Light detecting element, light sensor unit and receiving device

Abstract

To provide a novel light detection element, light sensor unit, and receiving device.SOLUTION: The light detection element has a meta-lens that includes a plurality of nano-structures arranged in a two-dimensional array, and a magnetic element that 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 magnetic element is irradiated by light that has passed through the meta-lens.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light detecting element, a light sensor unit, and a receiving device. [Background technology]

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

[0003] For example, Patent Document 1 describes a receiving device that receives an optical signal using a photodiode. The photodiode is, for example, a pn junction diode using a semiconductor pn junction. Furthermore, for example, Patent Document 2 describes an optical sensor using a semiconductor pn junction and an image sensor using this optical sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-292107 [Patent Document 2] U.S. Patent No. 9,842,874 Summary of the Invention [Problem to be solved by the invention]

[0005] Optical sensors using semiconductor pn junctions are widely used, but new breakthroughs are needed for further development.

[0006] The present invention has been made in view of the above problems, and has an object to provide a novel light detecting element, a light sensor unit, and a receiving device. [Means for solving the problem]

[0007] In order to solve the above problems, the following means are provided.

[0008] (1) A light-detecting element according to a first aspect includes a metalens having a plurality of nanostructures arranged two-dimensionally, and a magnetic element including a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and light passing through the metalens is irradiated onto the magnetic element.

[0009] (2) In the light-detecting element according to the above aspect, the metalens may have a first region when the arrangement surface on which the plurality of nanostructures are arranged is viewed in a planar view, and the area of ​​each of the plurality of nanostructures contained in the first region in a planar view may decrease from the center of the first region toward the outside.

[0010] (3) In the light-detecting element according to the above aspect, the metalens may further have an annular region outside the first region when the arrangement surface on which the plurality of nanostructures are arranged is viewed in a planar view, and the area of ​​each of the plurality of nanostructures contained in the annular region in a planar view may decrease from the inner periphery toward the outer periphery of the annular region.

[0011] (4) In the photodetector element according to the above aspect, when the array surface on which the plurality of nanostructures are arranged is viewed in a plane, the planar shape of each of the plurality of nanostructures has a longitudinal direction and a lateral direction, and the planar shape of at least one of the plurality of nanostructures may have an arrangement angle different from that of another nanostructure.

[0012] (5) In the light-detecting element according to the above aspect, the magnetic element may be disposed at a focal position of the light focused by the metalens.

[0013] (6) In the photodetector according to the above aspect, the light may be light in a specific wavelength range within a wavelength range of 380 nm or more and less than 800 nm.

[0014] (7) In the light-detecting element according to the above aspect, the light may be light in a specific wavelength range within a wavelength range of 800 nm or more and 1 mm or less.

[0015] (8) In the photodetector according to the above aspect, the light may be light in a specific wavelength range within a wavelength range of 200 nm or more and less than 380 nm.

[0016] (9) An optical sensor unit according to a second aspect has a plurality of optical detection elements, each of which is an optical detection element according to the above aspect.

[0017] (10) In the optical sensor unit according to the above aspect, the plurality of optical detecting elements may include at least a first optical detecting element and a second optical detecting element, and the magnetic element of the first optical detecting element may be disposed at a focal position of light in a first wavelength range focused by the metalens, and the magnetic element of the second optical detecting element may be disposed at a focal position of light in a second wavelength range different from the first wavelength range focused by the metalens.

[0018] (11) In the optical sensor unit according to the above aspect, the first wavelength range may be a specific wavelength range within the wavelength range of 380 nm or more and less than 800 nm, and the second wavelength range may be a specific wavelength range within the wavelength range of 800 nm or more and less than 1 nm.

[0019] (12) In the optical sensor unit according to the above aspect, the plurality of optical detecting elements may further include a third optical detecting element, and the magnetic element may be disposed at a focal position of light in a third wavelength range, which is different from the first wavelength range and the second wavelength range, that is focused by the metalens, and the third wavelength range may be a specific wavelength range that is equal to or greater than 200 nm and less than 380 nm.

[0020] (13) In the optical sensor unit according to the above aspect, the plurality of light detecting elements may be arranged one-dimensionally.

[0021] (14) In the optical sensor unit according to the above aspect, the plurality of light detecting elements may be arranged two-dimensionally.

[0022] (15) In the optical sensor unit according to the above aspect, at least one of the photodetecting elements constituting one pixel among the plurality of photodetecting elements may have a different configuration of the nanostructure of the metalens from the other photodetecting elements constituting the pixel.

[0023] (16) In the optical sensor unit according to the above aspect, at least one of the photodetecting elements constituting one pixel among the plurality of photodetecting elements may have a different distance between the metalens and the magnetic element than the other photodetecting elements constituting the pixel.

[0024] (17) A receiving device according to a third aspect includes the photodetector element according to the above aspect. [Effects of the Invention]

[0025] The light detecting element, the light sensor unit and the receiving device according to the above aspects operate on a novel principle. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 2 is a cross-sectional view of the photodetector according to the first embodiment. [Figure 2] FIG. 1 is a plan view of a metalens according to a first example. [Figure 3] FIG. 1 is a schematic diagram of one unit that constitutes a metalens according to a first example. [Figure 4] FIG. 10 is a plan view of a metalens according to a second example. [Figure 5] FIG. 10 is a schematic diagram of one unit that constitutes a metalens according to a second example. [Figure 6] 3A to 3C are schematic diagrams illustrating the operation of the light-detecting element according to the first embodiment. [Figure 7] 5A and 5B are diagrams illustrating a first mechanism of a first operation example of the photodetector according to the first embodiment. [Figure 8] 5A and 5B are diagrams illustrating a second mechanism of the first operation example of the photodetector according to the first embodiment. [Figure 9]5A and 5B are diagrams illustrating a first mechanism of a second operation example of the light-detecting element according to the first embodiment. [Figure 10] 10A and 10B are diagrams illustrating a second mechanism of a second operation example of the light-detecting element according to the first embodiment. [Figure 11] 10A and 10B are diagrams illustrating another example of the second operation example of the light-detecting element according to the first embodiment. [Figure 12] 10A and 10B are diagrams illustrating another example of the second operation example of the light-detecting element according to the first embodiment. [Figure 13] FIG. 1 is a conceptual diagram of an optical sensor device according to a first application example. [Figure 14] FIG. 10 is a diagram illustrating an example of a specific configuration of an optical sensor unit according to a first application example. [Figure 15] FIG. 10 is a conceptual diagram of a cross section of an optical sensor device according to a first application example. [Figure 16] FIG. 10 is a diagram showing an example of a specific configuration of an optical sensor unit according to a first modified example. [Figure 17] FIG. 10 is a conceptual diagram of a cross section of an optical sensor device according to a second modified example. [Figure 18] FIG. 10 is a conceptual diagram of a transmission / reception system according to a second application example. [Figure 19] FIG. 10 is a block diagram of a transmitting / receiving device according to a second application example. [Figure 20] 10 is an enlarged schematic diagram of the vicinity of a photodetector element of a transceiver device according to a second application example. FIG. [Figure 21] FIG. 1 is a conceptual diagram of another example of a communication system. [Figure 22] FIG. 1 is a conceptual diagram of another example of a communication system. DETAILED DESCRIPTION OF THE INVENTION

[0027] 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.

