Optical element

Abstract

To provide a light detection element with high light detection capability.SOLUTION: The light detection element includes a light-sensitive layer that generates a voltage when irradiated by light, a first electrode, and a second electrode. The light-sensitive layer is located between the first and second electrodes. The second electrode is a metal containing at least one element selected from the group consisting of ruthenium, molybdenum, and tungsten.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a light detection element.

Background Art

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

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although light detection elements using semiconductor pn junctions are widely used, new light detection elements are required for further development. Also, a light detection element that converts light into an electrical signal and has high light detection ability with high efficiency of converting light into an electrical signal is required.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide a light detection element with high light detection ability.

Means for Solving the Problems

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

[0008] (1) The photodetector according to the first embodiment comprises a photosensitive layer that generates a voltage when irradiated with light, a first electrode, and a second electrode, wherein the photosensitive layer is located between the first electrode and the second electrode, and the second electrode is a metal containing at least one element selected from the group consisting of ruthenium, molybdenum, and tungsten.

[0009] (2) In the photodetector according to the above embodiment, the first electrode may be a transparent electrode.

[0010] (3) In the photodetector according to the above embodiment, light with a wavelength of 400 nm to 1500 nm may be irradiated onto the photosensitive layer.

[0011] (4) In the photodetector according to the above embodiment, the photosensitive layer may include a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer located between the first ferromagnetic layer and the second ferromagnetic layer. [Effects of the Invention]

[0012] The photodetector according to the above embodiment has high photodetection capability. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view of the photodetector element according to the first embodiment. [Figure 2] This figure illustrates the first mechanism of a first operating example of a photodetector according to the first embodiment. [Figure 3] This figure illustrates the second mechanism of a first operational example of the photodetector element according to the first embodiment. [Figure 4] This figure illustrates the first mechanism of a second operating example of the photodetector element according to the first embodiment. [Figure 5] This figure illustrates the second mechanism of a second operating example of the photodetector element according to the first embodiment. [Figure 6] This figure illustrates another example of a second operation example of the photodetector element according to the first embodiment. [Figure 7] FIG. is a diagram for explaining another example of a second operation example of the photosensor according to the first embodiment. [Figure 8] FIG. is a cross-sectional view of a photosensor according to the first modification. [Figure 9] FIG. is a schematic diagram of a first application example of the photosensor. [Figure 10] FIG. is a block diagram of a transceiver according to the first application example. [Figure 11] FIG. is an enlarged schematic diagram of the vicinity of the photosensor of the transceiver according to the first application example. [Figure 12] FIG. is a conceptual diagram of another example of a communication system. [Figure 13] FIG. is a conceptual diagram of another example of a communication system. [Figure 14] FIG. is a schematic diagram of a second application example of the photosensor. [Figure 15] FIG. is a schematic diagram of an example of a terminal device.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, embodiments will be described in detail with appropriate reference to the drawings. The drawings used in the following description may show enlarged parts that are characteristic for the sake of clarity, and the dimensional ratios of each component may be different from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and can be appropriately changed and implemented within the scope where the effects of the present invention are achieved.

[0015] Define the directions. The stacking direction of the photosensor 100 is defined as the z direction, one direction in the plane orthogonal to the z direction is the x direction, and the direction orthogonal to the x direction and the z direction is the y direction. The z direction is an example of the stacking direction. Hereinafter, the +z direction may be expressed as "up" and the -z direction may be expressed as "down". The +z direction is the direction from the second electrode 22 to the first electrode 21. The up and down do not necessarily coincide with the direction in which gravity acts.

[0016] "First Embodiment" Figure 1 is a cross-sectional view of the photodetector element 100 according to the first embodiment. In Figure 1, the direction of magnetization in the initial state of the ferromagnetic material is indicated by an arrow.

[0017] The photodetector element 100 comprises a photosensitive layer 10, a first electrode 21, and a second electrode 22. The photosensitive layer 10 is located between the first electrode 21 and the second electrode 22. The photodetector element 100 may also have a buffer layer 4, a seed layer 5, a third ferromagnetic layer 6, a magnetic coupling layer 7, a perpendicular magnetization induction layer 8, a cap layer 9, and an insulating layer 90. The buffer layer 4, seed layer 5, third ferromagnetic layer 6, and magnetic coupling layer 7 are located between the photosensitive layer 10 and the second electrode 22, while the perpendicular magnetization induction layer 8 and cap layer 9 are located between the photosensitive layer 10 and the first electrode 21. The insulating layer 90 is located between the first electrode 21 and the second electrode 22 and covers the periphery of the laminate 30 including the photosensitive layer 10.

[0018] The photodetector 100 converts the state or change in state of the irradiated light into an electrical signal. In this specification, "light" is not limited to visible light, but also includes infrared radiation with longer wavelengths than visible light, and ultraviolet radiation with shorter wavelengths than visible light. For example, the wavelength of visible light is between 380 nm and less than 800 nm. For example, the wavelength of infrared radiation is between 800 nm and 1 mm. For example, the wavelength of ultraviolet radiation is between 200 nm and less than 380 nm. For example, the photodetector 100 (photosensitive layer 10) is irradiated with light having a wavelength between 400 nm and 1500 nm.

[0019] The photosensitive layer 10 generates a voltage when irradiated with light. When the state of the irradiated light changes, the resistance value in the z direction of the photosensitive layer 10 changes in accordance with the change in the state of the light. When the state of the light irradiated onto the photosensitive layer 10 changes, the output voltage from the photosensitive layer 10 changes in accordance with the change in the state of the light. The photosensitive layer 10 includes, for example, a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a spacer layer 3. The spacer layer 3 is located between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The photosensitive layer 10 may have other layers in addition to these.

