JPH07109881B2 - Quantum wire waveguide - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a waveguide structure of an electron wave or a wave equivalent thereto, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Electronic devices used in integrated circuits and communication circuits have been improved in performance by miniaturization. These electronic devices operate according to the operating principle of transistors proposed by Shockley, Bardeen, etc., but their performance such as power consumption, reliability, storage capacity, and response speed can be easily reduced by miniaturization. Has been achieved.

In recent years, however, this tendency has begun to show signs. This is because the limits of the microfabrication technology itself are beginning to be seen, and the limits of application of the operating principles of conventional electronic devices are emerging with the miniaturization. It is considered that such a tendency becomes stronger as the minimum dimension of the constituent elements of the device becomes 0.1 micron or less.

However, from a theoretical point of view, 0.1 Miku
In the region below Ron, electrons are not as classical mechanical particles.
Behaves as a quantum mechanical wave, positively
By using it, it operates differently from conventional electronic devices.
In principle, it has functions that could not be realized with conventional electronic devices
It is discussed that the device can be formed. In fact
Use a two-dimensional electron gas as a carrier using a toned structure
Electrons such as High Electron Mobility Transistors (HEMT)
The device has already been commercialized. But these electricity
Expected to have higher performance and more functions than the child element
Have two or three directions of trapping carriers
Quantum wires and boxes are still in the research stage. These quantum details
0.1 micron to ideally make lines and quantum boxes
With high controllability of one atomic layer order in the following areas
Complex structures must be formed. Currently, semiconductor substrate
In the direction perpendicular to the board, it is high enough to meet this requirement.
The crystal growth technology for producing structures every time is being established
But to make some structure in a different direction
Is difficult with conventional lithography and etching techniques.
Considered to be the foot. It makes quantum wires for example
Fine line width fluctuation (roughness) and complicated structure
Damage to the crystal that occurs in the process of manufacturing
Is a serious obstacle to the manifestation of
Cal Review Letters64, (1990) Eleventh
Pages 54 to 1157, (Phys. Rev. Lett.6
Four, 1154-1157 (1990))).

Even if the carriers are confined quantum mechanically, when the width of the quantum well becomes about 10 nm, the potential shape becomes sensitive to the fluctuation of the crystal interface, and the periodic boundary condition is broken. There is also a difficulty inherent to the quantum confinement effect that the wave function of tends to form a standing wave.

For these reasons, it has not been possible to realize an electronic device that makes full use of the quantum effect.

[0007]

As described above, an electronic element whose operating principle is a quantum mechanical wave function can be expected to have many performances and functions, but the roughness of the crystal interface, etc. Due to its small size, there are many difficult problems in manufacturing technology.

Further, in general, according to the prior art, a complicated process is required to manufacture an electronic device having a structure such as a quantum wire.

Further, even if a quantum wire having a well width with a potential of about 10 nm can be produced, the shape of the potential in such a narrow region is sensitive to the fluctuation of the crystal interface, and therefore the carrier wave function. However, it is difficult to form a standing wave as a confinement effect.

Further, assuming that a transistor can be formed by a quantum wire or the like, how to control the behavior of the carrier is determined by a conventional field effect control type method in order to reduce power consumption and improve operating speed. There is a shortage.

Therefore, one of the objects of the present invention is to easily realize the quantum effect (particularly, one-dimensional electron gas state) even though the device has a relatively large size structure. To provide various devices.

Another object of the present invention is to provide an electronic device which can be manufactured in a short time with a simple manufacturing method and a small number of steps as compared with the conventional method.

Another object of the present invention is not to set boundary conditions such as simply reducing the potential well width in the carrier wave function, but to set periodic boundary conditions that satisfy, for example, Bohr's quantum condition. Is to provide a delicate quantum wire that produces the same state in which the wave function is effectively confined.

Another object of the present invention is to provide an element capable of controlling carrier propagation as described above with good controllability, low power consumption, and high-speed response operation.

[0015]

According to the present invention, fluctuations in the crystal interface even with a size relatively larger than that of a quantum wire forming a one-dimensional electron (carrier) gas state due to the confinement effect in two directions. Even if is slightly larger, the wave function becomes a standing wave because one direction satisfies the periodic boundary condition, and a quantum wire capable of forming a one-dimensional electron gas state is provided.