[0028] The directions are defined as follows. The stacking direction of the magnetic element 10 is the z direction, one direction in a plane perpendicular to the z direction is the x direction, and the direction perpendicular to the x and z directions is the y direction. Hereinafter, the +z direction may be expressed as "up" and the -z direction as "down". The +z direction is the direction from the magnetic element 10 to the metalens 20. Up and down do not necessarily coincide with the direction in which gravity is applied.

[0029] "First embodiment" Fig. 1 is a cross-sectional view of a photodetector element 100 according to the first embodiment. In Fig. 1, the direction of magnetization of a ferromagnetic material in its initial state is indicated by an arrow.

[0030] The light detecting element 100 includes a magnetic element 10 and a metalens 20. The magnetic element 10 is irradiated with light that has passed through the metalens 20. The magnetic element 10 detects the light irradiated onto the magnetic element 10. The magnetic element 10 converts the light irradiated onto the magnetic element 10 into an electrical signal. The metalens 20 focuses the light toward the magnetic element 10. The magnetic element 10 is disposed, for example, at the focal position of the light focused by the metalens 20. An insulating layer 91, for example, is present between the magnetic element 10 and the metalens 20.

[0031] In this specification, light 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.

[0032] 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 buffer layer 4, a seed layer 5, a third ferromagnetic layer 6, a magnetic coupling layer 7, a perpendicular magnetization induction layer 8, a cap layer 9, and an insulating layer 90. The buffer layer 4, the seed layer 5, the third ferromagnetic layer 6, and the magnetic coupling layer 7 are located between the second ferromagnetic layer 2 and the second electrode 12, and the perpendicular magnetization induction layer 8 and the cap layer 9 are located between the first ferromagnetic layer 1 and the first electrode 11. The insulating layer 90 is located between the first electrode 11 and the second electrode 12 and covers the periphery of the stack 15.

[0033] 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.

[0034] The first ferromagnetic layer 1 is a light detection layer whose magnetization state changes when irradiated with external 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, externally irradiated light, a current flowing in the z 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.

[0035] 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 elements 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. 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.

[0036] The first ferromagnetic layer 1 may be an in-plane magnetization film having an axis of easy magnetization in the in-plane direction (any direction in the xy plane) or a perpendicular magnetization film having an axis of easy magnetization in the direction perpendicular to the film plane (z direction).

[0037] 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 z-direction 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.

[0038] 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.

[0039] 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 1.0 nm.

[0040] 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 has an easy axis of magnetization in the same direction as the first ferromagnetic layer 1, for example. The second ferromagnetic layer 2 may be an in-plane magnetization film or a perpendicular magnetization film.

[0041] 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.

[0042] The magnetization of the second ferromagnetic layer 2 may be fixed by, for example, magnetic coupling with the third ferromagnetic layer 6, which sandwiches the magnetic coupling layer 7. In this case, the combination of the second ferromagnetic layer 2, the magnetic coupling layer 7, and the third ferromagnetic layer 6 may be referred to as a magnetization fixed layer. Details of the magnetic coupling layer 7 and the third ferromagnetic layer 6 will be described later.

[0043] 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 current-carrying points 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 magnetizations of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 in the initial state, which will be described later.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The third ferromagnetic layer 6 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 M6 of the third ferromagnetic layer 6 are antiparallel to each other. The material constituting the third ferromagnetic layer 6 is, for example, the same as that of the first ferromagnetic layer 1.

[0049] The magnetic coupling layer 7 is located between the second ferromagnetic layer 2 and the third ferromagnetic layer 6. The magnetic coupling layer 7 is made of, for example, Ru, Ir, or the like.

[0050] The buffer layer 4 is a layer that reduces lattice mismatch between different crystals. The buffer layer 4 is, for example, a metal containing at least one element selected from the group consisting of Ta, Ti, Zr, and Cr, or a nitride containing at least one element selected from the group consisting of Ta, Ti, Zr, and Cu. More specifically, the buffer layer 4 is, for example, Ta (element), a NiCr alloy, TaN (tantalum nitride), or CuN (copper nitride). The buffer layer 4 has a thickness of, for example, 1 nm or more and 5 nm or less. The buffer layer 4 is, for example, amorphous. The buffer layer 4 is, for example, located between the seed layer 5 and the second electrode 12 and in contact with the second electrode 12. The buffer layer 4 suppresses the influence of the crystal structure of the second electrode 12 on the crystal structure of the second ferromagnetic layer 2.

[0051] The seed layer 5 improves the crystallinity of layers stacked on the seed layer 5. The seed layer 5 is located, for example, between the buffer layer 4 and the third ferromagnetic layer 6 and on the buffer layer 4. The seed layer 5 is made of, for example, Pt, Ru, Zr, or NiFeCr. The thickness of the seed layer 5 is, for example, 1 nm or more and 5 nm or less.

[0052] The cap layer 9 is located between the first ferromagnetic layer 1 and the first electrode 11. The cap layer 9 may include a perpendicular magnetization induction layer 8 stacked on the first ferromagnetic layer 1 and in contact with the first ferromagnetic layer 1. The cap layer 9 prevents damage to the lower layers during the process and improves the crystallinity of the lower layers during annealing. The thickness of the cap layer 9 is, for example, 10 nm or less so that the first ferromagnetic layer 1 is irradiated with sufficient light.

[0053] The perpendicular magnetization induction layer 8 induces perpendicular magnetic anisotropy in the first ferromagnetic layer 1. The perpendicular magnetization induction layer 8 is made of, for example, magnesium oxide, W, Ta, or Mo. When the perpendicular magnetization induction layer 8 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 8 is, for example, 0.5 nm or more and 5.0 nm or less.

