Light detection device and method for manufacturing the same

Abstract

The present invention provides a photodetector capable of suitably detecting target light propagating through an optical waveguide using a photodetector. [Solution] The photodetector 1A comprises an optical waveguide section 10 and a photodetector 20. The optical waveguide section 10 has a core layer 12 that guides target light and a first cladding layer 11 having a refractive index lower than that of the core layer 12. The photodetector 20 is provided at a predetermined position relative to the optical waveguide section 10 and has a first electrode layer 21, a photoelectric conversion layer 22, and a second electrode layer 23. The photoelectric conversion layer 22 in the photodetector 20 is configured to have a bulk heterojunction of a plurality of organic semiconductor materials. The photodetector 20 is also configured to include at least one metal layer in contact with the photoelectric conversion layer 22, and the interface between the metal layer and the photoelectric conversion layer 22 is configured to induce surface plasmons, and the target light is detected by coupling the waveguide mode in the optical waveguide section 10 with the surface plasmon mode at the interface.

Description

[Technical Field]

[0001] The present invention relates to a photodetector that detects target light propagating through an optical waveguide using a photodetector, and to a method for manufacturing the photodetector. [Background technology]

[0002] In recent years, with the advancement of optical integrated circuit technologies, including silicon photonics, research and development on their specific applications have been progressing. Furthermore, with the aim of expanding the field and realizing high-performance optical integrated circuits, research is also being conducted on optical waveguides using various material systems, such as optical waveguides using silicon nitride, silicon dioxide, aluminum oxide, and polymer resins as cores.

[0003] Among the optical waveguide material systems described above, optical waveguides using silicon nitride (SiN) as the core can be used in optical integrated circuits in the visible light region, which is difficult to achieve with other platforms such as Si waveguides and InP-based waveguides. Furthermore, because they can propagate light with lower loss than other materials, expectations for their use in optical integrated circuits in the communication wavelength region are increasing. In addition, elements such as resonators, interferometers, MMIs, and couplers have been developed as applications. Such SiN waveguides can be used, for example, in the wavelength range of approximately 500 nm to 2500 nm.

[0004] However, in configurations using SiN waveguides, it is difficult to directly fabricate optical elements such as photodetectors and light-emitting elements on the optical waveguide. In other words, while general optical elements use materials such as Si or III-V semiconductors, the mismatch between the lattice constant of silicon nitride and the lattice constant of these semiconductors makes it impossible to form a semiconductor layer with good crystallinity on silicon nitride. Furthermore, even when using crystal growth via a buffer layer, there are process-related challenges and it has not been applicable to SiN waveguides. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-76086 [Patent Document 2] Patent No. 3971785 [Non-patent literature]

[0006] [Non-Patent Document 1] B. Lamprecht et al., "Monolithically integrated organic waveguide photodiode", Phys. Stat.Sol. (RRL), Vol.2 No.6, pp.266-268, 2008 [Non-Patent Document 2] A. Melikyan et al., "Surface plasmon polariton absorption modulator", Optics Express, Vol.19 No.9, pp.8855-8869, 2011 [Overview of the project] [Problems that the invention aims to solve]

[0007] Regarding the application of optical elements to SiN waveguides and other materials as described above, integration techniques such as hybrid integration and heterogeneous integration are used. However, when using such integration techniques, there are problems with alignment, downsizing, throughput, and detection efficiency, emission efficiency, and coupling efficiency.

[0008] To address these problems, for example, Non-Patent Document 1 uses a configuration in which a photodiode made of an organic semiconductor material is formed on an optical waveguide that guides the target light, and the evanescent wave leaking from the optical waveguide is detected by the photodiode. Also, Patent Document 1 uses a configuration in which a metal-semiconductor-metal (MSM) photodetector is placed at a predetermined position on the optical waveguide, and the target light is detected by converting the waveguide mode of the target light propagating through the optical waveguide into a surface plasmon polariton mode in the photodetector. However, with these configurations, it is difficult to detect the target light with sufficient detection efficiency.

[0009] The present invention aims to provide a photodetector capable of suitably detecting target light propagating through an optical waveguide such as a SiN waveguide, and a method for manufacturing the photodetector. [Means for solving the problem]

[0010] A first embodiment of the present invention provides a photodetector comprising: (1) an optical waveguide section including a core layer that guides target light of a predetermined wavelength to be detected, and a first cladding layer having a refractive index lower than that of the core layer; (2) a photodetector section provided on the side of the optical waveguide section opposite to the core layer and the first cladding layer, and having at least a first electrode layer, a photoelectric conversion layer, and a second electrode layer in order from the optical waveguide section side; (3) the photoelectric conversion layer is configured to have a bulk heterojunction of a plurality of organic semiconductor materials, the photodetector section is configured to include at least one metal layer in contact with the photoelectric conversion layer, the interface between the metal layer and the photoelectric conversion layer is configured to induce surface plasmons; and (4) the photodetector section detects target light by coupling the waveguide mode in the optical waveguide section with the surface plasmon mode at the interface.

[0011] A method for manufacturing a photodetector according to a first embodiment of the present invention is a method for manufacturing a photodetector comprising an optical waveguide section for guiding target light of a predetermined wavelength to be detected, and a photodetector section for detecting target light, comprising: (1) a substrate preparation step of preparing a substrate section including at least a first cladding layer having a refractive index lower than that of a core layer; (2) a core layer formation step of forming a core layer on the first cladding layer, which together with the first cladding layer constitutes an optical waveguide section and guides target light; (3) a first electrode layer formation step of forming a first electrode layer on the side of the optical waveguide section opposite to the core layer and the first cladding layer; and (4) a plurality of electrodes on the side of the first electrode layer opposite to the core layer and the first electrode layer. (5) A photoelectric conversion layer formation step is to form a photoelectric conversion layer having a bulk heterojunction made of a semiconductor material; (6) A second electrode layer formation step is to form a second electrode layer on the side opposite to the first electrode layer with respect to the photoelectric conversion layer, which together with the first electrode layer and the photoelectric conversion layer constitutes a photodetector; (7) The photodetector is configured to detect target light by coupling the waveguide mode in the optical waveguide with the surface plasmon mode at the interface.

[0012] In the above-described photodetector and method for manufacturing the photodetector, a photodetector having a first electrode layer, a photoelectric conversion layer, and a second electrode layer is provided at a predetermined position relative to the optical waveguide portion including the core layer and the first cladding layer, and the photoelectric conversion layer has a configuration having a bulk heterojunction made of multiple organic semiconductor materials. Furthermore, the photodetector includes a metal layer in contact with the photoelectric conversion layer, and the interface between this metal layer and the photoelectric conversion layer is configured to induce surface plasmons.

[0013] With this configuration, the target light can be detected by coupling the waveguide mode of the target light in the optical waveguide section with the surface plasmon mode at the interface between the metal layer and the photoelectric conversion layer in the photodetector section. Furthermore, by using an organic semiconductor material as the material for the photoelectric conversion layer and forming a bulk heterojunction with multiple organic semiconductor materials, the detection efficiency of the target light by the photodetector section can be improved.

[0014] It should be noted that, as for the metal layer included in the photodetection section, for example, a metal layer additionally provided in the first electrode layer, the second electrode layer, or the photoelectric conversion layer can be used. Further, regarding the surface plasmon mode at the interface between the metal layer and the photoelectric conversion layer in the photodetection section, which is used for detecting target light, a configuration may be adopted in which a mode generated by the interaction between the surface plasmon mode at the interface between the metal layer and the photoelectric conversion layer and the surface plasmon mode at another interface between said metal layer or another metal layer and the photoelectric conversion layer is used.

[0015] Regarding the configuration of the photodetection device, specifically, in addition to the configuration of the first aspect described above, configurations of the following aspects may also be adopted.

[0016] In the photodetection device according to the second aspect, in the configuration of the first aspect described above, as said metal layer in the photodetection section, the first electrode layer may be configured by the first metal layer, and the first interface between the first metal layer and the photoelectric conversion layer may be configured as said interface so as to be capable of inducing surface plasmons.

[0017] In the above configuration, in the photodetection device, in the photodetection section, the second electrode layer may be configured by a second transparent electrode layer.

[0018] In the photodetection device according to the third aspect, in the configuration of the second aspect described above, the photodetection section is configured such that the interaction between the surface plasmon mode at the first interface and the surface plasmon mode at the lower interface on the optical waveguide section side of the first metal layer causes mode splitting into a coupled mode and an anti-coupled mode, and a configuration may be adopted in which the target light is detected by coupling the guided mode in the optical waveguide section with the coupled mode or the anti-coupled mode.

[0019] In the photodetection device according to the fourth aspect, in the configuration of the second aspect described above, in the photodetection section, the second electrode layer may be configured by a second metal layer, and the second interface between the second metal layer and the photoelectric conversion layer may be configured to be capable of inducing surface plasmons.

[0020] In the photodetection device according to the fifth aspect, in the configuration of the fourth aspect described above, the photodetection section is configured such that mode splitting into a coupled mode and an anti-coupled mode is caused by the interaction between the surface plasmon mode at the first interface and the surface plasmon mode at the second interface, and may be configured to detect target light by coupling the waveguide mode in the optical waveguide section with the coupled mode or the anti-coupled mode.

[0021] In the photodetection device according to the sixth aspect, in the configuration of the fourth aspect described above, the photodetection section is configured such that mode splitting into a plurality of modes is caused by the interaction between two or more of the following: the surface plasmon mode at the first interface, the surface plasmon mode at the second interface, and the surface plasmon mode at the lower interface on the optical waveguide section side of the first metal layer, and may be configured to detect target light by coupling the waveguide mode in the optical waveguide section with any one of the plurality of modes.

[0022] In the configuration described above, in the photodetection device, as the metal layer in the photodetection section, the second electrode layer may be constituted by the second metal layer, the second interface between the second metal layer and the photoelectric conversion layer may be configured as the above-mentioned interface to be capable of inducing surface plasmons, and the first electrode layer may be constituted by the first transparent electrode layer.

[0023] In the configuration described above, in the photodetection device, in the photodetection section, the first electrode layer and the second electrode layer may be respectively constituted by the first transparent electrode layer and the second transparent electrode layer.

[0024] In the photodetection device according to the seventh aspect, in the configuration of the first aspect described above, as the metal layer in the photodetection section, an intermediate metal layer is provided in the photoelectric conversion layer between the first electrode layer and the second electrode layer, and at least one of the first intermediate interface between the intermediate metal layer and the photoelectric conversion layer on the first electrode layer side and the second intermediate interface between the intermediate metal layer and the photoelectric conversion layer on the second electrode layer side may be configured as the above-mentioned interface to be capable of inducing surface plasmons.

[0025] In the photodetector of the eighth embodiment, in the configuration of the seventh embodiment, both the first intermediate interface and the second intermediate interface in the photodetector are configured to induce surface plasmons, and the interaction between the surface plasmon mode at the first intermediate interface and the surface plasmon mode at the second intermediate interface causes mode splitting into coupled and anticoupled modes, and the target light may be detected by coupling the waveguide mode in the optical waveguide with the coupled or anticoupled mode.

[0026] In the above configuration, the photodetector is configured such that in the photodetector, the first electrode layer is made of a first metal layer, and the first interface between the first metal layer and the photoelectric conversion layer is configured to induce surface plasmons, and two or more surface plasmon modes from among the surface plasmon mode at the first interface, the surface plasmon mode at the first intermediate interface, the surface plasmon mode at the second intermediate interface, and the surface plasmon mode at the lower interface on the optical waveguide side of the first metal layer interact to cause mode splitting into multiple modes, and the target light may be detected by coupling the waveguide mode in the optical waveguide with any of the multiple modes.

[0027] In the above configuration, the photodetector is configured such that in the photodetector, the second electrode layer is made of a second metal layer, the second interface between the second metal layer and the photoelectric conversion layer is configured to induce surface plasmons, and two or more surface plasmon modes from among the surface plasmon modes at the second interface, the surface plasmon modes at the first intermediate interface, and the surface plasmon modes at the second intermediate interface interact to cause mode splitting into multiple modes, and the target light may be detected by coupling the waveguide mode in the optical waveguide section with any of the multiple modes.

