Semiconductor optical element

Abstract

To provide a semiconductor optical element with excellent heat dissipation properties. [Solution] The semiconductor optical element comprises a substrate, a mesa structure protruding from the substrate and extending in a stretching direction parallel to the substrate and including an active layer, a first semiconductor embedding layer and a second semiconductor embedding layer located on the first side of the mesa structure in a cross section perpendicular to the stretching direction, and electrodes provided on the mesa structure and partially located on the first and second embedding layers, respectively, wherein the upper surface of the first embedding layer has a first inclined portion that slopes in the width direction of the mesa structure so as it moves away from the mesa structure it approaches the substrate, and the upper surface of the second embedding layer has a second inclined portion that slopes in the width direction so as it moves away from the mesa structure it approaches the substrate, and the electrodes cover the entirety of the first and second inclined portions, respectively.

Description

Technical Field

[0001] The present invention relates to a semiconductor optical element.

Background Art

[0002] Semiconductor optical elements are devices that form the core of modern optical communication. For example, devices such as semiconductor lasers that convert an applied electrical signal into light, and semiconductor optical amplifiers that amplify light are used. In addition, semiconductor photodetectors that convert light into an electrical signal are also widely used. One structure of a semiconductor optical element is a buried heterostructure (hereinafter referred to as a BH structure). The BH structure is a structure in which semiconductor layers are embedded on both sides of a mesa structure including an active layer and an absorption layer. The BH structure has excellent characteristics such as high reliability, high heat dissipation characteristics, and an aspect ratio of light close to 1. An example of a semiconductor optical element having a BH structure is disclosed in Patent Documents 1 and 2.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the BH structure has excellent heat dissipation, in order to meet the requirements of recent high-density mounting, high-power driving, etc., it is preferable to further improve the heat dissipation. In semiconductor lasers, further high-output characteristics are required. To meet this requirement, the drive current is increasing, and the amount of heat generation is tending to increase. The temperature rise during the drive of a semiconductor laser causes an increase in the threshold current, a decrease in efficiency, etc., and as a result, can lead to deterioration of the optical output characteristics. Similarly, in other types of semiconductor optical elements, heat generation causes deterioration of various characteristics, which is not preferable.

[0005] The present invention aims to provide a semiconductor optical element with excellent heat dissipation properties. [Means for solving the problem]

[0006] The semiconductor optical element comprises a substrate, a mesa structure protruding from the substrate and extending in a stretching direction parallel to the substrate and including an active layer, a first semiconductor embedding layer and a second semiconductor embedding layer located on the first side of the mesa structure in a cross section perpendicular to the stretching direction, and electrodes provided on the mesa structure and partially located on the first and second embedding layers, respectively, wherein the upper surface of the first embedding layer has a first inclined portion that slopes in the width direction of the mesa structure so as it moves away from the mesa structure it approaches the substrate, and the upper surface of the second embedding layer has a second inclined portion that slopes in the width direction so as it moves away from the mesa structure it approaches the substrate, and the electrodes cover the entirety of the first and second inclined portions, respectively. [Brief explanation of the drawing]

[0007] [Figure 1] This is a top view of a semiconductor optical element according to the first embodiment. [Figure 2] Figure 1 is a schematic cross-sectional view of a semiconductor optical device along line AA. [Figure 3] This is a schematic cross-sectional view showing the shape of the embedded layer. [Figure 4] This is a schematic cross-sectional view along the AA line of a semiconductor optical element according to Modification 1 of the First Embodiment. [Figure 5] This is a schematic cross-sectional view along the AA line of a semiconductor optical element according to a modified example 2 of the first embodiment. [Figure 6] This is a schematic cross-sectional view of a semiconductor optical element according to the second embodiment, along the AA line. [Figure 7] This is a top view of a semiconductor optical element according to the third embodiment. [Figure 8] Figure 7 is a schematic cross-sectional view of a semiconductor optical device along line AA. [Figure 9] This is a schematic cross-sectional view along the AA line of a semiconductor optical element according to a modified example of the third embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described specifically and in detail below with reference to the drawings. Components denoted by the same reference numerals in all figures have the same or equivalent function, and repeated explanations will be omitted. Note that the size of the figures does not necessarily correspond to the magnification.

[0009] [First Embodiment] Figure 1 is a top view of a semiconductor optical element according to the first embodiment. Figure 2 is a schematic cross-sectional view showing cross section AA of Figure 1. The semiconductor optical element according to this embodiment is a semiconductor laser.

[0010] The semiconductor optical element has a substrate 3, a first electrode 11 on the back surface of the substrate 3, and a second electrode 12 on the front surface of the substrate 3. The first electrode 11 and the second electrode 12 are metal layers. By injecting a current between the first electrode 11 and the second electrode 12, light is emitted from the end face. In the following description, the end face refers to the end face of the semiconductor optical element in the stretching direction D1 of the mesa structure 17 (the end face in the vertical direction in Figure 1). In this embodiment, a low-reflection end face coating film (not shown) is formed on both end faces. Alternatively, a high-reflection end face coating film may be formed on only one end face.

[0011] [Semiconductor multilayer] The semiconductor optical element includes a semiconductor multilayer in which a first conductivity type cladding layer 5, an active layer 7, a second conductivity type cladding layer 9, and a second conductivity type contact layer 15 are stacked from bottom to top on a first conductivity type substrate 3. A diffraction grating layer may also be formed above or below the active layer 7. The first conductivity type cladding layer 5 is not required. In this embodiment, the first conductivity type cladding layer 5 is a first conductivity type semiconductor layer placed between the first conductivity type substrate 3 and the active layer 7. The active layer 7 is formed, for example, as a multiple quantum well layer. An optical confinement layer may be placed above, below, or on one side of the active layer 7. In this embodiment, which uses a semiconductor laser as an example of a semiconductor optical element, the active layer 7 is a layer that generates light, but the active layer 7 is not limited to a layer that generates light. For example, the active layer may function as an absorption layer that converts light into electricity when a voltage is applied. That is, the active layer refers to a layer in which the conversion between electricity and light takes place when a voltage is applied. The second conductivity type cladding layer 9 is a second conductivity type semiconductor layer positioned between the active layer 7 and the second conductivity type contact layer 15, and may consist of multiple layers rather than a single layer. Hereafter, the second conductivity type cladding layer 9 refers to a second conductivity type semiconductor layer positioned above the active layer 7. In other words, the semiconductor multilayer according to this embodiment has a structure in which the active layer is sandwiched between a first conductivity type semiconductor layer and a second conductivity type semiconductor layer. The second conductivity type contact layer 15 is positioned to reduce the contact resistance between the semiconductor layer and the metal layer (second electrode 12). The resistivity of the second conductivity type contact layer 15 is lower than the resistivity of the second conductivity type cladding layer 9. The impurity concentration of the second conductivity type contact layer 15 is higher than the impurity concentration of the second conductivity type cladding layer 9. In this embodiment, the first conductivity type is n-type and the second conductivity type is p-type, but the reverse may also be true.