[0054] The insulating layer 90 is made of, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg. The insulating layer 90 is made of, for example, silicon oxide (SiOx ), silicon nitride (SiN x ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO x ) etc.

[0055] The first electrode 11 is disposed, for example, on the metalens 20 side of the magnetic element 10. Incident light is irradiated onto the magnetic element 10 from the first electrode 11 side, and is irradiated at least onto 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 light in the wavelength range used. The first electrode 11 is, for example, 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 configured to have multiple metal pillars in a transparent electrode material of these oxides. It is not essential to use such a transparent electrode material for the first electrode 11; a metal material such as Au, Cu, or Al may be used in a thin film thickness to allow the irradiated light to reach the first ferromagnetic layer 1. When a metal is used as the material of the first electrode 11, the film thickness of the first electrode 11 is, for example, 3 to 10 nm. The first electrode 11 may have an anti-reflection film on the surface that is irradiated with light.

[0056] The second electrode 12 is made of a conductive material. The second electrode 12 is made of, for example, 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.

[0057] 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.

[0058] The metalens 20 has a plurality of nanostructures 21. The plurality of nanostructures 21 are formed on, for example, a base 22. The metalens 20 is a lens that utilizes a metasurface. The metalens 20 functions as a lens by controlling the phase distribution of light. A metasurface exhibits the functions of a metamaterial through its planar structure. A metamaterial is a medium with a negative refractive index, or a medium designed to have a refractive index (dielectric constant, magnetic permeability) that does not exist in nature. The metalens 20 can reduce the focal length, thereby enabling the photodetector element 100 to be miniaturized. Furthermore, the metalens 20 can reduce the size of the focal point, thereby enabling high-energy light to be efficiently irradiated onto the magnetic element 10.

[0059] The metalens 20 includes, for example, a dielectric material in which surface plasmon excitation occurs. The metalens 20 also transmits light in the operating band. The nanostructure 21 is, for example, titanium oxide or gallium nitride. If the light incident on the photodetector element 100 is infrared, the nanostructure 21 may be amorphous silicon. The base 22 is, for example, silicon oxide or aluminum oxide.

[0060] The multiple nanostructures 21 are two-dimensionally arranged in the xy plane. The xy plane is an example of an arrangement plane on which the multiple nanostructures 21 are arranged. Figure 2 is a plan view of a metalens 20 according to a first example.

[0061] Fig. 3 is a schematic diagram of one unit 23 that constitutes the metalens 20 according to the first example. The upper view of Fig. 3 is a plan view from the z direction, and the lower view of Fig. 3 is a perspective view. Multiple units 23 are arranged in the same plane to form the metalens 20.

[0062] Nanostructure 21 is, for example, a cylinder with a diameter φ and a height H. In metalens 20, these nanostructures 21 are periodically arranged with a period U. In multiple nanostructures 21, diameter φ has multiple values. In multiple nanostructures 21, height H may have only one value or multiple values. Diameter φ and period U are equal to or less than the wavelength of the light used. In the example shown in FIG. 3 , the length in the x direction of base 22 in one unit 23 is U, and the length in the y direction is also U.

[0063] As shown in FIG. 2, metalens 20 has a first region A1 and an annular region A2, for example, in a plan view from the z direction. First region A1 is, for example, circular. Annular region A2 is located outside first region A1. The outer periphery of annular region A2 and the outer periphery of first region A1 are, for example, concentric circles. First region A1 contains a plurality of nanostructures 21. Annular region A2 also contains a plurality of nanostructures 21. Metalens 20 does not necessarily have to have annular region A2.

[0064] The area in a plan view of each of the multiple nanostructures 21 contained in the first region A1 decreases, for example, from the center of the first region A1 toward the outside. For example, the diameter φ of the nanostructures 21 in the first region A1 decreases from the center toward the outside.

[0065] The planar area of ​​each of the multiple nanostructures 21 contained in the annular region A2 decreases, for example, from the inner periphery toward the outer periphery of the annular region A2. For example, the diameter φ of the nanostructures 21 in the annular region A2 decreases from the inner periphery toward the outer periphery. The planar area of ​​the nanostructures 21 arranged on the innermost periphery of the annular region A2 is larger than the planar area of ​​the nanostructures 21 arranged on the outermost periphery of the first region A1, for example.

[0066] The metalens 20 can control the phase distribution of light by adjusting the arrangement of the multiple nanostructures 21, the size of each nanostructure 21, and the arrangement period of the multiple nanostructures 21.

[0067] For example, assuming that the diameter of metalens 20 is 3 μm, the focal length of light focused by metalens 20 is 3 μm, and metalens 20 consists only of first region A1, the size of each nanostructure 21 and the arrangement period of multiple nanostructures 21 are shown in Table 1. In this example, nanostructures 21 are made of titanium oxide, and insulating layer 91 is made of silicon oxide. In Table 1, λ is the wavelength of light focused to a focal length of 3 μm by metalens 20, and φ max is the diameter of the largest nanostructure 21, and φ min is the diameter of the smallest nanostructure 21, H is the height of the nanostructure 21, and U is the period between the nanostructures 21.

[0068] [Table 1]

[0069] As shown in Table 1, by adjusting the size and arrangement period of the nanostructures 21, the focal length of the metalens 20 can be made the same even if the wavelength of the incident light is different.

[0070] Furthermore, the structure of the metalens 20 is not limited to that shown in FIGS. 2 and 3. For example, one or more additional annular regions may be provided outside the annular region A2 of the metalens 20 shown in FIG. 2. FIG. 4 is a plan view of a metalens 20A according to a second example. FIG. 5 is a schematic diagram of one unit 23A that constitutes the metalens 20A according to the second example. The upper view of FIG. 5 is a plan view from the z direction, and the lower view of FIG. 5 is a perspective view. Multiple units 23A are arranged in the same plane to form the metalens 20A.

[0071] The plurality of nanostructures 21A are arranged two-dimensionally on the xy plane. When viewed in plan on the xy plane, the planar shape of at least one of the plurality of nanostructures 21A has a different arrangement angle from the planar shape of another nanostructure 21A.

[0072] Each nanostructure 21A has, for example, a longitudinal and lateral direction in plan view. The nanostructure 21A shown in FIG. 5 has a rectangular parallelepiped shape with a longitudinal length L, a lateral width W, and a height H, and a rectangular shape with a longitudinal length L and a lateral width W in plan view. The length L, width W, and period U are equal to or less than the wavelength of the light used. In the example shown in FIG. 5, the length of the base 22 in one unit 23A in the x direction is U, and the length in the y direction is also U. In the metalens 20A, these nanostructures 21A are periodically arranged with a period U. The longitudinal direction of the nanostructures 21A is inclined at an arrangement angle θ with respect to a reference axis (e.g., the x direction). In multiple nanostructures 21A, the arrangement angle θ may have multiple values, and for example, the distribution thereof may have the regularity of a Panchanratonam Berry geometric phase.

