Optical detection element, reception device, transmission / reception device, communication system, terminal device, and optical system

Abstract

The invention provides a light detection element with small interface reflection, a receiving device, a transmitting and receiving device, a communication system, a terminal device, and an optical system. The light detection element includes a light sensing layer that generates a voltage when irradiated with light, a first electrode, a second electrode, and a metal layer. The light sensing layer is located between the first electrode and the second electrode. The metal layer is located between the first electrode and the light sensing layer. When the light-sensitive layer is irradiated with light having a wavelength of 400 nm or more and 800 nm or less, the metal layer contains any one selected from the group consisting of Ti, Ta, Cr, Mo, W, and Pt. When the light-sensitive layer is irradiated with light having a wavelength of 400 nm or more and 1400 nm or less, the metal layer contains any one selected from the group consisting of Ti, Cr, Mo, W and Pt. When the light-sensitive layer is irradiated with light having a wavelength of 400 nm or more and 1500 nm or less, the metal layer contains any one selected from the group consisting of Ti, Cr, W, and Pt.

Description

Technical Field

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

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

[0003] For example, a receiving device that receives an optical signal using a photodiode is described in Patent Document 1. A photodiode is, for example, a pn junction diode using a pn junction of a semiconductor, and converts light into an electrical signal.

[0004] Furthermore, for example, a new optical device using a magnetic element is disclosed in Patent Document 2. In a magnetic element, when irradiated with light, the magnetic state changes, and the resistance value also changes.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-292107

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2023-90284 Summary of the Invention

[0009] Technical problem to be solved by the invention

[0010] The photodetector element converts light into an electrical signal. If light incident on the photoreceptor layer of the photodetector element is reflected, sufficient light may not be incident on the photoreceptor layer.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a light detection element, a receiving device, a transmitting and receiving device, a communication system, a terminal device, and an optical system capable of suppressing interface reflection.

[0012] Technical means for solving technical problems

[0013] In order to solve the above technical problems, the following technical means are provided.

[0014] This embodiment provides a photodetector element comprising a photoreceptor layer that generates a voltage when irradiated with light, a first electrode, a second electrode, and a metal layer. The photoreceptor layer is positioned between the first and second electrodes. The metal layer is positioned between the first and second electrodes. When the photoreceptor layer is irradiated with light having a wavelength of 400 nm to 800 nm, the metal layer contains any one selected from the group consisting of Ti, Ta, Cr, Mo, W, and Pt. When the photoreceptor layer is irradiated with light having a wavelength of 400 nm to 1400 nm, the metal layer contains any one selected from the group consisting of Ti, Cr, Mo, W, and Pt. When the photoreceptor layer is irradiated with light having a wavelength of 400 nm to 1500 nm, the metal layer contains any one selected from the group consisting of Ti, Cr, W, and Pt.

[0015] Effects of the Invention

[0016] The photodetection element of the above-described embodiment has low interface reflection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a cross-sectional view of the photodetection element according to the first embodiment.

[0018] Figure 2 These are the measurement results of the reflectivity at the interface between the first electrode and the metal layer in the photodetection element according to the first embodiment.

[0019] Figure 3 This is a diagram showing the relationship between the thermal conductivity of the metal layer and the light receiving sensitivity of the photosensitive layer in the photodetection element according to the first embodiment.

[0020] Figure 4 This is a diagram showing the relationship between the film thickness of the metal layer and the light receiving sensitivity of the photosensitive layer in the photodetection element according to the first embodiment.

[0021] Figure 5 It is a diagram for explaining an operation example of the photodetection element according to the first embodiment.

[0022] Figure 6 It is a diagram for explaining an operation example of the photodetection element according to the first embodiment.

[0023] Figure 7 is a cross-sectional view of a photodetection element according to a first modification.

[0024] Figure 8 Schematic diagram of an optical element according to a first application example.

[0025] Figure 9 This is a conceptual diagram of an optical system using the optical element of the first application example.

[0026] Figure 10 is a schematic diagram of a transceiver according to a second application example.

[0027] Figure 11 This is a conceptual diagram of an example of a communication system.

[0028] Figure 12 This is a conceptual diagram of another example of a communication system. DETAILED DESCRIPTION

[0029] The following description describes the embodiments in detail with reference to the accompanying drawings as appropriate. The drawings used in the following description may show enlarged portions of the components for ease of understanding, and the dimensional ratios of the components may differ from the actual values. The materials, dimensions, and other aspects illustrated in the following description are merely examples, and the present invention is not limited to these. The present invention can be implemented with appropriate modifications within the scope of achieving the desired effects.

[0030] Define the directions. Let the X direction be the direction within the plane where each layer extends, and let the Y direction be the direction perpendicular to the X direction within the plane. Furthermore, let the Z direction be the stacking direction perpendicular to each layer. 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 toward the first electrode 21. Up and down do not necessarily coincide with the direction in which gravity is applied.

[0031] "First Implementation Method"

[0032] Figure 1 : is a cross-sectional view of the light detection element 100 according to the first embodiment. Figure 1 In FIG, arrows indicate the direction of magnetization in the initial state of the ferromagnetic material.

