Semiconductor laser element and method for manufacturing the same

Abstract

To provide a semiconductor laser element with reduced parasitic capacitance. [Solution] The distributed feedback type semiconductor laser element 100 comprises a stacked structure 120 including an n-type semiconductor layer 122, an active layer 124, and a p-type semiconductor layer 126, and a pad electrode 173. The p-type semiconductor layer 126 has a current constriction structure 141 and a diffraction grating 150 including a plurality of first grooves 152 formed in a region adjacent to the current constriction structure 141. In addition, a periodic structure portion 180 is formed in the region of the p-type semiconductor layer 126 that overlaps with the pad electrode 173. The periodic structure portion 180 includes a plurality of second grooves 182 parallel to the first grooves 152, and the plurality of second grooves 182 are embedded with a first dielectric material having a lower dielectric constant than the p-type semiconductor layer 126.

Description

[Technical Field]

[0001] This disclosure relates to semiconductor laser devices. [Background technology]

[0002] GaN-based and GaAs-based distributed feedback laser diodes (DFB-LDs) that oscillate in the visible light region are being considered for use as light sources in smart glasses for visible light communication, Li-Fi, AR (Augmented Reality) / MR (Mixed Reality), etc. The generation of optical signals and gradation can be achieved by modulating the drive current of the DFB-LD.

[0003] The bandwidth of a DFB-LD is limited by the parasitic capacitance associated with the DFB-LD chip. Therefore, for applications requiring high-speed modulation exceeding 0.1 GHz to 1 GHz, it is necessary to reduce the parasitic capacitance of the DFB-LD chip. [Prior art documents] [Non-patent literature]

[0004] [Patent Document 1] Patent No. 6371609 [Overview of the project] [Problems that the invention aims to solve]

[0005] Patent Document 1 proposes a technique for reducing parasitic capacitance in an InP-based DFB-LD for communications, in which a semiconductor layer is excavated in the region below the pad electrodes and filled with resin. However, this method involves a complex process, which increases costs.

[0006] This disclosure is made in such circumstances, and one exemplary objective of a certain aspect thereof is to provide a semiconductor laser element with reduced parasitic capacitance. [Means for solving the problem]

[0007] Aspects of this disclosure relate to a distributed feedback semiconductor laser element. The semiconductor laser element comprises a substrate, a laminated structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer, and a pad electrode. The laminated structure is provided with a current constriction structure, a diffraction grating including a plurality of first grooves formed in a region adjacent to the current constriction structure of the second conductivity type semiconductor layer, and a periodic structure portion including a plurality of second grooves formed in a region overlapping with the pad electrode of the second conductivity type semiconductor layer and parallel to the first grooves, wherein the plurality of second grooves are embedded with a first dielectric material having a lower dielectric constant than the second conductivity type semiconductor layer.

[0008] Another aspect of the present disclosure relates to a method for manufacturing a distributed feedback semiconductor laser element. The manufacturing method comprises the steps of: forming a laminated structure on a substrate including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer; forming a current-constricting structure in the laminated structure; forming a diffraction grating including a plurality of first grooves in a region adjacent to the current-constricting structure of the second conductivity type semiconductor layer, and forming a plurality of second grooves parallel to the first grooves in a region of the second conductivity type semiconductor layer where pad electrodes are to be formed; and filling the plurality of second grooves with a first dielectric material having a lower dielectric constant than the second conductivity type semiconductor layer.