[0073] For example, assuming that the diameter of metalens 20A is 3 μm, the focal length of light focused by metalens 20A is 3 μm, and the distribution of the arrangement angle θ of nanostructures 21A satisfies the regularity of the Panchanratonam Berry geometric phase, Table 2 shows the size of each nanostructure 21A and the arrangement period of multiple nanostructures 21A. In this example, nanostructures 21A are made of titanium oxide, and insulating layer 91 is made of silicon oxide. In Table 2, λ is the wavelength of light focused to a focal length of 3 μm by metalens 20A, W is the width of nanostructure 21A in a planar view, L is the length of nanostructure 21A in a planar view, H is the height of nanostructure 21A, and U is the period between nanostructures 21A.

[0074] [Table 2]

[0075] As shown in Table 2, by adjusting the size and arrangement period of nanostructures 21A, the focal length of metalens 20A can be made the same even if the wavelength of incident light is different.

[0076] The insulating layer 91 is located between the magnetic element 10 and the metalens 20. The material of the insulating layer 91 is not particularly limited as long as it can transmit light in the used band. For example, the same material as the insulating layer 90 can be used for the insulating layer 91. The insulating layer 91 and the insulating layer 90 may be made of the same material or different materials. Furthermore, the insulating layer 91 and the base 22 may be made of the same material or different materials.

[0077] The photodetector element 100 is obtained by fabricating the second electrode 12, the magnetic element 10, the first electrode 11, the insulating layer 91, and the metalens 20 in this order.

[0078] The magnetic element 10 is fabricated through a process of stacking each layer, an annealing process, and a processing process. First, a buffer layer 4, a seed layer 5, a third ferromagnetic layer 6, a magnetic coupling layer 7, a second ferromagnetic layer 2, a spacer layer 3, a first ferromagnetic layer 1, a perpendicular magnetization induction layer 8, and a cap layer 9 are stacked in this order on the second electrode 12. Each layer is formed by, for example, sputtering.

[0079] Next, the stacked film is annealed. The annealing temperature is, for example, 250°C or higher and 400°C or lower. Thereafter, the stacked film is processed into a columnar stacked body 15 by photolithography and etching. The stacked body 15 may be a cylindrical or rectangular column. For example, the shortest width of the stacked body 15 when viewed from the z direction is 10 nm or higher and 1000 nm or lower.

[0080] Next, an insulating layer 90 is formed so as to cover the side surface of the laminated body 15. The insulating layer 90 may be laminated multiple times. Next, the upper surface of the cap layer 9 is exposed from the insulating layer 90 by chemical mechanical polishing, and the first electrode 11 is formed on the cap layer 9.

[0081] Next, an insulating layer 91 is formed on the first electrode 11. A resist having a predetermined pattern is formed on the upper surface of the insulating layer 91, and dry etching is performed. Holes having a predetermined pattern are formed on the upper surface of the insulating layer 91 by dry etching. Next, the metalens 20 is formed by forming a film while filling the holes with the material that constitutes the nanostructure 21. Through the above process, a photodetector element 100 is obtained. When a wavelength filter 40 (described later) is used, for example, a dielectric multilayer film that will become the wavelength filter 40 is formed, for example, between the first electrode 11 and the insulating layer 91. In this way, in the production of the photodetector element 100, the magnetic element 10 and the metalens 20 can be formed consecutively by a vacuum film formation process.

[0082] Next, the operation of the photodetector 100 according to the first embodiment will be described. Fig. 6 is a schematic diagram for explaining the operation of the photodetector 100. In Fig. 6, the insulating layer 91 between the magnetic element 10 and the metalens 20 is omitted.

[0083] Light L incident on the photodetector element 100 is focused by the metalens 20. As shown in FIG. 6, light L incident on the metalens 20 may be light that has passed through a polarizing filter 30. The photodetector element 100 may have a polarizing filter 30 on the side of the metalens 20 opposite the magnetic element 10. When using the metalens 20A shown in FIG. 4, it is preferable to use the polarizing filter 30. Even when using the metalens 20A shown in FIG. 4, the polarizing filter 30 may not be necessary if the light incident on the photodetector element 100 is polarized light such as laser light.

[0084] The magnetic element 10 is disposed at the focal position of light L in the usable band focused by the metalens 20. The focal position of light L in the usable band preferably overlaps, for example, with the first ferromagnetic layer 1. For example, when visible light is used, the magnetic element 10 is disposed at the focal position of light in a specific wavelength range of 380 nm or more and less than 800 nm. For example, when infrared light is used, the magnetic element 10 is disposed at the focal position of light in a specific wavelength range of 800 nm or more and less than 1000 nm. For example, when ultraviolet light is used, the magnetic element 10 is disposed at the focal position of light in a specific wavelength range of 200 nm or more and less than 380 nm.

[0085] Furthermore, the light L irradiated onto the magnetic element 10 may be light that has passed through a wavelength filter 40. The photodetector element 100 may include a wavelength filter 40. The wavelength filter 40 is disposed, for example, between the magnetic element 10 and the metalens 20, or on the side of the metalens 20 opposite the magnetic element 10. Then, the light L that has passed through the metalens 20 is irradiated onto the magnetic element 10.

[0086] The output voltage from the magnetic element 10 changes with changes in the intensity of light L irradiated onto the first ferromagnetic layer 1. The change in the output voltage from the magnetic element 10 is caused by changes in the resistance values ​​of the first ferromagnetic layer 1, the second ferromagnetic layer 2, and the spacer layer 3 in the stacking direction. In the first operation example, a case 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 intensity of the light with the second intensity is assumed to be greater than the intensity of the light with the first intensity. The first intensity may also be zero when the intensity of the light irradiated onto the first ferromagnetic layer 1.

[0087] 7 and 8 are diagrams illustrating a first operation example of the magnetic element 10. FIG. 7 is a diagram illustrating a first mechanism of the first operation example, and FIG. 8 is a diagram illustrating a second mechanism of the first operation example. In FIGS. 7 and 8, 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. 7 and 8, 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. 7 and 8, the vertical axis represents the resistance value of the magnetic element 10 in the z direction, and the horizontal axis represents time.

