Nitride-based semiconductor light-emitting device

Abstract

A nitride-based semiconductor light-emitting device (100) comprising: an N-type cladding layer (102); an N-side guide layer (103); an active layer (104); a P-type cladding layer (108); and a P-side guide layer (upper P-side guide layer (107)) and an electron barrier layer (106) that are disposed between the active layer (104) and the P-type cladding layer (108), wherein the N-type cladding layer (102), the N-side guide layer (103), the P-side guide layer, the electron barrier layer (106), and the P-type cladding layer (108) contain Al, the active layer (104) has an N-side barrier layer (104a), a well layer (104b) that is disposed above the N-side barrier layer (104a), and a P-side barrier layer (104c) that is disposed above the well layer (104b), the average band gap energy of the P-side barrier layer (104c) is larger than the average band gap energy of the N-side barrier layer (104a), and the thickness of the P-side barrier layer (104c) is smaller than the thickness of the N-side barrier layer (104a).

Description

Nitride-based semiconductor light-emitting device

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

[0002] Conventionally, nitride-based semiconductor light-emitting elements that emit light such as ultraviolet light have been known (see, for example, Patent Document 1). For example, if a watt-class ultraviolet laser light source can be realized using a nitride-based semiconductor light-emitting element, it can be used as a light source for exposure, a light source for processing, and the like.

[0003] JP 2010-258363 A

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

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

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

[0007] In order to solve the above problems, one aspect of the nitride-based semiconductor light-emitting device according to the present disclosure includes an N-type cladding layer, an N-side guide layer disposed above the N-type cladding layer, an active layer disposed above the N-side guide layer, a P-type cladding layer disposed above the active layer, a P-side guide layer and an electron barrier layer disposed between the active layer and the P-type cladding layer, wherein the N-type cladding layer, the N-side guide layer, the P-side guide layer, the electron barrier layer and the P-type cladding layer contain Al, and the active layer has an N-side barrier layer, a well layer disposed above the N-side barrier layer, and a P-side barrier layer disposed above the well layer, wherein an average bandgap energy of the P-side barrier layer is larger than that of the N-side barrier layer, and a film thickness of the P-side barrier layer is smaller than that of the N-side barrier layer.

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

[0009] 1 is a schematic plan view showing the overall configuration of a nitride-based semiconductor light-emitting device according to a first embodiment. FIG. 2 is a schematic cross-sectional view showing the overall configuration of the nitride-based semiconductor light-emitting device according to the first embodiment. FIG. 3 is a schematic cross-sectional view showing the configuration of an active layer included in the nitride-based semiconductor light-emitting device according to the first embodiment. FIG. 4 is a graph showing the distribution of bandgap energy and refractive index in the stacking direction of well layers and barrier layers of a 405 nm band semiconductor light-emitting device. FIG. 5 is a graph showing the distribution of bandgap energy and refractive index in the stacking direction of well layers and barrier layers of a 375 nm band semiconductor light-emitting device. FIG. 6 is a graph showing the distribution of effective refractive index and gain in the horizontal direction of a 375 nm band semiconductor light-emitting device. FIG. 7 is a diagram showing the far-field pattern in the horizontal direction of a conventional ultraviolet semiconductor light-emitting device. FIG. 8 is a graph showing the light intensity distribution, bandgap energy distribution, and impurity concentration distribution in the stacking direction of a semiconductor stack according to a comparative example. FIG. 9 is a graph showing the light intensity distribution, bandgap energy distribution, and impurity concentration distribution of a semiconductor stack according to the first embodiment. 1 is a graph showing the relationship between the effective refractive index difference ΔN of a nitride-based semiconductor light-emitting element and the film thickness of a P-side barrier layer. 2 is a graph showing the relationship between the waveguide loss of a nitride-based semiconductor light-emitting element and the film thickness of a P-side barrier layer. 3 is a graph showing the relationship between the light intensity distribution peak position in the stacking direction of a nitride-based semiconductor light-emitting element and the film thickness of a P-side barrier layer. 4 is a graph showing the relationship between the light intensity distribution peak position in the stacking direction of a nitride-based semiconductor light-emitting element and the film thickness of a P-side barrier layer. 5 is a graph showing the coordinates of positions in the stacking direction of a nitride-based semiconductor light-emitting element. 6 is a graph showing a bandgap energy distribution of a semiconductor stack of a nitride-based semiconductor light-emitting element according to a first modification of the first embodiment. 7 is a graph showing a bandgap energy distribution of a semiconductor stack of a nitride-based semiconductor light-emitting element according to a second modification of the first embodiment. 8 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting element according to the second embodiment. 9 is a graph showing a bandgap energy distribution of a semiconductor stack of a nitride-based semiconductor light-emitting element according to the second embodiment.1 is a graph schematically showing a bandgap energy distribution of a semiconductor laminate of a nitride-based semiconductor light-emitting device according to a second modification of the second embodiment. FIG. 2 is a schematic cross-sectional view showing an overall configuration of a nitride-based semiconductor light-emitting device according to a third embodiment. FIG. 3 is a graph schematically showing a bandgap energy distribution of a semiconductor laminate of a nitride-based semiconductor light-emitting device according to a third embodiment. FIG. 4 is a graph schematically showing a bandgap energy distribution of a semiconductor laminate of a nitride-based semiconductor light-emitting device according to a first modification of the third embodiment. FIG. 5 is a graph schematically showing a bandgap energy distribution of a semiconductor laminate of a nitride-based semiconductor light-emitting device according to a second modification of the third embodiment.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, and the arrangement and connection of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0011] Furthermore, each figure is a schematic diagram and is not necessarily an exact representation. Therefore, the scales and the like do not necessarily match in each figure. In each figure, the same reference numerals are used to denote substantially the same components, and redundant explanations will be omitted or simplified.

[0012] In this specification, the terms "above" and "below" do not refer to vertically above and below in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. The terms "above" and "below" are used not only when two components are arranged with a gap between them and another component is present between them, but also when two components are arranged in contact with each other.

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

[0014] [1-1. Overall Configuration] First, the overall configuration of the nitride-based semiconductor light-emitting device according to this embodiment will be described with reference to FIGS. 1, 2A, and 2B. FIGS. 1 and 2A are a schematic plan view and a cross-sectional view, respectively, showing the overall configuration of a nitride-based semiconductor light-emitting device 100 according to this embodiment. FIG. 2A shows a cross section taken along line II-II in FIG. 1. FIG. 2B is a schematic cross-sectional view showing the configuration of an active layer 104 included in the nitride-based semiconductor light-emitting device 100 according to this embodiment. Note that each figure shows an X-axis, a Y-axis, and a Z-axis, which are orthogonal to each other. The X-axis, the Y-axis, and the Z-axis represent a right-handed Cartesian coordinate system. The stacking direction of the nitride-based semiconductor light-emitting device 100 is parallel to the Z-axis direction, and the main emission direction of light (laser light) is parallel to the Y-axis direction.

[0015] As shown in FIG. 2A , the nitride-based semiconductor light-emitting element 100 includes a semiconductor stack 100S including nitride-based semiconductor layers, and emits light from a facet 100F (see FIG. 1 ) perpendicular to the stacking direction (i.e., the Z-axis direction) of the semiconductor stack 100S. In this embodiment, the nitride-based semiconductor light-emitting element 100 is a semiconductor laser element having two facets 100F and 100R that form a cavity. The facet 100F is a front facet from which laser light is emitted, and the facet 100R is a rear facet having a higher reflectivity than the facet 100F. The nitride-based semiconductor light-emitting element 100 also has a waveguide formed between the facets 100F and 100R. In this embodiment, the reflectivities of the facets 100F and 100R are 5% or more and 30% or less, and 95% or more, respectively. The cavity length of nitride-based semiconductor light-emitting element 100 according to the present embodiment (i.e., the distance between facet 100F and facet 100R) is 500 μm or more and 2000 μm or less. Nitride-based semiconductor light-emitting element 100 emits ultraviolet light having a peak wavelength in the 375 nm band, for example. Nitride-based semiconductor light-emitting element 100 may emit ultraviolet light having a peak wavelength outside the 375 nm band, or may emit light having a peak wavelength in a wavelength band other than ultraviolet light.

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

[0017] The substrate 101 is a plate-like member that serves as a base for the nitride-based semiconductor light-emitting device 100. In this embodiment, the substrate 101 is disposed below the N-type cladding layer 102 and is made of N-type GaN. More specifically, the substrate 101 has an average concentration of 1×10 １８ cm －３ The substrate is a GaN substrate with a thickness of 85 μm and doped with Si.

[0018] The N-type cladding layer 102 is an N-type nitride-based semiconductor layer disposed above the substrate 101. The N-type cladding layer 102 has a smaller average refractive index and a larger average band gap energy than the active layer 104. In this embodiment, the N-type cladding layer 102 contains Al. Specifically, the N-type cladding layer 102 is an N-type Al layer having a thickness of 800 nm. ０．０６５ Ga ０．９３５ The N-type cladding layer 102 contains impurities at an average concentration of 1×10 １８ cm －３ of Si is added.

[0019] In the present disclosure, the average band gap energy of a certain layer refers to the value of the band gap energy obtained by integrating the magnitude of the band gap energy at a certain position in the stacking direction of the layer in the stacking direction from the position of the interface on the substrate side in the stacking direction of the layer to the position of the interface on the side farther from the substrate, and dividing the result by the film thickness of the layer (the distance between the interface on the substrate side and the interface on the side farther from the substrate).

[0020] The average refractive index of a layer is the refractive index at a certain position in the stacking direction of the layer, integrated in the stacking direction from the interface position on the substrate side to the interface position on the side farther from the substrate, and divided by the film thickness of the layer (the distance between the interface on the substrate side and the interface on the side farther from the substrate).

