Light-sensing element

Abstract

To provide a novel light detection element.SOLUTION: A light detection element includes a magnetic element and an optical waveguide. The magnetic element has a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. The optical waveguide is formed by at least a core and a clad covering at least a portion of the core. The magnetic element is irradiated with light propagating through the optical waveguide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light-sensing element. [Background technology]

[0002] Photoelectric conversion elements are used for a variety of purposes.

[0003] With the spread of the Internet, communication volume has increased dramatically, and the importance of optical communication has increased. Optical communication is a communication method that converts electrical signals into optical signals and transmits and receives them using optical signals.

[0004] 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 that uses a semiconductor pn junction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-292107 Summary of the Invention [Problem to be solved by the invention]

[0006] Photodetectors using semiconductor pn junctions are widely used as photoelectric conversion elements, but new breakthroughs are needed for further development.

[0007] The present invention has been made in view of the above problems, and has an object to provide a novel photodetector element. [Means for solving the problem]

[0008] In order to solve the above problems, the following means are provided.

[0009] (1) A first aspect of the optical detection element includes a magnetic element and an optical waveguide, wherein the magnetic element has a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and the optical waveguide is formed by at least a core and a cladding covering at least a portion of the core, and light propagating through the optical waveguide is irradiated onto the magnetic element.

[0010] (2) In the light detection element according to the above aspect, the core may include a main portion extending in a first direction intersecting the stacking direction of the magnetic element and a first portion connected to the main portion, and the optical waveguide may have an inclined reflecting surface that is part of the boundary surface between the first portion, which is part of the core, and the cladding and that intersects the stacking direction and the first direction, and the light reflected by the inclined reflecting surface may be irradiated onto the magnetic element.

[0011] (3) In the light-detecting element according to the above aspect, the position of the inclined reflecting surface in the stacking direction may be different from the position of the magnetic element in the stacking direction.

[0012] (4) The light detection element according to the above aspect may further include a substrate, the magnetic element and the optical waveguide being on the substrate, and the position of the magnetic element in the direction perpendicular to the surface of the substrate may be between the position of the inclined reflecting surface in the direction perpendicular to the surface and the position of the substrate in the direction perpendicular to the surface.

[0013] (5) The light detection element according to the above aspect may further include a substrate, the magnetic element and the optical waveguide being on the substrate, and the position of the inclined reflecting surface in a direction perpendicular to the surface of the substrate may be between the position of the magnetic element in the direction perpendicular to the surface and the position of the substrate in the direction perpendicular to the surface.

[0014] (6) The light detection element according to the above aspect may further include a substrate, the substrate having a first surface and a second surface opposing each other in a thickness direction, the optical waveguide being located on the first surface side of the substrate, and the magnetic element being located on the second surface side.

[0015] (7) In the light-detecting element according to the above aspect, the substrate may be in contact with the core.

[0016] (8) In the light detection element according to the above aspect, the core may include a main portion extending in a first direction intersecting the stacking direction of the magnetic element, and a second portion connected to the main portion, the second portion curved in a direction toward the magnetic element based on the first direction, and the light propagating through the second portion may be irradiated onto the magnetic element.

[0017] (9) In the light-detecting element according to the above aspect, the position of the second portion in the stacking direction may be different from the position of the magnetic element in the stacking direction.

[0018] (10) The light-detecting element according to the above aspect may further include an electrode, the electrode being electrically connected to the magnetic element and in contact with the core, and the absolute value of the refractive index difference between the core and the electrode being smaller than the absolute value of the refractive index difference between the core and the cladding. [Effects of the Invention]

[0019] The light-sensing element according to the above embodiment can detect changes in the state of light based on a novel principle. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a perspective view of a light-detecting element according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the photodetector according to the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view of the photodetector according to the first embodiment. [Figure 4] FIG. 2 is a plan view of the light-detecting element according to the first embodiment. [Figure 5] FIG. 1 is a cross-sectional view of a magnetic element according to a first embodiment. [Figure 6] 5A and 5B are diagrams for explaining a first mechanism of a first operation example of the magnetic element according to the first embodiment. [Figure 7]6A and 6B are diagrams illustrating a second mechanism of the first operation example of the magnetic element according to the first embodiment. [Figure 8] 6A and 6B are diagrams illustrating a first mechanism of a second operation example of the magnetic element according to the first embodiment. [Figure 9] 10A and 10B are diagrams illustrating a second mechanism of a second operation example of the magnetic element according to the first embodiment. [Figure 10] 10A and 10B are diagrams illustrating another example of the second operation example of the magnetic element according to the first embodiment. [Figure 11] 10A and 10B are diagrams illustrating another example of the second operation example of the magnetic element according to the first embodiment. [Figure 12] FIG. 10 is a perspective view of a light-detecting element according to a second embodiment. [Figure 13] FIG. 10 is a cross-sectional view of a photodetector according to a second embodiment. [Figure 14] FIG. 10 is a cross-sectional view of a photodetector according to a second embodiment. [Figure 15] FIG. 10 is a cross-sectional view of a magnetic element according to a modified example of the second embodiment. [Figure 16] FIG. 10 is a perspective view of a light-detecting element according to a third embodiment. [Figure 17] FIG. 10 is a cross-sectional view of a light-detecting element according to a third embodiment. [Figure 18] FIG. 10 is a cross-sectional view of a light-detecting element according to a third embodiment. [Figure 19] FIG. 10 is a cross-sectional view of a modified example of the light-detecting element according to the third embodiment. [Figure 20] FIG. 10 is a perspective view of a light-detecting element according to a fourth embodiment. [Figure 21] FIG. 10 is a cross-sectional view of a light-detecting element according to a fourth embodiment. [Figure 22] FIG. 10 is a perspective view of a light-detecting element according to a fifth embodiment. [Figure 23] FIG. 10 is a cross-sectional view of a photodetector according to a fifth embodiment. [Figure 24] FIG. 10 is a cross-sectional view of a light-detecting element according to a first modified example. [Figure 25] FIG. 10 is a cross-sectional view of a light-detecting element according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for convenience in order to make the features easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the effects of the present invention.

[0022] The directions are defined as follows. One direction in the plane in which the substrate 30 extends is the x-direction, and the direction in the plane perpendicular to the x-direction is the y-direction. For example, the direction in which the main part of the core of the optical waveguide described below extends is the x-direction. The direction perpendicular to the plane of the substrate 30 (the direction perpendicular to the x- and y-directions) is the z-direction. Hereinafter, the +z direction may be expressed as "up" and the -z direction as "down". Up and down do not necessarily coincide with the direction in which gravity is applied.

[0023] "First embodiment" Fig. 1 is a perspective view of a photodetector 100 according to the first embodiment. Figs. 2 and 3 are cross-sectional views of the photodetector 100 according to the first embodiment. Fig. 2 is an xz cross section passing through the center in the width direction of the core 21. Fig. 3 is a yz cross section passing through the center of the magnetic element 10. Fig. 4 is a plan view of the photodetector 100 according to the first embodiment. In Fig. 4, the cladding 25 and the insulating layer 40 are removed.

[0024] The photodetector element 100 includes, for example, a magnetic element 10, a first electrode 11, a second electrode 12, an optical waveguide 20, a substrate 30, and an insulating layer 40. Light propagating through the optical waveguide 20 is irradiated onto the magnetic element 10.

[0025] Light emitted from a light source propagates through the optical waveguide 20. The light source is, for example, a laser diode, an LED, or the like. An optical member may be present between the light source and the input end of the optical waveguide 20. The optical member may be, for example, a lens, a metalens, a wavelength filter, an optical fiber, a reflector, or the like. For example, light emitted from the light source and propagated through the optical waveguide 20 via the optical member is irradiated onto the magnetic element 10. Alternatively, part of the light emitted from the light source may propagate directly through the optical waveguide 20 and be irradiated onto the magnetic element 10.

[0026] The light propagating through the optical waveguide 20 is, for example, monochromatic light with a single wavelength, such as laser light. The light propagating through the optical waveguide 20 does not have to be monochromatic light; it may be light with a wavelength limited to a certain range, or light with a continuous spectrum. The light propagating through the optical waveguide 20 is not limited to visible light, but also includes infrared light, which has a longer wavelength than visible light, and ultraviolet light, which has a shorter wavelength than visible light. The wavelength of visible light is, for example, 380 nm or more and less than 800 nm. The wavelength of infrared light is, for example, 800 nm or more and 1 mm or less. The wavelength of ultraviolet light is, for example, 200 nm or more and less than 380 nm. The light propagating through the optical waveguide 20 is, for example, light containing a high-frequency optical signal and whose intensity varies, or light with a controlled wavelength range (for example, light that has passed through a wavelength filter). The high-frequency optical signal is, for example, a signal having a frequency of 100 MHz or more.

[0027] The optical waveguide 20 is formed by at least a core 21 and a clad 25. At least a portion of the core 21 is covered with the clad 25.

[0028] The core 21 contains, for example, lithium niobate as a main component. Some elements of the lithium niobate may be substituted with other elements. The clad 25 is, for example, SiO2, Al2O3, MgF2, La2O3, ZnO, HfO2, MgO, Y2O3, CaF2, In2O3, or a mixture thereof. The materials of the core 21 and the clad 25 are not limited to these examples. For example, the core 21 may be silicon or silicon oxide doped with germanium oxide, and the clad 25 may be silicon oxide. Tantalum oxide, silicon nitride (Si3N4), or the like may also be used for the core 21. The optical waveguide 20 may be a plasmonic waveguide. When the optical waveguide 20 is a plasmonic waveguide, the core 21 is, for example, silicon or silicon oxide, and the clad 25 is, for example, a metal such as Au, Ag, or Al.

