JPH02192777A - Superconductor transistor - Google Patents

Abstract

PURPOSE:To improve operation characteristics by arranging an insulator between a base region and a collector region, making tunnel current flow in an insulating layer, and eliminating a Schottky junction. CONSTITUTION:An insulator 4 is arranged between an emitter region 1 and a collector region 2 composed of superconductor. A collector region 3 composed of degenerated semiconductor of P-type or N-type is arranged, and an insulating layer 5 is interposed between the base region 2 and the collector region 3. The insulating layer is made so thin that tunnel current flows between the regions 2, 3. Since the superconductor 2 and the insulator 4 form a ohmic contact, a Schottky barrier is not generated. As a result, quasi-particle in the base region is injected into the collector region 3 without hindrance, via the insulating layer 5. By eliminating the Schottky junction in this manner, superconducting transistor excellent in operation characteristics can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a base injection type superconducting transistor having a base region and an emitter region made of a superconductor and a collector region made of a semiconductor.

[Conventional technology]

FIG. 3 is a schematic diagram showing the structure of a conventional base injection type superconducting transistor, in which an insulator 4 is sandwiched between an emitter region 1 made of a superconductor and a base region 2 made of a superconductor. The base region 2 and the collector region 3 made of a p-type or n-type semiconductor are directly connected to each other.

[Problem to be solved by the invention]

FIG. 4 is an energy diagram of a conventional superconducting transistor having such a configuration. For example, 30 meV for a Bi-based 80-phase superconductor, and 5 meV for a TR-based superconductor.
Since there is a band gap of Q m eV, depending on the type of superconductor constituting the base region 2,
The excited quasiparticle (electron or hole) 6 in is in a higher energy state than the Fermi level.

However, in conventional superconducting transistors, the base region 2
and the collector region 3 are directly connected to each other, a Schottky junction is formed, and a Schottky barrier (interface level)
B occurs. Since the height of this Schottky barrier generated at both interfaces is about 50 to 100 meV,
If the height is high, the quasiparticle 6 cannot overcome this Schottky barrier and moves from the base region 2 to the collector region 3.
is not injected into the Therefore, conventional superconducting transistors have a problem in that their operating characteristics are seriously impaired.

The present invention was made in view of the above circumstances, and by interposing a thin insulating layer between the base region and the collector region, the conventional Schottky junction is eliminated and a superconducting transistor with excellent operating characteristics is created. The purpose is to provide.

[Means to solve the problem]

A superconducting transistor according to the present invention has a base region made of a superconductor and a collector region made of a semiconductor, and a thin insulating layer or It is characterized by having a semiconductor layer close to an insulator.

[Function] In the superconducting transistor of the present invention, an insulating layer (or a semiconductor layer close to an insulator) thin enough to produce a tunnel effect is provided between the base region and the collector region.

Then the superconductor (base region) and insulator (insulating layer)
Since this is an ohmic connection, a Schottky barrier as in the conventional case does not occur. Therefore, quasiparticles in the base region can be injected into the collector region through the insulating layer without any hindrance.

〔Example〕

Hereinafter, the present invention will be explained based on drawings showing embodiments thereof.

FIG. 1 is a schematic diagram showing the structure of a superconducting transistor according to the present invention, in which numerals 1 and 2 respectively indicate an emitter region and a base region made of a superconductor. An insulator 4 is interposed between the emitter region 1 and the base region 2. 3 in the figure is a collector region made of a p-type or n-type degenerate semiconductor, and in the present invention, an insulating layer 5 is interposed between the base region 2 and the collector region 3.

The thickness of the insulating layer 5 provided in the present invention is the same as that of the base region 2. It is set to such an extent that a tunnel current can flow between the collector regions 3. Specifically, if the coherence length of the superconductor constituting the base region 2 is ξ, then the insulating layer 5
The film thickness is approximately ξ to 2ξ. More specifically, since the coherence length of a Bi-based superconductor is 20 to 30 nm, when a Bi-based superconductor is used as the base region 2, the thickness of the insulating layer 5 is 30 to 50 nm. The degree and skin surface are fine.

FIG. 2 is an energy diagram of the superconducting transistor according to the present invention. In the present invention, since the insulating layer 5 is interposed between the base region 2 and the collector region 3, the base region 2
(superconductor) and insulating layer 5 (insulator), an ohmic contact is formed between the superconductor 5 and insulating layer 5, no Schottky barrier occurs as in the conventional case, and quasiparticles 6 are easily injected into insulating layer 5 from base region 2.

Since the thickness of the insulating layer 5 is set to be thin enough to produce a tunnel effect, the quasiparticles 6 injected into the insulating layer 5 pass through the insulating layer 5 and are injected into the collector region 3.

As the material of the above-mentioned insulating layer 5, an intrinsic semiconductor which is very similar to an insulator can be used. In particular, when using a semiconductor having a superlattice structure as the insulating layer 5 and the collector region 3, it is desirable to improve the matching between the base region 2 and the collector region 3 in the following manner. For example, Ga
When using an As semiconductor, if the thickness of a unit layer consisting of one Ga@ layer and one As layer is made to match the thickness of one crystal of the superconductor constituting the base region 2, the base region 2 and The alignment of both interfaces with the collector region 3 is improved.

In the above-described embodiments, a horizontal superconducting transistor has been described, but the present invention is not limited to this, and it goes without saying that a similar structure can be applied to a vertical superconducting transistor.

[Effects of the Invention] As detailed above, the superconducting transistor of the present invention includes an insulating layer or a semiconductor layer close to the y1 edge that is thin enough to allow tunneling current to flow between the base region and the collector region. Therefore, the conventional Schottky junction can be avoided, and no Schottky barrier occurs. As a result, quasiparticles can be easily injected from the base region into the collector region, allowing rapid transistor operation.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the configuration of a superconducting transistor according to the present invention, Figure 2 is its energy diagram, Figure 3 is a schematic diagram showing the configuration of a conventional superconducting transistor, and Figure 4 is its energy diagram. be. 1... Emitter region 2... Base region 3...
Collector head 4... Insulator 5... Insulating layer patent Applicant Sanyo Electric Co., Ltd. agent Patent attorney
Funeral map of Noboru Kono

Claims (1)

[Claims] 1. In a superconducting transistor having a base region made of a superconductor and a collector region made of a semiconductor, a thin insulating layer or a thin insulating layer through which a tunnel current can flow between the base region and the collector region. A superconducting transistor characterized by having a semiconductor layer that is similar to an insulator.