JP2000090816A - Poralized electron beam generating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarized electron beam generating element capable of providing high quantum efficiency and spin polarization degree by extending lifetime of a polarized electron in a semiconductor and restraining non- polarization. SOLUTION: A polarized electron generated in a semiconductor photoelectric layer 14 due to excitation by a circularly polarized laser beam 27 is immediately moved into a silicon board 12 by an external electric field generated by electrodes 20, 22 constituting a polarized electron injecting means and an injection voltage generating device 24, and then a polarized electron beam is extracted through the silicon board 12. In this method, comparing with the case of extracting the polarized electron beam through an incident surface 18 of the circularly polarized laser beam, lifetime of the polarized electron is extended and the occurrence of non-polarization is restrained, and therefore the polarized electron beam having high quantum efficiency and spin polarization degree is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a polarized electron beam generating element for generating a polarized electron beam in which the spin direction is unevenly distributed.

[0002]

2. Description of the Related Art Spin directions are unevenly distributed in one of two types.
A polarized electron beam consisting of a group of
Interaction between elementary particles in the field of experiments of energetic particles
In order to verify the theory of application, the magnetic domain structure inside the nucleus was
In the field of condensed matter physics, the magnetic domain structure on the material surface
It is used as an effective means for investigating. this
Polarized electron beams have band splitting in the valence band.
Using a polarized electron beam generator having a semiconductor photoelectric layer to
Excitation light such as circularly polarized laser light enters the semiconductor photoelectric layer.
It can be taken out by shooting. This bias
As the polar electron beam generating element, for example, GaAs_1-xP_x
On a semiconductor, the band gap is smaller and
GaAs semiconductors with different lattice constants as semiconductor photoelectric layers
Strained semiconductors obtained by crystal growth are known. This
According to this, GaAs_1-xP_xLattice constant for semiconductor
GaAs semiconductors of different
Since lattice strain is given to the aAs semiconductor, its Ga
Band splitting occurs in the valence band of As semiconductor
And the heavy hole sub-band and the light hole sub-band.
Energy difference between the subband and
The spin directions of electrons extracted by excitation of
Therefore, the higher energy level, that is, the conduction band
Excites only the subband with the smaller energy gap
By injecting the possible light energy into the GaAs semiconductor,
Spin electrons are generated in the spin direction of
An electron beam with a certain degree can be extracted. The above Ga
As_1-xP _xSemiconductors are more bandgap than GaAs semiconductors.
Electron generated in the GaAs semiconductor
It also functions as a potential barrier. Semiconduct
The body photoelectric layer is made of the above-mentioned strained GaAs semiconductor.
In addition, Calco which has band splitting originally
Pyrite semiconductors, superlattice semiconductors, strained superlattice semiconductors
Are used.

[0003]

By the way, in the above-mentioned polarized electron beam generating element, the polarized electron beam is taken out from the incident surface on which the excitation laser beam is incident, that is, the photoelectric surface. Polarized electrons generated in the semiconductor are not always emitted to the outside immediately, but they disappear or recombine with holes while staying in the semiconductor for a long time, and depolarization occurs. For example, the quantum efficiency and the spin polarization were not sufficiently obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to extend the lifetime of polarized electrons in a semiconductor and suppress non-polarization.
It is an object of the present invention to provide a polarized electron beam generating element that can obtain high quantum efficiency and spin polarization.

[0005]

The inventors of the present invention have made various studies on the background described above, and as a result, have immediately moved polarized electrons generated in the semiconductor photoelectric layer into the silicon substrate, and It has been found that a polarized electron beam having high quantum efficiency and spin polarization can be obtained by taking out the polarized electron beam through. In the silicon substrate,
It is presumed that the lifetime of polarized electrons is prolonged and the occurrence of non-polarization is suppressed. The present invention has been made based on such findings.

That is, the gist of the present invention is as follows.
A polarized electron of a type including a semiconductor photoelectric layer having band splitting in a valence band, wherein polarized light whose spin direction is unevenly distributed is generated from the semiconductor photoelectric layer when excitation light is incident on the semiconductor photoelectric layer. A line generating element, (a) a silicon substrate supporting the semiconductor photoelectric layer,
(b) polarized electron injection means for injecting the polarized electrons generated from the semiconductor photoelectric layer through the silicon substrate into the silicon substrate by using the gradient of the potential energy to extract the polarized electrons through the silicon substrate. It is in.

