WO2023026858A1 - 窒化物系半導体発光素子 - Google Patents

窒化物系半導体発光素子 Download PDF

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WO2023026858A1
WO2023026858A1 PCT/JP2022/030468 JP2022030468W WO2023026858A1 WO 2023026858 A1 WO2023026858 A1 WO 2023026858A1 JP 2022030468 W JP2022030468 W JP 2022030468W WO 2023026858 A1 WO2023026858 A1 WO 2023026858A1
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layer
side guide
nitride
guide layer
semiconductor light
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French (fr)
Japanese (ja)
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徹 高山
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Nuvoton Technology Corp Japan
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Nuvoton Technology Corp Japan
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/34333—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
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    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H01S5/0425—Electrodes, e.g. characterised by the structure
    • H01S5/04252—Electrodes, e.g. characterised by the structure characterised by the material
    • H—ELECTRICITY
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    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H01S5/2004—Confining in the direction perpendicular to the layer structure
    • H01S5/2009—Confining in the direction perpendicular to the layer structure by using electron barrier layers
    • H—ELECTRICITY
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    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
    • H—ELECTRICITY
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    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/305—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure
    • H01S5/3054—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure p-doping
    • H01S5/3063—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure p-doping using Mg
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/34346—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser characterised by the materials of the barrier layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
    • H01S5/4031—Edge-emitting structures

Definitions

  • the present disclosure relates to a nitride-based semiconductor light-emitting device.
  • nitride-based semiconductor light-emitting elements have been used as light sources for processing equipment.
  • Light sources for processing apparatuses are required to have higher output and higher efficiency.
  • techniques for reducing operating voltages are known (see, for example, Patent Literature 1, etc.).
  • the present disclosure is intended to solve such problems, and aims to provide a nitride-based semiconductor light-emitting device capable of reducing the operating voltage and increasing the light confinement factor in the active layer.
  • one aspect of the nitride-based semiconductor light-emitting device is a nitride-based semiconductor light-emitting device that includes a semiconductor laminate and emits light from an end face in a direction perpendicular to the stacking direction of the semiconductor laminate.
  • the semiconductor laminate includes an N-type first clad layer, an N-side guide layer arranged above the N-type first clad layer, and an N-side guide layer arranged above the N-side guide layer.
  • an active layer including a well layer and a barrier layer and having a quantum well structure, a P-side guide layer disposed above the active layer, and a P-type cladding layer disposed above the P-side guide layer wherein the bandgap energy of the N-side guide layer monotonically increases with distance from the active layer, and the bandgap energy of the N-side guide layer continuously increases with distance from the active layer
  • the average bandgap energy of the P-side guide layer is equal to or greater than the average bandgap energy of the N-side guide layer
  • the film thickness of the P-side guide layer is Tp
  • the film thickness of the N-side guide layer is is Tn, Tn ⁇ Tp Satisfying relationships.
  • a nitride-based semiconductor light-emitting device capable of reducing the operating voltage and increasing the light confinement factor in the active layer.
  • FIG. 1 is a schematic plan view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 1.
  • FIG. 2A is a schematic cross-sectional view showing the overall configuration of the nitride-based semiconductor light-emitting device according to Embodiment 1.
  • FIG. 2B is a schematic cross-sectional view showing the configuration of an active layer included in the nitride-based semiconductor light-emitting device according to Embodiment 1.
  • FIG. FIG. 3 is a schematic diagram showing an overview of the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting device according to Embodiment 1.
  • FIG. 4 is a graph showing coordinates of positions in the stacking direction of the nitride-based semiconductor light-emitting device according to the first embodiment.
  • FIG. 5 is a schematic graph showing bandgap energy distributions of the active layer and adjacent layers of the nitride-based semiconductor light-emitting device according to the first embodiment.
  • 6 is a graph showing the refractive index distribution and the light intensity distribution in the stacking direction of the nitride semiconductor light emitting devices of Comparative Examples 1 to 3 and the nitride semiconductor light emitting device according to Embodiment 1.
  • FIG. 7 shows distributions of valence band potential and hole Fermi level in the stacking direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device according to Embodiment 1. It is a graph which shows a simulation result.
  • FIG. 8 is a graph showing simulation results of carrier concentration distribution in the lamination direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device according to the first embodiment.
  • FIG. 9 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer and the optical confinement coefficient ( ⁇ v) according to the first embodiment.
  • FIG. 10 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer and the operating voltage according to the first embodiment.
  • FIG. 11 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light-emitting device of Comparative Example 3, and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction band potential.
  • FIG. 12 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light emitting device according to Embodiment 1, and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction band potential.
  • FIG. 11 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light-emitting device of Comparative Example 3, and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction band potential.
  • FIG. 12 is a graph showing the
  • FIG. 13 is a graph showing a simulation result of the relationship between the average In composition ratio in the N-side guide layer of the nitride-based semiconductor light emitting device according to Embodiment 1 and the light confinement factor ( ⁇ v).
  • FIG. 14 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer of the nitride-based semiconductor light emitting device according to Embodiment 1 and waveguide loss.
  • FIG. 15 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer of the nitride-based semiconductor light emitting device according to Embodiment 1 and the operating voltage.
  • FIG. 16 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer and the position P1 according to the first embodiment.
  • FIG. 17 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer and the difference ⁇ P according to the first embodiment.
  • 18 is a graph showing a simulation result of the relationship between the film thickness of the P-type cladding layer and the optical confinement factor ( ⁇ v) according to Embodiment 1.
  • FIG. 19 is a graph showing simulation results of the relationship between the thickness of the P-type cladding layer and the waveguide loss according to the first embodiment.
  • FIG. 20 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer and the effective refractive index difference ⁇ N according to the first embodiment.
  • FIG. 21 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer and the position P1 according to the first embodiment.
  • FIG. 22 is a graph showing simulation results of the relationship between the thickness of the P-type cladding layer and the difference ⁇ P according to the second embodiment.
  • 23A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 2.
  • FIG. 23B is a schematic cross-sectional view showing the configuration of an active layer included in the nitride-based semiconductor light-emitting device according to Embodiment 2.
  • FIG. FIG. 24 is a schematic graph showing bandgap energy distributions of the active layer and adjacent layers of the nitride-based semiconductor light-emitting device according to the second embodiment.
  • 25 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 3.
  • FIG. FIG. 26 is a schematic graph showing bandgap energy distributions of the active layer and adjacent layers of the nitride-based semiconductor light-emitting device according to the third embodiment.
  • FIG. 27 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 4.
  • FIG. FIG. 28 is a schematic graph showing bandgap energy distributions of the active layer and adjacent layers of the nitride-based semiconductor light-emitting device according to the fourth embodiment.
  • FIG. 29 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer and the optical confinement coefficient ( ⁇ v) according to the fourth embodiment.
  • FIG. 30 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer and the waveguide loss according to the fourth embodiment.
  • FIG. 31 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer and the operating voltage according to the fourth embodiment.
  • FIG. 32 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer and the position P1 according to the fourth embodiment.
  • FIG. 33 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer and the difference ⁇ P according to the fourth embodiment.
  • 34 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 5.
  • FIG. 35 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 6.
  • FIG. 36A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 7.
  • FIG. 36B is a schematic cross-sectional view showing the configuration of an active layer included in the nitride-based semiconductor light-emitting device according to Embodiment 7.
  • FIG. 37 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 8.
  • FIG. 38 is a schematic graph showing bandgap energy distributions of the active layer and adjacent layers of the nitride-based semiconductor light-emitting device according to Embodiment 8.
  • FIG. 39A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 9.
  • FIG. 39B is a schematic cross-sectional view showing the configuration of an active layer included in the nitride-based semiconductor light-emitting device according to Embodiment 9.
  • FIG. 40 is a schematic graph showing bandgap energy distributions of the active layer and adjacent layers of the nitride-based semiconductor light-emitting device according to the ninth embodiment.
  • 41 is a schematic graph showing bandgap energy distributions of an active layer and adjacent layers of a nitride-based semiconductor light-emitting device according to Modification 1 of Embodiment 9.
  • FIG. 42 is a schematic graph showing bandgap energy distributions of an active layer and adjacent layers of a nitride-based semiconductor light-emitting device according to Modification 2 of Embodiment 9.
  • FIG. 43 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Modification 1.
  • FIG. 44 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Modification 2.
  • FIG. 43 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Modification 1.
  • each figure is a schematic diagram and is not necessarily strictly illustrated. Therefore, the scales and the like are not always the same in each drawing.
  • symbol is attached
  • the terms “upper” and “lower” do not refer to the upward direction (vertically upward) and the downward direction (vertically downward) in absolute spatial recognition, but are based on the stacking order in the stacking structure. It is used as a term defined by a relative positional relationship. Also, the terms “above” and “below” are used not only when two components are spaced apart from each other and there is another component between the two components, but also when two components are spaced apart from each other. It also applies when they are arranged in contact with each other.
  • Embodiment 1 A nitride-based semiconductor light-emitting device according to Embodiment 1 will be described.
  • FIGS. 1, 2A and 2B 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 along line II-II of FIG.
  • FIG. 2B is a schematic cross-sectional view showing the configuration of the active layer 105 included in the nitride-based semiconductor light emitting device 100 according to this embodiment.
  • Each figure shows an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other.
  • the X, Y, and Z axes are 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.
  • the nitride-based semiconductor light-emitting device 100 includes a semiconductor laminate 100S including nitride-based semiconductor layers. Light is emitted from the end face 100F (see FIG. 1).
  • the nitride-based semiconductor light-emitting device 100 is a semiconductor laser device having two facets 100F and 100R forming a resonator.
  • the end surface 100F is a front end surface that emits laser light
  • the end surface 100R is a rear end surface having a higher reflectance than the end surface 100F.
  • the reflectances of the end faces 100F and 100R are 16% and 95%, respectively.
  • the cavity length of nitride-based semiconductor light-emitting device 100 according to the present embodiment (that is, the distance between facet 100F and facet 100R) is about 1200 ⁇ m.
  • the nitride-based semiconductor light emitting device 100 includes a semiconductor laminate 100S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114.
  • the semiconductor laminate 100S includes a substrate 101, an N-type first clad layer 102, an N-type second clad layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 106, and an intermediate layer 108. , an electron barrier layer 109 , a P-type clad layer 110 and a contact layer 111 .
  • the substrate 101 is a plate-like member that serves as a base for the nitride-based semiconductor light emitting device 100 .
  • substrate 101 is an N-type GaN substrate.
  • the N-type first clad layer 102 is an example of an N-type clad layer arranged above the substrate 101 .
  • the N-type first clad layer 102 has a lower refractive index and a higher bandgap energy than the active layer 105 .
  • the N-type first clad layer 102 is an N-type Al 0.035 Ga 0.965 N layer with a thickness of 1200 nm.
  • the N-type first clad layer 102 is doped with Si at a concentration of 1 ⁇ 10 18 cm ⁇ 3 as an impurity.
  • the N-type second clad layer 103 is an example of an N-type clad layer arranged above the substrate 101 .
  • the N-type second clad layer 103 is arranged above the N-type first clad layer 102 .
  • the N-type second clad layer 103 has a lower refractive index and a higher bandgap energy than the active layer 105 .
  • the N-type second clad layer 103 is an N-type GaN layer with a thickness of 100 nm.
  • the N-type second clad layer 103 is doped with Si at a concentration of 1 ⁇ 10 18 cm ⁇ 3 as an impurity.
  • the bandgap energy of the N-type second clad layer 103 is smaller than the bandgap energy of the N-type first clad layer 102 and equal to or greater than the maximum bandgap energy of the P-side guide layer 106 .
  • the N-side guide layer 104 is an optical guide layer arranged above the N-type second clad layer 103 .
  • the N-side guide layer 104 has a higher refractive index and a lower bandgap energy than the N-type first clad layer 102 and the N-type second clad layer 103 .
  • the bandgap energy of the N-side guide layer 104 monotonically increases with distance from the active layer 105 (that is, as it approaches the N-type first cladding layer 102 in the direction opposite to the crystal growth direction of each semiconductor layer).
  • the configuration in which the bandgap energy monotonously increases includes a configuration in which there is a region in which the bandgap energy is constant in the stacking direction.
  • the N-side guide layer 104 includes a portion where the bandgap energy continuously increases with distance from the active layer 105 .
  • the configuration in which the bandgap energy continuously and monotonically increases in the stacking direction does not include a configuration in which the bandgap energy changes discontinuously in the stacking direction.
  • a configuration in which the bandgap energy continuously increases monotonically is a configuration in which the amount of discontinuous increase in the bandgap energy is less than 2% of the bandgap energy at that position.
  • the configuration in which the bandgap energy in the N-side guide layer 104 monotonically increases continuously as it moves away from the active layer 105 means that the bandgap energy at a certain position in the N-side guide layer 104 is In this configuration, the amount of increase in bandgap energy at a position displaced by a minute distance in the opposite direction is less than 2% of the bandgap energy at that position.
  • the structure in which the bandgap energy continuously increases monotonously does not include a structure in which the bandgap energy increases stepwise by 2% or more in the direction opposite to the stacking direction, but the bandgap energy increases in the stacking direction. Configurations are included that change in steps by less than 2%.
  • the bandgap energy of the entire N-side guide layer 104 increases continuously as the distance from the active layer 105 increases, but the configuration of the N-side guide layer 104 is not limited to this.
  • the ratio of the film thickness of the portion where the bandgap energy continuously increases with distance from the active layer 105 to the total film thickness of the N-side guide layer 104 may be 50% or more.
  • the ratio may be 70% or more, or may be 90% or more.
  • the amount of increase in the bandgap energy of the N-side guide layer 104 in the direction toward the N-type second cladding layer 103 is ⁇ Egn.
  • the amount of increase in the bandgap energy of the N-side guide layer 104 in the direction opposite to the crystal growth direction is, for example, the bandgap energy at the interface of the N-side guide layer 104 on the side closer to the active layer 105 and the N-type secondary It is defined by the difference from the bandgap energy at the interface on the side closer to the clad layer 103 .
