-emitting element. Thus, the nitride semiconductor light-emitting element of the comparative example cannot solve the problems of this disclosure.

[0107] Figure 18 shows, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, the region where positions PS1 and PS2 are both between -5 nm and 18 nm, and ΔP is 20 nm or less, is indicated by hatched lines and dots. Furthermore, within this range, the region where ΔP is 5 nm or less is indicated by hatched dots, and the region where ΔP is greater than 5 nm and 10 nm or less is indicated by hatched lines. As shown in Figure 18, in the hatched region, the effective refractive index difference ΔN is 2.8 × 10⁻⁶. -3 The following applies. Therefore, the nitride-based semiconductor light-emitting element 100 according to this embodiment can satisfy the above conditions even when the distance dc is about 40 nm.

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

[0109] FIG. 19 is a schematic cross-sectional view showing the overall configuration of the nitride semiconductor light-emitting device 200 according to the present embodiment. As shown in FIG. 19, the nitride semiconductor light-emitting device 200 according to the present 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 the present embodiment is an N-type Al 0.036 Ga 0.964 N layer having a film thickness of 1200 nm. The N-type first cladding layer 202 is doped with Si at a concentration of 1 × 10 18 cm -3 as an impurity.

[0111] The P-type cladding layer 210 according to the present embodiment is a P-type Al 0.026 Ga 0.974 [[ID=2']]N layer having a film thickness of 450 nm. The P-type cladding layer 210 is doped with Mg as an impurity. Also, the impurity concentration at the end portion of the P-type cladding layer 210 closer to the active layer 105 is lower than the impurity concentration at the end portion farther from the active layer 105. Specifically, the P-type cladding layer 210 includes a P-type Al 18 cm -3 N layer having a film thickness of 150 nm doped with Mg at a concentration of 2 × 10 0.026 Ga 0.974 and a P-type Al 19 cm -3 N layer having a film thickness of 300 nm doped with Mg at a concentration of 1 × 10 0.026 Ga 0.974 arranged on the side farther from the active layer 1

[0112] It should be noted that there seems to be a small error in the original text where it says "active layer 105 from the active layer 105" in the description of the P-type cladding layer 210. I have translated it as best as possible based on the overall context. If this is a significant error, it may need to be corrected in the original text for a more accurate translation.Furthermore, the P-type cladding layer 210 has a ridge 210R formed on it, similar to the P-type cladding layer 110 according to Embodiment 1. In addition, the P-type cladding layer 210 has two grooves 210T formed on it, which are arranged along the ridge 210R and extend in the Y-axis direction.

[0113] The nitride-based semiconductor light-emitting element 200 according to this embodiment also produces the same effects as the nitride-based semiconductor light-emitting element 100 according to Embodiment 1.

[0114] Furthermore, in this embodiment, the N-type first cladding layer 202 and the P-type cladding layer 210 contain Al, and 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, Ync>Ypc (10) It satisfies the following relationship.

[0115] Here, if 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 represent the average Al composition ratio. For example, if the N-type first cladding layer 202 includes multiple GaN layers with a thickness of 2 nm and multiple AlGaN layers with a thickness of 2 nm and an Al composition ratio of 0.07, and each of the multiple GaN layers and each of the multiple AlGaN layers are stacked alternately, then Ync will be 0.035, which is the average Al composition ratio for the entire N-type first cladding layer 202. If the P-type cladding layer 210 includes multiple GaN layers with a thickness of 2 nm and multiple AlGaN layers with a thickness of 2 nm and an Al composition ratio of 0.07, and each of the multiple GaN layers and each of the multiple AlGaN layers are stacked alternately, then Ypc will be 0.035, which is the average Al composition ratio for 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 that of the P-type cladding layer 210. Therefore, even if the film thickness of the P-type cladding layer 210 is reduced to lower the operating voltage of the nitride semiconductor light-emitting element 200, the refractive index of the N-type first cladding layer 202 is smaller than that of the P-type cladding layer 210, which suppresses the shift of the peak of the light intensity distribution in the stacking direction from the active layer 105 towards the N-type first cladding layer 202.

