JP2006032569A - Spin filter and spinning state separating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spin filter capable of obtaining a spin deflection angle sufficient for separating a spinning state of different carriers propagating through a semiconductor, and to provide a spinning state separating method. <P>SOLUTION: When a gate insulation layer 12 of different thickness is inserted in the y-axis direction, an effective gate voltage being applied to a two-dimensional electron gas channel 14 has a gradient in the spin filter 10, and spin orbit interaction of the two-dimensional electron gas channel 14 beneath a gate electrode 11 causes spatial gradient in the y-axis direction. When an electron spin propagates through that space in the x-axis direction, spin upward carrier and downward carrier receive a force in reverse direction and being separated spatially. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spin filter and a spin state separation method for separating spin states of carriers propagating in a semiconductor.

  In the conventional semiconductor device, only the charge property of the electrons has been used. Electrons have a spin degree of freedom as well as an electric charge, but until now no device has actively used the spin properties of electrons. Recently, semiconductor devices are reaching the limit of miniaturization, and the field of spintronics has been attracting attention as a new device with an unprecedented function by simultaneously using the "charge" and "spin" possessed by electrons. It has come to be. In order to realize a spin device in a semiconductor, an operation method has been established: (1) generation of spin-polarized carriers, (2) spin transport, storage, arithmetic operation, and (2) final spin state detection. There is a need to.

  Among these, as the most established technique for generating spin-polarized electrons in a semiconductor, there is a method of exciting spin-polarized electrons from a valence band to a conductor with circularly polarized light. However, in this method, it is impossible to obtain 100% spin-polarized electrons due to the restriction by the selection rule, and holes are generated in pairs with electrons. There has been a problem that the relaxation time of cannot be made sufficiently long.

  Further, it has been theoretically pointed out that spin injection from a ferromagnetic electrode to a semiconductor makes it difficult to obtain a large degree of spin polarization in the semiconductor due to the difference in conductance between the metal and the semiconductor. As a method for overcoming such a difference in conductance, a method of inserting a tunnel barrier between a ferromagnet and a semiconductor has been proposed, but at present, a large degree of spin polarization has not been obtained.

  Recently, it has become possible to synthesize III-V dilute magnetic semiconductors in which Group III is partially substituted with Mn, but also in this regard, carriers are p-type and spin relaxation is fast due to the influence of spin-orbit interaction. Also, there is a problem that the ferromagnetic dislocation temperature (Curie temperature Tc) is below room temperature (Tc = 110 K).

  Under such circumstances, from the viewpoint of generation and transport of spin-polarized electrons, and detection of the spin state, a spin filter using a non-uniform magnetic field using the Stern-Gerach effect (hereinafter referred to as SG effect) has been proposed. (For example, refer nonpatent literature 1).

FIG. 8 is a diagram conceptually showing the SG effect. Stern-Gerlach (1922) developed a spin-up and down-spin by conducting an experiment in which silver (Ag) atoms having a spin 1/2 are removed from the oven furnace through a slit and passed through this non-uniform magnetic field gradient. Succeeded in spatially separating atoms e ₁ and e ₂ each having

Non-Patent Document 1 proposes a spin filter that combines a one-dimensional or two-dimensional electron gas of GaAs (gallium arsenide) and a non-uniform magnetic field using the SG effect.
J. Wroebel, T. Dietl, K. Fronc, A. Lusakowski, M. Czeczott, G. Grabecki, R. Hey, and KH Ploog, Physica E 10, 91 (2001).

  However, since the spin filter using the SG effect described above has a high electron velocity in the semiconductor channel and the interaction time passing through the inhomogeneous magnetic field is short, a sufficient deflection angle of the upward and downward spins cannot be obtained. It was impossible to realize.

  In addition, inhomogeneous magnetic field using a magnetic material, it is difficult to make the component perpendicular to the two-dimensional electron gas zero, and the perpendicular component of this magnetic field acts as Lorentz force on electrons, so spin upwards and downwards. Regardless, there is a problem that it works as an effect of bending the trajectory in a certain direction and prevents the carrier spin space separation due to the SG effect.

