Semiconductor optical integrated components

Abstract

The semiconductor optical integrated element disclosed in the present invention comprises: a laser diode section (12) which is arranged on one end side of a substrate (10), has a first optical waveguide (43) and generates laser light; a modulator section (14) which is arranged on the other end side, has a second optical waveguide (53) and modulates the laser light; a separation region (16) which is arranged between the laser diode section (12) and the modulator section (14); and a pair of grooves (22, 24) which are arranged on both sides along the first optical waveguide (43) and the second optical waveguide (53), wherein the second optical waveguide in the separation region (16) and a part of the second optical waveguide (53) in the modulator section (14) close to the separation region are of buried structure, and the remaining part of the second optical waveguide (53) in the modulator section (14) has a high terrace ridge structure.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor optical integrated device. Background Art

[0002] In the optical communication system between the relay station and the user, that is, the access system, directly modulated semiconductor laser transmitters (DML: Directly Modulated Laser) suitable for low-speed modulation have been mostly used in the past. However, in the case of high-speed communication of 10Gb / s or above, a semiconductor optical integrated element (EML: Electro-absorption Modulator integrated Laser) is used, which integrates a laser diode (Laser Diode, sometimes also referred to as LD for simplicity) as a light source and an electric field absorption semiconductor optical modulator (EAM: Electro-absorption Modulator, hereinafter referred to as EA modulator) suitable for high-speed modulation on the same substrate.

[0003] As optical waveguide structures constituting the laser diode part and the EA modulator part of the semiconductor optical integrated element, optical waveguide structures such as an embedded optical waveguide in which both side surfaces of a core layer for guiding or modulating laser light are buried through a semiconductor layer (hereinafter appropriately referred to as an embedded structure), a high-mesa-ridge optical waveguide in which both side surfaces of the core layer are not buried through a semiconductor layer (hereinafter appropriately referred to as a high-mesa-ridge structure), and a low-mesa-ridge optical waveguide in which the grooves do not reach the core layer are used according to the respective purposes of the semiconductor optical integrated element.

[0004] In the existing semiconductor optical integrated element, the optical waveguide of the EA modulator part is composed of the same structure along the optical axis direction, that is, the same cross-sectional shape relative to the optical axis. In addition, in order to improve the heat dissipation of the EA modulator part, a structure in which the semiconductor layer is embedded in both side surfaces of the core layer and a heat sink is provided on the outer side of the embedded semiconductor layer (Patent Document 1), a structure in which an electrode pad is arranged on the light input side of the EA modulator part that generates more heat to improve the heat dissipation (Patent Document 2), and a structure in which a metal thin film heat sink is arranged on both side surfaces of the ridge-type optical waveguide along the optical axis direction to improve the heat dissipation (Patent Document 3).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-53525

[0006] Patent Document 2: Japanese Patent Application Publication No. 2009-222965

[0007] Patent Document 3: Japanese Patent Application Publication No. 2001-142037

[0008] When the entire conventional EA modulator portion is formed into a buried structure, heat dissipation is improved, but the buried structure portion becomes a capacitance component, and therefore the high frequency characteristics are inferior to those of the high mesa ridge structure.

[0009] On the other hand, when the entire EA modulator portion is formed into a high mesa ridge structure, the capacitance can be reduced, so the high frequency characteristics are excellent, but the heat generated by the light absorbing layer is difficult to diffuse to the surroundings, so the heat dissipation is inferior to the embedded structure.

[0010] Therefore, when the optical input power to the EA modulator is high, the semiconductor optical integrated device generates more heat, which may deteriorate the device characteristics (Patent Document 1, Patent Document 2). In addition, there is a possibility that the device may be destroyed due to excessive heat (Patent Document 3). Summary of the invention

[0011] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to obtain a semiconductor optical integrated device that can have both high-frequency characteristics and required heat dissipation in an EA modulator portion.

[0012] The semiconductor optical integrated device involved in the present disclosure comprises: a substrate; a laser diode section, which is arranged on one end side of the above-mentioned substrate, has a first optical waveguide including a first core layer, and generates laser light; a modulator section, which is arranged on the other end side of the above-mentioned substrate, has a second optical waveguide including a second core layer for guiding the above-mentioned laser light incident from the above-mentioned first core layer, and modulates the above-mentioned laser light; a separation region, which is arranged between the above-mentioned laser diode section and the above-mentioned modulator section on the above-mentioned substrate, has the above-mentioned second optical waveguide, and electrically separates the above-mentioned laser diode section from the above-mentioned modulator section; and a pair of grooves, which are arranged on both sides along the above-mentioned first optical waveguide and the above-mentioned second optical waveguide, wherein the above-mentioned second optical waveguide in the above-mentioned separation region and a part of the above-mentioned second optical waveguide in the above-mentioned modulator section on the side of the above-mentioned separation region are buried structures, and the remaining part of the above-mentioned second optical waveguide in the above-mentioned modulator section is a high mesa ridge structure.

