Photodetector, receiver, and optical sensor device

Abstract

To provide a photodetector, a receiver, and a photosensor device with a large signal-to-noise ratio (SN ratio).SOLUTION: A photodetector has a plurality of magnetic elements, and each of the plurality of magnetic elements includes a first ferromagnetic layer irradiated with light, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and at least two of the plurality of magnetic elements are arranged to fall within a spot of the light with which the magnetic elements are irradiated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light detection element, a receiving device, and an optical sensor device. [Background Art]

[0002] Photoelectric conversion elements are used in various applications.

[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, and converts light into an electrical signal.

[0004] Further, for example, Patent Document 2 describes an optical sensor using a semiconductor pn junction and an image sensor using the optical sensor. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2001-292107 [Patent Document 2] U.S. Patent No. 9842874 Specification [Summary of the Invention] [Problem to be Solved by the Invention]

[0006] Light detection elements using semiconductor pn junctions are widely used, but new light detection elements are demanded for further development. Further, a light detection element converts light into an electrical signal, and improvement in the SN ratio, which is the ratio of signal to noise in light detection, is demanded.

[0007] The present invention has been made in view of the above problem, and an object of the present invention is to provide a light detection element, a receiving device, and an optical sensor device having a high SN ratio. [Means for Solving the Problem]

[0008] To solve the above problems, the following means are provided.

[0009] (1) The photodetector according to the first embodiment comprises a plurality of magnetic elements, each of the plurality of magnetic elements comprising a first ferromagnetic layer to which light is irradiated, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and at least two of the plurality of magnetic elements are arranged to be within the spot of the irradiated light.

[0010] (2) In the photodetector according to the above embodiment, the plurality of magnetic elements include a first magnetic element and a second magnetic element arranged to be within the spot, and the volumes of the first ferromagnetic layer of the first magnetic element and the second magnetic element may be different from each other.

[0011] (3) In the photodetector according to the above embodiment, the first magnetic element is located closer to the center of the spot than the second magnetic element, and the volume of the first ferromagnetic layer of the first magnetic element may be larger than that of the second magnetic element.

[0012] (4) In the photodetector according to the above embodiment, the plurality of magnetic elements include a first magnetic element and a second magnetic element arranged to be within the spot, and the saturation magnetization of the first ferromagnetic layer of the first magnetic element and the second magnetic element may be different from each other.

[0013] (5) In the photodetector according to the above embodiment, the first magnetic element is located closer to the center of the spot than the second magnetic element, and the saturation magnetization of the first ferromagnetic layer of the first magnetic element may be greater than that of the second magnetic element.

[0014] (6) In the photodetector according to the above embodiment, the plurality of magnetic elements include a third magnetic element and a fourth magnetic element arranged to be within the spot, further having a first intermediate layer between the first ferromagnetic layer of the third magnetic element and the light-irradiating surface which is the side of the photodetector that is irradiated with light, further having a second intermediate layer between the first ferromagnetic layer of the fourth magnetic element and the light-irradiating surface, the third magnetic element being closer to the light-irradiating surface than the fourth magnetic element, and the volume of the first ferromagnetic layer of the third magnetic element being larger than that of the fourth magnetic element.

[0015] (7) In the photodetector according to the above embodiment, the plurality of magnetic elements include a third magnetic element and a fourth magnetic element arranged to be within the spot, further comprising a first intermediate layer between the first ferromagnetic layer of the third magnetic element and the light-irradiating surface which is the side of the photodetector that is irradiated with light, and further comprising a second intermediate layer between the first ferromagnetic layer of the fourth magnetic element and the light-irradiating surface, wherein the third magnetic element is closer to the light-irradiating surface than the fourth magnetic element, and the saturation magnetization of the first ferromagnetic layer of the third magnetic element may be greater than that of the fourth magnetic element.

[0016] (8) In the photodetector according to the above embodiment, the plurality of magnetic elements include a fifth magnetic element and a sixth magnetic element arranged to be within the spot, wherein the fifth magnetic element is located closer to the center of the spot than the sixth magnetic element, and further has a third intermediate layer between the first ferromagnetic layer of the fifth magnetic element and the light-irradiating surface which is the side of the photodetector that is irradiated with light, and further has a fourth intermediate layer between the first ferromagnetic layer of the sixth magnetic element and the light-irradiating surface, wherein the fourth intermediate layer may have a higher transmittance of light than the third intermediate layer.

[0017] (9) The receiving device according to the second embodiment has the photodetector according to the above embodiment.

[0018] (10) The optical sensor device according to the third embodiment has an optical sensing element according to the above embodiment. [Effects of the Invention]

[0019] The light detection element, the receiving device, and the optical sensor device according to the above aspect have a high signal-to-noise ratio of light. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [Figure 1] FIG. 1 is a perspective view of the light detection element according to the first embodiment. [Figure 2] FIG. 2 is a plan view of the light detection element according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view of the magnetic element according to the first embodiment. [Figure 4] FIG. 4 is a diagram for explaining a first mechanism of a first operation example of the magnetic element according to the first embodiment. [Figure 5] FIG. 5 is a diagram for explaining a second mechanism of the first operation example of the magnetic element according to the first embodiment. [Figure 6] FIG. 6 is a diagram for explaining a first mechanism of a second operation example of the magnetic element according to the first embodiment. [Figure 7] FIG. 7 is a diagram for explaining a second mechanism of the second operation example of the magnetic element according to the first embodiment. [Figure 8] FIG. 8 is a diagram for explaining another example of the second operation example of the magnetic element according to the first embodiment. [Figure 9] FIG. 9 is a diagram for explaining another example of the second operation example of the magnetic element according to the first embodiment. [Figure 10] FIG. 10 is a plan view of a light detection element according to a first modification of the first embodiment. [Figure 11] FIG. 11 is a plan view of a light detection element according to a second modification of the first embodiment. [Figure 12] FIG. 12 is a plan view of a light detection element according to a third modification of the first embodiment. [Figure 13] FIG. 13 is a plan view of a light detection element according to a second embodiment. [Figure 14] FIG. 14 is a partial cross-sectional view of the light detection element according to the second embodiment. [Figure 15] FIG. 15 shows a change in output voltage of a first magnetic element with respect to light intensity. [Figure 16]This shows the change in output voltage of the second magnetic element with respect to light intensity. [Figure 17] This shows the change in the combined output voltage of the first and second magnetic elements with respect to the light intensity. [Figure 18] This is a plan view of the photodetector according to the third embodiment. [Figure 19] This is a plan view of the photodetector according to the fourth embodiment. [Figure 20] This is a plan view of the photodetector according to the fifth embodiment. [Figure 21] This is a cross-sectional view of a part of the photodetector according to the sixth embodiment. [Figure 22] This is a cross-sectional view of a part of the photodetector according to the seventh embodiment. [Figure 23] This is a cross-sectional view of a part of the photodetector element according to the eighth embodiment. [Figure 24] This is a cross-sectional view of a part of the photodetector element according to the ninth embodiment. [Figure 25] This is a cross-sectional view of a part of a photodetector according to the first modified example of the ninth embodiment. [Figure 26] This is a cross-sectional view of a part of a photodetector according to a second modified example of the ninth embodiment. [Figure 27] This is a cross-sectional view of a part of a photodetector according to a third modified example of the ninth embodiment. [Figure 28] This is a block diagram of a transmitting and receiving device according to the first application example. [Figure 29] This is a conceptual diagram of an example of a communication system. [Figure 30] This is a conceptual diagram of a cross-section of an optical sensor device relating to the second application example. [Figure 31] This is a schematic diagram of an example of a terminal device. [Modes for carrying out the invention]

[0021] The embodiments will be described in detail below, with reference to the figures as appropriate. The drawings used in the following description may be enlarged for convenience to clearly illustrate the features, and the dimensional ratios of each component may differ from those in reality. The materials, dimensions, etc., exemplified in the following description are examples only, and the present invention is not limited to them. It is possible to modify and implement the invention as appropriate within the scope of achieving its effects.

[0022] The directions are defined below. The stacking direction of the magnetic element 10 is defined as the z direction, one direction in the plane perpendicular to the z direction is defined as the x direction, and the direction perpendicular to both the x and z directions is defined as the y direction. The z direction is an example of a stacking direction. Hereafter, the +z direction may be expressed as "up" and the -z direction as "down". The +z direction is the direction from the second ferromagnetic layer 2 to the first ferromagnetic layer 1. Up and down do not necessarily coincide with the direction in which gravity acts.

[0023] "First Embodiment" Figure 1 is a perspective view of the photodetector 200 according to the first embodiment. Figure 2 is a plan view of the photodetector 200 according to the first embodiment, viewed from the z direction.

[0024] The photodetector 200 converts the state or change in state of the irradiated light L into an electrical signal. The photodetector 200 has a plurality of magnetic elements 10. The plurality of magnetic elements 10 are arranged to be within the spot sp of the irradiated light L.

[0025] Light L is not limited to visible light, but also includes infrared rays with longer wavelengths than visible light, and ultraviolet rays with shorter wavelengths than visible light. For example, the wavelength of visible light is between 380 nm and less than 800 nm. For example, the wavelength of infrared rays is between 800 nm and 1 mm. For example, the wavelength of ultraviolet rays is between 200 nm and less than 380 nm. Light L is, for example, light that includes a high-frequency optical signal and changes in intensity, or light with a controlled wavelength range (for example, light that has passed through a wavelength filter). A high-frequency optical signal is, for example, a signal with a frequency of 100 MHz or higher. Light L may also be laser light.

[0026] The spot sp is the area on the irradiated object that is illuminated by light L. The spot sp is a continuous region including the center where light with an intensity of 13.5% or more of the light intensity at the center is irradiated.

[0027] The range of the spot sp of light L is determined by the optical components. These optical components include, for example, waveguides, lenses, and light sources. For instance, light passing through a waveguide forms a spot sp. Alternatively, for example, light focused after passing through a lens also forms a spot sp. The photodetector 200 may have these optical components that form the spot sp of light L. In this case, for example, the optical components are positioned between the magnetic element 10 and the first electrode, which will be described later.

