Optical modulator and method for manufacturing the same, and apparatus including an optical modulator

Abstract

This invention provides an optical modulator, a method for manufacturing the same, and an electronic device including an optical modulator. [Solution] An optical modulator according to one embodiment includes a first semiconductor layer, a second semiconductor layer provided on the first semiconductor layer in the form of a microdisk and including a high-doping region with a relatively high doping concentration and a low-doping region with a relatively low doping concentration, a first optical waveguide arranged adjacent to the second semiconductor layer, and a first electrode layer and a second electrode layer provided spaced apart from each other on the high-doping region, wherein the second semiconductor layer includes at least one recess, the second semiconductor layer has at least one step due to the recess, and the high-doping region, the low-doping region and the recess are concentric.

Description

Technical Field

[0001] The present invention relates to an optical element, and more specifically, to an optical modulator for a photonic integrated circuit (PIC), a method for manufacturing the same, and an apparatus including such an optical modulator.

Background Art

[0002] In a photonic integrated circuit (PIC) including a silicon (Si) substrate, as an optical modulator, mainly a Mach-Zehnder interferometer (MZI), a micro-ring modulator (MRM), etc. are used.

[0003] Techniques for increasing the modulation speed of an optical modulator for broadband information transmission and wavelength division multiplexing (WDM) technology in which signals of multiple wavelengths are simultaneously transmitted through a single waveguide for parallel processing of signals are applied.

[0004] Since the MRM modulates only light having a wavelength that coincides with the resonance wavelength of the micro-ring, a WDM optical circuit can be configured relatively simply, high-speed modulation is possible, and it is widely used.

[0005] In order to widen the WDM bandwidth, it is necessary to gradually reduce the diameter of the micro-ring, but in this process, since the curvature of the micro-ring increases, there is a risk that the optical loss increases. For this reason, as an alternative to the micro-ring, a method of forming a resonator in the form of a micro-disk has been introduced, but it includes elements that limit the optical modulation speed.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem that this invention aims to solve is to provide an optical modulator that can increase the optical modulation speed.

[0007] Furthermore, the problem that this invention aims to solve is to provide an optical modulator capable of mode filtering.

[0008] Furthermore, the present invention aims to solve the problem of providing a method for manufacturing such an optical modulator.

[0009] Furthermore, the problem that the present invention aims to solve is to provide an apparatus including such an optical modulator. [Means for solving the problem]

[0010] An optical modulator according to an exemplary embodiment includes a first semiconductor layer, a second semiconductor layer provided on the first semiconductor layer in the form of a microdisk and including a high-doping region with a relatively high doping concentration and a low-doping region with a relatively low doping concentration, a first optical waveguide disposed adjacent to the second semiconductor layer, and a first electrode layer and a second electrode layer provided spaced apart from each other on the high-doping region, wherein the second semiconductor layer includes at least one recess. The second semiconductor layer has at least one step due to the recess, and the high-doping region, the low-doping region and the recess are concentric.

[0011] In one example, the second semiconductor layer includes a first recess, the bottom surface of the first recess includes the upper surface of the high-doping region and the upper surface of the low-doping region, the side surface of the first recess includes the inner surface of the low-doping region, and the first recess creates a first step in the low-doping region. In one example, the high-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant; the low-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant; the bottom surface of the first recess includes the upper surface of the N-doping region and the upper surface of the P-doping region of the high-doping region, and the first upper surface of the P-doping region of the low-doping region; the side surface of the first recess includes the inner surface of the P-doping region of the low-doping region; and the first step corresponds to the height difference between the first upper surface of the P-doping region of the low-doping region and a second upper surface located higher than the first upper surface. In one example, the high-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant; the low-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant; the bottom surface of the first recess includes the upper surface of the N-doping region and the upper surface of the P-doping region of the high-doping region, and the first upper surface of the P-doping region of the low-doping region; and the side surface of the first recess is inside the P-doping region of the low-doping region. The surface includes the inner surface of the N-doping region of the low-doping region, the first step corresponds to the height difference between the first upper surface of the P-doping region of the low-doping region and the upper surface of the N-doping region of the low-doping region, the N-doping region of the low-doping region is located between the P-doping region and the first semiconductor layer and completely surrounds the P-doping region of the low-doping region around the first recess, and the outer surface of the N-doping region of the low-doping region is the side surface of the second semiconductor layer.

[0012] In one example, the P-doping region and the N-doping region of the high-doping area are concentric, a step exists between the center and the edge of the N-doping region of the high-doping area, the thickness of the edge of the N-doping region of the high-doping area is thinner than the thickness of the center, the P-doping region of the high-doping area overlaps with the edge of the N-doping region of the high-doping area, and the upper surface of the P-doping region and the upper surface of the N-doping region of the high-doping area form the same surface.

[0013] In one example, the second semiconductor layer is provided inside the first recess and includes a second recess that forms a concentric circle with the first recess, the side and bottom surfaces of the second recess include the surface of the high-doping region, the second recess creates a second step inside the first recess, the first step and the second step are spaced apart from each other in a horizontal direction parallel to the upper surface of the first semiconductor layer, and the first step and the second step are at different heights.

[0014] In one example, the high-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant, the N-doping region and the P-doping region are concentric, the bottom surface of the second recess is the top surface of the N-doping region, the side surface of the second recess includes the side surface of the P-doping region, and the second step corresponds to the height difference between the top surface of the N-doping region and the top surface of the P-doping region of the high-doping region.

[0015] In one example, the high-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant, the N-doping region and the P-doping region are concentric, the N-doping region and the P-doping region are separated from each other in a direction perpendicular to the upper surface of the first semiconductor layer, the bottom surface of the second recess is the upper surface of the N-doping region, the side surface of the second recess includes the side surface of the P-doping region, and the second step corresponds to the height difference between the upper surface of the N-doping region and the upper surface of the P-doping region of the high-doping region, and they are separated from each other. A portion of the low-doping region exists between the N-doping region and the P-doping region, the side surface of the second recess is composed of a portion of the low-doping region and the side surface of the P-doping region, the low-doping region includes an N-doping region doped with an N-dopant and a P-doping region doped with a P-dopant, the N-doping region and the P-doping region of the low-doping region are concentric, the bottom surface of the first recess includes the top surface of the P-doping region of the low-doping region, and the inner surface of the first recess includes the side surface of the P-doping region of the low-doping region.

[0016] In one example, the second semiconductor layer includes a first recess, the bottom surface of the first recess includes the top surface of the low-doping region, the side surface of the first recess includes the inner surface of the low-doping region, and the first recess creates a first step in the low-doping region. In another example, the second semiconductor layer is provided inside the first recess and includes a second recess that forms a concentric circle with the first recess, the bottom surface of the second recess includes the surface of the high-doping region, the side surface of the second recess includes the inner surface of the low-doping region, and the second recess creates a second step inside the first recess, the first step and the second step are separated from each other in a horizontal direction parallel to the top surface of the first semiconductor layer, and the first step and the second step are at different heights. In one example, the highly doped region includes an N-doped region doped with an N-type dopant and a P-doped region doped with a P-type dopant, the N-doped region and the P-doped region are concentric, the N-doped region and the P-doped region are separated from each other in a direction perpendicular to the upper surface of the first semiconductor layer, the bottom surface of the second recess is the upper surface of the N-doped region, the P-doped region is on the bottom surface of the first recess, and the inner surface of the P-doped region and the side surface of the second recess form the same surface. The second step corresponds to the height difference between the upper surface of the N-doping region in the high-doping region and the bottom surface of the first recess, the low-doping region includes an N-doping region doped with N-dopant and a P-doping region doped with P-dopant, the N-doping region and the P-doping region in the low-doping region are concentric, the bottom surface of the first recess includes the upper surface of the P-doping region in the low-doping region, and the inner surface of the first recess includes the side surface of the P-doping region in the low-doping region.

[0017] In one example, the second semiconductor layer includes a first recess, the side and bottom surfaces of the first recess include the surface of the high-doping region, and the first recess creates a first step in the high-doping region. In one example, the high-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant, the bottom surface of the first recess includes the top surface of the N-doping region, the side surface of the first recess includes the side surface of the P-doping region, the N-doping region and the P-doping region are arranged to overlap each other around the first recess, and on a plane, the low-doping region is arranged to completely surround the high-doping region, the low-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant, and the N-doping region and the P-doping region of the low-doping region are arranged sequentially in a direction perpendicular to the top surface of the first semiconductor layer.

[0018] In one example, the second semiconductor layer includes a first recess, the bottom surface of the first recess includes the top surface of the first doping region of the high-doping region, the side surface of the first recess includes the side surface of the low-doping region and the side surface of the second doping region of the high-doping region, the first doping region and the second doping region are separated from each other, the first doping region, the second doping region and the first recess are concentric, the first recess creates a step between the top surface of the first doping region and the top surface of the second doping region, the first doping region and the second doping region contain opposite types of dopants, they are separated from each other in a direction perpendicular to the top surface of the first semiconductor layer, the outer diameter of the first doping region and the inner diameter of the second doping region are the same, and the top surface of the second doping region and the top surface of the low-doping region are arranged to form the same surface.

[0019] In one example, the optical modulator further includes a second optical waveguide separated from the second semiconductor layer, the second semiconductor layer being positioned between the first optical waveguide and the second optical waveguide.

[0020] A method for manufacturing an optical modulator according to one exemplary embodiment involves forming a second semiconductor layer in the form of a microdisk on a first semiconductor layer, forming a circular first doping region in a part of the second semiconductor layer, then forming a second doping region in the second semiconductor layer surrounding the first doping region, so that it surrounds the first doping region on a plane. Next, a first step is formed in one of the first and second doping regions, and then an electrode layer is formed on the first doping region, which has a higher doping concentration than the second doping region.

[0021] In one example, the first step is formed in the first doping region.

[0022] In one example, the manufacturing method further includes the step of forming a second step in the second doping region. In one example, the step of forming the second doping region further includes the steps of forming a first doping layer, forming a second doping layer on the first doping layer so as to include the second step, and forming a third doping layer that covers the outer portion of the second step of the second doping layer and is in contact with the first doping layer, wherein the first doping layer and the third doping layer contain the same type of dopant.

[0023] An electronic device according to an exemplary embodiment includes an optical waveguide through which light emitted from the light source is transmitted, a semiconductor layer disposed adjacent to the optical waveguide and provided in the form of a microdisk and including a plurality of doping regions, and an amplifier provided to amplify the light transmitted through the optical waveguide. The semiconductor layer includes first and second doping regions included in the plurality of doping regions at the center, and the remaining doping regions of the plurality of doping regions except the first and second doping regions are disposed around the first and second doping regions. The first and second doping regions are regions doped with dopants of opposite types to each other, and the doping concentrations of the first and second doping regions are higher than those of the remaining doping regions. The semiconductor layer includes at least one step.

Advantages of the Invention

[0024] The disclosed optical modulator in the form of a microdisk includes a semiconductor layer in the form of a microdisk, and at least one step is formed in the pn doping region of the semiconductor layer. In the inner pn doping region doped at a high concentration, a step is formed so that the pn junction region decreases. In the outer pn doping region doped at a low concentration, an n-doping region is formed so as to surround the outside of the p-doping region, and a step is formed at a predetermined position of the p-doping region. The position of such a step can be adjusted in the manufacturing process. By adjusting the position of the step formed in the inner pn doping region doped at a high concentration, the capacitance of the optical modulator can be lowered, and the modulation speed of the optical modulator can be increased. In the pn doping region doped at a low concentration, optical mode filtering is possible by adjusting the position where the step is formed to adjust the ring width. Further, in the pn doping region doped at a low concentration, by forming the n-doping region in a U shape surrounding the p-doping region, the junction region between the n-doping region and the p-doping region can be increased to enhance the optical modulation efficiency.

Brief Description of the Drawings

[0025] [Figure 1] It is a plan view showing a first optical modulator according to an exemplary embodiment. [Figure 2] It is a cross-sectional view obtained by cutting FIG. 1 in the direction of 2-2'. [Figure 3] It is a cross-sectional view obtained by cutting FIG. 1 in the direction of 3-3'. [Figure 4] It is a cross-sectional view showing a second optical modulator according to an exemplary embodiment. [Figure 5] It is a plan view showing a third optical modulator according to an exemplary embodiment. [Figure 6] It is a cross-sectional view obtained by cutting FIG. 5 in the direction of 6-6'. [Figure 7] It is a cross-sectional view obtained by cutting FIG. 5 in the direction of 7-7'. [Figure 8] It is a cross-sectional view showing a modified example of the third optical modulator illustrated in FIG. 5. [Figure 9] It is a cross-sectional view showing a modified example of the third optical modulator illustrated in FIG. 5. [Figure 10] It is a cross-sectional view showing a fourth optical modulator according to an exemplary embodiment. [Figure 11] It is a plan view showing a fifth optical modulator according to an exemplary embodiment. [Figure 12] It is a cross-sectional view obtained by cutting FIG. 11 in the direction of 12-12'. [Figure 13] It is a cross-sectional view obtained by cutting FIG. 11 in the direction of 13-13'. [Figure 14] It is a cross-sectional view showing a sixth optical modulator according to an exemplary embodiment. [Figure 15] It is a cross-sectional view showing a seventh optical modulator according to an exemplary embodiment. [Figure 16] It is a cross-sectional view showing an eighth optical modulator according to an exemplary embodiment. [Figure 17] It is a plan view exemplarily showing a case where the optical modulators illustrated in FIGS. 1 to 16 include a plurality of optical waveguides. [Figure 18] It is a cross-sectional view showing step by step a manufacturing method of a third optical modulator according to an exemplary embodiment. [Figure 19]This is a stepwise cross-sectional view illustrating a method for manufacturing a third optical modulator according to an exemplary embodiment. [Figure 20] This is a stepwise cross-sectional view illustrating a method for manufacturing a third optical modulator according to an exemplary embodiment. [Figure 21] This is a stepwise cross-sectional view illustrating a method for manufacturing a third optical modulator according to an exemplary embodiment. [Figure 22] This is a stepwise cross-sectional view illustrating a method for manufacturing a third optical modulator according to an exemplary embodiment. [Figure 23] This is a stepwise cross-sectional view illustrating a method for manufacturing a third optical modulator according to an exemplary embodiment. [Figure 24] This is a stepwise cross-sectional view illustrating a method for manufacturing a third optical modulator according to an exemplary embodiment. [Figure 25] This is a stepwise cross-sectional view illustrating a method for manufacturing a third optical modulator according to an exemplary embodiment. [Figure 26] This is a stepwise cross-sectional view illustrating a method for manufacturing a third optical modulator according to an exemplary embodiment. [Figure 27] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 28] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 29] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 30] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 31] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 32] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 33] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 34] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 35] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 36] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 37] This is a stepwise cross-sectional view illustrating a method for manufacturing a fifth optical modulator according to an exemplary embodiment. [Figure 38] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 39] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 40] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 41A] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 41B] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 42] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 43] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 44] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 45] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 46] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 47] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 48] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 49] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 50] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 51] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 52] This is a stepwise cross-sectional view illustrating a method for manufacturing an eighth optical modulator according to an exemplary embodiment. [Figure 53] This is a cross-sectional view showing one step in the manufacturing process of a seventh optical modulator according to an exemplary embodiment. [Figure 54] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 55] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 56] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 57] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 58] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 59] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 60] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 61] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 62] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 63] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 64] This is a stepwise cross-sectional view illustrating a method for manufacturing a first optical modulator according to an exemplary embodiment. [Figure 65]These are cross-sectional views showing the first and second models used in simulations conducted to confirm the differences (effects) between cases where there is a step in the high-doping region of the optical modulator and cases where there is no step. [Figure 66] This is a schematic block diagram showing an electronic device according to one exemplary embodiment. [Modes for carrying out the invention]

[0026] Hereinafter, an optical modulator according to exemplary embodiments, a method for manufacturing the same, and an apparatus including the optical modulator will be described in detail with reference to the attached drawings. In this process, the thicknesses of layers and regions shown in the drawings may be slightly exaggerated for clarity in the specification.

[0027] The embodiments described below are merely illustrative, and various modifications are possible from these embodiments. Furthermore, in the layered structures described below, the terms "upper" and "above" include not only elements that are in contact and directly above, but also elements that are not in contact and located above. In the following description, the same reference numeral in each drawing indicates the same component.

[0028] A singular expression includes multiple expressions unless the context clearly indicates otherwise. Furthermore, when a part "contains" a component, this means, unless otherwise specified, that it can contain other components, rather than excluding them.

[0029] The term "the foregoing" and similar referential terms can be used in either singular or plural. Unless the steps constituting the method are clearly described in order or otherwise, the steps may be performed in any order. The order in which the steps are described is not necessarily limited to the order in which they are described.

[0030] Furthermore, terms such as "~part" and "~module" as used in the specification refer to a unit that processes at least one function or operation, which may be embodied in hardware or software, or in a combination of hardware and software.

[0031] The lines or connecting members between components shown in the drawings are illustrative examples of functional and / or physical or circuit connections, and in actual devices, these may be interchangeable or represented as various additional functional, physical, or circuit connections.

[0032] All use of examples or illustrative terms is solely for the purpose of illustrating the technical idea in detail, and the scope of the invention is not limited by these examples or illustrative terms unless otherwise defined by the claims.

[0033] Figure 1 is a plan view showing a first optical modulator 20 according to an exemplary embodiment. Figure 2 is a cross-sectional view obtained by cutting Figure 1 in the direction of 2-2', and Figure 3 is a cross-sectional view obtained by cutting Figure 1 in the direction of 3-3'.

[0034] Referring to Figures 1 to 3, an optical waveguide 10 and a first optical modulator 20 according to one embodiment are provided on an insulating layer 14. In one example, the first optical modulator 20 and the optical waveguide 10 may be collectively referred to as the optical modulator. Other elements may be provided on the insulating layer 14. In one example, the insulating layer 14 includes an oxide insulating layer. In one example, the insulating layer 14 includes silicon oxide, but is not limited to this. The optical waveguide 10 and the first optical modulator 20 can be separated from each other by a first spacing G1, as shown in Figure 3. In Figure 1, the optical waveguide 10 is shown as a straight line next to the first optical modulator 20, but the optical waveguide 10 may include a curved portion. In one example, the portion of the optical waveguide 10 close to the first optical modulator 20 may be a curved portion having the same or substantially the same curvature as the curvature of the edge of the first optical modulator 20. The curved section and the first optical modulator 20 can be separated by a distance of approximately the first interval G1.

[0035] In one example, the first interval G1 has a range of spacing sufficient to transmit light traveling through the optical waveguide 10 to the first optical modulator 20. For example, a portion of the light traveling through the optical waveguide 10 in the first interval G1 may be concentrated in a predetermined region of the first optical modulator 20 in a whispering gallery mode. In one example, the first interval G1 is approximately 50 nm to 300 nm, but is not limited to this. A portion of the light includes fundamental mode (TE0) and / or first-order mode (TE1) light, and may also include higher-order mode light. The predetermined region of the first optical modulator 20 is the outermost region, edge region, or end region of the first optical modulator 20, and may include the PN junction region. Depending on the width and cross-sectional layer structure of the predetermined region, only fundamental mode light may be transmitted to the predetermined region of the first optical modulator 20, or fundamental mode and first-order mode light may be transmitted, or higher-order mode light may be transmitted. Therefore, depending on the width of the predetermined region and the layer structure design of the first optical modulator 20, the modes of light transmitted from the optical waveguide 10 to the first optical modulator 20 can be filtered.