[0012] [Mesa structure] The semiconductor optical element has a mesa structure 17 that protrudes from the substrate 3. The bottom of the mesa structure 17 is composed of a part of the first conductivity type cladding layer 5. The mesa structure 17 extends in a stretching direction D1 parallel to the substrate 3, reaching both end faces. In Figure 1, the interface between the mesa structure 17 and the left embedded layer 19a and the right embedded layer 19b, which will be described later, is shown by a dashed line. The mesa structure 17 includes an active layer 7, a second conductivity type cladding layer 9, and a second conductivity type contact layer 15. In the mesa structure 17, a part of the first conductivity type cladding layer 5, the active layer 7, the second conductivity type cladding layer 9, and the second conductivity type contact layer 15 are stacked in this order from bottom to top. In this embodiment, the second conductivity type contact layer 15 is the uppermost layer of the mesa structure 17.

[0013] [Buried layer] In a cross-section perpendicular to the stretching direction D1, a left embedded semiconductor layer 19a (first embedded layer) is located on the left side (first side) of the mesa structure 17, and a right embedded semiconductor layer 19b (second embedded layer) is located on the right side (second side) of the mesa structure 17. The left embedded layer 19a and the right embedded layer 19b are either a laminated structure of a semi-insulating semiconductor layer, a first conductivity type semiconductor layer, and a second conductivity type semiconductor layer, or a laminated structure of a semi-insulating semiconductor layer, a first conductivity type semiconductor layer, and a second conductivity type semiconductor layer. Here, it is desirable that the material constituting the main regions of the left embedded layer 19a and the right embedded layer 19b is the same as the material constituting the first conductivity type cladding layer 5 and the second conductivity type cladding layer 9. Such a material is, for example, InP. Here, "the same material" means that the basic composition (in this case, InP) is the same, excluding the doping material.

[0014] The upper surface of the left embedded layer 19a includes a left inclined portion Sa (first inclined portion) that inclines in the width direction D2 of the mesa structure 17 so as to approach the substrate 3 as it moves away from the mesa structure 17, and a left flat portion (first flat portion) Fa that is substantially parallel to the upper surface of the substrate 3 and is continuous with the left inclined portion Sa. Further, the upper surface of the right embedded layer 19b includes a right inclined portion Sb (second inclined portion) that inclines in the width direction D2 of the mesa structure 17 so as to approach the substrate 3 as it moves away from the mesa structure 17, and a right flat portion (second flat portion) Fb that is substantially parallel to the upper surface of the substrate 3 and is continuous with the right inclined portion Sb. In the height direction D3 of the mesa structure 17 (the normal direction of the substrate 3), the height of the upper surface of the left embedded layer 19a in the left flat portion Fa from the substrate 3 is lower than the height of the upper surface of the mesa structure 17 from the substrate 3 (the same applies to the right flat portion Fb). In FIG. 2, the left inclined portion Sa and the right inclined portion Sb descend from the upper surface of the mesa structure 17 (the upper surface of the second conductive type contact layer 15), but it is not limited thereto.

[0015] The left inclined portion Sa and the right inclined portion Sb are composed of a combination of straight lines and curves. The height of the upper surface of the left embedded layer 19a in the left inclined portion Sa from the substrate 3 basically decreases monotonically (the same applies to the right inclined portion Sb), but since the left embedded layer 19a and the right embedded layer 19b are formed by crystal growth, the left inclined portion Sa and the right inclined portion Sb may include some undulations. Note that at least one of the left inclined portion Sa and the right inclined portion Sb may include one or more steps.

[0016] The left flat portion Fa and the right flat portion Fb are parts of the upper surfaces of the left embedded layer 19a and the right embedded layer 19b that are away from the mesa structure 17 and are approximately parallel to the surface of the substrate 3. In the width direction D2, the left flat portion Fa is continuous with the left inclined portion Sa, and the right flat portion Fb is continuous with the right inclined portion Sb. Since the left embedded layer 19a and the right embedded layer 19b are formed by crystal growth, some waviness may exist in the flat portion F. However, even if there are some height variations, the left flat portion Fa and the right flat portion Fb are positioned lower than the upper surface of the mesa structure 17 relative to the substrate 3. Furthermore, the left flat portion Fa is defined as the flat portion adjacent to the left inclined portion Sa, which is part of the upper surface of the left embedded layer 19a that is continuous with the left inclined portion Sa (the same applies to the right inclined portion Sb). Multiple crystal growth and etching processes may be performed before the left embedded layer 19a and the right embedded layer 19b are formed. In this case, the surface that serves as the substrate for crystal growth of the left embedded layer 19a and the right embedded layer 19b (in this case, the upper surface of the first conductivity type cladding layer 5) may not be flat. Specifically, the height of the upper surface of the first conductivity type cladding layer 5 from the substrate 3 may differ between the region immediately next to the mesa structure 17 and the region further away from the mesa structure 17. In this case, when the left embedded layer 19a and the right embedded layer 19b are formed on the upper surface of the first conductivity type cladding layer 5, the shape of the upper surfaces of the left embedded layer 19a and the right embedded layer 19b may also differ between the region immediately next to the mesa structure 17 and the region further away from the mesa structure 17. That is, the upper surfaces of the left embedded layer 19a and the right embedded layer 19b may be flat in the region immediately next to the mesa structure 17, but not in the region further away from the mesa structure 17. However, in this embodiment, the shape of the upper surfaces of the left embedding layer 19a and the right embedding layer 19b in the region that is far enough away from the mesa structure 17 that it does not affect the light distribution D described later does not have to be flat. For this reason, the left flat portion Fa is defined on the upper surface of the left embedding layer 19a as a flat portion adjacent to the left sloping portion Sa (the same applies to the right flat portion Fb).