[0029] The core 21 includes, for example, a main portion 22 and a first portion 23. The main portion 22 extends, for example, in the x direction. The x direction is an example of a first direction that intersects with the stacking direction of the magnetic element 10. The stacking direction of the magnetic element 10 coincides, for example, with the z direction. The width of the core 21 in the y direction is, for example, not less than 0.4 μm and not more than 8 μm. The thickness of the main portion 22 of the core 21 in the z direction is, for example, not less than 0.2 μm and not more than 8 μm. When the optical waveguide 20 is a plasmonic waveguide, the width of the core 21 in the y direction is, for example, not less than 20 nm and not more than 100 nm, and the thickness of the main portion 22 of the core 21 in the z direction is, for example, not less than 20 nm and not more than 100 nm.

[0030] The first portion 23 is connected to the main portion 22. The first portion 23 is connected to an end portion of the main portion 22 opposite to the light incident end. Light propagates from the main portion 22 toward the first portion 23.

[0031] The optical waveguide 20 has an inclined reflecting surface 24. The inclined reflecting surface 24 is part of the boundary surface between the cladding 25 and the first portion 23, which is part of the core 21. The inclined reflecting surface 24 intersects with the stacking direction of the magnetic element 10 and the first direction described above. The inclined reflecting surface 24 intersects with, for example, the x-direction and the z-direction. The thickness of the first portion 23 in the z-direction becomes thinner, for example, as it gets further away from the connection surface between the first portion 23 and the main portion 22. Light that propagates through the main portion 22 and is reflected by the inclined reflecting surface 24 is irradiated onto the magnetic element 10. The position of the inclined reflecting surface 24 in the z-direction (the stacking direction of the magnetic element 10) is different from the position of the magnetic element 10 in the z-direction. For example, the inclined reflecting surface 24 is located at a position overlapping the magnetic element 10 when viewed from the stacking direction of the magnetic element 10. For example, the position of the inclined reflecting surface 24 in the z-direction is higher than that of the magnetic element 10.

[0032] The magnetic element 10 is located at a position where it is irradiated with light that has propagated through the optical waveguide 20 (a position where it is irradiated with light that has reflected from the inclined reflecting surface 24). Fig. 5 is a cross-sectional view of the magnetic element 10 according to the first embodiment. In Fig. 5, the first electrode 11 and the second electrode 12 are both shown, and the direction of magnetization of the ferromagnetic material in its initial state, which will be described later, is indicated by an arrow.

[0033] The magnetic element 10 includes at least a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a spacer layer 3. The spacer layer 3 is located between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The magnetic element 10 may also include a third ferromagnetic layer 4, a magnetic coupling layer 5, an underlayer 6, a perpendicular magnetization induction layer 7, and a cap layer 8. The third ferromagnetic layer 4, the magnetic coupling layer 5, and the underlayer 6 are located between the second ferromagnetic layer 2 and the second electrode 12, and the perpendicular magnetization induction layer 7 and the cap layer 8 are located between the first ferromagnetic layer 1 and the first electrode 11. The magnetic element 10 has a maximum width in a plan view from the stacking direction of, for example, 10 nm to 2000 nm, preferably 30 nm to 500 nm. The thickness of the magnetic element 10 in the stacking direction is, for example, 15 nm to 40 nm.

[0034] The magnetic element 10 is, for example, an MTJ (Magnetic Tunnel Junction) element in which the spacer layer 3 is made of an insulating material. The resistance value of the magnetic element 10 changes when irradiated with external light. The resistance value of the magnetic element 10 in the z direction (the resistance value when a current is passed in the z direction) changes according to the relative change between the state of magnetization M1 of the first ferromagnetic layer 1 and the state of magnetization M2 of the second ferromagnetic layer 2. Such an element is also called a magnetoresistance effect element.

[0035] The first ferromagnetic layer 1 is a light detection layer whose magnetization state changes when irradiated with light. The first ferromagnetic layer 1 is also called a magnetization free layer. The magnetization free layer is a layer containing a magnetic material whose magnetization state changes when a predetermined external energy is applied. The predetermined external energy is, for example, light irradiated from outside, a current flowing in the stacking direction of the magnetic element 10, or an external magnetic field. The magnetization M1 of the first ferromagnetic layer 1 changes state depending on the intensity of the irradiated light.

[0036] The first ferromagnetic layer 1 includes a ferromagnetic material. The first ferromagnetic layer 1 includes at least one of magnetic elements such as Co, Fe, or Ni. The first ferromagnetic layer 1 may include a non-magnetic element such as B, Mg, Hf, or Gd in addition to the magnetic elements described above. The first ferromagnetic layer 1 may be, for example, an alloy including a magnetic element and a non-magnetic element. The first ferromagnetic layer 1 may be composed of multiple layers. The first ferromagnetic layer 1 may be, for example, a CoFeB alloy, a stacked body in which a CoFeB alloy layer is sandwiched between Fe layers, or a stacked body in which a CoFeB alloy layer is sandwiched between CoFe layers.

[0037] The first ferromagnetic layer 1 may also be a laminate in which magnetic layers and non-magnetic layers are alternately stacked, such as a laminate in which Co and Pt are alternately stacked, or a laminate in which Co and Ni are alternately stacked. Generally, "ferromagnetic" includes "ferrimagnetic." The first ferromagnetic layer 1 may exhibit ferrimagnetic properties. On the other hand, the first ferromagnetic layer 1 may exhibit ferromagnetic properties that are not ferrimagnetic. For example, a CoFeB alloy exhibits ferromagnetic properties that are not ferrimagnetic.

[0038] The first ferromagnetic layer 1 may be an in-plane magnetization film having an axis of easy magnetization in the in-plane direction, or a perpendicular magnetization film having an axis of easy magnetization in the direction perpendicular to the film plane (the stacking direction of the magnetic element 10).

[0039] The thickness of the first ferromagnetic layer 1 is, for example, 1 nm or more and 5 nm or less. The thickness of the first ferromagnetic layer 1 is preferably, for example, 1 nm or more and 2 nm or less. When the first ferromagnetic layer 1 is a perpendicular magnetization film, if the thickness of the first ferromagnetic layer 1 is thin, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 1 is strengthened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is increased. In other words, if the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is high, the force that causes the magnetization M1 to return to the direction perpendicular to the film surface (to its original state) is strengthened. On the other hand, if the thickness of the first ferromagnetic layer 1 is thick, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 1 is relatively weakened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is weakened.

[0040] As the thickness of the first ferromagnetic layer 1 decreases, its volume as a ferromagnetic material decreases, and as it increases, its volume as a ferromagnetic material increases. The responsiveness of the magnetization of the first ferromagnetic layer 1 when external energy is applied is inversely proportional to the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 1. In other words, as the product of the magnetic anisotropy and volume of the first ferromagnetic layer 1 decreases, its responsiveness to light increases. From this perspective, in order to enhance its responsiveness to light, it is preferable to reduce the volume of the first ferromagnetic layer 1 after appropriately designing the magnetic anisotropy of the first ferromagnetic layer 1.

[0041] If the thickness of the first ferromagnetic layer 1 is greater than 2 nm, an insertion layer made of, for example, Mo or W may be provided within the first ferromagnetic layer 1. That is, the first ferromagnetic layer 1 may be a stack in which a ferromagnetic layer, an insertion layer, and a ferromagnetic layer are stacked in this order in the z direction. The interfacial magnetic anisotropy at the interface between the insertion layer and the ferromagnetic layer enhances the perpendicular magnetic anisotropy of the entire first ferromagnetic layer 1. The thickness of the insertion layer is, for example, 0.1 nm to 0.6 nm.

[0042] The second ferromagnetic layer 2 is a magnetization fixed layer. The magnetization fixed layer is a layer made of a magnetic material whose magnetization state is less likely to change when a predetermined external energy is applied than the magnetization free layer. For example, the magnetization direction of the magnetization fixed layer is less likely to change when a predetermined external energy is applied than the magnetization free layer. Also, for example, the magnitude of the magnetization of the magnetization fixed layer is less likely to change when a predetermined external energy is applied than the magnetization free layer. The coercive force of the second ferromagnetic layer 2 is, for example, greater than the coercive force of the first ferromagnetic layer 1. The second ferromagnetic layer 2 may be an in-plane magnetized film or a perpendicular magnetized film. In the example shown in FIG. 5, the direction of the magnetization M2 of the second ferromagnetic layer 2 is the z-direction. The film thickness of the second ferromagnetic layer 12 is, for example, 1 nm to 5 nm.

[0043] The material constituting the second ferromagnetic layer 2 is, for example, the same as that of the first ferromagnetic layer 1. The second ferromagnetic layer 2 may be, for example, a multilayer film in which Co layers having a thickness of 0.4 nm to 1.0 nm and Pt layers having a thickness of 0.4 nm to 1.0 nm are alternately stacked several times. The second ferromagnetic layer 2 may be, for example, a laminate in which Co layers having a thickness of 0.4 nm to 1.0 nm, Mo layers having a thickness of 0.1 nm to 0.5 nm, a CoFeB alloy layers having a thickness of 0.3 nm to 1.0 nm, and Fe layers having a thickness of 0.3 nm to 1.0 nm are stacked in this order.

[0044] The magnetization M2 of the second ferromagnetic layer 2 may be fixed by, for example, magnetic coupling with the third ferromagnetic layer 4 via the magnetic coupling layer 5. In this case, the combination of the second ferromagnetic layer 2, the magnetic coupling layer 5, and the third ferromagnetic layer 4 may be referred to as a magnetization fixed layer. Details of the third ferromagnetic layer 4 and the magnetic coupling layer 5 will be described later.

[0045] The spacer layer 3 is a layer disposed between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The spacer layer 3 is a layer made of a conductor, an insulator, or a semiconductor, or a layer containing a current-carrying point made of a conductor in an insulator. The spacer layer 3 is, for example, a non-magnetic layer. The thickness of the spacer layer 3 can be adjusted depending on the orientation directions of the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 in the initial state, which will be described later.

