Semiconductor light emitting element

Abstract

A semiconductor light emitting element (1) according to the present invention comprises: a substrate (10); a first cladding layer (30) of a first conductivity type, the first cladding layer (30) being arranged above the substrate (10); an active layer (40) which is arranged above the first cladding layer (30); a second cladding layer (50) of a second conductivity type, which is different from the first conductivity type, the second cladding layer (50) being arranged above the active layer (40); and a light guide layer (60) which is arranged between the first cladding layer (30) and the second cladding layer (50). The peak photon energy of the photoluminescence of the active layer (40) is higher than the peak photon energy of the laser light emitted from the semiconductor light emitting element (1), into which an electric current has been injected, by 0.050 eV or more.

Description

Semiconductor light emitting device

[0001] The present disclosure relates to semiconductor light emitting devices.

[0002] Conventionally, semiconductor light-emitting elements such as semiconductor laser elements that emit light from an active layer have been known (see, for example, Patent Document 1). The semiconductor light-emitting element described in Patent Document 1 includes an active layer having a quantum well structure including a well layer made of InGaN. The semiconductor laser element described in Patent Document 1 oscillates near the peak wavelength of the photoluminescence (PL) spectrum of the active layer (i.e., a wavelength region where high optical gain can be obtained).

[0003] JP 2009-252861 A

[0004] However, when the laser oscillation wavelength is near the peak wavelength of the PL spectrum, the laser light generated by the semiconductor light-emitting element is absorbed in the active layer, which reduces the optical output efficiency of the semiconductor light-emitting element. Furthermore, the energy of the absorbed laser light increases the temperature of the active layer, which can lead to thermal saturation, where the optical output saturates, and catastrophic optical damage (COD).

[0005] To address COD caused by absorption of laser light near the cavity facets of a semiconductor light-emitting device, a known measure is to reduce absorption of laser light by increasing the bandgap energy of the active layer near the cavity facets. While this can suppress COD near the cavity facets, it cannot reduce absorption of laser light outside the cavity facets. Therefore, this measure is not very effective in suppressing thermal saturation.

[0006] The present disclosure is intended to solve such problems, and has an object to provide a semiconductor light-emitting device that can reduce light absorption in the active layer.

[0007] In order to solve the above problems, one aspect of the semiconductor light-emitting device according to the present disclosure comprises a substrate, a first cladding layer of a first conductivity type arranged above the substrate, an active layer arranged above the first cladding layer, a second cladding layer of a second conductivity type different from the first conductivity type arranged above the active layer, and an optical guide layer arranged between the first cladding layer and the second cladding layer, wherein the peak photon energy of photoluminescence of the active layer is higher by 0.050 eV or more than the peak photon energy of laser light emitted from the semiconductor light-emitting device when a current is injected therein.

[0008] In order to solve the above problem, another aspect of the semiconductor light-emitting element according to the present disclosure comprises a substrate, a first cladding layer of a first conductivity type arranged above the substrate, an active layer arranged above the first cladding layer, a second cladding layer of a second conductivity type different from the first conductivity type arranged above the active layer, and an optical guide layer arranged between the first cladding layer and the second cladding layer, wherein in the photoluminescence spectrum of the active layer, the intensity of the photoluminescence at the peak photon energy of laser light emitted from the semiconductor light-emitting element upon injection of current is 40% or less of the peak intensity of the spectrum.

[0009] In order to solve the above-described problems, another aspect of the semiconductor light-emitting device according to the present disclosure is a semiconductor light-emitting device including an active layer, wherein the peak photon energy of photoluminescence from the active layer is higher by 0.070 eV or more than the peak photon energy of spontaneous emission light emitted from the semiconductor light-emitting device upon injection of current.

[0010] In order to solve the above-described problems, another aspect of the semiconductor light-emitting device according to the present disclosure includes a substrate, a first cladding layer of a first conductivity type disposed above the substrate, an active layer disposed above the first cladding layer, a second cladding layer of a second conductivity type different from the first conductivity type disposed above the active layer, and an optical guide layer disposed between the first cladding layer and the second cladding layer, wherein the active layer has a quantum well structure in which two or more barrier layers and one or more well layers are alternately stacked, and a difference in band gap energy between each of the two or more barrier layers and each of the one or more well layers is 0.140 eV or less, and the optical guide layer is a quantum well structure in which two or more barrier layers and one or more well layers are alternately stacked, and a difference in band gap energy between each of the two or more barrier layers and each of the one or more well layers is 0.140 eV or less, and the active layer and the second cladding layer, and at least one of a first optical guiding layer disposed between the active layer and the second cladding layer, and a second optical guiding layer disposed between the active layer and the second cladding layer, each of the first optical guiding layer and the second optical guiding layer having a smaller band gap energy than the two or more barrier layers and a larger band gap energy than the one or more well layers, the difference in band gap energy between the first optical guiding layer and the barrier layer of the two or more barrier layers that is closest to the first optical guiding layer being less than 0.080 eV, and the difference in band gap energy between the second optical guiding layer and the barrier layer of the two or more barrier layers that is closest to the second optical guiding layer being less than 0.080 eV.

[0011] According to the present disclosure, it is possible to provide a semiconductor light emitting device capable of reducing light absorption in the active layer.

[0012] 1 is a schematic top view showing the overall configuration of a semiconductor light emitting device according to an embodiment; FIG. 2 is a schematic cross-sectional view showing the overall configuration of a semiconductor light emitting device according to an embodiment; FIG. 3 is a graph showing an example of a PL spectrum of a semiconductor light emitting device according to an embodiment; FIG. 4 is a graph showing an example of a PL spectrum of an element obtained by removing the active layer from the semiconductor light emitting device according to an embodiment; FIG. 5 is a graph showing an example of a PL spectrum of an active layer according to an embodiment; FIG. 6 is a diagram showing the layer configuration of each example of a semiconductor light emitting device according to an embodiment; FIG. 7 is a schematic cross-sectional view showing the configuration of the active layer of a semiconductor light emitting device according to Example 1; FIG. 8 is a graph showing the band gap energy distribution in the stacking direction of a semiconductor light emitting device according to Example 1; FIG. 9 is a graph showing the band gap energy distribution in the stacking direction of a semiconductor light emitting device according to Example 2; FIG. 10 is a graph showing the characteristics of each example of an embodiment; FIG. 11 is a graph showing the relationship between injection current and optical output of a semiconductor light emitting device according to Example 5; FIG. 12 is a graph showing the relationship between optical output of a semiconductor light emitting device according to Example 5 and the ratio of optical output to input power; FIG. 13 is a graph showing the laser light spectrum and PL spectrum of a semiconductor light emitting device of a comparative example. 1 is a graph showing the laser light spectrum and PL spectrum of the semiconductor light emitting element according to Example 1. FIG. 2 is a graph showing the relationship between the PL-laser light energy difference and the optical output at the output saturation onset point of the semiconductor light emitting element according to each Example and the semiconductor light emitting element according to the comparative example. FIG. 3 is a graph showing the relationship between the slope efficiency and the PL-laser light energy difference when the optical output of the semiconductor light emitting element according to each Example and the semiconductor light emitting element according to the comparative example is 0.5 W or more and 1.0 W or less. FIG. 4 is a graph showing the spontaneous emission spectrum and PL spectrum of the semiconductor light emitting element according to the comparative example. FIG. 5 is a graph showing the spontaneous emission spectrum and PL spectrum of the semiconductor light emitting element according to Example 1. FIG. 6 is a graph showing the spontaneous emission spectrum and PL spectrum of the semiconductor light emitting element according to Example 2. FIG. 7 is a graph showing the spontaneous emission spectrum and PL spectrum of the semiconductor light emitting element according to Example 5.1 is a graph showing the relationship between the PL-spontaneous emission light energy difference and the optical output at the output saturation onset point of the semiconductor light-emitting element according to each example and the semiconductor light-emitting element according to the comparative example. 2 is a graph showing the relationship between the slope efficiency and the PL-laser light energy difference when the optical output of the semiconductor light-emitting element according to each example and the semiconductor light-emitting element according to the comparative example is 0.5 W or more and 1.0 W or less.