[0021] The average impurity concentration of a certain layer is the value of the impurity concentration obtained by integrating the magnitude of the impurity concentration at a certain position in the stacking direction of the layer from the position of the interface on the substrate side in the stacking direction of the layer to the position of the interface on the side farther from the substrate in the stacking direction of the layer, and dividing the result by the film thickness of the layer (the distance between the interface on the substrate side and the interface on the side farther from the substrate). In an N-type semiconductor layer, the impurity refers to the impurity doped to obtain N-type conductivity, and in a P-type semiconductor layer, it refers to the impurity doped to obtain P-type conductivity.

[0022] The N-side guide layer 103 is an optical guide layer made of a nitride-based semiconductor and disposed above the N-type cladding layer 102. The N-side guide layer 103 has a larger average refractive index and a smaller average band gap energy than the N-type cladding layer 102. The N-side guide layer 103 contains Al.

[0023] 2A, the N-side guide layer 103 includes 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 first N-side guide layer 103a is an N-type Al 101B layer having a thickness of 127 nm. ０．０３ Ga ０．９７ The first N-side guide layer 103a contains an N-type impurity at an average concentration of 1×10 １８ cm －３ The second N-side guide layer 103b is an undoped AlN layer with a thickness of 60 nm. ０．０３ Ga ０．９７ The second N-side guide layer 103b has an average N-type impurity concentration of 1×10 １８ cm －３ Hereinafter, the N-type impurity concentration in each layer on the N side and the P-type impurity concentration in each layer on the P side will also be simply referred to as the impurity concentration.

[0024] The active layer 104 is disposed above the N-side guide layer 103 and is a light-emitting layer made of a nitride-based semiconductor. In this embodiment, the active layer 104 has a quantum well structure and emits ultraviolet light. Specifically, as shown in FIG. 2B , the active layer 104 includes an N-side barrier layer 104a, a well layer 104b disposed above the N-side barrier layer 104a, and a P-side barrier layer 104c disposed above the well layer 104b. The N-side barrier layer 104a and the P-side barrier layer 104c are each a nitride-based semiconductor layer disposed above the N-side guide layer 103 and functioning as a barrier in the quantum well structure. The well layer 104b is a nitride-based semiconductor layer functioning as a well in the quantum well structure. The average bandgap energy of the P-side barrier layer 104c is larger than that of the N-side barrier layer 104a, and the thickness of the P-side barrier layer 104c is smaller than that of the N-side barrier layer 104a.

[0025] The average bandgap energy of the N-side barrier layer 104a is smaller than the average bandgap energy of the N-type cladding layer 102. In other words, the average refractive index of the N-side barrier layer 104a is larger than the average refractive index of the N-type cladding layer 102. This makes it possible to suppress a shift of the peak of the light intensity distribution in the stacking direction from the active layer 104 toward the N-type cladding layer 102.

[0026] In this embodiment, the N-side barrier layer 104a is an undoped AlN layer having a thickness of 18 nm. ０．０４ Ga ０．９６ The well layer 104b is an undoped In layer with a thickness of 17.5 nm. ０．０１ Ga ０．９９ The P-side barrier layer 104c is an undoped Al layer with a thickness of 10 nm. ０．１２ Ga ０．８８ This is the N layer.

[0027] The electron barrier layer 106 is a nitride-based semiconductor layer disposed between the active layer 104 and the P-type cladding layer 108. The average band gap energy of the electron barrier layer 106 is larger than the average band gap energy of the P-side barrier layer 104c. This makes it possible to suppress leakage of electrons from the active layer 104 to the P-type cladding layer 108. The electron barrier layer 106 contains Al. In this embodiment, the average band gap energy of the electron barrier layer 106 is larger than the average band gap energy of the P-type cladding layer 108. The electron barrier layer 106 is a 5 nm-thick P-type Al ０．３６ Ga ０．６４ The electron barrier layer 106 contains a P-type impurity at an average concentration of 1×10 １９ cm －３ of Mg is added.

[0028] The upper P-side guide layer 107 is an example of an optical guide layer included in a P-side guide layer disposed between the active layer 104 and the P-type cladding layer 108. The upper P-side guide layer 107 is a nitride-based semiconductor layer containing Al. In this embodiment, the optical guide layer has the upper P-side guide layer 107 disposed above the electron barrier layer 106. The average band gap energy of the upper P-side guide layer 107 is smaller than the average band gap energy of the P-type cladding layer 108. In addition, the average refractive index of the upper P-side guide layer 107 is larger than the average refractive index of the P-type cladding layer 108. The upper P-side guide layer 107 is a 40 nm-thick P-type Al ０．０３ Ga ０．９７ The upper P-side guide layer 107 is doped with Mg as a P-type impurity, and the Mg concentration in the upper P-side guide layer 107 decreases as it approaches the P-type cladding layer 108. The Mg concentration in the upper P-side guide layer 107 near the interface closer to the electron barrier layer 106 is 4×10 １８ cm －３ The Mg concentration near the interface closer to the P-type cladding layer 108 is 3.2×10 １８ cm －３ is.

[0029] The P-type cladding layer 108 is disposed above the active layer 104 and is a P-type nitride-based semiconductor layer. The P-type cladding layer 108 has a smaller average refractive index and a larger average band gap energy than the active layer 104. The P-type cladding layer 108 contains Al. In this embodiment, the P-type cladding layer 108 is disposed above the upper P-side guide layer 107. The P-type cladding layer 108 is a P-type Al layer having a thickness of 450 nm. ０．０６５ Ga ０．９３５ The P-type cladding layer 108 is an N layer. Mg is added to the P-type impurity. The P-type cladding layer 108 has a first region with a thickness of 60 nm, a second region with a thickness of 180 nm located on the first region, a third region with a thickness of 100 nm located on the second region, and a fourth region with a thickness of 110 nm located on the third region. In the first region, the Mg concentration decreases from 3.2×10 to 5.0 with increasing distance from the active layer 104. １８ cm －３ From 2.0 x 10 １８ cm －３ In the second region, the Mg concentration decreases to 2.0×10 １８ cm －３ In the third region, the Mg concentration decreases from 2.0×10 to 1.0×10 with increasing distance from the active layer 104. １８ cm －３ to 1.0 x 10 １９ cm －３ In the fourth region, the Mg concentration increases to 1.0×10 １９ cm －３ is constant.

[0030] As shown in FIGS. 1 and 2A, a ridge 108R is formed in the P-type cladding layer 108. Two grooves 108T are formed in the P-type cladding layer 108, arranged along the ridge 108R and extending in the Y-axis direction. In this embodiment, the ridge width W is approximately 30 μm. As shown in FIG. 2A, the distance between the lower end of the ridge 108R (i.e., the bottom of the groove 108T) and the active layer 104 is defined as dp. The distance between the lower end of the ridge 108R and the electron barrier layer 106 is defined as dc.

[0031] The contact layer 109 is a nitride-based semiconductor layer disposed above the P-type cladding layer 108 and in contact with the P-side electrode 111. In this embodiment, the contact layer 109 is a P-type GaN layer with a film thickness of 100 nm. The contact layer 109 contains impurities with an average concentration of 1×10 ２０ cm －３ of Mg is added.

[0032] The current blocking layer 110 is disposed above the P-type cladding layer 108 and is an insulating layer that is transparent to light from the active layer 104. The current blocking layer 110 is disposed in a region of the upper surfaces of the P-type cladding layer 108 and the contact layer 109 other than the upper surface of the ridge 108R. The current blocking layer 110 may also be disposed in a partial region of the upper surface of the ridge 108R. For example, the current blocking layer 110 may be disposed in an edge region of the upper surface of the ridge 108R. In this embodiment, the current blocking layer 110 is made of SiO ２ It is a layer.

[0033] The P-side electrode 111 is a conductive layer disposed above the P-type cladding layer 108. In this embodiment, the P-side electrode 111 is disposed above the contact layer 109 and the current blocking layer 110. The P-side electrode 111 is a single-layer film or a multi-layer film formed of at least one of Cr, Ti, Ni, Pd, Pt, Ag, and Au, for example.

[0034] Furthermore, by using Ag, which has a low refractive index for light from the ultraviolet to infrared regions, for at least a portion of the P-side electrode 111 on the contact layer 109, it is possible to reduce the leakage of light propagating through the waveguide into the P-side electrode 111, thereby reducing waveguide loss in the P-side electrode 111. Ag has a refractive index of 0.5 or less in the wavelength range of 325 nm to 1500 nm and a refractive index of 0.2 or less in the wavelength range of 360 nm to 950 nm. As a result, the P-side electrode 111 containing Ag can reduce optical loss in the P-side electrode 111 over a wide wavelength range of 325 nm to 950 nm. In this case, even if the thickness of the P-type cladding layer 108 is 0.4 μm or less, the leakage of light propagating through the waveguide into the P-side electrode 111 can be reduced, thereby reducing the series resistance of the nitride-based semiconductor light-emitting device 100 and suppressing an increase in waveguide loss. As a result, the operating voltage and operating current can be reduced.

[0035] In order to stably confine the light propagating through the waveguide within the ridge 108R, it is necessary to form 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, as will be described later. Specifically, a SiO 2 layer having a refractive index lower than that of the P-type cladding layer 108 is formed on the sidewall of the ridge 108R. ２ In this case, if the thickness of the P-type cladding layer 108 becomes too thin, the SiO ２ Therefore, the thickness of the P-type cladding layer 108 may be 150 nm or more.

[0036] The thickness of the P-type cladding layer 108 may be greater than the total thickness of the P-side optical guide layers (in this embodiment, the thickness of the upper P-side guide layer 107) and the total thickness of the N-side optical guide layers (in this embodiment, the thickness of the N-side guide layer 103). This allows the P-type cladding layer 108 to have a thickness sufficient to confine light below the P-side electrode 111, thereby suppressing waveguide loss. Furthermore, when the P-side electrode 111 contains Ag, the thickness of the P-type cladding layer 108 may be, for example, 200 nm or more and 400 nm or less. This allows the operating voltage and operating current to be reduced while suppressing waveguide loss.