[0028] Each of the magnetic elements 10 is electrically connected, for example, in series or parallel with other magnetic elements 10. In this case, the photodetector 200 outputs, for example, the combined resistance, combined potential, etc., of the multiple magnetic elements 10. Each of the magnetic elements 10 may be connected separately to a downstream device. In this case, the photodetector 200 outputs, for example, the resistance, potential, etc., of each of the multiple magnetic elements 10. The downstream device superimposes, for example, the outputs from each of the magnetic elements 10.

[0029] When the state of the light L irradiated onto each of the magnetic elements 10 changes, the voltage output from each of the magnetic elements 10 (the potential difference between the z-direction ends of each magnetic element) changes in accordance with the change in the state of the light L. Figure 3 is a cross-sectional view of a magnetic element 10 according to the first embodiment. Each of the magnetic elements 10 has, for example, 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 have other layers besides these. Light is irradiated onto the magnetic element 10 from the side of the first ferromagnetic layer 1. Hereinafter, the side of the magnetic element 10 that is irradiated with light will be referred to as the irradiation surface.

[0030] 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. In this case, the magnetic element 10 is an element in which the resistance value in the z direction (resistance value when current is passed in the z direction) changes according to the relative change in the magnetization state of the first ferromagnetic layer 1 and the magnetization state of the second ferromagnetic layer 2. Such an element is also called a magnetoresistive element.

[0031] The first ferromagnetic layer 1 is a photosensitive layer whose magnetization state changes when light is irradiated from the outside. The first ferromagnetic layer 1 is also called the magnetization free layer. The magnetization free layer is a layer containing a magnetic material whose magnetization state changes when a predetermined external force is applied. The predetermined external force is, for example, light L irradiated from the outside, a current flowing in the z direction of the magnetic element 10, or an external magnetic field. The magnetization of the first ferromagnetic layer 1 changes state according to the intensity of the light L irradiated onto the first ferromagnetic layer 1.

[0032] The first ferromagnetic layer 1 contains a ferromagnetic material. The first ferromagnetic layer 1 contains at least one of the magnetic elements such as Co, Fe, or Ni. The first ferromagnetic layer 1 may also contain non-magnetic elements such as B, Mg, Hf, and Gd along with the magnetic elements described above. The first ferromagnetic layer 1 may be an alloy containing a magnetic element and a non-magnetic element, for example. The first ferromagnetic layer 1 may be composed of multiple layers. The first ferromagnetic layer 1 may be, for example, a CoFeB alloy, a laminate in which a CoFeB alloy layer is sandwiched between Fe layers, or a laminate in which a CoFeB alloy layer is sandwiched between CoFe layers.

[0033] The first ferromagnetic layer 1 may be an in-plane magnetized film having an easy magnetization axis in the direction within the film plane (either direction in the xy plane), or a perpendicular magnetized film having an easy magnetization axis perpendicular to the film plane (z direction).

[0034] The thickness of the first ferromagnetic layer 1 is, for example, 1 nm to 5 nm. Preferably, the thickness of the first ferromagnetic layer 1 is, for example, 1 nm to 2 nm. 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 increases. In other words, if the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is high, the force that tries to return the magnetization 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.

[0035] When the thickness of the first ferromagnetic layer 1 decreases, its volume as a ferromagnetic material decreases, and when its thickness increases, its volume as a ferromagnetic material increases. The reactivity 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, when the product of the magnetic anisotropy and volume of the first ferromagnetic layer 1 decreases, its reactivity to light increases. From this viewpoint, in order to increase the reactivity to light, it is preferable to appropriately design the magnetic anisotropy of the first ferromagnetic layer 1 and then reduce the volume of the first ferromagnetic layer 1.

[0036] If the thickness of the first ferromagnetic layer 1 is greater than 2 nm, an insertion layer made of, for example, Mo and W may be provided within the first ferromagnetic layer 1. That is, the first ferromagnetic layer 1 may be a laminate in which a ferromagnetic layer, an insertion layer, and a ferromagnetic layer are stacked in the z direction in order. The interfacial magnetic anisotropy at the interface between the insertion layer and the ferromagnetic layer increases 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.

[0037] 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 changes less easily than that of the magnetization-free layer when a predetermined external energy is applied. For example, the magnetization direction of the magnetization-fixed layer changes less easily than that of the magnetization-free layer when a predetermined external energy is applied. Also, for example, the magnitude of magnetization of the magnetization-fixed layer changes less easily than that of the magnetization-free layer when a predetermined external energy is applied. The coercivity of the second ferromagnetic layer 2 is greater than that of the first ferromagnetic layer 1, for example. The second ferromagnetic layer 2 has an easy magnetization axis in the same direction as the first ferromagnetic layer 1, for example. The second ferromagnetic layer 2 may be an in-plane magnetized film or a perpendicular magnetized film.

[0038] 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 a laminate in which Co with a thickness of 0.4 nm to 1.0 nm, Mo with a thickness of 0.1 nm to 0.5 nm, a CoFeB alloy with a thickness of 0.3 nm to 1.0 nm, and Fe with a thickness of 0.3 nm to 1.0 nm are stacked in that order.

[0039] The magnetization of the second ferromagnetic layer 2 may be fixed, for example, by magnetic coupling with the third ferromagnetic layer via a magnetic coupling layer. In this case, the second ferromagnetic layer 2, the magnetic coupling layer, and the third ferromagnetic layer together may be referred to as the magnetization-fixing layer.

[0040] The third ferromagnetic layer is magnetically coupled to, for example, the second ferromagnetic layer 2. This magnetic coupling is, for example, an antiferromagnetic coupling, resulting from the RKKY interaction. The material constituting the third ferromagnetic layer is, for example, the same as that of the first ferromagnetic layer 1. The magnetically coupled layer is, for example, Ru, Ir, etc.

[0041] The spacer layer 3 is a non-magnetic layer placed between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The spacer layer 3 is composed of a conductor, an insulator, or a semiconductor, or a layer containing a current-carrying point composed of a conductor within an insulator. The thickness of the spacer layer 3 can be adjusted according to the orientation direction of the magnetization of the first ferromagnetic layer 1 and the magnetization of the second ferromagnetic layer 2 in the initial state, as described later.

[0042] For example, if the spacer layer 3 is made of an insulator, the magnetic element 10 has a magnetic tunnel junction (MTJ) consisting of a first ferromagnetic layer 1, a spacer layer 3, and a 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, if 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.

[0043] When the spacer layer 3 is composed of an insulating material, materials containing aluminum oxide, magnesium oxide, titanium oxide, or silicon oxide can be used. 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 change rate can be obtained by adjusting the film 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 film thickness of the spacer layer 3 may be approximately 0.5 to 5.0 nm, or approximately 1.0 to 2.5 nm.

[0044] When the spacer layer 3 is made of a non-magnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. In order to efficiently utilize the GMR effect, the film thickness of the spacer layer 3 may be around 0.5 to 5.0 nm, or it may be around 2.0 to 3.0 nm.

[0045] When the spacer layer 3 is made of a non-magnetic semiconductor material, materials such as zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, or ITO can be used. In this case, the film thickness of the spacer layer 3 may be about 1.0 to 4.0 nm.

[0046] When a layer containing current-carrying points composed of conductors in a non-magnetic insulator is applied as the spacer layer 3, the structure may include current-carrying points composed of non-magnetic conductors such as Cu, Au, and Al in a non-magnetic insulator composed of aluminum oxide or magnesium oxide. Alternatively, the conductors may be composed of magnetic elements such as Co, Fe, and Ni. In this case, the film thickness of the spacer layer 3 may be about 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 from a direction perpendicular to the film surface. As mentioned above, the magnetic element 10 may be called by different names such as MTJ element or GMR element depending on the constituent material of the spacer layer 3, but it is collectively also called a magnetoresistive element.

[0047] The magnetic element 10 may also have a base layer, a cap layer, a perpendicular magnetization induction layer, etc. The base layer is located below the second ferromagnetic layer 2. The base layer is either a seed layer or a buffer layer. The seed layer enhances the crystallinity of the layer laminated on top of it. The seed layer is, for example, Pt, Ru, Hf, Zr, or NiFeCr. The thickness of the seed layer is, for example, 1 nm to 5 nm. The buffer layer is a layer that alleviates lattice mismatch between different crystals. The buffer layer is, for example, Ta, Ti, W, Zr, Hf, or nitrides of these elements. The thickness of the buffer layer is, for example, 1 nm to 5 nm.

[0048] The capping layer is located above the first ferromagnetic layer 1. The capping layer prevents damage to the underlying layer during the process and enhances the crystallinity of the underlying layer during annealing. The thickness of the capping layer is, for example, 3 nm or less, so that sufficient light is irradiated onto the first ferromagnetic layer 1. The capping layer can be, for example, MgO, W, Mo, Ru, Ta, Cu, Cr, or a multilayer film of these materials.

[0049] The perpendicular magnetization induction layer is formed when the first ferromagnetic layer 1 is a perpendicular magnetization film. The perpendicular magnetization induction layer is laminated on the first ferromagnetic layer 1. The perpendicular magnetization induction layer induces perpendicular magnetic anisotropy in the first ferromagnetic layer 1. The perpendicular magnetization induction layer can be, for example, magnesium oxide, W, Ta, Mo, etc. When the perpendicular magnetization induction layer is magnesium oxide, it is preferable that the magnesium oxide is oxygen-deficient to enhance conductivity. The thickness of the perpendicular magnetization induction layer is, for example, 0.5 nm to 2.0 nm.

[0050] The photodetector element 200 may further have a first electrode and a second electrode connected to each magnetic element 10. The first electrode is in contact with the first surface (irradiation surface) of the magnetic element 10. The first surface is the surface of the magnetic element 10 on the side of the first ferromagnetic layer 1 in the z direction. The second electrode is in contact with the second surface of the magnetic element 10. The second surface is the surface of the magnetic element 10 on the side of the second ferromagnetic layer 2 in the z direction. The first electrode and the second electrode sandwich the magnetic element 10 in the z direction, for example.

[0051] The first and second electrodes are made of a conductive material. The first and second electrodes are made of metals such as Cu, Al, Au, or Ru. 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 as the first and second electrodes. Alternatively, TiN or TaN may be used as the first and second electrodes.

[0052] The first and second electrodes may be transparent to the wavelength range of light irradiated onto the magnetic element 10. For example, the first and second electrodes may be transparent electrodes containing transparent electrode materials of oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium gallium zinc oxide (IGZO). Alternatively, the first and second electrodes may have a configuration in which multiple columnar metals are contained within these transparent electrode materials.

