WO2023281902A1 - 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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WO2023281902A1
WO2023281902A1 PCT/JP2022/018699 JP2022018699W WO2023281902A1 WO 2023281902 A1 WO2023281902 A1 WO 2023281902A1 JP 2022018699 W JP2022018699 W JP 2022018699W WO 2023281902 A1 WO2023281902 A1 WO 2023281902A1
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layer
side guide
nitride
semiconductor light
emitting device
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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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Priority to EP22837323.9A priority Critical patent/EP4369538A4/en
Priority to CN202280047450.9A priority patent/CN117597841A/zh
Priority to US18/063,487 priority patent/US20230140710A1/en
Publication of WO2023281902A1 publication Critical patent/WO2023281902A1/ja
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    • 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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    • H01S5/3215—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures characterised by special cladding layers, e.g. details on band-discontinuities graded composition cladding layers
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    • 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
    • H01S5/2202—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 by making a groove in the upper laser structure
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    • 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
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    • H10H20/825—Materials of the light-emitting regions comprising only Group III-V materials, e.g. GaP containing nitrogen, e.g. GaN

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 P-side guide layer monotonically increases with distance from the active layer, and the bandgap energy of the P-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, and the bandgap energy of the barrier layer is equal to the N-side guide layer and the P-side guide layer.
  • 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 film thickness of the N-side guide layer and the optical confinement coefficient according to the first embodiment.
  • FIG. 10 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer and waveguide loss according to the first embodiment.
  • FIG. 11 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer and the effective refractive index difference according to the first embodiment.
  • FIG. 12 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. 13 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.
  • FIG. 14 is a graph showing simulation results of the relationship between the thickness of the P-type cladding layer and the optical confinement coefficient according to the first embodiment.
  • FIG. 15 is a graph showing simulation results of the relationship between the thickness of the P-type clad layer and waveguide loss according to the first embodiment.
  • FIG. 16 is a graph showing simulation results of the relationship between the thickness of the P-type cladding layer and the effective refractive index difference according to the first embodiment.
  • FIG. 17 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. 18 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 first embodiment.
  • FIG. 19 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 2.
  • FIG. 20 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.
  • FIG. 21 is a graph showing simulation results of distributions of valence band potential and hole Fermi level in the stacking direction of the nitride-based semiconductor light emitting device according to the second embodiment.
  • FIG. 22 is a graph showing simulation results of carrier concentration distribution in the stacking direction of the nitride-based semiconductor light-emitting device according to the second embodiment.
  • FIG. 23 is a graph showing simulation results of the relationship between the average In composition ratio in the P-side guide layer and the waveguide loss according to the second embodiment.
  • FIG. 24 is a graph showing simulation results of the relationship between the average In composition ratio in the P-side guide layer and the optical confinement coefficient according to the second embodiment.
  • FIG. 25 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer and the optical confinement coefficient according to the second embodiment.
  • FIG. 26 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer and waveguide loss according to the second embodiment.
  • FIG. 27 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer and the effective refractive index difference according to the second embodiment.
  • FIG. 28 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 second embodiment.
  • FIG. 29 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 second embodiment.
  • 30 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 3.
  • FIG. 31 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 4.
  • FIG. 32A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 5.
  • FIG. 32B is a cross-sectional view showing the structure of an active layer included in the nitride-based semiconductor light-emitting device according to Embodiment 5.
  • FIG. 33 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 6.
  • FIG. 34 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 sixth embodiment.
  • FIG. 35 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 according to the sixth embodiment.
  • FIG. 36 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 sixth embodiment.
  • 37 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. 38 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light emitting device according to Embodiment 6, and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction band potential.
  • FIG. 39 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 the sixth embodiment and the light confinement factor.
  • FIG. 40 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 6 and waveguide loss.
  • FIG. 41 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 6 and the operating voltage.
  • FIG. 42 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 7.
  • FIG. 43 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Embodiment 8.
  • FIG. 44 is a graph showing the distribution of the Al composition ratio in the stacking direction of the electron barrier layer according to Embodiment 8.
  • FIG. 45 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Modification 1.
  • FIG. 46 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device according to Modification 2.
  • 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 0.026 Ga 0.974 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 N-side guide layer 104 is an undoped In 0.04 Ga 0.96 N layer with a thickness of 160 nm.
  • 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 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 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 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 P-side guide layer 106 includes a portion where the bandgap energy continuously increases with distance from the active layer 105 .
  • the configuration in which the bandgap energy continuously increases does not include the configuration in which the bandgap energy changes discontinuously in the stacking direction.
  • a structure in which the bandgap energy continuously increases monotonically means that the discontinuous increase in the bandgap energy at a certain position in the stacking direction is less than 2% of the bandgap energy at that position.
  • the structure in which the bandgap energy increases continuously does not include a structure in which the bandgap energy increases stepwise by 2% or more in the stacking direction, but the bandgap energy increases stepwise by 2% in the stacking direction. Constructs that increase by less than % are included.
  • the bandgap energy of the entire P-side guide layer 106 continuously increases with increasing distance from the active layer 105, but the configuration of the P-side guide layer 106 is not limited to this.
  • 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 ( ⁇ Egp) in the stacking direction of the bandgap energy of the P-side guide layer 106 is preferably 100 meV or more.
  • 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 near the end face of the P-side guide layer 106 on the side closer to the active layer 105 and the bandgap energy in the P-type cladding layer 110 It is defined by the difference from the bandgap energy near the end surface on the near side.
  • the continuously increasing bandgap energy in ⁇ Egp should be 70% or more.
  • the ratio may be 80% or more, or may be 90% or more.
  • 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 monotonically increases with distance from the active layer 105 .
  • the configuration in which the In composition ratio Xp continuously and monotonously decreases includes a configuration in which there is a region in which the In composition ratio Xp is constant in the stacking direction.
  • the P-side guide layer 106 includes a portion in which the In composition ratio Xp continuously decreases as the distance from the active layer 105 increases.
  • the configuration in which the In composition ratio Xp continuously 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 Xp at a certain position in the P-side guide layer 106 decreases continuously means that the amount of discontinuous decrease in the stacking direction of the In composition ratio Xp at that position is less than 20% of the In composition ratio Xp at that position. Means a configuration.
  • 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 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 larger than the average In composition ratio of the P-side guide layer 106 .
  • Tn the film thickness of the P-side guide layer 106 is Tp and the film thickness of the N-side guide layer 104 is Tn, then Tn ⁇ Tp (1) Satisfying relationships.
  • 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 0.026 Ga 0.974 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 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 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 in the stacking direction of the end face of the active layer 105 on the N side of the well layer 105b 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.
  • 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 factor in the active layer is lowered, and accordingly the thermal saturation level of the optical output is 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 greater than or equal to the average bandgap energy 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 (inequality (1) above).
  • the P-side guide layer 106 has a portion where the bandgap energy continuously and monotonically increases with distance from the active layer 105 .