[0036] In one example, the optical waveguide 10 may be an optical waveguide provided for transmitting light in the infrared band, but is not limited to infrared light. In one example, multiple lights of different wavelengths are transmitted simultaneously or with a time difference through the optical waveguide 10. The multiple lights are included in the infrared band. In one example, the optical waveguide 10 is a waveguide formed of a material with a lower infrared absorption rate than visible light, and may, for example, be an optical waveguide containing a silicon substrate, but is not limited to this. In one example, the optical waveguide 10 may be a silicon layer or contain a silicon layer. In one example, the silicon layer may include a single-crystal silicon layer, but is not limited to this. In one example, the optical waveguide 10 may contain a III-V compound semiconductor with a low infrared absorption rate or one that does not absorb infrared light. In one example, the optical waveguide 10 may contain silicon nitride (SiN).

[0037] The width of the optical waveguide 10 may be constant or substantially constant in the direction in which light is transmitted. In one example, in the first optical modulator 20, the material (substance) in the region where optical modulation occurs, excluding the first and second electrode layers 16 and 18, may be the same as, but may not be the same as, the optical waveguide 10.

[0038] The optical waveguide 10 and the first optical modulator 20 may be covered with an upper insulating layer having a refractive index different from that of silicon. In one example, the upper insulating layer is a layer of material with a refractive index lower than that of silicon. Such an upper insulating layer can maintain the internal total internal reflection conditions of light transmitted through the optical waveguide 10 and also maintain the internal total internal reflection conditions of light transmitted through the first optical modulator 20. In one example, the upper insulating layer may include, and is not limited to, a gas (e.g., air) or a solid material layer (e.g., a silicon oxide layer).

[0039] The first optical modulator 20 includes sequentially stacked first semiconductor layers 22 and an insulating layer 14, and a second semiconductor layer 12 provided on the insulating layer 14. In one example, the first semiconductor layer 22 includes a silicon layer, but is not limited to this. The sequentially stacked first semiconductor layers 22 and insulating layer 14 form an SOI (silicon on insulator) substrate. The second semiconductor layer 12 is provided on one surface (e.g., the top surface) of the insulating layer 14. The insulating layer 14 is provided between the first semiconductor layer 22 and the second semiconductor layer 12. The first semiconductor layer 22 and the second semiconductor layer 12 are separated from each other and do not contact each other. In one example, the first semiconductor layer 22 and the second semiconductor layer 12 contain the same semiconductor material, but they may also contain different semiconductor materials. In one example, the second semiconductor layer 12 contains a semiconductor layer with a lower light absorption rate in the infrared band compared to visible light. Such semiconductor layers may include a single-component or binary or higher-component semiconductor material. In one example, the second semiconductor layer 12 includes a silicon layer, for example, a single-crystal silicon layer. In another example, the second semiconductor layer 12 may include a III-V compound semiconductor with low infrared absorption or no infrared absorption. In yet another example, the second semiconductor layer 12 may include silicon nitride (SiN).

[0040] As can be seen from Figure 2, the second semiconductor layer 12 includes a recess 13. The recess 13 may also be described as a recess, trench, or groove. The recess 13 is located at the center of the second semiconductor layer 12, and its depth is constant throughout the recess 13. The planar shape of the recess 13 is circular, and the center of the recess 13 coincides with the center of the second semiconductor layer 12. In one example, the second semiconductor layer 12 and the recess 13 are concentric, but are not limited to this. The boundary of the recess 13 is separated from the edge of the second semiconductor layer 12. Therefore, the radius of the recess 13 is smaller than the radius of the second semiconductor layer 12. The recess 13 allows the second semiconductor layer 12 to have two upper surfaces 2S1 and 2S2 of different heights. That is, the upper surface of the second semiconductor layer 12 may consist of a flat first upper surface 2S1 in the recess 13 region and a flat second upper surface 2S2 surrounding the recess 13. The first upper surface 2S1 may be the bottom surface of the recess 13. The recess 13 may be formed by etching a portion of the upper surface of the second semiconductor layer 12, which is not present in the recess 13 state, to a predetermined depth. Therefore, the height of the first upper surface 2S1 is lower than the height of the second upper surface 2S2. As a result, a step exists between the first upper surface 2S1 and the second upper surface 2S2. The size (e.g., height) of such a step can be adjusted during the recess formation process.

[0041] The second semiconductor layer 12 includes a region where optical modulation actually occurs. The second semiconductor layer 12 may include multiple regions with different dopant and / or doping concentrations. In one example, the second semiconductor layer 12 includes a high-doping region where the dopant is doped at a relatively high concentration and a low-doping region where it is doped at a relatively low concentration.

[0042] In one example, the second semiconductor layer 12 includes a circular first region 12A in the center having a predetermined radius. The first region 12A is located within a recess 13 and forms a concentric circle with the recess 13. The first region 12A is a region doped with a first dopant at a first concentration. In one example, the first dopant includes a p-type impurity (e.g., boron (B)) or an n-type impurity (e.g., phosphorus (P)). In one example, the first concentration is 1 × 10⁻⁶ 19 / cm 3 ~3×10 20 / cm 3 However, this is not the only example.

[0043] In one example, the radius of the first region 12A is smaller than the radius 12R1 of the second semiconductor layer 12 and smaller than the radius 12R3 of the recess 13. The edges of the first region 12A are separated from the edges of the second semiconductor layer 12 and the boundary of the recess 13. The thickness of the first region 12A may vary radially. Since the central portion of the second semiconductor layer 12 is included in the recess 13 region, the thickness of the central portion is thinner than the thickness of the edges of the second semiconductor layer 12. The first region 12A includes a first portion having a first thickness in the center of the second semiconductor layer 12 and a second portion surrounding the first portion having a second thickness. The second thickness is thinner than the first thickness. The upper surface of the first portion may be part of the bottom surface of the recess 13, i.e., part of the first upper surface 2S1 of the second semiconductor layer 12. The second portion is separated from the first upper surface 2S1. The second portion is in contact with the insulating layer 14. The bottom surface of the second part and the bottom surface of the first part are at the same height and form the same plane. In one example, the bottom surface of the first part and the bottom surface of the second part may be part of the bottom surface of the second semiconductor layer 12. Because the heights of the top surface of the first part and the top surface of the second part are different, a step exists between the first part and the second part of the first region 12A. The thickness of the first part of the first region 12A may be uniform overall or substantially uniform. The thickness of the second part of the first region 12A may be uniform overall or substantially uniform. The thickness of the first part may be the same as the thickness of the second semiconductor layer 12 within the recess 13. The first and second parts of the first region 12A may be concentric.

[0044] The second semiconductor layer 12 includes a second region 12B located vertically on the second portion of the first region 12A. The second region 12B is formed directly above the second portion of the first region 12A. The second region 12B is separated from the center of the first region 12A. The second region 12B is located within the recess 13 and separated from the boundary of the recess 13. The thickness of the second region 12B is the same as or substantially the same as the second thickness of the second portion. As can be seen from Figure 1, the second region 12B may be formed to completely surround the first portion of the first region 12A. In one example, the second region 12B has a thickness corresponding to the step between the first portion and the second portion of the first region 12A. However, since a depletion layer may be formed between the second region 12B and the first region 12A, the thickness of the second region 12B cannot be said to be exactly the same as the step. Since the thickness of the depletion layer is very thin compared to the thickness of the second region 12B, it can be said that the thickness of the second region 12B and the step are substantially the same, and the second region 12B can be considered to have a thickness corresponding to the step.

[0045] The upper surface of the second region 12B and the upper surface of the first portion of the first region 12A are flat, at the same height, and form the same plane. In one example, the upper surface of the first portion of the first region 12A and the upper surface of the second region 12B may be part of the first upper surface of the second semiconductor layer 12.

[0046] The width of the radial second region 12B may be the same as or substantially the same as the width of the second portion of the first region 12A. Because the depletion layer between the first region 12A and the second region 12B is very thin, the inner diameter of the second region 12B may be substantially the same as the radius 12R2 of the first portion of the first region 12A. The outer diameter of the second region 12B may be the same as the radius of the second portion of the first region 12A. During the manufacturing process of the first optical modulator 20, the radii of the first and second regions 12A and 12B may be adjusted within a predetermined range.

[0047] As a result, in plan view, the second region 12B can be strip-shaped or ring-shaped. In cross-sectional view, the second portion of the first region 12A and the second region 12B form a layered structure in which they are sequentially stacked in a direction perpendicular to the upper surface of the insulating layer 14.

[0048] In one example, the second region 12B is a region doped with a second dopant of the opposite type to the first dopant at a second concentration. As a result, a depletion layer may be formed between the first region 12A and the second region 12B, as described above. The depletion layer is extremely thin and is therefore not shown in Figures 1 to 3 for convenience. In one example, the second dopant contains either a p-type impurity or an n-type impurity. For example, if the first dopant contains a p-type impurity, the second dopant may contain an n-type impurity, or vice versa. In one example, the second concentration is the same as or substantially the same as the first concentration.

[0049] Since the first region 12A and the second region 12B are doping regions, the distance from the center of the first region 12A to the second region 12B can be adjusted during the manufacturing process of the first optical modulator 20. This also allows the area of ​​the junction region between the first region 12A and the second region 12B to be adjusted. Such adjustments can also adjust the capacitance caused by the junction region between the first region 12A and the second region 12B. For example, the narrower the width of the second region 12B, the lower the capacitance, and the wider the width of the second region 12B, the higher the capacitance. By adjusting the capacitance in this way, the optical modulation speed of the first optical modulator 20 can also be adjusted. As an example, by adjusting the width of the second region 12B so that the capacitance decreases, the optical modulation speed of the first optical modulator 20 can be increased.

[0050] A first electrode layer 16 is provided on a first portion of the first region 12A. The center of the first electrode layer 16 is identical to or substantially coincides with the center of the first region 12A. In a plan view, the first electrode layer 16 is circular, elliptical, or polygonal, but is not limited to these shapes. In one example, the first electrode layer 16 and the first region 12A are arranged concentrically.

[0051] The first electrode layer 16 is separated from the second region 12B. The upper surface of the first electrode layer 16 is flat, and the height of the upper surface of the first electrode layer 16 is the same as the height of the second upper surface (highest upper surface) of the second semiconductor layer 12, although this is not always the case. The first electrode layer 16 may contain, but is not limited to, metals or alloys that can be used as electrode materials.

[0052] A second electrode layer 18 is provided on the second region 12B. In a plan view, the geometric form of the second electrode layer 18 is identical or substantially identical to the geometric form of the second region 12B. In one example, the second electrode layer 18 is provided so as to be in direct contact with the upper surface of the second region 12B. The second electrode layer 18 is provided so as to form concentric circles with the first region 12A, the second region 12B, and the first electrode layer 16, but not necessarily. The second electrode layer 18 is provided at the same height as the first electrode layer 16, or substantially the same height, but not necessarily. Here, "substantially the same height" means that a height difference between the first and second electrode layers 16 and 18 occurs unintentionally during the manufacturing process, and that height difference is within the allowable tolerance. The second electrode layer 18 is a single layer or a multilayer, and so is the first electrode layer 16. The material of the second electrode layer 18 is identical to, but not limited to, the material of the first electrode layer 16.

[0053] The second semiconductor layer 12 includes a third region 12C and a fourth region 12D that surround the first region 12A and the second region 12B in a planar manner. The third region 12C may be formed to completely surround the second portion of the first region 12A. The fourth region 12D may be formed to completely surround the first portion of the first region 12A and the second region 12B. The third region 12C is in contact with the second portion of the first region 12A horizontally. The thickness of the third region 12C is the same as or substantially the same as the thickness of the second portion. The bottom surface of the third region 12C is in contact with the insulating layer 14 and may become part of the bottom surface of the second semiconductor layer 12. Part of the third region 12C is located below the recess 13 and inside the recess 13, while the remainder of the third region 12C is outside the recess 13. In a planar manner, the edge of the third region 12C coincides with the edge of the second semiconductor layer 12. The side surface of the third region 12C becomes part of the side surface of the second semiconductor layer 12.

[0054] The fourth region 12D is located on the third region 12C. The fourth region 12D is horizontal and in contact with the second region 12B. In the horizontal direction, a portion of the fourth region 12D is within the recess 13 region, and the remainder is outside the recess 13 region. In other words, the first portion 12D1 of the fourth region 12D is located between the boundary of the recess 13 and the second region 12B, that is, between the step between the first upper surface 2S1 and the second upper surface 2S2 of the second semiconductor layer 12 and the second region 12B, and the remainder (second portion) 12D2 of the fourth region 12D is located between the step and the side surface of the second semiconductor layer 12. The first portion 12D1 can be said to be the horizontal portion of the fourth region 12D, and the second portion 12D2 connected to the first portion 12D1 can be said to be the vertical portion of the fourth region 12D. The upper surface of the first portion 12D1 is part of the first upper surface 2S1 of the second semiconductor layer 12, and the upper surface of the second portion 12D2 is part of the second upper surface 2S2 of the second semiconductor layer 12. Therefore, there may also be a step between the first portion 12D1 and the second portion 12D2 of the fourth region 12D. The thickness of the first portion 12D1 is thinner than the thickness of the second portion 12D2.

[0055] On a plane, the edges of the fourth region 12D coincide with the edges of the second semiconductor layer 12 and the third region 12C. The side surface of the fourth region 12D is part of the side surface of the second semiconductor layer 12.

[0056] The third region 12C and the fourth region 12D are regions formed sequentially in a direction perpendicular to the upper surface of the insulating layer 14. The third region 12C and the fourth region 12D are the remaining regions of the second semiconductor layer 12, excluding the first region 12A and the second region 12B.

[0057] On a plane, the shape of the third region 12C is a band-shaped or ring-shaped circle with a predetermined width and radius, and the center of the third region 12C is the same as the center of the first and second regions 12A and 12B, and the fourth region 12D is the same as the third region 12C. That is, the third and fourth regions 12C and 12D form concentric circles with the first and second regions 12A and 12B.

[0058] The second portion 12D2 of the fourth region 12D has a predetermined ring width Rw1 in the radial direction. The ring width Rw1 corresponds to the gap or distance between the step 15 and the side surface of the second semiconductor layer 12. The ring width Rw1 can vary depending on the radius 12R3 of the recess 13. Therefore, the ring width Rw1 can be adjusted during the process of forming the recess 13.

[0059] The third region 12C and the fourth region 12D are PN junction regions. Light traveling along the optical waveguide 10 is transmitted to the PN junction region of the first optical modulator 20, but the modes of light transmitted from the optical waveguide 10 to the first optical modulator 20 may be limited depending on the ring width Rw1. For example, the narrower the ring width Rw1, the more fundamental mode or single-mode (e.g., TE0) light is transmitted from the optical waveguide 10 to the first optical modulator 20, and the wider the ring width Rw1, the more higher-order modes or multiple-mode (e.g., TE0, TE1) light is transmitted from the optical waveguide 10 to the first optical modulator 20.

[0060] As a result, by suitably setting the radius 12R3 of the recess 13 during the process of forming the recess 13, the modes of light transmitted from the optical waveguide 10 to the first optical modulator 20 can be limited, so that only fundamental mode light is transmitted to the PN junction region, and higher-order mode light is not transmitted or is minimized.

[0061] For the sake of explanation, the fourth region 12D has been divided into a first part 12D1 and a second part 12D2. However, the first part 12D1 and the second part 12D2 are a single, continuous region, and there may not be a physical boundary between the first part 12D1 and the second part 12D2.

[0062] In one example, region 3 12C is the region doped with the first dopant at a third concentration. The third concentration is lower than the first concentration. Region 4 12D is the region doped with the second dopant at a fourth concentration. The fourth concentration is lower than the second concentration. The third and fourth concentrations are identical or substantially identical to each other.

[0063] When a voltage is applied to the first region 12A and the second region 12B via the first electrode layer 16 and the second electrode layer 18, the charge carrier concentration in the third region 12C and the fourth region 12D changes in response to this voltage, and the resulting change in refractive index can modulate the light coupled to the microdisk, i.e., the second semiconductor layer 12.

[0064] Figure 4 shows a second optical modulator 400 according to an exemplary embodiment. The second optical modulator 400 is an example of a modified version of the first optical modulator 20. Therefore, only the parts that differ from the first optical modulator 20 will be described.

[0065] Referring to Figure 4, the second optical modulator 400 includes a third semiconductor layer 32 on the insulating layer 14. The third semiconductor layer 32 corresponds to the second semiconductor layer 12 of the first optical modulator 20 and can be the same semiconductor material layer as the second semiconductor layer 12. The layer structure and configuration of the third semiconductor layer 32 are different from those of the second semiconductor layer 12.

[0066] The third semiconductor layer 32 includes a second recess 43 located within the first recess 13. The center of the second recess 43 coincides with the center of the first recess 13, and the first recess 13 and the second recess 43 are concentric in a plane. The geometric shape of the second recess 43 in a plane is not limited to a circle. The second recess 43 is located inside the second region 12B. The second recess 43 exposes a side surface of the second region 12B. The exposed side surface of the second region 12B may also be the side surface of the second recess 43. The depth of the second recess 43 is substantially the same as the thickness of the second region 12B. The second region 12B and the second recess 43 are concentric. The top surface of the fifth region 32A is exposed through the second recess 43. The top surface 2S3 of the fifth region 32A is flat and may be the bottom surface of the second recess 43 or the third top surface of the third semiconductor layer 32. The entire region between the bottom surface of the second recess 43 and the bottom surface of the third semiconductor layer 32 can become the fifth region 32A. The fifth region 32A extends below the second region 12B. The edge or boundary of the fifth region 32A coincides with the outer edge (outer boundary) of the second region 12B. The fifth region 32A, the second region 12B, and the second recess 43 are concentric. The radius of the fifth region 32A is the same as the radius of the second portion of the first region 12A in Figure 2. The thickness of the fifth region 32A is uniform or substantially uniform overall. In one example, the doping characteristics of the fifth region 32A (e.g., dopant type, doping concentration, etc.) are the same as those of the first region 12A. In one example, the dopant injected into the fifth region 32A is the same n-type dopant as the dopant injected into the third region 12C. The doping concentration of the fifth region 32A is higher than that of the third region 12C. The doping concentration in the fifth region 32A is the same as or substantially the same as the doping concentration in the second region 12B. In the high-doping region, a depletion layer is formed between the second region 12B and the fifth region 32A, where opposite dopants are injected. That is, the second region 12B and the fifth region 32A form a PN junction, and capacitance is generated in the second optical modulator 400. Such capacitance can vary depending on the radius of the second recess 43.In other words, as the radius of the second recess 43 increases, the junction area between the second region 12B and the fifth region 32A decreases, and the capacitance decreases. Conversely, as the radius of the second recess 43 decreases, the junction area increases, and the capacitance increases. Therefore, in the manufacturing process of the second optical modulator 400, the optical modulation time of the second optical modulator 400 can be optimized by suitably setting the radius of the second recess 43 so as to minimize the capacitance within an acceptable range.