[0013] According to the semiconductor optical integrated component involved in the present disclosure, since the second optical waveguide in the separation area and a part of the second optical waveguide in the modulator part on the separation area side are of buried structure, and the remaining part of the second optical waveguide in the modulator part is of high terrace ridge structure, it is possible to have both the high-frequency characteristics and the required heat dissipation required by the modulator part, and play an effect of suppressing characteristic degradation or component damage when high light input occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a plan view showing the semiconductor optical integrated device according to the first embodiment.

[0015] Figure 2 In the semiconductor optical integrated device according to the first embodiment, Figure 1 A cross-sectional view of the laser diode portion taken along line AA shown in the top view.

[0016] Figure 3 In the semiconductor optical integrated device according to the first embodiment, Figure 1 The top view is a cross-sectional view of the separation area taken along line BB.

[0017] Figure 4 In the semiconductor optical integrated device according to the first embodiment, Figure 1 A cross-sectional view of the embedded EA modulator portion taken along line CC shown in the top view.

[0018] Figure 5 In the semiconductor optical integrated device according to the first embodiment, Figure 1 A cross-sectional view of the high-top EA modulator portion taken along line DD shown in the top view.

[0019] Figure 6 1 and 2 are views showing a method for manufacturing the semiconductor optical integrated device according to the first embodiment, and are views showing the LD portion, the isolation region, and the EA modulator portion when the semiconductor optical integrated device is viewed from the top surface.

[0020] Figure 7 It is a diagram showing a method for manufacturing the semiconductor optical integrated device according to the first embodiment and is a cross-sectional view including a core layer along the optical waveguide direction.

[0021] Figure 8 It is a diagram showing a method for manufacturing the semiconductor optical integrated device according to the first embodiment and is a diagram showing an insulating film pattern on a semiconductor multilayer structure.

[0022] Fig. 9 is a diagram showing a method for manufacturing a semiconductor optical integrated device according to Embodiment 1, and is Figure 8 Cross-sectional view of the ridge structure of the embedded EA modulator section at line AA.

[0023] Fig.10 is a diagram showing a method for manufacturing a semiconductor optical integrated device according to Embodiment 1, and is Figure 8 Cross-sectional view of the ridge structure of the high-table EA modulator section at line BB.

[0024] Fig.11 is a diagram showing a method for manufacturing a semiconductor optical integrated device according to Embodiment 1, and is Figure 8 A cross-sectional view of the ridge structure of the laser diode portion at line CC.

[0025] Fig.12 It is a diagram showing the method for manufacturing the semiconductor optical integrated device according to the first embodiment and is a plan view after the groove is formed.

[0026] Fig.13 It is a top view of the semiconductor optical integrated device according to the second embodiment.

[0027] Fig.14 In the semiconductor optical integrated device according to the second embodiment, Fig.13 Sectional view taken along line AA.

[0028] Fig.15 It is a plan view showing a semiconductor optical integrated device according to the third embodiment.

[0029] Fig.16 It is a diagram showing an insulating film pattern of a semiconductor optical integrated device according to the third embodiment.

[0030] Fig.17 is equivalent to the semiconductor optical integrated device involved in the fourth embodiment. Figure 1 A cross-sectional view of the embedded EA modulator portion taken along line CC.

[0031] Fig.18 is equivalent to the semiconductor optical integrated device involved in embodiment 5 Figure 1 A cross-sectional view of the embedded EA modulator portion taken along line CC. DETAILED DESCRIPTION

[0032] Implementation Method 1

[0033] Figure 1 1 is a top view showing a semiconductor optical integrated element according to Embodiment 1. A laser diode unit (hereinafter referred to as LD unit) 12 and an EA modulator unit 14 are integrated on an n-type InP substrate 10. The laser diode unit 12 includes an LD unit core layer (first core layer) 42 for guiding laser light, and the EA modulator unit 14 includes an EA modulator unit core layer (second core layer) 46 for guiding and modulating the laser light generated by the LD unit 12. A separation region 16 is provided between the laser diode unit 12 and the EA modulator unit 14. The separation region 16 functions in a manner that electrically separates the LD unit 12 from the EA modulator unit 14.

[0034] The LD section 12 is typically composed of a distributed feedback laser structure. In the LD section 12, the two side faces of the LD section core layer 42 for laser waveguide are buried by a semiconductor layer. Here, the two side faces of the LD section core layer 42 refer to the two side faces of the LD section core layer 42 in a direction perpendicular to the direction in which the laser waveguide is conducted and parallel to the surface of the n-type InP substrate 10. In addition, the two side faces of the EA modulator section core layer 46 are also synonymous.