Originally, the SG effect experiment was performed using silver atoms with zero charge and spin 1/2 as described above, and therefore the SG effect of charged atoms or electrons is subject to Lorentz force. Therefore, it has been predicted that it is difficult to verify the SG effect. The reason is that uncertainty is generated in the spin deflection angle due to the Lorentz force. The reason is as follows. According to electromagnetism, the magnetic field B satisfies ▽ · B = 0 because there is no magnetic charge.

Here, for the sake of simplicity, assuming that ∂B _x / す_ると_x = 0 in the coordinate system of FIG. 8, if the magnetic field gradient ∂B _y / ∂y in the y-axis direction is not zero, it is perpendicular to the carrier propagation direction. There is also a non-zero magnetic field gradient ∂B _z / ∂z = − (∂B _y / ∂y) in the z-axis direction (in this case, the magnitude of the magnetic field component in the z direction | ∂B _z / ∂z | Maximum).

Due to the presence of the magnetic field gradient ∂B _z / ∂z in the z-axis direction, electrons distributed in the z-axis direction receive different forces, and an uncertainty Δφ _SG occurs in the spin deflection angle. That is, it is pointed out that carriers with electric charges are subjected to Lorentz force, and therefore the spin deflection angle is uncertain, and the widening of this deflection angle is an essential problem in the observation of the SG effect.

  The present invention has been made in order to solve the above-described problem. The spin deflection angle is sufficient to separate different spin states of carriers propagating in a semiconductor without using any magnetic field or magnetic material. It is an object of the present invention to provide a spin filter and a spin state separation method that can obtain the above.

  To achieve the above object, the present invention according to claim 1 is a spin filter that separates carriers for each spin state of carriers propagating in a semiconductor, the semiconductor channel confining and propagating the carriers, and Gate voltage applying means for applying a gate voltage to the semiconductor channel, and the gate voltage causes a spatial gradient in a direction perpendicular to a direction in which the carriers propagate by the intensity of the spin-orbit interaction of the semiconductor channel. It is characterized by being controlled so as to be non-uniform.

  According to a second aspect of the present invention, in the first aspect of the invention, the spin filter inserts layers having different thicknesses on the semiconductor channel, thereby providing a spatial gradient in the strength of the spin-orbit interaction. It is characterized by.

  According to a third aspect of the present invention, in the first aspect of the present invention, the gate voltage application means includes a plurality of gate electrodes with different voltages to be applied, thereby providing a spatial gradient in the strength of the spin-orbit interaction. It is characterized by having it.

  The present invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein an elastic scatterer is introduced into the semiconductor channel.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, an electrode for spin detection using a magnetic material is provided on the output side.

  The present invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein an electrode for spin injection using a magnetic material is provided on the input side.

  The present invention according to claim 7 is a spin state separation method for separating carriers for each spin state of carriers propagating in a semiconductor, wherein a gate voltage is applied to a semiconductor channel confining the carriers and propagating the carriers. And applying the gate voltage to control the intensity of the spin-orbit interaction of the semiconductor channel to be non-uniform with a spatial gradient in a direction perpendicular to the direction of propagation of the carriers. To do.

  According to an eighth aspect of the present invention, in the spin filter including the semiconductor channel according to the seventh aspect, a layer having a different thickness is inserted on the semiconductor channel, and the strength of the spin-orbit interaction is increased. It is characterized by having a gradient.

  According to a ninth aspect of the present invention, in the seventh aspect of the present invention, the gate voltage applying means for applying the gate voltage includes a plurality of gate electrodes having different voltages to be applied, thereby increasing the strength of the spin orbit interaction. It is characterized by a spatial gradient.

  According to a tenth aspect of the present invention, in the invention according to any one of the seventh to ninth aspects, an elastic scatterer is introduced into the semiconductor channel.

  The invention according to claim 11 is the invention according to any one of claims 7 to 10, characterized in that an electrode using a magnetic material is provided on the output side to detect the spin state of the carrier. To do.

  A twelfth aspect of the present invention is the method according to any one of the seventh to eleventh aspects, wherein an electrode using a magnetic material is provided on the input side, and spin-polarized carriers are injected. To do.