[0053] The magnetic element 10 is manufactured, for example, by a lamination process for each layer, an annealing process, and a processing process. Each layer is deposited, for example, by sputtering. Annealing is performed, for example, at a temperature of 250°C to 450°C. Processing of the laminated film is performed, for example, using photolithography and etching. The laminated film becomes a columnar magnetic element 10. The magnetic element 10 may be cylindrical or prismatic. For example, the shortest width of the magnetic element 10 when viewed from the z direction may be 10 nm to 2000 nm, or 30 nm to 500 nm. The magnetic element 10 is obtained by the above process.

[0054] Figure 3 shows an example of a magnetic element 10. However, any magnetic element that has a ferromagnetic material whose magnetization state changes upon irradiation with light, and whose resistance value changes in accordance with the change in magnetization state, is acceptable. In addition to the MTJ element and GMR element described above, anisotropic magnetoresistance (AMR) effect element, colossal magnetoresistance (CMR) effect element, etc., can be used as magnetic elements.

[0055] Next, some examples of the operation of the magnetic element 10 will be described. The first ferromagnetic layer 1 is irradiated with light whose light intensity changes. The resistance value of the magnetic element 10 in the z direction changes as light is irradiated onto the first ferromagnetic layer 1. The output voltage from the magnetic element 10 changes as light is irradiated onto the first ferromagnetic layer 1. In the first example of operation, the case in which the intensity of the light irradiated onto the first ferromagnetic layer 1 is in two stages, first intensity and second intensity, will be explained. The intensity of the second intensity light is assumed to be greater than the intensity of the first intensity light. The first intensity may also be zero when the intensity of the light irradiated onto the first ferromagnetic layer 1 is zero.

[0056] Figures 4 and 5 are diagrams illustrating a first operation example of the magnetic element 10 according to the first embodiment. Figure 4 is a diagram illustrating the first mechanism of the first operation example, and Figure 5 is a diagram illustrating the second mechanism of the first operation example. In the upper graphs of Figures 4 and 5, the vertical axis represents the intensity of light irradiated onto the first ferromagnetic layer 1, and the horizontal axis represents time. In the lower graphs of Figures 4 and 5, the vertical axis represents the resistance value of the magnetic element 10 in the z direction, and the horizontal axis represents time.

[0057] First, in the initial state when the first ferromagnetic layer 1 is irradiated with light of 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, and the resistance value of the magnetic element 10 in the z direction is the first resistance value R1. The resistance value of the magnetic element 10 in the z direction can be determined by passing a sense current Is in the z direction of the magnetic element 10, which generates a voltage across the z-sides of the magnetic element 10, and then using Ohm's law from that voltage value. The output voltage from the magnetic element 10 is generated between the first electrode and the second electrode. In the example shown in Figure 4, the sense current Is is passed from the first ferromagnetic layer 1 towards the second ferromagnetic layer 2. By passing the sense current Is in this direction, a spin transfer torque in the same direction as the magnetization M2 of the second ferromagnetic layer 2 acts on the magnetization M1 of the first ferromagnetic layer 1, and in the initial state, the magnetizations M1 and M2 become parallel. Furthermore, by passing a sense current Is in this direction, it is possible to prevent the magnetization M1 of the first ferromagnetic layer 1 from reversing during operation.

[0058] Next, the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity to the 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 magnetization M1 of the first ferromagnetic layer 1 when it is not irradiated with light is different from the state of magnetization M1 of the first ferromagnetic layer 1 at the second intensity. The state of magnetization M1 refers to, for example, the angle of inclination with respect to the z direction, the magnitude, etc.

[0059] For example, as shown in Figure 4, when the intensity of light irradiated onto 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, for example, as shown in Figure 5, when the intensity of light irradiated onto the first ferromagnetic layer 1 changes from a 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°.

[0060] When the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state, the resistance value of the magnetic element 10 in the z direction exhibits a second resistance value R2. The second resistance value R2 is greater than the first resistance value R1. The second resistance value R2 is between the resistance value when magnetization M1 and magnetization M2 are parallel (first resistance value R1) and the resistance value when magnetization M1 and magnetization M2 are antiparallel.

[0061] In the case shown in Figure 4, 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, magnetization M1 tries to return to a state parallel to magnetization M2, and when the intensity of light irradiated onto 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 Figure 5, when the intensity of light irradiated onto 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 both cases, 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 light irradiated onto 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.

[0062] The resistance of the magnetic element 10 in the z direction changes in response to changes in the intensity of light irradiated onto the first ferromagnetic layer 1. The output voltage from the magnetic element 10 also changes in response to changes in the intensity of light irradiated onto the first ferromagnetic layer 1. In other words, the magnetic element 10 can convert changes in the intensity of the irradiated light into changes in the output voltage. That is, the magnetic element 10 can convert light into an electrical signal. For example, if the output voltage from the magnetic element 10 is above a threshold, it is processed as a first signal (e.g., "1"), and if it is below the threshold, it is processed as a second signal (e.g., "0").

[0063] Here, we have explained the case where magnetizations M1 and M2 are parallel in the initial state, but magnetizations M1 and M2 may be antiparallel in the initial state. In this case, the resistance value of the magnetic element 10 in the z direction decreases as the state of magnetization M1 changes (for example, as the angle change from the initial state of magnetization M1 increases). When the initial state is when magnetizations M1 and 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 in the opposite direction to the magnetization M2 of the second ferromagnetic layer 2 acts on the magnetization M1 of the first ferromagnetic layer 1, causing magnetizations M1 and M2 to be antiparallel in the initial state.

[0064] In the first operational example, we explained the case where the light irradiated onto the first ferromagnetic layer 1 has two intensity levels, a first intensity and a second intensity. In the second operational example, we will explain the case where the intensity of the light irradiated onto the first ferromagnetic layer 1 changes in multiple stages or analogously.

[0065] Figures 6 and 7 are diagrams illustrating a second operation example of the magnetic element 10 according to the first embodiment. Figure 6 is a diagram illustrating the first mechanism of the second operation example, and Figure 7 is a diagram illustrating the second mechanism of the second operation example. In the upper graphs of Figures 6 and 7, the vertical axis represents the intensity of light irradiated onto the first ferromagnetic layer 1, and the horizontal axis represents time. In the lower graphs of Figures 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.

[0066] In the case of Figure 6, 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 from the light irradiation. The angle between the direction of the magnetization M1 of the first ferromagnetic layer 1 when it is not irradiated with light and the angle between the direction of the magnetization M1 when it is irradiated with light is greater than 0° and less than 90° in both cases.

[0067] As the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state, the resistance value of the magnetic element 10 in the z direction 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 to the second resistance value R2, the third resistance value R3, and the fourth resistance value R4. The resistance values ​​increase in the order of first resistance value R1, second resistance value R2, third resistance value R3, and fourth resistance value R4. In other words, depending on the tilt of the magnetization M1 of the first ferromagnetic layer 1, the output voltage from the magnetic element 10 changes from the first voltage value to the second voltage value, third voltage value, and fourth voltage value. The output voltage increases in the order of first voltage value, second voltage value, third voltage value, and fourth voltage value.

[0068] The magnetic element 10 changes its resistance in the z direction when the intensity of light irradiated onto the first ferromagnetic layer 1 changes. The output voltage from the magnetic element 10 also changes when the intensity of light irradiated onto the first ferromagnetic layer 1 changes. For example, if the first voltage value is defined as "0", the second voltage value as "1", the third voltage value as "2", and the fourth voltage value as "3", the magnetic element 10 can output four values ​​of information. Here, we have shown an example of reading out four values, but the number of values ​​to be read can be freely designed by setting the threshold of the output voltage. The magnetic element 10 may also output analog values ​​directly.

[0069] Similarly, in the case of Figure 7, 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 the external energy from the light irradiation. When the magnetization M1 of the first ferromagnetic layer 1 decreases from its initial state, the resistance value in the z direction of the magnetic element 10 changes. For example, depending on the magnitude of the magnetization M1 of the first ferromagnetic layer 1, the resistance value in the z direction of the magnetic element 10 changes to a second resistance value R2, a third resistance value R3, and a fourth resistance value R4. That is, depending on the magnitude of the magnetization M1 of the first ferromagnetic layer 1, the output voltage from the magnetic element 10 changes from a first voltage value to a second voltage value, a third voltage value, and a fourth voltage value. Therefore, as in the case of Figure 6, the magnetic element 10 can output these differences in output voltage as multi-level or analog data.

[0070] In the second operation example, as in the first operation example, when the intensity of the light irradiated onto the first ferromagnetic layer 1 returns to the first intensity, the magnetization M1 state of the first ferromagnetic layer 1 returns to its original state, and the magnetic element 10 returns to its initial state.

[0071] Here, we have explained the case where magnetization M1 and magnetization M2 are parallel in the initial state, but in the second example of operation, magnetization M1 and magnetization M2 may be antiparallel in the initial state as well.

[0072] Furthermore, while the first and second operation examples illustrate cases where magnetization M1 and magnetization M2 are parallel or antiparallel in the initial state, magnetization M1 and magnetization M2 may also be orthogonal in the initial state. For example, this case applies when the first ferromagnetic layer 1 is an in-plane magnetization film in which magnetization M1 is oriented in one direction in the xy plane, and the second ferromagnetic layer 2 is a perpendicular magnetization film in which magnetization M2 is oriented in the z direction. Due to magnetic anisotropy, magnetization M1 is oriented in one direction in the xy plane, and magnetization M2 is oriented in the z direction, so that magnetization M1 and magnetization M2 are orthogonal in the initial state.

[0073] Figures 8 and 9 illustrate another example of a second operation example of the photodetector element 200 according to the first embodiment. Figures 8 and 9 differ in the direction of flow of the sense current Is applied to the magnetic element 10. In Figure 8, the sense current Is flows from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. In Figure 9, the sense current Is flows from the second ferromagnetic layer 2 to the first ferromagnetic layer 1.