[0067] The first electrode layer 16 is provided on the fifth region 32A and is positioned apart from the second region 12B and the second electrode layer 18.

[0068] By providing a second recess 43 within the first recess 13 of the third semiconductor layer 32, the third semiconductor layer 32 can have first to third upper surfaces 2S1 to 2S3 of different heights. As a result, a first step 15 may exist between the first upper surface 2S1 and the second upper surface 2S2, and a second step 25 may exist between the second upper surface 2S2 and the third upper surface 2S3. The horizontal positions of the first step 15 and the second step 25 can be adjusted during the formation of the first recess 13 and the second recess 43.

[0069] The remaining region of the third semiconductor layer 32 is identical to that of the second semiconductor layer 12.

[0070] The second optical modulator 400 corresponds to the case where the thickness of the second semiconductor layer 12 in the first part of the first region 12A of the first optical modulator 20 becomes as thin as the thickness of the second part of the first region 12A.

[0071] Figure 5 is a plan view showing a third optical modulator 500 according to an exemplary embodiment. Figure 6 shows a cross-section obtained by cutting Figure 5 in the 6-6' direction, and Figure 7 shows a cross-section obtained by cutting Figure 5 in the 7-7' direction. The same reference numbers as those described for the first optical modulator 20 and the second optical modulator 400 refer to the same components, and their descriptions are omitted.

[0072] Referring to Figures 5 to 7, the optical waveguide 10 and the third optical modulator 500 are provided on the insulating layer 14. The optical waveguide 10 and the third optical modulator 500 can be separated from each other by a first spacing G1, as shown in Figure 7. The third optical modulator 500 includes sequentially stacked first semiconductor layers 22 and insulating layer 14, and includes a fourth semiconductor layer 42 provided on the insulating layer 14. The fourth semiconductor layer 42 is provided on one surface (e.g., the top surface) of the insulating layer 14. In one example, the first semiconductor layer 22 and the fourth semiconductor layer 42 contain the same semiconductor material, but they may not be the same. In one example, the fourth semiconductor layer 42 contains the same semiconductor material as the second semiconductor layer 12 of the first optical modulator 20. Therefore, the semiconductor properties and optical characteristics of the fourth semiconductor layer 42 may be the same as those of the second semiconductor layer 12.

[0073] The fourth semiconductor layer 42 includes a region where optical modulation actually occurs. The fourth semiconductor layer 42 may include multiple regions with different dopant and / or doping concentrations. In one example, the fourth semiconductor layer 42 includes a circular sixth region 62A with a predetermined radius in the center. In one example, the sixth region 62A is a region doped with a dopant at a predetermined concentration. In one example, the type of dopant injected into the sixth region 62A and the doping concentration of the sixth region 62A are the same as the dopant injected into the first region 12A of the second semiconductor layer 12 of the first optical modulator 20 and the doping concentration of the first region 12A.

[0074] The fourth semiconductor layer 42 includes a second region 12B formed on the sixth region 62A. The second region 12B is formed in a strip or ring shape with a predetermined width on the edge region of the sixth region 62A. The second region 12B is separated from the center of the sixth region 62A. The height of the upper surface of the second region 12B is different from the height of the upper surface of the sixth region 62A. That is, the upper surface of the second region 12B is higher than the upper surface of the sixth region 62A. Therefore, a step difference corresponding to the thickness of the second region 12B is created between the sixth region 62A and the second region 12B.

[0075] The distance from the center of the sixth region 62A to the second region 12B is adjusted during the manufacturing process of the optical modulator 20, thereby also adjusting the junction area of ​​the junction region between the sixth region 62A and the second region 12B. Such adjustments can also adjust the capacitance of the third optical modulator 500 caused by the junction region between the sixth region 62A and the second region 12B. For example, the greater the distance between the inner boundary of the second region 12B and the center of the sixth region 62A, i.e., the larger the radius 12R2 of the inner boundary of the second region 12B, the greater the capacitance. The closer the distance between the inner boundary of the second region 12B and the center of the sixth region 62A, the greater the capacitance. By adjusting the capacitance in this way, the optical modulation speed of the third optical modulator 500 can be adjusted. As an example, the capacitance can be reduced by narrowing the width of the second region 12B in the radial direction, thereby increasing the optical modulation speed of the third optical modulator 500.

[0076] The outer boundary of the second region 12B coincides with or substantially coincides with the outer boundary of the sixth region 62A. In other words, the outer radius of the second region 12B and the radius of the sixth region 62A, measured at the center of the sixth region 62A, are identical or substantially identical to each other. The interior of the second region 12B has a second radius 12R2 that is smaller than the radius of the sixth region 62A. The second region 12B and the sixth region 62A define the recess region corresponding to the second recess 43 in Figure 4. The sides of the second region 12B become the sides of the recess region, and the top surface of the sixth region 62A becomes the bottom surface of the recess region.

[0077] On the plan view, the shape of the second region 12B is a circular band or ring with a predetermined width. The sixth region 62A and the second region 12B are concentric circles.

[0078] A first electrode layer 16 is provided on the sixth region 62A. The center of the first electrode layer 16 is the same as or substantially coincides with the center of the sixth region 62A. In one example, the first electrode layer 16 and the sixth region 62A are concentric. The first electrode layer 16 is separated from the second region 12B.

[0079] A second electrode layer 18 is provided on the second region 12B. In the plan view, the shape of the second electrode layer 18 is identical or substantially identical to the shape of the second region 12B. In one example, the second electrode layer 18 is formed to cover the entire upper surface of the second region 12B and to be in direct contact with the entire upper surface. In one example, the second electrode layer 18 may be formed only on a portion of the upper surface of the second region 12B. The second electrode layer 18 is provided to form concentric circles with the sixth region 62A, the second region 12B, and the first electrode layer 16, but this is not always the case. The second electrode layer 18 is provided at the same height as the first electrode layer 16 or substantially the same height. The second electrode layer 18 is provided only on the second region 12B.

[0080] The material of the second electrode layer 18 is the same as the material of the first electrode layer 16, but is not limited to this.

[0081] The fourth semiconductor layer 42 includes a seventh region 62C around the sixth region 62A and an eighth region 62D around the second region 12B. The seventh region 62C and the eighth region 62D are regions formed sequentially in a direction perpendicular to the upper surface of the insulating layer 14. The seventh region 62C is provided so as to completely surround the sixth region 62A, and the eighth region 62D is provided so as to completely surround the second region 12B. The seventh region 62C and the eighth region 62D are the remaining regions of the fourth semiconductor layer 42 excluding the second region 12B and the sixth region 62A. In a plan view, the shape of the seventh region 62C is a band-shaped or ring-shaped circle with a predetermined width and radius. The center of the seventh region 62C is the same as the center of the sixth region 62A. Therefore, the seventh region 62C, the sixth region 62A, and the second region 12B can be concentric circles.

[0082] In the plan view, the shape of the eighth region 62D is a band-shaped or ring-shaped circle with a predetermined width and radius. The center of the eighth region 62D is the same as the center of the sixth region 62A. Therefore, the eighth region 62D, the seventh region 62C, the sixth region 62A, and the second region 12B can be concentric circles. The seventh region 62C includes a first portion 62C1, a second portion 62C2, and a third portion 62C3. The first portion 62C1 is a portion formed with the same thickness as the sixth region 62A. The second portion 62C2 is a portion formed perpendicular to the first portion 62C1. The third portion 62C3 extends from the second portion 62C2 toward the center of the sixth region 62A and is parallel to the first portion 62C1. The first portion 62C1 and the third portion 62C3 are separated from each other in a direction perpendicular to the upper surface of the insulating layer 13. The second portion 62C2 is a region formed perpendicular to the upper surface of the insulating layer 13. The side surface of the second portion 62C2 is the side surface of the fourth semiconductor layer 42 and is located at a first radius 12R1 from the center of the sixth region 62A. For the sake of explanation, the seventh region 62C is divided into the first to third portions 62C1 to 62C3, but the first to third portions 62C1 to 62C3 are a single continuous region, and there are no physical boundaries between each portion 62C1 to 62C3.

[0083] The eighth region 62D includes a first portion 62D1 having the same thickness as the second region 12B, and a second portion 62D2 formed perpendicular to the first portion 62D1. The height of the vertical boundary, i.e., the upper boundary, of the second portion 62D2 is higher than the upper surface of the first portion 62D1. Thus, a step is formed between the upper surface of the first portion 62D1 and the upper boundary of the second portion 62D2. The size of such a step can be adjusted by adjusting the length of the second portion 62D2 perpendicular to the upper surface of the insulating layer 14. The length of the second portion 62D2 can be adjusted by adjusting the etching depth for forming the second portion 62D2 during the manufacturing process of the third optical modulator 500. For the sake of explanation, the eighth region 62D has been divided into a first part 62D1 and a second part 62D2. However, the first part 62D1 and the second part 62D2 are a single, continuous region, and there is no physical boundary between them.

[0084] The first parts 62C1 and 62D1 of the seventh region 62C and the eighth region 62D are parallel to each other. The second parts 62C2 and 62D2 of the seventh region 62C and the eighth region 62D are parallel to each other. The seventh region 62C may be formed in such a way that it encloses the eighth region 62D on the outside. That is, the seventh region 62C may be provided so as to cover the entire underside, sides, and top of the eighth region 62D. In other words, for the sake of explanation, if we consider the boundary between the eighth region 62D and the seventh region 62C as a surface, the bottom surface, outer surface, and top surface of the eighth region 62D may be completely covered by the seventh region 62C.

[0085] The uppermost surface of the seventh region 62C corresponds to the upper surface of the third portion 62C3 of the seventh region 62C or the uppermost surface of the fourth semiconductor layer 42. The upper surface of the second electrode layer 18 may be at the same height as the uppermost surface. The inner surface of the third portion 62C3 of the seventh region 62C and the inner surface of the second portion 62D2 of the eighth region 62D (the inner surface of the stepped portion) form the same side surface 12S1, and side surface 12S1 is separated from the second electrode layer 18 and the second region 12B. Side surface 12S1 is at a distance corresponding to the third radius 12R3 from the center of the sixth region 62A, and this distance can be adjusted during the manufacturing process of the third optical modulator 500. That is, the distance between side surface 12S1 and the second electrode layer 18 can be adjusted during the manufacturing process of the third optical modulator 500. The seventh region 62C and the eighth region 62D form a low-doping PN junction region, and a portion of the light propagating along the optical waveguide 10 is transmitted to the PN junction region of the third optical modulator 500. Depending on the size of the PN junction region, higher-order modes (e.g., the first-order mode) may also be transmitted to the PN junction region in addition to the fundamental mode (TE0). Therefore, the size of the PN junction region can be controlled so that only fundamental-mode light is transmitted to the PN junction region, and higher-order mode light is not transmitted or is minimized. The larger the PN junction region, the smaller the influence of the high-doping region, i.e., the sixth region 62A and the second region 12B, on the fundamental mode transmitted to the PN junction region. Therefore, the distance between the side surface 12S1 and the second electrode layer 18 can be determined taking this into consideration.

[0086] The distance from side surface 12S1 to the outer surface of the seventh region 62C, i.e., the outer surface of the fourth semiconductor layer 42 (Rw1 = first radius 12R1 - third radius 12R3), is the ring width. Since the size of the PN junction region increases or decreases in accordance with the increase or decrease of the ring width Rw1, the ring width can be set so that only fundamental mode light is transmitted from the optical waveguide 10 to the PN junction region, and the transmission of higher-order mode light is minimized. In other words, by setting the ring width, higher-order mode light transmitted from the optical waveguide 10 to the PN junction region can be blocked.

[0087] In one example, region 7, 62C, is the region doped with the first dopant at concentration 3. The third concentration is lower than the first concentration. Region 8, 62D, is the region doped with the second dopant at concentration 4. The fourth concentration is lower than the second concentration. The third and fourth concentrations are identical or substantially identical to each other.

[0088] When a voltage is applied to the sixth region 62A and the second region 12B via the first electrode layer 16 and the second electrode layer 18, the charge carrier concentrations in the seventh region 62C and the eighth region 62D change in response to this voltage, and the resulting change in refractive index can modulate the light coupled to the microdisk, i.e., the fourth semiconductor layer 42.

[0089] Figures 8 and 9 show modified examples of the third optical modulator 500 illustrated in Figure 6. Only the parts that differ from those in Figure 6 will be described, and the same reference numerals as those described in Figure 6 indicate the same components, and their explanations will be omitted.

[0090] Referring to Figure 8, a fifth semiconductor layer 82 is provided on the insulating layer 14. The fifth semiconductor layer 82 corresponds to the case where the sixth region 62A of the fourth semiconductor layer 42 of the third optical modulator 500 is replaced by the first region 12A of the first semiconductor layer 22 of the first optical modulator 20.

[0091] The layer structure and doping configuration of the remaining portion of the fifth semiconductor layer 82 are the same as those of the fourth semiconductor layer 42. In the eighth region 62D of the fifth semiconductor layer 82, the height difference between the upper end of the second portion 62D2 and the upper surface of the first portion 62D1, i.e., the step difference t1, is the same as or different from the thickness t2 of the first portion 62D1. For example, in the fifth semiconductor layer 82, the step difference t1 may be smaller than the thickness t2, but as illustrated in Figure 9, the step difference t1 may be larger than the thickness t2. The step difference t1 corresponds to the step difference between the first portion 62D1 and the second portion 62D2.

[0092] On the other hand, one of the first region 12A and the second region 12B is a region doped with a P-type conductive impurity, i.e., a P-type dopant (P region), and the other is a region doped with an N-type conductive impurity, i.e., an N-type dopant (N region). Therefore, a depletion layer is formed at the interface (junction region) between the first region 12A and the second region 12B by a PN junction. This depletion layer acts as an insulating layer. In the drawing, the solid line between the first region 12A and the second region 12B symbolically represents the depletion layer. For the same reason, the solid line between the seventh region 62C and the eighth region 62D also symbolically represents the depletion layer formed between the seventh region 62C and the eighth region 62D. However, the solid lines between the first region 12A and the seventh region 62C, and between the second region 12B and the eighth region 62D, do not represent depletion layers, but are simply introduced to separate two adjacent regions.

[0093] Figure 10 shows a fourth optical modulator 1000 according to an exemplary embodiment. The fourth optical modulator 1000 is an example of a modification of the third optical modulator 500.

[0094] Regarding the fourth optical modulator 1000, only the parts that differ from the third optical modulator 500 will be described. Reference numbers that are the same as those mentioned above refer to the same components, and their explanation will be omitted.

[0095] Referring to Figure 10, the fourth optical modulator 1000 includes a sixth semiconductor layer 102 on the insulating layer 14. The material (substance) of the sixth semiconductor layer 102 is the same as that of the fourth semiconductor layer 42 of the third optical modulator 500, but this is not always the case. The sixth semiconductor layer 102 includes dopant-doped second region 12B, third region 12C, sixth region 62A, and ninth region 102D. The ninth region 102D is located adjacent to the second region 12B and may be formed to completely surround the second region 12B in a plane. The ninth region 102D is located on the third region 12C and extends downward along the outer surface of the third region 12C. That is, the ninth region 102D may be formed to include a first portion 102D1 covering the upper surface of the third region 12C and a second portion 102D2 covering the outer surface of the third region 12C. The second portion 102D2 of the ninth region 102D contacts the upper surface of the insulating layer 14. As a result, the ninth region 102D of the sixth semiconductor layer 102 can completely cover the top and sides of the third region 12C.

[0096] On the third region 12C, the thickness of the first portion 102D1 of the ninth region 102D is uniform overall and is the same as or substantially the same as the thickness of the second region 12B. The second portion 102D2 of the ninth region 102 has a predetermined width in the lateral direction, and this width varies according to the outer diameter of the third region 12C. The upper surface of the first portion 102D1 becomes part of the uppermost surface of the sixth semiconductor layer 102, and the side surface of the second portion 102D2 becomes the side surface of the sixth semiconductor layer 102.

[0097] In one example, the doping concentration and injected dopant type in region 9 102 are the same as the doping concentration and injected dopant type in region 7 62C of the fourth semiconductor layer 42 of the third optical modulator 500.

[0098] Figure 11 is a plan view showing an optical waveguide 10 and a fifth optical modulator 1100 according to one embodiment, which is arranged adjacent to it.

[0099] Figure 12 is a cross-sectional view obtained by cutting Figure 11 in the 12-12' direction, and Figure 13 is a cross-sectional view obtained by cutting Figure 11 in the 13-13' direction.

[0100] In one example, the fifth optical modulator 1100 is a variation of the second optical modulator 400 shown in Figure 4. Therefore, only the parts that differ from the second optical modulator 400 will be explained.

[0101] Referring to Figures 11 to 13, the fifth optical modulator 1100 includes a seventh semiconductor layer 122 on the insulating layer 14. The seventh semiconductor layer 122 is a semiconductor layer of the same material as the third semiconductor layer 32 of the second optical modulator 400, but it may be a semiconductor layer of different materials. The planar shape of the seventh semiconductor layer 122 is circular or non-circular (e.g., elliptical). As an example, the seventh semiconductor layer 122 has a disk shape.

[0102] In order to simultaneously modulate many wavelengths of light with the fifth optical modulator 1100, the wavelength division multiplexing (WDM) bandwidth of the fifth optical modulator 1100 must be wide. To increase the WDM bandwidth, the free spectral range (FSR) of the fifth optical modulator 1100 must be expanded. The FSR increases as the radius of the seventh semiconductor layer 122 decreases, and decreases as the radius increases. In one example, the FSR is several tens of nanometers, and for this, the radius of the seventh semiconductor layer 122 is a few micrometers or less. Considering the size of the radius of the seventh semiconductor layer 122, the seventh semiconductor layer 122 is sometimes described as a microdisk.

[0103] The seventh semiconductor layer 122 includes first to fourth regions 42A, 42B, 42C, and 42D doped with p-type or n-type dopants. The basic arrangement of the first to fourth regions 42A to 42D is similar to or identical to the arrangement of the doped regions 12B, 12C, 12D, and 32A of the third semiconductor layer 32 of the second optical modulator 400. For example, the formation positions and arrangement relationships of the first and second regions 42A and 42B of the seventh semiconductor layer 122 are identical to the formation positions and arrangement relationships of the fifth region 32A and the second region 12B of the third semiconductor layer 32 of the second optical modulator 400.

[0104] Furthermore, the formation location of the third region 42C of the seventh semiconductor layer 122 is the same as the third region 12C of the third semiconductor layer 32 of the second optical modulator 400. The formation location of the fourth region 42D of the seventh semiconductor layer 122 is the same as the fourth region 12D of the third semiconductor layer 32 of the second optical modulator 400. The doping morphology and doping concentration of the first region 42A, second region 42B, third region 42C, and fourth region 42D of the seventh semiconductor layer 122 are the same as the doping morphology and doping concentration of the fifth region 32A, second region 12B, third region 12C, and fourth region 12D of the third semiconductor layer 32 of the second optical modulator 400.