  According to the present invention, since the spin-orbit interaction of the semiconductor channel can be controlled by the gate voltage, the SG effect can be realized in the semiconductor by using the spatial gradient of the spin-orbit interaction.

  As a result, a spin deflection angle sufficient to separate different spin states of carriers propagating in the semiconductor can be obtained without using any magnetic field or magnetic material.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Basic matters>
First, basic matters that are preconditions for carrying out the present invention will be described. The basic matters described below are common to all embodiments of the present invention.

Since spin-orbit interaction is given by Dirac from relativistic considerations, it can be ignored in many cases, but in III-V semiconductors, spin-orbit interaction due to the breaking of spatial inversion symmetry cannot be ignored. It may disappear. The Rashba spin-orbit interaction is caused by the electric field created by the semiconductor heterointerface, and it is expected that the effect of the electric field will become stronger and the spin-orbit interaction will increase as the shape of the quantum well confining the electrons becomes spatially asymmetric. It was. According to the k · p perturbation method, the strength α of the spin orbit interaction is given by (Th. Schaepers, G. Engels, J. Lange, Th. Klocke, M. Hollfelder, and H. Lueth, J Appl. Phys. 83,4324 (1998)).

Where Ψ (z) is the electron wave function of the quantum well, E _p is the band parameter of the k · p perturbation, E _F is the Fermi energy, m _o is the effective mass of free electrons, E _Γ7 (z) and E _Г8 ( z) corresponds to the spin separation band energy and band edge energy of the valence band, and h corresponds to the Planck constant. From the equation (1), it is expected that the narrow orbital semiconductor such as InAs and InSb increases the spin-orbit interaction. In addition, the larger the potential gradient that forms a quantum well, the greater the spin-orbit interaction. The inventors have analyzed the beat appearing in the Shubnikov-Dohers vibration (see T. Koga, J. Nitta, T. Akazaki, and H. Takayanagi, Phys. Rev. Lett. 89, 46801 (2002)) From experiments on weak localization effects (see Th. Schaepers, G. Engels, J. Lange, Th. Klocke, M. Hollfelder, and H. Lueth, J. Appl. Phys. 83,4324 (1998)) It was confirmed that the symmetry of the well can be modulated by the gate voltage, and the Rashba spin-orbit interaction can be controlled by the gate voltage.

FIG. 1 (a) is a diagram showing the gate voltage dependence of the Shubnikov-Dohers oscillation of an InGaAs / InAlAs two-dimensional electron gas heterostructure with an InAs layer inserted. The solid line is the experimental value, and the dotted line is the theoretical value. FIG. 1B is a diagram showing the carrier concentration dependence of the spin-orbit interaction α obtained by analyzing the beat appearing in the Shubnikov-Dohers oscillation, and the spin-orbit interaction calculated from the result of FIG. The relationship between α and carrier concentration is shown. Here, the carrier concentration corresponds to the gate voltage (for example, Vg = 0V corresponds to Ns = 2.45 × 10 ¹² cm ⁻² , and Vg = −0.7 V corresponds to Ns = 1.7 × 10 ¹² cm ⁻² ). This shows that the strength α of the spin orbit interaction can be controlled by the gate voltage. It is also experimentally confirmed that the spin-orbit interaction changes by changing only the potential shape of the quantum well without changing the carrier concentration by using two gate electrodes of the back gate and the front gate. Has been.

Spin degeneracy is eliminated by the Rashba spin-orbit interaction, and the energy difference Δ _R between the upward and downward spins in the vicinity of the Fermi energy is given by Δ _R = ± αk _F. Here, k _F corresponds to the Fermi wave number. Therefore, the electron g- factor and Bohr electron mu _B, though equivalent to feels effective magnetic field as follows.

  Here, the SG effect shown in FIG. 8 will be described. The Hamiltonian due to the Zeeman effect is given by the following equation in the magnetic field B.

