JPH01173766A - Superhigh frequency generating element - Google Patents

Abstract

PURPOSE:To make possible the generation of an electromagnetic wave of a remarkably high frequency by a method wherein the recombination of pairs of electrons and holes, which are injected in a superconductor of a diode structure; wherein necessary first and second semiconductor layers, whose conductivity types are different from each other, are provided through interlayer insulating films, which hold a superconductor between them; is utilized. CONSTITUTION:A superconductor of a diode structure is formed of a substrate 1, which is an N-type semiconductor layer and consists of GaAs or the like, a Ge thin film which is a P-type semiconductor film 5, and ohmic electrodes 6 and 7 through interlayer insulating films 2 and 4 holding a Pb thin film, which is a superconductor, between them, having a film thickness capable of tunneling and consisting of an Si oxide or the like. The film 5 is made smaller its energy difference between a Fermi level and a conduction band than that of the substrate 1 and is made larger its energy difference between the Fermi level and the end of a valence band than that of the substrate 1. Electrons and holes are injected in the film 3 from both of the side of the substrate 1 and the film 5 in a low voltage and an electromagnetic wave of a remarkably high frequency is generated by the recombination of electron-hole pairs.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrahigh frequency generating element using a superconductor as a part of the element.

2. Description of the Related Art Conventionally, Gunn diodes, Invat diodes, and the like have been known as high-frequency generating elements. These methods utilize the eating resistance phenomenon and transit time effect of electrons in the semiconductor bulk.

Problems to be Solved by the Invention All of these high-frequency generating elements require electrons to be accelerated in a high electric field, and the time it takes for the electrons to receive that energy affects the upper limit of the high frequency that can be generated. Therefore, there is a criticality, and although frequencies up to about 100 GHz have been obtained, it is difficult to generate frequencies higher than that.

The present invention was made in view of this point, and uses a superconductor as a part of the diode structure, and uses the recombination of electron-hole pairs injected into the superconductor to generate high frequencies. High frequencies of 100 HGHz or higher can be easily generated.

Means for Solving the Problems In order to solve the above problems, the present invention includes a first semiconductor on one side of the superconductor with an interlayer insulating film having a thickness that allows tunneling. , the energy difference from the Fermi level to the conduction band edge is smaller than that of the first semiconductor, and the energy difference from the Fermi level to the valence band edge is smaller than that of the first semiconductor, and the energy difference from the Fermi level to the valence band edge is smaller than that of the first semiconductor, via an interlayer insulating film having a thickness that allows tunneling. It has a structure including a first semiconductor and a second semiconductor having a different conductivity type, with a large energy difference up to the edge.

Operation The present invention has the structure described above, and when one semiconductor is an n-type semiconductor, electrons are tunnel-injected from the n-type semiconductor to the superconductor, and holes are tunnel-injected from the other p-type semiconductor to the superconductor. The injected electrons and holes within the superconductor are controlled by setting the energy band structure such that the voltage required is lower than the voltage required for the tunnel-injected electrons or holes to tunnel into the other semiconductor. By accumulating and recombining there, a high frequency wave with a wavelength corresponding to the energy band gap of the superconductor is generated.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

About 20 silicon oxide (SiO7) films were formed by chemical vapor deposition (CVD) on a gallium arsenide (GaAs) substrate, which is an n-type semiconductor, and then A lead (Pb) thin film of approximately 1 μm is formed by vacuum evaporation. Furthermore, about 20 silicon oxides (
Germanium (Ge), which is a p-type semiconductor, is formed on top of the film by vacuum evaporation.
A film is formed and ohmic electrodes are provided on GaAs and Ge.

Its structure is shown in FIG. In FIG. 1, 1 is an n-type semiconductor GaAs substrate, and 2 is a first Si formed thereon.
, a thin film, 3 a PB thin film, 4 a second S formed thereon.
in, the membrane. 5 is a p-type semiconductor Ge thin film. 6 is an ohmic electrode formed on the other surface of the GaAs substrate;
7 is an ohmic electrode formed on the top surface of the Ge thin film.

pb is a superconductor that becomes superconducting at about 7.2%.