[0074] In both Figure 8 and Figure 9, a sense current Is flows through the magnetic element 10, causing a spin transfer torque to act on the magnetization M1 in the initial state. In Figure 8, the spin transfer torque acts so that the magnetization M1 is parallel to the magnetization M2 of the second ferromagnetic layer 2. In Figure 9, the spin transfer torque acts so that the magnetization M1 is antiparallel to the magnetization M2 of the second ferromagnetic layer 2. In both Figure 8 and Figure 9, 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 in the xy plane.

[0075] 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 from the light irradiation. This is because the sum of the effect of light irradiation and the effect of spin transfer torque on the magnetization M1 becomes greater than the effect due to magnetic anisotropy on the magnetization M1. As the intensity of light irradiated onto the first ferromagnetic layer 1 increases, in the case of Figure 8, the magnetization M1 tilts to be parallel to the magnetization M2 of the second ferromagnetic layer 2, while in the case of Figure 9, the magnetization M1 tilts to be antiparallel to the magnetization M2 of the second ferromagnetic layer 2. The direction of the tilt of magnetization M1 differs between Figure 8 and Figure 9 because the direction of the spin transfer torque acting on the magnetization M1 is different.

[0076] When the intensity of light irradiated onto the first ferromagnetic layer 1 increases, the resistance of the magnetic element 10 decreases in the case of Figure 8, and increases in the case of Figure 9. In other words, when the intensity of light irradiated onto the first ferromagnetic layer 1 increases, the output voltage from the magnetic element 10 decreases in the case of Figure 8, and increases in the case of Figure 9.

[0077] When the intensity of light irradiated onto the first ferromagnetic layer 1 returns to the first intensity, the magnetization M1 state of the first ferromagnetic layer 1 returns to its original state due to the effect of magnetic anisotropy on the magnetization M1. As a result, the magnetic element 10 returns to its initial state.

[0078] Here, we have explained an example where the first ferromagnetic layer 1 is an in-plane magnetized film and the second ferromagnetic layer 2 is a perpendicular magnetized film, but this relationship can also 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.

[0079] In the first embodiment of the photodetector 200, multiple magnetic elements 10 are located within the same spot sp. The multiple magnetic elements 10 behave similarly to light L. The photodetector 200 can combine the outputs from each of the magnetic elements 10 that behave similarly to light L. Furthermore, in the photodetector 200, the multiple magnetic elements 10 simultaneously receive the same optical signal. Therefore, noise in the output signal can be suppressed in the photodetector 200. Consequently, the photodetector 200 according to the first embodiment has a high signal-to-noise ratio (SNR).

[0080] Although the first embodiment has been described in detail above with reference to the drawings, the first embodiment is not limited to this example.

[0081] For example, the magnetic elements 10 may be arranged concentrically within the spot sp, as shown in the photodetector element 200A in Figure 10. Alternatively, the magnetic elements 10 may be arranged in a triangular lattice within the spot sp, as shown in the photodetector element 200B in Figure 11. The arrangement of the magnetic elements 10 is not limited to these cases; various arrangements, such as a hexagonal lattice, can be selected.

[0082] Furthermore, as shown in Figure 12, for example, the planar shape of each magnetic element 10 may be rectangular.

[0083] "Second Embodiment" Figure 13 is a plan view of the photodetector element 201 according to the second embodiment, viewed from the z direction. In the second embodiment, components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0084] The photodetector 201 has a plurality of magnetic elements 20. The plurality of magnetic elements 20 are arranged so as to be within the spot sp of the irradiated light L.

[0085] The multiple magnetic elements 20 include a first magnetic element 21 and a second magnetic element 22. The first magnetic element 21 and the second magnetic element 22 are arranged to be within the spot sp of the irradiated light L. The first magnetic element 21 and the second magnetic element 22 are electrically connected to each other, for example, in series or in parallel. Figure 14 is a cross-sectional view of the photodetector element 201 according to the second embodiment. Figure 14 is a cross-section along line AA in Figure 13. Each of the magnetic elements 20 has a layer structure similar to that of the magnetic element 10. Figure 14 simultaneously shows the first electrode 11 and the second electrode 12 connected to each of the magnetic elements 20, and the insulating layer In covering the periphery of the magnetic elements 20. The material of the insulating layer In is, for example, an oxide, nitride, or oxynitride containing one or more metallic or metalloid elements. More specifically, the material of the insulating layer In is, for example, an oxide, nitride, or oxynitride containing one or more elements selected from the group consisting of Al, Si, Ta, In, Hf, Sn, Zn, Ti, Cu, Ce, Zr, Nb, Mg, B, Pb, Ca, La, and Ge.

[0086] The first magnetic element 21 and the second magnetic element 22 have different volumes of the first ferromagnetic layer 1. The first magnetic element 21 has a larger volume of the first ferromagnetic layer 1 than the second magnetic element 22. Because the first magnetic element 21 and the second magnetic element 22 have different volumes of the first ferromagnetic layer 1, they have different sensitivities to irradiated light. The degree to which the magnetization M1 state of the first ferromagnetic layer 1 changes in response to changes in the intensity of irradiated light increases as the volume of the first ferromagnetic layer 1 decreases. Therefore, the sensitivity of the magnetic element 20 to irradiated light increases as the volume of the first ferromagnetic layer 1 decreases.

[0087] In the example shown in Figure 14, the volume of the first ferromagnetic layer 1 differs between the first magnetic element 21 and the second magnetic element 22 because the area of ​​the first ferromagnetic layer 1 as viewed from the z direction is different. In the example shown in Figure 14, the thickness of the first ferromagnetic layer 1 is the same for both the first magnetic element 21 and the second magnetic element 22. The volume of the first ferromagnetic layer 1 may be differed not only by its area as viewed from the z direction, but also by varying the thickness of the first ferromagnetic layer 1. Furthermore, among the multiple magnetic elements 20, there may be some in which the volume of the first ferromagnetic layer 1 differs from that of either the first magnetic element 21 or the second magnetic element 22. In the example shown in Figure 14, the first magnetic element 21 and the second magnetic element 22 are positioned at different distances from the center of spot sp (the distance between the center of spot sp and the center of each magnetic element in a plan view from the z direction), but the first magnetic element 21 and the second magnetic element 22 may be positioned at the same distance from the center of spot sp.

[0088] Figure 15 shows the change in output voltage from the first magnetic element 21 with respect to the intensity of the irradiated light. Figure 16 shows the change in output voltage from the second magnetic element 22 with respect to the intensity of the irradiated light.

[0089] As shown in Figure 16, the second magnetic element 22, which has a relatively small volume of the first ferromagnetic layer 1, experiences a large change in resistance in the low-intensity region where the intensity of light L is low. That is, the output voltage of the second magnetic element 22 changes significantly in the low-intensity region of light L, resulting in relatively high sensitivity to light L. On the other hand, because the second magnetic element 22 quickly reaches its maximum resistance, the change in resistance is small in the high-intensity region where the intensity of light L is high. That is, in the high-intensity region of light L, the output voltage of the second magnetic element 22 changes little in response to changes in the intensity of light L, making it difficult to detect changes in the intensity of light L. Therefore, while the second magnetic element 22 has relatively high sensitivity to light, the range in which it can detect changes in the intensity of light L is relatively narrow.

[0090] In contrast, as shown in Figure 15, the first magnetic element 21, which has a relatively large volume of the first ferromagnetic layer 1, exhibits a gradual change in resistance in the low-intensity region where the intensity of light L is small. That is, the first magnetic element 21 exhibits a gradual change in output voltage in the low-intensity region of light L, and has relatively low sensitivity to light L. On the other hand, because the resistance of the first magnetic element 21 is less likely to saturate, it shows a sufficiently large change in resistance even in the high-intensity region where the intensity of light L is large. That is, even in the high-intensity region of light L, the first magnetic element 21 can obtain a change in output voltage in response to a change in the intensity of light L, and can detect changes in the intensity of light L. Therefore, while the first magnetic element 21 has relatively low sensitivity to light L, it has a relatively wide range over which it can detect changes in the intensity of light L.

[0091] Figure 17 shows the change in the intensity of light L of the combined output voltage of the first magnetic element 21 and the second magnetic element 22 with respect to the intensity of light L. The combined output voltage is, for example, the sum of the output voltages of the first magnetic element 21 and the second magnetic element 22. Therefore, the combined output voltage changes significantly in the low-intensity region of light L, and also shows a sufficiently large change in the high-intensity region of light L. In other words, the photodetector element 201 having the first magnetic element 21 and the second magnetic element 22 has high sensitivity to light L in the low-intensity region of light L, and can detect changes in the intensity of light L over a wide range of light intensity.

[0092] "Third Embodiment" Figure 18 is a plan view of the photodetector element 202 according to the third embodiment, as seen from the z direction. In the third embodiment, components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0093] The photodetector 202 has a plurality of magnetic elements 30. The plurality of magnetic elements 30 are arranged so as to be within the spot sp of the irradiated light L.

[0094] Each of the multiple magnetic elements 30 has a layer structure similar to that of the magnetic element 10. In the example shown in Figure 18, the volume of the first ferromagnetic layer 1 of the magnetic element 30 is larger for magnetic elements 30 closer to the center of spot sp, and smaller for magnetic elements 30 further from the center. That is, when viewed from a plane in the z direction, the shorter the distance between the center of the magnetic element 30 and the center of spot sp, the larger the volume of the first ferromagnetic layer 1, and the longer the distance between the center of the magnetic element 30 and the center of spot sp, the smaller the volume of the first ferromagnetic layer 1. Hereinafter, expressions such as "close to or far from the center of the spot" and "on the side of the spot or away from the center of the spot" refer to the distance between the center of spot sp and the center of the magnetic element when viewed from the z direction. When a particular magnetic element is "close to the center of the spot" or "on the side of the spot," the distance between the center of that particular magnetic element and the center of spot sp is shorter than the distance between the center of the magnetic element being compared and the center of spot sp. Furthermore, if a particular magnetic element is "far from the center of the spot" or "away from the center of the spot," the distance between the center of that particular magnetic element and the center of spot sp is longer than the distance between the center of the magnetic element being compared and the center of spot sp.