Further, according to the present invention, there is provided a control method for rapidly controlling, with low power consumption, the electrons conducted by the magnetic field induced in the quantum wire formed as described above, and a method for forming the electrode thereof. Provided.

Further, according to the present invention, since the above-mentioned quantum wires are formed at the stage of crystal growth, the number of steps is smaller than in the prior art, and the production can be precisely controlled on the order of one atomic layer. A method is provided.

[0018]

According to the present invention, the formation of the one-dimensional electron (carrier) gas is different in the two directions perpendicular to the electron (carrier) propagation direction. One is a method of forming a standing wave of an electron (carrier) wave function by a confinement effect by a quantum well that has been conventionally performed, while the other is a method of forming an electron (carrier) wave function by a side surface of a waveguide. It is a method of forming a standing wave by orbiting so as to satisfy the periodic boundary condition in the direction and causing it to interfere with itself.

This will be described in more detail with reference to FIG. FIG. 1 is a perspective view of a cylindrical quantum wire according to the present invention. The central axis side of the quantum wire is made of a material having a higher electron affinity than the outer semiconductor material. Also,
The semiconductor material on the outside is doped with impurities and also plays a role of a carrier supply layer. In FIG. 1, only the portion of the electron wave waveguide formed by the above configuration is extracted and drawn. The wave function 2 in the radial direction (kr) of the electrons is confined by the side surface of the electron wave waveguide 1 to form a standing wave. In addition, the lateral direction of the waveguide (kφ)
Since the wave function 3 of is like the side surface of the ring, the periodic boundary condition is satisfied, and the standing wave is formed again. This is essentially the same as the Bohr's quantum condition in which the wave function of an electron in an atom in a vacuum forms a standing wave.
Therefore, the wave vector component of the electron becomes zero in the above two directions, and the electron wave propagates only in the axial direction of the cylinder, resulting in a one-dimensional electron gas state. Even if the waveguide itself becomes slightly larger than usual, such an electron gas state can satisfy Bohr's quantum condition if it is guaranteed that the spread of the electron's wave function covers the lateral direction of the waveguide. As long as it satisfies, it can be realized. When the confinement effect by the quantum well is used, the well-shaped potential is a function inversely proportional to the square of the well width.
When it becomes as small as 0 nm, it becomes extremely sensitive to fluctuations in the crystal interface, but if the Bohr quantum condition as in the present invention is used as the periodic boundary condition, it is possible to make it less susceptible to the crystal interface in at least one direction. I can.

Further, a method of controlling the one-dimensional electron gas according to the present invention will be described. Electrodes are provided on the side surfaces of the electron wave waveguide according to the present invention. When a current is passed through this, a magnetic field is induced around the electrode, and the guided electron receives a Lorentz force, and the spiral motion starts from that position, and the electron does not propagate. What is important here is that the electric current is not stored in the electrodes merely by passing a current. Therefore, it is possible to realize an electronic device which requires less time for accumulating electric charges as compared with the field effect type control electrode and has low power consumption.

[0021]

(Embodiment 1) FIG. 3 shows an electron wave waveguide according to an embodiment of the present invention. The structure of this element is manufactured as follows. (11 of the InAs substrate 12 on which the n + layer 10 is implanted to guide electrons to the electrodes.
1) Agglomerates (size, about 10 nm) of Au or the like are vapor-deposited on the surface by using STM (scanning tunneling microscope). Next, a reduced pressure MOC is formed on this substrate.
The needle crystal 11 is grown by using the VD method (organic metal vapor phase growth method). The growth conditions at this time are a substrate temperature of 450 ° C., a V / III ratio of trimethyl indium and arsine of about 120, and a growth time of 50 seconds.
grow up. Here, the gas to be filled is switched from trimethyl indium to trimethyl gallium, and n
Disilane gas is also enclosed as a shape dopant. The growth conditions at this time are a substrate temperature of 450 ° C., a V / III ratio of about 120, and a growth time of several seconds.
grow up. Then, as shown in FIG. 3, the structure of the crystal grown at this time is undoped In having a diameter of 50 nm and a length of 2 μm.
20 nm thick n-type GaA on the surface of the needle crystal 11 of As
It has a structure in which s5 is attached. This needle crystal is subjected to a sulfur treatment to keep the surface state stable, and then spin-on-glass (SOG) 9 is applied to embed the needle crystal. Electrodes 8 made of Au / Ge / Ni are provided above and below this element. In this way, the electron waveguide shown in FIG. 3 is constructed.