H _z = sgμ _B B (3)
Here, spin s = ± 1/2, g is a g-factor, μ _B is a Bohr magneton, and B is a magnetic field. This spatial change in Zeeman energy corresponds to the spatial change in potential and exerts a force on electron spin. For example, when a spatial gradient is given to the y-axis component of the magnetic field B shown in FIG.

However, spins that are upward and downward with respect to the y-axis direction receive forces in opposite directions, and separation occurs when the spin propagates through this spatial magnetic field gradient. The spin deflection angle φ _SG due to the SG effect is given as follows.

Here, Delta] t corresponds to the time the electron spin propagates in nonuniform magnetic field, which corresponds to result in a change in momentum Delta] p _y in the y-axis direction. p _x is the momentum component of the electron spin in the x-axis direction, and F _y · Δt is the impulse that the electron spin receives in the y-axis direction.

The main point of the present invention is that by applying a spatial gradient to the spin upward energy difference Δ _R = ± αk _F generated by the Rashba spin-orbit interaction, a reverse force is applied to the spin upward carrier and the downward carrier, thereby separating the space. The spin filter. This corresponds to realizing a spin filter function in which the effective magnetic field B _eff resulting from the Rashba spin orbit interaction is provided with a spatial gradient by the gate electrode when considered in contrast with the SG effect described above. In this case, since there is no spatial gradient of the magnetic field B, the magnetic field in the z-axis direction perpendicular to the two-dimensional digitized gas can be made zero, and the Lorentz effect that hinders the SG effect can be eliminated.

  As described above, in a conventional spin filter using a magnetic field gradient created by a ferromagnetic material, electrons have a charge together with spin, and therefore, the Lorentz force is generated by a magnetic field component perpendicular to the two-dimensional electron gas plane (xy plane). The effect of bending the electron spin trajectory cannot be ignored, and it is difficult to construct a spin filter.

On the other hand, the present invention uses a potential gradient due to the Rashba spin orbit interaction, and therefore does not require any external magnetic field. Therefore, the effect of bending the electron trajectory due to the Lorentz force is completely negligible. If the direction of the electric field due to the heterointerface is the z-axis direction, the Hamiltonian of the Rashba spin orbit interaction is given by the following equation.

Here, σ corresponds to Pauli's spin matrix, and p corresponds to momentum. By this Rashba Hamiltonian, the dispersion energy of electrons is

Given in. Here, k is the wave number and m ^* is the effective mass of the electrons. If the spin-orbit interaction α has a spatial gradient in the y-axis direction, Expression (7) can be expressed as follows.

The spin upward and downward energies at the Fermi wavenumber k _F are ± αk _F , respectively. Therefore, when the spatial gradient α (y) is given to the strength α of the spin orbit interaction, the upward and downward spins receive forces in opposite directions, and can be expressed as follows.

Similar to the SG effect, spin separation can be achieved. The spin deflection angle φ _SG due to the SG effect is

Given in. Here, Δt = L / v _F and p _x = hk _F. L is the length of the semiconductor channel, and v _F is the Fermi velocity.

It is sufficiently possible to change the strength of the spin orbit interaction by Δα (y) = 5 × 10 ⁻¹² [eVm] by the gate to the channel width from the experimental result of FIG. is there. When the region where the spin-orbit interaction is spatially changed in the y-axis direction is L = 2 μm, the carrier concentration is n _s = 1 × 10 ¹¹ cm ⁻² , and the effective mass m ^* = 0.04, the Fermi velocity v _F is v _F = 2.2 × 10 ⁵ m / s, and φ _SG = 9.1 [deg] is obtained by substituting into the above equation. By lengthening the region L in which the spin-orbit interaction varies, the spin deflection angle can be increased. For example, if L = 5 μm, φ _SG = 21.6 deg.

  In the above basic matter, the spin filter using the Rashba spin-orbit interaction has been described. However, the present invention is not limited to the Rashba spin-orbit interaction, but other spin-orbit interaction. However, since it can be controlled by the gate voltage, it may be a spin filter using other spin-orbit interaction.