[0095] For example, a plurality of magnetic elements 30 includes a first magnetic element 31 and a second magnetic element 32. The first magnetic element 31 and the second magnetic element 32 are arranged so as to be within the spot sp of the irradiated light L. The first magnetic element 31 and the second magnetic element 32 are electrically connected to each other, for example, in series or in parallel. The first magnetic element 31 is located closer to the center of the spot sp than the second magnetic element 32. That is, when viewed from the z direction in a plan view, the distance between the center of the first magnetic element 31 and the center of the spot sp is shorter than the distance between the center of the second magnetic element 32 and the center of the spot sp. The volume of the first ferromagnetic layer 1 of the first magnetic element 31 is greater than the volume of the first ferromagnetic layer 1 of the second magnetic element 32. Because the volumes of the first ferromagnetic layer 1 are different, the first magnetic element 31 and the second magnetic element 32 have different sensitivities to light L.

[0096] In the example shown in Figure 18, the volume of the first ferromagnetic layer 1 differs between the first magnetic element 31 and the second magnetic element 32 because the area of ​​the first ferromagnetic layer 1 as viewed from the z direction is different. In the example shown in Figure 18, the thickness of the first ferromagnetic layer 1 is the same for the first magnetic element 31 and the second magnetic element 32. The volume of the first ferromagnetic layer 1 may be differed not only by the area as viewed from the z direction, but also by varying the thickness of the first ferromagnetic layer 1. Furthermore, among the multiple magnetic elements 30, there may be some in which the volume of the first ferromagnetic layer 1 differs from both the first magnetic element 31 and the second magnetic element 32.

[0097] The light intensity on the irradiated surface of each magnetic element 30 is greater towards the center of the spot sp. The first magnetic element 31, which has a relatively large volume of the first ferromagnetic layer 1, is less likely to experience output saturation even when irradiated with higher intensity light than the second magnetic element 32 (see Figures 15 and 16). Furthermore, the second magnetic element 32, which has a relatively small volume of the first ferromagnetic layer 1, is more sensitive to light L than the first magnetic element 31 (see Figures 15 and 16). Therefore, even if the intensity of the irradiated light is lower than that of the first magnetic element 31, a certain amount of output can be obtained from the second magnetic element 32. Thus, in the photodetector element 202 according to the third embodiment, both the output from the first magnetic element 31 and the output from the second magnetic element 32 can be effectively utilized in detecting the intensity of light, resulting in a high signal-to-noise ratio for the photodetector element 202 according to the third embodiment.

[0098] "Fourth Embodiment" Figure 19 is a plan view of the photodetector element 203 according to the fourth embodiment, viewed from the z direction. In the fourth embodiment, components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0099] The photodetector 203 has a plurality of magnetic elements 40. The plurality of magnetic elements 40 are arranged so as to be within the spot sp of the irradiated light L. Each of the plurality of magnetic elements 40 has a layered structure similar to that of the magnetic element 10.

[0100] The multiple magnetic elements 40 include a first magnetic element 41 and a second magnetic element 42. The first magnetic element 41 and the second magnetic element 42 are arranged so as to be within the spot sp of the irradiated light L. The first magnetic element 41 and the second magnetic element 42 are electrically connected to each other, for example, in series or in parallel. The first magnetic element 41 and the second magnetic element 42 have different saturation magnetizations of the first ferromagnetic layer 1. The saturation magnetization of the first ferromagnetic layer 1 of the first magnetic element 41 is greater than that of the second magnetic element 42. Among the multiple magnetic elements 40, there may be elements whose saturation magnetization of the first ferromagnetic layer 1 differs from both the first magnetic element 41 and the second magnetic element 42. In Figure 19, an example of the saturation magnetization of each magnetic element 40 is written below each magnetic element 40. In the example shown in Figure 19, the first magnetic element 41 and the second magnetic element 42 are positioned at different distances from the center of spot sp (distance between the center of spot sp and the center of each magnetic element in a plan view), but the first magnetic element 41 and the second magnetic element 42 may be positioned at the same distance from the center of spot sp. The magnitude of the saturation magnetization of the first ferromagnetic layer 1 can be varied by using different materials to constitute the first ferromagnetic layer 1. For example, if the first ferromagnetic layer 1 is composed of a CoFeB alloy, increasing the ratio of Fe to Co will increase the saturation magnetization of the first ferromagnetic layer 1, and decreasing the ratio of Fe to Co will decrease the saturation magnetization of the first ferromagnetic layer 1.

[0101] The first magnetic element 41 and the second magnetic element 42 have different saturation magnetizations of the first ferromagnetic layer 1, resulting in different sensitivities to irradiated light. The degree of change in the magnetization M1 state of the first ferromagnetic layer 1 in response to changes in the intensity of irradiated light increases as the saturation magnetization of the first ferromagnetic layer 1 decreases. Therefore, the sensitivity of the magnetic element 40 to irradiated light increases as the saturation magnetization of the first ferromagnetic layer 1 decreases. Consequently, the first magnetic element 41, which has a relatively large saturation magnetization of the first ferromagnetic layer 1, has relatively low sensitivity to light L, but a relatively wide range over which it can detect changes in the intensity of light L. The output voltage from the first magnetic element 41 behaves similarly to the first magnetic element 21 shown in Figure 15 in response to changes in the intensity of light L. The second magnetic element 42, which has a relatively small saturation magnetization of the first ferromagnetic layer 1, has relatively high sensitivity to light L, but a relatively narrow range over which it can detect changes in light intensity. The output voltage from the second magnetic element 42 exhibits the same behavior as the second magnetic element 22 shown in Figure 16 in response to changes in the intensity of light L. The combined output voltage of the first magnetic element 41 and the second magnetic element 42 exhibits the same behavior as the combined output voltage shown in Figure 17 in response to changes in the intensity of light L.

[0102] The photodetector 203, having a first magnetic element 41 and a second magnetic element 42, is similar to the photodetector 201 according to the second embodiment in that it has high sensitivity to light L in the low-intensity region of light L and can detect changes in the intensity of light L over a wide range of light intensity.

[0103] Here, the photodetector 203 according to the fourth embodiment and the photodetector 201 according to the second embodiment share the common feature of including elements with different sensitivities to irradiated light among a plurality of magnetic elements. Therefore, the characteristic configuration of the photodetector 201 and the characteristic configuration of the photodetector 203 may be combined to make the sensitivity of one of the elements among the plurality of magnetic elements to irradiated light different from that of the other magnetic elements. Specifically, at least two magnetic elements arranged to enter the spot sp may have different volumes and saturation magnetizations of the first ferromagnetic layer 1.

[0104] "Fifth Embodiment" Figure 20 is a plan view of the photodetector element 204 according to the fifth embodiment, viewed from the z direction. In the fifth embodiment, components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0105] The photodetector 204 has a plurality of magnetic elements 50. The plurality of magnetic elements 50 are arranged so as to be within the spot sp of the irradiated light L.

[0106] Each of the multiple magnetic elements 50 has a layer structure similar to that of the magnetic element 10. In the example shown in Figure 20, the saturation magnetization of the first ferromagnetic layer 1 of the magnetic element 50 is larger for magnetic elements 30 closer to the center of spot sp and smaller for magnetic elements 30 further from the center. That is, when viewed from a plan view in the z direction, the saturation magnetization of the first ferromagnetic layer 1 is larger for magnetic elements 50 whose center is closer to the center of spot sp, and smaller for magnetic elements 50 whose center is further from the center of spot sp. In Figure 20, an example of the saturation magnetization of each magnetic element 50 is shown below each magnetic element 50.

[0107] For example, a plurality of magnetic elements 50 includes a first magnetic element 51 and a second magnetic element 52. The first magnetic element 51 and the second magnetic element 52 are arranged so as to be within the spot sp of the irradiated light L. The first magnetic element 51 and the second magnetic element 52 are electrically connected to each other, for example, in series or in parallel. Among the plurality of magnetic elements 50, there may be elements whose saturation magnetization of the first ferromagnetic layer 1 is different from that of both the first magnetic element 51 and the second magnetic element 52. The first magnetic element 51 is located closer to the center of the spot sp than the second magnetic element 52. That is, when viewed from the z direction in a plan view, the distance between the center of the first magnetic element 51 and the center of the spot sp is shorter than the distance between the center of the second magnetic element 52 and the center of the spot sp. The saturation magnetization of the first ferromagnetic layer 1 of the first magnetic element 51 is greater than the saturation magnetization of the first ferromagnetic layer 1 of the second magnetic element 52. The first magnetic element 51 and the second magnetic element 52 have different saturation magnetizations of the first ferromagnetic layer 1, and therefore have different sensitivities to light L.

[0108] The light intensity on the irradiated surface of each magnetic element 50 is greater towards the center of the spot sp. The first magnetic element 51, which has a relatively large saturation magnetization of the first ferromagnetic layer 1, is less likely to saturate even when irradiated with light of higher intensity than the second magnetic element 52. Also, the second magnetic element 52, which has a relatively small saturation magnetization of the first ferromagnetic layer 1, is more sensitive to light L than the first magnetic element 51, so even if the intensity of the irradiated light is lower than that of the first magnetic element 51, a certain amount of output can be obtained from the second magnetic element 52. Thus, in the photodetector element 204 according to the fifth embodiment, both the output from the first magnetic element 51 and the output from the second magnetic element 52 can be effectively utilized in detecting the intensity of light, and therefore the photodetector element 204 according to the fifth embodiment has a high signal-to-noise ratio.

[0109] Here, the photodetector 204 according to the fifth embodiment and the photodetector 202 according to the third embodiment share the characteristic that the first magnetic elements 31 and 51, which are less prone to output saturation, are located inside the spot sp, and the second magnetic elements 32 and 52, which are highly sensitive to the irradiated light, are located outside the spot sp. Therefore, the characteristic configuration of the photodetector 202 and the characteristic configuration of the photodetector 204 may be combined to make the sensitivity of one of the multiple magnetic elements to the irradiated light different from that of the other elements. Specifically, in at least two magnetic elements arranged to be inside the spot sp, the product of the saturation magnetization of the first ferromagnetic layer 1 and its volume may be larger for the magnetic element closer to the center of the spot sp.

[0110] "Sixth Embodiment" Figure 21 is a cross-sectional view of a part of the photodetector element 205 according to the sixth embodiment. In the sixth embodiment, components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted. Figure 21 simultaneously shows the first electrode 11 and the second electrode 12 connected to each of the magnetic elements 60, and the insulating layers In1, In2, and In3 that cover the periphery of the magnetic elements 60.