[0028] In the ninth embodiment of the photodetector, in the configuration of the seventh embodiment, the photodetector is configured such that the first electrode layer is made of a first metal layer, the first interface between the first metal layer and the photoelectric conversion layer is configured to induce surface plasmons, the second electrode layer is made of a second metal layer, the second interface between the second metal layer and the photoelectric conversion layer is configured to induce surface plasmons, and two or more surface plasmon modes from among the surface plasmon mode at the first interface, the surface plasmon mode at the second interface, the surface plasmon mode at the first intermediate interface, the surface plasmon mode at the second intermediate interface, and the surface plasmon mode at the lower interface on the optical waveguide side of the first metal layer interact to cause mode splitting into multiple modes, and the target light may be detected by coupling the waveguide mode in the optical waveguide with any of the multiple modes.

[0029] In the tenth embodiment of the photodetector, in any of the configurations of the first to ninth embodiments, the photodetector may be configured to perform the detection operation of target light in an unbiased state in which no voltage is applied between the first electrode layer and the second electrode layer.

[0030] In the 11th embodiment of the photodetector, in any of the configurations of the first to tenth embodiments, an intermediate layer may be provided in the photodetector between the first electrode layer and the photoelectric conversion layer, and between the second electrode layer and the photoelectric conversion layer, at least one of the two.

[0031] In the configuration in which an intermediate layer is provided as described above, specifically, in the photodetector, the first intermediate layer may be provided between the first electrode layer and the photoelectric conversion layer. Alternatively, in the photodetector, the second intermediate layer may be provided between the second electrode layer and the photoelectric conversion layer.

[0032] In the twelfth embodiment of the photodetector, in any of the configurations of the first to eleventh embodiments, the optical waveguide portion may include a second cladding layer provided between the core layer and the first electrode layer of the photodetector, and having a lower refractive index than the core layer.

[0033] In the above configuration, the photodetector may have a lower intermediate layer provided between the second cladding layer of the optical waveguide section and the first electrode layer of the photodetector section.

[0034] In the 13th embodiment of the photodetector, in any of the configurations of the 1st to 12th embodiments, a lower intermediate layer may be provided between the optical waveguide section and the first electrode layer of the photodetector section. In the above configuration, the lower intermediate layer may be made of the same material as the photoelectric conversion layer.

[0035] In the above configuration, the photodetector may be configured such that a passivation film is provided on the outer periphery of the photodetector.

[0036] In the 14th embodiment of the photodetector, in any of the configurations of the 1st to 13th embodiments, the plurality of organic semiconductor materials constituting the photoelectric conversion layer may include one or more materials selected from the group consisting of thiophene, benzothiophene, phenylene vinylene, carbazole, thienopyrrole, diketopyrrolopyrrole, fullerene, carbon nanotube, dithiophene, and derivatives thereof.

[0037] In the photodetector according to the 15th embodiment, in any of the configurations of the 1st to 14th embodiments, the thickness of the photoelectric conversion layer may be set to a thickness within the range of 0.01 μm to 5 μm.

[0038] In the 16th embodiment of the photodetector, in any of the configurations of the 1st to 15th embodiments, the material of the metal layer in the photodetector may include at least one of Cu, Al, Ag, Au, and Pt.

[0039] Regarding the configuration of the manufacturing method for the light detection device, in addition to the configuration of the first embodiment described above, the configurations of each of the following embodiments may also be used.

[0040] In the manufacturing method of the photodetector according to the second embodiment, in the configuration of the first embodiment, in the first electrode layer formation step, a first electrode layer composed of the first metal layer is formed as the metal layer in the photodetector, and the first interface between the first metal layer and the photoelectric conversion layer is configured to induce surface plasmons as the interface.

[0041] In the above configuration, the method for manufacturing the photodetector may also involve forming a second electrode layer composed of a second transparent electrode layer in the second electrode layer formation step.

[0042] In the manufacturing method of the photodetector according to the third embodiment, in the configuration of the second embodiment, a second electrode layer composed of a second metal layer may be formed in the second electrode layer formation step, and the second interface between the second metal layer and the photoelectric conversion layer may be configured to induce surface plasmons.

[0043] In the above configuration, the method for manufacturing the photodetector may also be configured such that, in the second electrode layer formation step, a second electrode layer composed of the second metal layer is formed as the metal layer in the photodetector, and the second interface between the second metal layer and the photoelectric conversion layer is configured to induce surface plasmons as the interface, and in the first electrode layer formation step, a first electrode layer composed of the first transparent electrode layer is formed.

[0044] In the above configuration, the method for manufacturing the photodetector may be configured such that, in the first electrode layer formation step, a first electrode layer composed of a first transparent electrode layer is formed, and in the second electrode layer formation step, a second electrode layer composed of a second transparent electrode layer is formed.

[0045] In the manufacturing method of the photodetector according to the fourth embodiment, the configuration according to the first embodiment further includes an intermediate metal layer formation step of forming an intermediate metal layer in the photoelectric conversion layer between the first electrode layer and the second electrode layer as the metal layer in the photodetector, and at least one of the first intermediate interface between the intermediate metal layer and the photoelectric conversion layer on the first electrode layer side, and the second intermediate interface between the intermediate metal layer and the photoelectric conversion layer on the second electrode layer side, is configured to induce surface plasmons as the interface.

[0046] In the fifth embodiment of the method for manufacturing a photodetector, in any of the configurations of the first to fourth embodiments, the photodetector may be configured to perform the detection operation of target light in an unbiased state in which no voltage is applied between the first electrode layer and the second electrode layer.

[0047] In the sixth embodiment of the method for manufacturing a photodetector, in any of the configurations of the first to fifth embodiments, the configuration may further include an intermediate layer formation step in which an intermediate layer is formed in at least one of the spaces between the first electrode layer and the photoelectric conversion layer, and between the second electrode layer and the photoelectric conversion layer, in the photodetector.

[0048] In the configuration for forming the intermediate layer as described above, the configuration may further include a first intermediate layer formation step in which a first intermediate layer is formed between the first electrode layer and the photoelectric conversion layer in the photodetector. Alternatively, the configuration may further include a second intermediate layer formation step in which a second intermediate layer is formed between the second electrode layer and the photoelectric conversion layer in the photodetector.

[0049] In the seventh embodiment of the method for manufacturing a photodetector, in any of the configurations of the first to sixth embodiments, the configuration may further include a second cladding layer formation step in which a second cladding layer is formed in the optical waveguide section, provided between the core layer and the first electrode layer of the photodetector section, and having a lower refractive index than the core layer.

[0050] In the above configuration, the method for manufacturing the photodetector may further include a lower intermediate layer formation step in which a lower intermediate layer is formed between the second cladding layer of the optical waveguide section and the first electrode layer of the photodetector section.

[0051] In the eighth embodiment of the method for manufacturing a photodetector, the configuration may further include a lower intermediate layer formation step in which a lower intermediate layer is formed between the optical waveguide section and the first electrode layer of the photodetector section, in any of the configurations of the first to seventh embodiments described above. In the above configuration, the lower intermediate layer may be made of the same material as the photoelectric conversion layer.

[0052] In the above configuration, the method for manufacturing the photodetector may further include a passivation film formation step in which a passivation film is formed on the outer periphery of the photodetector.

[0053] In the above configuration, in the method for manufacturing the photodetector, in the photoelectric conversion layer formation step, the plurality of organic semiconductor materials constituting the photoelectric conversion layer may include one or more materials selected from the group consisting of thiophene, benzothiophene, phenylene vinylene, carbazole, thienopyrrole, diketopyrrolopyrrole, fullerene, carbon nanotube, dithiophene, and derivatives thereof.

[0054] In the above configuration, the method for manufacturing the photodetector may be configured such that the thickness of the photoelectric conversion layer is set to a thickness within the range of 0.01 μm to 5 μm in the photoelectric conversion layer formation step.

[0055] In the above configuration, the manufacturing method of the photodetector may include at least one of Cu, Al, Ag, Au, and Pt as the material of the metal layer in the photodetector.

[0056] In the manufacturing method of the photodetector according to the ninth embodiment, in any of the configurations of the first to eighth embodiments described above, in the photoelectric conversion layer formation step, a plurality of organic semiconductor materials may be prepared, a photoelectric conversion layer forming material may be created by stirring the plurality of organic semiconductor materials, and a photoelectric conversion layer having a bulk heterojunction may be formed using the photoelectric conversion layer forming material.

[0057] In the manufacturing method of the photodetector according to the 10th embodiment, in the configuration of the 9th embodiment described above, in the photoelectric conversion layer formation step, a photoelectric conversion layer forming material may be prepared by stirring a plurality of organic semiconductor materials and a solvent in a predetermined container, and the photoelectric conversion layer may be formed by a dispenser method, inkjet method, die coating method, spin coating method, or printing method.

[0058] In the manufacturing method of the photodetector according to the 11th embodiment, in the configuration of the 9th embodiment described above, the photoelectric conversion layer may be formed by simultaneously depositing multiple organic semiconductor materials by sputtering or evaporation in the photoelectric conversion layer formation step.

[0059] In the manufacturing method of the photodetector according to the 12th embodiment, in any of the configurations of the 9th to 11th embodiments, the photoelectric conversion layer formation step may be configured such that, after forming the photoelectric conversion layer, the photoelectric conversion layer is fired in an atmospheric environment, an inert gas atmosphere, or a vacuum environment.

[0060] In the manufacturing method of the photodetector according to the 13th embodiment, in any of the configurations of the 1st to 12th embodiments described above, the core layer formation step may involve forming a core layer formation layer by CVD, ALD, sputtering, vapor deposition, or coating, forming a resist pattern on the core layer formation layer by photolithography or electron beam lithography, and then forming a core layer by etching using the resist pattern as a mask.

[0061] In the manufacturing method of the photodetector according to the 14th embodiment, in any of the configurations of the 1st to 13th embodiments, the first electrode layer and the second electrode layer may be formed by sputtering or vapor deposition in the first electrode layer formation step and the second electrode layer formation step, respectively. [Effects of the Invention]

[0062] According to the light detection device and the method for manufacturing the light detection device of the present invention, it is possible to suitably detect target light propagating through an optical waveguide using a light detection unit. [Brief explanation of the drawing]