[0009] Furthermore, any combination of the above components, or any substitution of components or expressions between methods, apparatus, systems, etc., are also valid as embodiments of the present invention or this disclosure. Moreover, the description in this section (means for solving the problem) does not describe all the indispensable features of the present invention, and therefore, subcombinations of these described features may also constitute the present invention. [Effects of the Invention]

[0010] According to certain aspects of this disclosure, the parasitic capacitance of a semiconductor laser element can be reduced. [Brief explanation of the drawing]

[0011] [Figure 1] It is a perspective view of a distributed feedback semiconductor laser device according to an embodiment. [Figure 2] It is a cross-sectional view taken along line B-B' of the semiconductor laser device in FIG. 1. [Figure 3] It is a plan view of a semiconductor laser device according to an embodiment. [Figure 4] It is a plan view of a semiconductor laser device according to an embodiment. [Figure 5] It is a plan view of a semiconductor laser device according to an embodiment. [Figure 6] It is a plan view of a semiconductor laser device according to an embodiment. [Figure 7] It is a plan view of a semiconductor laser device according to an embodiment. [Figure 8] It is a diagram for explaining a method of manufacturing a semiconductor laser device. [Figure 9] It is a cross-sectional view of a semiconductor laser device according to Modification 1. [Figure 10] It is a cross-sectional view of a semiconductor laser device according to Modification 2. [Figure 11] It is a diagram for explaining an example of a method of manufacturing the periodic structure portion in FIG. 10. [Figure 12] It is a plan view of a semiconductor laser device according to Modification 3.

Embodiments for Carrying Out the Invention

[0012] (Outline of the Embodiment) An outline of some exemplary embodiments of the present disclosure will be described. This outline is provided as a prelude to the detailed description that follows or for the purpose of a basic understanding of the embodiments. The outline simplifies and describes some concepts of one or more embodiments and does not limit the scope of the invention or disclosure. Also, this outline is not an all-inclusive overview of all possible embodiments and does not limit the essential components of the embodiments. For convenience, "one embodiment" may be used to refer to one embodiment (example or modification) or a plurality of embodiments (examples or modifications) disclosed in this specification.

[0013] A distributed feedback type semiconductor laser element according to one embodiment comprises a substrate, a laminated structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer, and a pad electrode. The laminated structure is provided with a current constriction structure, a diffraction grating including a plurality of first grooves formed in a region adjacent to the current constriction structure of the second conductivity type semiconductor layer, and a periodic structure portion formed in a region overlapping with the pad electrode of the second conductivity type semiconductor layer, including a plurality of second grooves parallel to the first grooves, wherein the plurality of second grooves are embedded with a first dielectric material having a lower dielectric constant than the second conductivity type semiconductor layer.

[0014] In this configuration, multiple second grooves are formed in the second conductivity semiconductor layer beneath the pad electrodes, and by filling them with a material with a lower dielectric constant than the second conductivity semiconductor layer, the effective dielectric constant can be reduced, thereby reducing parasitic capacitance. The multiple second grooves are formed in the second conductivity semiconductor layer, similar to the multiple first grooves in a diffraction grating. Therefore, since the multiple second grooves can be formed using the same process as the multiple first grooves, the complexity and cost of the manufacturing process can be suppressed.

[0015] In one embodiment, the period of the periodic structure may coincide with the period of the diffraction grating. This allows the first and second grooves to be formed simultaneously, thereby increasing throughput.

[0016] In one embodiment, the periodic structure may be formed adjacent to the diffraction grating. In this case, the second groove of the periodic structure may be formed continuously with the first groove of the diffraction grating. This allows the first and second grooves to be formed simultaneously.

[0017] In one embodiment, the periodic structure may be formed adjacent to the diffraction grating. In this case, the second groove of the periodic structure may be formed discontinuously with the first groove of the diffraction grating.

[0018] In one embodiment, the width of the second groove in the periodic structure may differ from the width of the first groove in the diffraction grating. For example, the width of the second groove in the periodic structure may be wider than the width of the first groove in the diffraction grating, thereby further reducing parasitic capacitance.

[0019] In one embodiment, the diffraction grating may be formed on both sides of the current constriction structure.

[0020] In one embodiment, the diffraction grating may be formed only on one side of the current-constricting structure. In this case, the periodic structure may be formed adjacent to the diffraction grating. Alternatively, the periodic structure may be formed on the opposite side of the current-constricting structure from the diffraction grating, i.e., not adjacent to the diffraction grating.

