Receiving device, transmitting and receiving device, communication system, portable terminal device, and light detecting element

Abstract

A reception device of the present application is provided with a magnetic element provided with a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched by the first ferromagnetic layer and the second ferromagnetic layer, light containing a light signal having a light intensity variation is irradiated to the first ferromagnetic layer, and the light signal is received based on an output voltage from the magnetic element.

Description

Technical Field

[0001] This invention relates to receiving devices, transmitting and receiving devices, communication systems, portable terminal devices, and optical detection elements. Background Technology

[0002] With the widespread adoption of the internet, communication volume has increased dramatically, making optical communication extremely important. Optical communication is a communication unit 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, for example, is a pn-junction diode that uses a semiconductor pn-junction.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2001-292107 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] With the development of information and communication technology, there is a demand for further increases in communication speed. In optical communication, to achieve high-speed communication, the frequency of signal modulation needs to be increased to a higher frequency. In the semiconductor photodiode shown in Patent Document 1, there is a problem that the receiving sensitivity decreases significantly with the increase in frequency, requiring new breakthroughs for further development.

[0009] The present invention was made in view of the above-mentioned problems, and its object is to provide a new receiving device, receiving system, transmitting and receiving device, communication system and optical detection element, and to provide a receiving device, receiving system, transmitting and receiving device, communication system and optical detection element capable of high-speed communication.

[0010] Methods for solving problems

[0011] To address the aforementioned issues, the following methods are provided.

[0012] (1) The receiving device of the first method 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 includes light containing an optical signal having a light intensity variation, which is irradiated onto the first ferromagnetic layer, and the optical signal is received based on the output voltage from the magnetic element.

[0013] (2) The receiving device described above may also be configured such that the output voltage from the magnetic element changes in accordance with the change in the intensity of the light irradiated onto the first ferromagnetic layer.

[0014] (3) In the receiving device described above, the magnetization direction of the first ferromagnetic layer when the first ferromagnetic layer is not irradiated with the light may be greater than 0° and less than 90° from the magnetization direction of the first ferromagnetic layer when the light is irradiated with the first ferromagnetic layer.

[0015] (4) The receiving device described above may also be configured such that the optical signal has at least two levels of intensity, the magnitude of the output voltage from the magnetic element, displays a first value when the intensity of the light irradiating the first ferromagnetic layer is a first intensity, displays a second value when the intensity of the light irradiating the first ferromagnetic layer is a second intensity, and when the second intensity is greater than the first intensity, and when the second value is greater than the first value: current flows from the first ferromagnetic layer to the second ferromagnetic layer, and when the second value is less than the first value, current flows from the second ferromagnetic layer to the first ferromagnetic layer.

[0016] (5) The receiving device described above may also include a hard bias layer that applies a bias magnetic field to the first ferromagnetic layer. When viewed from any direction orthogonal to the stacking direction of the magnetic element, the hard bias layer is located at a position overlapping the first ferromagnetic layer, and the magnetization direction of the hard bias layer is opposite to the magnetization direction of the first ferromagnetic layer in the state where the light is not irradiated.

[0017] (6) In the receiving device described above, the magnetic element may also include a first electrode connected to the first ferromagnetic layer and a second electrode connected to the second ferromagnetic layer, wherein the first electrode is transmissive to light in the wavelength range of the optical signal.

[0018] (7) The receiving device described above may also include a soft magnetic body, which covers at least a portion of the outer periphery of the magnetic element when viewed from the stacking direction of the magnetic element.

[0019] (8) In the receiving device described above, the soft magnetic body may also be located above and below the stacking direction of the magnetic element, and the soft magnetic body located above and below the magnetic element on the side of the first ferromagnetic layer has an opening.

[0020] (9) In the receiving device described above, the opening may also have a mesh-like magnetic mesh connected to the soft magnetic body.

[0021] (10) In the receiving device described above, the case where the output voltage from the magnetic element is above a threshold can be used as the first signal, and the case where it is below the threshold can be used as the second signal.

[0022] (11) In the receiving device described above, the change of the output voltage from the magnetic element within a specified time period may be used as a first signal, and the unchanged output voltage from the magnetic element within a specified time period may be used as a second signal for processing.

[0023] (12) The receiving device described above may also include an integrated circuit, wherein the magnetic element and the integrated circuit are formed on the same substrate via an interlayer insulating film, and the integrated circuit and the magnetic element are connected via a through wiring through the interlayer insulating film.

[0024] (13) The transmitting and receiving device of the second method includes the receiving device of the above method and the transmitting device for transmitting optical signals.

[0025] (14) The communication system of the third method has multiple transmitting and receiving devices of the above methods.

[0026] (15) The portable terminal device of the fourth method has the receiving device of the above method.

[0027] (16) The photodetector of the fifth method includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and the output voltage varies in response to the change in the intensity of light irradiating the first ferromagnetic layer.

[0028] (17) In the light detection element described above, the magnetization direction of the first ferromagnetic layer in the state where the first ferromagnetic layer is not irradiated with the light may be greater than 0° and less than 90° from the magnetization direction of the first ferromagnetic layer in the state where the first ferromagnetic layer is irradiated with the light.

[0029] (18) The light detection element described above can also be configured to be irradiated with a light signal having at least two levels of intensity. When the intensity of the light irradiating the first ferromagnetic layer is the first intensity, the magnitude of the output voltage displays a first value. When the intensity of the light irradiating the first ferromagnetic layer is the second intensity, the magnitude of the output voltage displays a second value. When the second intensity is greater than the first intensity, and when the second value is greater than the first value, current flows from the first ferromagnetic layer to the second ferromagnetic layer. When the second value is less than the first value, current flows from the second ferromagnetic layer to the first ferromagnetic layer.

[0030] Invention Effects

[0031] The receiving device, transmitting and receiving device, communication system, portable terminal device, and optical detection element described above are novel and represent a new breakthrough. Furthermore, the receiving device, transmitting and receiving device, communication system, portable terminal device, and optical detection element described above are capable of high-speed communication. Attached Figure Description

[0032] Figure 1 This is a conceptual diagram of the communication system according to the first embodiment.

[0033] Figure 2 This is a block diagram of the transmitting and receiving apparatus according to the first embodiment.

[0034] Figure 3 This is a circuit diagram of the transmitting and receiving device according to the first embodiment.

[0035] Figure 4 This is a cross-sectional view of the receiving device according to the first embodiment.

[0036] Figure 5 This is a cross-sectional view of the light detection element in the first embodiment.

[0037] Figure 6 This is a schematic diagram illustrating the operation of the first mode of the light detection element in the first embodiment, based on the first mechanism.

[0038] Figure 7 This is a schematic diagram illustrating the operation of the first mode of the light detection element in the first embodiment using the second mechanism.

[0039] Figure 8 This is a schematic diagram illustrating the operation of the second mode of the light detection element in the first embodiment, based on the first mechanism.

[0040] Figure 9 This is a schematic diagram illustrating the operation of the second mode of the light detection element in the first embodiment using the second mechanism.

[0041] Figure 10 This is a schematic diagram illustrating the operation of a light detection element when multiple values ​​are output using the light detection element of the first embodiment, based on the first mechanism.

[0042] Figure 11 This is a schematic diagram illustrating the operation of a photodetector when multiple values ​​are output using the photodetector of the first embodiment, based on the second mechanism.

[0043] Figure 12 The diagram shown is a schematic representation of the behavior of the light detection element when an abnormality occurs in the light detection element of the first embodiment.

[0044] Figure 13This is a graph showing the simulation results of the sensitivity of the embodiment and Comparative Example 1.

[0045] Figure 14 This is a graph showing the simulation results of the sensitivity of the embodiment and Comparative Example 2.

[0046] Figure 15 This is a circuit diagram of the transmitting and receiving device of the first variation.

[0047] Figure 16 This is a cross-sectional view of the optical detection element of the second modified example, cut along the z-direction.

[0048] Figure 17 This is a cross-sectional view of the optical detection element and its surroundings of the second modified example, cut through the xy plane of the first ferromagnetic layer 1.

[0049] Figure 18 This is a cross-sectional view of the optical detection element of the third modified example, cut along the z-direction.

[0050] Figure 19 This is a cross-sectional view of the receiving device of the fourth modified example, cut along the z-direction.

[0051] Figure 20 This is a top view of the receiving device of the fourth modified example, viewed from the z-direction.

[0052] Figure 21 This is a cross-sectional view of the receiving device of the fifth modified example, cut along the z-direction.

[0053] Figure 22 This is a top view of the receiving device of the fifth modified example, viewed from the z-direction.

[0054] Figure 23 This is a cross-sectional view of the receiving device in the sixth modified example.

[0055] Figure 24 This is a diagram illustrating the operation of the receiving device according to the second embodiment.

[0056] Figure 25 This is a conceptual diagram of another example of a communication system.

[0057] Figure 26 This is a conceptual diagram of another example of a communication system.