[0046] For example, when the spacer layer 3 is made of an insulator, the magnetic element 10 has a magnetic tunnel junction (MTJ) consisting of the first ferromagnetic layer 1, the spacer layer 3, and the second ferromagnetic layer 2. Such an element is called an MTJ element. In this case, the magnetic element 10 can exhibit a tunnel magnetoresistance (TMR) effect. For example, when the spacer layer 3 is made of a metal, the magnetic element 10 can exhibit a giant magnetoresistance (GMR) effect. Such an element is called a GMR element. The magnetic element 10 may be called an MTJ element, a GMR element, or other names depending on the material of the spacer layer 3, but is also collectively called a magnetoresistance effect element.

[0047] When the spacer layer 3 is made of an insulating material, a material containing aluminum oxide, magnesium oxide, titanium oxide, silicon oxide, or the like can be used as the material for the spacer layer 3. These insulating materials may also contain elements such as Al, B, Si, and Mg, or magnetic elements such as Co, Fe, and Ni. A high magnetoresistance ratio can be obtained by adjusting the thickness of the spacer layer 3 so that a high TMR effect is exhibited between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. To efficiently utilize the TMR effect, the thickness of the spacer layer 3 may be approximately 0.5 to 5.0 nm, or approximately 1.0 to 2.5 nm.

[0048] When the spacer layer 3 is made of a nonmagnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. To efficiently utilize the GMR effect, the thickness of the spacer layer 3 may be about 0.5 to 5.0 nm, or about 2.0 to 3.0 nm.

[0049] When the spacer layer 3 is made of a non-magnetic semiconductor material, it can be made of zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, ITO, etc. In this case, the thickness of the spacer layer 3 may be about 1.0 to 4.0 nm.

[0050] When a layer including current-carrying points formed by a conductor in a nonmagnetic insulator is used as the spacer layer 3, the current-carrying points may be formed by a nonmagnetic conductor such as Cu, Au, or Al in a nonmagnetic insulator made of aluminum oxide or magnesium oxide. The conductor may also be made of a magnetic element such as Co, Fe, or Ni. In this case, the thickness of the spacer layer 3 may be approximately 1.0 to 2.5 nm. The current-carrying points are, for example, columnar bodies with a diameter of 1 nm to 5 nm when viewed perpendicular to the film surface.

[0051] The third ferromagnetic layer 4 is magnetically coupled to, for example, the second ferromagnetic layer 2. The magnetic coupling is, for example, antiferromagnetic coupling, which occurs due to RKKY interaction. The direction of the magnetization M2 of the second ferromagnetic layer 2 and the direction of the magnetization M4 of the third ferromagnetic layer 4 are antiparallel to each other. The material constituting the third ferromagnetic layer 4 is, for example, the same as that of the first ferromagnetic layer 1.

[0052] The magnetic coupling layer 5 is located between the second ferromagnetic layer 2 and the third ferromagnetic layer 4. The magnetic coupling layer 5 is made of, for example, Ru, Ir, or the like.

[0053] The underlayer 6 is located between the third ferromagnetic layer 4 and the second electrode 12. The underlayer 6 is a seed layer or a buffer layer. The seed layer improves the crystallinity of the layer in contact with the seed layer. The seed layer is made of, for example, Pt, Ru, Hf, Zr, or NiFeCr. The thickness of the seed layer is, for example, 1 nm or more and 5 nm or less. The buffer layer is a layer that alleviates lattice mismatch between different crystals. The buffer layer is made of, for example, Ta, Ti, W, Zr, Hf, or nitrides of these elements. The thickness of the buffer layer is, for example, 1 nm or more and 5 nm or less.

[0054] The cap layer 8 is located between the first ferromagnetic layer 1 and the first electrode 11. The cap layer 8 improves the crystallinity of the layer in contact with the cap layer 8 during annealing. The thickness of the cap layer 8 is, for example, 10 nm or less so that the first ferromagnetic layer 1 is irradiated with sufficient light. The cap layer 8 is, for example, made of MgO, W, Mo, Ru, Ta, Cu, Cr, or a laminated film of these materials.

[0055] The perpendicular magnetization induction layer 7 induces perpendicular magnetic anisotropy in the first ferromagnetic layer 1. The perpendicular magnetization induction layer 7 is made of, for example, magnesium oxide, W, Ta, or Mo. When the perpendicular magnetization induction layer 7 is made of magnesium oxide, it is preferable that the magnesium oxide has oxygen deficiency to increase conductivity. The film thickness of the perpendicular magnetization induction layer 7 is, for example, 0.5 nm to 5.0 nm.

[0056] The first electrode 11 is disposed, for example, on the side of the magnetic element 10 where light is irradiated. In this case, at least a portion of the first electrode 11 is sandwiched between the magnetic element 10 and the first portion 23. The first electrode 11 is, for example, electrically connected to the magnetic element 10. Furthermore, the first electrode 11 is in contact with the first portion 23 of the core 21, for example.

[0057] The light propagating through the optical waveguide 20 is irradiated onto the magnetic element 10 from the first electrode 11 side, and is irradiated onto at least the first ferromagnetic layer 1. The first electrode 11 is made of a conductive material. The first electrode 11 is, for example, a transparent electrode that is transparent to light in the wavelength range used. The first electrode 11 preferably transmits, for example, 80% or more of the light in the wavelength range used.

[0058] The first electrode 11 is made of an oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). The first electrode 11 may be made of a transparent electrode material of such an oxide and have a plurality of metal columns in it. It is not essential to use such a transparent electrode material for the first electrode 11, and a metal material such as Au, Cu, or Al may be used with a thin film thickness to allow the irradiated light to reach the first ferromagnetic layer 1. When a metal is used as the material for the first electrode 11, the film thickness of the first electrode 11 is, for example, 3 to 10 nm. The first electrode 11 may also have an anti-reflection film on the surface to be irradiated with light.

[0059] When the first electrode 11 is in contact with the core 21, it is preferable that the absolute value of the refractive index difference between the first electrode 11 and the core 21 is smaller than the absolute value of the refractive index difference between the core 21 and the cladding 25. For example, when the cladding 25 is aluminum oxide, the above-mentioned refractive index difference condition is met if the first electrode 11 is ITO (a mixture of indium oxide and tin oxide in a 2:1 ratio) and the core 21 is lithium niobate. When the above-mentioned refractive index difference condition is met, reflection of light propagating through the core 21 at the interface between the core 21 and the first electrode 11 can be suppressed, and more of the light propagating through the core 21 can be irradiated onto the magnetic element 10. Here, an example has been given in which the refractive index of the first electrode 11 is smaller than that of the core 21, but the refractive index of the first electrode 11 may be larger than that of the core 21, or the refractive index of the first electrode 11 may be the same as that of the core 21.

[0060] The second electrode 12 is located on the opposite side of the magnetic element 10 to the first electrode 11. The second electrode 12 is, for example, electrically connected to the magnetic element 10. The second electrode 12 is made of a conductive material. The second electrode 12 is made of a metal such as Cu, Al, or Au. Ta or Ti may be laminated above and below these metals. Alternatively, a laminated film of Cu and Ta, a laminated film of Ta, Cu, and Ti, or a laminated film of Ta, Cu, and TaN may be used. Alternatively, TiN or TaN may be used as the second electrode 12. The film thickness of the second electrode 12 is, for example, 200 nm to 800 nm.

[0061] The second electrode 12 may be transparent to light irradiated onto the magnetic element 10. As with the first electrode 11, the second electrode 12 may be made of a transparent oxide electrode material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). Even when light is irradiated from the first electrode 11, the light may reach the second electrode 12 depending on the intensity of the light. In this case, since the second electrode 12 is made of a transparent oxide electrode material, light reflection at the interface between the second electrode 12 and a layer adjacent to it can be suppressed compared to when the second electrode 12 is made of a metal.

[0062] The first electrode 11 is connected to a via wiring 51. The second electrode 12 is connected to a via wiring 52. The via wiring 51 connects the first electrode 11 and an external electrode 53. The via wiring 52 connects the second electrode 12 and an external electrode 54. Each of the via wirings 51 and 52 penetrates at least one of the clad 25 and the insulating layer 40 in the z-direction. Each of the external electrodes 53 and 54 is exposed on the upper surface of the clad 25, for example. The via wirings 51 and 52 and the external electrodes 53 and 54 contain a conductive material.

[0063] The via wirings 51 and 52 each have a maximum width in a plan view from the stacking direction of, for example, 10 nm to 2000 nm, and preferably 30 nm to 500 nm. The maximum width of the via wiring 51 in a plan view from the stacking direction is, for example, shorter than the width of the first electrode 11 in the x direction. The maximum width of the via wiring 52 in a plan view from the stacking direction is, for example, shorter than the width of the second electrode 12 in the x direction.

[0064] The insulating layer 40 covers the periphery of the magnetic element 10. The insulating layer 40 is an interlayer insulating layer. The insulating layer 40 is, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg. The insulating layer 40 is, for example, silicon oxide (SiO x ), silicon nitride (SiN x ), silicon carbide (SiC), chromium nitride (CrN), silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO x The insulating layer 40 may be made of the same material as the clad 25, or the insulating layer 40 and the clad 25 may be integrated.

[0065] The magnetic element 10 and the optical waveguide 20 are, for example, on a substrate 30. The position of the magnetic element 10 in the z direction is between the position of the inclined reflecting surface 24 in the z direction and the position of the substrate 30 in the z direction. For example, the magnetic element 10 is sandwiched between the substrate 30 and the inclined reflecting surface 24 in the z direction.

[0066] The substrate 30 includes, for example, aluminum oxide. The substrate 30 is, for example, sapphire. The substrate 30 may also be a semiconductor substrate such as silicon.

[0067] Next, a method for manufacturing the photodetector element 100 will be described. First, a laminated film is formed on a substrate 30, in which a second electrode 12, an underlayer 6, a third ferromagnetic layer 4, a magnetic coupling layer 5, a second ferromagnetic layer 2, a spacer layer 3, a first ferromagnetic layer 1, a perpendicular magnetization induction layer 7, and a cap layer 8 are laminated in this order. Each layer is formed by, for example, sputtering.

