Optical element

Abstract

To provide an electrode structure and a light detection element which can sufficiently extract an electric signal from an element while sufficiently transmitting a light signal to the element.SOLUTION: A light detection element 1 comprises: a first electrode 10A; a second electrode 20; and a magnetic element 30 disposed between the first electrode and the second electrode. The first electrode 10A has: a metal film 11A; an opening 12A provided on a portion of the metal film 11A; and a transparent conductive film 13A disposed on the opening 12A. The transparent conductive film 13A is electrically connected to the magnetic element 30, and it is disposed so as to overlap the magnetic element 30 in plan view from the thickness direction of the transparent conductive film 13A.SELECTED DRAWING: Figure 3B

Description

Technical Field

[0001] The present invention relates to an electrode structure and an optical sensing element including the electrode structure.

Background Art

[0002] With the spread of the Internet, the communication volume has increased exponentially, and the importance of optical communication has been extremely enhanced. Optical communication is a communication means that converts an electrical signal into an optical signal and performs transmission and reception using the optical signal.

[0003] For example, Patent Document 1 describes a receiving device that receives an optical signal using a photodiode. The photodiode is, for example, a pn junction diode using a semiconductor pn junction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] With the development of information and communication technologies, further increase in communication speed is required. Examples of high-speed communication include optical communication using far-infrared light used in long-distance networks and optical communication using visible light used between terminals. However, when visible light is used for high-speed optical communication, there is a problem that the reception sensitivity of a photodiode made of Si semiconductor significantly decreases when the frequency becomes several tens of GHz or more. On the other hand, the inventors have found that a magnetic element including a spacer layer between two ferromagnetic layers can respond to a high-frequency optical signal and can be used as a receiving element for a high-frequency optical signal. In order to use such a magnetic element as a receiving element for an optical signal, a new structure capable of efficiently transmitting an optical signal to the element and efficiently extracting an electrical signal from the element is required.

[0006] The present invention has been made in view of the above problems, and aims to provide an electrode structure that enables efficient transmission of optical signals to an element while efficiently extracting electrical signals from the element, and a photodetector element equipped with the electrode structure. [Means for solving the problem]

[0007] To solve the above problems, the following means are provided.

[0008] (1) The electrode structure according to the first embodiment comprises a metal film, an opening provided in a part of the metal film, and a transparent conductive film disposed in the opening, wherein the transparent conductive film is electrically connected to the element and overlaps with the element in a plan view from the thickness direction of the transparent conductive film.

[0009] (2) In the above embodiment, the element may be provided so as to encompass the element in a plan view from the thickness direction.

[0010] (3) In the above embodiment, the length of the opening may be less than the wavelength of light irradiated onto the transparent conductive film.

[0011] (4) A photodetector according to a second embodiment comprises a first electrode and a second electrode, a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and a magnetic element disposed between the first electrode and the second electrode, wherein the first electrode comprises a metal film, an opening provided in a part of the metal film, and a transparent conductive film disposed in the opening, the transparent conductive film is electrically connected to the magnetic element, overlaps with the magnetic element in a plan view from the thickness direction of the transparent conductive film, and light is irradiated onto the transparent conductive film.

[0012] (5) In the above embodiment, the opening may be provided so as to enclose the magnetic element in a plan view from the thickness direction.

[0013] (6) In the above embodiment, the length of the opening may be less than the wavelength of light irradiated onto the transparent conductive film.

[0014] (7) In the above embodiment, the photodetector further comprises a light transmission unit that irradiates the transparent conductive film with light, the light transmission unit having a first diffraction grating unit provided at one end of the light transmission unit and irradiated with light from the outside, a second diffraction grating unit provided at the other end of the light transmission unit and emitting light transmitted from the first diffraction grating unit, and a waveguide provided between the first diffraction grating unit and the second diffraction grating unit, wherein in a plan view of the light transmission unit, the area of ​​the first diffraction grating unit may be larger than the area of ​​the second diffraction grating unit.