[0033] The photodetection element 100 includes a photoreceptor layer 10, a first electrode 21, a second electrode 22, and a metal layer 30. The photoreceptor layer 10 is located between the first electrode 21 and the second electrode 22. The metal layer 30 is located between the first electrode 21 and the photoreceptor layer 10.

[0034] In addition, the photodetector element 100 may also include a buffer layer 4, a seed layer 5, a third ferromagnetic layer 6, a magnetic coupling layer 7, a perpendicular magnetization sensing 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 sensing layer 8 and cap layer 9 are located between the photosensitive layer 10 and the metal layer 30. The insulating layer 90 is located between the first electrode 21 and the second electrode 22 and covers the entire stack including the photosensitive layer 10.

[0035] The photodetector element 100 converts the state or changes in the state of the irradiated light into an electrical signal. The term "light" in this specification is not limited to visible light but also includes infrared light with longer wavelengths than visible light and ultraviolet light with shorter wavelengths. For example, the wavelength of visible light is between 380 nm and 800 nm. For example, the wavelength of infrared light is between 800 nm and 1 mm. For example, the wavelength of ultraviolet light is between 200 nm and 380 nm. For example, the photodetector element 100 (photoreceptor layer 10) is irradiated with light having a wavelength between 400 nm and 1500 nm. Depending on the intended use of the photodetector element 100, the photoreceptor layer 10 may also be irradiated with light having a wavelength between 400 nm and 800 nm.

[0036] The photoreceptor layer 10 generates a voltage when irradiated with light. In the photoreceptor layer 10, as the state of the irradiated light changes, the resistance value in the Z direction changes accordingly. As the state of the light irradiating the photoreceptor layer 10 changes, the output voltage from the photodetector element 100 changes accordingly. The photoreceptor layer 10, for example, includes a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a spacer layer 3. The spacer layer 3 is located between the first and second ferromagnetic layers 1 and 2. The photoreceptor layer 10 may also include other layers.

[0037] The photosensitive layer 10 is a magnetic element composed of a ferromagnetic material. For example, if the spacer layer 3 is composed of an insulator, the photosensitive layer 10 forms a magnetic tunnel junction (MTJ) consisting of the first ferromagnetic layer 1, the spacer layer 3, and the second ferromagnetic layer 2. This type of element is called an MTJ element. In this case, the photosensitive layer 10 can exhibit the tunnel magnetoresistance (TMR) effect. If the spacer layer 3 is composed of a metal, the photosensitive layer 10 can exhibit the giant magnetoresistance (GMR) effect. This type of element is called a GMR element. Depending on the material constituting the spacer layer 3, the photosensitive layer 10 may be referred to differently than an MTJ element or a GMR element, but is generally referred to as a magnetoresistance element. The photosensitive layer 10's resistance in the Z direction (the resistance when current flows in the Z direction) changes based on the relative changes in the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2.

[0038] The first ferromagnetic layer 1 is a photodetecting layer whose magnetization changes when exposed to external light. 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 changes when a predetermined external energy is applied. Examples of the predetermined external energy include externally irradiated light, a current flowing in the Z direction of the photosensitive layer 10, and an external magnetic field. The magnetization M1 of the first ferromagnetic layer 1 changes depending on the intensity of the light irradiating the first ferromagnetic layer 1 (the light irradiating the photosensitive layer 10).

[0039] The first ferromagnetic layer 1 includes a ferromagnetic material. The first ferromagnetic layer 1 contains, for example, 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 together with the magnetic elements mentioned above. The first ferromagnetic layer 1 may also be, for example, an alloy containing a magnetic element and a non-magnetic element. The first ferromagnetic layer 1 may also be composed of multiple layers. The first ferromagnetic layer 1 may be, for example, a stack of Fe layers sandwiching a CoFeB alloy, a stack of CoFeB alloy layers, or a stack of CoFe layers sandwiching a CoFeB alloy layer. "Ferromagnetism" generally includes "ferrimagnetism." The first ferromagnetic layer 1 may also exhibit ferrimagnetism. On the other hand, the first ferromagnetic layer 1 may also exhibit ferromagnetism without exhibiting ferrimagnetism. For example, the CoFeB alloy exhibits ferromagnetism without exhibiting ferrimagnetism.

[0040] The first ferromagnetic layer 1 may be an in-plane magnetization film having an easy magnetization axis in the film plane direction (any direction in the XY plane) or a perpendicular magnetization film having an easy magnetization axis in the film normal direction (Z direction).

[0041] The thickness of the first ferromagnetic layer 1 is, for example, not less than 1 nm and not more than 5 nm. The thickness of the first ferromagnetic layer 1 is preferably, for example, not less than 1 nm and not more than 2 nm. When the first ferromagnetic layer 1 is a perpendicular magnetization film, a thinner thickness increases the effect of the perpendicular magnetic anisotropy exerted by the layers above and below the first ferromagnetic layer 1, resulting in a higher perpendicular magnetic anisotropy in the first ferromagnetic layer 1. In other words, a higher perpendicular magnetic anisotropy in the first ferromagnetic layer 1 strengthens the force that restores the magnetization M1 in the Z direction. On the other hand, a thicker thickness decreases the effect of the perpendicular magnetic anisotropy exerted by the layers above and below the first ferromagnetic layer 1, resulting in a weaker perpendicular magnetic anisotropy in the first ferromagnetic layer 1.