  • the P-side guide layer 106 has a portion where the refractive index continuously and monotonically increases as it approaches the active layer 105 . Since the refractive index of the P-side guide layer 106 increases as it approaches the active layer 105 in this manner, the peak of the light intensity distribution in the stacking direction can be brought closer to the active layer 105 .
  • 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 .
  • the refractive index of each barrier layer can be made equal to or higher than the maximum values of the P-side guide layer 106 and the N-side guide layer 104 .
  • This effect can be further enhanced by making the refractive index of each barrier layer larger than the maximum values of the P-side guide layer 106 and the 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 1.3 nm. That is, the peak of the light intensity distribution can be located in the well layer 105b of the active layer 105 (see FIG. 4). Also, ⁇ P can be suppressed to 5.6 nm. As a result, the light confinement factor in the active layer 105 can be increased to about 1.49%.
  • 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 3.2 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 2.1 ⁇ 10 ⁇ 3 . Therefore, in the present embodiment, the higher-order mode (that is, 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 2.1 ⁇ 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 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. Become. In order to suppress such an increase 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.
  • 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 is a P-side first guide layer composed of an undoped In 0.04 Ga 0.96 N layer with a thickness of 140 nm disposed above the active layer 105. 1306a, and a P-side second guide layer 1306b formed of an undoped In 0.02 Ga 0.98 N layer with a film thickness of 140 nm and disposed above the P-side first guide layer 1306a.
  • 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 second guide layer 1306b, which is the region far from the active layer 105, in the P-side guide layer 1306 is set to It is made smaller than the refractive index of the first guide layer 1306a.
  • graph (c) of FIG. 6 the peak of the light intensity distribution in the stacking direction is closer to the active layer 105 than the nitride-based semiconductor light emitting device of Comparative Example 2.
  • the light confinement factor is 1.47%, which is further improved from that of the nitride-based semiconductor light-emitting device of Comparative Example 2.
  • the concentration of electrons in the stacking direction of the P-side guide layer 1306 spikes at portions where the valence charge potential changes discontinuously.
  • the hole concentration in the P-side guide layer 1306 also exceeds 1 ⁇ 10 17 cm ⁇ 3 .
  • the nitride-based semiconductor light-emitting device of Comparative Example 3 cannot achieve a reduction in free carrier loss and a reduction in non-radiative recombination probability.
  • the effective refractive index difference ⁇ N was 2.5 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution were 10.7 nm and 4.4 nm, respectively.
  • the difference ⁇ P is 6.3 nm.
  • the waveguide loss is 3.93 cm ⁇ 1 and the guide layer free carrier loss is 2.56 cm ⁇ 1 .
  • the refractive index of the P-side guide layer 106 increases as it approaches the active layer 105.
  • the peak of the light intensity distribution in the direction 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 from that of the nitride-based semiconductor light-emitting device of Comparative Example 3.
  • the bandgap energy of the P-side guide layer 106 monotonically increases continuously with distance from the active layer 105, as shown in graph (d) of FIG. The charging potential decreases continuously.
  • the concentration of holes and electrons in the stacking direction of the P-side guide layer 106 can be reduced and kept substantially constant.
  • ⁇ Egp amount of increase in the stacking direction of the bandgap energy of the P-side guide layer 106
  • the effect is reduced, so ⁇ Egp is preferably 100 meV or more.
  • ⁇ Egp is too large, the bandgap energy at the end on the active layer 105 side in the bandgap energy of the P-side guide layer 106 may become small.
  • ⁇ Egp may be 400 meV or less.
  • the nitride-based semiconductor light emitting device 100 reduces free carrier loss and reduces the non-radiative recombination probability. can be realized.
  • 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 nm, respectively. .3 nm and the difference ⁇ P is 5.6 nm.
  • the graph showing the IL characteristics is less likely to have non-linear portions.
  • the waveguide loss is 3.20 cm ⁇ 1 and the guide layer free carrier loss is 1.8 cm ⁇ 1 .
  • waveguide loss and free carrier loss can be reduced compared to each comparative example.
  • FIG. 9 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the optical confinement coefficient ( ⁇ v) according to this embodiment.
  • FIG. 10 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the waveguide loss according to this embodiment.
  • FIG. 11 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the effective refractive index difference ⁇ N according to this embodiment.
  • FIG. 9 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the optical confinement coefficient ( ⁇ v) according to this embodiment.
  • FIG. 10 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the waveguide loss according to this embodiment.
  • FIG. 11 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the effective refractive index difference ⁇ N according to this embodiment.
  • FIG. 12 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the position P1 according to this embodiment.
  • FIG. 13 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the difference ⁇ P 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 is 4%
  • the In composition ratio of the P-side guide layer 106 is 4% near the interface near the active layer 105
  • the In composition ratio of the P-side guide layer 106 is changed at a constant rate of change in the stacking direction.
  • 9 to 13 also show, as a comparative example, simulation results of an example in which the In composition ratio of the P-side guide layer is constant at 2%, as indicated by broken lines.
  • the optical confinement coefficient can be increased.
  • the film thickness Tn of the N-side guide layer 104 may be 100 nm or more. This can prevent the light intensity distribution from moving too much from the active layer 105 toward the P-side guide layer 106 due to the film thickness Tn of the N-side guide layer 104 becoming too thin. Further, as shown in FIG. 9, as shown in FIG. 9, 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 optical confinement coefficient can be increased. can.
  • the film thickness Tn of the N-side guide layer 104 may be 100 nm or more. This can prevent the light intensity distribution from moving too much from the active layer 105 toward the P-side guide layer 106 due to the film thickness Tn of the N-side guide layer 104 becoming too thin. Further, as shown in FIG.
  • the film thickness of the N-side guide layer 104 is made smaller than the film thickness of the P-side guide layer 106. In this way, the optical confinement factor can be increased.
  • the light confinement factor can be further increased by using the
  • the In composition ratio is lower when the In composition ratio is continuously and monotonously decreased as the distance from the active layer 105 increases.
  • the waveguide loss can be reduced more than when is constant at 2%. Further, in the present embodiment, even when the film thickness of the N-side guide layer 104 is changed, the waveguide loss can be kept substantially constant at 3.5 cm ⁇ 1 or less.
  • the effective refractive index difference ⁇ N can be reduced.
  • the In composition ratio is continuously and monotonically decreased as the distance from the active layer 105 increases, the In The effective refractive index difference ⁇ N can be reduced more than when the composition ratio is constant at 2%.
  • the film thickness Tn of the N-side guide layer 104 may be 100 nm or more and 190 nm or less. In other words, the film thickness of the N-side guide layer 104 may be 23% or more and 43% or less of the sum of the film thicknesses of the N-side guide layer 104 and the P-side guide layer.
  • 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 film thickness of the N-side guide layer 104 is 23% or more and 43% or less of the sum of the film thicknesses of the N-side guide layer 104 and the P-side guide layer, and the distance dc is 40 nm, as shown in FIG.