[0015] (8) In the above embodiment, a plurality of the tunnel magnetic elements may be arranged in a sequence, and the opening may be provided such that it encloses the plurality of magnetic elements in a plan view from the thickness direction of the transparent conductive film. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an electrode structure and a photodetector that enable efficient transmission of optical signals to an element while efficiently extracting electrical signals from the element. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a schematic perspective view showing the configuration of a photodetector element according to an embodiment of the present invention. [Figure 2] Figure 2 is a plan view showing the configuration of the optical transmission section in Figure 1. [Figure 3A] Figure 3A is an enlarged perspective view of the light-sensing element in Figure 1. [Figure 3B] Figure 3B is a cross-sectional view along line II in Figure 3A. [Figure 4] Figure 4 is a cross-sectional view showing the configuration of the magnetic element provided in the photodetector element of Figure 1. [Figure 5A] Figure 5A is a plan view showing the configuration of the first electrode in Figure 1. [Figure 5B] FIG. 5B is a plan view showing a modification of the first electrode of FIG. 5A. [Figure 6A] FIG. 6A is a diagram for explaining an example of the length of the opening in the present invention. [Figure 6B] FIG. 6A is a diagram for explaining another example of the length of the opening in the present invention. [Figure 7] FIG. 7 is a plan view showing a modification of the first electrode of FIG. 5B. [Figure 8] FIG. 8 is a diagram showing an example of a communication system using the light detection element of FIG. 1. MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in order to make the features easy to understand, there are cases where the characteristic parts are enlarged for convenience, and the dimensional ratios of each component may be different from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and it can be appropriately modified and implemented within the range in which the effects of the present invention can be achieved.

[0019] Define the directions. The stacking direction of the light detection element 1 (the stacking direction of the magnetic element 30) is defined as the z direction, one direction in the plane orthogonal to the z direction is defined as the x direction, and the direction orthogonal to the x direction and the z direction is defined as the y direction. The z direction is an example of the stacking direction. Hereinafter, the +z direction may be expressed as "up" and the -z direction may be expressed as "down". The +z direction is the direction from the first electrode to the second electrode described later. The up and down do not necessarily coincide with the direction in which gravity acts.

[0020] FIG. 1 is a perspective view schematically showing the configuration of a light detection element according to an embodiment of the present invention. As shown in Figure 1, the photodetector 1 comprises a first electrode 10A, a second electrode 20, and a magnetic element 30 positioned between the first electrode and the second electrode. The magnetic element 30 will be described later. The photodetector 1 also further comprises a light transmission unit 40 that irradiates light onto a transparent conductive film provided on the first electrode 10A, which will be described later. The first electrode 10A and the second electrode 20 are electrically connected to a constant current drive circuit 51 and a signal processing circuit 52, respectively. Furthermore, in this invention, "light" is used to mean not only visible light, but also infrared rays with longer wavelengths than visible light, and ultraviolet rays with shorter wavelengths than visible light.

[0021] Figure 2 is a plan view showing the configuration of the optical transmission section 40 in Figure 1. As shown in Figure 2, the optical transmission section 40 has a first diffraction grating section 41 provided at one end 40a of the optical transmission section 40, to which external light is irradiated; a second diffraction grating section 42 provided at the other end 40b of the optical transmission section, from which light transmitted from the first diffraction grating section 41 is emitted; and a waveguide 43 provided between the first diffraction grating section 41 and the second diffraction grating section 42. The shape of the optical transmission section 40 is not particularly limited, but for example, it is composed of a long plate-like body. The optical transmission section 40 has a core through which light propagates and a cladding arranged on the outside to cover the core. The core is made of, for example, tantalum oxide (Ta2O5). The cladding is made of, for example, silicon oxide (SiOx, x=1~2) or aluminum oxide (Ai2O3).

[0022] The first diffraction grating section 41 is provided on one main surface 41a of the light transmission section 40 and has a plurality of grooves 41B extending in the y direction of the light transmission section 40. In this embodiment, the x direction is the longitudinal direction of the light transmission section 40, the y direction is the width direction (lateral direction) of the light transmission section 40, and the plurality of grooves 41B extend along the width direction of the light transmission section 40.

[0023] The second diffraction grating section 42 is provided on the other main surface 41b of the light transmission section 40 and has a plurality of grooves 42B that extend in the y-direction of the light transmission section 40. In this embodiment, the plurality of grooves 42B extend along the width direction of the light transmission section 40.

[0024] In a plan view of the light transmission section 40, it is preferable that the area of ​​the first diffraction grating section 41 is larger than the area of ​​the second diffraction grating section 42. The plan view shapes of the first diffraction grating section 41 and the second diffraction grating section 42 are not particularly limited, but are, for example, substantially rectangular. The dimensions and cross-sectional shape of the groove 41B constituting the first diffraction grating section 41 are preferably the same as the dimensions and cross-sectional shape of the groove 42B constituting the second diffraction grating section 42, but they may be different.