[0042] As the thickness of the first ferromagnetic layer 1 decreases, its volume as a ferromagnetic material decreases. As the thickness of the first ferromagnetic layer 1 increases, its volume as a ferromagnetic material increases. The ease with which the magnetization M1 of the first ferromagnetic layer 1 responds to external energy is inversely proportional to the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 1. In other words, as the product of the magnetic anisotropy and volume of the first ferromagnetic layer 1 decreases, its reactivity to light increases. From this perspective, to improve its reactivity to light, it is preferable to appropriately design the magnetic anisotropy of the first ferromagnetic layer 1 and then reduce its volume.

[0043] If the thickness of the first ferromagnetic layer 1 is greater than 2 nm, an insertion layer composed of Mo and W, for example, may be provided within the first ferromagnetic layer 1. In other words, the first ferromagnetic layer 1 may be a stack of a ferromagnetic layer, an insertion layer, and a ferromagnetic layer stacked in this 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.

[0044] The second ferromagnetic layer 2 is a fixed magnetization layer. The fixed magnetization layer is a layer composed of a magnetic material whose magnetization M2 is less likely to change when a predetermined external energy is applied than that of the free magnetization layer. For example, the direction of magnetization of the fixed magnetization layer is less likely to change when a predetermined external energy is applied than that of the free magnetization layer. Alternatively, for example, the magnitude of magnetization of the fixed magnetization layer is less likely to change when a predetermined external energy is applied than that of the free magnetization layer. The coercive force 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 that of the first ferromagnetic layer 1. The second ferromagnetic layer 2 can be an in-plane magnetization film or a perpendicular magnetization film.

[0045] 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 also 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 layered multiple 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 layered in this order.

[0046] The magnetization M2 of the second ferromagnetic layer 2 can also be fixed by, for example, magnetic coupling with the magnetization M6 of the third ferromagnetic layer 6. In this case, the layer comprising the second ferromagnetic layer 2, the magnetic coupling layer 7, and the third ferromagnetic layer 6 is sometimes referred to as a magnetization-fixed layer. Details of the magnetic coupling layer 7 and the third ferromagnetic layer 6 will be described later.

[0047] Spacer layer 3 is positioned between first ferromagnetic layer 1 and second ferromagnetic layer 2. Spacer layer 3 is formed of a conductor, insulator, or semiconductor, or an insulator containing a conductive point. Spacer layer 3 is, for example, a nonmagnetic layer. The thickness of spacer layer 3 can be adjusted based on the orientation of the magnetization of first ferromagnetic layer 1 and the magnetization of second ferromagnetic layer 2 in the initial state, as described later.

[0048] When spacer layer 3 is composed of an insulating material, materials containing aluminum oxide, magnesium oxide, titanium oxide, or silicon oxide can be used. These insulating materials may also contain elements such as Al, B, Si, and Mg, or magnetic elements such as Co, Fe, and Ni. A high magnetoresistance change ratio is achieved by adjusting the thickness of spacer layer 3 to achieve a high TMR effect between first ferromagnetic layer 1 and second ferromagnetic layer 2. To effectively utilize the TMR effect, the thickness of spacer layer 3 can be set to approximately 0.5 to 5.0 nm, or even 1.0 to 2.5 nm.

[0049] When the spacer layer 3 is formed of a non-magnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. To effectively utilize the GMR effect, the thickness of the spacer layer 3 can be set to about 0.5 to 5.0 nm, or about 2.0 to 3.0 nm.

[0050] When the spacer layer 3 is formed 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 thickness of the spacer layer 3 can also be set to about 1.0 to 4.0 nm.

[0051] When using a layer containing energization points formed by a conductor within a non-magnetic insulator as spacer layer 3, a structure can also be employed in which energization points formed by a non-magnetic conductor such as Cu, Au, or Al are contained within a non-magnetic insulator formed of aluminum oxide or magnesium oxide. Alternatively, the conductor can be formed of a magnetic element such as Co, Fe, or Ni. In this case, the thickness of spacer layer 3 can be approximately 1.0 to 2.5 nm. For example, the energization points are columnar structures with a diameter of at least 1 nm and no more than 5 nm when viewed perpendicular to the film surface.

[0052] The third ferromagnetic layer 6 is, for example, magnetically coupled to the second ferromagnetic layer 2. The magnetic coupling is, for example, antiferromagnetic coupling and is generated by RKKY interaction. The material constituting the third ferromagnetic layer 6 is, for example, the same as that of the first ferromagnetic layer 1.

[0053] The magnetic coupling layer 7 is located between the second ferromagnetic layer 2 and the third ferromagnetic layer 6. The magnetic coupling layer 7 is made of, for example, Ru, Ir, or the like.