[0063] [Figure 1] Figure 1 is a schematic side cross-sectional view showing the configuration of the first embodiment of the photodetector and the operation of the photodetector in detecting target light. [Figure 2] Figure 2 is a graph showing the dispersion relations for the waveguide modes in the optical waveguide section and the surface plasmon modes in the photodetector section. [Figure 3] Figure 3 schematically illustrates the mode splitting into coupled and antibonded modes due to the interaction of multiple surface plasmon modes. [Figure 4] Figures 4 (a) to (c) show the mode splitting into coupled and anticoupled modes in the photodetector section of the photodetector shown in Figure 1. [Figure 5] Figure 5 is a graph showing the dispersion relations for the waveguide modes in the optical waveguide section, the surface plasmon modes in the photodetector section, and the anticoupled and coupled modes generated by mode splitting. [Figure 6] Figure 6 is a graph showing the dispersion relations for the surface plasmon mode in the photodetector, and for the antibonding and bonding modes generated by mode splitting. [Figure 7] Figure 7 shows the mode splitting into multiple modes when three surface plasmon modes interact at three interfaces (a) to (d). [Figure 8] Figure 8 shows (a) a side cross-sectional view and (b) a top view illustrating the specific configuration of the photodetector. [Figure 9] Figure 9 is a cross-sectional view showing the configuration of the light detection device shown in Figure 8. [Figure 10] Figure 10 shows (a) a side view and (b) a cross-sectional view of the first step in the manufacturing method of a photodetector. [Figure 11] Figure 11 shows (a) a side view and (b) a cross-sectional view of the second step in the manufacturing method of the photodetector. [Figure 12]Figure 12 shows (a) a side view and (b) a cross-sectional view of the third step in the manufacturing method of the photodetector. [Figure 13] Figure 13 shows (a) a side view and (b) a cross-sectional view of the fourth step in the manufacturing method of the photodetector. [Figure 14] Figure 14 shows (a) a side view and (b) a cross-sectional view of the fifth step in the manufacturing method of the photodetector. [Figure 15] Figure 15 shows (a) a side view and (b) a cross-sectional view of the sixth step in the manufacturing method of the photodetector. [Figure 16] Figure 16 shows (a) a side view and (b) a cross-sectional view of the seventh step in the manufacturing method of the photodetector. [Figure 17] Figure 17 shows (a) a side view and (b) a cross-sectional view of the eighth step in the manufacturing method of the photodetector. [Figure 18] Figure 18 is a schematic side cross-sectional view showing the configuration of a second embodiment of the photodetector. [Figure 19] Figure 19 is a schematic side cross-sectional view showing the configuration of the third embodiment of the photodetector. [Figure 20] Figure 20 is a schematic side cross-sectional view showing the configuration of the fourth embodiment of the photodetector. [Figure 21] Figure 21 is a schematic side cross-sectional view showing the configuration of the fifth embodiment of the photodetector. [Figure 22] Figure 22 is a schematic side cross-sectional view showing the configuration of the sixth embodiment of the photodetector. [Figure 23] Figure 23 is a schematic side cross-sectional view showing the configuration of the seventh embodiment of the photodetector. [Figure 24] Figure 24 is a schematic side cross-sectional view showing the configuration of the eighth embodiment of the photodetector. [Figure 25] Figure 25 is a schematic side cross-sectional view showing the configuration of the ninth embodiment of the photodetector. [Figure 26] Figure 26 is a schematic side cross-sectional view showing the configuration of the tenth embodiment of the photodetector. [Figure 27] Figure 27 is a schematic side cross-sectional view showing the configuration of the 11th embodiment of the photodetector. [Figure 28] Figure 28 is a schematic side cross-sectional view showing the configuration of the twelfth embodiment of the photodetector. [Figure 29] Figure 29 is a schematic side cross-sectional view showing the configuration of a first modified example of the photodetector. [Figure 30] Figure 30 is a schematic side cross-sectional view showing the configuration of a second modified example of the photodetector. [Figure 31] Figure 31 is a schematic side cross-sectional view showing the configuration of a third modified example of the photodetector. [Modes for carrying out the invention]

[0064] The following describes in detail embodiments of the light detection device and the method for manufacturing the light detection device, along with the drawings. In the description of the drawings, identical elements are denoted by the same reference numeral, and redundant explanations are omitted. Furthermore, the dimensional ratios in the drawings do not necessarily correspond to those in the description.

[0065] Figure 1 is a schematic side cross-sectional view showing the configuration of the first embodiment of the photodetector and the operation of the photodetector to detect target light. The photodetector 1A according to this embodiment is a device for detecting target light of a predetermined wavelength propagating through an optical waveguide. The photodetector 1A is configured to include an optical waveguide section 10 and a photodetector section 20.

[0066] In the following figures, the xyz Cartesian coordinate system will be shown as needed. In this xyz Cartesian coordinate system, the direction of light guidance in the optical waveguide section 10 is the z-axis direction, the stacking direction of each layer in the optical waveguide section 10 and the photodetector section 20 is the x-axis direction, and the direction perpendicular to the z-axis and x-axis directions is the y-axis direction.

[0067] The optical waveguide section 10 is composed of a first cladding layer 11 and a core layer 12. The first cladding layer 11 is a layer that functions as a substrate (base) for forming the core layer 12 and each layer that constitutes the photodetector section 20, and has a lower refractive index than the core layer 12. Such a first cladding layer 11 is composed of, for example, an SiO2 layer.

[0068] The core layer 12 is provided on the first cladding layer 11 by a pattern of a predetermined width extending in the z-axis direction, and guides target light of a predetermined wavelength to be detected by the photodetector 1A in the z-axis direction. Such a core layer 12 is composed of, for example, a SiN (silicon nitride) layer. In this embodiment, as shown by the dashed line in the figure, the air layer present in the region above the core layer 12 where the photodetector 20 is not provided (the region on the left in the figure) functions as a second cladding layer 13 having a lower refractive index than the core layer 12.

[0069] The photodetector 20 is provided on a predetermined region (the right-hand region in the figure) opposite to the first cladding layer 11 with respect to the core layer 12 of the optical waveguide 10. The photodetector 20 is composed of a first electrode layer, a photoelectric conversion layer 22, and a second electrode layer. In this embodiment, the first electrode layer is composed of a first metal layer 21 made of a metallic material. The second electrode layer is composed of a second metal layer 23 made of the same or a different metallic material as the first metal layer 21.

[0070] In the photodetector 20, the photoelectric conversion layer 22 located between the first metal layer 21 and the second metal layer 23 functions as a light absorption layer in the detection operation of target light, and is composed of a bulk heterojunction made of multiple organic semiconductor materials. The bulk heterojunction is a structure in which microscopic heterojunctions are formed throughout the photoelectric conversion layer 22. Furthermore, for example, P3HT, which functions as a p-type semiconductor material, and PCBM, which functions as an n-type semiconductor material, can be used as the multiple organic semiconductor materials.

[0071] In this configuration, as shown in Figure 1, the first interface 31 between the first metal layer 21 and the photoelectric conversion layer 22 is configured to induce surface plasmons. The photodetector 20 detects the target light by coupling the waveguide mode A of the target light in the optical waveguide section 10 with the surface plasmon mode B at the first interface 31 in the photodetector 20 to generate a surface plasmon polariton (SSP) C.

[0072] This section describes the waveguide modes in the optical waveguide section 10, the surface plasmon modes in the photodetector section 20, and the detection operation of target light through their coupling.

[0073] First, we will explain the waveguide modes of the target light in the optical waveguide section 10. The characteristic equations for the waveguide modes of the target light propagating within the core layer 12 of the optical waveguide section 10 are expressed by equations (1) and (2) below, starting from Maxwell's equations.

number

number

[0074] Furthermore, in the above equation, ω is the angular frequency, c is the speed of light, λ is the wavelength, and n eff ε is the effective refractive index. Also, ε0 is the permittivity of vacuum, μ0 is the permeability of vacuum, and ε wi μ is the dielectric constant of the medium. wi is the permeability of the medium. Also, n wi =√ε wi √μ wi β is the propagation constant, where β = k0n effk0 is the wave number of vacuum, where k0 = ω / c = 2π / λ. Furthermore, γ, κ, and γ' are as shown in equation (3) below.

number

[0075] Next, we will explain the surface plasmon modes at the first interface 31 between the first metal layer 21 and the photoelectric conversion layer 22 in the photodetector 20. Surface plasmons are electromagnetic waves (transverse waves) that seep onto the metal surface from the collective vibrations (compression waves, longitudinal waves) of free electrons in the metal. This can also be thought of as a field created by the collective vibrations of free electrons. Furthermore, the state in which these surface plasmons and electromagnetic waves of light are coupled is called a surface plasmon polariton.

[0076] Similar to the waveguide modes in the optical waveguide section 10 described above, the characteristic equations for the surface plasmon modes at the first interface 31 can also be derived starting from Maxwell's equations. Specifically, the characteristic equations for the surface plasmon modes are expressed by equations (4) and (5) below.

number

number

[0077] The characteristic equations (4) and (5) above represent the dispersion relationship between the propagation constant β or wavenumber k and the angular frequency ω in the surface plasmon mode at the first interface 31 between the first metal layer 21 and the photoelectric conversion layer 22. In order to generate surface plasmons, it is necessary to select materials for the first metal layer 21 and the photoelectric conversion layer 22 such that the dielectric constants ε1 and ε2 satisfy equation (4), or the magnetic permeability μ1 and μ2 satisfy equation (5).

[0078] Next, the coupling between the waveguide mode in the optical waveguide section 10 and the surface plasmon mode at the first interface 31 in the photodetector section 20 will be explained. Figure 2 is a graph showing the dispersion relations for the waveguide mode in the optical waveguide section 10 and the surface plasmon mode in the photodetector section 20, respectively. In the graph of Figure 2, the horizontal axis represents the wavenumber k (nm). -1 The graph shows the angular frequency ω (rad / s) on the vertical axis.

[0079] In Figure 2, graph G0 shows the light line corresponding to the dispersion relationship of light in a vacuum, graph G1 shows the dispersion relationship of the waveguide modes in the optical waveguide section 10, and graph G2 shows the dispersion relationship of the surface plasmon modes in the photodetector section 20. Note that in each of the following graphs, the dispersion relationships shown in the graphs all represent the dispersion relationships in the TM mode. Graph G1 shows the dispersion relationship when a SiN waveguide is used as the optical waveguide section 10. Graph G2 shows the dispersion relationship when the material of the first metal layer 21 is Ag and the material of the photoelectric conversion layer 22 is a mixed material of P3HT and PCBM.

[0080] In order to generate a surface plasmon polariton by coupling the waveguide mode in the optical waveguide section 10 with the surface plasmon mode in the photodetector section 20, the dispersion relations of both the waveguide mode and the surface plasmon mode must match (i.e., the wavenumber k and angular frequency ω must match). Specifically, in the case of the TM mode, a solution must exist between equation (1), which is the characteristic equation of the waveguide mode, and equation (4), which is the characteristic equation of the surface plasmon mode. Similarly, in the case of the TE mode, a solution must exist between equation (2), which is the characteristic equation of the waveguide mode, and equation (5), which is the characteristic equation of the surface plasmon mode.

[0081] In the example of dispersion relations shown in Figure 2, at points P1, P2, and P3, the dispersion relations of the waveguide modes in the optical waveguide section 10 and the dispersion relations of the surface plasmon modes in the photodetector section 20 coincide. In order for the photodetector section 20 to detect the target light propagating through the optical waveguide section 10, materials should be selected for the first metal layer 21 and the photoelectric conversion layer 22 such that the points where these dispersion relations coincide correspond to the target light to be detected, with dielectric constants ε1 and ε2 or magnetic permeability μ1 and μ2.

[0082] In the above description, a configuration was described in which the first interface 31 between the first metal layer 21 and the photoelectric conversion layer 22 is configured to induce surface plasmons, and the photodetector 20 detects the target light by coupling the waveguide mode in the optical waveguide section 10 with the surface plasmon mode at the first interface 31. However, the configuration is not limited to this. For example, in the configuration shown in Figure 1, the second interface 32 between the second metal layer 23 and the photoelectric conversion layer 22 is configured to induce surface plasmons, and the photodetector 20 detects the target light by coupling the waveguide mode in the optical waveguide section 10 with the surface plasmon mode at the second interface 32.

[0083] Next, the detection of target light by coupling the waveguide mode in the optical waveguide section 10 with the surface plasmon mode in the photodetector section 20 will be described. When the waveguide mode and the surface plasmon mode are coupled, the target light propagating within the optical waveguide section 10 is guided to the first interface 31 in the photodetector section 20 via the surface plasmon polariton.

[0084] At this time, the photoelectric conversion layer 22 absorbs the light that has moved to the first interface 31, generating electron-hole pairs (excitons). Then, within the photoelectric conversion layer 22, the generated electron-hole pairs undergo exciton diffusion, exciton dissociation (charge transfer), charge separation, etc., and are collected by the first electrode layer and the second electrode layer, which are the first metal layer 21 and the second metal layer 23, and read out as an electrical signal indicating the detection of target light.

[0085] The effects of the light detection device 1A according to the above embodiment will be explained.

[0086] In the photodetector 1A shown in Figure 1, a photodetector 20 is provided at a predetermined position relative to the optical waveguide section 10, which includes the core layer 12 and the first cladding layer 11. The photodetector 20 has a first metal layer 21 which is a first electrode layer, a photoelectric conversion layer 22, and a second metal layer 23 which is a second electrode layer. The photoelectric conversion layer 22 has a configuration that includes a bulk heterojunction made of multiple organic semiconductor materials. Furthermore, the photodetector 20 includes a metal layer in contact with the photoelectric conversion layer 22, specifically the first metal layer 21 or the second metal layer 23, and the first interface 31 or second interface 32 between this metal layer and the photoelectric conversion layer 22 is configured to induce surface plasmons.

