Optical integrated devices

Abstract

To obtain an optical integrated device that enables high optical coupling efficiency through precise positional control of optical functional elements and optical circuit elements.SOLUTION: An optical integrated device 300 is integrated with an optical functional element 100 and an optical circuit element 200. The optical functional element 100 includes a high-mesa part 16 that partially includes a compound semiconductor substrate 11, has an active layer 12 and a contact layer 13, and has a convex shape and a terrace part 14 that is provided along the high-mesa part 16 and presents a flat surface. The optical circuit element 200 has a lower cladding layer 22, a core layer 23, and an upper cladding layer 25 formed on a semiconductor substrate 21, and is provided with a laminated structure substrate 40 having a first recess 27a and a second recess 27b. The optical functional element 100 and the optical circuit element 200 are flip-chip mounted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to optical integrated devices S To relate to. [Background technology]

[0002] In recent years, silicon photonics technology, which integrates optical functional elements on silicon (Si) substrates, has attracted attention in the field of optical devices such as communications. Silicon photonics technology allows for the application of mature silicon substrate processing techniques cultivated in the manufacturing of electronic circuits. Furthermore, because silicon has a higher refractive index than glass and other materials commonly used as optical elements, it is possible to confine light to minute regions, thus promising the realization of large-scale optical integrated devices that are inexpensive and can be miniaturized.

[0003] Optical waveguides are the most fundamental components in optical semiconductor devices made from various materials, including silicon, indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), lithium niobate (LiNbO3), and compound semiconductors composed of these materials. By increasing the refractive index of the waveguide compared to its surroundings, light can be locally confined to a specific region, and by forming this specific region linearly, or in a stripe shape, light can be propagated to a desired region. Optical integrated devices made of semiconductors, including silicon optical circuit elements, can be realized as large-scale optical integrated devices with various functions by interconnecting various functional blocks such as semiconductor lasers, optical receivers, modulators, and optical filters using the aforementioned optical waveguides.

[0004] On the other hand, there is a major problem with using silicon optical circuit elements as optical semiconductor devices. Specifically, because silicon is an indirect bandgap semiconductor, the interaction between electrons and light is limited, making it difficult to realize active functions such as semiconductor lasers and optical amplifiers with silicon alone. Therefore, in order to realize active functions, direct bandgap semiconductors, such as compound semiconductors like InP, are essential as constituent materials.

[0005] Therefore, in silicon photonics technology, integration techniques that realize passive and active functions using different materials are being widely investigated. Due to the difference in lattice constants between silicon and compound semiconductor materials, monolithic integration on the same substrate using epitaxial crystal growth is difficult. Consequently, currently, so-called hybrid integration structures are widely applied, in which active elements made of compound semiconductor materials (hereinafter referred to as optical functional elements) are mounted and integrated on silicon optical circuit elements. In the following explanation, silicon optical circuit elements and optical functional elements may be collectively referred to simply as optical elements.

[0006] Various types of hybrid integrated structures combining silicon optical circuit elements and optical functional elements have been proposed. One example of a hybrid integrated structure is a butt coupling method, in which a silicon optical circuit element and an optical functional element, each having the aforementioned optical waveguides extending to their optical end faces, are placed in close proximity to each other such that the cross-sections of the optical waveguides on the end faces of each optical element face each other, thereby introducing light propagating within one optical element into the other optical element via free space.

[0007] Another example of a hybrid integrated structure is a grating coupler system, in which light propagating through an optical waveguide formed on a silicon optical circuit element or optical functional element is reflected perpendicularly to the optical element by a grating, and then introduced into the optical waveguide of another optical element via a grating formed on another optical element positioned opposite the first optical element.

[0008] Furthermore, one bonding method involves physically bonding a silicon optical circuit element and an optical functional element so that their optical waveguides run parallel to each other in close proximity, thereby introducing light propagating within one optical element into the other optical element via evanescence.

[0009] However, in the butt coupling method, the cross-sectional size of typical optical waveguides in silicon optical circuit elements and optical functional elements is small, ranging from submicrons to at most a few microns. Therefore, if there is even a slight misalignment in the mounting positions of the silicon optical circuit element and the optical functional element, the light emitted from one optical element cannot be properly introduced into the other optical element, resulting in a significant loss of optical power.

[0010] To reduce the misalignment of the mounting positions of these two components, techniques have been developed to precisely adjust the relative positions of the optical elements in the in-plane direction using alignment marks. However, the method using alignment marks does not guarantee accuracy in the vertical direction of the optical element surface, i.e., the height direction, and there is a problem that the manufacturing error of each optical element directly affects the optical coupling efficiency.

[0011] The mounting accuracy of the optical elements described above typically requires submicron-level precision both in-plane and perpendicular to the plane, i.e., in the height direction. Furthermore, the grating coupler method allows for a wider distribution of light using the grating, thus reducing the mounting accuracy of the optical elements by approximately an order of magnitude compared to the butt coupling method. However, the grating coupler method has the disadvantage that, because the grating is polarization-dependent and wavelength-dependent, the optical coupling loss also fluctuates depending on the polarization and wavelength of the propagating light.

[0012] In the bonding method, it is necessary to tightly bond optical elements or wafers made of different materials, requiring wafer manufacturing technology and bonding processes free from dust and particles, and demanding extremely high manufacturing precision.

[0013] This disclosure focuses on the butt coupling method, which is relatively easy to manufacture among the above-mentioned methods and can achieve both low polarization dependence and wavelength dependence.

[0014] As a technique to solve the problem of positional accuracy in the perpendicular direction of the surfaces of silicon optical circuit elements and optical functional elements in butt coupling systems, for example, Patent Document 1 discloses a technique to improve relative positional accuracy in the perpendicular direction, i.e., the height direction, between two optical elements by forming an etching stop layer between the core layer and the substrate layer within the optical functional element, where a different chemical reaction from the surroundings occurs, and by bringing the surface defined based on this etching stop layer into contact with the surface on the silicon optical circuit element. In other words, by forming the etching stop layer in an epitaxial crystal growth process on a compound semiconductor substrate, it becomes possible to control the relative distance between the core layer and the etching stop layer with high precision. This method realizes highly efficient optical coupling between silicon optical circuit elements and optical functional elements. [Prior art documents] [Patent Documents]

[0015] [Patent Document 1] Patent No. 6696151 [Overview of the project] [Problems that the invention aims to solve]

[0016] Patent Document 1 discloses a manufacturing technique and device structure that utilizes an etching stop layer to improve the relative positional accuracy of silicon optical circuit elements and optical functional elements in the vertical direction, i.e., the height direction, of the element surfaces. However, although the manufacturing technique and device structure described in Patent Document 1 utilize an etching stop layer to achieve high precision, there is a problem that if the etching stop layer is formed near the core layer (active layer) through which light propagates, the propagating light modes are deformed, and optical loss occurs during propagation or optical coupling between different optical elements.

[0017] In addition, since the etching stop layer is made of a material different from its surroundings, there is also a concern that it may hinder the smooth movement of carriers such as electrons and holes. Furthermore, since the energy distribution of the propagating optical mode generally has a shape where it is mostly localized on the semiconductor substrate side having a high equivalent refractive index, when the etching stop layer is located on the semiconductor substrate side, the influence of the phenomenon of deformation of the propagating optical mode becomes greater.

[0018] In order to avoid the above problems, the core layer (active layer) and the etching stop layer should be separated by a certain distance, or even when the etching stop layer is in the vicinity of the core layer (active layer), it needs to be present on the surface side opposite to the semiconductor substrate as viewed from the core layer. Also, these problems become more prominent in a so-called high mesa structure where, as an optical waveguide structure of an optical functional element, upper and lower contact layers including the core layer (active layer) are dug in to narrow the width of the core layer (active layer). This is because in the optical waveguide structure called the high mesa structure, light and carriers are confined in a narrower region.

[0019] The present disclosure has been made to solve the above problems, and an optical integration device and a method for manufacturing an optical integration device that improve the relative position accuracy in the vertical direction, that is, the height direction, of the surfaces of an optical circuit element and an optical functional element so that excessive light loss and the like can be prevented even when the optical functional element has a high mesa structure.

Means for Solving the Problems

[0020] The optical integration device according to the present disclosure is an optical integration device integrating an optical functional element and an optical circuit element, where the optical functional element is a compound semiconductor substrate, partially including the compound semiconductor substrate, and having at least The layer thickness is d That is , That is an active layer and a contact layer, and a high mesa portion having a convex shape, It comprises a terrace section provided along the aforementioned high mesa section and having a planar shape, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along the side surface of the first recess, spaced apart from the side surface, A protrusion formed between the first recess and the second recess, The optical waveguide portion is provided in contact with a side of the first recess that is different from the side surface and the side surface opposite to the side surface, and includes the lower cladding layer, the core layer and the upper cladding layer, The height of the surface of the terrace section is -d with reference to the surface of the active layer on the contact layer side. AL height The height of the top of the protrusion is set to the surface of the core layer on the upper cladding layer side. height The surface of the terrace portion and the top of the convex portion are in contact. The active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled. [Effects of the Invention]

[0022] According to the optical integrated device and method for manufacturing the optical integrated device described herein, the surface of the terrace portion of the optical functional element is formed to be located at a predetermined height relative to the active layer. This allows for precise control of the relative positional misalignment in the height direction between the optical functional element and the optical circuit element, resulting in the acquisition of an optical integrated device and method for manufacturing an optical integrated device with high optical coupling efficiency. [Brief explanation of the drawing]