[0054] The buffer layer 4 mitigates the lattice mismatch between different crystals. For example, the buffer layer 4 is a metal containing at least one element selected from Ta, Ti, Zr, and Cr, or a nitride containing at least one element selected from Ta, Ti, Zr, and Cu. More specifically, the buffer layer 4 is, for example, Ta (elemental), a NiCr alloy, TaN (tantalum nitride), or CuN (copper nitride). The thickness of the buffer layer 4 is, for example, not less than 1 nm and not more than 5 nm. The buffer layer 4 is, for example, amorphous. For example, the buffer layer 4 is located between the seed layer 5 and the second electrode 22, in contact with the second electrode 22. The buffer layer 4 prevents the crystalline structure of the second electrode 22 from affecting the crystalline structure of the photoreceptor layer 10.

[0055] The seed layer 5 improves the crystallinity of the layers stacked on the seed layer 5. The seed layer 5 is located, for example, between the buffer layer 4 and the third ferromagnetic layer 6, and on the buffer layer 4. The seed layer 5 is made of, for example, Pt, Ru, Zr, or NiFeCr. The thickness of the seed layer 5 is, for example, not less than 1 nm and not more than 5 nm.

[0056] The capping layer 9 is positioned between the first ferromagnetic layer 1 and the first electrode 21. The capping layer 9 may also include a perpendicular magnetization-sensing layer 8 stacked on and in contact with the first ferromagnetic layer 1. The capping layer 9 prevents damage to the underlying layer during processing and improves the crystallinity of the underlying layer during annealing. The thickness of the capping layer 9 is, for example, 10 nm or less to ensure sufficient light exposure to the first ferromagnetic layer 1.

[0057] Perpendicular magnetization induction layer 8 senses the perpendicular magnetic anisotropy of first ferromagnetic layer 1. Perpendicular magnetization induction layer 8 can be made of, for example, magnesium oxide, W, Ta, or Mo. When magnesium oxide is used, it is preferably oxygen-deficient to improve conductivity. The thickness of perpendicular magnetization induction layer 8 is, for example, not less than 0.5 nm and not more than 5.0 nm.

[0058] The insulating layer 90 is made of, 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 (ZrO x )wait.

[0059] The first electrode 21 is positioned on the side of the photodetector element 100 where incident light enters. The incident light strikes the photoreceptor layer 10 from the side of the first electrode 21. The first electrode 21 is made of a conductive material. For example, the first electrode 21 is a transparent electrode that transmits light within the operating wavelength range. For example, the first electrode 21 preferably transmits at least 80% of the light within the operating wavelength range. The operating wavelength range is, for example, 300 nm to 2 μm, preferably 400 nm to 1500 nm, and may also be 400 nm to 800 nm. For example, the first electrode 21 is made of 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 also have a structure in which a plurality of metal pillars are incorporated into the transparent electrode material of these oxides. Furthermore, the first electrode 21 may have an antireflection coating on the surface where the light is irradiated.

[0060] The second electrode 22 is made of a conductive material. For example, the second electrode 22 is made of a metal such as Cu, Al, or Au. Alternatively, Ta or Ti may be stacked above or below these metals. Alternatively, a laminated film of Cu and Ta, a laminated film of Ta, Cu, and Ti, or a laminated film of Ta, Cu, and TaN may be used for the second electrode 22. Alternatively, TiN or TaN may be used for the second electrode 22.

[0061] The second electrode 22 may also be a metal containing at least one element selected from ruthenium, molybdenum, and tungsten. The second electrode 22 may be a single-layer film of any of ruthenium, molybdenum, and tungsten, or a laminated film comprising at least one layer of any of ruthenium, molybdenum, and tungsten. Ruthenium, molybdenum, and tungsten have high melting points (above 2000°C) and excellent heat resistance. The second electrode 22 containing these elements is less susceptible to degradation even during heat treatment during crystallization of the laminate including the photosensitive layer 10 or during heat treatment during semiconductor processing.

[0062] The second electrode 22 reflects a portion of incident light from the first electrode 21 side at the interfaces with the layers 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 at their interfaces, particularly for light with wavelengths between 400 nm and 1500 nm. The light reflected by the second electrode 22 strikes the photoreceptor layer 10. Since the second electrode 22 is made of a specified material (a metal containing at least one element selected from ruthenium, molybdenum, and tungsten), it reflects more incident light than would be the case if it were not made of the specified material. Consequently, in the photodetector element 100, the amount of light striking the photoreceptor layer 10 is greater.

[0063] The metal layer 30 is located between the photoreceptor layer 10 and the first electrode 21. For example, the metal layer 30 is located between the cover layer 9 and the first electrode 21.

[0064] When the photoreceptor layer 10 is irradiated with light having a wavelength of 400 nm to 800 nm, the metal layer 30 contains any one selected from the group consisting of Ti, Ta, Cr, Mo, W, and Pt. When the photoreceptor layer 10 is irradiated with light having a wavelength of 400 nm to 1400 nm, the metal layer 30 contains any one selected from the group consisting of Ti, Cr, Mo, W, and Pt. When the photoreceptor layer 10 is irradiated with light having a wavelength of 400 nm to 1500 nm, the metal layer 30 contains any one selected from the group consisting of Ti, Cr, W, and Pt.