[0013] 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.

[0014] 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.

[0015] In this specification, the terms "above" and "below" do not refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. Furthermore, the terms "above" and "below" are used not only when two components are arranged with a gap between them and another component is present between the two components, but also when two components are arranged in contact with each other.

[0016] (Embodiment) A semiconductor light emitting device according to an embodiment will be described.

[0017] [1. Basic Configuration] The basic configuration of a semiconductor light-emitting device according to this embodiment will be described with reference to Fig. 1. Figs. 1 and 2 are a schematic top view and a cross-sectional view, respectively, showing the basic configuration of a semiconductor light-emitting device 1 according to this embodiment. 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 form a right-handed Cartesian coordinate system. The stacking direction of the semiconductor light-emitting device 1 (i.e., the thickness direction of each layer included in the semiconductor light-emitting device 1) is parallel to the Z-axis direction, and the main propagation direction of light (laser light) is parallel to the Y-axis direction.

[0018] The semiconductor light-emitting element 1 is an element that emits light in response to current injection. In this embodiment, the semiconductor light-emitting element 1 is a semiconductor laser element that emits laser light with a peak wavelength of 400 nm or less (peak photon energy of 3.1 eV or less). As shown in FIG. 1 , the semiconductor light-emitting element 1 has two end faces 1F and 1R that form a resonator. The end face 1F is a front end face that emits laser light, and the end face 1R is a rear end face that has a higher reflectivity than the end face 1F. The semiconductor light-emitting element 1 also has a waveguide formed between the end face 1F and the end face 1R.

[0019] The cavity length of the semiconductor light-emitting element 1, i.e., the distance between the end faces 1F and 1R in the propagation direction of the laser light (the Y-axis direction in each figure, i.e., the resonance direction), is not particularly limited, but in this embodiment it is 1200 μm. The semiconductor light-emitting element 1 may also include a reflective film disposed at the end in the propagation direction of the laser light. The reflective film is a film for adjusting the reflectivity of the end faces 1F and 1R, respectively. A dielectric multilayer film or the like can be used as the reflective film.

[0020] 2 , the semiconductor light-emitting element 1 includes a substrate 10, a first cladding layer 30 disposed above the substrate 10, an active layer 40 disposed above the first cladding layer 30, a second cladding layer 50 disposed above the active layer 40, and a light-guiding layer 60 disposed between the first cladding layer 30 and the second cladding layer 50. In this embodiment, the semiconductor light-emitting element 1 further includes an underlayer 21 disposed between the substrate 10 and the first cladding layer 30, a crack prevention layer 22 disposed between the underlayer 21 and the first cladding layer 30, an electron blocking layer 70 disposed between the active layer 40 and the second cladding layer 50, an insulating layer 80 disposed above the second cladding layer 50, an upper electrode 91 disposed above the insulating layer 80, and a lower electrode 92 disposed on the lower surface of the substrate 10 (i.e., the main surface behind the main surface on which the respective semiconductor layers are stacked).

[0021] The substrate 10 is a plate-like member that serves as a base for the semiconductor light-emitting device 1. In this embodiment, the first conductivity type is N-type.

[0022] The base layer 21 is a semiconductor layer of a first conductivity type disposed above the substrate 10. In this embodiment, the base layer 21 is laminated on the main surface of the substrate 10.

[0023] The crack prevention layer 22 is a semiconductor layer of the first conductivity type disposed above the substrate 10. In this embodiment, the crack prevention layer 22 is disposed above the base layer 21.

[0024] The first cladding layer 30 is a semiconductor layer of a first conductivity type disposed above the substrate 10. The average refractive index of the first cladding layer 30 is lower than the average refractive index of the active layer 40. Here, the average refractive index of the first cladding layer 30 or the like is defined as the value obtained by integrating the refractive index in the thickness direction of the layer and dividing it by the thickness of the layer. In this embodiment, the first cladding layer 30 is disposed above the crack prevention layer 22.

[0025] The active layer 40 is a light-emitting layer disposed above the first cladding layer 30. In this embodiment, the peak photon energy of PL in the active layer 40 is higher by 0.050 eV or more than the peak photon energy of laser light emitted from the semiconductor light-emitting element 1 into which current is injected.

[0026] Here, the measurement direction of the peak photon energy of PL of the active layer 40 will be described with reference to FIGS. 3 to 5. FIG. 3 is a graph showing an example of the PL spectrum of the semiconductor light emitting device 1 according to this embodiment. FIG. 4 is a graph showing an example of the PL spectrum of an element obtained by removing the active layer 40 from the semiconductor light emitting device 1 according to this embodiment. FIG. 5 is a graph showing an example of the PL spectrum of the active layer 40 according to this embodiment. The horizontal axis of each of the graphs in FIGS. 3 to 5 represents photon energy corresponding to the PL wavelength, and the vertical axis represents normalized PL intensity.

[0027] To measure the PL spectrum of the active layer 40, the semiconductor light-emitting element 1 is first optically excited using a 325 nm He—Cd laser or the like, and the PL spectrum emitted from the semiconductor light-emitting element 1 is measured. For example, in GaN-based semiconductor laser elements with a peak wavelength of 400 nm or less, GaN is often used as the substrate and InGaN is often used as the crack prevention layer 22. In this case, the bandgap energy of the crack prevention layer 22 is lower than that of the underlayer 21 and the first cladding layer 30, so the PL spectrum obtained by the above-described measurement includes not only the PL of the active layer 40 but also that of the crack prevention layer 22, as shown in FIG. 3 . Therefore, a portion of the semiconductor light-emitting element 1 obtained by removing the portion above the optical guide layer 60 including the active layer 40 is optically excited using a 325 nm He—Cd laser or the like, and the PL spectrum ( FIG. 4 ) emitted from this portion is measured. By removing the PL component of the crack prevention layer 22 shown in FIG. 4 from the PL spectrum of the semiconductor light-emitting element 1 shown in FIG. 3 , the PL spectrum of the active layer 40 shown in FIG. 5 can be obtained. In this case, the intensity of the spectrum shown in FIG. 4 is adjusted so that the peak of the PL spectrum of the crack prevention layer 22 does not remain in the spectrum after removal shown in FIG. 5 . Specifically, the peak intensity at a position near 3.31 eV in FIG. 3 is 0.91, whereas the intensity is adjusted so that the peak intensity in FIG. 4 is 0.84. As a result, no peak is observed near 3.31 eV in the spectrum shown in FIG. 5 , which is obtained by subtracting the spectral intensity in FIG. 4 from the spectral intensity in FIG. 3 .

[0028] When removing the active layer 40 from the semiconductor light emitting device 1, for example, wet etching can be used. Specifically, first, the upper electrode 91 and the lower electrode 92 are removed using an aqua regia-based etchant. Next, the insulating layer 80 is removed using a hydrofluoric acid-based etchant. Next, the active layer 40 and the semiconductor layers disposed thereover are removed by reactive ion etching. For example, the first light guide layer 61 and the semiconductor layers disposed thereover may also be removed by reactive ion etching.

[0029] In this embodiment, the active layer 40 has a quantum well structure in which two or more barrier layers and one or more well layers are alternately stacked. The difference in bandgap energy between each of the two or more barrier layers and each of the one or more well layers is 0.140 eV or less.

[0030] The second cladding layer 50 is a semiconductor layer of a second conductivity type different from the first conductivity type, which is disposed above the active layer 40. The average refractive index of the second cladding layer 50 is lower than the average refractive index of the active layer 40. In this embodiment, the second cladding layer 50 is disposed above the optical guiding layer 60 and the electron blocking layer 70. The second conductivity type is P-type.