[0035] Figure 2 Yes means Figure 1 The illustrated diagram is a plan view of the semiconductor optical integrated device according to the first embodiment and is a cross-sectional view of the LD portion 12 taken along line AA.

[0036] The LD unit 12 has a structure in which an n-type InP cladding layer 44 , an LD unit core layer 42 (first core layer), a p-type InP first cladding layer 47 , a diffraction grating 50 , and a p-type InP second cladding layer 52 are stacked on an n-type InP substrate 10 .

[0037] In the vertical direction of the LD core layer 42, an n-type InP cladding layer 44 and a p-type InP first cladding layer 47 having a refractive index smaller than that of the LD core layer 42 are provided to form an optical waveguide. The optical waveguide including the LD core layer 42, the n-type InP cladding layer 44 and the p-type InP first cladding layer 47 is referred to as a first optical waveguide 43. In addition, the first optical waveguide 43 also includes a buried structure described later.

[0038] The two side surfaces of the LD core layer 42 are buried by a p-type InP first buried layer 54, an n-type InP second buried layer 56, and a p-type InP third buried layer 58 having a larger band gap energy than the LD core layer 42. Hereinafter, the p-type InP first buried layer 54, the n-type InP second buried layer 56, and the p-type InP third buried layer 58 are collectively referred to as a semiconductor buried layer 59.

[0039] As described above, in the LD portion 12 , a buried structure is adopted in which both side surface portions of the LD portion core layer 42 are buried in the semiconductor buried layer 59 .

[0040] Furthermore, a p-type InP third cladding layer 60 and a p-type contact layer 62 are stacked on the p-type InP second cladding layer 52 and the p-type InP third buried layer 58. Grooves 22 and 24 are formed along the optical waveguide direction in the semiconductor buried layer 59 on both side surfaces of the LD portion core layer 42. The LD portion 12 is protected by a passivation film 64 covering the surface of the LD portion 12 including the side surfaces and the bottom surface of the grooves 22 and 24. The p-electrode 26 as the anode electrode is electrically connected to the p-type contact layer 62 via an opening provided in the passivation film 64 located above the n-type InP substrate 10 of the LD portion core layer 42.

[0041] On the other hand, an n-electrode 66 serving as a cathode electrode is provided on the back surface side of the n-type InP substrate 10 and is electrically connected to the n-type InP substrate 10 .

[0042] The region where current is injected into the LD section 12 and the surrounding region of the semiconductor optical integrated device are electrically isolated by the grooves 22 and 24. The LD section 12 is provided with a p-electrode 26. The LD section core layer 42 functions as an active layer of the LD section 12.

[0043] Figure 3 Yes means Figure 1 The illustrated diagram is a plan view of the semiconductor optical integrated device according to the first embodiment and is a cross-sectional view of the isolation region 16 taken along line BB.

[0044] In the separation region 16, an n-type InP cladding layer 44, an EA modulator core layer 46, and a p-type InP fourth cladding layer 48 are stacked on the n-type InP substrate 10. Similar to the LD section 12, both side surfaces of the EA modulator core layer 46 are buried by a semiconductor buried layer 59 composed of a p-type InP first buried layer 54 having a larger band gap energy than the EA modulator core layer 46, an n-type InP second buried layer 56, and a p-type InP third buried layer 58.

[0045] In addition, in the separation region 16, unlike the EA modulator section 14, optical modulation of the laser generated in the LD section 12 is not performed, but the structure of the core layer of the optical waveguide is the same as the core layer of the EA modulator section 14. Therefore, for the sake of convenience, the core layer of the optical waveguide possessed by the separation region 16 is also referred to as the EA modulator section core layer 46.

[0046] In the up-down direction of the EA modulator core layer 46, an n-type InP cladding layer 44 and a p-type InP fourth cladding layer 48 having a refractive index smaller than that of the EA modulator core layer 46 are provided to form an optical waveguide. The optical waveguide including the LD core layer 42, the n-type InP cladding layer 44 and the p-type InP fourth cladding layer 48 is referred to as a second optical waveguide 53. In addition, the second optical waveguide 53 also includes a buried structure or a high mesa ridge structure described later.

[0047] Furthermore, a p-type InP third cladding layer 60 is stacked on the p-type InP fourth cladding layer 48 and the p-type InP third buried layer 58. Unlike the LD section 12 or the EA modulator section 14, on the p-type InP third buried layer 58, there is no p-type contact layer 62 and p-electrode 26 as provided in the LD section 12 or the EA modulator section 14.

[0048] In this way, the isolation region 16 adopts a buried structure in which both side surfaces of the EA modulator core layer 46 are buried in the semiconductor buried layer 59 .