[0023] [Figure 1] This is an overview diagram showing the structure of the optical integrated device according to Embodiment 1. [Figure 2] This is a top view showing the structure of the optical integrated device according to Embodiment 1. [Figure 3]This is an overview view of the optical integrated device according to Embodiment 1, as seen from a cross-section along line A in Figure 1. [Figure 4] This is a cross-sectional view along line A in Figure 1 of the optical integrated device according to Embodiment 1. [Figure 5] This is a cross-sectional view along line B in Figure 1 of the optical integrated device according to Embodiment 1. [Figure 6] This is a cross-sectional view along line C in Figure 1 of the optical integrated device according to Embodiment 1. [Figure 7A] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 1. [Figure 7B] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 1. [Figure 7C] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 1. [Figure 7D] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 1. [Figure 7E] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 1. [Figure 7F] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 1. [Figure 7G] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 1. [Figure 7H] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 1. [Figure 8] This figure shows the relationship between optical coupling efficiency and misalignment in the optical integrated device according to Embodiment 1. [Figure 9] This figure shows the relationship between optical coupling efficiency and misalignment in the optical integrated device according to Embodiment 1. [Figure 10] This is a top view showing the structure of an optical integrated device according to a modified example of Embodiment 1. [Figure 11] This is a cross-sectional view along line A in Figure 10 of an optical integrated device according to a modified example of Embodiment 1. [Figure 12]This is a cross-sectional view along line B in Figure 10 of an optical integrated device according to a modified example of Embodiment 1. [Figure 13] This is an overview diagram showing the structure of the optical integrated device according to Embodiment 2. [Figure 14] This is a top view showing the structure of the optical integrated device according to Embodiment 2. [Figure 15] This is an overview view of the optical integrated device according to Embodiment 2, as seen from a cross-section along line A in Figure 13. [Figure 16] This is a cross-sectional view along line A in Figure 13 of the optical integrated device according to Embodiment 2. [Figure 17] This is a cross-sectional view along line B in Figure 13 of the optical integrated device according to Embodiment 2. [Figure 18] This is a cross-sectional view along line C in Figure 13 of the optical integrated device according to Embodiment 2. [Figure 19A] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 2. [Figure 19B] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 2. [Figure 19C] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 2. [Figure 19D] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 2. [Figure 19E] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 2. [Figure 19F] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 2. [Figure 19G] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 2. [Figure 19H] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 2. [Figure 20] This is a top view showing the structure of an optical integrated device according to a modified example of Embodiment 2. [Figure 21] This is a cross-sectional view along line A in Figure 20 of an optical integrated device according to a modified example of Embodiment 2. [Figure 22] This is a cross-sectional view along line B in Figure 20 of an optical integrated device according to a modified example of Embodiment 2. [Figure 23] This is an overview diagram showing the structure of the optical integrated device according to Embodiment 3. [Figure 24] This is a top view showing the structure of the optical integrated device according to Embodiment 3. [Figure 25] This is an overview view of the optical integrated device according to Embodiment 3, as seen from a cross-section along line A in Figure 19. [Figure 26] This is a cross-sectional view along line A in Figure 19 of the optical integrated device according to Embodiment 3. [Figure 27] This is a cross-sectional view along line B in Figure 19 of the optical integrated device according to Embodiment 3. [Figure 28] This is a cross-sectional view along line C in Figure 19 of the optical integrated device according to Embodiment 3. [Figure 29A] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 3. [Figure 29B] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 3. [Figure 29C] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 3. [Figure 29D] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 3. [Figure 29E] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 3. [Figure 29F] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 3. [Figure 29G] This is a cross-sectional view showing a method for manufacturing an optical integrated device according to Embodiment 3. [Figure 30] This is a top view showing the structure of an optical integrated device according to a modified example of Embodiment 3. [Figure 31] This is a cross-sectional view along line A in Figure 30 of an optical integrated device according to a modified example of Embodiment 3. [Figure 32]This is a cross-sectional view along line B in Figure 30 of an optical integrated device according to a modified example of Embodiment 3. [Figure 33] This is an overview diagram showing the structure of the optical integrated device according to Embodiment 4. [Figure 34] This is a top view showing the structure of the optical integrated device according to Embodiment 4. [Figure 35] This is an overview view of the optical integrated device according to Embodiment 4, as seen from a cross-section along line A in Figure 33. [Figure 36] This is a cross-sectional view along line A in Figure 33 of the optical integrated device according to Embodiment 4. [Figure 37] This is a cross-sectional view along line B in Figure 33 of the optical integrated device according to Embodiment 4. [Figure 38] This is a cross-sectional view along line C in Figure 33 of the optical integrated device according to Embodiment 4. [Figure 39] This is a top view showing the structure of an optical integrated device according to a modified example of Embodiment 4. [Figure 40] This is a cross-sectional view along line A in Figure 39 of an optical integrated device according to a modified example of Embodiment 4. [Figure 41] This is a cross-sectional view along line B in Figure 39 of an optical integrated device according to a modified example of Embodiment 4. [Figure 42] This is an overview diagram showing the structure of the optical integrated device according to Embodiment 5. [Figure 43] This is a top view showing the structure of the optical integrated device according to Embodiment 5. [Figure 44] This is a cross-sectional view along line A in Figure 42 of the optical integrated device according to Embodiment 5. [Figure 45] This is a cross-sectional view along line B in Figure 42 of the optical integrated device according to Embodiment 5. [Figure 46] This is a cross-sectional view along line C in Figure 42 of the optical integrated device according to Embodiment 5. [Figure 47] This is a top view showing the structure of an optical integrated device according to a modified example of Embodiment 5. [Figure 48]This is a cross-sectional view along line A in Figure 47 of an optical integrated device according to a modified example of Embodiment 5. [Figure 49] This is a cross-sectional view along line B in Figure 47 of an optical integrated device according to a modified example of Embodiment 5. [Figure 50] This is a cross-sectional view of an optical integrated device according to Embodiment 6. [Figure 51] This is a cross-sectional view of an optical integrated device according to Embodiment 7. [Modes for carrying out the invention]

[0024] Embodiment 1. Figure 1 is an overview diagram showing the structure of the optical integrated device 300 according to Embodiment 1. Figure 2 is a top view showing the structure of the optical integrated device 300 according to Embodiment 1, Figure 3 is an overview diagram of the optical integrated device 300 according to Embodiment 1 viewed from a cross section along line A in Figure 1, Figure 4 is a cross section of the optical integrated device 300 according to Embodiment 1 along line A in Figure 1, Figure 5 is a cross section of the optical integrated device 300 according to Embodiment 1 along line B in Figure 1, and Figure 6 is a cross section of the optical integrated device 300 according to Embodiment 1 along line C in Figure 1. Also, in Figures 1 to 6, the x, y, and z axes are shown for convenience of explanation. Figure 6 schematically shows the spread 81 of the optical modes propagating in the high mesa portion 16 in the optical functional element 100.

[0025] <Configuration of the optical integrated device according to Embodiment 1> The optical integrated device 300 consists of an optical functional element 100 and an optical circuit element 200. The optical functional element 100 is made of a compound semiconductor material such as InP. The optical circuit element 200 is made of a semiconductor material such as Si.

[0026] <Configuration of optical functional elements in the optical integrated device according to Embodiment 1> The optical functional element 100 comprises an active layer 12 and a contact layer 13 formed on a compound semiconductor substrate 11; a convex high mesa portion 16 that includes part of the compound semiconductor substrate 11 and has at least the active layer 12 and the contact layer 13 from the compound semiconductor substrate 11 side; a first electrode formed on the top of the high mesa portion 16; and planar terrace portions 14 provided along the high mesa portion 16 and located at a predetermined height relative to the active layer 12.

[0027] The active layer 12 has a higher refractive index than the material constituting the compound semiconductor substrate 11 and has the function of interacting with electricity and light, for example, in a multiple quantum well structure. The active layer 12 is formed on the compound semiconductor substrate 11 by epitaxial crystal growth.

[0028] The contact layer 13 is composed of a material with a lower refractive index than the active layer 12 and functions as a cladding that confines light to the active layer 12. The contact layer 13 also has the function of making electrical contact with electrodes formed on its surface. The contact layer 13 is formed on the active layer 12 by epitaxial crystal growth.

[0029] The high-mesa portion 16 is processed to have a mesa width of submicrons to several microns and exhibits a convex shape relative to the surface of the compound semiconductor substrate 11. The high-mesa portion 16 includes part of the compound semiconductor substrate 11 and has at least an active layer 12 and a contact layer 13 from the compound semiconductor substrate 11 side. The high-mesa portion 16 is formed by etching the active layer 12 and contact layer 13, which are formed on the compound semiconductor substrate 11 by epitaxial crystal growth, from the surface side of the contact layer 13 to provide a pair of mesa grooves 15. The mesa groove width of the pair of mesa grooves 15 is each several microns.

[0030] A first electrode 17 is formed at the top of the high mesa portion 16, made of a highly conductive metallic material such as gold (Au), titanium (Ti), or platinum (Pt), so as to enable the injection of current into the contact layer 13 of the high mesa portion 16.

[0031] The terrace portions 14 are provided along the stripe-shaped high-mesa portions 16 via each mesa groove 15. The terrace portions 14 are planar in shape. The surface of the terrace portions 14 is the outermost surface of the compound semiconductor substrate 11. That is, the height of the surface of the terrace portions 14 coincides with the height of the interface between the compound semiconductor substrate 11 and the active layer 12. The terrace portions 14 are formed by selectively removing the active layer 12 on the compound semiconductor substrate 11 by etching or the like.

[0032] Since the terrace portion 14 is configured as described above, the surface of the terrace portion 14 is located at a predetermined height relative to the active layer 12. In the case of the optical functional element 100 in the optical integrated device 300 according to Embodiment 1, the surface of the terrace portion 14 is located lower than the surface of the active layer 12 on the contact layer 13 side by the thickness of the active layer 12. AL Therefore, with reference to the surface of the active layer 12 on the contact layer 13 side, the surface of the terrace portion 14 is -d AL This will result in the element being located at a certain height. In the optical functional element 100, the direction from the surface of the compound semiconductor substrate 11 toward the surface of the contact layer 13 is called the height direction. In other words, the direction toward the negative in the y-axis direction is the height direction. The same treatment applies to other embodiments. The above is an overview of the various components of the optical functional element 100.

[0033] <Configuration of optical circuit elements in the optical integrated device according to Embodiment 1> The optical circuit element 200 comprises a semiconductor substrate 21, a laminated substrate 40 having a lower cladding layer 22, a core layer 23, and an upper cladding layer 25 formed on the semiconductor substrate 21, a first recess 27a provided in the laminated substrate 40 with one side being an opening, second recesses 27b provided at a predetermined distance apart along both sides of the first recess 27a, one end of which is in contact with the opening, and an optical waveguide section 24 provided in contact with one side of the first recess 27a facing the opening, and including the lower cladding layer 22, the core layer 23, and the upper cladding layer 25. Although the core layer originally refers to a layer that guides light, for the sake of explanation, a thin film layer formed simultaneously with the light-guiding core layer is also called the core layer 23, even if it does not have the function of guiding light.

[0034] An example of a semiconductor substrate 21 is a Si substrate. The lower cladding layer 22 and upper cladding layer 25 formed on the semiconductor substrate 21 have a structure similar to a so-called Buried Oxide layer (BOX layer) and are composed of an insulating material such as silicon dioxide (SiO2). Insulating materials such as SiO2 have a lower refractive index than the semiconductor substrate 21.

[0035] The core layer 23 is formed between the lower cladding layer 22 and the upper cladding layer 25 and is composed of, for example, a thin-film semiconductor layer. The thin-film semiconductor layer constituting the core layer 23 may be made of a material with a higher refractive index than the lower cladding layer 22, such as silicon (Si).

[0036] The first recess 27a is provided in the laminated substrate 40, and one of the four sides of the first recess 27a is an opening. The second recess 27b is provided in the laminated substrate 40 at a predetermined distance apart along the two sides of the first recess 27a, one end of which is in contact with the opening. Although the first recess 27a is given as an example with one side being an opening, it is not limited to a recess with one opening, and all four sides may be sides.

[0037] The optical waveguide section 24 includes a lower cladding layer 22, a core layer 23, and an upper cladding layer 25, and both sides are carved out by an etching process, resulting in a rectangular or convex cross-sectional structure with an optical waveguide width of submicrons to several microns. One end of the optical waveguide section 24 is provided in contact with one surface facing the opening of the first recess 27a. Since the core layer 23 is sandwiched on both sides by the lower cladding layer 22 and the upper cladding layer 25, which have lower refractive indices than the core layer 23, light incident from the end face of the core layer 23 becomes guided light that guides within the core layer 23.

[0038] A protrusion 26 is formed between the first recess 27a and the second recess 27b of the optical circuit element 200. The top 26a of the protrusion 26 exposes the surface of the core layer 23. In other words, the outermost surface of the core layer 23 on the side in contact with the upper cladding layer 25 is exposed. The upper cladding layer 25 is removed in an area equal to or larger than that of the optical functional element 100, exposing the outermost surface of the core layer 23.

[0039] A second electrode 28 made of a highly conductive metal material is formed in a portion of the bottom of the first recess 27a. The above is an overview of the configuration of the optical circuit element 200. In the optical circuit element 200, the direction from the surface of the semiconductor substrate 21 toward the surface of the upper cladding layer 25 is called the height direction. In other words, the direction toward the positive y-axis is the height direction. The same treatment applies to other embodiments.

[0040] <Implementation configuration of optical functional elements and optical circuit elements in an optical integrated device according to Embodiment 1> The optical functional element 100 and the optical circuit element 200 described above are integrated into an optical integrated device 300 by being mounted in a flip-chip configuration. The mounting configuration of the optical functional element 100 and the optical circuit element 200 is described below.

[0041] The optical functional element 100 is joined to the optical circuit element 200 in an inverted orientation, with the compound semiconductor substrate 11 facing upwards. In other words, the optical functional element 100 and the optical circuit element 200 are flip-chip mounted. During flip-chip mounting, the optical functional element 100 is positioned so that the center of the high mesa portion 16 coincides with the center of the first recess 27a of the optical circuit element 200.

[0042] The terrace portion 14 of the optical functional element 100 is in contact with the top portion 26a of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 200.

[0043] Furthermore, the top of the high mesa portion 16 is joined to the bottom of the first recess 27a. Specifically, the first electrode 17 formed on the top of the high mesa portion 16 and the second electrode 28 formed on the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. Examples of the joining member 30 include solder and conductive adhesive.

