Photodetector and receiver

Abstract

To provide novel light detection element and receiving device.SOLUTION: A light detection element includes a magnetic element having a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and light including an optical signal having a change in optical intensity is irradiated onto the first ferromagnetic layer, and the optical signal is received on the basis of an output voltage from the magnetic element, and the magnetization of the first ferromagnetic layer when the first ferromagnetic layer is irradiated with the light is smaller than the magnetization of the first ferromagnetic layer when the first ferromagnetic layer is not irradiated with the light.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a photodetector and a receiving device. [Background technology]

[0002] With the spread of the internet, the volume of data traffic has increased dramatically, making optical communication extremely important. Optical communication is a communication method that converts electrical signals into optical signals and uses these optical signals for transmission and reception.

[0003] For example, Patent Document 1 describes a receiving device that uses a photodiode to receive optical signals. The photodiode is, for example, a pn junction diode using a semiconductor pn junction. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-292107 [Overview of the project] [Problems that the invention aims to solve]

[0005] With the advancement of information and communication technology, there is a growing demand for even faster communication speeds. In optical communication, this requires increasing the frequency of signal modulation. However, the semiconductor photodiode shown in Patent Document 1 suffers from a significant decrease in receiving sensitivity as the frequency increases, and a new breakthrough is needed for further development.

[0006] The present invention has been made in view of the above problems, and aims to provide a novel receiving device, receiving system, transmitting / receiving device, communication system, and optical detection element, and to provide a receiving device, receiving system, transmitting / receiving device, communication system, and optical detection element that enable high-speed communication. [Means for solving the problem]

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

[0008] (1) The receiving device according to the first embodiment includes a magnetic element comprising a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, wherein light containing an optical signal having a change in light intensity is irradiated onto the first ferromagnetic layer, and the optical signal is received based on the output voltage from the magnetic element.

[0009] (2) In the above embodiment, the receiving device may be configured such that the output voltage from the magnetic element changes in response to a change in the intensity of the light irradiated onto the first ferromagnetic layer.

[0010] (3) In the receiving device according to the above embodiment, the angle between the magnetization direction of the first ferromagnetic layer when the first ferromagnetic layer is not irradiated with light and the magnetization direction of the first ferromagnetic layer when the first ferromagnetic layer is irradiated with light may be greater than 0° and less than 90°.

[0011] (4) In the above embodiment, the receiving device has at least two levels of intensity, the optical signal has at least two levels of intensity, the magnitude of the output voltage from the magnetic element shows a first value when the intensity of the light irradiated onto the first ferromagnetic layer is a first intensity, and shows a second value when the intensity of the light irradiated onto the first ferromagnetic layer is a second intensity, and under the condition that the second intensity is greater than the first intensity, if the second value is greater than the first value, a current may be passed from the first ferromagnetic layer to the second ferromagnetic layer, and if the second value is less than the first value, a current may be passed from the second ferromagnetic layer to the first ferromagnetic layer.

[0012] (5) The receiving device according to the above embodiment further comprises a hard bias layer for applying a bias magnetic field to the first ferromagnetic layer, wherein the hard bias layer is located in a position that overlaps with the first ferromagnetic layer when viewed from any direction perpendicular to the stacking direction of the magnetic elements, and the magnetization direction of the hard bias layer may be opposite to the magnetization direction of the first ferromagnetic layer when the light is not irradiated.

[0013] (6) In the receiving device according to the above embodiment, the magnetic element further comprises a first electrode connected to the first ferromagnetic layer and a second electrode connected to the second ferromagnetic layer, wherein the first electrode may be transparent to light in the wavelength range used for the optical signal.

[0014] (7) The receiving device according to the above embodiment further comprises a soft magnetic material, the soft magnetic material may cover at least a portion of the outer circumference of the magnetic element from the outside in a plan view from the stacking direction of the magnetic element.

[0015] (8) In the receiving device according to the above embodiment, the soft magnetic material is also located above and below the stacking direction of the magnetic element, and the soft magnetic material located above and below the magnetic element on the side of the first ferromagnetic layer may have an opening.

[0016] (9) In the receiving device according to the above embodiment, the opening may have a mesh-like magnetic net connected to the soft magnetic material.

[0017] (10) In the receiving device according to the above embodiment, the case in which the output voltage from the magnetic element is equal to or greater than a threshold is treated as a first signal, and the case in which it is less than a threshold is treated as a second signal.

[0018] (11) In the receiving device according to the above embodiment, a change in the output voltage from the magnetic element within a predetermined time may be treated as a first signal, and no change in the output voltage from the magnetic element within a predetermined time may be treated as a second signal.

[0019] (12) The receiving device according to the above aspect further comprises an integrated circuit, wherein the magnetic element and the integrated circuit are formed on the same substrate with an interlayer insulating film interposed therebetween, and the integrated circuit and the magnetic element may be connected to each other via a through-wiring penetrating the interlayer insulating film.

[0020] (13) A transmitting / receiving device according to the second aspect comprises the receiving device according to the above aspect, and a transmitting device configured to transmit an optical signal.

[0021] (14) A communication system according to the third aspect comprises a plurality of the transmitting / receiving devices according to the above aspect.

[0022] (15) A portable terminal device according to the fourth aspect comprises the receiving device according to the above aspect.

[0023] (16) A light detection element according to the fifth aspect comprises a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, wherein an output voltage changes in accordance with a change in intensity of light applied to the first ferromagnetic layer.

[0024] (17) In the light detection element according to the above aspect, an angle between a magnetization direction of the first ferromagnetic layer in a state where the light is not applied to the first ferromagnetic layer and a magnetization direction of the first ferromagnetic layer in a state where the light is applied to the first ferromagnetic layer may be larger than 0° and smaller than 90°.

[0025] (18) The light detection element according to the above aspect is irradiated with an optical signal having at least two levels of intensity, wherein when the intensity of the light applied to the first ferromagnetic layer is a first intensity, the magnitude of the output voltage indicates a first value, when the intensity of the light applied to the first ferromagnetic layer is a second intensity, the magnitude of the output voltage indicates a second value, and under a condition that the second intensity is larger than the first intensity, when the second value is larger than the first value, a current flows from the first ferromagnetic layer toward the second ferromagnetic layer, and when the second value is smaller than the first value, a current flows from the second ferromagnetic layer toward the first ferromagnetic layer. The configuration may be such as described above. [Effects of the Invention]

[0026] The receiving device, transmitting / receiving device, communication system, mobile terminal device, and optical detection element according to the above embodiment are novel and will generate a new breakthrough. Furthermore, the receiving device, transmitting / receiving device, communication system, mobile terminal device, and optical detection element according to the above embodiment are capable of high-speed communication. [Brief explanation of the drawing]

[0027] [Figure 1] This is a conceptual diagram of the communication system according to the first embodiment. [Figure 2] This is a block diagram of the transmitting and receiving device according to the first embodiment. [Figure 3] This is a circuit diagram of the transmitting and receiving device according to the first embodiment. [Figure 4] This is a cross-sectional view of the receiving device according to the first embodiment. [Figure 5] This is a cross-sectional view of the photodetector element according to the first embodiment. [Figure 6] This is a schematic diagram illustrating the operation of the first pattern of the photodetector element according to the first embodiment using the first mechanism. [Figure 7] This is a schematic diagram illustrating the operation of the first pattern of the photodetector element according to the first embodiment using a second mechanism. [Figure 8] This is a schematic diagram illustrating the operation of the second pattern of the photodetector element according to the first embodiment using the first mechanism. [Figure 9] This is a schematic diagram illustrating the operation of the second pattern of the photodetector element according to the first embodiment using a second mechanism. [Figure 10] This is a schematic diagram illustrating the operation of the photodetector when it outputs multiple levels using the photodetector according to the first embodiment, using the first mechanism. [Figure 11] This is a schematic diagram illustrating the operation of the photodetector when it outputs multiple levels using the photodetector according to the first embodiment, as shown in the second mechanism. [Figure 12]This is a schematic diagram showing the behavior of the photodetector when an abnormality occurs in the photodetector according to the first embodiment. [Figure 13] This figure shows the simulation results of the sensitivity of the example and comparative example 1. [Figure 14] This figure shows the simulation results of the sensitivity of the Example and Comparative Example 2. [Figure 15] This is a circuit diagram of a transmitting and receiving device according to the first modified example. [Figure 16] This is a cross-sectional view of the photodetector element according to the second modified example, cut along a plane in the z-direction. [Figure 17] This is a cross-sectional view of the photodetector element and its surroundings according to the second modified example, cut by the xy plane passing through the first ferromagnetic layer 1. [Figure 18] This is a cross-sectional view of the photodetector element according to the third modified example, cut along a plane in the z-direction. [Figure 19] This is a cross-sectional view of the receiving device according to the fourth modified example, taken from a plane along the z-direction. [Figure 20] This is a plan view from the z-direction of the receiving device relating to the fourth modified example. [Figure 21] This is a cross-sectional view of the receiving device according to the fifth modified example, taken from a plane along the z-direction. [Figure 22] This is a plan view from the z-direction of the receiving device according to the fifth modified example. [Figure 23] This is a cross-sectional view of the receiving device according to the sixth modified example. [Figure 24] This is a diagram illustrating the operation of the receiving device according to the second embodiment. [Figure 25] This is a conceptual diagram of another example of a communication system. [Figure 26] This is a conceptual diagram of another example of a communication system. [Modes for carrying out the invention]