[0037] Furthermore, a layer with a high Al composition ratio, such as the P-type cladding layer 108, causes a large strain on the substrate 101 made of N-type GaN. By reducing the film thickness of the P-type cladding layer 108, the total Al content in the P-type cladding layer 108 can be reduced, thereby reducing the strain on the substrate 101 in the P-type cladding layer 108. Therefore, cracking of the nitride-based semiconductor light-emitting element 100 caused by the strain in the P-type cladding layer 108 can be suppressed.

[0038] The Ag contained in the p-side electrode 111 may be in ohmic contact with the contact layer 109. That is, the p-side electrode 111 may include an Ag film that is in ohmic contact with the contact layer 109. This allows light to be confined below the contact layer 109, thereby further reducing optical loss in the p-side electrode 111.

[0039] The N-side electrode 112 is a conductive layer disposed below the substrate 101 (i.e., on the principal surface of the substrate 101 opposite to the principal surface on which the N-type cladding layer 102 and the like are disposed). The N-side electrode 112 is a single-layer film or a multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt, and Au, for example.

[0040] 2A , the nitride-based semiconductor light-emitting element 100 has the above-described configuration, and therefore an effective refractive index difference ΔN occurs between the inner portion of the ridge 108R and the outer portion (groove 108T portion) of the ridge 108R, which allows light generated in the portion of the active layer 104 below the ridge 108R to be confined in the horizontal direction (i.e., the X-axis direction).

[0041] [1-2. Problems of Ultraviolet Semiconductor Light-Emitting Devices] 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 described in detail with reference to FIGS. 3 to 6. Hereinafter, FIG. 3 is a graph showing the distribution of bandgap energy (Eg) and refractive index in the stacking direction of well layers and barrier layers of a semiconductor light-emitting device operating in the 405 nm band, which has a wavelength longer than that of ultraviolet light. FIG. 4 is a graph showing the distribution of bandgap energy (Eg) and refractive index in the stacking direction of well layers and barrier layers of a semiconductor light-emitting device operating in the 375 nm band, which is the ultraviolet range. FIG. 5 is a graph showing the distribution of effective refractive index and gain in the horizontal direction (corresponding to the X-axis direction in FIGS. 1 to 2B ) of a 375 nm band semiconductor light-emitting device. FIG. 6 is a diagram showing the far-field pattern in the horizontal direction of a conventional ultraviolet semiconductor light-emitting device. The horizontal axis of FIG. 6 represents the radiation angle in the horizontal direction, and the vertical axis represents the light intensity.

[0042] 3, in a 405 nm band semiconductor light emitting device, the band gap energy of the well layer is relatively small, so the difference ΔEc between the conduction band potential energy of the barrier layer and the electron quantum level energy can be set to a relatively large value (198 meV). In this case, the Fermi energy Ef of electrons is sufficiently smaller than the conduction band potential energy of the barrier layer, so that leakage of electrons from the well layer, across the barrier layer, to the P-side semiconductor layer can be suppressed.

[0043] On the other hand, in an ultraviolet semiconductor light-emitting device, the band gap energy of the well layer is relatively large, so the difference ΔEc between the conduction band potential energy of the barrier layer and the electron quantum level energy is small (67 meV), as shown in Figure 4. In this case, the Fermi energy Ef of electrons can be larger than the conduction band potential energy of the barrier layer, so electrons tend to leak from the well layer, over the barrier layer, and into the P-side semiconductor layer. As a result, more carriers cannot contribute to light emission in the well layer, and the operating carrier density in the well layer increases.

[0044] Increasing the operating carrier density in the well layer in this way increases the amplification gain of light in the well layer. Meanwhile, due to the relationship between the real and imaginary parts of the complex refractive index of the well layer in the current injection region, the refractive index of the well layer decreases as the amplification gain in the well layer increases. Furthermore, as the carrier density in the well layer in the current injection region increases, the refractive index of the well layer in the current injection region decreases due to the plasma effect. As a result, the effective refractive index in the current injection region may be lower than the effective refractive index outside the current injection region. For example, if the semiconductor light-emitting device is a laser device having a ridge and current is injected into the ridge, the effective refractive index in the ridge, which is the current injection region, may be lower than the effective refractive index outside the current injection region, as shown in FIG. 5 .

[0045] As a result, the waveguide mechanism of the laser light propagating through the waveguide corresponding to the ridge of the semiconductor light-emitting device becomes a refractive index anti-guiding gain waveguide mechanism. Therefore, a higher proportion of the laser light propagates outside the current injection region (the region below the ridge) in the well layer, resulting in a peak at the base of the far-field pattern of the semiconductor light-emitting device, as shown in FIG. 6 . In this case, light is absorbed outside the current injection region in the well layer, increasing absorption loss in the well layer. This increases the oscillation threshold current of the semiconductor light-emitting device and reduces the thermal saturation level. This means that the temperature characteristics of the laser device deteriorate. Furthermore, a nonlinear bend (a so-called kink) may occur in a graph showing the current-light output (IL) characteristics of the semiconductor light-emitting device. This means that the stability of the light output of the semiconductor light-emitting device deteriorates.

[0046] The nitride-based semiconductor light-emitting device 100 according to this embodiment solves such problems associated with ultraviolet semiconductor light-emitting devices.

[0047] 7 and 8, the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be described in comparison with a comparative example. Fig. 7 is a graph schematically showing the light intensity distribution, band gap energy distribution, and impurity concentration distribution in the stacking direction of the semiconductor stack according to the comparative example. Fig. 8 is a graph schematically showing the light intensity distribution, band gap energy distribution, and impurity concentration distribution of the semiconductor stack 100S according to this embodiment.

[0048] 7 corresponds to the semiconductor stack described in Patent Document 1. The semiconductor stack according to the comparative example includes an N-type cladding layer 902, an N-side guide layer 903, an active layer (an N-side barrier layer 904a, a well layer 904b, and a P-side barrier layer 904c), an electron barrier layer 906, an upper P-side guide layer 907, and a P-type cladding layer 908. The semiconductor stack according to the comparative example differs from the semiconductor stack 100S according to the present embodiment mainly in that the band gap energies of the N-side barrier layer 904a and the P-side barrier layer 904c are equal to each other.

[0049] In this semiconductor stack according to the comparative example, when the N-type cladding layer 902 and the P-type cladding layer 908 are made of AlGaN and have the same Al composition ratio, the P-type cladding layer 908 has a higher refractive index than the N-type cladding layer 902. This is thought to be because the ionization energy of the P-type impurity, Mg, is greater than the ionization energy of the N-type impurity, Si, so the P-type impurity concentration must be set higher than the N-type impurity concentration. The P-type layer, which forms a relatively deep energy level, absorbs more light than the N-type layer, resulting in a higher refractive index. Therefore, as shown in FIG. 7 , the peak position of the light intensity distribution is biased toward the P-type cladding layer 908 from the center of the well layer 904b of the active layer (see the dashed-dotted line in FIG. 7 ). As a result, in the semiconductor stack according to the comparative example, the optical confinement coefficient of the active layer is reduced, and the operating carrier density is increased. This reduces the refractive index of the well layer 904b.

[0050] 8 , in the semiconductor stack 100S according to this embodiment, the average bandgap energy of the P-side barrier layer 104c is larger than the average bandgap energy of the N-side barrier layer 104a. That is, the average refractive index of the P-side barrier layer 104c is smaller than the average refractive index of the N-side barrier layer 104a. With this configuration, it is possible to shift the peak position of the light intensity distribution in the stacking direction toward the N-side barrier layer 104a. In other words, the nitride-based semiconductor light-emitting element 100 according to this embodiment can improve the controllability of the peak position of the light intensity distribution.

[0051] In this way, by moving the peak position of the light intensity distribution closer to the active layer 104, that is, by moving the peak position of the light intensity distribution away from the upper P-side guide layer 107 and the P-type cladding layer 108, it is possible to reduce free carrier loss due to impurities in the upper P-side guide layer 107 and the P-type cladding layer 108. This makes it possible to reduce the oscillation threshold current value and improve the thermal saturation level. In other words, it is possible to realize a nitride-based semiconductor light-emitting element 100 with excellent temperature characteristics and high slope efficiency. This enables the nitride-based semiconductor light-emitting element 100 to operate at high temperatures and with high output power.

[0052] Furthermore, in this embodiment, the thickness of the P-side barrier layer 104c is smaller than the thickness of the N-side barrier layer 104a. This reduces the distance from the well layer 104b to the bottom end of the ridge 108R. That is, the low-refractive-index region in the trench 108T can be brought closer to the well layer. This increases the effective refractive index difference ΔN. Therefore, the optical confinement factor in the waveguide of the nitride-based semiconductor light-emitting element 100 can be increased. This allows the nitride-based semiconductor light-emitting element 100 to stably confine the horizontal transverse mode of laser light in the waveguide, thereby suppressing the occurrence of kinks in the current-light output characteristics.

[0053] Furthermore, in this embodiment, the average bandgap energy of the upper P-side guide layer 107 is smaller than the average bandgap energy of the P-type cladding layer 108. In other words, the average refractive index of the upper P-side guide layer 107 is larger than the average refractive index of the P-type cladding layer 108. This makes it possible to prevent the peak position of the light intensity distribution in the stacking direction from approaching the P-type cladding layer 108. This makes it possible to reduce free carrier loss caused by impurities in the P-type cladding layer 108.