[0025] Waveguide 43 transmits light incident on the first diffraction grating section 41 to the second diffraction grating section 42. In this embodiment, waveguide 43 has a tapered shape, and the y-direction dimension (width dimension) of waveguide 43 gradually decreases from the first diffraction grating section 41 to the second diffraction grating section 42. By configuring waveguide 43 so that the cross-sectional area along the y-direction decreases from the first diffraction grating section 41 to the second diffraction grating section 42, the spot diameter of the light ray S2 emitted from the second diffraction grating section 42 becomes smaller than the spot diameter of the light ray S1 incident on the first diffraction grating section 41. The spot diameter of the light ray S1 is, for example, 1 μm or more and 2 μm or less. The spot diameter of the optical signal S2 is approximately the wavelength of the optical signal. For example, when light (ray) with a wavelength of 500 nm is irradiated onto the first diffraction grating section 41 with a spot diameter of 1 μm to 2 μm, the waveguide 43 causes light (ray) with a spot diameter of, for example, 500 nm to be emitted from the second diffraction grating section. In this way, the first diffraction grating section 41 receives a ray S1 with a relatively large spot diameter on the order of several microns, and by transmitting it through the waveguide 43, a ray S2 with a small spot diameter, approximately the wavelength of light, can be emitted from the second diffraction grating section 42.

[0026] In this embodiment, the end face 43A in the width direction of the waveguide 43 has a straight shape in a plan view, but it is not limited to this, and it is sufficient if the width dimension of the end 43b on the second diffraction grating portion 42 side is smaller than the width dimension of the end 43a on the first diffraction grating portion 41 side of the waveguide 43. For example, the end face 43A in the width direction of the waveguide 43 may have a curved shape or a stepped shape in a plan view. Furthermore, the waveguide 43 may have a first portion in which the cross-sectional area along the y-direction decreases from the first diffraction grating portion 41 to the second diffraction grating portion 42, and a second portion in which the cross-sectional area along the y-direction is substantially the same.

[0027] Figure 3A is an enlarged perspective view of the photodetector element 1 in Figure 1, and Figure 3B is a cross-sectional view along line II in Figure 3A. As shown in Figures 3A and 3B, the first electrode 10A has a metal film 11A, an opening 12A provided in a part of the metal film 11A, and a transparent conductive film 13A positioned in the opening 12A. The transparent conductive film 13A is electrically connected to the magnetic element 30 (element) and is positioned to overlap with the magnetic element 30 in a plan view from the thickness direction (z direction) of the transparent conductive film 13A. The transparent conductive film 13A has main surfaces 13a and 13b that face each other in the thickness direction. In the example shown in Figures 3A and 3B, a part of one main surface 13a of the transparent conductive film 13A is in contact with at least a part of the z-direction (stacking direction) end surface 30a of the magnetic element 30. When light is shone on the other main surface 13b of the transparent conductive film 13A, the light transmitted through the transparent conductive film 13A is shone on the magnetic element 30. The first electrode 10A may have a thin film between the transparent conductive film 13A and the magnetic element 30 that is electrically conductive and transmits light.

[0028] The shape of the first electrode 10A is not particularly limited, but for example, it is composed of a long, plate-like body extending in the x-direction. The thickness (z-direction dimension) of the metal film 11A is, for example, 50 nm to 100 nm. The metal film 11A is composed of a metal such as copper, silver, or gold.

[0029] The opening 12A is provided at the longitudinal end 10a of the first electrode 10A and has a substantially rectangular shape when viewed from a plan view, for example, in the z direction. The opening 12A is formed by penetrating the metal film along the z direction.