[0049] The EA modulator section 14 is a region that operates as an EA modulator. A portion of the EA modulator section 14 on the LD section 12 side (light input side), in other words, a portion that is in contact with the separation region 16, is formed by a buried EA modulator section 18 formed by a buried structure, and the remaining portion of the EA modulator section 14 is a high-table EA modulator section 20 formed by a high-table ridge structure. The EA modulator section core layer 46 of the EA modulator section 14 functions as an absorption layer for the laser light guided from the LD section 12 via the separation region 16. Figure 1 As shown in the top view of FIG. 4 , an EA modulator section electrode 36 and an EA modulator section bonding pad 34 are provided in order to apply a voltage to the EA modulator section core layer 46 .

[0050] Similar to the LD section 12 , in the EA modulator section 14 , the region to which voltage is applied and the surrounding region of the semiconductor optical integrated device are electrically separated by the grooves 22 and 24 .

[0051] Figure 4 Yes means Figure 1 The illustrated diagram is a plan view of the semiconductor optical integrated device according to the first embodiment and is a cross-sectional view of the embedded EA modulator portion 18 taken along line CC.

[0052] In the embedded EA modulator section 18, an n-type InP cladding layer 44, an EA modulator section core layer 46, and a p-type InP fourth cladding layer 48 are stacked on an n-type InP substrate 10. Both side surfaces of the EA modulator section core layer 46 are embedded in a semiconductor embedded layer 59 composed of a p-type InP first embedded layer 54 having a larger band gap energy than the EA modulator section core layer 46, an n-type InP second embedded layer 56, and a p-type InP third embedded layer 58.

[0053] A p-type InP third cladding layer 60 and a p-type contact layer 62 are stacked on the p-type InP fourth cladding layer 48 and the p-type InP third buried layer 58. Thus, in the buried EA modulator section 18, a buried structure is adopted in which both side surfaces of the EA modulator section core layer 46 are buried by the semiconductor buried layer 59.

[0054] Figure 5Yes means Figure 1 The illustrated diagram is a plan view of the semiconductor optical integrated device according to the first embodiment and is a cross-sectional view of the high-mesa EA modulator section 20 taken along line DD.

[0055] In the high-mesa EA modulator section 20, an n-type InP cladding layer 44, an EA modulator section core layer 46, and a p-type InP fourth cladding layer 48 are stacked on the n-type InP substrate 10. Furthermore, a p-type InP third cladding layer 60 and a p-type contact layer 62 are stacked on the p-type InP fourth cladding layer 48.

[0056] The two side surfaces of the EA modulator core layer 46 are protected by a passivation film 64 made of an insulating material such as a nitride film (SiN), and the outside thereof is air. Thus, in the high-top EA modulator section 20, a high-top ridge structure is adopted in which the two side surfaces of the EA modulator core layer 46 are not buried by a buried layer such as a semiconductor buried layer.

[0057] The EA modulator core layer 46 is sandwiched from top to bottom by the n-type InP cladding layer 44 and the p-type InP fourth cladding layer 48, which are cladding layers having a smaller refractive index than the EA modulator core layer 46. Therefore, the laser light generated by the LD unit 12 is mainly confined to the EA modulator core layer 46 and is guided along the EA modulator core layer 46.

[0058] The width 30 of the embedded structure portion embedded in the EA modulator portion 18 is, for example, 10 μm. On the other hand, the width of the EA modulator portion core layer 46 is, for example, 1.5 μm. The width 30 of the embedded structure portion refers to the distance between the side surfaces facing each other through the embedded structure in the grooves 22 and 24.

[0059] As an example, regarding the length of the EA modulator section 14 in the optical waveguide direction, the overall length of the EA modulator section 14 is 200 μm, the length of the embedded EA modulator section 18 is 30 μm, and the length of the high-mesa EA modulator section 20 is 170 μm.

[0060] A method for manufacturing the semiconductor optical integrated device according to the first embodiment will be described below.

[0061] First, if Figure 6 A top view showing each region of a semiconductor optical integrated device and Figure 6 The cross-sectional view of line AA in Figure 7As shown in the cross-sectional view cut along the optical waveguide direction, a semiconductor stacked structure 90 having an LD portion core layer 42 and an EA modulator portion core layer 46 is formed on an n-type InP substrate 10. The semiconductor stacked structure 90 is structured as follows: in the region where the LD portion 12 is formed, an n-type InP cladding layer 44, an LD portion core layer 42, a p-type InP first cladding layer 47, a diffraction grating 50, and a p-type InP second cladding layer 52 are stacked on the n-type InP substrate 10, and on the other hand, in the region where the EA modulator portion 14 and the separation region 16 are formed, an n-type InP cladding layer 44, an EA modulator portion core layer 46, and a p-type InP fourth cladding layer 48 are stacked on the n-type InP substrate 10.