[0058] Explanation of reference numerals in the attached figures

[0059] 1…First ferromagnetic layer

[0060] 2…Second ferromagnetic layer

[0061] 3…spacer layer

[0062] 4…Third ferromagnetic layer

[0063] 5…Magnetic coupling layer

[0064] 6…Basal layer

[0065] 7…Vertical magnetization induced layer

[0066] 8…cap layer

[0067] 9…Sidewall insulation layer

[0068] 10…Optical detection element

[0069] 11…Signal Processing Department

[0070] 15…Electrode 1

[0071] 16…Electrode 2

[0072] 20…integrated circuits

[0073] 30… interlayer insulating film

[0074] 40… Hard bias layer

[0075] 50… Wiring layer

[0076] 60, 61... soft magnetic materials

[0077] 62…opening

[0078] 63…Magnetic mesh

[0079] 64…Insulation layer

[0080] 100, 101, 102, 103… Receiving devices

[0081] 200…transmitting device

[0082] 201…light source

[0083] 202…Electrical signal generating element

[0084] 203… Optical modulation element

[0085] 300, 301... Transmitting and receiving devices

[0086] 500… Portable terminal device

[0087] 600…Information Processing Device

[0088] 1000, 1001, 1002… communication system

[0089] AD…Analog-to-digital converter

[0090] FB… Fiber Optics

[0091] G…grounding

[0092] Is…sensing current

[0093] M1, M2, M40… Magnetization

[0094] P G …reference potential terminal

[0095] P in …input terminals

[0096] P out …output terminals

[0097] PS… power supply

[0098] w…through wiring Detailed Implementation

[0099] Hereinafter, embodiments will be described in detail with appropriate reference to the accompanying drawings. In the drawings used in the following description, for ease of understanding, some parts of the features are sometimes shown as enlarged for convenience, and the size ratios of the constituent elements may sometimes differ from the actual dimensions. The materials, dimensions, etc., illustrated in the following description are examples, and the present invention is not limited thereto; appropriate modifications can be made within the scope of achieving the effects of the present invention.

[0100] The directions are defined as follows: The stacking direction of the photodetector element 10 is defined as the z-direction; a direction within a plane orthogonal to the z-direction is defined as the x-direction; and a direction orthogonal 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. Hereinafter, the +z-direction may be represented 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 may not necessarily coincide with the direction in which gravity is applied.

[0101] [First Implementation]

[0102] Figure 1 This is a conceptual diagram of the communication system 1000 according to the first embodiment. Figure 1 The communication system 1000 shown includes multiple transmitting and receiving devices 300 and fiber optic cables (FBs) connecting the transmitting and receiving devices 300. The communication system 1000 can be used for short- and medium-distance communication, such as within and between data centers, and for long-distance communication, such as between cities. The transmitting and receiving devices 300 are, for example, located within data centers, as base stations or backbones of long-distance communication networks. The fiber optic cables (FBs) connect data centers, for example. The communication system 1000 enables communication between the transmitting and receiving devices 300, for example, via the fiber optic cables (FBs). The communication system 1000 can also enable wireless communication between the transmitting and receiving devices 300 without using fiber optic cables (FBs).

[0103] Figure 2This is a block diagram of the transmitting and receiving apparatus 300 according to the first embodiment. The transmitting and receiving apparatus 300 includes a receiving apparatus 100 and a transmitting apparatus 200. The receiving apparatus 100 receives optical signal L1, and the transmitting apparatus 200 transmits optical signal L2. The light used in this specification is not limited to visible light, but also includes infrared light with a wavelength longer than visible light and ultraviolet light with a wavelength shorter than visible light.

[0104] 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.

[0105] 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 also be located outside the transmitting device 200. The electrical signal generating element 202 generates an electrical signal based on the transmitted information. The electrical signal generating element 202 may also 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.

[0106] Figure 3 This is a circuit diagram of the transmitting and receiving device 300 according to the first embodiment. Figure 3 The signal processing unit 11 is omitted in the text.

[0107] The receiving device 100 includes, for example, a photodetector 10, a first electrode 15, a second electrode 16, and an input terminal P. in Output terminal P out and reference potential terminal P G The first electrode 15 and the second electrode 16 sandwich the photodetector 10 in the stacking direction. The first electrode 15 is, for example, the electrode on the side that is irradiated with light containing the light signal L1.

[0108] The first electrode 15, for example, is connected to the input terminal P. in and output terminal P out Connection. The second electrode 16, for example, is connected to the reference potential terminal P. G Connection. Input terminal P in It is connected to a power supply PS. The power supply PS can also be located outside the receiving device 100. The power supply PS applies sensing current, reset current, etc., to the photodetector 10. If it is not necessary to flow current to the photodetector 10 from the outside, the input terminal P may not be required. in And power supply PS. Output terminal P outFor example, the output voltage is the voltage between the first electrode 15 and the second electrode 16 of the photodetector element 10 sandwiched in the stacking direction. The resistance value of the photodetector element 10 in the stacking direction is calculated according to Ohm's law by the sensing current flowing through the photodetector element 10 in the stacking direction. Output terminal P out Connected to signal processing unit 11. Reference potential terminal P G It is connected to a reference potential to determine the reference potential of the receiving device 100. Figure 3 The reference potential is ground G. Ground G can also be located outside the receiving device 100. The reference potential can also be a potential other than ground G.

[0109] The receiving device 100 and the transmitting device 200 are connected, for example, to a common reference potential (ground G). The reference potentials of the receiving device 100 and the transmitting device 200 may also be different. If the reference potentials of the receiving device 100 and the transmitting device 200 are the same, noise generation can be reduced.

[0110] Figure 4 This is a cross-sectional view of the receiving device 100 according to the first embodiment. The receiving device 100 includes, 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.

[0111] The integrated circuit 20 includes a signal processing unit 11 that processes the signal output from the photodetector element 10. For example, the integrated circuit 20 processes signals where the output voltage (resistance value in the z-direction of the photodetector element 10) from the photodetector element 10 is above a threshold as a first signal (e.g., "1"), and signals below the threshold as a second signal (e.g., "0"). When 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 element 10 are connected, for example, via a through-wire w that penetrates the interlayer insulating film 30. Alternatively, they may be connected by wire bonding instead of the through-wire w.

[0112] Interlayer insulating film 30 is an insulator used to insulate between wirings and components in multilayer wiring. Interlayer insulating film 30 is, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg. 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 (ZrO2) x )wait.

[0113] Figure 5This is a cross-sectional view of the light detection element 10 according to the first embodiment. Figure 5 The diagram also shows the first electrode 15 and the second electrode 16, with arrows indicating the direction of magnetization in the initial state of the ferromagnetic material.

[0114] The photodetector 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 10 may also have a third ferromagnetic layer 4, a magnetic coupling layer 5, a substrate layer 6, a vertical magnetization induction layer 7, a capping layer 8, and a sidewall insulating layer 9.

[0115] The photodetector 10 is, for example, an MTJ (Magnetic Tunnel Junction) element where the spacer layer 3 is made of an insulating material. In this case, the photodetector 10 is an element whose resistance value in the z-direction (resistance value when current flows in the z-direction) changes in response 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.

[0116] The first ferromagnetic layer 1 is a photodetector layer whose magnetization direction changes when light is incident from the outside. The first ferromagnetic layer 1 is also called a magnetization-free layer. A magnetization-free layer is a layer containing a magnetic material whose magnetization direction changes when energy is applied from a specified external source. This specified external energy can be, for example, light incident from the outside, a current flowing in the z-direction of the photodetector element 10, or an external magnetic field. Since the magnetization of the ferromagnetic material can change direction in response to rapid changes in the intensity of light incident on the ferromagnetic material (high-frequency light signals), by using the first ferromagnetic layer 1 as a photodetector layer, the receiving device 100 can receive high-frequency light signals and perform high-speed optical communication.

[0117] The first ferromagnetic layer 1 contains a ferromagnetic material. The first ferromagnetic layer 1 may contain at least one of Co, Fe, and Ni. The first ferromagnetic layer 1 may contain 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 aforementioned magnetic elements. The first ferromagnetic layer 1 may also be an alloy containing both magnetic and non-magnetic elements. The first ferromagnetic layer 1 may also consist of multiple layers. The first ferromagnetic layer 1 may be, for example, a CoFeB alloy, a laminate containing a CoFeB alloy layer sandwiched by Fe layers, or a laminate containing a CoFe alloy layer sandwiched by CoFe layers. Generally, "ferromagnetism" includes "ferrimagnetism." The first ferromagnetic layer 1 may also exhibit ferrimagnetism. Furthermore, the first ferromagnetic layer 1 may also exhibit ferromagnetism other than ferrimagnetism. For example, a CoFeB alloy exhibits ferromagnetism other than ferrimagnetism.