  • the effective refractive index difference ⁇ N can be maintained within the range of 2 ⁇ 10 ⁇ 3 or more and 2.2 ⁇ 10 ⁇ 3 or less.
  • the film thickness of the N-side guide layer 104 is made smaller than the film thickness of the P-side guide layer 106.
  • the absolute value of the position P1 can be reduced.
  • the absolute value of the position P1 can be further reduced when the In composition ratio is continuously and monotonously decreased.
  • 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 film thickness of the N-side guide layer should be smaller than that of the P-side guide layer 106.
  • the In composition ratio increases with increasing distance from the active layer 105, as in the P-side guide layer 106 according to the present embodiment.
  • the difference ⁇ P can be further reduced by continuously and monotonously decreasing.
  • 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
  • the bandgap energy of each barrier layer is equal to or higher than the minimum bandgap energy of the N-side guide layer 104 and the P-side guide layer 106, and other configurations are used.
  • the nitride-based semiconductor light-emitting device of Comparative Example 4 shows the simulation results of the nitride-based semiconductor light-emitting device of Comparative Example 4, which is the same as the nitride-based semiconductor light-emitting device 100 according to the present embodiment.
  • the light confinement factor was 1.39%
  • the effective refractive index difference ⁇ N was 2.3 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution were are 0.35 nm and ⁇ 21.9 nm, respectively
  • the difference ⁇ P is 22.3 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 1.84 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.
  • FIG. 14 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. 15 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer 110 and the waveguide loss according to the present embodiment.
  • FIG. 16 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. 14 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. 15 is a graph showing simulation results of the relationship between the film thickness of the P-type cladding layer 110 and the waveguide loss according to the present embodiment.
  • FIG. 16 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
  • FIG. 17 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. 18 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.
  • 14 to 18 also show simulation results of two comparative examples in which the In composition ratio of the P-side guide layer is constant at 2% and 4%, respectively.
  • 14 to 18 also show simulation results of a nitride-based semiconductor light-emitting device 400 according to Embodiment 4, which will be described later.
  • the nitride-based semiconductor light-emitting device 100 can have a larger optical confinement factor than the nitride-based semiconductor light-emitting devices of the comparative examples. 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.
  • 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 devices of the respective comparative examples.
  • the absolute value of the position P1 and the difference ⁇ P can be reduced more than the nitride-based semiconductor light-emitting devices of the comparative examples.
  • 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.
  • 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 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. 19 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 200 according to this embodiment.
  • FIG. 20 is a schematic graph showing the distribution of the bandgap energy of the active layer 105 of the nitride-based semiconductor light-emitting device 200 according to the present embodiment and each layer in the vicinity thereof.
  • a 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 105, 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 bandgap energy of the P-side guide layer 206 monotonously increases with increasing distance from the active layer 105 , similarly to the P-side guide layer 106 according to the first embodiment. Also, the P-side guide layer 206 includes a portion where the bandgap energy continuously increases with distance from the active layer 105 . In this embodiment, the P-side guide layer 206 is an undoped In Xp Ga 1-Xp N layer, and the interface of the P-side guide layer 206 near the active layer 105 is separated from the center of the P-side guide layer 206 in the stacking direction.
  • the curve showing the relationship between the position in the stacking direction of the P-side guide layer 206 and the In composition ratio has a downward convex shape.
  • the curve showing the relationship between the position of the P-side guide layer 206 in the stacking direction and the bandgap energy has an upward convex shape (see FIG. 20).
  • the P-side guide layer 206 has a P-side first guide layer 206a and a P-side second guide layer 206b.
  • the P-side first guide layer 206a is an undoped In Xp Ga 1-Xp N layer with a thickness of 140 nm. More specifically, the P-side first guide layer 206a has a composition represented by In Xp1 Ga 1-Xp1 N near the interface near the active layer 105, and near the interface far from the active layer 105. has a composition represented by In X pm Ga 1-X pm N.
  • the In composition ratio Xp of the P-side first guide layer 206a decreases at a constant rate of change as the distance from the active layer 105 increases.
  • the P-side second guide layer 206b is an undoped In Xp Ga 1-Xp N layer with a thickness of 140 nm. More specifically, the P-side second guide layer 206b has a composition represented by In Xpm Ga 1-Xpm N near the interface near the active layer 105, and near the interface far from the active layer 105. has a composition represented by In Xp2 Ga 1-Xp2 N.
  • FIG. 21 is a graph showing simulation results of the distribution of the valence band potential and the hole Fermi level in the stacking direction of the nitride-based semiconductor light emitting device 200 according to the present embodiment.
  • FIG. 22 is a graph showing simulation results of carrier concentration distribution in the stacking direction of the nitride-based semiconductor light emitting device 200 according to the present embodiment.
  • the curve indicating the valence band potential in the P-side guide layer 206 can be made convex downward.
  • the curve indicating the hole Fermi level in the P-side guide layer 206 has a downward convex shape. Therefore, by making the curve indicating the valence band potential in the P-side guide layer 206 convex downward, the difference between the hole Fermi level and the valence band potential in the P-side guide layer 206 can It can be made more uniform than the P-side guide layer 106 according to the first embodiment. Therefore, as shown in FIG.
  • the concentration of holes in the region of the P-side guide layer 206, particularly near the active layer 105, can be reduced.
  • the free carrier loss in the P-side guide layer 206 can be further reduced.
  • the guide layer free carrier loss can be reduced to 1.7 cm ⁇ 1 and the waveguide loss can be reduced to 3.1 cm ⁇ 1 .
  • the effective refractive index difference ⁇ N is 1.9 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution are ⁇ 3.8 nm and ⁇ 3.8 nm, respectively. 15.8 nm and the difference ⁇ P is 12 nm.
  • the graph showing the IL characteristics is less likely to have non-linear portions.
  • FIG. 23 and 24 are graphs showing simulation results of the relationship between the average In composition ratio in the P-side guide layer 206, waveguide loss, and optical confinement factor ( ⁇ v), respectively, according to this embodiment.
  • the In composition ratio Xp1 near the interface of the P-side guide layer 206 near the active layer 105 is 4%
  • the In composition ratio Xp2 near the interface far from the active layer 105 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 105 increases. More specifically, in FIGS. 23 and 24, the average In composition ratio in the P-side guide layer 206 is changed by changing the In composition ratio Xpm in the central portion of the P-side guide layer 206 in the stacking direction. The waveguide loss and optical confinement factor for the case are shown. In the examples shown in FIGS. 23 and 24, when the average In composition ratio is less than 2%, the curve showing the relationship between the position in the lamination direction of the P-side guide layer 206 and the In composition ratio has a downward convex shape. becomes.
  • the case where the average In composition ratio is 1.5% corresponds to the nitride-based semiconductor light emitting device 200 according to the present embodiment
  • the case where the average In composition ratio is 2% corresponds to the nitridation according to the first embodiment. It corresponds to the material-based semiconductor light emitting device 100 .
