JPH01276681A - Superconducting transistor - Google Patents

Abstract

PURPOSE:To facilitate switching operation between a superconducting state and a normal conducting state by a method wherein a stress in a superconducting channel part is varied to vary the superconduction transition temperature. CONSTITUTION:If a strain induced by the piezoelectric effect of a piezoelectric element 4 is given to the piezoelectric element 4 by applying a voltage to a gate electrode 5, a stress is induced in a superconductor 1 jointed with the piezoelectric element 4 and a superconduction transition temperature Tc is varied. With this constitution, if, for instance, the specific resistivity characteristics of a channel part are as shown by a curve 21, in a superconducting state which shows a higher transition temperature Tco than the transition temperature Tc under a predetermined ambient temperature T, the superconducting state is switched to the normal conducting state by lowering the transition temperature Tco to the transition temperature Tc1 lower than the temperature Tc as shown by a curve 22 by the change of the stress, so that the state between the first and second electrodes (source and drain) 2 and 3 can be switched from for instance, ON to OFF.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to superconducting transistors, particularly piezoelectric superconducting transistors.

[Summary of the invention]

In the present invention, the transition temperature Tc is changed by changing the superconducting channel portion by 1.6 degrees to perform, for example, a switching operation by switching between superconducting and non-conducting states.

[Conventional technology]

Conventionally, electronic active devices using superconducting materials include two-terminal devices using the Jasefson effect, various field-effect superconducting transistors using the proximity effect of electron pairs, and bipolar transistors based on superconductors. There are proposals for elements, etc. Among these, field-effect transistors that utilize the proximity effect to semiconductors have many advantages in terms of circuit configuration and have high expectations. In this case, the device configuration is such that the superconductor is used as the source and drain, and the part corresponding to the gate is made into a semiconductor. @
It is controlled by three electric wires (gate electrodes). Therefore, in this case, the distance between the source and drain needs to be approximately the length of the wave function of electron pairs seeping out from the superconductor, resulting in an extremely fine structure. One of the criteria is the coherence length. However, there is an inverse correlation between the coherence length and the superconducting transition temperature 1'c of the superconductor, and the higher the temperature of the superconductor, the shorter the coherence length, which poses the problem of requiring ultrafine processing.

On the other hand, in recent years, the development and property research of high-temperature superconductors has progressed rapidly. For example, Japanese Journal Off Applied Physics (Japanese Jo
urnal of Applied Physics
) Vol.

27. No. 1. In January, 198B, a high-temperature superconductor with a layered perovskite structure, Nd1+x Ba2-*
Cu30? -6 characteristics have been reported.

As can be seen from the relationship between the superconducting transition temperature "l'c" and the structure of La-based, Y-thread + Bi-based, and their substitutional materials, the environment surrounding the electron pair path (for example, the Cu-0 two-dimensional surface) Subtle changes in changes (mainly ionic bond distances) affect the transition temperature Tc.

In fact, changes in '1゛c due to the application of hydrostatic pressure have also been reported.

[Problem to be solved by the invention]

The present invention utilizes the properties of the structure-sensitive high-temperature superconductor described above to provide a transistor with a piezoelectric configuration, thereby solving the problems of ultrafine processing described above.

[Means to solve the problem]

As shown in FIG. 1, the present invention relates to a superconductor (1) made of, for example, Ndi+x Ba2-x Cll30%J, which is an oxide-based superconducting material with a layered perovskite structure containing, for example, CuO, and this superconductor. First and second electrode parts (2) and (3) arranged at a required interval in (1)
i.e. source and drain? I electrode and superconductor (11
The first and! ! A piezoelectric gate portion (having a piezoelectric body (4) disposed in a portion corresponding to between the electrode portions (2) and (3) of 82 and a gate electrode (5) adhered to this piezoelectric body (4)
6) is provided, and the gate 'M! The stress in the channel between the first and second electrode portions (3) and (4) of the superconductor fil is changed by applying a voltage to the i-pole (5) to modulate the superconducting transition temperature ゛l''C. The channel section is then switched between superconducting and normal conducting states.