[0028] 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.

[0029] The directions are defined below. The stacking direction of the photodetector 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-direction and the z-direction 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 substrate Sb toward the photodetector element 10. Up and down do not necessarily coincide with the direction in which gravity acts.

[0030] "First Embodiment" Figure 1 is a conceptual diagram of a communication system 1000 according to the first embodiment. The communication system 1000 shown in Figure 1 comprises a plurality of transceivers 300 and fiber FBs connecting the transceivers 300. The communication system 1000 can be used for short- and medium-distance communication, such as within and between data centers, and long-distance communication, such as between cities. The transceivers 300 are installed, for example, within data centers, at base stations and trunk stations of long-distance communication networks. The fiber FBs connect, for example, data centers. The communication system 1000 communicates between the transceivers 300, for example, via the fiber FBs. The communication system 1000 may also communicate wirelessly between the transceivers 300 without using the fiber FBs.

[0031] Figure 2 is a block diagram of a transceiver 300 according to the first embodiment. The transceiver 300 comprises a receiving device 100 and a transmitting device 200. The receiving device 100 receives an optical signal L1, and the transmitting device 200 transmits an optical signal L2. In this specification, light is not limited to visible light, but also includes infrared rays with wavelengths longer than visible light and ultraviolet rays with wavelengths shorter than visible light.

[0032] The receiving device 100 includes, for example, a photodetector 10 and a signal processing unit 11. The photodetector 10 converts the optical signal L1 into an electrical signal. Details of the photodetector 10 will be described later. The signal processing unit 11 processes the electrical signal converted by the photodetector 10. The signal processing unit 11 receives the signal contained in the optical signal L1 by processing the electrical signal generated from the photodetector 10.

[0033] The transmitting device 200 includes, for example, a light source 201, an electrical signal generating element 202, and an optical modulation element 203. The light source 201 is, for example, a laser element. The light source 201 may be located outside the transmitting device 200. The electrical signal generating element 202 generates an electrical signal based on the transmission information. The electrical signal generating element 202 may be integrated with the signal conversion element of the signal processing unit 11. The optical modulation element 203 modulates the light output from the light source 201 based on the electrical signal generated by the electrical signal generating element 202 and outputs an optical signal L2.

[0034] Figure 3 is a circuit diagram of the transceiver 300 according to the first embodiment. In Figure 3, the signal processing unit 11 is omitted.

[0035] The receiving device 100 includes, for example, a photodetector 10, a first electrode 15, a second electrode 16, and an input terminal P. in and output terminal P out and reference potential terminal P G The device comprises the first electrode 15 and the second electrode 16 sandwiching the photodetector 10 in the stacking direction. The first electrode 15 is, for example, the electrode on the side to which light containing the optical signal L1 is irradiated.

[0036] The first electrode 15 is connected, for example, to the input terminal Pin and the output terminal Pout. The second electrode 16 is connected, for example, to the reference potential terminal PG. The input terminal Pin is connected to the power supply PS. The power supply PS may be located outside the receiving device 100. The power supply PS applies a sense current, reset current, etc., to the photodetector element 10. If it is not necessary to supply current to the photodetector element 10 from an external source, the input terminal Pin and the power supply PS may be omitted. The output terminal Pout outputs, for example, the voltage between the first electrode 15 and the second electrode 16 that sandwich the photodetector element 10 in the stacking direction. The resistance value of the photodetector element 10 in the stacking direction can be determined from Ohm's law by applying a sense current in the stacking direction of the photodetector element 10. out It is connected to the signal processing unit 11. Reference potential terminal P G This is connected to a reference potential and determines the reference potential of the receiving device 100. In Figure 3, the reference potential is ground G. Ground G may be provided outside the receiving device 100. The reference potential may be something other than ground G.

[0037] The receiving device 100 and the transmitting device 200 are connected to a common reference potential (ground G), for example. The reference potentials of the receiving device 100 and the transmitting device 200 may be different. If the reference potentials of the receiving device 100 and the transmitting device 200 are the same, the generation of noise can be reduced.

[0038] Figure 4 is a cross-sectional view of a receiving device 100 according to the first embodiment. The receiving device 100 comprises, for example, a photodetector 10, an integrated circuit 20, and an interlayer insulating film 30. The photodetector 10, the integrated circuit 20, and the interlayer insulating film 30 are formed, for example, on the same substrate Sb.

[0039] The integrated circuit 20 includes a signal processing unit 11 that processes the signal output from the photodetector 10. For example, the integrated circuit 20 processes the output voltage from the photodetector 10 (the resistance value of the photodetector 10 in the z direction) as a first signal (e.g., "1") when it is above a threshold, and as a second signal (e.g., "0") when it is below the threshold. If the transmitting device 200 is formed on the same substrate Sb, the integrated circuit 20 may also include a light source 201, an electrical signal generating element 202, and an optical modulation element 203. The integrated circuit 20 and the photodetector 10 are connected, for example, via through-wiring w that penetrates the interlayer insulating film 30. Instead of through-wiring w, they may be connected by wire bonding.

[0040] The interlayer insulating film 30 is an insulator that insulates between wirings and elements in multilayer wiring. The interlayer insulating film 30 is, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg. The interlayer insulating film 30 is, for example, silicon oxide (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.

[0041] Figure 5 is a cross-sectional view of the photodetector element 10 according to the first embodiment. In Figure 5, the first electrode 15 and the second electrode 16 are shown simultaneously, and the direction of magnetization in the initial state of the ferromagnetic material is indicated by an arrow.

[0042] The photodetector element 10 is a magnetic element having at least a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a spacer layer 3. The spacer layer 3 is located between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. In addition to these, the photodetector element 10 may also have a third ferromagnetic layer 4, a magnetic coupling layer 5, a base layer 6, a perpendicular magnetization induction layer 7, a cap layer 8, and a sidewall insulating layer 9.

[0043] The photodetector 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 photodetector 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 change in the relative angle between the magnetization direction of the first ferromagnetic layer 1 and the magnetization direction of the second ferromagnetic layer 2. Such an element is also called a magnetoresistive element.

[0044] The first ferromagnetic layer 1 is a photodetector layer whose magnetization direction 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 direction changes when a predetermined external energy is applied. The predetermined external energy is, for example, light irradiated from the outside, a current flowing in the z direction of the photodetector element 10, or an external magnetic field. Since the magnetization of a ferromagnetic material can change direction in response to a rapid change in the intensity of light irradiated onto the ferromagnetic material (high-frequency optical signal), by using the first ferromagnetic layer 1 as a photodetector layer, the receiving device 100 can receive high-frequency optical signals, enabling high-speed optical communication.