[0020] The photosensitive layer 10 is a magnetic element containing a ferromagnetic material. For example, if the spacer layer 3 is made of an insulator, the photosensitive layer 10 has a magnetic tunnel junction (MTJ) consisting of a first ferromagnetic layer 1, a spacer layer 3, and a second ferromagnetic layer 2. Such an element is called an MTJ element. In this case, the photosensitive layer 10 can exhibit a tunnel magnetoresistance (TMR) effect. If the spacer layer 3 is made of a metal, the photosensitive layer 10 can exhibit a giant magnetoresistance (GMR) effect. Such an element is called a GMR element. The photosensitive layer 10 may be called an MTJ element, a GMR element, etc., depending on the constituent material of the spacer layer 3, but it is collectively called a magnetoresistance effect element. The photosensitive layer 10 changes its resistance in the z direction (resistance when current is passed in the z direction) in accordance with the relative change in the magnetization state of the first ferromagnetic layer 1 and the magnetization state of the second ferromagnetic layer 2.

[0021] The first ferromagnetic layer 1 is a photosensitive layer whose magnetization state changes when light is irradiated from the outside. The first ferromagnetic layer 1 is also called the magnetization free layer. The magnetization free layer is a layer containing a magnetic material whose magnetization state changes when a predetermined external energy is applied. The predetermined external energy is, for example, light irradiated from the outside, a current flowing in the z direction of the photosensitive layer 10, or an external magnetic field. The magnetization of the first ferromagnetic layer 1 changes state according to the intensity of the light irradiated onto the first ferromagnetic layer 1 (light irradiated onto the photosensitive layer 10).

[0022] The first ferromagnetic layer 1 contains a ferromagnetic material. The first ferromagnetic layer 1 contains at least one of the magnetic elements such as Co, Fe, or Ni. The first ferromagnetic layer 1 may also contain elements such as B, Mg, Hf, and Gd along with the magnetic elements mentioned above. The first ferromagnetic layer 1 may be an alloy containing a magnetic element and a non-magnetic element, for example. The first ferromagnetic layer 1 may be composed of multiple layers. The first ferromagnetic layer 1 may be, for example, a CoFeB alloy, a laminate in which a CoFeB alloy layer is sandwiched between Fe layers, or a laminate in which a CoFeB alloy layer is sandwiched between CoFe layers. Generally, "ferromagnetism" includes "ferrimagnetism". The first ferromagnetic layer 1 may exhibit ferrimagnetism. On the other hand, the first ferromagnetic layer 1 may exhibit ferromagnetism that is not ferrimagnetism. For example, a CoFeB alloy exhibits ferromagnetism that is not ferrimagnetism.

[0023] The first ferromagnetic layer 1 may be an in-plane magnetized film having an easy magnetization axis in the direction within the film plane (either direction in the xy plane), or a perpendicular magnetized film having an easy magnetization axis perpendicular to the film plane (z direction).

[0024] The thickness of the first ferromagnetic layer 1 is, for example, 1 nm to 5 nm. Preferably, the thickness of the first ferromagnetic layer 1 is, for example, 1 nm to 2 nm. When the first ferromagnetic layer 1 is a perpendicular magnetization film, if the thickness of the first ferromagnetic layer 1 is thin, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 1 is strengthened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 increases. In other words, if the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is high, the force that causes the magnetization M1 to return to the z direction is strengthened. On the other hand, if the thickness of the first ferromagnetic layer 1 is thick, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 1 is relatively weakened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is weakened.

[0025] When the thickness of the first ferromagnetic layer 1 decreases, its volume as a ferromagnetic material decreases, and when its thickness increases, its volume as a ferromagnetic material increases. The reactivity of the magnetization of the first ferromagnetic layer 1 when external energy is applied is inversely proportional to the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 1. In other words, when the product of the magnetic anisotropy and volume of the first ferromagnetic layer 1 decreases, its reactivity to light increases. From this viewpoint, in order to increase the reactivity to light, it is preferable to appropriately design the magnetic anisotropy of the first ferromagnetic layer 1 and then reduce the volume of the first ferromagnetic layer 1.

[0026] If the thickness of the first ferromagnetic layer 1 is greater than 2 nm, an insertion layer made of, for example, Mo and W may be provided within the first ferromagnetic layer 1. That is, the first ferromagnetic layer 1 may be a laminate in which a ferromagnetic layer, an insertion layer, and a ferromagnetic layer are stacked in order in the z direction. The interfacial magnetic anisotropy at the interface between the insertion layer and the ferromagnetic layer increases the perpendicular magnetic anisotropy of the entire first ferromagnetic layer 1. The thickness of the insertion layer is, for example, 0.1 nm to 1.0 nm.

[0027] The second ferromagnetic layer 2 is a magnetization-fixed layer. The magnetization-fixed layer is a layer made of a magnetic material whose magnetization state changes less easily than that of the magnetization-free layer when a predetermined external energy is applied. For example, the magnetization direction of the magnetization-fixed layer changes less easily than that of the magnetization-free layer when a predetermined external energy is applied. Also, for example, the magnitude of magnetization of the magnetization-fixed layer changes less easily than that of the magnetization-free layer when a predetermined external energy is applied. The coercivity of the second ferromagnetic layer 2 is greater than that of the first ferromagnetic layer 1, for example. The second ferromagnetic layer 2 has an easy magnetization axis in the same direction as the first ferromagnetic layer 1, for example. The second ferromagnetic layer 2 may be an in-plane magnetized film or a perpendicular magnetized film.

[0028] The material constituting the second ferromagnetic layer 2 is, for example, the same as that of the first ferromagnetic layer 1. The second ferromagnetic layer 2 may be a multilayer film in which Co with a thickness of 0.4 nm to 1.0 nm and Pt with a thickness of 0.4 nm to 1.0 nm are alternately stacked several times. The second ferromagnetic layer 2 may also be a laminate in which Co with a thickness of 0.4 nm to 1.0 nm, Mo with a thickness of 0.1 nm to 0.5 nm, a CoFeB alloy with a thickness of 0.3 nm to 1.0 nm, and Fe with a thickness of 0.3 nm to 1.0 nm are stacked in that order.

