Semiconductor optical modulators, semiconductor optical integrated elements, and semiconductor optical devices

Abstract

To provide a semiconductor optical modulator with excellent characteristics. [Solution] The semiconductor optical modulator comprises a semiconductor multilayer stacked in the order of a first conductivity semiconductor layer, an optical functional layer, and a second conductivity semiconductor layer, a first electrode connected to the first conductivity semiconductor layer, and a second electrode connected to the second conductivity semiconductor layer, wherein a part of the first conductivity semiconductor layer, the optical functional layer, and the second conductivity semiconductor layer form a mesa structure stretched in the stretching direction, and the width of the first conductivity semiconductor layer is narrower than the width of the semiconductor optical modulator.

Description

[Technical Field]

[0001] The present invention relates to a semiconductor optical modulator, a semiconductor optical integrated device and a semiconductor optical apparatus. [Background Art]

[0002] As one of semiconductor optical devices used for optical communication, a modulator that converts input light into a modulated optical signal is known. Patent Document 1 discloses a modulator-integrated laser element including a modulation section where an anode electrode and a cathode electrode are disposed on a surface, and differential signals are input to these two electrodes. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-222795 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] As disclosed in Patent Document 1, one example of a modulator structure is known in which an n-type semiconductor layer, an absorption layer, and a p-type semiconductor layer are stacked on a substrate in that order. Furthermore, these layers have a mesa structure that is narrower than the substrate in the direction perpendicular to the optical axis. In Patent Document 1, the absorption layer and the p-type semiconductor layer are arranged only within the mesa structure. On the other hand, a part of the n-type semiconductor layer is arranged within the mesa structure, but the other part close to the substrate is also arranged on the side of the mesa structure. The anode electrode is connected to the p-type semiconductor layer on the top surface of the mesa structure, and the cathode electrode is connected to the n-type semiconductor layer on the side of the mesa structure. Therefore, the structure from the connection point between the electrode and the semiconductor layer to the absorption layer differs between the anode side and the cathode side. This difference causes a difference in the frequency characteristics from the anode electrode to the absorption layer and from the cathode electrode to the absorption layer. This difference in frequency characteristics, for example, when a differential signal is applied to the anode and cathode electrodes, causes a difference in the transmission of the electrical signal on the anode side (amplitude, phase, etc.) and the transmission of the electrical signal on the cathode side, ultimately affecting the characteristics of the modulator. It should be noted that this problem is not limited to the field absorption modulator disclosed in Patent Document 1, but can also occur in direct modulation lasers.

[0005] The present invention aims to provide a semiconductor optical modulator with excellent characteristics. [Means for solving the problem]

[0006] The semiconductor optical modulator comprises a semiconductor multilayer stacked in the order of a first conductivity type semiconductor layer, an optical functional layer, and a second conductivity type semiconductor layer, a first electrode connected to the first conductivity type semiconductor layer, and a second electrode connected to the second conductivity type semiconductor layer, wherein a portion of the first conductivity type semiconductor layer, the optical functional layer, and the second conductivity type semiconductor layer form a mesa structure stretched in the stretching direction, and the width of the first conductivity type semiconductor layer is narrower than the width of the semiconductor optical modulator. [Brief explanation of the drawing]

[0007] [Figure 1] This is a top view of a semiconductor optical modulator according to the first embodiment. [Figure 2]Figure 1 is a cross-sectional view of the semiconductor optical modulator shown along line II-II. [Figure 3] Figure 1 is a cross-sectional view of a semiconductor optical modulator taken along line III-III. [Figure 4] Figures 2 and 3 are top views showing the AA line cross-section of the semiconductor optical modulator. [Figure 5] This is a cross-sectional view of a semiconductor optical modulator according to a second embodiment. [Figure 6] Figure 5 is a top view showing a cross-sectional view of the semiconductor optical modulator along the AA line. [Figure 7] This is a top view of a semiconductor optical modulator according to a modified example of the second embodiment. [Figure 8] This is a top view of a semiconductor optical modulator according to the third embodiment. [Figure 9] Figure 8 is a cross-sectional view of the semiconductor optical modulator along the line IX-IX. [Figure 10] This is a top view of a semiconductor optical modulator according to the fourth embodiment. [Figure 11] Figure 10 is a top view showing a cross-sectional view of the semiconductor optical modulator along the AA line. [Figure 12] This is a top view of a semiconductor optical modulator according to the fifth embodiment. [Figure 13] Figure 12 is a cross-sectional view of the semiconductor optical modulator shown along line XIII-XIII. [Figure 14] This is a top view of a semiconductor optical integrated device according to the sixth embodiment. [Figure 15] Figure 14 is a cross-sectional view of a semiconductor optical integrated device shown along the BB line. [Figure 16] This is a top view of a semiconductor optical integrated device according to the seventh embodiment. [Figure 17] Figure 16 is a cross-sectional view of the semiconductor optical modulator shown along line XVII-XVII. [Figure 18] Figure 16 is a cross-sectional view of the semiconductor optical modulator shown along line XVIII-XVIII. [Figure 19] This is a top view of a semiconductor optical device according to the eighth embodiment. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments of the present invention will be described specifically and in detail with reference to the drawings. In all the drawings, members denoted by the same reference numerals have the same or equivalent functions, and repeated description thereof will be omitted. Note that the dimensions of the figures do not necessarily correspond to the drawing scale.

[0009] [First Embodiment] FIG. 1 is a top view of a semiconductor optical modulator 1 according to the first embodiment. FIG. 2 is a cross-sectional view schematically showing the II-II cross-section of FIG. 1. FIG. 3 is a cross-sectional view schematically showing the III-III cross-section of FIG. 1. FIG. 4 is a top view schematically showing the A-A cross-section of FIGS. 2 and 3.