[0054] Furthermore, in this embodiment, the average band gap energy of the P-side barrier layer 104c is smaller than the average band gap energy of the electron barrier layer 106. As a result, electrons that pass over the P-side barrier layer 104c and travel toward the P-type cladding layer 108 are blocked by the electron barrier layer 106, and the electrons can be returned to the active layer 104. Therefore, electrons that do not contribute to light emission but cause heat generation can be reduced, thereby reducing the oscillation threshold current value and improving 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.

[0055] [1-4. Simulation Results] The characteristics of the nitride-based semiconductor light-emitting device 100 according to this embodiment will be described using simulation results. Note that the configuration of the nitride-based semiconductor light-emitting device used in this simulation is the same as that of the nitride-based semiconductor light-emitting device 100 according to this embodiment described above, except for the N-side barrier layer 104a, the P-side barrier layer 104c, the upper P-side guide layer 107, and the P-type cladding layer 108.

[0056] The upper P-side guide layer 107 used in this simulation is a P-type Al ０．０３ Ga ０．９７ The upper P-side guide layer 107 is doped with Mg as a P-type impurity, and the Mg concentration in the upper P-side guide layer 107 decreases as it approaches the P-type cladding layer 108. The Mg concentration in the upper P-side guide layer 107 near the interface closer to the electron barrier layer 106 is 4×10 １８ cm －３ The Mg concentration near the interface closer to the P-type cladding layer 108 is 2.8×10 １８ cm －３ is.

[0057] The P-type cladding layer 108 used in this simulation was a P-type Al ０．０６５ Ga ０．９３５ The P-type cladding layer 108 is an N layer. Mg is added to the P-type impurity. The P-type cladding layer 108 has a first region with a thickness of 40 nm, a second region with a thickness of 180 nm located on the first region, a third region with a thickness of 100 nm located on the second region, and a fourth region with a thickness of 130 nm located on the third region. In the first region, the Mg concentration decreases from 2.8×10 to 1.5 with increasing distance from the active layer 104. １８ cm －３ From 2.0 x 10 １８ cm －３ In the second region, the Mg concentration decreases to 2.0×10 １８ cm －３ In the third region, the Mg concentration decreases from 2.0×10 to 1.0×10 with increasing distance from the active layer 104. １８ cm －３ to 1.0 x 10 １９ cm －３ In the fourth region, the Mg concentration increases to 1.0×10 １９ cm －３ is constant.

[0058] The optical confinement coefficient, effective refractive index difference ΔN, waveguide loss, and light intensity distribution peak position in the stacking direction of the nitride-based semiconductor light-emitting element will be described below with reference to Fig. 9 to Fig. 12. Fig. 9, Fig. 10, Fig. 11, and Fig. 12 are graphs showing the relationship between the optical confinement coefficient, effective refractive index difference ΔN, waveguide loss, and light intensity distribution peak position in the stacking direction of the nitride-based semiconductor light-emitting element and the film thickness of the P-side barrier layer 104c, respectively.

[0059] In this simulation, the total thickness (Tb1+Tb2) of the thickness Tb2 of the P-side barrier layer 104c and the thickness Tb1 of the N-side barrier layer 104a is set to 28 nm. That is, when the thickness Tb2 of the P-side barrier layer 104c is 2 nm, the thickness Tb1 of the N-side barrier layer 104a is 26 nm. That is, the left half of the graph in each figure shows the case where Tb1>Tb2, and the right half shows the case where Tb1<Tb2.

[0060] Each figure also shows the relationship between the Al composition ratio Xb2 of the P-side barrier layer 104c and the Al composition ratio Xb1 of the N-side barrier layer 104a. In each figure, curve (broken line) a shows the relationship when Xb1=0.02 and Xb2=0.14, curve b shows the relationship when Xb1=0.04 and Xb2=0.12, curve c shows the relationship when Xb1=0.06 and Xb2=0.10, curve d shows the relationship when Xb1=0.08 and Xb2=0.08, curve e shows the relationship when Xb1=0.10 and Xb2=0.06, curve f shows the relationship when Xb1=0.12 and Xb2=0.04, and curve g shows the relationship when Xb1=0.14 and Xb2=0.02.

[0061] First, the relationship between the optical confinement coefficient of the nitride-based semiconductor light-emitting device and the film thickness of the P-side barrier layer 104c (and the N-side barrier layer 104a) will be described with reference to FIG.

[0062] 9 , the optical confinement factor tends to be large when the thickness Tb2 of the P-side barrier layer 104c is smaller than the thickness Tb1 of the N-side barrier layer 104a and the Al composition ratio Xb2 of the P-side barrier layer 104c is larger than the Al composition ratio Xb1 of the N-side barrier layer 104a (i.e., the average bandgap energy of the P-side barrier layer 104c is larger than the average bandgap energy of the N-side barrier layer 104a). Therefore, as in the nitride-based semiconductor light-emitting element 100 according to this embodiment, the optical confinement factor can be increased by making the average bandgap energy of the P-side barrier layer 104c larger than the average bandgap energy of the N-side barrier layer 104a and making the thickness Tb2 of the P-side barrier layer 104c smaller than the thickness Tb1 of the N-side barrier layer 104a.

[0063] Next, the relationship between the effective refractive index difference ΔN of the nitride-based semiconductor light-emitting element and the film thickness of the P-side barrier layer 104c (and the N-side barrier layer 104a) will be described with reference to FIG.

[0064] 10 , when the thickness Tb2 of the P-side barrier layer 104c is smaller than the thickness Tb1 of the N-side barrier layer 104a and the Al composition ratio Xb2 of the P-side barrier layer 104c is larger than the Al composition ratio Xb1 of the N-side barrier layer 104a, the effective refractive index difference ΔN tends to be larger. Therefore, as in the nitride-based semiconductor light-emitting element 100 according to this embodiment, the effective refractive index difference ΔN can be increased by making the average bandgap energy of the P-side barrier layer 104c larger than the average bandgap energy of the N-side barrier layer 104a and making the thickness Tb2 of the P-side barrier layer 104c smaller than the thickness Tb1 of the N-side barrier layer 104a.

[0065] Next, the relationship between the waveguide loss of the nitride-based semiconductor light-emitting device and the film thickness of the P-side barrier layer 104c (and the N-side barrier layer 104a) will be described with reference to FIG.

[0066] 11 , when the thickness Tb2 of the P-side barrier layer 104c is smaller than the thickness Tb1 of the N-side barrier layer 104a and the Al composition ratio Xb2 of the P-side barrier layer 104c is larger than the Al composition ratio Xb1 of the N-side barrier layer 104a, the waveguide loss tends to be smaller. Therefore, as in the nitride-based semiconductor light-emitting element 100 according to this embodiment, the average bandgap energy of the P-side barrier layer 104c is made larger than the average bandgap energy of the N-side barrier layer 104a and the thickness Tb2 of the P-side barrier layer 104c is made smaller than the thickness Tb1 of the N-side barrier layer 104a, thereby making it possible to reduce the waveguide loss.

[0067] Next, the relationship between the peak position of the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element and the film thickness of the P-side barrier layer 104c (and the N-side barrier layer 104a) will be described with reference to Fig. 12. Here, the position of the light intensity distribution in the stacking direction will be described with reference to Fig. 13.

[0068] 13 is a graph showing coordinates of positions in the stacking direction of the nitride-based semiconductor light-emitting element. As shown in Fig. 13, the coordinate of the position in the stacking direction of the N-side end facet of the well layer 104b of the active layer 104, i.e., the boundary surface between the well layer 104b and the N-side barrier layer 104a, is set to zero, and the downward direction (toward the N-type cladding layer 102) is set to the negative direction of the coordinate, and the upward direction (toward the P-type cladding layer 108) is set to the positive direction of the coordinate.

[0069] 12 , when the thickness Tb2 of the P-side barrier layer 104c is smaller than the thickness Tb1 of the N-side barrier layer 104a and the Al composition ratio Xb2 of the P-side barrier layer 104c is larger than the Al composition ratio Xb1 of the N-side barrier layer 104a, the peak position of the light intensity distribution tends to move closer to the well layer 104b. Therefore, as in the nitride-based semiconductor light-emitting element 100 according to this embodiment, by making the average bandgap energy of the P-side barrier layer 104c larger than the average bandgap energy of the N-side barrier layer 104a and making the thickness Tb2 of the P-side barrier layer 104c smaller than the thickness Tb1 of the N-side barrier layer 104a, the peak position of the light intensity distribution in the stacking direction can be moved closer to the well layer 104b of the active layer 104.

[0070] From the results of a simulation similar to the above simulation, according to this embodiment, the optical confinement coefficient is 3.85%, and the effective refractive index difference ΔN is 0.22.9×10 －３ and the waveguide loss is 22.8 cm －１ It was confirmed that a nitride-based semiconductor light-emitting device 100 could be realized in which the light intensity distribution peak position in the stacking direction was 1.81 nm (that is, the peak position was within the well layer 104b).

[0071] [1-5. Modification 1] A nitride-based semiconductor light-emitting device according to Modification 1 of the present embodiment will be described. The nitride-based semiconductor light-emitting device according to this modification differs from nitride-based semiconductor light-emitting device 100 according to the present embodiment in the configuration of the P-side barrier layer, but is identical in other configurations. The nitride-based semiconductor light-emitting device according to this modification will be described below with reference to FIG. 14, focusing on the differences from nitride-based semiconductor light-emitting device 100 according to the present embodiment. FIG. 14 is a graph schematically showing the bandgap energy distribution of the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification.

[0072] 14, the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 124, an electron barrier layer 106, an upper P-side guide layer 107, and a P-type cladding layer 108. Although not shown in FIG. 14, the semiconductor stack of this modification further includes a contact layer 109, similar to the semiconductor stack 100S according to the present embodiment.