At the interface between InAs and GaAs,
The electron gas 7 is accumulated because it locally has a modulation-doped structure. This situation will be described with reference to FIG. FIG. 2A shows a core portion 4 made of a material having a high electron affinity.
2B shows a structure in which the carrier supply layer 5 made of a material having a small electron affinity is wrapped around, and FIG. 2B shows a band diagram thereof. As shown in FIG. 2 (b), there is a potential well formed in a modulation-doped structure in the radial direction, and the electrons are confined in the potential well. As shown in FIG. 1, the wave function of the electron is A standing wave 2 is created in this direction. On the other hand, also in the circumferential direction, since the potential wells are connected in an annular shape, the periodic boundary condition is satisfied, and therefore the wave function in this direction also has a standing wave 3
Is formed. This is none other than Bohr's quantum condition satisfied by the electrons in the atom. Due to this condition, a standing wave of the wave function is formed even if the diameter of the cylinder is somewhat large. Since there is no confinement or periodicity only in the axial direction of the cylinder, it becomes a traveling wave. Therefore, the electron gas present here is a one-dimensional electron gas. However, the electron gas here is different from the conventional one-dimensional electron gas in that the periodicity of the potential is used instead of the confinement effect that is usually performed in the circumferential direction.

As shown in the following examples, in the present invention, it is also possible to control electric conduction by using such peculiarities of electronic states.

(Example 2) Needle crystals can be grown laterally with respect to a substrate by using the following method. A hole as shown in FIG. 4A is formed by using a dry etching technique, and Au or the like 13, which is a seed for acicular crystal growth, is vapor-deposited on this side wall using STM to grow acicular crystals. The growth conditions are the same as in the method shown in Example 1.
A cross-sectional view of the electron wave waveguide thus configured is shown in FIG.
It shows in (b). The n + layer 10 for inputting / outputting electrons can be formed by normal implantation.

(Embodiment 3) As shown in FIG. 5A, a control electrode 14 is provided on the side surface of an electron wave waveguide along the direction in which electrons are guided. When an electric current is passed therethrough as indicated by the arrow in the figure, a magnetic field B is generated as indicated by the arrow in FIG. Then, as shown in the figure, the magnetic flux density is different between the part near the electrode of the waveguide and the part far from the electrode, because the direction and the area of the magnetic field lines that link the electron with the magnetic flux are different. The wave functions of the electrons in the directions are out of phase with each other depending on the position, and they can interfere with each other while being guided and can be reflected. What is important here for application is that, unlike the electric field control type control method, it is not necessary to store charges in the control electrode. A magnetic field is generated as long as an electric current is applied to the electric field, so that the response time is short, the power consumption is low, and the energy loss can be suppressed only to Joule heat.

When a circuit is constructed with an electron wave waveguide, wiring may surround the waveguide as shown in FIG. 8. At this time, the magnetic field is generated in the same direction as the electron wave propagation direction. Therefore, it does not disturb the phase of the electron wave.

The control method using the control electrode can be realized by applying a magnetic field in a direction different from the electron wave propagation direction.

(Embodiment 4) Similar to the embodiment 3, FIG.
The waveguide can be configured as follows. This waveguide is a current control type branch waveguide which can branch the propagation direction of the electron wave by passing a current through the control electrode.

FIG. 7 shows a directional coupler using the above waveguide.
It shows in (a). A directional coupler can also be manufactured by constructing an electron wave waveguide as shown in FIG. 7A using a needle crystal.

However, the cross-sectional view of the coupling portion of the waveguide is shown in FIG.
As shown in (b), the method of coupling electron waves is complicated.

In the cylindrical electron wave waveguide according to the embodiment of the present invention, even in the case of electrons having the same wavelength, the portion where the electrons are present is bent in an annular shape. , The area occupied by the electron wave waveguide can be reduced by π times with respect to the substrate.

Further, the electron wave waveguide of the present invention is, for example, an elliptic cylinder, as long as at least one component of the electron wave function is a standing wave due to a periodic boundary condition such as Bohr's quantum condition. It can be realized in either a shape or a polygonal prism.

Further, although the electron wave waveguide of the present invention relates to the transport of electron waves, it goes without saying that it can be realized by using an exciton state (for example, a polariton state) caused by the eigenstate of a solid. Absent.