[0030] The transparent conductive film 13A is provided substantially parallel to the metal film 11A so as to completely cover the opening 12A. In this embodiment, the transparent conductive film 13A, like the opening 12A, has a substantially rectangular shape in plan view. The thickness of the transparent conductive film 13A may be the same as or less than the thickness of the metal film, for example, 25 nm to 100 nm. The transparent conductive film 13A is transparent to light in the wavelength range used by the light ray S1. The wavelength range used by the light ray S1 is, for example, 300 nm to 2000 nm, including the visible light range. The transparent conductive film 13A is composed of a nonmetallic material, for example, an oxide. The transparent conductive film 13A is composed of one or more selected from, for example, indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium gallium zinc oxide (IGZO). Although the electrical resistivity of the transparent conductive film 13A is greater than that of the metal film, since the transparent conductive film 13A is positioned in an opening 12A provided in a part of the metal film, the resistance of the first electrode 10A can be reduced compared to the case where the entire structure is composed of a transparent conductive film. Therefore, according to the electrode structure of the first electrode 10A, it is possible to efficiently transmit the light ray S1 to the magnetic element 30 while efficiently extracting the electrical signal from the magnetic element 30.

[0031] The shape of the second electrode 20 is not particularly limited, but for example, it is composed of a long, plate-like body extending in the y-direction. The thickness (z-direction dimension) of the second electrode 20 is, for example, 20 nm to 80 nm. The second electrode 20 is composed of, for example, a multilayer film of Ta, Cu, and Ta, a multilayer film of Ta, Cu, and Ti, or a multilayer film of Ta, Cu, and TaN.

[0032] Figure 4 is a cross-sectional view showing the configuration of the magnetic element 30 provided in the photodetector 1 of Figure 1. As shown in Figure 4, the magnetic element 30 has at least a first ferromagnetic layer 31, a second ferromagnetic layer 32, and a spacer layer 33. The spacer layer 33 is located between the first ferromagnetic layer 31 and the second ferromagnetic layer 32 and is sandwiched between them. The magnetic element 30 also has an underlayer 34 located between the second ferromagnetic layer 32 and the second electrode 20. In this specification, ferromagnetism includes ferrimagnetism. In addition to the layers described above, the magnetic element 30 may also have other ferromagnetic layers, magnetic coupling layers, perpendicular magnetization induction layers, cap layers, sidewall insulating layers, etc.

[0033] The magnetic element 30 is, for example, an MTJ (Magnetic Tunnel Junction) element in which the spacer layer 33 is made of an insulating material. In this case, the magnetic element 30 is an element whose resistance in the z direction (resistance when current is passed in the z direction) changes in accordance with the relative change between the magnetization state of the first ferromagnetic layer 31 and the magnetization state of the second ferromagnetic layer 32. Such an element is also called a magnetoresistive element. For example, the magnetic element 30's resistance in the z direction (resistance when current is passed in the z direction) changes in accordance with the change in the relative angle between the magnetization direction of the first ferromagnetic layer 31 and the magnetization direction of the second ferromagnetic layer 32. Also, for example, the magnetic element 30's resistance in the z direction (resistance when current is passed in the z direction) changes in accordance with the change in the magnitude of the magnetization of the first ferromagnetic layer 31. The overall thickness of the magnetic element 30 is, for example, 15 nm to 40 nm.

[0034] The first ferromagnetic layer 31 is a photosensitive layer whose magnetization state (e.g., magnetization direction or magnitude) changes when light is irradiated from the outside. The first ferromagnetic layer 31 is also called the magnetization free layer. The magnetization free layer is a layer containing a magnetic material whose magnetization state (e.g., magnetization direction or magnitude) changes when a predetermined external force is applied. The predetermined external force is, for example, light irradiated from the outside, a current flowing in the z direction of the magnetic element 30, or an external magnetic field.

[0035] The first ferromagnetic layer 31 contains a ferromagnetic material. The first ferromagnetic layer 31 contains magnetic elements such as Co, Fe, and Ni. The first ferromagnetic layer 31 may also contain non-magnetic elements such as B, Mg, Hf, and Gd along with the magnetic elements. Alternatively, the first ferromagnetic layer 31 may be an alloy containing both magnetic and non-magnetic elements. The first ferromagnetic layer 31 may be composed of multiple layers. In that case, the first ferromagnetic layer 31 may be, for example, a CoFeB alloy, a laminate in which a CoFeB alloy layer is sandwiched between Fe layers, or a laminate in which a CoFeB alloy layer is sandwiched between CoFe layers.

[0036] The first ferromagnetic layer 31 may be an in-plane magnetized film having an easy magnetization axis in the direction within the film plane (either direction in the xy plane), or a perpendicular magnetized film having an easy magnetization axis perpendicular to the film plane (z direction).