[0105] However, the planar and cross-sectional shapes of the third region 42C and the fourth region 42D of the seventh semiconductor layer 122 may differ from those of the third region 12C and the fourth region 12D of the third semiconductor layer 32 of the second optical modulator 400. For example, in the seventh semiconductor layer 122, the third region 42C and the fourth region 42D are formed sequentially in a direction perpendicular to the upper surface of the insulating layer 14, and the third region 42C and the fourth region 42D completely overlap each other in the vertical direction. Unlike the third and fourth regions 12C and 12D of the third semiconductor layer 32 of the second optical modulator 400, the third region 42C and the fourth region 42D include only portions parallel to the upper surface of the insulating layer 14 and do not include portions that extend in a direction perpendicular to the upper surface of the insulating layer 14. In other words, the outer surfaces of the third region 42C and the fourth region 42D form the same plane, the upper surface of the fourth region 42D is separated from the third region 42C, and the radii 9R2 of the inner surfaces (boundaries) of the third region 42C and the fourth region 42D, which have a ring-shaped plane, are the same, and the radii 9R1 of the outer surfaces of the third region 42C and the fourth region 42D may also be the same. The radius 9R1 of the outer surface corresponds to the radius of the seventh semiconductor layer 122. The radius 9R1 of the seventh semiconductor layer 122 is determined considering the FSR of the fifth optical modulator 1100.

[0106] The seventh semiconductor layer 122 can be described in other terms as follows: it includes a recess 123 of a predetermined depth, a first region 42A below the recess 123, and a second region 42B and a fourth region 42D distributed around the recess 123. The center of the recess 123 coincides with the center of the first region 42A, and the recess 123 and the first region 42A, second region 42B, third region 42C, and fourth region 42D are concentric. A first electrode layer 16 is provided on the first region 42A within the recess 123, and a second electrode layer 18 is provided around the recess 123. The recess 123 is sometimes described as a groove or trench.

[0107] In the seventh semiconductor layer 122, the second width Rw2 of the region comprising the second region 42B and the fourth region 42D, measured radially from the center of the first region 42A (for example, in the radial direction of the first region 42A), i.e., the ring width Rw2 of the seventh semiconductor layer 122, can be adjusted during the manufacturing process of the fifth optical modulator 1100. The second width Rw2 is the same as the sum of the width of the second region 42B (=9R2-9R3) and the third width Rw3 of the fourth region 42D (=9R1-9R2).

[0108] For optical modulation, if the light transmitted from the optical waveguide 10 to the third region 42C and fourth region 42D of the fifth optical modulator 1100 approaches or contacts the highly doped region, i.e., the first region 42A and second region 42B, optical loss occurs, reducing the optical modulation efficiency. Therefore, the ring width Rw2 can be adjusted to minimize optical loss during the optical modulation process. For example, the third width Rw3 of the third region 42C and fourth region 42D is set to be greater than the volume of the fundamental mode of light (TE0). However, in order to prevent or minimize the inclusion of higher-order mode light (e.g., TE1) in the optical modulation, the width of the third width Rw3 may be set narrowly so that a portion of the optical modes overlap with the highly doped region.

[0109] In Figures 11 to 13, the fifth optical modulator 1100 and the optical waveguide 10 are sometimes collectively referred to as the optical modulator. This can also be applied to other optical modulators described later.

[0110] Figure 14 shows a sixth optical modulator 1200 according to an exemplary embodiment. Only the parts that differ from the fifth optical modulator 1100 will be described.

[0111] Referring to Figure 14, in the eighth semiconductor layer 142 of the sixth optical modulator 1200, the second region 42B is not located on the first region 42A, but is separate from the first region 42A. In the eighth semiconductor layer 142, the second region 42B, the third region 42C, and the fourth region 42D may be arranged so as to overlap each other in a perpendicular direction on the upper surface of the insulating layer 14. For example, the second region 42B is formed in part of the fourth region 42D, and the second electrode layer 18 is provided on such a second region 42B. Comparing the seventh semiconductor layer 122 of the fifth optical modulator 1100 with the eighth semiconductor layer 142 of the sixth optical modulator 1200, the second region 42B of the eighth semiconductor layer 142 can be considered to correspond to the case where a part of the fourth region 42D of the seventh semiconductor layer 122 is changed into a highly doped region similar to the second region 42B. Therefore, in order to form the second region 42B of the eighth semiconductor layer 142, a separate mask for ion implantation may be used.

[0112] In the eighth semiconductor layer 142, the second region 42B is separated from the third region 42C, and the fourth region 42D exists between the second region 42B and the third region 42C. The upper surface of the second region 42B and the upper surface of the fourth region 42D are at the same height, and therefore the two upper surfaces form the same plane. In the plan view, the upper surfaces of the second region 42B and the upper surfaces of the fourth region 42D form a circular or non-circular (e.g., elliptical) band with the center of the first region 42A as the reference point. In the plan view, the first region 42A, the second region 42B, and the fourth region 42D are concentric, and the second region 42B is located between the upper surface of the fourth region 42D and the first region 42A.

[0113] In the eighth semiconductor layer 142, the thickness of the second region 42B is thinner than the thickness of the fourth region 42D, and the horizontal length of the second region 42B (the radial ring width in the plan view) can be adjusted considering the volume of the fundamental mode of the modulated light, or to minimize optical loss during the optical modulation process.

[0114] In the eighth semiconductor layer 142, the first region 42A and the second region 42B, which are highly doped regions, are separated from each other and do not form a PN junction. Therefore, capacitance due to a PN junction is not formed or is minimized. Consequently, the optical modulation speed is increased.

[0115] The material of the eighth semiconductor layer 142 is the same as the material of the second semiconductor layer 12 in Figure 2, but they may be different.

[0116] Figure 15 shows a seventh optical modulator 1300 according to an exemplary embodiment.

[0117] The seventh optical modulator 1300 is a combination of the third optical modulator 500 and the features of the sixth optical modulator 1200.

[0118] Referring to Figure 15, in the ninth semiconductor layer 152, the second region 12B is provided separately from the sixth region 62A, and a part of the first portion 62D1 of the eighth region 62D is provided between the second region 12B and the sixth region 62A. That is, in the same configuration as in the sixth optical modulator 1200 where the second region 42B is provided in the fourth region 42D, the second region 12B of the ninth semiconductor layer 152 is provided in the first portion 62D1 of the eighth region 62D. By providing the second region 12B in the first portion 62D1 of the eighth region 62D, the eighth region 62D can contain three regions of different thicknesses. For example, in the eighth region 62D, the left portion of the step 15 has a first thickness, the portion between the step 15 and the second region 12B has a second thickness that is thinner than the first thickness, and the portion below the second region 12B has a third thickness that is thinner than the second thickness.

[0119] In other words, by providing the second region 12B in the first portion 62D1 of the eighth region 62D, the eighth region 62D can include a physical step 15 and a non-physical step 15' that arise when the ninth semiconductor layer 152 is etched and a recess is formed. The non-physical step 15' exists in the portion of the ninth semiconductor layer 152 with a constant thickness, located to the right of the physical step 15. Due to the presence of the second region 12B, the first portion 62D1 to the right of the step 15 can be divided into a thick portion of the doping region and a thin portion (the portion below the second portion 12B). In the cross-sectional profile of the eighth region 62D, a step is created between the thick portion and the thin portion of the first portion 62D1 due to the difference in thickness. This step 15' is not an external step that appears due to direct etching of the material layer, but rather exists inside the ninth semiconductor layer 152 corresponding to the first portion 62D1 of the eighth region 62D. Therefore, the non-physical step 15' can also be expressed as an internal step in the ninth semiconductor layer 152 or a step in the doping region inside the ninth semiconductor layer 152.

[0120] As a result, in Figure 15, the eighth region 62D includes two steps 15 and 15'.

[0121] The remaining portion of the ninth semiconductor layer 152 of the seventh optical modulator 1300 is identical to the fourth semiconductor layer 42 of the third optical modulator 500.

[0122] The material of the ninth semiconductor layer 152 is the same as the material of the second semiconductor layer 12 in Figure 2, but they may be different.

[0123] Figure 16 shows an eighth optical modulator 1400 according to an exemplary embodiment.

[0124] The eighth optical modulator 1400 is one of the modified versions of the seventh optical modulator 1300. Therefore, only the parts that differ from the seventh optical modulator 1300 will be explained.

[0125] Referring to Figure 16, in the eighth optical modulator 1400, the layer structure and layer profile of the tenth semiconductor layer 162 provided on the insulating layer 14 are similar to those of the ninth semiconductor layer 152 in the seventh optical modulator 1300. For example, in the tenth semiconductor layer 162, the second region 12B is located on the upper surface of the first portion 62D1 of the eighth region 62D, and the second electrode 18 is provided on the second region 12B. In the eighth optical modulator 1400, since the second region 12B is located on the upper surface of the first portion 62D1 of the eighth region 62D, the non-physical step 15' described in Figure 15 does not appear in the first portion 62D1. The remaining configuration of the eighth optical modulator 1400 is the same as that of the seventh optical modulator 1300. The material of the tenth semiconductor layer 162 is the same as the material of the second semiconductor layer 12 in Figure 2, but they may be different.

[0126] The aforementioned optical modulator may include multiple optical waveguides. Figure 17 shows an example of this.

[0127] Referring to Figure 17, the first optical waveguide 13A is located adjacent to the semiconductor layer 132, and the second optical waveguide 13B is located parallel to the first optical waveguide 13A, narrowing the semiconductor layer 132. In one example, the first optical waveguide 13A and the second optical waveguide 13B may be parallel to each other only in the portion corresponding to the semiconductor layer 132, and the remaining portions may not be parallel. The isolation distance (spacing) between the semiconductor layer 132 and the first optical waveguide 13A is the same as or substantially the same as the isolation distance between the semiconductor layer 132 and the second optical waveguide 13B. The isolation distance between the semiconductor layer 132 and the first optical waveguide 13A and the second optical waveguide 13B is the same as or substantially the same as the first spacing G1 in Figure 3. The semiconductor layer 132 is one of the semiconductor layers 12, 32, 42, 42', 52, 102, and 122 mentioned in Figures 1 to 16 and related explanations. The materials and function of the first optical waveguide 13A are the same as those of optical waveguide 10. In one example, the materials of the first optical waveguide 13A are different from those of optical waveguide 10. The materials and specifications of the second optical waveguide 13B are the same as, or substantially the same as, the first optical waveguide 13A, but are not limited to these.

[0128] The optical IL input from the light source (e.g., 330 in Figure 66) to the first optical waveguide 13A is transmitted to the semiconductor layer 132 and modulated by the voltage applied to the semiconductor layer 132. A portion of the optical ML modulated in the semiconductor layer 132, ML1, is output through the first optical waveguide 13A, and the remaining modulated optical ML2 is output through the second optical waveguide 13B.

[0129] Next, a method for manufacturing an optical modulator according to an exemplary embodiment will be described.

[0130] Figures 18 to 26 show, step by step, a method for manufacturing a third optical modulator 500 according to an exemplary embodiment.

[0131] In the following explanation, the same reference numerals used in the above-mentioned explanation of the third optical modulator 500 indicate the same components, and a detailed explanation of them will be omitted.

[0132] First, as shown in Figure 18, the substrate is prepared by sequentially stacking or forming the first semiconductor layer 22 and the insulating layer 14. An SOI substrate is used as such a substrate. The fourth semiconductor layer 42 is formed on the insulating layer 14. In one example, the fourth semiconductor layer 42 is formed on a separate temporary substrate and then transferred onto the insulating layer 14, but this method is not limited to this method.

[0133] A first mask M1 is formed on the fourth semiconductor layer 42, limiting a portion of the fourth semiconductor layer 42. The first mask M1 is an ion implantation mask, but is not limited to this. In one example, the first mask M1 is a photoresist mask, but it may be a mask of another material.

[0134] In a plan view, the first mask M1 restricts the exposure of a portion of the fourth semiconductor layer 42 in a circular band shape, but it may also restrict the exposure to a non-circular (e.g., elliptical) band shape. The portion of the fourth semiconductor layer 42 restricted by the first mask M1 corresponds to the first portion 12C1 of the third region 12C of the third optical modulator 500.

[0135] A first dopant is implanted (DP1) into the region of the fourth semiconductor layer 42 that is limited and exposed by the first mask M1. In one example, the first dopant is implanted using an ion implantation method, but is not limited thereto. In one example, the first dopant contains p-type or n-type conductive impurities. In one example, the first dopant contains n-type conductive impurities. In the first dopant implantation step (DP1), the first dopant is implanted as a first ion implantation energy. The first dopant implantation step (DP1) forms a first doping layer 12C' in the region corresponding to the first portion 12C1 of the third region 12C of the fourth semiconductor layer 42. The first doping layer 12C' is doped with a concentration corresponding to the doping concentration of the third region 12C of the third optical modulator 500. The first doping layer 12C' may be represented as a first doping region. After the first doping layer 12C' is formed, the first mask M1 is removed.

[0136] Next, as shown in Figure 19, a second mask M2 is formed on the fourth semiconductor layer 42, exposing a portion of the fourth semiconductor layer 42. The second mask M2 is for forming the fourth region 12D of the third optical modulator 500, and is formed so that the surface of the fourth semiconductor layer 42 corresponding to the fourth region 12D of the third optical modulator 500 is exposed. A second dopant is implanted into the exposed region of the fourth semiconductor layer 42 (DP2). The second dopant is implanted by an ion implantation method, but is not limited to this. In one example, the second dopant contains a p-type or n-type conductive impurity, but may also contain a dopant of the opposite type to the first dopant. In one example, the second dopant contains a p-type conductive impurity. In one example, in the second dopant implantation step (DP2), the second dopant is implanted as a second ion implantation energy. The second ion implantation energy is smaller than the first ion implantation energy. A second dopant injection step (DP2) forms a second doping layer 12D' on the first doping layer 12C'. The radial width of the second doping layer 12D' is narrower than that of the first doping layer 12C'. The second doping layer 12D' is doped with the same concentration as the first doping layer 12C'. The second doping layer 12D' may also be represented as a second doping region. The formation location of the second doping layer 12D' corresponds to the position of the horizontal portion of the fourth region 12D of the fourth semiconductor layer 42 of the third optical modulator 500. Therefore, the second doping layer 12D' is separated from the upper surface 19S of the fourth semiconductor layer 42. In one example, the second doping layer 12D' may be formed before the first doping layer 12C'.

[0137] While the first and second doping layers 12C' and 12D' are formed, a depletion layer may be formed on the surface where the first doping layer 12C' and the second doping layer 12D' join to each other. If the thicknesses of the first and second doping layers 12C' and 12D' are the same, the depletion layer is formed vertically midway between the first and second doping layers 12C' and 12D'. However, the position where the depletion layer is formed can be adjusted by adjusting the formation conditions of the first doping layer 12C' and / or the formation conditions of the second doping layer 12D'. That is, the thicknesses of the first doping layer 12C' and the second doping layer 12D' can be made different. As an example, the second doping layer 12D' can be made thinner than the first doping layer 12C', so that the depletion layer is formed closer to the upper surface of the second doping layer 12D' than to the bottom surface of the first doping layer 12C'.

[0138] The first doping layer 12C' and the second doping layer 12D' do not have a visually identifiable physical boundary, but for the sake of illustration and explanation, the boundary is indicated by a solid line. Furthermore, for the sake of explanation, the solid line shown in the drawing to indicate the boundary between the first doping layer 12C' and the second doping layer 12D' is considered to be the plane of the first doping layer 12C' and the second doping layer 12D'. The same applies to solid lines indicating the boundaries of other doping layers hereafter.

[0139] After forming the second doping layer 12D', the second mask M2 is removed.

[0140] Next, as shown in Figure 20, a third mask M3 is formed on the upper surface of the fourth semiconductor layer 42. The third mask M3 is the same as the first mask M1 in terms of its application and material, but is not limited to it.

[0141] The third mask M3 is formed to cover and protect the first and second doping layers 12C' and 12D' while limiting a portion of the fourth semiconductor layer 42. In one example, the third mask M3 is formed such that the region of the fourth semiconductor layer 42 corresponding to the sixth region 62A of the third optical modulator 500 is exposed, while the remaining region of the fourth semiconductor layer 42 is covered.

[0142] With the third mask M3 in place, a third dopant is implanted into the fourth semiconductor layer 42 (DP3). The material of the third dopant is the same as that of the first dopant, but within the same group of conductive impurities, the third dopant and the first dopant may contain different conductive impurities. In the third dopant implantation step (DP3), the third dopant is implanted by ion implantation and implanted as a third ion implantation energy. The third ion implantation energy is the same as or substantially the same as the first ion implantation energy. The third dopant implantation step (DP3) can form a third doping layer 62A, i.e., a sixth region 62A, in the fourth semiconductor layer 42. The sixth region 62A is doped at a higher concentration than the first and second doping layers 12C' and 12D'. The execution time of the third dopant implantation step (DP3) is the same as or substantially the same as the execution time of the first dopant implantation step (DP1), but they may differ.

[0143] Next, while maintaining the third mask M3, a fourth dopant is implanted into the fourth semiconductor layer 42 (DP4). The material of the fourth dopant is the same as that of the second dopant, but within the same group of conductive impurities, the fourth dopant and the second dopant may contain different conductive impurities. In the fourth dopant implantation step (DP4), the fourth dopant is implanted by an ion implantation method and implanted as a fourth ion implantation energy. The fourth ion implantation energy is the same as or substantially the same as the second ion implantation energy. The fourth dopant implantation step (DP4) can form a fourth doping layer 12B' in the fourth semiconductor layer 42. The fourth doping layer 12B' is a region formed to form the second region 12B of the third optical modulator 500. The fourth doping layer 12B' is doped at a higher concentration than the first and second doping layers 12C' and 12D', and at the same or substantially the same concentration as the third doping layer 62A. The execution time of the fourth dopant injection step (DP4) is the same as or substantially the same as the execution time of the second dopant injection step (DP2), but may differ from each other. After the fourth doping layer 12B' is formed, the third mask M3 is removed. In one example, the fourth doping layer 12B' may be formed before the third doping layer 62A.

[0144] A depletion layer may be formed at the junction between the third doping layer 62A and the fourth doping layer 12B' while the third doping layer 62A and the fourth doping layer 12B' are being formed. This depletion layer serves as an insulating layer. Similar to the depletion layers formed at the junctions of the first and second doping layers 12C' and 12D' described above, the position of the depletion layer formed at the junction of the third doping layer 62A and the fourth doping layer 12B' can also be adjusted. That is, the thickness of the third doping layer 62A and the fourth doping layer 12B' can be controlled by controlling the formation process of the third doping layer 62A and the fourth doping layer 12B'. In one example, the position of the depletion layer formed between the third doping layer 62A and the fourth doping layer 12B' in the vertical direction is the same as the position of the depletion layer formed between the first and second doping layers 12C' and 12D'. In other words, the height of the depletion layer formed between the third doping layer 62A and the fourth doping layer 12B' is the same as the height of the depletion layer formed between the first and second doping layers 12C' and 12D'.