[0118] The first ferromagnetic layer 1 can be an in-plane magnetized film having an easy magnetization axis in the in-plane direction (any direction in the xy plane), or a perpendicularly magnetized film having an easy magnetization axis in the direction perpendicular to the film (z direction). To make the first ferromagnetic layer 1 a perpendicularly magnetized film, the first ferromagnetic layer 1 can also be an Fe-rich layer. For example, the Fe composition ratio in the first ferromagnetic layer 1 can be 50 atomic percent or more. Furthermore, for example, the Fe composition ratio in a CoFeB alloy can be 50 atomic percent or more.

[0119] The thickness of the first ferromagnetic layer 1 is, for example, 1 nm or more and 5 nm or less. The thickness of the first ferromagnetic layer 1 is preferably, for example, 1 nm or more and 2 nm or less. When the first ferromagnetic layer 1 is a perpendicularly magnetized film, if the thickness of the first ferromagnetic layer 1 is thin, the effect of applying perpendicular magnetic anisotropy from the layers above and below the first ferromagnetic layer 1 is enhanced, and the perpendicular magnetic anisotropy of the first ferromagnetic layer is increased. That is, if the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is high, the force that magnetization wants to return in the z-direction is enhanced. On the other hand, if the thickness of the first ferromagnetic layer 1 is thick, the effect of applying perpendicular magnetic anisotropy 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.

[0120] If the thickness of the first ferromagnetic layer 1 is thinned, the volume of the ferromagnetic material decreases; if it is thickened, the volume of the ferromagnetic material increases. The ease with which the first ferromagnetic layer 1 is magnetized when external energy is applied is inversely proportional to the product of the magnetic anisotropy (Ku) and the volume (V) of the first ferromagnetic layer 1 (KuV). That is, if the product of the magnetic anisotropy and the volume of the first ferromagnetic layer 1 decreases, the responsiveness to the ultra-high-speed optical signal L1 increases. From this point of view, it is preferable to reduce the volume of the first ferromagnetic layer 1 while appropriately designing the magnetic anisotropy of the first ferromagnetic layer 1 as optical communication becomes ultra-high-speed. In other words, the higher the speed of communication, the thinner the thickness of the first ferromagnetic layer 1 is preferred.

[0121] When the thickness of the first ferromagnetic layer 1 is greater than 2 nm, an intercalation layer, for example, composed of Mo or W, can be provided within the first ferromagnetic layer 1. That is, the first ferromagnetic layer 1 can also be a stack in which a ferromagnetic layer, an intercalation layer, and a ferromagnetic layer are sequentially stacked in the z-direction. The overall perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is improved by the interfacial magnetic anisotropy at the interface between the intercalation layer and the ferromagnetic layer. The thickness of the intercalation layer is, for example, 0.1 nm to 0.6 nm.

[0122] The second ferromagnetic layer 2 is a magnetization-fixed layer. A magnetization-fixed layer is a layer composed of a magnetic material whose magnetization direction is less likely to change than that of a magnetization-free layer when energy is applied from a specified external source. The coercivity of the second ferromagnetic layer 2 is, for example, greater than that 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 can be an in-plane magnetization film or a perpendicular magnetization film.

[0123] The material constituting the second ferromagnetic layer 2 is, for example, the same as that constituting the first ferromagnetic layer 1. The second ferromagnetic layer 2 may be, for example, 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 sequentially stacked.

[0124] The magnetization of the second ferromagnetic layer 2 can also be fixed, for example, by magnetic coupling with the third ferromagnetic layer 4 via the magnetic coupling layer 5. In this case, the combination of the second ferromagnetic layer 2, the magnetic coupling layer 5, and the third ferromagnetic layer 4 is sometimes referred to as a magnetization fixing layer.

[0125] The third ferromagnetic layer 4 is magnetically coupled to the second ferromagnetic layer 2, for example. This magnetic coupling is, for example, antiferromagnetic coupling, occurring through RKKY interactions. The material constituting the third ferromagnetic layer 4 is, for example, the same as the first ferromagnetic layer 1. The third ferromagnetic layer 4 is, for example, a laminated film composed of alternating layers of Co and Pt, or a laminated film composed of alternating layers of Co and Ni. The magnetic coupling layer 5 is, for example, Ru, Ir, etc. The thickness of the magnetic coupling layer 5 is, for example, the thickness of the film through which the second ferromagnetic layer 2 and the third ferromagnetic layer 4 are antiferromagnetically coupled via RKKY interactions.

[0126] Spacer layer 3 is a non-magnetic layer disposed between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. Spacer layer 3 is a layer made of a conductor, an insulator, or a semiconductor, or a layer containing current-carrying points made of conductors in an insulator. The thickness of spacer layer 3 can be adjusted according to the orientation directions of the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 in the initial state, as described later.

[0127] For example, when the spacer layer 3 is made of an insulator, the photodetector 10 has a magnetic tunnel junction (MTJ) composed of a first ferromagnetic layer 1, a spacer layer 3, and a second ferromagnetic layer 2. This type of element is called an MTJ element. In this case, the photodetector 10 can exhibit a tunnel magnetoresistance (TMR) effect. For example, when the spacer layer 3 is made of metal, the photodetector 10 can exhibit a giant magnetoresistance (GMR) effect. This type of element is called a GMR element. Depending on the material of the spacer layer 3, the photodetector 10 is sometimes referred to differently from MTJ elements, GMR elements, etc., but is generally also called a magnetoresistance effect element.

[0128] 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. Furthermore, these insulating materials can also contain elements such as Al, B, Si, Mg, and magnetic elements such as Co, Fe, and Ni. By adjusting the thickness of the spacer layer 3 to exhibit a high TMR effect between the first ferromagnetic layer 1 and the second ferromagnetic layer 2, a high magnetoresistivity change rate can be obtained. To effectively utilize the TMR effect, the thickness of the spacer layer 3 can be approximately 0.5–5.0 nm or approximately 1.0–2.5 nm.

[0129] When the spacer layer 3 is composed of a non-magnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. In order to effectively utilize the GMR effect, the film thickness of the spacer layer 3 can be about 0.5 to 5.0 nm or about 2.0 to 3.0 nm.

[0130] 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 can be approximately 1.0 to 4.0 nm.

[0131] When the spacer layer 3 is used as a layer containing a conductor in a non-magnetic insulator with a current-carrying point, a structure can also be used in which a non-magnetic insulator made of alumina or magnesium oxide contains a current-carrying point made of a non-magnetic conductor such as Cu, Au, or Al. Alternatively, a conductor made of a magnetic element such as Co, Fe, or Ni can also be used. In this case, the thickness of the spacer layer 3 can be about 1.0 to 2.5 nm. The current-carrying point is, for example, a columnar shape with a diameter of 1 nm or more and 5 nm or less when viewed from a direction perpendicular to the film surface.

[0132] Figure 5The substrate layer 6 shown is, for example, located on the second electrode 16. The substrate layer 6 is a seed layer or a buffer layer. The seed layer improves the crystallinity of the layers stacked on it. The seed layer is, for example, Pt, Ru, Hf, Zr, or NiFeCr. The thickness of the seed layer is, for example, 1 nm or more and 5 nm or less. The buffer layer is a layer that mitigates lattice mismatch between different crystals. The buffer layer is, for example, Ta, Ti, W, Zr, Hf, or nitrides of these elements. The thickness of the buffer layer is, for example, 1 nm or more and 5 nm or less.

[0133] A vertical magnetization-induced layer 7 is formed when the first ferromagnetic layer 1 is a vertically magnetized film. The vertical magnetization-induced layer 7 is stacked on the first ferromagnetic layer 1. The vertical magnetization-induced layer 7 induces vertical magnetic anisotropy in the first ferromagnetic layer 1. The vertical magnetization-induced layer 7 is, for example, magnesium oxide, W, Ta, Mo, etc. When the vertical magnetization-induced layer 7 is magnesium oxide, magnesium oxide with oxygen deficiency is preferred to improve conductivity. The film thickness of the vertical magnetization-induced layer 7 is, for example, 0.5 nm or more and 2.0 nm or less.

[0134] 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 manufacturing process and improves the crystallinity of the underlying layer during annealing. The thickness of the capping layer 8 is, for example, less than 3 nm, to allow sufficient light to irradiate the first ferromagnetic layer 1.

[0135] The sidewall insulating layer 9 covers the periphery of the laminate containing the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The sidewall insulating layer 9 is, for example, made of the same material as the interlayer insulating film 30.

[0136] The first electrode 15 is, for example, transmissive to light in the wavelength range used by the optical signal L1. The wavelength range used by the optical signal L1 is, for example, 300 nm or more and 2 μm or less, encompassing the visible light region and the near-infrared light region. The first electrode 15 is, for example, a transparent electrode containing oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium gallium zinc oxide (IGZO). The first electrode 15 may also be configured to have multiple columnar metals 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 necessary to use the transparent electrode material described above as the first electrode 15; external light can also reach the first ferromagnetic layer 1 by using metal materials such as Au, Cu, or Al with a thin film thickness. When using a metal as the material of 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 for light wavelengths near the blue range than other metal materials. In addition, the first electrode 15 may also have an anti-reflective film on the surface of the irradiated light.