[0073] 14 , the active layer 124 according to this modification includes an N-side barrier layer 104a, a well layer 104b, and a P-side barrier layer 124c. The P-side barrier layer 124c includes a first P-side barrier layer 124ca and a second P-side barrier layer 124cb disposed above the first P-side barrier layer 124ca. In the nitride-based semiconductor light-emitting device according to this modification having such a configuration, the average bandgap energy of the P-side barrier layer 124c is larger than the average bandgap energy of the N-side barrier layer 104a, and the (total) film thickness of the P-side barrier layer 124c is smaller than the film thickness of the N-side barrier layer 104a, as in the P-side barrier layer 104c according to the present embodiment.

[0074] 14, the average band gap energy of the second P-side barrier layer 124cb is larger than the average band gap energy of the first P-side barrier layer 124ca. This reduces the band spike formed between the P-side barrier layer 124c and the electron barrier layer 106. Therefore, the electrical resistance of the nitride-based semiconductor light-emitting element caused by the band spike can be reduced, and the operating voltage of the nitride-based semiconductor light-emitting element can be reduced.

[0075] The average band gap energy of the second P-side barrier layer 124cb is smaller than the average band gap energy of the electron barrier layer 106. This makes it possible to prevent electrons traveling from the well layer 104b toward the upper P-side guide layer 107 from exceeding the electron barrier layer 106.

[0076] The first P-side barrier layer 124ca is a nitride-based semiconductor layer containing Al. The first P-side barrier layer 124ca is, for example, an AlGaN layer or an AlInGaN layer. The average impurity concentration of the first P-side barrier layer 124ca is 1×10 １８ cm －３ The following is the result.

[0077] The second P-side barrier layer 124cb is a nitride-based semiconductor layer containing Al. The second P-side barrier layer 124cb is, for example, an AlGaN layer or an AlInGaN layer. The average impurity concentration of the second P-side barrier layer 124cb is 1×10 １８ cm －３ This reduces the free carrier loss in the second P-side barrier layer 124cb, thereby reducing the waveguide loss of the nitride-based semiconductor light-emitting element.

[0078] [1-6. Modification 2] A nitride-based semiconductor light-emitting device according to Modification 2 of this embodiment will now be described. The nitride-based semiconductor light-emitting device according to this modification differs from the nitride-based semiconductor light-emitting device according to Modification 1 of this embodiment mainly in the arrangement positions of the electron barrier layer and the upper P-side guide layer (i.e., the stacking order). The nitride-based semiconductor light-emitting device according to this modification will be described below with reference to FIG. 15, focusing on the differences from the nitride-based semiconductor light-emitting device according to Modification 1 of this embodiment. FIG. 15 is a graph schematically showing the bandgap energy distribution of the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification.

[0079] 15, the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 124, an upper P-side guide layer 107a, an electron barrier layer 106, and a P-type cladding layer 108. Although not shown in FIG. 15, the semiconductor stack of this modification further includes a contact layer 109, similar to the semiconductor stack 100S according to the present embodiment.

[0080] The upper P-side guide layer 107a according to this modification is an example of an optical guide layer included in a P-side guide layer disposed between the active layer 104 and the P-type cladding layer 108. The upper P-side guide layer 107a is a nitride-based semiconductor layer containing Al. In the semiconductor stack according to this modification, the upper P-side guide layer 107a is disposed above the active layer 124. The electron barrier layer 106 is disposed above the upper P-side guide layer 107a. That is, the upper P-side guide layer 107a is disposed between the active layer 124 and the electron barrier layer 106.

[0081] The average bandgap energy of the upper P-side guide layer 107a is smaller than the average bandgap energy of the P-type cladding layer 108. The average refractive index of the upper P-side guide layer 107a is larger than the average refractive index of the P-type cladding layer 108. The upper P-side guide layer 107a is, for example, an AlGaN layer or an AlInGaN layer. The average impurity concentration of the upper P-side guide layer 107a is 1×10 １８ cm －３ The upper P-side guide layer 107a is, for example, a P-type Al 104 having a thickness of 60 nm.０．０２ Ga ０．９８ This is the N layer.

[0082] In this way, by disposing the upper P-side guide layer 107a, which has a lower Mg concentration than the electron barrier layer 106, between the electron barrier layer 106, which has a high Mg concentration, and the active layer 124, it is possible to reduce Mg that thermally diffuses into the active layer 124. Therefore, it is possible to further reduce the free carrier loss in the active layer 124, and therefore to further reduce the waveguide loss of the nitride-based semiconductor light-emitting element.

[0083] The nitride-based semiconductor light-emitting device according to this modification also includes a P-side electrode 111 disposed above the contact layer 109. In this modification, the P-side electrode 111 may contain Ag. More specifically, the P-side electrode 111 may include an Ag film in ohmic contact with the contact layer 109. By including such a P-side electrode 111 in the nitride-based semiconductor light-emitting device, it is possible to reduce the operating voltage and operating current while suppressing waveguide loss, as described above. Furthermore, as described above, by including Ag in the P-side electrode 111, it is possible to reduce the film thickness of the P-type cladding layer 108 while suppressing waveguide loss. This reduces the total Al content in the P-type cladding layer 108, thereby reducing strain in the P-type cladding layer 108 relative to the substrate 101. Therefore, cracking of the nitride-based semiconductor light-emitting device 100 due to strain in the P-type cladding layer 108 can be suppressed.

[0084] (Embodiment 2) A nitride-based semiconductor light-emitting element according to embodiment 2 will be described. The nitride-based semiconductor light-emitting element according to this embodiment differs from nitride-based semiconductor light-emitting element 100 according to embodiment 1 mainly in the configuration of the P-side light guide layer. The nitride-based semiconductor light-emitting element according to this embodiment will be described below, focusing on the differences from nitride-based semiconductor light-emitting element 100 according to embodiment 1.

[0085] [2-1. Overall Configuration] The overall configuration of the nitride-based semiconductor light-emitting device according to this embodiment will be described with reference to Fig. 16 and Fig. 17. Fig. 16 is a schematic cross-sectional view showing the overall configuration of nitride-based semiconductor light-emitting device 200 according to this embodiment. Fig. 17 is a graph schematically showing the bandgap energy distribution of semiconductor stack 200S of nitride-based semiconductor light-emitting device 200 according to this embodiment.

[0086] 16 , a nitride-based semiconductor light-emitting device 200 according to this embodiment includes a substrate 101, a semiconductor stack 200S, a current blocking layer 110, a P-side electrode 111, and an N-side electrode 112. The semiconductor stack 200S includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, a P-side guide layer 250, an electron barrier layer 106, a P-type cladding layer 208, and a contact layer 109.

[0087] The P-side guide layer 250 according to this embodiment is an optical guide layer disposed between the active layer 104 and the P-type cladding layer 208. In this embodiment, the P-side guide layer 250 includes an upper P-side guide layer 207 and a lower P-side guide layer 205.

[0088] The upper P-side guide layer 207 is an optical guide layer disposed above the electron barrier layer 106, and differs from the upper P-side guide layer 107 according to the first embodiment in film thickness and impurity concentration distribution. In this embodiment, the upper P-side guide layer 207 is a P-type Al ０．０３ Ga ０．９７ The upper P-side guide layer 207 is an N layer. Mg is added to the upper P-side guide layer 207 as a P-type impurity. The upper P-side guide layer 207 has a first region with a thickness of 100 nm and a second region with a thickness of 30 nm located on the first region. In the first region, the Mg concentration decreases from 4.0×10 to 5.0×10 with increasing distance from the active layer 104. １８ cm －３ From 2.0 x 10 １８ cm －３ In the second region, the Mg concentration decreases to 2.0×10 １８ cm －３ is constant.

[0089] The lower P-side guide layer 205 is an optical guide layer disposed between the active layer 104 and the electron barrier layer 106. In this embodiment, as shown in FIG. 17 , the average band gap energy of the lower P-side guide layer 205 is equal to or lower than the average band gap energy of the upper P-side guide layer 207. The lower P-side guide layer 205 is, for example, an AlGaN layer or an AlInGaN layer. The average impurity concentration of the lower P-side guide layer 205 is 1×10 １８ cm －３ The lower P-side guide layer 205 is, for example, a P-type Al layer having a thickness of 60 nm. ０．０３ Ga ０．９７ N layer or P-type Al with a thickness of 60 nm ０．０２ Ga ０．９８ In FIG. 17, the lower P-side guide layer 205 is a P-type Al ０．０３ Ga ０．９７ The band gap energy distribution for the N layer is shown.

[0090] The P-type cladding layer 208 differs from the P-type cladding layer 108 according to the first embodiment in the impurity concentration distribution. In this embodiment, the P-type cladding layer 208 is a P-type Al 104 layer having a thickness of 450 nm. ０．０６５ Ga ０．９３５ The P-type cladding layer 208 is an N layer. Mg is added to the P-type cladding layer 208 as a P-type impurity. The P-type cladding layer 208 has a first region with a thickness of 150 nm, a second region with a thickness of 100 nm located on the first region, and a third region with a thickness of 200 nm located on the second region. In the first region, the Mg concentration is 2.0×10 １８ cm －３ In the second region, the Mg concentration decreases from 2.0×10 to 1.0×10 with increasing distance from the active layer 104. １８ cm －３ to 1.0 x 10 １９ cm －３ In the third region, the Mg concentration increases to 1.0×10 １９ cm －３ is constant.

[0091] The P-type cladding layer 208 has a ridge 208R and a groove 208T formed therein, similar to the P-type cladding layer 108 according to the first embodiment.

[0092] In this embodiment, the P-side guide layer 250 has the lower P-side guide layer 205 disposed between the active layer 104 and the electron barrier layer 106, so that the electron barrier layer 106, which has a high impurity concentration, can be separated from the active layer 104. Therefore, the free carrier loss in the electron barrier layer 106 can be reduced, and the waveguide loss of the nitride-based semiconductor light-emitting element 200 can be reduced.

