Nitride semiconductor light-emitting diodes

Abstract

To provide a nitride-based semiconductor light-emitting element with excellent temperature characteristics. [Solution] The nitride semiconductor light-emitting element 100 comprises an N-type cladding layer 102, an N-side guide layer 103 positioned above the N-type cladding layer 102, an active layer 104 positioned above the N-side guide layer 103, a first P-side guide layer 105 positioned above the active layer 104, an electron barrier layer 106 positioned above the first P-side guide layer 105, a second P-side guide layer 107 positioned above the electron barrier layer 106, and a P-type cladding layer 108 positioned above the second P-side guide layer 107. The average band gap energy of the second P-side guide layer 107 is greater than the average band gap energy of the first P-side guide layer 105, and the average band gap energy of the P-type cladding layer 108 is smaller than the average band gap energy of the electron barrier layer 106.

Description

[Technical Field]

[0001] This disclosure relates to nitride-based semiconductor light-emitting devices. [Background technology]

[0002] Conventionally, nitride-based semiconductor light-emitting devices that emit blue light are known, but there is a need for high-power nitride-based semiconductor light-emitting devices that emit shorter wavelength ultraviolet light (see, for example, Patent Document 1). For example, if a watt-class ultraviolet laser light source can be realized using a nitride-based semiconductor light-emitting device, it can be used as a light source for exposure, a light source for processing, etc. [Prior art documents] [Patent Documents]

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

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

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

[0006] This disclosure aims to solve these problems and to provide a nitride-based semiconductor light-emitting element with excellent temperature characteristics. [Means for solving the problem]

[0007] To solve the above problems, one embodiment of a nitride-based semiconductor light-emitting element according to the present disclosure comprises an N-type cladding layer, an N-side guide layer disposed above the N-type cladding layer, an active layer disposed above the N-side guide layer, a first P-side guide layer disposed above the active layer, an electron barrier layer disposed above the first P-side guide layer, a second P-side guide layer disposed above the electron barrier layer, and a P-type cladding layer disposed above the second P-side guide layer, wherein the average bandgap energy of the second P-side guide layer is greater than the average bandgap energy of the first P-side guide layer, and the average bandgap energy of the P-type cladding layer is smaller than the average bandgap energy of the electron barrier layer. [Effects of the Invention]

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

[0009] [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 graph showing the distribution of bandgap energy and refractive index in the well layer and barrier layer of a 405 nm band semiconductor light-emitting device in the stacking direction. [Figure 4] Figure 4 is a graph showing the distribution of bandgap energy and refractive index in the well layer and barrier layer of a 375 nm semiconductor light-emitting device in the stacking direction. [Figure 5] Figure 5 is a graph showing the distribution of effective refractive index and gain in the horizontal direction for a semiconductor light-emitting device in the 375 nm band. [Figure 6] Figure 6 shows the far-field pattern in the horizontal direction of a conventional ultraviolet semiconductor light-emitting device. [Figure 7] Figure 7 is a schematic graph showing the bandgap energy distribution and light intensity distribution in the stacking direction of the semiconductor stack according to Comparative Example 1. [Figure 8] Figure 8 is a schematic graph showing the bandgap energy distribution and light intensity distribution in the stacking direction of the semiconductor stack according to Comparative Example 2. [Figure 9] Figure 9 is a schematic graph showing the bandgap energy distribution and light intensity distribution of the semiconductor stack according to Embodiment 1. [Figure 10]Figure 10 shows the main configurations and characteristic calculation results of Examples E01 to E03 and Comparative Examples C01 to C06. [Figure 11] Figure 11 shows the main configurations and characteristic calculation results of Examples E04 to E06 and Comparative Examples C11 to C16. [Figure 12] Figure 12 shows the main configurations and characteristic calculation results of Comparative Examples C02, C12, and C21 to C26. [Figure 13] Figure 13 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 14] Figure 14 is a graph showing the relationship between the operating voltage of the nitride-based semiconductor light-emitting element according to Embodiment 1 during 200mA operation and the film thickness of the first P-side guide layer. [Figure 15] Figure 15 is a graph showing the relationship between the waveguide loss of the nitride-based semiconductor light-emitting element according to Embodiment 1 and the film thickness of the first P-side guide layer. [Figure 16] Figure 16 is a graph showing the relationship between the effective refractive index difference ΔN of the nitride-based semiconductor light-emitting element according to Embodiment 1 and the film thickness of the first P-side guide layer. [Figure 17] Figure 17 is a graph showing the relationship between the photoconfinement coefficient of the nitride semiconductor light-emitting element according to Embodiment 1 and the film thickness of the first P-side guide layer. [Figure 18] Figure 18 is a schematic graph showing the bandgap energy distribution and light intensity distribution in the stacking direction of the semiconductor stack of Example E02. [Figure 19] Figure 19 is a schematic graph showing the bandgap energy distribution and light intensity distribution in the stacking direction of the semiconductor stack of Example E07. [Figure 20] Figure 20 is a graph showing the relationship between the band gap energy in the AlxGa1-x-yInyN layer and the band gap energy in the AlzGa1-zN layer. [Figure 21]Figure 21 is a schematic side view showing the warping of the substrate and semiconductor laminate that occurs when a semiconductor laminate is stacked on a substrate according to Embodiment 1. [Figure 22] Figure 22 is a graph showing the relationship between the position in the stacking direction and the bandgap energy of the semiconductor stack in Example E11. [Figure 23] Figure 23 is a graph showing the relationship between position and stress in the stacking direction of the semiconductor stack of Example E11. [Figure 24] Figure 24 is a graph showing the relationship between the position in the stacking direction of the semiconductor stack in Example E11 and the integral stress. [Figure 25] Figure 25 is a graph showing the relationship between the position in the stacking direction and the bandgap energy of the semiconductor stack in Example E12. [Figure 26] Figure 26 is a graph showing the relationship between position and stress in the stacking direction of the semiconductor stack of Example E12. [Figure 27] Figure 27 is a graph showing the relationship between the position in the stacking direction of the semiconductor stack in Example E12 and the integral stress. [Figure 28] Figure 28 is a graph illustrating the required composition for the well layer of Example E13. [Figure 29] Figure 29 is a graph showing the relationship between the In composition ratio of the well layer and the lattice disorder with respect to GaN. [Figure 30] Figure 30 is a schematic graph showing the bandgap energy distribution in the stacking direction of the semiconductor stack of Example E14. [Figure 31] Figure 31 is a schematic graph showing the bandgap energy distribution in the stacking direction of the semiconductor stack of Example E15. [Figure 32] Figure 32 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to Embodiment 2. [Figure 33] Figure 33 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to Embodiment 3. [Modes for carrying out the invention]

[0010] 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.

[0011] 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.

[0012] 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.

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

[0014] [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 view and cross-sectional view, 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 line II-II in Figure 1. Figure 2B is a schematic cross-sectional view showing the configuration of the active layer 104 of 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.

[0015] 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. The nitride-based semiconductor light-emitting element 100 also has a waveguide formed between end face 100F and end face 100R. In this embodiment, the reflectivity of end faces 100F and 100R is 16% and 95%, respectively. The resonator length (i.e., the distance between end face 100F and end face 100R) of the nitride-based semiconductor light-emitting element 100 according to this embodiment is approximately 1200 μm. The nitride-based semiconductor light-emitting element 100 emits ultraviolet light having a peak wavelength in the 375 nm band, for example. However, the nitride-based semiconductor light-emitting element 100 may also emit ultraviolet light having a peak wavelength in a wavelength band other than 375 nm, or it may emit light having a peak wavelength in a wavelength band other than ultraviolet light.

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

[0017] The substrate 101 is a plate-shaped member that serves as the base for the nitride-based semiconductor light-emitting element 100. In this embodiment, the substrate 101 is placed below the N-type cladding layer 102 and is made of N-type GaN. More specifically, the substrate 101 has a concentration of 1 × 10⁻¹⁶ 18 cm -3 This is a silicon-doped GaN substrate with a thickness of 8500 nm.

[0018] The N-type cladding layer 102 is an N-type nitride semiconductor layer positioned above the substrate 101. The N-type cladding layer 102 has a lower refractive index and a higher average bandgap energy than the active layer 104. In this embodiment, the N-type cladding layer 102 contains Al. Furthermore, the average Al composition ratio of the N-type cladding layer 102 is less than or equal to the average Al composition ratio of the P-type cladding layer 108. The N-type cladding layer 102 contains impurities at a concentration of 5 × 10⁻¹⁶ 17 cm -3 The Si is doped.