<Device configuration of spin filter>
FIG. 2 is a block diagram showing an outline of a functional configuration of the spin filter 1 configured based on the basic items described above. The spin filter 1 shown in FIG. 2 confines carriers and propagates the semiconductor channel 2, the gate voltage application unit 3 that applies a gate voltage to the semiconductor channel 2, and the applied gate voltage causes the spin orbit interaction of the semiconductor channel 2. A spin orbit interaction space gradient generation unit 4 for generating a space gradient is provided.

The semiconductor channel 2 has a two-dimensional region in which the movable region in one spatial dimension direction of the carrier is so small that it can be ignored as compared with the movable regions in the other two spatial dimension directions. It behaves as a two-dimensional electron gas (hereinafter, this two-dimensional region is referred to as a “two-dimensional electron gas channel”). The two-dimensional electron gas channel confines carriers in a two-dimensional region by forming a semiconductor quantum well structure, for example. As is well known, for example, a semiconductor quantum well structure having a narrow width in the one-dimensional direction of space, for example, can be formed by laminating both surfaces of a GaAs thin film with Al _0.3 Ga _0.7 As, or _{A 0.53} Ga _0.47 As thin film can be formed by sandwiching and laminating both surfaces of InP.

  The gate voltage application unit 3 applies an effective gate voltage to the semiconductor channel 2 below the gate electrode. The gate electrode may be either a top gate or a back gate, and may include two gate electrodes, a top gate and a back gate.

  The spin orbit interaction space gradient generation unit 4 is a characteristic part of the present invention, and specifically, various modes are conceivable as described later. Hereinafter, a specific configuration of the spin filter will be described.

  3A is a schematic view of the spin filter 10 according to one embodiment of the present invention as viewed from the z-axis direction (top view), and FIG. 3B is a cross-sectional view taken along line AB of FIG. It is sectional drawing.

  As shown in FIG. 3B, the spin filter 10 has an effective gate voltage gradient applied to the two-dimensional electron gas channel 14 by inserting the gate insulating layers 12 having different thicknesses in the y-axis direction. For this reason, the spin-orbit interaction of the two-dimensional electron gas channel 14 under the gate electrode 11 has a spatial gradient in the y-axis direction. Accordingly, while electron spin propagates in this space in the x-axis direction, spin-up carriers and spin-down carriers receive forces in opposite directions, and the spins are spatially separated. For example, if a Y-shaped branch is provided behind the gate electrode 11, an upward spin flows into the terminal T1 and a downward spin flows into the terminal T2.

Here, as shown in FIG. 3, if the length of the two-dimensional electron gas channel 14 is L and the width is W, the conditions for separating the 100% spin-polarized electrons in the Y-type branch are as follows:
tanφ _SG > W / L
It is. For example, when L = 2 μm, it is possible to sufficiently reduce W to 1 μm or less. For example, if φ _SG = 22 deg, W = 0.8 μm and the above condition is satisfied.

  The configuration of the spin detection means is not limited to the Y-type branch described above, and any configuration is possible as long as the separated spin state can be measured along the y-axis direction in FIG. May be. The gate insulating layer 12 is not necessarily an insulator, and may be a semiconductor.

  FIG. 4 is a schematic view of the spin filter 20 according to one embodiment of the present invention viewed from the z-axis direction. The spin filter 10 described above has a spatial gradient in the spin-orbit interaction by inserting the gate insulating layers 12 having different thicknesses in the y-axis direction. Are provided with a plurality of gate electrodes 21i having different gate voltages (i = a, b,..., N; three in FIG. 4), so that the spin-orbit interaction has a spatial gradient. It is. Other configurations are the same as those of the spin filter 10. In the following embodiments, only configurations and functions different from those in the first embodiment will be described, and with regard to other configurations and functions, the same portions are denoted by the same reference numerals, and description thereof will be omitted.

  FIG. 5 is a schematic view of the spin filter 30 according to one embodiment of the present invention viewed from the z-axis direction. The spin filter 30 introduces anti-dots or artificial impurities into the two-dimensional electron gas channel 14 of the spin filter 10 or 20, slows the propagation of electron spin, which is a carrier, to a drift velocity, and increases the relaxation length of the spin. It is something to keep.