[0017] The boundary between the left inclined portion Sa and the left flat portion Fa is not necessarily clear (the same applies to the right inclined portion Sb and the right flat portion Fb). In the present embodiment, the left inclined portion Sa is a portion that inclines in the width direction D2 so as to approach the substrate 3 as it moves away from the mesa structure 17, and is defined as the portion from the point where the thickness in the height direction D3 of the left embedded layer 19a is the thickest to the point where it is the thinnest (the same applies to the right inclined portion Sb). Here, the point where the thickness in the height direction D3 of the left embedded layer 19a and the right embedded layer 19b is the thinnest is defined as the lowest point P. In FIG. 2, the left inclined portion Sa and the left flat portion Fa are smoothly connected, but it is not limited thereto. The shape of the upper surface of the left embedded layer 19a may incline upward once after inclining from the upper surface of the mesa structure 17 to the lowest point P and then be continuous with the left flat portion Fa (the same applies to the right inclined portion Sb and the right flat portion Fb). Note that depending on the thickness in the height direction D3 of the left embedded layer 19a and the right embedded layer 19b, the widths of the left inclined portion Sa and the right inclined portion Sb in the width direction D2 are about several μm to 5 μm.

[0018] [Insulating film] A left insulating film (first insulating film) 21a is disposed on a part of the upper surface of the left embedded layer 19a, and a right insulating film (second insulating film) 21b is disposed on a part of the upper surface of the right embedded layer 19b. Since the left insulating film 21a and the right insulating film 21b are not disposed on the upper surface of the mesa structure 17, they are in contact with the second conductive type contact layer 15 and the second electrode 12. The left insulating film 21a and the right insulating film 21b are formed of, for example, a silicon oxide film or a silicon nitride film. In the present embodiment, the left insulating film 21a is not disposed on the left inclined portion Sa but is disposed on the left flat portion Fa (the same applies to the right insulating film 21b).

[0019] [Electrode] The first electrode 11 is broadly arranged on the back surface of the substrate 3. In this embodiment, the first electrode 11 is arranged to both ends in the width direction D2 of the substrate 3, but is not limited to this. For example, the first electrode 11 does not need to reach both ends of the substrate 3 in the width direction D2. The second electrode 12 has a laminated structure including at least Au. For example, the second electrode 12 has a three-layer structure in which Ti / Pt / Au are laminated in order from the second conductive contact layer 15 side (from bottom to top). This configuration is merely an example. The second electrode 12 is arranged to cover at least the entirety of the left-sloping portion Sa and the right-sloping portion Sb on both sides of the mesa structure 17, sandwiching the mesa structure 17. In this embodiment, the second electrode 12 is also arranged on a part of the left flat portion Fa and the right flat portion Fb. The second electrode 12 has an electrode left-sloping portion that slopes along the left-sloping portion Sa and an electrode left flat portion that is flat along the left flat portion Fa. In this embodiment, the second electrode 12 directly covers the entirety of the left-sloping portion Sa and the right-sloping portion Sb, but it may also cover them indirectly. That is, another member may be interposed between the second electrode 12 and the left-sloping portion Sa (the same applies to the right-sloping portion Sb). In that case, the other member also has a portion that slopes along the left-sloping portion Sa.

[0020] [effect] When the semiconductor optical element is driven, that is, when a voltage is applied between the first electrode 11 and the second electrode 12, the mesa structure 17 becomes a heat source. There are multiple heat sources, but the active layer 7 is a particularly large heat source. The heat generated in the active layer 7 is dissipated through the semiconductor layer surrounding the active layer 7. The distance from the active layer 7 to the first electrode 11 is generally several tens of times greater than the distance from the active layer 7 to the second electrode 12. Therefore, a large amount of heat is dissipated from the second electrode 12 side. The second electrode 12 is a metal layer, has excellent thermal conductivity, and is a good heat dissipation material. Therefore, by reducing the distance between the heat source (active layer 7) and the heat dissipation material (second electrode 12), heat dissipation is improved, and a semiconductor optical element with excellent high-temperature characteristics can be realized. In this embodiment, as shown in Figure 2, the left embedded layer 19a and the right embedded layer 19b are provided with a left-sloping portion Sa and a right-sloping portion Sb, and the second electrode 12 is placed on the left-sloping portion Sa and the right-sloping portion Sb. Therefore, compared to the semiconductor optical element of Patent Document 1, the semiconductor optical element according to this embodiment has a closer distance from the active layer 7 to the second electrode 12, resulting in superior heat dissipation. Furthermore, in Patent Document 2, the embedded layer has a sloped portion, but the electrodes are not arranged in the sloped portion. In contrast, in the semiconductor optical element according to this embodiment, the second electrode 12 is arranged throughout both the left sloped portion Sa and the right sloped portion Sb, so this embodiment has superior heat dissipation.

[0021] Here, in order to further improve heat dissipation, it is conceivable to make the left embedded layer 19a and the right embedded layer 19b thinner. However, this is undesirable from the viewpoint of optical properties. Figure 2 shows the outer edge of the light distribution D guiding the mesa structure 17 with a dashed line. The light distribution D spreads out in a circular shape from the active layer 7. The light distribution D is generally elliptical. The light intensity is highest at the center of the light distribution D, and decreases as it spreads outwards. In Figure 2, the light distribution D is shown up to the region where the light intensity distribution is 2σ. In the second conductivity type contact layer 15, where the impurity concentration is high, there is a large loss of light. Therefore, the thickness of the second conductivity type cladding layer 9 in the height direction D3 is set so that the outer edge of the light distribution D does not overlap with the second conductivity type contact layer 15. Note that the second conductivity type cladding layer 9 is also a source of light loss, and its resistance increases as it becomes thicker in the height direction D3. Therefore, it is desirable for the second conductivity type cladding layer 9 to be thinner as well. However, the thickness of the second conductive cladding layer 9 in the height direction D3 is intentionally set to a certain size in order to avoid light loss due to the second conductive contact layer 15. Here, we assume that the left embedded layer 19a and the right embedded layer 19b are set to the same height as the mesa structure 17, as shown in Patent Document 1. In other words, we assume that the left embedded layer 19a and the right embedded layer 19b do not have a left-sloping portion Sa and a right-sloping portion Sb. In this structure, the light distribution D naturally fits within the semiconductor layer surrounding the active layer 7, and a good light distribution shape is maintained. From this state, if the left embedded layer 19a and the right embedded layer 19b are made thinner, that is, if a left-sloping portion Sa and a right-sloping portion Sb are provided and the left-sloping portion Sa and the right-sloping portion Sb are brought closer to the side surface of the mesa structure 17, at a certain point the outer edge of the light distribution D will overlap with the left-sloping portion Sa and the right-sloping portion Sb. More precisely, the shape of the light distribution D changes to remain within the semiconductor layer due to the difference in refractive index between the left embedded layer 19a and the right embedded layer 19b (semiconductor) and the surrounding environment (e.g., air). Specifically, the light distribution D changes into a vertically elongated ellipse shape. This change in the shape of the light distribution D is undesirable because it leads to a decrease in the coupling efficiency between the output light from the semiconductor optical element and the optical system (lens or waveguide) into which it is input.