[0010] The semiconductor optical modulator 1 includes a semiconductor multilayer stacked in the order of a first conductivity-type semiconductor layer 4, an optical functional layer 6, and a second conductivity-type semiconductor layer 8 on a semi-insulating semiconductor substrate 2. Here, the first conductivity type is n-type and the second conductivity type is p-type, but they may be reversed. A part of the first conductivity-type semiconductor layer 4, the optical functional layer 6, and the second conductivity-type semiconductor layer 8 have a mesa structure 30 extending in the stretching direction D1. The stretching direction D1 is also the optical axis direction. In the width direction D2 of the mesa structure 30 perpendicular to the stretching direction D1, burying layers 10 are disposed on both sides of the mesa structure 30 respectively. The semiconductor optical modulator 1 has a first electrode 14 and a second electrode 18 on its surface. A part of the first electrode 14 is disposed on the surface of the semiconductor optical modulator 1 on the right side (one side) of the mesa structure 30 in the width direction D2. A part of the second electrode 18 is disposed on the surface of the semiconductor optical modulator 1 on the left side (the other side) of the mesa structure 30 in the width direction D2. Another part of the second electrode 18 is disposed on the mesa structure 30. Note that the part of the first electrode 14 may be disposed on the left side, and the part of the second electrode 18 may be disposed on the right side. Alternatively, both the first electrode 14 and the second electrode 18 may be disposed on either one of the right side and the left side of the mesa structure 30 in the width direction D2. The first electrode 14 and the second electrode 18 are metal layers. The semiconductor optical modulator 1 includes an insulating film 12. The normal direction of the substrate 2 is defined as the stacking direction D3. Hereinafter, the description will be given with the stacking direction D3 as the vertical direction.

[0011] The first conductivity type semiconductor layer 4 includes a central portion 4c formed of a portion forming the mesa structure 30 and a portion continuous below said portion and having the same width as the width of the mesa structure 30, and a first side portion 4s continuous to the central portion 4c on the right side of the mesa structure 30. The embedding layer 10 has a groove 32, and the first conductivity type semiconductor layer 4 is disposed below the bottom of the groove 32. The insulating film 12 is disposed on a part of the bottom surface and the side surface of the groove 32, but the insulating film 12 is not disposed on another part of the bottom surface of the groove. The first electrode 14 is electrically and physically connected to the first conductivity type semiconductor layer 4 at a portion on the bottom surface of the groove 32 where the insulating film 12 is not disposed. In a plan view, the region where the first electrode 14 is connected to the first conductivity type semiconductor layer 4 is hereinafter referred to as a first connection region 24. In the present specification, "plan view" refers to viewing along the lamination direction D3. For explanation, the first connection region 24 is shown by a broken line in FIG. 1. The first side portion 4s is provided in the first connection region 24 in a plan view. The first electrode 14 is composed of a first conducting electrode portion 14e disposed above the first connection region 24, a first bridge electrode portion 14b continuous to the first conducting electrode portion 14e and extending in the width direction D2, and a first pad electrode portion 14p continuous to the first bridge electrode portion 14b. The first pad electrode portion 14p is disposed on the embedding layer 10. The first pad electrode portion 14p is connected to an external electric wiring not shown. The dimension of the first bridge electrode portion 14b in the extension direction D1 is narrower than the dimensions of the first conducting electrode portion 14e and the first pad electrode portion 14p in the extension direction D1.

[0012] The insulating film 12 is not disposed on a part of the top surface of the mesa structure 30. The second electrode 18 is electrically and physically connected to the second conductivity type semiconductor layer 8 at a region on the top surface of the mesa structure 30 where the insulating film 12 is not disposed. In a plan view, the region where the second electrode 18 is connected to the second conductivity type semiconductor layer 8 is hereinafter referred to as a second connection region 28. For explanation, the second connection region 28 is shown by a broken line in FIG. 1. Note that the width of the second connection region 28 may be the same as or different from the width of the mesa structure 30.

[0013] Here, the semiconductor optical modulator 1 is an electro-absorption type modulator. The optical functional layer 6 is a layer that absorbs light in accordance with the voltage applied between the first electrode 14 and the second electrode 18. The optical functional layer 6 may be composed of multiple layers. For example, the optical functional layer 6 may be composed of a multiple quantum well layer and optical confinement layers arranged above and below it. The second conductivity type semiconductor layer 8 may also be composed of multiple layers. For example, the second conductivity type semiconductor layer 8 may have a cladding layer and a contact layer arranged on top of it. If the semiconductor optical modulator 1 is a direct modulation type semiconductor laser, the optical functional layer 6 becomes an emitting layer.

[0014] The semiconductor optical modulator 1 has a first end face E1 and a second end face E2, which are end faces in the stretching direction D1. The output light from an external light source (not shown) is input from the first end face E1 and output as a modulated optical signal from the second end face E2. The input and output faces may be reversed. The semiconductor optical modulator 1 also has a first side face S1 in the width direction D2, which is the side where the first electrode 14 is located (right side in Figures 1 and 2), and a second side face S2, which is the side where the second electrode 18 is located (left side in Figures 1 and 2).

[0015] Figure 4 is a top view of the AA cross-section in Figures 2 and 3. For illustrative purposes, the first electrode 14, the second electrode 18, the first connection region 24, and the second connection region 28 are shown with dashed lines. A characteristic feature of the semiconductor optical modulator 1 according to this embodiment is the shape of the first conductivity type semiconductor layer 4. That is, as described above, the first conductivity type semiconductor layer 4 includes a central portion 4c and a first lateral portion 4s. A part of the first lateral portion 4s is in contact with the first electrode 14. The side surface of the first lateral portion 4s does not extend to the first side surface S1. In other words, the side surface of the first conductivity type semiconductor layer 4 is located inward from the side surface of the semiconductor optical modulator 1. Note that the first conductivity type semiconductor layer 4 may consist of multiple layers.

[0016] [effect] Here, we assume that differential electrical signals are input to the first electrode 14 and the second electrode 18. The electrical signal input to the first electrode 14 is transmitted to the first conductivity type semiconductor layer 4 in the first connection region 24, and then to the optical functional layer 6 via the first conductivity type semiconductor layer 4. Hereafter, this transmission route will be called the first transmission route. The electrical signal input to the second electrode 18 is transmitted to the second conductivity type semiconductor layer 8 in the second connection region 28, and then to the optical functional layer 6 via the second conductivity type semiconductor layer 8. Hereafter, this transmission route will be called the second transmission route. If the frequency characteristics of the first transmission route and the frequency characteristics of the second transmission route are different, a difference will occur in the transmission of electrical signals input to the upper and lower parts of the optical functional layer 6. This difference will lead to a deterioration of the frequency characteristics of the optical modulation signal.