[0065] Figure 2 These are the reflectivity measurement results at the interface between the first electrode 21 and the underlying layer in the photodetection element of the first embodiment. Comparative Example 1 shows the reflectivity measurement results at the interface between the first electrode 21 and the photoreceptor layer 10 when no metal layer 30 is provided between the first electrode 21 and the photoreceptor layer 10. Other examples use any of Ti, Ta, Cr, Mo, W, and Pt as the metal layer 30. The photoreceptor layer 10 primarily contains Co.

[0066] like Figure 2 As shown, when the photoreceptor layer 10 is irradiated with light having a wavelength of 400 nm to 800 nm, a metal layer 30 containing any one of Ti, Ta, Cr, Mo, W, and Pt is provided between the first electrode 21 and the photoreceptor layer 10, thereby reducing reflection at the interface between them. Furthermore, when the photoreceptor layer 10 is irradiated with light having a wavelength of 400 nm to 1400 nm, a metal layer 30 containing any one of Ti, Cr, Mo, W, and Pt is provided between the first electrode 21 and the photoreceptor layer 10, thereby reducing reflection at the interface between them. Furthermore, when the photoreceptor layer 10 is irradiated with light having a wavelength of 400 nm to 1500 nm, a metal layer 30 containing any one of Ti, Cr, W, and Pt is provided between the first electrode 21 and the photoreceptor layer 10, thereby reducing reflection at the interface between them. When reflection at the interface is reduced, the amount of light irradiating the photoreceptor layer 10 increases, thereby improving the light detection capability of the photodetection element 100.

[0067] Furthermore, when the first electrode 21 is made of ITO, IZO, ZnO, or IGZO, the metal layer 30 preferably contains any one selected from the group consisting of Ti, Ta, Cr, Mo, W, and Pt. When this structure is satisfied, the complex refractive indices of the first electrode 21 and the metal layer 30 can be made close to each other, and in particular, reflection between the first electrode 21 and the metal layer 30 can be suppressed.

[0068] Furthermore, when the cover layer 9 is made of Ru, the metal layer 30 preferably contains any one selected from Ru and Ti. Furthermore, when the cover layer 9 is made of Ta, the metal layer 30 preferably contains any one selected from Ta, Cr, Mo, W, and Pt. When the cover layer 9 and the metal layer 30 satisfy these combinations, reflection between the cover layer 9 and the metal layer 30 can be suppressed.

[0069] Furthermore, the thermal conductivity of the metal layer 30 is preferably 60 W / mK or less. Figure 3 This is a diagram showing the relationship between the thermal conductivity of the metal layer 30 and the light receiving sensitivity of the photosensitive layer 10 in the photodetection element 100 according to the first embodiment. Figure 3 The horizontal axis is the thermal conductivity of the metal layer 30, Figure 3 The vertical axis represents the light sensitivity of each example normalized by the light sensitivity of the photoreceptor layer 10 in Comparative Example 1. Comparative Example 1 shows the light sensitivity of the photoreceptor layer 10 when no metal layer 30 is provided between the first electrode 21 and the photoreceptor layer 10. The other examples use any of Ti, Cr, Mo, W, Ru, and Cu as the metal layer 30. The light sensitivity is the light sensitivity when irradiated with a sinusoidal laser of 850 nm wavelength, 4.8 mW peak power, and 1 GHz. The thickness of the metal layer is set to

[0070] like Figure 3 As shown, when the thermal conductivity of the metal layer 30 is low, the light sensitivity of the photosensitive layer 10 increases. This is believed to be because the metal layer 30 acts as a heat bath, reducing heat diffusion from the photosensitive layer 10. When the temperature of the photosensitive layer 10 is high, the magnetization M1 of the first ferromagnetic layer 1 easily shifts, increasing the sensitivity of the photodetector element 100 to light. The metal layer 30 is preferably made of Ti or Cr.

[0071] Figure 4 This is a diagram showing the relationship between the film thickness of the metal layer 30 and the light receiving sensitivity of the photosensitive layer 10 in the photodetection element 100 according to the first embodiment. Figure 4 The light receiving sensitivity when irradiated with a sin wave laser having a wavelength of 850 nm, a peak power of 4.8 mW, and a frequency of 1 GHz is shown, and the film thickness of the metal layer 30 composed of Ti is changed.

[0072] like Figure 4 As shown, the thickness of the metal layer 30 is preferably Above and The following are more preferably Above and The following is more preferably Above and It is considered that when the metal layer 30 is too thick, heat diffuses from the metal layer 30 to the surrounding insulating layer 90 , and the amount of heat transferred from the metal layer 30 to the photosensitive layer 10 decreases.

[0073] The photodetector element 100 is manufactured through a process of laminating, annealing, and processing 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 sensing layer 8, a cap layer 9, and a metal layer 30 are sequentially stacked on the second electrode 22. Each layer is deposited, for example, by sputtering.

[0074] Next, the laminated film is annealed. The annealing temperature is, for example, 250°C to 400°C. The laminated film is then processed into a columnar laminate by photolithography and etching. The laminate can be cylindrical or prism-shaped. For example, the shortest width of the laminate when viewed in the Z direction is 10 nm to 1000 nm.