[0093] Furthermore, in this embodiment, the average bandgap energy of the lower P-side guide layer 205 is equal to or lower than the average bandgap energy of the upper P-side guide layer 207. In other words, the average refractive index of the lower P-side guide layer 205 is equal to or higher than the average refractive index of the upper P-side guide layer 207. This allows the lower P-side guide layer 205, which has a higher refractive index than the upper P-side guide layer 207, to be disposed near the active layer 104, so that the peak position of the light intensity distribution in the stacking direction can be moved closer to the active layer 104 than the upper P-side guide layer 207. This makes it possible to increase the optical confinement factor.

[0094] In this embodiment, the average impurity concentration of the lower P-side guide layer 205 is 1×10 １８ cm －３ This reduces free carrier loss in the lower P-side guide layer 205 close to the active layer 104, thereby reducing waveguide loss in the nitride-based semiconductor light-emitting element 200.

[0095] From the results of a simulation similar to the above simulation, it is found that, according to this embodiment, the lower P-side guide layer 205 is a P-type Al ０．０３ Ga ０．９７ In the case of an N layer (i.e., when the average band gap energy of the lower P-side guiding layer 205 is equal to the average band gap energy of the upper P-side guiding layer 207), the optical confinement factor is 3.35% and the effective refractive index difference ΔN is 19.2×10 －３ and the waveguide loss is 13.3 cm －１ It was confirmed that a nitride-based semiconductor light-emitting device 200 could be realized in which the light intensity distribution peak position in the stacking direction is 5.68 nm (that is, the peak position is within the well layer 104b).

[0096] The lower P-side guide layer 205 is a P-type AlN layer having a thickness of 60 nm. ０．０２ Ga ０．９８ In the case of an N layer (i.e., when the average band gap energy of the lower P-side guiding layer 205 is smaller than the average band gap energy of the upper P-side guiding layer 207), the optical confinement coefficient is 3.76% and the effective refractive index difference ΔN is 0.20.4×10 －３ and the waveguide loss is 10.6 cm －１ It was confirmed that a nitride-based semiconductor light-emitting device 200 having a light intensity distribution peak position of 56.1 nm in the stacking direction could be realized.

[0097] As a comparative example, a simulation was also performed on a nitride-based semiconductor light-emitting device in which the average band gap energy of the lower P-side guide layer was larger than the average band gap energy of the upper P-side guide layer. ０．０４ Ga ０．９６ N layer (average Mg concentration 1×10 １８ cm －３ ) and the upper P-side guide layer is a P-type Al ０．０３ Ga ０．９７ Simulation was performed on a nitride-based semiconductor light-emitting device having an N layer (the Mg concentration distribution is the same as that of the upper P-side guide layer 207). In this nitride-based semiconductor light-emitting device of the comparative example, the optical confinement coefficient is 2.94% and the effective refractive index difference ΔN is 18.1×10 －３ and the waveguide loss is 16.9 cm －１ The light intensity distribution peak position in the stacking direction is 142.6 nm. As described above, it was confirmed that the nitride-based semiconductor light-emitting element 200 of this embodiment is improved in all characteristics compared to the nitride-based semiconductor light-emitting element of the comparative example.

[0098] [2-2. Modification 1] A nitride-based semiconductor light-emitting device according to Modification 1 of the present embodiment will be described. The nitride-based semiconductor light-emitting device according to this modification differs from the nitride-based semiconductor light-emitting device 200 according to the present embodiment in the configuration of the P-side guide layer, but is identical in other configurations. The nitride-based semiconductor light-emitting device according to this modification will be described below with reference to FIG. 18 , focusing on the differences from the nitride-based semiconductor light-emitting device 200 according to the present embodiment. FIG. 18 is a graph schematically showing the bandgap energy distribution of the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification.

[0099] 18, the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, an electron barrier layer 106, a P-side guide layer 251, and a P-type cladding layer 208. Although not shown in FIG. 18, the semiconductor stack of this modification further includes a contact layer 109, similar to the semiconductor stack 200S according to the present embodiment.

[0100] The P-side guide layer 251 according to this modification is an optical guide layer disposed between the active layer 104 and the P-type cladding layer 208 , and includes an upper P-side guide layer 207 and a lower P-side guide layer 225 .

[0101] The lower p-side guide layer 225 includes a first lower p-side guide layer 225a and a second lower p-side guide layer 225b disposed above the first lower p-side guide layer 225a. The average bandgap energy of the first lower p-side guide layer 225a is smaller than the average bandgap energy of the second lower p-side guide layer 225b. That is, the average refractive index of the first lower p-side guide layer 225a is larger than the average refractive index of the second lower p-side guide layer 225b. The first lower p-side guide layer 225a is, for example, a GaN layer, an AlGaN layer, or an AlInGaN layer. The second lower p-side guide layer 225b is, for example, an AlGaN layer or an AlInGaN layer. The average impurity concentrations of the first lower p-side guide layer 225a and the second lower p-side guide layer 225b are 1×10 １８ cm －３ The following is the result.

[0102] As described above, in the nitride-based semiconductor light-emitting device according to this modification, the lower P-side guide layer 225 has the first lower P-side guide layer 225a with a large refractive index in a region close to the active layer 104. This allows the peak position of the light intensity distribution to be closer to the active layer 104. Therefore, a high optical confinement factor and low waveguide loss can be achieved.

[0103] Furthermore, the presence of an interface between the first lower P-side guide layer 225a and the second lower P-side guide layer 225b, which have different compositions, can suppress impurity diffusion from the P-type layer to the active layer 104, thereby suppressing deterioration of the active layer 104.

[0104] Here, by using a GaN layer as the first lower p-side guide layer 225a, the refractive index can be increased while reducing the tensile strain caused by lattice mismatch between the first lower p-side guide layer 225a and the substrate 101, compared to when an AlGaN layer is used. As a result, the peak position of the light intensity distribution can be moved closer to the active layer 104 while suppressing the occurrence of lattice defects.

[0105] Furthermore, by using AlInGaN as the first lower p-side guide layer 225a, compared to when an AlGaN layer is used, it is possible to increase the refractive index while reducing the tensile strain caused by lattice mismatch between the first lower p-side guide layer 225a and the substrate 101. As a result, it is possible to move the peak position of the light intensity distribution closer to the active layer 104 while suppressing the occurrence of lattice defects.

[0106] The average impurity concentration of the first lower P-side guide layer 225a and the second lower P-side guide layer 225b is set to 1×10 １８ cm －３ By satisfying the following conditions, it is possible to reduce free carrier loss in the lower P-side guide layer 225. Therefore, it is possible to reduce waveguide loss in the nitride-based semiconductor light-emitting element.

[0107] [2-3. Modification 2] A nitride-based semiconductor light-emitting device according to Modification 2 of the present embodiment will now be described. The nitride-based semiconductor light-emitting device according to this modification differs from the nitride-based semiconductor light-emitting device 200 according to the present embodiment in the configuration of the P-side guide layer, but is identical in other configurations. The nitride-based semiconductor light-emitting device according to this modification will be described below with reference to FIG. 19 , focusing on the differences from the nitride-based semiconductor light-emitting device 200 according to the present embodiment. FIG. 19 is a graph schematically showing the bandgap energy distribution of the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification.

[0108] 19, the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, an electron barrier layer 106, a P-side guide layer 252, and a P-type cladding layer 208. Although not shown in FIG. 19, the semiconductor stack of this modification further includes a contact layer 109, similar to the semiconductor stack 200S according to the present embodiment.

[0109] The P-side guide layer 252 according to this modification is an optical guide layer disposed between the active layer 104 and the P-type cladding layer 208 , and includes an upper P-side guide layer 207 and a lower P-side guide layer 235 .

[0110] The lower P-side guide layer 235 is an optical guide layer disposed between the active layer 104 and the electron barrier layer 106. The band gap energy of the lower P-side guide layer 235 increases as it approaches the electron barrier layer 106. That is, the refractive index of the lower P-side guide layer 235 decreases as it approaches the electron barrier layer 106. The lower P-side guide layer 235 is, for example, a GaN layer, an AlGaN layer, or an AlInGaN layer. For example, the Al composition ratio of the lower P-side guide layer 235 may increase as it approaches the electron barrier layer 106. The average impurity concentration of the lower P-side guide layer 235 is 1×10 １８ cm －３ The following is the result.

[0111] As described above, in the nitride-based semiconductor light-emitting device according to this modification, the refractive index of the lower P-side guide layer 235 increases toward the active layer 104. By increasing the refractive index in the region of the lower P-side guide layer 235 that is close to the active layer 104 in this manner, the peak position of the light intensity distribution can be moved closer to the active layer 104. Therefore, a high optical confinement factor and low waveguide loss can be achieved.

[0112] The average impurity concentration of the lower P-side guide layer 235 is set to 1×10 １８ cm －３ By satisfying the following conditions, it is possible to reduce free carrier loss in the lower P-side guide layer 235. Therefore, it is possible to reduce waveguide loss in the nitride-based semiconductor light-emitting element.

[0113] (Embodiment 3) A nitride-based semiconductor light-emitting device according to embodiment 3 will be described. The nitride-based semiconductor light-emitting device according to this embodiment differs from the nitride-based semiconductor light-emitting device 100 according to embodiment 1 mainly in the configuration of the P-side light guide layer. The nitride-based semiconductor light-emitting device according to this embodiment will be described below, focusing on the differences from the nitride-based semiconductor light-emitting device 100 according to embodiment 1.

[0114] 20 and 21, the overall configuration of the nitride-based semiconductor light-emitting device according to the present embodiment will be described. Fig. 20 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 300 according to the present embodiment. Fig. 21 is a graph showing a schematic bandgap energy distribution of a semiconductor stack 300S of the nitride-based semiconductor light-emitting device 300 according to the present embodiment.