  • the ratio of the continuously increasing bandgap energy to ⁇ Egn in ⁇ Egn should be 70% or more.
  • the ratio may be 80% or more, or may be 90% or more.
  • the In composition ratio Xn of the N-side guide layer 104 monotonically decreases with increasing distance from the active layer 105 .
  • the bandgap energy of the N-side guide layer 104 monotonically increases with distance from the active layer 105 .
  • the configuration in which the In composition ratio Xn monotonously decreases includes a configuration in which there is a region in which the In composition ratio Xn is constant in the stacking direction.
  • the N-side guide layer 104 includes a portion in which the In composition ratio continuously decreases as the distance from the active layer 105 increases.
  • the configuration in which the In composition ratio Xn continuously and monotonously decreases does not include a configuration in which the In composition ratio Xp changes discontinuously in the stacking direction.
  • the configuration in which the In composition ratio Xn at a certain position of the N-side guide layer 104 decreases discontinuously in the stacking direction is less than 20% of the In composition ratio Xn at that position. be.
  • the average bandgap energy of the N-side guide layer 104 is less than or equal to the average bandgap energy of the P-side guide layer 106 .
  • the average In composition ratio of the N-side guide layer 104 is equal to or higher than the average In composition ratio of the P-side guide layer 106 .
  • the average In composition ratio of the N-side guide layer 104 is equal to the average In composition ratio of the P-side guide layer 106 . That is, the average bandgap energy of the N-side guide layer 104 is equal to the average bandgap energy of the P-side guide layer 106 .
  • Tn the film thickness of the N-side guide layer 104
  • Tp the film thickness of the P-side guide layer 106
  • the maximum value of the In composition ratio in the N-side guide layer 104 is equal to or less than the In composition ratio of each barrier layer.
  • the N-side guide layer 104 is an N-type In Xn Ga 1-Xn N layer with a thickness of 160 nm.
  • the N-side guide layer 104 is doped with Si at a concentration of 3 ⁇ 10 17 cm ⁇ 3 as an impurity. More specifically, the N-side guide layer 104 has a composition represented by In 0.04 Ga 0.96 N near the interface near the active layer 105 and near the interface far from the active layer 105 . has a composition represented by GaN in The In composition ratio Xn of the N-side guide layer 104 decreases at a constant rate of change as the distance from the active layer 105 increases.
  • the active layer 105 is a light-emitting layer arranged above the N-side guide layer 104 and having a quantum well structure.
  • the active layer 105 has well layers 105b and 105d and barrier layers 105a, 105c and 105e, as shown in FIG. 2B.
  • the barrier layer 105a is a layer arranged above the N-side guide layer 104 and functioning as a barrier for the quantum well structure.
  • the barrier layer 105a is an undoped In 0.05 Ga 0.95 N layer with a thickness of 7 nm.
  • the well layer 105b is a layer arranged above the barrier layer 105a and functioning as a well of the quantum well structure.
  • the well layer 105b is arranged between the barrier layers 105a and 105c.
  • the well layer 105b is an undoped In 0.18 Ga 0.82 N layer with a thickness of 3 nm.
  • the barrier layer 105c is a layer arranged above the well layer 105b and functioning as a barrier for the quantum well structure.
  • the barrier layer 105c is an undoped In 0.05 Ga 0.95 N layer with a thickness of 7 nm.
  • the well layer 105d is a layer arranged above the barrier layer 105c and functioning as a well of a quantum well structure.
  • Well layer 105d is disposed between barrier layer 105c and barrier layer 105e.
  • the well layer 105d is an undoped In 0.18 Ga 0.82 N layer with a thickness of 3 nm.
  • the barrier layer 105e is a layer arranged above the well layer 105d and functioning as a barrier for the quantum well structure.
  • the barrier layer 105e is an undoped In 0.05 Ga 0.95 N layer with a thickness of 5 nm.
  • the nitride-based semiconductor light-emitting device 100 can emit light with a wavelength of 430 nm or more and 455 nm or less by including the active layer 105 having the above configuration.
  • the bandgap energy of each barrier layer is equal to or less than the minimum bandgap energy of the N-side guide layer 104 and the P-side guide layer 106 . That is, the refractive index of each barrier layer is greater than the refractive indices of the N-side guide layer 104 and the P-side guide layer 106 . Therefore, the light confinement factor to the active layer 105 can be increased.
  • the In composition ratio of each barrier layer is the maximum In composition ratio of the N-side guide layer 104. and the maximum In composition ratio of the P-side guide layer 106 or more.
  • the P-side guide layer 106 is an optical guide layer arranged above the active layer 105 .
  • the P-side guide layer 106 has a higher refractive index and a lower bandgap energy than the P-type cladding layer 110 .
  • the bandgap energy of the P-side guide layer 106 monotonically increases with distance from the active layer 105 .
  • the structure in which the bandgap energy in the P-side guide layer 106 monotonously increases includes a structure in which there is a region in which the bandgap energy is constant in the stacking direction.
  • the P-side guide layer 106 includes a portion where the bandgap energy continuously increases as the distance from the active layer 105 increases.
  • the configuration in which the bandgap energy continuously increases monotonically does not include the configuration in which the bandgap energy changes discontinuously in the stacking direction.
  • the configuration in which the bandgap energy continuously and monotonically increases means that the discontinuous increase in the bandgap energy at a certain position is the same as the N-side guide layer described above.
  • the composition is less than 2%.
  • a structure in which the bandgap energy continuously increases monotonically does not include a structure in which the bandgap energy increases stepwise by 2% or more in the stacking direction. Configurations are included that change by less than 2%.
  • the ratio of the film thickness of the portion where the bandgap energy continuously increases with increasing distance from the active layer 105 to the total film thickness of the P-side guide layer 106 may be 50% or more.
  • the ratio may be 70% or more, or may be 90% or more.
  • the amount of increase in the bandgap energy of the P-side guide layer 106 in the direction of the N-type second cladding layer is ⁇ Egp.
  • the amount of increase in the bandgap energy of the P-side guide layer 106 in the stacking direction is, for example, the bandgap energy at the interface of the P-side guide layer 106 closer to the active layer 105 and the interface closer to the P-type cladding layer 110. is defined as the difference from the bandgap energy at
  • the ratio of the continuously increasing bandgap energy to ⁇ Egp in ⁇ Egp should be 70% or more. Moreover, the ratio may be 80% or more, or may be 90% or more.
  • the refractive index of the P-side guide layer 106 increases continuously and monotonically as it approaches the active layer 105 .
  • the peak of the light intensity distribution in the stacking direction can be brought closer to the active layer 105 .
  • ⁇ Egp may be 100 meV or more and 400 meV or less.
  • the In composition ratio Xp of the P-side guide layer 106 monotonically decreases with increasing distance from the active layer 105 .
  • the bandgap energy of the P-side guide layer 106 increases continuously and monotonically as the distance from the active layer 105 increases.
  • the P-side guide layer 106 includes a portion where the In composition ratio Xp continuously increases as the distance from the active layer 105 increases.
  • the bandgap energy of the P-side guide layer 106 includes a portion that continuously increases with increasing distance from the active layer 105 .
  • the average bandgap energy of the P-side guide layer 106 is greater than or equal to the average bandgap energy of the N-side guide layer 104 .
  • the average In composition ratio of the P-side guide layer 106 is equal to or less than the average In composition ratio of the N-side guide layer 104 .
  • the average In composition ratio of the P-side guide layer 106 is equal to the average In composition ratio of the N-side guide layer 104 .
  • the film thickness Tp of the P-side guide layer 106 is larger than the film thickness Tn of the N-side guide layer 104 .
  • the maximum value of the In composition ratio in the P-side guide layer 106 is equal to or less than the In composition ratio of each barrier layer.
  • the P-side guide layer 106 is an undoped In Xp Ga 1-Xp N layer with a thickness of 280 nm. More specifically, the P-side guide layer 106 has a composition represented by In 0.04 Ga 0.96 N near the interface near the active layer 105 and near the interface far from the active layer 105. has a composition represented by GaN in The In composition ratio Xp of the P-side guide layer 106 decreases at a constant rate of change as the distance from the active layer 105 increases.
  • the intermediate layer 108 is a layer arranged above the active layer 105 .
  • the intermediate layer 108 is arranged between the P-side guide layer 106 and the electron barrier layer 109, and due to the difference in lattice constant between the P-side guide layer 106 and the electron barrier layer 109, reduce the resulting stress. Thereby, the occurrence of crystal defects in the nitride-based semiconductor light emitting device 100 can be suppressed.
  • the intermediate layer 108 is an undoped GaN layer with a thickness of 20 nm.
  • the electron barrier layer 109 is arranged above the active layer 105 and is a nitride-based semiconductor layer containing at least Al. In this embodiment, the electron barrier layer 109 is arranged between the intermediate layer 108 and the P-type cladding layer 110 .
  • the electron barrier layer 109 is a P-type Al 0.36 Ga 0.64 N layer with a thickness of 5 nm.
  • the electron barrier layer 109 is doped with Mg at a concentration of 1 ⁇ 10 19 cm ⁇ 3 as an impurity.
  • the electron barrier layer 109 can prevent electrons from leaking from the active layer 105 to the P-type cladding layer 110 .
  • the P-type clad layer 110 is a P-type clad layer arranged above the active layer 105 .
  • the P-type cladding layer 110 is arranged between the electron barrier layer 109 and the contact layer 111 .
  • the P-type clad layer 110 has a lower refractive index and a higher bandgap energy than the active layer 105 .
  • the thickness of the P-type cladding layer 110 may be 460 nm or less.
  • the nitride-based semiconductor light emitting device 100 can operate at high output.
  • the film thickness of the P-type cladding layer 110 in order for the P-type cladding layer 110 to sufficiently exhibit its function as a cladding layer, the film thickness of the P-type cladding layer 110 should be 200 nm or more. good. Also, the film thickness of the P-type cladding layer 110 may be 250 nm or more.
  • the P-type clad layer 110 is a P-type Al 0.035 Ga 0.965 N layer with a thickness of 450 nm.
  • the P-type clad layer 110 is doped with Mg as an impurity.
  • the impurity concentration at the end of the P-type cladding layer 110 closer to the active layer 105 is lower than the impurity concentration at the end farther from the active layer 105 .
  • the P-type cladding layer 110 is a 150-nm-thick P-type Al 0.035 Ga 0.965 layer doped with Mg at a concentration of 2 ⁇ 10 18 cm ⁇ 3 located on the side closer to the active layer 105 . It has an N layer and a P-type Al 0.035 Ga 0.965 N layer with a thickness of 300 nm doped with Mg at a concentration of 1 ⁇ 10 19 cm ⁇ 3 and disposed on the far side from the active layer 105 .
  • a ridge 110R is formed in the P-type cladding layer 110 of the nitride-based semiconductor light emitting device 100.
  • the P-type cladding layer 110 is formed with two grooves 110T arranged along the ridge 110R and extending in the Y-axis direction.
  • the ridge width W is approximately 30 ⁇ m.
  • the distance between the lower end of the ridge 110R (that is, the bottom of the trench 110T) and the active layer 105 is dp.
  • the thickness of the P-type clad layer 110 at the lower end of the ridge 110R (that is, the distance between the lower end of the ridge 110R and the interface between the P-type clad layer 110 and the electron barrier layer 109) is dc.
  • the contact layer 111 is a layer arranged above the P-type cladding layer 110 and in ohmic contact with the P-side electrode 113 .
  • the contact layer 111 is a P-type GaN layer with a thickness of 60 nm.
  • the contact layer 111 is doped with Mg at a concentration of 1 ⁇ 10 20 cm ⁇ 3 as an impurity.
  • the current blocking layer 112 is an insulating layer arranged above the P-type cladding layer 110 and having transparency to light from the active layer 105 .
  • the current blocking layer 112 is arranged in a region of the upper surface of the P-type cladding layer 110 other than the upper surface of the ridge 110R.
  • the current blocking layer 112 is a SiO2 layer.
  • the P-side electrode 113 is a conductive layer arranged above the contact layer 111 .
  • the P-side electrode 113 is arranged above the contact layer 111 and the current blocking layer 112 .
  • the P-side electrode 113 is, for example, a single layer film or a multilayer film made of at least one of Cr, Ti, Ni, Pd, Pt and Au.
  • the N-side electrode 114 is a conductive layer arranged below the substrate 101 (that is, on the main surface opposite to the main surface on which the N-type first cladding layer 102 and the like of the substrate 101 are arranged).
  • the N-side electrode 114 is, for example, a single layer film or a multilayer film made of at least one of Cr, Ti, Ni, Pd, Pt and Au.
  • the nitride-based semiconductor light emitting device 100 has an effective refractive index difference ⁇ N between the portion below the ridge 110R and the portion below the groove 110T, as shown in FIG. 2A. occurs.
  • the light generated in the portion of the active layer 105 below the ridge 110R can be confined in the horizontal direction (that is, in the X-axis direction).
  • FIG. 3 is a schematic diagram showing an overview of the light intensity distribution in the stacking direction of the nitride-based semiconductor light emitting device 100 according to this embodiment.
  • FIG. 3 shows a schematic cross-sectional view of the nitride-based semiconductor light emitting device 100 and a graph showing an overview of the light intensity distribution in the stacking direction at positions corresponding to the ridges 110R and the grooves 110T.
  • a nitride-based semiconductor light-emitting device light is generated in the active layer, but the light intensity distribution in the lamination direction depends on the lamination structure, and the peak of the light intensity distribution is not necessarily located in the active layer.
  • the layered structure of the nitride-based semiconductor light emitting device 100 according to the present embodiment differs between the portion below the ridge 110R and the portion below the groove 110T, the light intensity distribution is also different in the portion below the ridge 110R. and the portion below the groove 110T.
  • P1 be the peak position of the light intensity distribution in the stacking direction at the center in the horizontal direction (that is, in the X-axis direction) of the portion below the ridge 110R.