[0031] In this embodiment, a ridge 50R extending in the light propagation direction (i.e., the Y-axis direction) is formed in the second cladding layer 50. In other words, two grooves 50T extending along the light propagation direction are formed in the upper surface of the second cladding layer 50, and the ridge 50R is formed between the two grooves 50T. A waveguide is formed along the ridge 50R. Note that in FIG. 1, the upper surface of the ridge 50R and the outline of the groove 50T are indicated by dashed lines. The width of the ridge 50R (i.e., the dimension of the upper surface of the ridge 50R in the X-axis direction) is, for example, 15 μm.

[0032] The optical guiding layer 60 is a semiconductor layer disposed between the first cladding layer 30 and the second cladding layer 50. The optical guiding layer 60 has at least one of a first optical guiding layer 61 disposed between the first cladding layer 30 and the active layer 40, and a second optical guiding layer 62 disposed between the active layer 40 and the second cladding layer 50. Note that Fig. 2 shows an example in which the optical guiding layer 60 has both the first optical guiding layer 61 and the second optical guiding layer 62. The first optical guiding layer 61 and the second optical guiding layer 62 each have a smaller band gap energy than the barrier layers 41 and 43, and a larger band gap energy than the well layer 42.

[0033] The electron blocking layer 70 is a semiconductor layer disposed between the active layer 40 and the second cladding layer 50. The electron blocking layer 70 is a semiconductor layer having a band gap energy larger than that of the second cladding layer 50. As a result, the electron blocking layer 70 functions as a barrier to electrons traveling from the active layer 40 to the second cladding layer 50, thereby confining the electrons in the active layer 40. In the example shown in FIG. 2 , the electron blocking layer 70 is disposed between the second optical guiding layer 62 and the second cladding layer 50.

[0034] The insulating layer 80 is an electrically insulating layer disposed above the second cladding layer 50. In this embodiment, the insulating layer 80 is disposed on the upper surface of the second cladding layer 50 in a region other than the upper surface of the ridge 50R.

[0035] The upper electrode 91 is a conductive layer disposed above the second cladding layer 50. In this embodiment, the upper electrode 91 is used as an electrode for injecting current into the semiconductor light emitting device 1 through the opening in the insulating layer 80. The upper electrode 91 is disposed on at least a portion of the upper surface of the ridge 50R of the second cladding layer 50.

[0036] The lower electrode 92 is an electrode disposed on the lower surface of the substrate 10 and is used as an electrode for injecting current into the semiconductor light emitting element 1 .

[0037] [2. Examples] Examples of the semiconductor light-emitting element 1 according to this embodiment will be described with reference to FIG. 6 . FIG. 6 is a diagram showing the layer configuration of each example of the semiconductor light-emitting element 1 according to this embodiment. FIG. 6 shows the composition and film thickness of each layer included in the semiconductor light-emitting element 1 according to each example and the semiconductor light-emitting element of the comparative example. FIG. 6 also shows the difference in bandgap energy between the barrier layer and the well layer, the difference in bandgap energy (Eg) between the bottommost barrier layer (the barrier layer closest to the first light guide layer 61) and the first light guide layer, and the difference in bandgap energy (Eg) between the topmost barrier layer (the barrier layer closest to the second light guide layer 62) and the second light guide layer 62. The detailed configurations of the semiconductor light-emitting element of the comparative example and the semiconductor light-emitting element 1 according to each example will be described below.

[0038] 6 includes a substrate, an underlayer, a crack prevention layer, a first cladding layer, a first light guide layer, an active layer, an electron blocking layer, a second light guide layer, and a second cladding layer, similar to the semiconductor light emitting device 1 according to the present embodiment. Although not shown in FIG. 6, the semiconductor light emitting device of the comparative example also includes an insulating layer, an upper electrode, and a lower electrode, similar to the semiconductor light emitting device 1 according to the present embodiment.

[0039] The substrate of the semiconductor light emitting device of the comparative example is an N-type GaN substrate doped with Si as an impurity. The underlayer is an N-type Al 1000 nm thick. ０．０２ Ga ０．９８ The crack prevention layer is an N-type In layer with a thickness of 150 nm. ０．０３ Ga ０．９７ The first clad layer is an N layer with a thickness of 540 nm and a concentration of 5×10 １７ cm －３ Si-doped N-type Al ０．０６５ Ga ０．９３５ The first optical guide layer is an N layer with a thickness of 127 nm and a concentration of 5×10 １７ cm －３ Si-doped N-type Al ０．０３ Ga ０．９７ An N layer and an undoped Al layer with a thickness of 180 nm placed on the N layer. ０．０２ Ga ０．９８ N layers.

[0040] The active layer is an undoped In layer with a thickness of 7.5 nm. ０．０１ Ga ０．９９ The well layer is an N layer, and an undoped Al layer with a thickness of 12 nm is disposed below the well layer. ０．０５ Ga ０．９５ The barrier layer is an N layer, and the undoped Al layer with a thickness of 12 nm is disposed above the well layer. ０．０５ Ga ０．９５ 6 , the active layer of the comparative example differs from active layer 40 of the present embodiment in that the difference in bandgap energy between each barrier layer and the well layer is greater than 0.140 eV. The difference in bandgap energy between each barrier layer and the well layer of the active layer of the comparative example is 0.163 eV.

[0041] The second optical guide layer is a P-type Al layer with a thickness of 66 nm. ０．０２ Ga ０．９８ The electron blocking layer is a P-type Al layer with a thickness of 5.5 nm. ０．３６ Ga ０．６４ The second clad layer is an N layer with a thickness of 660 nm and a concentration of 8×10 １８ cm －３ P-type Al with Mg added ０．０６５ Ga ０．９３５ This is the N layer.

[0042] In the semiconductor light-emitting element of the comparative example, the difference in bandgap energy between the first optical guide layer and the barrier layer in the active layer that is closest to the first optical guide layer is 0.080 eV, and the difference in bandgap energy between the second optical guide layer and the barrier layer in the active layer that is closest to the second optical guide layer is 0.053 eV.

[0043] [2-2. Example 1] A semiconductor light emitting device 1 according to Example 1 includes a substrate 10, an underlayer 21, a crack prevention layer 22, a first cladding layer 30, a first optical guide layer 61, an active layer 40, a second optical guide layer 62, an electron blocking layer 70, and a second cladding layer 50. The second optical guide layer 62 according to Example 1 is disposed between the active layer 40 and the electron blocking layer 70.

[0044] The substrate 10, underlayer 21, anti-crack layer 22, first light guide layer 61, and second cladding layer 50 of the semiconductor light emitting device 1 according to Example 1 have the same configuration as those of the semiconductor light emitting device of the comparative example.

[0045] The first cladding layer 30 according to Example 1 has a thickness of 800 nm and a concentration of 5×10 １７ cm －３ Si-doped N-type Al ０．０６５ Ga ０．９３５ This is the N layer.

[0046] The active layer 40 according to Example 1 will be described with reference to FIG. 7 . FIG. 7 is a schematic cross-sectional view showing the configuration of the active layer 40 of the semiconductor light-emitting device 1 according to Example 1. FIG. 7 shows a cross-section of the semiconductor light-emitting device 1 at the same position as in FIG. 2 . As shown in FIG. 7 , the active layer 40 according to Example 1 has a barrier layer 41, a well layer 42 arranged above the barrier layer 41, and a barrier layer 43 arranged above the well layer 42. The barrier layer 41 is a 12-nm-thick undoped Al ０．０４ Ga ０．９６ The well layer 42 is an undoped In layer with a thickness of 17.5 nm. ０．０１ Ga ０．９９ The barrier layer 43 is an undoped AlN layer. ０．０３ Ga ０．９７ As shown in FIG. 6, the barrier layer 43 and the second optical guide layer 62 have the same composition (Al ０．０３ Ga ０．９７ The total thickness of the barrier layer 43 and the second optical guiding layer 62 is 130 nm. ０．０３ Ga ０．９７ The portion of the N layer close to the well layer 42 functions as a barrier layer 43 , and the portion far from the well layer 42 functions as a second optical guide layer 62 .