  • FIG. 23 and FIG. 24 also show simulation results in the case where the In composition ratio in the P-side guide layer is uniform.
  • the In composition ratio in the P-side guide layer 206 increases.
  • the waveguide loss can be reduced and the optical confinement factor can be increased compared to the uniform case.
  • the average In composition ratio is less than 2%, the waveguide loss can be further reduced and the optical confinement factor can be increased.
  • FIG. 25 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the optical confinement coefficient ( ⁇ v) according to this embodiment.
  • FIG. 26 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the waveguide loss according to this embodiment.
  • FIG. 27 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the effective refractive index difference ⁇ N according to the present embodiment.
  • FIG. 28 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the position P1 according to this embodiment.
  • FIG. 29 is a graph showing simulation results of the relationship between the film thickness of the N-side guide layer 104 and the difference ⁇ P according to the present embodiment.
  • the sum of the film thicknesses of the N-side guide layer 104 and the P-side guide layer 206 was kept constant at 440 nm, each of the N-side guide layer 104 and the P-side guide layer 206 changing the film thickness.
  • the In composition ratio of the N-side guide layer 104 is 4%
  • the In composition ratio of the P-side guide layer 106 is 4% near the interface near the active layer 105
  • 4% near the interface far from the active layer 105 It is 0% in the vicinity and 1% in the central portion in the stacking direction of the P-side guide layer 206 .
  • 25 to 29 also show, as a comparative example, simulation results of an example in which the In composition ratio of the P-side guide layer is constant at 1.5%, as indicated by dashed lines.
  • the film thickness Tn of the N-side guide layer 104 may be 100 nm or more. This can prevent the light intensity distribution from moving too much from the active layer 105 toward the P-side guide layer 206 due to the film thickness Tn of the N-side guide layer 104 becoming too thin. Further, as shown in FIG. 25, even when the In composition ratio of the P-side guide layer 206 is kept constant at 1.5%, the film thickness of the N-side guide layer 104 is smaller than that of the P-side guide layer. However, if the In composition ratio is continuously and monotonously decreased as the distance from the active layer 105 increases, as in the P-side guide layer 206 according to this embodiment, can further increase the optical confinement factor.
  • the In composition ratio is lower when the In composition ratio is continuously and monotonically decreased as the distance from the active layer 105 increases. is constant at 1.5%, the waveguide loss can be reduced. Further, in the present embodiment, even when the film thickness of the N-side guide layer 104 is changed, the waveguide loss can be kept substantially constant at 3.2 cm ⁇ 1 or less.
  • the effective refractive index difference ⁇ N can be reduced.
  • the In composition ratio is continuously and monotonously decreased as the distance from the active layer 105 increases, as in the P-side guide layer 206 according to the present embodiment, the In The effective refractive index difference ⁇ N can be reduced more than when the composition ratio is constant at 1.5%.
  • the film thickness Tn of the N-side guide layer 104 may be 100 nm or more and 165 nm or less. In other words, the film thickness of the N-side guide layer 104 may be 23% or more and 38% or less of the sum of the film thicknesses of the N-side guide layer 104 and the P-side guide layer.
  • 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 film thickness of the N-side guide layer 104 is 23% or more and 38% or less of the sum of the film thicknesses of the N-side guide layer 104 and the P-side guide layer, and the distance dc is 40 nm, as shown in FIG.
  • the effective refractive index difference ⁇ N can be maintained within the range of 1.85 ⁇ 10 ⁇ 3 or more and 2.0 ⁇ 10 ⁇ 3 or less.
  • the thickness of the N-side guide layer 104 is greater than the thickness of the P-side guide layer 206.
  • the absolute value of the position P1 can be reduced by making it smaller, when the film thickness of the N-side guide layer is 160 nm or more, it becomes distant from the active layer 105 like the P-side guide layer 106 according to the present embodiment.
  • the absolute value of the position P1 can be further reduced when the In composition ratio is continuously and monotonously decreased according to .
  • 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 206 .
  • the difference ⁇ P can be made 13 nm or less.
  • the difference ⁇ P can be reduced. The difference ⁇ P can be further reduced.
  • each barrier layer of the active layer 105 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 206 .
  • the composition of each barrier layer is undoped GaN
  • the bandgap energy of each barrier layer is equal to or greater than the minimum bandgap energy of the N-side guide layer 104 and the P-side guide layer 206, and other configurations are used.
  • the nitride-based semiconductor light-emitting device of Comparative Example 5 shows the simulation results of the nitride-based semiconductor light-emitting device of Comparative Example 5, which is the same as the nitride-based semiconductor light-emitting device 100 according to the present embodiment.
  • the light confinement factor was 1.37%
  • the effective refractive index difference ⁇ N was 2.7 ⁇ 10 ⁇ 3
  • the peak positions P1 and P2 of the light intensity distribution were are 28.1 nm and 9.2 nm, respectively
  • the difference ⁇ P is 18.9 nm.
  • the waveguide loss is 4 cm ⁇ 1 and the free carrier loss in the N-side guide layer and the P-side guide layer is 2.5 cm ⁇ 1 .
  • the nitride-based semiconductor light-emitting device of Comparative Example 5 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-based semiconductor light-emitting device of the present embodiment. It is smaller than that of the physical semiconductor light emitting device 200 .
  • other evaluation indexes of the nitride-based semiconductor light-emitting device of Comparative Example 5 are also worse than those of the nitride-based semiconductor light-emitting device 200 according to the present embodiment, except for the position P2.
  • 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 206.
  • 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 3 A nitride-based semiconductor light-emitting device according to Embodiment 3 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. 30, focusing on differences from the nitride-based semiconductor light-emitting device 100 according to the first embodiment.
  • FIG. 30 is a schematic cross-sectional view showing the overall configuration of a 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 302, 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 309 , a P-type clad layer 110 and a contact layer 111 .
  • the N-type first clad layer 302 is an N-type Al 0.036 Ga 0.964 N layer with a thickness of 1200 nm.
  • the N-type first clad layer 302 is doped with Si at a concentration of 1 ⁇ 10 18 cm ⁇ 3 as an impurity.
  • the P-type cladding layer 110 is a P-type Al 0.026 Ga 0.974 N layer with a thickness of 450 nm as described above.
  • the N-type first cladding layer 302 and the P-type cladding layer 110 contain Al, and the Al composition ratios of the N-type first cladding layer 302 and the P-type cladding layer 110 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 302 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 laminated, Ync is 0.035, which is the average Al composition ratio of the entire N-type first clad layer 302 .
  • the P-type cladding layer 110 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 110 .
  • the refractive index of the N-type first clad layer 302 can be made lower than that of the P-type clad layer 110 . Therefore, even if the film thickness of the P-type clad layer 110 is reduced in order to reduce the operating voltage of the nitride-based semiconductor light-emitting device 300, the refractive index of the N-type first clad layer 302 is the same as that of the P-type clad layer 110. 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 lamination direction from the active layer 105 toward the N-type first clad layer 302 .