[0019] In this disclosure, the average bandgap energy of a layer is the value of the bandgap energy obtained by integrating the magnitude of the bandgap energy at a certain position in the stacking direction of the layer from the substrate-side interface to the interface on the farther side of the substrate in the stacking direction of the layer, and dividing it by the thickness of the layer (the distance between the substrate-side interface and the interface on the farther side of the substrate).

[0020] The average refractive index of a layer is the value obtained by integrating the magnitude of the refractive index at a certain position in the stacking direction of that layer from the substrate-side interface to the interface on the farther side of the substrate, and then dividing this by the thickness of the layer (the distance between the substrate-side interface and the interface on the farther side of the substrate).

[0021] The average Al composition ratio of a layer is the value of the Al composition ratio obtained by integrating the magnitude of the Al composition ratio at a certain position in the stacking direction of that layer from the substrate-side interface to the interface on the farther side of the substrate, and then dividing this by the thickness of the layer (the distance between the substrate-side interface and the interface on the farther side of the substrate).

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

[0023] The N-side guide layer 103 is positioned above the N-type cladding layer 102 and is an optical guide layer made of a nitride-based semiconductor. The N-side guide layer 103 has a higher refractive index and a lower bandgap energy than the N-type cladding layer 102. In this embodiment, the average bandgap energy of the N-side guide layer 103 is greater than the average bandgap energy of the first P-side guide layer 105 and less than the average bandgap energy of the second P-side guide layer 107. The N-side guide layer 103 contains Al. Furthermore, the N-side guide layer 103 is an undoped nitride-based semiconductor layer. In other words, the average N-type impurity concentration of the N-side guide layer 103 is 1 × 10⁻⁶. 18 cm -3 It is less than [value]. In the following, the N-type impurity concentration in each layer on the N side and the P-type impurity concentration in each layer on the P side will both be simply referred to as the impurity concentration.

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

[0025] Each of the barrier layers 104a and 104c is a nitride-based semiconductor layer positioned above the N-side guide layer 103 and functioning as a barrier in the quantum well structure. Barrier layer 104c is positioned above barrier layer 104a. In this embodiment, the band gap energies of each of the barrier layers 104a and 104c are greater than the band gap energy of the well layer 104b, the average band gap energy of the first P-side guide layer 105, and the average band gap energy of the N-side guide layer 103, and less than the average band gap energy of the electron barrier layer 106.

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

[0027] The first P-side guide layer 105 is positioned above the active layer 104 and is an optical guide layer made of a nitride-based semiconductor. The first P-side guide layer 105 has a higher refractive index and a lower bandgap energy than the P-type cladding layer 108. In this embodiment, the first P-side guide layer 105 contains Al. The first P-side guide layer 105 is an undoped nitride-based semiconductor layer. In other words, the average impurity concentration of the first P-side guide layer 105 is 1 × 10⁻⁶. 18 cm -3It is less than. The film thickness of the first P-side guide layer 105 is thicker than the film thickness of each of the two barrier layers 104a and 104c. The film thickness of the first P-side guide layer 105 is thinner than the film thickness of the second P-side guide layer 107. Also, the average bandgap energy of the first P-side guide layer 105 is smaller than the bandgap energies of the barrier layers 104a and 104c.

[0028] The electron barrier layer 106 is a nitride semiconductor layer disposed above the first P-side guide layer 105. The bandgap energy of the electron barrier layer 106 is larger than the bandgap energy of the barrier layer 104c. Thereby, it is possible to suppress electrons from leaking from the active layer 104 to the P-type clad layer 108. In the present embodiment, the bandgap energy of the electron barrier layer 106 is larger than the bandgap energy of the P-type clad layer 108.

[0029] The second P-side guide layer 107 is an optical guide layer made of a nitride semiconductor and is disposed above the electron barrier layer 106. The second P-side guide layer 107 has a refractive index larger than that of the P-type clad layer 108 and a smaller bandgap energy. Also, the average bandgap energy of the second P-side guide layer 107 is larger than the bandgap energy of the first P-side guide layer 105. In the present embodiment, the second P-side guide layer 107 contains Al. The second P-side guide layer 107 is doped with impurities. In other words, the average impurity concentration of the second P-side guide layer 107 is 1×10 18 cm -3 or more.

[0030] The P-type cladding layer 108 is positioned above the second P-side guide layer 107 and is a cladding layer made of a P-type nitride semiconductor. The P-type cladding layer 108 has a lower refractive index and a higher average bandgap energy than the active layer 104. The average bandgap energy of the P-type cladding layer 108 is smaller than the average bandgap energy of the electron barrier layer 106. In this embodiment, the P-type cladding layer 108 contains Al. The P-type cladding layer 108 is doped with Mg as an impurity. The impurity concentration at the end of the P-type cladding layer 108 closer to the active layer 104 is lower than the impurity concentration at the end further away from the active layer 104. Specifically, the P-type cladding layer 108 is an AlGaN layer with a thickness of 450 nm, and the concentration located on the side closer to the active layer 104 is 2 × 10⁻¹⁶. 18 cm -3 A 150 nm thick P-type AlGaN layer doped with Mg, and a concentration of 1 × 10¹⁶ located on the side furthest from the active layer 104. 19 cm -3 It has a 300 nm thick P-type AlGaN layer doped with Mg.

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

[0032] The contact layer 109 is a nitride-based semiconductor layer positioned above the P-type cladding layer 108 and making ohmic contact with the P-side electrode 111. In this embodiment, the contact layer 109 is a P-type GaN layer with a thickness of 60 nm. The contact layer 109 contains impurities with a concentration of 1 × 10⁻⁶ 20 cm -3 It is doped with magnesium.

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

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

[0035] Furthermore, by using Ag, which has a low refractive index for light in the 375 nm wavelength band, in at least a portion of the P-side electrode 111 on the contact layer 109, the leakage of light propagating through the waveguide to the P-side electrode 111 can be reduced, thereby reducing waveguide loss generated at the P-side electrode 111. Ag has a refractive index of 0.5 or less in the wavelength range of 325 nm to 1500 nm, and a refractive index of 0.2 or less in the wavelength range of 360 nm to 950 nm. In this case, even if the film thickness of the P-type cladding layer 108 is 0.4 μm or less, the leakage of light propagating through the waveguide to the P-side electrode 111 can be reduced, making it possible to reduce the series resistance of the nitride semiconductor light-emitting element 100 while suppressing the increase in waveguide loss. As a result, the operating voltage and operating current can be reduced.

[0036] Here, in order to stably confine the light propagating through the waveguide within the ridge 108R, as will be described later, it is necessary to create an effective refractive index difference (ΔN) such that the effective refractive index of the inner region of the ridge 108R is greater than the effective refractive index of the outer region. Specifically, it is necessary to form SiO2 with a refractive index lower than that of the P-type cladding layer 108 on the sidewalls of the ridge 108R, thereby reducing the effective refractive index of the outer region of the ridge 108R. In this case, if the thickness of the P-type cladding layer 108 becomes too thin, the region in the thickness direction of the sidewalls of the ridge 108R where SiO2 is formed will become smaller, and the effect of reducing the effective refractive index of the outer region of the ridge 108R will be reduced. For this reason, the thickness of the P-type cladding layer 108 needs to be 0.15 μm or more.

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

[0038] As a result of having the above configuration, the nitride semiconductor light-emitting element 100 generates an effective refractive index difference ΔN between the inner portion of the ridge 108R and the outer portion of the ridge 108R (groove 108T portion), as shown in Figure 2A. This allows the light generated in the lower portion of the ridge 108R of the active layer 104 to be confined in the horizontal direction (i.e., in the X-axis direction).

[0039] [1-2. Challenges of UV semiconductor light-emitting devices] The problems that may arise in ultraviolet semiconductor light-emitting devices, as described in the "Problems to be Solved by the Invention" section of this disclosure, will be explained in detail using Figures 3 to 6. Below, Figure 3 is a graph showing the distribution of bandgap energy (Eg) and refractive index in the well layer and barrier layer of a semiconductor light-emitting device in the 405 nm band, which has a wavelength longer than ultraviolet light, in the stacking direction. Figure 4 is a graph showing the distribution of bandgap energy (Eg) and refractive index in the well layer and barrier layer of a semiconductor light-emitting device in the 375 nm band, which is in the ultraviolet region, in the stacking direction. Figure 5 is a graph showing the distribution of effective refractive index and gain in the horizontal direction (corresponding to the X-axis direction in Figures 1 to 2B) of a semiconductor light-emitting device in the 375 nm band. Figure 6 is a diagram showing the far-field pattern in the horizontal direction of a conventional ultraviolet semiconductor light-emitting device. In Figure 6, the horizontal axis shows the radiation angle in the horizontal direction, and the vertical axis shows the light intensity.