[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 lower part of ridge 210R is 2.5 nm, ΔP is 6.4 nm, the light confinement coefficient to the active layer 105 is 1.45%, and the waveguide loss is 1.9 cm -1 This enables the realization of a nitride-based semiconductor light-emitting element 200.

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

[0119] Figure 20 is a schematic cross-sectional view showing the overall configuration of the nitride-based semiconductor light-emitting element 300 according to this embodiment. As shown in Figure 20, the nitride-based semiconductor light-emitting element 300 according to this embodiment comprises a semiconductor laminate 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 a conductive film that is placed above the P-type cladding layer 210 and transmits at least a portion of the light generated by the nitride-based semiconductor light-emitting element 300. As the translucent conductive film 320, for example, an oxide film that is transparent to visible light and exhibits low electrical conductivity can be used, such as tin-doped indium oxide (ITO), Ga-doped zinc oxide, Al-doped zinc oxide, or In and Ga-doped zinc oxide.

[0121] The nitride-based semiconductor light-emitting element 300 according to this embodiment also produces the same effects as the nitride-based semiconductor light-emitting element 200 according to Embodiment 2.

[0122] Furthermore, in this embodiment, since a translucent conductive film 320 is provided above the P-type cladding layer 210, the loss of light propagating above the P-type cladding layer 210 can be reduced. In addition, since the film thickness of the P-type cladding layer 210 can be further reduced, the electrical resistance of the nitride-based semiconductor light-emitting element 300 can be further reduced. As a result, the slope efficiency of the nitride-based semiconductor light-emitting element 300 can be increased and the operating voltage can be reduced.

[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 lower part of ridge 210R is 2.0 nm, ΔP is 5.7 nm, the light confinement coefficient to the active layer 105 is 1.47%, and the waveguide loss is 1.9 cm -1 This enables the realization of a nitride-based semiconductor light-emitting element 300.

[0124] (Embodiment 4) A nitride-based semiconductor light-emitting element according to Embodiment 4 will now be described. The nitride-based semiconductor light-emitting element according to this embodiment differs from the nitride-based semiconductor light-emitting element 200 according to Embodiment 2 in the configuration of the active layer. Hereinafter, the nitride-based semiconductor light-emitting element according to this embodiment will be described using Figures 21A and 21B, focusing on the differences from the nitride-based semiconductor light-emitting element 200 according to Embodiment 2.

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

[0126] As shown in Figure 21A, the nitride-based semiconductor light-emitting element 400 according to this embodiment comprises a semiconductor laminate 400S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor laminate 400S has 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] The active layer 405 according to this embodiment has a single quantum well structure, as shown in Figure 21B, and comprises a single well layer 105b and barrier layers 105a and 105c sandwiching the well layer 105b. The well layer 105b has the same configuration as the well layer 105b according to Embodiment 1, and the barrier layers 105a and 105c have the same configuration as the barrier layers 105a and 105c according to Embodiment 1.

[0128] The nitride-based semiconductor light-emitting element 400 according to this embodiment provides the same effects as the nitride-based semiconductor light-emitting element 200 according to Embodiment 2. In particular, in the nitride-based semiconductor light-emitting element 400 having a single quantum well structure as described above, the active layer 405 has a single well layer 105b. Thus, even in the nitride-based semiconductor light-emitting element 400, which has 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 light confinement coefficient 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 lower part of ridge 210R is 2.1 nm, ΔP is 6.3 nm, the light confinement coefficient to the active layer 405 is 0.72%, and the waveguide loss is 1.8 cm -1 This enables the realization of a nitride-based semiconductor light-emitting element 400. In this embodiment, the total film thickness of the active layer 405 is 8 nm smaller than that of the active layer 105 in Embodiment 2, so the photoconfinement coefficient is smaller than in Embodiment 2.

[0130] (Torture, etc.) The nitride-based semiconductor light-emitting devices described above have been explained based on various embodiments, but this disclosure is not limited to the above embodiments.

