JP6534462B2 - Tunnel layer - Google Patents

Description

  The present invention relates to a spin injection electrode structure and a spin transport device.

  In recent years, techniques for accumulating spin in a channel using a semiconductor are known. The spin diffusion length in semiconductor-based channels is much longer than the spin diffusion length in metal-based channels. For example, the following non-patent documents 1 to 4 describe techniques for injecting spins into silicon.

JP, 2010-239011, A

Tomoyuki Sasaki et al., Applied Physics Express 2, p053003-1-0503-3, (2009) O. M. J. van't Erve et al., APPLIED PHYSICS LETTERS 91, p212109-1-212109-3, (2007) Y. Ando et al., APPLIED PHYSICS LETTERS 94, p182105-1 to 182105-3, (2009) Saroj P. Dash et al., Nature, vol. 462, p 491-494, (2009). T. Suzuki et al., Applied Physics Express 4, p023003-1-023003-3, (2011)

  By the way, for the application of spin injection / conduction / detection in silicon, it is desired to obtain sufficient output characteristics at room temperature. In Non-Patent Documents 1 to 3 described above, although injection, conduction, and detection of spins in silicon are reported, all are events at low temperatures of 150 K or less. Although Non-Patent Document 4 observes the accumulation of spins in silicon at 300 K, the conduction phenomenon of spins in silicon at room temperature is not observed, and a wide range of applications can not be expected at present. Recently, in the above Non-Patent Document 5, the conduction of spins in silicon at room temperature has been observed. However, its output is not sufficient. One of the reasons why it is difficult to increase the output at room temperature is considered to be the occurrence of spin scattering at the interface due to the lattice constant shift between silicon and the tunnel layer. Thus, it is desirable to realize effective injection to realize spin conduction in a semiconductor at room temperature, not limited to silicon.

  Patent Document 1 describes a method of suppressing spin scattering at an interface by a lattice constant shift between silicon and a tunnel layer. According to Patent Document 1, the formation of the first amorphous magnesium oxide on silicon suppresses spin scattering due to lattice mismatch between silicon and magnesium oxide, and the first amorphous magnesium oxide is formed on the first amorphous magnesium oxide. By forming monocrystalline magnesium oxide, high output is achieved by leaving a part of the coherent effect. However, it is necessary to suppress spin scattering also at the interface between the first ferromagnetic layer and the magnesium oxide that is the tunnel layer.

  The present invention has been made to solve the above problems, and to provide a spin injection electrode structure and a spin conduction device that enable efficient injection of spins in a semiconductor channel layer at room temperature than before. With the goal.

In order to solve the above problems, the spin injection electrode structure of the present invention comprises a semiconductor channel layer, a tunnel layer provided on the semiconductor channel layer, and a ferromagnetic layer provided on the tunnel layer, The lattice constant of the tunnel layer in contact with the layer is different from the lattice constant of the tunnel layer in contact with the ferromagnetic layer.

The tunnel layer is a structure having a tunnel layer lower region and a tunnel layer upper region. The composition of the material in the lower region of the tunnel layer and the upper region of the tunnel layer continuously change, and the basic structure of the crystal structure does not change. That is, the lattice constant of the tunnel layer continuously changes from the side in contact with the semiconductor channel layer to the side in contact with the ferromagnetic layer. Also, the boundaries between the two areas are not clear.

In order to form a tunnel layer as described above, the material of the tunnel layer is composed of a material that is a single crystal structure. In general, the oxide can maintain a system of the same crystal structure even if oxygen defects or partial substitution of constituent elements occur. Therefore, by changing the composition of elements in the tunnel layer, it is possible to form a tunnel layer in which the strain at both the interface of the semiconductor channel layer and the tunnel layer and at the interface of the ferromagnetic layer and the tunnel layer is minimized. .

The tunnel layer preferably has a spinel structure for high output. Spinel structure, the composition ratio of AB ₂ O ₄ as a basic structure, by the amount and type of A site element is changed, it is possible to vary continuously the lattice constant without breaking a spinel structure. In particular, when the semiconductor channel layer is silicon, a tunnel layer having a spinel structure is most preferable.

  The tunnel layer is a nonmagnetic spinel layer composed of an oxide containing any element of Al, Mg, Si, Zn, and Ti, and the film thickness is 0.6 nm or more and 2.2 nm or less. Is preferred. When the film thickness of the tunnel layer is 2.2 nm or less, the film thickness when combined with the nonmagnetic spinel layer is small and the resistance value of the laminated film is small, so the interface resistivity is low with respect to the obtained spin output. Since the noise can be suppressed, spin injection can be made preferable. When the film thickness of the tunnel layer exceeds 2.2 nm, an increase in spin output is suppressed, and an increase in noise due to an increase in interface resistivity can not be obtained to obtain a high signal ratio. When the film thickness of the tunnel layer is 0.6 nm or more, a uniform tunnel layer can be formed on the semiconductor channel layer. When the film thickness of the tunnel layer is less than 0.6 nm, it is not formed as a film, and a layer is formed in an island shape, so that it does not function as a tunnel layer.

The semiconductor channel layer is made of silicon, germanium, gallium arsenide, or a compound of silicon and germanium. These materials have long spin diffusion lengths and high spin resistance, so high power can be obtained.

The side of the tunnel layer in contact with the semiconductor channel layer, that is, the lower region of the tunnel layer is preferably an oxide film containing aluminum as a main component. In the case of an oxide film containing aluminum as a main component, since the lattice constant is close to that of the semiconductor channel layer, spin scattering at the interface between the semiconductor channel layer and the tunnel layer can be suppressed. In the present application, the term "main component" means that 2/3 or more of the cation elements are contained among all the cation elements contained in the composition elements.

The side in contact with the ferromagnetic layer of the tunnel layer, that is, the upper region of the tunnel layer, is preferably an oxide film containing aluminum as a main component and at least one of magnesium and zinc. Such an oxide film has a lattice constant close to that of a ferromagnetic layer typified by iron or the like, so that spin scattering at the interface between the ferromagnetic layer and the tunnel layer can be suppressed.

Providing the spin injection electrode structure described above in a first portion of the semiconductor channel layer, and further forming a second tunnel layer provided on the second portion of the semiconductor channel layer and a second ferromagnetic layer provided on the second tunnel layer It is preferable that it is a spin transport element provided with a layer. By providing the first spin injection electrode structure and the second spin injection electrode structure on the semiconductor channel layer, it is possible to detect spins injected from the spin injection electrode structure with another spin injection electrode structure. By this, it can function as a magnetic sensor, Spin-MOSFET, or a spin conduction element.

  The crystal structure of the ferromagnetic layer is preferably a body-centered cubic lattice structure (BCC). In this case, the ferromagnetic layer can be partially epitaxially grown on the nonmagnetic spinel tunnel layer.

