JPS62179782A - Superconducting 3-terminal element - Google Patents

Abstract

PURPOSE:To simplify the steps by providing source and drain electrodes of superconducting metal formed separately in a semiconductor substrate and a gate electrode formed to generate a Schottky barrier in a boundary to a semiconductor in the substrate between the electrodes. CONSTITUTION:Source and drain electrodes 2, 3 are operated at sufficiently low temperature to become superconducting, and sufficiently high density impurity is implanted to generate a superconducting pass due to superconducting proximity effect in a semiconductor 1. A material is so selected as to generate a Schottky barrier in a boundary between a gate electrode 5 and the semiconductor 1, and a depletion layer region under the electrode 5 is controlled by varying a voltage applied to the electrode 5. When the depletion region is increased, a channel width is narrowed, while when decreased, a carrier density is increased so that the channel becomes a superconducting state due to superconducting proximity effect. Thus, a voltage applied to the gate electrode is varied to switch the conducting stage between the source and drain electrodes 2 and 3 to s superconducting state or nonsuperconducting state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J This invention relates to the structure of a superconducting three-terminal element.

[Prior art J Figure 2 shows, for example, a magazine (aTournal of App
liedPhys.

5L 2736 (1980)) is a cross-sectional view showing the conventional superconducting three-terminal element shown in
) is a semiconductor substrate, (2) is a source electrode made of a superconducting metal, (3) is a drain electrode made of a superconducting metal% (4)
is an insulator made of an oxide film, and (5) is a gate electrode.

Next, the operation will be explained. The structure shown in FIG. 2 is similar to a conventional MOS (metal-oxide monolithic) transistor. The difference is source (2), drain (3)
The electrode is made of superconducting metal. The device is operated at a sufficiently low temperature so that the source and drain electrodes exhibit superconductivity.

When a voltage is applied to the gate electrode (5), a part called a channel where electrons are accumulated is generated in the semiconductor (1) under the gate. At that time, source and drain electrodes (2),
Since (3) is a superconductor, the channel portion has superconductivity due to the proximity effect. Therefore, when this transistor is in the "ON" state, the source and drain (2)
, (3) becomes zero.

The proximity effect of the superconductor shown here is expressed by the amount of quantum mechanical superconducting wave function seeping into the channel,
It is expressed by the following formula. 1ψ(1)io+eXp (-x1
5) Here, ψ←) is the strength of the superconducting wave IEIJ function, X is the distance from the superconducting metal, and ri is the coherence length. The length of this coherence indicates the distance at which the superconducting wave function oozes out, and is generally a very small amount of less than llIm. In general, if a material with a small effective mass is selected for the semiconductor (1), the length of coherence becomes longer.
Furthermore, as the carrier density in the channel portion increases, the length of the coherence ring also increases. Semiconductors that exhibit the proximity effect of superconductors well include, for example, InP and InP.
etc. can be mentioned. However, these InSb, I
nP Ku It was difficult to form a good oxide film.

[Problem J to be Solved by the Invention Since the conventional superconducting three-terminal element is constructed as described above, an oxide film had to be formed. Furthermore, it was necessary to use a specific semiconductor material that can form a good oxide film.

This invention was made in order to solve the above-mentioned problems, and it does not require an oxide film, so the oxide film formation process is not necessary, and the process is simplified, and it is possible to use a semiconductor in which a good oxide film cannot be formed. The aim is to obtain a superconducting three-terminal device that can be used with any material.

[Means for Solving the Problems] The superconducting three-terminal element of the present invention has 1III on a semiconductor substrate.
A source electrode and a drain electrode made of a superconducting metal formed over a period of time, and a gate electrode formed on the semiconductor substrate between the source and drain electrodes so as to create a Schottky barrier at the boundary with the semiconductor. It is.

[Operation J] Since the gate electrode in this invention forms a Schottky barrier at the contact portion with the semiconductor, the carrier density in the channel portion can be controlled by IJ even without an oxide film.

[Embodiment J Hereinafter, one embodiment of the present invention will be described with reference to the drawings. 1st
In the cross-sectional view of the figure, (1) is a semiconductor substrate, (2) is a source electrode made of a superconducting metal, (3) is a drain electrode made of a superconducting metal, and (5) is a Schottky at the boundary with the semiconductor directly on the semiconductor substrate. This is a gate electrode formed to create a barrier. That is, this superconducting three-terminal element does not use an oxide film and has a so-called MESFET (metal semiconductor field effect transistor) structure in which the gate electric field fi (5) is in direct contact with the channel portion. In this example, nP was used as the semiconductor, rabbit was used as the superconducting metal, and the gate electrode (5) was formed of Au.

The device shown in Figure 1 has source and drain electrodes (2) (3).
) is operated at an upper temperature at a low temperature so that it becomes superconducting.

A high concentration impurity is implanted into the semiconductor (1) for a time period of t so that a superconducting path is generated due to the superconducting proximity effect. Materials are selected so that a Schottky barrier is created at the boundary between the gate i1 pole (5) and the semiconductor (1) (some combinations do not create a Schottky barrier). A depletion layer caused by a Schottky barrier exists under the gate electrode (5), and the depletion layer region can be controlled by changing the voltage applied to the gate electrode (5). As the depletion layer region increases, the channel becomes narrower. When the depletion layer tilt decreases, the carrier density increases, and the channel becomes superconductive due to the superconducting proximity effect. By changing the voltage applied to the gate electrode in this manner, the conduction state between the source and drain electrodes (2) and (3) can be switched between a superconducting state and a non-superconducting state.

Note that the gate electrode (5) may be made of metal or a metalloid such as Bi as long as it can form a Schottky barrier at the boundary with the semiconductor.

[Effect of the Invention 1 As described above, according to the present invention, the source electrode and the drain electrode made of a superconducting metal formed by Mm on a semiconductor substrate, and the boundary with the semiconductor on the semiconductor substrate between the source and drain electrodes are provided. By providing a gate electrode formed to create a Schottky barrier, an oxide film is no longer necessary, which has the effect of simplifying the manufacturing process. Furthermore, semiconductor materials that cannot form a good oxide film can also be used.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a superconducting three-terminal element according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional superconducting three-terminal element. (1) is a semiconductor, (2) is an electrode made of superconducting metal, (3) is a drain electrode made of superconducting metal, (4)
is an insulator, and (5) is a gate electrode. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A source electrode and a drain electrode made of a superconducting metal are formed separately on a semiconductor substrate, and a gate electrode is formed on the semiconductor substrate between the source and drain electrodes so as to create a Schottky barrier at the boundary with the semiconductor. superconducting three-terminal device.