[0131] For example, in the embodiments described above, the nitride-based semiconductor light-emitting element is shown to be 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 laminate of the nitride-based semiconductor light-emitting element with respect to the light emitted from the semiconductor laminate may be 0.1% or less. Such reflectance can be achieved, for example, by forming an anti-reflective film made of a dielectric multilayer film on the end face. Alternatively, if the ridge that becomes the waveguide is tilted at 5° or more from the normal direction of the front end face and intersects the front end face, the proportion of the component in which the waveguided light reflected from the front end face re-couples with the waveguide and becomes waveguided light can be made to a small value of 0.1% or less.

[0132] Furthermore, in embodiments 1 to 3 described above, the nitride semiconductor light-emitting element had a structure in which the active layer 105 included two well layers, but it may also have a structure that includes only a single well layer. In this way, even when there is only one well layer with a high refractive index included in the active layer, by using the N-side guide layer 104, P-side first guide layer 106, and P-side second guide layer 107 of this disclosure, the controllability of the position of the vertical light distribution can be improved, so that the peak of the vertical light distribution can be positioned near the well layer. Therefore, it is possible to realize a nitride semiconductor light-emitting element with a low oscillation threshold, low waveguide loss, a high optical confinement coefficient, and current-optical output (IL) characteristics with excellent linearity.

[0133] Furthermore, in each of the above embodiments, the nitride semiconductor light-emitting element had a single ridge, but the nitride semiconductor light-emitting element may have multiple ridges. Such a nitride semiconductor light-emitting element will be explained with reference to Figure 22. Figure 22 is a schematic cross-sectional view showing the overall configuration of the nitride semiconductor light-emitting element 500 according to Modification 1. As shown in Figure 22, the nitride semiconductor light-emitting element 500 according to Modification 1 has a configuration in which multiple nitride semiconductor light-emitting elements 100 according to Embodiment 1 are arranged in a horizontal array. In Figure 22, the nitride semiconductor light-emitting element 500 has a configuration in which three nitride semiconductor light-emitting elements 100 are arranged integrally, but the number of nitride semiconductor light-emitting elements 100 in the nitride semiconductor light-emitting element 500 is not limited to three. The number of nitride semiconductor light-emitting elements 100 in the nitride semiconductor light-emitting element 500 may be two or more. Each nitride semiconductor light-emitting element 100 has a light-emitting section 100E that emits light. The light-emitting portion 100E is the part of the active layer 105 that emits light, and corresponds to the part of the active layer 105 located below the ridge 110R. Thus, the nitride semiconductor light-emitting element 500 according to Modification 1 has a plurality of light-emitting portions 100E arranged in an array. As a result, multiple emitted lights can be obtained from a single nitride semiconductor light-emitting element 500, thus realizing a high-power nitride semiconductor light-emitting element 500. In Modification 1, the nitride semiconductor light-emitting element 500 comprises a plurality of nitride semiconductor light-emitting elements 100, but the plurality of nitride semiconductor light-emitting elements comprising the nitride semiconductor light-emitting element 500 are not limited to this and may be nitride semiconductor light-emitting elements according to other embodiments.

[0134] Furthermore, as shown in the modified example 2 of the nitride-based semiconductor light-emitting element 500a in Figure 23, each light-emitting section 100E may be separated by a separation groove 100T with 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 adopting such a structure, even when the distance between adjacent light-emitting sections 100E is narrowed to 300 μm or less, thermal interference due to self-heating during the operation of each light-emitting section 100E can be reduced.

[0135] Furthermore, since the nitride-based semiconductor light-emitting element of the present invention has a small ΔN and can reduce the horizontal spreading angle, even if the distance between the centers of the light-emitting sections 100E shown in Figures 22 and 23 is narrowed, the light emitted from each light-emitting section 100E is less likely to interfere with each other, and the distance between the centers of the light-emitting sections 100E can be narrowed to 250 μm or less. In Modification 2, this distance is 225 μm.

[0136] Furthermore, while the nitride-based semiconductor light-emitting element according to each of the above embodiments includes an N-type second cladding layer 103, an intermediate layer 108, an electron barrier layer 109, and a current blocking layer 112, these layers are not necessarily required.

[0137] Furthermore, this disclosure also includes forms obtained by applying various modifications to each of the above embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of each of the above embodiments without departing from the spirit of this disclosure.