[0022] Therefore, in this embodiment, the thickness of the left embedded layer 19a and the right embedded layer 19b in the height direction D3 is set within a range that does not affect the light distribution D. The positional relationship between the left inclined portion Sa and the left flat portion Fa is determined by crystal growth (the same applies to the right inclined portion Sb and the right flat portion Fb). Figure 3 shows the changes in the upper surface shape of the left embedded layer 19a and the right embedded layer 19b, which were carefully studied by the inventors of this application. In Figure 3, for the sake of simplicity, only the shape of the right side of the mesa structure 17 is shown, but the shape of the left side is substantially the same. Also, the second electrode 12 is not shown in Figure 3.

[0023] As shown in Figure 3, as the height of the right embedded layer 19b in the right flat portion Fb decreases relative to the substrate 3, the right inclined portion Sb moves away from the side surface of the mesa structure 17 and the outer edge of the light distribution D. In Figure 3, the outer edge of the light distribution D is shown by a dashed circle when the upper surface of the right embedded layer 19b in the right flat portion Fb is positioned at the same height as the upper surface of the mesa structure 17 relative to the substrate 3. As described above, the distance between the active layer 7 and the second conductive contact layer 15 is set so that the outer edge of the light distribution D does not overlap. Let H be the distance (height) between the upper surface of the active layer 7 and the lower surface of the second conductive contact layer 15 in the height direction D3. For example, in Figure 3, the solid line labeled "0%" shows the shape of the upper surface of the right embedded layer 19b when the position of the upper surface of the right embedded layer 19b in the right flat portion Fb coincides with the position of the upper surface of the active layer 7 in the height direction D3. Similarly, in Figure 3, the solid line labeled "100%" shows the shape of the upper surface of the right embedded layer 19b when the position of the upper surface of the right embedded layer 19b in the right flat section Fb coincides with the position of the lower surface of the second conductive contact layer 15 in the height direction D3. The solid line labeled "25%" shows the shape of the upper surface of the right embedded layer 19b when the position of the upper surface of the right embedded layer 19b in the right flat section Fb is 25% of the height H, with the upper surface of the active layer 7 as the base point. The same applies to the other values.

[0024] As is clear from Figure 3, if the upper surface of the right embedded layer 19b in the right flat section Fb is at a height of 0% or more of the height H with the upper surface of the active layer 7 as the base point, the right inclined section Sb does not overlap with the outer edge of the light distribution D, and the light distribution D remains good. Furthermore, by minimizing the distance between the active layer 7 and the second electrode 12 positioned on the right inclined section Sb within a range that does not affect the light distribution D, the state with the best heat dissipation can be achieved. On the other hand, if the upper surface of the right embedded layer 19b in the right flat section Fb is positioned below 0% of the height H with the upper surface of the active layer 7 as the base point (for example, at -25%), it is undesirable because it affects the light distribution D. Also, the higher the position of the upper surface of the right embedded layer 19b in the right flat section Fb, the further the right inclined section Sb moves from the outer edge of the light distribution D, so the influence on the light distribution D is reduced, but the heat dissipation decreases. The inventors of this invention have found that good heat dissipation can be obtained if the upper surface of the right embedded layer 19b in the right flat section Fb is located at a position of 50% or less of the height H, with the upper surface of the active layer 7 as the base point. The shape of the light distribution D changes depending on the light confinement rate of the active layer 7, etc. For example, the diameter of the light distribution D may be smaller than that shown in Figures 2 and 3. However, even in that case, the height H also becomes smaller, so the relationship of the upper surface shape of the right embedded layer 19b shown in Figure 3 is generally the same, and by positioning the upper surface of the right embedded layer 19b in the right flat section Fb at a position of 0% to 50% of the height H (0H to 0.5H with the front surface of the active layer 7 as the base point), it is possible to improve heat dissipation while suppressing the effect on the light distribution D. Furthermore, considering manufacturing variations, differences in the aspect ratio of the light distribution, and the need to ensure better heat dissipation, it is more preferable that the upper surface of the right embedded layer 19b in the right flat section Fb be positioned at a height of 10% to 30% (0.1H to 0.3H) relative to the height H, with the upper surface of the active layer 7 as the base point.

[0025] Furthermore, a feature of this embodiment is that the left insulating film 21a is not placed in the left-sloping portion Sa (the same applies to the right-sloping portion Sb and the right insulating film 21b). The left insulating film 21a has low thermal conductivity and hinders heat dissipation. The left insulating film 21a has particularly low thermal conductivity when it is made of silicon oxide. Therefore, in this embodiment, in order to obtain the maximum effect of heat dissipation, the left insulating film 21a is not placed in the left-sloping portion Sa, which serves as the heat dissipation path. However, if it is a very thin insulating film or a silicon nitride film with relatively high thermal conductivity, it may be placed in the left-sloping portion Sa.

[0026] As described above, in this embodiment, a semiconductor optical element with excellent heat dissipation is realized by forming a left-sloping portion Sa and a right-sloping layer 19b in the left-sloping layer 19a and the right-sloping layer 19b, and arranging a second electrode 12, which serves as a heat dissipation material, thereon. As mentioned above, the second electrode 12 can enhance heat dissipation by covering the entire left-sloping portion Sa and the right-sloping layer 19b in the width direction D2. In addition, in the stretching direction D1, the heat dissipation is maximized by covering the entire left-sloping portion Sa and the right-sloping layer 19b. However, it is not always necessary for the second electrode 12 to cover the entire left-sloping portion Sa and the right-sloping layer 19b in the stretching direction D1. For example, in the chipping process in which each element is separated after the wafer process is completed, it is preferable that the second electrode 12 is not placed in the region that becomes the exit end face. Therefore, it is not necessary to place the second electrode 12 near the exit end face and the opposite end face (the end face on the stretching direction D1 side). Naturally, the larger the area where the second electrode 12 is not placed, the lower the heat dissipation performance will be. From the viewpoint of heat dissipation, it is preferable that the second electrode 12 covers 80% or more of both the left inclined portion Sa and the right embedded layer 19b in the stretching direction D1. Although the second electrode 12 is also placed on the upper surface of the mesa structure 17, it is not necessarily required to cover the entire upper surface of the mesa structure 17. For example, near the end face of the mesa structure 17, there may be parts on the mesa structure 17 where the second electrode 12 is not placed.