[0007]

In this way, the polarized electrons generated in the semiconductor photoelectric layer are immediately moved into the silicon substrate by the polarized electron injection means, and then the polarized electron beam is extracted through the silicon substrate. Therefore, compared to the case of taking out a polarized electron beam from the incident surface of the excitation laser light,
Since the lifetime of polarized electrons is extended and the occurrence of non-polarization is suppressed, a polarized electron beam having high quantum efficiency and spin polarization can be obtained.

[0008]

In another embodiment of the present invention, preferably, the silicon substrate is provided on a side opposite to the semiconductor photoelectric layer to take out polarized electrons generated from the semiconductor photoelectric layer and injected into the silicon substrate. It is provided with an electron beam emission projection whose cross-sectional area decreases toward the tip. In this way, when the polarized electrons injected into the silicon substrate are extracted to the outside from the electron beam emission projections having a smaller cross-sectional area toward the tip, the position of the polarized electron beam extraction becomes constant, so It is easy to observe the magnetic domain structure,
There is an advantage that it can be extracted outside with a relatively low extraction voltage.

[0009] Preferably, the polarized electron injection means includes a pair of electrodes provided so as to sandwich the semiconductor photoelectric layer, and an injection voltage generator for applying an injection voltage between the pair of electrodes. And In this way, an electric field is formed between the excitation light incident side of the semiconductor photoelectric layer and the silicon substrate side, and polarized electrons generated in the semiconductor photoelectric layer by the external electric field are immediately injected into the silicon substrate. Is done.

Preferably, the polarized electron injection means has a lower doping concentration on the silicon substrate side so that the potential energy of a conduction band in the semiconductor photoelectric layer is smaller on the silicon substrate side. It is an impurity in the semiconductor photoelectric layer. With this configuration, the potential energy of the conduction band in the semiconductor photoelectric layer is reduced toward the silicon substrate by the impurity whose concentration is graded in the semiconductor photoelectric layer. Since the polar electrons easily move to the silicon substrate side, the polarized electrons generated in the semiconductor photoelectric layer by the internal electric field due to the gradient of the potential energy are immediately injected into the silicon substrate.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following examples, the dimensional ratios and the like of each part are not necessarily drawn accurately.

FIG. 1 is a view showing a configuration of a polarized electron beam generating element 10 which is an embodiment of the surface emitting element of the present invention. In the figure, a polarized electron beam generating element 10 is, for example, an MOC.
A semiconductor photoelectric layer 14 formed by crystal growth on a silicon substrate 12 by an epitaxial growth technique such as a metal organic chemical vapor deposition (VD) method or a molecular beam epitaxy (Molecular Beam Epitaxy) method, and a cap. It is composed of a layer 16.

The silicon substrate 12 has a thickness of, for example, 300 μm.
It is a semiconductor made of a single crystal of Si having a thickness of about m. The semiconductor photoelectric layer 14 has a thickness of, for example, about 850.degree.
Is a compound semiconductor composed of a p-GaAs single crystal doped with a gradient concentration. Since the compound semiconductor GaAs has a lattice constant of 5.6533 Å, which is relatively different from the lattice constant of 5.4309 Å of the silicon substrate 12, it is grown on the silicon substrate 12 by so-called two-step growth. That is, after being grown at a low temperature in an amorphous state, the temperature is raised to a normal growth temperature, for example, 800 ° C., and the crystal is grown in a single crystal state.

Since the semiconductor photoelectric layer 14 has a large lattice constant with respect to the silicon substrate 12 as described above, when grown on the silicon substrate 12, the semiconductor photoelectric layer 14 causes lattice distortion. Hetero-bonded in the state of having. Due to this lattice distortion, band splitting is generated in the valence band of the semiconductor photoelectric layer 14, and the energy level difference δs between the heavy hole and the light hole is generated.
On the other hand, since the spin directions of the electrons excited from both sub-bands are opposite to each other, the higher the energy level, the light energy that excites only the heavy-hole sub-band in this case, For example, when a circularly polarized laser beam having a wavelength of 860 nm is incident, a polarized electron group localized in one spin direction is exclusively excited, and the semiconductor photoelectric layer 1 is excited.
4 is generated.