[0040] As shown in Figure 3, in a 405 nm semiconductor light-emitting element, the bandgap energy of the well layer is relatively small, allowing the difference ΔEc between the conduction band potential energy and the electron quantum level energy of the barrier layer to be a relatively large value (198 meV). In this case, the electron Fermi energy Ef becomes sufficiently smaller than the conduction band potential energy of the barrier layer, thus suppressing electron leakage from the well layer through the barrier layer to the P-side semiconductor layer.

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

[0042] As the operating carrier density in the well layer increases, the amplification gain of light in the well layer increases. On the other hand, due to the relationship between the real and imaginary parts of the complex refractive index in the current injection region of the well layer, the refractive index of the well layer decreases as the amplification gain in the well layer increases. Furthermore, as the carrier density in the current injection region of the well layer increases, the refractive index in the current injection region of the well layer decreases due to the plasma effect. Therefore, the refractive index of the current injection region of the well layer can be lower than the refractive index outside the current injection region of the well layer. For example, if the semiconductor light-emitting element is a laser element with a ridge, and current is injected into the ridge, the effective refractive index in the ridge, which is the current injection region, can be lower than that outside the current injection region, as shown in Figure 5.

[0043] As a result, the waveguide mechanism of the laser light propagating through the waveguide corresponding to the ridge of the semiconductor light-emitting element becomes a refractive index anti-guide type gain waveguide mechanism. Therefore, the proportion of the laser light that propagates outside the current injection region (the region located below the ridge) in the well layer increases, and a peak occurs at the base of the far-field pattern of the semiconductor light-emitting element, as shown in Figure 6. In this case, light is absorbed outside the current injection region in the well layer, so the absorption loss in the well layer increases. Consequently, the oscillation threshold current value of the semiconductor light-emitting element increases and the thermal saturation level decreases. In other words, the temperature characteristics of the semiconductor light-emitting element deteriorate. In addition, a nonlinear bend (so-called kink) may occur in the graph showing the current-light output (IL) characteristics of the semiconductor light-emitting element. In other words, the stability of the optical output of the semiconductor light-emitting element decreases.

[0044] The nitride-based semiconductor light-emitting element 100 according to this embodiment solves the problems of such ultraviolet semiconductor light-emitting elements.

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

[0046] The semiconductor laminate according to Comparative Example 1 shown in Figure 7 comprises an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, a P-side guide layer 915, an electron barrier layer 916, and a P-type cladding layer 108. The semiconductor laminate according to Comparative Example 1 differs from the semiconductor laminate 100S according to this embodiment in the configuration of the P-side guide layer 915. In the semiconductor laminate according to Comparative Example 1, the composition and film thickness of the N-side guide layer 103 and the P-side guide layer 915 are the same. Furthermore, the electron barrier layer 916 is arranged between the P-side guide layer 915 and the P-type cladding layer 108.

[0047] In the semiconductor laminate according to Comparative Example 1, when the N-type cladding layer 102 and the P-type cladding layer 108 are made of AlGaN and have the same Al composition ratio, the refractive index of the P-type cladding layer 108 is higher than that of the N-type cladding layer 102. This is because the ionization energy of Mg, a P-type impurity, is greater than that of Si, an N-type impurity. Therefore, the concentration of P-type impurities must be set higher than that of N-type impurities, and the P-type layer, which forms relatively deeper energy levels, absorbs more light and thus has a higher refractive index. Consequently, as shown in Figure 7, the peak position of the light intensity distribution is biased toward the P-type cladding layer 108 from the active layer 104. As a result, in the semiconductor laminate according to Comparative Example 1, the light confinement coefficient to the active layer 104 decreases, and the operating carrier density increases. Consequently, the refractive index of the well layer 104b decreases.

[0048] Furthermore, in the semiconductor laminate according to Comparative Example 1, similar to the nitride-based semiconductor light-emitting element 100 shown in Figure 2A, the effective refractive index difference ΔN depends on the distance dp from the lower end of the ridge 108R to the active layer 104. Since the semiconductor laminate according to Comparative Example 1 does not have a second P-side guide layer 107, in order to position the peak position of the vertical light intensity distribution near the active layer 104, it is necessary to increase the thickness of the P-side guide layer 915, which has a higher refractive index than the P-type cladding layer 108. For this reason, the distance dp in the semiconductor laminate according to Comparative Example 1 is thicker than the distance dp in this embodiment. Consequently, the effective refractive index difference ΔN in the semiconductor laminate according to Comparative Example 1 is smaller than the effective refractive index difference ΔN in this embodiment. As a result, the stability of the transverse modes of the laser light during operation is reduced in the semiconductor laminate according to Comparative Example 1.

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

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

[0051] As shown in Figure 9, the semiconductor laminate 100S according to this embodiment includes a first P-side guide layer 105 with a small bandgap energy (i.e., a large refractive index) between the active layer 104 and the electron barrier layer 106. Furthermore, the average bandgap energy of the first P-side guide layer 105 is smaller than the average bandgap energy of the second P-side guide layer 107, and the average refractive index of the first P-side guide layer 105 is larger than that of the second P-side guide layer 107. As a result, in the semiconductor laminate 100S according to this embodiment, the peak position of the light intensity distribution can be brought closer to the active layer 104 than in the semiconductor laminates according to Comparative Examples 1 and 2. In addition, the average impurity concentration of the first P-side guide layer 105 is 1 × 10⁻⁶ 18 cm -3 Less than, specifically 7 x 10 17 cm -3Because it is a nitride-based semiconductor layer (see Figure 9), free carrier loss in the first P-side guide layer 105 can be reduced. Therefore, in this embodiment, in the light intensity distribution in the stacking direction, the proportion of light distribution present in the undoped region near the active layer 104 and the first P-side guide layer 105 with a low impurity concentration becomes large, resulting in smaller free carrier loss and reduced waveguide loss. This reduces the oscillation threshold current value and the thermal saturation level. In other words, a nitride-based semiconductor light-emitting element 100 with excellent temperature characteristics and high slope efficiency can be realized. This enables high-temperature, high-power operation in the nitride-based semiconductor light-emitting element 100. Figure 9 shows the case where the impurity concentration of the first P-side guide layer 105 is constant with respect to the stacking direction, but the impurity concentration may monotonically increase as it moves away from the active layer 104 in the stacking direction. In this case, the impurity concentration in the region close to the active layer 104, where the light intensity is high, can be made relatively lower in the first P-side guide layer 105 compared to the impurity concentration in the region farther from the active layer 104. This makes it possible to reduce free carrier loss while suppressing an increase in the series resistance of the nitride semiconductor light-emitting element 100.

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

[0053] Furthermore, in this embodiment, the distance dp is reduced by making the film thickness of the first P-side guide layer 105 thinner than the film thickness of the second P-side guide layer 107. Therefore, in this embodiment, the effective refractive index difference ΔN can be increased. Consequently, the optical confinement coefficient of the nitride semiconductor light-emitting element 100 into the waveguide can be increased. As a result, in the nitride semiconductor light-emitting element 100, the horizontal transverse modes of the laser light can be stably confined into the waveguide, thereby suppressing the occurrence of kinks in the current-optical output characteristics. Moreover, in this embodiment, the total film thickness of the first P-side guide layer 105 and the second P-side guide layer 107 is greater than or equal to the film thickness of the N-side guide layer 103. This makes it possible to further increase the distance dc, and thus further increase the effective refractive index difference ΔN and the optical confinement coefficient.

[0054] Furthermore, in this embodiment, the average Al composition ratio of the second P-side guide layer 107 is made greater than that of the first P-side guide layer 105, thereby increasing the average bandgap energy of the second P-side guide layer 107 compared to the first P-side guide layer 105. As a result, the average refractive index of the first P-side guide layer 105 can be made greater than that of the second P-side guide layer 107, allowing the peak position of the light intensity distribution to be brought even closer to the active layer 104. Therefore, in this embodiment, waveguide losses of the nitride semiconductor light-emitting element 100 can be reduced.