[0111] The photodetector 205 has a plurality of magnetic elements 60. The plurality of magnetic elements 60 are arranged so as to be within the spot sp of the irradiated light L.

[0112] Each of the multiple magnetic elements 60 has a layer configuration similar to that of the magnetic element 10. For example, the multiple magnetic elements 60 include a first magnetic element 61 and a second magnetic element 62. The first magnetic element 61 and the second magnetic element 62 are arranged to be within the spot sp of the irradiated light L. The first magnetic element 61 and the second magnetic element 62 are electrically connected to each other, for example, in series or in parallel.

[0113] The first magnetic element 61 is located at a different hierarchical level from the second magnetic element 62. A first electrode 11 is located between the first magnetic element 61 and the light irradiation surface S1, and an insulating layer In1 and the first electrode 11 are located between the second magnetic element 62 and the light irradiation surface S1. The light irradiation surface S1 is the surface to which light from the photodetector element, including the magnetic elements, electrodes, and insulating layer, is irradiated. The light irradiation surface S1 is different from the irradiation surface of each magnetic element 60. Among the multiple magnetic elements 60, there may be some located at a different hierarchical level from both the first magnetic element 61 and the second magnetic element 62.

[0114] At least two of the multiple magnetic elements 60 do not overlap with the other magnetic elements 60 when viewed from the stacking direction. For example, the first magnetic element 61 and the second magnetic element 62 do not overlap with the other magnetic elements 60 when viewed from the stacking direction. When this configuration is satisfied, light L is irradiated onto the first magnetic element 61 and the second magnetic element 62 without being obstructed by the other magnetic elements 60. It is preferable that each of the multiple magnetic elements 60 does not overlap with the other magnetic elements 60 when viewed from the stacking direction.

[0115] The photodetector 205 according to the sixth embodiment has a high signal-to-noise ratio, similar to the photodetector 200 according to the first embodiment, because multiple magnetic elements 60 are located within the same spot sp.

[0116] "Seventh Embodiment" Figure 22 is a cross-sectional view of a part of the photodetector 206 according to the seventh embodiment. In the example shown in Figure 22, when viewed from the z direction in a plan view, the distance between the center of each of the three magnetic elements 70 and the center of the spot sp is the same. In the seventh embodiment, components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted. Figure 22 simultaneously shows the first electrode 11 and the second electrode 12 connected to each of the magnetic elements 70, and the insulating layers In1, In2, and In3 covering the periphery of the magnetic elements 70.

[0117] The photodetector 206 has a plurality of magnetic elements 70. The plurality of magnetic elements 70 are arranged so as to be within the spot sp of the irradiated light L.

[0118] Each of the multiple magnetic elements 70 has a layer configuration similar to that of the magnetic element 10. For example, the multiple magnetic elements 70 include a first magnetic element 71 and a second magnetic element 72. The first magnetic element 71 and the second magnetic element 72 are arranged to be within the spot sp of the irradiated light L. The first magnetic element 71 and the second magnetic element 72 are electrically connected to each other, for example, in series or in parallel. The first magnetic element 71 is an example of the third magnetic element in the claims. The second magnetic element 72 is an example of the fourth magnetic element in the claims.

[0119] The first magnetic element 71 is located at a different hierarchical level from the second magnetic element 72. A first electrode 11 is located between the first magnetic element 71 and the light irradiation surface S1, and an insulating layer In1 and the first electrode 11 are located between the second magnetic element 72 and the light irradiation surface S1. The first electrode 11 between the first magnetic element 71 and the light irradiation surface S1 is an example of the first intermediate layer in the claims. The insulating layer In1 and the first electrode 11 between the second magnetic element 72 and the light irradiation surface S1 are an example of the second intermediate layer in the claims. Among the multiple magnetic elements 70, there may be elements located at a different hierarchical level from both the first magnetic element 71 and the second magnetic element 72.

[0120] The first magnetic element 71 is closer to the light irradiation surface S1 of light L than the second magnetic element 72. The total thickness of the insulating layer In1 and the first electrode 11 (thickness of the second intermediate layer) between the second magnetic element 72 and the light irradiation surface S1 is greater than the thickness of the first electrode 11 (thickness of the first intermediate layer) between the first magnetic element 71 and the light irradiation surface S1. The transmittance of light L between the light irradiation surface S1 and the first magnetic element 71 is higher than the transmittance of light L between the light irradiation surface S1 and the second magnetic element 72.

[0121] The first magnetic element 71 and the second magnetic element 72 have different volumes of the first ferromagnetic layer 1. The first magnetic element 71 has a larger volume of the first ferromagnetic layer 1 than the second magnetic element 72. Because the first magnetic element 71 and the second magnetic element 72 have different volumes of the first ferromagnetic layer 1, they have different sensitivities to light L.

[0122] In the example shown in Figure 22, the volume of the first ferromagnetic layer 1 differs between the first magnetic element 71 and the second magnetic element 72 because the area of ​​the first ferromagnetic layer 1 as viewed from the z direction is different. In the example shown in Figure 22, the thickness of the first ferromagnetic layer 1 is the same for both the first magnetic element 71 and the second magnetic element 72. The volume of the first ferromagnetic layer 1 may be made different not only by varying the area as viewed from the z direction, but also by varying the thickness of the first ferromagnetic layer 1. Furthermore, among the multiple magnetic elements 70, there may be some whose volume of the first ferromagnetic layer 1 differs from both the first magnetic element 71 and the second magnetic element 72. For example, the volume of the first ferromagnetic layer 1 of each of the multiple magnetic elements 70 may be smaller for the magnetic element 70 that is further away from the light irradiation surface S1 of the light L.

[0123] The light intensity irradiated onto each magnetic element 70 decreases as it moves away from the light irradiation surface S1. The first magnetic element 71, which has a relatively large volume of the first ferromagnetic layer 1, is less likely to experience output saturation even when irradiated with higher intensity light than the second magnetic element 72 (see Figures 15 and 16). Furthermore, the second magnetic element 72, which has a relatively small volume of the first ferromagnetic layer 1, is more sensitive to light L than the first magnetic element 71 (see Figures 15 and 16). Therefore, even if the intensity of the irradiated light is lower than that of the first magnetic element 71, a certain amount of output can be obtained from the second magnetic element 72. Thus, in the photodetector element 206 according to the seventh embodiment, both the output from the first magnetic element 71 and the output from the second magnetic element 72 can be effectively utilized in detecting the light intensity, resulting in a high signal-to-noise ratio for the photodetector element 206 according to the seventh embodiment.

[0124] "Eighth Embodiment" Figure 23 is a cross-sectional view of a part of the photodetector 207 according to the eighth embodiment. In the example shown in Figure 23, when viewed from the z direction in a plan view, the distance between the center of each of the three magnetic elements 80 and the center of the spot sp is the same. In the eighth embodiment, components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted. Figure 23 simultaneously shows the first electrode 11 and the second electrode 12 connected to each of the magnetic elements 80, and the insulating layers In1, In2, and In3 covering the periphery of the magnetic elements 80.

[0125] The photodetector 207 has a plurality of magnetic elements 80. The plurality of magnetic elements 80 are arranged so as to be within the spot sp of the irradiated light L.

[0126] Each of the multiple magnetic elements 80 has a layer configuration similar to that of the magnetic element 10. For example, the multiple magnetic elements 80 include a first magnetic element 81 and a second magnetic element 82. The first magnetic element 81 and the second magnetic element 82 are arranged to be within the spot sp of the irradiated light L. The first magnetic element 81 and the second magnetic element 82 are electrically connected to each other, for example, in series or in parallel. The first magnetic element 81 is an example of the third magnetic element in the claims. The second magnetic element 82 is an example of the fourth magnetic element in the claims.

[0127] The first magnetic element 81 is located at a different hierarchical level from the second magnetic element 82. A first electrode 11 is located between the first magnetic element 81 and the light irradiation surface S1, and an insulating layer In1 and the first electrode 11 are located between the second magnetic element 82 and the light irradiation surface S1. The first electrode 11 between the first magnetic element 81 and the light irradiation surface S1 is an example of the first intermediate layer in the claims. The insulating layer In1 and the first electrode 11 between the second magnetic element 82 and the light irradiation surface S1 are an example of the second intermediate layer in the claims. Among the multiple magnetic elements 80, there may be elements located at a different hierarchical level from both the first magnetic element 81 and the second magnetic element 82.

[0128] The first magnetic element 81 is closer to the light irradiation surface S1 of light L than the second magnetic element 82. The total thickness of the insulating layer In1 and the first electrode 11 (thickness of the second intermediate layer) between the second magnetic element 82 and the light irradiation surface S1 is greater than the thickness of the first electrode 11 (thickness of the first intermediate layer) between the first magnetic element 81 and the light irradiation surface S1. The transmittance of light L between the light irradiation surface S1 and the first magnetic element 81 is higher than the transmittance of light L between the light irradiation surface S1 and the second magnetic element 82.

[0129] The first magnetic element 81 and the second magnetic element 82 have different saturation magnetizations of the first ferromagnetic layer 1. Figure 23 shows an example of the saturation magnetization of each magnetic element 80. In the example shown in Figure 23, the saturation magnetization of the first ferromagnetic layer 1 of the magnetic element 80 is smaller the further the magnetic element 80 is from the light irradiation surface S1 of the light L. The saturation magnetization of the first ferromagnetic layer 1 of the first magnetic element 81 is greater than the saturation magnetization of the first ferromagnetic layer 1 of the second magnetic element 82.

[0130] The light intensity irradiated onto each magnetic element 70 decreases as it moves away from the light irradiation surface S1. The first magnetic element 81, which has a relatively large saturation magnetization of the first ferromagnetic layer 1, is less likely to experience output saturation even when irradiated with higher intensity light than the second magnetic element 82. Furthermore, the second magnetic element 82, which has a relatively small saturation magnetization of the first ferromagnetic layer 1, is more sensitive to light L than the first magnetic element 81. Therefore, even if the intensity of the irradiated light is lower than that of the first magnetic element 81, a certain amount of output can be obtained from the second magnetic element 82. Thus, in the photodetector element 207 according to the eighth embodiment, both the output from the first magnetic element 81 and the output from the second magnetic element 82 can be effectively utilized in detecting the light intensity, resulting in a high signal-to-noise ratio for the photodetector element 207 according to the eighth embodiment.

