Nitride semiconductor light-emitting element

Abstract

The nitride-based semiconductor light-emitting element (100) includes a semiconductor stack (100S), which has: an N-type first cladding layer (102), an N-side guiding layer (104), an active layer (105), a P-side first guiding layer (106), a P-side second guiding layer (107), and a P-type cladding layer (110). The band gap energy of the P-side second guiding layer (107) is greater than that of the N-side guiding layer (104), and the band gap energy of the N-side guiding layer (104) is greater than that of the P-side first guiding layer (106). When the film thickness of the P-side first guiding layer (106) is set to Tp1, the film thickness of the P-side second guiding layer (107) is set to Tp2, and the film thickness of the N-side guiding layer (104) is set to Tn1, the relationship Tn1 < Tp1 + Tp2 is satisfied.

Description

Technical Field

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

[0002] Previously, nitride-based semiconductor light-emitting elements have been used as light sources in processing equipment, etc. Higher output and efficiency are required in the light sources of processing equipment. To improve the efficiency of nitride-based semiconductor light-emitting elements, there are known techniques for reducing operating voltage (e.g., see Patent Document 1, etc.).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-131019 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In nitride-based semiconductor light-emitting devices, an effective way to reduce the operating voltage is to decrease the thickness of the P-type cladding layer. However, as the thickness of the P-type cladding layer decreases, the peak value of the light intensity distribution in the stacking direction (i.e., the growth direction of each semiconductor layer) shifts from the active layer to the N-type cladding layer. Therefore, the optical confinement factor for the active layer decreases, resulting in a lower thermal saturation level of light output. Consequently, achieving high output in nitride-based semiconductor light-emitting devices remains challenging.

[0008] In order to solve this problem, the present disclosure aims to provide a nitride-based semiconductor light-emitting element that can both reduce the operating voltage and improve the optical confinement factor for the active layer.

[0009] Methods for solving problems

[0010] To address the aforementioned issues, one embodiment of the nitride-based semiconductor light-emitting element disclosed herein includes a semiconductor stack that emits light from an end face perpendicular to the stacking direction of the semiconductor stack. The semiconductor stack comprises: an N-type first cladding layer; an N-side guiding layer disposed above the N-type first cladding layer; an active layer disposed above the N-side guiding layer, comprising a well layer and a barrier layer, and having a quantum well structure; and a P-side first guiding layer disposed above the active layer. A second guide layer on the P side is disposed above the first guide layer on the P side; and a P-type coating layer is disposed above the second guide layer on the P side. The band gap energy of the second guide layer on the P side is greater than the band gap energy of the guide layer on the N side, and the band gap energy of the guide layer on the N side is greater than the band gap energy of the first guide layer on the P side. When the film thickness of the first guide layer on the P side is set to Tp1, the film thickness of the second guide layer on the P side is set to Tp2, and the film thickness of the guide layer on the N side is set to Tn1, the relationship Tn1 < Tp1 + Tp2 is satisfied.

[0011] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the average refractive index of the first P-side guiding layer and the second P-side guiding layer is smaller than the average refractive index of the N-side guiding layer.

[0012] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the first guiding layer on the P-side is composed of In... Xp1 Ga 1-Xp1 N is composed of In. Xn1 Ga 1-Xn1 N forms a group that satisfies the relationship Xn1≤Xp1.

[0013] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the relationship Xn1 < Xp1 can be satisfied.

[0014] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the second guiding layer on the P-side is composed of In... Xp2 Ga 1-Xp2 N is composed of elements that satisfy the relationship Xp2 < Xn1.

[0015] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the barrier layer is composed of In... Xb Ga 1-Xb N constitutes a set of elements that satisfy the relationship Xp1 < Xb.

[0016] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the bandgap energy of the N-side guiding layer is greater than the bandgap energy of the P-side first guiding layer.

[0017] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the relationship Tp1 < Tp2 can be satisfied.

[0018] Furthermore, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the relationship Tp1 < Tn1 is satisfied.

[0019] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the peak of the light intensity distribution in the stacking direction may be located in the active layer.

[0020] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the impurity concentration in the end of the P-type cladding layer closer to the active layer is lower than the impurity concentration in the end of the P-type cladding layer farther from the active layer.

[0021] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, an electron blocking layer is provided between the second guiding layer on the P-side and the P-type cladding layer, the electron blocking layer having an Al composition variation region in which the Al composition ratio monotonically increases with distance from the active layer.

[0022] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the N-type first cladding layer and the P-type cladding layer contain Al, and when the Al composition ratios of the N-type first cladding layer and the P-type cladding layer are set to Ync and Ypc respectively, the relationship Ync > Ypc is satisfied.

[0023] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the thickness of the P-type cladding layer may be less than 460 nm.

[0024] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, a light-transmitting conductive film may be disposed above the P-type cladding layer.

[0025] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, an N-type second cladding layer is provided between the N-type first cladding layer and the N-side guiding layer, wherein the bandgap energy of the N-type second cladding layer is smaller than that of the N-type first cladding layer and larger than that of the P-side second guiding layer.

[0026] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, a plurality of light-emitting portions are arranged in a matrix.

[0027] Alternatively, in one embodiment of the nitride-based semiconductor light-emitting element disclosed herein, the reflectivity of the end face of the semiconductor stack is less than 0.1%.

[0028] The effects of the invention

[0029] This disclosure provides a nitride-based semiconductor light-emitting element that can both reduce the operating voltage and improve the optical confinement factor for the active layer. Attached Figure Description

[0030] Figure 1 This is a schematic plan view showing the overall configuration of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0031] Figure 2A This is a schematic cross-sectional view showing the overall structure of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0032] Figure 2B This is a schematic cross-sectional view showing the structure of the active layer of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0033] Figure 3 This is a schematic diagram showing a general outline of the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0034] Figure 4 It is a line graph showing the coordinates of the position in the stacking direction of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0035] Figure 5 This is a schematic line diagram showing the bandgap energy distribution and light intensity distribution in the stacking direction of the portion below the ridge of the nitride-based semiconductor light-emitting element in the comparative example.

[0036] Figure 6 This is a schematic line diagram showing the bandgap energy distribution and light intensity distribution in the stacking direction of the portion below the groove of the nitride-based semiconductor light-emitting element in the comparative example.

[0037] Figure 7 This is a line graph showing the simulation results of the light intensity distribution and refractive index distribution in the portion below the ridge of the nitride-based semiconductor light-emitting element in Comparative Example 1.

[0038] Figure 8This is a line graph showing the simulation results of the light intensity distribution and refractive index distribution in the portion below the ridge of the nitride-based semiconductor light-emitting element in Comparative Example 2.

[0039] Figure 9 This is a line graph showing the simulation results of the light intensity distribution and refractive index distribution in the portion below the ridge of the nitride-based semiconductor light-emitting element in Comparative Example 3.

[0040] Figure 10 This is a line graph showing the simulation results of the light intensity distribution and refractive index distribution in the portion below the ridge of the nitride-based semiconductor light-emitting element in Comparative Example 4.

[0041] Figure 11 This is a schematic line diagram showing the bandgap energy distribution and light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0042] Figure 12 This is a line graph showing the simulation results of the light intensity distribution and refractive index distribution of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0043] Figure 13 This is a line graph showing the simulation results of the relationship between the radiation angle and light intensity of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0044] Figure 14 This is a line graph showing the simulation results of the IL characteristics of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0045] Figure 15 This is a line graph showing the simulation results of the relationship between the In composition ratio and film thickness of the second guiding layer on the P side and various parameters when the In composition ratio of each barrier layer of the nitride-based semiconductor light-emitting element according to Embodiment 1 is 4%.

[0046] Figure 16 This is a line graph showing the simulation results of the relationship between the In composition ratio and film thickness of the second guiding layer on the P side and various parameters when the In composition ratio of each barrier layer of the nitride-based semiconductor light-emitting element according to Embodiment 1 is 0%.

[0047] Figure 17 This is a line graph showing the film thickness of the second guiding layer on the P side, the film thickness of the P-type cladding layer, and the relationship between various parameters of the nitride-based semiconductor light-emitting element in the comparative example.

[0048] Figure 18 This is a line graph showing the film thickness of the second guiding layer on the P side, the film thickness of the P-type cladding layer, and the relationship between various parameters of the nitride-based semiconductor light-emitting element according to Embodiment 1.

[0049] Figure 19 This is a schematic cross-sectional view showing the overall structure of the nitride-based semiconductor light-emitting element according to Embodiment 2.

[0050] Figure 20 This is a schematic cross-sectional view showing the overall structure of the nitride-based semiconductor light-emitting element according to Embodiment 3.

[0051] Figure 21A This is a schematic cross-sectional view showing the overall structure of the nitride-based semiconductor light-emitting element according to Embodiment 4.

[0052] Figure 21B This is a cross-sectional view showing the structure of the active layer of the nitride-based semiconductor light-emitting element according to Embodiment 4.

[0053] Figure 22 This is a schematic cross-sectional view showing the overall structure of the nitride-based semiconductor light-emitting element involved in Modified Example 1.

[0054] Figure 23 This is a schematic cross-sectional view showing the overall structure of the nitride-based semiconductor light-emitting element involved in Modified Example 2. Detailed Implementation

[0055] The embodiments of this disclosure will now be described with reference to the accompanying drawings. Furthermore, the embodiments described below are merely specific examples of this disclosure. Therefore, the numerical values, shapes, materials, constituent elements, and the arrangement and connection methods of the constituent elements shown in the following embodiments are all examples and are not intended to limit the scope of this disclosure.

[0056] Furthermore, these figures are schematic diagrams, not rigorous illustrations. Therefore, the scales and other parameters are not consistent across the figures. Additionally, substantially identical components are given the same symbols across the figures, and repetitive descriptions are omitted or simplified.

[0057] Furthermore, the terms "above" and "below" in this specification do not refer to the absolute spatial direction of upward (vertical above) and downward (vertical below), but are defined by relative positional relationships based on the stacking order in a layered composition. Moreover, the terms "above" and "below" apply not only to situations where two constituent elements are arranged with gaps between them and other constituent elements exist between them, but also to situations where two constituent elements are arranged in contact with each other.

[0058] (Implementation Method 1)

[0059] The nitride-based semiconductor light-emitting element according to Embodiment 1 will be described.