[0044] As described above, when the optical functional element 100 and the optical circuit element 200 are flip-chip mounted and integrated, the active layer 12 of the high mesa portion 16 on the optical functional element 100 side and the core layer 23 of the optical waveguide portion 24 on the optical circuit element 200 side are optically coupled. Further details will be described later.

[0045] In Figures 3 and 4, the direction of light propagation 80 is indicated by an arrow when the optical functional element 100 is a light-emitting device such as a semiconductor laser or a semiconductor optical amplifier (SOA). The arrows indicating the direction of light propagation 80 in Figures 3 and 4 are reversed when the optical functional element 100 is a light-receiving device, such as a photodiode (PD). However, in Embodiment 1, light-receiving devices can be treated the same as light-emitting devices, so the two are not distinguished here. Figure 6 schematically shows the spread 81 of the optical modes propagating through the high mesa portion 16 in the optical functional element 100.

[0046] <Method for manufacturing an optical functional element in an optically integrated device according to Embodiment 1> The method for manufacturing the optical functional element in the optical integrated device 300 according to Embodiment 1 will be described below with reference to Figures 7A to 7H.

[0047] First, as shown in Figure 7A, an active layer 12 and a contact layer 13 are sequentially epitaxially grown on a compound semiconductor substrate 11 made of, for example, InP. The active layer 12 is made of a multi-quantum well (MQW) structure made of indium gallium arsenide phosphide (InGaAsP) with a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, or aluminum gallium indium arsenide (AlGaInAs) with a composition ratio corresponding to a similar peak wavelength. Examples of epitaxial crystal growth methods include metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). The contact layer 13 is made of, for example, n-type or p-type doped InP.

[0048] After epitaxial crystal growth, as shown in Figure 7B, a mask 51 made of an insulating film such as SiO2 is formed using photolithography and etching techniques to protect the high mesa portion 16 and the non-terrace portion, i.e., the portion other than the terrace portion 14.

[0049] As shown in Figure 7C, the contact layer 13 in areas not covered by the mask 51 is removed using a highly perpendicular dry etching 52. After etching, the outermost layer of the active layer 12 is exposed in the areas not covered by the mask 51.

[0050] Next, as shown in Figure 7D, the active layer 12 in areas not covered by the mask 51 is selectively etched and removed by wet etching using, for example, a mixture 53 of tartaric acid and hydrogen peroxide as an etchant. In the areas not covered by the mask 51, the outermost layer of the compound semiconductor substrate 11 is exposed.

[0051] Next, as shown in Figure 7E, a mask 54 made of an insulating film such as SiO2 is formed to cover the portion covered by the mask 51 and the terrace portion 14. Openings are provided in the mask 54 in the portion where the mesa groove 15 is to be formed.

[0052] After the mask 54 is formed, as shown in Figure 7F, a portion of the compound semiconductor substrate 11 not covered by the mask 54 is removed using dry etching 55 with high verticality to form mesa grooves 15, thereby completing the convex high mesa portion 16.

[0053] Next, as shown in Figure 7G, masks 51 and 54 are removed by dry etching or wet etching.

[0054] Finally, as shown in Figure 7H, a first electrode 17 is formed at the top of the high mesa portion 16. Examples of metallic materials that make up the first electrode 17 include Au, Ti, and Pt. The first electrode 17 is formed by, for example, electron beam deposition. After going through the above manufacturing processes, the optical functional element 100 is completed.

[0055] <Method for manufacturing an optical circuit element in an optically integrated device according to Embodiment 1> The optical circuit element 200 is manufactured by a known manufacturing method that applies silicon processing technology. Therefore, details of the manufacturing method of the optical circuit element 200 are omitted.

[0056] <Manufacturing method for an optically integrated device according to Embodiment 1> The optical functional element 100 and the optical circuit element 200 are flip-chip mounted by arranging them in an inverted orientation so that the compound semiconductor substrate 11 of the optical functional element 100 is on top of the optical functional element 200, and so that the center of the high mesa portion 16 of the optical functional element 100 coincides with the center of the first recess 27a of the optical circuit element 200.

[0057] In the optical functional element 100 and the optical circuit element 200, the terrace portion 14 of the optical functional element 100 is in contact with the top portion 26a of the convex portion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 200. On the other hand, the first electrode 17 formed at the top of the high mesa portion 16 and the second electrode 28 formed at the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. After going through the above manufacturing processes, the optical integrated device 300 is completed by flip-chip mounting the optical functional element 100 and the optical circuit element 200.

[0058] By going through each of the above manufacturing processes for the optical functional element 100, and utilizing selective etching of the constituent materials of the active layer 12 and the constituent materials other than the active layer 12, it becomes possible to control the relative positional displacement in the height direction between the optical functional element 100 and the optical circuit element 200 with high precision without using a so-called etching stop layer.

[0059] On the other hand, if the above-described height control method is used, the position of the terrace portion 14 is limited to the interface between the active layer 12 and the compound semiconductor substrate 11. Therefore, in Embodiment 1, in the optical circuit element 200, the upper cladding layer 25 of the top portion 26a of the convex portion 26, which is the region on which the optical functional element 100 is mounted, is selectively removed, thereby setting the height distance between the active layer 12 of the high mesa portion 16 of the optical functional element 100 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 200 to match with an accuracy of submicron or less.

[0060] <Operation and characteristics of the optical integrated device according to Embodiment 1> The operation and features of the optical integrated device 300 according to Embodiment 1 will be described below. Figure 8 shows 1 / e 2 A photofunctional element 100 in which a half-angle far-field pattern (FFP) of 20 degrees and light with a wavelength of 1.55 μm is emitted from the active layer 12 of the high mesa portion 16, and 1 / e 2 The results of calculating the relationship between the relative positional displacement in the x and y directions and the optical coupling efficiency when two optical circuit elements 200, from which light with a half-angle FFP of 15 degrees is emitted from the core layer 23 of the optical waveguide section 24, are facing each other at a distance of 5 μm in the z direction as shown in Figure 1.

[0061] Assuming a target binding efficiency of -2 dB (= 63%), if the y-direction slip is 1.0 μm, the allowable x-direction slip to achieve the target value is approximately ±0.3 μm or less, which is a very strict value.

[0062] On the other hand, if the y-direction deviation can be controlled with high precision to 0.5 μm, the allowable x-direction deviation to achieve the target value is approximately ±1.0 μm or less, which is a reasonable value even when considering manufacturing variations.

[0063] Figure 9 shows 1 / e 2 A photofunctional element 100 in which light with a half-angle FFP of 20 degrees is emitted from the active layer 12 of the high mesa section 16, and 1 / e 2 The results of calculating the relative positional shifts in the y and z directions and the optical coupling efficiency when an optical circuit element 200, from which light with a half-angle FFP of 15 degrees is emitted from the core layer 23 of the optical waveguide section 24 is directly facing the optical circuit element 200 with an x-direction shift of 0 μm as shown in Figure 1 are shown.

[0064] Similar to the case in Figure 8, when the y-direction deviation is 1.0 μm, the x-direction deviation that can be allowed to achieve the target value is a tight 6 μm or less. On the other hand, if the y-direction deviation can be controlled with high precision to 0.5 μm, the z-direction deviation that can be allowed to achieve the target value is 10 μm or less, which is a value with ample margin even when considering manufacturing variations.

[0065] In Figure 8, the fact that the maximum value of the optical coupling efficiency is not at z=0μm when the y-direction displacement is 2.5μm or more indicates that when the relative positional displacement perpendicular to the optical propagation becomes too large, placing the optical functional element 100 at a position where the light is diffused, slightly further away than when the optical axis displacement is 0, allows more optical power to be guided to the core layer 23 of the optical waveguide portion 24 of the optical circuit element 200.

[0066] From the above calculation results, it can be seen that in order to obtain high optical coupling efficiency between the optical functional element 100 and the optical circuit element 200, the relative positional displacement in the height direction between the optical functional element 100 and the optical circuit element 200 should be 1 μm or less, more preferably about 0.5 μm, and the relative positional displacement in the optical axis direction should preferably be 6 μm or less.

[0067] In the optical integrated device 300 according to Embodiment 1, the terrace portion 14 located at the height directly below the active layer 12 of the optical functional element 100 and the top portion 26a of the convex portion 26 located at the height directly above the core layer 23 of the optical waveguide portion 24 of the optical circuit element 200 are in contact by flip-chip mounting. Structurally, the relative positional displacement in the height direction between the terrace portion 14 and the top portion 26a cannot exceed the relative positional displacement in the height direction between the active layer 12 of the optical functional element 100 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 200. Generally, the relative positional displacement in the height direction between the optical functional element 100 and the optical circuit element 200 is about 0.5 μm. Therefore, by adopting the optical integrated device 300 according to Embodiment 1, the target value of the optical coupling efficiency can be guaranteed.

[0068] On the other hand, regarding the relative positional misalignment in the axial direction, i.e., the y-direction, the requirement that the relative positional misalignment be 6 μm or less can be easily met by forming alignment marks, for example, in the shape of a cross, on the optical functional element 100 and the optical circuit element 200, and then performing alignment while observing their relative positions using a camera or the like.

[0069] Furthermore, the shape, material, and positional relationship of the optical integrated device 300 are not limited to the configuration of Embodiment 1. For example, the optical functional element 100 may be a light-receiving device such as a photodiode (PD) rather than a light-emitting device such as a semiconductor laser or SOA. In the case of a light-receiving device, the same consideration can be applied by reversing the direction of light input and output.

[0070] Furthermore, the optical integrated device may also be one in which both light incident from the optical circuit element 200 to the optical functional element 100 and light emitted from the optical functional element 100 to the optical circuit element 200 are present, such as an MZ (Mach-Zehnder) modulator or an EA (Electro-Absorption) modulator.

[0071] Furthermore, compound semiconductor materials can include not only InP but also GaAs-based materials or GaN-based materials, as well as various combinations of these, such as mixed crystal systems. For the optical circuit element 200, a configuration consisting of a lower cladding layer 22 made of SiO2, a core layer 23 made of a Si thin film, and an upper cladding layer 25 made of SiO2 on a Si substrate was described as an example. However, the core layer 23 may be formed using a silicon nitride film (SiN) or a silicon oxynitride film (SiON), or a non-silicon material such as lithium niobate (LiNbO3) may be used. While using SiN or SiN as the core layer 23 has the disadvantage of increasing device size due to a lower refractive index compared to Si, it has the advantage of enabling low-loss optical integrated devices because the optical loss of propagating light is smaller compared to Si.

[0072] Using SiN or SiON as the core layer 23 has the advantage of broadening the mode distribution of propagating light compared to a core layer 23 made of a Si thin film, thus mitigating the tolerance of the optical coupling efficiency to relative positional misalignment between the optical functional element 100 and the optical circuit element 200.

[0073] When LiNbO3 is used as the core layer 23, since LiNbO3 is a ferroelectric material with a high E / O coefficient, the refractive index can be changed by applying an electric field to LiNbO3, making it possible to provide functions such as an MZ modulator to the optical circuit element 200. Furthermore, by utilizing the change in the refractive index of LiNbO3, it is possible to adjust the optical mode distribution of the propagating light, for example, and actively correct the optical coupling efficiency for the relative positional misalignment between the optical functional element 100 and the optical circuit element 200.

[0074] <Effects of Embodiment 1> As described above, according to the optical integrated device and method for manufacturing the optical integrated device according to Embodiment 1, since the surface of the terrace portion of the optical functional element is the outermost surface of the compound semiconductor substrate, the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled, resulting in the effect of obtaining an optical integrated device and a method for manufacturing the optical integrated device with high optical coupling efficiency.

[0075] A modified example of Embodiment 1. Figure 10 is a top view showing the structure of the optical integrated device 301 according to a modified example of Embodiment 1, Figure 11 is a cross-sectional view of the optical integrated device 301 according to a modified example of Embodiment 1 along line A in Figure 10, and Figure 12 is a cross-sectional view of the optical integrated device 301 according to a modified example of Embodiment 1 along line B in Figure 10. Also, in Figures 10 to 12, the x, y, and z axes are indicated for the sake of explanation.