  The ferromagnetic layer also contains a metal selected from the group consisting of Co, Fe and Ni, an alloy containing one or more elements of the group, or one or more elements selected from the group and boron (B). It is preferred that it is a compound. Since these materials are ferromagnetic materials with large spin polarization, it is possible to preferably realize the function as a spin injection electrode.

Furthermore, the ferromagnetic layer is more preferably a Heusler alloy. The ferromagnetic layer contains an intermetallic compound having a chemical composition of X ₂ YZ, X is a transition metal element or noble metal element of Co, Fe, Ni or Cu group on the periodic table, Y is Mn, It is a transition metal of V, Cr or Ti group and can also take an element species of X, and Z is a typical element of Group III to V.
For example, Co ₂ FeSi, Co ₂ MnSi and the like can be mentioned.

  Further, it is preferable to further include an antiferromagnetic layer formed on the ferromagnetic layer, and the antiferromagnetic layer fixes the magnetization direction of the ferromagnetic layer. Exchange coupling between the antiferromagnetic layer and the ferromagnetic layer makes it possible to impart unidirectional anisotropy in the magnetization direction of the ferromagnetic layer. In this case, a ferromagnetic layer having a higher coercivity in one direction can be obtained than in the case where no antiferromagnetic layer is provided.

  In addition, it is preferable that a difference in coercivity between the first portion of the spin injection electrode structure provided in the semiconductor channel layer and the ferromagnetic layer of the second portion be provided by shape anisotropy. In this case, the antiferromagnetic layer for providing a difference in coercivity can be omitted.

  In general, ions for imparting conductivity are implanted in the semiconductor channel layer. The surface of the semiconductor channel layer may be damaged due to the ion implantation. Therefore, the semiconductor channel layer preferably has a recess between the first portion and the second portion, and the depth of the recess is preferably 10 nm or more and 20 nm or less.

  In addition, the spin conduction device preferably has the above-described spin injection electrode structure, and can provide a spin conduction device capable of effectively injecting spins in the semiconductor channel layer at room temperature.

  According to the present invention, there is provided an electrode structure capable of simultaneously suppressing spin scattering at the interface of the tunnel layer and the ferromagnetic layer while suppressing spin scattering at the interface of the semiconductor channel and the tunnel layer more than the conventional tunnel layer. As a result, it is possible to provide a spin injection electrode structure that enables efficient injection of spins in the semiconductor channel layer at room temperature, and a spin transport device using the same.

FIG. 1 is a perspective view of a spin transport device according to the present embodiment. FIG. 2A is a top view of the spin transport element according to the present embodiment. FIG.2 (b) is an enlarged view of area | region B shown to Fig.2 (a). FIG. 3 is a cross-sectional view taken along the line III-III of FIG. FIG. 4 shows a first tunnel layer lower region 16A, a first tunnel layer upper region 16B, a second tunnel layer lower region 16C, and a second tunnel layer upper region 16D, which constitute the first tunnel layer 13A and the second tunnel layer 13B, respectively. FIG. FIG. 5 is a graph showing the relationship between the applied magnetic field and the voltage output in the NL measurement method. FIG. 6 is a graph showing the relationship between the applied magnetic field and the voltage output in the NL-Hanle measurement method. FIG. 7 is a spectrum obtained by evaluating the first tunnel layer 13A and the second tunnel layer 13B by EDX. FIG. 8 shows the result of the lattice constant in the thickness direction with respect to the boundary between the tunnel layer and the silicon channel layer.

  Hereinafter, preferred embodiments of a spin transport device according to the present invention will be described in detail with reference to the drawings. In the figure, an XYZ orthogonal coordinate axis system is shown as necessary. FIG. 1 is a perspective view of a spin transport device according to the present embodiment. FIG. 2A is a top view of the spin transport element according to the present embodiment. FIG.2 (b) is an enlarged view of area | region B shown to Fig.2 (a). FIG. 3 is a cross-sectional view taken along the line III-III of FIG.

  As shown in FIG. 3, in the case where silicon is used as the semiconductor, the spin transport device 1 includes the silicon substrate 10, the silicon oxide film 11, the silicon channel layer 12, the first tunnel layer 13A, and the second tunnel layer. A first ferromagnetic layer 14A, a second ferromagnetic layer 14B, a first reference electrode 15A, a second reference electrode 15B, an oxide film 7a, and an oxide film 7b are provided. The silicon channel layer 12, the first tunnel layer 13A, and the first ferromagnetic layer 14A constitute a spin injection electrode structure IE.

  As shown in FIG. 4, the first tunnel layer 13A has a structure including a first tunnel layer lower region 16A and a first tunnel layer upper region 16B. However, the composition of the materials of the first tunnel layer lower region 16A and the first tunnel layer upper region 16B changes continuously, and the boundary between the two regions is not clear. Similarly, the second tunnel layer 13B has a structure including a second tunnel layer lower region 16C and a second tunnel layer upper region 16D. However, the compositions of the materials of the second tunnel layer lower region 16C and the second tunnel layer upper region 16D change continuously, and the boundary between the two regions is not clear. (Figure 4 is a diagram that explains the continuous change. How does hatching work?)

  For example, an SOI (Silicon On Insulator) substrate can be used as the substrate 10, the silicon oxide film 11, and the silicon channel layer 12. The substrate 10 is a silicon substrate, and the silicon oxide film 11 is provided on the substrate 10. The film thickness of the silicon oxide film 11 is, for example, 200 nm. The silicon channel layer 12 can obtain substantially the same result with germanium, gallium arsenide, or a compound of silicon and germanium.

The silicon channel layer 12 functions as a spin conduction layer. The upper surface of the silicon channel layer 12 is, for example, a (100) surface. The silicon channel layer 12 has, for example, a rectangular shape having the X axis as the long axis direction when viewed from the Z axis direction (thickness direction). The silicon channel layer 12 is mainly composed of silicon (I think that it is better to include it in consideration of translation), and impurity ions are added to the silicon channel layer 12 as needed. The ion concentration is, for example, 5.0 × 10 ¹⁹ cm ⁻³ . The film thickness of the silicon channel layer 12 is, for example, 100 nm. Alternatively, the peak of the ion concentration is 10 nm deep in the silicon channel layer 12 from the interface so that the Schottky barrier at the interface between the first tunnel layer 13A or the second tunnel layer 13B and the silicon channel layer 12 can be adjusted. It may be a silicon channel layer 12 having a certain structure. When the ion concentration of the silicon channel layer 12 is low, there is a method of applying a voltage to the silicon oxide film 11 to induce carriers in the silicon channel layer 12.