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

[0056] [1-4-1. Example E01] Example E01 will now be described. The nitride-based semiconductor light-emitting element 100 of Example E01 has the following configuration (see Figure 10). The N-type cladding layer 102 has a concentration of 5 × 10 17 cm -3 N-type Al with Si doped, 800 nm film thickness. 0.065 Ga 0.935 This is the N layer. The N-side guide layer 103 is an undoped aluminum layer with a thickness of 180 nm. 0.03 Ga 0.97 It is an N layer. Each of the barrier layers 104a and 104c is an undoped aluminum layer with a thickness of 10 nm. 0.04 Ga 0.96 This is the N layer. The well layer 104b is an undoped In layer with a film thickness of 17.5 nm. 0.01 Ga 0.99 This is the N layer. The first P-side guide layer 105 is an undoped aluminum layer with a thickness of 56 nm. 0.02 Ga 0.98 It is an N layer. The electron barrier layer 106 has a concentration of 1 × 10⁻⁶ 19cm -3 Mg-doped P-type Al with a film thickness of 5 nm 0.36 Ga 0.64 This is the N layer. The second P-side guide layer 107 has a concentration of 1 × 10⁻⁶. 18 cm -3 Mg-doped P-type Al with a film thickness of 124 nm 0.04 Ga 0.96 This is the N layer. The P-type cladding layer 108 is P-type Al with a thickness of 450 nm. 0.065 Ga 0.935 This is the N layer. The P-type cladding layer 108 is located closer to the active layer 104 and has a concentration of 2 × 10⁻¹⁴. 18 cm -3 P-type Al with Mg doped, 150 nm film thickness. 0.065 Ga 0.935 The N layer and the concentration 1 × 10 located on the side furthest from the active layer 104. 19 cm -3 P-type Al with Mg doped, 300 nm film thickness. 0.065 Ga 0.935 It has an N layer. The contact layer 109 has a concentration of 1 × 10 20 cm -3 This is a 100 nm thick P-type GaN layer doped with Mg.

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

[0058] On the other hand, in the nitride semiconductor light-emitting element 100 according to Example E01, since the Al composition ratio of the second P-side guide layer 107 is greater than that of the first P-side guide layer 105, the average bandgap energy of the second P-side guide layer 107 is greater than that of the first P-side guide layer 105. Comparing the characteristic calculation results of Example E01 with Comparative Examples C02 and C06 shown in Figure 10, it can be seen that in Example E01, because the average bandgap energy of the second P-side guide layer 107 is greater than that of the first P-side guide layer 105 (that is, because the refractive index of the first P-side guide layer 105 is higher than that of the second P-side guide layer 107), the proportion of light present in the undoped region near the active layer 104 and the first P-side guide layer 105 with a low impurity concentration is increased in the light distribution in the stacking direction, thereby increasing the light confinement coefficient and reducing waveguide loss.

[0059] Next, the film thickness of the first P-side guide layer 105 (Tpg1) and the impurity concentration in the second P-side guide layer 107 (Ppg2) will be explained using Figures 14 to 17. Figures 14 and 15 are graphs showing the relationship between the operating voltage and waveguide loss of the nitride-based semiconductor light-emitting element 100 according to this embodiment at 200 mA operation and the film thickness of the first P-side guide layer 105, respectively. In Figures 14 and 15, the total film thickness of the first P-side guide layer 105 and the second P-side guide layer 107 of the nitride-based semiconductor light-emitting element 100 according to Comparative Example C01 is set to 140 nm, and the operating voltage and waveguide loss are shown when the film thickness of the first P-side guide layer 105 is changed, respectively. Also, in Figures 14 and 15, the average impurity concentration (average Mg concentration) in the second P-side guide layer 107 is set to 1 × 10⁻¹⁶. 17 cm -3 From 5x10 18 cm -3 The operating voltage and waveguide loss when the values ​​are changed up to that point are shown. Figures 16 and 17 are graphs showing the relationship between the effective refractive index difference ΔN and the optical confinement coefficient of the nitride semiconductor light-emitting element 100 according to this embodiment and the film thickness of the first P-side guide layer 105, respectively.

[0060] As shown in Figure 14, the average impurity concentration of the second P-side guide layer 107 is 5 × 10⁻⁶ 17 cm -3 By doing so, the operating voltage can be reduced. As shown in Figure 15, the average impurity concentration of the second P-side guide layer 107 is 2 × 10⁻⁶. 18 cm -3 By doing the following, waveguide losses can be reduced. Therefore, the average impurity concentration of the second P-side guide layer 107 is set to 5 × 10 17 cm -3 The above 2 x 10 18 cm -3 By doing the following, both the operating voltage and waveguide loss can be reduced. Furthermore, the average impurity concentration of the second P-side guide layer 107 is set to 1 × 10⁻⁶. 18 cm -3 By doing the following, waveguide losses can be further reduced.

[0061] As shown in Figures 14 and 17, increasing the thickness of the first P-side guide layer 105 reduces the operating voltage and increases the optical confinement coefficient. On the other hand, as shown in Figure 16, decreasing the thickness of the first P-side guide layer 105 (i.e., increasing the thickness of the second P-side guide layer 107 (Tpg2)) increases the effective refractive index difference ΔN. However, decreasing the thickness of the first P-side guide layer 105 causes the electron barrier layer 106, which has a high Al composition and a low refractive index, to approach the active layer 104, thus reducing the optical confinement coefficient.

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

[0063] Furthermore, in the structure of Example E01, as shown in Figure 14, the average impurity concentration of the second P-side guide layer 107 is set to 5 × 10⁻⁶. 17cm -3 By doing so, the operating voltage can be reduced. Furthermore, as shown in Figure 15, the average impurity concentration of the second P-side guide layer 107 is 2 × 10⁻⁶. 18 cm -3 By doing the following, waveguide losses can be reduced. Therefore, the average impurity concentration of the second P-side guide layer 107 is set to 5 × 10 17 cm -3 The above 2 x 10 18 cm -3 By doing the following, it is possible to reduce both the operating voltage and waveguide loss. Furthermore, the average impurity concentration of the second P-side guide layer 107 is set to 1 × 10⁻⁶ 18 cm -3 By doing the following, the waveguide loss is 4.91 cm -1 This can be reduced even further.

[0064] Based on the above, as in Example E01, the film thickness of the second P-side guide layer 107 is made thicker than the film thickness of the first P-side guide layer 105, and the average impurity concentration of the second P-side guide layer 107 is set to 5 × 10⁻⁶. 17 cm -3 The above 2 x 10 18 cm -3 By doing the following, it is possible to increase the effective refractive index difference ΔN, reduce the operating voltage, and reduce waveguide losses.

[0065] In the structure of Example E01, 17.67 × 10 -3 1 x 10 -2 This enables the realization of a high effective refractive index difference ΔN. This also solves the problem in conventional ultraviolet semiconductor laser devices where a refractive index anti-guide type gain-guide mechanism is likely to occur due to the decrease in refractive index of the well layer as the operating carrier density increases. In the absence of current injection, ΔN determined by the waveguide structure is 1 × 10⁻⁶. -2 With the above conditions, even if the effective refractive index difference ΔN decreases during laser oscillation due to the decrease in the refractive index of the well layer as the operating carrier density of the well layer increases, the effective refractive index difference ΔN will not become negative, and a stable refractive index waveguide mechanism can be maintained. -2The reason why such a high effective refractive index difference ΔN can be obtained is that, in the semiconductor laminate 100S according to this embodiment, an electron barrier layer 106 is formed between the first P-side guide layer 105 and the second P-side guide layer 107, which reduces the distance dp between the electron barrier layer 106 and the active layer 104.

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

[0067] Here, a distribution example of the P-type impurity (Mg) concentration in the stacking direction of the nitride semiconductor light-emitting device 100 of Example E02 will be described using FIG. 18. FIG. 18 is a graph schematically showing the bandgap energy distribution and the light intensity distribution in the stacking direction of the semiconductor stack 100S of Example E02. In FIG. 18, a distribution example of the P-type impurity concentration in the stacking direction of the semiconductor stack 100S of Example E02 is also shown.

[0068] As described above, the average impurity (Mg) concentration of the first P-side guide layer 105 is 1.0×10 18 cm -3 less than. Thereby, an increase in the waveguide loss of the nitride semiconductor light-emitting device 100 can be suppressed, and the operating voltage can be reduced. Also, as in the P-type impurity concentration distribution example shown in FIG. 18, the impurity concentration of the first P-side guide layer 105 may increase as it moves away from the active layer 104. Thereby, in the region of the first P-side guide layer 105 close to the active layer 104, that is, in the region with high light intensity, the impurity concentration can be reduced, and in the region of the first P-side guide layer 105 far from the active layer 104, that is, in the region with low light intensity, the impurity concentration can be increased. Therefore, both reduction of the waveguide loss and reduction of the operating voltage of the nitride semiconductor light-emitting device 100 can be achieved. In this case, the average impurity concentration of the first P-side guide layer 105 may be 1.0×10 17 cm -3 or more and less than 1.0×10 18 cm -3 as well.