The cap layer 16 is, for example, a compound semiconductor made of p-GaAsP single crystal having a thickness of about 50 °. This cap layer 16 is formed of the semiconductor photoelectric layer 14.
Since it has a larger energy gap, it functions as a barrier that repels polarized electrons generated in the semiconductor photoelectric layer 14, that is, a barrier layer, and protects the semiconductor photoelectric layer 14 chemically by preventing oxidation. And functions. The cap layer 16 has a relatively small thickness so that the excitation laser beam can be efficiently incident on the semiconductor photoelectric layer 14.

Further, on the upper surface of the cap layer 16, a part of the incident surface 18 of the excitation laser beam and a position on the surface of the silicon substrate 12 which are separated from the semiconductor photoelectric layer 14 by a predetermined distance, , A pair of electrodes 20 and 22 made of metal such as silver, platinum, copper, and aluminum are fixed by a technique such as sputtering. The pair of electrodes 20,
An injection voltage output from an injection voltage generator 24 is applied to 22 to form an external electric field for positively injecting polarized electrons generated in the semiconductor photoelectric layer 14 into the silicon substrate 12. It has become so. On the lower side of the silicon substrate 12, there is formed a conical electron beam extraction projection 26 whose sectional area decreases toward the tip. In this embodiment, the pair of electrodes 20 and 22 and the injection voltage generator 24 for applying an injection voltage to them function as polarized electron injection means. The fact that the polarized electrons generated in the semiconductor photoelectric layer 14 are injected into the silicon substrate 12 is based on the fact that the inventors have found that the positive muons (μ ⁺ ) are incident upon the silicon substrate 12 from the silicon substrate 12 side. It has been confirmed based on the fact that the magnitude of the interaction with the polar electron changes depending on the spin direction of the polarized electron.

The polarized electron beam generating element 10 configured as described above is housed in a vacuum vessel (not shown) as shown in, for example, a surface magnetism observation apparatus disclosed in Japanese Patent Application Laid-Open No. 4-361144. At the same time when an extraction voltage is applied to a plurality of electrodes (not shown) arranged to extract a polarized electron beam from the polarized electron beam generating element 10, the laser light source 2
The circularly polarized laser light 27 of, for example, 860 nm output from 8 is made incident on the incident surface of the polarized electron beam generating element 10, and an injection voltage is applied to the pair of electrodes 20 and 22 from an injection voltage generator 24. You. As a result, a group of polarized electrons is generated in the polarized electron beam generating element 10 to which the circularly polarized laser light is incident, and the group of polarized electrons is generated by the pair of electrodes 20 and 2.
2 is immediately injected into the silicon substrate 12 by an external voltage formed by applying the injection voltage to the substrate 2. Then, the polarized electron beam 30 is emitted from the electron beam extraction projection 26 formed below the silicon substrate 12 by the extraction voltage, and is emitted, for example, toward the magnetic domain observation sample 32.

As described above, according to the present embodiment, the polarized electrons generated in the semiconductor photoelectric layer 14 by the excitation by the circularly polarized laser light 27 are converted into the polarized electrons 2 constituting the polarized electron injection means.
0, 22 and the external electric field generated by the injection voltage generator 24, the electron beam is immediately moved into the silicon substrate 12, and then the polarized electron beam is extracted through the silicon substrate 12. As compared with the conventional case in which the polarized electron beam is extracted from the polarized electron beam 18, the polarization electron has a longer lifetime and the occurrence of non-polarization is suppressed, so that the polarization having high quantum efficiency and spin polarization is achieved. An electron beam is obtained. That is, although the polarization lifetime (lifetime) of electrons is set to several tens ps (picoseconds) in the semiconductor photoelectric layer 14, the polarization lifetime is lengthened by being injected into the silicon substrate 12, so that the electrons are not polarized. The occurrence of polarization is suppressed.

Further, according to the present embodiment, the silicon substrate 1
Numeral 2 denotes an electron beam extraction projection 26 having a cross-sectional area decreasing toward the tip for taking out polarized electrons generated from the semiconductor photoelectric layer 14 and injected into the silicon substrate 12 on the side opposite to the semiconductor photoelectric layer 14. Because it is equipped with
When the polarized electrons injected into the silicon substrate 12 are extracted to the outside from the electron beam extraction projection 26 having a smaller cross-sectional area toward the tip, the extraction position of the polarized electron beam becomes constant, so that a fine magnetic domain structure is formed. There is an advantage that observation becomes easy, and that it can be extracted to the outside with a relatively low extraction voltage.