[0021] In one embodiment, the area of ​​the pad electrode is 8000 μm² per bonding wire connected to the pad electrode. 2 The following may also be used. This minimizes parasitic capacitance caused by the pad electrodes.

[0022] In one embodiment, a dielectric layer made of a second dielectric material having a lower dielectric constant than the second conductivity semiconductor layer may be formed between the pad electrode and the periodic structure. This further reduces parasitic capacitance.

[0023] In one embodiment, the area of ​​the dielectric layer may be larger than the area of ​​the pad electrode.

[0024] In one embodiment, the second dielectric material may be the same as the first dielectric material. This makes the dielectric layer less likely to peel off.

[0025] In one embodiment, the periodic structure may have a width of 100 nm or less in the resonator direction of the second groove.

[0026] In one embodiment, the interior of the first groove of the periodic structure may contain voids that are not filled with the first dielectric material. This allows for a further reduction in the effective dielectric constant of the periodic structure and a further reduction in parasitic capacitance.

[0027] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. Furthermore, the embodiments are illustrative and not limiting to the disclosure or invention, and not all features or combinations thereof described in the embodiments are necessarily essential to the disclosure or invention.

[0028] Furthermore, the dimensions (thickness, length, width, etc.) of each component shown in the drawing may be enlarged or reduced as appropriate for ease of understanding. Moreover, the dimensions of multiple components do not necessarily represent their relative sizes; even if component A is depicted as thicker than component B in the drawing, component A may actually be thinner than component B.

[0029] Figure 1 is a perspective view of a distributed feedback semiconductor laser element (DFB-LD) 100 according to an embodiment. The semiconductor laser element 100 comprises a substrate 110, a laminated structure 120 formed on the substrate 110, and a protective film 184.

[0030] The substrate 110 is a nitride semiconductor, In x Al y Ga 1-x-y The composition can be N(0≦x≦1, 0≦y≦1, 0≦x+y≦1). To generate 444nm blue laser light, the substrate 110 material can be GaN(x=y=0). Furthermore, the substrate 110 is not limited to this, as long as it has equivalent effects, for example, a Si substrate or a sapphire substrate may also be used.

[0031] The n-type semiconductor layer 122, the active layer 124, and the p-type semiconductor layer 126 are sequentially formed on the n-type substrate 110 by epitaxial growth, constituting a stacked structure 120.

[0032] The n-type semiconductor layer 122 may include an n-type cladding layer and an n-type guide layer. For example, the material of the n-type cladding layer is n-Al 0.05 Ga 0.95 N, and the material of the n-type guide layer is n-GaN.

[0033] An active layer (light-emitting layer) 124 having a quantum well structure is formed on the n-type semiconductor layer 122. When the oscillation wavelength is 444 nm, for the material of the quantum well structure, In 0.01 Ga 0.99 N can be selected as the barrier layer, and In 0.15 Ga 0.85 N can be selected as the well layer.

[0034] In order to suppress the diffusion of impurities from the n-type semiconductor layer 122 to the active layer 124, an undoped nitride guide layer (not shown) In 0.02 Ga 0.98 N can be inserted between them.

[0035] The p-type semiconductor layer 126 may include a carrier block (electron block EB) layer, a p-type guide layer, a p-type cladding layer, and a contact layer. For example, the material of the p-type guide layer is p-In 0.02 Ga 0.98 N, the material of the p-type cladding layer is p-Al 0.04 Ga 0.96 N, and the material of the contact layer is p-GaN.

[0036] In order to suppress the diffusion of impurities from the p-type semiconductor layer 126 to the active layer 124, an undoped nitride guide layer (not shown) can be inserted between them.