  • FIG. 4 is a graph showing coordinates of positions in the stacking direction of the nitride-based semiconductor light-emitting device 100 according to the present embodiment. As shown in FIG.
  • the coordinates of the position of the end surface of the active layer 105 on the N side of the well layer 105b, that is, the end surface of the well layer 105b closer to the N-side guide layer 104 in the stacking direction are set to zero, and downward ( The direction toward the N-side guide layer 104) is the negative direction of the coordinates, and the upward direction (the direction toward the P-side guide layer 106) is the positive direction of the coordinates. Also, the absolute value of the difference between the positions P1 and P2 is defined as the peak position difference ⁇ P.
  • FIG. 5 is a schematic graph showing the bandgap energy distribution of the active layer 105 and the layers in the vicinity thereof of the nitride-based semiconductor light-emitting device 100 according to this embodiment.
  • the film thickness of the P-type cladding layer 110 is set relatively thin in order to reduce the operating voltage.
  • the height of the ridge 110R (that is, the height of the ridge 110R from the bottom surface of the groove 110T) is also set relatively low.
  • the peak position of the light intensity distribution in the stacking direction shifts from the active layer 105 toward the N-type second cladding layer 103 .
  • the light confinement coefficient in the active layer 105 is lowered, and the thermal saturation level of the optical output is accordingly lowered. Therefore, it becomes difficult to operate the semiconductor light emitting device at a high output.
  • the average bandgap energy of the P-side guide layer 106 is equal to the average bandgap energy of the N-side guide layer 104, as described above.
  • the film thickness Tp of the P-side guide layer 106 is larger than the film thickness Tn of the N-side guide layer 104 (inequality (1) above).
  • the bandgap energies of the N-side guide layer 104 and the P-side guide layer 106 monotonically increase continuously with increasing distance from the active layer 105 .
  • the refractive indices of the N-side guide layer 104 and the P-side guide layer 106 monotonically increase continuously as they approach the active layer 105 . Since the refractive indices of the N-side guide layer 104 and the P-side guide layer 106 increase as they approach the active layer 105 in this manner, the peak of the light intensity distribution in the lamination direction can be brought closer to the active layer 105 .
  • the compositions of the N-side guide layer 104 and the P-side guide layer 106 are represented by In Xn Ga 1-Xn N and In Xp Ga 1-Xp N, respectively.
  • the compositions near and far from the interface of the N-side guide layer 104 to the active layer 105 are represented by In Xn1 Ga 1-Xn1 N and In Xn2 Ga 1-Xn2 N, respectively.
  • the compositions of the P-side guide layer 106 near the interface near the active layer 105 and near the interface far from it are represented by In Xp1 Ga 1-Xp1 N and In Xp2 Ga 1-Xp2 N, respectively.
  • the barrier layers 105a, 105c, and 105e of the active layer 105 are made of In Xb Ga 1-Xb N, and the In composition of each barrier layer, the N-side guide layer 104, and the P-side guide layer 106 is For the ratios Xb, Xn and Xp, Xp ⁇ Xb (2) Xn ⁇ Xb (3) Satisfying relationships.
  • the bandgap energy of each barrier layer becomes equal to or less than the minimum value of the bandgap energies of the N-side guide layer 104 and the P-side guide layer 106 . That is, the refractive index of each barrier layer can be made higher than that of the P-side guide layer 106 and N-side guide layer 104 .
  • the peak position P1 of the light intensity distribution in the stacking direction in the portion below the ridge 110R can be set to 15.9 nm. That is, the peak of the light intensity distribution can be located in the active layer 105 (see FIG. 4). Also, ⁇ P can be suppressed to 6.2 nm. As a result, the light confinement factor in the active layer 105 can be increased to about 1.44%.
  • the peak of the light intensity distribution in the lamination direction can be located in the active layer 105 .
  • the expression that the peak of the light intensity distribution in the stacking direction is located in the active layer 105 means that the peak of the light intensity distribution in the stacking direction is located in the active layer 105 at at least one position in the horizontal direction of the nitride-based semiconductor light emitting device 100. It is not limited to the state in which the peak of the light intensity distribution in the stacking direction is located in the active layer 105 at all positions in the horizontal direction.
  • the light intensity distribution peak in the P-type cladding layer 110 is reduced compared to when the peak of the light intensity distribution is positioned in the N-side guide layer 104 .
  • the P-type cladding layer 110 has a higher impurity concentration than the N-type first cladding layer 102 and the N-type second cladding layer 103, the portion of the light that is located in the P-type cladding layer 110 increases. , there is concern about an increase in free carrier loss in the P-type cladding layer 110 .
  • the P-side guide layer 106 is an undoped layer and the film thickness Tp of the P-side guide layer 106 is relatively large. can be enhanced. Therefore, an increase in free carrier loss can be suppressed. Specifically, in this embodiment, the waveguide loss can be suppressed to approximately 3.4 cm ⁇ 1 .
  • a portion below the ridge 110R and a portion below the groove 110T are formed. is set so that the effective refractive index difference .DELTA.N between the portion of .DELTA.
  • the effective refractive index difference ⁇ N is set by adjusting the distance dp between the current blocking layer 112 and the active layer 105 (see FIG. 2A).
  • the larger the distance dp the smaller the effective refractive index difference ⁇ N.
  • the effective refractive index difference ⁇ N is about 2.9 ⁇ 10 ⁇ 3 . Therefore, in the present embodiment, the higher-order mode (that is, the higher-order transverse mode) capable of propagating through the waveguide formed by the ridge 110R is higher than when the effective refractive index difference ⁇ N is larger than 2.9 ⁇ 10 ⁇ 3 . small number. Therefore, among all the transverse modes included in the light emitted from the nitride-based semiconductor light-emitting device 100, the proportion of each higher-order mode is relatively large. Therefore, the amount of change in the optical confinement coefficient to the active layer 105 due to the increase/decrease in the number of modes and the coupling between modes becomes relatively large.
  • the linearity of the optical output characteristic (so-called IL characteristic) with respect to the supplied current is degraded.
  • non-linear portions (so-called kinks) occur in the graph showing the IL characteristics.
  • the stability of the light output of the nitride-based semiconductor light emitting device 100 may be degraded.
  • the fundamental mode that is, the zero-order mode
  • the light intensity distribution below the groove 110T is Higher order modes are dominant.
  • the position P1 of the peak of the light intensity distribution in the stacking direction in the portion below the ridge 110R of the nitride-based semiconductor light emitting device 100 and the position of the peak of the light intensity distribution in the stacking direction in the portion below the groove 110T are
  • the difference ⁇ P from P2 is large, if the number of modes increases or decreases and inter-mode coupling occurs, the light confinement factor in the active layer 105 fluctuates, and the stability of the light output decreases.
  • the peak of the light intensity distribution obtained by summing the light intensity distributions in the lower portions of both the ridge 110R and the groove 110T moves closer to the position P1. Therefore, the larger the difference ⁇ P between the position P1 and the position P2, the larger the fluctuation of the light confinement coefficient in the active layer 105 when the number of modes changes. Therefore, the stability of the optical output is degraded.
  • the nitride-based semiconductor light-emitting device 100 includes the N-side guide layer 104 and the P-side guide layer 106 having the configurations described above, the portion below the ridge 110R and the groove 110T
  • the peak of the light intensity distribution can be located in the active layer 105 in both of the lower portions of the . That is, the difference ⁇ P between the peak positions P1 and P2 of the light intensity distribution can be reduced.
  • the position in the stacking direction of the peak of the light intensity distribution that is the sum of the light intensity distributions in the portions below both the ridge 110R and the groove 110T fluctuation is suppressed. Therefore, the stability of optical output can be enhanced.
  • the distance dp is set to a relatively large value in order to set the effective refractive index difference ⁇ N to a relatively small value.
  • the distance dp is set so that the lower end of the ridge 110R (that is, the bottom of the trench 110T) is positioned below the electron barrier layer 109, the electron barrier layer 109 has a large bandgap energy, so the contact Holes injected from layer 111 tend to leak out of ridge 110R from the sidewalls of ridge 110R when passing through electron barrier layer 109. FIG. As a result, holes flow below the trench 110T.
  • the probability of radiative recombination of electrons and holes injected into the active layer 105 decreases and non-radiative recombination increases.
  • Such an increase in non-radiative recombination makes the nitride-based semiconductor light-emitting device 100 more likely to deteriorate.
  • the lower end of the ridge 110R is set above the electron barrier layer 109.
  • FIG. 2A when the distance dc (see FIG. 2A) from the lower end of the ridge 110R to the electron barrier layer 109 becomes too large, holes flow from the ridge 110R between the trench 110T and the electron barrier layer 109, resulting in leakage current.
  • the distance dc is set to a value as small as possible.
  • the distance dc is, for example, 10 nm or more and 70 nm or less. In this embodiment, the distance dc is 40 nm.
  • FIG. 6 is a graph showing the refractive index distribution and the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device 100 according to the present embodiment. be.
  • Graphs (a) to (c) of FIG. 6 show the refractive index distribution and the light intensity distribution of the nitride-based semiconductor light emitting devices of Comparative Examples 1 to 3, respectively.
  • FIG. 6 shows the refractive index distribution and the light intensity distribution of the nitride-based semiconductor light-emitting device 100 according to the present embodiment.
  • the refractive index distribution is indicated by a solid line
  • the light intensity distribution is indicated by a broken line.
  • FIG. 7 shows the distribution of the valence band potential and the hole Fermi level in the stacking direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device 100 according to the present embodiment.
  • Graph (d) of FIG. 7 shows the distribution of the valence band potential and the hole Fermi level of the nitride-based semiconductor light-emitting device 100 according to the present embodiment.
  • the valence band potential is indicated by a solid line
  • the hole Fermi level is indicated by a dashed line.
  • FIG. 8 is a graph showing simulation results of carrier concentration distribution in the lamination direction of the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 and the nitride-based semiconductor light-emitting device 100 according to the present embodiment. .
  • Graphs (a) to (c) of FIG. 8 show the carrier concentration distributions of the nitride-based semiconductor light emitting devices of Comparative Examples 1 to 3, respectively.
  • Graph (d) of FIG. 8 shows the carrier concentration distribution of the nitride-based semiconductor light-emitting device 100 according to the present embodiment.
  • the concentration distribution of electrons is indicated by a solid line
  • the concentration distribution of holes is indicated by a broken line.
  • the nitride-based semiconductor light-emitting devices of Comparative Examples 1 to 3 differ from the nitride-based semiconductor light-emitting device 100 according to the present embodiment in the configurations of the N-side guide layer and the P-side guide layer.
  • the nitride - based semiconductor light-emitting device of Comparative Example 1 shown in graph (a) of FIG. and a P-side guide layer 1106 made of an undoped In 0.04 Ga 0.96 N layer.
  • the nitride - based semiconductor light-emitting device of Comparative Example 2 shown in graph (b) of FIG. and a P-side guide layer 1206 made of an undoped In 0.04 Ga 0.96 N layer.
  • the P-side guide layer 1306 of the nitride-based semiconductor light emitting device of Comparative Example 3 has the same configuration as the P-side guide layer 106 according to this embodiment.
  • the N-side guide layer 1104 and the P-side guide layer 1106 have the same composition, and the N-side guide layer 1104 is thicker than the P-side guide layer 1106 . Therefore, in the nitride-based semiconductor light-emitting device of Comparative Example 1, the peak of the light intensity distribution in the stacking direction is located in the N-side guide layer 1104, as shown in graph (a) of FIG. Therefore, in the nitride-based semiconductor light-emitting device of Comparative Example 1, the optical confinement coefficient is as low as 1.33%. Also, as shown in graph (a) of FIG. The hole Fermi level increases from the far side interface to the side closer to the active layer 105 .
  • the valence charge potential is substantially constant in the stacking direction of the P-side guide layer 1106 . Therefore, the difference between the hole Fermi level and the valence band potential in the P-side guide layer 1106 increases as the active layer 105 is approached. Therefore, as shown in graph (a) of FIG. 8, the concentration of holes and electrons in the stacking direction of the P-side guide layer 1106, that is, the concentration of free carriers, increases with increasing distance from the active layer 105.
  • FIG. thus, in the nitride-based semiconductor light-emitting device of Comparative Example 1, since the free carrier concentration in the stacking direction of the P-side guide layer 1106 cannot be reduced, it is not possible to reduce the free carrier loss and the non-radiative recombination probability.
  • the effective refractive index difference ⁇ N is 3.6 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution are ⁇ 34.1 nm and ⁇ 75.6 nm, respectively.
  • the difference ⁇ P is 41.5 nm.
  • the waveguide loss is 4.5 cm ⁇ 1
  • the free carrier loss in the N-side guide layer 1104 and the P-side guide layer 1106 (hereinafter also referred to as “guide layer free carrier loss”) is 2.8 cm ⁇ 1 . 1 .
  • the effective refractive index difference ⁇ N was 3.3 ⁇ 10 ⁇ 3 and the peak positions P1 and P2 of the light intensity distribution were 31.3 nm and 10.8 nm, respectively.
  • the difference ⁇ P is 20.5 nm.
  • the waveguide loss is 5.2 cm ⁇ 1 and the guide layer free carrier loss is 3.6 cm ⁇ 1 .
  • the refractive index of the P-side guide layer 1306 increases as it approaches the active layer 105, as shown in graph (c) of FIG.
  • the intensity distribution peak can be brought closer to the active layer 105 . Therefore, in the nitride-based semiconductor light-emitting device 100 according to the present embodiment, the light confinement factor is 1.49%, which is further improved over the nitride-based semiconductor light-emitting device of Comparative Example 2.
  • the bandgap energy of the P-side guide layer 1306 monotonically increases continuously with distance from the active layer 105, as shown in graph (d) of FIG. The charging potential decreases continuously.
  • the difference between the hole Fermi level and the valence band potential can be made substantially constant. Therefore, as shown in the graph (c) of FIG. 8, the concentration of holes and electrons in the stacking direction of the P-side guide layer 1306 can be reduced and kept substantially constant. Thus, the free carrier concentration in the stacking direction of the P-side guide layer 1306 can be reduced.