  • the electron barrier layer 309 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 309 is arranged between the intermediate layer 108 and the P-type cladding layer 110 .
  • the electron barrier layer 309 is a P-type AlGaN layer with a thickness of 5 nm. Further, the electron barrier layer 309 has an Al composition ratio increasing region in which the Al composition ratio monotonously increases as it approaches the P-type cladding layer 110 .
  • the configuration in which the Al composition ratio monotonously increases includes a configuration including a region in which the Al composition ratio is constant in the stacking direction.
  • the structure in which the Al composition ratio increases monotonously includes a structure in which the Al composition ratio increases stepwise.
  • the entire electron barrier layer 309 is the Al composition ratio increasing region, and the Al composition ratio increases at a constant rate of change in the stacking direction.
  • the electron barrier layer 309 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 110.
  • 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 110 .
  • the electron barrier layer 309 is doped with Mg at a concentration of 1 ⁇ 10 19 cm ⁇ 3 as an impurity.
  • the electron barrier layer 309 can prevent electrons from leaking from the active layer 105 to the P-type cladding layer 110 .
  • the electron barrier layer 309 has an Al composition ratio increasing region in which the Al composition ratio monotonically increases, the potential barrier of the valence band of the electron barrier layer 309 is reduced more than when the Al composition ratio is uniform. can. This facilitates the flow of holes from the P-type cladding layer 110 to the active layer 105 . Therefore, even when the thickness of the P-side guide layer 106, which is an undoped layer, is large as in this embodiment, an increase in electrical resistance of the nitride-based semiconductor light emitting device 300 can be suppressed.
  • the operating voltage of the nitride-based semiconductor light emitting device 300 can be reduced.
  • the temperature characteristics of the nitride-based semiconductor light-emitting device 300 can be improved. Therefore, the nitride-based semiconductor light emitting device 300 can operate at high output.
  • the effective refractive index difference ⁇ N is 1.9 ⁇ 10 ⁇ 3
  • the position P1 is 5.3 nm
  • the difference ⁇ P is 4.2 nm
  • the optical confinement coefficient to the active layer 105 is is 1.55%
  • waveguide loss is 3.6 cm ⁇ 1
  • guide layer free carrier loss is 2.4 cm ⁇ 1 .
  • 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 300 according to Embodiment 3 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. 31, focusing on differences from the nitride-based semiconductor light-emitting device 300 according to the third embodiment.
  • FIG. 31 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 400 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 400 according to the present embodiment includes a semiconductor laminate 400S, a current blocking layer 112, a P-side electrode 113, an N-side electrode 114, a translucent and a conductive film 420 .
  • the semiconductor laminate 400S includes a substrate 101, an N-type first clad layer 302, 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 309 , a P-type clad layer 410 and a contact layer 411 .
  • the P-type clad layer 410 is arranged between the electron barrier layer 309 and the contact layer 411 .
  • the P-type cladding layer 410 has a lower refractive index and a higher bandgap energy than the active layer 105 .
  • the P-type clad layer 410 is a P-type Al 0.026 Ga 0.974 N layer with a thickness of 330 nm.
  • the P-type cladding layer 410 is doped with Mg as an impurity. Also, the impurity concentration at the end of the P-type cladding layer 410 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 410 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 410R is formed in the P-type cladding layer 410 as in the nitride-based semiconductor light emitting device 300 according to the third embodiment. Also, the P-type cladding layer 410 is formed with two grooves 410T arranged along the ridge 410R and extending in the Y-axis direction.
  • the contact layer 411 is a layer arranged above the P-type cladding layer 410 and in ohmic contact with the P-side electrode 113 .
  • the contact layer 411 is a P-type GaN layer with a thickness of 10 nm.
  • the contact layer 411 is doped with Mg at a concentration of 1 ⁇ 10 20 cm ⁇ 3 as an impurity.
  • the translucent conductive film 420 is a conductive film that is arranged above the P-type cladding layer 410 and that transmits at least part of the light generated by the nitride-based semiconductor light emitting device 400 .
  • the light-transmitting conductive film 420 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 tin-doped indium oxide
  • Ga-doped zinc oxide Ga-doped zinc oxide
  • Al-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 translucent conductive film 420 may be formed at least above the P-type cladding layer 410 and may be formed between the current blocking layer 112 and the P-side electrode 113 .
  • the nitride-based semiconductor light-emitting device 400 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 420 is arranged above the P-type clad layer 410, the loss of light propagating above the P-type clad layer 410 can be reduced. As shown in FIG. 15, this effect is particularly remarkable when the thickness of the P-type cladding layer 410 is thin. Even if the film thickness of the P-type cladding layer 410 is reduced to 0.32 ⁇ m, a significant increase in waveguide loss can be suppressed. Furthermore, even if the thickness of the P-type cladding layer 410 is reduced to 0.25 ⁇ m, the increase in waveguide loss is 0.8 cm ⁇ 1 compared to the case where the thickness of the P-type cladding layer 410 is 0.6 ⁇ m.
  • the effective refractive index difference ⁇ N is 2.0 ⁇ 10 ⁇ 3
  • the position P1 is 1.4 nm
  • the difference ⁇ P is 4.0 nm
  • the optical confinement factor to the active layer 105 is is 1.51%
  • the waveguide loss is 3.8 cm ⁇ 1
  • the guide layer free carrier loss is 1.9 cm ⁇ 1 .
  • Embodiment 5 A nitride-based semiconductor light-emitting device according to Embodiment 5 will be described.
  • the nitride-based semiconductor light-emitting device according to this embodiment differs from the nitride-based semiconductor light-emitting device 300 according to the third 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. 32A and 32B, focusing on differences from the nitride-based semiconductor light-emitting device 300 according to the third embodiment.
  • FIG. 32A is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 500 according to this embodiment.
  • FIG. 32B is a cross-sectional view showing the configuration of an active layer 505 included in the nitride-based semiconductor light emitting device 500 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 500 includes a semiconductor stacked body 500S, a current blocking layer 112, a P-side electrode 113, an N-side electrode 114, a translucent and a conductive film 420 .
  • the semiconductor laminate 500S includes a substrate 101, an N-type first clad layer 302, an N-type second clad layer 103, an N-side guide layer 104, an active layer 505, a P-side guide layer 106, and an intermediate layer 108. , an electron barrier layer 309 , a P-type clad layer 110 and a contact layer 111 .
  • the active layer 505 according to the present embodiment 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
  • barrier layers 105a and 105c have the same configuration as barrier layers 105a and 105c according to the first embodiment.
  • the same effect as the nitride-based semiconductor light-emitting device 300 according to the third embodiment can be obtained.
  • the active layer 505 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 505 . Therefore, the optical confinement factor can be increased.
  • the effective refractive index difference ⁇ N is 2.1 ⁇ 10 ⁇ 3
  • the position P1 is 1.1 nm
  • the difference ⁇ P is 6.0 nm
  • the optical confinement factor in the active layer 505 is is 0.75%
  • the waveguide loss is 3.8 cm ⁇ 1
  • the guide layer free carrier loss is 2.4 cm ⁇ 1 .