[0045] The first ferromagnetic layer 1 contains a ferromagnetic material. The first ferromagnetic layer 1 contains, for example, at least one of Co, Fe, or Ni. The first ferromagnetic layer 1 contains, for example, 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, for example, an alloy containing magnetic elements and non-magnetic elements. 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 CoFeB alloy layers are sandwiched between Fe layers, or a laminate in which CoFeB alloy layers are sandwiched between CoFe layers.

[0046] 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).

[0047] 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 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.

[0048] 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 responsiveness of the magnetization of the first ferromagnetic layer 1 when external energy is applied is inversely proportional to the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 1. In other words, when the product of the magnetic anisotropy and volume of the first ferromagnetic layer 1 decreases, the responsiveness to the optical signal L1 at ultra-high speeds increases. From this viewpoint, as optical communication becomes ultra-high speed, 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. That is, it is preferable to make the thickness of the first ferromagnetic layer 1 thinner as the ultra-high speed of communication increases.

[0049] 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.

[0050] The second ferromagnetic layer 2 is a magnetization-fixed layer. The magnetization-fixed layer is a layer made of a magnetic material whose magnetization direction is less likely to change 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, for example, the coercivity of the first ferromagnetic layer 1. The second ferromagnetic layer 2 has an easy magnetization axis in the same direction as the first ferromagnetic layer 1. The second ferromagnetic layer 2 may be an in-plane magnetized film or a perpendicular magnetized film.

[0051] 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.

[0052] The magnetization of the second ferromagnetic layer 2 may be fixed, for example, by magnetic coupling with the third ferromagnetic layer 4 via the magnetic coupling layer 5. In this case, the second ferromagnetic layer 2, the magnetic coupling layer 5, and the third ferromagnetic layer 4 together may be referred to as the magnetization-fixing layer.

[0053] The third ferromagnetic layer 4 is magnetically coupled to, for example, the second ferromagnetic layer 2. This magnetic coupling is, for example, an antiferromagnetic coupling, and is caused by the RKKY interaction. The material constituting the third ferromagnetic layer 4 is, for example, the same as that of the first ferromagnetic layer 1. The third ferromagnetic layer 4 is, for example, a laminated film in which Co and Pt are alternately stacked, or a laminated film in which Co and Ni are alternately stacked. The magnetic coupling layer 5 is, for example, Ru, Ir, etc. The thickness of the magnetic coupling layer 5 is, for example, the thickness at which the second ferromagnetic layer 2 and the third ferromagnetic layer 4 are antiferromagnetically coupled by the RKKY interaction.

[0054] 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 M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 in the initial state described later.

[0055] For example, if the spacer layer 3 is made of an insulator, the photodetector 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 photodetector element 10 can exhibit a tunnel magnetoresistance (TMR) effect. For example, if the spacer layer 3 is made of a metal, the photodetector element 10 can exhibit a giant magnetoresistance (GMR) effect. Such an element is called a GMR element. The photodetector element 10 may be called an MTJ element, a GMR element, etc., depending on the constituent material of the spacer layer 3, but it is collectively called a magnetoresistance effect element.

[0056] When the spacer layer 3 is made 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] The underlying layer 6 shown in Figure 5 is, for example, located on the second electrode 16. The underlying layer 6 is either a seed layer or a buffer layer. The seed layer enhances the crystallinity of the layer stacked 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, between 1 nm and 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, between 1 nm and 5 nm.

[0061] The perpendicular magnetization induction layer 7 is formed when the first ferromagnetic layer 1 is a perpendicular magnetization film. The perpendicular magnetization induction layer 7 is laminated on the first ferromagnetic layer 1. The perpendicular magnetization induction layer 7 induces perpendicular magnetic anisotropy in the first ferromagnetic layer 1. The perpendicular magnetization induction layer 7 can be, for example, magnesium oxide, W, Ta, Mo, etc. When the perpendicular magnetization induction layer 7 is magnesium oxide, it is preferable that the magnesium oxide is oxygen-deficient to enhance conductivity. The thickness of the perpendicular magnetization induction layer 7 is, for example, 0.5 nm to 2.0 nm.

[0062] The capping layer 8 is located between the first ferromagnetic layer 1 and the first electrode 15. The capping layer 8 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 8 is, for example, 3 nm or less, so that sufficient light is irradiated onto the first ferromagnetic layer 1.

[0063] The sidewall insulating layer 9 surrounds the laminate containing the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The sidewall insulating layer 9 is made of a material similar to that of the interlayer insulating film 30, for example.

[0064] The first electrode 15 is, for example, transparent to light in the wavelength range used for the optical signal L1. The wavelength range used for the light used for the optical signal L1 is, for example, 300 nm to 2 μm, and includes the visible light range and the near-infrared light range. The first electrode 15 is a transparent electrode containing an oxide transparent electrode material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). The first electrode 15 may have a configuration in which multiple columnar metals are contained within these transparent electrode materials. In this case, the film thickness of the first electrode 15 is, for example, 10 nm to 300 nm. It is not essential to use the above-mentioned transparent electrode material as the first electrode 15; a thin film of a metallic material such as Au, Cu, or Al may be used to allow light from the outside to reach the first ferromagnetic layer 1. When a metal is used as the material for the first electrode 15, the film thickness of the first electrode 15 is, for example, 3 to 10 nm. In particular, Au has a higher transmittance of light with wavelengths near blue than other metallic materials. Furthermore, the first electrode 15 may have an anti-reflective coating on the irradiation surface to which the light is irradiated.

[0065] The second electrode 16 is made of a conductive material. The second electrode 16 is made of a metal such as Cu, Al, or Au. Ta or Ti may be laminated above or 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. TiN or TaN may also be used as the second electrode 16. The film thickness of the second electrode 16 is, for example, 200 nm to 800 nm. The second electrode 16 may be made transparent to light in the wavelength range used for the optical signal L1. As the material for the second electrode 16, similar to the first electrode 15, transparent electrode materials of oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium gallium zinc oxide (IGZO) may be used. Even when light is irradiated from the first electrode 15, depending on the intensity of the light, it may reach the second electrode 16. In this case, because the second electrode 16 is composed of a transparent oxide electrode material, the reflection of light at the interface between the second electrode 16 and the layer in contact with it can be suppressed compared to when the second electrode 16 is composed of metal.

[0066] The photodetector element 10 is manufactured by lamination, annealing, and processing steps for each layer. First, the base layer 6, third ferromagnetic layer 4, magnetic coupling layer 5, second ferromagnetic layer 2, spacer layer 3, first ferromagnetic layer 1, perpendicular magnetization induction layer 7, and cap layer 8 are laminated on the second electrode 16 in that order. Each layer is deposited by, for example, sputtering.

[0067] Next, the multilayer film is annealed. The annealing temperature is, for example, 250°C to 450°C. When the multilayer film is formed on the same substrate as the semiconductor circuit, it is preferable to anneal it at 400°C or higher. After that, the multilayer film is processed into a predetermined columnar shape by photolithography and etching. The columnar shape may be cylindrical or rectangular. For example, the shortest width of the columnar shape when viewed from the z direction may be 10 nm to 2000 nm, or 30 nm to 500 nm.

[0068] Next, an insulating layer is formed to cover the sides of the columnar body. This insulating layer becomes the sidewall insulating layer 9. The sidewall insulating layer 9 may be laminated multiple times. Then, the upper surface of the cap layer 8 is exposed from the sidewall insulating layer 9 by chemical mechanical polishing (CMP), and the first electrode 15 is fabricated on the cap layer 8. The photodetector element 10 is obtained through the above process.

[0069] Next, the operation of the photodetector 10 according to the first embodiment will be described. The first ferromagnetic layer 1 is irradiated with light containing an optical signal L1 having a change in light intensity. A lens may be placed on the side of the first ferromagnetic layer 1 in the stacking direction of the photodetector 10 so that the light focused on the first ferromagnetic layer 1 is irradiated through the lens. The lens may be formed in the wafer process in which the photodetector 10 is formed. The resistance value of the photodetector 10 in the z direction changes when light containing the optical signal L1 is irradiated onto the first ferromagnetic layer 1. An example will be given in which the intensity of the light irradiated onto the first ferromagnetic layer 1 is in two stages, a first intensity and a second intensity. The second intensity is assumed to be greater than the first intensity. The first intensity may be zero even when the intensity of the light irradiated onto the first ferromagnetic layer 1 is zero.