[0088] 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 across 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. 7, 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. Also, 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.

[0089] 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.

[0090] For example, as shown in Fig. 7, 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. Also, as shown in Fig. 8, 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 irradiation intensity of light, the tilt angle is greater than 0° and less than 90°.

[0091] 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.

[0092] In the case shown in FIG. 7, 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 state parallel to 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 magnetic element 10 returns to its initial state. In the case shown in FIG. 8, 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 original value, and the magnetic element 10 returns to its initial state. In either case, the resistance value of the magnetic element 10 in the z direction 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 of the magnetic element 10 in the z direction 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.

[0093] 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, when the output voltage from the magnetic element 10 is equal to or greater than a threshold, it is processed as a first signal (e.g., "1"), and when it is less than the threshold, it is processed as a second signal (e.g., "0").

[0094] 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). If the initial state is one in which the magnetization M1 and the magnetization M2 are antiparallel, 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.

[0095] 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.

[0096] 9 and 10 are diagrams illustrating a second operation example of the magnetic element 10 according to the first embodiment. FIG. 9 is a diagram illustrating a first mechanism of the second operation example, and FIG. 10 is a diagram illustrating a second mechanism of the second operation example. In FIGS. 9 and 10, 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. 9 and 10, 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. 9 and 10, the vertical axis represents the resistance value of the magnetic element 10 in the z direction, and the horizontal axis represents time.

[0097] 9, 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°.

[0098] 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.

[0099] 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.

[0100] Similarly, in the case of FIG. 10, 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. 9, the difference in these output voltages (resistance values) can be read from the photodetector element 100 as multi-valued or analog data.

[0101] Also, in the second operating example, as in the first operating example, when the intensity of the light irradiated to the first ferromagnetic layer 1 returns to the first intensity, the state of the magnetization M1 of the first ferromagnetic layer 1 returns to its original state, and the magnetic element 10 returns to its initial state.

[0102] 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.

[0103] 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.

[0104] 11 and 12 are diagrams illustrating another example of the second operation example of the magnetic element 10 according to the first embodiment. In FIGS. 11 and 12, 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. 11 and 12. In FIG. 11, the sense current Is flows from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. In FIG. 12, the sense current Is flows from the second ferromagnetic layer 2 to the first ferromagnetic layer 1.

[0105] 11 and 12, 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. 11, 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. 12, 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. 11 and 12, 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.

[0106] 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. 11 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. 12 tilts so as to be antiparallel to the magnetization M2 of the second ferromagnetic layer 2. The tilt directions of the magnetization M1 in FIGS. 11 and 12 are different because the directions of the spin transfer torque acting on the magnetization M1 are different.

[0107] 11, 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. 12, the resistance value of the magnetic element 10 increases, and the output voltage from the magnetic element 10 increases.

[0108] When the intensity of the light irradiated to the first ferromagnetic layer 1 returns to the first intensity, the state of the magnetization M1 of the first ferromagnetic layer 1 returns to its original state due to the effect of magnetic anisotropy on the magnetization M1, and as a result, the magnetic element 10 returns to its initial state.

[0109] 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.

[0110] As described above, the photodetector 100 according to the first embodiment can convert light into an electrical signal by using the metalens 20 to focus light toward the magnetic element 10 and converting the light irradiated onto the magnetic element 10 into an output voltage from the magnetic element 10.

[0111] 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 reduced 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. In other words, the photodetector 100 according to the first embodiment can detect light with high sensitivity.

[0112] 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.

[0113] Furthermore, the amount of light focused by the metalens 20 onto the magnetic element 10 increases as the area of ​​the metalens 20 increases. Because the magnetic element 10 can convert light into an electrical signal even when the amount of light irradiated is small, the area of ​​the metalens 20 can be reduced. By reducing the area of ​​the metalens 20 to match the area of ​​the magnetic element 10, the photodetector elements 100 can be integrated at a high density.

[0114] The light-detecting element according to the above embodiment can be applied to a receiving device of a communication system, a light sensor device such as an image sensor, and the like.

[0115] (First application example) 13 is a conceptual diagram of an optical sensor device 200 according to the first application example. The optical sensor device 200 shown in FIG.

[0116] The optical sensor unit 110 includes, for example, a plurality of optical sensing elements 100. Each of the optical sensing elements 100 is the optical sensing element described above. Each of the optical sensing elements 100 functions as an optical sensor. The optical sensing elements 100 preferably operate in the second operation example. The optical sensing elements 100 are, for example, two-dimensionally arranged in a matrix. Each of the optical sensing elements 100 is connected to a first selection line extending in the row direction and a second selection line extending in the column direction. The optical sensor unit 110 detects light using the plurality of optical sensing elements 100 and converts the light into an electrical signal.

[0117] The semiconductor circuit 120 is disposed, for example, outside the outer periphery of the optical sensor unit 110. The semiconductor circuit 120 may also be formed on a circuit board 101 (described later) and positioned so as to overlap the optical sensor unit 110 in the z direction.

[0118] The semiconductor circuit 120 is electrically connected to each of the photodetecting elements 100. The semiconductor circuit 120 performs an operation on the electrical signal sent from the photosensor unit 110. The semiconductor circuit 120 includes, for example, a row decoder 121 and a column decoder 122. The row decoder 121 and the column decoder 122 identify the position of the photodetecting element 100 that detected light. In addition to the row decoder 121 and the column decoder 122, the semiconductor circuit 120 may also include a memory, an arithmetic circuit, a register, etc.

[0119] FIG. 14 shows an example of a specific configuration of an optical sensor unit. The optical sensor unit 110 shown in FIG. 14 has multiple pixels p1. Each pixel p1 has, for example, a red sensor 100R, a green sensor 100G, a blue sensor 100B, an infrared sensor 100IR, and an ultraviolet sensor 100UV. The red sensor 100R, the green sensor 100G, the blue sensor 100B, the infrared sensor 100IR, and the ultraviolet sensor 100UV are each configured with a photodetector element 100. In the optical sensor unit 110 shown in FIG. 14, two green sensors 100G with high visibility are arranged in one pixel p1, but this is not limited to this example. For example, at least one of the infrared sensor 100IR and the ultraviolet sensor 100UV may be omitted.