[0115] 20 , a nitride-based semiconductor light-emitting device 300 according to this embodiment includes a substrate 101, a semiconductor stack 300S, a current blocking layer 110, a P-side electrode 111, and an N-side electrode 112. The semiconductor stack 300S includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, a lower P-side guide layer 305, an electron barrier layer 106, a P-type cladding layer 308, and a contact layer 109.

[0116] The lower P-side guide layer 305 according to the present embodiment is an example of an optical guide layer included in a P-side guide layer disposed between the active layer 104 and the P-type cladding layer 308. The lower P-side guide layer 305 is a nitride-based semiconductor layer containing Al. In the present embodiment, the P-side guide layer includes the lower P-side guide layer 305 disposed between the active layer 104 and the electron barrier layer 106. The average band gap energy of the lower P-side guide layer 305 is smaller than the average band gap energy of the P-type cladding layer 308.

[0117] The lower p-side guide layer 305 is, for example, an AlGaN layer or an AlInGaN layer. The average impurity concentration of the lower p-side guide layer 305 is 1×10 １８ cm －３ The lower P-side guide layer 305 is, for example, a P-type Al layer having a thickness of 60 nm. ０．０２ Ga ０．９８ This is the N layer.

[0118] The P-type cladding layer 308 differs from the P-type cladding layer 108 according to the first embodiment in the impurity concentration distribution. In this embodiment, the P-type cladding layer 308 is made of a P-type Al 2 O 3 layer having a thickness of 450 nm. ０．０６５ Ga ０．９３５ The P-type cladding layer 308 is an N layer. Mg is added to the P-type cladding layer 308 as a P-type impurity. The P-type cladding layer 308 has a first region with a thickness of 100 nm, a second region with a thickness of 180 nm located on the first region, a third region with a thickness of 100 nm located on the second region, and a fourth region with a thickness of 70 nm located on the third region. In the first region, the Mg concentration decreases from 4.0×10 to 5.0×10 with increasing distance from the active layer 104. １８ cm －３ From 2.0 x 10 １８ cm －３ In the second region, the Mg concentration decreases to 2.0×10 １８ cm －３ In the third region, the Mg concentration decreases from 2.0×10 to 1.0×10 with increasing distance from the active layer 104. １８ cm －３ to 1.0 x 10 １９ cm －３ In the fourth region, the Mg concentration increases to 1.0×10 １９ cm－３ is constant.

[0119] The P-type cladding layer 308 has a ridge 308R and a groove 308T formed therein, similar to the P-type cladding layer 108 according to the first embodiment.

[0120] In this embodiment, the P-side guide layer has the lower P-side guide layer 305 disposed between the active layer 104 and the electron barrier layer 106, so that the electron barrier layer 106, which has a high impurity concentration, can be separated from the active layer 104. Therefore, the free carrier loss in the electron barrier layer 106 can be reduced, and the waveguide loss of the nitride-based semiconductor light-emitting element 300 can be reduced.

[0121] In this embodiment, the average impurity concentration of the lower P-side guide layer 305 is 1×10 １８ cm －３ This reduces free carrier loss in the lower P-side guide layer 305 close to the active layer 104, thereby reducing waveguide loss in the nitride-based semiconductor light-emitting element 300.

[0122] From the results of a simulation similar to the above simulation, according to this embodiment, the optical confinement coefficient is 3.84% and the effective refractive index difference ΔN is 18.8×10 －３ and the waveguide loss is 18.8 cm －１ It was confirmed that a nitride-based semiconductor light-emitting device 300 could be realized in which the light intensity distribution peak position in the stacking direction is −0.16 nm (that is, the peak position is within the N-side barrier layer 104 a).

[0123] [3-2. Modification 1] A nitride-based semiconductor light-emitting device according to Modification 1 of the present embodiment will be described. The nitride-based semiconductor light-emitting device according to this modification differs from nitride-based semiconductor light-emitting device 300 according to the present embodiment in the configuration of the P-side guide layer, but is identical in other configurations. The nitride-based semiconductor light-emitting device according to this modification will be described below with reference to FIG. 22, focusing on the differences from nitride-based semiconductor light-emitting device 300 according to the present embodiment. FIG. 22 is a graph schematically showing the bandgap energy distribution of the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification.

[0124] 22 , the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, a lower P-side guide layer 325, an electron barrier layer 106, and a P-type cladding layer 308. Although not shown in FIG. 22 , the semiconductor stack according to this modification further includes a contact layer 109, similar to the semiconductor stack 300S according to the present embodiment.

[0125] The lower p-side guide layer 325 includes a first lower p-side guide layer 325a and a second lower p-side guide layer 325b disposed above the first lower p-side guide layer 325a. The average bandgap energy of the first lower p-side guide layer 325a is smaller than the average bandgap energy of the second lower p-side guide layer 325b. That is, the average refractive index of the first lower p-side guide layer 325a is larger than the average refractive index of the second lower p-side guide layer 325b. The first lower p-side guide layer 325a is, for example, a GaN layer, an AlGaN layer, or an AlInGaN layer. The second lower p-side guide layer 325b is, for example, an AlGaN layer or an AlInGaN layer. The average impurity concentrations of the first lower p-side guide layer 325a and the second lower p-side guide layer 325b are 1×10 １８ cm －３ The following is the result.

[0126] As described above, in the nitride-based semiconductor light-emitting device according to this modification, the lower P-side guide layer 325 has the first lower P-side guide layer 325a with a large refractive index in a region close to the active layer 104. This allows the peak position of the light intensity distribution to be closer to the active layer 104. Therefore, a high optical confinement factor and low waveguide loss can be achieved.

[0127] Furthermore, the presence of an interface between the first lower P-side guide layer 325a and the second lower P-side guide layer 325b, which have different compositions, can suppress impurity diffusion from the P-type layer to the active layer 104, thereby suppressing deterioration of the active layer 104.

[0128] Here, by using a GaN layer as the first lower p-side guide layer 325a, the refractive index can be increased while reducing the tensile strain caused by lattice mismatch between the first lower p-side guide layer 325a and the substrate 101, compared to when an AlGaN layer is used. As a result, the peak position of the light intensity distribution can be moved closer to the active layer 104 while suppressing the occurrence of lattice defects.

[0129] Furthermore, by using an AlInGaN layer as the first lower p-side guide layer 325a, the refractive index can be increased while reducing tensile strain caused by lattice mismatch between the first lower p-side guide layer 325a and the substrate 101, compared to when an AlGaN layer is used. As a result, the peak position of the light intensity distribution can be moved closer to the active layer 104 while suppressing the occurrence of lattice defects.

[0130] The average impurity concentration of the first lower P-side guide layer 325a and the second lower P-side guide layer 325b is set to 1×10 １８ cm －３ By satisfying the following conditions, it is possible to reduce free carrier loss in the lower P-side guide layer 325. Therefore, it is possible to reduce waveguide loss in the nitride-based semiconductor light-emitting element.

[0131] [3-3. Modification 2] A nitride-based semiconductor light-emitting device according to Modification 2 of the present embodiment will now be described. The nitride-based semiconductor light-emitting device according to this modification differs from nitride-based semiconductor light-emitting device 300 according to the present embodiment in the configuration of the P-side guide layer, but is identical in other configurations. The nitride-based semiconductor light-emitting device according to this modification will be described below with reference to FIG. 23, focusing on the differences from nitride-based semiconductor light-emitting device 300 according to the present embodiment. FIG. 23 is a graph schematically showing the bandgap energy distribution of the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification.

[0132] 23 , the semiconductor stack of the nitride-based semiconductor light-emitting device according to this modification includes an N-type cladding layer 102, an N-side guide layer 103, an active layer 104, a lower P-side guide layer 335, an electron barrier layer 106, and a P-type cladding layer 308. Although not shown in FIG. 23 , the semiconductor stack of this modification further includes a contact layer 109, similar to the semiconductor stack 300S according to the present embodiment.

[0133] The lower P-side guide layer 335 is an optical guide layer disposed between the active layer 104 and the electron barrier layer 106. The band gap energy of the lower P-side guide layer 335 increases as it approaches the electron barrier layer 106. That is, the refractive index of the lower P-side guide layer 335 decreases as it approaches the electron barrier layer 106. The lower P-side guide layer 335 is, for example, a GaN layer, an AlGaN layer, or an AlInGaN layer. For example, the Al composition ratio of the lower P-side guide layer 335 may increase as it approaches the electron barrier layer 106. The average impurity concentration of the lower P-side guide layer 335 is 1×10 １８ cm －３ The following is the result.

[0134] As described above, in the nitride-based semiconductor light-emitting device according to this modification, the refractive index of the lower P-side guide layer 335 increases toward the active layer 104. By increasing the refractive index in the region of the lower P-side guide layer 335 that is close to the active layer 104 in this manner, the peak position of the light intensity distribution can be moved closer to the active layer 104. Therefore, a high optical confinement factor and low waveguide loss can be achieved.

[0135] The average impurity concentration of the lower P-side guide layer 335 is set to 1×10 １８ cm －３ By satisfying the following conditions, it is possible to reduce free carrier loss in the lower P-side guide layer 335. Therefore, it is possible to reduce waveguide loss in the nitride-based semiconductor light-emitting element.

[0136] (Other Modifications, etc.) The nitride-based semiconductor light-emitting device according to the present disclosure has been described above based on the embodiments and their modifications, but the present disclosure is not limited to the above-described embodiments and their modifications.

[0137] For example, although the above-described embodiments and their modifications have been described with reference to semiconductor light-emitting devices that emit ultraviolet light, the semiconductor light-emitting device according to the present disclosure is not limited to semiconductor light-emitting devices that emit ultraviolet light. The characteristic configuration of the semiconductor light-emitting device according to the present disclosure can also be applied to semiconductor light-emitting devices that emit light in wavelength bands such as visible light and infrared light, and provides the same effects as those of the above-described embodiments and their modifications.