[0087] With this configuration, the target light can be detected by coupling the waveguide mode of the target light in the optical waveguide section 10 with the surface plasmon mode at the interface between the metal layer and the photoelectric conversion layer 22 in the photodetector section 20. Furthermore, by using an organic semiconductor material as the material for the photoelectric conversion layer 22 and forming a bulk heterojunction with multiple organic semiconductor materials, the detection efficiency of the target light by the photodetector section 20 can be improved.

[0088] In the configuration described in Non-Patent Document 1, a photodiode made of an organic semiconductor material is formed on the optical waveguide. However, Non-Patent Document 1 is configured to detect evanescent waves leaking from the optical waveguide using a photodiode, and does not consider the generation of surface plasmon modes or the detection of target light using the coupling between waveguide modes and surface plasmon modes. Furthermore, a planar heterojunction made of an organic semiconductor material is used, and in this respect as well, it is difficult to detect the target light with sufficient detection efficiency.

[0089] In contrast, the photodetector 1A according to this embodiment, as described above, detects target light by utilizing the coupling between the waveguide mode in the optical waveguide section 10 and the surface plasmon mode in the photodetector 20. This improves the detection efficiency of target light by the photodetector 20 compared to a configuration that simply detects evanescent waves.

[0090] Furthermore, by forming a bulk heterojunction using multiple organic semiconductor materials in the photoelectric conversion layer 22, the entire photoelectric conversion layer 22, where a microscopic heterojunction is formed, functions as a light absorption layer. This makes it possible to efficiently utilize surface plasmon polaritons, which attenuate exponentially as they move away from the interface between the metal layer and the photoelectric conversion layer 22, for detecting target light, compared to a configuration using a planar heterojunction.

[0091] Furthermore, in the configuration described in Patent Document 1, which uses an MSM photodetector, the semiconductor layer is composed of, for example, a single Ge layer, and no structure such as a heterojunction or pn junction is formed. With such a configuration, it is difficult to detect the target light with sufficient detection efficiency.

[0092] In contrast, in the photodetector 1A according to this embodiment, by forming a bulk heterojunction of multiple organic semiconductor materials in the photoelectric conversion layer 22, the entire photoelectric conversion layer 22 can function as a light absorption layer, thereby improving the detection efficiency of the target light.

[0093] Furthermore, the configuration described in Patent Document 1 states that the metal layer constituting the MSM photodetector functions as both a contact for applying voltage and an interface for exciting surface plasmon polaritons. In other words, in Patent Document 1, the photodetector is operated with a voltage applied between the metal layers provided on both sides of the semiconductor layer.

[0094] Regarding such a configuration, Non-Patent Document 2 points out that applying such a voltage changes the carrier density distribution and modulates the surface plasmon mode. When such modulation of the surface plasmon mode occurs, the detection operation of the target light by the photodetector may be hindered. Furthermore, in a configuration without a pn junction, as in Patent Document 1, the drift current generated by the voltage application becomes large, and the dark current increases accordingly.

[0095] In contrast, according to the photodetector 1A of this embodiment, by forming a bulk heterojunction of multiple organic semiconductor materials in the photoelectric conversion layer 22 as described above, the photodetector 20 can perform the detection operation of target light in an unbiased state where no voltage is applied between the first metal layer 21, which is the first electrode layer, and the second metal layer 23, which is the second electrode layer. In this case, interference with the detection operation of target light due to voltage application is prevented, and the detection of target light by the photodetector 20 can be preferably achieved with high efficiency.

[0096] As described above, when the photodetector 20 is operated in an unbiased state, in order to read out the detection signal between the first electrode layer and the second electrode layer, it is preferable to use a configuration that provides a potential difference by creating a work function difference between the first electrode layer and the second electrode layer, which function as an anode and a cathode respectively, thereby controlling the direction of carrier movement within the photoelectric conversion layer 22.

[0097] As a configuration for providing a work function difference between the electrodes, specifically, a configuration in which different metal materials are used for the first metal layer 21 serving as the first electrode layer and the second metal layer 23 serving as the second electrode layer may be employed. Alternatively, as will be described later, a configuration can be used in which a first intermediate layer and a second intermediate layer are respectively provided between the first metal layer 21 and the photoelectric conversion layer 22, and between the second metal layer 23 and the photoelectric conversion layer 22, and the work function is adjusted by these intermediate layers. Further, by providing a wide bandgap semiconductor layer as the intermediate layer, a configuration may be adopted in which one type of carrier is blocked to control the movement direction.

[0098] It should be noted that, regarding the metal layer included in the photodetection unit 20, in the above embodiment, both the first electrode layer and the second electrode layer are formed of metal layers, but a configuration may be adopted in which one of the first electrode layer and the second electrode layer is a metal layer. Alternatively, as will be described later, a configuration using an additionally provided metal layer in the photoelectric conversion layer 22 may also be adopted.

[0099] Regarding the plurality of organic semiconductor materials constituting the photoelectric conversion layer 22, for example, a configuration may be employed that uses two types of organic semiconductor materials: an organic semiconductor material that functions as a p-type semiconductor and an organic semiconductor material that functions as an n-type semiconductor. Alternatively, a configuration may be adopted in which three or more types of organic semiconductor materials are used as the plurality of organic semiconductor materials.

[0100] Specifically, it is preferable that the plurality of organic semiconductor materials constituting the photoelectric conversion layer 22 include one or more materials selected from the group consisting of thiophene, benzothiophene, phenylene vinylene, carbazole, thienopyrrole, diketopyrrolopyrrole, fullerene, carbon nanotubes, dithiophene, and derivatives thereof. Examples of such organic semiconductor materials include CuPc, BTP-Th, TAPC, BPy-TP2, PTB7, P3HT, PBDB-T, ITIC, PCBM, C 60 and the like can be used.

[0101] Among the organic semiconductor materials mentioned above, CuPc, PTB7, P3HT, etc., are generally considered to be p-type organic semiconductors. Also, ITIC, PCBM, C 60 These are generally considered to be n-type organic semiconductors. However, the conductivity type (p-type, n-type) of these semiconductor materials changes depending on the material system to which they are bonded. Therefore, it is preferable to select multiple organic semiconductor materials to be used in the photoelectric conversion layer 22, taking this into consideration.

[0102] Furthermore, it is preferable that the material of the metal layer included in the photodetector 20 includes at least one of Cu, Al, Ag, Au, and Pt.

[0103] Various materials can be used for the core layer 12 in the optical waveguide section 10, such as glass, plastic (PET, PEN, etc.), silicon, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride. Similarly, for the first cladding layer 11 in the optical waveguide section 10, materials such as glass, plastic (PET, PEN, etc.), air, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride can be used.

[0104] The configuration of the light detection device 1A according to this embodiment and the operation of the light detection device 1A in detecting target light will be further explained.

[0105] In the photodetector 1A shown in Figure 1, the first interface 31 between the first metal layer 21 and the photoelectric conversion layer 22 is configured to induce surface plasmons. Furthermore, as described above, the second interface 32 between the second metal layer 23 and the photoelectric conversion layer 22 may also be configured to induce surface plasmons in the same way as the first interface 31.

[0106] Thus, when both the first interface 31 and the second interface 32 are configured to induce surface plasmons, the photodetector 20 can be configured to produce mode splitting into coupled and anticoupled modes through the interaction of the surface plasmon modes at the first interface 31 and the surface plasmon modes at the second interface 32. In this case, the photodetector 20 can detect the target light by coupling the waveguide mode in the optical waveguide 10 with the coupled or anticoupled mode in the photodetector 20.

[0107] Figure 3 schematically illustrates the mode splitting into coupled and anticoupled modes due to the interaction of multiple surface plasmon modes. As shown in Figure 3, in the configuration shown in Figure 1, the surface plasmon mode M0 at the first interface 31 and the surface plasmon mode M0 at the second interface 32 interact, resulting in mode splitting into an anticoupled mode M1 on the high-frequency (high-energy) side and a coupled mode M2 ​​on the low-frequency (low-energy) side.

[0108] When mode splitting of surface plasmon modes occurs in this manner, either the antibonding mode M1 or the bonding mode M2 ​​can be used as the surface plasmon mode at the interface of the photodetector 20 used for detecting the target light. For reference, Figure 3 schematically shows the charge distribution at the interface for each mode. For further information on the bonding and antibonding modes of surface plasmon modes, see, for example, Patent Document 2.

[0109] Figure 4 shows the mode splitting into coupled and anticoupled modes in the photodetector unit 20 of the photodetector 1A shown in Figure 1. Figure 4(a) shows the laminated structure of the photodetector unit 20, consisting of a first metal layer 21, a photoelectric conversion layer 22, and a second metal layer 23. Here, the thickness of the photoelectric conversion layer 22, which corresponds to the distance between the first metal layer 21 and the second metal layer 23, is denoted as h. Figure 4(b) shows the magnetic field distribution in the anticoupled mode, and Figure 4(c) shows the magnetic field distribution in the coupled mode.

[0110] The characteristic equations for the antibonding and bonding modes due to surface plasmon modes at the first interface 31 and the second interface 32 can also be derived starting from Maxwell's equations, similar to the surface plasmon modes at a single interface. Specifically, the characteristic equations for the antibonding and bonding modes are expressed by equations (6) and (7) below.

number

number

[0111] The characteristic equations (6) and (7) above include the dispersion relation between the propagation constant β or wavenumber k and the angular frequency ω in both the anticoupled mode and the coupled mode, which arise from the interaction of surface plasmon modes at the first interface 31 and the second interface 32. Figure 5 is a graph showing the dispersion relation in the waveguide mode in the optical waveguide section 10, the surface plasmon mode in the photodetector section 20, and the anticoupled and coupled modes generated by mode splitting.

[0112] In Figure 5, graph G0 shows the light line, similar to the graph in Figure 2, and graph G1 shows the dispersion relationship of the waveguide modes in the optical waveguide section 10. Furthermore, graph G2 shows the dispersion relationship of the surface plasmon modes at a single interface in the photodetector section 20, graph G3 shows the dispersion relationship of the anticoupled modes generated by mode splitting, and graph G4 shows the dispersion relationship of the coupled modes.

[0113] Graph G1 shows the dispersion relationship when the material of the first cladding layer 11 is SiO2 and the material of the core layer 12 is SiN with a layer thickness of 500 nm. Graphs G2, G3, and G4 show the dispersion relationship when the materials of the first metal layer 21 and the second metal layer 23 are Ag and the material of the photoelectric conversion layer 22 is a mixed material of P3HT and PCBM.

[0114] Furthermore, graphs G3 and G4, which show the dispersion relationship when mode splitting occurs, represent the dispersion relationship when the thickness of the photoelectric conversion layer 22 is set to h = 100 nm. As shown in these graphs, for a constant wavenumber k, the dispersion relationship of the anticoupled mode (graph G3) is on the high-frequency side, while the dispersion relationship of the coupled mode (graph G4) is on the low-frequency side, compared to the dispersion relationship of the surface plasmon mode at a single interface (graph G2).

[0115] In the example of dispersion relations shown in Figure 5, similar to the example in Figure 2, a configuration in which the dispersion relations of the waveguide modes in the optical waveguide section 10 and the dispersion relations of the surface plasmon modes, anticoupled modes, or coupled modes in the photodetector section 20 coincide can be used for detecting the target light. For example, in the configuration of Figure 5, the wavenumber is k = 0.017 (nm). -1 ), the angular frequency is ω = 3.25 × 10 15 When the speed is (rad / s), the dispersion relation of the waveguide mode shown in graph G1 and the dispersion relation of the anticoupled mode shown in graph G3 coincide, and this can be used to detect the target light.