[0120] The red sensor 100R, the green sensor 100G, and the blue sensor 100B each detect light in a specific wavelength range of 380 nm or more and less than 800 nm (hereinafter referred to as the first wavelength range). The blue sensor 100B detects light in a wavelength range of 380 nm or more and less than 490 nm, for example. The green sensor 100G detects light in a wavelength range of 490 nm or more and less than 590 nm, for example. The red sensor 100R detects light in a wavelength range of 590 nm or more and less than 800 nm, for example. The infrared sensor 100IR detects light in a specific wavelength range of 800 nm or more and less than 1 mm (hereinafter referred to as the second wavelength range). The ultraviolet sensor 100UV detects light in a specific wavelength range of 200 nm or more and less than 380 nm (hereinafter referred to as the third wavelength range).

[0121] In the example shown in FIG. 14 , for example, red sensor 100R, green sensor 100G, and blue sensor 100B can be considered as first photodetecting elements, infrared sensor 100IR can be considered as second photodetecting elements, and ultraviolet sensor 100UV can be considered as third photodetecting elements. The first photodetecting elements are photodetecting elements in which magnetic element 10 is disposed at the focal position of light in a first wavelength range focused by metalens 20. The second photodetecting elements are photodetecting elements in which magnetic element 10 is disposed at the focal position of light in a second wavelength range focused by metalens 20. The third photodetecting elements are photodetecting elements in which magnetic element 10 is disposed at the focal position of light in a third wavelength range focused by metalens 20. The first wavelength range, second wavelength range, and third wavelength range are different from one another.

[0122] 15 is a conceptual diagram of a cross section of the optical sensor device 200 according to the first embodiment. The optical sensor device 200 includes, for example, a circuit board 101, a wiring layer 105, and a plurality of optical detection elements 100. The wiring layer 105 and the plurality of optical detection elements 100 are each formed on the circuit board 101.

[0123] The above-described semiconductor circuit 120 is formed on the circuit board 101. The circuit board 101 has, for example, an analog-to-digital converter 102 and an output terminal 103. The electrical signal sent from the light detecting element 100 is converted into digital data by the analog-to-digital converter 102 and output from the output terminal 103.

[0124] The wiring layer 105 has a plurality of wirings 106. An interlayer insulating film 107 is provided between the plurality of wirings 106. The wirings 106 electrically connect each of the photodetector elements 100 to the circuit board 101 and between each of the arithmetic circuits formed on the circuit board 101. Each of the photodetector elements 100 and the circuit board 101 are connected via, for example, through-wiring that penetrates the interlayer insulating film 107 in the z direction. Noise can be reduced by shortening the distance between the wirings between each of the photodetector elements 100 and the circuit board 101.

[0125] The wiring 106 is conductive. The wiring 106 is made of, for example, Al, Cu, or the like. The interlayer insulating film 107 is an insulator that provides insulation between the wirings of the multilayer wiring and between the elements. The interlayer insulating film 107 is made of, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg, and the same material as the insulating layer 90 can be used.

[0126] The wavelength filters 40 of the red sensor 100R, green sensor 100G, blue sensor 100B, infrared sensor 100IR, and ultraviolet sensor 100UV each transmit different wavelength ranges of light. The wavelength filter 40 of the red sensor 100R transmits light in the wavelength range of 590 nm or more and less than 800 nm, for example. The wavelength filter 40 of the green sensor 100G transmits light in the wavelength range of 490 nm or more and less than 590 nm, for example. The wavelength filter 40 of the blue sensor 100B transmits light in the wavelength range of 380 nm or more and less than 490 nm, for example. The wavelength filter 40 of the infrared sensor 100IR transmits light in a specific wavelength range, for example, from 800 nm or more to 1 nm or less. The wavelength filter 40 of the ultraviolet sensor 100UV transmits light in a specific wavelength range, for example, from 200 nm or more and less than 380 nm.

[0127] In the multiple photodetecting elements 100 that make up one pixel p1, the distance between the magnetic element 10 and the metalens 20 may be equal. In this case, at least one of the multiple photodetecting elements 100 that make up one pixel p1 has a different configuration of the nanostructure 21 of the metalens 20 than the other photodetecting elements 100 that make up the pixel p1. For example, the configurations of the nanostructures 21 of the metalenses 20 of the red sensor 100R, the green sensor 100G, the blue sensor 100B, the infrared sensor 100IR, and the ultraviolet sensor 100UV are different from one another. The configuration of the nanostructures 21 refers to, for example, the size of the shape of each nanostructure 21 in a planar view, the periodic arrangement of the multiple nanostructures, etc. For example, the configuration of the nanostructures 21 of each metalens 20 may be determined so that the focal length of the metalens 20 for the red sensor 100R for light with a wavelength of 633 nm, the focal length of the metalens 20 for the green sensor 100G for light with a wavelength of 530 nm, the focal length of the metalens 20 for the blue sensor 100B for light with a wavelength of 430 nm, the focal length of the metalens 20 for the infrared sensor 100IR for light with a wavelength of 1530 nm, and the focal length of the metalens 20 for the ultraviolet sensor 100UV for light with a wavelength of 290 nm are all equal.

[0128] In the photodetector element 100 shown in FIG. 15, one magnetic element 10 is disposed below one metalens 20, but multiple magnetic elements 10 may be disposed below one metalens 20.

[0129] Although examples have been shown up to this point in which the photodetecting elements 100 are arranged two-dimensionally, the photodetecting elements 100 may also be arranged one-dimensionally as shown in Fig. 16. Fig. 16 shows an example in which one pixel p2 is composed of a red sensor 100R, a green sensor 100G, a blue sensor 100B, an infrared sensor 100IR, and an ultraviolet sensor 100UV arranged one-dimensionally, but it is not necessary for the pixel p2 to have one or more of these. Furthermore, multiple photodetecting elements 100 may detect light in the same wavelength range, and the wavelength range of light detected by each photodetecting element 100 does not matter.

[0130] 17 , the optical sensor unit 110A may have multiple optical sensing elements 100 with different distances between the magnetic element 10 and the metalens 20. For example, at least one of the multiple optical sensing elements 100 constituting one pixel p1 may have a different distance between the metalens 20 and the magnetic element 10 than the other optical sensing elements 100 constituting one pixel p1. In this case, the configuration of the nanostructure 21 of the metalens 20 may be the same among the multiple optical sensing elements 100 constituting one pixel p1.