  • the bandgap energy becomes discontinuous at the interface of the N-side guide layer 1304 far from the active layer 105 (that is, the interface with the N-type second cladding layer 103)
  • the graph (c) in FIG. As shown, the hole concentration spikes at the interface.
  • the non-radiative recombination and free carrier loss in the N-side guide layer 1304 cannot be reduced also in the nitride-based semiconductor light-emitting device of the comparative example.
  • the effective refractive index difference ⁇ N is 2.1 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution are 1.3 nm and ⁇ 4.3 nm, respectively.
  • the difference ⁇ P is 5.6 nm.
  • the waveguide loss is 3.20 cm ⁇ 1 and the guide layer free carrier loss is 1.8 cm ⁇ 1 .
  • the optical confinement factor is 1.44%, which is equivalent to that of the nitride-based semiconductor light-emitting device of Comparative Example 3.
  • the bandgap energy of the N-side guide layer 104 monotonously increases continuously as the distance from the active layer 105 increases, the discontinuity of the bandgap energy at the interface of the N-side guide layer 104 farther from the active layer 105 can be reduced. Therefore, as shown in graph (d) of FIG. 8, the concentration of holes in the interface and the N-side guide layer 104 can be significantly reduced as compared with the nitride-based semiconductor light-emitting device of Comparative Example 3.
  • the free carrier concentration in the P-side guide layer 106 and the N-side guide layer 104 can be reduced, the nitride-based semiconductor light-emitting device 100 according to the present embodiment can reduce free carrier loss and non-radiative recombination.
  • the effective refractive index difference ⁇ N is 2.9 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution are 15.9 nm and 9.9 nm, respectively.
  • 7 nm and the difference ⁇ P is 6.2 nm.
  • the waveguide loss is 3.40 cm ⁇ 1 and the guide layer free carrier loss is 1.45 cm ⁇ 1 .
  • waveguide loss and free carrier loss can be reduced.
  • the free carrier loss can be reduced as compared with each comparative example.
  • FIG. 9 and 10 are graphs showing simulation results of the relationship between the average In composition ratio in the N-side guide layer 104, the optical confinement coefficient ( ⁇ v), and the operating voltage, respectively, according to this embodiment.
  • the In composition ratio Xn1 near the interface of the N-side guide layer 104 near the active layer 105 is 4%
  • the In composition ratio Xn2 near the interface far from the active layer 105 is 0%, 1%, 2%, 3%, and 4%
  • the optical confinement coefficient and the operating voltage are shown when the In composition ratio is decreased at a constant rate as the distance from the active layer 105 increases.
  • the operating voltage the voltage applied to the nitride-based semiconductor light-emitting device when the supply current to the nitride-based semiconductor light-emitting device is 3A is shown.
  • 9 and 10 also show the simulation results when the In composition ratio in the N-side guide layer is uniform.
  • the In composition ratio in the N-side guide layer is more uniform when the In composition ratio in the N-side guide layer 104 continuously and monotonously decreases as the distance from the active layer 105 increases. Since the high refractive index region of the N-side guide layer 104 can be brought closer to the active layer 105 than in the case of , the optical confinement factor can be increased and the operating voltage can be reduced. Moreover, when the average In composition ratio is less than 2%, the waveguide loss can be further reduced and the optical confinement factor can be increased.
  • the peak positions P1 and P2 of the light intensity distribution are 20.4 nm and 10.4 nm, respectively, and the difference ⁇ P is 10.0 nm.
  • the waveguide loss is 3.4 cm ⁇ 1 and the guide layer free carrier loss is 1.38 cm ⁇ 1 .
  • the peak of the light intensity distribution cannot be located in the active layer, and the light confinement factor is also lower than that of the nitride-based semiconductor light emitting device 100 according to the present embodiment. Become.
  • FIG. 11 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light-emitting device of Comparative Example 3, and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction band potential.
  • FIG. 12 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light emitting device 100 according to the present embodiment, and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction band potential.
  • Graphs (a), (b), and (c) of FIGS. 11 and 12 respectively show the position of each nitride-based semiconductor light-emitting device in the stacking direction, the piezoelectric polarization charge density, the piezoelectric polarization electric field, and the conduction charge. The relationship with rank is shown.
  • Graphs (c) of FIGS. 11 and 12 also show the hole Fermi level with a dashed line.
  • the piezoelectric polarization charge density of the N-side guide layer 1304 of the nitride-based semiconductor light emitting device of Comparative Example 3 is constant in the stacking direction. Therefore, the piezoelectric polarization charge density gap at each interface between the N-side guide layer 1304 and the N-type second cladding layer 103 and active layer 105 is large. Along with this, piezoelectric polarization charges are locally formed at each interface between the N-side guide layer 1304 and the N-type second cladding layer 103 and active layer 105 . This generates a large piezoelectric polarization electric field. Therefore, as shown in graph (b) of FIG.
  • a spike-like piezoelectric polarization electric field is generated at each interface between the N-side guide layer 1304 and the N-type second cladding layer 103 and active layer 105 .
  • holes are attracted to the vicinity of each interface between the N-side guide layer 1304 and the N-type second cladding layer 103 and the active layer 105, increasing the conduction band potential at the interface (graph (c) in FIG. 11). (see ⁇ E1 shown in ).
  • the polarization charge density of the N-side guide layer 104 of the nitride-based semiconductor light-emitting device 100 according to this embodiment is far from the interface closer to the active layer 105. It monotonically decreases as the interface is approached. Therefore, gaps in piezoelectric polarization charge density at each interface between the N-side guide layer 104 and the N-type second cladding layer 103 and active layer 105 are suppressed. Thereby, the piezoelectric polarization charge is dispersed in the stacking direction of the N-side guide layer 104 . Therefore, as shown in graph (b) of FIG.
  • the piezoelectric polarization electric field at each interface between the N-side guide layer 104 and the N-type second cladding layer 103 and active layer 105 can be suppressed.
  • An increase in conduction band potential ( ⁇ E1 shown in graph (c) of FIG. 12) can be suppressed. Accordingly, in the nitride-based semiconductor light emitting device 100 according to the present embodiment, the conductivity of electrons flowing from the N-type second cladding layer 103 toward the active layer 105 can be improved, so that the operating voltage can be reduced. .
  • FIG. 13, 14, and 15 show, respectively, the average In composition ratio in the N-side guide layer 104 of the nitride-based semiconductor light-emitting device 100 according to this embodiment, the optical confinement factor ( ⁇ v), waveguide loss, and operating voltage.
  • Graphs (a), (b), (c), and (d) of FIGS. 13 to 15 show that the impurity (Si) concentration in the N-side guide layer 104 is 0 (that is, undoped), 3 ⁇ , respectively. Simulation results are shown for 10 17 cm ⁇ 3 , 6 ⁇ 10 17 cm ⁇ 3 and 1 ⁇ 10 18 cm ⁇ 3 .
  • the In composition ratio Xn1 near the interface of the N-side guide layer 104 near the active layer 105 is 4%
  • the In composition ratio Xn2 near the interface far from the active layer 105 is 0%, 1%, 2%, 3%, and 4%
  • the optical confinement coefficient and the operating voltage are shown when the In composition ratio is decreased at a constant rate as the distance from the active layer 105 increases.
  • 13 to 15 also show the results of simulation when the In composition ratio in the N-side guide layer is uniform, by dashed lines.
  • the optical confinement coefficient can increase Also, from FIG. 13, it can be seen that in the nitride-based semiconductor light-emitting device 100 according to the present embodiment, the light confinement coefficient does not substantially depend on the impurity concentration.
  • the nitride of the comparative example in which the In composition ratio of the N-side guide layer is uniform The waveguide loss can be reduced compared to the conventional semiconductor light emitting device. This is probably because the addition of impurities increases the electron concentration, but decreases the hole concentration due to the bandgap energy distribution in the stacking direction of the N-side guide layer 104 .
  • the operating voltage is lower than that of the nitride-based semiconductor light-emitting device of the comparative example in which the N-side guide layer has a uniform In composition ratio. can. Further, by increasing the concentration of impurities added to the nitride-based semiconductor light emitting device 100, the electron concentration in the N-side guide layer 104 can be increased, so that the operating voltage can be further reduced.
  • the impurity concentration in the N-side guide layer 104 is 1 ⁇ 10 17 cm ⁇ 3 or more and 6 ⁇ 10 17 cm ⁇ 3 or less. , the operating voltage can be reduced while suppressing a significant increase in waveguide loss.
  • FIG. 16 and 17 are graphs showing simulation results of the relationship between the film thickness of the N-side guide layer 104, the position P1, and the difference ⁇ P, respectively, according to this embodiment.
  • the sum of the film thicknesses of the N-side guide layer 104 and the P-side guide layer 106 was kept constant at 440 nm, each of the N-side guide layer 104 and the P-side guide layer 106 changing the film thickness.
  • the In composition ratio of the N-side guide layer 104 and the P-side guide layer 106 is 4% near the interface near the active layer 105 and 0% near the interface far from the active layer 105 .
  • the In composition ratios of the N-side guide layer 104 and the P-side guide layer 106 are changed at a constant change rate in the stacking direction. 16 and 17 also show, as a comparative example, simulation results of an example in which the In composition ratio of the N-side guide layer is constant at 2%, indicated by broken lines.
  • the position P1 can be located in the active layer 105 by setting the film thickness Tn of the N-side guide layer 104 to 160 nm or more and 250 nm or less.
  • the film thickness of the N-side guide layer 104 may be 36% or more and 57% or less of the sum of the film thicknesses of the N-side guide layer 104 and the P-side guide layer 106 .
  • the position P1 can be set to -7 nm or more and 18 nm or less, that is, the peak of the light intensity distribution can be positioned within the active layer 105 .
  • the difference ⁇ P can be reduced by setting the film thickness Tn of the N-side guide layer 104 to less than 220 nm, that is, by making it smaller than the film thickness Tp of the P-side guide layer 106 .
  • the difference ⁇ P can be made 20 nm or less.
  • the difference .DELTA.P can be reduced. The difference ⁇ P can be reduced.
  • FIG. 18 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer 110 and the optical confinement factor ( ⁇ v) according to this embodiment.
  • FIG. 19 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer 110 and waveguide loss according to the present embodiment.
  • FIG. 20 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer 110 and the effective refractive index difference ⁇ N according to the present embodiment.
  • FIG. 18 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer 110 and the optical confinement factor ( ⁇ v) according to this embodiment.
  • FIG. 19 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer 110 and waveguide loss according to the present embodiment.
  • FIG. 20 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer 110 and the effective refractive index difference ⁇ N according to the present
  • FIG. 21 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer 110 and the position P1 according to this embodiment.
  • FIG. 22 is a graph showing simulation results of the relationship between the thickness of the P-type cladding layer 110 and the difference ⁇ P according to the present embodiment.
  • 18 to 22 also show, as a comparative example, simulation results of a comparative example in which the In composition ratio of both the N-side guide layer and the P-side guide layer is constant at 2%.
  • 18 to 22 also show simulation results of a nitride-based semiconductor light-emitting device 300 according to Embodiment 3, which will be described later.
  • the light confinement factor can be made larger than that of the nitride-based semiconductor light-emitting device of the comparative example. Further, in this embodiment, due to the configuration of each guide layer and each barrier layer described above, even if the film thickness of the P-type cladding layer 110 is reduced to 250 nm, the light confinement coefficient does not decrease.
  • the waveguide loss can be reduced more than in the nitride-based semiconductor light-emitting device of the comparative example. Further, in the nitride-based semiconductor light-emitting device 100 according to the present embodiment, even if the film thickness of the P-type cladding layer 110 is reduced to about 300 nm, it is possible to suppress a significant increase in waveguide loss.
  • the effective refractive index difference ⁇ N can be reduced more than the nitride-based semiconductor light-emitting device of the comparative example.
  • the P-type cladding layer 110 has a thickness of 250 nm or more and 820 nm or less, similarly to the nitride-based semiconductor light-emitting device of the comparative example.
  • the position P1 can be located in the active layer 105 over the entire range.
  • the thickness of the P-type cladding layer 110 is in the entire range of 250 nm or more and 820 nm or less. The difference ⁇ P can be reduced by the light emitting element.
  • the nitride-based semiconductor light-emitting device 100 it is possible to reduce the film thickness of the P-type cladding layer 110, thereby reducing the operating voltage.
  • each barrier layer of the active layer 105 the bandgap energy of each barrier layer is equal to or less than the minimum bandgap energies of the N-side guide layer 104 and the P-side guide layer 106 .
  • the composition of each barrier layer is undoped GaN to make the bandgap energy of each barrier layer larger than the minimum value of the bandgap energies of the N-side guide layer 104 and the P-side guide layer 106.
  • nitride-based semiconductor light-emitting device of Comparative Example 4 simulation results of a nitride-based semiconductor light-emitting device of Comparative Example 4 in which the configuration is the same as that of the nitride-based semiconductor light-emitting device 100 according to the present embodiment.
  • the light confinement factor was 1.34%
  • the effective refractive index difference ⁇ N was 3.2 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution were are 33.9 nm and 10.3 nm, respectively
  • the difference ⁇ P is 23.6 nm.
  • the waveguide loss is 3.6 cm ⁇ 1 and the guide layer free carrier loss is 1.32 cm ⁇ 1 .
  • the nitride-based semiconductor light-emitting device of Comparative Example 4 since the bandgap energy of each barrier layer is large, that is, since the refractive index of each barrier layer is small, the light confinement coefficient is reduced to that of the nitride semiconductor according to the present embodiment. It is smaller than that of the material-based semiconductor light emitting device 100 .
  • other evaluation indices of the nitride-based semiconductor light-emitting device of Comparative Example 4 are also worse than those of the nitride-based semiconductor light-emitting device 100 according to the present embodiment, except for the position P1.