[0070] The operation of the photodetector 10 according to the first embodiment can be in two patterns. The first pattern is when the output voltage from the photodetector 10 is higher in the second intensity case than in the first intensity case. The second pattern is when the output voltage from the photodetector 10 is higher in the first intensity case than in the second intensity case.

[0071] Figures 6 and 7 are diagrams illustrating the operation of the first pattern of the photodetector element 10 according to the first embodiment. Two mechanisms are considered for the operation of the photodetector element 10; Figure 6 is a diagram illustrating the first mechanism, and Figure 7 is a diagram illustrating the second mechanism. 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 photodetector element 10 in the z direction, and the horizontal axis represents time.

[0072] First, in the state where 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 in a parallel relationship, the resistance value of the photodetector element 10 in the z direction is a first resistance value R1, and the magnitude of the output voltage from the photodetector element 10 is a first value. The resistance value of the photodetector element 10 in the z direction can be determined using Ohm's law from the voltage value generated across the z-side of the photodetector element 10 by flowing a sense current Is in the z direction of the photodetector element 10. The output voltage from the photodetector element 10 is generated between the first electrode 15 and the second electrode 16. In the first pattern shown in Figure 6, it is preferable to flow the sense current Is from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. By applying a sense current Is in this direction, a spin transfer torque acts on the magnetization M1 of the first ferromagnetic layer 1 in the same direction as the magnetization M2 of the second ferromagnetic layer 2, causing the magnetizations M1 and M2 to be parallel in the initial state. Furthermore, applying a sense current Is in this direction prevents the magnetization M1 of the first ferromagnetic layer 1 from reversing during operation.

[0073] 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 due to the external energy from the light irradiation. The state of magnetization M1 refers to, for example, the angle of inclination with respect to the z direction, the magnitude, etc. For example, as shown in Figure 6, when the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity to the second intensity, the magnetization M1 tilts with respect to the z direction. The angle between the direction of magnetization M1 of the first ferromagnetic layer 1 when it is not irradiated with light containing the optical signal L1 and the direction of magnetization of the first ferromagnetic layer 1 at the second intensity is greater than 0° and less than 90°. Also, for example, as shown in Figure 7, when the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity to the second intensity, the magnitude of magnetization M1 decreases. When the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state, the resistance value in the z direction of the photodetector 10 exhibits a second resistance value R2, and the magnitude of the output voltage from the photodetector 10 exhibits a second value.

[0074] In other words, when the intensity of light irradiated onto the first ferromagnetic layer 1 changes from a first intensity to a second intensity, the resistance value in the z direction of the photodetector element 10 changes from a first resistance value R1 to a second resistance value R2. To put it another way, in response to the change in the intensity of light irradiated onto the first ferromagnetic layer from a first intensity to a second intensity, the resistance value in the z direction of the photodetector element 10 changes from a first resistance value R1 to a second resistance value R2. The second resistance value R2 is greater than the first resistance value R1, and the second value of the output voltage is greater than the first value. The second resistance value R2 is between the resistance value when magnetization M1 and magnetization M2 are parallel (first resistance value R1) and the resistance value when magnetization M1 and magnetization M2 are antiparallel. It is preferable that the magnetization M1 of the first ferromagnetic layer 1 does not reverse when light containing the optical signal L1 is irradiated onto the first ferromagnetic layer 1.

[0075] 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, as shown in Figure 6, 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 photodetector element 10 returns to its initial state. As shown in Figure 7, 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 photodetector element 10 returns to its initial state. In either case, when magnetization M1 returns to its initial state, the resistance value in the z direction of the photodetector element 10 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 in the z direction of the photodetector element 10 changes from the second resistance value R2 to the first resistance value R1. In other words, in response to the change in the intensity of light irradiated onto the first ferromagnetic layer from the second intensity to the first intensity, the resistance value in the z direction of the photodetector 10 changes from the second resistance value R2 to the first resistance value R1.

[0076] In either mechanism, when the photodetector 10 according to the first embodiment operates in the first pattern, the resistance value of the photodetector 10 in the stacking direction changes in response to changes in the intensity of light irradiated onto the first ferromagnetic layer 1. That is, the output voltage from the photodetector 10 changes in response to changes in the intensity of light irradiated onto the first ferromagnetic layer 1. As a result, the photodetector 10 can convert changes in the intensity of the optical signal L1 into changes in the resistance value of the photodetector 10 in the z direction, i.e., changes in the output voltage from the photodetector 10. In the examples shown in Figures 6 and 7, the resistance value of the photodetector 10 in the stacking direction, i.e., the output voltage from the photodetector 10, is a value corresponding to the intensity of light irradiated onto the first ferromagnetic layer 1. The output voltage signal from the photodetector 10, which represents the resistance value of the photodetector 10 in the z direction, is sent to the signal processing unit 11, and if the output voltage from the photodetector 10 (the resistance value of the photodetector 10 in the z direction) 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"). In other words, the receiving device 100 receives the optical signal L1 based on the output voltage from the photodetector 10 (the resistance value of the photodetector 10 in the z direction).

[0077] Figures 8 and 9 are diagrams illustrating the operation of the second pattern of the photodetector element 10 according to the first embodiment. Figure 8 is a diagram illustrating the first mechanism, and Figure 9 is a diagram illustrating the second mechanism. In the upper graphs of Figures 8 and 9, 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 8 and 9, the vertical axis represents the resistance value of the photodetector element 10 in the z direction, and the horizontal axis represents time.

[0078] The difference between the second pattern and the first pattern is that, in the initial state, the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 are in an antiparallel state, but the operating principle is the same as the first pattern.

[0079] First, when the first ferromagnetic layer 1 is irradiated with light of a first intensity, the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 are antiparallel, the resistance value in the z direction of the photodetector element 10 shows a first resistance value R1', and the magnitude of the output voltage from the photodetector element 10 shows a first value. In the second pattern shown in Figures 8 and 9, 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 opposite to that of 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 antiparallel. In the second pattern, by reversing the direction of the sense current Is compared to the first pattern, the magnetization direction (magnetization stabilization direction) of the first ferromagnetic layer 1 in the initial state is reversed.

[0080] 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. For example, as shown in Figure 8, when the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity to the second intensity, the magnetization M1 tilts with respect to the z direction. Also, for example, as shown in Figure 9, when the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity to the second intensity, the magnitude of the magnetization M1 decreases. When the magnetization M1 of the first ferromagnetic layer 1 changes, the resistance value of the photodetector element 10 in the z direction shows the second resistance value R2', and the magnitude of the output voltage from the photodetector element 10 shows the first value. In other words, when the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity to the second intensity, the resistance value of the photodetector element 10 in the z direction changes from the first resistance value R1' to the second resistance value R2'. In other words, in response to the change in the intensity of light irradiated onto the first ferromagnetic layer from the first intensity to the second intensity, the resistance value in the z direction of the photodetector 10 changes from the first resistance value R1' to the second resistance value R2'. The second resistance value R2' is smaller than the first resistance value R1', and the second value of the output voltage is smaller than the first value. The second resistance value R2' is between the resistance value when magnetization M1 and magnetization M2 are antiparallel (first resistance value R1') and the resistance value when magnetization M1 and magnetization M2 are parallel (first resistance value R1 in Figure 6).

[0081] A spin transfer torque acting on the magnetization M1 of the first ferromagnetic layer 1 is opposite to that acting on the magnetization M2 of the second ferromagnetic layer 2. Therefore, as shown in Figure 8, the magnetization M1, which is tilted from the initial state, returns to the initial state when the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the second intensity to the first intensity. As shown in Figure 9, when the intensity of the 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 photodetector element 10 returns to its initial state. When the magnetization M1 returns to its initial state, the resistance value in the z direction of the photodetector element 10 returns to the first resistance value R1'. In other words, when the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the second intensity to the first intensity, the resistance value in the z direction of the photodetector element 10 changes from the second resistance value R2' to the first resistance value R1'. In other words, in response to the change in the intensity of light irradiated onto the first ferromagnetic layer from the second intensity to the first intensity, the resistance value in the z direction of the photodetector 10 changes from the second resistance value R2' to the first resistance value R1'.