[0076] The difference between the modified optical integrated device 301 of Embodiment 1 and the optical integrated device 300 of Embodiment 1 is that in the optical integrated device 300, one of the four sides of the first recess 27a provided in the optical circuit element 200 forms an opening, whereas in the modified optical integrated device 301 of Embodiment 1, none of the four sides of the first recess 27c provided in the optical circuit element 201 form an opening. In other words, in a configuration in which the optical functional element 101 and the optical circuit element 201 are flip-chip mounted, the high mesa portion 16 of the optical functional element 101 is contained within the first recess 27c, and its periphery is surrounded by each side of the first recess 27c.

[0077] In the modified optical integrated device 301 of Embodiment 1, in addition to the propagation direction 80 of light emitted from the high mesa portion 16 of the optical functional element 101 toward the optical waveguide portion 24 of the optical circuit element 201, light emitted from the other end face of the high mesa portion 16 is also guided into the optical circuit element 201 and made available for use, thereby enabling further enhancement of the functionality of the optical integrated device 301.

[0078] <Effects of the modified example of Embodiment 1> As described above, with the modified optical integrated device according to Embodiment 1, the surface of the terrace portion of the optical functional element becomes the outermost surface of the compound semiconductor substrate. Therefore, in addition to the effect of precisely controlling the relative positional misalignment in the height direction between the optical functional element and the optical circuit element, the light emitted from the other end face of the high mesa portion of the optical functional element can also be utilized, thus enabling further enhancement of the functionality of the optical integrated device.

[0079] Embodiment 2. Figure 13 is an overview diagram showing the structure of the optical integrated device 310 according to Embodiment 2. Figure 14 is a top view showing the structure of the optical integrated device 300 according to Embodiment 1, Figure 15 is an overview diagram of the optical integrated device 310 according to Embodiment 2 viewed from a cross section along line A in Figure 13, Figure 16 is a cross section of the optical integrated device 310 according to Embodiment 2 along line A in Figure 13, Figure 17 is a cross section of the optical integrated device 310 according to Embodiment 2 along line B in Figure 13, and Figure 18 is a cross section of the optical integrated device 310 according to Embodiment 2 along line C in Figure 13. Also, in Figures 13 to 18, the x, y, and z axes are shown for convenience of explanation. Figure 18 schematically shows the spread 81 of the optical modes propagating in the high mesa portion 16 in the optical functional element 110.

[0080] <Configuration of the optical integrated device according to Embodiment 2> The optical integrated device 310 consists of an optical functional element 110 and an optical circuit element 210. The optical functional element 110 is made of a compound semiconductor material such as InP. The optical circuit element 210 is made of a semiconductor material such as Si.

[0081] <Configuration of optical functional elements in the optically integrated device according to Embodiment 2> The optical functional element 110 comprises an active layer 12 and a contact layer 13 formed on a compound semiconductor substrate 11, a convex high mesa portion 16 that includes part of the compound semiconductor substrate 11 and has at least the active layer 12 and the contact layer 13 from the compound semiconductor substrate 11 side, a first electrode 17 formed on the top of the high mesa portion 16, and planar terrace portions 14a provided along the high mesa portion 16 and located at a predetermined height relative to the active layer 12. In the following description, only the structurally different parts from the optical functional element 100 of the optical integrated device 300 according to Embodiment 1 will be described.

[0082] The terrace portions 14a are provided along the high mesa portions 16 via each mesa groove 15. The terrace portions 14a are planar in shape. The surface of the terrace portions 14a is the outermost surface of the active layer 12. That is, the height of the surface of the terrace portions 14a is the same as the height of the interface between the active layer 12 and the contact layer 13. The terrace portions 14a are formed by selectively removing the contact layer 13 on the active layer 12 by etching or the like.

[0083] Since the terrace portion 14a is configured as described above, the surface of the terrace portion 14a is located at a predetermined height relative to the active layer 12. In the case of the optical functional element 110 in the optical integrated device 310 according to Embodiment 2, the surface of the terrace portion 14a is located at the same height as the surface of the active layer 12 on the contact layer 13 side. In other words, with respect to the surface of the active layer 12 on the contact layer 13 side, the surface of the terrace portion 14 is located at a height of zero. The above is an overview of the characteristic features of each component of the optical functional element 110.

[0084] <Configuration of optical circuit elements in the optical integrated device according to Embodiment 2> The optical circuit element 210 according to Embodiment 2 has basically the same configuration as the optical circuit element 200 of Embodiment 1, but some of its configurations are different. Therefore, only the different configurations will be described below.

[0085] The top 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 210 exposes the lower cladding layer 22. In other words, the outermost surface of the lower cladding layer 22 on the side in contact with the core layer 23 is exposed. The upper cladding layer 25 and the core layer 23 are removed in an area equal to or larger than that of the optical functional element 110, exposing the outermost surface of the lower cladding layer 22. In this respect, it differs from the optical circuit element 200 of Embodiment 1, in which the core layer 23 is exposed at the top 26b of the protrusion 26. The above describes the characteristic features of the optical circuit element 210.

[0086] <Implementation configuration of optical functional elements and optical circuit elements in an optical integrated device according to Embodiment 2> By flip-chip mounting the above-described optical functional element 110 and optical circuit element 210 and integrating them, an optical integrated device 310 is formed. The mounting configuration of the optical functional element 110 and optical circuit element 210 is described below.

[0087] The optical functional element 110 is joined to the optical circuit element 210 in an inverted orientation, with the compound semiconductor substrate 11 facing upwards. In other words, the optical functional element 110 and the optical circuit element 210 are flip-chip mounted. During flip-chip mounting, the optical functional element 110 is positioned so that the center of the high mesa portion 16 coincides with the center of the first recess 27a of the optical circuit element 210.

[0088] The terrace portion 14a of the optical functional element 110 is in contact with the top portion 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 210.

[0089] Furthermore, the top of the high mesa portion 16 is joined to the bottom of the first recess 27a. Specifically, the first electrode 17 formed on the top of the high mesa portion 16 and the second electrode 28 formed on the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. Examples of the joining member 30 include solder and conductive adhesive.

[0090] As described above, when the optical functional element 110 and the optical circuit element 210 are flip-chip mounted and integrated, the active layer 12 of the high mesa portion 16 on the optical functional element 110 side and the core layer 23 of the optical waveguide portion 24 on the optical circuit element 210 side are optically coupled.

[0091] <Method for manufacturing an optical functional element in an optically integrated device according to Embodiment 2> The method for manufacturing the optical functional element 110 in the optical integrated device 310 according to Embodiment 2 will be described below with reference to Figures 19A to 19H.

[0092] First, as shown in Figure 19A, an active layer 12 with a multiple quantum well structure and a contact layer 13 are sequentially epitaxially grown on a compound semiconductor substrate 11 made of, for example, InP, consisting of InGaAsP with a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, or AlGaInAs with a composition ratio corresponding to a similar peak wavelength. Examples of epitaxial crystal growth methods include MOCVD and MBE. The contact layer 13 is made of, for example, n-type or p-type doped InP.

[0093] After epitaxial crystal growth, as shown in Figure 19B, a mask 51 made of an insulating film such as SiO2 is formed using photolithography and etching techniques to protect the high mesa portion 16 and the non-terrace portion, i.e., the portion other than the terrace portion 14a.

[0094] As shown in Figure 19C, a highly perpendicular dry etching 52 is used to remove the contact layer 13 in the areas not covered by the mask 51, leaving a small thickness.

[0095] Next, as shown in Figure 19D, the contact layer 13 in areas not covered by the mask 51 is selectively etched and removed by wet etching using, for example, a mixture 53 of hydrochloric acid and phosphoric acid as an etchant. After etching, the outermost layer of the active layer 12 is exposed in the areas not covered by the mask 51.

[0096] Next, as shown in Figure 19E, a mask 54 made of an insulating film such as SiO2 is formed to cover the portion covered by the mask 51 and the terrace portion 14a. Openings are provided in the mask 54 in the portion where the mesa groove 15 is to be formed.

[0097] After the mask 54 is formed, as shown in Figure 19F, a high-perpendicularity dry etching 55 is used again to remove a portion of the active layer 12 and compound semiconductor substrate 11 that are not covered by the mask 54, thereby forming a mesa groove 15 and completing the convex high-mesa portion 16.

[0098] Next, as shown in Figure 19G, masks 51 and 54 are removed by dry etching or wet etching.

[0099] Finally, as shown in Figure 19H, a first electrode 17 is formed at the top of the high mesa portion 16. Examples of metallic materials that make up the first electrode 17 include Au, Ti, and Pt. The first electrode 17 is formed by, for example, electron beam deposition. The optical functional element 110 is completed after going through the above manufacturing processes.

[0100] <Manufacturing method for an optically integrated device according to Embodiment 2> The optical functional element 110 and the optical circuit element 210 are flip-chip mounted by arranging them in an inverted orientation so that the compound semiconductor substrate 11 of the optical functional element 110 is on top of the optical functional element 210, and so that the center of the high mesa portion 16 of the optical functional element 110 coincides with the center of the first recess 27a of the optical circuit element 210.

[0101] In the optical functional element 110 and the optical circuit element 210, the terrace portion 14a of the optical functional element 110 is in contact with the top portion 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 210. On the other hand, the first electrode 17 formed at the top of the high mesa portion 16 and the second electrode 28 formed at the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. After going through the above manufacturing processes, the optical functional element 110 and the optical circuit element 210 are flip-chip mounted together to complete the optical integrated device 310.

[0102] By going through the above manufacturing processes for the optical functional element 110, and utilizing selective etching of the constituent materials of the active layer 12 and the constituent materials other than the active layer 12, it becomes possible to control the relative positional displacement in the height direction between the optical functional element 110 and the optical circuit element 210 with high precision without using a so-called etching stop layer.

[0103] On the other hand, if the above-described height control method is used, the position of the terrace portion 14a is limited to the interface between the active layer 12 and the contact layer 13. Therefore, in Embodiment 2, in the optical circuit element 210, the upper cladding layer 25 and the core layer 23 of the top portion 26b of the convex portion 26, which is the region on which the optical functional element 110 is mounted, are selectively removed so that the height distance between the active layer 12 of the high mesa portion 16 of the optical functional element 110 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 210 is made to match with an accuracy of submicron or less.

[0104] <Operation and Features of the Optical Integrated Device According to Embodiment 2> By applying this structure as the optical functional element 110, the terrace portion 14a located directly above the active layer 12 of the optical functional element 110 and the top portion 26b of the convex portion 26 located directly below the optical waveguide portion 24 of the optical circuit element 210 are in contact due to flip-chip mounting. Structurally, the relative positional displacement in the height direction between the optical functional element 110 and the optical circuit element 210 cannot exceed the relative positional displacement in the height direction between the active layer 12 of the optical functional element 110 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 210.

[0105] Generally, the relative positional displacement in the height direction between the optical functional element 110 and the optical circuit element 210 is about 0.5 μm. Therefore, by adopting the element structure of Embodiment 2, the relative positional displacement in the height direction between the optical functional element 110 and the optical circuit element 210 becomes 1 μm or less, satisfying the requirement of about 0.5 μm, thus ensuring the realization of high optical coupling efficiency.

[0106] In the optical integrated device 310 according to Embodiment 2, similar to Embodiment 1, by improving the element structure and manufacturing method, it is possible to achieve high mounting accuracy in the height direction of the optical functional element 110 and the optical circuit element 210 without using an etching stop layer. This has the effect of avoiding the problem of optical loss occurring during propagation or optical coupling between different optical elements due to deformation of the propagating optical mode caused by different refractive index regions, which is a problem when an etching stop layer is provided.

[0107] <Effects of Embodiment 2> As described above, according to the optical integrated device and method for manufacturing the optical integrated device according to Embodiment 2, since the surface of the terrace portion of the optical functional element becomes the outermost surface of the active layer, the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled, resulting in the effect of obtaining an optical integrated device and a method for manufacturing the optical integrated device with high optical coupling efficiency.