[0017] The main reason for the difference in frequency characteristics is the difference in structure between the first conductivity type semiconductor layer 4 and the second conductivity type semiconductor layer 8. In this embodiment, the main parts of the first conductivity type semiconductor layer 4 and the second conductivity type semiconductor layer 8 are made of the same semiconductor material. However, because the first conductivity type semiconductor layer 4 and the second conductivity type semiconductor layer 8 have different physical sizes and conductivity, a difference arises between the frequency characteristics of the first conductivity type semiconductor layer 4 and the frequency characteristics of the second conductivity type semiconductor layer 8. For example, in the structure disclosed in Patent Document 1, the anode-side semiconductor layer is arranged only within the mesa structure. On the other hand, the cathode-side semiconductor layer is arranged not only within the mesa structure but also widely to the side surface of the modulator-integrated laser element. In this embodiment, by making the size of the first conductivity type semiconductor layer 4 closer to the size of the second conductivity type semiconductor layer 8, the difference between the frequency characteristics of the first transmission route and the second transmission route is reduced, and a semiconductor optical modulator with excellent characteristics is realized.

[0018] The width of the first conductivity semiconductor layer 4 is narrower than the width of the semiconductor optical modulator 1. The first conductivity semiconductor layer 4 is composed of a central portion 4c and a first lateral portion 4s. The first lateral portion 4s has the minimum area necessary to include the first connection region 24 in a plan view. However, in this embodiment, taking into account manufacturing variations, the area of ​​the first lateral portion 4s is larger than the area of ​​the first connection region 24 in a plan view. Furthermore, it is preferable that the first connection region 24 and the mesa structure 30 be close to each other, but on the other hand, from the viewpoint of manufacturability, it is preferable that the first connection region 24 and the mesa structure 30 be separated from each other to some extent. Specifically, the width W of the first lateral portion 4s is preferably 1 / 3 or less of the distance Wa between the first mesa side surface, which is the right side surface of the mesa structure, and the first side surface S1, which is the side surface of the semiconductor optical modulator 1 on the right side. The width W of the first lateral portion 4s is the distance between the first mesa side surface and the right side surface of the first conductivity type semiconductor layer 4 in the width direction D2. To further reduce the difference in frequency characteristics between the first and second transmission routes, it is desirable that W be 1 / 4 or less of Wa. Alternatively, it is desirable that the right side edge of the first conductivity type semiconductor layer 4 overlaps with the first bridge electrode portion 14b in a plan view.

[0019] As described above, since the width of the first conductivity type semiconductor layer 4 is narrower than the width of the semiconductor optical modulator 1, the first conductivity type semiconductor layer 4 is arranged only in the region close to the mesa structure 30, and the difference in frequency characteristics between the first transmission route and the second transmission route is reduced. The central portion 4c of the first conductivity type semiconductor layer 4 extends to the first end face E1 and the second end face E2 in the stretching direction D1. The reason for extending the central portion 4c to the first end face E1 and the second end face E2 is to consider the propagation of light. However, the central portion 4c does not have to reach the first end face E1 and / or the second end face E2. For example, if another structure such as a window structure is arranged on the exit end face side, the first conductivity type semiconductor layer 4 does not have to be included in the window structure.

[0020] Furthermore, in the extension direction D1, it is desirable that both ends of the second connection region 28 are positioned inward from both ends of the first connection region 24. Here, the ends of the first connection region 24 and the ends of the second connection region 28 in the extension direction D1 are arranged in the same straight line in the width direction D2. In a plan view, the first connection region 24 and the second connection region 28 are positioned at the same location in the extension direction D1, while in the width direction D2, the first connection region 24 and the second connection region 28 are positioned offset from each other. In this embodiment, the ends of the first connection region 24 and the second connection region 28 do not extend to the first end face E1 and the second end face E2, but this is not limited to this.

[0021] [Second Embodiment] Figure 5 is a cross-sectional view of the semiconductor optical modulator 201 according to the second embodiment at the position corresponding to Figure 2. Figure 6 is a schematic cross-sectional view showing the AA section of Figure 5. In Figure 6, as in Figure 4, the two electrodes and two connection regions are shown with dashed lines for illustrative purposes.

[0022] The difference between the semiconductor optical modulator 1 according to the first embodiment and the semiconductor optical modulator 201 according to the second embodiment is the shape of the first conductivity semiconductor layer 204. The first conductivity semiconductor layer 204 has a symmetrical shape in the width direction D2 with respect to the mesa structure 30. Furthermore, the first conductivity semiconductor layer 204 extends in the stretching direction D1 with the same width from the first end face E1 to the second end face E2. The first conductivity semiconductor layer 204 has a central portion 204c consisting of a portion that forms the mesa structure 30 and a portion that is connected below the central portion and has the same width as the mesa structure 30, a first lateral portion 204s1 provided in the first connection region 24 in a plan view and connected to the central portion 204c on the right side of the mesa structure 30, and a second lateral portion 204s2 connected to the central portion 204c on the left side of the mesa structure 30. The first lateral portion 204s1 contacts the first electrode 14 in the first connection region 24. The second lateral portion 204s2 does not contact either electrode.

[0023] As described in the first embodiment, from the viewpoint of frequency characteristics, a smaller first conductivity semiconductor layer is preferable. However, from the viewpoint of crystal quality of the embedded layer 10, the second embodiment is superior. The procedure for forming the embedded layer 10 in the second embodiment is as follows. First, the mesa structure 30 and the first conductivity semiconductor layer 204 are formed to the shapes shown in Figures 5 and 6. Next, a mask is formed on the upper surface of the mesa structure 30. Then, crystal growth of the embedded layer 10 is performed. At this time, the embedded layer 10 is not formed on the upper surface of the mesa structure 30 where the mask is formed, and the embedded layer 10 is formed so as to be in contact with the side surface of the first conductivity semiconductor layer 204, the upper surface of the first conductivity semiconductor layer 204, and the side surface of the mesa structure 30. When growing the crystal of the embedded layer 10, if the shape of the underlying semiconductor layer is asymmetric in the width direction D2 with respect to the mesa structure 30, there is a risk that an abnormality will occur in the shape of the embedded layer 10. In this embodiment, a second lateral portion 204s2 is provided to avoid such an abnormality in the shape of the embedded layer 10. In this embodiment as well, in the width direction D2, the width W1 of the first lateral portion 204s1 is preferably 1 / 3 or less of Wa, and more preferably 1 / 4 or less of Wa. Similarly, the width W2 of the second lateral portion 204s2 is preferably 1 / 3 or less of the distance between the right side surface of the mesa structure 30 and the second side surface S2, and more preferably 1 / 4 or less of said distance.