[0145] Next, as shown in Figure 21, a fourth mask M4 is formed on the fourth semiconductor layer 42 to limit a portion of the fourth semiconductor layer 42. The fourth mask M4 is made of the same material as the first mask M1, but it may be made of a different material. The fourth mask M4 is formed to completely cover the third doping layer 62A and the fourth doping layer 12B', and also to cover a portion of the second doping layer 12D' adjacent to the fourth doping layer 12B'. The edges of the fourth mask M4 and the fourth semiconductor layer 42 are separated, and the upper surface of the fourth semiconductor layer 42 between the edges of the fourth mask M4 and the fourth semiconductor layer 42 is exposed. In the plan view, the fourth mask M4 is circular. The fourth mask M4 is a mask for forming the second portion 62C2 and the third portion 62C3 of the seventh region 62C of the third optical modulator 500. Therefore, the fourth mask M4 can be formed such that only a portion of the fourth semiconductor layer 42 corresponding to the second and third portions 62C2 and 62C3 is exposed.

[0146] The fourth mask M4 can be formed to cover the region of the fourth semiconductor layer 42 corresponding to the third radius 12R3 of the third optical modulator 500 in Figure 6. Therefore, by adjusting the radius of the fourth mask M4, the third radius 12R3 of the third optical modulator 500 can be adjusted, and the ring width Rw1 can also be adjusted. As a result, by adjusting the radius of the fourth mask M4, only the fundamental mode light can be transmitted to the third optical modulator 500, and the multiple-mode light can be filtered out.

[0147] Next, with the fourth mask M4 in place, the fifth dopant is implanted into the fourth semiconductor layer 42 (DP5). The fifth dopant contains the same conductive impurities as the first dopant. In one example, the fifth dopant is the same substance as the first dopant. The step of implanting the fifth dopant (DP5) is a step of ion implantation of the fifth dopant. In the step of implanting the fifth dopant (DP5), the fifth dopant is implanted as the fifth ion implantation energy. The fifth ion implantation energy is smaller than the second ion implantation energy. In the fifth dopant implantation step (DP5), a fifth doping layer (12C'' in Figure 22) is formed in the exposed region of the fourth semiconductor layer 42 on the second doping layer 12D', with the fifth dopant ion-implanted. In the fifth dopant implantation step (DP5), the fifth dopant is implanted at the same doping concentration as the first doping layer 12C''. Therefore, the concentration of the fifth doping layer 12C'' is the same as or substantially the same as the concentration of the first doping layer 12C''.

[0148] The exposed region of the fourth semiconductor layer 42 around the fourth mask M4 covers the upper surface of the second doping layer 12D' and covers the entire side surface. In the exposed region of the fourth semiconductor layer 42, the thickness of the region between the side surface of the second doping layer 12D' and the side surface of the fourth semiconductor layer 42 is slightly thicker than the region of the fourth semiconductor layer 42 on the upper surface of the second doping layer 12D', but the difference is not large. Therefore, due to annealing or heat treatment after ion implantation of the fifth dopant, the ion-implanted fifth dopant may diffuse into the region between the side surface of the second doping layer 12D' and the side surface of the fourth semiconductor layer 42, and as a result, the region between the side surface of the second doping layer 12D' and the side surface of the fourth semiconductor layer 42 can also become the fifth doping layer 12C''.

[0149] As a result, the fifth dopant injection step (DP5) forms a fifth doping layer 12C" in the region of the fourth semiconductor layer 42 corresponding to the second and third parts 62C2 and 62C3 of the seventh region 62C of the third optical modulator 500, as shown in Figure 22. The fifth doping layer 12C" is a region doped with the same conductive impurities as the first doping layer 12C', and is doped with substantially the same doping concentration as the first doping layer 12C'. Therefore, the first doping layer 12C' and the fifth doping layer 12C" can be a single doping region. In drawings other than Figure 22, the first doping layer 12C' and the fifth doping layer 12C" are separated, but this is simply for the convenience of explaining the manufacturing process and to aid understanding. In reality, the first doping layer 12C' and the fifth doping layer 12C" can be a single connected region, as shown in the seventh region 62C in Figure 6.

[0150] In one example, the order of the first to fifth dopant injection steps DP1 to DP5 may vary in the manufacturing process illustrated in Figures 18 to 21. For example, the third and fourth dopant injection steps DP3 and DP4, which form a high-doping region, may proceed before the first and second dopant injection steps DP1 and DP2, which form a low-doping region.

[0151] After the fifth doping layer 12C" is formed, the fourth mask M4 is removed.

[0152] After removing the fourth mask M4, a fifth mask M5 is formed on the fourth semiconductor layer 42, as shown in Figure 22. The fifth mask M5 is an etching mask and is made of the same material as the first mask M1, but it may be made of a different material. In the plan view, the fifth mask M5 is formed in the shape of a circular band, but it may be formed in a non-circular shape (e.g., elliptical). The fifth mask M5 is formed only on the upper surface of the fifth doping layer 12C''. The area on the upper surface of the fifth doping layer 12C'' in which the fifth mask M5 is formed can be adjusted considering the ring width or the position of the step formation. For example, the position (boundary) of the inner surface of the fifth mask M5 is adjusted between the inner and outer surfaces of the second doping layer 12D'.

[0153] As a result, the fifth mask M5 can be a mask that restricts the fourth semiconductor layer 42 such that the entire inner region of the fifth doping layer 12C'' and a portion of the fifth doping layer 12C'' are exposed in the fourth semiconductor layer 42.

[0154] Next, as shown in Figure 23, with the fifth mask M5 in place, the first etching is performed on the exposed region of the fourth semiconductor layer 42. The first etching is performed until the second doping layer 12D' and the fourth doping layer 12B' are exposed. In one example, the first etching may be further performed within a set time so that a step of a set thickness or depth is formed in the second doping layer 12D' even after the second doping layer 12D' and the fourth doping layer 12B' are exposed. In one example, the first etching is performed within a range where the fourth doping layer 12B' is not completely removed.

[0155] In other words, the first etching is performed within a range where the depletion layer between the third doping layer 62A and the fourth doping layer 12B' is not exposed. In the first etching, the thickness (depth) of the step formed in the second doping layer 12D' can also be adjusted by adjusting the set etching time. Therefore, in the first etching, the thickness of the step formed in the second doping layer 12D' can be adjusted to be greater or less than the thickness of the fourth doping layer 12B' remaining after the first etching. As a result of the first etching, the thickness of the fourth doping layer 12B' becomes thinner than the thickness of the second doping layer 12D' below the fifth mask M5. After the first etching, the fifth mask M5 is removed.

[0156] After removing the fifth mask M5, a sixth mask M6 is formed on the fourth semiconductor layer 42, as shown in Figure 24. The sixth mask M6 is an etching mask and is made of the same material as the fifth mask M5, but may be made of a different material. In the plan view, the fifth mask M5 is a circular strip, or it may be non-circular. The sixth mask M6 is an etching mask for forming the second region 12B of the third optical modulator 500. Therefore, the sixth mask M6 may be formed in such a way that only a portion of the fourth doping layer 12B' is exposed in the plan view, and the rest of the fourth semiconductor layer 42 is covered.

[0157] After forming the sixth mask M6, a second etching is performed on the exposed portion of the fourth semiconductor layer 42 while the sixth mask M6 is in place. The second etching is performed until the exposed portion of the fourth doping layer 12B' and the depletion layer beneath it are removed, and the third doping layer 62A beneath the depletion layer is exposed. In one example, the second etching can completely remove at least the exposed portion of the fourth doping layer 12B'.

[0158] Figure 25 shows the results of the second etching. The second etching reduces the junction region between the third and fourth doping layers 62A and 12B', thereby reducing the capacitance formed by the junction of the third and fourth doping layers 62A and 12B' during optical modulation operation, which can result in a higher optical modulation speed.

[0159] The region of the fourth doping layer 12B' remaining after the second etching is determined by the sixth mask M6. That is, by adjusting the radius of the inner surface of the sixth mask M6, which forms a concentric circle with the first region 12A, the region of the fourth doping layer 12B' remaining after the second etching increases or decreases. The capacitance also increases or decreases as the region of the fourth doping layer 12B' remaining after the second etching increases or decreases. As a result, by adjusting the inner diameter of the sixth mask M6, the capacitance caused by the junction between the third doping layer 62A and the fourth doping layer 12B' can be adjusted.

[0160] As shown in Figure 25, the second etching process forms the second region 12B of the third optical modulator 500 on the third doping layer 62A, creating a step between the third doping layer 62A and the second region 12B, i.e., between the sixth region 62A and the second region 12B. The degree of this step varies depending on the etching conditions of the first etching process.

[0161] After the second region 12B' is formed, the sixth mask M6 is removed.

[0162] As shown in Figure 26, the first electrode layer 16 is formed on the third doping layer (sixth region) 62A exposed by the second etching, and the second electrode layer 18 is formed on the second region 12B. The first and second electrode layers 16 and 18 are formed using a separate mask for forming only the first and second electrode layers 16 and 18. In one example, the first and second electrode layers 16 and 18 may be formed together with other components in other processes for forming a photonic integrated circuit including an optical modulator, but for example, in the stage of forming a grating coupler, the first and second electrode layers 16 and 18 may also be formed using the mask and etching process for forming the grating coupler. This reduces the number of masks and etching steps.

[0163] Figures 27 to 37 show, step by step, a method for manufacturing an optical modulator according to an exemplary embodiment.

[0164] The manufacturing method illustrated in Figures 27 to 37 is the manufacturing method for the fifth optical modulator 1100 illustrated in Figures 11 to 13. In the following description, the same reference numbers used in the description of the fifth optical modulator 1100 refer to the same components, and a detailed explanation of them is omitted.

[0165] First, as shown in Figure 27, a seventh semiconductor layer 122 is formed on the insulating layer 14. In one example, the seventh semiconductor layer 122 is formed by transferring a semiconductor layer grown on a separate temporary substrate onto the insulating layer 14, but it is not limited to this. The planar shape of the seventh semiconductor layer 122 can be a disk shape with a diameter of several micrometers. A seventh mask 22M is formed on the seventh semiconductor layer 122 to limit a portion of the seventh semiconductor layer 122. The seventh mask 22M is a mask made of the same material as the first mask M1 described in the manufacturing method of the third optical modulator 500, but it may be a mask made of other materials. The seventh mask 22M is a mask for forming the third region 42C and the fourth region 42D of the fifth optical modulator 1100. Therefore, the seventh mask 22M can be formed on the seventh semiconductor layer 122 such that the regions of the seventh semiconductor layer 122 corresponding to the third region and the fourth regions 42C and 42D are exposed. Although the seventh mask 22M is circular in the plan view, it may be non-circular (for example, elliptical). The seventh mask 22M forms concentric circles with the seventh semiconductor layer 122.

[0166] After forming the seventh mask 22M, the first dopant is implanted into the exposed region of the seventh semiconductor layer 122 while the seventh mask 22M is in place (22D). The first dopant implantation step (22D) is a step of ion implantation of the first dopant. The first dopant contains the same type of conductive impurity as the first dopant described in the manufacturing method of the third optical modulator 500. In the first dopant implantation step, the first dopant is implanted at the first ion implantation energy described in the manufacturing method of the third optical modulator 500. The first dopant implantation step (22D) forms a third region 42C in the seventh semiconductor layer 122 that is doped with the first dopant. The third region 42C may also be described as a doped layer to which the first dopant has been implanted. In the first dopant implantation step (22D), the first dopant is implanted at a predetermined concentration. The third region 42C forms concentric circles with the seventh semiconductor layer 122.

[0167] After forming the third region 42C, as shown in Figure 28, a second dopant is implanted into the exposed region of the seventh semiconductor layer 122 while maintaining the seventh mask 22M (23D). The second dopant implantation step is, but is not limited to, an ion implantation step. The second dopant contains the same type of conductive impurity as the second dopant described in the manufacturing method of the third optical modulator 500. In the second dopant implantation step (23D), the second dopant is implanted as a second ion implantation energy. The second ion implantation energy is smaller than the first ion implantation energy. The second dopant is doped at the same or substantially the same concentration as the first dopant. This second dopant implantation step (23D) forms a fourth region 42D in which the seventh semiconductor layer 122 is doped with the second dopant. The fourth region 42D may also be described as a doped layer implanted with the second dopant.

[0168] Since the dopants injected into the third region 42C and the fourth region 42D are of opposite types, a depletion layer can be formed between the third region 42C and the fourth region 42D by a PN junction.

[0169] After forming the fourth region 42D, the seventh mask 22M is removed.

[0170] Next, as shown in Figure 29, an eighth mask 24M is formed on the seventh semiconductor layer 122 on which the fourth region 42D is formed. The eighth mask 24M is a mask made of the same material as the seventh mask 22M, but it may be a mask made of a different material. The eighth mask 24M is a mask for forming the doped first and second regions 42A and 42B of the fifth optical modulator 1100. The eighth mask 24M is formed only on the fourth region 42D and is formed to cover the entire upper surface of the fourth region 42D. The eighth mask 24M forms concentric circles with the third region 42C and the fourth region 42D. Therefore, the inner portion of the fourth region 42D of the seventh semiconductor layer 122 may be exposed by the eighth mask 24M.

[0171] With the eighth mask 24M in place, a third dopant is implanted into the exposed portion of the seventh semiconductor layer 122 (24D). The third dopant is the same as the first dopant used to form the third region 42C, but may be different from the first dopant among the same type of conductive impurity group. In the third dopant implantation step (24D), the third dopant is implanted as the first ion implantation energy, but at a higher concentration than when the first dopant was implanted in the first dopant implantation step (22D). Through this third dopant implantation step (24D), the first region 42A is formed in the seventh semiconductor layer 122, as shown in Figure 30.

[0172] After the first region 42A is formed, while maintaining the eighth mask 24M, the fourth dopant is implanted into the exposed portion of the seventh semiconductor layer 122 (26D), as shown in Figure 31. In the fourth dopant implantation step (26D), the fourth dopant is implanted by ion implantation, but is not limited to this method. The fourth dopant contains the same conductive impurities as the second dopant used to form the fourth region 42D, but may also contain different conductive impurities from the second dopant within the same type (e.g., p-type) group of conductive impurities. In the fourth dopant implantation step (26D), the fourth dopant is implanted as the second ion implantation energy. Therefore, in the seventh semiconductor layer 122, the fourth dopant is implanted at a higher position than the first region 42A. In the fourth dopant implantation step (26D), the fourth dopant is doped at the same or substantially the same concentration as the third dopant. As shown in Figure 32, this fourth dopant injection step (26D) forms a doping layer 42B' on the first region 42A of the seventh semiconductor layer 122, in which the fourth dopant is doped. The doping layer 42B' may also be represented as a doping region.

[0173] After the doping layer 42B' is formed, the eighth mask 24M is removed. Figure 33 shows the result after the removal of the eighth mask 24M.

[0174] Next, as shown in Figure 34, a ninth mask 28M is formed on the seventh semiconductor layer 122. The ninth mask 28M forms concentric circles with the doping layer 42B', the fourth region 42D, and the seventh semiconductor layer 122. The ninth mask 28M is formed in a circular band shape. The ninth mask 28M is a mask of the same material as the seventh mask 22M, but it may be a mask of a different material. The ninth mask 28M is a mask for etching the doping layer 42B'. In a plan view, the ninth mask 28M may be formed in such a way that it covers the entire fourth region 42D, exposes the central portion of the doping layer 42B', and covers the rest of the doping layer 42B'. The exposed central portion of the doping layer 42B' is separated from the fourth region 42D.

[0175] Depending on the inner diameter of the ninth mask 28M, or the radius of the inner surface of the ninth mask 28M, the diameter and radius of the exposed area of ​​the doping layer 42B' may also change. Since the exposed portion of the doping layer 42B' is etched in a subsequent process, the size or inner radius of the portion of the doping layer 42B' remaining after etching can be adjusted by adjusting the radius of the ninth mask 28M. Therefore, the radius of the ninth mask 28M can be determined in consideration of the inner radius of the doping layer 42B' remaining after etching.

[0176] After forming the ninth mask 28M, the exposed portion of the doping layer 42B' is etched while the ninth mask 28M is in place. This etching is carried out until the first region 42A is exposed. Such etching can completely remove at least the exposed portion of the doping layer 42B', as shown in Figure 35. Such etching creates a step between the first region 42A and the remaining portion of the doping layer 42B', i.e., the second region 42B. The inner diameter or inner surface radius of the second region 42B is adjusted by adjusting the inner diameter of the ninth mask 28M, as described above. That is, by adjusting the inner diameter of the ninth mask 28M, the junction region between the highly doped first region 42A and the second region 42B is adjusted, and therefore the capacitance caused by the junction of the first and second regions 42A and 42B can also be adjusted by adjusting the inner diameter of the ninth mask 28M.

[0177] After the second region 42B is formed, the ninth mask 28M is removed. Figure 36 shows the result after the removal of the ninth mask 28M.

[0178] Next, as shown in Figure 37, a first electrode layer 16 is formed on the first region 42A, and a second electrode layer 18 is formed on the second region 42B. The first and second electrode layers 16 and 18 are formed simultaneously. The first and second electrode layers 16 and 18 may be formed using a separate mask, as described in the manufacturing method of the third optical modulator 500, or they may be formed together with other components by an etching process using a mask used when forming other components.

[0179] Figures 38 to 52 show a step-by-step method for manufacturing an optical modulator according to an exemplary embodiment. The manufacturing method illustrated in Figures 38 to 52 is the manufacturing method for the eighth optical modulator 1400 illustrated in Figure 16. In the following description, the same reference numbers used in the description of the eighth optical modulator 1400 and the above manufacturing method refer to the same components, and detailed explanations thereof are omitted.

[0180] As shown in Figure 38, a tenth semiconductor layer 162 is formed on the insulating layer 14. In one example, the seventh semiconductor layer 122 is formed by transferring a semiconductor layer grown on a separate temporary substrate onto the insulating layer 14.

[0181] A tenth mask 38M is formed on the tenth semiconductor layer 162, limiting a portion of the tenth semiconductor layer 162. In one example, the material of the tenth mask 38M is the same as that of the first mask M1 in Figure 18, but they may be different. The portion of the tenth semiconductor layer 162 limited by the tenth mask 38M includes the region where the first portion 62C1 of the seventh region 62C of the eighth optical modulator 1400 is formed.

[0182] The first dopant is injected (38D1) into the region of the tenth semiconductor layer 162 that is limited and exposed by the tenth mask 38M. In one example, the first dopant injection step (38D1) is carried out under the same process conditions (e.g., dopant type, injection energy, doping concentration, etc.) as the first dopant (DP1) injection step described in Figure 18, but they may be carried out under different process conditions. The first dopant injection step (38D1) forms the first portion 12C1 of the seventh region 62C in the tenth semiconductor layer 162. In one example, the first portion 62C1 is an n+ doping layer (doping region). After the first portion 62C1 is formed, the tenth mask 38M is removed.