[0062] Next, if Figure 8 As shown in the plan view of FIG. 8 , an insulating film 78 is formed on the upper surface of the semiconductor stacked structure 90 , and the insulating film 78 is patterned so that a portion of the insulating film 78 corresponding to the ridge structure 80 remains.

[0063] The semiconductor stack structure 90 is etched using an etching technique such as dry etching using the insulating film 78 as an etching mask, thereby forming Fig. 9 , Fig.10 as well as Fig.11 The ridge structure 80 is shown in the cross-sectional views of FIG. 8 . The ridge structure 80 is stripe-shaped in the light waveguide direction.

[0064] Fig. 9 express Figure 8 A cross-sectional view taken along line AA of FIG. 1 is a cross-sectional view showing a ridge structure 80 embedded in a formation region of the EA modulator portion 18. Fig.10 express Figure 8 A cross-sectional view taken along line BB of FIG. 1 is a cross-sectional view showing a ridge structure 80 in a formation region of the high-table EA modulator section 20 . Fig.11 express Figure 8 The cross-sectional view taken along the CC line of FIG. 1 is a cross-sectional view showing the ridge structure 80 in the region where the LD portion 12 is formed. The width of the ridge structure 80 in the region where the LD portion 12, the separation region 16, and the embedded EA modulator portion 18 are formed is set to be narrower than the width of the ridge structure 80 in the region where the high terrace EA modulator portion 20 is formed.

[0065] Next, the LD section 12, the isolation region 16, and both side surfaces of the ridge structure 80 in which the EA modulator section 18 is buried are buried by a semiconductor buried layer 59 composed of a p-type InP first buried layer 54, an n-type InP second buried layer 56, and a p-type InP third buried layer 58. Thereafter, the insulating film 78 is removed, and a p-type InP third cladding layer 60 and a p-type contact layer 62 are stacked.

[0066] Next, if Fig.12As shown in the top view of FIG. 8 , the ridge structure 80 and the semiconductor buried layer 59 composed of the p-type InP first buried layer 54, the n-type InP second buried layer 56 and the p-type InP third buried layer 58 are etched using the insulating film mask 82 as a mask to form the grooves 22 and 24. Figure 2 The LD portion 12 is shown in cross-sectional view. Figure 3 The separation area 16 is shown in cross-section. Figure 4 The embedded EA modulator section 18 is shown in cross-section and Figure 5 A cross-sectional view of the high-mesa EA modulator section 20 is shown.

[0067] At this time, the LD portion 12 , the isolation region 16 , and the embedded EA modulator portion 18 are formed into an embedded structure, while the high-mesa EA modulator portion 20 is formed into a high-mesa ridge structure.

[0068] Next, the operation of the above-mentioned semiconductor optical integrated device will be described.

[0069] If a forward current flows into the LD section 12, laser oscillation occurs, and laser light is emitted from the LD section 12. The laser light first enters the embedded EA modulator section 18 in the EA modulator section 14, and then is guided by the high-top EA modulator section 20, and is emitted to the outside from the emission end face 32. As described above, the LD section 12 is composed of a distributed feedback laser structure. In the distributed feedback laser structure, a diffraction grating 50 is provided. The diffraction grating 50 is periodically arranged along the traveling direction of the laser light, and functions in a manner of reflecting laser light of a specific wavelength. Therefore, through the action of the diffraction grating 50, a laser light of a single oscillation mode can be obtained.

[0070] On the other hand, the EA modulator has an electric field absorption effect that increases the amount of light absorbed when a reverse bias is applied. Using this electric field absorption effect, the input laser light is modulated according to the magnitude of the voltage applied to the EA modulator. When light is absorbed, a photocurrent is generated and heat is generated.

[0071] Assuming that the distance from the light incident end is x, the light distribution in the light waveguide direction in the EA modulator unit 14 is expressed by the following equation (1).

[0072] P(x)=P 0 *exp(-Γαx) (1)

[0073] Here, P 0 is the intensity of the laser light incident on the EA modulator 14, Γ is the light confinement coefficient of the optical waveguide, and α is the absorption coefficient. According to equation (1), it is derived that the light absorption is maximum at the incident end, and accordingly, the heat generation is also maximum near the incident end.

[0074] Next, the effects of the semiconductor optical integrated device according to the first embodiment will be described.

[0075] Embed the EA modulator section 18 as Figure 4 As shown in the cross-sectional view of the embedded EA modulator section 18, both side surfaces of the EA modulator section core layer 46 functioning as a light absorbing layer are embedded in the semiconductor embedding layer 59, so the semiconductor embedding layer 59 also functions as a heat sink.

[0076] Compared with the high-top EA modulator 20 in which the side portions of the EA modulator core layer 46 are not buried, the heat generated by the photocurrent around the EA modulator core layer 46 can be efficiently dissipated. This is because the thermal conductivity of the semiconductor buried layer 59 is higher than that of the high-top ridge structure in contact with air on the side portions.