[0024] In the width direction D2, it is desirable that the width W1 of the first lateral portion 204s1 and the width W2 of the second lateral portion 204s2 be the same, but they may be different. If the difference between the width W1 of the first lateral portion 204s1 and the width W2 of the second lateral portion 204s2 is within 20% of W1 or W2, there will be virtually no impact on the crystal quality. In this embodiment, the width of the first conductivity type semiconductor layer 204 is the same in all parts in the stretching direction D1, but the width of the portion of the first conductivity type semiconductor layer 204 near the first end face E1 or the second end face E2 may be narrower than the width of the other parts of the first conductivity type semiconductor layer 204. Note that "same" means the same within the range of manufacturing variation.

[0025] [Differentiation] Figure 7 is a top view of a semiconductor optical modulator 201 according to a modified example of the second embodiment. For illustrative purposes, the first conductivity type semiconductor layer 204 is shown as a transmission view with dashed lines. Similarly, the first connection region 24 and the second connection region 28 are also shown as transmission views with dashed lines.

[0026] The difference between this modified example and the second embodiment lies in the shape of the second electrode 218. The second electrode 218 consists of a second energizing electrode portion 218e positioned on the second connection region 28, a second bridge electrode portion 218b connected to the second energizing electrode portion 218e and extending in the width direction D2, and a second pad electrode portion 218p connected to the second bridge electrode portion 218b. The second pad electrode portion 218p is positioned on the embedded layer 10. The second pad electrode portion 218p is connected to external electrical wiring (not shown). The dimension of the second bridge electrode portion 218b in the extension direction D1 is smaller than the dimension of the second energizing electrode portion 218e and the first pad electrode portion 14p in the extension direction D1.

[0027] The left side surface of the first conductive semiconductor layer 204 does not extend to the second side surface S2. Therefore, as shown in Figure 5, a step may occur on the surface of the embedded layer 10. This step connects an upper step formed in accordance with the second lateral portion and a lower step located below the upper step. In this embodiment, the step is a portion that slopes from the upper step to the lower step. If the second pad electrode portion 218p is superimposed on the step, the second pad electrode portion 218p will no longer be flat, which may reduce the connectivity between the second pad electrode portion 218p and the external electrical wiring. Therefore, in this modified example, the second pad electrode portion 218p is positioned so as not to overlap with the step. In other words, in a plan view, the step overlaps with the second bridge electrode portion 218b. The same applies to the first side surface S1, where the step overlaps with the first bridge electrode portion 14b in a plan view.

[0028] Here, in a plan view, the first pad electrode portion 14p and the second pad electrode portion 218p are rectangular, but are not limited to this and may have polygonal or curved shapes.

[0029] [Third Embodiment] Figure 8 is a top view of the semiconductor optical modulator 301 according to the third embodiment. Figure 9 is a schematic cross-sectional view showing the IX-IX section of Figure 8. The difference between the semiconductor optical modulator 301 according to the third embodiment and the semiconductor optical modulator 201 according to the second embodiment is that a resin layer 350 is placed between the first electrode and the second electrode, and the embedded layer 10, respectively.

[0030] The first conductive semiconductor layer 304, as in the second embodiment, has a central portion 304c and first lateral portions 304s1 and second lateral portions 304s2 on both sides thereof. The second pad electrode portion 318p overlaps with the stepped portion of the embedded layer 10 in a plan view. Here, since a resin layer 350 is arranged between the second pad electrode portion 318p and the embedded layer 10, there is no step in the second pad electrode portion 318p that would affect connection with external electrical wiring.

[0031] The resin layer 350 is formed by applying a soft resin to the upper surface of the embedded layer 10, hardening the resin, and then etching it. The resin layer 350 absorbs the steps of the embedded layer 10, so the steps on the surface of the resin layer 350 are reduced. Therefore, the second pad electrode portion 318p can be positioned to overlap with the steps of the embedded layer 10 without moving it away from the mesa structure 30. This brings the second pad electrode portion 318p closer to the mesa structure 30, reducing the distance between the second pad electrode portion 318p and the second connection region 28, and consequently reducing parasitic capacitance and parasitic inductance. Reducing parasitic capacitance and parasitic inductance leads to an improvement in frequency characteristics. Since the resin layer 350 is also placed between the first pad electrode 314 and the embedded layer 10, the effect of reducing parasitic capacitance and parasitic inductance is similarly obtained for the first pad electrode portion 314p.

[0032] [Fourth Embodiment] Figure 10 is a top view of the semiconductor optical modulator 401 according to the fourth embodiment. Figure 11 is a schematic cross-sectional view showing the XI-XI cross section of Figure 10. The difference between the semiconductor optical modulator 401 according to the fourth embodiment and the semiconductor optical modulators according to the other embodiments is the shape of the first conductivity type semiconductor layer 404.

[0033] The first conductive semiconductor layer 404 has a central portion 404c consisting of a portion that forms the mesa structure 30 and a portion that is adjacent to the central portion below the central portion and has the same width as the mesa structure 30; a first lateral portion 404s1 provided in the first connection region 24 in a plan view and adjacent to the central portion 404c on the right side of the mesa structure 30; and a second lateral portion 404s2 adjacent to the central portion 404c on the left side of the mesa structure 30. The first lateral portion 404s1 is in contact with the first electrode 14 in the first connection region 24. The second lateral portion 404s2 is not in contact with any electrode. In the fourth embodiment, the widths of the first lateral portion 404s1 and the second lateral portion 404s2 are different. Here, the width of the second lateral portion 404s2 is Ws2. Ws2 is narrower than the width W of the first lateral portion 404s1.

[0034] As described in the second embodiment, the first conductive semiconductor layer 404 preferably has a symmetrical shape in the width direction D2 with respect to the central portion 404c. However, the region that is particularly important for crystal growth of the embedded layer 10 is the region immediately adjacent to the mesa structure 30. If members of the same height (first lateral portion 404s1 and second lateral portion 404s2) are arranged in this region, it is possible to grow crystals of sufficiently high quality embedded layer 10. As mentioned above, it is preferable that the size of the first conductive semiconductor layer 404 be small, and from that viewpoint, it is preferable to make the width of the second lateral portion 404s2 narrower than the width of the first lateral portion 404s1. For example, the difference between the width Ws2 of the second lateral portion 404s2 and the width Ws1 of the portion of the first lateral portion 404s1 between the first mesa side surface, which is the right-side surface of the mesa structure 30, and the side surface of the groove portion 32 facing the first mesa side surface, is sufficient from the viewpoint of crystal quality if it is within 20% of Ws2.