[0047] The electron blocking layer 70 is a P-type Al layer having a thickness of 1.6 nm. ０．３６ Ga ０．６４ This is the N layer.

[0048] The bandgap energy distribution of the semiconductor light emitting element 1 according to Example 1 will be described with reference to Fig. 8. Fig. 8 is a graph schematically showing the bandgap energy distribution in the stacking direction of the semiconductor light emitting element 1 according to Example 1.

[0049] As shown in FIG. 8 (and FIG. 6), in the semiconductor light emitting device 1 according to Example 1, the difference in band gap energy between each barrier layer of the active layer 40 and the well layer 42 is 0.140 eV or less.

[0050] 6, in the semiconductor light emitting device 1 according to Example 1, the difference in band gap energy between the first light guiding layer 61 and the barrier layer 41 is 0.053 eV. The second light guiding layer 62 and the barrier layer 43 have the same composition, and therefore there is no difference in band gap energy between them.

[0051] [2-3. Example 2] As shown in FIG. 6 , the semiconductor light-emitting device 1 according to Example 2 differs from the semiconductor light-emitting device 1 according to Example 1 mainly in the positional relationship between the electron blocking layer 70 and the second light guiding layer 62 and the composition of the first light guiding layer 61.

[0052] The substrate 10, underlayer 21, and crack prevention layer 22 of the semiconductor light emitting device 1 according to Example 2 have the same configurations as the substrate 10, underlayer 21, and crack prevention layer 22 of the semiconductor light emitting device 1 according to Example 1 (and the semiconductor light emitting device of the comparative example), respectively. The first cladding layer 30, well layer 42, and electron blocking layer 70 of the semiconductor light emitting device 1 according to Example 2 have the same configurations as the first cladding layer 30, well layer 42, and electron blocking layer 70 of the semiconductor light emitting device 1 according to Example 1, respectively.

[0053] The first optical guide layer 61 according to Example 2 has a thickness of 127 nm and a concentration of 5×10 １７ cm －３ Si-doped N-type Al ０．０３ Ga ０．９７ An N layer and an undoped Al layer with a thickness of 90 nm placed on the N layer. ０．０３ Ga ０．９７ The barrier layer 41 is an undoped AlN layer having a thickness of 10 nm. ０．０４ Ga ０．９６The barrier layer 43 is an undoped AlN layer having a thickness of 20 nm. ０．０３ Ga ０．９７ The second optical guide layer 62 is a P-type AlN layer having a thickness of 130 nm and disposed above the electron blocking layer 70. ０．０３ Ga ０．９７ The second optical guide layer 62 has a concentration of 3×10 １８ cm －３ The second cladding layer 50 is a 450 nm thick P-type AlN alloy. ０．０６５ Ga ０．９３５ This is the N layer.

[0054] The bandgap energy distribution of the semiconductor light emitting element 1 according to Example 2 will be described with reference to Fig. 9. Fig. 9 is a graph schematically showing the bandgap energy distribution in the stacking direction of the semiconductor light emitting element 1 according to Example 2.

[0055] 9 (and FIG. 6 ), in the semiconductor light-emitting device 1 according to Example 2, the difference in bandgap energy between each barrier layer of the active layer 40 and the well layer 42 is 0.140 eV or less. Furthermore, in Example 2, the difference in bandgap energy between the barrier layer 41 and the first optical guiding layer 61 is smaller than in Example 1.

[0056] 6 , in the semiconductor light emitting device 1 according to Example 2, the difference in band gap energy between the first light guiding layer 61 and the barrier layer 41 is 0.027 eV. The second light guiding layer 62 and the barrier layer 43 have the same composition, so there is no difference in band gap energy between them.

[0057] [2-4. Example 3] As shown in FIG. 6, the semiconductor light emitting device 1 according to Example 3 differs from the semiconductor light emitting device 1 according to Example 2 mainly in that the impurity (Mg) concentration of the second light guide layer 62 is low.

[0058] The substrate 10, underlayer 21, and crack prevention layer 22 of the semiconductor light emitting device 1 according to Example 3 have the same configurations as the substrate 10, underlayer 21, and crack prevention layer 22 of the semiconductor light emitting device 1 according to Example 2 (and the semiconductor light emitting device of the comparative example), respectively. The first cladding layer 30, first optical guide layer 61, well layer 42, barrier layer 43, electron blocking layer 70, and second cladding layer 50 of the semiconductor light emitting device 1 according to Example 3 have the same configurations as the first cladding layer 30, first optical guide layer 61, well layer 42, barrier layer 43, electron blocking layer 70, and second cladding layer 50 of the semiconductor light emitting device 1 according to Example 2, respectively.

[0059] The barrier layer 41 according to Example 3 is the same as the barrier layer 41 according to Example 1, and is made of undoped Al having a thickness of 12 nm. ０．０４ Ga ０．９６ The second optical guide layer 62 is a P-type Al layer having a thickness of 130 nm, similar to the second optical guide layer 62 in Example 2. ０．０３ Ga ０．９７ Although it is an N layer, the impurity concentration is lower than that of the second optical guide layer 62 according to Example 2. The Mg concentration of the second optical guide layer 62 according to Example 3 is 2×10 １８ cm －３ is.

[0060] The bandgap energy distribution of the semiconductor light emitting device 1 according to Example 3 is similar to that of the semiconductor light emitting device 1 according to Example 2. As shown in Fig. 6 , in the semiconductor light emitting device 1 according to Example 3, as in Example 2, the difference in bandgap energy between each barrier layer of the active layer 40 and the well layer 42 is 0.140 eV or less.

[0061] 2-5. Example 4 As shown in FIG. 6, the semiconductor light emitting device 1 according to Example 4 differs from the semiconductor light emitting device 1 according to Example 2 mainly in the composition of the barrier layer 43.

[0062] The substrate 10 and the underlayer 21 of the semiconductor light-emitting device 1 according to Example 4 have the same configurations as the substrate 10 and the underlayer 21 of the semiconductor light-emitting device 1 according to Example 2 (and the semiconductor light-emitting device of the comparative example), respectively. The first cladding layer 30, the first optical guide layer 61, the well layer 42, the electron blocking layer 70, the second optical guide layer 62, and the second cladding layer 50 of the semiconductor light-emitting device 1 according to Example 4 have the same configurations as the first cladding layer 30, the first optical guide layer 61, the well layer 42, the electron blocking layer 70, the second optical guide layer 62, and the second cladding layer 50 of the semiconductor light-emitting device 1 according to Example 2, respectively.

[0063] The crack prevention layer 22 according to Example 4 is an N-type In layer having a thickness of 150 nm. ０．０４ Ga ０．９６ The first optical guide layer 61 is an N layer having a thickness of 127 nm and a concentration of 5×10 １７ cm －３ Si-doped N-type Al ０．０３ Ga ０．９７ An N layer and an undoped Al layer with a thickness of 80 nm placed on the N layer. ０．０３ Ga ０．９７ The barrier layer 41 is an undoped AlN layer having a thickness of 14 nm. ０．０４ Ga ０．９６ The barrier layer 43 is an undoped AlN layer having a thickness of 10 nm. ０．０４ Ga ０．９６ This is the N layer.

[0064] The bandgap energy distribution of the semiconductor light emitting device 1 according to Example 4 will be described with reference to Fig. 10. Fig. 10 is a graph schematically showing the bandgap energy distribution in the stacking direction of the semiconductor light emitting device 1 according to Example 4.

[0065] 10 (and FIG. 6 ), in the semiconductor light emitting device 1 according to Example 4, the difference in band gap energy between each barrier layer of the active layer 40 and the well layer 42 is 0.140 eV or less, as in Example 2. Furthermore, in the semiconductor light emitting device 1 according to Example 4, the band gap energy of the barrier layer 43 is larger than the band gap energy of the barrier layer 43 according to Example 2.