  • the bandgap energy of each barrier layer is equal to or less than the minimum bandgap energy of the N-side guide layer 104 and the P-side guide layer 106.
  • the optical confinement factor can be increased.
  • the difference ⁇ P can be reduced, so that the graph showing the IL characteristics is less likely to have non-linear portions.
  • Embodiment 2 A nitride-based semiconductor light-emitting device according to Embodiment 2 will be described.
  • the nitride-based semiconductor light-emitting device according to this embodiment differs from the nitride-based semiconductor light-emitting device 100 according to the first embodiment mainly in the bandgap energy distribution of the P-side guide layer.
  • the nitride-based semiconductor light-emitting device according to the present embodiment will be described below, focusing on differences from the nitride-based semiconductor light-emitting device 100 according to the first embodiment.
  • FIG. 23A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 200 according to this embodiment.
  • FIG. 23B is a schematic graph showing the configuration of the active layer 205 included in the nitride-based semiconductor light emitting device 200 according to this embodiment.
  • FIG. 24 is a schematic graph showing the bandgap energy distribution of the active layer 205 and the layers in the vicinity thereof of the nitride-based semiconductor light-emitting device 200 according to this embodiment.
  • the nitride-based semiconductor light-emitting device 200 includes a semiconductor laminate 200S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114.
  • the semiconductor laminate 200S includes a substrate 101, an N-type first clad layer 102, an N-type second clad layer 103, an N-side guide layer 104, an active layer 205, a P-side guide layer 206, and an intermediate layer 108. , an electron barrier layer 109 , a P-type clad layer 110 and a contact layer 111 .
  • the active layer 205 has well layers 105b and 105d and barrier layers 205a, 105c and 205e, as shown in FIG. 23B.
  • the barrier layer 205a is a layer arranged above the N-side guide layer 104 and functioning as a barrier for the quantum well structure.
  • the barrier layer 205a is an undoped In 0.05 Ga 0.95 N layer with a thickness of 6 nm.
  • the barrier layer 205e is a layer arranged above the well layer 105d and functioning as a barrier for the quantum well structure.
  • the barrier layer 105e is an undoped In 0.05 Ga 0.95 N layer with a thickness of 6 nm.
  • the P-side guide layer 206 differs from the P-side guide layer 106 according to the first embodiment in that the bandgap energy is constant in the stacking direction.
  • the P-side guide layer 206 is an undoped In Xp Ga 1-Xp N layer with a thickness of 280 nm, and the In composition ratio Xp of the P-side guide layer 206 is 2%.
  • the operating voltage can be reduced and the active layer 206 can be reduced in the same manner as the nitride-based semiconductor light-emitting device 100 according to the first embodiment.
  • the optical confinement factor into layer 205 can be increased.
  • the effective refractive index difference ⁇ N is 3.5 ⁇ 10 ⁇ 3
  • the position P1 is 11.0 nm
  • the position P2 is 2.5 nm
  • the difference ⁇ P is 8.5 nm.
  • the light confinement factor in the active layer 205 is 1.33%
  • the waveguide loss is 5.1 cm ⁇ 1
  • the guide layer free carrier loss is 2.6 cm ⁇ 1 . realizable.
  • 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 200 according to the second embodiment in the bandgap energy distribution of the P-side guide layer.
  • the nitride-based semiconductor light-emitting device according to the present embodiment will be described below, focusing on differences from the nitride-based semiconductor light-emitting device 200 according to the second embodiment.
  • FIG. 25 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 300 according to this embodiment.
  • FIG. 26 is a schematic graph showing the bandgap energy distribution of the active layer 205 and the layers in the vicinity thereof of the nitride-based semiconductor light-emitting device 300 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 300 includes a semiconductor laminate 300S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114.
  • the semiconductor laminate 300S includes a substrate 101, an N-type first clad layer 102, an N-type second clad layer 103, an N-side guide layer 104, an active layer 205, a P-side guide layer 306, and an intermediate layer 108. , an electron barrier layer 109 , a P-type clad layer 110 and a contact layer 111 .
  • the P-side guide layer 306 differs from the P-side guide layer 206 according to Embodiment 2 in that the bandgap energy changes stepwise in the stacking direction as shown in FIG. .
  • the P-side guide layer 306 has a P-side first guide layer 306a and a P-side second guide layer 306b.
  • the P-side first guide layer 306 a is a guide layer arranged above the active layer 205 and having a bandgap energy higher than that of the active layer 205 .
  • the P-side second guide layer 306b is a guide layer disposed above the P-side first guide layer 306a and having a bandgap energy greater than that of the P-side first guide layer 306a.
  • the P-side first guide layer 306a is an undoped In 0.04 Ga 0.96 N layer with a thickness of 80 nm
  • the P-side second guide layer 306b is an undoped In 0.96 N layer with a thickness of 200 nm . 01 Ga 0.99 N layer.
  • the P-side first guide layer 306a has a higher In composition ratio than the P-side second guide layer 306b.
  • the operating voltage can be reduced, and the active layer 205 can The optical confinement factor can be increased.
  • the effective refractive index difference ⁇ N is 2.8 ⁇ 10 ⁇ 3
  • the position P1 is 13.0 nm
  • the position P2 is 9.1 nm
  • the difference ⁇ P is 3.9 nm
  • the light confinement factor in the active layer 205 is 1.47%
  • the waveguide loss is 3.9 cm ⁇ 1
  • the guide layer free carrier loss is 1.9 cm ⁇ 1 . realizable.
  • nitride-based semiconductor light-emitting device 300 The effect of the nitride-based semiconductor light-emitting device 300 according to the present embodiment will be described in comparison with the nitride-based semiconductor light-emitting devices of Comparative Examples 5-7.
  • the nitride-based semiconductor light-emitting device of Comparative Example 5 differs from the nitride-based semiconductor light-emitting device 300 according to the present embodiment in that the N-side guide layer has a constant bandgap energy in the stacking direction.
  • the N-side guide layer included in the nitride-based semiconductor light-emitting device of Comparative Example 5 is an N-type In 0.02 Ga 0.98 N layer with a film thickness of 160 nm, and Si with a concentration of 3 ⁇ 10 17 cm ⁇ 3 as an impurity. is doped.
  • the effective refractive index difference ⁇ N was 3.5 ⁇ 10 ⁇ 3
  • the position P1 was 12.6 nm
  • the position P2 was 4.7 nm
  • the difference ⁇ P was 7.9 nm
  • the optical confinement factor to the active layer 205 is 1.27%
  • the waveguide loss is 5.1 cm ⁇ 1
  • the guide layer free carrier loss is 2.5 cm ⁇ 1 .
  • the optical confinement coefficient is lower than that of the nitride-based semiconductor light-emitting device of Comparative Example 5.
  • the average bandgap energy of the P-side guide layer is smaller than the average bandgap energy of the N-side guide layer. It differs from the semiconductor light emitting device 300 .
  • the P-side guide layers included in the nitride-based semiconductor light-emitting devices of Comparative Examples 6 and 7 consist of a P-side first guide layer, which is an undoped In 0.04 Ga 0.96 N layer with a thickness of 100 nm, and a P-side second guide layer. 1 guide layer and a P-side second guide layer that is an undoped In 0.04 Ga 0.96 N layer with a thickness of 100 nm.
  • the N-side guide layer included in the nitride-based semiconductor light-emitting device of Comparative Example 6 has the same configuration as the N-side guide layer 104 according to the present embodiment.
  • the N-side guide layer included in the nitride-based semiconductor light-emitting device of Comparative Example 7 has a constant bandgap energy in the stacking direction.
  • the N-side guide layer included in the nitride-based semiconductor light-emitting device of Comparative Example 7 is an N-type In 0.04 Ga 0.96 N layer with a film thickness of 160 nm, and an impurity concentration of 3 ⁇ 10 17 cm. -3 Si is doped.
  • the position P1 was 32, 7 nm, and 38.3 nm, respectively, and the peak position of the light intensity distribution deviated from the active layer and shifted to the P-side guide layer. be. Therefore, when coupling occurs between a higher-order mode capable of propagating in the waveguide formed by the ridge 110R and a lower-order mode stably confined in the waveguide, the optical confinement diameter changes. Cheap. That is, the linearity of the IL characteristics tends to deteriorate.
  • the position P1 is 13.0 nm, which is much smaller than the position P1 of the nitride-based semiconductor light-emitting devices of Comparative Examples 6 and 7. Therefore, it is possible to suppress the deterioration of the linearity of the IL characteristics.
  • Embodiment 4 A nitride-based semiconductor light-emitting device according to Embodiment 4 will be described.
  • the nitride-based semiconductor light-emitting device according to this embodiment differs from the nitride-based semiconductor light-emitting device 100 according to the first embodiment mainly in the bandgap energy distribution of the N-side guide layer.
  • the nitride-based semiconductor light-emitting device according to the present embodiment will be described below, focusing on differences from the nitride-based semiconductor light-emitting device 100 according to the first embodiment.
  • FIG. 27 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light emitting device 400 according to this embodiment.
  • FIG. 28 is a schematic graph showing the bandgap energy distribution of the active layer 205 and the layers in the vicinity thereof of the nitride-based semiconductor light emitting device 400 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 400 includes a semiconductor laminate 400S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114.
  • the semiconductor laminate 400S includes a substrate 101, an N-type first clad layer 102, an N-type second clad layer 103, an N-side guide layer 404, an active layer 205, a P-side guide layer 106, and an intermediate layer 108. , an electron barrier layer 109 , a P-type clad layer 110 and a contact layer 111 .
  • the bandgap energy increases continuously and monotonically as the distance from the active layer 205 increases, similarly to the N-side guide layer 104 according to the first embodiment.
  • the N-side guide layer 404 is an N-type In Xn Ga 1-Xn N layer, and the N-side guide layer 404 is doped with Si at a concentration of 3 ⁇ 10 17 cm ⁇ 3 as an impurity. ing.
  • the absolute value of the average rate of change in the stacking direction of the In composition ratio in the region from the interface of the N-side guide layer 404 closer to the active layer 205 to the central portion of the N-side guide layer 404 in the stacking direction is It is smaller than the absolute value of the average rate of change in the stacking direction of the In composition ratio in the region up to the interface of the N-side guide layer 404 on the side closer to the N-type first cladding layer 102 .
  • the curve showing the relationship between the position in the stacking direction of the N-side guide layer 404 and the In composition ratio has an upwardly convex shape.
  • the curve showing the relationship between the position of the N-side guide layer 404 in the stacking direction and the bandgap energy has a downward convex shape (see FIG. 28).
  • the N-side guide layer 404 has an N-side first guide layer 404a and an N-side second guide layer 404b.
  • the N-side first guide layer 404 a is a guide layer arranged above the N-type second cladding layer 103 .
  • the N-side first guide layer 404a is an In Xn Ga 1-Xn N layer with a thickness of 80 nm. More specifically, the N-side first guide layer 404a has a composition represented by In Xn2 Ga 1-Xn2 N in the vicinity of the interface farther from the active layer 205 and near the interface near the active layer 205. has a composition represented by In Xnm Ga 1-Xnm N (see FIG. 28).
  • the In composition ratio Xn of the N-side first guide layer 404a decreases at a constant rate of change as the distance from the active layer 105 increases.
  • the N-side second guide layer 404b is a guide layer arranged above the N-side first guide layer 404a. In other words, the N-side second guide layer 404 b is arranged between the N-side first guide layer 404 a and the active layer 205 .
  • the N-side second guide layer 404b is an N-type In Xn Ga 1-Xn N layer with a thickness of 80 nm.
  • the N-side second guide layer 404b has a composition represented by In Xn1 Ga 1-Xn1 N in the vicinity of the interface closer to the active layer 205 and near the interface farther from the active layer 205. has a composition represented by In Xnm Ga 1-Xnm N.
  • the In composition ratio Xn of the N-side second guide layer 404b decreases at a constant rate of change as the distance from the active layer 105 increases.
  • FIG. 29 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer 404 and the optical confinement factor ( ⁇ v) according to this embodiment.
  • FIG. 30 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer 404 and the waveguide loss according to this embodiment.
  • FIG. 31 is a graph showing simulation results of the relationship between the average In composition ratio in the N-side guide layer 404 and the operating voltage according to this embodiment.
  • 32 and 33 are graphs showing simulation results of the relationship between the average In composition ratio in the N-side guide layer 404, the position P1, and the difference ⁇ P, respectively, according to this embodiment. 29 to 33, the In composition ratio Xp1 near the interface of the N-side guide layer 404 near the active layer 205 is 4%, and the In composition ratio Xp2 near the interface far from the active layer 205 is 0%. , the waveguide loss and the optical confinement factor when the In composition ratio is continuously and monotonically decreased as the distance from the active layer 205 increases. More specifically, in FIGS.
  • the average In composition ratio in the N-side guide layer 404 is changed by changing the In composition ratio Xnm in the central portion of the N-side guide layer 404 in the stacking direction.
  • Each simulation result is shown for each case.
  • FIGS. 29 to 33 also show simulation results when the In composition ratio in the N-side guide layer is uniform, by dashed lines.
  • the curve showing the relationship between the position in the stacking direction of the N-side guide layer 404 and the In composition ratio has a convex shape.
  • the average In composition ratio is 2.5% corresponds to the nitride-based semiconductor light emitting device 400 according to the present embodiment.
  • the In composition ratio in the N-side guide layer is more uniform when the In composition ratio in the N-side guide layer 404 continuously and monotonously decreases as the distance from the active layer 205 increases.
  • the optical confinement factor can be increased and the waveguide loss can be reduced.
  • the optical confinement factor can be further increased and the waveguide loss can be reduced.
  • the In composition ratio in the N-side guide layer is more uniform when the In composition ratio in the N-side guide layer 404 monotonously decreases continuously as the distance from the active layer 205 increases.
  • Operating voltage can be reduced than in some cases.
  • the operating voltage can be further reduced when the average In composition ratio is greater than 2%.