[0137] The second electrode 16 is made of a conductive material. For example, the second electrode 16 is made of metals such as Cu, Al, or Au. Ta or Ti may also be stacked on top of these metals. Alternatively, a Cu-Ta laminate, a Ta-Cu-Ti laminate, or a Ta-Cu-TaN laminate 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 is also transmissive to light in the wavelength range used for the optical signal L1. Similar to the first electrode 15, transparent electrode materials such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium gallium zinc oxide (IGZO) may also be used as the material for the second electrode 16. Even when light is irradiated from the first electrode 15, depending on the intensity of the light, there may be a situation where light reaches the second electrode 16. However, in this case, since the second electrode 16 is made of a transparent electrode material containing oxides, compared to the case where the second electrode 16 is made of metal, it is possible to suppress the reflection of light at the interface between the second electrode 16 and the layer adjacent to it.

[0138] The photodetector 10 is fabricated through a layer stacking process, an annealing process, and a processing process. First, a base layer 6, a third ferromagnetic layer 4, a magnetic coupling layer 5, a second ferromagnetic layer 2, a spacer layer 3, a first ferromagnetic layer 1, a vertical magnetization induction layer 7, and a capping layer 8 are sequentially stacked on the second electrode 16. Each layer is formed into a film, for example, by sputtering.

[0139] Next, the laminated film is annealed. The annealing temperature is, for example, 250°C to 450°C. When the laminated film and the semiconductor circuit are formed on the same substrate, annealing at 400°C or higher is preferred. Then, the laminated film is processed into a specified columnar shape by photolithography and etching. The columnar shape can be a cylinder or a prism. For example, the shortest width of the columnar shape when viewed from the z-direction can be 10 nm or more and 2000 nm or less, or 30 nm or more and 500 nm or less.

[0140] 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 can also be stacked multiple times. Next, the upper surface of the capping layer 8 is exposed from the sidewall insulating layer 9 by chemical mechanical polishing (CMP), and the first electrode 15 is fabricated on the capping layer 8. Through the above processes, the photodetector element 10 is obtained.

[0141] Next, the operation of the light detection element 10 according to the first embodiment will be described. Light containing a light signal L1 with varying light intensity is irradiated onto the first ferromagnetic layer 1. A lens may also be disposed on the side of the first ferromagnetic layer 1 in the stacking direction of the light detection element 10, and light focused onto the first ferromagnetic layer 1 may be irradiated via the lens. The lens may also be formed during the wafer forming process of the light detection element 10. The resistance value in the z-direction of the light detection element 10 changes due to the irradiation of the first ferromagnetic layer 1 by light containing the light signal L1. An example will be given where the intensity of the light irradiating the first ferromagnetic layer 1 is at two levels: a first intensity and a second intensity. The second intensity is greater than the first intensity. The first intensity may also be the case where the intensity of the light irradiating the first ferromagnetic layer 1 is zero.

[0142] The operation of the light detection element 10 in the first embodiment has two modes. The first mode is when the output voltage from the light detection element 10 at the second intensity is higher than that at the first intensity. The second mode is when the output voltage from the light detection element 10 at the first intensity is higher than that at the second intensity.

[0143] Figure 6 and Figure 7 This diagram illustrates the operation of the light detection element 10 in a first mode according to the first embodiment. Two mechanisms are considered as the mechanism of operation of the light detection element 10. Figure 6 This is a diagram used to illustrate the first mechanism. Figure 7 This is a diagram used to illustrate the second mechanism. In Figure 6 and Figure 7 In the diagram above, the vertical axis represents the intensity of light illuminating the first ferromagnetic layer 1, and the horizontal axis represents time. Figure 6 and Figure 7 In the figure below, the vertical axis represents the resistance value of the photodetector 10 in the z-direction, and the horizontal axis represents time.

[0144] First, in the state where the first ferromagnetic layer 1 is irradiated with light of the first intensity (hereinafter referred to as the initial state), the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 are parallel. The resistance value in the z-direction of the photodetector element 10 shows the first resistance value R1, and the magnitude of the output voltage from the photodetector element 10 shows the first value. The resistance value in the z-direction of the photodetector element 10 generates a voltage across its terminals in the z-direction by the sensing current Is flowing through it, and this voltage value is calculated using Ohm's law. The output voltage from the photodetector element 10 is generated between the first electrode 15 and the second electrode 16. Figure 6In the first mode shown, it is preferable to allow the sensing current Is to flow from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. By allowing the sensing current Is to flow in this direction, a spin-transfer torque in the same direction as the magnetization M2 of the second ferromagnetic layer 2 acts on the magnetization M1 of the first ferromagnetic layer 1, and in the initial state, the magnetization M1 is parallel to the magnetization M2. Furthermore, by allowing the sensing current Is to flow in this direction, it is possible to prevent the magnetization M1 of the first ferromagnetic layer 1 from reversing during operation.

[0145] Next, the intensity of the light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity. The second intensity is greater than the first intensity, and through the energy generated from the external source by the light irradiation, the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state. The state of magnetization M1 can be, for example, its tilt angle relative to the z-direction, its magnitude, etc. For example, as... Figure 6 As shown, when the intensity of light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity, the magnetization M1 tilts relative to the z-direction. The angle between the direction of the magnetization M1 of the first ferromagnetic layer 1 in the state where it is not irradiated with light containing the optical signal L1 and the magnetization direction of the first ferromagnetic layer 1 at the second intensity is greater than 0° and less than 90°. Furthermore, for example, as... Figure 7 As shown, when the intensity of light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity, the magnetization M1 decreases. The magnetization M1 of the first ferromagnetic layer 1 when illuminated with light containing the optical signal L1 is smaller than the magnetization M1 of the first ferromagnetic layer 1 when not illuminated with light containing the optical signal L1. 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 displays a second resistance value R2, and the magnitude of the output voltage from the photodetector 10 displays a second value.

[0146] That is, when the intensity of light illuminating 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. In other words, corresponding to the change in intensity of light illuminating 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 (first resistance value R1) when magnetization M1 and magnetization M2 are parallel and the resistance value when magnetization M1 and magnetization M2 are antiparallel. Preferably, the magnetization M1 of the first ferromagnetic layer 1 is not reversed by the irradiation of the first ferromagnetic layer 1 by light containing the optical signal L1.

[0147] The magnetization M1 of the first ferromagnetic layer 1 has a spin-transfer torque in the same direction as the magnetization M2 of the second ferromagnetic layer 2. Therefore, in Figure 6 In the case shown, magnetization M1 wants to return to a state parallel to magnetization M2. If the intensity of light illuminating the first ferromagnetic layer 1 changes from the second intensity to the first intensity, the photodetector 10 returns to its initial state. Figure 7 In the illustrated case, if the intensity of the light illuminating the first ferromagnetic layer 1 returns to the first intensity, the magnetization M1 of the first ferromagnetic layer 1 is restored, and the photodetector 10 returns to its initial state. In any case, when the magnetization M1 returns to its initial state, the resistance value in the z-direction of the photodetector 10 returns to the first resistance value R1. That is, when the intensity of the light illuminating the first ferromagnetic layer 1 changes 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. In other words, corresponding to the change in intensity of the light illuminating 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.

[0148] In any mechanism, if the photodetector 10 of the first embodiment operates in the first mode, the resistance value in the stacking direction of the photodetector 10 changes correspondingly to the change in the intensity of light irradiating the first ferromagnetic layer 1. That is, the output voltage from the photodetector 10 changes corresponding to the change in the intensity of light irradiating the first ferromagnetic layer 1. As a result, the photodetector 10 can convert the change in the intensity of the light 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. Figure 6 and Figure 7In the example shown, the resistance value in the stacking direction of the photodetector 10, i.e., the output voltage from the photodetector 10, becomes a value corresponding to the intensity of light irradiating the first ferromagnetic layer 1. This operating method can also be applied, for example, when the first ferromagnetic layer 1 contains a CoFeB alloy. According to common sense, CoFeB alloy is a well-known material for hard disk read heads and MRAM, but there is no reason to use it as a photodetector layer. However, by using this operating method, the CoFeB alloy can function as a photodetector layer, and the magnetic element having the first ferromagnetic layer 1 containing the CoFeB alloy can function as a photodetector element. It is advantageous to use the CoFeB alloy for the first ferromagnetic layer 1 because the output voltage from the photodetector 10 increases when light is irradiated. Until now, no one has considered using the CoFeB alloy as a photodetector layer, but it is very advantageous to be able to use a magnetic material like the CoFeB alloy that makes a larger output voltage possible. The output voltage signal from the photodetector 10, representing the resistance value in the z-direction of the photodetector 10, is sent to the signal processing unit 11. If the output voltage (resistance value in the z-direction of the photodetector 10) is above a threshold, it is processed as a first signal (e.g., "1"); if it is below the threshold, it is processed as a second signal (e.g., "0"). That is, the receiving device 100 receives the optical signal L1 based on the output voltage (resistance value in the z-direction of the photodetector 10).