[0060] [1-1. Overall Composition]

[0061] First use Figure 1 , Figure 2A as well as Figure 2B The overall structure of the nitride-based semiconductor light-emitting element involved in this embodiment will be described. Figure 1 as well as Figure 2A These are schematic plan views and cross-sectional views showing the overall structure of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Figure 2A It shows Figure 1 The cross section at the IIA-IIA line. Figure 2B This is a schematic cross-sectional view showing the configuration of the active layer 105 of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Furthermore, the X-axis, Y-axis, and Z-axis are shown as mutually orthogonal axes. The X-axis, Y-axis, and Z-axis form a right-handed orthogonal coordinate system. The stacking direction of the nitride-based semiconductor light-emitting element 100 is parallel to the Z-axis direction, and the main emission direction of light (laser) is parallel to the Y-axis direction.

[0062] Nitride-based semiconductor light-emitting elements 100 Figure 2A As shown, a semiconductor stack 100S including a nitride-based semiconductor layer is provided. Light travels from the end face 100F (refer to) in a direction perpendicular to the stacking direction (i.e., the Z-axis direction) of the semiconductor stack 100S. Figure 1 In this embodiment, the nitride-based semiconductor light-emitting element 100 is a semiconductor laser element having two end faces 100F and 100R forming a resonator. End face 100F is the front end face that emits the laser, and end face 100R is the rear end face that has a higher reflectivity than end face 100F. In this embodiment, the reflectivities of end faces 100F and 100R are 16% and 95%, respectively. The resonator length (i.e., the distance between end faces 100F and 100R) of the nitride-based semiconductor light-emitting element 100 involved in this embodiment is approximately 1200 μm.

[0063] like Figure 2A As shown, the nitride-based semiconductor light-emitting element 100 includes: a semiconductor stack 100S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor stack 100S includes: a substrate 101, an N-type first cladding layer 102, an N-type second cladding layer 103, an N-side guiding layer 104, an active layer 105, a P-side first guiding layer 106, a P-side second guiding layer 107, an intermediate layer 108, an electron blocking layer 109, a P-type cladding layer 110, and a contact layer 111.

[0064] The substrate 101 is a plate-like component that serves as the base of the nitride-based semiconductor light-emitting device 100. In the present embodiment, the substrate 101 is an N-type GaN substrate.

[0065] The N-type first cladding layer 102 is an example of an N-type cladding layer disposed above the substrate 101. The N-type first cladding layer 102 is a layer having a smaller refractive index and a larger bandgap energy than the active layer 105. In the present embodiment, the N-type first cladding layer 102 is an N-type Al 0.035 Ga 0.965 N layer with a film thickness of 1200 nm. In the N-type first cladding layer 102, Si is doped as an impurity at a concentration of 1×10 18 cm -3 .

[0066] The N-type second cladding layer 103 is an example of an N-type cladding layer disposed above the substrate 101. In the present embodiment, the N-type second cladding layer 103 is disposed above the N-type first cladding layer 102. The N-type second cladding layer 103 is a layer having a smaller refractive index and a larger bandgap energy than the active layer 105. In the present embodiment, the N-type second cladding layer 103 is an N-type GaN layer with a film thickness of 100 nm. In the N-type second cladding layer 103, Si is doped as an impurity at a concentration of 1×10 18 cm -3 .

[0067] The N-side guiding layer 104 is an optical guiding layer disposed above the N-type second cladding layer 103. The N-side guiding layer 104 has a larger refractive index and a smaller bandgap energy than the N-type first cladding layer 102 and the N-type second cladding layer 103. In the present embodiment, the N-side guiding layer 104 is an undoped In 0.04 Ga 0.96 N layer with a film thickness of 160 nm.

[0068] The active layer 105 is a light-emitting layer having a quantum well structure disposed above the N-side guiding layer 104. In the present embodiment, as shown in Figure 2B , the active layer 105 has well layers 105b and 105d, and barrier layers 105a, 105c, and 105e.

[0069] The barrier layer 105a is a layer having a quantum well structure and serving as a barrier function disposed above the N-side guiding layer 104. In the present embodiment, the barrier layer 105a is an undoped In<​​​​​Well layer 105b is a layer disposed above barrier layer 105a and having a quantum well structure, serving as a potential well. Well layer 105b is disposed between barrier layer 105a and barrier layer 105c. In this embodiment, well layer 105b is an undoped In film with a thickness of 3 nm. 0.18 Ga 0.82 N layers.

[0071] The barrier layer 105c is a layer disposed above the well layer 105b and has a quantum well structure, serving as a barrier. In this embodiment, the barrier layer 105c is an undoped In film with a thickness of 7 nm. 0.05 Ga 0.95 N layers.

[0072] Well layer 105d is a layer disposed above barrier layer 105c and has a quantum well structure, functioning as a potential well. Well layer 105d is disposed between barrier layer 105c and barrier layer 105e. In this embodiment, well layer 105d is an undoped In film with a thickness of 3 nm. 0.18 Ga 0.82 N layers.

[0073] The barrier layer 105e is a layer disposed above the well layer 105d and having a quantum well structure, serving as a barrier. In this embodiment, the barrier layer 105e is an undoped In film with a thickness of 5 nm. 0.05 Ga 0.95 N layers.

[0074] The first P-side guiding layer 106 is a light guiding layer disposed above the active layer 105. Compared with the P-type cladding layer 110, the first P-side guiding layer 106 has a higher refractive index and a smaller band gap energy. In this embodiment, the first P-side guiding layer 106 is an undoped In film with a thickness of 80 nm. 0.045 Ga 0.955 N layers.

[0075] The second P-side guiding layer 107 is a light guiding layer disposed above the first P-side guiding layer 106. Compared with the P-type cladding layer 110, the second P-side guiding layer 107 has a higher refractive index and a lower band gap energy. In this embodiment, the second P-side guiding layer 107 is an undoped In film with a thickness of 195 nm. 0.01 Ga 0.99 N layers.

[0076] The intermediate layer 108 is a layer disposed above the active layer 105. In this embodiment, the intermediate layer 108 is disposed between the p-side second guiding layer 107 and the electron blocking layer 109 to reduce stress caused by the difference in lattice constants between the p-side second guiding layer 107 and the electron blocking layer 109. Accordingly, the occurrence of crystal defects in the nitride-based semiconductor light-emitting element 100 can be suppressed. In this embodiment, the intermediate layer 108 is an undoped GaN layer with a thickness of 20 nm.

[0077] The electron blocking layer 109 is a nitride-based semiconductor layer disposed above the active layer 105 and comprising at least Al. In this embodiment, the electron blocking layer 109 is disposed between the intermediate layer 108 and the p-type cladding layer 110. The electron blocking layer 109 is a p-type AlGaN layer with a thickness of 5 nm. Furthermore, the electron blocking layer 109 has an Al composition ratio tilt region where the Al composition ratio increases monotonically as it approaches the p-type cladding layer 110. Here, the configuration where the Al composition ratio increases monotonically also includes a region where the Al composition ratio remains unchanged in the stacking direction. For example, the configuration where the Al composition ratio increases monotonically also includes a configuration where the Al composition ratio increases in a stepwise manner. In the electron blocking layer 109 according to this embodiment, the entire electron blocking layer 109 is a region where the Al composition ratio increases, and the Al composition ratio increases at a certain rate of change in the stacking direction. Specifically, the electron blocking layer 109 has a region with Al composition ratio near the interface with the intermediate layer 108. 0.02 Ga 0.98 The component represented by N shows that the Al component ratio monotonically increases as it approaches the P-type coating layer 110, and there is an Al component near the interface with the P-type coating layer 110. 0.36 Ga 0.64 The component is represented by N. It is doped as an impurity in electron blocking layer 109 with a concentration of 1 × 10⁻⁶. 19 cm -3 Mg.

[0078] The electron blocking layer 109 suppresses electron leakage from the active layer 105 to the P-type cladding layer 110. Furthermore, since the electron blocking layer 109 has an Al composition variation region where the Al composition ratio monotonically increases, the valence band barrier of the electron blocking layer 109 is lowered compared to the case where the Al composition ratio remains unchanged. Consequently, holes can easily flow from the P-type cladding layer 110 to the active layer 105. Therefore, as shown in this embodiment, even when the combined thickness of the undoped layers, i.e., the first P-side guiding layer 106 and the second P-side guiding layer 107, increases, the increase in impedance of the nitride-based semiconductor light-emitting element 100 can be suppressed. Consequently, the operating voltage of the nitride-based semiconductor light-emitting element 100 can be reduced. Furthermore, since the heat generated by the nitride-based semiconductor light-emitting element 100 during operation can be reduced, the temperature characteristics of the nitride-based semiconductor light-emitting element 100 can be improved. Consequently, the nitride-based semiconductor light-emitting element 100 can operate with high output.

[0079] The P-type cladding layer 110 is a P-type cladding layer disposed above the active layer 105. In this embodiment, the P-type cladding layer 110 is disposed between the electron blocking layer 109 and the contact layer 111. The P-type cladding layer 110 is a layer with a lower refractive index and a higher band gap energy compared to the active layer 105. The film thickness of the P-type cladding layer 110 can be 460 nm or less. Accordingly, the impedance of the nitride-based semiconductor light-emitting element 100 can be suppressed. Therefore, the operating voltage of the nitride-based semiconductor light-emitting element 100 can be reduced. Furthermore, since the heat generated by the nitride-based semiconductor light-emitting element 100 during operation can be reduced, the temperature characteristics of the nitride-based semiconductor light-emitting element 100 can be improved. Accordingly, the nitride-based semiconductor light-emitting element 100 can operate with high output. Furthermore, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, in order to fully utilize the function of the P-type cladding layer 110 as a cladding layer, the film thickness of the P-type cladding layer 110 only needs to be 200 nm or more. Moreover, the film thickness of the P-type cladding layer 110 can also be 250 nm or more. In this embodiment, the P-type cladding layer 110 is a P-type Al with a film thickness of 450 nm. 0.035 Ga 0.965 N-layer. Mg is doped as an impurity in the P-type coating layer 110. Furthermore, the impurity concentration in the end of the P-type coating layer 110 closer to the active layer 105 is lower than the impurity concentration in the end farther from the active layer 105. Specifically, the P-type coating layer 110 has a doping concentration of 2 × 10⁻⁶ on the side disposed closer to the active layer 105. 18 cm -3 The Mg film thickness is 150 nm for P-type Al 0.035 Ga 0.965 The N layer, and the doped layer with a concentration of 1×10⁵ located on the side furthest from the active layer 105.19 cm -3 The Mg film thickness is 300 nm for P-type Al 0.035 Ga 0.965 N layers.