[0075] Next, an insulating layer 90 is formed to cover the side surfaces of the stack. The insulating layer 90 may be laminated multiple times. Next, chemical mechanical polishing is performed to expose the upper surface of the metal layer 30 from the insulating layer 90, and the first electrode 21 is formed on the metal layer 30. Through the above steps, the light detection element 100 is obtained.

[0076] Next, the operation of the photodetection element 100 will be described. The output voltage from the photodetection element 100 changes according to the intensity of light irradiating the photoreceptor layer 10. The output voltage from the photodetection element 100 changes as the resistance value of the photodetection element 100 in the Z direction changes.

[0077] When the intensity of light irradiating the photoreceptor layer 10 of the photodetector element 100 changes from a first intensity to a second intensity, the Z-direction resistance of the photodetector element 100 changes. The first intensity may also be when the intensity of light irradiating the photoreceptor layer 100 is zero. When the Z-direction resistance of the photodetector element 100 changes, the output voltage of the photodetector element 100 changes.

[0078] Figure 5 and Figure 6 It is a diagram for explaining an operation example of the photodetection element 100 according to the first embodiment. Figure 5 is a diagram for explaining the first mechanism of the operation example, Figure 6 This is a diagram for explaining the second mechanism of the operation example. Figure 5 and Figure 6 In the upper graph of , the vertical axis represents the intensity of light irradiating the first ferromagnetic layer 1 , and the horizontal axis represents time. Figure 5 and Figure 6 In the graph below , the vertical axis represents the resistance value of the light detection element 100 in the Z direction, and the horizontal axis represents time.

[0079] First, in a state where the first ferromagnetic layer 1 is irradiated with light of a first intensity W1 (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 antiparallel, and the Z-direction resistance value of the photodetection element 100 represents the second resistance value R2. Here, the state where the first ferromagnetic layer 1 is irradiated with light of the first intensity W1 can also be considered as the state where the first ferromagnetic layer 1 is irradiated with light of zero intensity W1.

[0080] When the sense current Is flows in the Z direction of the light detection element 100 , a voltage is generated at both ends of the light detection element 100 in the Z direction. The output voltage from the light detection element 100 is generated between the first electrode 21 and the second electrode 22 .

[0081] exist Figure 5 In the example shown, the sense current Is preferably flows from the second ferromagnetic layer 2 toward the first ferromagnetic layer 1. By flowing the sense current Is in this direction, a spin transfer torque in the opposite direction to the magnetization M2 of the second ferromagnetic layer 2 acts on the magnetization M1 of the first ferromagnetic layer 1, and in the initial state, the magnetizations M1 and M2 tend to be antiparallel.

[0082] Next, the intensity of the light irradiating the first ferromagnetic layer 1 changes from the first intensity W1 to the second intensity W2. For example, when a light pulse is irradiated on the photoreceptor layer 10, the intensity of the light irradiating the first ferromagnetic layer 1 changes from the first intensity W1 to the second intensity W2. The intensity of the light of the second intensity W2 is greater than the intensity of the light of the first intensity W1.

[0083] When the second intensity W2 is greater than the first intensity W1, the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state. The state of the magnetization M1 of the first ferromagnetic layer 1 when it is not irradiated with light differs from the state of the magnetization M1 of the first ferromagnetic layer 1 when it is irradiated with light of the second intensity W2. The state of the magnetization M1 can be determined, for example, by its tilt angle relative to the Z direction and its magnitude.

[0084] For example, Figure 5 As shown in FIG. 1 , when the intensity of light irradiating the first ferromagnetic layer 1 changes from the first intensity W1 to the second intensity W2, the magnetization M1 tilts relative to the Z direction. Figure 6 As shown, when the intensity of light irradiating the first ferromagnetic layer 1 changes from a first intensity W1 to a second intensity W2, the magnitude of the magnetization M1 decreases. For example, when the magnetization M1 of the first ferromagnetic layer 1 tilts relative to the Z direction according to the intensity of the light irradiation, the tilt angle is, for example, greater than 0° and less than 90°.

[0085] When the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state due to irradiation of the photoreceptor layer 10 with a light pulse, the Z-direction resistance of the photodetector element 100 changes to a first resistance value R1, and the magnitude of the output voltage from the photodetector element 100 changes from the first value to the second value. As a result, the output from the photodetector element 100 changes. The first resistance value R1 is smaller than the second resistance value R2. The second value is smaller than the first value. The first resistance value R1 is between the resistance value (second resistance value R2) when the magnetizations M1 and M2 are antiparallel and the resistance value when the magnetizations M1 and M2 are parallel.