[0027] [Example 1] Figure 4 is a schematic cross-sectional view of the AA section of Figure 1 of a semiconductor optical element according to Modification 1 of the First Embodiment. The difference from the First Embodiment is the shape of the upper surfaces of the left embedded layer 19a and the right embedded layer 19b.

[0028] In this modified example, the upper surface of the left embedded layer 19a includes a left sub-flat portion (first sub-flat portion) F2a that is continuous with the upper surface of the mesa structure 17 in the width direction D2. The upper surface of the right embedded layer 19b also includes a right sub-flat portion (second sub-flat portion) F2b that is continuous with the upper surface of the mesa structure 17 in the width direction D2. A left inclined portion Sa and a left flat portion Fa are formed continuous with the left sub-flat portion F2a. The left sub-flat portion F2a, like the left flat portion Fa, is a surface that is substantially parallel to the surface of the substrate 3. With respect to the substrate 3, the height of the sub-flat portion F2 in the height direction D3 is substantially the same as the height of the upper surface of the mesa structure 17 in the height direction D3. For example, if the inclination angle of the left inclined portion Sa is steeper compared to the first embodiment, providing the left sub-flat portion F2a allows the left inclined portion Sa to be moved away from the outer edge of the light distribution D, thus allowing the left inclined portion Sa to be brought closer to the mesa structure 17 without affecting the light distribution D. Furthermore, the above explanation regarding the left secondary flat section F2a also applies to the right secondary flat section F2b.

[0029] The left sub-flat section F2a and the right sub-flat section F2b can be formed by adjusting the mask size when forming the left embedded layer 19a and the right embedded layer 19b. When forming the left embedded layer 19a and the right embedded layer 19b, it is common to place the mask on top of the mesa structure 17. By making the width D2 of the mask wider than the width D2 of the mesa structure 17, the left sub-flat section F2a and the right sub-flat section F2b can be formed. However, if the mask width is too wide, the mask will act as an overhang, and there is a risk that the left embedded layer 19a and the right embedded layer 19b will not be formed on the sides of the mesa structure 17, especially near the top surface of the mesa structure 17. In addition, the gap between the mesa structure 17 and the left inclined section Sa (right inclined section Sb) will widen, which will reduce heat dissipation. Therefore, it is desirable to keep the width D2 of each of the left sub-flat section F2a and the right sub-flat section F2b to less than half the width D2 of the mesa structure 17.

[0030] [Differentiation 2] Figure 5 is a schematic cross-sectional view of the AA section of Figure 1 of a semiconductor optical element according to a modified example 2 of the first embodiment. The difference from the first embodiment is the shape of the upper surfaces of the left embedded layer 19a and the right embedded layer 19b.

[0031] In this modified example, the left embedded layer 19a is continuous with the upper surface of the mesa structure 17 and includes a left projection (first projection) Ra that protrudes from the substrate 3. The right embedded layer 19b is continuous with the upper surface of the mesa structure 17 and includes a right projection (second projection) Rb that protrudes from the substrate 3. A left inclined portion Sa and a left flat portion Fa are formed continuous with the left projection Ra (the same applies to the right projection Rb). For example, when forming the left embedded layer 19a and the right embedded layer 19b, if the width D2 in the width direction of the mask placed on the mesa structure 17 matches the width D2 of the mesa structure 17, a projection R may be formed as shown in Figure 5. If the left projection Ra and the right projection Rb are too large, the left inclined portion Sa and the right inclined portion Sb will move away from the mesa structure 17, resulting in reduced heat dissipation. Therefore, it is desirable that the thickness in the height direction D3 of the left projection Ra and the right projection Rb are thinner than the thickness in the height direction D3 of the second conductive contact layer 15. Here, the thickness of the left projection Ra and the right projection Rb are defined by the distance from the top surface of the mesa structure 17 to the highest point of the left projection Ra and the right projection Rb, respectively.

[0032] As described above, the left-sloping portion Sa and the right-sloping portion Sb do not necessarily originate from the upper surface of the mesa structure 17. The left-sloping portion Sa is the portion of the upper surface of the embedded layer 19 that slopes in the width direction D2 as it moves away from the mesa structure 17 and approaches the substrate 3 (the same applies to the right-sloping portion Sb). Furthermore, the left-sloping portion Sa is defined as the portion of the upper surface of the left embedded layer 19a that slopes in the width direction D2 as it moves away from the mesa structure 17 and approaches the substrate 3, and is the portion closest to the mesa structure 17 (the same applies to the right-sloping portion Sb).

[0033] [Second Embodiment] Figure 6 is a schematic cross-sectional view of a semiconductor optical element according to the second embodiment. It corresponds to cross-section AA in Figure 1. The difference from the first embodiment is the structure of the left embedded layer 19a and the right embedded layer 19b.

[0034] In this embodiment, the left embedded layer 19a includes a left current blocking layer (first current blocking layer) 23a and a left diffusion prevention layer (first diffusion prevention layer) 25a. The right embedded layer 19b includes a right current blocking layer (second current blocking layer) 23b and a right diffusion prevention layer (second diffusion prevention layer) 25b. Here, the left current blocking layer 23a and the right current blocking layer 23b are substantially the same as the left embedded layer 19a and the right embedded layer 19b shown in the first embodiment. In other words, the left current blocking layer 23a and the right current blocking layer 23b are high-resistance semiconductor layers for concentrating current in the mesa structure 17. Specifically, the left current blocking layer 23a and the right current blocking layer 23b are composed of semi-insulating InP, similar to the first embodiment. Note that the left current blocking layer 23a and the right current blocking layer 23b may also be a laminated structure of conductive semiconductor layers. The left diffusion prevention layer 25a and the right diffusion prevention layer 25b are the uppermost layers of the left embedding layer 19a and the right embedding layer 19b, respectively. The diffusion constants of Au in the left diffusion prevention layer 25a and the right diffusion prevention layer 25b are smaller than the diffusion constants of Au in the left current blocking layer 23a and the right current blocking layer 23b, respectively. For example, if the left current blocking layer 23a and the right current blocking layer 23b are InP, then the left diffusion prevention layer 25a and the right diffusion prevention layer 25b are composed of at least one of the following: InGaAs, InAlAs, InGaAsP, and InGaAlAs. The left diffusion prevention layer 25a and the right diffusion prevention layer 25b may be single layers composed of any of these materials, or multiple layers composed of several of these materials. Furthermore, the left diffusion prevention layer 25a and the right diffusion prevention layer 25b are undoped layers.