  As shown in FIG. 3, the silicon channel layer 12 has an inclined portion on the side surface, and the inclination angle θ is 50 degrees to 60 degrees. The inclination angle θ is the angle between the bottom of the silicon channel layer 12 and the side surface. The silicon channel layer 12 can be formed by wet etching.

  As shown in FIG. 3, the silicon channel layer 12 includes a first convex portion (first portion) 12A, a second convex portion (second portion) 12B, a third convex portion (third portion) 12C, and a fourth convex portion Fourth part) 12D, and main part 12E. The first convex portion 12A, the second convex portion 12B, the third convex portion 12C, and the fourth convex portion 12D are portions extending so as to protrude from the main portion 12E, and predetermined axes (shown in FIG. 3) In the example, they are arranged at predetermined intervals in the X axis direction).

  The film thickness (the length in the Z-axis direction in the example shown in FIG. 3) H1 of the first convex portion 12A, the second convex portion 12B, the third convex portion 12C, and the fourth convex portion 12D is, for example, 20 nm. The film thickness (length in the Z-axis direction in the example shown in FIG. 3) H2 of the main portion 12E is, for example, 80 nm. The distance L1 between the first convex portion 12A and the third convex portion 12C is, for example, 100 μm or less. The distance d between the central portion of the length of the first convex portion 12A in the X-axis direction and the central portion of the length of the second convex portion 12B in the X-axis direction is preferably equal to or less than the spin diffusion length. The spin diffusion length in the silicon channel layer 12 at room temperature (300 K) is, for example, 0.8 μm. The spins injected from the first ferromagnetic layer 14A to the first convex portion 12A or the spins injected from the second ferromagnetic layer 14B to the second convex portion 12B are the first convex portion 12A and the second convex portion in the main portion 12E. It diffuses and conducts the region between the convex portion 12B.

  The first tunnel layer 13A and the second tunnel layer 13B efficiently connect the spin polarization of the ferromagnetic material (the first ferromagnetic layer 14A and the second ferromagnetic layer 14B) and the spin polarization of the silicon channel layer 12 Function as a tunnel insulating film. The first tunnel layer 13 </ b> A is provided on the first convex portion 12 </ b> A which is the first portion of the silicon channel layer 12. The second tunnel layer 13 </ b> B is provided on the second convex portion 12 </ b> B which is the second portion of the silicon channel layer 12.

The first tunnel layer 13A and the second tunnel layer 13B are crystals grown on, for example, the (100) plane of the silicon channel layer 12. By providing the first tunnel layer 13A or the second tunnel layer 13B, a large amount of spin-polarized electrons are injected from the first ferromagnetic layer 14A or the second ferromagnetic layer 14B into the silicon channel layer 12. It becomes possible to increase the potential output of the spin transport element 1.

The film thickness of the first tunnel layer 13A and the second tunnel layer 13B is preferably 2.2 nm or less. In this case, since the interface resistivity can be lowered to 1 MΩμm ² or less with respect to the obtained spin output to suppress noise, spin injection and output can be suitably performed. Further, the film thickness of the first tunnel layer 13A and the second tunnel layer 13B is preferably 0.6 nm or more, and in this case, the first tunnel layer 13A uniformly deposited on the silicon channel layer 12 And the second tunnel layer 13B can be used.

  One of the first ferromagnetic layer 14A and the second ferromagnetic layer 14B functions as an electrode for injecting spins into the silicon channel layer 12, and the other as an electrode for detecting spins in the silicon channel layer 12. Function. The first ferromagnetic layer 14A is provided on the first tunnel layer 13A. The second ferromagnetic layer 14B is provided on the second tunnel layer 13B.

  The first ferromagnetic layer 14A and the second ferromagnetic layer 14B mainly consist of a ferromagnetic material. As an example of the material of the first ferromagnetic layer 14A and the second ferromagnetic layer 14B, a metal selected from the group consisting of Co and Fe, an alloy containing one or more elements of the group, or 1 selected from the group The compound which consists of the above element and boron (B) is mentioned. The crystal structure of the first ferromagnetic layer 14A and the second ferromagnetic layer 14B is preferably a body-centered cubic lattice structure. Thus, the first ferromagnetic layer can be partially epitaxially grown on the first tunnel layer, and the second ferromagnetic layer can be partially epitaxially grown on the second tunnel layer.

  In the example shown in FIG. 1, the first ferromagnetic layer 14A and the second ferromagnetic layer 14B have a rectangular parallelepiped shape whose major axis is the Y-axis direction. It is preferable that the first ferromagnetic layer 14A and the second ferromagnetic layer 14B have a difference in coercivity from the shape anisotropy of the first ferromagnetic layer 14A and the second ferromagnetic layer 14B. The width (length in the X-axis direction) of the first ferromagnetic layer 14A is, for example, about 350 nm. The width (length in the X-axis direction) of the second ferromagnetic layer 14B is, for example, about 2 μm. In the example shown in FIG. 1, the coercivity of the first ferromagnetic layer 14A is larger than the coercivity of the second ferromagnetic layer 14B.

  The first reference electrode 15A and the second reference electrode 15B have a function as an electrode for supplying a detection current to the silicon channel layer 12 and a function as an electrode for reading an output by spin. The first reference electrode 15 </ b> A is provided on the third convex portion 12 </ b> C of the silicon channel layer 12. The second reference electrode 15 </ b> B is provided on the fourth convex portion 12 </ b> D of the silicon channel layer 12. The first reference electrode 15A and the second reference electrode 15B are made of a conductive material, and are nonmagnetic metals having a low resistance to Si, such as Al.

  The oxide film 7 a is formed on the side surface of the silicon channel layer 12. The oxide film 7b is formed of the silicon channel layer 12, the oxide film 7a, the first tunnel layer 13A, the second tunnel layer 13B, the first ferromagnetic layer 14A, the second ferromagnetic layer 14B, the first reference electrode 15A, and the first reference electrode 15A. It is formed on the side surface of the two reference electrodes 15B. In the upper surface of silicon channel layer 12, oxidation is performed on main portion 12E where first ferromagnetic layer 14A, second ferromagnetic layer 14B, first reference electrode 15A, and second reference electrode 15B are not provided. The film 7b is formed. The oxide film 7b is provided on the main portion 12E of the silicon channel layer 12 between the first tunnel layer 13A and the second tunnel layer 13B. Oxide film 7b protects silicon channel layer 12, first tunnel layer 13A, second tunnel layer 13B, first ferromagnetic layer 14A, second ferromagnetic layer 14B, first reference electrode 15A, and second reference electrode 15B. It acts as a film and suppresses the degradation of these layers. The oxide film 7b is, for example, a silicon oxide film.