According to the present embodiment, the semiconductor photoelectric layer 1
4. A polarized electron injection means is constituted by a pair of electrodes 20 and 22 provided so as to sandwich the electrode 4 and an injection voltage generator 24 for applying an injection voltage between the pair of electrodes 20 and 22. Accordingly, an electric field is formed between the incident surface 18 side of the semiconductor photoelectric layer 14 and the silicon substrate 12 side, and polarized electrons generated in the semiconductor photoelectric layer 14 by the external electric field are immediately injected into the silicon substrate. So the silicon substrate 12
The step of doping the semiconductor photoelectric layer 14 with an impurity such that the impurity concentration becomes lower toward the side becomes unnecessary.

Next, another embodiment of the present invention will be described. In the following description, portions common to the above-described embodiments will be omitted using the same reference numerals.

FIG. 2 shows a polarized electron beam generator 40 according to another embodiment of the present invention. This polarized electron beam generating element 4
Reference numeral 0 denotes a semiconductor photoelectric layer 44 and a cap layer 46 which are sequentially crystal-grown on a silicon substrate 42 by an epitaxial growth technique, as in the case of the polarized electron beam generating element 10 described above.
Consists of The silicon substrate 42, the semiconductor photoelectric layer 44, and the cap layer 46 are made of the same material, thickness, and shape as those of the above-described embodiment.
In order to positively inject the group of polarized electrons generated in the polarized electron beam 4 into the silicon substrate 42, the polarized electron beam generating element 10 of the above-described embodiment employs a pair of electrodes 20 to which an injection voltage is applied.
And 22 are part of the incident surface 18 and the silicon substrate 12.
However, this embodiment is different from the first embodiment in that an impurity serving as a dopant for forming a p-type semiconductor, such as zinc, is doped in the semiconductor photoelectric layer 44 with a gradient of doping concentration. In this embodiment, the silicon substrate 4 is set so that the potential energy of the conduction band in the semiconductor photoelectric layer 44 becomes smaller toward the silicon substrate 42.
The semiconductor photoelectric layer 4 in which the doping concentration is reduced toward the second side.
The impurities in 4 function as polarized electron injection means.

The doping amount of zinc Zn as a dopant for the semiconductor photoelectric layer 44 is continuously reduced from the cap layer 46 side to the silicon substrate 42 side, and the portion closest to the silicon substrate 42 side, that is, the silicon substrate 42 Is about 5 × 10 ¹⁷ (cm ⁻³ ), for example, but the carrier concentration at the side of the cap layer 46, that is, at the boundary with the cap layer 46 is, for example, 1 × 10 ¹⁹ (cm ^−3). ).

In the semiconductor photoelectric layer 44, zinc Zn
Of the silicon substrate 4 from the cap layer 46 side
Because it is continuously reduced toward 2 sides,
As shown in FIG. 3, the energy difference between the energy level E _V of the Fermi level E _F and the valence band maximum (E _F -
E _V ) decreases from the inside toward the surface,
Accordingly, the energy level E _{C at the} lower end of the conduction band becomes lower toward the silicon substrate 42 side. FIG. 4 is a graph showing the relationship between the energy difference (E _F -E _V ) and the carrier concentration in the semiconductor photoelectric layer 44, that is, the GaAs semiconductor, where the carrier concentration is 1 × 10 ¹⁹ (c
m ⁻³ ), the energy difference (E _F −E _V ) is 34 meV
(Milli-electron volts) and the energy difference (E _F −) when the carrier concentration is 5 × 10 ¹⁷ (cm ⁻³ ).
E _V ) is 84 meV. Accordingly, the energy level E _C of the conduction band decreases by about 50 meV from the cap layer 46 side of the semiconductor photoelectric layer 44 toward the silicon substrate 42 side. In this embodiment, the impurity doping amount of the semiconductor photoelectric layer 44 is changed exponentially so that the energy difference changes linearly.