  • the total film thickness of the active layer 505 is smaller than that of the active layer 105 according to the third embodiment by 8 nm.
  • 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 100 according to the first embodiment mainly in the configuration 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. 33 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 600 according to this embodiment.
  • FIG. 34 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 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, and an N-side electrode 114.
  • the semiconductor laminate 600S includes a substrate 101, an N-type first clad layer 602, an N-type second clad layer 103, an N-side guide layer 604, 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 610 and a contact layer 111 .
  • the N-type first clad layer 602 is an N-type Al 0.035 Ga 0.965 N layer with a thickness of 1200 nm.
  • the N-type first clad layer 602 is doped with Si at a concentration of 1 ⁇ 10 18 cm ⁇ 3 as an impurity.
  • the P-type clad layer 610 is arranged between the electron barrier layer 109 and the contact layer 111 .
  • the P-type cladding layer 610 has a lower refractive index and a higher bandgap energy than the active layer 105 .
  • the P-type clad layer 610 is a P-type Al 0.035 Ga 0.965 N layer with a thickness of 450 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 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 610R is formed in the P-type cladding layer 610 as in the nitride-based semiconductor light emitting device 100 according to the first 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 N-side guide layer 604 is an optical guide layer arranged above the N-type second clad layer 103 .
  • the N-side guide layer 604 has a higher refractive index and a lower bandgap energy than the N-type first clad layer 602 and the N-type second clad layer 103 .
  • the bandgap energy of the N-side guide layer 604 increases continuously and monotonically as the distance from the active layer 105 increases.
  • the N-side guide layer 604 is made of In Xn Ga 1-Xn N
  • the In composition ratio Xn of the N-side guide layer 604 monotonously decreases continuously with increasing distance from the active layer 105 .
  • the bandgap energy of the N-side guide layer 604 increases continuously and monotonically as the distance from the active layer 105 increases.
  • the N-side guide layer 604 is an N-type In Xn Ga 1-Xn N layer with a thickness of 160 nm. More specifically, the N-side guide layer 604 has a composition represented by In Xn1 Ga 1-Xn1 N near the interface on the side closer to the active layer 105 and In It has a composition represented by Xn2Ga1 -Xn2N . In this embodiment, the In composition ratio Xn1 near the interface of the N-side guide layer 604 near the active layer 105 is 4%, and the In composition ratio Xn2 near the interface far from the active layer 105 is 0%. be. The In composition ratio Xn of the N-side guide layer 604 decreases at a constant rate of change as the distance from the active layer 105 increases.
  • FIG. 35 and 36 are graphs showing simulation results of the relationship between the average In composition ratio in the N-side guide layer 604, the optical confinement factor ( ⁇ v), and the operating voltage, respectively, according to this embodiment.
  • the In composition ratio Xn1 near the interface of the N-side guide layer 604 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.
  • each figure shows the operating voltage when the amount of supplied current is 3 A as the operating voltage.
  • FIGS. 35 and 36 also show the results of simulation when the In composition ratio in the N-side guide layer is uniform, indicated by dashed lines.
  • the In composition ratio in the N-side guide layer is more uniform when the In composition ratio in the N-side guide layer 604 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 604 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.
  • FIG. 37 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light emitting device 100 according to Embodiment 1, and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction band potential.
  • FIG. 37 is a graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light emitting device 100 according to Embodiment 1, and the piezoelectric polarization charge density, piezoelectric polarization electric field, and conduction band potential.
  • FIGS. 37 and 38 are graph showing the relationship between the position in the stacking direction of the nitride-based semiconductor light emitting device 600 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. 37 and 38 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. 37 and 38 also show the hole Fermi level with a dashed line.
  • the piezoelectric polarization charge density of the N-side guide layer 104 of the nitride-based semiconductor light emitting device 100 according to Embodiment 1 is constant in the stacking direction. Therefore, the piezoelectric polarization charge density gap at each interface between the N-side guide layer 104 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 104 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.
  • the polarization charge density of the N-side guide layer 604 of the nitride-based semiconductor light emitting device 600 according to this embodiment is far from the interface on the side closer to the active layer 105. It monotonically decreases as it approaches the side interface. Therefore, gaps in the piezoelectric polarization charge density at each interface between the N-side guide layer 604 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 604 . Therefore, as shown in graph (b) of FIG.
  • the piezoelectric polarization electric field at each interface between the N-side guide layer 604 and the N-type second cladding layer 103 and active layer 105 can be suppressed.
  • holes are attracted near the interfaces between the N-side guide layer 604 and the N-type second cladding layer 103 and the active layer 105.
  • An increase in conduction band potential ( ⁇ E1 shown in graph (c) of FIG. 38) can be suppressed. Accordingly, in the nitride-based semiconductor light emitting device 600 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. 39, 40, and 41 show, respectively, the average In composition ratio in the N-side guide layer 604 of the nitride-based semiconductor light-emitting device 600 according to this embodiment, the optical confinement factor ( ⁇ v), waveguide loss, and operating voltage.
  • Graphs (a), (b), (c), and (d) of FIGS. 39 to 41 indicate that the impurity (Si) concentration in the N-side guide layer 604 is 0 (that is, undoped), 3 ⁇ , respectively. Simulation results for 10 17 cm ⁇ 3 , 6 ⁇ 10 17 cm ⁇ 3 and 1 ⁇ 10 18 cm ⁇ 3 are shown.
  • FIG. 41 shows, as the operating voltage, the operating voltage when the amount of supplied current is 3A.
  • FIGS. 39 to 41 show simulation results when the In composition ratio in the N-side guide layer is uniform, indicated by dashed lines.
  • the light confinement coefficient can increase
  • the light confinement coefficient in the nitride-based semiconductor light emitting device 600 according to this embodiment does not substantially depend on the impurity concentration.
  • the N-side guide layer has a uniform In composition ratio.
  • 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 energy bandgap distribution in the stacking direction of the N-side guide layer 604 .
  • 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 600, the electron concentration in the N-side guide layer 604 can be increased, so that the operating voltage can be further reduced.
  • the impurity concentration in the N-side guide layer 604 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.
  • the effective refractive index difference ⁇ N is 2.9 ⁇ 10 ⁇ 3
  • the position P1 is 15.9 nm
  • the difference ⁇ P is 6.2 nm
  • the active layer 105 A nitride-based semiconductor light-emitting device 600 having a light confinement factor of 1.44%, a waveguide loss of 3.4 cm ⁇ 1 , and a guide layer free carrier loss of 1.45 cm ⁇ 1 can be realized.
  • 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 100 according to the first embodiment mainly in the configuration of the P-type clad layer.
  • the nitride-based semiconductor light-emitting device according to the present embodiment will be described below with reference to FIG. 42, focusing on differences from the nitride-based semiconductor light-emitting device 100 according to the first embodiment.