[0131] For example, the distance between the metalens 20 and the magnetic element 10 is different in the red sensor 100R, the green sensor 100G, and the blue sensor 100B. In a metalens 20 having a certain configuration, the focal length of the metalens 20 with respect to light L varies depending on the wavelength of the light L. In the red sensor 100R, the magnetic element 10 (first ferromagnetic layer 1 in the example of FIG. 17 ) and the metalens 20 are separated by a first focal length f1. In the green sensor 100G, the magnetic element 10 (first ferromagnetic layer 1 in the example of FIG. 17 ) and the metalens 20 are separated by a second focal length f2. In the blue sensor 100B, the magnetic element 10 (first ferromagnetic layer 1 in the example of FIG. 17 ) and the metalens 20 are separated by a third focal length f3. The first focal length f1 is the focal length of the metalens 20 with respect to light of a specific wavelength (e.g., light with a wavelength of 633 nm) within the wavelength range of 590 nm to 800 nm (red light). The second focal length f2 is the focal length of metalens 20 for light of a specific wavelength (e.g., light with a wavelength of 530 nm) within the wavelength range of 490 nm or more and 590 nm or less (green light). The third focal length f3 is the focal length of metalens 20 for light of a specific wavelength (e.g., light with a wavelength of 530 nm) within the wavelength range of 380 nm or more and 490 nm or less (blue light). The first focal length f1 is shorter than the second focal length f2, and the second focal length f2 is shorter than the third focal length f3.

[0132] The optical sensor devices 200, 201 measure the output voltage (resistance value of the magnetic element 10) from the magnetic element 10 of each light detecting element 100 of the optical sensor units 110, 110A together with position information obtained by the row decoder 121 and the column decoder 122, and read the intensity of light irradiating the optical sensor unit 110. The optical sensor devices 200, 201 are used, for example, in image sensors. Such image sensors can be used in information terminal devices such as smartphones, tablets, personal computers, and digital cameras.

[0133] Although an example of the optical sensor devices 200, 201 has been described above, the optical sensor device is not limited to this example. For example, if the optical sensor unit 110, 110A uses a metalens 20 as shown in FIG. 2 or if the light incident on the light detection element 100 is polarized light such as laser light, the polarizing filter 30 may not be provided. Furthermore, the focal length of light incident on a single metalens 20 varies depending on the wavelength. Therefore, the metalens 20 itself functions like a wavelength filter, limiting the wavelength range of light that is irradiated at high intensity onto the magnetic element 10. If the wavelength filtering effect of the metalens 20 is sufficient, the wavelength filter 40 may not be provided.

[0134] (Second application example) FIG. 18 is a conceptual diagram of a communication system 300 according to a second application example. The communication system 300 shown in FIG. 18 includes a plurality of transmitting / receiving devices 301 and an optical fiber FB connecting the transmitting / receiving devices 301. The communication system 300 can be used for short- or medium-distance communication, such as within a data center or between data centers, or for long-distance communication, such as between cities. The transmitting / receiving devices 301 are installed, for example, within a data center. The optical fiber FB connects, for example, between data centers. The communication system 300 performs communication between the transmitting / receiving devices 301 via, for example, the optical fiber FB. The communication system 300 may also perform communication between the transmitting / receiving devices 301 wirelessly, without using the optical fiber FB.

[0135] 19 is a block diagram of a transceiver 301 according to the second application example. The transceiver 301 includes a receiving device 310 and a transmitting device 320. The receiving device 310 receives an optical signal L1, and the transmitting device 320 transmits an optical signal L2. The light used for transmission and reception between the transceiver 301 via the optical fiber FB is, for example, near-infrared light having a wavelength of 1000 nm or more and 2000 nm or less.

[0136] The receiving device 310 includes, for example, a photodetector element 100 and a signal processing unit 311. The photodetector element 100 is the above-mentioned photodetector element, and converts the optical signal L1 into an electrical signal. The photodetector element 100 is irradiated with light containing the optical signal L1 having a change in light intensity. Alternatively, the photodetector element 100 may be irradiated with light that has passed through a waveguide. The light irradiated onto the photodetector element 100 (magnetic element 10) may be, for example, laser light. The signal processing unit 311 processes the electrical signal converted by the photodetector element 100. The signal processing unit 311 receives the signal contained in the optical signal L1 by processing the electrical signal generated from the photodetector element 100.

[0137] 20 is an enlarged schematic diagram of the vicinity of the photodetector 100 in a communication system 300 according to the second application example. For example, light propagating through an optical fiber FB, which is a waveguide, is focused by a metalens 20 and reaches the magnetic element 10. The photodetector 100 shown in FIG. 20 may include a polarizing filter 30, similar to that shown in FIG. 6.

[0138] The transmitting device 320 includes, for example, a light source 321, an electric signal generating element 322, and an optical modulation element 323. The light source 321 is, for example, a laser element. The light source 321 may be, for example, an LED element. The light emitted by the light source 321 may be light of a single wavelength (monochromatic light). The light source 321 may be located outside the transmitting device 320. The electric signal generating element 322 generates an electric signal based on transmission information. The electric signal generating element 322 may be integrated with a signal conversion element of the signal processing unit 311. The optical modulation element 323 modulates the light output from the light source 321 based on the electric signal generated by the electric signal generating element 322, and outputs an optical signal L2.

[0139] Although the example in which the transmitting / receiving device is applied to the communication system 300 shown in FIG. 18 has been shown up to this point, the communication system is not limited to this case.

[0140] For example, Fig. 21 is a conceptual diagram of another example of a communication system. A communication system 300A shown in Fig. 21 is communication between two mobile terminal devices 350. The mobile terminal devices 350 are, for example, smartphones, tablets, etc.

[0141] Each of the mobile terminal devices 350 includes a receiving device 310 and a transmitting device 320. An optical signal transmitted from the transmitting device 320 of one mobile terminal device 350 is received by the receiving device 310 of the other mobile terminal device 350. The transmission and reception of optical signals between the mobile terminal devices 350 is performed wirelessly. The light used for transmission and reception between the mobile terminal devices 350 is, for example, visible light. The light used for transmission and reception between the mobile terminal devices 350 may be, for example, near-infrared light with a wavelength of 800 nm or more and 2500 nm or less. The above-described photodetector element is used as the photodetector element 100 of each receiving device 310. In this case, the light including the optical signal transmitted from the transmitting device 320 may be irradiated onto the photodetector element 100 after propagating through a waveguide included in the receiving device 310, or may be irradiated onto the photodetector element 100 without passing through a waveguide.

[0142] Further, for example, Fig. 22 is a conceptual diagram of another example of a communication system. A communication system 300B shown in Fig. 22 is communication between a mobile terminal device 350 and an information processing device 360. The information processing device 360 ​​is, for example, a personal computer.