[0149] Figure 8 and Figure 9 This is a diagram illustrating the operation of the second mode of the light detection element 10 in the first embodiment. Figure 8 This is a diagram used to illustrate the first mechanism. Figure 9 This is a diagram used to illustrate the second mechanism. In Figure 8 and Figure 9 In the diagram above, the vertical axis represents the intensity of light illuminating the first ferromagnetic layer 1, and the horizontal axis represents time. Figure 8 and Figure 9 In the figure below, the vertical axis represents the resistance value of the photodetector 10 in the z-direction, and the horizontal axis represents time.

[0150] The difference between the second mode and the first mode 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, and the operating principle is the same as that of the first mode.

[0151] 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 in an antiparallel state. The resistance value in the z-direction of the photodetector 10 displays the first resistance value R1', and the magnitude of the output voltage from the photodetector 10 displays the first value. Figure 8 and Figure 9 In the second mode shown, it is preferable that the sensing current Is flows from the second ferromagnetic layer 2 to the first ferromagnetic layer 1. By causing the sensing current Is to flow in this direction, a spin-transfer torque is applied to the magnetization M1 of the first ferromagnetic layer 1 in the opposite direction to the magnetization M2 of the second ferromagnetic layer 2, so that magnetization M1 and magnetization M2 are antiparallel in the initial state. In the second mode, by making the direction of the sensing current Is opposite to that in the first mode, the magnetization direction (magnetization stability direction) of the first ferromagnetic layer 1 in the initial state is reversed.

[0152] Next, the intensity of the light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity. The second intensity is greater than the first intensity, and the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state. For example, as... Figure 8 As shown, when the intensity of light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity, the magnetization M1 tilts relative to the z-direction. Additionally, for example, as... Figure 9 As shown, when the intensity of light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity, the magnetization M1 decreases. When the magnetization M1 of the first ferromagnetic layer 1 changes, the resistance value in the z-direction of the photodetector 10 displays a second resistance value R2', and the magnitude of the output voltage from the photodetector 10 displays a first value. That is, when the intensity of light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity, the resistance value in the z-direction of the photodetector 10 changes from a first resistance value R1' to a second resistance value R2'. In other words, corresponding to the change in intensity of light illuminating the first ferromagnetic layer from a first intensity to a second intensity, the resistance value in the z-direction of the photodetector 10 changes from a first resistance value R1' to a second resistance value R2'. The second resistance value R2' is less than the first resistance value R1', and the second value of the output voltage is less than the first value. The second resistance value R2' is the resistance value when magnetization M1 and magnetization M2 are antiparallel (the first resistance value R1') and the resistance value when magnetization M1 and magnetization M2 are parallel ( Figure 6 The first resistance value R1 is between.

[0153] The magnetization M1 of the first ferromagnetic layer 1 exerts a spin-transfer torque in the opposite direction to the magnetization M2 of the second ferromagnetic layer 2. Therefore, in Figure 8 In the case shown, if the intensity of light illuminating the first ferromagnetic layer 1 changes from the second intensity to the first intensity, the magnetization M1, which was tilted from the initial state, returns to the initial state. Figure 9 In the illustrated case, if the intensity of the light illuminating the first ferromagnetic layer 1 returns to the first intensity, the magnetization M1 of the first ferromagnetic layer 1 is restored, and the photodetector 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 10 returns to the first resistance value R1'. That is, when the intensity of the light illuminating the first ferromagnetic layer 1 changes 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'. In other words, corresponding to the change in intensity of the light illuminating 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'.

[0154] In any mechanism, if the photodetector 10 of the first embodiment operates in the second mode, the resistance value in the stacking direction of the photodetector 10 changes correspondingly to the change in the intensity of light irradiating the first ferromagnetic layer 1. That is, the output voltage from the photodetector 10 changes corresponding to the change in the intensity of light irradiating the first ferromagnetic layer 1. As a result, the photodetector 10 can convert the change in the intensity of the light 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. Figure 8 and Figure 9 In the example shown, the resistance value in the stacking direction of the photodetector 10, i.e., the output voltage from the photodetector 10, becomes a value corresponding to the intensity of light irradiating the first ferromagnetic layer 1. The output voltage signal from the photodetector 10, representing the resistance value in the z-direction, is sent to the signal processing unit 11. If the output voltage (resistance value in the z-direction of the photodetector 10) is above a threshold, it is processed as a first signal (e.g., "1"); if it is below the threshold, it is processed as a second signal (e.g., "0"). That is, the receiving device 100 receives the optical signal L1 based on the output voltage (resistance value in the z-direction of the photodetector 10).

[0155] Thus, by applying a bias to the magnetization M1 of the first ferromagnetic layer 1 in a direction that is either parallel or antiparallel to the direction of magnetization M2, the resistance value of the photodetector element 10, i.e., the output voltage from the photodetector element 10, can change in response to changes in the intensity of light irradiating the first ferromagnetic layer 1. In the examples of the first and second modes described above, the effect of applying a spin-transfer torque based on the sensing current Is is used as the bias application effect. The bias application effect is not limited to the effect of applying a spin-transfer torque based on the sensing current Is; for example, other bias application effects as shown in the second to fourth modifications described later can also be used.

[0156] Here, we also consider the case where the orientation directions of magnetization M1 and magnetization M2 in the initial state are not correctly oriented due to external factors such as external magnetic fields or heat. Therefore, a reset current can be applied in the z-direction of the photodetector 10 before the photodetector 10 of the first embodiment is operated.

[0157] The reset current is a current with a current density sufficient to fully reverse the magnetization M1 of the first ferromagnetic layer 1. In the first mode, the reset current flows from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. In the second mode, the reset current flows from the second ferromagnetic layer 2 to the first ferromagnetic layer 1. If the reset current flows in the z-direction of the photodetector 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 mode, the value of the reset current is greater than the value of the sensing current.

[0158] So far, the example has been described with the light irradiating the first ferromagnetic layer 1 having two levels of intensity, namely the first intensity and the second intensity. However, the light detection element 10 of the first embodiment can also read out multi-value information from the light signal L1 by making the intensity of the light irradiating the first ferromagnetic layer 1 greater than the two levels.

[0159] Figure 10 and Figure 11 This describes the behavior of the light detection element 10 when it outputs multiple values ​​using the light detection element 10 of the first embodiment. Figure 10 This is a diagram used to illustrate the first mechanism. Figure 11 This is a diagram used to illustrate the second mechanism. Figure 10 and Figure 11 From left to right, these represent the magnetization state and z-direction resistance value of the photodetector 10 for each of the 1st, 2nd, 3rd, and 4th intensities. The intensity of light irradiating the first ferromagnetic layer 1 increases sequentially in the order of 4th, 3rd, 2nd, and 1st intensities. The 1st intensity can also be zero.

[0160] like Figure 10 As shown, when the magnetization M1 is tilted in accordance with the intensity of the irradiated light, the greater the intensity of the light irradiating the first ferromagnetic layer 1, the greater the change in the angle of magnetization M1 from the initial state. In the state where the first ferromagnetic layer 1 is not irradiated with light containing the optical signal L1, the angle between the direction of magnetization M1 of the first ferromagnetic layer 1 and the directions of magnetization M1 for the second, third, and fourth intensities is greater than 0° and less than 90°. The greater the change in the angle of magnetization M1 from the initial state, the greater the change in the resistance value of the photodetector element 10 in the z-direction relative to the initial state. Figure 10In the example shown, the greater the angle change of magnetization M1 from the initial state, the greater the resistance value in the z-direction of the photodetector 10. Therefore, the resistance value in the z-direction of the photodetector 10 is different for the first intensity, the second intensity, the third intensity, and the fourth intensity. The photodetector 10 of the first embodiment can read information such as four values, "0", "1", "2", and "3", by defining the threshold of the output voltage (the threshold of the resistance value) into multiple levels. Here, as an example, the case of reading four values ​​is shown, but by setting the threshold of the output voltage (the threshold of the resistance value), the number of values ​​read can be freely designed. The magnetization M1 of the first ferromagnetic layer 1 is preferably not reversed by the irradiation of light containing the light signal L1 onto the first ferromagnetic layer 1.

[0161] In addition, Figure 11 Similarly, if the intensity of the light illuminating the first ferromagnetic layer 1 increases, the magnetization M1 of the first ferromagnetic layer 1 decreases from its initial state due to the external energy generated by the light irradiation. If 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, corresponding to 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 a second resistance value R2, a third resistance value R3, and a fourth resistance value R4. Therefore, with... Figure 10 Similarly, the difference in output voltage from the photodetector 10 can be output as multi-valued or analog data.