[0082] In either mechanism, when the photodetector 10 according to the first embodiment operates in the second pattern, the resistance value of the photodetector 10 in the stacking direction changes in response to the change in the intensity of light irradiated onto the first ferromagnetic layer 1. That is, the output voltage from the photodetector 10 changes in response to the change in the intensity of light irradiated onto the first ferromagnetic layer 1. As a result, the photodetector 10 can convert the change in the intensity of the optical signal L1 into a change in the resistance value in the z direction of the photodetector 10, i.e., a change in the output voltage from the photodetector 10. In the examples shown in Figures 8 and 9, the resistance value of the photodetector 10 in the stacking direction, i.e., the output voltage from the photodetector 10, is a value corresponding to the intensity of light irradiated onto the first ferromagnetic layer 1. The output voltage signal from the photodetector 10, which represents the resistance value in the z direction of the photodetector 10, is sent to the signal processing unit 11, and if the output voltage from the photodetector 10 (the resistance value in the z direction of the photodetector 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"). In other words, the receiving device 100 receives the optical signal L1 based on the output voltage from the photodetector 10 (the resistance value of the photodetector 10 in the z direction).

[0083] In this way, by applying a bias to the magnetization M1 of the first ferromagnetic layer 1 that acts to orient the magnetization M1 in a direction either parallel or antiparallel to the direction of the magnetization M2, the resistance value of the photodetector 10, i.e., the output voltage from the photodetector 10, can be changed in response to changes in the intensity of light irradiated onto the first ferromagnetic layer 1. In the first and second pattern examples described above, the effect of applying spin transfer torque due to the sense current Is is used as the bias application effect. The bias application effect is not limited to the effect of applying spin transfer torque due to the sense current Is; for example, other bias application effects such as those shown in the second to fourth modified examples described later may also be used.

[0084] Here, the orientation directions of magnetization M1 and magnetization M2 in the initial state may not be aligned in the correct direction due to external factors such as an external magnetic field or heat. Therefore, a reset current may be applied in the z direction of the photodetector 10 before operating the photodetector 10 according to the first embodiment.

[0085] The reset current is a current with a current density sufficient to sufficiently reverse the magnetization M1 of the first ferromagnetic layer 1. In the first pattern, the reset current flows from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. In the second pattern, the reset current flows from the second ferromagnetic layer 2 to the first ferromagnetic layer 1. When the reset current flows in the z direction of the photodetector element 10, a spin transfer torque (STT) is applied to the magnetization M1, and the magnetization M1 of the first ferromagnetic layer 1 is oriented in the correct direction. In each pattern, the value of the reset current is greater than the value of the sense current.

[0086] Up to this point, we have described the case in which the light irradiated onto the first ferromagnetic layer 1 has two intensity levels, a first intensity and a second intensity. However, the photodetector 10 according to the first embodiment can also read out multi-level information from the optical signal L1 by increasing the intensity of the light irradiated onto the first ferromagnetic layer 1 to more than two levels.

[0087] Figures 10 and 11 show the behavior of the photodetector 10 when outputting multiple values ​​using the photodetector 10 according to the first embodiment. Figure 10 is a diagram for explaining the first mechanism, and Figure 11 is a diagram for explaining the second mechanism. Figures 10 and 11 show, from left to right, the magnetization state and the resistance value in the z direction of the photodetector 10 at the first intensity, second intensity, third intensity, and fourth intensity, respectively. The intensity of the light irradiated onto the first ferromagnetic layer 1 increases in the order of fourth intensity, third intensity, second intensity, and first intensity. The first intensity may be zero when the intensity of the irradiated light is zero.

[0088] As shown in Figure 10, when the magnetization M1 tilts according to the intensity of the irradiated light, the angular change of magnetization M1 from its initial state increases as the intensity of the light irradiated onto the first ferromagnetic layer 1 increases. The angle between the direction of magnetization M1 of the first ferromagnetic layer 1 when it is not irradiated with light containing the optical signal L1 and the direction of magnetization M1 at the second, third, and fourth intensities is greater than 0° and less than 90°. The change in the z-direction resistance of the photodetector element 10 relative to its initial state increases as the angular change of magnetization M1 from its initial state increases. In the example shown in Figure 10, the z-direction resistance of the photodetector element 10 increases as the angular change of magnetization M1 from its initial state increases. Therefore, the z-direction resistance of the photodetector element 10 differs for the first, second, third, and fourth intensities. The photodetector 10 according to the first embodiment can read out information for four values, for example, "0", "1", "2", and "3", by defining the output voltage threshold (resistance threshold) in multiple stages. Here, as an example, the case of reading out four values ​​is shown, but the number of values ​​to be read can be freely designed by setting the output voltage threshold (resistance threshold). It is preferable that the magnetization M1 of the first ferromagnetic layer 1 is not reversed by irradiation of the first ferromagnetic layer 1 with light containing the optical signal L1.

[0089] Similarly, in the case of Figure 11, 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 photodetector 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 photodetector element 10 changes to the second resistance value R2, the third resistance value R3, and the fourth resistance value R4. Therefore, as in the case of Figure 10, the difference in output voltage from the photodetector element 10 can be output as multi-level or analog data.

[0090] Furthermore, although the example given here is that magnetizations M1 and M2 are parallel in the initial state, magnetizations M1 and M2 may be antiparallel in the initial state. Similar to Figure 10, when magnetization M1 tilts according to the intensity of the irradiated light, the resistance value in the z direction of the photodetector element 10 decreases as the angular change of magnetization M1 from its initial state increases.

[0091] Next, the operation when an abnormality occurs in the photodetector 10 will be described. Figure 12 shows the behavior of the photodetector 10 when an abnormality occurs in the photodetector 10 according to the first embodiment. In the upper graph of Figure 12, the vertical axis is the intensity of light irradiated onto the first ferromagnetic layer 1, and the horizontal axis is time. In the lower graph of Figure 12, the vertical axis is the resistance value of the photodetector 10 in the z direction, and the horizontal axis is time.

[0092] Figure 12 shows an example of an abnormality that occurs when the photodetector 10 is operating in the first pattern. One example of an abnormality is when the intensity of a portion of the optical signal L1 irradiated onto the first ferromagnetic layer 1 becomes abnormally strong. The abnormality is not limited to cases where the light intensity becomes excessive; for example, it may also be caused by changes in operating temperature or changes in the intensity of the applied external magnetic field. When the operating temperature or external magnetic field changes, the stability of the magnetization M1 also changes.

[0093] When the photodetector 10 operates normally in the first pattern, the resistance value of the photodetector 10 in the z direction changes between the first resistance value R1 and the second resistance value R2. On the other hand, if excessive light is shone on the first ferromagnetic layer 1, the magnetization M1 may tilt significantly from its initial state, and the magnetization M1 may even reverse. In this case, the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 become antiparallel, and the resistance value becomes the third resistance value R3 (the same as the first resistance value R1' in the second pattern). The third resistance value R3 is greater than the first resistance value R1 and the second resistance value R2, and an abnormality is detected.

[0094] If an abnormality occurs in the photodetector element 10, the reset current described above is applied. By applying the reset current, the magnetization M1 of the first ferromagnetic layer 1 returns to the correct direction, and the photodetector element 10 can be used normally again. Here, the first mechanism has been explained, but the same principle applies to the second mechanism. In the case of the second mechanism, if the first ferromagnetic layer 1 is irradiated with excessive light, the magnetization M1 may decrease significantly from its initial state, and the magnetization M1 may even reverse.

[0095] As described above, the transmitting / receiving device 300 and receiving device 100 according to the first embodiment receive an optical signal based on the output voltage from the photodetector 10 (the resistance value of the photodetector 10). Furthermore, the photodetector 10 according to the first embodiment can convert changes in the intensity of the optical signal L1 into changes in the output voltage from the photodetector 10 (changes in the resistance value of the photodetector 10 in the z direction), enabling high-speed communication.