  As shown in FIG. 1, a wiring 18A is provided on the first reference electrode 15A and the oxide film 7b (the inclined side surface of the silicon channel layer 12). Similarly, a wiring 18B is provided on the first ferromagnetic layer 14A and the oxide film 7b. A wire 18C is provided on the second ferromagnetic layer 14B and the oxide film 7b. A wire 18D is provided on the second reference electrode 15B and the oxide film 7b. The wirings 18A to 18D are conductive materials such as Cu. By providing the wiring on the oxide film 7b, it is possible to suppress the absorption of the spin conducted in the silicon channel layer 12 by the wiring. Further, by providing the wiring on the oxide film 7b, it is possible to suppress the flow of current from the wiring to the silicon channel layer 12, and it is possible to improve the spin injection efficiency. In addition, measurement electrode pads E1 to E4 are provided at respective end portions of the wirings 18A to 18D. The ends of the wirings 18A to 18D and the electrode pads E1 to E4 for measurement are formed on the silicon oxide film 11. The electrode pads E1 to E4 are conductive materials such as Au.

  FIG. 4 is a cross-sectional view of the first tunnel layer 13A and the second tunnel layer 13B. The first tunnel layer 13A is composed of a first tunnel layer lower region 16A and a first tunnel layer upper region 16B. The first tunnel layer lower region 16 A is crystal-grown on the silicon channel layer 12 or partially crystal-grown on the silicon channel layer 12. The first tunnel layer upper region 16B is provided on the first tunnel layer lower region 16A, and the first ferromagnetic layer 14A is provided on the first tunnel layer upper region 16B. Similarly, the second tunnel layer 13B comprises a second tunnel layer lower region 16C and a second tunnel layer upper region 16D. The second tunnel layer lower region 16 </ b> C is crystal-grown on the silicon channel layer 12 or partially crystal-grown on the silicon channel layer 12. The second tunnel layer upper region 16D is provided on the second tunnel layer lower region 16C, and the second ferromagnetic layer 14B is provided on the second tunnel layer upper region 16D.

  Hereinafter, the first tunnel layer lower region 16A, the first tunnel layer upper region 16B, and the first ferromagnetic film 14A that constitute the first tunnel layer 13A will be described.

  The first tunnel layer 13A is suitably a tunnel layer containing aluminum, zinc, silicon, titanium or magnesium. When these materials crystallize, they function as a tunnel layer with high spin polarization due to coherent tunneling.

  In addition, a tunnel layer having a spinel structure is suitable for the first tunnel layer 13A. In this case, since the crystal lattice can be arbitrarily distorted depending on the type and concentration of the above-mentioned elements, the lattice constant can be changed in accordance with the underlying semiconductor channel or ferromagnetic layer.

The first tunnel layer lower region 16A has a composition of a γ-type aluminum oxide in which an element is deficient, and preferably has a spinel structure. This is a structure in which part or all of the element A of the composition formula AB ₂ O ₄ of the spinel structure is deficient. In this spinel structure, oxygen is tetracoordinated to the element A and oxygen is hexacoordinated to the element B. In the case of such a structure, since the lattice constant is close to that of the silicon channel 12, scattering of spins at the interface can be suppressed.

  The first tunnel layer upper region 16B has a composition of an oxide of aluminum and magnesium, and preferably has a spinel structure. In the case of such a structure, since the lattice constant is close to that of the first ferromagnetic layer 14A, scattering of spins at the interface can be suppressed.

The concentrations of the elements constituting the first tunnel layer lower region 16A and the first tunnel layer upper region 16B of the first tunnel layer 13A continuously change. In the above example, from a state in which part or all of the elements of A in the composition formula AB ₂ O ₄ of the spinel structure is deficient from the first tunnel layer lower region 16A toward the first tunnel layer upper region 16B It changes continuously to the structure where zinc is arranged in the element.

The first tunnel layer lower region 16A of the first tunnel layer 13A has the best structure in which all the elements of A in the composition formula AB ₂ O ₄ of the spinel structure are deficient, but even a structure in which part of the elements of A is deficient good. Similarly, the first tunnel layer upper region 16B preferably has a composition of an oxide of aluminum and magnesium, but may have a structure in which part of magnesium is deficient.

Furthermore, the concentration of the A element (site) in the first tunnel layer lower region 16A is preferably lower than the concentration of the A element (site) in the first tunnel layer upper region 16B. In this case, the lattice constant of each of the semiconductor channel layer and the ferromagnetic layer is close to each other, and spin scattering at the interface can be suppressed.

The same applies to the materials of the second tunnel layer lower region 16C and the second tunnel layer upper region 16D of the second tunnel layer 13B.

  The crystal structure of the first ferromagnetic layer 14A is preferably a body-centered cubic lattice structure (BCC). The material of the first ferromagnetic layer 14A contains a metal selected from the group consisting of Co and Fe, an alloy containing one or more elements of the group, or one or more elements selected from the group and boron (B) In the case of a compound, the first ferromagnetic layer 14A is likely to be epitaxially grown on the first upper tunnel region 16B.

For example, assuming that the composition of the first tunnel layer upper region 16B of the first tunnel layer 13A is MgAl ₂ O ₄ and the first ferromagnetic layer 14A is Fe, lattice constants of MgAl ₂ O ₄ and Fe substantially match. Because of this, it is possible to suppress spin scattering at the interface between the first tunnel layer upper region 16B of the first tunnel layer 13A and the first ferromagnetic layer 14A. The crystal structure and lattice constant can be analyzed by cross section TEM (Transmission Electorn Microscopy), XRD (X Ray Diffraction), or EDX (Energy Dispersive X-Ray analysis) of the laminated film.

Furthermore, the first ferromagnetic layer 14A is more preferably a Heusler alloy. Heusler alloy (also referred to as full-Heusler alloy) is a generic term for intermetallic compounds having the chemical composition of X ₂ YZ, where X is a transition of Co, Fe, Ni or Cu group on the periodic table It is a metal element or a noble metal element. Y is a transition metal of the Mn, V, Cr or Ti group, and can take the same species as X. Z is a typical element of Group III to Group V. The Heusler alloy X ₂ YZ is divided into three types of crystal structures based on the regularity of X · Y · Z. By the analysis such as X-ray diffraction utilizing the periodicity of the crystal, the most regular structure which can distinguish three elements X ≠ Y ≠ Z is the L21 structure, and then the more regular X ≠ Y = Z and Is a B2 structure, and a structure in which the three elements can not be distinguished X = Y = Z is an A2 structure.

  The second tunnel layer 13B is also similar to the first tunnel layer 13A.