  Here, the significance of introducing anti-dots or artificial impurities into the semiconductor channel 2 will be described.

  In general, it is predicted that spin information is not retained for a long distance due to spin relaxation in a system with strong spin-orbit interaction. However, according to the calculation of spin relaxation time in a two-dimensional electron gas system with Rashba spin-orbit interaction using a recent Monte Carlo simulation technique, an artificial elastic scatterer such as an anti-dot is introduced. This indicates that the spin relaxation time is increased to 1000 times or more of the electron momentum relaxation time. This result is attributed to the fact that when the spin relaxation mechanism is caused by the D'yakonov-Perel 'mechanism, the spin precession is suppressed by scattering and the relaxation time becomes longer. In InGaAs-based two-dimensional electron gas, the D'yakonov-Perel 'mechanism has been confirmed to play an important role in spin relaxation, and artificial anti-dots and impurity scatterers should be introduced into the channel. Makes it possible to lengthen spin relaxation (see T. Koga, J. Nitta, T. Akazaki, and H. Takayanagi, Phys. Rev. Lett. 89, 46801 (2002)).

In this case, the electron spin propagates in the non-uniform spin-orbit interaction region at the drift velocity v _d by the scatterer. Then, the stay time Δt in the non-uniform spin-orbit interaction region becomes long, and a large deflection angle φ _SG can be obtained. When electron spin propagates at the drift velocity v _d , the force received in the non-uniform spin-orbit interaction region is

However, the effective momentum in the x-axis direction is also <p _x > = m ^* v _d , and the deflection angle is given by the following equation.

Equation (12) is that Fermi velocity v _F of equation (10) is replaced by drift velocity v _d , and the channel stays in a non-uniform spin-orbit interaction region by making it a diffusive system. This shows that it is convenient to obtain a large deflection angle φ _SG by increasing the time Δt. By the way, due to impurity scattering, the electron mobility μ becomes μ = 10,000 cm ² / Vs, and the drift velocity v _d = 100 m / sec when an electric field E = 1 / cm for accelerating electrons in the x direction is applied, Even when Δα (y) = 5 × 10 ⁻¹³ [eVm] and L = 1 μm, a large deflection angle φ _SG = 82.5 deg can be obtained.

  FIG. 6 is a schematic view of the spin filter 40 according to one embodiment of the present invention viewed from the z-axis direction. The spin filter 40 uses magnetic electrodes for the output side terminals T1 and T2 of the spin filter 10, 20, or 30. By rotating the spin of each magnetic electrode in the reverse direction, the carrier is applied to only one terminal. Is to flow. For example, in FIG. 6, a current flows only through the terminal T1, but no current flows through the terminal T2. However, when a magnetic field is applied to each magnetic electrode to reverse the direction of each spin, current flows through the terminal T2 and no current flows through the terminal T1.

  Thus, in the spin filter 40, the current between the terminals can be controlled by controlling the magnetic electrode on the output side.

  FIG. 7 is a schematic view of the spin filter 50 according to one embodiment of the present invention as viewed from the z-axis direction. The spin filter 50 uses a magnetic electrode for the input-side terminal T0 of the spin filter 10, 20, or 30. Either of the output-side terminals T1 and T2 depending on the spin direction of the carriers injected from the terminal T0. The carrier flows through only one terminal. For example, in FIG. 7, a current flows only through the terminal T1, but no current flows through the terminal T2. However, when a magnetic field is applied to the magnetic electrode to reverse the direction of the spin, a current flows through the terminal T2 and no current flows through the terminal T1.

  Thus, in the spin filter 50, the current between the terminals can be controlled by controlling the magnetic material electrode on the input side.

  While the embodiments of the present invention have been described above, various modifications and changes can be made to the embodiments of the present invention without departing from the spirit of the present invention. For example, in the above embodiment, by inserting the gate insulating layers 12 having different thicknesses in the y-axis direction, or by providing the gate electrodes 21i having a plurality of different gate voltages in the y-axis direction, 11, the spin orbit interaction of the two-dimensional electron gas channel 14 below 11 has a spatial gradient in the y-axis direction, but the method of generating the spatial gradient of the spin orbit interaction is not limited to this, It may be a method. For example, the thickness of the two-dimensional electron gas channel 14 in the y-axis direction may be made nonuniform to generate a spatial gradient of the spin orbit interaction.