[0096] Furthermore, as mentioned above, the magnetization M1 of the first ferromagnetic layer 1 is more easily tilted as the volume of the first ferromagnetic layer 1 decreases. In other words, by reducing the volume of the first ferromagnetic layer 1, even a small amount of light can tilt the magnetization M1. That is, the photodetector element 10 according to the first embodiment can receive the optical signal L1 with high sensitivity.

[0097] More precisely, the ease with which the magnetization M1 tilts is determined by the magnitude of the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 1. The smaller the KuV, the easier it is for the magnetization to tilt with a smaller amount of light, and the larger the KuV, the more light is required for the magnetization to tilt. In other words, the KuV of the first ferromagnetic layer 1 is designed according to the amount of light irradiated from the outside used in the application. When considering extremely minute amounts of light, such as photon detection, it is possible to detect these minute amounts of light by reducing the KuV of the first ferromagnetic layer. Detecting such minute amounts of light is not possible with conventional photodetectors, making this a significant advantage. In other words, photon detection becomes possible by reducing the volume of the first ferromagnetic layer 1, i.e., reducing the element area, or by thinning the film thickness of the first ferromagnetic layer 1, in order to reduce KuV.

[0098] Furthermore, the photodetector 10 according to the first embodiment can receive the optical signal L1 regardless of the wavelength range of the irradiated light. For semiconductor photodetectors utilizing pn junctions, the appropriate semiconductor material differs depending on the wavelength of the irradiated light. For example, InGaAs is used for detecting near-infrared light with a wavelength of 1.3 μm to 1.5 μm. For example, silicon is used for detecting visible light with a wavelength of 400 nm to 800 nm.

[0099] Figure 13 shows the simulation results of the sensitivity of the photodetector 10 (Example) according to the first embodiment when the wavelength of the irradiated light is 1.5 μm (near-infrared light), and a curve representing the characteristic level of a conventional semiconductor photodiode using InGaAs (Comparative Example 1) (approximate curve of sensitivity data from multiple known examples). Figure 14 shows the simulation results of the sensitivity of the photodetector 10 (Example) according to the first embodiment when the wavelength of the irradiated light is 520 nm (visible light), and a curve representing the characteristic level of a conventional semiconductor photodiode using silicon (Comparative Example 2) (approximate curve of sensitivity data from multiple known examples).

[0100] The simulation conditions for the example were set as follows. The light detection element 10 has a square planar shape, with a side length of 200 nm and a sheet resistance (RA) of 5Ωμm 2 , and the magnetoresistance change rate (MR change rate) is set to 65%. The second ferromagnetic layer 2 (magnetization fixed layer) is an alloy layer containing CoFeB with a thickness of 2 nm, the spacer layer 3 is made of MgO, and the first ferromagnetic layer 1 is an alloy layer containing CoFeB with a thickness of 1.2 nm. The spot diameter of light irradiated onto the light detection element 10 is set to 900 nmφ. The sensitivity on the vertical axis of the graph is the output current amount per unit light irradiation amount. In the example, the output current amount was converted by dividing the output voltage, which is the potential difference between the first electrode 15 and the second electrode 16, by the minimum resistance value of the light detection element 10 (in the case of the first mechanism, the resistance value when the magnetization M1 and the magnetization M2 are in a parallel state).

[0101] Considering practical constraints (intensity of optical signals, matching with peripheral circuits), a sensitivity of 0.5 A / W or more is often required. As shown in FIG. 13, even Comparative Example 1 using InGaAs suitable for near-infrared light cannot receive high-speed optical signals exceeding 40 GHz with high sensitivity. In contrast, the light detection element 10 according to the example can receive even high-speed signals exceeding 100 GHz with high sensitivity. Further, as shown in FIG. 14, even Comparative Example 2 using silicon suitable for visible light can only receive optical signals of less than 3 GHz with high sensitivity, and cannot cope with high-speed signals. In contrast, the light detection element 10 according to the example can receive even high-speed signals exceeding 100 GHz with high sensitivity, similarly to the case of near-infrared light.

[0102] That is, the light detection element 10 according to the first embodiment can receive high-speed optical signals with high sensitivity regardless of whether they are visible light or near-infrared light. Although examples of visible light and near-infrared light are shown here, the present invention is not limited to these examples. For example, the light detection element 10 can also achieve high-speed response similarly to ultraviolet light with a wavelength of 200 nm or more and less than 400 nm.

[0103] The first embodiment has been described in detail above with reference to the drawings, but the first embodiment is not limited to this example.

[0104] (First Modification) Figure 15 is a circuit diagram of the transceiver 301 according to the first modified example. The transceiver 301 according to the first modified example differs from the transceiver 300 in that the receiving device 101 has an analog-to-digital converter (AD). Components identical to those in Figure 3 are denoted by the same reference numerals and their descriptions are omitted.

[0105] The analog-to-digital converter (AD) has a first electrode 15 and an output terminal P out It lies between the two. The analog-to-digital converter (AD) converts the output voltage from the photodetector 10 (the resistance value in the z direction of the photodetector 10) into digital data. In other words, the transmitting and receiving device 301 according to the first modified example is less susceptible to noise and the like. The transmitting and receiving device 301 according to the first modified example can be used particularly suitably when the photodetector 10 outputs multiple values.

[0106] (Second variation) Figure 16 is a cross-sectional view of the photodetector element and its periphery according to the second modified example, cut along the z-direction. Figure 17 is a cross-sectional view of the photodetector element and its periphery according to the second modified example, cut along the xy-plane passing through the first ferromagnetic layer 1. The receiving device according to the second modified example further includes a hard bias layer 40 for applying a bias magnetic field to the first ferromagnetic layer 1. Components identical to those in Figure 5 are denoted by the same reference numerals and their descriptions are omitted.

[0107] The hard bias layer 40 is positioned to overlap with the first ferromagnetic layer 1 when viewed from any direction perpendicular to the z-direction. A sidewall insulating layer 9 is located between the hard bias layer 40 and the first ferromagnetic layer 1. As shown in Figure 17, the hard bias layer 40 surrounds, for example, the first ferromagnetic layer 1. There may be multiple hard bias layers 40, for example, sandwiching the first ferromagnetic layer 1 in either direction within the xy-plane.

[0108] The hard bias layer 40 is a hard magnetic material. The hard bias layer 40 is, for example, a CoPt alloy, a CoPtCr alloy, an FePt alloy, or a laminated film in which Co layers and Pt layers are alternately stacked. The thickness of the hard bias layer 40 is, for example, 2 nm to 30 nm. The shortest width of the hard bias layer 40 in the xy plane is, for example, 10 nm to 500 nm.

[0109] The hard bias layer 40 has an easy magnetization axis in the same direction as the first ferromagnetic layer 1. The magnetization direction of the magnetization M40 of the hard bias layer 40 is opposite to the magnetization direction of the magnetization M1 of the first ferromagnetic layer 1 when no light is irradiated. The hard bias layer 40 may be an in-plane magnetized film or a perpendicular magnetized film.

[0110] The leakage magnetic field generated from the hard bias layer 40 acts on the magnetization M1 as a bias magnetic field applied to the first ferromagnetic layer 1. In the first pattern described above, magnetization M1 and magnetization M2 are parallel in the initial state, while in the second pattern described above, magnetization M1 and magnetization M2 are antiparallel in the initial state. Furthermore, the leakage magnetic field generated from the hard bias layer 40 prevents the magnetization M1 of the first ferromagnetic layer 1 from reversing during operation. In other words, the application of the leakage magnetic field generated from the hard bias layer 40 to the first ferromagnetic layer 1 produces a biasing effect on the magnetization M1 of the first ferromagnetic layer 1.

[0111] (Third variation) Figure 18 is a cross-sectional view of a photodetector element according to the third modified example, cut along a plane in the z-direction. The photodetector element according to the third modified example further comprises a wiring layer 50. Components identical to those in Figure 5 are denoted by the same reference numerals and their descriptions are omitted.

[0112] The wiring layer 50 is located between the first electrode 15 and the first ferromagnetic layer 1. The wiring layer 50 extends in either direction within the xy plane.