  Hereinafter, an example of the operation using the NL (non-local) measurement method of the spin transport element 1 according to the present embodiment will be described. In the NL measurement method, as shown in FIG. 3, the spin transport element 1 detects an external magnetic field B1 in the Y-axis direction, for example. The magnetization direction G1 (Y-axis direction) of the first ferromagnetic layer 14A is fixed in the same direction as the magnetization direction G2 (Y-axis direction) of the second ferromagnetic layer 14B. Further, as shown in FIG. 1, by connecting the electrode pads E1 and E3 to the alternating current source 70, a detection current is caused to flow through the first ferromagnetic layer 14A. The detection current flows from the first ferromagnetic layer 14A, which is a ferromagnetic substance, to the nonmagnetic silicon channel layer 12 via the first tunnel layer 13A, whereby the magnetization direction G1 of the first ferromagnetic layer 14A is obtained. Electrons having spins corresponding to H are injected into the silicon channel layer 12. The injected spins diffuse toward the second ferromagnetic layer 14B. As described above, the current and spin current flowing in the silicon channel layer 12 can be configured to flow mainly in the predetermined axis (X-axis) direction. The direction of the magnetization of the first ferromagnetic layer 14A, which is changed by the external magnetic field B1, that is, the interaction between the spins of electrons and the spins of electrons in the portion of the silicon channel layer 12 in contact with the second ferromagnetic layer 14B, An output is generated between the silicon channel layer 12 and the second ferromagnetic layer 14B. This output is detected by an output measuring device 80 connected to the electrode pads E2 and E4.

  Next, an example of the operation using the NL-Hanle measurement method of the spin transport element 1 according to the present embodiment will be described. The NL-Hanle measurement method utilizes the Hanle effect. The Hanle effect is that when an external magnetic field is applied from a direction perpendicular to the direction of spins when spins injected from the ferromagnetic electrode into the channel by current flow diffuse and conduct toward the other ferromagnetic electrode, Larmor is a phenomenon that causes an age difference. In the NL-Hanle measurement method, as shown in FIG. 3, the spin transport element 1 detects an external magnetic field B2 in the Z-axis direction, for example. The magnetization direction G1 (Y-axis direction) of the first ferromagnetic layer 14A is fixed in the same direction as the magnetization direction G2 (Y-axis direction) of the second ferromagnetic layer 14B. Then, by connecting the first ferromagnetic layer 14A and the first reference electrode 15A to the alternating current source 70, it is possible to flow a spin detection current through the first ferromagnetic layer 14A. The current flows from the first ferromagnetic layer 14A, which is a ferromagnetic substance, to the nonmagnetic silicon channel layer 12 via the first tunnel layer 13A, thereby corresponding to the magnetization direction G1 of the first ferromagnetic layer 14A. Electrons having oriented spins are injected into the first convex portion 12A of the silicon channel layer 12. The spins injected into the first convex portion 12A diffuse toward the second ferromagnetic layer 14B through the main portion 12E. As described above, the current and spin current flowing in the silicon channel layer 12 mainly flow in the X-axis direction.

  Here, when the external magnetic field B2 is not applied to the silicon channel layer 12, that is, when the external magnetic field is zero, the region between the first ferromagnetic layer 14A and the second ferromagnetic layer 14B in the silicon channel layer 12 is diffused. The direction of spin does not rotate. Therefore, the spin in the same direction as the magnetization direction G 2 of the second ferromagnetic layer 14 B set in advance is diffused to the region on the second ferromagnetic layer 14 B side in the silicon channel layer 12. Therefore, when the external magnetic field is zero, the output (for example, the resistance output or the voltage output) has an extreme value. Note that the maximum value or the minimum value can be obtained in the direction of current or magnetization. The output can be evaluated by an output measuring device 80 such as a voltage measuring device connected to the second ferromagnetic layer 14B and the second reference electrode 15B.

  On the other hand, the case where an external magnetic field B2 is applied to the silicon channel layer 12 is considered. The external magnetic field B2 is perpendicular to the magnetization direction G1 of the first ferromagnetic layer 14A (Y-axis direction in the example of FIG. 3) and the magnetization direction G2 of the second ferromagnetic layer 14B (Y-axis direction in the example of FIG. 3) Application (in the example of FIG. 3, in the Z-axis direction). When an external magnetic field B2 is applied, the direction of spins diffused and conducted in the silicon channel layer 12 rotates about the axial direction of the external magnetic field B2 (the Z-axis direction in the example of FIG. 3) (so-called Hanle effect). The direction of rotation of this spin when diffused to the region on the second ferromagnetic layer 14B side in the silicon channel layer 12, and the magnetization direction G2 of the second ferromagnetic layer 14B set in advance, that is, the direction of the spin, The output of the interface between the silicon channel layer 12 and the second ferromagnetic layer 14B (for example, the resistance output or the voltage output) is determined by the relative angle of. When the external magnetic field B2 is applied, the direction of the spins diffused in the silicon channel layer 12 rotates, so the direction and the direction of the magnetization of the second ferromagnetic layer 14B do not match. Therefore, when the external magnetic field takes a maximum value when the external magnetic field is zero, the output becomes equal to or less than the maximum value when an external magnetic field B2 is applied. In addition, when the external magnetic field is a minimum when the external magnetic field is zero, the output is equal to or higher than the local minimum when an external magnetic field B2 is applied.

  Therefore, in the NL-Hanle measurement method, a peak of the output appears when the external magnetic field is zero, and the output decreases when the external magnetic field B2 is increased or decreased. That is, since the output changes depending on the presence or absence of the external magnetic field B2, the spin transport element 1 according to the present embodiment can be used, for example, as a magnetic sensor.

  Moreover, it can be set as the magnetic detection apparatus provided with two or more said spin conduction elements 1. FIG. For example, a plurality of the spin transport elements 1 described above can be arranged in parallel or in layers to form a magnetic detection device. In this case, the output of each spin transport element 1 can be summed. Such a magnetic detection device can be applied to, for example, a biological sensor that detects a cancer cell or the like.

  Further, the spin injection electrode structure IE and the spin conduction element 1 described above can be used for various spin conduction devices such as, for example, a magnetic head, a magnetoresistive memory (MRAM), a logic circuit, a nuclear spin memory, and a quantum computer.

  Further, the configuration of the spin detection unit (the second ferromagnetic layer 14B, the second tunnel layer 13B, and the second convex portion 12B of the silicon channel layer 12) is not limited to the above embodiment. May be detected.

EXAMPLES Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited to these examples.

Example 1
First, an SOI substrate consisting of a substrate, an insulating film, and a silicon film was prepared. A silicon substrate was used as the substrate, a 200 nm silicon oxide layer was used as the insulating film, and the silicon film was 100 nm. Implantation of phosphorus ions to impart conductivity to the silicon film was performed. Thereafter, the impurity was diffused by annealing at 900 ° C. to adjust the electron concentration of the silicon film. At this time, the average electron concentration of the entire silicon film was made to be 5.0 × 10 ¹⁹ cm ⁻³ .