[0116] Furthermore, when mode splitting into antibonding and bonding modes occurs, the propagation constant β of the split surface plasmon mode takes a value farther than the propagation constant β of the surface plasmon mode in the case of a single interface as the distance h between the interfaces where the surface plasmon mode is generated decreases (the interfaces are close together), and the energy splitting width between the antibonding and bonding modes due to mode splitting increases. Figure 6 is a graph showing the dispersion relations for the surface plasmon mode in the photodetector 20, and for the antibonding and bonding modes generated by mode splitting, similar to Figure 5.

[0117] In Figure 6, graph G0 shows the light line, and graph G2 shows the dispersion relationship of the surface plasmon mode at a single interface in the photodetector 20. Graph G3 shows the dispersion relationship of the antibonding mode when the thickness of the photoelectric conversion layer 22 is h=100nm, and graph G4 shows the dispersion relationship of the coupling mode in the same case. Graph G5 shows the dispersion relationship of the antibonding mode when the thickness of the photoelectric conversion layer 22 is h=75nm, and graph G6 shows the dispersion relationship of the coupling mode in the same case.

[0118] As shown in Figure 6, the dispersion relationship between wavenumber k and angular frequency ω changes by changing the thickness h of the photoelectric conversion layer 22. In other words, in such a configuration, in addition to selecting the materials for the first metal layer 21, the photoelectric conversion layer 22, and the second metal layer 23, the conditions used for detecting the target light can be controlled and adjusted by setting the thickness h of the photoelectric conversion layer 22 and the thicknesses of the first metal layer 21 and the second metal layer 23, respectively.

[0119] Furthermore, in the above configuration, of the antibonding mode and the bonding mode, the antibonding mode is a mode in which the electric field is concentrated on the photoelectric conversion layer 22 side, and energy is less likely to be absorbed by the metal layers 21 and 23. In this case, more energy can be absorbed by the photoelectric conversion layer 22, and the target light can be detected suitably.

[0120] Furthermore, mode splitting due to the interaction of multiple surface plasmon modes as described above also occurs when the number of interfaces where surface plasmons are induced and the number of interacting surface plasmon modes are three or more. In this case, three or more modes are generated by mode splitting, and the photodetector 20 detects the target light by coupling the waveguide mode in the optical waveguide 10 with one of the multiple modes in the photodetector 20.

[0121] Figure 7 illustrates the mode splitting into multiple modes when three surface plasmon modes interact at three interfaces, as an example of such a configuration. Figures 7(a) to 7(d) show the magnetic field distribution in each mode resulting from mode splitting, respectively. Mode splitting into multiple modes also occurs when there are four or more interfaces. Furthermore, increasing the number of interfaces and the number of interacting surface plasmon modes increases the number of modes resulting from mode splitting, thereby improving the controllability of the dispersion relation.

[0122] For multiple modes arising from the interaction of three or more surface plasmon modes at three or more interfaces, if we designate the layers from the bottom as the sth layer, the 1st layer, ..., the ith layer, ..., the Nth layer, and the cth layer, then, similar to the antibonding and bonding modes described above, we can derive characteristic equations starting from Maxwell's equations. However, i is between 1 and N. Specifically, the characteristic equations for multiple modes are expressed by equations (8) and (9) below.

number

number

[0123] Furthermore, the definitions of the parameters included in equation (8), which represents the characteristic equation of the TM mode, are expressed in equations (10) and (11) below.

number

number

[0124] Similarly, the definitions of the parameters included in equation (9), which represents the characteristic equation for the TE mode, are expressed in equations (12) and (13) below.

number

number

[0125] Furthermore, in the above formula, γ s gamma c gamma i This is as shown in equation (14) below.

number

[0126] In the configuration of the photodetector 1A shown in Figure 1, in addition to the surface plasmon modes at the first interface 31 and the second interface 32 described above, the surface plasmon modes at the lower interface 30 on the optical waveguide portion 10 side of the first metal layer 21 may also contribute to the generation of multiple modes due to mode splitting.

[0127] In the configuration described above, the photodetector 20 can be configured to produce mode splitting into multiple modes through the interaction of two or more surface plasmon modes among the surface plasmon modes at the first interface 31, the second interface 32, and the lower interface 30. In this case, the photodetector 20 detects the target light by coupling the waveguide mode in the optical waveguide 10 with one of the multiple modes in the photodetector 20.

[0128] The configuration of the photodetector 1A according to this embodiment, and the operation of the photodetector 1A in detecting target light, etc., will be further explained along with an example of its configuration. Figure 8 is a diagram showing the specific configuration of the photodetector, where Figure 8(a) is an xz side cross-sectional view and Figure 8(b) is a yz top view. Figure 9 is an xy cross-sectional view showing the configuration of the photodetector shown in Figure 8. In Figure 9, the cross-sectional structure is shown at a slightly larger scale than in Figure 8. In this example configuration, the first metal layer 21 in the photodetector 20 has a first electrode structure formed on the first cladding layer 11 on one side of the core layer 12 in the top view of Figure 8(b). Similarly, the second metal layer 23 has a second electrode structure formed on the first cladding layer 11 on the other side of the core layer 12.

[0129] Furthermore, regarding the configuration of the photodetector 20, the thickness of the photoelectric conversion layer 22 is set to h, the thickness of the first metal layer 21 is set to t1, the thickness of the second metal layer 23 is set to t2, and the length of the photodetector 20 is set to l. Also, regarding the configuration of the optical waveguide 10, the thickness of the core layer 12 is set to d, and the width of the core layer 12 is set to w.

[0130] The length l of the photodetector 20 is the length of the region formed by the overlapping of the first electrode layer, the photoelectric conversion layer 22, and the second electrode layer. In a preferred configuration, the length of the photoelectric conversion layer 22 is set to be greater than the length of the first electrode layer (lower electrode layer), and the length of the first electrode layer (lower electrode layer) is set to be greater than or equal to the length of the second electrode layer (upper electrode layer). The configuration condition that the length of the photoelectric conversion layer 22 is longer than that of the electrode layers is a necessary condition to prevent short circuits between the first electrode layer and the second electrode layer.

[0131] In the above configuration, the thickness h of the photoelectric conversion layer 22 is preferably set within the range of 0.01 μm to 5 μm, and the upper limit is more preferably set within the range of 2 μm or less. The lower limit of thickness h, 0.01 μm, is the minimum thickness that can be suitably formed. If the photoelectric conversion layer 22 is made thinner than this, an uneven distribution of the organic semiconductor material occurs, and electrical characteristics such as current leakage also deteriorate. The upper limit of thickness h, 5 μm or 2 μm, is based on the condition that the generated carriers can be sufficiently and efficiently collected by the electrode layer when the photodetector 20 is operated in an unbiased state.

[0132] The thickness t1 of the first metal layer 21 or the first electrode layer is preferably set within the range of 0.005 μm or more and 1 μm or less, and the upper limit is more preferably set within the range of 0.5 μm or less. The lower limit of thickness t1, 0.005 μm, is the minimum thickness at which the metal layer or the like can be suitably formed. The upper limit of thickness t1, 1 μm, is based on the condition that the evanescent wave of the target light propagating through the optical waveguide 10 can reach the first interface 31. The upper limit of 0.5 μm is based on the condition that mode splitting is likely to occur between the surface plasmon mode at the lower interface 30 and the surface plasmon mode at the first interface 31.

[0133] The thickness t2 of the second metal layer 23 or the second electrode layer is preferably set within the range of 0.005 μm or more and 1 μm or less, and the upper limit is more preferably set within the range of 0.5 μm or less. The lower limit of thickness t2, 0.005 μm, is the minimum thickness at which the metal layer, etc., can be suitably formed. The upper limit of thickness t2, 1 μm, is based on the condition that metal peeling, etc., does not occur. Furthermore, the upper limit of 0.5 μm is based on the condition that there is no light transmission and electrical conductivity can be ensured.

[0134] The length l of the photodetector 20 is preferably set within the range of 0.01 μm to 5000 μm, and its upper limit is more preferably set within the range of 2000 μm or less. The lower limit of 0.01 μm for length l is the minimum length that can be suitably formed. The upper limit of 5000 μm for length l is based on the condition that the transmitted light intensity after the target light has passed through the photodetector 20 is about 8 to 10 orders of magnitude smaller than the incident light intensity. The upper limit of 2000 μm is based on the condition that the transmitted light intensity is about 3 to 4 orders of magnitude smaller than the incident light intensity.

[0135] The thickness d of the core layer 12 is preferably set within the range of 0.01 μm to 10 μm, and its upper limit is more preferably set within the range of 5 μm or less, or 2 μm or less. The lower limit of thickness d, 0.01 μm, is the minimum thickness that can be suitably formed. The upper limit of thickness d, 10 μm, is based on the condition that target light of a predetermined wavelength can propagate stably. Specifically, for target light with a wavelength of about 2000 nm, which is on the longer wavelength side of the assumed wavelength range, this thickness allows for about 10 to 15 waveguide modes. If there are more waveguide modes than this, the propagation loss increases, making it difficult for the target light to propagate over long distances.

[0136] Furthermore, the upper limit of thickness d, 5 μm, is a thickness at which approximately 5 to 6 waveguide modes exist. This is roughly equivalent to the number of modes present in typical multimode fibers. Moreover, the upper limit of 2 μm is a thickness at which approximately 1 to 3 waveguide modes exist. In this case, a single-mode optical waveguide can be realized within the expected wavelength range, allowing the target light to propagate over longer distances.

[0137] The width w of the core layer 12 is preferably set within the range of 0.01 μm to 10 μm, and its upper limit is more preferably set within the range of 5 μm or less, or 2 μm or less. The conditions for the upper and lower limits of the width w of the core layer 12 are the same as those for the thickness d of the core layer 12.

[0138] A specific example of the configuration of the photodetector 1A will be described. This example configuration is assumed when determining the dispersion relation graphs shown in Figures 2, 5, and 6. In the optical waveguide section 10, the material of the core layer 12 is silicon nitride (Si3N4), the material of the first cladding layer 11 is borosilicate glass, and the thickness of the core layer 12 is d = 500 nm.

[0139] Furthermore, in the photodetector 20, the material of the first metal layer 21 is silver (Ag), the material of the second metal layer 23 is also silver (Ag), the material of the photoelectric conversion layer 22 is a P3HT / PCBM mixed material with a mass ratio of 1.3:1.0, and the thickness of the photoelectric conversion layer 22 is h=100nm. The refractive index of the photoelectric conversion layer 22 is the refractive index obtained when 16.8 mg of P3HT and 13.2 mg of PCBM are dissolved in 1 ml of chlorobenzene, coated, and dried to form a solid film.

[0140] A method for manufacturing the photodetector 1A according to this embodiment will now be described. Figures 10 to 17 show the first to eighth steps of the manufacturing method of the photodetector 1A, respectively. In each of Figures 10 to 17, (a) shows an xz side view in the y-axis direction, and (b) shows an xy cross-sectional view in the z-axis direction. The configuration of the photodetector basically assumes the materials and the like described in the above-mentioned configuration example.

[0141] In the first step shown in Figure 10, a substrate 50 is prepared, which includes at least a first cladding layer 11 made of silicon dioxide (SiO2) (substrate preparation step). The substrate 50 may consist only of the first cladding layer 11 as shown in Figure 10, or it may include a support substrate in addition to the first cladding layer 11 that supports the first cladding layer 11 and the core layer 12, and the first cladding layer 11 may be formed on the support substrate.

[0142] In the second step shown in Figure 11, a core layer forming layer 51 made of silicon nitride (Si3N4) is formed on the first cladding layer 11. For forming this core layer forming layer 51, CVD, ALD, sputtering, vapor deposition, or coating methods are preferred, and specifically, plasma CVD is used, for example.

[0143] In the third step shown in Figure 12, a resist pattern 52 having a waveguide pattern of a predetermined width extending in the z-axis direction is formed on the core layer formation layer 51. It is preferable to use photolithography or electron beam lithography to form this resist pattern 52.