[0066] 6 , in the semiconductor light emitting device 1 according to Example 4, the difference in band gap energy between the first light guiding layer 61 and the barrier layer 41 is 0.027 eV. The difference in band gap energy between the second light guiding layer 62 and the barrier layer 43 is also 0.027 eV.

[0067] 2-6. Example 5 As shown in FIG. 6, the semiconductor light emitting device 1 according to Example 5 differs from the semiconductor light emitting device 1 according to Example 1 mainly in that the well layer 42 is an AlInGaN layer.

[0068] The substrate 10, underlayer 21, anti-crack layer 22, and second cladding layer 50 of the semiconductor light-emitting device 1 according to Example 5 have the same configurations as the substrate 10, underlayer 21, anti-crack layer 22, and second cladding layer 50 of the semiconductor light-emitting device 1 according to Example 1 (and the semiconductor light-emitting device of the comparative example), respectively. The first cladding layer 30, barrier layer 41, and electron blocking layer 70 of the semiconductor light-emitting device 1 according to Example 5 have the same configurations as the first cladding layer 30, barrier layer 41, and electron blocking layer 70 of the semiconductor light-emitting device 1 according to Example 1, respectively.

[0069] The first optical guide layer 61 according to Example 5 has a thickness of 127 nm and a concentration of 5×10 １７ cm －３ Si-doped N-type Al ０．０３ Ga ０．９７ An N layer and a P-type Al layer with a thickness of 90 nm placed on the N layer. ０．０３ Ga ０．９７ The well layer 42 is an undoped AlN layer with a thickness of 17.5 nm. ０．０２ In ０．０３５ Ga ０．９４５ The barrier layer 43 is an undoped AlN layer. ０．０３ Ga ０．９７ As shown in FIG. 6, the barrier layer 43 and the second optical guide layer 62 have the same composition (Al ０．０３ Ga ０．９７ The total thickness of the barrier layer 43 and the second optical guide layer 62 is 70 nm. ０．０３ Ga ０．９７The portion of the N layer close to the well layer 42 functions as a barrier layer 43 , and the portion far from the well layer 42 functions as a second optical guide layer 62 .

[0070] The bandgap energy distribution of the semiconductor light emitting device 1 according to Example 5 is similar to that of the semiconductor light emitting device 1 according to Example 1. As shown in Fig. 6 , in the semiconductor light emitting device 1 according to Example 5, as in Example 1, the difference in bandgap energy between each barrier layer of the active layer 40 and the well layer 42 is 0.140 eV or less.

[0071] [3. Characteristics and Effects] The characteristics and effects of the semiconductor light-emitting device 1 according to this embodiment will be described using FIG. 6 and FIG. 11 , comparing the comparative example with each example. FIG. 11 is a diagram showing the characteristics of each example of this embodiment. In FIG. 11 , characteristics obtained by experiments on the semiconductor light-emitting device 1 according to each example are also shown, along with characteristics obtained by experiments on the semiconductor light-emitting device of the comparative example. Note that in FIG. 11 , characteristics that have not been measured at the time of filing this disclosure are marked with "Not Measured." Furthermore, the laser oscillation characteristics of each semiconductor light-emitting device shown in FIG. 11 are shown when the device is operated in continuous wave (CW) oscillation at room temperature with an optical output of 0.3 W.

[0072] The peak photon energy (peak position) and half width (full width at half maximum) of the spontaneous emission light shown in Fig. 11 are values ​​obtained by measuring, with a spectrum analyzer, the emission spectrum of each semiconductor light-emitting element into which a current less than the oscillation threshold is injected. The peak photon energy (peak position) and half width (full width at half maximum) of the laser light shown in Fig. 11 are values ​​obtained by measuring, with a spectrum analyzer, the emission spectrum of each semiconductor light-emitting element into which a current greater than the oscillation threshold is injected.

[0073] The PL-laser light energy difference shown in FIG. 11 is the difference between the peak photon energy of the PL spectrum measured by the above-described method shown in FIG. 11 and the peak photon energy of the laser light.

[0074] The PL-spontaneous emission light energy difference shown in FIG. 11 is the difference between the peak photon energy of the PL spectrum measured by the above-described method and the peak photon energy of the spontaneous emission light shown in FIG.

[0075] The PL intensity ratio at the laser light peak position shown in FIG. 11 is the ratio of the PL intensity at the peak photon energy of the laser light emitted from the semiconductor light emitting element into which current is injected to the peak PL intensity.

[0076] The PL intensity ratio at a position 0.050 eV lower in energy than the PL peak position shown in FIG. 11 is the ratio of the PL intensity at a photon energy 0.050 eV lower in energy than the peak photon energy of the PL spectrum to the peak PL intensity.

[0077] The slope efficiency and output saturation onset point shown in Fig. 11 will be described using, as an example, the characteristics of the semiconductor light-emitting element 1 of Example 5 shown in Figs. 12A and 12B. Fig. 12A is a graph showing the relationship between the injection current and the optical output of the semiconductor light-emitting element 1 of Example 5, with the I-L curve shown as a solid line and the slope efficiency curve (the slope of the I-L curve) shown as a dashed line. Fig. 12B is a graph showing the relationship between the optical output of the semiconductor light-emitting element 1 of Example 5 and the ratio of the optical output to the input power (i.e., wall-plug efficiency WPE).

[0078] The slope efficiency is the increase in light output per increase in current, and is a value corresponding to the slope of the IL curve shown in Fig. 12A. Fig. 11 shows the slope efficiency for each light output range.

[0079] The output saturation onset point corresponds to the inflection point where the slope of the IL curve begins to decrease, and the optical output at the output saturation onset point is 2.1 W (2100 mW) as shown in Fig. 12A. Alternatively, the output saturation onset point may be defined as the point at which the ratio of the optical output to the input power to the semiconductor light emitting device is maximized as shown in Fig. 12B.

[0080] First, the relationship between the peak photon energy of the laser light and the PL peak photon energy of the semiconductor light emitting element 1 according to the present embodiment will be described with reference to Fig. 13 and Fig. 14, while comparing it with a comparative example. Fig. 13 and Fig. 14 are graphs showing the laser light spectrum and the PL spectrum of the semiconductor light emitting element of the comparative example and the semiconductor light emitting element 1 according to Example 1, respectively. In Fig. 13 and Fig. 14, the laser light spectrum is shown by a solid line, and the PL spectrum is shown by a dashed line.

[0081] As shown in FIG. 13 , in the semiconductor light-emitting device of the comparative example, the peak photon energy of PL is 0.049 eV higher than the peak photon energy of laser light. In contrast, in the semiconductor light-emitting device 1 of Example 1, the peak photon energy of PL is 0.112 eV higher than the peak photon energy of laser light. Thus, the PL-laser light energy difference is larger in the semiconductor light-emitting device 1 of Example 1 than in the semiconductor light-emitting device of the comparative example. As a result, the PL intensity at the peak photon energy of laser light in the semiconductor light-emitting device 1 of Example 1 is smaller than that in the semiconductor light-emitting device of the comparative example. As shown in FIGS. 11 and 13 , the PL intensity ratio at the laser light peak position in the semiconductor light-emitting device of the comparative example is 0.84, whereas in the semiconductor light-emitting device 1 of Example 1, as shown in FIGS. 11 and 14 , it is 0.02. Here, it is considered that the PL intensity corresponds to the magnitude of light absorption. Therefore, the semiconductor light-emitting device 1 of Example 1 can reduce the absorption of laser light in the active layer 40 more than the semiconductor light-emitting device of the comparative example. As a result, as shown in FIG. 11, the semiconductor light emitting device 1 according to Example 1 can improve the output saturation starting point light output, output saturation starting point current density, and slope efficiency compared to the semiconductor light emitting device of the comparative example.