[0035] In this embodiment as well, the left insulating film 21a and the right insulating film 21b are not placed on the left inclined portion Sa and the right inclined portion Sb. Therefore, among the layers constituting the second electrode 12, the Au contained in the Au layer may penetrate the Ti layer and Pt layer located below the Au layer and reach the left embedded layer 19a and the right embedded layer 19b. Au has the property of diffusing within the InP that constitutes the left current blocking layer 23a and the right current blocking layer 23b (left embedded layer 19a and right embedded layer 19b). The diffusion of Au contained in the second electrode 12 into the left current blocking layer 23a and the right current blocking layer 23b may lead to deterioration of characteristics. In this embodiment, however, the left diffusion prevention layer 25a and the right diffusion prevention layer 25b, which are composed of at least one of InGaAs, InGaAsP, InGaAlAs, and InAlAs, are placed on the left current blocking layer 23a and the right current blocking layer 23b, respectively. Since the diffusion constants of Au in InGaAs, InGaAsP, InGaAlAs, and InAlAs are smaller than the diffusion constant of InP, by arranging a left diffusion prevention layer 25a and a right diffusion prevention layer 25b composed of at least one of these materials, it is possible to prevent Au from diffusing into the left current blocking layer 23a and the right current blocking layer 23b, which are composed of InP.

[0036] [Third Embodiment] Figure 7 is a top view of a semiconductor optical element according to the third embodiment. Figure 8 is a schematic cross-sectional view showing cross section AA of Figure 7. The semiconductor optical element according to this embodiment is a semiconductor optical amplifier.

[0037] The semiconductor optical element has a substrate 203, with a first electrode 211 on the back surface of the substrate 203 and a second electrode 212 on the front surface. The first electrode 211 and the second electrode 212 are metal layers. The semiconductor optical element has a mesa structure 217 that is stretched in the stretching direction D1, amplifies an optical signal input from one end face on the stretching direction D1 side, and outputs it from the opposite end face. In this embodiment, a current is injected between the first electrode 211 and the second electrode 212 for optical amplification, and low-reflection end-face coating films (not shown) are formed on both end faces.

[0038] [Semiconductor multilayer] The semiconductor optical element includes a semiconductor multilayer in which an active layer 207, a second conductivity type cladding layer 209, and a second conductivity type contact layer 215 are stacked from bottom to top on a first conductivity type substrate 203. A diffraction grating layer may also be formed above or below the active layer 207. In this embodiment, the substrate 203 functions as the first conductivity type cladding layer 5. However, as in the first embodiment, the first conductivity type cladding layer may be placed as a separate layer between the substrate 203 and the active layer 207. The active layer 207 is formed, for example, as a multiple quantum well layer. An optical confinement layer may be placed above, below, or on one side of the multiple quantum well layer. The second conductivity type cladding layer 209 is a second conductivity type semiconductor layer placed between the active layer 207 and the second conductivity type contact layer 215, and may be a single layer or multiple layers. As in the first embodiment, the semiconductor optical element according to this embodiment has a structure in which the active layer is sandwiched between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer. The second conductivity type contact layer 215 is arranged to reduce the contact resistance between the semiconductor layer and the metal layer (second electrode 212). The resistivity of the second conductivity type contact layer 215 is lower than that of the second conductivity type cladding layer 209. The impurity concentration of the second conductivity type contact layer 215 is higher than that of the second conductivity type cladding layer 209. In this embodiment, the first conductivity type is n-type and the second conductivity type is p-type.

[0039] [Mesa structure] The semiconductor optical element has a mesa structure 217. The bottom of the mesa structure 217 is composed of a part of the substrate 203. The mesa structure 217 is stretched in the stretching direction D1, extending to both end faces. The mesa structure 217 includes an active layer 207, a second conductivity type cladding layer 209, and a second conductivity type contact layer 215. In the mesa structure 17, a part of the substrate 203, the active layer 207, the second conductivity type cladding layer 209, and the second conductivity type contact layer 215 are stacked in this order from bottom to top. In this embodiment, the second conductivity type contact layer 215 is the uppermost layer of the mesa structure 17.

[0040] [Bank Department] The semiconductor optical element has a left bank portion (first bank portion) 230a located to the left of the mesa structure 217 in a cross section perpendicular to the stretching direction D1, and a right bank portion (second bank portion) 230b located to the right of the mesa structure 217. The left bank portion 230a and the right bank portion 230b each have the same semiconductor multilayer as the mesa structure 217. That is, in the left bank portion 230a and the right bank portion 230b, a part of the substrate 203, the active layer 207, the second conductivity type cladding layer 209, and the second conductivity type contact layer 215 are stacked from bottom to top in this order.

[0041] [Mizobe] The semiconductor optical element has a left groove (first groove) 240a located to the left of the mesa structure 217 in a cross section perpendicular to the stretching direction D1, and a right groove (second groove) 240b located to the right of the mesa structure 217. The left groove 240a is located between the mesa structure 217 and the left bank portion 230a in a cross section perpendicular to the stretching direction D1. The right groove 240b is located between the mesa structure 217 and the right bank portion 230b in a cross section perpendicular to the stretching direction D1. The bottoms of the left groove 240a and the right groove 240b extend to the substrate 203. When the first conductive cladding layer is arranged as a separate layer, as in the first embodiment, at least the bottoms of the left groove 240a and the right groove 240b extend to the first conductive cladding layer.