[0037] The thickness of the first ferromagnetic layer 31 is, for example, 1 nm to 5 nm, preferably 1 nm to 2 nm. When the first ferromagnetic layer 31 is a perpendicular magnetization film, if the thickness of the first ferromagnetic layer 31 is thin, the perpendicular magnetic anisotropy of the first ferromagnetic layer 31 increases. If the thickness of the first ferromagnetic layer 31 is thicker than 2 nm, an insertion layer made of, for example, Mo,W may be provided within the first ferromagnetic layer 31. That is, the first ferromagnetic layer 31 may be a laminate in which a ferromagnetic layer, an insertion layer, and a ferromagnetic layer are sequentially stacked in the z direction. The interfacial magnetic anisotropy at the interface between the insertion layer and the ferromagnetic layer increases the overall perpendicular magnetic anisotropy of the first ferromagnetic layer 31.

[0038] The second ferromagnetic layer 32 is a magnetization-fixed layer. The magnetization-fixed layer is a layer made of a magnetic material whose magnetization state (e.g., direction of magnetization or magnitude of magnetization) changes less easily than that of the magnetization-free layer when a predetermined external force is applied. The coercivity of the second ferromagnetic layer 32 is greater than that of the first ferromagnetic layer 31, for example. The second ferromagnetic layer 32 has an easy magnetization axis in the same direction as the first ferromagnetic layer 31. The second ferromagnetic layer 32 may be an in-plane magnetized film or a perpendicular magnetized film.

[0039] In this embodiment, the second ferromagnetic layer 32 is composed of an inner ferromagnetic layer 32A, a non-magnetic layer 32B, and an outer ferromagnetic layer 32C. In this case, the magnetization of the inner ferromagnetic layer 32A is fixed by magnetic coupling with the outer ferromagnetic layer 32C via the non-magnetic layer 32B.

[0040] The material constituting the inner ferromagnetic layer 32A is, for example, the same as that of the first ferromagnetic layer 31. The inner ferromagnetic layer 32A may be a laminate in which, for example, Co with a thickness of 0.4 nm to 1.0 nm, Mo with a thickness of 0.1 nm to 0.5 nm, a CoFeB alloy with a thickness of 0.3 nm to 1.0 nm, and Fe with a thickness of 0.3 nm to 1.0 nm are stacked in that order.

[0041] The outer ferromagnetic layer 32C is magnetically coupled to, for example, the inner ferromagnetic layer 32A. This magnetic coupling is, for example, an antiferromagnetic coupling and is caused by the RKKY interaction. The material constituting the outer ferromagnetic layer 32C is, for example, the same as that of the first ferromagnetic layer 31. The outer ferromagnetic layer 32C is, for example, a multilayer film in which Co and Pt are alternately stacked, or a multilayer film in which Co and Ni are alternately stacked.

[0042] The non-magnetic layer 32B is, for example, Ru, Ir, etc. The thickness of the non-magnetic layer 32B is, for example, the thickness at which the inner ferromagnetic layer 32A and the outer ferromagnetic layer 32C are antiferromagnetically coupled by the RKKY interaction.

[0043] The spacer layer 33 is a non-magnetic layer placed between the first ferromagnetic layer 31 and the second ferromagnetic layer 32. The spacer layer 33 is composed of a conductor, an insulator, or a semiconductor, or a layer containing a current-carrying point composed of a conductor within an insulator. The thickness of the spacer layer 33 can be adjusted according to the orientation direction of the magnetization of the first ferromagnetic layer 31 and the magnetization of the second ferromagnetic layer 32 in the initial state.

[0044] In this embodiment, the spacer layer 33 is made of an insulator. In this case, the magnetic element 30 has a magnetic tunnel junction (MTJ) consisting of a first ferromagnetic layer 31, a spacer layer 33, and a second ferromagnetic layer 32. Such an element is called an MTJ element. However, the spacer layer 33 may be made of a metal. In that case, the magnetic element 30 can exhibit a giant magnetoresistance (GMR) effect. Such an element is called a GMR element.

[0045] When the spacer layer 33 is made of an insulating material, materials such as aluminum oxide, magnesium oxide, titanium oxide, or silicon oxide can be used. By adjusting the film thickness of the spacer layer 33 so that a high TMR (Tunnel Magnetoresistance) effect is exhibited between the first ferromagnetic layer 31 and the second ferromagnetic layer 32, a high rate of change in magnetoresistance can be obtained. In order to efficiently utilize the TMR effect, the film thickness of the spacer layer 33 may be set to approximately 0.5 nm to 10.0 nm.