  • FIG. 42 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light emitting device 700 according to this embodiment.
  • a nitride-based semiconductor light-emitting device 700 includes a semiconductor laminate 700S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114.
  • the semiconductor laminate 700S 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 709 , a P-type clad layer 710 and a contact layer 111 .
  • the electron barrier layer 709 is a P-type Al 0.36 Ga 0.64 N layer with a thickness of 1.6 nm.
  • the electron barrier layer 709 is doped with Mg at a concentration of 1.5 ⁇ 10 19 cm ⁇ 3 as an impurity.
  • the P-type clad layer 710 is arranged between the electron barrier layer 709 and the contact layer 111 .
  • the P-type cladding layer 710 has a lower refractive index and a higher bandgap energy than the active layer 105 .
  • a ridge 710R is formed in the P-type clad layer 710, like the P-type clad layer 110 according to the first embodiment.
  • the P-type cladding layer 710 is formed with two grooves 710T arranged along the ridge 710R and extending in the Y-axis direction.
  • the P-type cladding layer 710 is a P-type Al 0.026 Ga 0.974 N layer with a thickness of 450 nm.
  • the P-type clad layer 710 is doped with Mg as an impurity.
  • the impurity concentration at the end of the P-type cladding layer 710 closer to the active layer 105 is lower than the impurity concentration at the end farther from the active layer 105 .
  • the impurity concentration of the P-type cladding layer 710 has a region in which it monotonically increases with distance from the active layer 105 .
  • the configuration in which the impurity concentration monotonously increases includes a configuration in which there is a region in which the impurity concentration is constant in the stacking direction.
  • the P-type cladding layer 710 is a 150-nm- thick P-type Al 0.026 Ga 0 . 974 N layer and a 180 nm thick P-type Al 0.026 Ga 0.974 N layer doped with Mg at a concentration of 1 ⁇ 10 19 cm ⁇ 3 disposed thereabove and a concentration disposed thereabove. 120 nm thick P-type Al 0.026 Ga 0.974 N layer doped with 1.3 ⁇ 10 19 cm ⁇ 3 Mg.
  • the P-type cladding layer 710 includes a first layer closest to the active layer 105, a second layer having a higher impurity concentration than the first layer, and a second layer having a higher impurity concentration than the second layer. 3 layers.
  • the film thickness of the P-side guide layer 106 is larger than the film thickness of the N-side guide layer 104 .
  • the peak of the light intensity distribution in the lamination direction is distributed in the active layer 105 vicinity region, the spread of light to the P-type cladding layer 710 is suppressed. Therefore, the light intensity in the P-type cladding layer 710 is weak. Therefore, even if the Mg concentration in the region of the P-type cladding layer 710 near the contact layer 111 is increased, an increase in waveguide loss can be suppressed. Also, by increasing the Mg concentration, it is possible to reduce the series resistance of the nitride-based semiconductor light emitting device 700 (that is, the resistance between the P-side electrode 113 and the N-side electrode 114).
  • the Mg concentration is set to 1.3 ⁇ 10 ⁇ m in the region within 0.15 ⁇ m from the interface of the P-type cladding layer 710 with the contact layer 111 .
  • the light intensity is sufficiently reduced to the extent that an increase in waveguide loss can be suppressed even when the intensity is increased to 19 cm ⁇ 3 or more.
  • the Mg concentration in the P-type cladding layer 710 may be 1.6 ⁇ 10 19 cm ⁇ 3 or less. As a result, it is possible to suppress the decrease in carrier mobility caused by excessively increasing the Mg concentration, thereby suppressing the increase in series resistance.
  • the thickness of the P-side guide layer 106 is 250 nm or more, the light intensity in the P-type clad layer 710 is further weakened. , it is possible to suppress an increase in waveguide loss.
  • the Mg concentration in the P-type cladding layer 710 does not have to be changed stepwise in the stacking direction, and may be changed continuously.
  • the Mg concentration in the P-type cladding layer 710 may have the following configuration. At the interface of the P-type clad layer 710 closer to the active layer 105 , the Mg concentration is approximately equal to the Mg concentration of 1.5 ⁇ 10 19 cm ⁇ 3 in the electron barrier layer 709 . As the distance from the interface of the P-type cladding layer 710 is within 100 nm, the Mg concentration reaches the range of 1 ⁇ 10 18 cm ⁇ 3 to 3 ⁇ 10 18 cm ⁇ 3 or less. Therefore, the Mg concentration may decrease monotonically.
  • the P-type cladding layer 710 may have a decreasing concentration region in the region closest to the active layer 105 where the impurity concentration monotonically decreases as the distance from the active layer 105 increases. Furthermore, the P-type clad layer 710 may have a low-concentration region located above the reduced-concentration region, having a small change in Mg concentration in the stacking direction, and having the lowest Mg concentration in the P-type clad layer 710 . In the low-concentration region, for example, the Mg concentration is 1 ⁇ 10 18 cm ⁇ 3 or more and 3 ⁇ 10 18 cm ⁇ 3 or less.
  • the P-type cladding layer 710 may have a concentration increasing region located above the low concentration region, where the Mg concentration monotonically increases as the distance from the active layer 105 increases.
  • concentration increasing region for example, the Mg concentration monotonously increases from the range of 1 ⁇ 10 18 cm ⁇ 3 to 3 ⁇ 10 18 cm ⁇ 3 to 1.3 ⁇ 10 19 cm ⁇ 3 .
  • the concentration increasing region may have a high increasing rate region arranged on the side closer to the active layer 105 and a low increasing rate region arranged above the high increasing rate region.
  • the rate of change in the stacking direction of the Mg concentration in the high increase rate region is greater than the rate of change in the stacking direction of the Mg concentration in the low increase rate region.
  • the effective refractive index difference ⁇ N is 1.9 ⁇ 10 ⁇ 3
  • the position P1 is 3.6 nm
  • the difference ⁇ P is 2.8 nm
  • the optical confinement factor to the active layer 105 is is 1.54%
  • waveguide loss is 3.6 cm ⁇ 1
  • guide layer free carrier loss is 2.4 cm ⁇ 1 .
  • Embodiment 8 A nitride-based semiconductor light-emitting device according to Embodiment 8 will be described.
  • the nitride-based semiconductor light-emitting device according to this embodiment differs from the nitride-based semiconductor light-emitting device 700 according to the seventh embodiment in the structure of the electron barrier layer.
  • the nitride-based semiconductor light-emitting device according to this embodiment will be described below with reference to FIGS. 43 and 44, focusing on differences from the nitride-based semiconductor light-emitting device 700 according to the seventh embodiment.
  • FIG. 43 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 800 according to this embodiment.
  • FIG. 44 is a graph showing distribution of the Al composition ratio in the stacking direction of the electron barrier layer 809 according to this embodiment. The horizontal axis of the graph shown in FIG. 44 indicates the position x in the stacking direction, and the vertical axis indicates the Al composition ratio.