[0029] The magnetization of the second ferromagnetic layer 2 may be fixed, for example, by magnetic coupling with the third ferromagnetic layer 6, which is separated by a magnetic coupling layer 7. In this case, the second ferromagnetic layer 2, the magnetic coupling layer 7, and the third ferromagnetic layer 6 together may be referred to as the magnetization-fixing layer. Details of the magnetic coupling layer 7 and the third ferromagnetic layer 6 will be described later.

[0030] The spacer layer 3 is a layer placed between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The spacer layer 3 is composed of a conductor, an insulator, or a semiconductor, or a layer containing a current-carrying point composed of a conductor within an insulator. For example, the spacer layer 3 is a non-magnetic layer. The thickness of the spacer layer 3 can be adjusted according to the orientation direction of the magnetization of the first ferromagnetic layer 1 and the magnetization of the second ferromagnetic layer 2 in the initial state, as described later.

[0031] When the spacer layer 3 is composed of an insulating material, materials containing aluminum oxide, magnesium oxide, titanium oxide, or silicon oxide can be used as the material for the spacer layer 3. These insulating materials may also contain elements such as Al, B, Si, and Mg, or magnetic elements such as Co, Fe, and Ni. A high magnetoresistance change rate can be obtained by adjusting the film thickness of the spacer layer 3 so that a high TMR effect is exhibited between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. In order to efficiently utilize the TMR effect, the film thickness of the spacer layer 3 may be around 0.5 to 5.0 nm, or around 1.0 to 2.5 nm.

[0032] When the spacer layer 3 is made of a non-magnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. In order to efficiently utilize the GMR effect, the film thickness of the spacer layer 3 may be around 0.5 to 5.0 nm, or it may be around 2.0 to 3.0 nm.

[0033] When the spacer layer 3 is made of a non-magnetic semiconductor material, materials such as zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, or ITO can be used. In this case, the film thickness of the spacer layer 3 may be about 1.0 to 4.0 nm.

[0034] When a layer containing current-carrying points composed of conductors in a non-magnetic insulator is applied as the spacer layer 3, the structure may include current-carrying points composed of non-magnetic conductors such as Cu, Au, and Al in a non-magnetic insulator composed of aluminum oxide or magnesium oxide. Alternatively, the conductors may be composed of magnetic elements such as Co, Fe, and Ni. In this case, the film thickness of the spacer layer 3 may be about 1.0 to 2.5 nm. The current-carrying points are, for example, columnar bodies with a diameter of 1 nm to 5 nm when viewed from a direction perpendicular to the film surface.

[0035] The third ferromagnetic layer 6 is magnetically coupled to, for example, the second ferromagnetic layer 2. This magnetic coupling is, for example, an antiferromagnetic coupling, and is caused by the RKKY interaction. The material constituting the third ferromagnetic layer 6 is, for example, the same as that of the first ferromagnetic layer 1.

[0036] The magnetic coupling layer 7 is located between the second ferromagnetic layer 2 and the third ferromagnetic layer 6. The magnetic coupling layer 7 is made of, for example, Ru, Ir, etc.

[0037] The buffer layer 4 is a layer that mitigates lattice mismatch between different crystals. The buffer layer 4 is, for example, a metal containing at least one element selected from the group consisting of Ta, Ti, Zr, and Cr, or a nitride containing at least one element selected from the group consisting of Ta, Ti, Zr, and Cu. More specifically, the buffer layer 4 is, for example, elemental Ta, NiCr alloy, TaN (tantalum nitride), or CuN (copper nitride). The thickness of the buffer layer 4 is, for example, 1 nm to 5 nm. The buffer layer 4 is, for example, amorphous. The buffer layer 4 is located, for example, between the seed layer 5 and the second electrode 22 and is in contact with the second electrode 22. The buffer layer 4 suppresses the influence of the crystal structure of the second electrode 22 on the crystal structure of the photosensitive layer 10.

[0038] The seed layer 5 enhances the crystallinity of the layers stacked on top of it. The seed layer 5 is located, for example, between the buffer layer 4 and the third ferromagnetic layer 6, and is situated on the buffer layer 4. The seed layer 5 is made of, for example, Pt, Ru, Zr, or NiFeCr. The thickness of the seed layer 5 is, for example, between 1 nm and 5 nm.

[0039] The capping layer 9 is located between the first ferromagnetic layer 1 and the first electrode 21. The capping layer 9 may also include a perpendicular magnetization-inducing layer 8 that is laminated on the first ferromagnetic layer 1 and in contact with the first ferromagnetic layer 1. The capping layer 9 prevents damage to the underlying layer during the process and enhances the crystallinity of the underlying layer during annealing. The thickness of the capping layer 9 is, for example, 10 nm or less, so that the first ferromagnetic layer 1 is sufficiently irradiated with light.

[0040] The perpendicular magnetization induction layer 8 induces perpendicular magnetic anisotropy in the first ferromagnetic layer 1. The perpendicular magnetization induction layer 8 is, for example, magnesium oxide, W, Ta, Mo, etc. When the perpendicular magnetization induction layer 8 is magnesium oxide, it is preferable that the magnesium oxide is oxygen-deficient in order to enhance conductivity. The thickness of the perpendicular magnetization induction layer 8 is, for example, 0.5 nm to 5.0 nm.

[0041] The insulating layer 90 is, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg.x ), silicon nitride (SiN x ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO3) x ) etc.