  • the In composition ratio in the N-side guide layer is better when the In composition ratio in the N-side guide layer 404 continuously and monotonically decreases as the distance from the active layer 205 increases. is uniform, the peak position P1 of the light intensity distribution can be brought closer to the active layer 205, and the difference .DELTA.P can be reduced. Also, when the average In composition ratio is greater than 2%, the position P1 can be positioned within the active layer 205 and the difference ⁇ P can be further reduced. This is because when the average In composition ratio is greater than 2%, the refractive index of the region near the active layer 205 in the N-side guide layer 404 can be increased, so that light can be guided to the vicinity of the active layer 205. It is thought that it is due to the fact that it can be done.
  • each barrier layer is equal to or less than the minimum bandgap energy of the N-side guide layer 404 and the P-side guide layer 106 .
  • each barrier layer is undoped GaN
  • the bandgap energy of each barrier layer is made larger than the minimum value of the bandgap energies of the N-side guide layer 404 and the P-side guide layer 106
  • the simulation results of the nitride-based semiconductor light-emitting device of Comparative Example 8 having the same configuration as the nitride-based semiconductor light-emitting device 400 according to the present embodiment are shown.
  • the light confinement factor was 1.36%
  • the effective refractive index difference ⁇ N was 3.4 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution were 22.8 nm and 2.2 nm, respectively
  • the difference ⁇ P is 20.6 nm.
  • the waveguide loss is 3.4 cm ⁇ 1 and the free carrier loss in the N-side guide layer and the P-side guide layer is 1.4 cm ⁇ 1 .
  • the light confinement factor is 1.44%
  • the effective refractive index difference ⁇ N is 3.4 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution are They are 10.9 nm and 5.5 nm respectively
  • the difference ⁇ P is 5.4 nm.
  • the waveguide loss is 3.4 cm ⁇ 1 and the guide layer free carrier loss is 1.7 cm ⁇ 1 .
  • the bandgap energy of each barrier layer is lower than that of each guide layer, that is, the refractive index of each barrier layer is higher than that of each guide layer. It can be higher than that of a nitride-based semiconductor light emitting device. Accordingly, in the present embodiment, the position P1 and the difference ⁇ P can also be reduced as compared with the nitride-based semiconductor light emitting device of Comparative Example 8. In this manner, since the difference ⁇ P can be reduced in the present embodiment, it becomes difficult for the graph showing the IL characteristics to have a non-linear portion.
  • Embodiment 5 A nitride-based semiconductor light-emitting device according to Embodiment 5 will be described.
  • the relationship of the Al composition ratio between the N-type first clad layer and the P-type clad layer and the structure of the electron barrier layer are the same as those of the nitride-based semiconductor light-emitting device according to the first embodiment. It is different from the semiconductor light emitting device 100 of the related art.
  • the nitride-based semiconductor light-emitting device according to the present embodiment will be described below with reference to FIG. 34, focusing on differences from the nitride-based semiconductor light-emitting device 100 according to the first embodiment.
  • FIG. 34 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 500 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 500 includes a semiconductor laminate 500S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114.
  • the semiconductor laminate 500S includes a substrate 101, an N-type first clad layer 502, an N-type second clad layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 106, and an intermediate layer 108. , an electron barrier layer 509 , a P-type clad layer 510 and a contact layer 111 .
  • the N-type first clad layer 502 is an N-type Al 0.036 Ga 0.964 N layer with a thickness of 1200 nm.
  • the N-type first clad layer 502 is doped with Si at a concentration of 1 ⁇ 10 18 cm ⁇ 3 as an impurity.
  • the P-type cladding layer 510 is arranged between the electron barrier layer 509 and the contact layer 111 .
  • the P-type cladding layer 510 has a lower refractive index and a higher bandgap energy than the active layer 105 .
  • the P-type clad layer 510 is a P-type Al 0.026 Ga 0.974 N layer with a thickness of 450 nm.
  • the P-type clad layer 510 is doped with Mg as an impurity. Also, the impurity concentration at the end of the P-type cladding layer 510 closer to the active layer 105 is lower than the impurity concentration at the end farther from the active layer 105 .
  • the P-type cladding layer 510 is made of P-type Al 0.026 Ga 0.974 with a thickness of 150 nm doped with Mg at a concentration of 2 ⁇ 10 18 cm ⁇ 3 located on the side closer to the active layer 105 . It has an N layer and a P-type Al 0.026 Ga 0.974 N layer with a thickness of 300 nm doped with Mg at a concentration of 1 ⁇ 10 19 cm ⁇ 3 and disposed on the far side from the active layer 105 .
  • a ridge 510R is formed in the P-type clad layer 510, as in the nitride-based semiconductor light emitting device 100 according to the first embodiment. Also, the P-type cladding layer 510 is formed with two grooves 510T arranged along the ridge 510R and extending in the Y-axis direction.
  • the N-type first cladding layer 502 and the P-type cladding layer 510 contain Al, and the Al composition ratios of the N-type first cladding layer 502 and the P-type cladding layer 510 are respectively Ync and Ypc, then Ync > Ypc (4) Satisfying relationships.
  • the composition ratios Ync and Ypc indicate average Al composition ratios.
  • the N-type first cladding layer 502 includes a plurality of 2 nm thick GaN layers and a plurality of 2 nm thick AlGaN layers with an Al composition ratio of 0.07, each of the plurality of GaN layers and a plurality of When the AlGaN layers are alternately stacked, Ync is 0.035, which is the average Al composition ratio of the entire N-type first clad layer 502 .
  • the P-type cladding layer 510 includes a plurality of GaN layers with a thickness of 2 nm and a plurality of AlGaN layers with an Al composition ratio of 0.07 with a thickness of 2 nm, each of the plurality of GaN layers and each of the plurality of AlGaN layers. are alternately stacked, Ypc is 0.035, which is the average Al composition ratio of the entire P-type cladding layer 510 .
  • the refractive index of the N-type first clad layer 502 can be made lower than the refractive index of the P-type clad layer 510 . Therefore, even if the film thickness of the P-type clad layer 510 is reduced in order to reduce the operating voltage of the nitride-based semiconductor light-emitting device 500, the refractive index of the N-type first clad layer 502 is the same as that of the P-type clad layer 510. Since it is smaller than the refractive index, it is possible to suppress the shift of the peak of the light intensity distribution in the stacking direction from the active layer 105 toward the N-type first clad layer 502 .
  • the electron barrier layer 509 is arranged above the active layer 105 and is a nitride-based semiconductor layer containing at least Al. In this embodiment, electron blocking layer 509 is positioned between intermediate layer 108 and P-type cladding layer 510 .
  • the electron barrier layer 509 is a P-type AlGaN layer with a thickness of 5 nm. Further, the electron barrier layer 509 has an Al composition ratio gradient region in which the Al composition ratio monotonically increases as it approaches the P-type cladding layer 510 .
  • the structure in which the Al composition ratio monotonously increases includes a structure including a region in which the Al composition ratio is constant in the stacking direction.
  • the structure in which the Al composition ratio monotonously increases includes a structure in which the Al composition ratio increases stepwise.
  • the entire electron barrier layer 509 is the Al composition ratio increasing region, and the Al composition ratio increases at a constant change rate in the stacking direction.
  • the electron barrier layer 509 has a composition represented by Al 0.02 Ga 0.98 N in the vicinity of the interface with the intermediate layer 108 , and the Al composition decreases as it approaches the P-type cladding layer 510 .
  • the ratio monotonically increases, and the composition represented by Al 0.36 Ga 0.64 N is present near the interface with the P-type cladding layer 510 .
  • the electron barrier layer 509 is doped with Mg at a concentration of 1 ⁇ 10 19 cm ⁇ 3 as an impurity.
  • the electron barrier layer 509 can prevent electrons from leaking from the active layer 105 to the P-type clad layer 510 . Further, since the electron barrier layer 509 has an Al composition change region in which the Al composition ratio monotonously increases, the potential barrier in the valence band of the electron barrier layer 509 can be reduced as compared with the case where the Al composition ratio is uniform. . This facilitates the flow of holes from the P-type cladding layer 510 to the active layer 105 . Therefore, even when the P-side guide layer 106, which is an undoped layer, has a large film thickness as in the present embodiment, an increase in electrical resistance of the nitride-based semiconductor light emitting device 500 can be suppressed.
  • the operating voltage of the nitride-based semiconductor light emitting device 500 can be reduced.
  • the self-heating of the nitride-based semiconductor light-emitting device 500 during operation can be reduced, the temperature characteristics of the nitride-based semiconductor light-emitting device 500 can be improved. Therefore, the nitride-based semiconductor light emitting device 500 can operate at high output.
  • the effective refractive index difference ⁇ N is 3.0 ⁇ 10 ⁇ 3
  • the position P1 is 17.3 nm
  • the difference ⁇ P is 7.0 nm
  • the optical confinement factor to the active layer 105 is is 1.45%
  • the waveguide loss is 3.3 cm ⁇ 1
  • the guide layer free carrier loss is 1.3 cm ⁇ 1 .
  • Embodiment 6 A nitride-based semiconductor light-emitting device according to Embodiment 6 will be described.
  • the nitride-based semiconductor light-emitting device according to this embodiment differs from the nitride-based semiconductor light-emitting device 500 according to Embodiment 5 mainly in that a translucent conductive film is provided on the contact layer in the ridge.
  • the nitride-based semiconductor light-emitting device according to the present embodiment will be described below with reference to FIG. 35, focusing on differences from the nitride-based semiconductor light-emitting device 500 according to the fifth embodiment.
  • FIG. 35 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 600 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 600 includes a semiconductor laminate 600S, a current blocking layer 112, a P-side electrode 113, an N-side electrode 114, a translucent and a conductive film 620 .
  • the semiconductor laminate 600S includes a substrate 101, an N-type first clad layer 502, an N-type second clad layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 106, and an intermediate layer 108. , an electron barrier layer 509 , a P-type clad layer 610 and a contact layer 611 .
  • the P-type clad layer 610 is arranged between the electron barrier layer 509 and the contact layer 611 .
  • the P-type cladding layer 610 has a lower refractive index and a higher bandgap energy than the active layer 105 .
  • the P-type cladding layer 610 is a P-type Al 0.026 Ga 0.974 N layer with a thickness of 330 nm.
  • the P-type clad layer 610 is doped with Mg as an impurity. Also, the impurity concentration at the end of the P-type cladding layer 610 closer to the active layer 105 is lower than the impurity concentration at the end farther from the active layer 105 .
  • the P-type cladding layer 610 is made of P-type Al 0.026 Ga 0.974 with a thickness of 150 nm doped with Mg at a concentration of 2 ⁇ 10 18 cm ⁇ 3 located on the side closer to the active layer 105 . It has an N layer and a P-type Al 0.026 Ga 0.974 N layer with a thickness of 180 nm doped with Mg at a concentration of 1 ⁇ 10 19 cm ⁇ 3 and disposed on the far side from the active layer 105 .
  • a ridge 610R is formed in the P-type clad layer 610, as in the nitride-based semiconductor light emitting device 500 according to the fifth embodiment. Also, the P-type cladding layer 610 is formed with two grooves 610T arranged along the ridge 610R and extending in the Y-axis direction.
  • the contact layer 611 is a layer arranged above the P-type cladding layer 610 and in ohmic contact with the P-side electrode 113 .
  • the contact layer 611 is a P-type GaN layer with a thickness of 10 nm.
  • the contact layer 611 is doped with Mg at a concentration of 1 ⁇ 10 20 cm ⁇ 3 as an impurity.
  • the translucent conductive film 620 is a conductive film that is arranged above the P-type cladding layer 610 and that transmits at least part of the light generated by the nitride-based semiconductor light emitting device 600 .
  • the translucent conductive film 620 for example, tin-doped indium oxide (ITO), Ga-doped zinc oxide, Al-doped zinc oxide, In- and Ga-doped zinc oxide, or the like, which is transparent to visible light.
  • ITO indium oxide
  • Ga-doped zinc oxide Al-doped zinc oxide, In- and Ga-doped zinc oxide, or the like, which is transparent to visible light.
  • an oxide film exhibiting electrical conductivity with low resistance can be used.
  • the nitride-based semiconductor light-emitting device 600 according to the present embodiment also has the same effect as the nitride-based semiconductor light-emitting device 100 according to the first embodiment. .
  • the translucent conductive film 620 is arranged above the P-type clad layer 610, loss of light propagating above the P-type clad layer 610 can be reduced. As shown in FIG. 19, this effect is particularly remarkable when the thickness of the P-type cladding layer 610 is small. Moreover, since the film thickness of the P-type cladding layer 610 can be further reduced, the electrical resistance of the nitride-based semiconductor light emitting device 600 can be further reduced. As a result, the slope efficiency of the nitride-based semiconductor light emitting device 600 can be enhanced, and the operating voltage can be reduced.
  • the effective refractive index difference ⁇ N is 2.7 ⁇ 10 ⁇ 3
  • the position P1 is 15.1 nm
  • the difference ⁇ P is 5.4 nm
  • the optical confinement factor to the active layer 105 is is 1.47%
  • waveguide loss is 4.0 cm ⁇ 1
  • guide layer free carrier loss is 1.3 cm ⁇ 1 .
  • Embodiment 7 A nitride-based semiconductor light-emitting device according to Embodiment 7 will be described.
  • the nitride-based semiconductor light-emitting device according to this embodiment differs from the nitride-based semiconductor light-emitting device 500 according to the fifth embodiment in the configuration of the active layer.
  • the nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIGS. 36A and 36B, focusing on differences from the nitride-based semiconductor light-emitting device 500 according to the fifth embodiment.
  • FIG. 36A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 700 according to this embodiment.
  • FIG. 36B is a cross-sectional view showing the configuration of an active layer 705 included in the nitride-based semiconductor light emitting device 700 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 700 includes a semiconductor stacked body 700S, a current blocking layer 112, a P-side electrode 113, an N-side electrode 114, a translucent and a conductive film 620 .