[0108] A modified example of Embodiment 2. Figure 20 is a top view showing the structure of the optical integrated device 311 according to a modified example of Embodiment 2, Figure 21 is a cross-sectional view of the optical integrated device 311 according to a modified example of Embodiment 2 along line A in Figure 20, and Figure 22 is a cross-sectional view of the optical integrated device 311 according to a modified example of Embodiment 2 along line B in Figure 20. Also, in Figures 20 to 22, the x, y, and z axes are indicated for the sake of explanation.

[0109] The difference between the modified optical integrated device 311 of Embodiment 2 and the optical integrated device 310 of Embodiment 2 is that in the optical integrated device 310, one of the four sides of the first recess 27a provided in the optical circuit element 210 forms an opening, whereas in the modified optical integrated device 311 of Embodiment 2, none of the four sides of the first recess 27c provided in the optical circuit element 211 form an opening. In other words, in a configuration in which the optical functional element 111 and the optical circuit element 211 are flip-chip mounted, the high mesa portion 16 of the optical functional element 111 is contained within the first recess 27c, and its periphery is surrounded by each side of the first recess 27c.

[0110] In the modified optical integrated device 311 of Embodiment 2, in addition to the propagation direction 80 of light emitted from the high mesa portion 16 of the optical functional element 111 toward the optical waveguide portion 24 of the optical circuit element 211, light emitted from the other end face of the high mesa portion 16 is also guided into the optical circuit element 211 and made available for use, thereby achieving even higher functionality for the optical integrated device 311.

[0111] <Effects of the modified example of Embodiment 2> As described above, with the modified optical integrated device of Embodiment 2, the surface of the terrace portion of the optical functional element becomes the outermost surface of the active layer, so the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled. In addition to the effect of obtaining an optical integrated device with high optical coupling efficiency, the light emitted from the other end face of the high mesa portion of the optical functional element can also be utilized, thus enabling further enhancement of the functionality of the optical integrated device.

[0112] Embodiment 3. Figure 23 is an overview diagram showing the structure of the optical integrated device 320 according to Embodiment 3. Figure 24 is a top view showing the structure of the optical integrated device 320 according to Embodiment 3, Figure 25 is an overview diagram of the optical integrated device 320 according to Embodiment 3 viewed from a cross section along line A in Figure 23, Figure 26 is a cross section of the optical integrated device 320 according to Embodiment 3 along line A in Figure 23, Figure 27 is a cross section of the optical integrated device 320 according to Embodiment 3 along line B in Figure 23, and Figure 28 is a cross section of the optical integrated device 320 according to Embodiment 3 along line C in Figure 23. Also, in Figures 23 to 28, the x, y, and z axes are shown for convenience of explanation. Figure 28 schematically shows the spread 81 of optical modes propagating in the high mesa portion 16 in the optical functional element 120.

[0113] <Configuration of the optical integrated device according to Embodiment 3> The optical integrated device 320 consists of two optical functional elements 120. The optical functional elements 120 are made of a compound semiconductor material such as InP. The optical circuit elements 220 are made of a semiconductor material such as Si.

[0114] <Configuration of the optical functional element in the optical integrated device according to Embodiment 3> The optical functional element 120 comprises an active layer 12, an etching stop layer 18, and a contact layer 13 formed on a compound semiconductor substrate 11; a convex high mesa portion 16a that includes part of the compound semiconductor substrate 11 and has at least the active layer 12, the etching stop layer 18, and the contact layer 13 from the compound semiconductor substrate 11 side; a first electrode 17 formed on the top of the high mesa portion 16a; and planar terrace portions 14b provided along the high mesa portion 16a and located at a predetermined height relative to the active layer 12.

[0115] The etching stop layer 18 has a property of showing a reactivity different from that of the contact layer 13 described later in a specific etching process. Providing the etching stop layer 18 between the active layer 12 and the contact layer 13 of the high mesa portion 16a is a feature of the optical functional element 120 of the third embodiment. In the following description, only the parts structurally different from the optical functional element 100 of the optical integration device 300 according to the first embodiment will be described.

[0116] The terrace portions 14b are provided along the high mesa portions 16a via the respective mesa grooves 15. The terrace portions 14b have a planar shape. The surface of the terrace portion 14b is the outermost surface of the etching stop layer 18. That is, the height of the surface of the terrace portion 14b coincides with the height of the interface between the etching stop layer 18 and the contact layer 13. The terrace portion 14b is formed by removing the contact layer 13 on the etching stop layer 18 by selective etching or the like.

[0117] Since the terrace portion 14b is configured as described above, the surface of the terrace portion 14b will be located at a preset height with respect to the active layer 12. In the case of the optical functional element 120 in the optical integration device 320 according to the third embodiment, the surface of the terrace portion 14b is located at the same height as the surface of the etching stop layer 18 on the contact layer 13 side. Let the layer thickness of the etching stop layer 18 be d ESL Then, with reference to the surface of the active layer 12 on the etching stop layer 18 side, the surface of the terrace portion 14b will be located at a height of +d ESL The above is an overview of the characteristic parts among the respective configurations of the optical functional element 120.

[0118] <Configuration of the optical circuit element in the optical integration device according to the third embodiment> ​The optical circuit element 220 according to Embodiment 3 has the same configuration as the optical circuit element 210 of Embodiment 2. That is, the top 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 220 has the lower cladding layer 22 exposed. In other words, the outermost surface of the lower cladding layer 22 on the side in contact with the core layer 23 is exposed. The upper cladding layer 25 and the core layer 23 are removed in an area equal to or larger than that of the optical functional element 120, exposing the outermost surface of the lower cladding layer 22.

[0119] <Implementation configuration of optical functional elements and optical circuit elements in an optical integrated device according to Embodiment 3> The optical functional element 120 and the optical circuit element 220 described above are integrated into an optical integrated device 320 by flip-chip mounting. The mounting configuration of the optical functional element 120 and the optical circuit element 220 is described below.

[0120] The optical functional element 120 is joined to the optical circuit element 220 in an inverted orientation, with the compound semiconductor substrate 11 facing upwards. In other words, the optical functional element 120 and the optical circuit element 220 are flip-chip mounted. During flip-chip mounting, the optical functional element 120 is positioned so that the center of the high mesa portion 16a and the center of the first recess 27a of the optical circuit element 220 coincide.

[0121] The terrace portion 14b of the optical functional element 120 is in contact with the top portion 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 220.

[0122] Furthermore, the top of the high mesa portion 16a is joined to the bottom of the first recess 27a. Specifically, the first electrode 17 formed on the top of the high mesa portion 16a and the second electrode 28 formed on the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. Examples of the joining member 30 include solder and conductive adhesive.

[0123] As described above, when the optical functional element 120 and the optical circuit element 220 are flip-chip mounted and integrated, the active layer 12 of the high mesa portion 16a on the optical functional element 120 side and the core layer 23 of the optical waveguide portion 24 on the optical circuit element 220 side are optically coupled.

[0124] <Method for manufacturing an optical functional element in an optically integrated device according to Embodiment 3> The method for manufacturing the optical functional element in the optical integrated device 320 according to Embodiment 3 will be described below with reference to Figures 29A to 29H.

[0125] First, as shown in Figure 29A, an active layer 12 of MQW made of InGaAsP with a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, or AlGaInAs with a composition ratio corresponding to a similar peak wavelength, an etching stop layer 18 made of AlInAs with a layer thickness of 0.1 μm or less, and a contact layer 13 are sequentially epitaxially grown on a compound semiconductor substrate 11 made of InP, for example. Examples of epitaxial crystal growth methods include MOCVD and MBE. The contact layer 13 is made of, for example, n-type or p-type doped InP.

[0126] After epitaxial crystal growth, as shown in Figure 29B, a mask 51 made of an insulating film such as SiO2 is formed using photolithography and etching techniques to protect the high mesa portion 16a and the non-terrace portion, i.e., the portion other than the terrace portion 14b.

[0127] After the mask 51 is formed, as shown in Figure 29C, the contact layer 13 in the areas not covered by the mask 51 is selectively removed by reactive ion etching using a highly perpendicular dry etching 52. After etching, the outermost layer of the etching stop layer 18 is exposed in the areas not covered by the mask 51. Methane gas is preferred as the etching gas used in the dry etching 52. However, the etching gas is not limited to methane gas.

[0128] Next, as shown in Figure 29D, a mask 54 made of an insulating film such as SiO2 is formed to cover the portion covered by the mask 51 and the terrace portion 14b. Openings are provided in the mask 54 in the portion where the mesa groove 15 is to be formed.

[0129] After the mask 54 is formed, as shown in Figure 29E, a highly perpendicular dry etching 55 is used again to remove the etching stop layer 18, the active layer 12, and a portion of the compound semiconductor substrate 11 that are not covered by the mask 54, thereby forming a mesa groove 15 and completing the convex high mesa portion 16a.

[0130] Next, as shown in Figure 29F, masks 51 and 54 are removed by dry etching or wet etching.

[0131] Finally, as shown in Figure 29G, a first electrode 17 is formed at the top of the high mesa portion 16a. Examples of metallic materials that make up the first electrode 17 include Au, Ti, and Pt. The first electrode 17 is formed by, for example, electron beam deposition. After going through the above manufacturing processes, the optical functional element 120 is completed.

[0132] <Method for manufacturing an optical circuit element in an optically integrated device according to Embodiment 3> The optical circuit element 220 is manufactured by a known manufacturing method that applies silicon processing technology. Therefore, details of the manufacturing method of the optical circuit element 220 are omitted.

[0133] <Manufacturing method for an optically integrated device according to Embodiment 3> The optical functional element 120 is positioned in an inverted orientation so that the compound semiconductor substrate 11 of the optical functional element 120 is on top of the optical functional element 220, and so that the center of the high mesa portion 16a of the optical functional element 120 coincides with the center of the first recess 27a of the optical circuit element 220, and is then joined to the optical circuit element 220.

[0134] In the optical functional element 120 and the optical circuit element 220, the terrace portion 14b of the optical functional element 120 is in contact with the top portion 26b of the convex portion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 220. On the other hand, the first electrode 17 formed at the top of the high mesa portion 16a and the second electrode 28 formed at the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. After going through the above manufacturing processes, the optical functional element 120 and the optical circuit element 220 are flip-chip mounted together to complete the optical integrated device 320.

[0135] <Operation and characteristics of the optical integrated device according to Embodiment 3> By going through the above-described manufacturing processes for the optical functional element 120, and in particular by utilizing the selective etching of AlInAs, which is the constituent material of the etching stop layer 18, and InP, which is the constituent material of the contact layer 13, using methane gas, it becomes possible to control the relative positional misalignment in the height direction of the optical functional element 120 and the optical circuit element 220 with high precision.

[0136] On the other hand, if the above-described height control method is used, the position of the terrace portion 14b is limited to the interface between the etching stop layer 18 and the contact layer 13. Therefore, in Embodiment 3, in the optical circuit element 220, the upper cladding layer 25 and the core layer 23 of the top portion 26b of the convex portion 26, which is the region on which the optical functional element 120 is mounted, are selectively removed so that the height distance between the active layer 12 of the high mesa portion 16a of the optical functional element 120 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 220 is made to match with an accuracy of submicron or less.

[0137] By applying this structure as the optical functional element 120, the terrace portion 14b located directly above the active layer 12 of the optical functional element 120 and the top portion 26b of the convex portion 26 located directly below the core layer 23 of the optical waveguide portion 24 of the optical circuit element 220 are in contact due to flip-chip mounting. Structurally, the relative positional displacement in the height direction between the optical functional element 120 and the optical circuit element 220 cannot exceed the relative positional displacement in the height direction between the active layer 12 of the optical functional element 120 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 220.

[0138] In the optical functional element 120 of Embodiment 3, the thickness of the etching stop layer 18 is set to 0.1 μm or less. Therefore, the relative positional displacement in the height direction between the optical functional element 120 and the optical circuit element 220 is 1 μm or less, satisfying approximately 0.5 μm, thus ensuring the realization of high optical coupling efficiency.