[0042] The first electrode 21 is positioned on the side into which the incident light enters the photodetector element 100. The incident light is irradiated onto the photosensitive layer 10 from the side of the first electrode 21. The first electrode 21 is made of a conductive material. The first electrode 21 is, for example, a transparent electrode that is transparent to light in the usable wavelength range. Preferably, the first electrode 21 transmits 80% or more of the light in the usable wavelength range. The usable wavelength range of the light is, for example, 300 nm to 2 μm, preferably 400 nm to 1500 nm. The first electrode 21 is, for example, an oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). The first electrode 21 may have a configuration in which a plurality of columnar metals are contained within the transparent electrode material of these oxides. The first electrode 21 may also have an anti-reflective coating on the irradiation surface to which the light is irradiated.

[0043] The second electrode 22 is made of a conductive material. The second electrode 22 is a metal containing at least one element selected from the group consisting of ruthenium, molybdenum, and tungsten. The second electrode 22 may be a single layer film of ruthenium, molybdenum, or tungsten, or a multilayer film having at least one layer of ruthenium, molybdenum, or tungsten. For example, the second electrode 22 may be a multilayer film in which ruthenium and tungsten are alternately layered, a multilayer film in which ruthenium and molybdenum are alternately layered, or a multilayer film in which molybdenum and tungsten are alternately layered.

[0044] Ruthenium, molybdenum, and tungsten have high melting points (above 2000°C) and excellent heat resistance. The second electrode 22, which contains these elements, is less prone to degradation even when subjected to heat treatment during crystallization of the photosensitive layer 10 and heat treatment during semiconductor processes.

[0045] The second electrode 22 reflects a portion of the incident light incident from the first electrode 21 side at the interface between the second electrode 22 and the layer in contact with it (the interface between the buffer layer 4 and the second electrode 22, and the interface between the insulating layer 90 and the second electrode 22). Ruthenium, molybdenum, and tungsten have high reflectivity of light at these interfaces, and in particular, they have high reflectivity of light with wavelengths between 400 nm and 1500 nm at these interfaces. The reflected light reflected by the second electrode 22 is irradiated onto the photosensitive layer 10. Since the second electrode 22 is made of a predetermined material (a metal containing at least one element selected from the group consisting of ruthenium, molybdenum, and tungsten), it reflects more incident light than would be possible if it were made of a different material. Therefore, the photodetector element 100 receives a large amount of light irradiated onto the photosensitive layer 10.

[0046] The photodetector element 100 is manufactured by lamination, annealing, and processing steps for each layer. First, a buffer layer 4, a seed layer 5, a third ferromagnetic layer 6, a magnetic coupling layer 7, a second ferromagnetic layer 2, a spacer layer 3, a first ferromagnetic layer 1, a perpendicular magnetization induction layer 8, and a cap layer 9 are laminated on the second electrode 22 in that order. Each layer is deposited by, for example, sputtering.

[0047] Next, the laminated film is annealed. The annealing temperature is, for example, between 250°C and 400°C. After that, the laminated film is processed into a columnar laminate 30 by photolithography and etching. The laminate 30 may be cylindrical or prismatic. For example, the shortest width of the laminate 30 when viewed from the z direction is between 10 nm and 1000 nm.

[0048] Next, an insulating layer 90 is formed to cover the side surface of the laminate 30. The insulating layer 90 may be laminated multiple times. Then, the upper surface of the cap layer 9 is exposed from the insulating layer 90 by chemical mechanical polishing, and the first electrode 21 is fabricated on the cap layer 9. A photodetector element 100 is obtained through the above steps.

[0049] Next, some examples of the operation of the photodetector 100 will be described. The photosensitive layer 10 is irradiated with light whose light intensity changes. The output voltage from the photodetector 100 changes with the change in the intensity of the light irradiated onto the photosensitive layer 10. One of the factors contributing to the change in the output voltage from the photodetector 100 is, for example, the change in the resistance of the photosensitive layer 10. In the first example of operation, we will explain the case where the intensity of the light irradiated onto the photosensitive layer 10 is in two stages: a first intensity and a second intensity. The intensity of the second intensity light is assumed to be greater than the intensity of the first intensity light. The first intensity may be zero when the intensity of the light irradiated onto the photosensitive layer 10 is zero.

[0050] Figures 2 and 3 are diagrams illustrating a first operation example of the photodetector 100 according to the first embodiment. Figure 2 is a diagram illustrating the first mechanism of the first operation example, and Figure 3 is a diagram illustrating the second mechanism of the first operation example. In Figures 2 and 3, only the photosensitive layer 10 of the photodetector 100 is shown. In the upper graphs of Figures 2 and 3, the vertical axis represents the intensity of light irradiated onto the photosensitive layer 10, and the horizontal axis represents time. In the lower graphs of Figures 2 and 3, the vertical axis represents the resistance value in the z direction of the photodetector 100, and the horizontal axis represents time.

[0051] First, in the state where the photosensitive layer 10 is irradiated with light of first intensity (hereinafter referred to as the initial state), the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 are in a parallel relationship, the resistance value of the photodetector element 100 in the z direction is a first resistance value R1, and the magnitude of the output voltage from the photodetector element 100 is a first value. The resistance value of the photodetector element 100 in the z direction can be determined by passing a sense current Is in the z direction of the photodetector element 100, which generates a voltage across the z-sides of the photodetector element 100, and then using Ohm's law from that voltage value. The output voltage from the photodetector element 100 is generated between the first electrode 21 and the second electrode 22. In the example shown in Figure 2, the sense current Is is passed from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. By applying a sense current Is in this direction, a spin transfer torque acts on the magnetization M1 of the first ferromagnetic layer 1 in the same direction as the magnetization M2 of the second ferromagnetic layer 2, causing the magnetizations M1 and M2 to be parallel in the initial state. Furthermore, applying a sense current Is in this direction prevents the magnetization M1 of the first ferromagnetic layer 1 from reversing during operation.

[0052] Next, the intensity of the light irradiated onto the photosensitive layer 10 changes from the first intensity to the second intensity. The second intensity is greater than the first intensity, and the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state. The state of magnetization M1 of the first ferromagnetic layer 1 when no light is irradiated onto the photosensitive layer 10 is different from the state of magnetization M1 of the first ferromagnetic layer 1 at the second intensity. The state of magnetization M1 refers to, for example, the tilt angle with respect to the z direction, the magnitude, etc.