[0035] Furthermore, the width of the portion of the first conductivity type semiconductor layer 404 near the first end face E1 and the second end face E2 is narrower than the width of the rest of the first conductivity type semiconductor layer 204. In addition, the width change is gradual in the width direction D2. However, the shape of the width change is not limited to this, and it may change in a curved or stepped manner. Also, the change may occur only on one end face side. The shape of the first conductivity type semiconductor layer in plan view is not limited to this embodiment and can be applied to the above and other embodiments shown below.

[0036] [Fifth Embodiment] Figure 12 is a top view of the semiconductor optical modulator 501 according to the fifth embodiment. Figure 13 is a schematic cross-sectional view showing the XIII-XIII section of Figure 12. The difference between the semiconductor optical modulator 501 according to the fifth embodiment and the semiconductor optical modulator 201 according to the second embodiment is that it does not have an embedded layer 10.

[0037] Similar to the other embodiments, in the fifth embodiment, a first conductivity type semiconductor layer 504 is disposed on the substrate 2, and a mesa structure 30 is formed thereon. The first conductivity type semiconductor layer 504 includes a central portion 504c, which consists of a portion that forms the mesa structure 30 and a portion that extends below the central portion and has the same width as the mesa structure 30. The first conductivity type semiconductor layer 504 also includes a first lateral portion 504s1 provided in the first connection region 24 in a plan view in the width direction D2, which is on the right side of the mesa structure 30 and extends to the central portion 504c, and a second lateral portion 504s2 connected to the central portion 504c on the left side of the mesa structure 30. The insulating film 12 is disposed on the upper surface of the substrate 2, the upper surface of the first lateral portion 504s1, and the upper surface of the second lateral portion 504s2. The insulating film 12 is not disposed in the first connection region 24 where the first electrode 14 and the first lateral portion 504s1 are in contact. The insulating film 12 is not placed in the second connection region 28 where the second conductivity type semiconductor layer 8 and the second electrode 18 are in contact.

[0038] Similar to the other embodiments, in the fifth embodiment, the width of the first conductive semiconductor layer 504 is narrower than the width of the semiconductor optical modulator 501. This reduces the difference between the frequency characteristics of the first transmission route and the frequency characteristics of the second transmission route, resulting in a semiconductor optical modulator with excellent high-frequency characteristics. Furthermore, the first conductive semiconductor layer 504 does not necessarily have to include the second lateral portion 504s2, similar to the first conductive semiconductor layer 4 in the first embodiment.

[0039] [Sixth Embodiment] Figure 14 is a top view of a semiconductor optical integrated element 600 according to the sixth embodiment. Figure 15 is a schematic cross-sectional view showing the BB cross section of Figure 14. The semiconductor optical integrated element 600 has a structure in which a semiconductor optical modulator 601 having the same structure as the semiconductor optical modulator 201 according to the second embodiment, a laser section 660, and a waveguide section 670 are integrated on a substrate 2. However, the semiconductor optical modulator 601 may be a semiconductor optical modulator according to an embodiment other than the second embodiment. A mesa structure 630 is formed over the semiconductor optical modulator 601, the waveguide section 670, and the laser section 660. An embedded layer is arranged on the side of the mesa structure 630 in the width direction D2.

[0040] The laser unit 660 has a first conductivity type semiconductor layer 604, an active layer 666, and a second conductivity type semiconductor layer 608 on the substrate 2. A groove is formed in the embedded layer so as to reach the first conductivity type semiconductor layer 604, and the first laser unit electrode 664 is in contact with the first conductivity type semiconductor layer 604 at the bottom surface of the groove. The second laser unit electrode 668 is in contact with the second conductivity type semiconductor layer 608 at the upper surface of the mesa structure 630. The laser unit 660 oscillates continuous light in response to the voltage (current injection) applied between the two electrodes.

[0041] The waveguide section 670 has a first conductivity type semiconductor layer 604, a waveguide layer 676, and a second conductivity type semiconductor layer 608 on the substrate 2. The waveguide section 670 transmits the output light from the laser section 660 to the semiconductor optical modulator 601.

[0042] The boundary between the semiconductor optical modulator 601 and the waveguide section 670 is defined by the interface between the optical functional layer 6 and the waveguide layer 676. The boundary between the waveguide section 670 and the laser section 660 is defined by the interface between the waveguide layer 676 and the active layer 666.

[0043] The first conductivity semiconductor layer 604 is a common layer in the semiconductor optical modulator 601, the waveguide section 670, and the laser section 660. However, the width of the first conductivity semiconductor layer 604 differs in each of the semiconductor optical modulator 601, the waveguide section 670, and the laser section 660. For illustrative purposes, the first conductivity semiconductor layer 604 is shown as a dashed line in Figure 14. In the semiconductor optical modulator 601, the first conductivity semiconductor layer 604 does not extend to the first side surface S1 and the second side surface S2. Here, the first side surface S1 and the second side surface S2 are the end faces in the width direction D2 of the semiconductor optical integrated element 600. Similarly, in the waveguide section 670, the first conductivity semiconductor layer 604 does not extend to the first side surface S1 and the second side surface S2. The width of the first conductivity semiconductor layer 604 in the waveguide section 670 is narrower than the width of the first conductivity semiconductor layer 604 in the semiconductor optical modulator 601. On the other hand, in the laser section 660, the first conductivity type semiconductor layer 604 is provided so as to extend from the first side surface S1 to the second side surface S2. The width of the first conductivity type semiconductor layer 604 gradually changes near the boundary between the semiconductor optical modulator 601 and the waveguide section 670, and near the boundary between the waveguide section 670 and the laser section 660. It is desirable that the portion of the first conductivity type semiconductor layer 604 in which the width gradually changes does not overlap, in a plan view, with the connection region between the first electrode 14 and the first conductivity type semiconductor layer 604 (first connection region), and the connection region between the first laser section electrode 664 and the first conductivity type semiconductor layer 604.