The polarized electron beam generating element 40 constructed as described above is housed in a vacuum vessel (not shown) as described above, and is used for extracting a polarized electron beam from the polarized electron beam generating element 40. At the same time as the extraction voltage is applied to a plurality of electrodes (not shown) arranged at the same time, the circularly polarized laser light 27 of, for example, 860 nm output from the laser light source 28 is incident on the incident surface of the polarized electron beam generator 40. As a result, a group of polarized electrons is generated in the semiconductor photoelectric layer 44 of the polarized electron beam generating element 40 on which the circularly polarized laser light is incident, and the group of polarized electrons is inclined by the energy level E _C of the conduction band. Immediately due to the internal electric field generated by the
It is positively moved to the side and implanted into the silicon substrate 42. Then, the polarized electron beam 30 is emitted from the electron beam extraction projection 26 formed below the silicon substrate 42 by the extraction voltage, and is emitted, for example, toward the magnetic domain observation sample 32. This reduces the possibility that the polarized electrons staying in the semiconductor photoelectric layer 44 disappear due to recombination with holes and the like, and the polarized electrons are efficiently extracted. In particular, in this embodiment, since the cap layer 46 that functions as a potential barrier for repelling electrons is provided on the semiconductor photoelectric layer 44, the efficiency of taking out polarized electron beams is further improved.

As described above, according to the polarized electron beam generator 40 of this embodiment, the polarized electrons generated in the semiconductor photoelectric layer 44 by the excitation of the circularly polarized laser light 27 are transferred to the semiconductor photoelectric layer 44. After being immediately moved into the silicon substrate 42 by the internal electric field formed by the gradient of the doped impurity concentration, the polarized electron beam is extracted through the silicon substrate 42, so that the circularly polarized laser light is incident from the incident surface 18. Compared to the conventional case of taking out polarized electron beam,
Since the lifetime of polarized electrons is extended and the occurrence of non-polarization is suppressed, a polarized electron beam having high quantum efficiency and spin polarization can be obtained.

Also in this embodiment, the silicon substrate 42 is provided on the opposite side of the semiconductor photoelectric layer 44 to take out the polarized electrons generated from the semiconductor photoelectric layer 44 and injected into the silicon substrate 42. The polarized electron injected into the silicon substrate 42 has a smaller cross-sectional area as it goes to the front end, so that the polarized electron injected into the silicon substrate 42 becomes smaller. When the polarized electron beam is taken out, the position where the polarized electron beam is taken out becomes constant, so that it is easy to observe a fine magnetic domain structure, and there is an advantage that the electron beam can be taken out with a relatively low drawing voltage.

According to the present embodiment, the semiconductor photoelectric layer 4
The potential energy of the conduction band in the silicon substrate 4
Since zinc Zn, which is an impurity in the semiconductor photoelectric layer 44 whose doping concentration is reduced toward the silicon substrate 42 so as to decrease toward the silicon substrate 42 side, functions as polarized electron injection means, a pair of electrodes is provided. As compared with the case where the injection voltage generator 24 is used to apply the injection voltage to the devices 20 and 22, there is an advantage that the device can be downsized.

While one embodiment of the present invention has been described in detail with reference to the drawings, the present invention may be embodied in still another embodiment.

For example, in the above-described semiconductor photoelectric layer 44 of the polarized electron beam generating element 40, zinc doping in which the doping concentration is continuously reduced toward the silicon substrate 42 is performed. In other words, the doping concentration may be reduced in a stepwise manner.

The polarized electron beam generating element 1 shown in FIG.
2 so that the potential energy of the conduction band in the semiconductor photoelectric layer 14, similar to the semiconductor photoelectric layer 44 of the polarized electron beam generating element 40 in FIG. Zinc doping may be performed with a lower doping concentration on the silicon substrate 12 side. This has the advantage that the polarized electrons generated in the semiconductor photoelectric layer 14 can be easily injected into the silicon substrate 12.

The polarized electron beam generating element 1 shown in FIG.
At 0, phosphorus (P) doping is performed in the silicon substrate 12 so that the doping concentration is reduced toward the electron beam extraction protrusion 26 so that the potential energy of the conduction band decreases toward the electron beam extraction protrusion 26. Is also good. By doing so, the extraction efficiency of the electron beam can be further enhanced.

In the above-mentioned polarized electron beam generating elements 10 and 40, the excitation laser beam 27 transmitted through the semiconductor photoelectric layers 14 and 44 is interposed between the semiconductor photoelectric layers 14 and 44 and the silicon substrates 12 and 42. A reflective layer that reflects light may be provided. The reflection layer is formed by laminating two kinds of semiconductor thin films having different refractive indexes with an optical thickness of, for example, １ ／ wavelength, so that a so-called Bragg reflector that reflects the excitation laser beam 27 by light wave interference is provided. It is preferably used, but is doped with impurities so that the polarized electrons generated in the semiconductor photoelectric layers 14 and 44 do not hinder the injection into the silicon substrates 12 and 42.