[0042] [Buried layer] In a cross-section perpendicular to the stretching direction D1, a left embedded semiconductor layer 219a is positioned on the left side of the mesa structure 217, and a right embedded semiconductor layer 219b is positioned on the right side of the mesa structure 217. The left embedded layer 219a is positioned within the left groove 240a, and the right embedded layer 219b is positioned within the right groove 240b. The materials of the left embedded layer 219a and the right embedded layer 219b are the same as in the first embodiment. The upper surface of the left embedded layer 19a has, similar to the first embodiment, a left inclined portion Sa that slopes in the width direction D2 of the mesa structure 17 so as it moves away from the mesa structure 17 it approaches the substrate 3, and a left flat portion Fa that is substantially parallel to the upper surface of the substrate 3 and continuous with the left inclined portion Sa. Furthermore, the upper surface of the right embedded layer 19b has a right-sloping portion Sb that slopes in the width direction D2 of the mesa structure 17 so as it moves away from the mesa structure 17 it approaches the substrate 3, and a right-flat portion Fb that is substantially parallel to the upper surface of the substrate 3 and continuous with the right-sloping portion Sb. As shown in Figure 8, the left embedded layer 219a and the right embedded layer 219b also have portions that slope downward from the upper surfaces of the left bank portion 230a and the right bank portion 230b, respectively, but in Figure 8 only the portions that start from the upper surface of the mesa structure 217 are shown as the left-sloping portion Sa and the right-sloping portion Sb. The characteristics of the left-sloping portion Sa, the right-sloping portion Sb, the left-flat portion Fa and the right-flat portion Fb are the same as in the first embodiment. Note that the height of the upper surface of the mesa structure 217 from the substrate 203 in this embodiment is lower than the height of the upper surface of the mesa structure 17 from the substrate 3 in the first embodiment. Furthermore, the thickness of the left flat portion Fa in the height direction D3 according to this embodiment is thinner than the thickness of the left flat portion Fa in the height direction D3 according to the first embodiment (the same applies to the right flat portion Fb). However, in this embodiment as well, the relationship between the left inclined portion Sa (right inclined portion Sb) and the left flat portion Fa (right flat portion Fb) is the same as in the first embodiment.

[0043] [Insulated film] The left insulating film 221a is placed on the left bank portion 230a, and the right insulating film 221b is placed on the right bank portion 230b. The left insulating film 221a and the right insulating film 221b are not placed on the mesa structure 217, on the left embedded layer 219a, and on the right embedded layer 219b. However, as in the first embodiment, they may be placed on at least a portion of the left embedded layer 219a and the right embedded layer 219. However, even in that case, as in the first embodiment, it is desirable that the left insulating film 221a and the right insulating film 221b are not provided on the left inclined portion Sa and the right inclined portion Sb, respectively.

[0044] [electrode] The first electrode 211 is broadly distributed on the back surface of the substrate 203. In the first embodiment, the first electrode 211 is distributed to both ends in the width direction D2 of the substrate 203, but is not limited to this. The second electrode 212 has a laminated structure including at least Au. For example, it has a three-layer structure in which Ti / Pt / Au are laminated in order from the second conductive contact layer 215 side. This configuration is just one example. The second electrode 12 is arranged to cover at least the entirety of the left-sloping portion Sa and the right-sloping portion Sb, which sandwich the mesa structure 217. In this embodiment, the second electrode 212 is arranged to extend to the upper surface of the left bank portion 230a and the right bank portion 230b, except near the input end face and the output end face. Near the input end face and the output end face, the second electrode 212 is arranged only on top of the mesa structure 217, a part of the left embedded layer 219a, and a part of the right embedded layer 219b. From the standpoint of heat dissipation, it is desirable for the second electrode 212 to cover the entire area of ​​both the left-sloping portion Sa and the right-sloping portion Sb. However, it is also acceptable for the second electrode 212 to not cover only the vicinity of the end faces of both the left-sloping portion Sa and the right-sloping portion Sb. The ratio of the area covered by the second electrode 212 to the left-sloping portion Sa and the right-sloping portion Sb should be determined by the required amount of heat dissipation. For example, sufficient heat dissipation can be obtained if the second electrode 212 covers 80% or more of both the left-sloping portion Sa and the right-sloping portion Sb. It is more preferable for the second electrode 212 to cover 90% or more of both the left-sloping portion Sa and the right-sloping portion Sb.

[0045] [effect] In the third embodiment, similar to the first embodiment, the left-sloping portion Sa and the right-sloping portion Sb are positioned as close as possible to the mesa structure 217 without affecting the light distribution D. Therefore, according to this embodiment, a semiconductor optical element with excellent heat dissipation can be realized. In the first embodiment, the uppermost surface of the semiconductor optical element is the upper surface of the mesa structure 217. When mounting the semiconductor optical element on a substrate with the second electrode 212 side facing the substrate, there is a risk that the semiconductor optical element may be mounted at an angle to the substrate because the upper part of the mesa structure is protruding. In this embodiment, this problem can be solved because the left bank portion 230a and the right bank portion 230b are arranged. In the height direction D3, the height of the upper surface of the left bank portion 230a from the substrate 203 is higher than the height of the upper surface of the mesa structure 217 from the substrate 203 by the thickness of the left insulating film 221a in the height direction D3 (the same applies to the right bank portion 230b). Furthermore, since the left bank portion 230a and the right bank portion 230b have a larger area than the mesa structure 217, it is possible to prevent the semiconductor optical element from being mounted on the substrate in a tilted position relative to the substrate. The width in the width direction D2 of the left bank portion 230a (right bank portion 230b) and the left groove portion 240a (right groove portion 240b) is arbitrary, but if the left groove portion 240 and the right groove portion 240b are too narrow, the left embedded layer 219a and the right embedded layer 219b may not be formed in a normal shape. For this reason, the width in the width direction D2 of the left groove portion 240 and the right groove portion 240b is preferably 25 times or more the width in the width direction D2 of the mesa structure 217. The semiconductor optical element according to this embodiment may also be a semiconductor laser.

[0046] [Differentiation] Figure 9 is a schematic cross-sectional view of the AA section of Figure 7 of a semiconductor optical element according to a modified example of the third embodiment. The difference from the third embodiment lies in the structure within the left groove 240a and the right groove 240b.

[0047] In this modified example, the left embedded layer 219a does not cover the entire left groove 240a, and the right embedded layer 219b does not cover the entire right groove 240b. That is, in a cross section perpendicular to the extension direction D1, the left embedded layer 219a does not reach the side surface of the left bank 230a. Similarly, the right embedded layer 219b does not reach the side surface of the right bank 230b in a cross section perpendicular to the extension direction D1. The left embedded layer 219a has a left side portion (first side portion) Wa that faces the left bank 230a in the width direction D2 and is spaced away from the left bank 230a. The right embedded layer 219b has a right side portion (second side portion) Wb that faces the right bank 230b in the width direction D2 and is spaced away from the right bank 230b. The left side portion Wa and the right side portion Wb are located outside the outer edge of the light distribution D. The left insulating film 221a is placed on the bottom surface of the left groove 240a and on the side surface of the left bank 230a on the left groove 240a side. The right insulating film 221b is placed on the bottom surface of the right groove 240b and on the side surface of the right bank 230b on the right groove 240b side. The second electrode 212 is positioned to cover the left inclined portion Sa, the left flat portion Fa, and the left side portion Wa of the left embedded layer 219a.