Next, RCA cleaning was used to remove deposits on the surface of the SOI substrate, organic substances, and natural oxide films. Thereafter, the surface of the SOI substrate was terminated with hydrogen using an HF cleaning solution. Subsequently, the SOI substrate was carried into a molecular beam epitaxy (MBE) apparatus. The base vacuum degree (vacuum degree in the apparatus before the lamination process is actually performed) was set to 2.0 × 10 ⁻⁹ Torr or less. A flushing process was performed by heating the SOI substrate. Thereby, hydrogen on the silicon film surface was released to form a clean surface.

Next, a first tunnel layer was formed on the silicon film using MBE. First, aluminum oxide was crystallized to form a lower region of the first tunnel layer, and magnesium was simultaneously formed with aluminum oxide to form a first tunnel layer upper region containing magnesium, aluminum and oxygen. In the process of forming these layers, when several atomic layers were formed, the formation of oxygen was stopped once and oxygen ions were irradiated to the surface of the film to compensate. The above was repeated to form a first tunnel layer. Thereafter, an iron film as a ferromagnetic layer and a titanium film as a protective film were formed in this order to obtain a laminate. The degree of vacuum at the time of film formation was 5 × 10 ⁻⁸ Torr or less. The titanium film is a cap layer for suppressing characteristic deterioration due to oxidation of the iron film.

In the present embodiment, the spinel layer of the tunnel layer, the iron film of the ferromagnetic layer, and the titanium film of the protective film are formed in the same step in the first portion and the second portion, so the first portion and the second portion The laminated structure of is the same.

  Subsequently, in order to stabilize the crystallization of the first tunnel layer, annealing was performed at 200 ° C. for 3 hours after flash annealing at 500 ° C.

  Next, after cleaning the surface of the laminate, a Ta alignment mark was formed on the substrate by photolithography and lift-off. Subsequently, the silicon film was patterned by anisotropic wet etching using a mask. Thus, the silicon channel layer 12 having the sloped portion on the side surface was obtained. At this time, the size of the silicon channel layer 12 was 23 μm × 300 μm. Further, the side surface of the obtained silicon channel layer 12 was oxidized to form a silicon oxide film (oxide film 7a).

  Next, the titanium film, the iron film, and the silicon channel layer were patterned using a photolithography method to form the first ferromagnetic layer 14A and the second ferromagnetic layer 14B as shown in FIG. The oxide film and the magnesium film located except between the silicon channel layer 12 and the first ferromagnetic layer 14A and the second ferromagnetic layer 14B were removed. Thereby, the first tunnel layer 13A and the second tunnel layer 13B were obtained. An Al film was formed on one end side and the other end side of the exposed silicon channel layer 12 to obtain a first reference electrode 15A and a second reference electrode 15B.

  Next, among the surfaces of the silicon channel layer 12, the first ferromagnetic layer 14A, the second ferromagnetic layer 14B, the first reference electrode 15A and the second reference electrode 15B are not formed by using ion milling and etching. In the portion, the silicon channel layer 12 was dug down to a depth of 20 nm from the surface of the silicon channel layer 12. Thus, the silicon channel layer 12 has a structure including the first convex portion 12A, the second convex portion 12B, the third convex portion 12C, the fourth convex portion 12D, and the main portion 12E. The first convex portion 12A, the second convex portion 12B, the third convex portion 12C, and the fourth convex portion 12D are arranged in this order at predetermined intervals in the X-axis direction, and extend so as to protrude from the main portion 12E. It is a part that exists. The film thickness H1 of the first convex portion 12A, the second convex portion 12B, the third convex portion 12C, and the fourth convex portion 12D was 10 nm. With such a structure, the surface damage formed at the time of ion implantation for imparting conductivity to the silicon film to be the silicon channel layer 12 is removed.

  Furthermore, on the side surfaces of oxide film 7a, first tunnel layer 13A, second tunnel layer 13B, first ferromagnetic layer 14A, second ferromagnetic layer 14B, first reference electrode 15A and second reference electrode 15B, and silicon channel A silicon oxide film (oxide film) on the main portion 12E where the first ferromagnetic layer 14A, the second ferromagnetic layer 14B, the first reference electrode 15A and the second reference electrode 15B are not formed among the upper surfaces of the layer 12 7b).

  Next, wirings 18A to 18D were formed on the first ferromagnetic layer 14A, the second ferromagnetic layer 14B, the first reference electrode 15A, and the second reference electrode 15B, respectively. A stacked structure of Ta (10 nm in thickness), Cu (50 nm in thickness), and Ta (10 nm in thickness) was used as the wirings 18A to 18D. Furthermore, electrode pads E1 to E4 were formed at the end portions of the respective wirings 18A to 18D. A laminated structure of Cr (50 nm in thickness) and Au (150 nm in thickness) was used as the electrode pads E1 to E4. Thus, the spin transport device of Example 1 having the same configuration as that of the spin transport device 1 shown in FIGS. 1 to 4 was produced.

(Result of NL measurement)
In the NL measurement method, in the spin transport device manufactured in Example 1, the magnetization direction G1 of the first ferromagnetic layer 14A and the magnetization direction G2 of the second ferromagnetic layer 14B are the same as the magnetization direction of the external magnetic field B1 (FIG. 3) Fixed in the Y-axis direction). An external magnetic field B1 was applied to the spin transport element from a direction (Y-axis direction) parallel to the magnetization directions of the first ferromagnetic layer 14A and the second ferromagnetic layer 14B. Spins were injected from the first ferromagnetic layer 14A to the silicon channel layer 12 by flowing the detection current from the alternating current source 70 to the first ferromagnetic layer 14A. Then, the output based on the magnetization change due to the external magnetic field B1 was measured by the output measuring device 80. At this time, all measurements were performed at room temperature.

  FIG. 5 is a graph showing the relationship between the applied magnetic field and the voltage output in the NL measurement method. F1 of FIG. 5 shows the case where the external magnetic field B1 is changed from the minus side to the positive side, and F2 of FIG. 5 shows the case where the external magnetic field B1 is changed from the plus side to the negative side. As shown in F1 and F2 of FIG. 5, the spin transport device had a voltage output of about 26.8 μV.

(Result of NL-Hanle measurement)
In the NL-Hanle measurement method, in the spin transport device manufactured in Example 1, the direction (Z-axis direction shown in FIG. 3) of the applied external magnetic field B2 is the magnetization direction (Y in FIG. 3) of the first ferromagnetic layer 14A. Axial direction) G1 and the magnetization direction (Y-axis direction shown in FIG. 3) G2 of the second ferromagnetic layer 14B were perpendicular to each other. FIG. 6 is a graph showing the relationship between the applied magnetic field and the voltage output in the NL-Hanle measurement method. FIG. 6 is a measurement result in the case where the magnetization direction of the first ferromagnetic layer 14A is fixed in parallel to the magnetization direction of the second ferromagnetic layer 14B.