[0144] In the fourth step shown in Figure 13, the core layer formation layer 51 is etched using the resist pattern 52 as a mask to form a core layer 12 with a predetermined pattern. For etching this core layer 12, reactive ion etching, for example, can be used. The second to fourth steps shown in Figures 11 to 13 correspond to the core layer formation steps for forming the core layer 12.

[0145] In the fifth step shown in Figure 14, a resist pattern 53 having a predetermined electrode pattern is formed on the first cladding layer 11 and the core layer 12. It is preferable to use photolithography or electron beam lithography to form this resist pattern 53. For the planar shape of the electrode pattern in the resist pattern 53, for example, the shape of the first electrode layer shown in the top view of Figure 8(b) can be referenced. The same applies to the planar shapes of each layer formed in subsequent steps.

[0146] In the sixth step shown in Figure 15, a first metal layer 21, which is a first electrode layer made of silver (Ag), is formed using the resist pattern 53 as a mask (first electrode layer formation step). For the formation of this first electrode layer, sputtering or vapor deposition is preferred; specifically, vapor deposition using a vacuum deposition apparatus is used. The lift-off process is performed by removing the resist pattern using acetone.

[0147] In the seventh step shown in Figure 16, a photoelectric conversion layer 22 having a bulk heterojunction made of multiple organic semiconductor materials is formed on the first metal layer 21 (photoelectric conversion layer formation step). This photoelectric conversion layer 22 is formed, for example, by simultaneously heating and depositing multiple organic semiconductor materials using a vacuum deposition apparatus with a shadow mask (co-deposition).

[0148] In the eighth step shown in Figure 17, a second metal layer 23, which is a second electrode layer made of aluminum (Al), is formed on the photoelectric conversion layer 22 (second electrode layer formation step). For the formation of this second electrode layer, sputtering or vapor deposition is preferably used, and specifically, for example, vapor deposition using a vacuum deposition apparatus with a shadow mask is used.

[0149] Furthermore, in forming the photoelectric conversion layer 22, a configuration can be used in which multiple organic semiconductor materials are prepared, and the multiple organic semiconductor materials are placed in a predetermined container and stirred in the container to create a photoelectric conversion layer forming material having a bulk heterostructure (layer separation state), and this photoelectric conversion layer forming material is used to form the photoelectric conversion layer 22 having a bulk heterojunction.

[0150] When using a photoelectric conversion layer forming material as described above, the photoelectric conversion layer forming material may be prepared by stirring multiple organic semiconductor materials and a solvent in a predetermined container, and the photoelectric conversion layer 22 may be formed by a dispenser method, inkjet method, die coating method, spin coating method, or printing method. Alternatively, the photoelectric conversion layer 22 may be formed by simultaneously depositing multiple organic semiconductor materials using a sputtering method or a vapor deposition method.

[0151] Furthermore, in forming the photoelectric conversion layer 22, the photoelectric conversion layer 22 may be fired in an atmospheric environment, an inert gas atmosphere, or a vacuum environment after its formation.

[0152] The configuration of the optical detection device, which includes an optical waveguide and an optical detection unit, and the operation of the optical detection device in detecting target light will be further explained. In the following figures, the metal layer included in the optical detection unit 20 is shown with hatching. Also, the following figures are side cross-sectional views similar to Figure 1, and the xyz Cartesian coordinate system is omitted from the illustration.

[0153] Figure 18 is a schematic side cross-sectional view showing the configuration of the second embodiment of the photodetector. In this embodiment, the configuration of the photodetector 1B is the same as that shown in Figure 1 for the optical waveguide section 10, but the configuration of the photodetector section 20 is different.

[0154] The photodetector 20 is composed of a first electrode layer, a photoelectric conversion layer 22, and a second electrode layer. In this embodiment, the first electrode layer is composed of a first metal layer 21 made of a metal material. The second electrode layer is composed of a second transparent electrode layer 25 made of a transparent conductive material.

[0155] In the configuration shown in Figure 18, the photodetector 20 can use a configuration in which the first interface 31 between the first metal layer 21 and the photoelectric conversion layer 22 is configured to induce surface plasmons, and the target light is detected by coupling the waveguide mode in the optical waveguide section 10 with the surface plasmon mode at the first interface 31.

[0156] Furthermore, the photodetector 20 is configured such that the interaction between the surface plasmon mode at the first interface 31 and the surface plasmon mode at the lower interface 30 of the first metal layer 21 causes mode splitting into coupled and anticoupled modes, and a configuration can be used in which the target light is detected by coupling the waveguide mode in the optical waveguide 10 with the coupled or anticoupled mode.

[0157] When the photodetector 20 has a second transparent electrode layer 25, the manufacturing method of the photodetector involves forming a second electrode layer composed of the second transparent electrode layer 25 in the second electrode layer formation step. Furthermore, as the transparent conductive material for the second transparent electrode layer 25, for example, ITO, AZO, FTO, ZnO, PEDOT:PSS, etc., can be used.

[0158] Figure 19 is a schematic side cross-sectional view showing the configuration of the third embodiment of the photodetector. In this embodiment, the configuration of the photodetector 1C is the same as that shown in Figure 1 for the optical waveguide section 10, but the configuration of the photodetector section 20 is different.

[0159] The photodetector 20 is composed of a first electrode layer, a photoelectric conversion layer 22, and a second electrode layer. In this embodiment, the first electrode layer is composed of a first transparent electrode layer 24 made of a transparent conductive material. The second electrode layer is composed of a second metal layer 23 made of a metallic material.

[0160] In the configuration shown in Figure 19, the photodetector 20 can use a configuration in which the second interface 32 between the second metal layer 23 and the photoelectric conversion layer 22 is configured to induce surface plasmons, and the target light is detected by coupling the waveguide mode in the optical waveguide section 10 with the surface plasmon mode at the second interface 32.

[0161] When the photodetector 20 has a first transparent electrode layer 24, the manufacturing method of the photodetector device involves forming a first electrode layer composed of the first transparent electrode layer 24 in the first electrode layer formation step. Furthermore, as the transparent conductive material for the first transparent electrode layer 24, for example, ITO, AZO, FTO, ZnO, PEDOT:PSS, etc., can be used.

[0162] Figure 20 is a schematic side cross-sectional view showing the configuration of the fourth embodiment of the photodetector. The configuration of the photodetector 1D according to this embodiment is the same as that shown in Figure 1 for the photodetector unit 20, but the configuration of the optical waveguide unit 10 is different.

[0163] The optical waveguide section 10 is composed of a first cladding layer 11, a core layer 12, and a second cladding layer 14 provided between the core layer 12 and the first metal layer 21 of the photodetector 20, and having a lower refractive index than the core layer 12. The second cladding layer 14 is provided over the entire area on the core layer 12, including the region between the core layer 12 and the first metal layer 21 and the region where the photodetector 20 is not provided.

[0164] Furthermore, when the optical waveguide section 10 has a second cladding layer 14, the manufacturing method of the photodetector further includes a second cladding layer formation step for forming the second cladding layer 14. The material of the second cladding layer 14 is the same as the material of the first cladding layer 11.

[0165] Figure 21 is a schematic side cross-sectional view showing the configuration of the fifth embodiment of the photodetector. In this embodiment, the configuration of the photodetector 1E is the same as that shown in Figure 1 for the photodetector unit 20, but the configuration of the optical waveguide unit 10 is different.

[0166] The optical waveguide section 10 is composed of a first cladding layer 11, a core layer 12, a second cladding layer 14, and a lower intermediate layer 15 provided between the second cladding layer 14 and the first metal layer 21 of the photodetector section 20.

[0167] Furthermore, when the optical waveguide section 10 has a lower intermediate layer 15, the manufacturing method of the photodetector device further includes a lower intermediate layer formation step for forming the lower intermediate layer 15. Regarding the material of the lower intermediate layer 15, for example, a dielectric material, the same material as the photoelectric conversion layer 22 of the photodetector section 20, etc., can be used.

[0168] Figure 22 is a schematic side cross-sectional view showing the configuration of the sixth embodiment of the photodetector. In this embodiment, the configuration of the photodetector 1F is the same as that shown in Figure 1 for the optical waveguide section 10, but the configuration of the photodetector section 20 is different.

[0169] The photodetector 20 is composed of a first metal layer 21 which is a first electrode layer, a photoelectric conversion layer 22, a second metal layer 23 which is a second electrode layer, and a lower intermediate layer 26 provided between the optical waveguide 10 and the first metal layer 21. The lower intermediate layer 26 is made of, for example, the same material as the photoelectric conversion layer 22. Such a configuration is effective, for example, in generating surface plasmon modes at the lower interface 30 of the first metal layer 21.

[0170] Furthermore, when the photodetector 20 has a lower intermediate layer 26, the manufacturing method of the photodetector device further includes a lower intermediate layer formation step of forming the lower intermediate layer 26 between the optical waveguide 10 and the first electrode layer of the photodetector 20. In this case as well, the lower intermediate layer 26 is made of the same material as, for example, the photoelectric conversion layer 22.

[0171] Figure 23 is a schematic side cross-sectional view showing the configuration of the seventh embodiment of the photodetector. In this embodiment, the configuration of the photodetector 2A is the same as that shown in Figure 1 for the optical waveguide section 10, but the configuration of the photodetector section 20 is different.

[0172] The photodetector 20 is composed of a first metal layer 21 which is a first electrode layer, a photoelectric conversion layer 22, a second metal layer 23 which is a second electrode layer, and an intermediate metal layer 27 provided within the photoelectric conversion layer 22 between the first metal layer 21 and the second metal layer 23.

[0173] In the configuration shown in Figure 23, the photodetector 20 can use a configuration in which at least one of the first intermediate interface 33 between the intermediate metal layer 27 and the photoelectric conversion layer 22 on the first metal layer 21 side, and the second intermediate interface 34 between the intermediate metal layer 27 and the photoelectric conversion layer 22 on the second metal layer 23 side, is configured to induce surface plasmons, and the target light is detected by coupling the waveguide mode in the optical waveguide section 10 with the surface plasmon mode at the first intermediate interface 33 or the second intermediate interface 34.

[0174] Furthermore, the photodetector 20 is configured such that both the first intermediate interface 33 and the second intermediate interface 34 are capable of inducing surface plasmons, and the interaction between the surface plasmon mode at the first intermediate interface 33 and the surface plasmon mode at the second intermediate interface 34 causes mode splitting into coupled and anticoupled modes. This configuration allows for the detection of target light by coupling the waveguide mode in the optical waveguide 10 with either the coupled or anticoupled mode. Such a configuration can also be used in other embodiments having an intermediate metal layer 27.

[0175] Furthermore, the photodetector 20 is configured such that the first interface 31 is capable of inducing surface plasmons, and the second interface 32 is also capable of inducing surface plasmons, and that two or more surface plasmon modes from among the surface plasmon modes at the first interface 31, the second interface 32, the first intermediate interface 33, the second intermediate interface 34, and the lower interface 30 of the first metal layer 21 interact to cause mode splitting into multiple modes, and a configuration can be used in which the waveguide mode in the optical waveguide section 10 is coupled with one of the multiple modes to detect the target light.

[0176] Furthermore, when the photodetector 20 has an intermediate metal layer 27, the manufacturing method of the photodetector device further includes an intermediate metal layer formation step of forming the intermediate metal layer 27 as a metal layer in the photoelectric conversion layer 22 between the first electrode layer and the second electrode layer. The material of the intermediate metal layer 27 is the same as the material of the first metal layer 21 and the second metal layer 23.

[0177] Furthermore, the length, width, etc. of the intermediate metal layer 27 are appropriately set considering the length, width, etc. of the first electrode layer and the second electrode layer. In addition, in order to prevent short circuits between the intermediate metal layer 27 and the first electrode layer or the second electrode layer, it is preferable that the size of the intermediate metal layer 27 be set to be smaller than that of the photoelectric conversion layer 22. Furthermore, the thickness of the photoelectric conversion layer 22 on the first metal layer 21 side relative to the intermediate metal layer 27 is preferably 0.01 μm or more, and similarly, the thickness of the photoelectric conversion layer 22 on the second metal layer 23 side relative to the intermediate metal layer 27 is preferably 0.01 μm or more.