[0080] A ridge 110R is formed in the P-type cladding layer 110 of the nitride-based semiconductor light-emitting element 100. Two grooves 110T extending in the Y-axis direction and arranged along the ridge 110R are formed in the P-type cladding layer 110. In this embodiment, the ridge width W is approximately 30 μm. Figure 2A As shown, the distance between the lower end of the ridge 110R (i.e., the bottom of the groove 110T) and the active layer 105 is set as dp. Furthermore, the film thickness of the P-type coating layer 110 in the lower end of the ridge 110R (i.e., the distance between the lower end of the ridge 110R and the interface between the P-type coating layer 110 and the electron blocking layer 109) is set as dc.

[0081] Contact layer 111 is a layer disposed above the P-type cladding layer 110 and in ohmic contact with the P-side electrode 113. In this embodiment, contact layer 111 is a P-type GaN layer with a thickness of 100 nm. Contact layer 111 is doped with a concentration of 1 × 10⁻⁶ as an impurity. 20 cm -3 Mg.

[0082] The current blocking layer 112 is an insulating layer disposed above the P-type cladding layer 110, and is transmissive to light from the active layer 105. The current blocking layer 112 is disposed in the area of ​​the upper surface of the P-type cladding layer 110, excluding the upper surface of the ridge 110R. In this embodiment, the current blocking layer 112 is a SiO2 layer.

[0083] The P-side electrode 113 is a conductive layer disposed above the contact layer 111. In this embodiment, the P-side electrode 113 is disposed 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 formed of at least one of Cr, Ti, Ni, Pd, Pt, and Au.

[0084] The N-side electrode 114 is a conductive layer disposed below the substrate 101 (i.e., the main surface of the substrate 101 opposite to the main surface where the N-type first cladding layer 102 is disposed). The N-side electrode 114 is, for example, a single-layer film or a multilayer film formed of at least one of Cr, Ti, Ni, Pd, Pt and Au.

[0085] The nitride-based semiconductor light-emitting element 100, by having the above-described configuration, therefore... Figure 2AAs shown, an effective refractive index difference ΔN is generated between the portion below the ridge 110R and the portion below the groove 110T. Accordingly, light generated in the portion below the ridge 110R of the active layer 105 can be confined to the horizontal direction (i.e., the X-axis direction).

[0086] [1-2. Light intensity distribution and stability of light output]

[0087] Next, the light intensity distribution and light output stability of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be described.

[0088] First, using Figure 3 The light intensity distribution along the stacking direction (Z-axis direction in each figure) of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be described. Figure 3 This is a schematic diagram showing the light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Figure 3 It is both a cross-sectional view showing the nitride-based semiconductor light-emitting element 100 in a schematic diagram and a line drawing showing the outline of the light intensity distribution in the stacking direction at the positions corresponding to the ridge 110R and the groove 110T, respectively.

[0089] In typical nitride-based semiconductor light-emitting devices, although light is generated in the active layer, the light intensity distribution in the stacking direction depends on the stacking structure; therefore, the peak of the light intensity distribution may not be located in the active layer. Furthermore, since the stacking structure of the nitride-based semiconductor light-emitting device 100 according to this embodiment differs between the portion below the ridge 110R and the portion below the trench 110T, the light intensity distribution below the ridge 110R and the portion below the trench 110T also differs. Figure 3 As shown, the peak position of the light intensity distribution in the horizontal direction (i.e., the X-axis direction) at the center of the portion below the ridge 110R is set as PS1. Furthermore, the peak position of the light intensity distribution in the stacking direction of the portion below the groove 110T is set as PS2. Here, using... Figure 4 Explanation of positions PS1 and PS2. Figure 4 This is a line graph showing the coordinates of the positions of the nitride-based semiconductor light-emitting element 100 according to this embodiment in the stacking direction. Figure 4 As shown, the coordinates of the N-side end face of the well layer 105b of the active layer 105 are set to zero. That is, the coordinates of the end face of the well layer 105b closest to the N-side guide layer 104 in the stacking direction are set to zero. The downward direction (towards the N-side guide layer 104) is set to the negative coordinate direction, and the upward direction (towards the P-side first guide layer 106) is set to the positive coordinate direction. Furthermore, the absolute value of the difference between position PS1 and position PS2 is set as the difference ΔP between the peak positions.

[0090] In the nitride-based semiconductor light-emitting element 100 according to this embodiment, the thickness of the P-type cladding layer 110 is set to be relatively thin in order to reduce the operating voltage. Correspondingly, the height of the ridge 110R (i.e., the height starting from the bottom surface of the groove 110T of the ridge 110R) is also set to be relatively low. Generally, in semiconductor light-emitting elements with this configuration, the peak position of the light intensity distribution in the stacking direction deviates from the active layer towards the direction closer to the N-type cladding layer. Therefore, the optical confinement factor for the active layer is reduced, thereby reducing the thermal saturation level of light output. As a result, it becomes difficult for the semiconductor light-emitting element to operate at high output. In this embodiment, the bandgap energy of the second P-side guiding layer 107 is greater than the bandgap energy of the N-side guiding layer 104, and the bandgap energy of the N-side guiding layer 104 is greater than or equal to the bandgap energy of the first P-side guiding layer 106. Furthermore, when the film thickness of the first guiding layer 106 on the P side is set to Tp1, the film thickness of the second guiding layer 107 on the P side is set to Tp2, and the film thickness of the guiding layer 104 on the N side is set to Tn1, the following relationship (1) is satisfied.

[0091] Tn1<Tp1+Tp2 (1)

[0092] Therefore, in the nitride-based semiconductor light-emitting element 100, the bandgap energy of the N-side guiding layer 104 is higher than the bandgap energy of the P-side first guiding layer 106. Specifically, the P-side first guiding layer 106 is composed of In... Xp1 Ga 1-Xp1 N-structure, N-side guiding layer 104 is composed of In Xn1 Ga 1-Xn1 N is composed of the following relationship (2).

[0093] Xn1≤Xp1 (2)

[0094] Therefore, the refractive index of the N-side guiding layer 104 is lower than that of the P-side first guiding layer 106. Accordingly, for example, compared to the case where the refractive index of the N-side guiding layer 104 is greater than that of the P-side first guiding layer 106, the light intensity distribution can be shifted from the active layer 105 toward the direction closer to the P-side first guiding layer 106.

[0095] In this embodiment, the In component ratios Xn1 and Xp1 of the N-side guide layer 104 and the P-side first guide layer 106 satisfy the relationship shown in (3) below.

[0096] Xn1<Xp1 (3)

[0097] More specifically, the N-side guide layer 104 is In 0.04 Ga 0.96 N layer, P side first guide layer 106 is In 0.045 Ga0.955 N-layer. Here, in the InGaN layer, as the In composition ratio increases, the band gap energy decreases and the refractive index increases. Therefore, the band gap energy of the N-side guiding layer 104 is greater than that of the P-side first guiding layer 106. That is, the refractive index of the N-side guiding layer 104 is smaller than that of the P-side first guiding layer 106. Accordingly, for example, compared to the case where the refractive index of the N-side guiding layer 104 is greater than or equal to that of the P-side first guiding layer 106, the light intensity distribution can be shifted from the active layer 105 towards the direction closer to the P-side first guiding layer 106.

[0098] Furthermore, as described above, the sum of the film thickness Tp1 of the first guiding layer 106 on the P-side and the film thickness Tp2 of the second guiding layer 107 on the P-side is greater than the film thickness Tn1 of the guiding layer 104 on the N-side. Thus, by making the sum of the film thicknesses of the first guiding layer 106 and the second guiding layer 107 on the P-side, which have relatively high refractive indices, greater than the film thickness Tn1 of the guiding layer 104 on the N-side, compared to the case where the sum of the film thicknesses of the first guiding layer 106 and the second guiding layer 107 on the P-side is less than or equal to the film thickness Tn1 of the guiding layer 104 on the N-side, it is possible to shift the light intensity distribution from the active layer 105 towards the direction closer to the first guiding layer 106 on the P-side. Therefore, it is possible to suppress the deviation of the peak value of the light intensity distribution in the stacking direction from the active layer 105 towards the direction closer to the N-type second cladding layer 103. Here, the band gap energy of the second guiding layer 107 on the P-side is greater than the band gap energy of the guiding layer 104 on the N-side. That is, the refractive index of the second guiding layer 107 on the P side is smaller than the refractive index of the guiding layer 104 on the N side. Accordingly, it is possible to suppress the light intensity distribution from the active layer 105 from shifting too far toward the P-type coating layer 110.

[0099] Furthermore, as described above, the bandgap energy of the second guiding layer 107 on the P side is greater than that of the guiding layer 104 on the N side. Specifically, the second guiding layer 107 on the P side is composed of In... Xp2 Ga 1-Xp2 The N-structure has an In composition ratio Xp2 of the second guide layer 107 on the P side and an In composition ratio Xn1 of the guide layer 104 on the N side, which satisfy the following relationship (4).

[0100] Xp2<Xn1 (4)

[0101] More specifically, the N-side guide layer 104 is In 0.04 Ga 0.96 N layer, P side second guide layer 107 is In 0.01 Ga 0.99 N-layer. Therefore, the refractive index of the N-side guiding layer 104 is greater than that of the P-side second guiding layer 107. Accordingly, it is possible to suppress the light intensity distribution from the active layer 105 from shifting too far toward the P-type coating layer 110.

[0102] Furthermore, in this embodiment, the barrier layers 105a, 105c, and 105e of the active layer 105 are made of In Xb Ga 1-Xb The N composition has the following relationship as shown in (5) regarding the In composition ratios Xb and Xp1 of each barrier layer and the first guiding layer 106 on the P side.