[0053] For example, as shown in Figure 2, when the intensity of light irradiated onto the photosensitive layer 10 changes from a first intensity to a second intensity, the magnetization M1 tilts with respect to the z direction. Also, for example, as shown in Figure 3, when the intensity of light irradiated onto the photosensitive layer 10 changes from a first intensity to a second intensity, the magnitude of the magnetization M1 decreases. For example, when the magnetization M1 of the first ferromagnetic layer 1 tilts with respect to the z direction due to the light irradiation intensity, the tilt angle is greater than 0° and less than 90°.

[0054] When the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state, the resistance value of the photodetector element 100 in the z direction exhibits a second resistance value R2, and the magnitude of the output voltage from the photodetector element 100 exhibits a second value. The second resistance value R2 is greater than the first resistance value R1, and the second value of the output voltage is greater than the first value. The second resistance value R2 is between the resistance value when magnetization M1 and magnetization M2 are parallel (first resistance value R1) and the resistance value when magnetization M1 and magnetization M2 are antiparallel.

[0055] In the case shown in Figure 2, a spin transfer torque acts on the magnetization M1 of the first ferromagnetic layer 1 in the same direction as the magnetization M2 of the second ferromagnetic layer 2. Therefore, magnetization M1 tries to return to a state parallel to magnetization M2, and when the intensity of light irradiated onto the photosensitive layer 10 changes from the second intensity to the first intensity, the photodetector element 100 returns to its initial state. In the case shown in Figure 3, when the intensity of light irradiated onto the photosensitive layer 10 returns to the first intensity, the magnitude of the magnetization M1 of the first ferromagnetic layer 1 returns to its original value, and the photodetector element 100 returns to its initial state. In both cases, the resistance value of the photodetector element 100 in the z direction returns to the first resistance value R1. In other words, when the intensity of light irradiated onto the photosensitive layer 10 changes from the second intensity to the first intensity, the resistance value of the photodetector element 100 in the z direction changes from the second resistance value R2 to the first resistance value R1, and the magnitude of the output voltage from the photodetector element 100 changes from the second value to the first value.

[0056] The output voltage from the photodetector 100 changes in response to changes in the intensity of light irradiated onto the photosensitive layer 10, and the change in the intensity of the irradiated light can be converted into a change in the output voltage from the photodetector 100. In other words, the photodetector 100 can convert light into an electrical signal. For example, if the output voltage from the photodetector 100 is above a threshold, it is processed as a first signal (e.g., "1"), and if it is below the threshold, it is processed as a second signal (e.g., "0").

[0057] Here, we have explained the case where magnetizations M1 and M2 are parallel in the initial state, but magnetizations M1 and M2 may be antiparallel in the initial state. In this case, the resistance value in the z direction of the photodetector element 100 decreases as the state of magnetization M1 changes (for example, as the angle change from the initial state of magnetization M1 increases). When the initial state is when magnetizations M1 and M2 are antiparallel, it is preferable to flow the sense current Is from the second ferromagnetic layer 2 toward the first ferromagnetic layer 1. By flowing the sense current Is in this direction, a spin transfer torque opposite to that of magnetization M2 in the second ferromagnetic layer 2 acts on the magnetization M1 of the first ferromagnetic layer 1, causing magnetizations M1 and M2 to be antiparallel in the initial state.

[0058] In the first operational example, we explained the case where the light irradiated onto the photosensitive layer 10 has two intensity levels, a first intensity and a second intensity. In the second operational example, we will explain the case where the intensity of the light irradiated onto the photosensitive layer 10 changes in multiple stages or analogously.

[0059] Figures 4 and 5 are diagrams illustrating a second operation example of the photodetector 100 according to the first embodiment. Figure 4 is a diagram illustrating the first mechanism of the second operation example, and Figure 5 is a diagram illustrating the second mechanism of the second operation example. In Figures 4 and 5, only the photosensitive layer 10 of the photodetector 100 is shown. In the upper graphs of Figures 4 and 5, the vertical axis represents the intensity of light irradiated onto the photosensitive layer 10, and the horizontal axis represents time. In the lower graphs of Figures 4 and 5, the vertical axis represents the resistance value in the z direction of the photodetector 100, and the horizontal axis represents time.

[0060] In the case of Figure 4, as the intensity of light irradiated onto the photosensitive layer 10 increases, the magnetization M1 of the first ferromagnetic layer 1 tilts from its initial state due to the external energy from the light irradiation. The angle between the direction of the magnetization M1 of the first ferromagnetic layer 1 when it is not irradiated with light and the angle between the direction of the magnetization M1 when it is irradiated with light is greater than 0° and less than 90° in both cases.

[0061] When the magnetization M1 of the first ferromagnetic layer 1 deviates from its initial state, the resistance value in the z direction of the photodetector element 100 changes. Consequently, the output voltage from the photodetector element 100 changes. For example, depending on the deviation of the magnetization M1 of the first ferromagnetic layer 1, the resistance value in the z direction of the photodetector element 100 changes to the second resistance value R2, the third resistance value R3, and the fourth resistance value R4, and the output voltage from the photodetector element 100 changes to the second value, the third value, and the fourth value. The resistance values ​​increase in the order of the first resistance value R1, the second resistance value R2, the third resistance value R3, and the fourth resistance value R4. The output voltage from the photodetector element 100 increases in the order of the first value, the second value, the third value, and the fourth value.