[0069] Also, as described above, the average impurity concentration of the second P-side guide layer 107 is 1.0×10 18 cm -3The foregoing is the case. Thereby, the operating voltage of the nitride semiconductor light-emitting device 100 can be reduced. Further, the impurity concentration of the second P-side guide layer 107 may increase as it moves away from the active layer 104. Thereby, in a region of the second P-side guide layer 107 close to the active layer 104, that is, in a region where the light intensity is high, the impurity concentration can be reduced, and in a region of the second P-side guide layer 107 far from the active layer 104, that is, in a region where the light intensity is low, the impurity concentration can be increased. Therefore, both reduction of waveguide loss and reduction of operating voltage of the nitride semiconductor light-emitting device 100 can be achieved. More specifically, the average impurity concentration in a region of the second P-side guide layer 107 close to the active layer 104, that is, in a region from the interface close to the active layer 104 to the center in the stacking direction of the second P-side guide layer 107 is 1.0×10 18 cm -3 or more and 3.0×10 18 cm -3 or less, and the average impurity concentration in a region of the second P-side guide layer 107 from the center in the stacking direction to the interface far from the active layer 104 may be 1.0×10 19 cm -3 or more and 1.0×10 20 cm -3 or less.

[0070] Further, in the electron barrier layer 106 having a large Al composition ratio, since the activation rate of Mg which is an impurity is low, in order to reduce the electrical resistance in the electron barrier layer 106, it is necessary to increase the impurity concentration. Along with such high-concentration Mg doping to the electron barrier layer 106, Mg diffuses into the second P-side guide layer 107. Therefore, as shown in FIG. 18, at the interface between the second P-side guide layer 107 and the electron barrier layer 106, the impurity concentration becomes high, and as it approaches the position (Px1 or Px2) where the impurity concentration becomes minimum from the interface, the impurity concentration becomes low.

[0071] Therefore, regarding the impurity concentration in the second P-side guide layer 107 and the P-type cladding layer 108, as shown in the example of the P-type impurity concentration distribution (solid and dashed lines) in Figure 18, there is a position (Px1 or Px2) where the impurity concentration is minimum at a distance of 0.2 μm or less in the stacking direction from the electron barrier layer 106 toward the P-type cladding layer 108 (i.e., toward upward), and the impurity concentration may increase monotonically toward upward from this position. This makes it possible to reduce the impurity concentration in the region of the second P-side guide layer 107 and the P-type cladding layer 108 that is close to the active layer 104, thereby suppressing the increase in waveguide loss. Note that the position where the impurity concentration is minimum may be located in the second P-side guide layer 107 or in the P-type cladding layer 108.

[0072] In the ultraviolet region of 375 nm, the influence of light absorption loss between the impurity levels of Mg (used as a P-type impurity) and the conduction band increases as the Al composition ratio of the AlGaN layer decreases to 6% or less. Therefore, by keeping the Mg concentration as low as possible in the AlGaN layer with an Al composition ratio of 6% or less, the influence of free carrier loss and light absorption loss via the Mg impurity levels can be reduced.

[0073] Therefore, the second P-side guide layer 107 preferably has a region where the Mg concentration decreases as it moves away from the active layer 104. This reduces the effects of free carrier loss associated with Mg doping and light absorption loss via Mg impurity levels.

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

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

[0076] As the average Al composition ratio of the N-type cladding layer decreases compared to the average Al composition ratio of the P-type cladding layer, the average refractive index of the N-type cladding layer can be increased. Therefore, it is possible to suppress the peak position of the light intensity distribution in the stacking direction of the nitride semiconductor light-emitting element (i.e., the vertical light distribution peak position shown in Figure 10) from being too biased toward the direction from the active layer to the P-type cladding layer. As a result, as shown in the characteristic calculation results of Comparative Examples C04, C02, and C05 in Figure 10, waveguide loss can be reduced as the average Al composition ratio of the N-type cladding layer decreases compared to the average Al composition ratio of the P-type cladding layer.

[0077] Similar to Comparative Example C04, in the nitride-based semiconductor light-emitting element 100 of Example E03, the average Al composition ratio of the N-type cladding layer 102 is smaller than the average Al composition ratio of the P-type cladding layer 108, thus reducing waveguide loss.

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

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

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

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

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

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

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

[0085] Furthermore, in the nitride semiconductor light-emitting element 100, if the average Al composition ratios of the N-type cladding layer 102 and the P-type cladding layer 108 are different from each other, the average value of the average Al composition ratios of the N-side guide layer 103, the first P-side guide layer 105, and the second P-side guide layer 107 (i.e., the average values ​​of Xng, Xpg1, and Xpg2) may be 60% or less or 50% or less of the average value of the average Al composition ratios of the N-type cladding layer 102 and the P-type cladding layer 108 (i.e., the average values ​​of Xnc and Xpc). However, if the average Al composition ratios of the N-side guide layer 103, the first P-side guide layer 105, and the second P-side guide layer 107 are made too small, the difference between the Fermi energy of electrons and the conduction charge in the three layers during laser oscillation will decrease, increasing the electron concentration and thus increasing free carrier loss. To suppress this, the average Al composition ratio of the N-side guide layer 103, the average Al composition ratio of the first P-side guide layer 105, and the average Al composition of the second P-side guide layer 107 should each be 1.5% or more.

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

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

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

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

[0090] Similar to Comparative Example C14, in the nitride-based semiconductor light-emitting element 100 of Example E06, the average Al composition ratio of the N-type cladding layer 102 is smaller than the average Al composition ratio of the P-type cladding layer 108, thus reducing waveguide loss.

[0091] [1-4-7. Example E07] Example E07 will be described using Figure 19. Figure 19 is a schematic graph showing the bandgap energy distribution and light intensity distribution in the stacking direction of the semiconductor laminate 100S of Example E07. As shown in Figure 19, Example E07 differs from Example E01 in that it includes a region in which the Al composition ratio of the first P-side guide layer 105 and the second P-side guide layer 107 increases monotonically as it moves away from the active layer 104, but it is the same in other configurations. In other words, in Example E07, the first P-side guide layer 105 and the second P-side guide layer 107 include a bandgap gradient region in which the bandgap energy increases as it moves away from the active layer 104. Here, the configuration in which the Al composition ratio increases monotonically also includes a configuration in which there is a region in which the Al composition ratio is constant in the stacking direction. For example, it also includes a configuration in which the Al composition ratio increases in a step-like manner. In Example E07, the Al composition ratios of the first P-side guide layer 105 and the second P-side guide layer 107 are represented by Xpg1 and Xpg2, respectively. For example, the Al composition ratio Xpg1 of the first P-side guide layer 105 near the interface closer to the active layer 104 and near the interface further away from the active layer 104 are 1.5% and 2.5%, respectively. The Al composition ratio Xpg2 of the second P-side guide layer 107 near the interface closer to the active layer 104 and near the interface further away from the active layer 104 are 3.5% and 4.5%, respectively.

[0092] In this way, by monotonically increasing the Al composition ratio in the first P-side guide layer 105 and the second P-side guide layer 107 as the distance from the active layer 104 increases, the refractive index of each layer can be increased as it approaches the active layer 104. Therefore, since the refractive index of the region close to the active layer 104 in the first P-side guide layer 105 and the second P-side guide layer 107 can be increased, it is possible to suppress the peak position of the light intensity distribution in the stacking direction from being too biased toward the P-type cladding layer 108. This reduces waveguide loss.

[0093] According to Example E07, the optical confinement coefficient is 5.52%, and the effective refractive index difference ΔN is 20.9 × 10⁻⁶. -3 The waveguide loss is 4.71 cm².-1 Therefore, a nitride-based semiconductor light-emitting element 100 with a vertical light distribution peak position of 15.1 nm can be realized.

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

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

[0096] In Examples E07 and E08, both the first P-side guide layer 105 and the second P-side guide layer 107 included a bandgap gradient region. However, at least one of the first P-side guide layer 105 and the second P-side guide layer 107 may also include a bandgap gradient region. Similar effects can be achieved with this configuration as well.

[0097] According to Example E08, the optical confinement coefficient is 6.06%, and the effective refractive index difference ΔN is 22.1 × 10⁻⁶. -3 The waveguide loss is 4.37 cm². -1 Therefore, a nitride-based semiconductor light-emitting element 100 with a vertical light distribution peak position of 13.2 nm can be realized.