[0046] When the spacer layer 33 is made of a non-magnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. In order to efficiently utilize the GMR effect, the film thickness of the spacer layer 33 may be set to approximately 0.5 nm to 3.0 nm.

[0047] When the spacer layer 33 is made of a non-magnetic semiconductor material, materials such as zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, or ITO can be used. In this case, the thickness of the spacer layer 33 may be approximately 1.0 nm to 4.0 nm.

[0048] When applying a layer containing current-carrying points composed of conductors in a non-magnetic insulator as the spacer layer 33, it is preferable to have a structure in which current-carrying points composed of conductors such as CoFe, CoFeB, CoFeSi, CoMnGe, CoMnSi, CoMnAl, Fe, Co, Au, Cu, Al, or Mg are included in a non-magnetic insulator composed of aluminum oxide or magnesium oxide. In this case, the film thickness of the spacer layer 33 may be approximately 0.5 nm to 2.0 nm or more. The current-carrying points are, for example, columnar bodies with a diameter of 1 nm to 5 nm. As described above, the magnetic element 30 may be called by different names such as MTJ element or GMR element depending on the constituent material of the spacer layer 33, but it is collectively also called a magnetoresistive element.

[0049] The photodetector element 1, configured as described above, is manufactured by lamination, heat treatment, and processing steps for each layer. First, the base layer 34, outer ferromagnetic layer 32C, non-magnetic layer 32B, inner ferromagnetic layer 32A, spacer layer 33, and first ferromagnetic layer 31 are laminated on the second electrode 20 in that order. Each layer is formed by, for example, sputtering. In addition, other layers may be laminated as needed, such as forming a cap layer on the first ferromagnetic layer 31.

[0050] Next, the multilayer film obtained above is subjected to heat treatment such as annealing. When annealing is performed, the heating temperature is, for example, 400°C or higher. After that, the multilayer film is processed into a predetermined columnar shape by photolithography and etching. The columnar shape may be cylindrical or rectangular. For example, the shortest width of the columnar shape when viewed from the z direction is between 10 nm and 1000 nm.

[0051] Next, a first electrode 10A is fabricated on the first ferromagnetic layer 31 or on a cap layer (not shown). Then, an opening 12A is formed in a part of the first electrode 10A by known methods such as resist and etching, and a transparent conductive film 13A is formed in the opening 12A by known methods such as sputtering. Through the above steps, a photodetector element 1 is obtained.

[0052] When light is shone onto the transparent conductive film 13A and then onto the first ferromagnetic layer 31 of the magnetic element 30, the magnetization state of the first ferromagnetic layer 31 (for example, the direction or magnitude of magnetization) changes, and the resistance value of the magnetic element 30 changes. The photodetector 1 outputs the light ray S1 shone onto the magnetic element 30 via the transparent conductive film 13A as a change in voltage between the first electrode 10A and the second electrode 20.

[0053] Figure 5A is a plan view showing the configuration of the first electrode 10A in Figure 1, and Figure 5B is a plan view showing a modified example of the first electrode 10A in Figure 5A.

[0054] As shown in Figure 5A, it is preferable that the opening 12A is provided so as to enclose the magnetic element 30 in a plan view from the z direction. In this embodiment, in a plan view from the z direction, the opening 12A has a circular shape with a y-direction dimension of L1, and the transparent conductive film 13A also has a circular shape with a y-direction dimension of L1. Furthermore, it is preferable that the magnetic element 30 has a circular shape with a y-direction dimension d1 that is smaller than the y-direction dimension L1 of the opening 12A. The magnetic element 30 may also have a square shape with a y-direction dimension d1 that is smaller than the y-direction dimension L1 of the opening 12A. This allows the light ray S1 to be transmitted throughout the magnetic element 30, and the optical signal can be transmitted to the magnetic element 30 more efficiently.

[0055] Furthermore, as shown in Figure 5B, it is preferable that the opening 12B is provided in the metal film 11B so as to enclose the magnetic element 30 in a plan view from the z direction. In a plan view from the z direction, the opening 12B may have a square shape with a length in the y direction of L2, and similarly, the transparent conductive film 13B may also have a square shape with a length in the y direction of L2. In this case, the magnetic element 30 has a circular shape with a y-direction dimension d2 that is smaller than the y-direction dimension L2 of the opening 12B. The magnetic element 30 may have a square shape with a y-direction dimension d2 that is smaller than the y-direction dimension L2 of the opening 12B.