[0048] According to this modified example, in addition to heat dissipation from the left-sloping portion Sa and the right-sloping portion Sb, heat dissipation effects can also be obtained from the left-side portion Wa and the right-side portion Wb, thereby realizing a semiconductor optical element with even greater heat dissipation capabilities.

[0049] In the above embodiments, the semiconductor optical elements were described as semiconductor lasers and semiconductor optical amplifiers, but the invention is not limited to these. For example, the semiconductor optical elements may be semiconductor modulators or semiconductor photodetectors. However, generally, the amount of heat generated from the active layer is greater when it functions as an emitting layer or an amplifying layer than when it functions as an absorbing layer. Therefore, the present invention is particularly effective when applied to semiconductor lasers and semiconductor optical amplifiers. Furthermore, each embodiment and its variations may be combined. [Explanation of Symbols]

[0050] 3,203 Substrate, 5 First conductivity cladding layer, 7,207 Active layer, 9,209 Second conductivity cladding layer, 11,211 First electrode, 12,212 Second electrode, 15,215 Second conductivity contact layer, 17,217 Mesa structure, 19a,219a Left embedded layer, 19b,219b Right embedded layer, 21a,221a Left insulating film, 21b,221b Right insulating film, 23a Left current blocking layer, 23b Right current blocking layer, 25a Left diffusion prevention layer, 25b Right diffusion prevention layer, D1 Stretching direction, D2 Width direction, D3 Height direction, D Light distribution, H Height, Sa Left inclined portion, Sb Right inclined portion, Fa Left flat portion, Fb Right flat portion, P Bottom point, Wa Left side portion, Wb Right side, F2a left secondary flat area, F2b right secondary flat area, Ra left protrusion, Rb right protrusion.

Claims

1. circuit board and It protrudes from the substrate, extends in a stretching direction parallel to the substrate, and has a mesa structure including an active layer, In a cross section perpendicular to the extension direction, a first embedded semiconductor layer is located on the first side of the mesa structure, and a second embedded semiconductor layer is located on the second side of the mesa structure. The structure comprises electrodes provided on the mesa structure and partially positioned on the first and second embedding layers, respectively. The upper surface of the first embedded layer has a first inclined portion that slopes in the width direction of the mesa structure so as it moves away from the mesa structure, it approaches the substrate. The upper surface of the second embedded layer has a second inclined portion that slopes in the width direction so as it moves away from the mesa structure, and approaches the substrate. The electrode is a semiconductor optical element that covers the entirety of the first inclined portion and the second inclined portion, respectively.

2. A semiconductor optical element according to claim 1, The upper surface of the first embedded layer further has a first flat portion continuous with the first inclined portion, wherein the semiconductor optical element.

3. A semiconductor optical element according to claim 2, The aforementioned mesa structure has a conductive contact layer in the uppermost layer, In the height direction of the mesa structure, when the distance between the upper surface of the active layer and the lower surface of the conductive contact layer is H, the upper surface of the first embedded layer in the first flat portion is positioned at a height of 0H or more and 0.5H or less, starting from the upper surface of the active layer, in a semiconductor optical element.

4. A semiconductor optical element according to claim 3, The upper surface of the embedded layer in the first flat portion is positioned at a height of 0.1H to 0.3H from the upper surface of the active layer, and is a semiconductor optical element.

5. A semiconductor optical element according to claim 2, The electrode is partially positioned on the first flat portion, forming a semiconductor optical element.

6. A semiconductor optical element according to claim 2, The upper surface of the first embedded layer further includes a sub-flat portion that is continuous with the upper surface of the mesa structure, The first inclined portion is a semiconductor optical element that is continuous with the sub-flat portion.

7. A semiconductor optical element according to claim 6, A semiconductor optical element in which, in the width direction, the width of the sub-flat portion is less than or equal to half the width of the mesa structure.

8. A semiconductor optical element according to claim 2, The first embedded layer is continuous with the upper surface of the mesa structure and further includes a first projection that protrudes from the substrate. The first inclined portion is a semiconductor optical element that is continuous with the first projection.

9. A semiconductor optical element according to claim 8, The aforementioned mesa structure has a conductive contact layer in the uppermost layer, A semiconductor optical element wherein, in the height direction of the mesa structure, the thickness of the first projection is smaller than the thickness of the conductive contact layer.

10. A semiconductor optical element according to claim 1, The first insulating film is further disposed on the first embedded layer, A semiconductor optical element in which the first insulating film is not disposed on the first inclined portion.

11. A semiconductor optical element according to claim 10, The first embedded layer includes a first current blocking layer and a first diffusion prevention layer in that order from the substrate. The electrode includes Au, A semiconductor optical element in which the diffusion constant of the Au in the first diffusion prevention layer is smaller than the diffusion constant of the first current blocking layer.

12. A semiconductor optical element according to claim 11, The first current blocking layer is composed of InP, The first diffusion-blocking layer is composed of at least one of InGaAs, InGaAsP, InGaAlAs, or InAlAs, in a semiconductor optical device.

13. A semiconductor optical element according to claim 11, The first diffusion prevention layer is an undoped layer in a semiconductor optical device.

14. A semiconductor optical element according to claim 1, In the cross-section, the first bank portion is located on the first side of the mesa structure, and the second bank portion is located on the second side, A first groove is disposed between the mesa structure and the first bank portion, A second groove is disposed between the mesa structure and the second bank portion, It further possesses, A semiconductor optical element in which the first embedded layer is disposed within the first groove and the second embedded layer is disposed within the second groove.

15. A semiconductor optical element according to claim 14, A semiconductor optical element in which a portion of the electrode is continuously arranged on the mesa structure, on the first embedding layer, on the second embedding layer, on a portion of the first bank portion, and on a portion of the second bank portion.

16. A semiconductor optical element according to claim 14, The first insulating film is further disposed on the first embedded layer, A semiconductor optical element wherein the first insulating film is not disposed on the mesa structure and the first embedding layer.

17. A semiconductor optical element according to claim 14, The first embedded layer has a first side portion that faces the first bank portion in the width direction and is spaced apart from the first bank portion. The electrode is a semiconductor optical element arranged along the first side portion.

18. A semiconductor optical element according to claim 17, The first insulating film is further disposed on the first embedded layer, The first insulating film is not disposed on the first side portion of the semiconductor optical element.

19. A semiconductor optical element according to claim 1, A semiconductor optical element in which the substrate, the first embedded layer, and the second embedded layer are made of the same semiconductor material.

20. A semiconductor optical element according to claim 1, The electrode is a semiconductor optical element that covers 80% or more of the first inclined portion in the stretching direction.

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