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

[0099] Here, Al x Ga 1-x-y In y The band gap energy in the N layer and Al z Ga 1-z The relationship with the band gap energy in the N layer (0≦z<1) is explained using Figure 20. Figure 20 shows Al x Ga 1-x-y In y The band gap energy in the N layer and Al z Ga 1-z This graph shows the relationship with the band gap energy in the N layer. In Figure 20, the horizontal axis is Al x Ga 1-x-y In y This shows the In composition ratio y in the N layer, with the vertical axis representing Al x Ga 1-x-y In y Figure 20 shows the Al composition ratio x in the N layer. x Ga 1-x-y In y In the N layer, Al z Ga 1-zThe relationship between the In composition ratio y and the Al composition ratio x required to obtain the same bandgap energy as the N layer is shown. Note that in Figure 20, Al z Ga 1-z The relationships for each case where the Al composition ratio z of the N layer is 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40 are shown. Also, Figure 20 shows Al x Ga 1-x-y In y The relationship between the In composition ratio y and the Al composition ratio x, which is necessary to make the lattice constant of the N layer equal to that of the GaN layer, is shown by the dashed line. Therefore, the region above (or to the left of) the dashed line in the graph of Figure 20 is Al x Ga 1-x-y In y The composition shows that the lattice constant of the N layer is smaller than that of the GaN layer, and the region below (or to the right of) the dashed line is Al x Ga 1-x-y In y The composition exhibits a lattice constant greater than that of the GaN layer in the N layer. For the lattice constant calculations, the lattice constants used for AlN, GaN, and InN were 0.311 nm, 0.3182 nm, and 0.354 nm, respectively.

[0100] Al x Ga 1-x-y In y Al in the N layer z Ga 1-z In order to obtain the same bandgap energy as the N layer, the following equation (1) must hold, as shown in Figure 20.

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

[0102] Thus, the first P-side guide layer 105 made of an AlGaN layer in each of the above embodiments can be replaced with a first P-side guide layer 105 made of an AlGaInN layer without changing the bandgap energy.

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

[0104] As shown in Figure 21, when a semiconductor laminate 100S is laminated on a substrate 101 (i.e., crystal growth is performed), warping occurs in both the substrate 101 and the semiconductor laminate 100S due to the tensile strain on the substrate 101 caused by the AlGaN layer within the semiconductor laminate 100S. For example, in Example E02, the tensile strain on the substrate 101 caused by the AlGaN layer results in warping in a direction that causes the upper surface of the semiconductor laminate 100S to become concave. Here, the amount of warping when the upper surface of the semiconductor laminate 100S becomes concave (i.e., the depth ΔR of the concave part indicated by the arrow in Figure 21) is expressed as a negative number. On the other hand, the amount of warping when the upper surface of the semiconductor laminate 100S becomes convex (i.e., the height of the convex part) is expressed as a positive number.

[0105] In Example E09, by adjusting the In composition ratio y and Al composition ratio x of the first P-side guide layer 105, the lattice constant of the first P-side guide layer 105 can be adjusted independently of the bandgap energy, thereby reducing the tensile strain of the first P-side guide layer 105 relative to the substrate 101. Consequently, the warping of the nitride-based semiconductor light-emitting element 100 can be reduced. This makes it possible to suppress wafer cracking and the occurrence of cracks in the wafer when the semiconductor laminate 100S is laminated onto the GaN wafer that serves as the base material of the substrate 101 and processed.

[0106] According to Example E09, the optical confinement coefficient is 5.62%, and the effective refractive index difference ΔN is 19.6 × 10⁻⁶. -3 The waveguide loss is 4.90 cm². -1 Therefore, a nitride-based semiconductor light-emitting element 100 with a vertical light distribution peak position of 14.3 nm can be realized.

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

[0108] Episode 1 <Epg2<Epc (2)

[0109] Episode 1 <Eng<Epg2 (3)

[0110] This will be explained below using equation (1). By transforming equation (1), we obtain the following equation (4).

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

[0112] Here, Al z Ga 1-z As the Al composition ratio z increases in the N layer, the band gap energy increases, so when the following equation (5) holds, Al z Ga 1-z The band gap energy of the N layer is, Google x Ga 1-x-y In y It will be larger than the band gap energy of the N layer.

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

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

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

[0116] Furthermore, the P-type cladding layer 108 is Al Xpc Ga 1-Xpc-Ypc In Ypc If N consists of N, then equation (2) holds if equation (7) below is satisfied.

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

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

[0119] Furthermore, the N-side guide layer 103 is Al Xng Ga 1-Xng-Yng In Yng If N consists of N, then equation (3) holds if equation (8) below is satisfied.

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

[0121] This makes it possible to make the refractive index of the first P-side guide layer 105 greater than that of the N-side guide layer 103 and the second P-side guide layer 107. Therefore, the position of the vertical light distribution peak can be brought even closer to the center of the stacking direction of the active layer 104.

[0122] [1-4-10. Example E10] Example E10 will now be described. Example E10 differs from Example E05 in that the first P-side guide layer 105 contains Al and In, but is otherwise identical in its configuration. In Example E10, the composition of the first P-side guide layer 105 is Al 0.04 Ga 0.9516 In 0.0084 It is N. Thus, by including Al and In in the first P-side guide layer 105, the same effect as in Example E09 is achieved in Example E10.

[0123] According to Example E10, the optical confinement coefficient is 6.12%, and the effective refractive index difference ΔN is 22.3 × 10⁻⁶. -3 The waveguide loss is 4.02 cm². -1 Therefore, a nitride-based semiconductor light-emitting element 100 with a vertical light distribution peak position of 14.0 nm can be realized.

[0124] [1-4-11. Example E11] Example E11 will now be described. Example E11 differs from Example E02 in that the N-type cladding layer 102 contains Al and In, but is otherwise identical in its composition. In Example E11, the composition of the N-type cladding layer 102 is Al 0.065 Ga 0.925 In 0.01It is N. The effects of the N-type cladding layer 102 containing Al and In will be explained using Figures 22 to 24. Figure 22 is a graph showing the relationship between the position in the stacking direction and the bandgap energy of the semiconductor laminate 100S of Example E11. Figure 23 is a graph showing the relationship between the position in the stacking direction and the stress of the semiconductor laminate 100S of Example E11. The stress shown in Figure 23 is the stress on the substrate 101, and a positive stress value means that the stress is compressive, and a negative stress value means that the stress is tensile. Note that in Figure 23, the N-type cladding layer 102 contains Al, similar to Example E02. 0.065 Ga 0.935 The stress when N is used is also shown by a dotted line. Figure 24 is a graph showing the relationship between the position in the stacking direction of the semiconductor laminate 100S of Example E11 and the integral stress. Here, the integral stress refers to the value obtained by integrating the stress at each position in the stacking direction of the semiconductor laminate 100S from the interface between the N-type cladding layer 102 and the substrate 101 upwards in the stacking direction. In other words, the integral stress refers to the value obtained by integrating the stress shown in Figure 23 from position zero to each position in the stacking direction. Note that in Figure 24, the N-type cladding layer 102 is Al, similar to Example E02. 0.065 Ga 0.935 The integral stress for the case where N is the dominant component is also shown by the dotted line.

[0125] As shown in Figure 22, in Example E11, the bandgap energy of the N-type cladding layer 102 can be reduced compared to Example E02. In other words, in Example E11, the refractive index of the N-type cladding layer 102 can be increased compared to Example E02. Therefore, it is possible to suppress the peak position of the light intensity distribution in the stacking direction from being too biased toward the direction from the active layer 104 toward the P-type cladding layer 108.

[0126] Furthermore, as shown in Figures 23 and 24, in Example E11, the tensile stress (strain) in the N-type cladding layer 102 can be reduced compared to Example E02. For example, when the semiconductor laminate 100S of Example E02 is laminated on a GaN substrate that is 5 cm square and 85 μm thick, the integral stress is -725.8 Pa·m, and the wafer warpage (see Figure 21) is 553.6 μm. On the other hand, when the semiconductor laminate 100S of Example E11 is laminated on a GaN substrate that is 5 cm square and 85 μm thick, the integral stress is -436.4 Pa·m, and the wafer warpage is 335.0 μm. Thus, according to Example E11, wafer warpage can be reduced, and therefore wafer cracking and the occurrence of cracks in the wafer can be suppressed.