Furthermore, the electron wave waveguide of the present invention is n-Al.
GaAs and u-GaAs, p-AlGaAs and u-Ga
Of course, it is also possible to use other semiconductor materials or dopants such as As, n-Si, and u-Ge.

[0035]

As described above, according to the present invention, if the standing wave of the wave function of an electron is formed by a waveguide that satisfies the periodic boundary condition (Bohr's quantum condition), the quantum confinement effect causes Is easy to realize even with a large size, and is not easily affected by fluctuations in the crystal interface.

Further, according to the present invention, the electron transport control can be performed at high speed and with low power consumption by configuring the electrodes that generate a magnetic field by passing a current.

[Brief description of drawings]

FIG. 1 is a perspective view showing one state in which an electron wave waveguide of the present invention is constituted by a cylindrical waveguide.

2A and 2B are a perspective view and a band diagram showing a state when the electron wave waveguide of the present invention is realized with a semiconductor material.

FIG. 3 is a cross-sectional view when the electron wave waveguide of the present invention is formed using a needle crystal.

FIG. 4 is a cross-sectional view when the electron wave waveguide of the present invention is formed parallel to a substrate.

5A and 5B are a perspective view and a cross-sectional view showing a state of an electrode for controlling a state of an electron wave in the electron wave waveguide of the present invention.

FIG. 6 is a perspective view showing a state in which a branching waveguide is formed using the electron wave waveguide of the present invention.

7A and 7B are a perspective view and a cross-sectional view of a directional coupler configured using the electron wave waveguide of the present invention.

FIG. 8 is a cross-sectional view for explaining a state when a wiring crosses the electron wave waveguide of the present invention.

[Explanation of symbols]

1 ... Electron Waveguide, 2 ... Electron Wave Function in Kr Direction, 3
... Wave function of electrons in kφ direction, 4 ... u-InAs, 5 ...
n-GaAs, 6 ... Fermi surface, 7 ... Energy level of electron gas, 8 ... Ohmic electrode (Au / Ge / Ni),
9 ... Spin-on-glass (SOG), 10 ... n + layer,
11 ... u-InAs needle crystal, 12 ... u-InAs substrate, 13 ... Au seed, 14 ... Control electrode, 15 ... One-dimensional electron gas, 16 ... Branch waveguide.

Claims (14)

[Claims] 1. A quantum wire characterized in that a wave function of an electron in at least one direction different from a propagation direction of an electron forms a standing wave by satisfying a periodic boundary condition and is in a one-dimensional electron gas state. Waveguide. 2. The quantum wire waveguide according to claim 1, wherein the periodic boundary condition to be satisfied by the wave function is Bohr's quantum condition. 3. A core portion of the quantum wire waveguide is made of a first semiconductor material having a high electron affinity, and a surrounding portion is made of a second semiconductor material doped with donor or acceptor ions and having a low electron affinity. The quantum wire waveguide according to claim 1, which is configured. 4. The quantum wire waveguide according to claim 2, wherein the first semiconductor material is made of u-InAs, and the second semiconductor material is made of n-GaAs. 5. The quantum wire waveguide according to claim 2, wherein the first semiconductor material is made of u-GaAs and the second semiconductor material is made of n-AlGaAs. 6. The quantum wire waveguide according to claim 2, wherein the first semiconductor material is made of needle crystals. 7. The quantum wire waveguide according to claim 1, wherein the waveguide has a cylindrical shape. 8. The quantum wire waveguide according to claim 1, wherein the shape of the waveguide is an elliptic cylinder. 9. The quantum wire waveguide according to claim 1, wherein the shape of the waveguide is a polygonal prism. 10. The quantum wire waveguide according to claim 1, wherein the quantum wire waveguide according to claim 1 is provided with an electric field control type control electrode to control the propagation of electrons. 11. The quantum wire waveguide according to claim 1 is provided with a current control type control electrode for changing a phase component of a wave function of an electron by generating a magnetic field around the quantum wire waveguide to control the propagation of the electron. The quantum wire waveguide according to claim 1. 12. The quantum wire waveguide according to claim 1, wherein propagation of electrons is controlled by forming a branch waveguide. 13. The quantum wire waveguide according to claim 1, wherein the propagation of electrons is controlled by forming a directional coupler. 14. When the wiring crosses the quantum wire waveguide according to claim 1, the wiring does not disturb the phase component of the wave function of the electron by crossing in the direction perpendicular to the electron propagation direction. 1. The quantum wire waveguide described in 1.