  • the semiconductor laminate 700S includes a substrate 101, an N-type first clad layer 502, an N-type second clad layer 103, an N-side guide layer 104, an active layer 705, a P-side guide layer 106, and an intermediate layer 108. , an electron barrier layer 509 , a P-type clad layer 510 and a contact layer 111 .
  • the active layer 705 has a single quantum well structure and includes a single well layer 105b and barrier layers 105a and 105c sandwiching the well layer 105b.
  • Well layer 105b has the same configuration as well layer 105b according to the first embodiment, and barrier layers 105a and 105c have the same configuration as barrier layers 105a and 105c according to the first embodiment.
  • the same effects as those of the nitride-based semiconductor light-emitting devices according to the fifth and sixth embodiments can be obtained.
  • the active layer 705 has a single well layer 105b.
  • the structure of the N-side guide layer 104, the P-side guide layer 106, and the like allows the peak of the light intensity distribution in the stacking direction to be reduced. It can be located in or near the active layer 705 . Therefore, the optical confinement factor can be increased.
  • the effective refractive index difference ⁇ N is 2.9 ⁇ 10 ⁇ 3
  • the position P1 is 9.7 nm
  • the difference ⁇ P is 8.6 nm
  • the optical confinement factor to the active layer 705 is is 0.75%
  • the waveguide loss is 3.3 cm ⁇ 1
  • the guide layer free carrier loss is 1.4 cm ⁇ 1 .
  • the total film thickness of the active layer 705 is smaller than that of the active layer 105 according to the fifth embodiment by 8 nm.
  • the nitride-based semiconductor light-emitting device according to the present embodiment is the nitride-based semiconductor light-emitting device according to Embodiment 1 in that the average bandgap energy of the P-side guide layer is larger than the average bandgap energy of the N-side guide layer. It differs from device 100 .
  • the nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIGS. 37 and 38, focusing on differences from the nitride-based semiconductor light-emitting device 100 according to the first embodiment.
  • FIG. 37 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 800 according to this embodiment.
  • FIG. 38 is a schematic graph showing the bandgap energy distribution of the active layer 105 and the layers in the vicinity thereof of the nitride-based semiconductor light-emitting device 800 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 800 includes a semiconductor laminate 800S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114.
  • the semiconductor laminate 800S includes a substrate 101, an N-type first clad layer 102, an N-type second clad layer 103, an N-side guide layer 104, an active layer 105, a P-side guide layer 806, and an intermediate layer . , an electron barrier layer 109 , a P-type clad layer 110 and a contact layer 111 .
  • the P-side guide layer 806 is an undoped In Xp Ga 1-Xp N layer with a thickness of 280 nm. More specifically, the P-side guide layer 806 has a composition represented by In 0.03 Ga 0.97 N near the interface near the active layer 105 and near the interface far from the active layer 105 . has a composition represented by GaN in The In composition ratio Xp of the P-side guide layer 806 decreases at a constant rate of change as the distance from the active layer 105 increases.
  • the average In composition ratio of the P-side guide layer 806 is less than the average In composition ratio of the N-side guide layer 104 . Therefore, the average bandgap energy of the P-side guide layer 806 is greater than the average bandgap energy of the N-side guide layer 104 (see FIG. 38). In other words, the average refractive index of the P-side guide layer 806 is less than the average refractive index of the N-side guide layer 104 .
  • the film thickness of the P-side guide layer 806 is larger than the film thickness of the N-side guide layer 104 , the peak of the light intensity distribution can be biased toward the P-side guide layer 806 with respect to the active layer 105 .
  • the average refractive index of the P-side guide layer 806 is less than the average refractive index of the N-side guide layer 104, the peak of the light intensity distribution is closer to the P-side guide layer 806 than the active layer 105. bias can be suppressed.
  • the In composition ratio of the P-side guide layer 806 continuously and monotonically decreases as the distance from the active layer 105 increases. That is, the refractive index of the P-side guide layer 806 monotonously increases continuously as it approaches the active layer 105 . This makes it possible to bring the peak of the light intensity distribution in the lamination direction closer to the active layer 105 .
  • the effective refractive index difference ⁇ N is 2.8 ⁇ 10 ⁇ 3
  • the position P1 is 9.9 nm
  • the position P2 is 2.1 nm
  • the difference ⁇ P is 7.8 nm
  • the light confinement factor in the active layer 105 is 1.42%
  • the waveguide loss is 3.4 cm ⁇ 1
  • the guide layer free carrier loss is 1.30 cm ⁇ 1 . realizable.
  • the average bandgap energy of the P-side guide layer 806 is greater than the average bandgap energy of the N-side guide layer 104, so the light intensity in the stacking direction is The peak of the distribution can be brought closer to the center of the active layer 105 in the stacking direction than in the nitride-based semiconductor light emitting device 100 according to the first embodiment.
  • Embodiment 9 A nitride-based semiconductor light-emitting device according to Embodiment 9 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 the first embodiment mainly in the wavelength band of emitted light.
  • 39A, 39B, and 40 the nitride-based semiconductor light-emitting device according to the present embodiment will be described with a focus on differences from the nitride-based semiconductor light-emitting device 100 according to the first embodiment. .
  • FIG. 39A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 900 according to this embodiment.
  • FIG. 39B is a schematic cross-sectional view showing the configuration of an active layer 905 included in the nitride-based semiconductor light emitting device 900 according to this embodiment.
  • FIG. 40 is a schematic graph showing the bandgap energy distribution of the active layer 905 and the layers in the vicinity thereof of the nitride-based semiconductor light-emitting device 900 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 900 includes a semiconductor laminate 900S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114.
  • the semiconductor laminate 900S includes a substrate 101, an N-type first clad layer 902, an N-side guide layer 904, an active layer 905, a P-side guide layer 906, an electron barrier layer 909, and a P-type clad layer 910. , and the contact layer 111 .
  • the N-type first clad layer 902 is an N-type Al 0.10 Ga 0.90 N layer with a thickness of 740 nm.
  • the N-type first clad layer 902 is doped with Si at a concentration of 5 ⁇ 10 17 cm ⁇ 3 as an impurity.
  • the N-side guide layer 904 is an N-type Al Xna Ga 1-Xna N layer with a thickness of 130 nm.
  • the N-side guide layer 904 is doped with Si at a concentration of 5 ⁇ 10 17 cm ⁇ 3 as an impurity. More specifically, the N-side guide layer 904 has a composition represented by Al Xna1 Ga 1-Xna1 N near the interface closer to the active layer 905 , and Al It has a composition represented by Xna2Ga1 -Xna2N .
  • the Al composition ratio Xna1 near the interface of the N-side guide layer 904 closer to the active layer 905 is 0, and the Al composition ratio near the interface of the N-side guide layer 904 farther from the active layer 905 is 0.
  • Xna2 is 0.06 (or 6%).
  • the Al composition ratio Xna of the N-side guide layer 904 increases at a constant rate of change as the distance from the active layer 905 increases.
  • the active layer 905 has a well layer 905b and barrier layers 905a and 905c, as shown in FIG. 39B.
  • the barrier layer 905a is a layer arranged above the N-side guide layer 904 and functioning as a barrier for the quantum well structure.
  • the barrier layer 905a is an undoped Al 0.05 Ga 0.95 N layer with a thickness of 11 nm.
  • the well layer 905b is a layer arranged above the barrier layer 905a and functioning as a well of the quantum well structure.
  • Well layer 905b is disposed between barrier layer 905a and barrier layer 905c.
  • the well layer 905b is an undoped In 0.01 Ga 0.99 N layer with a thickness of 17.5 nm.
  • the barrier layer 905c is a layer arranged above the well layer 905b and functioning as a barrier for the quantum well structure.
  • the barrier layer 905c is an undoped Al 0.05 Ga 0.95 N layer with a thickness of 11 nm.
  • the nitride-based semiconductor light-emitting device 900 can emit light with a wavelength of 350 nm or more and 390 nm or less by including the active layer 905 having the above configuration.
  • the P-side guide layer 906 is an undoped Al 0.05 Ga 0.95 N layer with a thickness of 280 nm.
  • the electron barrier layer 909 is a P-type Al 0.36 Ga 0.64 N layer with a thickness of 5 nm.
  • the electron barrier layer 909 is doped with Mg at a concentration of 1 ⁇ 10 19 cm ⁇ 3 as an impurity.
  • the P-type clad layer 910 is arranged between the electron barrier layer 909 and the contact layer 111 .
  • the P-type cladding layer 910 has a lower refractive index and a higher bandgap energy than the active layer 905 .
  • the P-type cladding layer 910 is a P-type Al 0.10 Ga 0.90 N layer with a thickness of 660 nm.
  • the P-type clad layer 910 is doped with Mg as an impurity. Also, the impurity concentration at the end portion of the P-type cladding layer 910 closer to the active layer 905 is lower than the impurity concentration at the end portion farther from the active layer 905 .
  • the P-type cladding layer 910 is a 250-nm-thick P-type Al 0.10 Ga 0.90 layer doped with Mg at a concentration of 2 ⁇ 10 18 cm ⁇ 3 located on the side closer to the active layer 905 . It has an N layer and a P-type Al 0.10 Ga 0.90 N layer with a thickness of 410 nm doped with Mg at a concentration of 1 ⁇ 10 19 cm ⁇ 3 and disposed on the far side from the active layer 905 .
  • a ridge 910R is formed in the P-type cladding layer 910, as in the nitride-based semiconductor light emitting device 100 according to the first embodiment. Also, the P-type cladding layer 910 is formed with two grooves 910T arranged along the ridge 910R and extending in the Y-axis direction. In this embodiment, the film thickness dc of the P-type cladding layer 910 at the lower end of the ridge 910R is 30 nm.
  • the Al composition ratio Xna of the N-side guide layer 904 monotonically increases with increasing distance from the active layer 905 . That is, the refractive index of the N-side guide layer 904 increases monotonically as it approaches the active layer 905 . This makes it possible to bring the peak of the light intensity distribution in the lamination direction closer to the active layer 905 .
  • the film thickness of the P-side guide layer 906 is larger than the film thickness of the N-side guide layer 904 .
  • the distance dp between the lower end of the ridge 910R and the active layer 905 becomes larger than when the thickness of the P-side guide layer 906 is equal to or less than the thickness of the N-side guide layer 904, so that the effective refractive index difference ⁇ N can be reduced. Therefore, the stability of the light output of the nitride-based semiconductor light emitting device 900 can be enhanced.
  • the Al composition ratio of the P-side guide layer 906 is larger than the average Al composition ratio of the N-side guide layer 904 . That is, the average bandgap energy of the P-side guide layer 906 is greater than the average bandgap energy of the N-side guide layer 904 (see FIG. 40). Therefore, the average refractive index of the P-side guide layer 906 is less than the average refractive index of the N-side guide layer 904 . As described above, since the thickness of the P-side guide layer 906 is greater than the thickness of the N-side guide layer 904 , the peak of the light intensity distribution can be biased toward the P-side guide layer 906 with respect to the active layer 905 .
  • the average refractive index of the P-side guide layer 906 is less than the average refractive index of the N-side guide layer 904, the peak of the light intensity distribution is closer to the P-side guide layer 906 than the active layer 905. bias can be suppressed.
  • the series resistance of the nitride-based semiconductor light emitting device 900 can be reduced as in the first embodiment.
  • the minimum bandgap energy of the N-side guide layer 904 (that is, the bandgap energy near the interface of the N-side guide layer 904 with the active layer 905) is the barrier layer less than the bandgap energy of 905a.
  • the N-side guide layer 904 can be doped with N-type impurities. , an increase in the hole concentration in the N-side guide layer 904 can be suppressed. As a result, the probability of nonradiative recombination of electrons and holes in the N-side guide layer 904 can be reduced, so that deterioration of the luminous efficiency and long-term reliability of the nitride-based semiconductor light emitting device 900 can be suppressed.
  • the barrier layers 905a and 905c are formed of Al0.05Ga0.95N layers having an Al composition of 0.04 or more, the bandgap energy of the barrier layers 905a and 905c is 3.47 eV or more, and the energy 3.3. Since it is sufficiently higher than 28 eV, it is possible to easily form a quantum level with an emission wavelength in the 375 nm band in the well layer 905b.
  • the luminous efficiency of the nitride-based semiconductor light-emitting device 900 can be improved, so that the temperature characteristics of the nitride-based semiconductor light-emitting device 900 can be improved.
  • the effective refractive index difference ⁇ N is 2.2 ⁇ 10 ⁇ 3
  • the position P1 is 2.9 nm
  • the position P2 is 2.3 nm
  • the difference ⁇ P is 0.6 nm
  • the light confinement factor to the active layer 905 is 6.7%
  • the waveguide loss is 2.8 cm ⁇ 1 .
  • the nitride-based semiconductor light-emitting devices of Comparative Examples 9 and 10 differ from the nitride-based semiconductor light-emitting device 900 according to the present embodiment in that the Al composition ratios of the P-side guide layers are 3% and 2%, respectively. and are otherwise identical.
  • the average bandgap energy of the P-side guide layer is equal to the average bandgap energy of the N-side guide layer 904 .
  • the average bandgap energy of the P-side guide layer is less than the average bandgap energy of the N-side guide layer 904 .
  • the effective refractive index difference ⁇ N was 1.8 ⁇ 10 ⁇ 3
  • the position P1 was 10.8 nm
  • the position P2 was 9.9 nm
  • the difference ⁇ P was 0. 9
  • the optical confinement factor to the active layer 905 is 5.7%
  • the waveguide loss is 3.2 cm ⁇ 1 .
  • the effective refractive index difference ⁇ N was 3.1 ⁇ 10 ⁇ 3
  • the position P1 was 80.4 nm
  • the position P2 was 68.9 nm
  • the difference ⁇ P was 11 nm.
  • the optical confinement factor to the active layer 905 is 4.7%
  • the waveguide loss is 3.5 cm ⁇ 1 .
  • the average bandgap energy of the P-side guide layer is larger than the average bandgap energy of the N-side guide layer 904, compared to the nitride-based semiconductor light-emitting devices of Comparative Examples 9 and 10, The light confinement factor, waveguide loss and peak position of light intensity distribution can be improved.