[0037] In the p-type semiconductor layer 126 (p-type cladding layer), a ridge portion (also referred to as a mesa portion) 142 is formed as the current confinement structure 141. The height of the ridge portion 142 can be several hundred nm, and the width (mesa width) of the ridge portion 142 can be several microns. For example, the height can be 500 nm and the width can be 2 μm.

[0038] The coupling coefficient κ also changes with the mesa width; the narrower the mesa width, the larger the coupling coefficient κ becomes. However, when the mesa width is less than 1 μm, lateral confinement weakens, and the laser characteristics begin to deteriorate. On the other hand, when the mesa width exceeds 3 μm, the laser changes from lateral single-mode to lateral multi-mode. Therefore, in order to obtain a high coupling coefficient κ in lateral single-mode, it is preferable that the mesa width Wm be 1 μm ≤ Wm ≤ 3 μm.

[0039] The p-type semiconductor layer 126 having a ridge portion 142, together with the active layer 124 and the n-type semiconductor layer 122, forms a ridge-type waveguide 144. The ridge-type waveguide 144 extends in the first direction (z-axis direction in the figure).

[0040] The n-side electrode 171 is formed on the back surface of the substrate 110, and the p-side first electrode (also called the p1 electrode) 172 is formed on the upper surface of the ridge portion 142 of the p-type semiconductor layer 126. Furthermore, the p-side second electrode (also called the p2 electrode) 174 is formed on the upper surface of the p1 electrode 172.

[0041] The semiconductor laser element 100 is a transversely coupled DFB-LD, and diffraction gratings 150_1 and 150_2 are formed on both sides of the mesa adjacent to the ridge-type waveguide 144 in the second direction (x-axis direction). Each diffraction grating 150_1 and 150_2 has a plurality of first grooves 152 formed in the p-type semiconductor layer 126 adjacent to the mesa. The plurality of first grooves 152 are adjacent in the first direction (z-direction), and the first grooves 152 extend in the second direction (x-direction).

[0042] A protective film 184 is formed on the p-type semiconductor layer 126. The protective film 184 is a passivation film made of a dielectric material that protects the p-type semiconductor layer 126 from water, oxygen, and other impurities. The interior of the first groove 152 of the diffraction grating 150 is filled with the dielectric material of this protective film 184. The diffraction grating 150 has a periodic structure in which the dielectric constant ε1 of the dielectric material in the first groove 152 and the dielectric constant ε2 of the p-type semiconductor layer 126 alternate with respect to a first direction.

[0043] The semiconductor laser element 100 includes a pad electrode 173. Bonding wires (not shown) are connected to the pad electrode 173 when mounting the semiconductor laser element 100. The pad electrode 173 is electrically connected to the p1 electrode 172 via the p2 electrode 174.

[0044] A periodic structure 180 is provided in the region overlapping with the pad electrode 173. The periodic structure 180 includes a plurality of second grooves 182 formed in the region overlapping with the pad electrode 173 of the second conductivity type semiconductor layer 126. The second grooves 182 are parallel to the first grooves 152 of the diffraction grating 150, and the second grooves 182 extend in the second direction (x direction).

[0045] The dielectric material of the protective film 184 also fills the interiors of the multiple second grooves 182. The dielectric material inside the second grooves 182 is selected to have a dielectric constant ε1 lower than the dielectric constant ε2 of the second conductivity type semiconductor layer 126. Therefore, the material of the protective film 184 is an oxide containing one or more elements from Si, Zr, Al, Ta, Nb, Ti, In, O, and N, specifically SiN x SiO2, ZrO2, Al2O3, Ta2O5, Nb2O5, TiO2, AlN, AlON, AlInN, etc. can be used.

[0046] Figure 2 is a cross-sectional view of the semiconductor laser element 100 in Figure 1 along the line B-B'. The line B-B' is defined to pass through the pad electrode 173 and the periodic structure 180.