[0131] Here, the photodetector element 207 according to the eighth embodiment and the photodetector element 206 according to the seventh embodiment share the characteristic that the first magnetic elements 71 and 81, whose output is less likely to saturate, are relatively close to the light irradiation surface S1 of the light L. Therefore, the characteristic configuration of the photodetector element 206 and the characteristic configuration of the photodetector element 207 may be combined to make the sensitivity of one of the multiple magnetic elements to the irradiated light different from that of the other elements. Specifically, in at least two magnetic elements arranged to enter the spot sp, the product of the saturation magnetization of the first ferromagnetic layer 1 and its volume may be larger for the magnetic element that is closer to the light irradiation surface S1 of the light L.

[0132] "Ninth Embodiment" Figure 24 is a cross-sectional view of a part of the photodetector element 208 according to the ninth embodiment. In the ninth embodiment, components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted. Figure 24 simultaneously shows the first electrode 11 and the second electrode 12 connected to each of the magnetic elements 90, and the insulating layers In1, In2, and In3 covering the periphery of the magnetic elements 90. Also in Figure 24, the left side (-x side) is closer to the center of the spot sp.

[0133] The photodetector 208 has a plurality of magnetic elements 90. The plurality of magnetic elements 90 are arranged so as to be within the spot sp of the irradiated light L.

[0134] Each of the multiple magnetic elements 90 has a layer configuration similar to that of the magnetic element 10. For example, the multiple magnetic elements 90 include a first magnetic element 91 and a second magnetic element 92. The first magnetic element 91 and the second magnetic element 92 are arranged to be within the spot sp of the irradiated light L. The first magnetic element 91 and the second magnetic element 92 are electrically connected to each other, for example, in series or in parallel. The first magnetic element 91 is an example of the fifth magnetic element in the claims. The second magnetic element 92 is an example of the sixth magnetic element in the claims.

[0135] The first magnetic element 91 is located closer to the center of the spot sp than the second magnetic element 92. The first magnetic element 91 is in a different layer than the second magnetic element 92. Between the first magnetic element 91 and the light irradiation surface S1 are insulating layer In1, insulating layer In2, and the first electrode 11, and between the second magnetic element 92 and the light irradiation surface S1 are insulating layer In1 and the first electrode 11. The insulating layer In1, insulating layer In2, and the first electrode 11 between the first magnetic element 91 and the light irradiation surface S1 are an example of the third intermediate layer in the claims. The insulating layer In1 and the first electrode 11 between the second magnetic element 92 and the light irradiation surface S1 are an example of the fourth intermediate layer in the claims. Among the multiple magnetic elements 90, there may be elements that are in a different layer than both the first magnetic element 91 and the second magnetic element 92.

[0136] The second magnetic element 92 is closer to the light irradiation surface S1 of light L than the first magnetic element 91. The total thickness of the insulating layer In1, insulating layer In2, and first electrode 11 between the first magnetic element 91 and the light irradiation surface S1 (thickness of the third intermediate layer) is greater than the total thickness of the insulating layer In1 and first electrode 11 between the second magnetic element 92 and the light irradiation surface S1 (thickness of the fourth intermediate layer). The fourth intermediate layer has a higher transmittance of light L than the third intermediate layer. In the example shown in Figure 24, the magnetic element 90 is closer to the light irradiation surface S1 of light L the further it is from the center of the spot sp. Also, in the example shown in Figure 24, the volume of the first ferromagnetic layer 1 and the saturation magnetization of the first ferromagnetic layer 1 are the same for the first magnetic element 91 and the second magnetic element 92.

[0137] The light intensity on the light-irradiated surface S1 is greater towards the center of the spot sp. In the photodetector 208 according to the ninth embodiment, the second magnetic element 92, which is relatively far from the center of the spot sp, has a higher transmittance of light L between itself and the light-irradiated surface S1 than the first magnetic element 91. When this configuration is satisfied, light L of sufficient intensity can be irradiated to the magnetic element 90, which is located on the outer periphery of the spot sp where the light intensity is weak. Therefore, the variation in light intensity irradiated to the first magnetic element 91 and the second magnetic element 92 can be reduced. As a result, a certain level of output can be obtained from both the first magnetic element 91 and the second magnetic element 92 without saturating the output. In other words, in the photodetector 208 according to the ninth embodiment, both the output from the first magnetic element 91 and the output from the second magnetic element 92 can be effectively utilized in detecting the light intensity, so the photodetector 208 according to the ninth embodiment has a high signal-to-noise ratio.

[0138] Although an example of the ninth embodiment has been described in detail, the ninth embodiment is not limited to this example.

[0139] (First variation) For example, Figure 25 is a cross-sectional view of a part of the photodetector element 208A according to the first modified example of the ninth embodiment. In Figure 25, the left side (-x side) is closer to the center of the spot sp.

[0140] The photodetector element 208A has a plurality of magnetic elements 100 and a protective film 105. The plurality of magnetic elements 100 are arranged so as to be within the spot sp of the irradiated light L. Each of the plurality of magnetic elements 100 has a layer configuration similar to that of the magnetic element 10. For example, the plurality of magnetic elements 100 has a first magnetic element 101 and a second magnetic element 102. The first magnetic element 101 and the second magnetic element 102 are arranged so as to be within the spot sp of the irradiated light L. The first magnetic element 101 and the second magnetic element 102 are electrically connected to each other, for example, in series or in parallel. The first magnetic element 101 is an example of the fifth magnetic element in the claims. The second magnetic element 102 is an example of the sixth magnetic element in the claims. The first magnetic element 101 is located closer to the center of the spot sp than the second magnetic element 102.

[0141] In the example shown in Figure 25, the protective film 105 is thicker closer to the center of the spot sp. The protective film 105 has, for example, a light irradiation surface S1 that is inclined with respect to the xy plane. The light irradiation surface S1 of the protective film 105 may also be stepped. The protective layer 105 and the first electrode 11 between the first magnetic element 101 and the light irradiation surface S1 is an example of the third intermediate layer in the claims. The protective layer 105 and the first electrode 11 between the second magnetic element 102 and the light irradiation surface S1 is an example of the fourth intermediate layer in the claims. The fourth intermediate layer has a higher transmittance of light L than the third intermediate layer.

[0142] In the photodetector element 208A, the second magnetic element 102, which is relatively far from the center of the spot sp, has a higher transmittance of light L between it and the light irradiation surface S1 than the first magnetic element 101. Therefore, the variation in light intensity irradiated to the first magnetic element 101 and the second magnetic element 102 can be reduced.

[0143] (Second variation) For example, Figure 26 is a cross-sectional view of a part of the photodetector element 208B according to a second modified example of the ninth embodiment. In Figure 26, the left side (-x side) is closer to the center of the spot sp. In Figure 26, components similar to those in Figure 25 are denoted by the same reference numerals.

[0144] The photodetector element 208B has dielectric films 106, 107, and 108. The materials of the dielectric films 106, 107, and 108 are, for example, oxides, nitrides, or oxynitrides containing one or more metallic or metalloid elements. More specifically, the materials of the dielectric films 106, 107, and 108 are, for example, oxides, nitrides, or oxynitrides containing one or more elements selected from the group consisting of Al, Si, Ta, In, Hf, Sn, Zn, Ti, Cu, Ce, Zr, Nb, Mg, B, Pb, Ca, La, and Ge. Dielectric film 106 is located on the first magnetic element 101. Dielectric film 107 is located on the second magnetic element 102. Dielectric film 108 is located on the third magnetic element 103. Dielectric film 106 has a lower transmittance of light L than dielectric film 107. Dielectric film 107 has a lower transmittance of light L than dielectric film 108. The transmittance of light L of a dielectric film can be varied, for example, by the dielectric material. It can also be varied by varying the amount of additives added to the dielectric. As an example, consider a combination where the material of dielectric film 106 is hafnium oxide (HfO2), the material of dielectric film 107 is aluminum oxide (Al2O3), and the material of dielectric film 108 is silicon oxide (SiO2). In this case, for example, the transmittance for light with a wavelength of 500 nm is lowest for hafnium oxide (HfO2), followed by aluminum oxide (Al2O3), and then silicon oxide (SiO2). Therefore, when the wavelength of light L is 500 nm, dielectric film 106 has a lower transmittance of light L than dielectric film 107, and dielectric film 107 has a lower transmittance of light L than dielectric film 108.

[0145] In the photodetector element 208B, the second magnetic element 102, which is relatively far from the center of the spot sp, has a higher transmittance of light L between itself and the light-irradiated surface S1 than the first magnetic element 101. Therefore, the variation in light intensity irradiated to the first magnetic element 101 and the second magnetic element 102 can be reduced.

[0146] (Third variation) For example, Figure 27 is a cross-sectional view of a part of the photodetector element 208C according to a third modified example of the ninth embodiment. In Figure 27, the left side (-x side) is closer to the center of the spot sp. In Figure 27, components similar to those in Figure 25 are denoted by the same reference numerals.

[0147] The light-detecting element 208C has different light transmittances L for each of its first electrodes 11A, 11B, and 11C. The first electrode 11A has a lower light transmittance L than the first electrode 11B. The first electrode 11B has a lower light transmittance L than the first electrode 11C. The transmittance of the first electrodes can be varied, for example, by varying the composition of the first electrodes. For example, if indium tin oxide (ITO) is used as the material for the first electrodes, the light transmittance can be increased by increasing the composition ratio of tin to indium.

[0148] In the photodetector element 208C, the second magnetic element 102, which is relatively far from the center of the spot sp, has a higher transmittance of light L between itself and the light-irradiated surface S1 than the first magnetic element 101. Therefore, the variation in light intensity irradiated to the first magnetic element 101 and the second magnetic element 102 can be reduced.

[0149] The present invention is not limited to the embodiments and modifications described above, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims. For example, characteristic configurations of the embodiments and modifications described above may be combined.

[0150] The light-detecting elements according to the above embodiments and modifications can be applied to light-sensing devices such as image sensors, transceivers in communication systems, and the like.

[0151] Figure 28 is a block diagram of a transceiver 1000 according to the first application example. The transceiver 1000 comprises a receiving device 300 and a transmitting device 400. The receiving device 300 receives an optical signal L1, and the transmitting device 400 transmits an optical signal L2.