[0178] Furthermore, even in a configuration where the photodetector 20 has an intermediate metal layer 27, the reading of the electrical signal indicating the detection of the target light is performed using the first electrode layer and the second electrode layer, and the intermediate metal layer 27 is not used for reading the electrical signal.

[0179] Figure 24 is a schematic side cross-sectional view showing the configuration of the eighth embodiment of the photodetector. The configuration of the photodetector 2B according to this embodiment is the same as that shown in Figure 1 for the optical waveguide section 10, but the configuration of the photodetector 20 is different.

[0180] The photodetector 20 is composed of a first metal layer 21 which is a first electrode layer, a photoelectric conversion layer 22, a second transparent electrode layer 25 which is a second electrode layer, and an intermediate metal layer 27 provided in the photoelectric conversion layer 22 between the first metal layer 21 and the second transparent electrode layer 25.

[0181] In the configuration shown in Figure 24, the photodetector 20 is configured such that the first interface 31 is capable of inducing surface plasmons, and two or more surface plasmon modes from among the surface plasmon modes at the first interface 31, the first intermediate interface 33, the second intermediate interface 34, and the lower interface 30 of the first metal layer 21 interact to cause mode splitting into multiple modes. A configuration can be used in which the target light is detected by coupling the waveguide mode in the optical waveguide section 10 with one of the multiple modes.

[0182] Figure 25 is a schematic side cross-sectional view showing the configuration of the ninth embodiment of the photodetector. In this embodiment, the configuration of the photodetector 2C is the same as that shown in Figure 1 for the optical waveguide section 10, but the configuration of the photodetector section 20 is different.

[0183] The photodetector 20 is composed of a first transparent electrode layer 24 which is a first electrode layer, a photoelectric conversion layer 22, a second metal layer 23 which is a second electrode layer, and an intermediate metal layer 27 provided within the photoelectric conversion layer 22 between the first transparent electrode layer 24 and the second metal layer 23.

[0184] In the configuration shown in Figure 25, the photodetector 20 is configured such that the second interface 32 is capable of inducing surface plasmons, and two or more surface plasmon modes from among the surface plasmon modes at the second interface 32, the first intermediate interface 33, and the second intermediate interface 34 interact to cause mode splitting into multiple modes. A configuration can be used in which the target light is detected by coupling the waveguide mode in the optical waveguide section 10 with one of the multiple modes.

[0185] Figure 26 is a schematic side cross-sectional view showing the configuration of the tenth embodiment of the photodetector. The configuration of the photodetector 2D according to this embodiment is the same as that shown in Figure 1 for the optical waveguide section 10, but the configuration of the photodetector section 20 is different.

[0186] The photodetector 20 is composed of a first transparent electrode layer 24 which is a first electrode layer, a photoelectric conversion layer 22, a second transparent electrode layer 25 which is a second electrode layer, and an intermediate metal layer 27 provided in the photoelectric conversion layer 22 between the first transparent electrode layer 24 and the second transparent electrode layer 25.

[0187] In the configuration shown in Figure 26, both the first intermediate interface 33 and the second intermediate interface 34 are configured to induce surface plasmons, and the interaction between the surface plasmon mode at the first intermediate interface 33 and the surface plasmon mode at the second intermediate interface 34 causes mode splitting into coupled and anticoupled modes. This configuration allows for the detection of target light by coupling the waveguide mode in the optical waveguide section 10 with the coupled or anticoupled mode.

[0188] Furthermore, the photodetector 20 can also be configured as shown in Figure 26, with the first electrode layer and the second electrode layer being composed of a first transparent electrode layer 24 and a second transparent electrode layer 25, respectively. In this case, it is necessary to provide a metal layer other than the first and second electrode layers that is in contact with the photoelectric conversion layer 22, such as the intermediate metal layer 27 described above.

[0189] Figure 27 is a schematic side cross-sectional view showing the configuration of the 11th embodiment of the photodetector. The configuration of the photodetector 2E according to this embodiment is the same as that shown in Figure 1 for the optical waveguide section 10, but the configuration of the photodetector section 20 is different.

[0190] The photodetector 20 is composed of a first metal layer 21 which is a first electrode layer, a photoelectric conversion layer 22, a second metal layer 23 which is a second electrode layer, a first intermediate layer 28 provided between the first metal layer 21 and the photoelectric conversion layer 22, and a second intermediate layer 29 provided between the second metal layer 23 and the photoelectric conversion layer 22. The thickness of each intermediate layer is preferably set to be sufficiently thin with respect to the wavelength of the target light, for example, 0.1 nm to 50 nm. In this case, such intermediate layers, together with the photoelectric conversion layer 22, define an effective refractive index and can be treated as an effective photoelectric conversion layer. In this case, the interface between the metal layer and the intermediate layer functions as the interface between the effective metal layer and the photoelectric conversion layer.

[0191] Furthermore, when the photodetector 20 has a first intermediate layer 28, the method for manufacturing the photodetector device further includes a first intermediate layer formation step of forming the first intermediate layer 28 between the first electrode layer and the photoelectric conversion layer 22. Also, when the photodetector 20 has a second intermediate layer 29, the method for manufacturing the photodetector device further includes a second intermediate layer formation step of forming the second intermediate layer 29 between the second electrode layer and the photoelectric conversion layer 22. In addition, the photodetector 20 may be configured to have only one of the first intermediate layer 28 and the second intermediate layer 29.

[0192] The first intermediate layer 28 and the second intermediate layer 29 can each be layers with various functions, depending on the specific configuration of the photodetector 20. Examples of such functional layers include spacer layers, carrier block layers, carrier transport layers, work function adjustment layers, and gas trap layers.

[0193] Spacer layers are provided to adjust optical conditions such as reflectance, transmittance, and waveguide modes. Materials that can be used for spacer layers include, for example, resins (PET, PEN, etc.), silicon dioxide, aluminum oxide, and titanium oxide.

[0194] The carrier blocking layer is provided to restrict the movement of carriers between the electrode layer and the photoelectric conversion layer 22. For example, if the electrode layer is the anode, a layer that blocks the passage of electrons can be used. If the electrode layer is the cathode, a layer that blocks the passage of holes can be used. Examples of materials that can be used for the carrier blocking layer include organic semiconductors (T2T, TAPC, Alq3, etc.) and transition metal oxides (titanium oxide, zinc oxide, molybdenum oxide, etc.).

[0195] The carrier transport layer is constructed considering conditions such as the overlap of electron wave functions and the ease of electron transitions. Examples of materials that can be used for the carrier transport layer include organic semiconductors (T2T, TAPC, Alq3, etc.) and transition metal oxides (titanium oxide, zinc oxide, molybdenum oxide, etc.).

[0196] A work function adjustment layer is provided to eliminate interfaces with work function relationships that could act as carrier barriers. Examples of materials that can be used for the work function adjustment layer include alkali metals (Li, etc.) and transition metal oxides (titanium oxide, zinc oxide, molybdenum oxide, etc.).

[0197] The gas trap layer is provided to trap gases such as oxygen and water vapor that could lead to the degradation of the photoelectric conversion layer 22, thereby preventing degradation of the characteristics of the photodetector 20. Materials such as aluminum and titanium can be used for the gas trap layer.

[0198] Figure 28 is a schematic side cross-sectional view showing the configuration of the twelfth embodiment of the photodetector. In this embodiment, the configuration of the photodetector 2F is the same as that shown in Figure 1 for the optical waveguide section 10, but the configuration of the photodetector 20 is different.

[0199] In the configuration shown in Figure 28, a passivation film 16 is provided on the outer periphery of the photodetector 20 to protect it. The thickness of the passivation film 16 is preferably set to be sufficiently thin relative to the wavelength of the target light, for example, 0.1 nm to 50 nm. In this case, such a passivation film 16 can be treated in conjunction with the photoelectric conversion layer 22 to define an effective refractive index.

[0200] Furthermore, when the photodetector 20 has a passivation film 16, the method for manufacturing the photodetector device further includes a passivation film formation step of forming the passivation film 16 on the outer periphery of the photodetector 20.

[0201] For example, the passivation film 16 can be made from a single layer or multilayer film of an inorganic material, or a single layer or multilayer film of an organic material.

[0202] Modified configurations of the photodetector are described below. In the configuration of the photodetector shown in the above embodiment, the photodetector 20 is applied to an optical waveguide section 10 having a core layer and a first cladding layer that guide the target light, in order to detect the target light. However, the above configuration of the photodetector 20, such as a configuration that utilizes mode splitting due to the interaction of multiple surface plasmon modes, or a configuration that provides an intermediate metal layer in the photoelectric conversion layer between the first electrode layer and the second electrode layer, can also be applied to optical coupling structures (light incident structures) other than the optical waveguide section 10.

[0203] In such a case, the photodetector comprises an optical coupling structure used for the incidence and coupling of target light of a predetermined wavelength to be detected, and a photodetector unit provided at a predetermined position relative to the optical coupling structure, having at least a first electrode layer, a photoelectric conversion layer, and a second electrode layer in order from the optical coupling structure side. The photoelectric conversion layer is composed of a bulk heterojunction made of multiple organic semiconductor materials, and the photodetector unit is composed of at least one metal layer in contact with the photoelectric conversion layer, with the interface between the metal layer and the photoelectric conversion layer being configured to induce surface plasmons, and the photodetector unit detects the target light by coupling the target light incident from the optical coupling structure with the surface plasmon mode at the interface.

[0204] Figure 29 is a schematic side cross-sectional view showing the configuration of a first modified example of the photodetector. In the photodetector 3A according to this embodiment, a substrate 56 capable of transmitting target light is provided as an optical coupling structure for the photodetector 20, which has a first metal layer 21 as a first electrode layer, a photoelectric conversion layer 22, and a second metal layer 23 as a second electrode layer. In Figures 29 to 31 below, the dashed arrows shown in the figures indicate the optical path of the target light.

[0205] For example, consider a case where the photodetector 20 uses a configuration in which the surface plasmon mode at the first interface 31 and the surface plasmon mode at the second interface 32 interact to cause mode splitting into coupled and anticoupled modes. In this case, in the dispersion relation shown in Figure 5, the anticoupled mode, whose dispersion relation is near the light line, is configured to match the wavenumber of the target light, which is spatially propagated light, thereby enabling the detection of the target light.

[0206] Figure 30 is a schematic side cross-sectional view showing the configuration of a second modified example of the photodetector. In the photodetector 3B according to this embodiment, a configuration is used in which a diffraction grating 57 is formed in a predetermined region on the lower surface side of the substrate 56 as the optical coupling structure.

[0207] In this configuration, the target light incident from the diffraction grating 57 is diffracted by the diffraction grating 57 to obtain diffracted light with a high wavenumber. Then, by coupling this diffracted light with a coupled mode or an anti-coupled mode, the target light can be detected.

[0208] Figure 31 is a schematic side cross-sectional view showing the configuration of a third modified example of the photodetector. In the photodetector 3C according to this embodiment, a configuration is used in which a prism 58 is provided on the lower side of the substrate 56 as the optical coupling structure.

[0209] In this configuration, similar to the configuration shown in Figure 29, the anti-coupled mode is configured to match the wavenumber of the target light, which is spatially propagated light, in the dispersion relation shown in Figure 5, thereby enabling the detection of the target light. Furthermore, by providing the prism 58 with respect to the substrate 56 as described above, evanescent waves with large wavenumbers reach the light detection unit 20 at a total reflection angle greater than or equal to the total reflection angle of the prism 58. The target light can then be detected by coupling these evanescent waves with either the coupled mode or the anti-coupled mode.

[0210] The photodetector and the method for manufacturing the photodetector are not limited to the embodiments and configuration examples described above, and various modifications are possible. For example, the configurations of the optical waveguide section and the photodetector section in the photodetector are not limited to those shown in the embodiments described above, and various configurations may be used. Furthermore, a configuration combining the configurations of the embodiments described above may also be used.