[0127] According to Example E11, the optical confinement coefficient is 4.95%, and the effective refractive index difference ΔN is 9.29 × 10⁻⁶. -3 The waveguide loss is 4.23 cm². -1 Therefore, a nitride-based semiconductor light-emitting element 100 with a vertical light distribution peak position of 8.2 nm can be realized.

[0128] [1-4-12. Example E12] Example E12 will now be described. Example E12 differs from Example E05 in that the N-type cladding layer 102 contains Al and In, but is otherwise identical in its composition. In Example E12, the composition of the N-type cladding layer 102 is Al 0.10 Ga 0.89 In 0.01 It is N. The effects of the N-type cladding layer 102 containing Al and In will be explained using Figures 25 to 27. Figure 25 is a graph showing the relationship between the position in the stacking direction and the bandgap energy of the semiconductor laminate 100S of Example E12. Figure 26 is a graph showing the relationship between the position in the stacking direction and the stress of the semiconductor laminate 100S of Example E12. Note that in Figure 26, the N-type cladding layer 102 contains Al, similar to Example E05. 0.10 Ga 0.90The stress when N is used is also shown by a dotted line. Figure 27 is a graph showing the relationship between the position in the stacking direction of the semiconductor laminate 100S of Example E12 and the integral stress. Note that in Figure 27, the N-type cladding layer 102 is Al, similar to Example E05. 0.10 Ga 0.90 The integral stress for the case where N is the dominant component is also shown by the dotted line.

[0129] When the semiconductor laminate 100S of Example E12 is laminated on a GaN substrate that is 5 cm square and 85 μm thick, the integral stress is -835.5 Pa·m, and the wafer warpage (see Figure 21) is 639.4 μm. On the other hand, the N-type cladding layer 102 is Al, similar to Example E05. 0.10 Ga 0.90 When a semiconductor laminate 100S consisting of N is laminated on a GaN substrate measuring 5 cm square and 85 μm thick, the integral stress becomes -1126.4 Pa·m and the wafer warpage becomes 858.9 μm. As shown in Figures 25 to 27, the inclusion of Al and In in the N-type cladding layer 102 results in the same effects in Example E12 as in Example E11.

[0130] According to Example E12, the optical confinement coefficient is 5.87%, and the effective refractive index difference ΔN is 10.9 × 10⁻⁶. -3 The waveguide loss is 3.5 cm². -1 Therefore, a nitride-based semiconductor light-emitting element 100 with a vertical light distribution peak position of 11.0 nm can be realized.

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

[0132] In the nitride-based semiconductor light-emitting element 100, in order to emit light between 375 nm and 380 nm,0.01 Ga 0.99 It is necessary to use a well layer 104b having a band gap energy greater than or equal to the band gap energy of N and less than or equal to the band gap energy of GaN. The composition of the well layer 104b will be explained below with reference to Figure 28. Figure 28 is a graph illustrating the composition required for the well layer 104b of Example E13. The horizontal axis of Figure 28 shows the In composition ratio y, and the vertical axis shows the Al composition ratio x.

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

[0134] 2.34y≧x≧2.34y-0.234 (9)

[0135] In other words, if the Al composition ratio x and In composition ratio y of the well layer 104b correspond to the region between the solid and dashed lines shown in Figure 28, then it is possible to emit light between 375 nm and 380 nm.

[0136] Here, the lattice imperfections of well layer 104b with respect to GaN will be explained using Figure 29. Figure 29 is a graph showing the relationship between the In composition ratio of well layer 104b and the lattice imperfections with respect to GaN.

[0137] For example, In 0.01 Ga 0.99 Since N has a compressible lattice disorder of 0.11% relative to GaN, the composition of the well layer 104b is set to In 0.01 Ga 0.99 When N is used, the compressible lattice irregularity occurring in the well layer 104b is at most 0.11%. In contrast, when the composition of the well layer 104b is Al having Al composition ratio x and In composition ratio y that satisfy equation (9) x Ga 1-x-y Iny Let's explain the case where N is used. In this case, for example, if the In composition ratio y is 0.04, as shown in Figure 29, the compressible lattice irregularity occurring in the well layer 104b will be between 0.23% and 0.28%. Thus, by including Al and In in the well layer 104b, the compressible lattice irregularity occurring in the well layer 104b can be increased. Therefore, the tensile strain in the active layer 104 and its surrounding region can be reduced. If the In composition ratio in the well layer 104b is, for example, 0.06, as shown in Figure 29, the compressible lattice irregularity of the well layer 104b can be increased to between 0.34% and 0.38%, so that the tensile strain in the active layer 104 and its surrounding region can be further reduced.

[0138] Furthermore, increasing the compressible strain of the well layer 104b increases the energy difference between the ground state of heavy holes and light holes formed in the well layer 104b. As a result, when the nitride semiconductor light-emitting element 100 is operated by supplying current, the number of heavy holes in the ground state can be increased, thereby reducing the oscillation threshold current value. Therefore, the operating carrier density can be reduced, which suppresses the refractive index change in the current injection region of the well layer 104b and the refractive index decrease due to the plasma effect. From this, the decrease in the effective refractive index difference ΔN can be suppressed, and the horizontal transverse modes of the laser beam can be stabilized.

[0139] According to Example E13, the optical confinement coefficient is 5.69%, and the effective refractive index difference ΔN is 18.79 × 10⁻⁶. -3 The waveguide loss is 4.96 cm². -1 Therefore, a nitride-based semiconductor light-emitting element 100 with a vertical light distribution peak position of 12.84 nm can be realized.

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

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

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

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

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

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

[0146] To explain the effects of Example E14, we will describe them in comparison with the semiconductor laminate of Comparative Example C30. The semiconductor laminate 100S of Comparative Example C30 is an example of the semiconductor laminate 100S according to Embodiment 1, and differs from Example E14 in that the band gap energy of the first N-side guide layer 103a is smaller than the band gap energy of the second N-side guide layer 103b, but is the same in other configurations. The first N-side guide layer 103a of Comparative Example C30 is an undoped Al with a film thickness of 90 nm. 0.02Ga 0.98 It is an N layer, and the second N-side guide layer 103b is an undoped Al with a film thickness of 90 nm. 0.04 Ga 0.96 This is an N layer. Thus, in Comparative Example C30, the average Al composition of the N-side guide layer 103 is the same as in Examples E01 and E14. The Al composition of the first N-side guide layer 103a, which is a region of the N-side guide layer 103 far from the active layer 104, is 2%, and the Al composition ratio of the second N-side guide layer 103b, which is a region of the N-side guide layer 103 close to the active layer 104, is 4%.

[0147] In the nitride-based semiconductor light-emitting element of Comparative Example C30, the optical confinement coefficient is 5.1%, and the effective refractive index difference ΔN is 16.8 × 10⁻⁶. -3 The waveguide loss is 6.1 cm -1 The vertical light distribution peak position is 11.6 nm. Thus, the nitride-based semiconductor light-emitting element with the semiconductor stack of Comparative Example C30 does not exhibit the same characteristics as Example E01.

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

[0149] Specifically, according to Example E14, the optical confinement coefficient is 6.2%, and the effective refractive index difference ΔN is 17.4 × 10⁻⁶. -3 The waveguide loss is 3.6 cm². -1 Therefore, a nitride-based semiconductor light-emitting element 100 with a vertical light distribution peak position of 5.6 nm can be realized.

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

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

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

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

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

[0155] As described above, reducing the Al composition ratio in the region of the N-side guide layer 103 close to the active layer 104 makes the refractive index of the region of the N-side guide layer 103 close to the active layer 104 higher than the refractive index of the region of the N-side guide layer 103 farther from the active layer 104. Therefore, the proportion of light located in the undoped N-side guide layer 103 and the first P-side guide layer 105 near the active layer 104 increases. Consequently, in the nitride-based semiconductor light-emitting element 100 equipped with the semiconductor stack 100S of Example E15, waveguide loss is further reduced and the light confinement coefficient to the active layer 104 is further increased compared to the nitride-based semiconductor light-emitting element 100 equipped with the semiconductor stack 100S of Example E01.

[0156] Specifically, according to Example E15, the optical confinement coefficient is 5.9%, and the effective refractive index difference ΔN is 17.4 × 10⁻⁶. -3 The waveguide loss is 4.1 cm -1 Therefore, a nitride-based semiconductor light-emitting element 100 with a vertical light distribution peak position of 6.5 nm can be realized.

[0157] Thus, according to Example E15, the position of the vertical light distribution peak is located in the well layer 104b region of the active layer 104, 10 × 10 -3 This method achieves the above effective refractive index difference ΔN, while also reducing waveguide losses and increasing the optical confinement coefficient.