  As can be seen from the measurement results in FIG. 6, it is understood that the spins conducting in the silicon channel layer are rotating and decayed by the application of the external magnetic field B2. Therefore, it can be proved that the measurement result of FIG. 6 is a signal generated by spin conduction.

(Analysis of membrane)
The evaluation of the tunnel layer was performed at cross-sectional TEM and EDX. From the result of the cross-sectional TEM, the thickness of the tunnel layer was 2.1 nm. The tunnel layer portion was cut out from the photograph of the cross-sectional TEM, and the lattice constant was estimated by performing the Fourier analysis and analyzing the Bragg point. The cut-out portion is a portion in contact with the silicon channel layer, a portion in contact with the ferromagnetic layer, and an intermediate portion between a portion in contact with the silicon channel layer and a portion in contact with the ferromagnetic layer. The lattice constant of the portion of the tunnel layer in contact with silicon was 7.8 Å. This lattice constant indicates that it is a spinel γ-type aluminum oxide. The lattice constant of the portion of the tunnel layer in contact with the ferromagnetic layer was 8.1 Å. This lattice constant indicates that it is an oxide of magnesium and aluminum having a spinel structure.

Furthermore, analysis of magnesium, aluminum, oxygen, iron and silicon was performed by EDX. As shown in FIG. 7, according to the profile in the depth direction, the silicon channel layer side of the tunnel layer is a spinel layer in which part or all of magnesium having a low content of magnesium is deficient and the ferromagnetic layer side of the tunnel layer is It is understood that the spinel layer is a magnesium-rich spinel layer containing a large amount of magnesium. Further, FIG. 8 shows the results of the lattice constant in the thickness direction based on the boundary between the tunnel layer and the silicon channel layer. A systematic change was observed in the thickness direction.

(Example 2)
A device was prepared in the same manner as in Example 1. However, zinc was used instead of magnesium when forming the first tunnel layer upper region of the first tunnel layer. The method of producing the spin transport device was the same as in Example 1.

The evaluation of the tunnel layer was performed in the same manner as in Example 1, and the thickness of the tunnel layer was 2.2 nm. The lattice constant of the portion of the tunnel layer in contact with the silicon channel layer is 7.85 Å, which indicates that it is a spinel γ-type aluminum oxide. The lattice constant of the portion of the tunnel layer in contact with the ferromagnetic layer was 8.03 Å, which was an oxide of zinc and aluminum having a spinel structure.

(Example 3)
A device was prepared in the same manner as in Example 1. However, a Heusler alloy film was used as the ferromagnetic layer. This Heusler alloy is represented by a composition formula of Co ₂ FeAl _0.5 Si _0.5 . The Heusler alloy film was formed at 300 ° C. on the substrate. The method of producing the spin transport device was the same as in Example 1.

  The evaluation of the tunnel layer was performed in the same manner as in Example 1, and the thickness of the tunnel layer was 2.2 nm. The lattice constant of the portion of the tunnel layer in contact with the silicon channel layer is 7.8 Å, which indicates that it is a spinel γ-type aluminum oxide. The lattice constant of the portion of the tunnel layer in contact with the ferromagnetic layer was 8.08 Å, which was an oxide of magnesium and aluminum having a spinel structure. It was also confirmed that the constituent elements of the Heusler alloy did not diffuse to the silicon channel layer.

(Comparative example 1)
Next, using? -Type aluminum oxide of spinel structure as the first tunnel layer, the first tunnel layer lower region and the second tunnel layer region have the same composition, and flash annealing is not performed at 230 ° C. Annealing for 3 hours was performed. The spin transport device was prepared in the same manner as in Example 1.

Table 1 shows the results of measuring the spin output by the NL-Hanle measurement method for the spin transport device obtained in this manner.

  In Example 1, Example 2 and Example 3, substantially similar results were obtained at room temperature. Example 3 used a Heusler alloy having a spin polarization ratio higher than that of iron as the ferromagnetic layer, so a somewhat higher output was obtained.

(Example 4)
A spin transport device was produced in the same manner as in Example 1. However, germanium was used as a semiconductor channel layer.

First, a GOI substrate comprising a substrate, an insulating film, and a germanium film was prepared. A germanium substrate was used for the substrate, a silicon oxide layer of 200 nm was used for the insulating film, and the germanium film was 100 nm. Impurities for providing conductivity to the germanium film were implanted. Thereafter, the impurity was diffused by annealing at 900 ° C. to adjust the electron concentration. At this time, the average electron concentration of the entire germanium film was made to be 2.0 × 10 ¹⁹ cm ⁻³ .

Next, RCA cleaning was used to remove deposits, organic matter, and native oxide films on the surface of the GOI substrate. Thereafter, the surface of the GOI substrate was terminated with hydrogen using an HF cleaning solution. Subsequently, the GOI substrate was carried into a molecular beam epitaxy (MBE) apparatus. The base vacuum degree (vacuum degree in the apparatus before the lamination process is actually performed) was set to 2.0 × 10 ⁻⁹ Torr or less. A flushing process was performed by heating the GOI substrate. Thereby, hydrogen on the germanium film surface was released to form a clean surface.

Next, a first tunnel layer was formed on the germanium film using MBE. First, the ratio of aluminum oxide to magnesium oxide was 2 to 0.7. At this time, the partial pressure of oxygen in the chamber was adjusted for crystallization to form a first tunnel layer lower region. It adjusted so that the ratio of magnesium might become high every time film-forming progressed, and it adjusted so that the ratio of aluminum and magnesium might become 2 to 1 before ferromagnetic layer formation. Thus, a tunnel layer having a spinel structure containing magnesium and aluminum was formed. In the process of forming these layers, oxygen which has been deficient is compensated by forming several atomic layers, stopping deposition once, and irradiating oxygen ions on the surface of the film. This process was repeated to form a first tunnel layer. Thereafter, an iron film as a first ferromagnetic layer and a titanium film as a protective film were formed in this order to obtain a laminate. The degree of vacuum at the time of film formation was 5 × 10 ⁻⁸ Torr or less. The titanium film is a cap layer for suppressing characteristic deterioration due to oxidation of the iron film.

  Subsequently, in order to stabilize the crystallization of the first tunnel layer, annealing was performed at 200 ° C. for 3 hours after flash annealing at 500 ° C.

The evaluation of the tunnel layer was performed in the same manner as in Example 1, and the thickness of the tunnel layer was 2.0 nm. The lattice constant of the portion of the tunnel layer in contact with the germanium channel layer is 7.8 Å, which indicates that it is a spinel γ-type aluminum oxide. The lattice constant of the portion of the tunnel layer in contact with the ferromagnetic layer was 8.09 Å, which was an oxide of magnesium and aluminum having a spinel structure. Furthermore, analysis of magnesium, aluminum, oxygen, iron and germanium was performed by EDX. From the profile in the depth direction, the germanium channel layer side of the tunnel layer is a spinel layer with a low content of magnesium, and the ferromagnetic layer side of the tunnel layer is a spinel layer containing a large amount of magnesium.