[0068] Next, the stacked film is annealed. The annealing temperature is, for example, 250°C to 450°C. The stacked film is then processed into a predetermined columnar shape by photolithography and etching. The columnar shape may be a cylindrical or rectangular columnar shape. For example, the width of the columnar shape as viewed from the stacking direction may be 10 nm to 2000 nm, or 30 nm to 500 nm.

[0069] Next, an insulating layer 40 is formed to cover the side surfaces of the pillars. The insulating layer 40 may be laminated multiple times. Next, the upper surface of the cap layer 8 is exposed from the insulating layer 40 by chemical mechanical polishing (CMP), and the first electrode 11 is formed on the cap layer 8.

[0070] Next, a clad 25 is formed so as to cover the periphery of the first electrode 11. Next, the height positions of the upper surfaces of the first electrode 11 and the clad 25 are aligned by chemical mechanical polishing (CMP). Next, a core 21 is formed in a position where a portion thereof overlaps with the first electrode 11. After laminating the layers that will become the core 21, the core 21 is formed by processing it into a predetermined shape by photolithography and etching. Thereafter, a clad 25 is formed so as to cover the core 21. Next, a through hole is formed in the clad 25, and the inside is filled with a conductor, thereby forming via wirings 51 and 52.

[0071] As described above, the magnetic element 10 and the optical waveguide 20 can be formed on the same substrate 30 by, for example, a vacuum film formation process.

[0072] Next, the operation of the photodetector element 100 will be described. Light emitted from a light source is input to the optical waveguide 20. The light input to the optical waveguide 20 is light having intensity variations, and includes, for example, an optical signal having optical intensity variations. Such light is used, for example, in optical communication systems. The light input to the optical waveguide 20 propagates through the core 21 of the optical waveguide 20. The light propagating through the core 21 is reflected by the inclined reflecting surface 24 toward the magnetic element 10.

[0073] The light reflected by the inclined reflecting surface 24 is irradiated onto the magnetic element 10. The resistance value in the z direction of the magnetic element 10 changes when the first ferromagnetic layer 1 is irradiated with light propagated through the optical waveguide 20. An example will be described in which the intensity of the light irradiated onto the first ferromagnetic layer 1 has two levels: a first intensity and a second intensity. The second intensity is assumed to be greater than the first intensity. The first intensity may be zero when the intensity of the light irradiated onto the first ferromagnetic layer 1 is zero. FIGS. 6 and 7 are diagrams illustrating a first operation example of the magnetic element 10. FIG. 6 is a diagram illustrating a first mechanism of the first operation example, and FIG. 7 is a diagram illustrating a second mechanism of the first operation example. FIGS. 6 and 7 illustrate only the first ferromagnetic layer 1, the second ferromagnetic layer 2, and the spacer layer 3 of the magnetic element 10. In the upper graphs of FIGS. 6 and 7, the vertical axis represents the intensity of the light irradiated onto the first ferromagnetic layer 1, and the horizontal axis represents time. In the lower graphs of FIGS. 6 and 7, the vertical axis represents the resistance value of the magnetic element 10 in the z direction, and the horizontal axis represents time.

[0074] First, in a state where the first ferromagnetic layer 1 is irradiated with light of a first intensity (hereinafter referred to as the initial state), the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 are parallel, the resistance value of the magnetic element 10 in the z direction exhibits a first resistance value R1, and the magnitude of the output voltage from the magnetic element 10 exhibits a first value. The resistance value of the magnetic element 10 in the z direction is determined by Ohm's law from the voltage value generated at both ends of the magnetic element 10 in the z direction by passing a sense current Is through the magnetic element 10 in the z direction. The output voltage from the magnetic element 10 is generated between the first electrode 11 and the second electrode 12. In the example shown in FIG. 6, the sense current Is is passed from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. By passing the sense current Is in this direction, a spin transfer torque acts on the magnetization M1 of the first ferromagnetic layer 1 in the same direction as the magnetization M2 of the second ferromagnetic layer 2, and the magnetizations M1 and M2 become parallel in the initial state. In the example shown in Figure 6, the directions of the magnetizations M1 and M2 are both in the +z direction in the initial state. Furthermore, by passing the sense current Is in this direction, it is possible to prevent the magnetization M1 of the first ferromagnetic layer 1 from reversing during operation.

[0075] Next, the intensity of the light irradiated to the first ferromagnetic layer 1 changes from the first intensity to a second intensity. The second intensity is greater than the first intensity, and the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state. The state of the magnetization M1 of the first ferromagnetic layer 1 when no light is irradiated to the first ferromagnetic layer 1 is different from the state of the magnetization M1 of the first ferromagnetic layer 1 when light of the second intensity is irradiated to the first ferromagnetic layer 1. The state of the magnetization M1 refers to, for example, the tilt angle or magnitude with respect to the z direction.

[0076] For example, as shown in Fig. 6, when the intensity of light irradiated to the first ferromagnetic layer 1 changes from a first intensity to a second intensity, the magnetization M1 tilts with respect to the z direction. Furthermore, as shown in Fig. 7, when the intensity of light irradiated to the first ferromagnetic layer 1 changes from the first intensity to a second intensity, the magnitude of the magnetization M1 decreases. For example, when the magnetization M1 of the first ferromagnetic layer 1 tilts with respect to the z direction due to the intensity of light irradiation, the tilt angle is greater than 0° and less than 90°.

[0077] When the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state, the resistance value in the z direction of the magnetic element 10 exhibits a second resistance value R2, and the magnitude of the output voltage from the magnetic element 10 exhibits a second value. The second resistance value R2 is greater than the first resistance value R1, and the second value of the output voltage is greater than the first value. The second resistance value R2 is between the resistance value (first resistance value R1) when the magnetization M1 and the magnetization M2 are parallel and the resistance value when the magnetization M1 and the magnetization M2 are antiparallel.

[0078] In the case shown in FIG. 6, a spin transfer torque acts on the magnetization M1 of the first ferromagnetic layer 1 in the same direction as the magnetization M2 of the second ferromagnetic layer 2. Therefore, the magnetization M1 attempts to return to a parallel state with the magnetization M2, and when the intensity of the light irradiated to the first ferromagnetic layer 1 changes from the second intensity to the first intensity, the magnetization M1 returns to a parallel state with the magnetization M2. In the case shown in FIG. 7, when the intensity of the light irradiated to the first ferromagnetic layer 1 returns to the first intensity, the magnitude of the magnetization M1 of the first ferromagnetic layer 1 returns to its initial state. In either case, the resistance value in the z direction of the magnetic element 10 returns to the first resistance value R1. In other words, when the intensity of the light irradiated to the first ferromagnetic layer 1 changes from the second intensity to the first intensity, the resistance value in the z direction of the magnetic element 10 changes from the second resistance value R2 to the first resistance value R1, and the magnitude of the output voltage from the magnetic element 10 changes from the second value to the first value.

[0079] The output voltage from the magnetic element 10 changes in response to changes in the intensity of light irradiated onto the first ferromagnetic layer 1, and can convert changes in the intensity of the irradiated light into changes in the output voltage from the magnetic element 10. In other words, the magnetic element 10 can convert light into an electrical signal. For example, an optical signal receiving device processes the output voltage from the magnetic element 10 as a first signal (e.g., "1") when it is equal to or greater than a threshold, and as a second signal (e.g., "0") when it is less than the threshold.

[0080] Here, the case where the magnetization M1 and the magnetization M2 are parallel in the initial state has been described as an example, but the magnetization M1 and the magnetization M2 may be antiparallel in the initial state. In this case, the resistance value in the z direction of the magnetic element 10 decreases as the state of the magnetization M1 changes (for example, as the angle change of the magnetization M1 from the initial state increases). When the magnetization M1 and the magnetization M2 are antiparallel in the initial state, it is preferable to flow the sense current Is from the second ferromagnetic layer 2 toward the first ferromagnetic layer 1. By flowing the sense current Is in this direction, a spin transfer torque acts on the magnetization M1 of the first ferromagnetic layer 1 in the opposite direction to the magnetization M2 of the second ferromagnetic layer 2, and the magnetization M1 and the magnetization M2 become antiparallel in the initial state.

[0081] In the first operating example, the case where the light irradiated to the first ferromagnetic layer 1 has two levels of intensity, a first intensity and a second intensity, is described, but in the second operating example, the case where the intensity of the light irradiated to the first ferromagnetic layer 1 changes in multiple levels or in an analog manner is described.

[0082] 8 and 9 are diagrams illustrating a second operation example of the magnetic element 10 according to the first embodiment. FIG. 8 is a diagram illustrating a first mechanism of the second operation example, and FIG. 9 is a diagram illustrating a second mechanism of the second operation example. In FIGS. 8 and 9, only the first ferromagnetic layer 1, the second ferromagnetic layer 2, and the spacer layer 3 of the magnetic element 10 are illustrated. In the upper graphs of FIGS. 8 and 9, the vertical axis represents the intensity of light irradiated to the first ferromagnetic layer 1, and the horizontal axis represents time. In the lower graphs of FIGS. 8 and 9, the vertical axis represents the resistance value of the magnetic element 10 in the z direction, and the horizontal axis represents time. In the example shown in FIG. 8, in the initial state, the directions of the magnetization M1 and the magnetization M2 are both in the +z direction.

[0083] 8, as the intensity of light irradiated onto the first ferromagnetic layer 1 increases, the external energy caused by the light irradiation tilts the magnetization M1 of the first ferromagnetic layer 1 from its initial state. The angle between the direction of the magnetization M1 of the first ferromagnetic layer 1 when no light is irradiated onto the first ferromagnetic layer 1 and the direction of the magnetization M1 when light is irradiated onto the first ferromagnetic layer 1 is both greater than 0° and smaller than 90°.