[0077] As can be seen from equation (1), the light absorption amount is maximum near the incident end of the EA modulator unit 14 and decays exponentially toward the emission end. Therefore, a sufficiently large heat dissipation effect can be obtained simply by making a part of the incident end side a buried structure.

[0078] On the other hand, since most of the EA modulator section 14 is composed of the high-table EA modulator section 20 with a small capacitance, the capacitance component is small, and thus the high-frequency characteristics are also excellent. In the semiconductor optical integrated element involved in embodiment 1, it is possible to have both the high-frequency characteristics required by the EA modulator section 14 and the required heat dissipation, thereby achieving the effect of suppressing characteristic degradation or component damage when high light input occurs.

[0079] The semiconductor stacked structure of the semiconductor buried layer 59 in the EA modulator section 18 can be manufactured by the same epitaxial growth process as the semiconductor buried layer 59 in the LD section 12, so there is no need to add a new epitaxial process, thereby simplifying the manufacturing process. Of course, it is self-evident that it can also be manufactured by another process.

[0080] In addition, a p-type InP substrate or a semi-insulating InP substrate may be used instead of the n-type InP substrate 10. When the n-type InP substrate 10 is used, since the upper surface side becomes a p-type semiconductor, the electrical isolation between the LD section 12 and the EA modulator section 14 becomes higher than when the p-type InP substrate is used.

[0081] A traveling wave electrode can also be used for the EA modulator 14. However, when a traveling wave electrode is used, it is essential that the loss of microwaves is particularly small.

[0082] In addition, as the semiconductor material constituting the p-type InP first buried layer 54 and the n-type InP second buried layer 56 , a semiconductor material such as an Fe-doped InP layer may be used instead of p-type InP or n-type InP.

[0083] The LD core layer 42 of the LD unit 12 is composed of, for example, an AlGaInAs-based or InGaAsP-based multiple quantum well layer (Multiple Quantum Well Layer), and the band gap wavelength of the multiple quantum well layer is 1.2 to 1.62 μm.

[0084] On the other hand, the EA modulator core layer 46 of the EA modulator 14 is composed of a multi-quantum well layer of, for example, AlGaInAs or InGaAsP, and the band gap wavelength of the multi-quantum well layer is 0.9 to 1.55 μm. That is, the band gap wavelength of the EA modulator core layer 46 is set shorter than the oscillation wavelength of the LD 12.

[0085] The LD core layer 42 and the EA modulator portion 14 may also be formed by applying a selective growth technique, or may be connected by separate growth through butt-joint growth.

[0086] Furthermore, the depths of the grooves 22 and 24 may be changed in the LD section 12, the separation region 16, and the EA modulator section 14. For example, the depths of the grooves 22 and 24 in the LD section 12 may be 7 μm, the depths of the grooves 22 and 24 in the separation region 16 may be 5 μm, and the depths of the grooves 22 and 24 in the EA modulator section 14 may be 4 μm.

[0087] In addition, it is preferable that the p-type contact layer 62 is not provided in the isolation region 16. This has the effect of reducing the loss of laser light and increasing the isolation resistance between the LD unit 12 and the EA modulator unit 14.

[0088] In the above description of the semiconductor optical integrated element, the semiconductor buried layer 59 for burying the EA modulator section 18 is configured on both side surfaces of the EA modulator section core layer 46. However, it may be selectively configured only on one side surface instead of on both side surfaces, depending on the needs, such as for applications with low optical input power.

[0089] When the semiconductor buried layer 59 is provided only on one side surface, the capacitance component generated by the semiconductor buried layer 59 is reduced, so the high-frequency characteristics are improved compared with the case where the semiconductor buried layer 59 is provided on both side surfaces. This is effective when the light input amount to the EA modulator unit 14 is small and high-frequency characteristics are required as element characteristics rather than heat dissipation.

[0090] Implementation Method 2

[0091] Fig.13The upper surface of the semiconductor optical integrated device according to the second embodiment is shown, and in addition to the semiconductor embedded layer 59 functioning as a heat sink, the arrangement of the heat dissipation metal 76 provided to further improve the heat dissipation performance is also shown. Fig.14 It is along Fig.13 A cross-sectional view of the embedded EA modulator section 18 cut along the line AA in the top view. In the semiconductor optical integrated device according to the second embodiment, Fig.13 as well as Fig.14 As shown, the heat dissipation metal 76 is arranged as close as possible to the semiconductor buried layer 59 to promote heat dissipation by the EA modulator core layer 46 .

[0092] Gold is an example of a metal material constituting the heat dissipation metal 76. By using gold having a high thermal conductivity, heat dissipation can be further improved compared to a case where no metal, in other words, air, is present. In addition, since the heat dissipation metal 76 is not electrically connected to the p-electrode 26 of the LD section 12, the EA modulator section electrode 36 of the EA modulator section 14, and the EA modulator section bonding pad 34, it does not affect the high frequency characteristics of the EA modulator section 14.