  Therefore, according to the embodiment of the present invention, since the spin orbit interaction of the semiconductor channel can be controlled by the gate voltage, the SG effect is realized in the semiconductor by using the spatial gradient of the spin orbit interaction. be able to.

  As a result, a spin deflection angle sufficient to separate different spin states of carriers propagating in the semiconductor can be obtained without using any magnetic field or magnetic material.

  In addition, by introducing an elastic scatterer into the semiconductor channel, spin relaxation can be made sufficiently long, so that it can be operated even at room temperature.

It is a figure which shows the relationship between the spin-orbit interaction of a semiconductor channel, and carrier concentration (gate voltage). It is a block diagram which shows the function structure of the spin filter which concerns on one Embodiment of this invention. FIG. 3 is a diagram illustrating a specific example 1 of the spin filter of FIG. 1. FIG. 6 is a diagram illustrating a specific example 2 of the spin filter of FIG. 1. FIG. 6 is a diagram illustrating a specific example 3 of the spin filter of FIG. 1. FIG. 6 is a diagram illustrating a specific example 4 of the spin filter of FIG. 1. FIG. 9 is a diagram illustrating a specific example 5 of the spin filter of FIG. 1. It is explanatory drawing which shows the experiment of Stern-Gerlach notionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10,20,30,40,50 ... Spin filter 2 ... Semiconductor channel 3 ... Gate voltage application part 4 ... Spin-orbit interaction space gradient production | generation part 11, 21i ... Gate electrode 12 ... Gate insulating layer 14 ... Two-dimensional electron Gas channel

Claims (12)

A spin filter for separating carriers for each spin state of carriers propagating in a semiconductor,
A semiconductor channel that confines and propagates the carrier; and
Gate voltage applying means for applying a gate voltage to the semiconductor channel;
The strength of the spin orbit interaction of the semiconductor channel is controlled by the gate voltage so as to be nonuniform with a spatial gradient in a direction perpendicular to the direction of propagation of the carriers. Spin filter.   2. The spin filter according to claim 1, wherein layers having different thicknesses are inserted on the semiconductor channel to give a spatial gradient to the strength of the spin-orbit interaction.   2. The spin filter according to claim 1, wherein the gate voltage applying unit includes a plurality of gate electrodes having different voltages to be applied, thereby giving a spatial gradient to the strength of the spin-orbit interaction.   4. The spin filter according to claim 1, wherein an elastic scatterer is introduced into the semiconductor channel.   The spin filter according to any one of claims 1 to 4, further comprising an electrode for spin detection using a magnetic material on an output side.   The spin filter according to any one of claims 1 to 5, further comprising an electrode for spin injection using a magnetic material on an input side. A spin state separation method for separating carriers for each spin state of carriers propagating in a semiconductor,
Applying a gate voltage to the semiconductor channel confining the carrier and propagating the carrier,
The spin state characterized by controlling the intensity of the spin-orbit interaction of the semiconductor channel by the gate voltage so as to be non-uniform with a spatial gradient in a direction perpendicular to the direction of propagation of the carriers. Separation method.   The spin state separation method according to claim 7, wherein the spin filter including the semiconductor channel inserts layers having different thicknesses on the semiconductor channel to give a spatial gradient to the strength of the spin-orbit interaction. .   8. The spin according to claim 7, wherein the gate voltage applying means for applying the gate voltage includes a plurality of gate electrodes having different applied voltages to give a spatial gradient to the strength of the spin-orbit interaction. State separation method.   10. The spin state separation method according to claim 7, wherein an elastic scatterer is introduced into the semiconductor channel.   The spin state separation method according to any one of claims 7 to 10, wherein an electrode using a magnetic material is provided on an output side to detect the spin state of the carrier. 12. The spin state separation method according to claim 7, wherein an electrode using a magnetic material is provided on an input side, and spin-polarized carriers are injected.

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