[Function] According to the present invention described above, when a voltage is applied to the gate electrode (5) and strain is applied to the piezoelectric body (4) due to its piezoelectric effect, stress is generated in the superconductor (11) that is bonded to the piezoelectric body (4). , the superconducting transition temperature Tc changes.Therefore, for example, under a set ambient temperature r, the resistivity characteristic of the channel section becomes a transition temperature higher than the temperature ゛l''C, as shown by curve (21) in Fig. 2. When the superconducting state exhibits rco, the transition temperature ' increases as shown by curve (22) in Figure 2 due to changes in stress.
1゛c decreases to 'l''c1, the state is switched to the normal conduction state, and the first and second electrode parts (source and drain)
(21 and (3) can be switched to the off state, for example.

〔Example〕

As shown in FIG. 1, for example, an oxide superconductor with a layered perovskite structure containing CuO, for example, Nd
x Ba2-x Cll30 > δ, or for example Nd
A thin model superconductor (11 is provided) formed of a material in which a part of is replaced with Y, a part of Ba is replaced with St, a part of O is replaced with F or S, etc. , the first and second electrode parts (2) and (3) are arranged on the first main surface (1a) by depositing a metal such as Ag while maintaining the required spacing. Located between the main surface (1a) or the main surface (lb) opposite to this, the first and second electrode parts (2) and (3), and as far as possible between these electrode parts (2) and (3). ZnO over the entire current path between
A piezoelectric material (4) such as the following is deposited by vapor deposition, sputtering, etc.
For example, a gate electrode (5) such as a metal electrode is deposited on the upper surface of the piezoelectric body (4) to form a piezoelectric gate portion (6).

Then, the gate electrode (5) and the first and second electrode parts (
2) and (3), the above-mentioned change in the transition temperature 'r c is obtained under the gate part (6) of the superconductor (11).

In the illustrated example, the first and second electrode parts (3) and (4)
) and the piezoelectric gate part (6) are arranged on the same main surface (la) of the superconductor (1).
) can also be deposited on the main surface (1b) of the first and second electrode parts (2) and (3) opposite to the arrangement main surface (la).

In addition, in the illustrated example, the gate electrode (5) is entirely deposited on the surface of the piezoelectric body (4), but the piezoelectric body (4)
A pair of electrodes is provided on opposite end surfaces of the piezoelectric body (4), and a required voltage is applied between the pair of electrodes to generate strain in the piezoelectric body (4).
It is also possible to cause stress to occur in the superconductor +11. In addition, superconductors (both principal surfaces (la) and (1b) of 11)
Various embodiments are possible, such as a pair of piezoelectric gate parts (6) being provided opposite to each other, and a voltage applied to one to produce contraction stress and the other to produce tension stress. 6) applies uniaxial stress to the superconductor (1) mainly in the film thickness direction and the film surface direction.

〔Effect of the invention〕

As described above, according to the present invention, the first and second electrodes (2) and (3) are controlled by the voltage applied to the gate electrode (3).
) to a predetermined temperature 'T' by modulating the stress in the channel part between
” s, the superconducting transition temperature of the channel part is set to temperature ′I
Since the transition is made between a temperature T co that is higher than S and a concentration T cx lower than S, significant modulation of the conductivity can be performed, and the structure is simple and does not require microfabrication on the order of coherent length. There are great industrial benefits from not doing so.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of a transistor according to the present invention, and FIG. 2 is a diagram showing a temperature characteristic curve of resistivity. (1) is a superconductor, (2) and (3) are first and second electrode parts, (4) is a piezoelectric material, (5) is a gate electrode, (6)
is the piezoelectric gate part.

Claims (1)

[Scope of Claims] A superconductor, first and second electrode parts arranged at a required interval on the superconductor, and the first and second electrode parts of the superconductor. a piezoelectric gate portion having a piezoelectric body disposed in a corresponding portion between the piezoelectric bodies and a gate electrode attached to the piezoelectric body; A superconducting transistor characterized in that the channel portion is switched between superconducting and normal conducting states by changing the stress in the channel between the second electrode portions and modulating the superconducting transition temperature.