[0082] As shown in FIG. 11 , the semiconductor light-emitting element 1 according to each of Examples 2 to 5 exhibits characteristics similar to those of the semiconductor light-emitting element 1 according to Example 1. Here, the relationship between the output saturation onset point, slope efficiency, and PL-laser light energy difference of the semiconductor light-emitting element 1 according to each Example and the semiconductor light-emitting element according to the comparative example will be described with reference to FIGS. 15 and 16 . FIG. 15 is a graph showing the relationship between the optical output and PL-laser light energy difference at the output saturation onset point of the semiconductor light-emitting element 1 according to each Example and the semiconductor light-emitting element according to the comparative example. FIG. 16 is a graph showing the relationship between the slope efficiency and PL-laser light energy difference when the optical output of the semiconductor light-emitting element 1 according to each Example and the semiconductor light-emitting element according to the comparative example is 0.5 W or more and 1.0 W or less. In FIGS. 15 and 16 , black circles represent data for each Example, and black squares represent data for the comparative example. Here, the range of optical output power of 0.5 W or more and 1.0 W or less includes a high-output region where the slope efficiency decreases in the comparative example, but in this embodiment, this range is one where the output does not reach saturation and the slope efficiency is stable.

[0083] As shown in FIGS. 15 and 16 , in the semiconductor light-emitting device of the comparative example, the PL-laser light energy difference is less than 0.050 eV, whereas in the semiconductor light-emitting device 1 according to each example, the PL-laser light energy difference is 0.050 eV or more. More specifically, in the semiconductor light-emitting device 1 according to each example, the peak photon energy of PL in the active layer 40 is higher than the peak photon energy of the laser light by 0.050 eV or more. This reduces the absorption of laser light in the active layer 40 as described above, and as shown in FIGS. 15 and 16 , the optical output and slope efficiency at the output saturation onset can be increased. For example, the optical output at the output saturation onset can be set to 0.7 W or more, and the slope efficiency can be set to 0.7 W / A or more. In other words, the optical output increases linearly with the injection current at least in the range of optical output power between 0.5 W and 0.7 W. In addition, in this case, the current density at the output saturation onset is 60 kA / mm ２ That's all.

[0084] The semiconductor light emitting device 1 having the above-described characteristics can achieve high output. In each example, it has been confirmed by experiment that continuous oscillation for at least 100 hours or more is possible with an optical output of 1 W at room temperature.

[0085] It was also confirmed that the larger the PL-laser light energy difference, the more the output characteristics such as the output saturation starting point and slope efficiency tend to improve.

[0086] Furthermore, in the semiconductor light emitting device 1 according to this embodiment, the peak photon energy of PL from the active layer 40 may be 0.103 eV or more higher than the peak photon energy of the laser light. This allows for a further increase in slope efficiency at the onset of output saturation. Specifically, the slope efficiency can be set to 0.75 W / A or more. Furthermore, the peak photon energy of PL from the active layer 40 may be 0.111 V or more higher than the peak photon energy of the laser light. This allows for a further increase in optical output and slope efficiency at the onset of output saturation. Specifically, the optical output at the onset of output saturation can be set to 1.4 W or more, and the slope efficiency can be set to 1.1 W / A or more. Accordingly, a further increase in output power of the semiconductor light emitting device 1 can be achieved. In these cases, the current density at the onset of output saturation is 78 kA / mm ２ It may be more than that.

[0087] In the semiconductor light emitting element 1 according to the present embodiment, the difference between the peak photon energy of the PL in the active layer 40 and the peak photon energy of the laser light may be 0.250 eV or less. This allows a gain to be reliably obtained in the active layer 40 of the semiconductor light emitting element 1.

[0088] 11 , in the semiconductor light-emitting device 1 according to the present embodiment, the PL intensity at the peak photon energy of the laser light in the PL spectrum of the active layer 40 may be 40% or less of the peak intensity of the PL spectrum. This reduces the absorption of laser light in the active layer 40, thereby increasing the optical output at the onset of output saturation. When the PL-laser light energy difference is 0.050 eV, the PL intensity at the peak photon energy of the laser light in the example with the widest half-width among the PL spectra of the active layer 40 in this example was about 40% of the peak intensity of the PL spectrum.

[0089] 11 , in the semiconductor light emitting device 1 according to the present embodiment, the PL intensity at the peak photon energy of the laser light in the PL spectrum of the active layer 40 may be 8% or less of the peak intensity of the PL spectrum, which further reduces the absorption of the laser light in the active layer 40 and further increases the optical output at the onset of output saturation.

[0090] Furthermore, in the semiconductor light-emitting element 1 according to this embodiment, when the peak photon energy of the laser light is 3.1 eV or more, as in each example, the effect of the semiconductor light-emitting element 1 according to this embodiment is more pronounced. In other words, when the peak photon energy is large, the energy per photon is large, and therefore the influence of heat generation due to light absorption is large. In particular, when the peak photon energy of the laser light is 3.1 eV or more, the effect of reduced light absorption of the semiconductor light-emitting element 1 according to this embodiment is remarkable. Therefore, it is also possible to suppress optical damage to the semiconductor light-emitting element 1 due to light absorption.

[0091] Next, the relationship between the spontaneous emission light and PL spectra of the semiconductor light-emitting element 1 according to the present embodiment will be described with reference to FIGS. 17 to 22. FIGS. 17, 18, 19, and 20 are graphs showing the spontaneous emission light spectrum and the PL spectrum of the semiconductor light-emitting elements according to the comparative example, Example 1, Example 2, and Example 5, respectively. In FIGS. 17 to 20, the spontaneous emission light spectrum is indicated by a solid line, and the PL spectrum is indicated by a dashed line. FIG. 21 is a graph showing the relationship between the optical output and the PL-spontaneous emission light energy difference at the output saturation onset point of the semiconductor light-emitting element 1 according to each example and the semiconductor light-emitting element according to the comparative example. FIG. 22 is a graph showing the relationship between the slope efficiency and the PL-spontaneous emission light energy difference when the optical output of the semiconductor light-emitting element 1 according to each example and the semiconductor light-emitting element according to the comparative example is 0.5 W or more and 1.0 W or less. In FIGS. 21 and 22, black circles indicate data for each example, and black squares indicate data for the comparative example.

[0092] 17, 21, and 22, the PL-spontaneous emission energy difference is less than 0.070 eV in the semiconductor light-emitting device of the comparative example, whereas the PL-spontaneous emission energy difference is 0.070 eV or more in the semiconductor light-emitting devices 1 according to Examples 1, 2, and 5, as shown in FIGS. 18 to 20. More specifically, in the semiconductor light-emitting devices 1 according to each Example, the peak photon energy of PL in the active layer 40 is higher than the peak photon energy of spontaneous emission by 0.070 eV or more. The semiconductor light-emitting devices 1 according to Examples 3 and 4 also have similar characteristics to the semiconductor light-emitting device 1 according to Example 2, as shown in FIG.

[0093] It is known that the peak photon energy of laser light from a semiconductor light-emitting device varies depending on the conditions of the resonator, and may be greater or smaller than the peak photon energy of the spontaneously emitted light within the gain region of the spontaneously emitted light (the photon energy range in which gain can be obtained). In the semiconductor light-emitting device 1 according to each example, the peak photon energy of PL in the active layer 40 is higher by 0.070 eV or more than the peak photon energy of the spontaneously emitted light. Therefore, in the semiconductor light-emitting device 1 according to this embodiment, even if the oscillation wavelength deviates from the target wavelength depending on the conditions of the resonator, a sufficiently large difference in peak photon energy between PL and laser light can be ensured, thereby reducing absorption of laser light in the active layer 40. Therefore, the optical output at the onset of output saturation can be increased.

[0094] Furthermore, in the semiconductor light emitting device 1 according to this embodiment, the peak photon energy of PL in the active layer 40 may be higher than the peak photon energy of spontaneous emission by 0.090 eV or more. This further increases the optical output at the onset of output saturation and the slope efficiency. As a result, the semiconductor light emitting device 1 can achieve even higher output power.