The output was evaluated by non-local measurement as in Example 1.

(Example 5)
A device was prepared in the same manner as in Example 4. Zinc was used instead of magnesium when forming the tunnel region. The method for producing the element and the evaluation are the same as in Example 4.

(Example 6)
A device was prepared in the same manner as in Example 4. However, a Heusler alloy film was formed as a ferromagnetic layer. This Heusler alloy is represented by a composition formula of Co ₂ FeAl _0.5 Si _0.5 . In addition, when forming a Heusler alloy, the substrate was formed at 300 ° C. The method of producing the spin transport device is the same as that of the first embodiment.

(Comparative example 2)
A device was prepared in the same manner as in Example 4. However, the first tunnel region and the second tunnel region of the first tunnel layer were made to have the same composition, and magnesium oxide was used for the first tunnel layer. Also, unlike Example 4, flash annealing was not performed, and annealing at 250 ° C. for 3 hours was performed.

  Table 2 shows the measurement results. Almost similar results were obtained in Example 4, Example 5, and Example 6 at room temperature. In Example 6, since a Heusler alloy having a spin polarization ratio higher than that of iron is used as the ferromagnetic layer, a somewhat higher output is obtained.

(Example 7)
Next, as a semiconductor channel layer, using gallium arsenide, a spin transport device was formed in the same manner as in Example 1. The film forming method is as follows.

First, a substrate consisting of a substrate, an insulating film, and a gallium arsenide film was prepared. Gallium arsenide was used as the substrate, and a 200 nm silicon oxide layer was used as the insulating film, and the gallium arsenide film was 100 nm. Implantation was performed using silicon as an impurity to impart conductivity to the gallium arsenide film. Thereafter, the impurity was diffused by annealing at 900 ° C. to adjust the electron concentration of the gallium arsenide film. At this time, the average electron concentration of the entire gallium arsenide film was made to be 5.0 × 10 ¹⁹ cm ⁻³ .

Then, RCA cleaning was used to remove the deposit on the surface of the gallium arsenide substrate, the organic matter, and the native oxide film. Thereafter, the surface of the gallium arsenide substrate was terminated with hydrogen using an HF cleaning solution. Subsequently, the substrate was carried into a molecular beam epitaxy (MBE) apparatus. The base vacuum degree (vacuum degree in the apparatus before the lamination process is actually performed) was set to 2.0 × 10 ⁻⁹ Torr or less. A flushing process was performed by heating the gallium arsenide substrate.

Next, the first tunnel layer was formed on the gallium arsenide substrate using the MBE method. First, aluminum oxide was crystallized to form a lower region of the first tunnel layer, and magnesium was simultaneously formed with aluminum oxide to form a first tunnel layer upper region containing magnesium, aluminum and oxygen. In the process of forming these layers, when several atomic layers were formed, the formation of oxygen was stopped once and oxygen ions were irradiated to the surface of the film to compensate. The above was repeated to form a first tunnel layer. Thereafter, an iron film as a ferromagnetic layer and a titanium film as a protective film were formed in this order to obtain a laminate. The degree of vacuum at the time of film formation was 5 × 10 ⁻⁸ Torr or less. The titanium film is a cap layer for suppressing characteristic deterioration due to oxidation of the iron film.

  Subsequently, in order to stabilize the crystallization of the first tunnel layer, annealing was performed at 200 ° C. for 3 hours after flash annealing at 500 ° C.

The evaluation of the tunnel layer was performed in the same manner as in Example 1, and the thickness of the tunnel layer was 2.2 nm. The lattice constant of the portion of the tunnel layer in contact with the gallium arsenide channel layer is 7.9 Å, which indicates that it is a spinel γ-type aluminum oxide. The lattice constant of the portion of the tunnel layer in contact with the ferromagnetic layer was 8.06 Å, which was an oxide of magnesium and aluminum having a spinel structure. Furthermore, analysis of magnesium, aluminum, oxygen, iron and gallium arsenide was performed by EDX. From the profile in the depth direction, the gallium arsenide channel layer side of the tunnel layer is a spinel layer with a low content of magnesium, and the ferromagnetic layer side of the tunnel layer is a spinel layer containing a large amount of magnesium.

The output was evaluated by non-local measurement as in Example 1.

(Example 8)
A device was prepared in the same manner as in Example 7. Zinc was used instead of magnesium when forming the tunnel region. The preparation method and evaluation of the device are the same as in Example 7.

(Example 9)
A device was prepared in the same manner as in Example 7. However, a Heusler alloy film was formed as a ferromagnetic layer. This Heusler alloy is represented by a composition formula of Co ₂ FeAl _0.5 Si _0.5 . In addition, when forming a Heusler alloy, the substrate was formed at 300 ° C. The method of producing the device is the same as that of the embodiment.

(Comparative example 3)
A device was prepared in the same manner as in Example 7. However, the first tunnel region and the second tunnel region of the first tunnel layer were made to have the same composition, and magnesium oxide was used for the first tunnel layer. Further, unlike Example 7, flash annealing was not performed, and annealing at 250 ° C. for 3 hours was performed.

  Table 3 shows the measurement results. In Example 7, Example 8, and Example 9, substantially similar results were obtained at room temperature. Example 9 used a Heusler alloy having a spin polarization ratio higher than that of iron as the ferromagnetic layer, so a somewhat higher output was obtained.

  IE: spin injection electrode structure, 1: spin conductive element, 10: substrate, 11: silicon oxide film, 12: silicon channel layer, 13A: first tunnel layer, 13B: second tunnel layer, 14A: first ferromagnetic layer , 14B: second ferromagnetic layer, 15A: first reference electrode, 15B: second reference electrode, 16A: first tunnel layer lower region, 16B: first tunnel layer upper region, 16C: second tunnel layer lower region, 16D ... second tunnel layer upper region, 70 ... alternating current source, 80 ... output measuring instrument.

Claims (3)

It has a structure in which part or all of the element located at the A site of the spinel structure represented by the composition formula AB ₂ O ₄ is deficient, and the concentration of the element located at the A site changes continuously in the film thickness direction A tunnel layer characterized by Composition formula AB ₂ O ₄ When the film thickness direction is the vertical direction, the concentration of the element located at the A site in the lower region is: A tunnel layer characterized by being lower than the concentration of the element located at the A site in the upper region. Al, Mg, Si, consists of an oxide containing any of the elements Zn, tunnel layer according to claim 1 or 2.

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