[0152] The receiving device 300 includes, for example, a photodetector 301 and a signal processing unit 302. The photodetector 301 is a photodetector in any of the embodiments or modifications described above. In the receiving device 300, the first ferromagnetic layer 1 of the plurality of magnetic elements is irradiated with light that includes a high-frequency optical signal L1 and changes in intensity. The photodetector 301 converts the optical signal L1 into an electrical signal. The operation of the photodetector 301 may be either the first operation example or the second operation example. The signal processing unit 302 processes the electrical signal converted by the photodetector 301. The signal processing unit 302 receives the signal contained in the optical signal L1 by processing the electrical signal generated from the photodetector 301. The receiving device 300 receives the signal contained in the optical signal L1 based, for example, on the combined output voltage of the plurality of magnetic elements.

[0153] The transmitting device 400 includes, for example, a light source 401, an electrical signal generating element 402, and an optical modulation element 403. The light source 401 is, for example, a laser element. The light source 401 may be located outside the transmitting device 400. The electrical signal generating element 402 generates an electrical signal based on the transmission information. The electrical signal generating element 402 may be integrated with the signal conversion element of the signal processing unit 302. The optical modulation element 403 modulates the light output from the light source 401 based on the electrical signal generated by the electrical signal generating element 402 and outputs an optical signal L2.

[0154] Figure 29 is a conceptual diagram of an example of a communication system. The communication system shown in Figure 29 has two terminal devices 500. The terminal devices 500 are, for example, smartphones, tablets, personal computers, etc.

[0155] Each terminal device 500 includes a receiving device 300 and a transmitting device 400. The receiving device 300 of the other terminal device 500 receives the optical signal transmitted from the transmitting device 400 of the other terminal device 500. The light used for transmission and reception between the terminal devices 500 is, for example, visible light. The receiving device 300 has the above-mentioned photodetector element as a photodetector element 301. Because the above-mentioned photodetector element has an excellent signal-to-noise ratio, the communication system shown in Figure 29 is highly reliable.

[0156] Figure 30 is a conceptual cross-sectional view of a photosensor device 2000 according to a second application example. The photosensor device 2000 includes, for example, a circuit board 120, a wiring layer 130, and a plurality of photosensors S. Each of the wiring layer 130 and the plurality of photosensors S is formed on the circuit board 120.

[0157] Each of the multiple light sensors S includes, for example, a photodetector 200, a wavelength filter F, and a lens R. Figure 30 shows an example using the photodetector 200, but a photodetector according to another embodiment and modification may be used. The photodetector 200 is irradiated with light that has passed through the wavelength filter F. As described above, the photodetector 200 converts the light irradiated onto the multiple magnetic elements 10 into an electrical signal. The photodetector 200 preferably operates in the second operating example.

[0158] A wavelength filter F selects light of a specific wavelength and transmits light within a specific wavelength range. The wavelength ranges of light transmitted by each wavelength filter F may be the same or different. For example, the optical sensor device 2000 may have an optical sensor S (hereinafter referred to as the blue sensor) having a wavelength filter F that transmits blue light (wavelength range of 380 nm to less than 490 nm), an optical sensor S (hereinafter referred to as the green sensor) having a wavelength filter F that transmits green light (wavelength range of 490 nm to less than 590 nm), and an optical sensor S (hereinafter referred to as the red sensor) having a wavelength filter F that transmits red light (wavelength range of 590 nm to less than 800 nm). By treating the blue sensor, green sensor, and red sensor as one pixel and arranging these pixels, the optical sensor device 2000 can be used as an image sensor.

[0159] Lens R focuses light toward multiple magnetic elements 10. Multiple photodetectors 200 are positioned below a single wavelength filter F.

[0160] The circuit board 120 includes, for example, an analog-to-digital converter 121 and an output terminal 122. The electrical signal sent from the optical sensor S is converted into digital data by the analog-to-digital converter 121 and output from the output terminal 122.

[0161] The wiring layer 130 has multiple wirings 131. Between the multiple wirings 131 is an interlayer insulating film 132. The wirings 131 electrically connect each of the light sensors S to the circuit board 120, and to each of the arithmetic circuits formed on the circuit board 120. Each of the light sensors S and the circuit board 120 are connected, for example, via through-wiring that penetrates the interlayer insulating film 132 in the z direction. Noise can be reduced by shortening the wiring distance between each of the light sensors S and the circuit board 120.

[0162] The wiring 131 is conductive. The wiring 131 is, for example, Al, Cu, etc. The interlayer insulating film 132 is an insulator that insulates between wirings and elements in multilayer wiring. The interlayer insulating film 132 is, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg. The interlayer insulating film 132 is, for example, silicon dioxide (SiO₂). x ), silicon nitride (SiN x ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO3) x ) etc.

[0163] The above-described optical sensor device 2000 can be used, for example, in a terminal device. Figure 31 is a schematic diagram of an example of a terminal device 600. The left side of Figure 31 is the front surface of the terminal device 600, and the right side is the back surface of the terminal device 600. The terminal device 600 has a camera CA. The above-described optical sensor device 2000 can be used as the image sensor of this camera CA. In Figure 31, a smartphone is used as an example of a terminal device 600, but it is not limited to this case. In addition to smartphones, terminal devices 600 can be, for example, tablets, personal computers, digital cameras, etc. [Explanation of Symbols]

[0164] 1…First ferromagnetic layer, 2…Second ferromagnetic layer, 3…Spacer layer, 10,20,30,40,50,60,70,80,90,100…Magnetic elements, 21,31,41,51,61,71,81,91,101…First magnetic elements, 22,32,42,52,62,72,82,92,102…Second magnetic elements, 11,11A,11B,11C…First electrode, 12…Second electrode, 105…Protective film, 106,107,108…Dielectric film, 200,200A,200B,200C,201,202,203,204,205,20 6,207,208,208A,208B,208C…Photodetector, 120…Circuit board, 121…Analog-to-digital converter, 122…Output terminal, 130…Wiring layer, 131…Wiring, 132…Interlayer insulating film, 300…Receiver, 301…Photodetector, 302…Signal processing unit, 400…Transmitter, 401…Light source, 402…Electrical signal generation element, 403…Optical modulation element, 500,600…Terminal device, 1000…Transmitting / receiving device, 2000…Optical sensor device, CA…Camera, F…Wavelength filter, R…Lens, S…Optical sensor

Claims

1. Equipped with multiple magnetic elements, Each of the plurality of magnetic elements comprises a first ferromagnetic layer to which light is irradiated, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. At least two of the plurality of magnetic elements are arranged to fall within the spot of light being irradiated. The plurality of magnetic elements include a first magnetic element and a second magnetic element arranged to enter the spot, The first magnetic element and the second magnetic element have different volumes of the first ferromagnetic layer. The first magnetic element is located closer to the center of the spot than the second magnetic element. The first magnetic element is a photodetector in which the volume of the first ferromagnetic layer is larger than that of the second magnetic element.

2. The plurality of magnetic elements include a first magnetic element and a second magnetic element, which are arranged to enter the spot. The photodetector according to claim 1, wherein the first magnetic element and the second magnetic element have different saturation magnetizations of the first ferromagnetic layer.

3. Equipped with multiple magnetic elements, Each of the plurality of magnetic elements comprises a first ferromagnetic layer to which light is irradiated, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. At least two of the plurality of magnetic elements are arranged to fall within the spot of light being irradiated. The plurality of magnetic elements include a first magnetic element and a second magnetic element arranged to enter the spot, The first magnetic element and the second magnetic element have different saturation magnetizations of the first ferromagnetic layer. The first magnetic element is located closer to the center of the spot than the second magnetic element. The first magnetic element is a photodetector in which the saturation magnetization of the first ferromagnetic layer is greater than that of the second magnetic element.

4. Equipped with multiple magnetic elements, Each of the plurality of magnetic elements comprises a first ferromagnetic layer to which light is irradiated, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. At least two of the plurality of magnetic elements are arranged to fall within the spot of light being irradiated. The plurality of magnetic elements include a third magnetic element and a fourth magnetic element arranged to enter the spot, The third magnetic element further has a first intermediate layer between the first ferromagnetic layer and the light-irradiating surface of the photodetector, which is the side of the photodetector that is irradiated with light. The fourth magnetic element further has a second intermediate layer between the first ferromagnetic layer and the light irradiation surface, The third magnetic element is located closer to the light irradiation surface than the fourth magnetic element. The third magnetic element is a photodetector in which the volume of the first ferromagnetic layer is larger than that of the fourth magnetic element.

5. Equipped with multiple magnetic elements, Each of the plurality of magnetic elements comprises a first ferromagnetic layer to which light is irradiated, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. At least two of the plurality of magnetic elements are arranged to fall within the spot of light being irradiated. The plurality of magnetic elements include a third magnetic element and a fourth magnetic element arranged to enter the spot, The third magnetic element further has a first intermediate layer between the first ferromagnetic layer and the light-irradiating surface of the photodetector, which is the side of the photodetector that is irradiated with light. The fourth magnetic element further has a second intermediate layer between the first ferromagnetic layer and the light irradiation surface, The third magnetic element is located closer to the light irradiation surface than the fourth magnetic element. The third magnetic element is a photodetector in which the saturation magnetization of the first ferromagnetic layer is greater than that of the fourth magnetic element.

6. The plurality of magnetic elements include a fifth magnetic element and a sixth magnetic element arranged to enter the spot, The fifth magnetic element is located closer to the center of the spot than the sixth magnetic element. The fifth magnetic element further has a third intermediate layer between the first ferromagnetic layer and the light-irradiating surface, which is the side of the photodetector that is irradiated with light. The sixth magnetic element further has a fourth intermediate layer between the first ferromagnetic layer and the light irradiation surface, The photodetector according to any one of claims 1 to 5, wherein the fourth intermediate layer has a higher light transmittance than the third intermediate layer.

7. The photodetector according to any one of claims 1 to 6, wherein each of the plurality of magnetic elements has an output that changes in response to a change in the intensity of light irradiated onto the first ferromagnetic layer.

8. A receiving device having a photodetector element according to any one of claims 1 to 7.

9. A light sensor device having a light-detecting element according to any one of claims 1 to 7.

Images