[0143] The mobile terminal device 350 includes a transmitting device 320, and the information processing device 360 ​​includes a receiving device 310. An optical signal transmitted from the transmitting device 320 of the mobile terminal device 350 is received by the receiving device 310 of the information processing device 360. The optical signal is transmitted and received wirelessly between the mobile terminal device 350 and the information processing device 360. The light used for transmission and reception between the mobile terminal device 350 and the information processing device 360 ​​is, for example, visible light. The light used for transmission and reception between the mobile terminal device 350 and the information processing device 360 ​​may be, for example, near-infrared light having a wavelength of 800 nm or more and 2500 nm or less. The above-mentioned photodetector element is applied as the photodetector element 100 of the receiving device 310.

[0144] 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. [Explanation of symbols]

[0145] 1...first ferromagnetic layer, 2...second ferromagnetic layer, 3...spacer layer, 4...buffer layer, 5...seed layer, 6...third ferromagnetic layer, 7...magnetic coupling layer, 8...perpendicular magnetization induction layer, 9...cap layer, 10...magnetic element, 11...first electrode, 12...second electrode, 15...stacked body, 20, 20A...metalens, 21, 21A...nanostructure, 22...base, 23, 23A...unit, 30...polarizing filter, 40...wavelength filter, 90, 91...insulating layer, 100...photodetector, 100B...blue sensor, 100G...green sensor, 100R...red sensor, 100IR...infrared sensor, 100UV...ultraviolet sensor , 101...circuit board, 102...analog-to-digital converter, 103...output terminal, 105...wiring layer, 106...wiring, 107...interlayer insulating layer, 110...sensor unit, 120...semiconductor circuit, 121...row decoder, 122...column decoder, 200, 201...optical sensor device, 300, 300A, 300B...communication system, 301...transmitting / receiving device, 310...receiving device, 311...signal processing unit, 320...transmitting device, 321...light source, 322...electrical signal generating element, 323...light modulation element, 350...information terminal device, 360...information processing device, L...light, L1, L2...optical signal, p1, p2...pixel

Claims

1. a metalens including a plurality of nanostructures arranged two-dimensionally; a magnetic element including a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; the light that has passed through the metalens is irradiated onto the magnetic element; an output voltage from the magnetic element changes in accordance with the intensity of the irradiated light when the light is irradiated onto the first ferromagnetic layer; A photodetector element configured to pass a sense current from the second ferromagnetic layer to the first ferromagnetic layer when the magnetization of the first ferromagnetic layer and the magnetization of the second ferromagnetic layer are antiparallel to each other, for measuring the output voltage from the magnetic element.

2. the metalens has a first region when an arrangement surface on which the plurality of nanostructures are arranged is viewed in plan view, The light-detecting element according to claim 1 , wherein the area in a plan view of each of the plurality of nanostructures contained in the first region decreases from the center of the first region toward the outside.

3. the metalens further has an annular region outside the first region when the arrangement surface on which the plurality of nanostructures are arranged is viewed in plan; The light-detecting element according to claim 2 , wherein the area in a plan view of each of the plurality of nanostructures contained in the annular region decreases from the inner periphery toward the outer periphery of the annular region.

4. When the arrangement surface on which the plurality of nanostructures are arranged is viewed in plan, the planar shape of each of the plurality of nanostructures has a longitudinal direction and a lateral direction, The photodetector element of claim 1 , wherein the planar shape of at least one of the plurality of nanostructures is different from the planar shape of another nanostructure at an angle.

5. The light-sensing element according to any one of claims 1 to 4, wherein the magnetic element is disposed at a focal position of the light focused by the metalens.

6. The light-sensing element according to claim 5 , wherein the light is light in a specific wavelength range within a wavelength range of 380 nm or more and less than 800 nm.

7. The light-sensing element according to claim 5 , wherein the light is light in a specific wavelength range within a wavelength range of 800 nm to 1 mm.

8. A metalens having a plurality of nanostructures arranged two-dimensionally; a magnetic element including a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; the light that has passed through the metalens is irradiated onto the magnetic element; the magnetic element is disposed at a focal position of the light focused by the metalens, The light detecting element, wherein the light is light in a specific wavelength range within a wavelength range of 200 nm or more and less than 380 nm.

9. a plurality of light-sensing elements; An optical sensor unit, wherein each of the plurality of optical sensing elements is the optical sensing element according to any one of claims 1 to 8.

10. the plurality of photodetecting elements include at least a first photodetecting element and a second photodetecting element; the first photodetector element has the magnetic element disposed at a focal position of light in a first wavelength range focused by the metalens; 10. The optical sensor unit according to claim 9, wherein the second photodetector element has the magnetic element disposed at a focal position of light in a second wavelength range that is different from the first wavelength range and that is focused by the metalens.

11. the first wavelength range is a specific wavelength range within a wavelength range of 380 nm or more and less than 800 nm, The optical sensor unit according to claim 10 , wherein the second wavelength range is a specific wavelength range within a wavelength range of 800 nm or more and 1 mm or less.

12. A photodetector having a plurality of photodetecting elements, Each of the plurality of light-sensing elements a metalens including a plurality of nanostructures arranged two-dimensionally; a magnetic element including a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; the light that has passed through the metalens is irradiated onto the magnetic element; the plurality of photodetecting elements include at least a first photodetecting element, a second photodetecting element, and a third photodetecting element; the first photodetector element has the magnetic element disposed at a focal position of light in a first wavelength range focused by the metalens; the second photodetector element has the magnetic element disposed at a focal position of light in a second wavelength range that is different from the first wavelength range and that is focused by the metalens; the third photodetector element has the magnetic element disposed at a focal position of light in a third wavelength range different from the first wavelength range and the second wavelength range that is focused by the metalens; The optical sensor unit, wherein the third wavelength range is a specific wavelength range within a wavelength range of 200 nm or more and less than 380 nm.

13. The optical sensor unit according to any one of claims 9 to 12, wherein the plurality of light detecting elements are arranged one-dimensionally.

14. The optical sensor unit according to any one of claims 9 to 12, wherein the plurality of light detecting elements are arranged two-dimensionally.

15. 15. The optical sensor unit according to claim 9, wherein at least one of the photodetecting elements constituting one pixel among the plurality of photodetecting elements has a different configuration of the nanostructure of the metalens from the other photodetecting elements constituting the one pixel.

16. 15. The optical sensor unit according to claim 9, wherein at least one of the photodetecting elements constituting one pixel among the plurality of photodetecting elements has a distance between the metalens and the magnetic element that is different from that of other photodetecting elements constituting the pixel.

17. A receiving device comprising a photodetector element according to any one of claims 1 to 8.

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