[0044] In the waveguide section 670, narrowing the width of the first conductivity type semiconductor layer 604 leads to increased electrical isolation between the semiconductor optical modulator 601 and the laser section 660. Furthermore, the second conductivity type semiconductor layer 608 is a common layer in the semiconductor optical modulator 601, the waveguide section 670, and the laser section 660. Here, the thickness of the second conductivity type semiconductor layer 608 in the waveguide section 670 (dimension in the stacking direction D3) is smaller than the thickness of the second conductivity type semiconductor layer 608 in the semiconductor optical modulator 601 and the laser section 660. Thus, the fact that the thickness of the second conductivity type semiconductor layer 608 in the waveguide section 670 is smaller than the thickness of the second conductivity type semiconductor layer 608 in the semiconductor optical modulator 601 and the laser section 660 also leads to increased electrical isolation between the semiconductor optical modulator 601 and the laser section 660.

[0045] In the laser unit 660, the first conductivity type semiconductor layer 604 is arranged from the first side surface S1 to the second side surface S2, while the second conductivity type semiconductor layer 608 is arranged only within the mesa structure 630. Therefore, the frequency characteristics from the first laser unit electrode 664 to the active layer 666 and the frequency characteristics from the second laser unit electrode 668 to the active layer 666 are significantly different from each other. However, since the laser unit 660 operates in DC, this difference in frequency characteristics does not affect the characteristics of the laser unit 660. In addition, in the laser unit 660, the first conductivity type semiconductor layer 604 does not need to extend to the first side surface S1 and the second side surface S2.

[0046] [Seventh Embodiment] Figure 16 is a top view of a semiconductor optical integrated element 700 according to the seventh embodiment. Figure 17 is a schematic cross-sectional view showing the cross section XVII-XVII in Figure 16. Figure 18 is a schematic cross-sectional view showing the cross section XVIII-XVIII in Figure 16. Similar to the sixth embodiment, in the seventh embodiment, a semiconductor optical modulator 701, a waveguide section 770, and a laser section 760 are integrated on a substrate 2. A mesa structure 730 is formed across the semiconductor optical modulator 701, the waveguide section 770, and the laser section 760.

[0047] The semiconductor optical modulator 701 has a semiconductor multilayer in which a first conductivity type semiconductor layer 704, an optical functional layer 6, and a second conductivity type semiconductor layer 708 are stacked on a substrate 2 in that order. The first conductivity type semiconductor layer 704 has a central portion 704c consisting of a portion that forms a mesa structure 30 and a portion that is connected below the central portion and has the same width as the mesa structure 30, a first lateral portion 704S1 provided in the first connection region 24 in a plan view and connected to the central portion 204c on the right side of the mesa structure 30, and a second lateral portion 704S2 connected to the central portion 204c on the left side of the mesa structure 30. Here, the width of the second lateral portion 704S2 is narrower than the width of the first lateral portion 704S1. However, it is not limited to this, and as in other embodiments, the width of the second lateral portion 704S2 and the width of the first lateral portion 704S1 may be the same. Also, the second lateral portion 704S2 may not be provided. Furthermore, an insulating film 12 is placed on the side of the mesa structure 730 of the semiconductor optical modulator 701, and the embedding layer 710 is not placed therein.

[0048] The laser unit 760 has a structure in which a first conductivity type semiconductor layer 704, an active layer 766, and a second conductivity type semiconductor layer 708 are stacked on the substrate 2 in that order. In the laser unit 760, the first conductivity type semiconductor layer 704 is provided so as to extend from the first side surface S1 to the second side surface S2. That is, the width of the first conductivity type semiconductor layer 704 and the width of the laser unit 760 are the same. An embedded layer 710 is arranged on the side surface of the mesa structure 730 of the laser unit 760. A groove is formed in the embedded layer 710 so as to extend to the first conductivity type semiconductor layer 704, and the first laser unit electrode 764 is in contact with the first conductivity type semiconductor layer 704 at the bottom surface of the groove. Also, the second laser unit electrode 768 is in contact with the second conductivity type semiconductor layer 708 at the top surface of the mesa structure 730.

[0049] The first conductivity type semiconductor layer 704 is a common layer in the semiconductor optical modulator 701, the waveguide section 770, and the laser section 760. However, the width of the first conductivity type semiconductor layer 604 differs in the semiconductor optical modulator 601, the waveguide section 670, and the laser section 660. The width of the first conductivity type semiconductor layer 704 in the waveguide section 770 is narrower than the width of the first conductivity type semiconductor layer 704 in the semiconductor optical modulator 601 and the laser section 660. Also, in a plan view, the left side edge (lower side in Figure 16) of the first conductivity type semiconductor layer 704 is straight across the waveguide section 770 and the semiconductor optical modulator 701. On the other hand, the right side edge (upper side in Figure 16) of the first conductivity type semiconductor layer 704 is not straight. Since the semiconductor optical modulator 701 does not have an embedded layer, the width of the first side section 704s1 and the width of the second side section 704s2 do not need to be the same. In the seventh embodiment, the width of the first lateral portion 704s1 and the width of the second lateral portion 704s2 are different. However, as in the fourth embodiment, in a structure in which the semiconductor optical modulator 701 has an embedded layer, the widths of the first lateral portion 704s1 and the width of the second lateral portion 704s2 may be different from each other. The embedded layer 710 is also arranged near the connection between the waveguide portion 770 and the laser portion 760.

[0050] [Eighth Embodiment] Figure 19 is a top view of a semiconductor optical device 870 according to the eighth embodiment. The semiconductor optical device 870 has a structure in which a semiconductor optical modulator 801 is mounted on a submount 875. The structure of the semiconductor optical modulator 801 according to the eighth embodiment is the same as that of the semiconductor optical modulator 1 according to the first embodiment, except that the shapes of the first electrode 814 and the second electrode 818 are different. In Figure 19, the first conductivity type semiconductor layer 804 is shown with a dashed line for illustrative purposes.

[0051] The submount 875 has a structure in which the surface of the ceramic substrate is metallized. The submount 875 includes a first transmission line 884 and a second transmission line 888. Electrical signals are applied to the two transmission lines from an external source. The submount 875 includes two matching resistors 877 and a conductive pattern 879. The conductive pattern 879 is connected to a reference potential (ground potential). Electrodes for connection to the submount 875 are formed on the back surface of the semiconductor optical modulator 801, and these connection electrodes and the conductive pattern 879 are connected by solder.