[0084] When the magnetization M1 of the first ferromagnetic layer 1 tilts from its initial state, the resistance value of the magnetic element 10 in the z direction changes. Consequently, the output voltage from the magnetic element 10 changes. For example, depending on the tilt of the magnetization M1 of the first ferromagnetic layer 1, the resistance value of the magnetic element 10 in the z direction changes from a second resistance value R2 to a third resistance value R3 to a fourth resistance value R4, and the output voltage from the magnetic element 10 changes from a second value to a third value to a fourth value. The resistance values ​​increase in the order of the first resistance value R1, the second resistance value R2, the third resistance value R3, and the fourth resistance value R4. The output voltage from the magnetic element 10 increases in the order of the first value, the second value, the third value, and the fourth value.

[0085] When the intensity of light irradiated to the first ferromagnetic layer 1 changes, the output voltage from the magnetic element 10 (the resistance value of the magnetic element 10 in the z-direction) changes. For example, if the first value (first resistance value R1) is defined as "0," the second value (second resistance value R2) as "1," the third value (third resistance value R3) as "2," and the fourth value (fourth resistance value R4) as "3," four values ​​of information can be read from the magnetic element 10. While the case where four values ​​are read is shown here as an example, the number of values ​​to be read can be freely designed by setting the threshold value of the output voltage from the magnetic element 10 (the resistance value of the magnetic element 10). The analog value of the output from the magnetic element 10 may also be used as is.

[0086] Similarly, in the case of FIG. 9, as the intensity of light irradiated onto the first ferromagnetic layer 1 increases, the magnitude of the magnetization M1 of the first ferromagnetic layer 1 decreases from its initial state due to external energy from the light irradiation. When the magnetization M1 of the first ferromagnetic layer 1 decreases from its initial state, the resistance value of the magnetic element 10 in the z direction changes. Consequently, the output voltage from the magnetic element 10 changes. For example, depending on the magnitude of the magnetization M1 of the first ferromagnetic layer 1, the resistance value of the magnetic element 10 in the z direction changes to a second resistance value R2, a third resistance value R3, and a fourth resistance value R4, and the output voltage from the magnetic element 10 changes to a second value, a third value, and a fourth value. Therefore, similar to the case of FIG. 8, the light detecting element 100 can read the difference in these output voltages (resistance values) as multi-valued or analog data.

[0087] Also in the second operation example, as in the first operation example, when the intensity of light irradiated on the first ferromagnetic layer 1 returns to the first intensity, the state of the magnetization M1 of the first ferromagnetic layer 1 returns to the initial state. According to the second operation example, the photodetector element 100 can be used as an element that detects the intensity of light as multi-value or analog data, and can be applied not only to optical communication systems but also to photodetector devices such as image sensors.

[0088] Here, the case where the magnetization M1 and the magnetization M2 are parallel in the initial state has been described as an example, but also in the second operation example, the magnetization M1 and the magnetization M2 may be antiparallel in the initial state.

[0089] Although the first and second operation examples illustrate cases in which the magnetization M1 and the magnetization M2 are parallel or antiparallel in the initial state, the magnetization M1 and the magnetization M2 may be orthogonal in the initial state. For example, this applies to a case in which the first ferromagnetic layer 1 is an in-plane magnetization film in which the magnetization M1 is oriented in one direction in the xy plane in the initial state, and the second ferromagnetic layer 2 is a perpendicular magnetization film in which the magnetization M2 is oriented in the z direction. Due to magnetic anisotropy, the magnetization M1 is oriented in one direction in the xy plane, and the magnetization M2 is oriented in the z direction, so that the magnetization M1 and the magnetization M2 are orthogonal in the initial state.

[0090] 10 and 11 are diagrams illustrating another example of the second operation example of the magnetic element 10 according to the first embodiment. In FIGS. 10 and 11, only the first ferromagnetic layer 1, the second ferromagnetic layer 2, and the spacer layer 3 of the magnetic element 10 are illustrated. The flow direction of the sense current Is applied to the magnetic element 10 differs between FIGS. 10 and 11. In FIG. 10, the sense current Is flows from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. In FIG. 11, the sense current Is flows from the second ferromagnetic layer 2 to the first ferromagnetic layer 1.

[0091] 10 and 11, a spin transfer torque acts on the magnetization M1 in the initial state when the sense current Is flows through the magnetic element 10. In the case of FIG. 10, the spin transfer torque acts so that the magnetization M1 becomes parallel to the magnetization M2 of the second ferromagnetic layer 2. In the case of FIG. 11, the spin transfer torque acts so that the magnetization M1 becomes antiparallel to the magnetization M2 of the second ferromagnetic layer 2. In both the cases of FIG. 10 and 11, in the initial state, the effect of magnetic anisotropy on the magnetization M1 is greater than the effect of the spin transfer torque, so the magnetization M1 is oriented in one of the directions within the xy plane.

[0092] As the intensity of light irradiated onto the first ferromagnetic layer 1 increases, the magnetization M1 of the first ferromagnetic layer 1 tilts from its initial state due to the external energy generated by the light irradiation. This is because the sum of the effect of the light irradiation and the effect of the spin transfer torque acting on the magnetization M1 becomes greater than the effect of the magnetic anisotropy associated with the magnetization M1. As the intensity of light irradiated onto the first ferromagnetic layer 1 increases, the magnetization M1 in the case of FIG. 10 tilts so as to be parallel to the magnetization M2 of the second ferromagnetic layer 2, while the magnetization M1 in the case of FIG. 11 tilts so as to be antiparallel to the magnetization M2 of the second ferromagnetic layer 2. The tilt direction of the magnetization M1 in FIGS. 10 and 11 is different because the direction of the spin transfer torque acting on the magnetization M1 is different.

[0093] 10, when the intensity of light irradiated to the first ferromagnetic layer 1 increases, the resistance value of the magnetic element 10 decreases, and the output voltage from the magnetic element 10 decreases. In the case of FIG. 11, the resistance value of the magnetic element 10 increases, and the output voltage from the magnetic element 10 increases.

[0094] When the intensity of the light irradiated on the first ferromagnetic layer 1 returns to the first intensity, the state of the magnetization M1 of the first ferromagnetic layer 1 returns to the initial state due to the effect of magnetic anisotropy on the magnetization M1.

[0095] Although the first ferromagnetic layer 1 is an in-plane magnetization film and the second ferromagnetic layer 2 is a perpendicular magnetization film, this relationship may be reversed. That is, in the initial state, the magnetization M1 may be oriented in the z direction, and the magnetization M2 may be oriented in any direction within the xy plane.

[0096] The magnetic element 10 converts the light having the intensity variation into an electric signal. The electric signal is output to the outside from, for example, the external electrodes 53 and 54. The electric signal is, for example, an output voltage from the magnetic element 10.

[0097] The photodetector 100 according to the first embodiment can convert light that has propagated through the optical waveguide 20 and is irradiated onto the magnetic element 10 into an output voltage from the magnetic element 10, thereby converting the light into an electrical signal.

[0098] Furthermore, the smaller the volume of the first ferromagnetic layer 1, the more easily the magnetization M1 of the first ferromagnetic layer 1 changes in response to light irradiation. In other words, the smaller the volume of the first ferromagnetic layer 1, the more easily the magnetization M1 of the first ferromagnetic layer 1 is tilted or decreased by light irradiation. In other words, by reducing the volume of the first ferromagnetic layer 1, the magnetization M1 can be changed even with a small amount of light.

[0099] More precisely, the changeability of the magnetization M1 is determined by the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 1. The smaller the KuV, the smaller the amount of light required to change the magnetization M1; the larger the KuV, the larger the amount of light required to change the magnetization M1. In other words, the KuV of the first ferromagnetic layer 1 must be designed according to the amount of external light used in the application. When considering extremely small amounts of light, such as photon detection, reducing the KuV of the first ferromagnetic layer 1 enables the detection of such small amounts of light. This is a significant advantage, as detecting such small amounts of light becomes difficult with conventional pn junction semiconductors when the element size is reduced. In other words, reducing the KuV by reducing the volume of the first ferromagnetic layer 1, i.e., the element area, or the film thickness of the first ferromagnetic layer 1, also enables photon detection.

[0100] Furthermore, the photodetector 100 according to the first embodiment can detect light regardless of the wavelength range of the irradiated light. For semiconductor photodetectors using pn junctions, the appropriate semiconductor material varies depending on the wavelength of the irradiated light. For example, InGaAs or the like is used to detect near-infrared light with a wavelength of 1.3 μm or more and 1.5 μm or less. Furthermore, for example, silicon is used to detect visible light with a wavelength of 400 nm or more and 800 nm or less. In contrast, the photodetector 100 according to the first embodiment can detect light with high sensitivity regardless of the wavelength of light, such as visible light or near-infrared light.

[0101] The photodetector 100 according to the first embodiment can be formed in one step, with the optical waveguide 20 through which light propagates and the magnetic element 10 that converts light into an electrical signal being formed on the same substrate 30. Furthermore, the photodetector 100 according to the first embodiment can be handled as a single packaged electronic component.

[0102] "Second embodiment" Fig. 12 is a perspective view of a photodetector 101 according to the second embodiment. Figs. 13 and 14 are cross-sectional views of the photodetector 101 according to the second embodiment. Fig. 13 is an xz cross section passing through the center in the width direction of the core 21A. Fig. 14 is a yz cross section passing through the center of the magnetic element 10.

[0103] The photodetector element 101 has, for example, a magnetic element 10, a first electrode 11A, a second electrode 12A, an optical waveguide 20A, a substrate 30, and an insulating layer 40. Light propagating through the optical waveguide 20A is irradiated onto the magnetic element 10. In the photodetector element 101 according to the second embodiment, the same components as those in the photodetector element 100 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0104] Light emitted from a light source propagates through the optical waveguide 20 A. The light propagating through the optical waveguide 20 A is similar to the light propagating through the optical waveguide 20 according to the first embodiment.

[0105] The optical waveguide 20A is formed by at least a core 21A and a clad 25. At least a portion of the core 21A is covered with the clad 25. The material forming the core 21A is the same as that of the core 21 according to the first embodiment.