[0086] exist Figure 5 In the case shown, a spin transfer torque in the opposite direction to the magnetization M2 of the second ferromagnetic layer 2 acts on the magnetization M1 of the first ferromagnetic layer 1. Therefore, the magnetization M1 is restored to an antiparallel state with respect to the magnetization M2. When the intensity of the light irradiating the first ferromagnetic layer 1 changes from the second intensity to the first intensity, the magnetization M1 is restored to an antiparallel state with respect to the magnetization M2. Figure 6 In the illustrated case, when the intensity of the light irradiating the first ferromagnetic layer 1 returns to the first intensity W1, the magnetization M1 of the first ferromagnetic layer 1 is restored, and the photodetection element 100 returns to its initial state. In either case, the Z-direction resistance of the photodetection element 100 also returns to the second resistance R2. Specifically, when the intensity of the light irradiating the first ferromagnetic layer 1 changes from the second intensity W2 to the first intensity W1, the Z-direction resistance of the photodetection element 100 changes from the first resistance R1 to the second resistance R2.

[0087] The output voltage from the photodetector element 100 can change in response to changes in the intensity of light irradiating the photoreceptor layer 10, converting changes in the intensity of the irradiated light into changes in the output voltage from the photodetector element 100. In other words, the photodetector element 100 can convert light into an electrical signal. For example, if the output voltage from the photodetector element 100 is above a threshold, it is processed as a first signal (e.g., "1"), while if it is below the threshold, it is processed as a second signal (e.g., "0").

[0088] While the example described here uses the case where magnetizations M1 and M2 are initially antiparallel, magnetizations M1 and M2 can also be initially parallel. In this case, the Z-direction resistance of the photodetector element 100 increases as the state of magnetization M1 changes (for example, as the angle of magnetization M1 changes from the initial state increases). For the case where magnetizations M1 and M2 are initially parallel, it is preferable to flow a sense current Is from the first ferromagnetic layer 1 toward the second ferromagnetic layer 2. By flowing the sense current Is in this direction, a spin transfer torque in the same direction as magnetization M2 in the second ferromagnetic layer 2 acts on magnetization M1 of the first ferromagnetic layer 1, causing magnetizations M1 and M2 to become initially parallel.

[0089] While the example described here uses a case where the light irradiating the photoreceptor layer 10 has two levels of intensity, a first intensity and a second intensity, the intensity of the light irradiating the photoreceptor layer 10 may also be varied in multiple steps or in an analog manner. In this case, the output voltage from the photodetector element 100 varies in multiple steps or in an analog manner.

[0090] The photodetection element 100 of the first embodiment converts light incident on the photoreceptor layer 10 into an electrical signal by converting it into an output voltage from the photodetection element 100. The photodetection element 100 of the first embodiment includes a metal layer 30 between the first electrode 21 and the photoreceptor layer 10, thereby reducing interface reflection and improving light detection capabilities.

[0091] Although the first embodiment has been used as an example to describe the present invention, the present invention is not limited to this embodiment.

[0092] For example, Figure 7 4 is a cross-sectional view of a photodetection element 101 according to a first modification. Figure 7 The metal layer 31 is different from the light detection element 100 in that it has a different shape from the metal layer 30. When viewed in the Z direction, the metal layer 31 extends further outward from the photoreceptor layer 10. The light detection element 101 of the first modified example achieves the same effects as the light detection element 100.

[0093] The photodetection element 100 according to the above-described embodiment and modified examples can be used for various applications.

[0094] Figure 8 Schematic diagram of an optical element 200 according to a first application example. Figure 8The optical element 200 shown includes a waveguide element 110 and a light source 120. The waveguide element 110 includes the aforementioned light detection element 100 and a waveguide 111. The waveguide 111 includes an output waveguide 112 and a monitor waveguide 113. The output waveguide 112 is a waveguide for outputting light from the light source 120 to the outside. The monitor waveguide 113 is a waveguide that branches a portion of the light propagating in the output waveguide 112 toward the light detection element 100. The monitor waveguide 113 propagates light toward the light detection element 100.

[0095] Light source 120 is, for example, a laser light source. Light source 120 includes, for example, red laser light 121, green laser light 122, and blue laser light 123. Light output from light source 120 propagates through output waveguide 112 and is output to the outside. A portion of the light output from light source 120 propagates through monitor waveguide 113 and reaches photodetector 100.

[0096] The optical element 200 outputs laser light to the outside while monitoring the output from the light source 120 using the light detection element 100. The optical element 200 can adjust the white balance of the light output from the output waveguide 112 to the outside by adjusting the intensity of the light output from each laser.

[0097] Figure 9 2 is a conceptual diagram of an optical system 300 using the optical element 200. The optical system 300 can be attached to the glasses 1000, for example.

[0098] The optical system 300 includes the aforementioned optical element 200, an optical system 310, drivers 320 and 321, and a controller 330. The optical system 310 includes, for example, a collimating lens 301, a slit 302, an ND filter 303, and a light scanning mirror 304. The optical system 310 guides the light output from the optical element 200 to the irradiated object (in this example, the eye). The light scanning mirror 304 is, for example, a two-axis MEMS mirror that changes the reflection direction of the laser light into the horizontal and vertical directions. The optical system 310 is an example and is not limited to this example. The driver 320 controls the output of the light source 120 from the optical element 200. The driver 321 is a control system for moving the light scanning mirror 304. The controller 330 controls the drivers 320 and 321.