[0162] Furthermore, this explanation uses the case where magnetization M1 and magnetization M2 are parallel in the initial state as an example, but magnetization M1 and magnetization M2 can also be antiparallel in the initial state. Figure 10 Similarly, when the magnetization M1 is tilted in accordance with the intensity of the irradiated light, the greater the change in the angle of the magnetization M1 from the initial state, the smaller the resistance value of the photodetector 10 in the z direction.

[0163] Next, the operation of the photodetector 10 in the event of an abnormality will be explained. Figure 12 This describes the behavior of the light detection element 10 when a malfunction occurs in the light detection element 10 of the first embodiment. Figure 12 In the diagram above, the vertical axis represents the intensity of light illuminating the first ferromagnetic layer 1, and the horizontal axis represents time. Figure 12 In the figure below, the vertical axis represents the resistance value of the photodetector 10 in the z-direction, and the horizontal axis represents time.

[0164] Figure 12This is an example of an abnormal situation that occurred when the photodetector 10 was operating in the first mode. One example of an abnormality is a case where the intensity of a portion of the light signal L1 irradiating the first ferromagnetic layer 1 is abnormally increased. The abnormality is not limited to excessive light intensity; for example, it could be due to changes in operating temperature or 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.

[0165] When the photodetector 10 operates normally in the first mode, the resistance value in the z-direction of the photodetector 10 varies between the first resistance value R1 and the second resistance value R2. On the other hand, if excessive light is irradiated onto the first ferromagnetic layer 1, the magnetization M1 may tilt significantly from its initial state, or the magnetization M1 may 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 mode). The third resistance value R3 is larger than both the first resistance value R1 and the second resistance value R2, and an anomaly is detected.

[0166] In the event of an malfunction in the photodetector 10, the aforementioned reset current is applied. By applying the reset current, the magnetization M1 of the first ferromagnetic layer 1 returns to the correct direction, allowing the photodetector 10 to function normally again. This has been explained using the first mechanism, but the same principle applies to the second mechanism. In the case of the second mechanism, if excessive light is irradiated onto the first ferromagnetic layer 1, the magnetization M1 may sometimes decrease significantly from its initial state, causing the magnetization M1 to reverse.

[0167] As described above, the transmitting and receiving apparatus 300 and the receiving apparatus 100 of the first embodiment receive optical signals based on the output voltage (resistance value of the optical detection element 10) from the optical detection element 10. Furthermore, the optical detection element 10 of the first embodiment can convert changes in the intensity of the optical signal L1 into changes in the output voltage (changes in the resistance value of the optical detection element 10 in the z-direction), enabling high-speed communication.

[0168] Furthermore, as described above, the smaller the volume of the first ferromagnetic layer 1, the easier it is for the magnetization M1 of the first ferromagnetic layer 1 to tilt. In other words, if the volume of the first ferromagnetic layer 1 is reduced, even a small amount of light can cause the magnetization M1 to tilt. That is, the photodetector 10 of the first embodiment can receive the light signal L1 with high sensitivity.

[0169] More precisely, the ease with which magnetization M1 can tilt is determined by the product of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 1 (KuV). A smaller KuV allows for tilting of magnetization with a smaller amount of light, while a larger KuV requires a larger amount of light to tilt magnetization. In other words, the KuV of the first ferromagnetic layer 1 is designed based on the amount of externally irradiated light used in the application. In cases where extremely small amounts of light are considered, such as photon detection, these minute light amounts can be detected by reducing the KuV of the first ferromagnetic layer. This is a significant advantage, as such detection of minute light amounts is impossible in existing photodetector devices. Furthermore, to reduce KuV, photon detection can also be achieved 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.

[0170] Furthermore, the photodetector 10 of the first embodiment can receive the optical signal L1 regardless of the wavelength range of the irradiated light. In semiconductor photodetectors using pn junctions, the appropriate semiconductor material varies depending on the wavelength of the irradiated light. For example, InGaAs is used for detecting near-infrared light with wavelengths of 1.3 μm or more and 1.5 μm or less. Alternatively, silicon is used, for example, for detecting visible light with wavelengths of 400 nm or more and 800 nm or less.

[0171] Figure 13 This is a graph showing the simulation results of the sensitivity of the photodetector 10 (example) of the first embodiment when the wavelength of the irradiated light is 1.5 μm (near-infrared light), and a curve (approximation curve of sensitivity data from several known examples) showing the characteristic level of the semiconductor photodiode using InGaAs (Comparative Example 1) using the prior art. Additionally, Figure 14 This is a graph showing the simulation results of the sensitivity of the light detection element 10 (example) of the first embodiment when the wavelength of the irradiated light is 520nm (visible light), and a curve (approximation curve of sensitivity data of several known examples) showing the characteristic level of the prior art silicon-based semiconductor photodiode (Comparative Example 2).

[0172] The simulation conditions for this embodiment are set as follows: The planar shape of the photodetector 10 is square, with one side length of 200 nm and an area resistivity (RA) of 5 Ωμm. 2The magnetoresistance change rate (MR change rate) is 65%. The second ferromagnetic layer 2 (magnetization fixation layer) is a 2nm thick alloy layer containing CoFeB, the spacer layer 3 is MgO, and the first ferromagnetic layer 1 is a 1.2nm thick alloy layer containing CoFeB. Furthermore, the spot diameter of the light irradiating the photodetector element 10 is 900nmφ. The sensitivity on the vertical axis of the graph is the output current relative to a unit light irradiation. In this embodiment, the output current is calculated 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 photodetector element 10 (in the case of the first mechanism, the resistance values ​​of magnetization M1 and magnetization M2 in a parallel state).

[0173] If practical constraints are considered (intensity of the optical signal, matching with surrounding circuits), a sensitivity of 0.5 A / W or higher is often required. For example... Figure 13 As shown, even Comparative Example 1, which uses InGaAs suitable for near-infrared light, cannot receive high-speed optical signals exceeding 40 GHz with high sensitivity. In contrast, the photodetector 10 of the embodiment can receive high-speed signals exceeding 100 GHz with good sensitivity. Furthermore, as... Figure 14 As shown, even Comparative Example 2, which uses silicon suitable for visible light, can only receive light signals with good sensitivity up to 3 GHz and cannot handle high-speed signals. In contrast, the photodetector 10 of the embodiment, similar to the near-infrared case, can receive high-speed signals exceeding 100 GHz with good sensitivity.

[0174] That is, the light detection element 10 of the first embodiment can receive high-speed light signals with high sensitivity regardless of visible light or near-infrared light. Here, examples of visible light and near-infrared light are shown, but it is not limited to these examples. For example, the light detection element 10 can also respond at high speed to ultraviolet light with a wavelength of 200 nm or more and less than 400 nm.

[0175] The first embodiment has been described in detail above with reference to the accompanying drawings, but the first embodiment is not limited to this example.

[0176] (First variation)

[0177] Figure 15 This is a circuit diagram of the transmitting / receiving device 301 of the first modification. The transmitting / receiving device 301 of the first modification differs from the transmitting / receiving device 300 in that the receiving device 101 has an analog-to-digital converter (AD). Regarding... Figure 3 The same structures are labeled with the same reference numerals and the descriptions are omitted.

[0178] The analog-to-digital converter (AD) is located at electrode 15 and output terminal P. outBetween. The analog-to-digital converter (AD) converts the output voltage (resistance value in the z-direction of the photodetector 10) from the photodetector 10 into digital data. That is, the transmitting and receiving device 301 of the first modification is not easily affected by noise, etc. The transmitting and receiving device 301 of the first modification can be used particularly preferably when the photodetector 10 outputs multiple values.

[0179] (Second variation)

[0180] Figure 16 This is a cross-sectional view of the optical detection element and its surroundings in the second modified example, cut along the z-direction. Figure 17 This is a cross-sectional view of the optical detection element and its surroundings in the second modified example, cut through the xy plane of the first ferromagnetic layer 1. The receiving device in the second modified example also includes a hard bias layer 40 that applies a bias magnetic field to the first ferromagnetic layer 1. Regarding... Figure 5 The same structures are labeled with the same reference numerals and the descriptions are omitted.

[0181] Viewed from any direction orthogonal to the z-direction, the hard bias layer 40 is located at the position overlapping with the first ferromagnetic layer 1. A sidewall insulating layer 9 is present between the hard bias layer 40 and the first ferromagnetic layer 1. Figure 17 As shown, the hard bias layer 40, for example, surrounds the first ferromagnetic layer 1. Multiple hard bias layers 40 may also exist, for example, sandwiching the first ferromagnetic layer 1 in any direction within the xy plane.

[0182] The hard bias layer 40 is a hard magnetic material. For example, the hard bias layer 40 is a laminated film composed of alternating layers of CoPt alloy, CoPtCr alloy, FePt alloy, Co layers, and Pt layers. The thickness of the hard bias layer 40 is, for example, 2 nm or more and 30 nm or less. The shortest width in the xy plane of the hard bias layer 40 is, for example, 10 nm or more and 500 nm or less.