[0103] Xp1<Xb (5)

[0104] Accordingly, the refractive index of each barrier layer can be made greater than that of the first guiding layer 106 on the P side and the guiding layer 104 on the N side. Accordingly, the peak of the light intensity distribution in the stacking direction can be located in the active layer 105. Furthermore, it is possible to suppress the light intensity distribution from the active layer 105 from shifting too far toward the P-type cladding layer 110.

[0105] Furthermore, in this embodiment, the average refractive index of the first guide layer 106 and the second guide layer 107 on the P side is smaller than the average refractive index of the guide layer 104 on the N side. Accordingly, it is possible to suppress the light intensity distribution from the active layer 105 from shifting too far toward the P-type coating layer 110.

[0106] Furthermore, in this embodiment, the film thicknesses Tp1 and Tp2 of the first guiding layer 106 on the P side and the second guiding layer 107 on the P side satisfy the relationship shown in (6) below.

[0107] Tp1<Tp2 (6)

[0108] Thus, due to the low bandgap energy, i.e., by making the thickness of the P-side first guiding layer 106 with a high refractive index relatively small, it is possible to suppress the light intensity distribution from the active layer 105 from shifting too far towards the P-type cladding layer 110. Furthermore, by making the thickness of the P-side first guiding layer 106 with a low In composition relatively small, it is possible to avoid placing the P-side first guiding layer 106 with a low In composition and a large film thickness near the well layers 105b and 105d within the semiconductor stack 100S, where the In composition ratio is at its maximum. Therefore, the occurrence of lattice defects can be suppressed.

[0109] Furthermore, in this embodiment, the film thicknesses Tp1 and Tn1 of the first guiding layer 106 on the P side and the guiding layer 104 on the N side satisfy the relationship shown in (7) below.

[0110] Tp1<Tn1 (7)

[0111] Thus, due to the small band gap energy, that is, by making the thickness of the first guiding layer 106 on the P side with a large refractive index smaller than the thickness of the guiding layer 104 on the N side, it is possible to suppress the light intensity distribution from the active layer 105 to move too close to the P-type coating layer 110.

[0112] In this embodiment, the bandgap energy of the N-type second cladding layer 103 is smaller than that of the N-type first cladding layer 102 and larger than that of the P-side second guiding layer 107. Because its bandgap energy is smaller than that of the N-type first cladding layer 102, that is, by distributing the N-type second cladding layer 103 with a higher refractive index between the N-type first cladding layer 102 and the N-side guiding layer 104, it is possible to suppress the light intensity distribution from the active layer 105 from shifting too far towards the P-type cladding layer 110. Furthermore, by making the bandgap energy of the N-type second cladding layer 103 greater than that of the P-side second guiding layer 107, it is possible to suppress the light intensity distribution from the active layer 105 from shifting too far towards the N-type second cladding layer 103.

[0113] With the configuration described above, in this embodiment, the peak position PS1 of the light intensity distribution in the stacking direction below the ridge 110R can be set to 2.5 nm. That is, the peak of the light intensity distribution can be located in the active layer 105. Furthermore, ΔP can be suppressed to 6.4 nm. Accordingly, the optical confinement factor for the active layer 105 can be increased to approximately 1.45%.

[0114] As described above, the nitride-based semiconductor light-emitting element 100 according to this embodiment enables the peak value of the light intensity distribution in the stacking direction to be located in the active layer 105. Furthermore, "the peak value of the light intensity distribution in the stacking direction is located in the active layer 105" means that the peak value 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 element 100, and is not limited to the state where the peak value of the light intensity distribution in the stacking direction is located in the active layer 105 at all positions in the horizontal direction.

[0115] As shown in this embodiment, when the peak of the light intensity distribution in the stacking direction is located in the active layer 105, compared to the case where the peak of the light intensity distribution is located in the N-side guiding layer 104, the proportion of the light in the P-type cladding layer 110 can be increased. Here, since 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, increasing the proportion of the light in the P-type cladding layer 110 may increase the free carrier loss in the P-type cladding layer 110. However, in this embodiment, the P-side first guiding layer 106 and the P-side second guiding layer 107 are undoped layers, and by making the sum of the film thickness Tp1 of the P-side first guiding layer 106 and the film thickness Tp2 of the P-side second guiding layer 107 larger, the proportion of the light intensity distribution in the undoped layer can be increased. Therefore, the increase in free carrier loss can be suppressed. Specifically, in this embodiment, waveguide loss can be suppressed to 1.6 cm. -1 about.

[0116] Furthermore, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, in order to reduce the diffusion angle of the emitted light in the horizontal direction (i.e., the X-axis direction), the effective refractive index difference ΔN between the portion below the ridge 110R and the portion below the groove 110T is set to be relatively small. Specifically, the effective refractive index difference ΔN is adjusted by adjusting the distance dp between the current blocking layer 112 and the active layer 105 (refer to...). Figure 2A This is determined by the distance dp. Here, the greater the distance dp, the smaller the effective refractive index difference ΔN. In this embodiment, the effective refractive index difference ΔN is 2.4 × 10⁻⁶. -3 Approximately. Therefore, in this embodiment, the ratio of the effective refractive index difference ΔN to 2.4 × 10⁻⁶ is... -3 Compared to larger cases, the number of higher-order modes (i.e., higher-order transverse modes) that can propagate in the waveguide formed by the ridge 110R is smaller. Therefore, among all the transverse modes included in the emitted light of the nitride-based semiconductor light-emitting element 100, the proportion of higher-order modes is relatively large. Consequently, the change in the optical confinement factor of the active layer 105 due to the increase or decrease in the number of modes and inter-mode coupling is relatively large. Therefore, when the number of modes increases or decreases and inter-mode coupling occurs in the nitride-based semiconductor light-emitting element 100, the linearity of the light output characteristic (so-called IL characteristic) relative to the supplied current decreases. In other words, a non-linear portion (so-called kink) is generated in the line graph showing the IL characteristic. Correspondingly, the stability of the light output of the nitride-based semiconductor light-emitting element 100 decreases.

[0117] The following will explain the decrease in light output stability. In the nitride-based semiconductor light-emitting element 100, the light intensity distribution below the ridge 110R is dominated by the fundamental mode (i.e., the 0th-order mode), while the light intensity distribution below the groove 110T is dominated by higher-order modes. Therefore, when the difference ΔP between the peak position PS1 of the light intensity distribution in the stacking direction below the ridge 110R and the peak position PS2 of the light intensity distribution in the stacking direction below the groove 110T is large, the stability of light output decreases due to changes in the optical confinement factor for the active layer 105 when the number of modes increases or decreases and inter-mode coupling occurs.

[0118] For example, when the number of higher-order modes decreases, the peak value of the light intensity distribution after adding the light intensity distributions in the lower portions of both the ridge 110R and the groove 110T shifts to a position closer to position PS1. Therefore, the larger the difference ΔP between position PS1 and position PS2, the greater the variation in the optical confinement factor of the active layer 105 under the change in the number of modes. Consequently, the stability of the light output decreases.

[0119] In the nitride-based semiconductor light-emitting element 100 according to this embodiment, since it has an N-side guiding layer 104, a P-side first guiding layer 106, and a P-side second guiding layer 107 with the above-described configuration, the peak value of the light intensity distribution can be located in the active layer 105 in both the portion below the ridge 110R and the portion below the groove 110T. That is, the difference ΔP between the position PS1 and the position PS2 of the peak value of the light intensity distribution can be reduced. Accordingly, even if the number of modes increases or decreases and inter-mode coupling occurs, the variation in the position of the peak value of the light intensity distribution in the stacking direction after adding the light intensity distributions of the portions below the ridge 110R and the groove 110T can be suppressed. Therefore, the stability of light output can be improved.

[0120] Furthermore, as mentioned above, to set a relatively small effective refractive index difference ΔN, the distance dp must be set to a relatively large value. When setting the distance dp, if the lower end of the ridge 110R (i.e., the bottom of the groove 110T) is positioned below the electron blocking layer 109, the high bandgap energy of the electron blocking layer 109 will cause holes injected from the contact layer 111 to easily leak from the sidewalls of the ridge 110R to the outside of the ridge 110R as they pass through the electron blocking layer 109. This results in holes flowing into the lower part of the groove 110T. Correspondingly, in the active layer 105 below the groove 110T, the low light distribution intensity reduces the radiative recombination probability of electrons and holes injected into the active layer 105, while increasing non-radiative recombination. Consequently, the nitride-based semiconductor light-emitting element 100 is prone to degradation. Therefore, the lower end of the ridge 110R is positioned above the electron blocking layer 109. Furthermore, if the distance dc from the lower end of the ridge 110R to the electron blocking layer 109 is... Figure 2A If the distance dc is too large, holes will flow from the ridge 110R into the space between the groove 110T and the electron blocking layer 109, resulting in leakage current. To suppress the increase of this leakage current, the distance dc is set to the smallest possible value.

[0121] [1-3. Effects]

[0122] Regarding the effects of the nitride-based semiconductor light-emitting element 100 according to the above embodiment, a comparison will be made with the nitride-based semiconductor light-emitting element in the comparative example, and the effects will be utilized... Figures 5 to 12 Let me explain. Figure 5 as well as Figure 6 These are schematic line diagrams showing the bandgap energy distribution and light intensity distribution in the stacking direction of the portion below the ridge 110R and the portion below the groove 110T of the nitride-based semiconductor light-emitting element in the comparative example. Figure 5Line graphs (a) to (c) show the bandgap energy distribution and light intensity distribution in the portion below the ridge 110R of the nitride-based semiconductor light-emitting elements of Comparative Examples 1 to 3, respectively. Figure 6 Line graphs (a) to (c) show the bandgap energy distribution and light intensity distribution in the portion below the groove 110T of the nitride-based semiconductor light-emitting elements of Comparative Examples 1 to 3, respectively. Figures 7 to 10 These are line graphs showing the simulation results of the light intensity distribution and refractive index distribution of the portion below the ridge 110R of the nitride-based semiconductor light-emitting elements in Comparative Examples 1 to 4. Figure 11 This is a schematic line diagram showing the bandgap energy distribution and light intensity distribution in the stacking direction of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Figure 11 Line graphs (a) and (b) show the bandgap energy distribution and light intensity distribution of the portion below the ridge 110R and the portion below the groove 110T of the nitride-based semiconductor light-emitting element 100, respectively. Figure 12 This is a line graph showing the simulation results of the light intensity distribution and refractive index distribution of the nitride-based semiconductor light-emitting element 100 according to this embodiment.