[0095] In the semiconductor light emitting device 1 according to the present embodiment, the difference between the peak photon energy of PL in the active layer 40 and the peak photon energy of the spontaneously emitted light may be 0.250 eV or less. This allows a gain to be reliably obtained in the active layer 40 of the semiconductor light emitting device 1.

[0096] Here, the configuration of the semiconductor light-emitting device 1 that can obtain the above-described characteristics will be described. In this embodiment, as shown in FIG. 6 , the difference in bandgap energy between the barrier layers 41 and 43 and the well layer 42 is 0.140 eV or less. Although the detailed mechanism has not been elucidated, when the difference in bandgap energy between each barrier layer and the well layer 42 is small, as in the semiconductor light-emitting device 1 according to this embodiment, some of the carriers injected into the well layer 42 flow out beyond each barrier layer into the first optical guiding layer 61 or the second optical guiding layer 62. It is presumed that the carriers that flow out into each optical guiding layer shift the PL spectrum of the active layer 40 to a higher energy side.

[0097] 6 , in this embodiment, the difference in bandgap energy between the first optical guiding layer 61 and the barrier layer 41 closest to the first optical guiding layer 61 is less than 0.080 eV. Also, the difference in bandgap energy between the second optical guiding layer 62 and the barrier layer 43 closest to the second optical guiding layer 62 is less than 0.080 eV. By reducing the bandgap energy between each optical guiding layer and the barrier layer closest to that optical guiding layer in this way, carriers that have flowed over the barrier into that optical guiding layer can return to the well layer 42 again.

[0098] Furthermore, like the semiconductor light-emitting device 1 according to Examples 2 to 4, the semiconductor light-emitting device 1 according to the present embodiment may further include an electron blocking layer disposed above the barrier layer 43 closest to the second cladding layer 50 and in contact with the barrier layer 43. Electrons injected into the well layer 42 of the semiconductor light-emitting device 1 have a smaller effective mass than holes, and therefore are more likely to overflow the barrier layer 43. Therefore, there are more carriers overflowing the barrier layer 43 closer to the second cladding layer 50, which is a P-type cladding layer, than there are holes overflowing the barrier layer 41 closer to the first cladding layer 30. Therefore, the semiconductor light-emitting device 1 according to Examples 2 to 4 includes an electron blocking layer 70 disposed above the barrier layer 43 and in contact with the barrier layer 43. This prevents the formation of a region between the barrier layer 43 and the electron blocking layer 70 that has a lower bandgap energy than the barrier layer 43 and the electron blocking layer 70. Therefore, electrons that overflow the barrier layer 43 are more likely to return to the well layer 42. This reduces the probability of recombination of electrons and holes in regions other than the well layer 42, thereby improving the luminous efficiency (and slope efficiency, etc.) of the semiconductor light-emitting device 1.

[0099] Furthermore, when adjacent barrier layers 43 and second light guide layers 62 have the same composition, as in the case of the barrier layers 43 and second light guide layers 62 in the semiconductor light emitting devices 1 according to Examples 1 and 5, they may be regarded as a single barrier layer. In this case, in the semiconductor light emitting devices 1 according to Examples 1 and 5, it can be regarded that the electron blocking layer is in contact with the barrier layer that combines the barrier layer 43 and the second light guiding layer 62. Therefore, the semiconductor light emitting devices 1 according to Examples 1 and 5 also achieve the same effect as that of the semiconductor light emitting devices 1 according to Examples 2 to 4, due to the electron blocking layer 70.

[0100] Furthermore, the semiconductor light-emitting element 1 according to this embodiment has at least one of a first optical guide layer 61 disposed between the first cladding layer 30 and the active layer 40 and a second optical guide layer 62 disposed between the active layer 40 and the second cladding layer 50, and the thickness of the well layer 42 may be 17.5 nm or more.

[0101] The synergistic effect of the thick well layer 42 and the presence of carriers in each optical guide layer makes it possible to increase the PL spectrum by 0.050 eV above the peak photon energy of the laser light. Although the active layer 40 in each embodiment has a single well layer 42, it may have multiple well layers. In other words, the active layer 40 may have a multiple quantum well structure. In this case, the total thickness of the multiple well layers may be 17.5 nm.

[0102] Also, like the semiconductor light emitting device 1 according to Example 5, each barrier layer is made of Al ｚ Ga １－ｚ N (0<z<1), and the well layer 42 is made of Al ｘ In ｙ Ga １－ｘ－ｙ N (0<x<1, 0<y<1). This makes it possible to obtain the same PL-laser light energy difference and PL-spontaneous emission light energy difference as in the semiconductor light-emitting device 1 according to Examples 1 to 4, where the well layer 42 is made of InGaN. Furthermore, in the semiconductor light-emitting device 1 according to Example 5, the optical output at the output saturation onset point and the slope efficiency can be increased compared to the semiconductor light-emitting device 1 according to Examples 1 to 4.

[0103] When the active layer 40 has a multiple quantum well structure, three or more barrier layers may be made of AlzGa1-zN (0<z<1), and two or more well layers may be made of AlxInyGa1-x-yN (0<x<1, 0<y<1). In this case, too, the same effects as in the case of a single quantum well structure (for example, Example 5) can be obtained.

[0104] (Modifications, etc.) Although the semiconductor light emitting device according to the present disclosure has been described above based on each example of the embodiment, the present disclosure is not limited to each example of the above embodiment.

[0105] For example, in each of the above examples, the semiconductor light-emitting element 1 is a semiconductor laser element, but the semiconductor light-emitting element 1 is not limited to a semiconductor laser element. For example, the semiconductor light-emitting element according to the present disclosure may include an active layer 40, and the peak photon energy of PL in the active layer 40 may be 0.070 eV or more higher than the peak photon energy of spontaneous emission light emitted from the semiconductor light-emitting element upon current injection. The semiconductor light-emitting element according to the present disclosure may be, for example, a superluminescent diode.

[0106] The semiconductor light emitting device 1 according to each of the above examples includes one second light guiding layer 62 between the active layer 40 and the second cladding layer 50, but may include two or more second light guiding layers 62. For example, the semiconductor light emitting device according to the present disclosure may include a second light guiding layer 62 disposed between the active layer 40 and the electron blocking layer 70, and a second light guiding layer 62 disposed between the electron blocking layer 70 and the second cladding layer 50. In this case, the configurations of the second light guiding layers 62 may be different from each other.

[0107] The active layer 40 of the semiconductor light emitting device 1 according to each of the above-described embodiments has a single quantum well structure, but may have a multiple quantum well structure, i.e., a structure in which three or more barrier layers and two or more well layers are alternately stacked.

[0108] In the above embodiment, the well layer 42 is made of InGaN or AlInGaN, but the configuration of the well layer 42 is not limited to this. The well layer 42 may be made of, for example, GaN.

[0109] This disclosure also includes forms obtained by applying various modifications to the above embodiments and modifications that a person skilled in the art would conceive, and forms realized by arbitrarily combining the components and functions of the above embodiments and modifications within the scope that does not deviate from the intent of this disclosure.

[0110] The semiconductor light emitting device and the like according to the present disclosure can be used, for example, as a high-output, highly efficient light source in a light source for laser processing.

[0111] REFERENCE SIGNS LIST 1 Semiconductor light emitting element 1F, 1R End face 10 Substrate 21 Underlayer 22 Crack prevention layer 30 First cladding layer 40 Active layer 41, 43 Barrier layer 42 Well layer 50 Second cladding layer 50R Ridge 50T Groove 60 Optical guide layer 61 First optical guide layer 62 Second optical guide layer 70 Electron blocking layer 80 Insulating layer 91 Upper electrode 92 Lower electrode

Claims

1. A semiconductor light emitting device, A substrate; a first cladding layer of a first conductivity type disposed above the substrate; an active layer disposed above the first cladding layer; a second cladding layer of a second conductivity type different from the first conductivity type, the second cladding layer being disposed above the active layer; an optical guiding layer disposed between the first cladding layer and the second cladding layer; The peak photon energy of the photoluminescence of the active layer is higher by 0.050 eV or more than the peak photon energy of the laser light emitted from the semiconductor light emitting element to which a current is injected. Semiconductor light emitting element.