[0093] Implementation 3

[0094] Fig.15 It is a plan view showing a semiconductor optical integrated device according to the third embodiment.

[0095] Composed of Figure 4 The width 30 of the embedded structure portion in the embedded EA modulator portion 18 shown becomes wider as it approaches the light input side, that is, the separation region 16 side. Alternatively, the width 30 of the embedded structure portion may be further widened from the embedded EA modulator portion 18 side to a portion of the separation region 16.

[0096] For example, the width 30 of the embedded structure portion in the light incident end side of the embedded EA modulator portion 18, i.e., the portion connected to the separation region 16, is 10 μm, and the width 30 of the embedded structure portion in the emission end side of the embedded EA modulator portion 18, i.e., the portion connected to the high-table EA modulator portion 20, is 3 μm.

[0097] Fig.16 The pattern of the insulating film mask 82 required for forming the grooves 22 and 24 of the semiconductor optical integrated device according to Embodiment 3 is shown. The pattern of the insulating film mask 82 is formed so that the width 30 of the embedded structure portion embedded in the EA modulator section 18 becomes wider toward the light input side.

[0098] By adopting a structure in which the width 30 of the embedded structure portion embedded in the EA modulator unit 18 becomes wider toward the light input side, the heat dissipation on the light incident side of the embedded EA modulator unit 18 where the heat generation is large is improved. On the other hand, since the larger the width 30 of the embedded structure portion embedded in the EA modulator unit 18, the more it becomes a capacitance component and the high-frequency characteristics deteriorate, the width is narrowed on the light emission side where the heat generation is relatively less to reduce the capacitance.

[0099] When used in applications where the amount of light input to the EA modulator unit 14 is small, by optimally designing the width 30 of the embedded structure portion embedded in the EA modulator unit 18 with respect to the amount of light input, both high frequency characteristics and heat dissipation can be achieved.

[0100] Implementation 4

[0101] Fig.17 is equivalent to the semiconductor optical integrated device involved in the fourth embodiment. Figure 1 A cross-sectional view of a portion of the embedded EA modulator section 18 taken along line CC.

[0102] The embedded portion of the EA modulator unit 18 is not composed of the semiconductor embedded layer 59 like the semiconductor optical integrated device involved in the first embodiment, but is composed of the passivation film 64 and the heat sink 74, which is different from the structure of the semiconductor optical integrated device involved in the first embodiment.

[0103] The heat sink 74 is made of a material having a higher thermal conductivity than the EA modulator section core layer 46 of the EA modulator section 14 .

[0104] For example, materials include aluminum nitride (AlN), silicon (Si), silicon carbide (SiC), diamond-like carbon (DLC), etc.

[0105] The passivation film 64 is preferably made of a material with a higher thermal conductivity than the EA modulator core layer 46. However, even if the passivation film 64 is made of a material with a thermal conductivity equal to or lower than that of the EA modulator core layer 46 from the perspective of reliability or the adhesion of the passivation film 64, heat dissipation to the heat sink 74 can be promoted by reducing the film thickness of the passivation film 64.

[0106] For example, the passivation film 64 is made of silicon dioxide (SiO 2 ) or an insulating material such as SiN, with a thickness of 0.2 μm, and the heat sink 74 is AlN. In addition, the passivation film 64 and the heat sink 74 can also be made of the same material.

[0107] In addition, since a heat sink corresponding to the heat sink 74 is not disposed in the high-mesa EA modulator section 20 , the capacitance component of the high-mesa EA modulator section 20 is not affected.

[0108] The thermal conductivity of InP is about 70 W / (m·K), whereas the thermal conductivity of AlN is about 170 W / (m·K). Compared with the semiconductor optical integrated element involved in embodiment 1, the heat dissipation is more excellent and the characteristic degradation or element damage under high light input can be suppressed.

[0109] Implementation method 5

[0110] Fig.18 is a cross-sectional view showing a semiconductor optical integrated device according to Embodiment 5, and is equivalent to Figure 1 sectional view of the portion where the EA modulator portion 18 is embedded, taken along line CC. In the semiconductor optical integrated device according to the fifth embodiment, the portions of the groove 22 and the groove 24 where the EA modulator portion 18 is embedded in the semiconductor optical integrated device according to the first embodiment are embedded with a heat sink 75.

[0111] The heat sink 75 is made of a material having a higher thermal conductivity than InP, which is a constituent material of the semiconductor embedded layer 59. For example, it is AlN, Si, SiC, DLC, or the like.