[0106] Core 21A is in contact with substrate 30. For example, the bottom surface of core 21A is in contact with substrate 30. Light is reflected at the interface between substrate 30 and core 21A, and substrate 30 forms part of cladding 25. The refractive index of substrate 30 is smaller than the refractive index of core 21A.

[0107] The core 21A includes, for example, a main portion 22 and a first portion 23A. The first portion 23A is connected to the main portion 22. The optical waveguide 20A has an inclined reflecting surface 24A. The inclined reflecting surface 24A is part of the boundary between the first portion 23A, which is part of the core 21A, and the clad 25. The inclined reflecting surface 24A intersects with the stacking direction of the magnetic element 10 and the first direction. Light that propagates through the main portion 22 and is reflected by the inclined reflecting surface 24A is irradiated onto the magnetic element 10 from the second electrode 12A side. The light irradiated onto the magnetic element 10 transmits through each layer constituting the magnetic element 10 and is irradiated onto the first ferromagnetic layer 1. The position of the inclined reflecting surface 24A in the z direction (the stacking direction of the magnetic element 10) is different from the position of the magnetic element 10 in the z direction. For example, the inclined reflecting surface 24A is located at a position overlapping the magnetic element 10 when viewed from the stacking direction of the magnetic element 10. For example, the inclined reflecting surface 24A is located below the magnetic element 10 in the z direction.

[0108] The magnetic element 10 and the optical waveguide 20A are, for example, on a substrate 30. The position of the inclined reflecting surface 24A in the z direction is between the positions of the magnetic element 10 in the z direction and the substrate 30 in the z direction. For example, at least a portion of the inclined reflecting surface 24A is sandwiched in the z direction between the magnetic element 10 and the substrate 30. The magnetic element 10 is located at a position where it is irradiated with light that has propagated through the optical waveguide 20A (a position where it is irradiated with light reflected by the inclined reflecting surface 24A), and is located, for example, above the inclined reflecting surface 24A.

[0109] The first electrode 11A and the second electrode 12A are each electrically connected to, for example, the magnetic element 10. The first electrode 11A is connected to a via wiring 51. The second electrode 12A is connected to a via wiring 52. At least a portion of the second electrode 12A is sandwiched between the magnetic element 10 and the first portion 23A. The second electrode 12A is in contact with, for example, the first portion 23A of the core 21A. The configuration of the second electrode 12A is similar to the configuration of the first electrode 11 in the first embodiment. The configuration of the first electrode 11A is similar to the configuration of the second electrode 12 in the first embodiment. When the second electrode 12A is in contact with the core 21A, it is preferable that the absolute value of the refractive index difference between the second electrode 12A and the core 21A is smaller than the absolute value of the refractive index difference between the core 21A and the clad 25. When the above condition for the refractive index difference is satisfied, it is possible to suppress reflection of light that has propagated through core 21A at the boundary surface between core 21A and second electrode 12A, and more of the light that has propagated through core 21A can be irradiated onto magnetic element 10. The refractive index of second electrode 12A may be smaller than that of core 21A, or may be larger than that of core 21A, or may be the same as that of core 21A.

[0110] Next, a method for manufacturing the light-detecting element 101 will be described. First, a layer that will become the core 21A is formed on the substrate 30. For example, lithium niobate crystal is grown on a single crystal sapphire substrate. Next, the formed layer is processed into a predetermined shape by photolithography and etching, forming the core 21A.

[0111] Next, a laminated film is formed on the first portion 23A of the core 21A, in which the second electrode 12A, underlayer 6, third ferromagnetic layer 4, magnetic coupling layer 5, second ferromagnetic layer 2, spacer layer 3, first ferromagnetic layer 1, perpendicular magnetization induction layer 7, and cap layer 8 are laminated in this order. The laminated film is then annealed and processed into a predetermined columnar body to produce the magnetic element 10. Thereafter, the first electrode 11A is formed on the cap layer 8. The magnetic element 10 can be produced regardless of the material that constitutes the underlayer, and can be formed on the first portion 23A, which is part of the core 21A, without an adhesive layer or the like.

[0112] Next, the cladding 25 is formed so as to cover the core 21A. Next, the insulating layer 40 is formed so as to cover the magnetic element 10. Next, by forming through holes in the insulating layer 40 and filling the insides with a conductor, via wirings 51 and 52 are formed, and the photodetector element 101 is obtained.

[0113] FIG. 15 is a cross-sectional view of a magnetic element 10A according to a modified example of the second embodiment. The magnetic element 10A can be substituted for the magnetic element 10 of the above-described light-detecting element 101. In this case, the magnetic element 10A is disposed such that the first electrode 11 is closer to the first portion 23A than the second electrode 12, and at least a portion of the first electrode 11 is sandwiched between the magnetic element 10A and the first portion 23A. The magnetic element 10A is irradiated with light reflected by the inclined reflecting surface 24A from the first electrode 11 side. In this case, the first electrode 11 contacts, for example, the first portion 23A of the core 21A. When the first electrode 11 contacts the core 21A, it is preferable that the absolute value of the refractive index difference between the first electrode 11 and the core 21A is smaller than the absolute value of the refractive index difference between the core 21A and the cladding 25. The refractive index of the first electrode 11 may be smaller than the refractive index of the core 21A, or may be larger than the refractive index of the core 21A, or may be the same as the refractive index of the core 21A.

[0114] The magnetic element 10A has at least a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a spacer layer 3. The spacer layer 3 is located between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. In addition to these layers, the magnetic element 10A also has, for example, a third ferromagnetic layer 4, a magnetic coupling layer 5, an underlayer 6, a perpendicular magnetization induction layer 7, a cap layer 8, a seed layer 9A, and a buffer layer 9B.

[0115] In the magnetic element 10A, the stacking order of the cap layer 8, perpendicular magnetization induction layer 7, first ferromagnetic layer 1, spacer layer 3, second ferromagnetic layer 2, magnetic coupling layer 5, and third ferromagnetic layer 4 is opposite to that of the magnetic element 10. Unlike the magnetic element 10, in the magnetic element 10A, the underlayer 6 is located between the cap layer 8 and the first electrode 11, and the underlayer 6, cap layer 8, perpendicular magnetization induction layer 7, first ferromagnetic layer 1, spacer layer 3, second ferromagnetic layer 2, magnetic coupling layer 5, third ferromagnetic layer 4, seed layer 9A, and buffer layer 9B are stacked in this order from the first electrode layer 11 side between the first electrode 11 and the second electrode 12. The seed layer 9A and buffer layer 9B can each be made of the same material as the seed layer and buffer layer of the underlayer 6, respectively.

[0116] The operation of the photodetector element 101 is similar to that of the photodetector element 100. The photodetector element 101 according to the second embodiment can convert light that has propagated through the optical waveguide 20A and irradiated the magnetic element 10 into an output voltage from the magnetic element 10, thereby converting the light into an electrical signal. The photodetector element 101 according to the second embodiment achieves the same effects as the photodetector element 100 according to the first embodiment.

[0117] "Third embodiment" Fig. 16 is a perspective view of a photodetector 102 according to the third embodiment. Figs. 17 and 18 are cross-sectional views of the photodetector 102 according to the third embodiment. Fig. 17 is an xz cross section passing through the center in the width direction of the core 21B. Fig. 18 is a yz cross section passing through the center of the magnetic element 10.

[0118] The photodetector 102 has, for example, a magnetic element 10, a first electrode 11B, a second electrode 12B, an optical waveguide 20B, a substrate 30, and an insulating layer 40. In the photodetector 102 according to the third embodiment, the same components as those in the photodetector 100 according to the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0119] Light emitted from a light source propagates through the optical waveguide 20 B. The light propagating through the optical waveguide 20 B is similar to the light propagating through the optical waveguide 20 according to the first embodiment.

[0120] The optical waveguide 20B is formed by at least a core 21B and a clad 25. The material constituting the core 21B is the same as that of the core 21 according to the first embodiment. The core 21B includes, for example, a main portion 22B and a first portion 23B. The optical waveguide 20B has an inclined reflecting surface 24B. The first portion 23B is connected to the main portion 22B.

[0121] The magnetic element 10 and the optical waveguide 20B are both formed on a substrate 30. The substrate 30 has a first surface 31 and a second surface 32 that face each other in the thickness direction. The optical waveguide 20B is on the first surface 31 side of the substrate 30. The magnetic element 10 has a core 21B of the optical waveguide 20B on the second surface 32 side of the substrate 30 that contacts the substrate 30. For example, the bottom surface of the core 21B contacts the substrate 30. Light is reflected at the interface between the substrate 30 and the core 21B, and the substrate 30 forms part of the cladding 25. The refractive index of the substrate 30 is smaller than that of the core 21B.

[0122] The position of the substrate 30 in the z direction is between the position of the inclined reflecting surface 24B of the optical waveguide 20 in the z direction and the position of the magnetic element 10 in the z direction. For example, a part of the substrate 30 is sandwiched in the z direction between the inclined reflecting surface 24B and the magnetic element 10. The magnetic element 10 is located at a position where it is irradiated with light propagated through the optical waveguide 20B (a position where it is irradiated with light reflected by the inclined reflecting surface 24), and is located, for example, below the inclined reflecting surface 24B. The position of the inclined reflecting surface 24B in the z direction (the stacking direction of the magnetic element 10) is different from the position of the magnetic element 10 in the z direction. For example, the inclined reflecting surface 24B is located at a position overlapping with the magnetic element 10 when viewed from the stacking direction of the magnetic element 10. The light propagated through the optical waveguide 20B is reflected by the inclined reflecting surface 24B, passes through the substrate 30, and is irradiated onto the magnetic element 10 from the second electrode 12B side. The light irradiated onto the magnetic element 10 passes through each layer constituting the magnetic element 10 and is irradiated onto the first ferromagnetic layer 1.