[0183] Next, as shown in Figure 39, an eleventh mask 39M is formed on the tenth semiconductor layer 162, exposing a portion of the tenth semiconductor layer 162. The eleventh mask 39M is for forming the sixth region 62A of the eighth optical modulator 1400, and is formed so that the surface of the tenth semiconductor layer 162 corresponding to the sixth region 62A of the eighth optical modulator 1400 is exposed. In one example, the material of the eleventh mask 39M is the same as that of the third mask M3 described in Figure 20, but they may be different. A second dopant is injected into the exposed region of the tenth semiconductor layer 162 (39D1). In one example, the step of injecting the second dopant (39D1) is carried out under the same process conditions as the dopant injection step (DP3) for forming the sixth region (doping layer) 62A described in Figure 20, but they may be carried out under different process conditions. In one example, the type of the second dopant may be the same as that of the first dopant, but even if the impurities are of the same type, the materials of the impurities may be different.

[0184] The second dopant injection step (39D1) forms a sixth region 62A in the tenth semiconductor layer 162. The first portion 62C1 and the sixth region 62A are separated from the upper surface of the tenth semiconductor layer 162.

[0185] Next, as shown in Figure 40, a 12th mask 40M is formed on the 10th semiconductor layer 162. The 12th mask 40M is a mask for limiting the region corresponding to the diameter of the 8th region 62D of the 10th semiconductor layer 162 of the 8th optical modulator 1400. Therefore, the 12th mask 40M can be formed such that the region corresponding to the diameter of the 8th region 62D in the 10th semiconductor layer 162 is exposed. The material of the 12th mask 40M is the same as the material of the 10th mask 38M or the 11th mask 39M, but they may be different from each other. With the 12th mask 40M in place, a third dopant is injected into the exposed region of the 10th semiconductor layer 162 (40D1). In one example, the step of injecting the third dopant (40D1) is carried out under the same process conditions as the step of injecting the second dopant (DP2) described in Figure 19, but it may be carried out under different process conditions. In one example, the dopant used in the step of injecting the third dopant (40D1) is the same as the dopant used in the step of injecting the second dopant (DP2), and although they are of the same type (for example, a p-type dopant), dopants of different substances may be used.

[0186] The third dopant injection step (40D1) forms a doping layer 62D' covering the first portion 62C1 and the sixth region 62A of the tenth semiconductor layer 162. The doping layer 62D' is represented as a doping region. The doping layer 62D' is in contact with the first portion 62C1 and the sixth region 62A. Since the doping layer 62D' and the first portion 62C1 and the sixth region 62A contain opposite types of dopants, a depletion layer may be formed between the doping layer 62D' and the first portion 62C1 and the sixth region 62A. By adjusting the process conditions of the dopant injection step (e.g., injection energy), the doping layer 62D' may be formed to be thinner or thicker than illustrated in the drawings. The doping layer 62D' is separated from the upper surface of the tenth semiconductor layer 162 in a direction perpendicular to the upper surface of the insulating layer 14. The doping layer 62D' is separated from the side surface of the tenth semiconductor layer 162 in a direction parallel to the upper surface of the insulating layer 14, i.e., in a lateral direction. The distance from the doping layer 62D' to the upper surface and side surface of the tenth semiconductor layer 162 is adjusted in the process for forming the doping layer 62D' by adjusting the width of the twelfth mask 40M or by adjusting the dopant injection energy, etc.

[0187] Next, as shown in Figure 41A, a 13th mask 41M is formed on the 10th semiconductor layer 162 on which the doping layer 62D' is formed. The material of the 13th mask 41M is the same as, but not limited to, the 11th mask 39M and the 12th mask 40M. The 13th mask 41M is for forming the 2nd region 12B of the 8th optical modulator 1400. In one example, the 13th mask 41M may be formed such that a region of the 10th semiconductor layer 162 corresponding to the diameter of the 2nd region 12B is exposed. That is, the 13th mask 41M is formed such that a region of the 10th semiconductor layer 162 corresponding to the diameter of the 2nd region 12B is limited. After forming the 13th mask 41M, the 4th dopant is injected into the exposed region of the 10th semiconductor layer 162 while the 13th mask 41M is in place (41D1). The step of injecting the fourth dopant (41D1) proceeds under the same conditions as the step of injecting the fourth dopant (DP4) to form the fourth doping layer 12B' in Figure 20, but is not limited to these conditions. The step of injecting the fourth dopant (41D1) forms a doping layer 12B'' on the tenth semiconductor layer 162. The doping layer 12B'' is represented as a doping region. The doping layer 12B'' is doped at the same concentration as the sixth region 62A, and at a higher concentration than the first portion 62C1 of the seventh region 62C and the doping layer 62D'. The diameter and planar shape of the doping layer 12B'' are the same as the diameter and shape of the eighth optical modulator 1400. The doping layer 12B" forms a concentric circle with the sixth region 62A formed below it, and the diameter and planar outline of the doping layer 12B" are the same as those of the sixth region 62A. The doping layer 12B" is formed vertically, separated from the sixth region 62A. A doping layer 62D' exists between the doping layer 12B" and the sixth region 62A. The diameter of the doping layer 12B" is smaller than the diameter of the doping layer 62D'. The doping layers 12B" and 62D' are concentric. The height of the lower boundary of the doping layer 12B" is lower than the height of the upper boundary of the doping layer 62D'. For convenience, the "lower boundary" and "upper boundary" may be expressed as the "bottom surface" and "top surface". The upper boundary (top surface) of the doping layer 12B" coincides with the top surface of the tenth semiconductor layer 162.In other words, the upper surface of the doping layer 12B'' is the upper surface of the tenth semiconductor layer 162.

[0188] As a result, the doping layer 12B" starts from the upper surface of the 10th semiconductor layer 162, passes through the upper boundary of the doping layer 62D', and diffuses to a depth set within the doping layer 62D'. Therefore, the thickness of the doping layer 62D' around the doping layer 12B" is greater than the thickness of the doping layer 62D' between the doping layer 12B" and the 6th region 62A. In other words, a step is formed in the doping layer 62D' while the doping layer 12B" is being formed. The doping layer 12B" is formed with a uniform thickness throughout the entire region. In the subsequent etching process, a portion of the doping layer 12B" becomes the 2nd region 12B of the 8th optical modulator 1400.

[0189] After the doping layer 12B" is formed, the 13th mask 41M is removed.

[0190] On the other hand, in one example, the doping layer 12B'' may be formed such that the height of its upper boundary (upper surface) is the same as the height of the upper boundary (upper surface) of the doping layer 62D', as illustrated in Figure 41B. In this case, the doping layer 12B'' is separated from the upper surface of the tenth semiconductor layer 162.

[0191] Next, as shown in Figure 42, a 14th mask 42M is formed on the doping layer 12B''. The 14th mask 42M is formed to cover the entire upper surface of the doping layer 12B''. The material of the 14th mask 42M is the same as, but not limited to, that of the 10th mask 38M1. The 14th mask 42M is a mask for forming the second portion 62C2 and the third portion 62C3 of the 7th region 62C of the 8th optical modulator 1400. With the formation of the 14th mask 42M, the 10th semiconductor layer 162 surrounding the 14th mask 42M is exposed.

[0192] With the 14th mask 42M in place, the 5th dopant is injected into the exposed region of the 10th semiconductor layer 162 (42D1). The step of injecting the 5th dopant (42D1) is carried out under the same process conditions as the step of injecting the 5th dopant (DP5) in Figure 21, but it may be carried out under different process conditions. The step of injecting the 5th dopant (42D1) forms a doping layer 62C' in the region between the upper surface of the 10th semiconductor layer 162 and the doping layer 62D', and in the region between the side surface of the 10th semiconductor layer 162 and the doping layer 62D'. The doping layer 62C' is formed with the same doping concentration as the first portion 62C1 and doping layer 62D', and with a lower concentration than the sixth region 62A and doping layer 12B''. The doping layer 62C' corresponds to the second and third portions 62C2 and 62C3 of the seventh region 62C of the tenth semiconductor layer 162 of the eighth optical modulator 1400. The doping layer 62C' covers the upper surface of the doping layer 62D' surrounding the doping layer 12B'' and covers the sides of the doping layer 62D'.

[0193] After forming the doping layer 62C', the 14th mask 42M is removed.

[0194] Next, as shown in Figure 43, a 15th mask 43M is formed on the doping layer 62C' of the 10th semiconductor layer 162. The 15th mask 43M is a mask used to prevent etching of a predetermined area during the etching process. In one example, the material of the 15th mask 43M is a photosensitive film such as a photoresist, but is not limited to this. The 15th mask 43M is formed to cover the portion corresponding to the 3rd portion 62C3 of the 7th region 62C of the 10th semiconductor layer 162 of the 8th optical modulator 1400. In other words, the 15th mask 43M is formed to limit the portion of the doping layer 62C" corresponding to the third portion 62C3, leaving the remaining area of ​​the upper surface of the 10th semiconductor layer 162 exposed. With the 15th mask 43M in place, the exposed area of ​​the upper surface of the 10th semiconductor layer 162 is etched. In one example, the etching proceeds by dry etching, but is not limited to this. Such etching can be carried out until the doping layer 62D' is exposed, as illustrated in Figure 44. In one example, the etching is carried out until the upper boundary (upper surface) of the doping layer 62D' is exposed. During etching, the doping layer 62C" between the 15th mask 43M and the doping layer 12B" is etched, and the portion of the doping layer 12B" that is higher than the upper boundary of the doping layer 62D' is also etched. Etching creates a recess 44R in the tenth semiconductor layer 162, as shown in Figure 44, where the bottom surfaces are the surface (e.g., top surface) of the doping layer 62D' and the surface (e.g., top surface) of the doping layer 12B''. The depth of the recess 44R is the same as the thickness of the doping layer 62C' between the fifteenth mask 43M and the doping layer 62D'. The formation of the recess 44R creates a step between the top surface of the doping layer 62C' and the top surface of the doping layer 62D'.

[0195] Figure 45 shows the result after etching and removal of the 15th mask 43M.

[0196] The horizontal portion of the doping layer 62C' covering the upper surface of the doping layer 62D' becomes the third portion 62C3 of the seventh region 62C of the tenth semiconductor layer 162 of the eighth optical modulator 1400. The vertical portion of the doping layer 62C' covering the side surface of the doping layer 62D' becomes the second portion 62C2 of the seventh region 62C of the tenth semiconductor layer 162 of the eighth optical modulator 1400. Therefore, in Figure 45, the first portion 62C1 and the doping layer 62C' become the seventh region 62C of the tenth semiconductor layer 162 of the eighth optical modulator 1400.

[0197] Next, as shown in Figure 46, a 16th mask 47M is formed on the doping layer 12B" and the doping layer 62C'. The 16th mask 47M is an etching mask, similar to the 15th mask 43M. The 16th mask 47M is formed to cover the entire upper surface of the doping layer 12B" and the entire upper surface of the doping layer 62C'. As the 16th mask 47M is formed, the upper surface of the doping layer 62D' is exposed. With the 16th mask 47M in place, the exposed upper surface of the doping layer 62D' is etched. This etching is carried out until a depth equivalent to the thickness of the doping layer 12B" is formed in the doping layer 62D'. As a result of this etching, the side surface of the doping layer 12B" is completely exposed, as illustrated in Figure 47. As a result of this etching, the step difference between the doping layer 62D' and the doping layer 62C' becomes even larger. The doping layer 62D' also has a step difference. In other words, etching creates upper surfaces of different heights on the doping layer 62D', while also creating a step between the two upper surfaces. Specifically, as a result of etching, the doping layer 62D' includes an upper surface 62S2 that is at the same height as the upper surface 62S1 covered by the doping layer 62C' and the bottom surface of the doping layer 12B'', and is lower than the upper surface 62S1. After etching, the 16th mask 47M is removed.

[0198] Figure 48 shows the configuration after the 16th mask 47M has been removed.

[0199] Next, as shown in Figure 49, a 17th mask 49M is formed to cover the doping layers 12B”, 62C', and 62D'. The 17th mask 49M is formed to cover the entire upper surface of doping layer 62C' and the entire upper surface 62S2 of doping layer 62D' between doping layer 62C' and doping layer 12B”. The 17th mask 49M forms a concentric circle with doping layer 12B”, covering only the edges of doping layer 12B”, leaving the inner region of the edges of doping layer 12B”, exposed. The 17th mask 49M is an etching mask, similar to the 16th mask 47M.

[0200] With the 17th mask 49M in place, the exposed region of the doping layer 12B" is etched. This etching is carried out until the doping layer 12B" and the doping layer 62D' below it are sequentially etched, and until the 6th region 62A is exposed. As shown in Figure 50, this etching exposes the inner region of the edge of the 6th region 62A. That is, the upper inner surface of the edge of the 6th region 62A is exposed. After etching, the planar shapes of the doping layer 62D' and the doping layer 12B" become ring-shaped. The ring width of the doping layer 62D' and the ring width of the doping layer 12B" are different from each other. The ring-shaped doping layer 62D' remaining after etching corresponds to the 8th region 62D of the 10th semiconductor layer 162 of the 8th optical modulator 1400. The horizontal portion of the doping layer 62D' corresponds to the first portion 62D1 of the eighth region 62D, and the vertical portion of the doping layer 62D' corresponds to the second portion 62D2 of the eighth region 62D. Furthermore, the doping layer 12B'' remaining after etching corresponds to the second region 12B of the tenth semiconductor layer 162 of the eighth optical modulator 1400. After etching, the seventeenth mask 49M is removed.

[0201] Figure 51 shows the results after removing the 17th mask, 49M.

[0202] Next, as shown in Figure 52, the first electrode 16 is formed on the exposed region of the sixth region 62A, and the second electrode 18 is formed on the doping layer 12B''.

[0203] In this way, the eighth optical modulator 1400 is formed.

[0204] Next, an example of the manufacturing process for the seventh optical modulator 1300 shown in Figure 15 will be described.

[0205] First, the process is carried out according to the steps illustrated in Figures 38 to 44. During this process, the doping layer 12B" may be formed in the form illustrated in Figure 41B. In addition, during the etching stage in which the recess 44R in Figure 44 is formed, the etching is further advanced to form a step in the doping layer 62D' itself, as illustrated in Figure 53. Taking this into consideration, during the stage in which the doping layer 12B" is formed, the thickness of the doping layer 12B" is made greater than the height of the step formed in the doping layer 62D' itself. This allows a doping layer 12B" of a certain thickness to remain even after the step is formed in the doping layer 62D' itself.

[0206] After forming a step in the doping layer 62D' itself, the etching process of the doping layer 12B'' and the doping layer 62D', and the process of forming electrodes on the sixth region 62A exposed after etching and on the remaining doping layer 12B'' after etching are carried out according to Figures 49 to 52.

[0207] Figures 54 to 64 show, step by step, a method for manufacturing an optical modulator according to an exemplary embodiment.

[0208] The manufacturing method illustrated in Figures 54 to 64 is the manufacturing method for the first optical modulator 20 illustrated in Figures 1 to 3. In the following description, the same reference numbers used in the description of the first optical modulator 20 and the above manufacturing method refer to the same components, and detailed explanations thereof are omitted.

[0209] First, as shown in Figure 54, a second semiconductor layer 12 is formed on the insulating layer 14. An 18th mask 54M is formed on the second semiconductor layer 12, covering (limiting) the central portion of the second semiconductor layer 12. The formation location, material, and role of the 18th mask 54M are the same as those of the 7th mask 22M in Figure 27. With the 18th mask 54M in place, a first dopant is injected into the second semiconductor layer 12 (54D1). The injection of the first dopant (54D1) forms a third region 12C on the second semiconductor layer 12. The injection of the first dopant (54D1) is the same as the injection of the first dopant (22D) described in Figure 27. The formation location and process of the third region 12C are the same as those of the third region 42C in Figure 27.

[0210] After forming the third region 12C, as illustrated in Figure 55, the second dopant is injected into the exposed region of the second semiconductor layer 12 while maintaining the 18th mask 54M (55D1). In one example, the step of injecting the second dopant (55D1) is the same as the second dopant injection step (23D) described in Figure 28. The step of injecting the second dopant (55D1) can form a doping layer 12D' on the second semiconductor layer 12. The doping layer 12D' may be represented as a doping region. The location of the doping layer 12D' corresponds to the fourth region 12D of the first optical modulator 20. In a subsequent step, the morphology of the doping layer 12D' changes to the morphology of the fourth region 12D. The formation location and formation process of the doping layer 12D' are the same as those of the fourth region 42D in Figure 28. In one example, during the stage of forming the doping layer 12D', the thickness of the doping layer 12D' in the direction perpendicular to the upper surface of the insulating layer 14 is formed differently from the thickness of the third region 12C. For example, the thickness of the doping layer 12D' is formed to be thicker than that of the third region 12C. In the subsequent etching process, the thickness of a portion of the doping layer 12D' becomes thinner than its initial thickness so that the doping layer 12D' becomes the fourth region 12D.

[0211] Since the dopants injected into the third region 12C and the doping layer 12D' are of opposite types, a depletion layer can be formed between the third region 12C and the doping layer 12D' by a PN junction.

[0212] After the doping layer 12D' is formed, the 18th mask 54M is removed.

[0213] Next, as shown in Figure 56, a 19th mask 56M is formed on the second semiconductor layer 12. The 19th mask 56M is a mask made of the same material as the 18th mask 54M, but it may be a mask made of a different material. The 19th mask 56M is a mask for forming a part of the doped first region 12A of the first optical modulator 20, i.e., a wide portion. The 19th mask 56M is formed only on the doping layer 12D' and is formed to cover the entire upper surface of the doping layer 12D'. The 19th mask 56M forms concentric circles with the third region 12C and the doping layer 12D'. Therefore, the 19th mask 56M can expose the inner portion of the doping layer 12D' of the second semiconductor layer 12.

[0214] With the 19th mask 56M in place, the third dopant is injected into the exposed portion of the second semiconductor layer 12 (56D1). The step of injecting the third dopant (56D1) is the same as the step of injecting the third dopant (24D) illustrated in Figure 29, and is carried out under the same process conditions as the step of injecting the third dopant (24D), although it may be carried out under different process conditions.

[0215] In the third dopant injection step (56D1), a doping layer 12A' is formed on the second semiconductor layer 12, as shown in Figure 57. The doping layer 12A' becomes the first part of the first region 12A of the first optical modulator 20. That is, the formation position and width of the doping layer 12A' correspond to the formation position and width of the wider portion of the first region 12A of the first optical modulator 20. In one example, the doping layer 12A' is formed at the same height and thickness as the third region 12C, but is not limited to this. After the doping layer 12A' is formed, the 19th mask 56M is removed.

[0216] Next, as illustrated in Figure 58, a 20th mask 58M is formed on the second semiconductor layer 12. The 20th mask 58M is formed to cover the entire upper surface of the doping layer 12D' and to cover a portion of the second semiconductor layer 12 inside the doping layer 12D'. The 20th mask 58M is a mask for forming the second portion of the first region 12A of the first optical modulator 20. That is, the 20th mask 58M is a mask for forming the narrow portion of the first region 12A of the first optical modulator 20. Therefore, the 20th mask 58M may be formed so that the upper surface of the second semiconductor layer 12 corresponding to the narrow portion of the first region 12A of the first optical modulator 20 is exposed. The 20th mask 58M forms concentric circles with the doping layer 12D'. In one example, the material of the 20th mask 58M is the same as the material of the 19th mask 56M, but is not limited to this.