[0099] The light L output from the light source 120 of the optical element 200 G The light propagates through the optical system 310, is reflected by the lens of the glasses 1000, and enters the eye. Here, an example in which the light is reflected by the lens of the glasses 1000 is shown, but the eye may also be directly illuminated.

[0100] The red, green, and blue lights L emitted from the light source 120 GThe image is displayed. The image can be freely controlled. The output intensity of each of the red laser 121, green laser 122, and blue laser 123 can be adjusted based on the measurement results of the output from the light detection element 100 irradiated with visible light output from the red laser 121, green laser 122, and blue laser 123, respectively.

[0101] When the optical system 300 is used, an image can be projected onto the glasses 1000. In addition, by monitoring the intensity of the projected light using the light detection element 100, the color tone of the image can be adjusted.

[0102] Figure 10 1 is a block diagram of a transceiver 400 according to a second application example. The transceiver 400 includes a receiver 410 and a transmitter 420. The receiver 410 receives an optical signal L1, and the transmitter 420 transmits an optical signal L2.

[0103] The receiving device 410 includes, for example, a light detection device 411 and a signal processing unit 412. The light detection device 411 can use the aforementioned light detection element 100. In the receiving device 410, the light detection element 100 of the light detection device 411 is irradiated with, for example, a light pulse. The light signal L1 is composed of light pulses. The light detection device 411 converts the light signal L1 into an electrical signal. The signal processing unit 412 processes the electrical signal converted by the light detection device 411. By processing the electrical signal generated by the light detection device 411, the signal processing unit 412 receives the signal contained in the light signal L1. The receiving device 410 receives the signal contained in the light signal L1 based on the output signal from the light detection device 411.

[0104] Transmitting device 420 includes, for example, a light source 421, an electrical signal generating element 422, and a light modulating element 423. Light source 421 is, for example, a laser element. Light source 421 may also be external to transmitting device 420. Electrical signal generating element 422 generates an electrical signal based on transmission information. Electrical signal generating element 422 may also be integrated with the signal conversion element of signal processing unit 412. Light modulating element 423 modulates the light output from light source 421 based on the electrical signal generated by electrical signal generating element 422, and outputs light signal L2.

[0105] Figure 11 This is a conceptual diagram of an example of a communication system. Figure 11 The communication system shown has two terminal devices 500. The terminal devices 500 are, for example, smartphones, tablets, personal computers, and the like.

[0106] Each terminal device 500 includes a receiving device 410 and a transmitting device 420. An optical signal transmitted from the transmitting device 420 of one terminal device 500 is received by the receiving device 410 of another terminal device 500. The light used for transmission and reception between the terminal devices 500 is, for example, visible light. The receiving device 410 includes a light detection device 411.

[0107] in addition, Figure 12 This is a conceptual diagram of an example of a communication system. Figure 11 , the terminal devices 500 are all smartphones, but the terminal devices 500 may be different in the transmitting side and the receiving side. Figure 12 The terminal device 500 shown is a smartphone, and the terminal device 501 is a personal computer.

[0108] Description of Reference Numerals

[0109] 1First ferromagnetic layer

[0110] 2 Second ferromagnetic layer

[0111] 3 compartment layers

[0112] 4 buffer layer

[0113] 5 seed layer

[0114] 6Third ferromagnetic layer

[0115] 7 Magnetic coupling layer

[0116] 8Perpendicular magnetization sensing layer

[0117] 9 covering layers

[0118] 10 Photoreceptor layer

[0119] 21 first electrode

[0120] 22 second electrode

[0121] 30 metal layers

[0122] 100, 101 light detection elements

Claims

1. A light detection element, wherein: A photosensitive layer that generates a voltage when irradiated with light, a first electrode, a second electrode, and a metal layer are provided. The photosensitive layer is located between the first electrode and the second electrode, The metal layer is located between the first electrode and the photosensitive layer, When the photosensitive layer is irradiated with light having a wavelength of 400 nm to 800 nm, the metal layer contains any one selected from the group consisting of Ti, Ta, Cr, Mo, W, and Pt; and when the photosensitive layer is irradiated with light having a wavelength of 400 nm to 1400 nm, the metal layer contains any one selected from the group consisting of Ti, Cr, Mo, W, and Pt. When the photosensitive layer is irradiated with light having a wavelength of 400 nm to 1500 nm, the metal layer contains any one selected from the group consisting of Ti, Cr, W, and Pt.

2. The light detecting element according to claim 1, wherein The first electrode is a transparent electrode.

3. The light detecting element according to claim 1, wherein The photosensitive layer includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer located between the first ferromagnetic layer and the second ferromagnetic layer.

4. The light detecting element according to claim 1, wherein The thermal conductivity of the metal layer is less than 60 W / mK.

5. The light detecting element according to claim 1, wherein The thickness of the metal layer is Above and the following.

6. A receiving device, wherein: A light detecting element according to claim 1 is provided.

7. A transceiver, wherein: A receiving device according to claim 6.

8. A communication system, wherein: A receiving device according to claim 6.

9. A terminal device, wherein: A receiving device according to claim 6.

10. An optical system, wherein: A light detecting element according to claim 1 is provided.

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