[0138] Furthermore, in the above-described embodiments and their modifications, examples have been shown in which the nitride-based semiconductor light-emitting element is a semiconductor laser element. However, the nitride-based semiconductor light-emitting element is not limited to a semiconductor laser element. For example, the nitride-based semiconductor light-emitting element may be a superluminescent diode. In this case, the reflectance of the end face of the semiconductor stack included in the nitride-based semiconductor light-emitting element with respect to light emitted from the semiconductor stack may be 0.1% or less. Such a reflectance can be achieved, for example, by forming an anti-reflection film made of a dielectric multilayer film or the like on the end face. Alternatively, by using an inclined stripe structure in which the ridge serving as the waveguide intersects with the front end face at an angle of 5° or more from the normal direction of the front end face, the proportion of the component of the guided light reflected at the front end face that recouples with the waveguide and becomes guided light can be reduced to a small value of 0.1% or less.

[0139] In the above-described embodiments and their modifications, each P-type cladding layer has a uniform Al composition ratio, but the configuration of the P-type cladding layer is not limited to this. For example, the P-type cladding layer may have a superlattice structure in which a plurality of AlGaN layers and a plurality of GaN layers are alternately stacked.

[0140] In addition, although the active layer has a single quantum well structure in the above-described embodiments and their modifications, it may have a multiple quantum well structure. In this case, the N-side barrier layer configuration according to the above-described embodiments and their modifications is applied to the barrier layer of the multiple quantum well structure that is closest to the N-type cladding layer, and the P-side barrier layer configuration according to the above-described embodiments and their modifications is applied to the barrier layer of the multiple quantum well structure that is closest to the P-type cladding layer, thereby achieving the same effects as those of the above-described embodiments and their modifications.

[0141] This disclosure also includes forms obtained by applying various modifications to the above-mentioned embodiments that a person skilled in the art would conceive, and forms realized by arbitrarily combining the components and functions of the above-mentioned embodiments within the scope of the present disclosure.

[0142] For example, the configuration of the P-side barrier layer 124c according to the modification of the first embodiment may be applied to the P-side barrier layers of the second and third embodiments and their modifications.

[0143] The nitride-based semiconductor light-emitting device of the present disclosure can be applied, for example, as a high-output, high-efficiency light source, particularly to light sources for exposure devices and processing machines.

[0144] 100, 200, 300 Nitride-based semiconductor light-emitting device 100F, 100R Facet 100S, 200S, 300S Semiconductor laminate 101 Substrate 102, 902 N-type cladding layer 103, 903 N-side guide layer 103a First N-side guide layer 103b Second N-side guide layer 104, 124 Active layer 104a, 904a N-side barrier layer 104b, 904b Well layer 104c, 124c, 904c P-side barrier layer 106, 906 Electron barrier layer 107, 107a, 207, 907 Upper P-side guide layer 108, 208, 308, 908 P-type cladding layer 108R, 208R, 308R Ridge 108T, 208T, 308T Groove 109 Contact layer 110 Current blocking layer 111 P-side electrode 112 N-side electrode 124ca First P-side barrier layer 124cb Second P-side barrier layer 205, 225, 235, 305, 325, 335 Lower P-side guide layer 225a, 325a First lower P-side guide layer 225b, 325b Second lower P-side guide layer 250, 251, 252 P-side guide layer

Claims

1. An N-type cladding layer; an N-side guide layer disposed above the N-type cladding layer; an active layer disposed above the N-side guide layer; a P-type cladding layer disposed above the active layer; a P-side guide layer and an electron barrier layer disposed between the active layer and the P-type cladding layer; the N-type cladding layer, the N-side guide layer, the P-side guide layer, the electron barrier layer, and the P-type cladding layer contain Al; the active layer includes an N-side barrier layer, a well layer disposed above the N-side barrier layer, and a P-side barrier layer disposed above the well layer; the average band gap energy of the P-side barrier layer is greater than the average band gap energy of the N-side barrier layer; The thickness of the P-side barrier layer is smaller than the thickness of the N-side barrier layer. Nitride-based semiconductor light-emitting element.

2. An N-type cladding layer; an N-side guide layer disposed above the N-type cladding layer; an active layer disposed above the N-side guide layer; a P-type cladding layer disposed above the active layer; a P-side guide layer and an electron barrier layer disposed between the active layer and the P-type cladding layer; the N-type cladding layer, the electron barrier layer, and the P-type cladding layer contain Al; the active layer includes an N-side barrier layer, a well layer disposed above the N-side barrier layer, and a P-side barrier layer disposed above the well layer; the average band gap energy of the P-side barrier layer is greater than the average band gap energy of the N-side barrier layer; The thickness of the P-side barrier layer is smaller than the thickness of the N-side barrier layer, the P-side guide layer comprises a lower P-side guide layer disposed between the active layer and the electron barrier layer; The band gap energy of the lower P-side guide layer increases toward the electron barrier layer. Nitride-based semiconductor light-emitting element.

3. The lower P-side guide layer has a first lower P-side guide layer and a second lower P-side guide layer arranged above the first lower P-side guide layer, The average band gap energy of the first lower P-side guide layer is smaller than the average band gap energy of the second lower P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 2 .

4. The P-side guide layer has an upper P-side guide layer disposed above the electron barrier layer, The average band gap energy of the lower P-side guide layer is equal to or lower than the average band gap energy of the upper P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 2 or 3.

5. 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 P-type cladding layer disposed above the active layer; a P-side guide layer and an electron barrier layer disposed between the active layer and the P-type cladding layer; the N-type cladding layer, the electron barrier layer, and the P-type cladding layer contain Al; the active layer includes an N-side barrier layer, a well layer disposed above the N-side barrier layer, and a P-side barrier layer disposed above the well layer; the average band gap energy of the P-side barrier layer is greater than the average band gap energy of the N-side barrier layer; The thickness of the P-side barrier layer is smaller than the thickness of the N-side barrier layer, the P-side guide layer comprises a lower P-side guide layer disposed between the active layer and the electron barrier layer; the lower p-side guide layer includes a first lower p-side guide layer and a second lower p-side guide layer disposed above the first lower p-side guide layer, The average band gap energy of the first lower P-side guide layer is smaller than the average band gap energy of the second lower P-side guide layer. Nitride-based semiconductor light-emitting element.

6. The P-side guide layer has an upper P-side guide layer disposed above the electron barrier layer, The average band gap energy of the lower P-side guide layer is equal to or lower than the average band gap energy of the upper P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 5 .

7. The P-side guide layer includes an upper P-side guide layer disposed above the electron barrier layer. The nitride-based semiconductor light-emitting device according to claim 1 .

8. the average band gap energy of the upper P-side guide layer is smaller than the average band gap energy of the P-type cladding layer; The nitride-based semiconductor light-emitting device according to claim 7 .

9. The P-side guide layer includes a lower P-side guide layer disposed between the active layer and the electron barrier layer. The average band gap energy of the lower P-side guide layer is equal to or lower than the average band gap energy of the upper P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 7 or 8.

10. The P-side guide layer includes a lower P-side guide layer disposed between the active layer and the electron barrier layer. The nitride-based semiconductor light-emitting device according to claim 1 .

11. the average band gap energy of the lower P-side guide layer is smaller than the average band gap energy of the P-type cladding layer; The nitride-based semiconductor light-emitting device according to claim 10 .

12. the lower p-side guide layer includes a first lower p-side guide layer and a second lower p-side guide layer disposed above the first lower p-side guide layer, The average band gap energy of the first lower P-side guide layer is smaller than the average band gap energy of the second lower P-side guide layer. The nitride-based semiconductor light-emitting device according to claim 9 .

13. The band gap energy of the lower P-side guide layer increases toward the electron barrier layer. The nitride-based semiconductor light-emitting device according to claim 9 .

14. the lower P-side guide layer is an AlGaN layer or an AlInGaN layer, The average impurity concentration of the lower P-side guide layer is 1×10 １８ cm －３ is less than or equal to The nitride-based semiconductor light-emitting device according to claim 9 .

15. the first lower P-side guide layer is a GaN layer, an AlGaN layer, or an AlInGaN layer; the second lower P-side guide layer is an AlGaN layer or an AlInGaN layer, The first lower P-side guide layer and the second lower P-side guide layer have an average impurity concentration of 1×10 １８ cm －３ is less than or equal to The nitride-based semiconductor light-emitting device according to claim 12 .

16. the lower P-side guide layer is a GaN layer, an AlGaN layer, or an AlInGaN layer; The average impurity concentration of the lower P-side guide layer is 1×10 １８ cm －３ is less than or equal to The nitride-based semiconductor light-emitting device according to claim 13 .

17. The average band gap energy of the N-side barrier layer is smaller than the average band gap energy of the N-type cladding layer.

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

18. The average band gap energy of the P-side barrier layer is smaller than the average band gap energy of the electron barrier layer.

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

19. the P-side barrier layer includes a first P-side barrier layer and a second P-side barrier layer disposed above the first P-side barrier layer, The average band gap energy of the second P-side barrier layer is greater than the average band gap energy of the first P-side barrier layer.

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

20. The average band gap energy of the second P-side barrier layer is smaller than the average band gap energy of the electron barrier layer. The nitride-based semiconductor light-emitting device according to claim 19 .

21. the second P-side barrier layer is an AlGaN layer or an AlInGaN layer, The average impurity concentration of the second P-side barrier layer is 1×10 １８ cm －３ is less than or equal to The nitride-based semiconductor light-emitting device according to claim 19 .

22. a P-side electrode disposed above the P-type cladding layer; The P-side electrode contains Ag.

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