[0047] A periodic structure 180 is formed directly beneath the pad electrode 173. The periodic structure 180 has a periodic structure in which the second groove 182 and the p-type semiconductor layer 126 alternately appear in the first direction (z-axis direction).

[0048] In one embodiment, the period (pitch) of the periodic structure 180 is approximately 89 nm, and the width of the second groove 182 in the first direction (z direction) is approximately 20 nm.

[0049] The parasitic capacitance Cp formed between the pad electrode 173 and the n-side electrode 171 is Cp = S × ε / d This is the result. d is the distance between the electrodes, ε is the effective dielectric constant between the pad electrode 173 and the n-side electrode 171, and S is the area on which the pad electrode 173 is formed.

[0050] If the periodic structure 180 is not provided, the dielectric constant directly beneath the pad electrode 173 is equal to the dielectric constant ε2 of the p-type semiconductor layer 126. In contrast, if the periodic structure 180 is provided, the dielectric constant ε1 inside the second groove 182 becomes lower, so the effective dielectric constant becomes lower than ε2. This reduces the parasitic capacitance Cp, making it possible to increase the modulation bandwidth of the semiconductor laser element 100.

[0051] Here, multiple second grooves 182 can be formed using the same process when forming multiple first grooves 152. Therefore, complexity and cost of the manufacturing process can be suppressed.

[0052] To reduce parasitic capacity Cp, reducing the area S is also effective. On the other hand, a minimum area (space) is required for bonding the bonding wire. From this perspective, the area of ​​the pad electrode 173 per bonding wire should be at most 8000 μm². 2 The following is preferable. This minimizes parasitic capacitance caused by the pad electrode 173.

[0053] Figure 3 is a plan view of a semiconductor laser element 100 according to one embodiment. The periodic structure 180 and one of the diffraction gratings 150 (150_2) are formed adjacent to each other in the second direction (x direction). This minimizes the area in which the first groove 152 and the second groove 182 must be formed. When the grooves 152 and 182 are formed by EB (electron beam) lithography, the lithography time can be shortened and throughput can be increased.

[0054] The period (pitch) of the periodic structure 180 may coincide with the period of the diffraction grating 150.

[0055] Furthermore, the second groove 182 of the periodic structure 180 may be formed continuously with the first groove 152 of the diffraction grating 150_2. This allows the first groove 152 and the second groove 182 to be formed simultaneously.

[0056] Figure 4 is a plan view of a semiconductor laser element 100 according to one embodiment. The widths of the multiple second grooves 182 can be formed to differ from the widths of the multiple first grooves 152. Specifically, the width of the second grooves 182 can be set to approximately 30 nm, while the width of the first grooves 152 is approximately 20 nm. This further reduces the effective dielectric constant directly beneath the pad electrode 173, and therefore further reduces the parasitic capacitance Cp. Changing the widths of the first grooves 152 and the second grooves 182 in this way can be easily achieved, for example, by increasing the dose amount of the periodic structure portion compared to the dose amount of the diffraction grating portion when forming by EB lithography.

[0057] Figure 5 is a plan view of a semiconductor laser element 100 according to one embodiment. In this embodiment, the multiple second grooves 182 are formed discontinuously with the multiple first grooves 152.

[0058] Figure 6 is a plan view of a semiconductor laser element 100 according to one embodiment. In this embodiment, the diffraction grating 150 is provided on only one side of the current constriction structure 141, and the periodic structure 180 is provided on the opposite side of the current constriction structure 141 from the diffraction grating 150.

[0059] Figure 7 is a plan view of a semiconductor laser element 100 according to one embodiment. In this embodiment, the diffraction grating 150 is provided only on one side of the current constriction structure 141. The periodic structure 180 is provided adjacent to the diffraction grating 150.

[0060] Figure 8 is a diagram illustrating the manufacturing method of the semiconductor laser element 100.

[0061] A laminated structure 120, including an n-type semiconductor layer 122, an active layer 124, and a p-type semiconductor layer 126, is formed on the substrate 110 by epitaxial growth (S100).