[0139] In the optical integrated device 320 according to Embodiment 3, compared to the optical integrated devices 300 and 310 according to Embodiments 1 and 2, the introduction of the etching stop layer 18 results in the disadvantage that optical loss occurs during optical propagation or optical coupling between different optical elements due to the deformation of the propagating optical mode caused by the different refractive index regions of the etching stop layer 18. However, by selecting a material with high selectivity for etching, it is possible to significantly suppress manufacturing errors in the manufacturing process of the optical integrated device.

[0140] <Effects of Embodiment 3> As described above, according to the optical integrated device and method for manufacturing the optical integrated device according to Embodiment 3, since the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled, resulting in the effect of obtaining an optical integrated device and a method for manufacturing the optical integrated device with high optical coupling efficiency.

[0141] A modified example of Embodiment 3. Figure 30 is a top view showing the structure of the optical integrated device 321 according to a modified example of Embodiment 3, Figure 31 is a cross-sectional view of the optical integrated device 321 according to a modified example of Embodiment 3 along line A in Figure 30, and Figure 32 is a cross-sectional view of the optical integrated device 321 according to a modified example of Embodiment 3 along line B in Figure 30. Also, in Figures 30 to 32, the x, y, and z axes are indicated for the sake of explanation.

[0142] The difference between the modified optical integrated device 321 of Embodiment 3 and the optical integrated device 320 of Embodiment 3 is that in the optical integrated device 320, one of the four sides of the first recess 27a provided in the optical circuit element 220 forms an opening, whereas in the modified optical integrated device 321 of Embodiment 3, none of the four sides of the first recess 27c provided in the optical circuit element 221 form an opening. In other words, in a configuration in which the optical functional element 121 and the optical circuit element 221 are flip-chip mounted, the high mesa portion 16a of the optical functional element 121 is contained within the first recess 27c, and its periphery is surrounded by each side of the first recess 27c.

[0143] In the modified optical integrated device 321 of Embodiment 3, in addition to the propagation direction 80 of light emitted from the high mesa portion 16a of the optical functional element 121 toward the optical waveguide portion 24 of the optical circuit element 221, light emitted from the other end face of the high mesa portion 16a is also guided into the optical circuit element 221 and made available for use, thereby enabling further enhancement of the functionality of the optical integrated device 321.

[0144] <Effects of the modified example of Embodiment 3> As described above, with the modified optical integrated device according to Embodiment 3, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, so the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled. In addition to the effect of obtaining an optical integrated device with high optical coupling efficiency, the light emitted from the other end face of the high mesa portion of the optical functional element can also be utilized, thus enabling further enhancement of the functionality of the optical integrated device.

[0145] Embodiment 4. Figure 33 is an overview diagram showing the structure of the optical integrated device 330 according to Embodiment 4. Figure 34 is a top view showing the structure of the optical integrated device 300 according to Embodiment 1, Figure 35 is an overview diagram of the optical integrated device 330 according to Embodiment 4, viewed from a cross section along line A in Figure 33, Figure 36 is a cross section of the optical integrated device 330 according to Embodiment 4, viewed along line A in Figure 33, Figure 37 is a cross section of the optical integrated device 330 according to Embodiment 4, viewed along line B in Figure 33, and Figure 38 is a cross section of the optical integrated device 330 according to Embodiment 4, viewed along line C in Figure 33. Also, in Figures 33 to 38, the x, y, and z axes are shown for convenience of explanation. Figure 38 schematically shows the spread 81 of the optical modes propagating in the high mesa portion 16b in the optical functional element 130.

[0146] <Configuration of the optical integrated device according to Embodiment 4> The optical integrated device 330 consists of an optical functional element 130 and an optical circuit element 230. The optical functional element 130 is made of a compound semiconductor material such as InP. The optical circuit element 230 is made of a semiconductor material such as Si.

[0147] <Configuration of the optical functional element in the optical integrated device according to Embodiment 4> The optical functional element 130 comprises an active layer 12 and a contact layer 13 formed on a compound semiconductor substrate 11, a convex high mesa portion 16b that includes part of the compound semiconductor substrate 11 and has at least the active layer 12, a first contact layer 13a, an etching stop layer 18, and a second contact layer 13b from the compound semiconductor substrate 11 side, a first electrode 17 formed on the top of the high mesa portion 16b, and planar terrace portions 14c provided along the high mesa portion 16b and positioned at a predetermined height relative to the active layer 12.

[0148] The first contact layer 13a and the second contact layer 13b are made of the same compound semiconductor material, InP. The etching stop layer 18 is formed on the first contact layer 13a and is made of a compound semiconductor material, such as AlInAs, which exhibits different reactivity from the second contact layer 13b in a specific etching process. In the following description, only the structurally different parts of the optical integrated device 300 according to Embodiment 1 and the optical functional element 100 will be described.

[0149] The terrace portions 14c are provided along the high mesa portions 16b via each mesa groove 15. The terrace portions 14c are planar in shape. The surface of the terrace portions 14c is the outermost surface of the etching stop layer 18. That is, the height of the surface of the terrace portions 14c is the same as the height of the interface between the etching stop layer 18 and the second contact layer 13b. The terrace portions 14c are formed by selectively removing the second contact layer 13b on the etching stop layer 18 by etching or the like.

[0150] Since the terrace portion 14c is configured as described above, the surface of the terrace portion 14c will be located at a predetermined height relative to the active layer 12. In the case of the optical functional element 130 in the optical integrated device 330 according to Embodiment 4, the surface of the terrace portion 14c is located at the same height as the surface of the etching stop layer 18 on the second contact layer 13b side. The thickness of the first contact layer 13a is d CN1 The thickness of the etching stop layer 18 is d ESL Therefore, with reference to the surface of the active layer 12 on the first contact layer 13a side, the surface of the terrace portion 14c is d CN1 +d ESL It will be located at a height of this level. The above is an overview of the characteristic parts of each component of the optical functional element 130.

[0151] <Configuration of optical circuit elements in the optical integrated device according to Embodiment 4> In the optical circuit element 230 according to Embodiment 4, the top 26c of the protrusion 26 formed between the first recess 27a and the second recess 27b exposes the semiconductor substrate 21. In other words, the interface where the semiconductor substrate 21 contacts the lower cladding layer 22 is exposed. The lower cladding layer 22, the core layer 23, and the upper cladding layer 25 are removed in an area equal to or larger than that of the optical functional element 130, exposing the semiconductor substrate 21.

[0152] <Implementation configuration of optical functional elements and optical circuit elements in an optical integrated device according to Embodiment 4> The optical functional element 130 and the optical circuit element 230 described above are integrated into an optical integrated device 330 by flip-chip mounting. The mounting configuration of the optical functional element 130 and the optical circuit element 230 is described below.

[0153] The optical functional element 130 is joined to the optical circuit element 230 in an inverted orientation, with the compound semiconductor substrate 11 facing upwards. In other words, the optical functional element 130 and the optical circuit element 230 are flip-chip mounted. During flip-chip mounting, the optical functional element 130 is positioned so that the center of the high mesa portion 16b coincides with the center of the first recess 27a of the optical circuit element 230.

[0154] The terrace portion 14c of the optical functional element 130 is in contact with the top portion 26b of the protrusion 26 formed between the first recess 27a and the second recess 27b of the optical circuit element 230.

[0155] Furthermore, the top of the high mesa portion 16b is joined to the bottom of the first recess 27a. Specifically, the first electrode 17 formed on the top of the high mesa portion 16b and the second electrode 28 formed on the bottom of the first recess 27a are electrically and mechanically joined to each other by a joining member 30. Examples of the joining member 30 include solder and conductive adhesive.

[0156] As described above, when the optical functional element 130 and the optical circuit element 230 are flip-chip mounted and integrated, the active layer 12 of the high mesa portion 16b on the optical functional element 130 side and the core layer 23 of the optical waveguide portion 24 on the optical circuit element 230 side are optically coupled.

[0157] Figures 35 and 36 show the direction of light propagation 80 when the optical functional element 130 is a light-emitting device such as a semiconductor laser or SOA, indicated by arrows. Figure 38 schematically shows the spread 81 of the optical modes propagating through the high mesa portion 16b in the optical functional element 130.

[0158] <Operation and characteristics of the optical integrated device according to Embodiment 4> By going through each manufacturing process of the optical functional element 130, and in particular by utilizing the selective etching of AlInAs, which is the constituent material of the etching stop layer 18, and InP, which is the constituent material of the second contact layer 13b, using methane gas, it becomes possible to control the relative positional displacement in the height direction between the optical functional element 130 and the optical circuit element 230 with high precision.

[0159] On the other hand, if the above-described height control method is used, the position of the surface of the terrace portion 14c is limited to the interface between the etching stop layer 18 and the second contact layer 13b. Therefore, in Embodiment 4, the thickness of the first contact layer 13a of the optical functional element 130 is set to be the same as the thickness of the lower cladding layer 22 of the optical circuit element 230. Furthermore, in the optical circuit element 230, the lower cladding layer 22, core layer 23, and upper cladding layer 25 of the top portion 26c of the convex portion 26, which is the region on which the optical functional element 130 is mounted, are selectively removed so that the height distance between the active layer 12 of the high mesa portion 16b of the optical functional element 120 and the core layer 23 of the optical waveguide portion 24 of the optical circuit element 230 is made to match with an accuracy of submicron or less.

[0160] By applying this structure as the optical functional element 130 and the optical circuit element 230, the terrace portion 14c located directly above the etching stop layer 18 of the optical functional element 130 and the top portion 26c of the protrusion 26 located directly below the lower cladding layer 22 of the optical circuit element 230 are in contact due to flip-chip mounting. Structurally, the relative positional displacement in the height direction between the optical functional element 130 and the optical circuit element 230 cannot exceed the sum of the thicknesses of the active layer 12, etching stop layer 18, and first contact layer 13a of the optical functional element 130, and the sum of the thicknesses of the lower cladding layer 22 and core layer 23 of the optical circuit element 230.

[0161] In the optical functional element 130 of Embodiment 4, the thickness of the etching stop layer 18 is set to 0.1 μm or less, and the variation in the thickness of the first contact layer 13a can be suppressed to about ±0.1 μm by high-precision thickness control during epitaxial crystal growth. Furthermore, the variation in the thickness of the lower cladding layer 22 of the optical circuit element 230 can be suppressed to a range of about ±0.1 μm by applying a typical BOX layer thickness of several μm and a thickness tolerance of ±5% used in SOI substrates and the like.

[0162] Based on the above values ​​regarding variations in layer thickness, the relative height position between the optical functional element 130 and the optical circuit element 230 is less than 1 μm, satisfying approximately 0.5 μm, thus ensuring the realization of high optical coupling efficiency.

[0163] In the optical integrated device 330 according to Embodiment 4, compared to Embodiments 1 to 3, the accuracy of the relative position in the height direction between the optical functional element 130 and the optical circuit element 230 is further complicated by variations in the thickness of the first contact layer 13a and the lower cladding layer 22. This can be a disadvantage in terms of accuracy of alignment in the height direction. However, it becomes possible to position the active layer 12 of the high mesa portion 16b that guides light at a distance equal to the thickness of the first contact layer 13a from the etching stop layer 18. This has the effect of avoiding the problem of optical loss occurring during light propagation or optical coupling between different optical elements due to the deformation of the propagating light mode caused by the different refractive index regions of the etching stop layer 18.

[0164] <Effects of Embodiment 4> As described above, according to the optical integrated device and method for manufacturing the optical integrated device according to Embodiment 4, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, and the active layer and the etching stop layer are spaced apart. Therefore, the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled, and the influence of the etching stop layer on propagating light can be reduced. This results in an optical integrated device and a method for manufacturing the optical integrated device with high optical coupling efficiency.

[0165] A modified example of Embodiment 4. Figure 39 is a top view showing the structure of the optical integrated device 331 according to a modified example of Embodiment 4, Figure 40 is a cross-sectional view of the optical integrated device 331 according to a modified example of Embodiment 4 along line A in Figure 39, and Figure 41 is a cross-sectional view of the optical integrated device 331 according to a modified example of Embodiment 4 along line B in Figure 39. Also, in Figures 39 to 41, the x, y, and z axes are indicated for the sake of explanation.