  • the nitride-based semiconductor light-emitting device of Comparative Example 3 is different from the nitride-based semiconductor light-emitting device 900 according to the present embodiment in that the composition of the N-side guide layer is uniform, but is identical in other respects.
  • the N-side guide layer of the nitride-based semiconductor light-emitting device of Comparative Example 3 is an N-type Al 0.03 Ga 0.97 N layer with a thickness of 130 nm.
  • the N-side guide layer is doped with Si at a concentration of 5 ⁇ 10 17 cm ⁇ 3 as an impurity.
  • the effective refractive index difference ⁇ N was 4.1 ⁇ 10 ⁇ 3
  • the position P1 was 49.5 nm
  • the position P2 was 35.7 nm
  • the difference ⁇ P was 13. 8 nm
  • the optical confinement factor to the active layer 905 is 5.0%
  • the waveguide loss is 3.4 cm ⁇ 1 .
  • the bandgap energy of the N-side guide layer 904 monotonically increases continuously as the distance from the active layer 905 increases.
  • the effective refractive index difference ⁇ N, the light confinement factor, and the peak position of the light intensity distribution can be improved.
  • FIG. 41 is a schematic graph showing the bandgap energy distribution of the active layer 905 and the layers in the vicinity thereof of the nitride-based semiconductor light-emitting device according to this modification.
  • the P-side guide layer 906A of the nitride-based semiconductor light emitting device has a P-side first guide layer 906a and a P-side second guide layer 906b.
  • the P-side first guide layer 906 a is a guide layer arranged above the active layer 905 .
  • the P-side second guide layer 906b is a guide layer disposed above the P-side first guide layer 906a and having a bandgap energy greater than that of the P-side first guide layer 906a.
  • the P-side first guide layer 906a is an undoped Al 0.01 Ga 0.99 N layer with a thickness of 70 nm
  • the P-side second guide layer 906b is an undoped Al 0.05 layer with a thickness of 210 nm. It is a Ga 0.95 N layer.
  • the P-side first guide layer 906a has a larger Al composition ratio than the P-side second guide layer 906b.
  • the nitride-based semiconductor light-emitting device according to this modified example also has the same effect as the nitride-based semiconductor light-emitting device 900 according to the ninth embodiment. Furthermore, in this modification, the Al composition ratio of the P-side guide layer 906A increases stepwise as the distance from the active layer 905 increases. As a result, the refractive index of the region near the active layer 905 of the P-side guide layer 906A can be made higher than the refractive index of the region far from the active layer 905, so that the peak of the light intensity distribution can be brought closer to the active layer 905. .
  • the effective refractive index difference ⁇ N is 1.24 ⁇ 10 ⁇ 3
  • the position P1 is 11.6 nm
  • the position P2 is 11.3 nm
  • the difference ⁇ P is 0.3 nm
  • a nitride-based semiconductor light-emitting device having a light confinement factor of 7.7% in the active layer 905 and a waveguide loss of 2.5 cm ⁇ 1 can be realized.
  • the nitride-based semiconductor light-emitting devices of Comparative Examples 11 and 12 have Al composition ratios of 3.67% and 2.3% in the P-side second guide layer, respectively. It differs from the semiconductor light-emitting device 900 of the related art, but is the same in other respects.
  • the average bandgap energy of the P-side guide layer is equal to the average bandgap energy of the N-side guide layer 904 .
  • the average bandgap energy of the P-side guide layer is less than the average bandgap energy of the N-side guide layer 904 .
  • the effective refractive index difference ⁇ N was 1.7 ⁇ 10 ⁇ 3
  • the position P1 was 34.8 nm
  • the position P2 was 33.3 nm
  • the difference ⁇ P was 1.
  • the optical confinement factor to the active layer 905 is 6.8%
  • the waveguide loss is 2.8 cm ⁇ 1 .
  • the effective refractive index difference ⁇ N was 2.5 ⁇ 10 ⁇ 3
  • the position P1 was 60.1 nm
  • the position P2 was 56.6 nm
  • the difference ⁇ P was 3 5 nm
  • the optical confinement factor to the active layer 905 is 5.4%
  • the waveguide loss is 3.3 cm ⁇ 1 .
  • the average bandgap energy of the P-side guide layer 906A is greater than the average bandgap energy of the N-side guide layer 904, compared to the nitride-based semiconductor light-emitting devices of Comparative Examples 11 and 12, The light confinement factor, waveguide loss and peak position of light intensity distribution can be improved.
  • FIG. 42 is a schematic graph showing the bandgap energy distribution of the active layer 905 and the layers in the vicinity thereof in the nitride-based semiconductor light-emitting device according to this modification.
  • the P-side guide layer 906B is an undoped Al Xpa Ga 1-Xpa N layer with a thickness of 280 nm. More specifically, the P-side guide layer 906B has a composition represented by GaN near the interface closer to the active layer 905 and Al 0.08 Ga 0.08 near the interface farther from the active layer 905 . It has a composition expressed as 92N .
  • the Al composition ratio Xpa of the P-side guide layer 906B increases at a constant rate of change as the distance from the active layer 905 increases. Therefore, the bandgap energy of the P-side guide layer 906B increases continuously and monotonically as the distance from the active layer 905 increases.
  • the nitride-based semiconductor light-emitting device according to this modified example also has the same effect as the nitride-based semiconductor light-emitting device 900 according to the ninth embodiment. Furthermore, in this modification, the Al composition ratio of the P-side guide layer 906B increases continuously and monotonically as the distance from the active layer 905 increases. As a result, the refractive index of the P-side guide layer 906B increases as it approaches the active layer 905, so that the peak of the light intensity distribution can be brought closer to the active layer 905.
  • the effective refractive index difference ⁇ N is 1.13 ⁇ 10 ⁇ 3
  • the position P1 is 22.2 nm
  • the position P2 is 21.3 nm
  • the difference ⁇ P is 0.9 nm
  • a nitride-based semiconductor light-emitting device having a light confinement factor of 7.3% in the active layer 905 and a waveguide loss of 2.6 cm ⁇ 1 can be realized.
  • the nitride-based semiconductor light-emitting devices of Comparative Examples 13 and 14 differ from this modification in that the Al composition ratios at the interface of the P-side guide layer farther from the active layer 905 are 6% and 4%, respectively. It differs from the nitride-based semiconductor light-emitting device, but is the same in other respects.
  • the average bandgap energy of the P-side guide layer is equal to the average bandgap energy of the N-side guide layer 904 .
  • the average bandgap energy of the P-side guide layer is less than the average bandgap energy of the N-side guide layer 904 .
  • the effective refractive index difference ⁇ N was 1.43 ⁇ 10 ⁇ 3
  • the position P1 was 36.4 nm
  • the position P2 was 34.9 nm
  • the difference ⁇ P was 1. 0.5 nm
  • the optical confinement factor to the active layer 905 is 6.6%
  • the waveguide loss is 2.8 cm ⁇ 1 .
  • the effective refractive index difference ⁇ N is 1.9 ⁇ 10 ⁇ 3
  • the position P1 is 54.6 nm
  • the position P2 is 52.3 nm
  • the difference ⁇ P is 2 .3 nm
  • the optical confinement factor to the active layer 905 is 5.7%
  • the waveguide loss is 3.1 cm ⁇ 1 .
  • the average bandgap energy of the P-side guide layer 906B is larger than the average bandgap energy of the N-side guide layer 904, compared to the nitride-based semiconductor light-emitting devices of Comparative Examples 13 and 14, The light confinement factor, waveguide loss and peak position of light intensity distribution can be improved.
  • the nitride-based semiconductor light-emitting device is a semiconductor laser device, but the nitride-based semiconductor light-emitting device is not limited to a semiconductor laser device.
  • the nitride-based semiconductor light emitting device may be a superluminescent diode.
  • the reflectance of the end face of the semiconductor laminate included in the nitride-based semiconductor light-emitting device with respect to the emitted light from the semiconductor laminate may be 0.1% or less.
  • Such a reflectance can be realized, for example, by forming an antireflection film made of a dielectric multilayer film or the like on the end face.
  • the guided light reflected by the front end face is coupled again with the waveguide to form a guided light component.
  • the guided light component can be set to a small value of 0.1% or less.
  • the film thickness of the well layers 105b and 105d of the active layer 105 is 35 ⁇ or less.
  • the effect of reducing waveguide loss and the effect of increasing the light confinement coefficient in the active layer 105 by the nitride-based semiconductor light emitting device according to the present disclosure even if the reflectance of the facet is reduced, the optical amplification gain can be increased. can be secured. Further, when such a nitride-based semiconductor light-emitting device is arranged in an external cavity including a wavelength selection element, the self-heating of the nitride-based semiconductor light-emitting device can be reduced, and the wavelength fluctuation of emitted light can be suppressed. , it becomes easier to achieve oscillation at a desired selected wavelength.
  • the nitride-based semiconductor light-emitting device has a structure including two well layers as the structure of the active layer 105, but the structure including only a single well layer. There may be.
  • the use of the N-side guide layer and the P-side guide layer of the present disclosure allows the position of the light intensity distribution in the stacking direction to be can be enhanced, the peak of the light intensity distribution in the lamination direction can be positioned near the well layer. Therefore, it is possible to realize a nitride-based semiconductor light-emitting device having a low oscillation threshold, a low waveguide loss, a high optical confinement factor, and excellent linear current-optical output (IL) characteristics.
  • IL linear current-optical output
  • the nitride-based semiconductor light-emitting device has a single ridge, but the nitride-based semiconductor light-emitting device may have a plurality of ridges.
  • FIG. 43 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 1000 according to Modification 1. As shown in FIG. As shown in FIG.
  • a nitride-based semiconductor light-emitting device 1000 according to Modification 1 has a configuration in which a plurality of nitride-based semiconductor light-emitting devices 100 according to Embodiment 1 are arranged in an array in the horizontal direction. .
  • the nitride-based semiconductor light-emitting device 1000 has a configuration in which three nitride-based semiconductor light-emitting devices 100 are integrally arranged.
  • the number of 100 is not limited to three.
  • the number of nitride-based semiconductor light-emitting devices 100 included in the nitride-based semiconductor light-emitting device 1000 may be two or more.
  • Each nitride-based semiconductor light emitting device 100 has a light emitting portion 100E for emitting light.
  • the light emitting portion 100E is a portion of the active layer 105 that emits light, and corresponds to a portion of the active layer 105 located below the ridge 110R.
  • the nitride-based semiconductor light emitting device 1000 according to Modification 1 has a plurality of light emitting portions 100E arranged in an array. As a result, a plurality of emitted light beams can be obtained from one nitride-based semiconductor light-emitting device 1000, so that a high-power nitride-based semiconductor light-emitting device 1000 can be realized.
  • the nitride-based semiconductor light-emitting device 1000 includes a plurality of nitride-based semiconductor light-emitting devices 100, but the plurality of nitride-based semiconductor light-emitting devices included in the nitride-based semiconductor light-emitting device 1000 It is not limited, and may be a nitride-based semiconductor light-emitting device according to another embodiment.
  • nitride-based semiconductor light-emitting device 1000a according to Modification 2 shown in FIG. dimension may be separated by a separation groove 100T of 1.0 ⁇ m or more and 1.5 ⁇ m or less.
  • the semiconductor laser device of the present disclosure has a small ⁇ N and can reduce the horizontal divergence angle, even if the distance between the centers of the light emitting portions 100E shown in FIGS.
  • the light emitted from the light emitting portions 100E is less likely to interfere with each other, and the distance between the centers of the light emitting portions 100E can be narrowed to 250 ⁇ m or less.
  • the distance is 225 ⁇ m.
  • each guide layer is an In 2 Xn Ga 1-Xn 3 N layer in each of the above-described embodiments and modifications thereof, the composition of each guide layer is not limited to this.
  • the N-side guide layer is made of Al Xna Ga 1-Xna N
  • the N-side guide layer is made of Al Xpa Ga 1-Xpa N.
  • the Al composition ratio of the N-side guide layer increases continuously and monotonically with increasing distance from the active layer
  • the average Al composition ratio of the N-side guide layer is the average Al composition ratio of the P-side guide layer. may be less than the value.
  • a nitride-based semiconductor light-emitting device having such a configuration can also reduce the operating voltage and increase the light confinement factor in the active layer.
  • the absolute value of the average rate of change in the stacking direction of the Al composition ratio in the region from the interface of the N-side guide layer closer to the active layer to the central portion of the N-side guide layer in the stacking direction is It may be smaller than the absolute value of the average rate of change in the stacking direction of the Al composition ratio in the region up to the interface on the side closer to the N-type first cladding layer.
  • the nitride-based semiconductor light-emitting device includes the N-type second cladding layer 103, the intermediate layer 108, the electron barrier layer 109, and the current blocking layer 112, but these layers are not necessarily included.
  • each P-type cladding layer 110, 510, and 610 are layers with a uniform Al composition ratio, but the configuration of each P-type clad layer is not limited to this.
  • each P-type cladding layer may have a superlattice structure in which each of a plurality of AlGaN layers and each of a plurality of GaN layers are alternately laminated.
  • each P-type cladding layer is composed of, for example, an AlGaN layer with an Al composition ratio of 0.052 (5.2%) and a thickness of 1.85 nm and a GaN layer with a thickness of 1.85 nm alternately stacked. may have a superlattice structure.
  • the Al composition ratio of each P-type clad layer is defined as the average Al composition ratio of 0.026 (2.6%) in the superlattice structure.
  • each clad layer according to Embodiment 1 may be applied to each nitride-based semiconductor light-emitting device according to Embodiments 5 and 6.
  • the translucent conductive film according to the sixth embodiment may be applied to each of the nitride-based semiconductor light-emitting devices according to the first to fifth embodiments.
  • the nitride-based semiconductor light-emitting device of the present disclosure can be applied, for example, as a light source for processing machines as a high-output and high-efficiency light source.

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