[0123] Figure 5 , Figure 6 as well as Figure 11 The horizontal axis represents the stacking direction, and the vertical axis represents the band gap energy and light intensity. Figures 7 to 10 as well as Figure 12 The horizontal axis represents the position in the stacking direction, and the vertical axes on the left and right represent light intensity and refractive index, respectively. Figures 7 to 10 as well as Figure 12 In the middle, the light intensity distribution in the stacking direction of the portion below the groove 110T is also shown, indicated by dashed lines.

[0124] Figures 5 to 9 The nitride-based semiconductor light-emitting elements of Comparative Examples 1 to 3 shown differ from the nitride-based semiconductor light-emitting element 100 according to this embodiment in the configuration of the N-side guiding layer and the P-side guiding layer. The nitride-based semiconductor light-emitting elements of Comparative Examples 1 to 3 have an N-side guiding layer 904 and a P-side guiding layer 906. The N-side guiding layer 904 and the P-side guiding layer 906 have the same bandgap energy.

[0125] In the nitride-based semiconductor light-emitting device of Comparative Example 1, the film thickness Tn0 of the N-side guiding layer 904 is greater than the film thickness Tp0 of the P-side guiding layer 906. Specifically, the N-side guiding layer 904 is an In film with a thickness of 340 nm. 0.03 Ga 0.97 The N-layer and the P-side guiding layer 906 are In films with a thickness of 100 nm. 0.03Ga 0.97 N-layer. In the nitride-based semiconductor light-emitting device of Comparative Example 2, the film thickness Tn0 of the N-side guiding layer 904 is equal to the film thickness Tp0 of the P-side guiding layer 906. Specifically, both the N-side guiding layer 904 and the P-side guiding layer 906 are In-type semiconductors with a film thickness of 220 nm. 0.03 Ga 0.97 N-layer. In the nitride-based semiconductor light-emitting device of Comparative Example 3, the film thickness Tn0 of the N-side guiding layer 904 is smaller than the film thickness Tp0 of the P-side guiding layer 906. Specifically, the N-side guiding layer 904 is an In film with a thickness of 100 nm. 0.03 Ga 0.97 The N-layer and the P-side guiding layer 906 are In films with a thickness of 340 nm. 0.03 Ga 0.97 N layers.

[0126] Figure 10 The difference between the nitride-based semiconductor light-emitting element of Comparative Example 4 and the nitride-based semiconductor light-emitting element 100 of this embodiment is the configuration of the N-side guiding layer and the P-side guiding layer. The nitride-based semiconductor light-emitting element of Comparative Example 4, like the nitride-based semiconductor light-emitting element 100 of this embodiment, has an N-side guiding layer, a first P-side guiding layer, and a second P-side guiding layer. In the nitride-based semiconductor light-emitting element of Comparative Example 4, the band gap energy of the second P-side guiding layer is greater than that of the first N-side guiding layer, and the band gap energy of the first N-side guiding layer is equal to that of the first P-side guiding layer. Regarding the film thickness Tp1 of the first P-side guiding layer, the film thickness Tp2 of the second P-side guiding layer, and the film thickness Tn1 of the first N-side guiding layer, the following (8) and (9) hold true.

[0127] Tn1=Tp1+Tp2 (8)

[0128] as well as

[0129] Tp1=Tp2 (9)

[0130] Specifically, the N-side guiding layer is an In film with a thickness of 220 nm. 0.03 Ga 0.97 The N-layer, the first guiding layer on the P-side is an In film with a thickness of 110 nm. 0.03 Ga 0.97 The N-layer, the second guiding layer on the P-side is an In film with a thickness of 110 nm. 0.01 Ga 0.99 N layers.

[0131] Furthermore, in the simulation, the Al composition ratio of the electron blocking layer 909 in Comparative Examples 1-4 and the electron blocking layer 109 according to this embodiment was the same. In other words, the Al composition ratio of each electron blocking layer was not tilted in the stacking direction.

[0132] The device structures used in the simulations of Comparative Examples 1 to 4 and the various nitride-based semiconductor light-emitting elements involved in this embodiment are shown in Table 1 below, and the values ​​obtained through simulation are shown in Table 2 below.

[0133] [Table 1]

[0134] Table 1

[0135]

[0136]

[0137] [Table 2]

[0138] Table 2

[0139]

[0140] Table 2 shows: the distance dc from the lower end of the ridge 110R to the electron blocking layer 109, the optical confinement factor, the waveguide loss, the effective refractive index difference ΔN, the peak position PS1 of the light intensity distribution in the stacking direction at the center of the horizontal direction below the ridge 110R, and the absolute value ΔP of the difference between the peak position PS1 and the peak position PS2 in the stacking direction of the waveguide-limited mode. Furthermore, the distance dc is set to allow the effective refractive index difference to be within 2.8 × 10⁻⁶. -3 The following distance. Furthermore, the waveguide-limited mode refers to the highest-order mode that can propagate in each nitride-based semiconductor light-emitting element. The peak position of the waveguide-limited mode in the stacking direction corresponds to the value of the peak position of the light intensity distribution in the portion below the groove 110T dominated by the higher-order mode.

[0141] In the nitride-based semiconductor light-emitting device of Comparative Example 1, such as Figure 5 as well as Figure 6 Their respective line graphs (a) and Figure 7 As shown, since the thickness of the N-side guiding layer 904 is greater than that of the P-side guiding layer 906, the peak of the light intensity distribution is located within the N-side guiding layer 904. Therefore, the optical confinement factor for the active layer 105 is low, and the thermal saturation level of the light output is low. Furthermore, since the thickness of the P-side guiding layer 906 is small, the distance dp between the lower end of the ridge 110R and the active layer 105 is smaller. Consequently, the horizontal diffusion angle of the emitted light increases due to the increase in the effective refractive index difference ΔN. Moreover, to reduce the effective refractive index difference ΔN, the distance dc between the lower end of the ridge 110R and the electron blocking layer 909 needs to be a relatively large 80 nm. As a result, the leakage current increases, and the oscillation threshold current of the nitride-based semiconductor light-emitting element increases.

[0142] Furthermore, in the nitride-based semiconductor light-emitting element of Comparative Example 1, since the thickness of the P-side guiding layer 906 is relatively small, it has a relatively large impact on the light intensity distribution of the current blocking layer 112 disposed in the trench 110T. Therefore, the difference ΔP between the peak position of the light intensity distribution in the stacking direction of the portion below the ridge 110R and the peak position of the light intensity distribution in the stacking direction of the portion below the trench 110T is relatively large (especially with reference to...). Figure 7 Therefore, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting element in Comparative Example 1 is low.

[0143] In the nitride-based semiconductor light-emitting device of Comparative Example 2, such as Figure 5 as well as Figure 6 Their respective line graphs (b) and Figure 8 As shown, since the thickness of the N-side guiding layer 904 is equal to the thickness of the P-side guiding layer 906, the peak of the light intensity distribution in the portion below the ridge 110R is located within the active layer 105. Therefore, the optical confinement factor for the active layer 105 is high in the portion below the ridge 110R. However, in the nitride-based semiconductor light-emitting element of Comparative Example 2, since the thickness of the P-side guiding layer 906 is not large, the light intensity distribution is affected by the current blocking layer 112 disposed in the trench 110T. Since the peak of the light intensity distribution in the stacking direction in the portion below the trench 110T is located in the N-side guiding layer 904, the optical confinement factor is low in the portion below the trench 110T. Furthermore, the difference ΔP between the peak position of the light intensity distribution in the stacking direction in the portion below the ridge 110R and the peak position of the light intensity distribution in the stacking direction in the portion below the trench 110T is relatively large. Therefore, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting element in Comparative Example 2 is low.

[0144] In the nitride-based semiconductor light-emitting device of Comparative Example 3, such as Figure 5 as well as Figure 6 Their respective line graphs (c) and Figure 9 As shown, since the thickness of the N-side guiding layer 904 is smaller than that of the P-side guiding layer 906, the peak of the light intensity distribution is located within the P-side guiding layer 906. Therefore, the optical confinement factor of the active layer 105 is low, and the thermal saturation level of the light output is low.

[0145] Furthermore, in the nitride-based semiconductor light-emitting element of Comparative Example 3, since the peak of the light intensity distribution is located in the P-side guiding layer 906, the current blocking layer 112 has a relatively large influence on the light intensity distribution. Therefore, the difference ΔP between the peak position of the light intensity distribution in the stacking direction below the ridge 110R and the peak position of the light intensity distribution in the stacking direction below the trench 110T is relatively large (especially with reference to...). Figure 9Therefore, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting element in Comparative Example 3 is low.

[0146] In the nitride-based semiconductor light-emitting element of Comparative Example 4, compared to the nitride-based semiconductor light-emitting element 100 according to this embodiment, the thickness of the second guiding layer on the P side is smaller, therefore... Figure 10 As shown, the current blocking layer 112 has a significant impact on the light intensity distribution. Consequently, the difference ΔP between the peak position of the light intensity distribution in the stacking direction below the ridge 110R and the peak position of the light intensity distribution in the stacking direction below the groove 110T is relatively large. Therefore, the linearity of the IL characteristics of the nitride-based semiconductor light-emitting element in Comparative Example 4 is low.

[0147] In relation to the comparative examples above, in the nitride-based semiconductor light-emitting element 100 of this embodiment, since the sum of the film thickness Tp1 of the first P-side guiding layer 106 and the film thickness Tp2 of the second P-side guiding layer 107 is greater than the film thickness Tn1 of the N-side guiding layer 104, the effective refractive index difference ΔN can be reduced. Therefore, the diffusion angle of the emitted light in the horizontal direction can be reduced. Furthermore, the distance dc from the lower end of the ridge 110R to the electron blocking layer 109 can be 40 nm, which is significantly reduced compared to the distance dc in the comparative examples. Accordingly, since the leakage current flowing into the lower end of the ridge 110R and the electron blocking layer 109 can be suppressed, the oscillation threshold current can be reduced.