2. The peak photon energy of the photoluminescence of the active layer is 0.112 eV or more higher than the peak photon energy of the laser light emitted from the semiconductor light emitting element to which a current is injected. The semiconductor light emitting device according to claim 1 .

3. The peak photon energy of the photoluminescence of the active layer is 0.115 eV or more higher than the peak photon energy of the laser light emitted from the semiconductor light emitting element to which a current is injected. The semiconductor light emitting device according to claim 2 .

4. The difference between the peak photon energy of the photoluminescence of the active layer and the peak photon energy of the laser light emitted from the semiconductor light-emitting element to which a current is injected is 0.250 eV or less. The semiconductor light emitting device according to claim 1 .

5. A semiconductor light emitting device, A substrate; a first cladding layer of a first conductivity type disposed above the substrate; an active layer disposed above the first cladding layer; a second cladding layer of a second conductivity type different from the first conductivity type, the second cladding layer being disposed above the active layer; an optical guiding layer disposed between the first cladding layer and the second cladding layer; The peak wavelength of the laser light emitted from the semiconductor light emitting element to which a current is injected is 12.8 nm or more longer than the peak wavelength of the photoluminescence of the active layer. Semiconductor light emitting element.

6. A semiconductor light emitting device, A substrate; a first cladding layer of a first conductivity type disposed above the substrate; an active layer disposed above the first cladding layer; a second cladding layer of a second conductivity type different from the first conductivity type, the second cladding layer being disposed above the active layer; an optical guiding layer disposed between the first cladding layer and the second cladding layer; The ratio of the peak wavelength of photoluminescence of the active layer to the peak wavelength of laser light emitted from the semiconductor light emitting element to which a current is injected is 0.9666 or less. Semiconductor light emitting element.

7. A semiconductor light emitting device, A substrate; a first cladding layer of a first conductivity type disposed above the substrate; an active layer disposed above the first cladding layer; a second cladding layer of a second conductivity type different from the first conductivity type, the second cladding layer being disposed above the active layer; an optical guiding layer disposed between the first cladding layer and the second cladding layer; In the photoluminescence spectrum of the active layer, the intensity of the photoluminescence at the peak photon energy of the laser light emitted from the semiconductor light emitting element to which a current is injected is 40% or less of the peak intensity of the spectrum. Semiconductor light emitting element.

8. In the photoluminescence spectrum of the active layer, the intensity of the photoluminescence at the peak photon energy of the laser light emitted from the semiconductor light emitting element to which a current is injected is 8% or less of the peak intensity of the spectrum. The semiconductor light emitting device according to claim 7 .

9. In the photoluminescence spectrum of the active layer, the intensity of the photoluminescence at the peak photon energy of the laser light emitted from the semiconductor light emitting element to which a current is injected is 3% or less of the peak intensity of the spectrum. The semiconductor light emitting device according to claim 8 .

10. The peak photon energy of the laser light emitted from the semiconductor light emitting element is 3.1 eV or more. The semiconductor light emitting device according to any one of claims 1 to 9.

11. The optical output of the semiconductor light emitting device at the output saturation starting point is 0.7 W or more. The semiconductor light emitting device according to any one of claims 1 to 9.

12. The current density at the output saturation starting point of the semiconductor light emitting device is 60 kA / mm ２ That's all. The semiconductor light emitting device according to any one of claims 1 to 9.

13. the active layer has a quantum well structure in which two or more barrier layers and one or more well layers are alternately stacked; A difference in band gap energy between each of the two or more barrier layers and each of the one or more well layers is 0.140 eV or less. The semiconductor light emitting device according to any one of claims 1 to 9.

14. the active layer has a quantum well structure in which two or more barrier layers and one or more well layers are alternately stacked; the optical guide layer includes at least one of a first optical guide layer disposed between the first cladding layer and the active layer, and a second optical guide layer disposed between the active layer and the second cladding layer; each of the first optical guiding layer and the second optical guiding layer has a band gap energy smaller than that of the two or more barrier layers and larger than that of the one or more well layers; a difference in band gap energy between the first optical guiding layer and a barrier layer among the two or more barrier layers that is closest to the first optical guiding layer is less than 0.080 eV; A difference in band gap energy between the second optical guiding layer and the barrier layer that is closest to the second optical guiding layer among the two or more barrier layers is less than 0.080 eV. The semiconductor light emitting device according to any one of claims 1 to 9.

15. an electron blocking layer disposed above and in contact with a barrier layer among the two or more barrier layers that is closest to the second cladding layer; The optical guide layer includes the first optical guide layer. The semiconductor light emitting device according to claim 14 .

16. the active layer has a quantum well structure in which two or more barrier layers and one or more well layers are alternately stacked; the optical guide layer includes at least one of a first optical guide layer disposed between the first cladding layer and the active layer, and a second optical guide layer disposed between the active layer and the second cladding layer; The total thickness of the one or more well layers is 17.5 nm or more. The semiconductor light emitting device according to any one of claims 1 to 9.

17. the active layer has a quantum well structure in which two or more barrier layers and one or more well layers are alternately stacked; The two or more barrier layers are made of Al ｚ G １－ｚ N, where 0<z<1, The one or more well layers are Al ｘ In ｙ G １－ｘ－ｙ N (0<x<1, 0<y<1) The semiconductor light emitting device according to any one of claims 1 to 9.

18. A GaN-based semiconductor light-emitting device, A substrate; a first cladding layer of a first conductivity type disposed above the substrate; an active layer disposed above the first cladding layer; a second cladding layer of a second conductivity type different from the first conductivity type, the second cladding layer being disposed above the active layer; an optical guiding layer disposed between the first cladding layer and the second cladding layer; the active layer has a quantum well structure in which two or more barrier layers and one or more well layers are alternately stacked; a difference in band gap energy between each of the two or more barrier layers and each of the one or more well layers is 0.140 eV or less; the optical guide layer includes at least one of a first optical guide layer disposed between the first cladding layer and the active layer, and a second optical guide layer disposed between the active layer and the second cladding layer; each of the first optical guiding layer and the second optical guiding layer has a band gap energy smaller than that of the two or more barrier layers and larger than that of the one or more well layers; a difference in band gap energy between the first optical guiding layer and a barrier layer among the two or more barrier layers that is closest to the first optical guiding layer is less than 0.080 eV; a difference in band gap energy between the second optical guiding layer and a barrier layer among the two or more barrier layers that is closest to the second optical guiding layer is less than 0.080 eV; The peak photon energy of the laser light emitted from the semiconductor light emitting element is 3.1 eV or more. Semiconductor light emitting element.

19. an electron blocking layer disposed above and in contact with a barrier layer among the two or more barrier layers that is closest to the second cladding layer; The optical guide layer includes the first optical guide layer. The semiconductor light emitting device according to claim 18 .

20. The total thickness of the one or more well layers is 17.5 nm or more. The semiconductor light-emitting device according to claim 18 or 19.

21. The two or more barrier layers are made of Al ｚ G １－ｚ N, where 0<z<1, The one or more well layers are Al ｘ In ｙ G １－ｘ－ｙ N (0<x<1, 0<y<1) The semiconductor light-emitting device according to claim 18 or 19.

22. The optical output of the semiconductor light emitting device at the output saturation starting point is 0.7 W or more. The semiconductor light-emitting device according to claim 18 or 19.

23. The current density at the output saturation starting point of the semiconductor light emitting device is 60 kA / mm ２ That's all. The semiconductor light-emitting device according to claim 18 or 19.