[0166] The difference between the modified optical integrated device 331 of Embodiment 4 and the optical integrated device 330 of Embodiment 4 is that in the optical integrated device 330, one of the four sides of the first recess 27a provided in the optical circuit element 230 forms an opening, whereas in the modified optical integrated device 331 of Embodiment 4, none of the four sides of the first recess 27c provided in the optical circuit element 231 form an opening. In other words, in a configuration in which the optical functional element 131 and the optical circuit element 231 are flip-chip mounted, the high mesa portion 16b of the optical functional element 131 is contained within the first recess 27c, and its periphery is surrounded by each side of the first recess 27c.

[0167] In the modified optical integrated device 331 of Embodiment 4, in addition to the propagation direction 80 of light emitted from the high mesa portion 16b of the optical functional element 131 toward the optical waveguide portion 24 of the optical circuit element 231, light emitted from the other end face of the high mesa portion 16b is also guided into the optical circuit element 231 and made available, thereby enabling further enhancement of the functionality of the optical integrated device 331.

[0168] <Effects of the modified example of Embodiment 4> As described above, according to the modified optical integrated device of Embodiment 4, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, and the active layer and the etching stop layer are spaced apart. Therefore, the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled, and the influence of the etching stop layer on propagating light can be reduced. This results in an optical integrated device with high optical coupling efficiency. In addition, since light emitted from the other end face of the high mesa portion of the optical functional element can also be utilized, it is possible to further enhance the functionality of the optical integrated device.

[0169] Embodiment 5. Figure 42 is an overview diagram showing the structure of the optical integrated device 340 according to Embodiment 5. The optical integrated device 340 according to Embodiment 5 consists of an optical functional element 140 and an optical circuit element 240. Figure 43 is a top view showing the structure of the optical integrated device 340 according to Embodiment 5, Figure 44 is a cross-sectional view of the optical integrated device 340 according to Embodiment 5 along line A in Figure 42, Figure 45 is a cross-sectional view of the optical integrated device 340 according to Embodiment 5 along line B in Figure 42, and Figure 46 is a cross-sectional view of the optical integrated device 340 according to Embodiment 5 along line C in Figure 42.

[0170] <Configuration of optical functional elements in the optical integrated device according to Embodiment 5> As shown in the cross-sectional views of Figures 44, 45, and 46, a key feature of the optical integrated device 340 according to Embodiment 5 is that there is no first contact layer 13a between the etching stop layer 18a and the active layer 12 in the optical functional element 140. Instead, the thickness of the etching stop layer 18a is increased by the same amount as the thickness of the first contact layer 13a.

[0171] In the optical integrated device 340 according to Embodiment 5, the layer structure of the high mesa portion 16c in the optical functional element 140 is reduced by one layer, that is, the first contact layer 13a is reduced, which makes it easier to manufacture compared to Embodiment 4. Furthermore, by making the thickness of the etching stop layer 18a sufficiently thick, the etching stop layer 18a itself functions as a cladding layer, and since there is no interface between the etching stop layer 18a and the first contact layer 13a with different refractive indices in the mode distribution of the propagating light, it is possible to suppress the deformation of the propagating light modes to a small extent, which has the effect of avoiding the problem of optical loss occurring during optical coupling between optical elements.

[0172] <Effects of Embodiment 5> As described above, according to the optical integrated device and the method for manufacturing the optical integrated device according to Embodiment 5, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, and the layer thickness is controlled by the etching stop layer. Therefore, the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled, resulting in the effect of obtaining an optical integrated device with high optical coupling efficiency, as well as the effect of being able to easily manufacture such an optical integrated device.

[0173] A modified example of Embodiment 5. Figure 47 is a top view showing the structure of the optical integrated device 341 according to a modified example of Embodiment 5, Figure 48 is a cross-sectional view of the optical integrated device 341 according to a modified example of Embodiment 5 along line A in Figure 47, and Figure 49 is a cross-sectional view of the optical integrated device 341 according to a modified example of Embodiment 5 along line B in Figure 47. Also, in Figures 47 to 49, the x, y, and z axes are indicated for the sake of explanation.

[0174] The difference between the modified optical integrated device 341 of Embodiment 5 and the optical integrated device 340 of Embodiment 5 is that in the optical integrated device 340, one of the four sides of the first recess 27a provided in the optical circuit element 240 forms an opening, whereas in the modified optical integrated device 341 of Embodiment 5, none of the four sides of the first recess 27c provided in the optical circuit element 241 form an opening. In other words, in a configuration in which the optical functional element 141 and the optical circuit element 241 are flip-chip mounted, the high mesa portion 16c of the optical functional element 141 is contained within the first recess 27c, and its periphery is surrounded by each side of the first recess 27c.

[0175] In the modified optical integrated device 341 of Embodiment 5, in addition to the propagation direction 80 of light emitted from the high mesa portion 16c of the optical functional element 141 toward the optical waveguide portion 24 of the optical circuit element 241, light emitted from the other end face of the high mesa portion 16c is also guided into the optical circuit element 241 and made available for use, thereby enabling further enhancement of the functionality of the optical integrated device 341.

[0176] <Effects of the modified example of Embodiment 5> As described above, according to the modified optical integrated device of Embodiment 5, the surface of the terrace portion of the optical functional element becomes the outermost surface of the etching stop layer, and since the layer thickness is controlled by the etching stop layer, the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled. This results in an optical integrated device with high optical coupling efficiency, and in addition, the light emitted from the other end face of the high mesa portion of the optical functional element can also be utilized, thus enabling further enhancement of the functionality of the optical integrated device.

[0177] Embodiment 6. <Configuration and features of the optical functional element in the optical integrated device according to Embodiment 6> Embodiment 6 is a modification of Embodiments 3 and 4. Figure 50 is a cross-sectional view of the optical integrated device 350 according to Embodiment 6. The optical integrated device 350 according to Embodiment 6 consists of an optical functional element 150 and an optical circuit element 250. The optical integrated device 350 according to Embodiment 6 is characterized in that the etching stop layer is composed of a laminated structure of at least two or more AlInAs layers with different compositions. Examples of the laminated structure of the etching stop layer include an etching stop layer composed of an Al(0.48)In(0.52)As composition that is lattice-matched with the InP substrate and a layer containing more Al than described above, for example, an Al(0.7)In(0.3)As composition.

[0178] A specific example of an etching stop layer consisting of two layers is a configuration in which the first etching stop layer 18b on the side adjacent to the active layer 12 is made of Al(0.48)In(0.52)As, and the second etching stop layer 18c on the side away from the active layer 12 is made of Al(0.7)In(0.3)As.

[0179] The optical integrated device 350 according to Embodiment 6 includes a layer made of AlInAs composition that deviates from the lattice matching conditions with the InP substrate, which can cause strain in the crystal and potentially lead to problems with crystal quality and reliability. However, if the etching stop layer is constructed with a layer containing a large amount of aluminum (Al) in its stacked structure, the oxidation phenomenon of Al becomes more pronounced during dry etching with methane gas, which increases the selectivity ratio for etching with InP, thus improving the function of the etching stop layer.

[0180] Furthermore, since the refractive index decreases in layers containing a large amount of Al, the refractive index of the first etching stop layer 18b on the side close to the active layer 12 is high, and the refractive index of the second etching stop layer 18c on the side farther from the active layer 12 is low. As a result, the two layers have a core layer and cladding layer relationship in the optical waveguide, which makes it possible to suppress deformation of the propagating light modes and avoid the problem of optical loss occurring during optical coupling between optical elements.

[0181] <Effects of Embodiment 6> As described above, according to the optical integrated device and the method for manufacturing the optical integrated device according to Embodiment 6, since the etching stop layer is in a stacked structure, the relative positional displacement in the height direction between the optical functional element and the optical circuit element can be precisely controlled, resulting in an optical integrated device with high optical coupling efficiency. In addition, this method also provides the advantage of being able to easily manufacture such an optical integrated device.

[0182] Embodiment 7. Embodiment 7 is a modification of Embodiments 1 to 6. Figure 51 is a cross-sectional view of the optical integrated device 360 ​​according to Embodiment 7. The optical integrated device 360 ​​according to Embodiment 7 consists of an optical functional element 160 and an optical circuit element 260. In the optical integrated device 360 ​​according to Embodiment 7, the tip of the core layer 23 of the optical waveguide portion 24 formed on the optical circuit element 260 has a tapered shape that becomes continuously narrower in the x-direction toward the direct opposite side of the optical functional element 160, and furthermore, the upper cladding layer 25 and the lower cladding layer 22 are integrated from the tip portion of the optical waveguide portion 24, and the x-direction thickness is the sum of the thicknesses of the upper cladding layer 25 and the lower cladding layer 22, resulting in a rectangular xy cross-sectional shape. It is also characterized by the formation of a second optical waveguide portion 29 with the cladding layer material as the core and air as the cladding material.

[0183] In the optical integrated device 360 ​​according to Embodiment 7, a second optical waveguide portion 29 with a smaller refractive index is formed at the tip of the optical waveguide portion 24 of the optical circuit element 260, thereby expanding the mode diameter of optical propagation, and functioning as a so-called spot size converter (SSC). By applying the spot size converter structure, it is possible to mitigate the optical coupling efficiency tolerance to mounting positional misalignment between the optical functional element 160 and the optical circuit element 260.

[0184] In the above description, a structure in which the SSC is provided on the optical circuit element 260 was given as an example, but the SSC may be provided not only on the optical circuit element 260 side but also on the optical functional element 160 side. The structure of the SSC does not have to be limited to the example in Embodiment 7, and for example, SiN or SiON material may be used in addition to SiO2. Also, instead of forming the second optical waveguide section 29, it is possible to simply provide a tapered shape at the tip of the core layer 23 of the optical waveguide section 24.

[0185] <Effects of Embodiment 7> As described above, according to the optical integrated device of Embodiment 7, since SSC is provided on the optical functional element side or the optical circuit element side, it is possible to mitigate the optical coupling efficiency tolerance to mounting position misalignment, thereby achieving the effect of obtaining an optical integrated device with high optical coupling efficiency.

[0186] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but can be applied individually or in various combinations to the embodiments.

[0187] Accordingly, countless variations not illustrated are conceivable within the scope of the technology disclosed herein. These include, for example, modifications, additions, or omissions of at least one component, as well as the extraction of at least one component and its combination with components of other embodiments. [Explanation of symbols]

[0188] 11 Compound semiconductor substrate, 12 Active layer, 13 Contact layer, 13a First contact layer, 13b Second contact layer, 14, 14a, 14b, 14c Terrace portion, 15 Mesa groove, 16, 16a, 16b, 16c High mesa portion, 17 First electrode, 18, 18a Etching stop layer, 18b First etching stop layer, 18c Second etching stop layer, 21 Semiconductor substrate, 22 Lower cladding layer, 23 Core layer, 24 Optical waveguide portion, 25 Upper cladding layer, 26 Convex portion, 26a, 26b, 26c Top portion, 27a, 27c First concave portion, 27b Second concave portion, 28 Second electrode, 29 Second optical waveguide portion, 30 Bonding member, 40 Laminated structure substrate, 51, 54 Mask, 52, 55 Dry etching, 53 Mixture, 80 Direction of light propagation, 81 Spread of light modes, 100, 101, 110, 111, 120, 121, 130, 131, 140, 141, 150, 160 Optical functional elements, 200, 201, 210, 211, 220, 221, 230, 231, 240, 241, 250, 260 Optical circuit elements, 300, 301, 310, 311, 320, 321, 330, 331, 340, 341, 350, 360 Optical integrated devices

Claims

1. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the high mesa portion has a convex shape, with an active layer and a contact layer having at least a layer thickness of d AL from the compound semiconductor substrate side, It comprises a terrace section provided along the aforementioned high mesa section and having a planar shape, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along the side surface of the first recess, spaced apart from the side surface, A protrusion formed between the first recess and the second recess, The optical waveguide portion is provided in contact with a side of the first recess that is different from the side surface and the side surface opposite to the side surface, and includes the lower cladding layer, the core layer and the upper cladding layer, The height of the surface of the terrace portion is set to a height of -d AL with respect to the surface of the active layer on the contact layer side, and the height of the top of the convex portion is set to the height of the surface of the core layer on the upper cladding layer side, and the surface of the terrace portion and the top of the convex portion are in contact. An optically integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled.

2. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the compound semiconductor substrate side has at least an active layer and a contact layer, and the high mesa portion exhibits a convex shape, It comprises a terrace section provided along the aforementioned high mesa section and having a planar shape, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along the side surface of the first recess, spaced apart from the side surface, A protrusion formed between the first recess and the second recess, The optical waveguide portion is provided in contact with a side of the first recess that is different from the side surface and the side surface opposite to the side surface, and includes the lower cladding layer, the core layer and the upper cladding layer, The height of the surface of the terrace portion is set to the height of the interface between the active layer and the contact layer, and the height of the top of the protrusion is set to the height of the surface of the lower cladding layer on the core layer side, and the surface of the terrace portion and the top of the protrusion are in contact. An optically integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled.

3. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the compound semiconductor substrate side has at least an active layer and a contact layer, and an etching stop layer with a thickness of d ESL provided between the active layer and the contact layer, and a convex high mesa portion, It comprises a terrace section provided along the aforementioned high mesa section and having a planar shape, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along the side surface of the first recess, spaced apart from the side surface, A protrusion formed between the first recess and the second recess, The optical waveguide portion is provided in contact with a side of the first recess that is different from the side surface and the side surface opposite to the side surface, and includes the lower cladding layer, the core layer and the upper cladding layer, The height of the terrace portion surface is set to a height of +d ESL relative to the surface of the active layer on the etching stop layer side, and the height of the top of the convex portion is set to the height of the surface of the lower cladding layer on the core layer side, and the surface of the terrace portion and the top of the convex portion are in contact. An optically integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled.

4. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the high mesa portion having a convex shape, comprising, from the compound semiconductor substrate side, at least an active layer, a first contact layer with a thickness of dCN1, an etching stop layer with a thickness of dESL, and a second contact layer, It comprises a terrace section provided along the aforementioned high mesa section and having a planar shape, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along the side surface of the first recess, spaced apart from the side surface, A protrusion formed between the first recess and the second recess, The optical waveguide portion is provided in contact with a side of the first recess that is different from the side surface and the side surface opposite to the side surface, and includes the lower cladding layer, the core layer and the upper cladding layer, The height of the surface of the terrace portion is set to a height of dCN1 + dESL with respect to the surface of the first contact layer on the active layer side, the height of the top of the protrusion is set to the height of the interface between the semiconductor substrate and the lower cladding layer, the thickness of the etching stop layer and the lower cladding layer are set to the same thickness, and the surface of the terrace portion and the top of the protrusion are in contact. An optically integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled.

5. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the high mesa portion having a convex shape, having at least an active layer, a contact layer, and an etching stop layer provided between the active layer and the contact layer, from the compound semiconductor substrate side, It comprises a terrace section provided along the aforementioned high mesa section and having a planar shape, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along the side surface of the first recess, spaced apart from the side surface, A protrusion formed between the first recess and the second recess, The optical waveguide portion is provided in contact with a side of the first recess that is different from the side surface and the side surface opposite to the side surface, and includes the lower cladding layer, the core layer and the upper cladding layer, The height of the surface of the terrace portion is set to the height of the interface between the etching stop layer and the contact layer, the height of the top of the protrusion is set to the height of the interface between the semiconductor substrate and the lower cladding layer, the thickness of the etching stop layer is set to the same thickness as the thickness of the lower cladding layer, and the surface of the terrace portion and the top of the protrusion are in contact. An optically integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled.

6. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the compound semiconductor substrate side has at least an active layer, a first contact layer, a first etching stop layer, a second etching stop layer, and a second contact layer, and a convex high mesa portion, It comprises a terrace section provided along the aforementioned high mesa section and having a planar shape, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along the side surface of the first recess, spaced apart from the side surface, A protrusion formed between the first recess and the second recess, The optical waveguide portion is provided in contact with a side of the first recess that is different from the side surface and the side surface opposite to the side surface, and includes the lower cladding layer, the core layer and the upper cladding layer, The height of the surface of the terrace portion is set to the height of the interface between the second etching stop layer and the second contact layer, and the height of the top of the protrusion is set to the height of the interface between the semiconductor substrate and the lower cladding layer, and the surface of the terrace portion and the top of the protrusion are in contact. The first etching stop layer and the second etching stop layer are composed of different compound semiconductor materials, the refractive index of the first etching stop layer is higher than that of the second etching stop layer, and the etching selectivity of the second etching stop layer is greater than that of the first etching stop layer. An optically integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled.

7. The optical integrated device according to claim 3, characterized in that the thickness of the etching stop layer is 0.1 μm or less.

8. The optical integrated device according to claim 4, characterized in that the thickness of the etching stop layer is 0.1 μm or less.

9. The optical integrated device according to claim 6, characterized in that the first etching stop layer is made of AlInAs, the second etching stop layer is made of AlInAs with a higher Al composition ratio than the first etching stop layer, and the second contact layer is made of InP.

10. The optical integrated device according to any one of claims 1 to 9, characterized in that the compound semiconductor substrate is made of InP, the active layer is a multiple quantum well structure composed of InGaAsP in a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, or AlGaInAs in a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, and the contact layer is made of InP.

11. The optical integrated device according to any one of claims 1 to 9, characterized in that either the tip of the high mesa portion on the optical waveguide portion side or the tip of the optical waveguide portion on the high mesa portion side is a spot size converter structure.

12. The optical integrated device according to any one of claims 1 to 9, characterized in that a first electrode formed on the top of the high mesa portion and a second electrode formed on the bottom of the first recess are mechanically and electrically joined via a conductive bonding member.

13. The optical integrated device according to any one of claims 1 to 9, characterized in that the distance between the active layer of the high mesa portion and the core layer of the optical waveguide portion is 6 μm or less.

14. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the compound semiconductor substrate side has at least an active layer and a contact layer, and the high mesa portion exhibits a convex shape, Each of the high mesa portions is provided along the aforementioned high mesa portion, and each terrace portion has a surface that is planar and is made from the outermost surface of the compound semiconductor substrate, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along two opposing sides of the first recess, spaced apart from the sides at a predetermined distance, The optical waveguide portion is provided in contact with a side of the first recess that is different from the two side surfaces, and includes the lower cladding layer, the core layer, and the upper cladding layer. The terrace portion of the optical functional element and the top portion of the protrusion formed between the first recess and the second recess of the optical circuit element, where the outermost surface of the core layer is exposed, are in contact. The optical functional element is positioned such that the center of the high mesa portion and the center of the first recess of the optical circuit element coincide. A first electrode formed at the top of the high mesa portion and a second electrode formed at the bottom of the first recess, opposite to the first electrode, are mechanically and electrically joined by a joining member. An optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled at a distance of 6 μm or less.

15. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the compound semiconductor substrate side has at least an active layer and a contact layer, and the high mesa portion exhibits a convex shape, Each of the above-mentioned high mesa portions is provided along the aforementioned high mesa portion, and each terrace portion has a planar surface that is on the contact layer side of the active layer, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along two opposing sides of the first recess, spaced apart from the sides at a predetermined distance, The optical waveguide portion is provided in contact with a side of the first recess that is different from the two side surfaces, and includes the lower cladding layer, the core layer, and the upper cladding layer. The terrace portion of the optical functional element and the top portion of the protrusion formed between the first recess and the second recess of the optical circuit element, where the outermost surface of the lower cladding layer is exposed, are in contact. The optical functional element is positioned such that the center of the high mesa portion and the center of the first recess of the optical circuit element coincide. A first electrode formed at the top of the high mesa portion and a second electrode formed at the bottom of the first recess, opposite to the first electrode, are mechanically and electrically joined by a joining member. An optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled at a distance of 6 μm or less.

16. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the compound semiconductor substrate side has at least an active layer and a contact layer, and an etching stop layer provided between the active layer and the contact layer, and the high mesa portion exhibits a convex shape, Each of the above-mentioned high mesa portions is provided along the above-mentioned high mesa portion, and is provided with a terrace portion that is planar in shape and located at a predetermined height relative to the active layer, the surface of which is the outermost surface of the etching stop layer, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer formed on the semiconductor substrate and having the same thickness as the etching stop layer, a core layer, and an upper cladding layer. The first recess provided in the semiconductor substrate, A second recess is provided along two opposing sides of the first recess, spaced apart from the sides at a predetermined distance, The optical waveguide portion is provided in contact with a side of the first recess that is different from the two side surfaces, and includes the lower cladding layer, the core layer, and the upper cladding layer. The terrace portion of the optical functional element and the top portion of the protrusion formed between the first recess and the second recess of the optical circuit element, where the semiconductor substrate is exposed, are in contact. The optical functional element is positioned such that the center of the high mesa portion and the center of the first recess of the optical circuit element coincide. A first electrode formed at the top of the high mesa portion and a second electrode formed at the bottom of the first recess, opposite to the first electrode, are mechanically and electrically joined by a joining member. An optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled at a distance of 6 μm or less.

17. An optical integrated device that integrates optical functional elements and optical circuit elements, The aforementioned optical functional element is Compound semiconductor substrate and The compound semiconductor substrate is partially included, and the high mesa portion having, in order from the compound semiconductor substrate side, at least an active layer, a first contact layer, a first etching stop layer made of AlInAs, a second etching stop layer made of AlInAs with an Al composition ratio greater than that of the first etching stop layer, and a second contact layer, and exhibiting a convex shape, Each of the high mesa portions is provided along the aforementioned high mesa portion, and is provided with a terrace portion that is planar in shape and located at a predetermined height relative to the active layer, the surface of which is the outermost surface of the second etching stop layer, The aforementioned optical circuit element is Semiconductor substrate and A lower cladding layer, a core layer, and an upper cladding layer formed on the semiconductor substrate, The first recess provided in the semiconductor substrate, A second recess is provided along two opposing sides of the first recess, spaced apart from the sides at a predetermined distance, The optical waveguide portion is provided in contact with a side of the first recess that is different from the two side surfaces, and includes the lower cladding layer, the core layer, and the upper cladding layer. The terrace portion of the optical functional element and the top portion of the protrusion formed between the first recess and the second recess of the optical circuit element, where the semiconductor substrate is exposed, are in contact. The optical functional element is positioned such that the center of the high mesa portion and the center of the first recess of the optical circuit element coincide. A first electrode formed at the top of the high mesa portion and a second electrode formed at the bottom of the first recess, opposite to the first electrode, are mechanically and electrically joined by a joining member. An optical integrated device in which the active layer of the high mesa portion and the core layer of the optical waveguide portion are optically coupled at a distance of 6 μm or less.

18. The optical integrated device according to any one of claims 14 to 17, characterized in that either the tip of the high mesa portion on the optical waveguide portion side or the tip of the optical waveguide portion on the high mesa portion side is a spot size converter structure.

19. The optical integrated device according to any one of claims 14 to 17, characterized in that a first electrode formed on the top of the high mesa portion and a second electrode formed on the bottom of the first recess are mechanically and electrically joined via a conductive bonding member.

20. The optical integrated device according to claim 17, characterized in that the first etching stop layer and the second etching stop layer are composed of different compound semiconductor materials, the refractive index of the first etching stop layer is higher than that of the second etching stop layer, and the etching selectivity ratio of the second etching stop layer is greater than that of the first etching stop layer.

21. The optical integrated device according to any one of claims 14 to 17, characterized in that the compound semiconductor substrate is made of InP, the active layer is a multiple quantum well structure composed of InGaAsP or AlGaInAs in a composition ratio corresponding to a photoluminescence peak wavelength of 1.2 μm or more, and the contact layer is made of InP.

Images