[0183] 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 hard bias layer 40, M40, is opposite to the magnetization direction of the first ferromagnetic layer 1, M1, in the unlit state. The hard bias layer 40 can be an in-plane magnetization film or a perpendicular magnetization film.

[0184] The leakage magnetic field generated from the hard bias layer 40 acts as a bias magnetic field applied to the first ferromagnetic layer 1, acting on the magnetization M1. In the first mode described above, magnetization M1 and magnetization M2 are parallel in the initial state; in the second mode 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. That is, by applying the leakage magnetic field generated from the hard bias layer 40 to the first ferromagnetic layer 1, a bias application effect is achieved on the magnetization M1 of the first ferromagnetic layer 1.

[0185] (3rd variation)

[0186] Figure 18 This is a cross-sectional view of the photodetector element of the third modified example, cut along the z-direction. The photodetector element of the third modified example also includes a wiring layer 50. (Regarding...) Figure 5 The same structures are labeled with the same reference numerals and the descriptions are omitted.

[0187] The wiring layer 50 is located between the first electrode 15 and the first ferromagnetic layer 1. The wiring layer 50 extends in any direction within the xy plane.

[0188] When current flows along the wiring layer 50, a spin current is generated due to the spin Hall effect, injecting spin into the first ferromagnetic layer 1. The spin injected into the first ferromagnetic layer 1 exerts a spin-orbit torque (SOT) on the magnetization M1 of the first ferromagnetic layer 1.

[0189] The wiring layer 50, for example, contains a non-magnetic heavy metal as the main element. The main element refers to the element with the highest proportion among the elements constituting the wiring layer 50. The wiring layer 50, for example, contains a heavy metal with a specific gravity of yttrium (Y) or higher. Non-magnetic heavy metals have a high atomic number of 39 or higher and possess d or f electrons in their outermost shell, thus generating strong spin-orbit interactions. The wiring layer 50, for example, contains any element selected from Pt, W, Ta, Au, Hf, and Mo. Pt, W, and Ta are particularly preferred elements. To enhance the spin-orbit interaction effect, W and Ta preferably use a β-phase crystal structure. The film thickness of the wiring layer 50 is preferably 1–10 nm, more preferably 1–5 nm.

[0190] By allowing current to flow through the wiring layer 50, spins are injected from the wiring layer 50 into the first ferromagnetic layer 1, creating a bias 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 spin 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 the initial state (the magnetization stability direction of magnetization M1). By controlling the orientation of the spin injected from the wiring layer 50 into the first ferromagnetic layer 1, magnetization M1 and magnetization M2 can be made parallel in the initial state in the first mode described above, and antiparallel in the second mode described above. Furthermore, the spin injected from the wiring layer 50 into the first ferromagnetic layer 1 prevents the magnetization M1 of the first ferromagnetic layer 1 from reversing during operation. The direction of the spin injected from the wiring layer 50 into the first ferromagnetic layer 1 can be freely controlled according to the direction of the current flowing along the wiring layer 50.

[0191] (4th variation)

[0192] Figure 19 This is a cross-sectional view of the receiving device 102 of the fourth modified example, cut along the z-direction. Figure 20 This is a top view of the receiving device 102 of the fourth modification, viewed from the z-direction. The receiving device 102 of the fourth modification also includes a soft magnetic material 60. Regarding... Figure 4 The same structures are labeled with the same reference numerals and the descriptions are omitted.

[0193] The soft magnetic material 60 is a magnetic shield. Viewed from above in the z-direction, the soft magnetic material 60 covers at least a portion of the outer periphery of the photodetector element 10. 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, the soft magnetic material 60 covers the entire outer periphery of the photodetector element 10 when viewed from above in the z-direction. Viewed from any direction in the xy-plane, the soft magnetic material 60 completely overlaps with the z-direction of the outer periphery of the first ferromagnetic layer 1.

[0194] 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 can also be an insulating magnetic material. The soft magnetic material 60 is, for example, a ferrite or other ceramic. The soft magnetic material 60 is, for example, a rare earth iron garnet (RIG). Yttrium iron garnet (YIG) is an example of a rare earth iron garnet (RIG).

[0195] The soft magnetic material 60 can suppress the application of an external magnetic field to the first ferromagnetic layer 1, thereby suppressing the first ferromagnetic layer 1 from exhibiting unintended behavior.

[0196] (5th variation)

[0197] Figure 21 This is a cross-sectional view of the receiving device 103 of the fifth modified example, cut along the z-direction. Figure 22 This is a top view of the receiving device 103 of the fifth modification, viewed from the z-direction. The receiving device 103 of the fifth modification also includes a soft magnetic material 61. Regarding... Figure 4 The same structures are labeled with the same reference numerals and the descriptions are omitted.

[0198] The soft magnetic material 61 is a magnetic shield. Unlike the soft magnetic material 60, the soft magnetic material 61 is also located above and below the photodetector element 10. The soft magnetic material 61 surrounds the photodetector element 10 except for the opening 62. The soft magnetic material 61 can be made of the same material as the soft magnetic material 60.

[0199] The soft magnetic body 61 has an opening 62 above the incident side of light to the light detection element 10. The opening 62 is formed on the side of the first ferromagnetic layer 1 in the soft magnetic body 61, which is located above and below the light detection element 10. A mesh-like magnetic mesh 63 connected to the soft magnetic body 61 is provided in the opening 62. The magnetic mesh 63 contains a magnetic body, for example, containing the same material as the soft magnetic body 61.

[0200] The wiring connected to the first electrode 15 and the second electrode 16 is connected to external contacts disposed on the outside of the soft magnetic body 61 through the insulating layer 64.

[0201] By also providing soft magnetic materials 61 above and below the photodetector element 10, the magnetic shielding effect is further improved. Furthermore, by providing an opening 62 in the soft magnetic material 61, light carrying the optical signal L1 can be efficiently irradiated onto the first ferromagnetic layer 1. Moreover, by providing a magnetic mesh 63 in the opening 62, the intrusion of external magnetic fields from the opening 62 can be suppressed.

[0202] (Sixth variation)

[0203] Figure 23 This is a cross-sectional view of the receiving device 104 in the sixth modified example. Regarding... Figure 4 The same structures are labeled with the same reference numerals and the descriptions are omitted.

[0204] In the sixth modification, the receiving device 104 has a photodetector element 10 formed on the substrate Sb. In the receiving device 104 of the sixth modification, the integrated circuit 20 may be formed on the periphery of the substrate Sb where the photodetector element 10 is not formed, or it may be formed outside the substrate. The integrated circuit 20 is connected to the photodetector element 10 via wiring.

[0205] [Second Implementation]

[0206] The operation of the light detection element in the receiving device of the second embodiment differs from that of the receiving device 100 of the first embodiment. The component structure of the receiving device of the second embodiment is the same as that of the receiving device of the first embodiment.

[0207] Figure 24 This diagram illustrates the operation of the receiving device according to the second embodiment. The receiving device of the second embodiment processes the change in the output voltage (resistance value in the z-direction of the photodetector 10) within a predetermined time as a first signal (e.g., "1"), and the lack of change in the output voltage (resistance value in the z-direction of the photodetector 10) within the predetermined time as a second signal (e.g., "0"). The predetermined time is determined by the modulation frequency of the optical signal.

[0208] The following is based on Figure 24The operation of the receiving device in the second embodiment will be specifically explained using the example shown. First, a light signal that illuminates the light detection element 10 is defined. Regarding the light signal, the case where the intensity of the light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity is defined as "1", and the case where the intensity of the light illuminating the first ferromagnetic layer 1 remains at the first intensity for a predetermined time is defined as "0". The intensity of the light that changes from the first intensity to the second intensity returns to the first intensity after a certain period of time.

[0209] An optical signal illuminates the first ferromagnetic layer 1 of the photodetector element 10. When the intensity of the light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity, the magnetization M1 of the first ferromagnetic layer 1 reverses. Conversely, when the intensity of the light illuminating the first ferromagnetic layer 1 returns from a second intensity to a first intensity, the magnetization M1 of the first ferromagnetic layer 1 does not reverse. If the intensity of the light illuminating 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 changes from a low resistance RL to a high resistance RH or from a high resistance RH to a low resistance RL. That is, if the intensity of the light illuminating the first ferromagnetic layer 1 changes from a first intensity to a second intensity, 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, the resistance value of the photodetector element 10, i.e., the output voltage from the photodetector element 10, changes in either case. That is, when the information "1" is input as an optical signal, the output voltage (resistance value of the optical detection element 10) from the optical detection element 10 changes. By setting the change of the output voltage (resistance value in the z-direction of the optical detection element 10) from the optical detection element 10 within a predetermined time as "1", the receiving device of the second embodiment can receive the optical signal of "1" as a signal of "1" based on the output voltage (resistance value of the optical detection element 10) from the optical detection element 10.