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

[0159] As shown in Figure 32, the nitride-based semiconductor light-emitting element 200 according to this embodiment comprises a substrate 101, a semiconductor laminate 200S, a current blocking layer 110, a P-side electrode 111, and an N-side electrode 112. The semiconductor laminate 200S according to this embodiment differs from the semiconductor laminate 100S according to Embodiment 1 in that it comprises a buffer layer 221, and is otherwise identical.

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

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

[0162] Furthermore, when a GaN substrate is used as the substrate 101, when light reaches the substrate 101, the refractive index of the substrate 101 is higher than the effective refractive index of the semiconductor laminate 200S with respect to the waveguide mode, causing the light to diffuse throughout the substrate 101. In this case, the optical confinement coefficient of the waveguide mode to the active layer 104 decreases, increasing waveguide loss and thus increasing the oscillation threshold current value. As a result, the operating carrier density in the well layer 104b increases, and the effective refractive index difference ΔN decreases due to the decrease in the refractive index of the current injection region in the well layer 104b. Consequently, the waveguide mechanism of light propagating through the waveguide including the ridge 108R becomes a refractive index anti-guide type waveguide mechanism. Therefore, the horizontal transverse mode becomes unstable, and kinks are more likely to occur in the current-optical output characteristics.

[0163] On the other hand, as in the nitride-based semiconductor light-emitting element 200 according to this embodiment, by including a buffer layer 221 made of InGaN having a bandgap energy smaller than the energy corresponding to ultraviolet light, light is absorbed in the buffer layer 221, thus suppressing light from reaching the substrate 101.

[0164] According to this embodiment, the optical confinement coefficient is 5.69%, and the effective refractive index difference ΔN is 18.79 × 10⁻⁶. -3 The waveguide loss is 4.96 cm². -1 Therefore, a nitride-based semiconductor light-emitting element 200 with a vertical light distribution peak position of 12.84 nm can be realized.

[0165] (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 two buffer layers. Hereinafter, the nitride-based semiconductor light-emitting element according to this embodiment will be described with reference to Figure 33, focusing on the differences from the nitride-based semiconductor light-emitting element 200 according to Embodiment 2. Figure 33 is a schematic cross-sectional view showing the overall configuration of the nitride-based semiconductor light-emitting element 300 according to this embodiment.

[0166] As shown in Figure 33, the nitride-based semiconductor light-emitting element 300 according to this embodiment comprises a substrate 101, a semiconductor laminate 300S, a current blocking layer 110, a P-side electrode 111, and an N-side electrode 112. The semiconductor laminate 300S according to this embodiment differs from the semiconductor laminate 200S according to Embodiment 2 in that it comprises a buffer layer 321, and is otherwise identical.

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

[0168] 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. For example, when the semiconductor laminate 300S is laminated on a GaN substrate that is 5 cm square and 85 μm thick, the integral stress becomes -227.5 Pa·m and the wafer warpage becomes 173.8 μm.

[0169] According to this embodiment, the optical confinement coefficient is 5.69%, and the effective refractive index difference ΔN is 18.79 × 10⁻⁶. -3 The waveguide loss is 4.96 cm². -1 Therefore, a nitride-based semiconductor light-emitting element 300 with a vertical light distribution peak position of 12.84 nm can be realized.

[0170] (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.

[0171] 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.

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

[0173] 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.

[0174] For example, each buffer layer according to Embodiment 2 and Embodiment 3 may be applied to each embodiment of the nitride-based semiconductor light-emitting element 100 according to Embodiment 1. [Industrial applicability]

[0175] 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 exposure equipment and processing machines. [Explanation of Symbols]

[0176] 100, 200, 300 Nitride-based semiconductor light-emitting elements 100F and 100R end faces 100S, 200S, and 300S semiconductor laminated bodies 101 substrate 102 N-type cladding layer 103 N-side guide layer 103a First N-side guide layer 103b Second N-side guide layer 104 active layer 104a and 104c barrier layers 104b well layer 105 First P-side guide layer 106, 916, and 926 electron barrier layers 107 Second P-side guide layer 108 P-type cladding layer 108R ridge 108T groove 109 contact layer 110 current blocking layer 111 P-side electrode 112 N-side electrode 221 and 321 buffer layers 915 and 925 P-side guide layers

Claims

1. N-type cladding layer, An N-side guide layer is positioned above the aforementioned N-type cladding layer, An active layer positioned above the N-side guide layer, A first P-side guide layer is positioned above the active layer, An electron barrier layer positioned above the first P-side guide layer, A second P-side guide layer is positioned above the aforementioned electron barrier layer, A P-type cladding layer is positioned above the second P-side guide layer, A contact layer positioned above the P-type cladding layer, The system comprises a P-side electrode positioned above the contact layer, Each of the first P-side guide layer, the second P-side guide layer, and the N-side guide layer is made of AlGaN. The aforementioned active layer emits ultraviolet light, The contact layer makes ohmic contact with the P-side electrode, At least a portion of the P-side electrode is Ag. Nitride semiconductor light-emitting element.

2. The film thickness of the second P-side guide layer is thicker than the film thickness of the first P-side guide layer. Ridges are formed in the second P-side guide layer. The nitride-based semiconductor light-emitting element according to claim 1.

3. The aforementioned active layer is Two barrier layers, Includes a well layer disposed between the two barrier layers. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

4. The bandgap energies of each of the two barrier layers are greater than the average bandgap energy of the first P-side guide layer and the average bandgap energy of the N-side guide layer, and less than the bandgap energy of the electron barrier layer. The nitride-based semiconductor light-emitting element according to claim 3.

5. The well layer comprises Al and In The nitride-based semiconductor light-emitting element according to claim 3.

6. The thickness of the first P-side guide layer is thicker than the thickness of each of the two barrier layers. The nitride-based semiconductor light-emitting element according to claim 3.

7. The average bandgap energy of the N-side guide layer is greater than the average bandgap energy of the first P-side guide layer. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

8. At least one of the first P-side guide layer and the second P-side guide layer includes a bandgap gradient region in which the bandgap energy increases as it moves away from the active layer. The nitride-based semiconductor light-emitting device according to claim 7.

9. The average bandgap energy of the N-side guide layer is smaller than the average bandgap energy of the second P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 7.

10. The combined thickness of the first P-side guide layer and the second P-side guide layer is thicker than the thickness of the N-side guide layer. The nitride-based semiconductor light-emitting device according to claim 7.

11. The average impurity concentration of the first P-side guide layer is 1 × 10⁻⁶ １８ cm －３ Less than Nitride-based semiconductor light-emitting element according to claim 1 or 2.

12. The average impurity concentration of the second P-side guide layer is 1 × 10⁻⁶ １８ cm －３ That's all. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

13. The aforementioned N-type cladding layer and the aforementioned P-type cladding layer contain Al, The average Al composition ratio of the N-type cladding layer is less than or equal to the average Al composition ratio of the P-type cladding layer. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

14. The average Al composition ratio of the N-side guide layer, the average Al composition ratio of the first P-side guide layer, and the average Al composition ratio of the second P-side guide layer are 1.5% or more, and are 60% or less of the average Al composition ratio of the P-type cladding layer. The nitride-based semiconductor light-emitting element according to claim 13.

15. The aforementioned N-type cladding layer comprises Al and In. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

16. Displaced below the aforementioned N-type cladding layer, a substrate made of GaN, The substrate and the N-type cladding layer are further comprising a buffer layer made of InGaN, disposed between them. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

17. The impurity concentration in the second P-side guide layer is lower than that in the electron barrier layer. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

18. The N-type cladding layer is further provided with a buffer layer located below it. The aforementioned N-type cladding layer is made of AlGaN, The aforementioned electron barrier layer is made of AlGaN, The aforementioned P-type cladding layer is made of AlGaN, The buffer layer has a bandgap energy smaller than the energy corresponding to ultraviolet light. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

19. The average bandgap energy of the second P-side guide layer is greater than the average bandgap energy of the first P-side guide layer. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

20. The average bandgap energy of the P-type cladding layer is smaller than the average bandgap energy of the electron barrier layer. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

21. The Al composition ratio at the position furthest from the active layer in the N-side guide layer is smaller than the average Al composition ratio of the second P-side guide layer. The Al composition ratio at the position of the N-side guide layer closest to the active layer is greater than the average Al composition ratio of the first P-side guide layer. Nitride-based semiconductor light-emitting element according to claim 1 or 2.

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