[0056] Here, the opening in this invention can take on various shapes, such as a distorted circle, a rectangle, or a polygon. In this invention, "length of the opening" refers to the length of the shortest line segment that passes through the centroid of the opening and overlaps with the opening in a plan view. For example, as shown in Figure 6A, the opening 12C has a distorted, approximately circular shape. In this case, the length L3 of the opening 12C is the length of the shortest line segment that passes through the centroid P1 of the opening 12C and overlaps with the opening 12C in a plan view. It is preferable that the magnetic element 30 has a circular or square shape with a y-direction dimension d1 smaller than the length L3 of the opening 12C.

[0057] Also, as shown in FIG. 6B, the opening 12D is octagonal. In this case, the length L4 of the opening 12D is defined as the length of the shortest line segment that passes through the centroid P2 of the opening 12D and overlaps with the opening 12D. The magnetic element 30 preferably has a circular or square shape with a y-direction dimension d2 smaller than the length L4 of the opening 12D.

[0058] Furthermore, the length of the opening in the present invention is preferably smaller than the wavelength of the light irradiated on the transparent conductive film. For example, the length L3 of the opening 12C is preferably smaller than the wavelength λ of the light (d1 < L3 < λ). Similarly, the length L4 of the opening 12D is preferably smaller than the wavelength λ of the light (d2 < L4 < λ). When the length of the opening is smaller than the wavelength λ of the light, when light is incident on the opening, radial near-field light is generated from the surface of the metal film of the opening, and this near-field light is transmitted to a relatively narrow range near the opening. Therefore, by making the length L3 of the opening 12C or the length L4 of the opening 12D smaller than the wavelength λ of the light, near-field light is generated by the light irradiated on the transparent conductive film 13A provided in the opening 12C or the opening 12D, and this near-field light is irradiated on the magnetic element 30. By using near-field light in this way, the light intensity can be increased, and the optical signal can be transmitted to the magnetic element 30 more efficiently.

[0059] FIG. 7 is a plan view showing a modified example of the first electrode 10B in FIG. 5B. As shown in FIG. 7, the first electrode 10E includes a metal film 11E, an opening 12E provided in a part of the metal film 11E, and a transparent conductive film 13E disposed in the opening 12E. The opening 12E extends in the y direction (the width direction of the first electrode 10E) and has a substantially rectangular shape in a plan view from the z direction. The opening 12E may have other shapes such as an elliptical shape or an oval shape that extends in the y direction.

[0060] In this modified example, a plurality of magnetic elements 30-1, 30-2, 30-3 are arranged and provided in the y direction. And the opening 12E is provided so as to encompass the plurality of magnetic elements 30-1, 30-2, 30-3 in a plan view from the z direction. Also, each of the magnetic elements 30-1, 30-2, 30-3 preferably has a circular or square shape with a y-direction dimension d5 smaller than the x-direction dimension L5 of the opening 12E. Thereby, the light beam S1 can be transmitted to the entire magnetic element 30, and an optical signal can be transmitted to the magnetic element 30 more efficiently.

[0061] Also, the length L5 of the opening 12E is preferably smaller than the wavelength λ of the light irradiated to the transparent conductive film 13E (d5 < L5 < λ). Thereby, the light intensity can be increased by the near-field light, and an optical signal can be transmitted to the magnetic element 30 more efficiently.

[0062] FIG. 8 is a diagram showing an example of a communication system using the optical detection element 1 of FIG. 1. As shown in FIG. 8, the communication system 60 includes a first terminal device 61 and a second terminal device 62. The first terminal device 61 and the second terminal device 62 are not particularly limited, but are, for example, mobile-type terminal devices. Examples of the mobile-type terminal device include a smartphone, a tablet, and the like.

[0063] Each of the first terminal device 61 and the second terminal device 62 has a receiving device and a transmitting device (not shown). An optical signal transmitted from the transmitting device of the first terminal device 61 is received by the receiving device of the second terminal device 62. The light used for transmission and reception between the first terminal device 61 and the second terminal device 62 is, for example, visible light. An optical detection element is provided in each receiving device, and the optical detection element 1 described above can be applied as this optical detection element.