[0112] The passivation film 64 is preferably made of a material having a higher thermal conductivity than InP, which is a constituent material of the semiconductor buried layer 59 of the semiconductor optical integrated element involved in embodiment 1. However, even when a material having a thermal conductivity equal to or lower than that of the EA modulator core layer 46 is used from the perspective of reliability or adhesion of the insulating film, heat dissipation to the heat sink 75 can be promoted by reducing the film thickness.

[0113] For example, the passivation film 64 is made of SiO 2 Or an insulating material such as SiN, with a thickness of 0.2 μm, and AlN as the heat sink 75. In addition, the passivation film 64 and the heat sink 75 may be made of the same material.

[0114] In addition, since a heat sink corresponding to the heat sink 75 is not disposed in the high-mesa EA modulator section 20 , the capacitance component of the high-mesa EA modulator section 20 is not affected.

[0115] The thermal conductivity of InP is about 70 W / (m·K), whereas the thermal conductivity of AlN is about 170 W / (m·K). Compared with the semiconductor optical integrated element involved in embodiment 1, the heat dissipation is more excellent and the characteristic degradation or element damage under high light input can be suppressed.

[0116] The present disclosure describes various exemplary embodiments and examples, but various features, modes, and functions described in one or more embodiments are not limited to application in specific embodiments and can be applied to the embodiments alone or in various combinations.

[0117] Therefore, numerous variations that are not illustrated can be imagined within the technical scope disclosed in the specification of this application, including, for example, the case where at least one constituent element is deformed, the case where at least one constituent element is added or omitted, and the case where at least one constituent element is extracted and combined with constituent elements of other embodiments.

[0118] Description of Reference Numerals

[0119] 10...n-type InP substrate; 12...laser diode; 14...EA modulator; 16...separation region; 18...buried EA modulator; 20...high terrace EA modulator; 22, 24...grooves; 26...p-electrode; 30...width of buried structure; 32...emission end face; 34...EA modulator bonding pad; 36...EA modulator electrode; 42...LD core layer; 43...first optical waveguide; 44...n-type InP cladding; 46...EA modulator core layer; 47...p-type InP first cladding; 48. ..p-type InP fourth cladding layer; 50...diffraction grating; 52...p-type InP second cladding layer; 53...second optical waveguide; 54...p-type InP first buried layer; 56...n-type InP second buried layer; 58...p-type InP third buried layer; 59...semiconductor buried layer; 60...p-type InP third cladding layer; 62...p-type contact layer; 64...passivation film; 66...n-electrode; 74, 75...heat sink; 76...heat sink metal; 78...insulating film; 80...ridge structure; 82...insulating film mask; 90...semiconductor stacked structure.

Claims

1. A semiconductor optical integrated component, characterized in that: have: substrate; a laser diode section, which is provided on one end side of the substrate, has a first optical waveguide including a first core layer, and generates laser light; a modulator section provided on the other end side of the substrate, including a second optical waveguide including a second core layer for guiding the laser light incident from the first core layer, and modulating the laser light; a separation region provided between the laser diode section and the modulator section on the substrate, having the second optical waveguide and electrically separating the laser diode section from the modulator section; as well as a pair of grooves provided on both sides along the first optical waveguide and the second optical waveguide, The second optical waveguide in the separation region and a portion of the second optical waveguide in the modulator section on the separation region side are of a buried structure, and the remaining portion of the second optical waveguide in the modulator section is of a high mesa ridge structure.

2. The semiconductor optical integrated component according to claim 1, characterized in that: The embedded structure is composed of a semiconductor embedded layer provided on a side surface portion of the second optical waveguide.

3. The semiconductor optical integrated device according to claim 1, characterized in that: Heat dissipation metal is provided on at least the side surfaces of the pair of grooves on the embedded structure side.

4. The semiconductor optical integrated device according to any one of claims 1 to 3, characterized in that: In a portion of the second optical waveguide in the modulator section on the isolation region side, the embedded structure defined by the pair of grooves has a shape in which the width thereof becomes wider toward the isolation region side.

5. The semiconductor optical integrated component according to claim 1, characterized in that: The embedded structure is composed of a heat sink.

6. The semiconductor optical integrated component according to claim 5, characterized in that: The heat conductivity of a material constituting the heat sink is greater than the heat conductivity of a material constituting the first optical waveguide and the second optical waveguide.

7. The semiconductor optical integrated device according to claim 1, characterized in that: The embedded structure is composed of a semiconductor embedded layer and a heat sink having a higher thermal conductivity than the semiconductor embedded layer.

8. The semiconductor optical integrated component according to claim 2, characterized in that: The semiconductor buried layer is formed on one side surface portion of the second optical waveguide.

9. The semiconductor optical integrated device according to any one of claims 1 to 3 and 5 to 8, characterized in that: The laser diode section has a distributed feedback laser structure.

10. The semiconductor optical integrated component according to claim 4, characterized in that: The laser diode section has a distributed feedback laser structure.

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