[0217] With the 20th mask 58M in place, the fourth dopant is injected into the exposed region of the second semiconductor layer 12 (58D1). In one example, the step of injecting the fourth dopant (58D1) is carried out under the same process conditions as the step of injecting the fourth dopant (26D) in Figure 31. However, the type of dopant used in the step of injecting the fourth dopant (58D1) illustrated in Figure 58 may be the opposite of the type of dopant used in the step of injecting the fourth dopant (26D) in Figure 31. For example, the dopant used in the step of injecting the fourth dopant (58D1) illustrated in Figure 58 is an N-type dopant, and the dopant used in the step of injecting the fourth dopant (26D) in Figure 31 is a P-type dopant.

[0218] As a result, the substance and type of dopant used in the step of injecting the fourth dopant exemplified in Figure 58 (58D1) are the same as, but not limited to, the substance and type of dopant used in the step of injecting the third dopant exemplified in Figure 56 (56D1).

[0219] In the step of injecting the fourth dopant (58D1), a doping layer 12A” is formed on the second semiconductor layer 12, as illustrated in Figure 59. The thickness of the doping layer 12A” is formed to be the same as or substantially the same as the thickness of the doping layer 12D’. The two doping layers 12A and 12A”, which are sequentially stacked, are concentric. In one example, the thickness of the doping layer 12A” is greater than the thickness of the doping layer 12A’ below it, but this is not limited to this. Also, the width of the doping layer 12A” is narrower than the width of the doping layer 12A’ below it. The doping layers 12A” and 12D’ are formed separated from each other. The doping layer 12A'' corresponds to the narrow portion of the first region 12A of the first optical modulator 20. Since the dopant material and type injected into the two doping layers 12A' and 12A'' are identical, the two doping layers 12A' and 12A'' constitute a single doping layer or doping region. That is, the region in the second semiconductor layer 12 containing the two doping layers 12A' and 12A'' corresponds to the first region 12A of the first optical modulator 20.

[0220] In one example, during the process of forming doping layers 12A', 12A'', 12D' and doping regions 12C, the injection energy into the dopant is adjusted to control the thickness of each doping layer 12A', 12A'', 12D' and doping region 12C.

[0221] After forming the doping layer 12A'', the 20th mask 58M is removed.

[0222] Next, as shown in Figure 60, a 21st mask 60M is formed on the second semiconductor layer 12. The material of the 21st mask 60M is the same as, but not limited to, the 8th mask 24M or the 20th mask 58M in Figure 27. The 21st mask 60M is a mask for forming a doping region corresponding to the second region 12B of the first optical modulator 20. Therefore, the 21st mask 60M can be formed to limit the upper surface of the second semiconductor layer 12 corresponding to the second region 12B of the first optical modulator 20. As a result, after the 21st mask 60M is formed, the upper surface of the second semiconductor layer 12 corresponding to the second region 12B of the first optical modulator 20 is exposed. In one example, the 21st mask 60M is formed only on the upper surfaces of the doping layer 12A'' and the doping layer 12D'. The 21st mask 60M is formed to cover the entire upper surfaces of the two doping layers 12A'' and 12D'. As the 21st mask 60M is formed, the region between the two doping layers 12A' and 12D' in the second semiconductor layer 12 is exposed.

[0223] With the 21st mask 60M in place, the 5th dopant is injected into the 2nd semiconductor layer 12 (60D1). In one example, the step of injecting the 5th dopant (60D1) is carried out under the same process conditions as the step of injecting the 4th dopant (26D) in Figure 31. The step of injecting the 5th dopant (60D1) can form a 2nd region 12B in the 2nd semiconductor layer 12 between the two doping layers 12D' and 12A'', as shown in Figure 61. In one example, the 2nd region 12B is formed to the same or substantially the same thickness as the doping layer 12A'. Since the type of dopant injected into the 2nd region 12B and the type of dopant injected into the doping layers 12A' and 12A'' are opposite to each other, a depletion layer is formed between the 2nd region 12B and the two doping layers 12A' and 12A''. After the 2nd region 12B' is formed, the 21st mask 60M is removed.

[0224] After removing the 21st mask 60M, a 22nd mask 62M is formed on the doping layer 12D' of the second semiconductor layer 12, as shown in Figure 62. The 22nd mask 62M forms a concentric circle with the doping layer 12D'. The boundary of the edge of the 22nd mask 62M is formed to coincide with the boundary of the edge of the doping layer 12D'. That is, the outer diameter of the 22nd mask 62M is the same as or substantially the same as the outer diameter of the doping layer 12D'. The inner diameter of the 22nd mask 62M is larger than the inner diameter of the doping layer 12D'. The 22nd mask 62M is separated from the inner boundary (edge) of the doping layer 12D'. The planar shape of the 22nd mask 62M is ring-shaped and has a predetermined ring width. Here, "ring width" is the width measured in the radial direction. The 22nd mask 62M is an etching mask used for etching to limit the second portion 12D2 of the fourth region 12D of the first optical modulator 20. In one example, the 22nd mask 62M is a photosensitive film mask, but is not limited to this.

[0225] The portion covered by the 22nd mask 62M in the doping layer 12D' determines the upper surface of the second portion 12D2 of the fourth region 12D of the first optical modulator 20, and also determines the ring width of the second portion 12D2. Therefore, these points are taken into consideration when forming the 22nd mask 62M on the doping layer 12D'.

[0226] As this 22nd mask 62M is formed, the entire upper surface of the doping layer 12A'' of the second semiconductor layer 12 and the entire upper surface of the second region 12B are exposed, and a portion of the upper surface of the doping layer 12D' adjacent to the second region 12B is also exposed.

[0227] With the 22nd mask 62M in place, the exposed region of the second semiconductor layer 12 is etched. This etching is performed to reduce the surface height of the exposed region of the second semiconductor layer 12. As a result of this etching, the thickness of the exposed region of the second semiconductor layer 12 becomes thinner than that of the unexposed region. That is, as illustrated in Figure 63, the thickness of the second region 12B and the doping layer 12A'' and the thickness of the exposed portion of the doping layer 12D' become thinner than the thickness of the portion of the doping layer 12D' covered by the 22nd mask 62M. This forms a recess 63R in the second semiconductor layer 12, as illustrated in Figure 63. In one example, the depth of the recess 63R, i.e., the thickness of the exposed portion of the second semiconductor layer 12 remaining after etching, can be adjusted by adjusting the etching process conditions (e.g., etching time, etching rate, etc.).

[0228] As a result of etching, as illustrated in Figure 63, two upper surfaces 2S1 and 2S2 of different heights appear on the doping layer 12D', as illustrated in Figure 2. Consequently, etching creates a step in the doping layer 12D' corresponding to the step 15 in Figure 2. After etching, the height of the upper surfaces of the second region 12B and the doping layer 12A'' is the same as the height of the upper surface 2S1 of the doping layer 12D'.

[0229] The combined region of the doping layers 12A' and 12A'' after etching is the same or substantially the same region as the first region 12A of the first optical modulator 20, and the doping layer 12D' is the same or substantially the same region as the fourth region 12D of the first optical modulator 20. That is, the horizontal and vertical portions of the doping layer 12D' after etching correspond to the first portion 12D1 and the second portion 12D2 of the fourth region 12D of the first optical modulator 20, respectively.

[0230] After etching, remove the 22nd mask 62M.

[0231] Next, as illustrated in Figure 64, the first optical modulator 20 is formed by forming the first electrode 16 on the doping layer 12A'' and the second electrode 18 on the second region 12B. The first and second electrodes 16 and 18 are formed spaced apart from each other. The first and second electrodes 16 and 18 are concentric. The first and second electrodes 16 and 18, the doping layer 12A'' and the second region 12B are concentric. The height of the upper surfaces of the first and second electrodes 16 and 18 is the same as or different from the height of the upper surface 2S2 of the doping layer 12D'.

[0232] In the various manufacturing methods described above as an example, optical waveguides may be formed on the SOI substrate while semiconductor layers 12, 42, 122, and 162 are formed on the SOI substrate. For example, one optical waveguide 10 or two optical waveguides 13A and 13B may be formed on the SOI substrate simultaneously with the semiconductor layers 12, 42, 122, and 162.

[0233] Next, we will explain the simulations conducted to confirm the effects of having a step in the high-doping region of the optical modulator and not having a step, and the results thereof.

[0234] Figure 65 is a cross-sectional view showing the first model (a) and the second model (b) used in the simulation. Both the first model (a) and the second model (b) show only the right-hand portion of the cross-section of the optical modulator.

[0235] Model 1(a) shows an exemplary optical modulator in which there is a step between the first doping region HD1, which is a high-doping region, and the second doping region HD2. In Model 1(a), reference numbers LD3 and LD4 represent the third doping region and the fourth doping region, which are low-doping regions, respectively. In both Model 1(a) and Model 2(b), reference number 33D represents the depletion layer.

[0236] Model 2(b) shows an existing optical modulator where there is no step between the first doping region HD1 and the second doping region HD2.

[0237] In the simulation, silicon (Si) layers were used as the semiconductor layers where the first to fourth doping regions HD1, HD2, LD3, and LD4 were formed. The first doping region HD1, which is highly doped, and the third doping region LD3, which is less doped, are regions doped with an n-type dopant, and phosphorus (P) was used as the n-type dopant. The second doping region HD2, which is highly doped, and the fourth doping region LD4, which is less doped, are regions doped with a p-type dopant, and boron (B) was used as the p-type dopant. Furthermore, the first and second doping regions HD1 and HD2 were each 1 × 10⁻⁶. 20 / cm 3 The drug is doped to the following concentration, and the third and fourth doping regions LD3 and LD4 are 3 × 10⁻⁶ each. 18 / cm 3 The drug was doped to achieve the specified concentration.

[0238] In the simulation, resistance (R), capacitance (C), and electrical modulation bandwidth (EBW) were measured while applying a voltage between the first doping region HD1 and the second doping region HD2.

[0239] Table 1 below summarizes the simulation results.

[0240] [Table 1]

[0241] Referring to Table 1, in the case of Model 1 (a), the number of junctions between the first and second doping regions HD1 and HD2, which are high-doping regions, is reduced compared to Model 2 (b), and the resistance increases slightly. However, the capacitance of Model 1 (a) is much smaller than that of Model 2 (b). The capacitance difference between Model 1 (a) and Model 2 (b) is much larger than the resistance difference between Model 1 (a) and Model 2 (b). As a result, the RC delay of Model 1 (a) is smaller than the RC delay of Model 2 (b), and the EBW of Model 1 (a) increases significantly compared to Model 2 (b). These results show that Model 1 (a) is far more advantageous from the viewpoint of high-speed optical modulation.

[0242] The optical modulator according to the exemplary embodiment described above can be used in a variety of electronic devices, but is particularly applicable to optical interconnects, optical computing, and optical communications that require high-speed optical modulation.

[0243] Figure 66 is a schematic block diagram showing an example of such an electronic device. The electronic device in Figure 66 is an optical transmitter.

[0244] Referring to Figure 66, the electronic device 300 includes an electric integrated circuit (EIC) 300A and a photonic integrated circuit (PIC) 300B.

[0245] The electronic integrated circuit unit 300A includes a multiplexer (MUX) 310 into which a plurality of electrical signals ES1 can be input, and a first amplifier 320 that amplifies the signal output from the multiplexer 310. The plurality of electrical signals ES1 are different individual electrical signals from each other, but are not limited thereto. The multiplexer 310 uses frequency division multiplexing (FDM), time division multiplexing (TDM), or code division multiplexing (CDM) technology according to a multiplexing method. The electrical signal ES2 amplified and output by the first amplifier 320 is transmitted (input) to the photonic integrated circuit unit 300B. The electronic integrated circuit unit 300A may further include other elements.

[0246] The photonic integrated circuit 300B includes a light source 330, an optical modulator 340, and a second amplifier 350. The photonic integrated circuit 300B may further include other elements. The optical modulator 340 is one of the optical modulators illustrated in Figures 1 to 17, or one of the optical modulators that can be inferred from a combination of the optical modulators illustrated in Figures 1 to 17. The light source 330 and the second amplifier 350 are connected to an optical waveguide 360. Along the optical waveguide 360, the optical modulator 340 is positioned between the light source 330 and the second amplifier 350. Light emitted from the light source 330 is transmitted to the second amplifier 350 via the optical waveguide 360. The light source 330 and the second amplifier 350 are optically coupled to the optical waveguide 360. Such coupling may or may not be limited to an optical coupler. The light source 330 includes a light source that emits laser light (for example, infrared laser light), which is continuous laser light but not limited to it. The light emitted from the light source 330 and transmitted through the optical waveguide 360 ​​may, as it passes through the optical modulator 340, have a portion of its light transmitted to a microdisk 370 located adjacent to the optical waveguide 360. The light transmitted to the microdisk 370 is in fundamental mode and travels along the edge (low-doping region) of the microdisk 370 in whispering gallery mode. In one example, the microdisk 370 includes one of the semiconductor layers 12, 32, 42, 82, 102, 122, 142, 152, or 162 of the optical modulator illustrated in Figures 1 to 17. The electrical signal ES2 output from the first amplifier 320 of the electronic integrated circuit section 300A becomes the voltage applied to the microdisk 370. In other words, the electrical signal ES2 output from the first amplifier 320 becomes the voltage applied to the first electrode layer (e.g., 16 in Figure 2) and the second electrode layer (e.g., 18 in Figure 2) located on the highly doped region of the microdisk 370.

[0247] As a result, the refractive index of the edge of the microdisk 370 changes due to the electrical signal ES2 applied from the first amplifier 320 to the microdisk 370, and the light traveling along the edge of the microdisk 370 is modulated. The light modulated in this way is transmitted to the optical waveguide 360, amplified by the second amplifier 350, and then output.

[0248] In one example, the optical modulator 340 of the photonic integrated circuit section 300B may further include an optical waveguide corresponding to the second optical waveguide 13B illustrated in FIG. 17.

[0249] Based on the above-described exemplary embodiments, the following various optical modulators, manufacturing methods, and electronic devices can be analogized.

[0250] An optical modulator according to one example includes a first semiconductor layer, a second semiconductor layer provided in the form of a microdisk on the first semiconductor layer, including a high-doping region with a relatively high doping concentration and a low-doping region with a relatively low doping concentration, a first optical waveguide disposed adjacent to the second semiconductor layer, and a first electrode layer and a second electrode layer provided separately from each other on the high-doping region. The second semiconductor layer includes at least one recess, The second semiconductor layer has at least one step due to the recess, The high-doping region, the low-doping region, and the recess are concentric.

[0251] In one example, the second semiconductor layer includes a first recess, the bottom surface of the first recess includes the upper surface of the high-doping region and the upper surface of the low-doping region, the side surface of the first recess includes the inner surface of the low-doping region, and a first step exists in the low-doping region due to the first recess.

[0252] In one example, the high-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant; the low-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant; the bottom surface of the first recess includes the upper surfaces of the N-doping region and the P-doping region of the high-doping region, and the first upper surface of the P-doping region of the low-doping region; the side surface of the first recess includes the inner surface of the P-doping region of the low-doping region; and the first step corresponds to the height difference between the first upper surface of the P-doping region of the low-doping region and a second upper surface located higher than the first upper surface.

[0253] In one example, the high-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant; the low-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant; the bottom surface of the first recess includes the top surface of the N-doping region and the top surface of the P-doping region of the high-doping region, and the first top surface of the P-doping region of the low-doping region; the side surface of the first recess includes the inner surface of the P-doping region and the inner surface of the N-doping region of the low-doping region; and the first step corresponds to the height difference between the first top surface of the P-doping region of the low-doping region and the top surface of the N-doping region of the low-doping region.

[0254] In one example, the N-doping region of the low-doping area is located between the P-doping region and the first semiconductor layer, completely surrounding the P-doping region of the low-doping area around the first recess, and the outer surface of the N-doping region of the low-doping area is the side surface of the second semiconductor layer.

[0255] In one example, the P-doping region and the N-doping region of the high-doping area are concentric, there is a step between the center and the edge of the N-doping region of the high-doping area, the thickness of the edge of the N-doping region of the high-doping area is thinner than the thickness of the center, the P-doping region of the high-doping area overlaps with the edge of the N-doping region of the high-doping area, and the upper surface of the P-doping region and the upper surface of the N-doping region of the high-doping area form the same surface.

[0256] In one example, the second semiconductor layer is located inside the first recess and includes a second recess that forms a concentric circle with the first recess, the side and bottom surfaces of the second recess include the surface of a highly doped region, a second step exists inside the first recess due to the second recess, the first step and the second step are spaced apart from each other in a horizontal direction parallel to the upper surface of the first semiconductor layer, and the first step and the second step are at different heights.

[0257] In one example, the high-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant, the N-doping region and the P-doping region are concentric, the bottom surface of the second recess is the top surface of the N-doping region, the side surface of the second recess includes the side surface of the P-doping region, and the second step corresponds to the height difference between the top surface of the N-doping region and the top surface of the P-doping region of the high-doping region.

[0258] In one example, the high-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant, the N-doping region and the P-doping region are concentric, the N-doping region and the P-doping region are separated from each other in a direction perpendicular to the upper surface of the first semiconductor layer, the bottom surface of the second recess is the upper surface of the N-doping region, the side surface of the second recess includes the side surface of the P-doping region, and the second step corresponds to the height difference between the upper surface of the N-doping region and the upper surface of the P-doping region of the high-doping region.

[0259] In one example, a portion of the low-doping region exists between the N-doping region and the P-doping region, which are separated from each other, and the side of the second recess is composed of a portion of the low-doping region and a portion of the P-doping region.

[0260] In one example, the low-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant, the N-doping region and the P-doping region of the low-doping region are concentric, the bottom surface of the first recess includes the top surface of the P-doping region of the low-doping region, and the inner surface of the first recess includes the side surface of the P-doping region of the low-doping region.

[0261] In one example, the P-doping region in the low-doping area includes three regions with different thicknesses and has a cross-sectional shape in which the thickness decreases towards the center of the second semiconductor layer. In another example, the P-doping region in the low-doping area includes steps with different physical thicknesses and steps with a constant physical thickness but different doping region thicknesses. In yet another example, the P-doping region in the low-doping area includes regions with a constant physical thickness but different doping region thicknesses.

[0262] In one example, the aspect of the first recess includes the inner aspect of the P-doping area in the low-doping region and the inner aspect of the N-doping area in the low-doping region.

[0263] In one example, the N-doping region of the low-doping area is located between the first semiconductor layer and the P-doping region of the low-doping area, completely surrounding the P-doping region of the low-doping area around the first recess, and the outer surface of the N-doping region of the low-doping area is the side surface of the first semiconductor layer.