[0062] Next, a ridge forming a current-constricting structure 141 is created in the p-type semiconductor layer 126 (S102).

[0063] Then, multiple grooves 152 are formed on both sides of the current-constricting structure 141 of the second conductivity type semiconductor layer 126 (S104). The multiple grooves 152 can be formed by EB drawing. At this time, multiple second grooves 182 are also formed in the region where the pad electrode 173 is to be formed. If the second grooves 182 and the first grooves 152 are continuous, they can be formed as a single unit.

[0064] Next, multiple second grooves 182 are filled with a dielectric material having a lower dielectric constant than the p-type semiconductor layer 126 (i.e., a protective film 184) (S106).

[0065] The above describes the manufacturing method for the semiconductor laser element 100. As the second groove 182 and the first groove 152 can be formed using the same process, the complexity of the manufacturing process due to the provision of the periodic structure 180 can be ignored.

[0066] Next, we will explain a modified example of the semiconductor laser element 100.

[0067] Figure 9 is a cross-sectional view of a semiconductor laser element 100A according to Modification 1. The semiconductor laser element 100A includes a dielectric layer 190 inserted between a pad electrode 173 and a periodic structure 180. The dielectric layer 190 is composed of a second dielectric material 192 having a lower dielectric constant (ε3) than the p-type semiconductor layer 126.

[0068] The area of ​​the dielectric layer 190 should be larger than the area of ​​the pad electrode 173. This allows the dielectric layer 190 to be inserted over the entire pad electrode 173.

[0069] With this configuration, by inserting the dielectric layer 190, the distance d between the pad electrode 173 and the n-side electrode 171 can be increased, and the parasitic capacitance Cp can be further reduced.

[0070] The second dielectric material 192 may be the same material as the protective film 184. As a result, the grooves of the periodic structure 180 act as anchors for the dielectric layer 190, increasing the adhesion strength and making the dielectric layer 190 less likely to peel off.

[0071] Figure 10 is a cross-sectional view of a semiconductor laser element 100B according to Modification 2. In the semiconductor laser element 100B, there is a void 186 inside the second groove 182 of the periodic structure 180B that is not filled with the first dielectric material, which is the protective film 184. Since the void 186 is a gas such as air, the dielectric constant is at its lowest, which further reduces the effective dielectric constant of the periodic structure 180B and further reduces the parasitic capacitance Cp.

[0072] Figure 11 illustrates an example of a manufacturing method for the periodic structure 180B shown in Figure 10. First, a laminated structure 120 is formed on the substrate 110, and a current-constricting structure 141 is formed on the p-type semiconductor layer 126. Figure 11 shows the p-type semiconductor layer 126 before the formation of the periodic structure 180B (S100).

[0073] Second grooves 182 are formed in the p-type semiconductor layer 126 at a predetermined pitch by etching (S102). Subsequently, a dielectric material that will become a protective film 184 is deposited on the p-type semiconductor layer 126 with the formed irregularities by the CVD (Chemical Vapor Deposition) method (S104).

[0074] As deposition continues, a large amount of dielectric material is deposited at the corners of the convex parts of the periodic structure, i.e., at the shallowest part of the second groove 182 (S106). Finally, at the surface of the p-type semiconductor layer 126, the dielectric materials connect to each other across the second groove 182, forming a protective film 184, and the protective film 184 and voids 186 are formed inside the p-type semiconductor layer 126 (S108).

[0075] In order to form the void 186 using the manufacturing method shown in Figure 11, the width of the second groove 182 is important, and by making it 100 nm or less, the void shown in S108 of Figure 11 can be formed.

[0076] Figure 12 is a plan view of a semiconductor laser element 100C according to modified example 3. There may be two or more pad electrodes 173. In this case, the multiple pad electrodes 173 may be grouped together on one side of the chip, and the periodic structures 180_1 and 180_2 are arranged adjacent to each other on that side.