[0210] In contrast, when light does not irradiate the first ferromagnetic layer 1 of the photodetector 10 or the intensity of the irradiated light is low, the magnetization M1 of the first ferromagnetic layer 1 remains in this state. Therefore, when the intensity of light irradiating the first ferromagnetic layer 1 remains 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 information "0" is input as a light signal, the output voltage (resistance value of the photodetector) from the photodetector 10 does not change. By setting the case where the output voltage (resistance value in the z-direction of the photodetector 10) from the photodetector 10 does not change for a predetermined period of time to "0", the receiving device of the second embodiment can receive the light signal "0" as a signal "0" based on the output voltage (resistance value of the photodetector 10) from the photodetector 10.

[0211] As described above, the receiving device of the second embodiment can receive the optical signal as the presence or absence of an output voltage change (a change in the resistance value of the optical detection element in the z-direction) from the photodetector 10 within a specified time period. Furthermore, the photodetector of the second embodiment detects the resistance change between the parallel and antiparallel states of the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2, resulting in a large change in the output voltage.

[0212] Furthermore, in the second embodiment, the direction of the sensing current flowing in the photodetector element can be either from the first ferromagnetic layer 1 towards the second ferromagnetic layer 2, or from the second ferromagnetic layer 2 towards the first ferromagnetic layer 1. In the third embodiment, it is preferable that the value of the sensing current is small so that the spin-transfer torque of the sensing current is not too large. Additionally, in the second embodiment, regardless of whether the initial state is parallel or antiparallel to the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2, a reset current may not be applied.

[0213] The second embodiment has been described in detail above with reference to the accompanying drawings, but 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.

[0214] Furthermore, up to this point, using the first and second embodiments as examples, it has been shown that the transmitting and receiving device is applied to... Figure 1 The example shown is of a communication system 1000, but the communication system is not limited to this case.

[0215] For example, Figure 25 This is a conceptual diagram of another example of a communication system. Figure 25 The communication system 1001 shown is for communication between two portable terminal devices 500. The portable terminal device 500 is, for example, a smartphone, a tablet computer, etc.

[0216] Each portable terminal device 500 includes a receiving device 100 and a transmitting device 200. An optical signal transmitted from the transmitting device 200 of one portable terminal device 500 is received by the receiving device 100 of another portable terminal device 500. The light used in the transmission and reception between the portable terminal devices 500 is, for example, visible light. As the light detection element 10 of each receiving device 100, any one of the light detection elements of the first embodiment and the second embodiment is used.

[0217] In addition, for example, Figure 26 This is a conceptual diagram of another example of a communication system. Figure 26 The communication system 1002 shown is for communication between a portable terminal device 500 and an information processing device 600. The information processing device 600 is, for example, a personal computer.

[0218] The portable terminal device 500 includes a transmitting device 200, and the information processing device 600 includes a receiving device 100. An optical signal transmitted from the transmitting device 200 of the portable 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 portable terminal device 500 and the information processing device 600 is, for example, visible light. As the light detection element 10 of each receiving device 100, any one of the light detection elements of the first to third embodiments is used.

[0219] The present invention is not limited to the above-described embodiments and variations. Various modifications and alterations can be made within the scope of the spirit of the invention as described in the claims.

Claims

1. A reception device characterized by comprising: a magnetic element including a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched by the first ferromagnetic layer and the second ferromagnetic layer, light including a light signal having a light intensity variation being irradiated to the first ferromagnetic layer, a resistance value of the magnetic element being varied according to a change in a magnetization direction of the first ferromagnetic layer, and the change in the resistance value of the magnetic element being converted into an output voltage from the magnetic element, the light signal being received based on the output voltage from the magnetic element, and the angle of the magnetization direction of the first ferromagnetic layer in a state where the light is not irradiated to the first ferromagnetic layer being larger than 0° and smaller than 90° than the angle of the magnetization direction of the first ferromagnetic layer in a state where the light is irradiated to the first ferromagnetic layer.

2. The reception device according to claim 1, characterized in that: the magnetization of the first ferromagnetic layer in the state where the light is irradiated to the first ferromagnetic layer is smaller than the magnetization of the first ferromagnetic layer in the state where the light is not irradiated to the first ferromagnetic layer.

3. The reception device according to claim 1 or 2, characterized in that: the light signal has at least two levels of intensity, the magnitude of the output voltage from the magnetic element shows a first value in a case where the intensity of the light irradiated to the first ferromagnetic layer is a first intensity, and shows a second value in a case where the intensity of the light irradiated to the first ferromagnetic layer is a second intensity, the second intensity being larger than the first intensity on the condition that: in a case where the second value is larger than the first value, a current is caused to flow from the first ferromagnetic layer to the second ferromagnetic layer, and in a case where the second value is smaller than the first value, a current is caused to flow from the second ferromagnetic layer to the first ferromagnetic layer.

4. The reception device according to claim 1 or 2, characterized in that: it further comprises a hard bias layer that applies a bias magnetic field to the first ferromagnetic layer, the hard bias layer is located at a position overlapping with the first ferromagnetic layer when viewed from any direction orthogonal to the stacking direction of the magnetic element, and the magnetization direction of the hard bias layer is opposite to the magnetization direction of the first ferromagnetic layer in a state where the light is not irradiated.

5. The reception device according to claim 1 or 2, characterized in that: the magnetic element further comprises a first electrode connected to the first ferromagnetic layer and a second electrode connected to the second ferromagnetic layer, and the first electrode has transmittance for light in a wavelength region used by the light signal.

6. The reception device according to claim 1 or 2, characterized in that: it further comprises a soft magnetic body, and the soft magnetic body covers at least a part of the outer periphery of the magnetic element from the outside when viewed from the stacking direction of the magnetic element.

7. The reception device according to claim 6, characterized in that: the soft magnetic body is also located above and below the stacking direction of the magnetic element, and the soft magnetic body located on the first ferromagnetic layer side among the soft magnetic bodies located above and below the magnetic element has an opening. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 8. The reception device according to claim 7, wherein the opening has a meshed magnetic mesh connected to the soft magnetic body.

9. The reception device according to claim 1 or 2, wherein a case where the output voltage from the magnetic element is above a threshold value is handled as a first signal, and a case where the output voltage is below the threshold value is handled as a second signal.

10. The reception device according to claim 1 or 2, wherein a case where the output voltage from the magnetic element changes within a prescribed time is handled as a first signal, and a case where the output voltage from the magnetic element does not change within the prescribed time is handled as a second signal.

11. The reception device according to claim 1 or 2, wherein further comprising an integrated circuit, the magnetic element and the integrated circuit are formed on the same substrate via an interlayer insulating film, the integrated circuit and the magnetic element are connected via a through wiring that penetrates the interlayer insulating film.

12. A transmission / reception device, comprising: a reception device according to any one of claims 1 to 11; and a transmission device that transmits an optical signal.

13. A communication system, comprising: a plurality of the transmission / reception device according to claim 12.

14. A portable terminal device, comprising: a reception device according to any one of claims 1 to 11.

15. An optical detection element, comprising: a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched by the first ferromagnetic layer and the second ferromagnetic layer, light including an optical signal having a light intensity variation is irradiated to the first ferromagnetic layer, a resistance value of the optical detection element changes according to a change in a magnetization direction of the first ferromagnetic layer, and a change in the resistance value of the optical detection element is converted into an output voltage from the optical detection element, an angle of the magnetization direction of the first ferromagnetic layer in a state where the light is not irradiated to the first ferromagnetic layer is larger than 0° and smaller than 90° with respect to a magnetization direction of the first ferromagnetic layer in a state where the light is irradiated to the first ferromagnetic layer.

16. The optical detection element according to claim 15, wherein the magnetization of the first ferromagnetic layer in the state where the light is irradiated to the first ferromagnetic layer is smaller than the magnetization of the first ferromagnetic layer in the state where the light is not irradiated to the first ferromagnetic layer.

17. The optical detection element according to claim 15 or 16, wherein an optical signal having an intensity of at least two levels is irradiated, in a case where the intensity of the light irradiated to the first ferromagnetic layer is a first intensity, a magnitude of the output voltage shows a first value, and in a case where the intensity of the light irradiated to the first ferromagnetic layer is a second intensity, the magnitude of the output voltage shows a second value, on a condition that the second intensity is larger than the first intensity: in a case where the second value is larger than the first value, a current flows from the first ferromagnetic layer to the second ferromagnetic layer, ​ In a case where the second value is smaller than the first value, a current flows from the second ferromagnetic layer to the first ferromagnetic layer.

18. The light detecting element according to claim 15 or 16, wherein: the first ferromagnetic layer is a perpendicular magnetization film.

19. The light detecting element according to claim 15 or 16, wherein: the first ferromagnetic layer exhibits ferromagnetism other than ferrimagnetism.

20. The light detecting element according to claim 15 or 16, wherein: the first ferromagnetic layer contains a CoFeB alloy.

21. The light detecting element according to claim 15 or 16, wherein: the first ferromagnetic layer contains Fe, and a composition ratio of Fe in the first ferromagnetic layer is 50 atomic % or more.

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