[0062] When the intensity of light irradiated onto the photosensitive layer 10 changes, the output voltage from the photodetector 100 (the resistance value in the z direction of the photodetector 100) changes. For example, if the first value (first resistance value R1) is defined as "0", the second value (second resistance value R2) as "1", the third value (third resistance value R3) as "2", and the fourth value (fourth resistance value R4) as "3", the photodetector 100 can output information for four values. Here, we have shown an example of reading out four values, but the number of values ​​to be read can be freely designed by setting the threshold value of the output voltage from the photodetector 100 (the resistance value of the photodetector 100). The photodetector 100 may also output analog values ​​directly.

[0063] Similarly, in the case of Figure 5, as the intensity of light irradiated onto the photosensitive layer 10 increases, the magnitude of the magnetization M1 of the first ferromagnetic layer 1 decreases from its initial state due to the external energy from the light irradiation. When the magnetization M1 of the first ferromagnetic layer 1 decreases from its initial state, the resistance value in the z direction of the photodetector element 100 changes. Consequently, the output voltage from the photodetector element 100 changes. For example, depending on the magnitude of the magnetization M1 of the first ferromagnetic layer 1, the resistance value in the z direction of the photodetector element 100 changes to the second resistance value R2, the third resistance value R3, and the fourth resistance value R4, and the output voltage from the photodetector element 100 changes to the second, third, and fourth values. Therefore, as in the case of Figure 4, the photodetector element 100 can output these differences in output voltage (resistance value) as multi-level or analog data.

[0064] In the second operation example, as in the first operation example, when the intensity of the light irradiated onto the photosensitive layer 10 returns to the first intensity, the magnetization M1 state of the first ferromagnetic layer 1 returns to its original state, and the photodetector element 100 returns to its initial state.

[0065] Here, we have explained the case where magnetization M1 and magnetization M2 are parallel in the initial state, but in the second example of operation, magnetization M1 and magnetization M2 may be antiparallel in the initial state as well.

[0066] Furthermore, while the first and second operation examples illustrate cases where magnetization M1 and magnetization M2 are parallel or antiparallel in the initial state, magnetization M1 and magnetization M2 may also be orthogonal in the initial state. For example, this case applies when the first ferromagnetic layer 1 is an in-plane magnetization film in which magnetization M1 is oriented in one direction in the xy plane, and the second ferromagnetic layer 2 is a perpendicular magnetization film in which magnetization M2 is oriented in the z direction. Due to magnetic anisotropy, magnetization M1 is oriented in one direction in the xy plane, and magnetization M2 is oriented in the z direction, so that magnetization M1 and magnetization M2 are orthogonal in the initial state.

[0067] Figures 6 and 7 illustrate another example of a second operation example of the photodetector element 100 according to the first embodiment. In Figures 6 and 7, only the photosensitive layer 10 of the photodetector element 100 is shown. Figures 6 and 7 differ in the direction of flow of the sense current Is applied to the photodetector element 100. In Figure 6, the sense current Is flows from the first ferromagnetic layer 1 to the second ferromagnetic layer 2. In Figure 7, the sense current Is flows from the second ferromagnetic layer 2 to the first ferromagnetic layer 1.

[0068] In both Figure 6 and Figure 7, a sense current Is flows through the photodetector element 100, causing a spin transfer torque to act on the magnetization M1 in the initial state. In Figure 6, the spin transfer torque acts so that the magnetization M1 is parallel to the magnetization M2 of the second ferromagnetic layer 2. In Figure 7, the spin transfer torque acts so that the magnetization M1 is antiparallel to the magnetization M2 of the second ferromagnetic layer 2. In both Figure 6 and Figure 7, in the initial state, the effect of magnetic anisotropy on the magnetization M1 is greater than the effect of the spin transfer torque, so the magnetization M1 is oriented in one of the directions in the xy plane.

[0069] As the intensity of light irradiated onto the photosensitive layer 10 increases, the magnetization M1 of the first ferromagnetic layer 1 tilts from its initial state due to the external energy from the light irradiation. This is because the sum of the effect of light irradiation and the effect of spin transfer torque on the magnetization M1 becomes greater than the effect due to magnetic anisotropy on the magnetization M1. As the intensity of light irradiated onto the photosensitive layer 10 increases, in the case of Figure 6, the magnetization M1 tilts to be parallel to the magnetization M2 of the second ferromagnetic layer 2, while in the case of Figure 7, the magnetization M1 tilts to be antiparallel to the magnetization M2 of the second ferromagnetic layer 2. The direction of the tilt of magnetization M1 differs between Figure 6 and Figure 7 because the direction of the spin transfer torque acting on the magnetization M1 is different.

[0070] When the intensity of light irradiated onto the photosensitive layer 10 increases, in the case of Figure 6, the resistance of the photodetector 100 decreases, and the output voltage from the photodetector 100 decreases. In the case of Figure 7, the resistance of the photodetector 100 increases, and the output voltage from the photodetector 100 increases.

[0071] When the intensity of light irradiated onto the photosensitive layer 10 returns to the first intensity, the magnetization M1 state of the first ferromagnetic layer 1 returns to its original state due to the effect of magnetic anisotropy on the magnetization M1. As a result, the photodetector element 100 returns to its initial state.

[0072] Here, we have explained an example where the first ferromagnetic layer 1 is an in-plane magnetized film and the second ferromagnetic layer 2 is a perpendicular magnetized film, but this relationship can also be reversed. That is, in the initial state, the magnetization M1 may be oriented in the z direction, and the magnetization M2 may be oriented in any direction within the xy plane.

[0073] As described above, the photodetector 100 according to the first embodiment can convert light into an electrical signal by replacing the light irradiated onto the photosensitive layer 10 with an output voltage from the photodetector 100.

[0074] Furthermore, the second electrode 22 of the photodetector 100 is made of a predetermined material. The second electrode 22 can reflect more of the incident light that reaches it than if it were made of a different material. The photosensitive layer 10 is irradiated with both incident light and reflected light from the second electrode 22. When the amount of reflected light from the second electrode 22 increases, even when the amount of light incident on the photodetector 100 is small, the photosensitive layer 10 can be irradiated with a large amount of light. Therefore, the photodetector 100 has high efficiency in converting incident light to electrical signals and high photodetection capability.