  • FIG. 44 also shows the Al composition ratio distribution in the intermediate layer 108 and part of the P-type clad layer 710 together with the electron barrier layer 709 .
  • 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 106, and an intermediate layer 108. , an electron barrier layer 809 , a P-type clad layer 710 and a contact layer 111 .
  • the electron barrier layer 809 is a P-type AlGaN layer.
  • the electron barrier layer 809 is doped with Mg at a concentration of 1.5 ⁇ 10 19 cm ⁇ 3 as an impurity.
  • the electron barrier layer 809 is arranged above the increased Al composition ratio region in which the Al composition ratio monotonically increases as it approaches the P-type clad layer 110 and the increased Al composition ratio region, and as it approaches the P-type clad layer 710 and an Al composition ratio decreasing region in which the Al composition ratio monotonously decreases.
  • the configuration in which the Al composition ratio monotonously decreases includes a configuration including a region in which the Al composition ratio is constant in the stacking direction.
  • the structure in which the Al composition ratio monotonically decreases includes a structure in which the Al composition ratio decreases stepwise.
  • the film thickness of the electron barrier layer 809 is 5 nm or less.
  • the thickness of the Al composition ratio increased region is 2 nm or less.
  • the film thickness of the Al composition ratio decreasing region is larger than the film thickness of the Al composition ratio increasing region.
  • the film thickness of the region having the maximum Al composition ratio in the electron barrier layer 809 is 0.5 nm or less.
  • the region with the maximum Al composition ratio means a region where the Al composition ratio is 95% or more of the maximum value of the Al composition ratio in the electron barrier layer 809 .
  • the graph shown in FIG. 44 shows straight lines g(x) and h(x) together with a curve f(x) showing the distribution of the Al composition ratio with respect to the position in the stacking direction of the electron barrier layer 809 .
  • the positive piezoelectric polarization charge formed at the interface between the electron barrier layer 809 and the intermediate layer 108 is reduced to the Al composition ratio It can be distributed over an increase area. Accordingly, the concentration of electrons attracted by positive piezoelectric polarization charges is reduced at the interface between the electron barrier layer 809 and the intermediate layer 108 . As a result, a decrease in the potential energy of the valence band at the interface between the electron barrier layer 809 and the intermediate layer 108 can be suppressed. As a result, the potential barrier against holes flowing from the P-type cladding layer 710 to the active layer 105 is reduced, and the operating voltage is reduced.
  • the film thickness of the region having the maximum Al composition ratio can be set to 0.5 nm or less, the potential barrier in the valence band for holes can be reduced, and the operating voltage can be reduced.
  • the film thickness of the electron barrier layer 809 is set to 5 nm or less.
  • the width (thickness) of the potential barrier of the valence band formed by the electron barrier layer 809 can be narrowed.
  • the electrical conduction barrier for holes from the P-type cladding layer 710 to the active layer 105 can be reduced, thereby reducing the operating voltage.
  • the thickness of the electron barrier layer 809 is less than 2 nm, the number of electrons flowing from the active layer 105 to the P-type cladding layer 710 over the electron barrier layer 809 increases. is.
  • the thickness of the decreased Al composition ratio region of the electron barrier layer 809 is set to 5 nm or less, while the thickness of the decreased Al composition ratio region of the electron barrier layer 809 is set to the thickness of the increased Al composition ratio region.
  • the positive piezoelectric polarization charge formed near the interface of the electron barrier layer 809 with the intermediate layer 108 is more likely to cause the change rate of the Al composition ratio than the region near the intermediate layer 108 where the change rate of the Al composition ratio is relatively small. becomes larger in regions where is relatively large.
  • the change rate of the Al composition ratio in the vicinity of the interface between the electron barrier layer 809 and the intermediate layer 108 can be reduced.
  • the width of the valence band potential barrier formed by the electron barrier layer 809 can be further narrowed.
  • the electrical conduction barrier for holes from the P-type cladding layer 710 to the active layer 105 can be reduced, and the operating voltage is reduced.
  • the Mg concentration in the electron barrier layer 809 may be 1.5 ⁇ 10 19 cm ⁇ 3 or less. Since the Al composition in the region of the electron barrier layer 809 closer to the active layer 105 (that is, the Al composition ratio increased region) is graded, even if the Mg concentration is 1.5 ⁇ 10 19 cm ⁇ 3 or less, the electron barrier layer The potential barrier for holes at 809 can be reduced. As a result, even if the Al composition ratio of the electron barrier layer 809 is increased to 30% or more, an increase in operating voltage can be suppressed.
  • the effect of suppressing the formation of a potential barrier in the valence band increases, making it possible to reduce the Mg concentration to 1 ⁇ 10 19 cm ⁇ 3 or less.
  • the Mg concentration may be 0.7 ⁇ 10 18 cm ⁇ 3 or higher. This can prevent the potential of the valence band of the electron barrier layer 809 from dropping too much.
  • the electron barrier layer 809 has a composition represented by Al 0.02 Ga 0.98 N near the interface with the intermediate layer 108 , and electrons
  • the Al composition ratio of the barrier layer 809 monotonously increases.
  • the electron barrier layer 809 has a composition represented by Al 0.36 Ga 0.64 N.
  • the electron barrier layer 809 has a composition represented by Al 0.026 Ga 0.974 N near the interface with the P-type cladding layer 710 .
  • the effective refractive index difference ⁇ N is 1.9 ⁇ 10 ⁇ 3
  • the position P1 is 3.6 nm
  • the difference ⁇ P is 2.8 nm
  • the optical confinement factor to the active layer 105 is is 1.54%
  • the waveguide loss is 3.6 cm ⁇ 1
  • the guide layer free carrier loss is 2.4 cm ⁇ 1 .
  • 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 nitride-based semiconductor light-emitting device due to the low waveguide loss effect and the optical confinement coefficient increasing effect in the active layer 105 of the nitride-based semiconductor light emitting device according to the present disclosure, optical amplification gain can be ensured even if the reflectance of the facet is reduced. 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 only a single well layer is included. It may be a structure.
  • the use of the N-side guide layer and the P-side guide layer of the present disclosure makes it possible to change the position of the light distribution in the vertical direction. Since the controllability can be enhanced, the peak of the light distribution in the vertical 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. 45 is a schematic cross-sectional view showing the overall configuration of a nitride-based semiconductor light-emitting device 900 according to Modification 1. As shown in FIG. As shown in FIG.
  • a nitride-based semiconductor light-emitting device 900 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 900 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 900 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 900 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 900, so that a high-power nitride-based semiconductor light-emitting device 900 can be realized.
  • the nitride-based semiconductor light-emitting device 900 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 900 It is not limited, and may be a nitride-based semiconductor light-emitting device according to another embodiment.
  • nitride-based semiconductor light-emitting device 900a 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.
  • 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 provided.
  • each P-type cladding layer 110, 410, 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 3 and 4.
  • the translucent conductive film according to the third embodiment may be applied to each of the nitride-based semiconductor light emitting devices according to the first and fourth 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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