[0211] Furthermore, regarding the configuration of the photoelectric conversion layer in the photodetector, in the embodiment described above, it is configured to have a bulk heterojunction made of multiple organic semiconductor materials, but other configurations may be used depending on the specific configuration of the photodetector. Such configurations include, for example, a configuration having a planar heterojunction made of organic semiconductor materials, or a configuration having a heterojunction or pn junction made of inorganic semiconductor materials.

[0212] Furthermore, regarding configurations that utilize mode splitting due to the interaction of multiple surface plasmon modes, various configurations can be used in addition to those described in relation to the embodiments described above. Generally, a configuration is available in which a surface plasmon mode at the interface between the metal layer and the photoelectric conversion layer contained in the photodetector interacts with the surface plasmon mode at that metal layer or at other interfaces between the metal layer and the photoelectric conversion layer, thereby causing mode splitting into multiple modes (for example, coupled modes and anti-coupled modes). [Industrial applicability]

[0213] The present invention can be used as a photodetector capable of suitably detecting target light propagating through an optical waveguide, and as a method for manufacturing the photodetector. [Explanation of symbols]

[0214] 1A-1F, 2A-2F, 3A-3C...Optical detection device, 10...Optical waveguide section, 11...First cladding layer, 12...Core layer, 13, 14...Second cladding layer, 15...Lower intermediate layer, 16...Passivation film 20...Photodetector, 21...First metal layer, 22...Photoelectric conversion layer, 23...Second metal layer, 24...First transparent electrode layer, 25...Second transparent electrode layer, 26...Lower intermediate layer, 27...Intermediate metal layer, 28...First intermediate layer, 29...Second intermediate layer, 30...Lower interface, 31...First interface, 32...Second interface, 33...First intermediate interface, 34...Second intermediate interface, 50...Substrate, 51...Core layer formation layer, 52...Resist pattern, 53...Resist pattern, 56...Substrate, 57...Diffraction grating, 58...Prism.

Claims

1. An optical waveguide section including a core layer that guides target light of a predetermined wavelength to be detected, and a first cladding layer having a lower refractive index than the core layer, A photodetector is provided on the side of the optical waveguide section opposite to the first cladding layer with respect to the core layer, and has, in order from the optical waveguide section side, at least a first electrode layer, a photoelectric conversion layer, and a second electrode layer. Equipped with, The photoelectric conversion layer is configured to have a bulk heterojunction of a plurality of organic semiconductor materials, the photodetector is configured to include at least one metal layer in contact with the photoelectric conversion layer, and the interface between the metal layer and the photoelectric conversion layer is configured to induce surface plasmons, The light detection unit is a light detection device that detects the target light by coupling the waveguide mode in the optical waveguide with the surface plasmon mode at the interface.

2. The photodetector according to claim 1, wherein the first electrode layer in the photodetector is composed of a first metal layer, and the first interface between the first metal layer and the photoelectric conversion layer is configured to induce surface plasmons as the interface.

3. The photodetector is configured such that a surface plasmon mode at the first interface and a surface plasmon mode at the lower interface of the first metal layer on the optical waveguide side interact to cause mode splitting into coupled and anticoupled modes, and the target light is detected by coupling the waveguide mode in the optical waveguide with the coupled or anticoupled mode, as described in claim 2.

4. The photodetector according to claim 2, wherein in the photodetector, the second electrode layer is composed of a second metal layer, and the second interface between the second metal layer and the photoelectric conversion layer is configured to induce surface plasmons.

5. The photodetector is configured such that a surface plasmon mode at the first interface and a surface plasmon mode at the second interface interact to cause mode splitting into a coupled mode and an anticoupled mode, and detects the target light by coupling the waveguide mode in the optical waveguide with the coupled mode or the anticoupled mode, as described in claim 4.

6. The photodetector is configured such that two or more surface plasmon modes, including a surface plasmon mode at the first interface, a surface plasmon mode at the second interface, and a surface plasmon mode at the lower interface of the first metal layer on the optical waveguide side, interact to cause mode splitting into multiple modes, and detects the target light by coupling the waveguide mode in the optical waveguide with any of the multiple modes, as described in claim 4.

7. The photodetector according to claim 1, wherein the metal layer in the photodetector is an intermediate metal layer provided in the photoelectric conversion layer between the first electrode layer and the second electrode layer, and at least one of the first intermediate interface between the intermediate metal layer and the photoelectric conversion layer on the first electrode layer side, and the second intermediate interface between the intermediate metal layer and the photoelectric conversion layer on the second electrode layer side, is configured to induce surface plasmons as the interface.

8. The photodetector according to claim 7, wherein both the first intermediate interface and the second intermediate interface are configured to induce surface plasmons, and the interaction between the surface plasmon mode at the first intermediate interface and the surface plasmon mode at the second intermediate interface causes mode splitting into a coupled mode and an anticoupled mode, and the target light is detected by coupling the waveguide mode in the optical waveguide with the coupled mode or the anticoupled mode.

9. The photodetector according to claim 7, wherein the first electrode layer is made of a first metal layer, the first interface between the first metal layer and the photoelectric conversion layer is configured to induce surface plasmons, the second electrode layer is made of a second metal layer, the second interface between the second metal layer and the photoelectric conversion layer is configured to induce surface plasmons, and two or more surface plasmon modes from among the surface plasmon mode at the first interface, the surface plasmon mode at the second interface, the surface plasmon mode at the first intermediate interface, the surface plasmon mode at the second intermediate interface, and the surface plasmon mode at the lower interface of the first metal layer on the optical waveguide side interact to cause mode splitting into multiple modes, and the target light is detected by coupling the waveguide mode in the optical waveguide with any of the multiple modes.

10. The photodetector according to any one of claims 1 to 9, wherein the photodetector is configured to perform the detection operation of the target light in an unbiased state in which no voltage is applied between the first electrode layer and the second electrode layer.

11. The photodetector according to any one of claims 1 to 9, wherein an intermediate layer is provided between the first electrode layer and the photoelectric conversion layer, and between the second electrode layer and the photoelectric conversion layer in the photodetector.

12. The optical waveguide portion includes a second cladding layer provided between the core layer and the first electrode layer of the photodetector, and having a lower refractive index than the core layer, according to any one of claims 1 to 9.

13. The photodetector according to any one of claims 1 to 9, wherein a lower intermediate layer is provided between the optical waveguide section and the first electrode layer of the photodetector section.

14. The photodetector according to any one of claims 1 to 9, wherein the plurality of organic semiconductor materials constituting the photoelectric conversion layer include one or more materials selected from the group consisting of thiophene, benzothiophene, phenylene vinylene, carbazole, thienopyrrole, diketopyrrolopyrrole, fullerene, carbon nanotube, dithiophene, and derivatives thereof.

15. The photodetector according to any one of claims 1 to 9, wherein the thickness of the photoelectric conversion layer is set to a thickness within the range of 0.01 μm or more and 5 μm or less.

16. The photodetector according to any one of claims 1 to 9, wherein the material of the metal layer in the photodetector comprises at least one of Cu, Al, Ag, Au, and Pt.

17. A method for manufacturing a photodetector comprising an optical waveguide section for guiding target light of a predetermined wavelength to be detected, and a photodetector section for detecting the target light, A substrate preparation step of preparing a substrate including at least a first cladding layer having a lower refractive index than the core layer, A core layer formation step is to form the core layer on the first cladding layer, which together with the first cladding layer constitutes the optical waveguide portion and guides the target light, A first electrode layer formation step is to form a first electrode layer on the side of the core layer of the optical waveguide portion opposite to the first cladding layer, A photoelectric conversion layer formation step is to form a photoelectric conversion layer having a bulk heterojunction made of a plurality of organic semiconductor materials on the side opposite to the core layer relative to the first electrode layer, A second electrode layer formation step is performed in which a second electrode layer is formed on the side opposite to the first electrode layer with respect to the photoelectric conversion layer, and together with the first electrode layer and the photoelectric conversion layer, the second electrode layer is formed to constitute the photodetector. Includes, The photodetector is configured to include at least one metal layer in contact with the photoelectric conversion layer, and the interface between the metal layer and the photoelectric conversion layer is formed to induce surface plasmons, A method for manufacturing a photodetector, wherein the photodetector is configured to detect the target light by coupling the waveguide mode in the optical waveguide with the surface plasmon mode at the interface.

18. The method for manufacturing a photodetector according to claim 17, wherein in the first electrode layer formation step, the first electrode layer composed of the first metal layer is formed as the metal layer in the photodetector, and the first interface between the first metal layer and the photoelectric conversion layer is configured to induce surface plasmons as the interface.

19. The method for manufacturing a photodetector according to claim 18, wherein in the second electrode layer formation step, the second electrode layer composed of a second metal layer is formed, and the second interface between the second metal layer and the photoelectric conversion layer is configured to induce surface plasmons.

20. The photodetector further includes an intermediate metal layer formation step, in which an intermediate metal layer is formed within the photoelectric conversion layer between the first electrode layer and the second electrode layer, as the metal layer in the photodetector. The method for manufacturing a photodetector according to claim 17, wherein at least one of the first intermediate interface between the intermediate metal layer and the photoelectric conversion layer on the first electrode layer side, and the second intermediate interface between the intermediate metal layer and the photoelectric conversion layer on the second electrode layer side, is configured to induce surface plasmons as the interface.

21. The method for manufacturing a light detection device according to any one of claims 17 to 20, wherein the light detection unit is configured to perform the detection operation of the target light in an unbiased state in which no voltage is applied between the first electrode layer and the second electrode layer.

22. A method for manufacturing a photodetector according to any one of claims 17 to 20, further comprising an intermediate layer formation step of forming an intermediate layer in at least one of the following locations in the photodetector: between the first electrode layer and the photoelectric conversion layer, and between the second electrode layer and the photoelectric conversion layer.

23. A method for manufacturing an optical detection device according to any one of claims 17 to 20, further comprising a second cladding layer formation step of forming a second cladding layer in the optical waveguide portion, which is provided between the core layer and the first electrode layer of the optical detection portion and has a lower refractive index than the core layer.

24. A method for manufacturing a photodetector according to any one of claims 17 to 20, further comprising a lower intermediate layer formation step of forming a lower intermediate layer between the optical waveguide portion and the first electrode layer of the photodetector portion.

25. A method for manufacturing a photodetector according to any one of claims 17 to 20, comprising: preparing the plurality of organic semiconductor materials in the photoelectric conversion layer formation step; creating a photoelectric conversion layer forming material by stirring the plurality of organic semiconductor materials; and forming the photoelectric conversion layer having the bulk heterojunction using the photoelectric conversion layer forming material.

26. A method for manufacturing a photodetector according to claim 25, wherein in the photoelectric conversion layer formation step, the photoelectric conversion layer forming material is prepared by stirring the plurality of organic semiconductor materials and a solvent in a predetermined container, and the photoelectric conversion layer is formed by a dispenser method, an inkjet method, a die coat method, a spin coat method, or a printing method.

27. The method for manufacturing a photodetector according to claim 25, wherein in the photoelectric conversion layer formation step, the photoelectric conversion layer is formed by simultaneously depositing the plurality of organic semiconductor materials by sputtering or vapor deposition.

28. The method for manufacturing a photodetector according to claim 25, wherein, in the photoelectric conversion layer formation step, after forming the photoelectric conversion layer, the photoelectric conversion layer is fired in an atmospheric environment, an inert gas atmosphere, or a vacuum environment.

29. A method for manufacturing a photodetector according to any one of claims 17 to 20, wherein in the core layer formation step, a core layer formation layer is formed by CVD, ALD, sputtering, vapor deposition, or coating, a resist pattern is formed on the core layer formation layer by photolithography or electron beam lithography, and the core layer is formed by etching using the resist pattern as a mask.

30. A method for manufacturing a photodetector according to any one of claims 17 to 20, wherein in the first electrode layer formation step and the second electrode layer formation step, the first electrode layer and the second electrode layer are formed by sputtering or vapor deposition, respectively.

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