[0123] The first electrode 11B and the second electrode 12B are each electrically connected to, for example, the magnetic element 10. The first electrode 11B is connected to a via wiring 51. The second electrode 12B is connected to a via wiring 52. At least a portion of the second electrode 12B is sandwiched between the magnetic element 10 and the first portion 23B. The configuration of the second electrode 12B is similar to the configuration of the first electrode 11 in the first embodiment. The configuration of the first electrode 11B is similar to the configuration of the second electrode 12 in the first embodiment.

[0124] Next, a method for manufacturing the light-detecting element 102 will be described. First, a layer that will become the core 21B is formed on the first surface 31 of the substrate 30. For example, lithium niobate is crystal-grown on a single-crystal sapphire substrate. Next, the formed layer is processed into a predetermined shape by photolithography and etching to form the core 21B. Next, a cladding 25 is formed to cover the core 21B.

[0125] Next, a stacked film is formed on the second surface 32 of the substrate 30, in which the second electrode 12B, underlayer 6, third ferromagnetic layer 4, magnetic coupling layer 5, second ferromagnetic layer 2, spacer layer 3, first ferromagnetic layer 1, perpendicular magnetization induction layer 7, and cap layer 8 are stacked in this order. The stacked film is then annealed and processed into a predetermined columnar body to produce the magnetic element 10. Thereafter, the first electrode 11B is formed on the cap layer 8.

[0126] Next, an insulating layer 40 is formed to cover the magnetic element 10. Next, through holes are formed in the insulating layer 40 and filled with a conductor to form via wirings 51 and 52, thereby obtaining a light-detecting element 102. In the third embodiment, the magnetic element 10 can also be replaced with the magnetic element 10A shown in FIG. 15. In this case, the magnetic element 10A is arranged so that the first electrode 11 is closer to the first portion 23B than the second electrode 12, and at least a portion of the first electrode 11 is sandwiched between the magnetic element 10A and the first portion 23B. Light reflected by the inclined reflecting surface 24B from the first electrode 11 side is irradiated onto the magnetic element 10A. In this case, the first electrode 11 contacts, for example, the first portion 23B of the core 21B. When the first electrode 11 contacts the core 21B, the absolute value of the refractive index difference between the first electrode 11 and the core 21B is preferably smaller than the absolute value of the refractive index difference between the core 21B and the cladding 25. The refractive index of the first electrode 11 may be smaller than the refractive index of the core 21B, or may be larger than the refractive index of the core 21B, or may be the same as the refractive index of the core 21B.

[0127] The operation of the photodetector element 102 is similar to that of the photodetector element 100. The photodetector element 102 according to the third embodiment can convert light that has propagated through the optical waveguide 20 and irradiated the magnetic element 10 into an output voltage from the magnetic element 10, thereby converting the light into an electrical signal. The photodetector element 102 according to the third embodiment achieves the same effects as the photodetector element 100 according to the first embodiment.

[0128] 19 is a cross-sectional view of a modified example of the photodetector 102 according to the third embodiment. The modified photodetector 102A differs from the photodetector 102 in that a part of the cladding 25 is located between the core 21 and the substrate 30. As in the modified photodetector 102A, the substrate 30 does not have to constitute a part of the cladding 25, and the core 21 does not have to be in direct contact with the substrate 30.

[0129] "Fourth embodiment" Fig. 20 is a perspective view of a photodetector 103 according to the fourth embodiment. Fig. 21 is a cross-sectional view of the photodetector 103 according to the fourth embodiment. Fig. 21 is an xz cross section passing through the center of the core 61 in the width direction.

[0130] The photodetector 103 has, for example, a magnetic element 10, an optical waveguide 60, a substrate 30, and an insulating layer 40. Light propagating through the optical waveguide 60 is irradiated onto the magnetic element 10. In the photodetector 103 according to the fourth embodiment, the same components as those in the photodetector 100 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0131] Light emitted from a light source propagates through the optical waveguide 60. The light propagating through the optical waveguide 60 is similar to the light propagating through the optical waveguide 20 according to the first embodiment.

[0132] The optical waveguide 60 is formed by at least a core 61 and a clad 65. At least a portion of the core 61 is covered with the clad 65. The material forming the core 61 is the same as that of the core 21 according to the first embodiment. The material forming the clad 65 is the same as that of the clad 25 according to the first embodiment.

[0133] The core 61 includes, for example, a main portion 62 and a second portion 63. The main portion 62 extends, for example, in the x direction. The width of the core 61 in the y direction is equal to that of the core 21. The thickness of the main portion 62 of the core 61 in the z direction is equal to that of the main portion 22 of the core 21.

[0134] The second portion 63 is connected to the main portion 62. The second portion 63 is connected to an end of the main portion 62 opposite to the light incident end. Light propagates from the main portion 62 toward the second portion 63. The second portion 63 is curved in a direction toward the magnetic element 10 with respect to the first direction. The second portion 63 is curved, for example, from the main portion 62 extending in the x-direction toward the magnetic element 10.

[0135] Light propagating through the second portion 63 is irradiated onto the magnetic element 10. The position of the second portion 63 in the z direction (the stacking direction of the magnetic element 10) is different from the position of the magnetic element 10 in the z direction. At least a portion of the second portion 63 is located at a position overlapping the magnetic element 10 when viewed from the stacking direction of the magnetic element 10, for example. For example, the second portion 63 is located above the magnetic element 10 in the z direction. The magnetic element 10 is irradiated with light propagated through the optical waveguide 60. When the first electrode 11 is in contact with the core 61, it is preferable that the absolute value of the refractive index difference between the first electrode 11 and the core 61 is smaller than the absolute value of the refractive index difference between the core 61 and the cladding 65. If this condition for the refractive index difference is satisfied, reflection of the light propagating through the core 61 at the boundary surface between the core 61 and the first electrode 11 can be suppressed, and most of the light propagating through the core 61 can be irradiated onto the magnetic element 10. In this case, the refractive index of the first electrode 11 may be smaller or larger than the refractive index of the core 61, or may be the same as the refractive index of the core .

[0136] The magnetic element 10 and the optical waveguide 60 are, for example, on a substrate 30. The position of the magnetic element 10 in the z direction is between the position of the second portion 63 in the z direction and the position of the substrate 30 in the z direction. For example, the magnetic element 10 is sandwiched between the substrate 30 and the second portion 63 in the z direction.

[0137] The photodetector 103 can be fabricated using the same procedure as the photodetector 100. The photodetector 103 operates when light propagating through the optical waveguide 60 is irradiated onto the magnetic element 10. The light propagating through the optical waveguide 60 is light having an intensity variation, and includes, for example, an optical signal having an optical intensity variation. The light propagating through the core 61 propagates through the second portion 63 and is irradiated onto the magnetic element 10. The magnetic element 10 converts the light into an electric signal. The operation of the magnetic element 10 to convert the light into an electric signal is the same as that of the photodetector 100 according to the first embodiment.

[0138] The photodetector 103 according to the fourth embodiment can convert light that has propagated through the optical waveguide 60 and is irradiated onto the magnetic element 10 into an electrical signal by converting the light into an output voltage from the magnetic element 10. The photodetector 103 according to the fourth embodiment has the same effects as the photodetector 100 according to the first embodiment.

[0139] Furthermore, in the fourth embodiment, the positional relationship between the magnetic element 10, the optical waveguide 60, and the substrate 30 is not limited to the configuration in FIG.

[0140] For example, as in the photodetector element 101 according to the second embodiment, the second portion 63 of the optical waveguide 60 may be located between the substrate 30 and the magnetic element 10. In this case, both the magnetic element 10 and the optical waveguide 60 are on the substrate 30. The position of the second portion 63 in the z direction may be between the position of the magnetic element 10 in the z direction and the position of the substrate 30 in the z direction. For example, at least a part of the second portion 63 is sandwiched between the magnetic element 10 and the substrate 30 in the z direction. The magnetic element 10 is located in a position where it is irradiated with light that has propagated through the optical waveguide 60, and may be located above the second portion 63 in the z direction, for example.

[0141] Furthermore, for example, as in the photodetector 102 according to the third embodiment, the optical waveguide 60 and the magnetic element 10 may be formed on different surfaces of the substrate 30. For example, the optical waveguide 60 may be on the first surface 31 side of the substrate 30, and the magnetic element 10 may be on the second surface 32 side of the substrate 30.

[0142] The position of the substrate 30 in the z direction may be between the position of the second portion 63 in the z direction and the position of the magnetic element 10 in the z direction. For example, a part of the substrate 30 may be sandwiched in the z direction between the second portion 63 and the magnetic element 10. The magnetic element 10 is located at a position where it is irradiated with light that has propagated through the optical waveguide 60, and may be located below the second portion 63 in the z direction, for example. In this case, the light that has propagated through the second portion 63 of the optical waveguide 60 passes through the substrate 30 and is irradiated onto the magnetic element 10.

[0143] "Fifth embodiment" Fig. 22 is a perspective view of a photodetector 104 according to the fifth embodiment. Fig. 23 is a cross-sectional view of the photodetector 104 according to the fifth embodiment. Fig. 23 is an xz cross section passing through the center of the core 71 in the width direction.

[0144] The photodetector 104 has, for example, a magnetic element 10, an optical waveguide 70, a substrate 30, and an insulating layer 40. Light propagating through the optical waveguide 70 is irradiated onto the magnetic element 10. In the photodetector 104 according to the fifth embodiment, the same components as those in the photodetector 100 according to the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0145] Light emitted from a light source propagates through the optical waveguide 70. The light propagating through the optical waveguide 70 is similar to the light propagating through the optical waveguide 20 according to the first embodiment.

[0146] The optical waveguide 70 is formed by at least a core 71 and a clad 75. At least a portion of the core 71 is covered with the clad 75. The material constituting the core 71 is the same as that of the core 21 according to the first embodiment. The material constituting the clad 75 is the same as that of the clad 25 according to the first embodiment. The width in the y direction and the thickness in the z direction of the core 71 are the same as those of the core 21.