[0264] In one example, the second semiconductor layer includes a first recess, the bottom surface of the first recess includes the top surface of the low-doping region, the side surface of the first recess includes the inner surface of the low-doping region, and the first recess creates a first step in the low-doping region.

[0265] In one example, the second semiconductor layer is located inside the first recess and includes a second recess that forms a concentric circle with the first recess, the bottom surface of the second recess includes the surface of a high-doping region, the side surface of the second recess includes the inner surface of a low-doping region, a second step exists inside the first recess due to the second recess, the first step and the second step are separated from each other in a horizontal direction parallel to the upper surface of the first semiconductor layer, and the first step and the second step are at different heights. In one example, the high-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant, the N-doping region and the P-doping region are concentric, the N-doping region and the P-doping region are separated from each other in a direction perpendicular to the upper surface of the first semiconductor layer, the bottom surface of the second recess is the upper surface of the N-doping region, the P-doping region is on the bottom surface of the first recess, the inner surface of the P-doping region and the side surface of the second recess form the same surface, and the second step corresponds to the height difference between the upper surface of the N-doping region of the high-doping region and the bottom surface of the first recess. In one example, the low-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant, the N-doping region and the P-doping region of the low-doping region are concentric, the bottom surface of the first recess includes the top surface of the P-doping region of the low-doping region, and the inner surface of the first recess includes the side surface of the P-doping region of the low-doping region. In one example, the side surface of the first recess includes the inner surface of the P-doping region of the low-doping region and the inner surface of the N-doping region of the low-doping region. In one example, the N-doping region of the low-doping region is located between the first semiconductor layer and the P-doping region of the low-doping region, completely surrounding the P-doping region of the low-doping region around the first recess, and the outer surface of the N-doping region of the low-doping region is the side surface of the first semiconductor layer. In one example, the N-doping region of the high-doping area, the P-doping region of the high-doping area, and the P-doping region of the low-doping area are arranged to overlap each other around the second recess.

[0266] In one example, the second semiconductor layer includes a first recess. The side surface and the bottom surface of the first recess include the surface of the highly doped region, and there is a first step in the highly doped region due to the first recess. In one example, the highly doped region includes an N-doped region into which an N-type dopant is implanted and a P-doped region into which a P-type dopant is implanted. The bottom surface of the first recess includes the upper surface of the N-doped region, the side surface of the first recess includes the side surface of the P-doped region, and the N-doped region and the P-doped region are provided to overlap each other around the first recess. In one example, in plan view, the lowly doped region is provided to completely surround the highly doped region. The lowly doped region includes an N-doped region into which an N-type dopant is implanted and a P-doped region into which a P-type dopant is implanted. The N-doped region and the P-doped region of the lowly doped region are sequentially arranged in a direction perpendicular to the upper surface of the first semiconductor layer. In one example, the P-doped region of the lowly doped region is provided to cover the vertical boundary and the lateral boundary of the N-doped region, and the side surface of the P-doped region of the lowly doped region is the outer surface of the second semiconductor layer. In one example, the N-doped region and the P-doped region are provided to overlap each other around the first recess.

[0267] In one example, the second semiconductor layer includes a first recess, the bottom surface of the first recess includes the top surface of the first doping region in the high-doping region, the side surface of the first recess includes the side surface of the low-doping region and the side surface of the second doping region in the high-doping region, the first doping region and the second doping region are separated from each other, the first doping region, the second doping region and the first recess are concentric, and a step exists between the top surface of the first doping region and the top surface of the second doping region due to the first recess. In one example, the first doping region and the second doping region include opposite types of dopants, are separated from each other in a direction perpendicular to the top surface of the first semiconductor layer, and the outer diameter of the first doping region and the inner diameter of the second doping region are the same. In one example, the second doping region is provided such that a step is formed in the low-doping region. In one example, the low-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant, and the N-doping region and the P-doping region are arranged sequentially in a direction perpendicular to the upper surface of the first semiconductor layer. In one example, the P-doping region is provided so as to cover the vertical and lateral boundaries of the N-doping region, and the side surface of the P-doping region is the outer surface of the second semiconductor layer.

[0268] In one example, the optical modulator further includes a second optical waveguide separated from the second semiconductor layer, the second semiconductor layer being located between the first optical waveguide and the second optical waveguide.

[0269] One example of a method for manufacturing an optical modulator is: The steps include forming a second semiconductor layer in the form of a microdisk on a first semiconductor layer, The steps include forming a circular first doping region in a portion of the second semiconductor layer, The steps include forming a second doping region in a second semiconductor layer surrounding the first doping region, creating a concentric circle with the first doping region, so that the second doping region surrounds the first doping region on a plane, The steps include forming a first step in one of the doping areas, the first and second doping areas, The method includes the step of forming an electrode layer on a first doping region where the doping concentration is higher than that of the second doping region.

[0270] In one example, the first step is formed in the first doping region. In one example, the manufacturing method further includes the step of forming a second step in the second doping region.

[0271] In one example, the step of forming the second doping area is: The first doping layer is formed, The steps include forming a second doping layer on the first doping layer, including a second step, The process further includes the step of forming a third doping layer that covers the outer portion of the second step of the second doping layer and comes into contact with the first doping layer, The first and third doping layers contain the same type of dopant.

[0272] An example of an electronic device is: Light source and An optical waveguide through which light emitted from a light source is transmitted, A semiconductor layer is provided adjacent to the optical waveguide, in the form of a microdisk, and includes multiple doping regions. The system includes an amplifier provided for amplifying light transmitted through an optical waveguide, The semiconductor layer includes first and second doping regions located in the center of a plurality of doping regions. Of the multiple doping areas, the remaining doping areas, excluding the first and second doping areas, are arranged around the first and second doping areas. The first and second doping regions are regions doped with opposite types of dopants. The doping concentrations in the first and second doping regions are higher than those in the remaining doping regions. The semiconductor layer includes at least one step.

[0273] Although many details are specifically described in the above description, these should not be interpreted as limiting the scope of the invention, but rather as examples of preferred embodiments. Therefore, the scope of the invention should be defined not by the described embodiments, but by the technical idea described in the claims. [Industrial applicability]

[0274] The disclosed optical modulator can be incorporated into a photonic integrated circuit (PIC) containing a silicon (Si) substrate. The disclosed optical modulator is applicable to devices that incorporate a PIC or devices that require optical modulation, such as optical interconnects, optical computing, and optical communications where high-speed optical modulation is required. [Explanation of symbols]

[0275] 2S1, 2S2, 2S3: First to third upper surfaces 9R1-9R3: Width 10: Optical waveguide 12: Second semiconductor layer 12A: 1st area 12A', 12A'': Doping layer 12B': Fourth doping layer 12C': First doping layer 12D': Second doping layer 12C”: Fifth doping layer 12B, 42B: 2nd area 12B: Doping layer 12C, 42C: Third area 12C1-12C3: Parts 1 to 3 12D, 42D: 4th area 12D1, 12D2: Parts 1 and 2 12R1, 12R2, 12R3: First to third radii 12D': Doping layer 13: Recess 13A: 1st optical waveguide 13B: Second optical waveguide 14: Insulating layer 15: 1st step (physical step) 15': Non-physical step 16, 18: First and second electrode layers 19S: Upper surface 20: First Optical Modulator 22: First semiconductor layer 22D: First dopant injection process 22M: Mask No. 7 23D: Second dopant injection process 24M: Mask No. 8 24D: Third dopant injection process 25: Second step 26D: Fourth dopant injection process 28M: 9th Mask 32: Third semiconductor layer 32A: 5th area 33D: Depletion layer 38D1: First dopant injection process 38M: 10th Mask 39D1: Second dopant injection process 39M: 11th Mask 40: Third Optical Modulator 40D1: Third dopant injection process 40M: Mask No. 12 41D1: Fourth dopant injection process 41M: 13th Mask 42: Fourth semiconductor layer 42A:First area 42B': Doping layer 42M: Mask No. 14 42D1: Fifth dopant injection process 43: Second recess 43M: Mask No. 15 44R: Recess 47M: Mask No. 16 49M: Mask No. 17 52: Eighth semiconductor layer 54D1: First dopant injection process 54M: Mask No. 18 55D1: Second dopant injection process 56D1: Third dopant injection process 56M: Mask No. 19 58D1: Fourth dopant injection process 58M: Mask No. 20 60D1: Fifth dopant injection process 60M: Mask No. 21 62A: 6th area 62C:7th area 62C1, 62C2, 62C3: Parts 1 to 3 62C': Doping layer 62D: 8th area 62D': Doping layer (doping region) 62D1, 62D2: Parts 1 and 2 62M: Mask No. 22 62S1, 62S2: Top surface 63R: Recess 72: Sixth Semiconductor Layer 82: Fifth semiconductor layer 102: Sixth semiconductor layer 102D:9th area 102D1, 102D2: Parts 1 and 2 122: Seventh semiconductor layer 123: Recess 132: Semiconductor layer 142: Eighth semiconductor layer 152: Ninth Semiconductor Layer 162: Tenth Semiconductor Layer 300:Electronic equipment 300A: Electronic Integrated Circuit Section 300B: Photonic Integrated Circuit Section 310: Multiplexer 320: First Amplifier 330: Light source 340: Optical modulator 350: Second Amplifier 360: Optical waveguide 370: Microdisc 400: Second Optical Modulator 500: Third Optical Modulator 1000: Fourth Optical Modulator 1100: Fifth Optical Modulator 1200: 6th Optical Modulator 1300: 7th Optical Modulator 1400: 8th Optical Modulator DP1-DP5: Dopant injection process 1 to 5 ES1: Multiple electrical signals input to the multiplexer ES2: Electrical signal output from the second amplifier G1: First interval HD1, HD2, LD3, LD4: Doping Zones 1 to 4 IL: Light input to the first optical waveguide 13A M1-M6: Masks 1 through 6 ML: Modulated light ML1: A portion of the modulated light output through the first optical waveguide. ML2: The remaining modulated light output through the second optical waveguide Rw1, Rw2: Ring width Rw3: 3rd width t1, t2: First and second thicknesses

Claims

1. The first semiconductor layer, A second semiconductor layer is provided on the first semiconductor layer in the form of a microdisk and includes a high-doping region with a relatively high doping concentration and a low-doping region with a relatively low doping concentration, A first optical waveguide is arranged adjacent to the second semiconductor layer, The high-doping region includes a first electrode layer and a second electrode layer provided spaced apart from each other, The second semiconductor layer includes at least one recess, The second semiconductor layer has at least one step due to the recess, An optical modulator in which the high-doping region, the low-doping region, and the recess are concentric circles.

2. The second semiconductor layer includes a first recess, The bottom surface of the first recess includes the upper surface of the high-doping region and the upper surface of the low-doping region, and the side surface of the first recess includes the inner surface of the low-doping region. The optical modulator according to claim 1, wherein a first step exists in the low-doping region due to the first recess.

3. The aforementioned high-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant. The low-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant. The bottom surface of the first recess includes the upper surface of the N-doping region and the upper surface of the P-doping region in the high-doping region, and the first upper surface of the P-doping region in the low-doping region. The side surface of the first recess includes the inner surface of the P-doping region of the low-doping region, The optical modulator according to claim 2, wherein the first step corresponds to the height difference between the first upper surface of the P-doping region in the low-doping region and the second upper surface located at a higher position than the first upper surface.

4. The aforementioned high-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant. The low-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant. The bottom surface of the first recess includes the upper surface of the N-doping region and the upper surface of the P-doping region in the high-doping region, and the first upper surface of the P-doping region in the low-doping region. The side surface of the first recess includes the inner surface of the P-doping region of the low-doping region and the inner surface of the N-doping region of the low-doping region, The first step corresponds to the difference in height between the first upper surface of the P-doping region in the low-doping area and the upper surface of the N-doping region in the low-doping area. The N-doping region of the low-doping region is located between the P-doping region and the first semiconductor layer, and completely surrounds the P-doping region of the low-doping region around the first recess. The optical modulator according to claim 2, wherein the outer surface of the N-doping region in the low-doping region is the side surface of the second semiconductor layer.

5. The P-doping region and the N-doping region of the high-doping region are concentric, and there is a step between the center and the edge of the N-doping region of the high-doping region. The thickness at the edges of the N-doping region of the high-doping region is thinner than the thickness at the center. The optical modulator according to claim 3, wherein the P-doping region of the high-doping region overlaps with the end of the N-doping region of the high-doping region, and the upper surface of the P-doping region and the upper surface of the N-doping region form the same surface.

6. The second semiconductor layer is provided inside the first recess and includes a second recess that forms a concentric circle with the first recess. The side and bottom surfaces of the second recess include the surface of the high-doping region. The second recess creates a second step inside the first recess. The optical modulator according to claim 2, wherein the first step and the second step are spaced apart from each other in a horizontal direction parallel to the upper surface of the first semiconductor layer, and the first step and the second step are at different heights from each other.

7. The aforementioned high-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant. The N-doping region and the P-doping region are concentric circles. The bottom surface of the second recess is the upper surface of the N-doping region, The side of the second recess includes the side of the P-doping region, The optical modulator according to claim 6, wherein the second step corresponds to the height difference between the upper surface of the N-doping region and the upper surface of the P-doping region in the high-doping region.

8. The aforementioned high-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant. The N-doping region and the P-doping region are concentric circles. The N-doping region and the P-doping region are separated from each other in a direction perpendicular to the upper surface of the first semiconductor layer. The bottom surface of the second recess is the upper surface of the N-doping region, The side of the second recess includes the side of the P-doping region, The second step corresponds to the height difference between the upper surface of the N-doping region and the upper surface of the P-doping region in the high-doping region. A portion of the low-doping region exists between the N-doping region and the P-doping region, which are separated from each other. The side of the second recess is composed of a part of the low-doping region and the side of the P-doping region. The low-doping region includes an N-doping region doped with an N-dopant and a P-doping region doped with a P-dopant. The N-doping region and the P-doping region of the low-doping region are concentric circles. The bottom surface of the first recess includes the upper surface of the P-doping region of the low-doping region, The optical modulator according to claim 6, wherein the inner surface of the first recess includes the side surface of the P-doping region of the low-doping region.

9. The second semiconductor layer includes a first recess, The bottom surface of the first recess includes the top surface of the low-doping region, and the side surface of the first recess includes the inner surface of the low-doping region. The optical modulator according to claim 1, wherein a first step exists in the low-doping region due to the first recess.

10. The second semiconductor layer is provided inside the first recess and includes a second recess that forms a concentric circle with the first recess. The bottom surface of the second recess includes the surface of the high-doping region, and the side surface of the second recess includes the inner surface of the low-doping region. The second recess creates a second step inside the first recess. The optical modulator according to claim 9, wherein the first step and the second step are spaced apart from each other in a horizontal direction parallel to the upper surface of the first semiconductor layer, and the first step and the second step are at different heights from each other.

11. The aforementioned high-doping region includes an N-doping region doped with an N-type dopant and a P-doping region doped with a P-type dopant. The N-doping region and the P-doping region are concentric circles. The N-doping region and the P-doping region are separated from each other in a direction perpendicular to the upper surface of the first semiconductor layer. The bottom surface of the second recess is the upper surface of the N-doping region, The P-doping region is located on the bottom surface of the first recess, and the inner surface of the P-doping region and the side surface of the second recess form the same surface. The second step corresponds to the height difference between the upper surface of the N-doping region in the high-doping region and the bottom surface of the first recess. The low-doping region includes an N-doping region doped with an N-dopant and a P-doping region doped with a P-dopant. The N-doping region and the P-doping region of the low-doping region are concentric circles. The bottom surface of the first recess includes the upper surface of the P-doping region of the low-doping region, The optical modulator according to claim 10, wherein the inner surface of the first recess includes the side surface of the P-doping region of the low-doping region.

12. The second semiconductor layer includes a first recess, The side and bottom surfaces of the first recess include the surface of the high-doping region, The optical modulator according to claim 1, wherein a first step exists in the high-doping region due to the first recess.

13. The aforementioned high-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant. The bottom surface of the first recess includes the upper surface of the N-doping region, The side of the first recess includes the side of the P-doping region, The N-doping region and the P-doping region are provided so as to overlap each other around the first recess, On a plane, the low-doping region is provided so as to completely surround the high-doping region. The low-doping region includes an N-doping region injected with an N-type dopant and a P-doping region injected with a P-type dopant. The optical modulator according to claim 12, wherein the N-doping region and the P-doping region of the low-doping region are sequentially arranged in a direction perpendicular to the upper surface of the first semiconductor layer.

14. The second semiconductor layer includes a first recess, The bottom surface of the first recess includes the upper surface of the first doping region of the high-doping region, The side of the first recess includes the side of the low-doping region and the side of the second doping region of the high-doping region, The first doping area and the second doping area are separated from each other. The first doping region, the second doping region, and the first recess are concentric circles. The first recess creates a step between the upper surface of the first doping area and the upper surface of the second doping area. The first doping region and the second doping region each contain dopants of opposite types. They are spaced apart from each other in a direction perpendicular to the upper surface of the first semiconductor layer, The outer diameter of the first doping region and the inner diameter of the second doping region are the same as each other. The optical modulator according to claim 1, wherein the upper surface of the second doping region and the upper surface of the low-doping region are provided to form the same surface.

15. The present invention further includes a second optical waveguide separated from the second semiconductor layer, The optical modulator according to claim 1, wherein the second semiconductor layer is disposed between the first optical waveguide and the second optical waveguide.

16. The steps include forming a second semiconductor layer in the form of a microdisk on a first semiconductor layer, The steps include forming a circular first doping region in a portion of the second semiconductor layer, The steps include forming a second doping region in the second semiconductor layer surrounding the first doping region, such that it forms a concentric circle with the first doping region on a plane, and the second doping region is formed in such a way that it surrounds the first doping region. The steps include forming a first step in one of the first and second doping regions, A method for manufacturing an optical modulator, comprising the step of forming an electrode layer on a first doping region having a higher doping concentration than the second doping region.

17. The method for manufacturing an optical modulator according to claim 16, wherein the first step is formed in the first doping region.

18. A method for manufacturing an optical modulator according to claim 17, further comprising the step of forming a second step in the second doping region.

19. The step of forming the second doping region is: The step of forming the first doping layer, The steps include forming a second doping layer on the first doping layer, including the second step, The process further includes the step of forming a third doping layer that covers the outer portion of the second step of the second doping layer and comes into contact with the first doping layer, The method for manufacturing an optical modulator according to claim 18, wherein the first doping layer and the third doping layer contain the same type of dopant.

20. Light source and An optical waveguide through which light emitted from the aforementioned light source is transmitted, A semiconductor layer is provided adjacent to the optical waveguide, in the form of a microdisk, and includes a plurality of doping regions. The system includes an amplifier provided for amplifying the light transmitted through the optical waveguide, The semiconductor layer includes first and second doping regions located in the center of the plurality of doping regions, Of the aforementioned multiple doping areas, the remaining doping areas, excluding the first and second doping areas, are arranged around the first and second doping areas. The first and second doping regions are regions doped with opposite types of dopants. The doping concentrations in the first and second doping regions are higher than those in the remaining doping regions. The semiconductor layer includes at least one step in the electronic device.

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