[0075] Up to this point, an example of the present invention has been described using the first embodiment as an example, but the present invention is not limited to this embodiment. For example, Figure 8 is a cross-sectional view of a photodetector element 100A according to the first modified example.

[0076] The photodetector element 100A according to the first modification has a different shape for the second electrode 24 compared to the second electrode 22 according to the first embodiment. The second electrode 24 contains the same material as the second electrode 22. The second electrode 24 is a metal containing at least one element selected from the group consisting of ruthenium, molybdenum, and tungsten. The width of the second electrode 24 in the x and y directions is narrower than the width of the second electrode 22 in the x and y directions, respectively.

[0077] The widths of the second electrode 24 in the x and y directions are narrower than the widths of the first electrode 21 in the x and y directions, respectively. The second electrode 24, together with the laminate 30 including the photosensitive layer 10, for example, constitutes a columnar body. The side surface of the second electrode 24 is continuous with the side surface of the laminate 30 including the photosensitive layer 10, for example. There is no step between the side surface of the second electrode 24 and the side surface of the laminate 30 including the photosensitive layer 10.

[0078] In the first modified photodetector element 100A, since the second electrode 24 is made of a predetermined material, for example, much of the incident light reaching the second electrode 24 can be reflected at the interface between the buffer layer 4 and the second electrode 24. Therefore, the photodetector element 100A according to the first modified example can obtain the same effects as the photodetector element 100 according to the first embodiment. Furthermore, when manufacturing the photodetector element 100A, processing the second electrode 24 together with the laminate 30 including the photosensitive layer 10 can prevent a part of the second electrode 24 from adhering to the side surface of the laminate 30 (redeposition occurring).

[0079] The light-detecting elements according to the above embodiments and modifications can be applied to light-sensing devices such as transceivers in communication systems and image sensors.

[0080] Figure 9 is a conceptual diagram of a communication system 1000 according to the first application example. The communication system 1000 shown in Figure 9 comprises a plurality of transceivers 200 and optical fiber FB connecting the transceivers 200. The communication system 1000 can be used for short- and medium-distance communication, such as within and between data centers, and long-distance communication, such as between cities. The transceivers 200 are installed, for example, within a data center. The optical fiber FB connects, for example, data centers. The communication system 1000 communicates between the transceivers 200, for example, via the optical fiber FB. The communication system 1000 may also communicate wirelessly between the transceivers 200 without using the optical fiber FB.

[0081] Figure 10 is a block diagram of a transceiver 200 according to the first application example. The transceiver 200 comprises a receiving device 110 and a transmitting device 120. The receiving device 110 receives an optical signal L1, and the transmitting device 120 transmits an optical signal L2. The light used for transmission and reception is, for example, near-infrared light with a wavelength of 400 nm to 1500 nm.

[0082] The receiving device 110 includes, for example, a photodetector 100 and a signal processing unit 101. The photodetector 100 may be replaced with a photodetector 100A. The photodetector 100 converts the optical signal L1 into an electrical signal. The photosensitive layer 10 is irradiated with light containing the optical signal L1, which has a change in light intensity. A lens may be placed on the first electrode 21 side in the stacking direction of the photodetector 100 so that the light that passes through the lens and is focused is irradiated onto the photosensitive layer 10. The lens may be formed in the wafer process in which the photodetector 100 is formed. Alternatively, the light that passes through the waveguide may be irradiated onto the photosensitive layer 10. The light irradiated onto the photosensitive layer 10 is, for example, laser light. The signal processing unit 101 processes the electrical signal converted by the photodetector 100. The signal processing unit 101 receives the signal contained in the optical signal L1 by processing the electrical signal generated from the photodetector 100.

[0083] Figure 11 is a schematic, enlarged view of the vicinity of the photodetector element 100 in the transceiver 200 according to the first application example. For example, light propagating through the optical fiber FB, which is a waveguide, is focused by the lens 105 and reaches the photodetector element 100. The lens 105 is, for example, a microlens.

[0084] The transmitting device 120 includes, for example, a light source 121, an electrical signal generating element 122, and an optical modulation element 123. The light source 121 is, for example, a laser element. The light source 121 may be located outside the transmitting device 120. The electrical signal generating element 122 generates an electrical signal based on the transmission information. The electrical signal generating element 122 may be integrated with the signal conversion element of the signal processing unit 101. The optical modulation element 123 modulates the light output from the light source 121 based on the electrical signal generated by the electrical signal generating element 122 and outputs an optical signal L2.

[0085] Furthermore, while we have shown an example of applying the transmitting and receiving device to the communication system 1000 shown in Figure 9, the communication system is not limited to this case.

[0086] For example, Figure 12 is a conceptual diagram of another example of a communication system. The communication system 1001 shown in Figure 12 is communication between two mobile terminal devices 300. The mobile terminal devices 300 are, for example, smartphones, tablets, etc.

[0087] Each of the mobile terminal devices 300 includes a receiving device 110 and a transmitting device 120. The transmitting device 120 of one mobile terminal device 300 receives the optical signal transmitted by the receiving device 110 of the other mobile terminal device 300. The light used for transmission and reception between the mobile terminal devices 300 is, for example, visible light. The above-described optical sensing element is used as the optical sensing element 100 of each receiving device 110.

[0088] For example, Figure 13 is a conceptual diagram of another example of a communication system. The communication system 1002 shown in Figure 13 is communication between a mobile terminal device 300 and an information processing device 400. The information processing device 400 is, for example, a personal computer.

[0089] The mobile terminal device 300 includes a transmitting device 120, and the information processing device 400 includes a receiving device 110. The optical signal transmitted from the transmitting device 120 of the mobile terminal device 300 is received by the receiving device 110 of the information processing device 400. The light used for transmission and reception between the mobile terminal device 300 and the information processing device 400 is, for example, visible light. The above-described optical sensing element is used as the optical sensing element 100 of each receiving device 110.