[0113] When current flows along the wiring layer 50, a spin current is generated by the spin Hall effect, and spins are injected into the first ferromagnetic layer 1. The spins injected into the first ferromagnetic layer 1 add a spin-orbit torque (SOT) to the magnetization M1 of the first ferromagnetic layer 1.

[0114] The wiring layer 50 contains, for example, a non-magnetic heavy metal as the main element. The main element is the element that makes up the highest proportion of the elements constituting the wiring layer 50. The wiring layer 50 contains, for example, a heavy metal with a specific gravity greater than or equal to yttrium (Y). Non-magnetic heavy metals have a large atomic number of 39 or higher and have d or f electrons in their outermost shell, resulting in strong spin-orbit interaction. The wiring layer 50 contains, for example, any element selected from the group consisting of Pt, W, Ta, Au, Hf, and Mo. In particular, Pt, W, and Ta are more preferred elements. For W and Ta, it is preferable to use a β-phase crystal structure to increase the spin-orbit interaction effect. The film thickness of the wiring layer 50 is preferably 1 to 10 nm, and more preferably 1 to 5 nm.

[0115] By passing an electric current through the wiring layer 50, spins are injected from the wiring layer 50 into the first ferromagnetic layer 1, resulting in a biasing effect on the magnetization M1 of the first ferromagnetic layer 1. By changing the direction of the current flowing through the wiring layer 50, the direction of the spins injected from the wiring layer 50 into the first ferromagnetic layer 1 can be changed, thereby changing the direction of the magnetization M1 of the first ferromagnetic layer 1 in its initial state (the magnetization stability direction of magnetization M1). Depending on the direction of the spins injected from the wiring layer 50 into the first ferromagnetic layer 1, in the first pattern described above, magnetization M1 and magnetization M2 can be controlled to be parallel in the initial state, and in the second pattern described above, magnetization M1 and magnetization M2 can be controlled to be antiparallel in the initial state. In addition, the spins injected from the wiring layer 50 into the first ferromagnetic layer 1 prevent the magnetization M1 of the first ferromagnetic layer 1 from reversing during operation. The direction of the spins injected from the wiring layer 50 into the first ferromagnetic layer 1 can be freely controlled by the direction of the current flowing along the wiring layer 50.

[0116] (Fourth variation) Figure 19 is a cross-sectional view of the receiving device 102 according to the fourth modified example, taken from a plane along the z-direction. Figure 20 is a plan view of the receiving device 102 according to the fourth modified example, taken from the z-direction. The receiving device 102 according to the fourth modified example further comprises a soft magnetic body 60. Components identical to those in Figure 4 are denoted by the same reference numerals and their descriptions are omitted.

[0117] The soft magnetic material 60 is a magnetic shield. In a plan view from the z direction, the soft magnetic material 60 covers at least a portion of the outer periphery of the photodetector element 10 from the outside. When viewed from any direction in the xy plane, the soft magnetic material 60 overlaps with at least a portion of the first ferromagnetic layer 1. For example, in a plan view from the z direction of the photodetector element, the soft magnetic material 60 covers the entire outer periphery of the photodetector element 10. When viewed from any direction in the xy plane, the soft magnetic material 60 overlaps with the entire outer periphery of the first ferromagnetic layer 1 in the z direction.

[0118] The soft magnetic material 60 is, for example, a metal or alloy containing at least one of Fe, Ni, and Co. The soft magnetic material 60 is, for example, a NiFe alloy. The soft magnetic material 60 may also be an insulating magnetic material. The soft magnetic material 60 is, for example, a ceramic such as ferrite. The soft magnetic material 60 is, for example, rare earth iron garnet (RIG). Yttrium iron garnet (YIG) is an example of rare earth iron garnet (RIG).

[0119] The soft magnetic material 60 can suppress the application of an external magnetic field to the first ferromagnetic layer 1, thereby preventing the first ferromagnetic layer 1 from exhibiting unexpected behavior.

[0120] (Fifth variation) Figure 21 is a cross-sectional view of the receiving device 103 according to the fifth modified example, taken from a plane along the z-direction. Figure 22 is a plan view of the receiving device 103 according to the fifth modified example, taken from the z-direction. The receiving device 103 according to the fifth modified example further comprises a soft magnetic material 61. Components identical to those in Figure 4 are denoted by the same reference numerals and their descriptions are omitted.

[0121] The soft magnetic material 61 is a magnetic shield. The soft magnetic material 61 differs from the soft magnetic material 60 in that it is also located above and below the photodetector element 10. The soft magnetic material 61 surrounds the photodetector element 10, except for the aperture 62. The soft magnetic material 61 can be made of the same material as the soft magnetic material 60.

[0122] The soft magnetic material 61 has an opening 62 on its upper side, which is the side where light is incident on the photodetector 10. The opening 62 is formed on the side of the soft magnetic material 61 that is above and below the photodetector 10, on the side of the first ferromagnetic layer 1. The opening 62 has a mesh-like magnetic network 63 connected to the soft magnetic material 61. The magnetic network 63 contains a magnetic material, for example, a material similar to that of the soft magnetic material 61.

[0123] The wiring connected to the first electrode 15 and the second electrode 16 is connected to external contacts provided outside the soft magnetic material 61, with an insulating layer 64 in between.

[0124] By providing soft magnetic materials 61 above and below the photodetector element 10, the magnetic shielding effect is further enhanced. Furthermore, by providing an aperture 62 in the soft magnetic material 61, light containing the optical signal L1 can be efficiently irradiated onto the first ferromagnetic layer 1. In addition, by providing a magnetic mesh 63 in the aperture 62, the intrusion of an external magnetic field from the aperture 62 can be suppressed.

[0125] (Sixth variation) Figure 23 is a cross-sectional view of the receiving device 104 according to the sixth modified example. Components identical to those in Figure 4 are denoted by the same reference numerals and their descriptions are omitted.

[0126] In the sixth modified example, the receiving device 104 has a photodetector 10 formed on a substrate Sb. In the sixth modified example, the integrated circuit 20 may be formed in the peripheral area of ​​the substrate Sb where the photodetector 10 is not formed, or it may be formed outside the substrate. The integrated circuit 20 is connected to the photodetector 10 via wiring.

[0127] "Second Embodiment" The receiving device according to the second embodiment differs from the receiving device 100 according to the first embodiment in the operation of the photodetector element. The element configuration of the receiving device according to the second embodiment is the same as that of the receiving device according to the first embodiment.

[0128] Figure 24 is a diagram illustrating the operation of the receiving device according to the second embodiment. In the receiving device according to the second embodiment, a change in the output voltage from the photodetector 10 (the resistance value in the z direction of the photodetector 10) within a predetermined time is treated as a first signal (e.g., "1"), and no change in the output voltage from the photodetector 10 (the resistance value in the z direction of the photodetector 10) within a predetermined time is treated as a second signal (e.g., "0"). The predetermined time is determined by the modulation frequency of the optical signal.

[0129] The operation of the receiving device according to the second embodiment will be specifically described below based on the example shown in Figure 24. First, the optical signal irradiated onto the photodetector 10 is defined. The optical signal is defined as "1" when the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from a first intensity to a second intensity, and as "0" when the intensity of the light irradiated onto the first ferromagnetic layer 1 is maintained at the first intensity for a predetermined period of time. The intensity of the light that has changed from the first intensity to the second intensity returns to the first intensity after a certain period of time has elapsed.

[0130] The optical signal is irradiated onto the first ferromagnetic layer 1 of the photodetector 10. When the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity to the second intensity, the magnetization M1 of the first ferromagnetic layer 1 reverses. However, when the intensity of the light irradiated onto the first ferromagnetic layer 1 returns from the second intensity to the first intensity, the magnetization M1 of the first ferromagnetic layer 1 does not reverse. The resistance value in the z direction of the photodetector decreases when the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity to the second intensity. L From high resistance R H or high resistance R H From low resistance R LThe resistance of the photodetector 10, i.e., the output voltage from the photodetector 10, changes regardless of whether the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 are parallel or antiparallel. In other words, when the information "1" is input as an optical signal, the output voltage from the photodetector 10 (the resistance of the photodetector 10) changes. By defining a change in the output voltage from the photodetector 10 (the resistance of the photodetector 10 in the z direction) within a predetermined time as "1", the receiving device according to the second embodiment can receive the optical signal of "1" as a signal of "1" based on the output voltage from the photodetector 10 (the resistance of the photodetector 10).