[0148] And in this embodiment, such as Figure 11 as well as Figure 12 As shown, the peak of the light intensity distribution in the stacking direction can be located in the active layer 105 in both the portion below the ridge 110R and the portion below the groove 110T. Therefore, the optical confinement factor can be higher than that in the comparative examples. Furthermore, since the difference in peak position ΔP can be reduced, the linearity of the IL characteristics can be improved.

[0149] Furthermore, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, since the peak of the light intensity distribution in the stacking direction is located in the active layer 105, the light intensity on the P-type cladding layer 110 is increased compared to the case shown in Comparative Example 1 where the peak of the light intensity distribution is located in the N-side guiding layer. This results in increased free carrier loss in the P-type cladding layer 110, which has a higher impurity concentration than the N-type first cladding layer 102 and the N-type second cladding layer 103. However, in this embodiment, since the P-side first guiding layer 106 and the P-side second guiding layer 107 are undoped layers, the sum of the film thickness Tp1 of the P-side first guiding layer 106 and the film thickness Tp2 of the P-side second guiding layer 107 is relatively large, thereby increasing the proportion of the light intensity distribution located in the undoped layer. Therefore, the increase in free carrier loss can be suppressed. Furthermore, in this embodiment, since the impurity concentration in the end of the P-type coating layer 110 closer to the active layer 105 is lower than the impurity concentration in the end of the P-type coating layer 110 farther from the active layer 105, the loss of free carriers in the end of the P-type coating layer 110 closer to the active layer 105, which has a higher light intensity, can be suppressed.

[0150] Here, utilizing Figure 13 as well as Figure 14 The output characteristics of the nitride-based semiconductor light-emitting element 100 according to this embodiment will be explained. Figure 13 This is a line graph showing the simulation results of the relationship between the radiation angle and light intensity of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Figure 13 A comparative example is also shown, where the effective refractive index difference ΔN is 7 × 10⁻⁶. -3 The relationship between the radiation angle and light intensity of the nitride-based semiconductor light-emitting element in the comparative example. Figure 14 This is a line graph showing the simulation results of the IL characteristics of the nitride-based semiconductor light-emitting element 100 according to this embodiment. Figure 14 The IL characteristics of the nitride-based semiconductor light-emitting element of Comparative Example 2 are also shown.

[0151] like Figure 13 As shown, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, the effective refractive index difference ΔN is 2.8 × 10⁻⁶. -3 Therefore, compared to the nitride-based semiconductor light-emitting element in the comparative example, the beam diffusion angle in the horizontal direction can be reduced. Figure 13 In the example shown, 1 / e can become the peak value. 2 The intensity of the beam is reduced to a total beam width of approximately 9.3°.

[0152] like Figure 14As shown, compared to the nitride-based semiconductor light-emitting element in the comparative example, the nitride-based semiconductor light-emitting element 100 according to this embodiment can achieve a high linearity IL characteristic. Furthermore, it can achieve a higher slope efficiency (approximately 1.9 W / A) than the comparative example.

[0153] Next, using Figure 15 as well as Figure 16 The relationship between the structure and effect of the second guide layer 107 on the P side involved in this embodiment will be explained. Figure 15 The line graph shows the simulation results of the relationship between the In composition ratio Xp2 and the film thickness Tp2 of the second guiding layer 107 on the P side and each parameter when the In composition ratio of each barrier layer of the nitride-based semiconductor light-emitting element 100 involved in this embodiment is 4%. Figure 16 This is a line graph showing the simulation results of the In composition ratio Xp2 and film thickness Tp2 of the second guiding layer 107 on the P side, and their relationship with various parameters, when the In composition ratio of each barrier layer of the nitride-based semiconductor light-emitting element 100 according to this embodiment is 0%. Figure 15 as well as Figure 16 Linear plots (a) to (f) show the film thickness Tp2 of the second guiding layer on the P side, the waveguide loss, the optical confinement factor Γv, and the effective refractive index difference ΔN[×10]. -3 The relationship between position PS1, position PS2, and ΔP is shown. Furthermore, line graphs are shown for the In composition ratio Xp2 of the second guiding layer 107 on the P side being 0%, 0.5%, 1%, 2%, 3%, and 4%. In the simulation, the In composition ratio Xn1 of the guiding layer 104 on the N side was set to 4%, and the film thickness was set to 160 nm. The In composition ratio Xp1 of the first guiding layer 106 on the P side was set to 4.5%, and the film thickness was set to 80 nm.

[0154] like Figure 15 as well as Figure 16 As shown in the line graph (a), for all In composition ratios Xp2, waveguide loss decreases as the film thickness Tp2 of the second guiding layer 107 on the P side increases. Furthermore, waveguide loss decreases as the In composition ratio Xp2 decreases.

[0155] like Figure 15 as well as Figure 16 As shown in line graph (b), among all In composition ratios Xp2, the optical confinement factor Γv is maximized when the film thickness Tp2 of the second guiding layer 107 on the P side is in the range of approximately 0 to 100 nm. As the film thickness Tp2 increases from 100 nm, the optical confinement factor Γv decreases. Furthermore, when the film thickness Tp2 is above 100 nm, the optical confinement factor Γv increases as the In composition ratio Xp2 decreases.

[0156] like Figure 15 as well as Figure 16 As shown in line graph (c), for all In composition ratios Xp2, the effective refractive index difference ΔN decreases as the film thickness Tp2 of the second guiding layer 107 on the P side increases. Furthermore, as the In composition ratio Xp2 decreases, the effective refractive index difference ΔN generally tends to decrease.

[0157] like Figure 15 as well as Figure 16 As shown in line graphs (d) and (e), for all In composition ratios Xp2, as the film thickness Tp2 of the second guiding layer 107 on the P side increases, the positions PS1 and PS2 also increase. Furthermore, as the In composition ratio Xp2 decreases, the positions PS1 and PS2 tend to decrease. Additionally, in... Figure 15 as well as Figure 16 In line graphs (d) and (e), as an example of the range of positions PS1 and PS2 that can improve the optical confinement factor, a range of -5 nm to 18 nm is shown. The range of positions PS1 and PS2 being 0 nm to 13 nm corresponds to any one of the well layer 105b, barrier layer 105c, and well layer 105d in the active layer 105. Furthermore, the range of positions PS1 and PS2 being -5 nm to 0 corresponds to a distance of 5 nm or less from the well layer 105b closest to the N-type second cladding layer 103 in the active layer 105 towards the N-type second cladding layer 103. Furthermore, the range of positions PS1 and PS2 being 13 nm to 18 nm corresponds to a distance of 5 nm or less from the well layer 105d closest to the P-type cladding layer 110 in the active layer 105 towards the P-type cladding layer 110. Therefore, by positioning the peak of the light intensity distribution above -5 nm and below 18 nm, the optical confinement factor Γv can be improved.

[0158] like Figure 15 as well as Figure 16 As shown in the line graph (f), except for the case where the In composition ratio Xp1 of the first guiding layer 106 on the P side is equal to the In composition ratio of the second guiding layer 107 on the P side (i.e., different from this embodiment), ΔP tends to decrease as the film thickness Tp2 of the second guiding layer 107 on the P side increases. Furthermore, in Figure 15 as well as Figure 16 In the line graph (f), as an example of the range of ΔP that can improve IL characteristics, the range of ΔP above 0 and below 20 nm is shown.

[0159] from Figure 15as well as Figure 16 As can be seen from the various line graphs, by making the film thickness Tp2 of the second guiding layer 107 on the P side 100 nm or more, the reduction of waveguide loss, the increase of optical confinement factor Γv, and the reduction of effective refractive index difference ΔN can be achieved simultaneously. Furthermore, to further improve the optical confinement factor Γv, the film thickness Tp2 can also be below 250 nm. Moreover, to ensure that positions PS1 and PS2 are near the well layers 105b and 105d of the active layer 105, the In composition ratio Xp2 of the second guiding layer 107 on the P side can also be above 0.5%.

[0160] Next, while comparing with the comparative example, refer to... Figure 17 as well as Figure 18 The film thickness Tp2 of the second guiding layer 107 on the P side and the film thickness of the P-type cladding layer 110 of the nitride-based semiconductor light-emitting element 100 involved in this embodiment, and their relationship with various parameters will be explained. Figure 17 This is a line graph showing the film thickness of the second guiding layer on the P side, the film thickness of the P-type cladding layer, and their relationship with various parameters in the nitride-based semiconductor light-emitting element of the comparative example. Figure 18 This is a line graph showing the film thickness of the second guiding layer 107 on the P-side, the film thickness of the P-type cladding layer 110, and their relationship with various parameters in the nitride-based semiconductor light-emitting element 100 according to this embodiment. Figure 17 as well as Figure 18 In the diagram, contour lines represent the various film thicknesses and waveguide losses α. i The relationship between the optical confinement factor Γv and the effective refractive index difference ΔN. Figure 17 The comparative example shown is similar to the nitride-based semiconductor light-emitting device of Comparative Example 2 described above, and has a single N-side guiding layer and a single P-side guiding layer having the same film thickness and In composition ratio.

[0161] exist Figure 17 As shown in the comparative example, in the nitride-based semiconductor light-emitting element, the regions where positions PS1 and PS2 are both -5 nm to 18 nm and ΔP is 20 nm or less are shaded. However, in this region, the effective refractive index difference ΔN is greater than 4 × 10⁻⁶. -3 The diameter is large, therefore the horizontal diffusion angle of the emitted light cannot be suppressed. Furthermore, ΔP cannot be less than 10 nm in this region. In contrast, in the comparative example nitride-based semiconductor light-emitting element, an effective refractive index difference ΔN of approximately 3 × 10⁻⁶ nm can be achieved by making the distance dc approximately 80 nm. -3However, in this case, due to the leakage current between the electron blocking layer 109 and the trench 110T as described above, the oscillation threshold current increases, thereby reducing the temperature characteristics of the nitride-based semiconductor light-emitting element. Therefore, the nitride-based semiconductor light-emitting element of the comparative example cannot solve the problems of this disclosure.

[0162] exist Figure 18 As shown, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, regions where positions PS1 and PS2 are both -5nm or more and 18nm or less, and where ΔP is 20nm or less, are represented by diagonal lines and dotted shadows. Furthermore, regions within this range where ΔP is 5nm or less are represented by dotted shadows, and regions where ΔP is greater than 5nm but less than 10nm are represented by diagonal lines. Figure 18 As shown, in the shaded region, the effective refractive index difference ΔN is 2.8 × 10⁻⁶. -3 Therefore, in the nitride-based semiconductor light-emitting element 100 according to this embodiment, even if the distance dc is about 40 nm, the above-mentioned conditions can be met.