[0147] Light propagating through the optical waveguide 70 is irradiated onto the magnetic element 10. A portion of the core 71 is located so as to overlap with the magnetic element 10, for example, when viewed from the stacking direction of the magnetic element 10. The first electrode 11 is in contact with the core 71, and the absolute value of the refractive index difference between the first electrode 11 and the core 71 is smaller than the absolute value of the refractive index difference between the core 71 and the cladding 75. As a result, reflection of the light propagating through the core 71 at the interface between the core 71 and the first electrode 11 can be suppressed, and the light propagating through the core 71 is irradiated onto the magnetic element 10 from the interface between the first electrode 11 and the core 71. The refractive index of the first electrode 11 may be smaller or larger than the refractive index of the core 71, or may be the same as the refractive index of the core 71.

[0148] The magnetic element 10 and the optical waveguide 70 are, for example, on a substrate 30. The position of the magnetic element 10 in the z direction is between the position of at least a part of the optical waveguide 70 in the z direction and the position of the substrate 30 in the z direction. For example, the magnetic element 10 is sandwiched between the substrate 30 and the optical waveguide 70 in the z direction.

[0149] The photodetector 104 can be fabricated using the same procedure as the photodetector 100. The photodetector 104 operates when light propagating through the optical waveguide 70 is irradiated onto the magnetic element 10. The light propagating through the optical waveguide 70 is light having intensity variations, and includes, for example, an optical signal having optical intensity variations. The magnetic element 10 converts the light into an electrical signal. The operation of the magnetic element 10 to convert light into an electrical signal is the same as that of the photodetector 100 according to the first embodiment.

[0150] The photodetector 104 according to the fifth embodiment can convert light that has propagated through the optical waveguide 70 and is irradiated onto the magnetic element 10 into an electrical signal by converting the light into an output voltage from the magnetic element 10. The photodetector 104 according to the fifth embodiment has the same effects as the photodetector 100 according to the first embodiment.

[0151] In the fifth embodiment, the positional relationship between the magnetic element 10, the optical waveguide 70, and the substrate 30 is not limited to the configuration in FIG.

[0152] For example, like the photodetector 101 according to the second embodiment, the optical waveguide 70 may be located between the substrate 30 and the magnetic element 10. The position in the z direction of at least a portion of the optical waveguide 70 may be between the position in the z direction of the magnetic element 10 and the position in the z direction of the substrate 30. In this case, for example, a portion of the optical waveguide 70 is sandwiched between the magnetic element 10 and the substrate 30 in the z direction.

[0153] Furthermore, for example, as in the photodetector 102 according to the third embodiment, the optical waveguide 70 and the magnetic element 10 may be formed on different surfaces of the substrate 30. For example, the optical waveguide 70 may be on the first surface 31 side of the substrate 30, and the magnetic element 10 may be on the second surface 32 side of the substrate 30. The core 71 of the optical waveguide 70 may or may not be in contact with the substrate 30.

[0154] The position of the substrate 30 in the z direction may be between the position of at least a part of the optical waveguide 70 in the z direction and the height position in the z direction of the magnetic element 10. For example, a part of the substrate 30 may be sandwiched between the optical waveguide 70 and the magnetic element 10 in the z direction.

[0155] As described above, the present invention is not limited to the above-described embodiments and modifications, and various modifications and changes are possible within the scope of the gist of the present invention as defined in the claims.

[0156] For example, Fig. 24 is a cross-sectional view of a photodetector 110 according to a first modified example. Fig. 24 is a yz cross-section passing through the center of the magnetic element 10. The photodetector 110 has via wirings 55, 56 and external electrodes 57, 58, and differs from the photodetector 100 in that the external electrodes 54, 58 are connected to a reference potential (for example, ground). The reference potential may be ground or something other than ground.

[0157] The via wiring 55 connects the first electrode 11 and the external electrode 57. The via wiring 56 connects the second electrode 12 and the external electrode 58.

[0158] The configuration in which via wiring 55 and external electrode 57 are connected to the first electrode 11, via wiring 56 and external electrode 58 are connected to the second electrode 12, and external electrodes 54 and 58 are connected to a reference potential may be applied to each of the second to fifth embodiments.

[0159] Further, for example, Fig. 25 is a cross-sectional view of a photodetector element 111 according to a second modified example. Fig. 25 is a yz cross-section passing through the center of the magnetic element 10. As shown in Fig. 25, an integrated circuit including a transistor Tr and the like may be formed on the substrate 30. For example, the via wiring 52 may be connected to the transistor Tr. The integrated circuit is, for example, electrically connected to the magnetic element 10, and processes, for example, when the output voltage from the magnetic element 10 is equal to or greater than a threshold, as a first signal (for example, "1"), and when it is less than the threshold, as a second signal (for example, "0").

[0160] The configuration in which an integrated circuit is formed on the substrate 30 may be applied to each of the second to fifth embodiments.

[0161] The light-detecting elements according to the above-described embodiments and modifications can be applied to light sensor devices such as image sensors, transmitters and receivers in communication systems, and the like. [Explanation of symbols]

[0162] 1...first ferromagnetic layer, 2...second ferromagnetic layer, 3...spacer layer, 4...third ferromagnetic layer, 5...magnetic coupling layer, 6...underlayer, 7...perpendicular magnetization induction layer, 8...cap layer, 10...magnetic element, 11...first electrode, 12...second electrode, 20, 20A...optical waveguide, 21, 21A, 61, 71...core, 22, 62...main portion, 23, 23A...first portion, 24, 24A...tilt Oblique reflecting surface, 25, 25A, 65, 75...clad, 30...substrate, 31...first surface, 32...second surface, 40...insulating layer, 51, 52, 55, 56...via wiring, 53, 54...external electrode, 57, 58...ground electrode, 60, 70...optical waveguide, 63...second portion, 100, 101, 102, 102A, 103, 104, 110, 111...photodetector

Claims

1. a magnetic element and an optical waveguide, the magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; the optical waveguide is formed by at least a core and a clad covering at least a part of the core; the light propagating through the optical waveguide is irradiated onto the magnetic element, the magnetic element comprises a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer between the first ferromagnetic layer and the second ferromagnetic layer; The spacer layer is made of a conductor, an insulator, or a layer including current-carrying points made of a conductor in an insulator.

2. the core includes a main portion extending in a first direction intersecting a stacking direction of the magnetic element, and a first portion connected to the main portion; the optical waveguide has an inclined reflecting surface that is part of the boundary surface between the first portion, which is part of the core, and the cladding, and that intersects with the stacking direction and the first direction; The light-sensing element according to claim 1 , wherein the light reflected by the inclined reflecting surface is irradiated onto the magnetic element.

3. The light-sensing element according to claim 2 , wherein a position of the inclined reflecting surface in the stacking direction is different from a position of the magnetic element in the stacking direction.

4. Further comprising a substrate; the magnetic element and the optical waveguide are on the substrate; 4. The light-detecting element according to claim 2, wherein the position of the magnetic element in the direction perpendicular to the surface of the substrate is between the position of the inclined reflecting surface in the direction perpendicular to the surface and the position of the substrate in the direction perpendicular to the surface.

5. A magnetic element and an optical waveguide, the magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; the optical waveguide is formed by at least a core and a clad covering at least a part of the core; the light propagating through the optical waveguide is irradiated onto the magnetic element, the core includes a main portion extending in a first direction intersecting a stacking direction of the magnetic element, and a first portion connected to the main portion; the optical waveguide has an inclined reflecting surface that is part of the boundary surface between the first portion, which is part of the core, and the cladding, and that intersects with the stacking direction and the first direction; the light reflected by the inclined reflecting surface is irradiated onto the magnetic element; Further comprising a substrate; the magnetic element and the optical waveguide are on the substrate; a position of the inclined reflecting surface in a direction perpendicular to the surface of the substrate between a position of the magnetic element in the direction perpendicular to the surface of the substrate;

6. A magnetic element and an optical waveguide, the magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; the optical waveguide is formed by at least a core and a clad covering at least a part of the core; the light propagating through the optical waveguide is irradiated onto the magnetic element, the core includes a main portion extending in a first direction intersecting a stacking direction of the magnetic element, and a first portion connected to the main portion; the optical waveguide has an inclined reflecting surface that is part of the boundary surface between the first portion, which is part of the core, and the cladding, and that intersects with the stacking direction and the first direction; the light reflected by the inclined reflecting surface is irradiated onto the magnetic element; Further comprising a substrate; the substrate has a first surface and a second surface opposed to each other in a thickness direction; the optical waveguide is located on the first surface side, The magnetic element is on the second surface side of the light-sensing element.

7. The photo-sensing element of claim 5 , wherein the substrate is in contact with the core.

8. The photo-sensing element of claim 6 , wherein the substrate is in contact with the core.

9. the core includes a main portion extending in a first direction intersecting a stacking direction of the magnetic element, and a second portion connected to the main portion; the second portion is curved in a direction toward the magnetic element with respect to the first direction; The light-sensing element of claim 1 , wherein the light that has propagated through the second portion is irradiated onto the magnetic element.

10. The light-sensing element according to claim 9 , wherein a position of the second portion in the stacking direction is different from a position of the magnetic element in the stacking direction.

11. Further comprising an electrode, the electrode is electrically connected to the magnetic element and in contact with the core; The photodetector element of claim 1 , wherein the absolute value of the refractive index difference between the core and the electrode is smaller than the absolute value of the refractive index difference between the core and the cladding.

12. When the magnetization of the first ferromagnetic layer and the magnetization of the second ferromagnetic layer are in a parallel relationship, a sense current is configured to flow from the first ferromagnetic layer to the second ferromagnetic layer, 2. The light-sensing element according to claim 1, wherein when the magnetization of the first ferromagnetic layer and the magnetization of the second ferromagnetic layer are in an antiparallel relationship, a sense current flows from the second ferromagnetic layer to the first ferromagnetic layer.

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