[0131] In contrast, if the first ferromagnetic layer 1 of the photodetector 10 is not irradiated with light or if the intensity of the irradiated light is low, the magnetization M1 of the first ferromagnetic layer 1 maintains that state. Therefore, if the intensity of the light irradiated onto the first ferromagnetic layer 1 is maintained at the first intensity for a predetermined period of time, the resistance value in the z direction of the photodetector 10, i.e., the output voltage from the photodetector 10, does not change. That is, when the information "0" is input as an optical signal, the output voltage from the photodetector 10 (the resistance value of the photodetector) does not change. By defining the absence of change in the output voltage from the photodetector 10 (the resistance value in the z direction of the photodetector 10) within a predetermined time as "0", the receiving device according to the second embodiment can receive the optical signal of "0" as a signal of "0" based on the output voltage from the photodetector 10 (the resistance value of the photodetector 10).

[0132] As described above, the receiving device according to the second embodiment can receive an optical signal as the presence or absence of a change in output voltage from the photodetector 10 (a change in the resistance value in the z direction of the photodetector) within a predetermined time. Furthermore, the photodetector according to the second embodiment detects the change in resistance between the cases where the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 are parallel and the cases where they are antiparallel, and the amount of change in output voltage is large.

[0133] In the second embodiment, the direction of the sense current flowing through the photodetector may be either from the first ferromagnetic layer 1 to the second ferromagnetic layer 2, or from the second ferromagnetic layer 2 to the first ferromagnetic layer 1. In the third embodiment, it is preferable that the value of the sense current be small so that the spin transfer torque due to the sense current does not become too large. Also, in the second embodiment, it is not necessary to apply a reset current, as it is not important whether the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 are parallel or antiparallel in the initial state.

[0134] Although the second embodiment has been described in detail above with reference to the drawings, the second embodiment is not limited to this example. For example, the first, fourth, fifth, and sixth modifications shown in the first embodiment can be applied.

[0135] Furthermore, while the first and second embodiments have been used as examples to illustrate how the transmitting and receiving device can be applied to the communication system 1000 shown in Figure 1, the communication system is not limited to these cases.

[0136] For example, Figure 25 is a conceptual diagram of another example of a communication system. The communication system 1001 shown in Figure 25 is communication between two mobile terminal devices 500. The mobile terminal devices 500 are, for example, smartphones, tablets, etc.

[0137] Each of the mobile terminal devices 500 includes a receiving device 100 and a transmitting device 200. An optical signal transmitted from the transmitting device 200 of one mobile terminal device 500 is received by the receiving device 100 of the other mobile terminal device 500. The light used for transmission and reception between the mobile terminal devices 500 is, for example, visible light. Either the optical sensing element 10 of the first embodiment or the optical sensing element of the second embodiment is applied to each receiving device 100.

[0138] For example, Figure 26 is a conceptual diagram of another example of a communication system. The communication system 1002 shown in Figure 26 is communication between a mobile terminal device 500 and an information processing device 600. The information processing device 600 is, for example, a personal computer.

[0139] The mobile terminal device 500 includes a transmitting device 200, and the information processing device 600 includes a receiving device 100. The optical signal transmitted from the transmitting device 200 of the mobile terminal device 500 is received by the receiving device 100 of the information processing device 600. The light used for transmission and reception between the mobile terminal device 500 and the information processing device 600 is, for example, visible light. Any of the optical sensing elements according to the first to third embodiments can be used as the optical sensing element 10 of each receiving device 100.

[0140] The present invention is not limited to the embodiments and modifications described above, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims. [Explanation of Symbols]

[0141] 1...First ferromagnetic layer, 2...Second ferromagnetic layer, 3...Spacer layer, 4...Third ferromagnetic layer, 5...Magnetic coupling layer, 6...Underlayment layer, 7...Perpendicular magnetization induction layer, 8...Cap layer, 9...Sidewall insulating layer, 10...Photodetector element, 11...Signal processing unit, 15...First electrode, 16...Second electrode, 20...Integrated circuit, 30...Interlayer insulating film, 40...Hard bias layer, 50...Wiring layer, 60,61...Soft magnetic material, 62...Aperture, 63...Magnetic network, 64...Insulating layer 100, 101, 102, 103… Receiving device, 200… Transmitting device, 201… Light source, 202… Electrical signal generating element, 203… Optical modulation element, 300, 301… Transceiver / receiver device, 500… Mobile terminal device, 600… Information processing device, 1000, 1001, 1002… Communication system, AD… Analog-to-digital converter, FB… Fiber, G… Ground, Is… Sense current, M1, M2, M40… Magnetization, P G ...Reference potential terminal, P in ...input terminal, P out ...Output terminal, PS...Power supply, w...Pass-through wiring

Claims

1. The magnetic element comprises a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. Light containing an optical signal having a change in light intensity is irradiated onto the first ferromagnetic layer. The optical signal is received based on the output voltage from the magnetic element. A photodetector in which the magnetization of the first ferromagnetic layer when the first ferromagnetic layer is irradiated with light is smaller than the magnetization of the first ferromagnetic layer when the first ferromagnetic layer is not irradiated with light.

2. The magnetic element comprises a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. The spacer layer is composed of a layer made of a conductor, an insulator, or a layer containing a current-carrying point made of a conductor within the insulator. Light containing an optical signal having a change in light intensity is irradiated onto the first ferromagnetic layer. The change in the light intensity of the aforementioned optical signal is received based on the output voltage from the magnetic element. When the output voltage from the magnetic element is above a threshold, it is considered the first signal, and when it is below the threshold, it is considered the second signal. A light-detecting element that processes signals.

3. It comprises a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer. The output voltage changes based on the intensity of the light irradiated onto the first ferromagnetic layer. A photodetector in which the magnetization of the first ferromagnetic layer when the first ferromagnetic layer is irradiated with light is smaller than the magnetization of the first ferromagnetic layer when the first ferromagnetic layer is not irradiated with light.

4. The device comprises a laminated film including a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first and second ferromagnetic layers, and a hard bias layer for applying a bias magnetic field to the first ferromagnetic layer. The spacer layer is composed of a layer made of a conductor, an insulator, or a layer containing a current-carrying point made of a conductor within the insulator. The laminated film is configured to convert the intensity of light irradiated onto the first ferromagnetic layer into an output voltage from the laminated film based on that intensity. The hard bias layer is located in a position that overlaps with the laminated film when viewed from any direction perpendicular to the lamination direction. A photodetector in which the magnetization direction of the hard bias layer is opposite to the magnetization direction of the first ferromagnetic layer when the light is not irradiated.

5. A first ferromagnetic layer, a second ferromagnetic layer, and sandwiched between the first ferromagnetic layer and the second ferromagnetic layer A spacer layer and a laminated film including, Equipped with a soft magnetic material, The laminated film is configured to convert the intensity of light irradiated onto the first ferromagnetic layer into an output voltage from the laminated film based on that intensity. The spacer layer is composed of a layer made of a conductor, an insulator, or a layer containing a current-carrying point made of a conductor within the insulator. The soft magnetic material covers at least a portion of the outer periphery of the laminated film from the outside in a plan view from the lamination direction of the laminated film, and is a photodetector element.

6. A laminated film comprising a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first and second ferromagnetic layers, Equipped with an integrated circuit, The laminated film is configured to convert the intensity of light irradiated onto the first ferromagnetic layer into an output voltage from the laminated film based on that intensity. The spacer layer is composed of a layer made of a conductor, an insulator, or a layer containing a current-carrying point made of a conductor within the insulator. The integrated circuit and the laminated film are formed on the same substrate with an interlayer insulating film in between. A photodetector in which the integrated circuit and the multilayer film are connected via through-wiring that penetrates the interlayer insulating film.

7. A receiving device comprising a photodetector element according to any one of claims 1 to 6.

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