In the above-mentioned polarized electron beam generating elements 10 and 40, cap layers 16 and 46 having a chemical protection of the semiconductor photoelectric layers 14 and 44 and a barrier function for preventing the polarized electrons from moving upward. May not necessarily be provided.

In the above-mentioned polarized electron beam generator 10, a transparent electrode provided on the entire surface of the incident surface 18 is used instead of the electrode 20 provided on a part of the incident surface 18 of the cap layer 16. You may be. By doing so, the electric field formed in the semiconductor photoelectric layer 14 becomes uniform, and the injection of polarized electrons into the silicon substrate 12 is suitably performed.

In the embodiment of FIG. 1, a voltage obtained by dividing the extraction voltage may be applied to the electrode 22 of the polarized electron beam generator 10 as an injection voltage. This has the advantage that the injection voltage generator 24 becomes unnecessary.

In the embodiment shown in FIG. 1, a voltage obtained by dividing the extraction voltage by a predetermined voltage divider may be applied to the electrode 22 of the polarized electron beam generator 10 as an injection voltage. This has the advantage that the injection voltage generator 24 becomes unnecessary.

In the above-mentioned polarized electron beam generating elements 10 and 40, the electron beam extraction projections 26 formed on the silicon substrates 12 and 42 have a conical shape with a relatively large taper angle, but have a pyramid shape. Alternatively, various shapes may be used, such as a needle-like or fine-line-shaped point provided at the top.

Further, in the above-mentioned polarized electron beam generating elements 10 and 40, the semiconductor photoelectric layers 14 and 44 are p-type.
Although it was a compound semiconductor made of GaAs single crystal, it may be a chalcopyrite type semiconductor having band splitting inherently, or a strained superlattice semiconductor formed by stacking a plurality of pairs of two types of semiconductor thin films having different lattice constants. No problem.

Although not specifically exemplified, the present invention
Various changes can be made without departing from the spirit of the invention.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a polarized electron beam generating element according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a polarized electron beam generating element according to another embodiment of the present invention, and is a diagram corresponding to FIG.

FIG. 3 is a diagram illustrating an electric field gradient resulting from continuously changing an impurity concentration in a semiconductor photoelectric layer of the polarized electron beam generator of FIG. 2;

FIG. 4 is a view for explaining a doping concentration for forming the electric field gradient shown in FIG. 3 in a semiconductor photoelectric layer of the polarized electron beam generating element of FIG.

[Explanation of symbols]

10, 40: polarized electron beam generating element 12, 42: silicon substrate 14, 44: semiconductor photoelectric layer 20, 22: electrode, 24: injection voltage generator (polarized electron injection means)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C030 BB17 BC06 5C035 CC05 CC10

Claims (4)

[Claims] 1. A semiconductor photoelectric layer having band splitting in a valence band is provided, and when excitation light is incident on the semiconductor photoelectric layer, polarized electrons whose spin directions are unevenly distributed are generated from the semiconductor photoelectric layer. A polarized electron beam generating element of the type, comprising: a silicon substrate supporting the semiconductor photoelectric layer; and a potential energy gradient for extracting polarized electrons generated from the semiconductor photoelectric layer through the silicon substrate. Polarized electron injecting means for injecting into the silicon substrate by utilizing the above method. 2. The silicon substrate has a smaller cross-sectional area toward the tip for taking out polarized electrons generated from the semiconductor photoelectric layer and injected into the silicon substrate on a side opposite to the semiconductor photoelectric layer. 2. The polarized electron beam generating element according to claim 1, further comprising an electron beam emitting projection. 3. The polarized electron injection means includes a pair of electrodes provided so as to sandwich the semiconductor photoelectric layer, and an injection voltage generator for applying an injection voltage between the pair of electrodes. The polarized electron beam generator according to claim 1 or 2. 4. The semiconductor photovoltaic layer, wherein the doping concentration is reduced toward the silicon substrate such that potential energy of a conduction band in the semiconductor photovoltaic layer decreases toward the silicon substrate. 3. The polarized electron beam generating element according to claim 1, wherein the element is an impurity.