[0163] (Implementation Method 2)

[0164] The nitride-based semiconductor light-emitting element according to Embodiment 2 will be described. The difference between the nitride-based semiconductor light-emitting element according to this embodiment and the nitride-based semiconductor light-emitting element 100 according to Embodiment 1 lies in the Al composition ratio of the N-type first cladding layer to the P-type cladding layer. The following will utilize... Figure 19 The nitride-based semiconductor light-emitting element of this embodiment will be described focusing on its differences from the nitride-based semiconductor light-emitting element 100 of Embodiment 1.

[0165] Figure 19 This is a schematic cross-sectional view showing the overall configuration of the nitride-based semiconductor light-emitting element 200 according to this embodiment. Figure 19 As shown, the nitride-based semiconductor light-emitting element 200 according to this embodiment includes: a semiconductor stack 200S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor stack 200S includes: a substrate 101, an N-type first cladding layer 202, an N-type second cladding layer 103, an N-side guiding layer 104, an active layer 105, a P-side first guiding layer 106, a P-side second guiding layer 107, an intermediate layer 108, an electron blocking layer 109, a P-type cladding layer 210, and a contact layer 111.

[0166] The N-type first cladding layer 202 involved in this embodiment is an N-type Al with a film thickness of 1200 nm. 0.036 Ga 0.964N layer. Si with a concentration of 1×10 18 cm -3 is doped as an impurity in the N-type first cladding layer 202.

[0167] The P-type cladding layer 210 according to this embodiment is a P-type Al 0.026 Ga 0.974 N layer with a film thickness of 450 nm. Mg is doped as an impurity in the P-type cladding layer 210. Moreover, the impurity concentration in the end portion of the P-type cladding layer 210 closer to the active layer 105 is lower than the impurity concentration in the end portion farther from the active layer 105. Specifically, the P-type cladding layer 210 has: a P-type Al 18 cm -3 with a film thickness of 150 nm and doped with Mg at a concentration of 2×10 0.026 Ga 0.974 N layer, and a P-type Al 19 cm -3 with a film thickness of 300 nm and doped with Mg at a concentration of 1×10 0.026 Ga 0.974 N layer, which is disposed on the side farther from the active layer 105.

[0168] And similar to the P-type cladding layer 110 according to Embodiment 1, a ridge portion 210R is formed in the P-type cladding layer 210. And two groove portions 210T are formed in the P-type cladding layer 210. The two groove portions 210T are arranged along the ridge portion 210R and extend in the Y-axis direction.

[0169] Even for the nitride-based semiconductor light-emitting device 200 according to this embodiment, the same effects as those of the nitride-based semiconductor light-emitting device 100 according to Embodiment 1 can be achieved.

[0170] Moreover, in this embodiment, the N-type first cladding layer 202 and the P-type cladding layer 210 contain Al. When the Al composition ratios of the N-type first cladding layer 202 and the P-type cladding layer 210 are set as Ync and Ypc, respectively, the following relationship (10) is satisfied.

[0171] Ync > Ypc (10)

[0172] Here, when at least one of the N-type first cladding layer 202 and the P-type cladding layer 210 is a superlattice structure, the composition ratios Ync and Ypc represent the average Al composition ratio. For example, the N-type first cladding layer 202 includes multiple GaN layers with a thickness of 2 nm and multiple AlGaN layers with a thickness of 2 nm and an Al composition ratio of 0.07. When the GaN layers and AlGaN layers are alternately stacked, Ync becomes the average Al composition ratio of the entire N-type first cladding layer 202, which is 0.035. The P-type cladding layer 210 includes multiple GaN layers with a thickness of 2 nm and multiple AlGaN layers with a thickness of 2 nm and an Al composition ratio of 0.07. When the GaN layers and AlGaN layers are alternately stacked, Ypc becomes the average Al composition ratio of the entire P-type cladding layer 210, which is 0.035.

[0173] Accordingly, the refractive index of the N-type first cladding layer 202 can be reduced to be lower than that of the P-type cladding layer 210. Therefore, even if the thickness of the P-type cladding layer 210 is reduced in order to lower the operating voltage of the nitride-based semiconductor light-emitting element 200, since the refractive index of the N-type first cladding layer 202 is lower than that of the P-type cladding layer 210, the shift of the peak of the light intensity distribution in the stacking direction from the active layer 105 toward the direction closer to the N-type first cladding layer 202 can be suppressed.

[0174] This implementation method enables an effective refractive index difference ΔN of 2.5 × 10⁻⁶. -3 The peak position of the light intensity distribution in the stacking direction below the ridge 210R is PS1 at 2.5 nm, ΔP at 6.4 nm, the optical confinement factor for the active layer 105 is 1.45%, and the waveguide loss is 1.9 cm. -1 Nitride-based semiconductor light-emitting element 200.

[0175] (Implementation Method 3)

[0176] The nitride-based semiconductor light-emitting element according to Embodiment 3 will be described. The difference between the nitride-based semiconductor light-emitting element according to this embodiment and the nitride-based semiconductor light-emitting element 200 according to Embodiment 2 is that a light-transmitting conductive film is provided on the contact layer 111 of the ridge 210R. The following describes the application of... Figure 20 The nitride-based semiconductor light-emitting element of this embodiment will be described, focusing on the differences from the nitride-based semiconductor light-emitting element 200 of Embodiment 2.

[0177] Figure 20 This is a schematic cross-sectional view showing the overall configuration of the nitride-based semiconductor light-emitting element 300 according to this embodiment. Figure 20As shown, the nitride-based semiconductor light-emitting element 300 according to this embodiment includes: a semiconductor laminate 200S, a current blocking layer 112, a P-side electrode 113, an N-side electrode 114, and a light-transmitting conductive film 320.

[0178] The light-transmitting conductive film 320 involved in this embodiment is a conductive film disposed above the P-type cladding layer 210, which allows at least a portion of the light generated in the nitride-based semiconductor light-emitting element 300 to pass through. As the light-transmitting conductive film 320, for example, indium oxide (ITO) doped with tin, zinc oxide doped with Ga, zinc oxide doped with Al, zinc oxide doped with In and Ga, etc., can be used as oxide films that are transmissive to visible light and exhibit low electrical conductivity.

[0179] Even the nitride-based semiconductor light-emitting element 300 described in this embodiment can achieve the same effect as the nitride-based semiconductor light-emitting element 200 described in Embodiment 2.

[0180] Furthermore, in this embodiment, since a light-transmitting conductive film 320 is provided above the P-type cladding layer 210, optical losses propagating above the P-type cladding layer 210 can be reduced. Moreover, since the film thickness of the P-type cladding layer 210 can be further reduced, the impedance of the nitride-based semiconductor light-emitting element 300 can be further reduced. As a result, the slope efficiency of the nitride-based semiconductor light-emitting element 300 can be improved, and the operating voltage can be reduced.

[0181] This implementation method enables an effective refractive index difference ΔN of 2.1 × 10⁻⁶. -3 The peak position of the light intensity distribution in the stacking direction below the ridge 210R is PS1 at 2.0 nm, ΔP at 5.7 nm, the optical confinement factor for the active layer 105 is 1.47%, and the waveguide loss is 1.9 cm. -1 300 nitride-based semiconductor light-emitting element.

[0182] (Implementation Method 4)

[0183] The nitride-based semiconductor light-emitting element according to Embodiment 4 will be described. The difference between the nitride-based semiconductor light-emitting element according to this embodiment and the nitride-based semiconductor light-emitting element 200 according to Embodiment 2 lies in the composition of the active layer. The following refers to... Figure 21A as well as Figure 21B The nitride-based semiconductor light-emitting element of this embodiment will be described, focusing on the differences from the nitride-based semiconductor light-emitting element 200 of Embodiment 2.

[0184] Figure 21AThis is a schematic cross-sectional view showing the overall structure of the nitride-based semiconductor light-emitting element 400 according to this embodiment. Figure 21B This is a cross-sectional view showing the structure of the active layer 405 of the nitride-based semiconductor light-emitting element 400 according to this embodiment.

[0185] like Figure 21A As shown, the nitride-based semiconductor light-emitting element 400 according to this embodiment includes: a semiconductor stack 400S, a current blocking layer 112, a P-side electrode 113, and an N-side electrode 114. The semiconductor stack 400S includes: a substrate 101, an N-type first cladding layer 202, an N-type second cladding layer 103, an N-side guiding layer 104, an active layer 405, a P-side first guiding layer 106, a P-side second guiding layer 107, an intermediate layer 108, an electron blocking layer 109, a P-type cladding layer 210, and a contact layer 111.

[0186] The active layer 405 involved in this embodiment is as follows: Figure 21B As shown, it has a single quantum well structure, having a well layer 105b and barrier layers 105a and 105c sandwiching the well layer 105b. The well layer 105b has the same configuration as the well layer 105b according to Embodiment 1, and the barrier layers 105a and 105c have the same configuration as the barrier layers 105a and 105c according to Embodiment 1.

[0187] The nitride-based semiconductor light-emitting element 400 according to this embodiment can achieve the same effect as the nitride-based semiconductor light-emitting element 200 according to Embodiment 2. In particular, in the nitride-based semiconductor light-emitting element 400 having the above-described single quantum well structure, the active layer 405 has a well layer 105b. Thus, even in a nitride-based semiconductor light-emitting element 400 with a small number of well layers 105b with high refractive index, the configuration of the N-side guiding layer 104, the first P-side guiding layer 106, the second P-side guiding layer 107, etc., can make the peak of the light intensity distribution in the stacking direction located in or near the active layer 405. Therefore, the optical confinement factor can be improved.

[0188] This implementation method enables an effective refractive index difference ΔN of 2.5 × 10⁻⁶. -3 The peak position of the light intensity distribution in the stacking direction below the ridge 210R is PS1 at 2.1 nm, ΔP at 6.3 nm, the optical confinement factor for the active layer 405 is 0.72%, and the waveguide loss is 1.8 cm. -1 The nitride-based semiconductor light-emitting element 400. Furthermore, in this embodiment, since the total film thickness of the active layer 405 is 8 nm smaller than that of the active layer 105 in Embodiment 2, the optical confinement factor is smaller than that in Embodiment 2.