[0077] Alternatively, multiple periodic structures 180 may be arranged on opposite sides of the chip, with the current-constricting structure 141 in between.

[0078] The embodiments merely illustrate the principles and applications of the present invention, and many modifications and changes in arrangement are permitted in the embodiments, without departing from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0079] 100 semiconductor laser elements 110 circuit boards 120 Laminated structure 122 n-type semiconductor layer 124 Active layer 126 p-type semiconductor layer 141 Current confinement structure 142 Ridge section 144 Ridge Waveguides 150 Diffraction Gratings 152 First groove 171 n-side electrode 172 p1 electrode 174 p2 electrode 173 Pad electrodes 180 Periodic structure 182 2nd groove 184 Protective film 190 Dielectric layer 192 Second Dielectric Materials

Claims

1. A distributed feedback type semiconductor laser element, circuit board and A laminated structure comprising a first conductivity semiconductor layer, an active layer, and a second conductivity semiconductor layer, Pad electrodes and Equipped with, The aforementioned laminated structure includes, Current-constricted structure, A diffraction grating including a plurality of first grooves is formed in a region adjacent to the current-constricting structure of the second conductivity semiconductor layer, The region of the second conductivity semiconductor layer overlaps with the pad electrode and includes a plurality of second grooves parallel to the first groove, the plurality of second grooves having a periodic structure in which a first dielectric material having a lower dielectric constant than the second conductivity semiconductor layer is embedded. A semiconductor laser element characterized by being provided with

2. The semiconductor laser element according to claim 1, characterized in that the period of the periodic structure is the same as the period of the diffraction grating.

3. The aforementioned periodic structure is formed adjacent to the diffraction grating, The semiconductor laser element according to claim 1 or 2, characterized in that the second groove of the periodic structure is formed continuously with the first groove of the diffraction grating.

4. The semiconductor laser element according to claim 1 or 2, characterized in that the width of the second groove of the periodic structure is different from the width of the first groove of the diffraction grating.

5. The semiconductor laser element according to claim 1 or 2, characterized in that the diffraction grating is formed on both sides of the current constriction structure.

6. The semiconductor laser element according to claim 1 or 2, characterized in that the diffraction grating is formed only on one side of the current constriction structure.

7. The area of ​​the pad electrode is 8000 μm² per bonding wire connected to the pad electrode. ２ The semiconductor laser element according to claim 1 or 2, characterized in that it is as follows:

8. The semiconductor laser element according to claim 1 or 2, characterized in that a dielectric layer made of a second dielectric material having a lower dielectric constant than the second conductivity semiconductor layer is formed between the pad electrode and the periodic structure.

9. The semiconductor laser element according to claim 8, characterized in that the area of ​​the dielectric layer is larger than the area of ​​the pad electrode.

10. The semiconductor laser element according to claim 8, characterized in that the second dielectric material is the same as the first dielectric material.

11. The semiconductor laser element according to claim 1 or 2, characterized in that the periodic structure portion has a width of 100 nm or less in the resonator direction of the second groove.

12. The semiconductor laser element according to claim 1 or 2, characterized in that the interior of the first groove of the periodic structure has voids that are not filled with the first dielectric material.

13. A method for manufacturing a distributed feedback type semiconductor laser element, The steps include forming a laminated structure on a substrate, which includes a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer. The steps include forming a current-constricting structure in the aforementioned laminated structure, The steps include forming a diffraction grating containing a plurality of first grooves in a region adjacent to the current-constricting structure of the second conductivity semiconductor layer, and forming a plurality of second grooves parallel to the first grooves in a region of the second conductivity semiconductor layer where pad electrodes are to be formed, The steps include filling the plurality of second grooves with a first dielectric material having a lower dielectric constant than the second conductivity semiconductor layer, A manufacturing method characterized by comprising the following:

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