[0064] In the communication system shown in Figure 8, the first terminal device 61 and the second terminal device 62 are mobile terminal devices, but the system is not limited to this; one or both of the two terminal devices may be stationary terminal devices. Furthermore, one or both of the two terminal devices may function as nodes for IoT communication, etc. Also, while the communication system in Figure 8 uses wireless one-to-one communication, the system is not limited to this; it may also use wireless one-to-many communication.

[0065] As described above, according to this embodiment, the transparent conductive film 13A (13B, 13E) is electrically connected to the magnetic element 30, and by arranging the transparent conductive film 13A (13B, 13E) in the opening 12A (12B, 12E) so as to overlap with the magnetic element 30 in a plan view from the z direction, optical signals can be efficiently transmitted to the magnetic element 30 and electrical signals can be extracted, and the resistance of the first electrode 10A (10B, 10E) can be reduced, so that electrical signals from the magnetic element 30 can be efficiently extracted.

[0066] The present invention is not limited to the embodiments and modifications described above, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims. [Explanation of symbols]

[0067] 1. Photodetector 10a Longitudinal end 10A 1st electrode 10B 1st electrode 10E 1st electrode 11A Metal film 11B Metal film 11E Metal film 12A opening 12B opening 12C opening 12D opening 12E opening 13A Transparent conductive film 13B Transparent conductive film 13a Main surface 13b Main surface 13E Transparent conductive film 20 2nd electrode 20a Main surface 30 Magnetic elements 30-1 Magnetic element 30-2 Magnetic elements 30-3 Magnetic elements 30a z direction end face 30b z direction end face 31 First ferromagnetic layer 32 Second ferromagnetic layer 32A inner ferromagnetic layer 32B Non-magnetic layer 32C outer ferromagnetic layer 33 Spacer layer 34 Base layer 40 Light transmission section 40a one end 40b Other end 41 First diffraction grating section 41a Main surface 41b Main surface 41B Groove 42 Second diffraction grating section 42B Groove 43 Waveguides 43a end 43A Width direction end face 43b End 51 Constant Current Drive Circuit 52 Signal Processing Circuits 60 Communication Systems 61. First Terminal Device 62 Second Terminal Device

Claims

1. First electrode, second electrode, A magnetic element having a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first and second ferromagnetic layers, and disposed between the first and second electrodes, A light transmission unit that irradiates light onto a transparent conductive film, Equipped with, When light is irradiated onto the transparent conductive film, The first electrode is Metal film and An opening provided in a part of the aforementioned metal film, The transparent conductive film disposed in the opening, It has, The transparent conductive film is electrically connected to the magnetic element and overlaps with the magnetic element in a plan view from the thickness direction of the transparent conductive film. The length of the opening is smaller than the wavelength of light irradiated onto the transparent conductive film. The length of the aforementioned opening refers to the length of the shortest line segment that passes through the centroid of the opening and overlaps with the opening in a plan view. The first electrode and the first ferromagnetic layer are positioned on the side of the second electrode and the second ferromagnetic layer that is incident on. The aforementioned optical transmission unit is A first diffraction grating is provided at one end of the light transmission section, and is irradiated with light from the outside, A second diffraction grating is provided at the other end of the light transmission section, from which light transmitted from the first diffraction grating is emitted, A waveguide provided between the first diffraction grating and the second diffraction grating, It has, In a plan view of the light transmission section, the area of ​​the first diffraction grating is larger than the area of ​​the second diffraction grating. The second diffraction grating portion of the light transmission unit, the transparent conductive film of the first electrode, and the first ferromagnetic layer of the magnetic element are arranged in this order along the direction of incidence of light. The first ferromagnetic layer is a photodetector layer whose magnetization state changes when light is irradiated from the outside. A photodetector that outputs a change in the resistance value of the magnetic element caused by the magnetization state as a change in voltage between the first electrode and the second electrode.

2. The photodetector element according to claim 1, wherein the opening is provided so as to enclose the magnetic element in a plan view from the thickness direction.

3. Multiple magnetic elements are arranged in a sequence, The photodetector according to claim 1 or 2, wherein the opening is provided so as to enclose the plurality of magnetic elements in a plan view from the thickness direction of the transparent conductive film.

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