[0189] (variant examples, etc.)

[0190] The above description of the nitride-based semiconductor light-emitting element involved in this disclosure is based on various embodiments, but this disclosure is not limited to the above embodiments.

[0191] For example, in the embodiments described above, although the nitride-based semiconductor light-emitting element is exemplified as a semiconductor laser element, the nitride-based semiconductor light-emitting element is not limited to a semiconductor laser element. For example, the nitride-based semiconductor light-emitting element can be a superluminescent diode. In this case, the reflectivity of the end face of the semiconductor stack of the nitride-based semiconductor light-emitting element can be 0.1% or less. Such reflectivity can be achieved, for example, by forming an anti-reflection film composed of multiple dielectric films or the like on the end face. Alternatively, if the ridge that becomes a waveguide is an inclined stripe structure that is inclined at 5° or more from the normal direction of the front face and intersects the front face, the waveguide light reflected at the front face can be recombined with the waveguide, and the proportion of the waveguide light component can be set to a small value of 0.1% or less.

[0192] Furthermore, although the nitride-based semiconductor light-emitting element in embodiments 1 to 3 described above has a structure including two well layers as the active layer 105, it can also have a structure including only one well layer. Thus, even if there is only one well layer with a high refractive index included in the active layer, by employing the N-side guiding layer 104, the P-side first guiding layer 106, and the P-side second guiding layer 107 of this disclosure, the controllability of the position of the light distribution in the vertical direction can be improved. Therefore, the peak of the light distribution in the vertical direction can be located near the well layer. Accordingly, a nitride-based semiconductor light-emitting element with a low oscillation threshold, low waveguide loss, high optical confinement factor, and good linear current-light output (IL) characteristics can be realized.

[0193] Furthermore, in the above embodiments, although the nitride-based semiconductor light-emitting element has one ridge, it may also have multiple ridges. Utilizing Figure 22 This paper describes such a nitride-based semiconductor light-emitting element. Figure 22 This is a schematic cross-sectional view showing the overall structure of the nitride-based semiconductor light-emitting element 500 involved in Modified Example 1. Figure 22 As shown, the nitride-based semiconductor light-emitting element 500 according to Modified Example 1 has a configuration in which multiple nitride-based semiconductor light-emitting elements 100 according to Embodiment 1 are arranged in a matrix in the horizontal direction. Figure 22In this embodiment, although the nitride-based semiconductor light-emitting element 500 has a configuration in which three nitride-based semiconductor light-emitting elements 100 are arranged in a single unit, the number of nitride-based semiconductor light-emitting elements 100 in the nitride-based semiconductor light-emitting element 500 is not limited to three. The number of nitride-based semiconductor light-emitting elements 100 in the nitride-based semiconductor light-emitting element 500 can be two or more. Each nitride-based semiconductor light-emitting element 100 has a light-emitting section 100E. The light-emitting section 100E is the portion of the active layer 105 that emits light, corresponding to the portion of the active layer 105 located below the ridge 110R. Thus, the nitride-based semiconductor light-emitting element 500 according to Modified Example 1 has multiple light-emitting sections 100E arranged in a matrix. Accordingly, since multiple emitted light beams can be obtained from a single nitride-based semiconductor light-emitting element 500, a high-output nitride-based semiconductor light-emitting element 500 can be achieved. Furthermore, in Modification 1, although the nitride semiconductor light-emitting element 500 has a plurality of nitride semiconductor light-emitting elements 100, the plurality of nitride semiconductor light-emitting elements 500 has not been limited to this, and may also be nitride semiconductor light-emitting elements involved in other embodiments.

[0194] And, as Figure 23 As shown in the nitride-based semiconductor light-emitting element 500a in Modification Example 2, each light-emitting section 100E can also be separated by a separation groove 100T with a width (dimension in the X-axis direction) of 8 μm to 20 μm and a depth (dimension in the Z-axis direction) of 1.0 μm to 1.5 μm. By adopting this configuration, even if the spacing between adjacent light-emitting sections 100E is narrow to 300 μm or less, thermal interference caused by the self-heating of each light-emitting section 100E during operation can be reduced.

[0195] Furthermore, since the ΔN of the nitride-based semiconductor light-emitting element of the present invention is small, the horizontal diffusion angle can be reduced, thus, even if the horizontal diffusion angle is reduced... Figure 22 as well as Figure 23 The distance between the centers of the light emitting sections 100E shown is narrowed, and the emitted light from each light emitting section 100E is less likely to interfere with each other. Therefore, the distance between the centers of the light emitting sections 100E can be narrowed to less than 250 μm. In Modified Example 2, this distance is 225 μm.

[0196] Furthermore, although the nitride-based semiconductor light-emitting elements described in the above embodiments have an N-type second cladding layer 103, an intermediate layer 108, an electron blocking layer 109, and a current blocking layer 112, these layers may not be necessary.

[0197] Furthermore, any modifications that can be conceived by those skilled in the art to the above embodiments, and any combination of the constituent elements and functions in the above embodiments without departing from the spirit of this disclosure, are all included in this disclosure.

[0198] For example, the configuration of each coating layer involved in Embodiment 1 can be applied to each nitride-based semiconductor light-emitting element involved in Embodiments 3 and 4. Furthermore, the light-transmitting conductive film involved in Embodiment 3 can also be applied to each nitride-based semiconductor light-emitting element involved in Embodiments 1 and 4.

[0199] Industrial applicability

[0200] The nitride-based semiconductor light-emitting element disclosed herein can be used as a high-output and high-efficiency light source for applications such as light sources in processing machinery.

[0201] Symbol Explanation

[0202] 100, 200, 300, 400, 500, 500a Nitride-based Semiconductor Light-Emitting Devices

[0203] 100E light exit part

[0204] 100F, 100R end faces

[0205] 100T Separation Tank

[0206] 100S, 200S, 400S semiconductor laminates

[0207] 101 substrate

[0208] 102, 202 N-type first cladding layer

[0209] 103 N-type second cladding layer

[0210] 104, 904 N-side guiding layer

[0211] 105, 405 active layer

[0212] 106 P-side first guiding layer

[0213] 107 P-side second guiding layer

[0214] 108 Intermediate Layer

[0215] 109, 909 electron blocking layers

[0216] 110, 210 P-type coating

[0217] 110R, 210R spine

[0218] 110T and 210T tank sections

[0219] 111 Contact Layer

[0220] 112 Current blocking layer

[0221] 113 P-side electrode

[0222] 114 N-side electrode

[0223] 320 Transparent Conductive Film

[0224] 906 P-side guiding layer

Claims

1. A nitride-based semiconductor light-emitting element comprising a semiconductor stack, wherein light is emitted from an end face perpendicular to the stacking direction of the semiconductor stack. The semiconductor stack has: N-type first cladding layer; N-side guiding layer, which is disposed above the N-type first covering layer; An active layer, which is disposed above the N-side guiding layer, includes a well layer and a barrier layer and has a quantum well structure; A first guiding layer on the P side is disposed above the active layer; The second guide layer on the P side is disposed above the first guide layer on the P side; as well as A P-type overlay layer is disposed above the second guide layer on the P side. The bandgap energy of the second guiding layer on the P side is greater than that of the guiding layer on the N side. The bandgap energy of the N-side guiding layer is greater than or equal to the bandgap energy of the first guiding layer on the P-side. When the film thickness of the first guiding layer on the P side is set to Tp1, the film thickness of the second guiding layer on the P side is set to Tp2, and the film thickness of the guiding layer on the N side is set to Tn1, The relationship Tn1 < Tp1 + Tp2 is satisfied.

2. The nitride-based semiconductor light-emitting element as described in claim 1, The average refractive index of the first guide layer on the P side and the second guide layer on the P side is smaller than the average refractive index of the guide layer on the N side.

3. The nitride-based semiconductor light-emitting element as described in claim 1, The P-side first guide layer is composed of In Xp1 Ga 1-Xp1 N, The N-side guide layer is composed of In Xn1 Ga 1-Xn1 N, The relationship Xn1 ≤ Xp1 is satisfied.

4. The nitride-based semiconductor light-emitting element as described in claim 3, The relationship Xn1 < Xp1 is satisfied.

5. The nitride-based semiconductor light-emitting element as described in claim 3, The P-side second guide layer is composed of In Xp2 Ga 1-Xp2 N, The relationship Xp2 < Xn1 is satisfied.

6. The nitride-based semiconductor light-emitting element as described in claim 3, The barrier layer consists of In Xb Ga 1-Xb N, The relationship Xp1 < Xb is satisfied.

7. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The bandgap energy of the N-side guiding layer is greater than that of the P-side first guiding layer.

8. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The relationship Tp1 < Tp2 is satisfied.

9. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The relationship Tp1 < Tn1 is satisfied.

10. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The peak of the light intensity distribution along the stacking direction is located in the active layer.

11. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The impurity concentration in the end of the P-type coating layer closer to the active layer is lower than the impurity concentration in the end of the P-type coating layer farther from the active layer.

12. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The nitride-based semiconductor light-emitting element includes an electron blocking layer disposed between the second guiding layer on the P-side and the P-type cladding layer. The electron blocking layer has an Al composition variation region in which the Al composition ratio monotonically increases with distance from the active layer.

13. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The N-type first coating layer and the P-type coating layer contain Al. When the Al composition ratios of the N-type first coating layer and the P-type coating layer are set to Ync and Ypc, respectively... The relationship Ync > Ypc is satisfied.

14. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The thickness of the P-type coating layer is less than 460 nm.

15. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The nitride-based semiconductor light-emitting element has a transparent conductive film disposed above the P-type cladding layer.

16. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The nitride-based semiconductor light-emitting element includes an N-type second cladding layer disposed between the N-type first cladding layer and the N-side guiding layer. The bandgap energy of the N-type second cladding layer is smaller than that of the N-type first cladding layer, but larger than that of the P-side second guiding layer.

17. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The nitride-based semiconductor light-emitting element has multiple light-emitting sections arranged in a matrix.

18. The nitride-based semiconductor light-emitting element according to any one of claims 1 to 6, The reflectivity of the end face of the semiconductor stack is less than 0.1%.

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