[0090] Figure 14 is a conceptual cross-sectional view of a photosensor device 2000 according to a second application example. The photosensor device 2000 includes, for example, a circuit board 510, a wiring layer 520, and a plurality of photosensors 500. Each of the wiring layer 520 and the plurality of photosensors 500 is formed on the circuit board 510.

[0091] Each of the multiple light sensors 500 includes, for example, a photodetector element 100, a wavelength filter 501, and a lens 502. The photodetector element 100 may be replaced with a photodetector element 100A. As described above, the photodetector element 100 converts the light irradiated onto the photosensitive layer 10 into an electrical signal. The photodetector element 100 preferably operates in the second operating example.

[0092] The wavelength filter 501 selects light of a specific wavelength and transmits light within a specific wavelength range. The wavelength range of light transmitted by each wavelength filter 501 may be the same or different. For example, the optical sensor device 2000 may have an optical sensor 500 (hereinafter referred to as the blue sensor) having a wavelength filter 501 that transmits blue light (wavelength range of 380 nm to less than 490 nm), an optical sensor 500 (hereinafter referred to as the green sensor) having a wavelength filter 501 that transmits green light (wavelength range of 490 nm to less than 590 nm), and an optical sensor 500 (hereinafter referred to as the red sensor) having a wavelength filter 501 that transmits red light (wavelength range of 590 nm to less than 800 nm). The blue sensor, green sensor, and red sensor are considered as one pixel, and by arranging these pixels, the optical sensor device 2000 can be used as an image sensor.

[0093] The lens 502 focuses the light toward the photodetector 100. The light that has passed through the lens 502 and been focused is irradiated onto the photosensitive layer 10. In the photosensor 500 shown in Figure 14, one photodetector 100 is positioned below one wavelength filter 501, but multiple photodetectors 100 may be positioned below one wavelength filter 501.

[0094] The circuit board 510 includes, for example, an analog-to-digital converter 511 and an output terminal 512. The electrical signal sent from the optical sensor 500 is converted into digital data by the analog-to-digital converter 511 and output from the output terminal 512.

[0095] The wiring layer 520 has multiple wirings 521. Between the multiple wirings 521 is an interlayer insulating film 522. The wirings 521 electrically connect each of the light sensors 500 to the circuit board 510 and to each of the arithmetic circuits formed on the circuit board 510. Each of the light sensors 500 and the circuit board 510 are connected, for example, via through-wiring that penetrates the interlayer insulating film 522 in the z direction. Noise can be reduced by shortening the wiring distance between each of the light sensors 500 and the circuit board 510.

[0096] The wiring 521 is conductive. The wiring 521 is, for example, Al, Cu, etc. The interlayer insulating film 522 is an insulator that insulates between wirings and elements in multilayer wiring. The interlayer insulating film 522 is, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg. The interlayer insulating film 522 is, for example, silicon dioxide (SiO₂). x ), silicon nitride (SiN x ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO3) x ) etc.

[0097] The above-described optical sensor device 2000 can be used, for example, in a terminal device. Figure 15 is a schematic diagram of an example of a terminal device 600. The left side of Figure 15 is the front surface of the terminal device 600, and the right side is the back surface of the terminal device 600. The terminal device 600 has a camera CA. The above-described optical sensor device 2000 can be used as the image sensor of this camera CA. In Figure 15, a smartphone is used as an example of a terminal device 600, but it is not limited to this case. In addition to smartphones, terminal devices 600 can be, for example, tablets, personal computers, digital cameras, etc.

[0098] Up to this point, we have shown examples of applying the photodetectors 100 and 100A to receiving devices and image sensor optical sensor devices, but the applications are not limited to these cases. The photodetectors 100 and 100A can replace conventional semiconductor photodetectors in a variety of other applications.

[0099] The present invention is not limited to the embodiments and modifications described above, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims. [Explanation of Symbols]

[0100] 1…First ferromagnetic layer, 2…Second ferromagnetic layer, 3…Spacer layer, 4…Buffer layer, 5…Seed layer, 6…Third ferromagnetic layer, 7…Magnetic coupling layer, 8…Perpendicular magnetization induction layer, 9…Cap layer, 10…Photosensitive layer, 21…First electrode, 22,24…Second electrode, 90…Insulating layer, 100,100A…Photodetector element, 101…Signal processing unit, 105,502…Lens, 110…Receiver, 120…Transmitter, 121…Light source, 122…Electrical signal generation element 123...Optical modulation element, 200...Transmitting / receiving device, 300...Mobile terminal device, 400...Information processing device, 500...Optical sensor, 501...Wavelength filter, 510...Circuit board, 511...Analog-to-digital converter, 512...Output terminal, 520...Wiring layer, 521...Wiring, 522...Interlayer insulating film, 600...Terminal device, 1000, 1001, 1002...Communication system, 2000...Optical sensor device, CA...Camera, FB...Optical fiber

Claims

1. It comprises a photosensitive layer that generates a voltage when irradiated with light, a first electrode, and a second electrode. The photosensitive layer is located between the first electrode and the second electrode, The second electrode is a metal containing at least one element selected from the group consisting of ruthenium, molybdenum, and tungsten. The light-sensitive layer comprises a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer located between the first ferromagnetic layer and the second ferromagnetic layer. The spacer layer is composed of a conductor, an insulator, or a layer containing a current-carrying point formed by a conductor within the insulator. A photodetector in which the output voltage from the photosensitive layer changes when the intensity of the light being irradiated changes while the light is irradiated onto the first ferromagnetic layer.

2. The photodetector element according to claim 1, wherein the first electrode is a transparent electrode.

3. The photodetector element according to claim 1 or 2, wherein light with a wavelength of 400 nm to 1500 nm is irradiated onto the photosensitive layer.

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