[0052] The center positions of the pad electrode portions of the first electrode 814 and the second electrode 818 are offset from each other in the extension direction D1. The first transmission line 884 is connected to the pad electrode portion of the first electrode 814 via the first wire 894. The second transmission line 888 is connected to the pad electrode portion of the second electrode 818 via the second wire 898. Here, the first electrode 814 and the second electrode 818 are arranged such that the second wire 898 is longer than the first wire 894. For example, consider the case where a pair of differential signals are transmitted to the first transmission line 884 and the second transmission line 888. In this case, it is preferable that the two electrical signals constituting the pair of differential signals are transmitted to the optical functional layer 6 with the same signal quality. As described above, the frequency characteristics of the first transmission route and the frequency characteristics of the second transmission route differ due to the difference in size between the first conductivity type semiconductor layer 4 and the second conductivity type semiconductor layer 8. In the above embodiment, this difference is reduced, but it can be further reduced by adjusting the wire length as in this embodiment. In other words, by intentionally making the wire through which the external electrical signal is transmitted in the second transmission route via the second conductivity semiconductor layer 8, which is smaller than the first conductivity semiconductor layer 4, longer, the overall frequency characteristics of the first transmission route and the second transmission route can be made closer. Therefore, in this embodiment, the second wire 898 is longer than the first wire 894.

[0053] The semiconductor optical modulator 801 may have a structure similar to that of the semiconductor optical modulators shown in other embodiments. Furthermore, the semiconductor optical device 870 may be equipped with a semiconductor optical integrated element similar to that of the fifth or seventh embodiment. In this case, the same effect can be obtained by making the length of the wire connected to the second electrode of each semiconductor optical modulator longer than the length of the wire connected to the first electrode.

[0054] The present invention is not limited to the embodiments described above. In the above embodiments, the case in which the substrate 2 is a semi-insulating semiconductor substrate is illustrated, but a conductive substrate may also be used. However, when a conductive substrate is used, a semi-insulating semiconductor layer is placed between the conductive substrate and the first conductivity type semiconductor layer. Furthermore, the semiconductor optical modulator is not limited to an electro-absorption type modulator, but may also be a direct modulation type laser. However, in the case of a semiconductor optical integrated element in which the semiconductor optical modulator is integrated together with the laser unit, it is preferable that the semiconductor optical modulator is an electro-absorption type modulator. In the above embodiments, the case in which the electrical signal applied to the semiconductor optical modulator is a differential signal is illustrated, but the electrical signal applied to the semiconductor optical modulator may also be a single-ended drive. The width of the first conductivity type semiconductor layer may differ between the central and lateral parts and the other parts. For example, the width of the portion of the first conductivity type semiconductor layer near the end face may be narrower or wider than the width of the central and lateral parts. Furthermore, the width of the portion of the first conductivity type semiconductor layer near the connection with the waveguide part may differ from the width of the other parts, not limited to the portion at the end face.

[0055] The present invention relates to a semiconductor optical modulator comprising a first conductivity semiconductor layer, an optical functional layer, and a second conductivity semiconductor layer, wherein the difference between the frequency characteristics from the first conductivity semiconductor layer to the optical functional layer and the frequency characteristics from the second conductivity semiconductor to the optical functional layer is reduced. A portion of the first conductivity semiconductor layer, the optical functional layer, and the second conductivity semiconductor layer form a mesa structure. The first conductivity semiconductor layer contacts a first electrode at a first connection region, and the second conductivity semiconductor layer contacts a second electrode on the upper surface of the mesa structure. The first conductivity semiconductor layer has a central portion consisting of a portion that forms the mesa structure and a portion that is continuous below the central portion and has the same width as the mesa structure, and a first lateral portion that is provided in the first connection region in a plan view and is continuous with the central portion on one side of the mesa structure, with the side surface of the first lateral portion positioned inward from the side surface of the semiconductor optical modulator on that side. The width of the first lateral portion is preferably 1 / 3 or less, and more preferably 1 / 4 or less, of the distance between the first mesa side surface, which is the side surface of the mesa structure on one side, and the first side surface, which is the side surface of the semiconductor optical modulator on that side. The first conductive semiconductor layer may include a second lateral portion that is connected to the central part on the other side of the mesa structure. The difference between the width of the first lateral portion and the width of the second lateral portion may be within 20% of the width of the first lateral portion. Furthermore, the difference between the width of the second lateral portion and the width of the portion of the first lateral portion between the first mesa side surface, which is the side surface of the mesa structure on one side, and the side surface of the groove facing the first mesa side surface may be within 20% of the width of the second lateral portion. An embedded layer or an insulating film may be arranged on the side of the mesa structure. When an embedded layer is placed to the side of the mesa structure, and a step is formed on the surface of the embedded layer, it is desirable that the pad electrode portion included in the first electrode and / or second electrode is not placed in the step region. A resin layer may be placed between the pad electrode portion and the embedded layer. In the direction in which the mesa structure extends, both ends of the second connection region may be placed inside both ends of the first connection region.

[0056] The present invention is also applicable to a semiconductor optical integrated element comprising a semiconductor optical modulator, a laser unit, and a waveguide unit disposed between the semiconductor optical modulator and the laser unit. The first conductivity type semiconductor layer is disposed across the semiconductor optical modulator, the laser unit, and the semiconductor optical modulator. In a plan view, the width of the first conductivity type semiconductor layer is narrowest in the waveguide unit. Furthermore, the present invention is also applicable to a semiconductor optical device having a submount on which either the semiconductor optical modulator or the semiconductor optical integrated element is mounted. The submount has a first transmission line and a second transmission line. The first transmission line and the first electrode of the semiconductor optical modulator are connected by a first wire, and the second transmission line and the second electrode are connected by a second wire. It is desirable that the second wire is longer than the first wire. [Explanation of Symbols]

[0057] 1,201,301,401,501,601,701,801 Semiconductor Optical Modulators 2 circuit boards 4,204,304,404,504,604,704,804 First Conductivity Semiconductor Layer 4c,204c,304c,404c,504c,704c Central part 4s1,204s1,304s1,404s1,504s1,704s1 First lateral section 4s2,204s2,304s2,404s2,504s2,704s2 2nd side part 6. Optical functional layer 8,608,708 Second Conductivity Semiconductor Layer 10,710 Embedding layer 12 Insulating film 14,314,714,818 1st electrode 14e,314e 1st current-carrying electrode part 14b,314b First connection area 14p, 314p First pad electrode section 18,218,318,718,818 2nd electrode 218e 2nd current-carrying electrode section 218b Second connection area Pages 218, 318p: Second pad electrode section 24. First connection area 28 Second Connection Area 30,630,730 Mesa structure 32 grooves 350 resin layer 600 Semiconductor Optical Integrated Devices 660,760 Laser section 664,764 First laser electrode 666,766 active layer 668,768 Second laser electrode 670,770 Waveguide section 676 Waveguide Layer 870 Semiconductor Optical Devices 875 Submount 877 matching resistor 879 Conductive Pattern 884 First transmission line 888 Second transmission line 894 First wire 898 Second wire D1 Stretching direction D2 Width direction D3 stacking direction E1 1st end surface E2 2nd end face S1 1st side S2 2nd side