[0138] For example, the configuration of each cladding layer according to Embodiment 1 may be applied to each nitride-based semiconductor light-emitting element according to Embodiments 3 and 4. Alternatively, the translucent conductive film according to Embodiment 3 may be applied to each nitride-based semiconductor light-emitting element according to Embodiments 1 and 4. [Industrial applicability]

[0139] The nitride-based semiconductor light-emitting element of this disclosure can be applied, for example, as a high-power and high-efficiency light source for processing machines and the like. [Explanation of symbols]

[0140] 100, 200, 300, 400, 500, 500a Nitride-based semiconductor light-emitting devices 100E Light Emitting Section 100F, 100R end face 100T separation groove 100S, 200S, 400S semiconductor stacks 101 circuit board 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 Block 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 stack, wherein light is emitted from an end face perpendicular to the stacking direction of the semiconductor stack, The semiconductor laminate is N-type first cladding layer, An N-side guide layer is positioned above the N-type first cladding layer, An active layer positioned above the N-side guide layer, A P-side first guide layer is positioned above the active layer, A second guide layer on the P side is positioned above the first guide layer on the P side, It has a P-type cladding layer positioned above the P-side second guide layer, The band gap energy of the P-side second guide layer is greater than the band gap energy of the N-side guide layer. The band gap energy of the N-side guide layer is greater than or equal to the band gap energy of the P-side first guide layer. If the thickness of the first guide layer on the P side is Tp1, the thickness of the second guide layer on the P side is Tp2, and the thickness of the guide layer on the N side is Tn1, Tn1<Tp1+Tp2 Satisfying the relationship Nitride semiconductor light-emitting element.

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

3. The first guide layer on the P side is In Ｘｐ１ Ga １－Ｘｐ１ Consists of N, The N-side guide layer is In Ｘｎ１ Ga １－Ｘｎ１ Consists of N, Xn1 ≤ Xp1 Satisfying the relationship Nitride-based semiconductor light-emitting element according to claim 1 or 2.

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

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

6. The active layer includes a barrier layer and has a quantum well structure, The aforementioned barrier layer is In Ｘｂ Ga １－Ｘｂ Consists of N, Xp1 < Xb Satisfying the relationship Nitride-based semiconductor light-emitting element according to any one of claims 3 to 5.

7. The band gap energy of the N-side guide layer is greater than the band gap energy of the P-side first guide layer. Nitride-based semiconductor light-emitting element according to any one of claims 1 to 6.

8. Tp1 < Tp2 Satisfying the relationship Nitride-based semiconductor light-emitting element according to any one of claims 1 to 7.

9. Tp1 < Tn1 Satisfying the relationship Nitride-based semiconductor light-emitting element according to any one of claims 1 to 8.

10. The peak of the light intensity distribution in the stacking direction is located in the active layer. Nitride-based semiconductor light-emitting element according to any one of claims 1 to 9.

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 of the P-type cladding layer further from the active layer. Nitride-based semiconductor light-emitting element according to any one of claims 1 to 10.

12. The electron barrier layer is 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 increases monotonically as it moves away from the active layer. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 11.

13. The aforementioned N-type first cladding layer and the P-type cladding layer contain Al, If the Al composition ratios of the N-type first cladding layer and the P-type cladding layer are Ync and Ypc, respectively, Ync > Ypc Satisfying the relationship Nitride-based semiconductor light-emitting element according to any one of claims 1 to 12.

14. The thickness of the P-type cladding layer is 460 nm or less. Nitride-based semiconductor light-emitting element according to any one of claims 1 to 13.

15. The P-type cladding layer is provided with a translucent conductive film positioned above it. Nitride-based semiconductor light-emitting element according to any one of claims 1 to 14.

16. The system comprises 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 larger than the band gap energy of the P-side second guide layer. Nitride-based semiconductor light-emitting element according to any one of claims 1 to 15.

17. It has multiple light-emitting parts arranged in an array. Nitride-based semiconductor light-emitting element 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. Nitride-based semiconductor light-emitting element according to any one of claims 1 to 17.

19. The active layer comprises a single well layer and has a quantum well structure. Nitride-based semiconductor light-emitting element according to any one of claims 1 to 18.

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