Claims

1. A semiconductor optical modulator, A semiconductor multilayer in which a first conductivity semiconductor layer, an optical functional layer, and a second conductivity semiconductor layer are stacked in that order, A first electrode connected to the first conductivity type semiconductor layer, The device comprises a second electrode connected to the second conductive semiconductor layer, A portion of the first conductivity semiconductor layer, the photofunctional layer, and the second conductivity semiconductor layer form a mesa structure that stretches in the stretching direction. A semiconductor optical modulator in which the width of the first conductive semiconductor layer is narrower than the width of the semiconductor optical modulator.

2. A semiconductor optical modulator according to claim 1, The first electrode and the second electrode are arranged on the surface of the semiconductor optical modulator. The semiconductor optical modulator according to claim 1.

3. A semiconductor optical modulator according to claim 2, In a plan view, the first electrode and the first conductivity type semiconductor layer are connected to each other in a first connection region. A semiconductor optical modulator, wherein the first conductive semiconductor layer has a central portion consisting of a part that forms the mesa structure and a portion that is connected below the part and has the same width as the mesa structure, and a first lateral portion provided in the first connection region in a plan view and connected to the central portion on one side of the mesa structure.

4. A semiconductor optical modulator according to claim 3, The width W of the first lateral portion is 1 / 3 or less of the distance Wa between the first mesa side surface, which is the side surface of the mesa structure on one side, and the first side surface, which is the side surface of the semiconductor optical modulator on that side. Semiconductor optical modulator.

5. A semiconductor optical modulator according to claim 3, The first conductive semiconductor layer has a second lateral portion that is connected to the central portion on the other side of the mesa structure, in a semiconductor optical modulator.

6. A semiconductor optical modulator according to claim 5, A semiconductor optical modulator in which the difference between the width of the first side portion and the width of the second side portion is within 20% of the width of the first side portion.

7. A semiconductor optical modulator according to claim 5, A first embedded layer in contact with the upper surface of the first lateral portion and the first mesa side surface, which is one side surface of the mesa structure, The upper surface of the second lateral portion and the second mesa side surface, which is the other side surface of the mesa structure, are in contact with each other. Furthermore, A semiconductor optical modulator wherein the upper surface of the second embedded layer has an upper section corresponding to the second lateral section, a lower section located below the upper section, and a stepped section connecting the upper section and the lower section.

8. A semiconductor optical modulator according to claim 7, The second electrode includes a current-carrying electrode portion disposed in the second connection region, a bridge electrode portion connected to the current-carrying electrode and extending in the width direction, and a pad electrode portion connected to the bridge electrode. The dimension of the bridge electrode portion in the extension direction is smaller than the dimension of the current-carrying electrode portion and the pad electrode portion in the extension direction. In a plan view, the stepped portion of the second embedded layer is superimposed on the bridge electrode portion, forming a semiconductor optical modulator.

9. A semiconductor optical modulator according to claim 7, The second electrode includes a current-carrying electrode portion disposed in the second connection region, a bridge electrode portion connected to the current-carrying electrode and extending in the width direction, and a pad electrode portion connected to the bridge electrode. The dimension of the bridge electrode portion in the extending direction is narrower than the dimension of the current-carrying electrode and the pad electrode in the extending direction. A resin layer is disposed between the pad electrode portion and the second embedded layer. The aforementioned resin layer is a semiconductor optical modulator that, in a plan view, overlaps with the stepped portion.

10. A semiconductor optical modulator according to claim 5, A groove is provided on one side of the mesa structure in the width direction, and further has a groove portion having the first connection region at its bottom, A semiconductor optical modulator, wherein the difference between the width of the second lateral portion and the width of the portion of the first lateral portion between the first mesa side surface, which is one side surface of the mesa structure, and the side surface of the groove portion facing the first mesa side surface is within 20% of the width of the second lateral portion.

11. A semiconductor optical modulator according to claim 1, A semiconductor optical modulator further comprising an insulating film disposed to the side of the mesa structure.

12. A semiconductor optical modulator according to claim 3, A semiconductor optical modulator, wherein both ends of the second connection region in the extension direction are positioned inward from both ends of the first connection region in the extension direction.

13. A semiconductor optical modulator according to claim 1, Laser section, The system comprises a waveguide section disposed between the semiconductor optical modulator and the laser section, The mesa structure is a semiconductor optical integrated element that extends in the stretching direction across the semiconductor optical modulator, the waveguide section, and the laser section.

14. A semiconductor optical integrated device according to claim 13, The first conductive semiconductor layer is commonly arranged across the semiconductor optical modulator, the waveguide section, and the laser section. A semiconductor optical integrated element wherein, in the width direction of the mesa structure, the width of the first conductivity type semiconductor layer in the waveguide portion is narrower than the width of the first conductivity type semiconductor layer in the semiconductor optical modulator.

15. A semiconductor optical integrated device according to claim 14, The semiconductor optical integrated element wherein one side surface of the first conductive semiconductor layer in the laser portion extends in the width direction to that side surface of the semiconductor optical integrated element.

16. A semiconductor optical integrated device according to claim 13, A semiconductor optical integrated element further comprising an embedded layer disposed to the side of the mesa structure in the width direction.

17. A semiconductor optical integrated device according to claim 13, In the width direction, an insulating film is disposed to the side of the mesa structure in the semiconductor optical modulator, A semiconductor optical integrated element further comprising: an embedded layer disposed to the side of the mesa structure in the laser portion.

18. A semiconductor optical modulator according to claim 1, A semiconductor optical device comprising a submount on which the aforementioned semiconductor optical modulator is mounted.

19. A semiconductor optical apparatus according to claim 18, The submount has a first transmission line and a second transmission line, A first wire connecting the first transmission line and the first electrode, The device further comprises a second wire connecting the second transmission line and the second electrode, The second wire is longer than the first wire in the semiconductor optical device.

20. A semiconductor optical integrated element according to claim 13, A semiconductor optical device comprising a submount on which the aforementioned semiconductor integrated element is mounted.

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