Therefore, if an element with such a structure is cooled below the critical temperature, for example, below 7, a single superconductor will be sandwiched between an n-type semiconductor and a p-type semiconductor separated by a thin glabella insulating film. There is. The energy band diagram at this time is shown in FIG. Energy band gap of GaAs, E
g+ is approximately 1.5e■. E is the energy from the Fermi level to the conduction band edge, E1' is the energy from the Fermi level to the valence band hand edge, and E.

10E, '-Eg. By making the n-type impurity concentration extremely high, the conduction band edge comes close to the Fermi level. Pb has an energy bandgap of about 1.34 m e V in the superconducting state. The energy bandgap of pb is 2Δ
Then, the Fermi level will be in the middle of the energy band gap.

The energy bandgap of Ge, Egg, is approximately 0.8e
It is v. Ez is the energy from the Fermi level to the conduction band edge, Ex' is the energy from the Fermi level to the valence band edge, and E2''EX' = E
It is gz. By increasing the n-type impurity concentration, the valence band edge comes close to the Fermi level. Therefore, an energy band diagram as shown in FIG. 2 is obtained. At this time, the electrons, which are the majority carriers on the GaAs side, are transferred to E, -Δ〉0, because the interlayer insulation film is sufficiently thin.
In the case of , the voltage is extremely low, E, -∆
By applying a voltage of Δ, it easily enters the Pb superconductor due to the tunnel effect. However, tunnel injection is not performed from the Pb superconductor to Ge because there is no energy level to tunnel to GeO at this voltage. On the other hand, at this time, the holes, which are the majority carriers on the Ge side, are
In, since the film is sufficiently thin, the voltage is also extremely low when E2゛ −Δ〉O, and when E2° −Δ〈O, E2′
At a voltage of -Δ, it easily enters the Pb superconductor due to the tunnel effect. However, from Pb superconductor to GaAs,
Again, at this voltage, there is no energy level to be tunneled toward GaAs0, so tunnel injection is not performed. That is, at this time, a large amount of electrons and holes are injected and accumulated in the Pb superconductor.

These electrons and holes recombine with an appropriate relaxation time. The energy difference between electrons and holes at this time approximately corresponds to the energy band gap of the pb superconductor in an equilibrium state. The energy bandgap of a pb superconductor is about 1.3 meV, and the wavelength corresponding to this energy is about 1 Tsuru, and the frequency is about 300 Gllz. Therefore, by applying the larger voltage of El-∆ or E2゛-∆ to an element with this structure, electrons and holes are tunnel-injected into the superconductor, where they recombine and
Generates a high frequency of 0CIIz.

In this state, the bias voltage between GaAs and Ge is increased. When the Ge side is set as positive, electron tunneling from the superconductor to Ge becomes possible only when a bias voltage of E2-Δ is applied, and current begins to flow rapidly.

In this example, since E2-E is smaller than E+'E2', current flows at E and -E, but
If El'' -E2° is smaller, a current begins to flow at E, -E2'. Therefore, the state in which both electrons and holes are accumulated in the superconductor is E2gl>o, and E,' -
E, ° 〉0, in other words, if the energy band structure of one semiconductor has a smaller energy difference from the Fermi level to the conduction band edge than the other semiconductor, and a larger energy difference from the Fermi level to the valence band edge. It is.

In this example, Pb was used as the superconductor, but Ln,
Bag Cu3 oxide (However, Ln is Y, Nd, Sm,
Eus Gd, Tb, Dy% HO% Er.

At least one of Tm, Yb, Lu), etc. 9
0 degree superconductor, La+, as Ael)15
By using a superconductor such as -Cul oxide (where Ae is at least one of Ba, Sr, and Ca) whose critical temperature is around 30, the same voltage as in this example can be achieved at a higher temperature. - It is clear that a high frequency generation effect can be obtained by hole recombination. In this case 1. n, Bat
The energy bandgap of Cu3 oxide as a superconductor is 20-30 meV, and ultra-high frequencies of about 5-77 Hz can be generated.

Even if Ba is replaced with Sr in Ln, BatCu, and oxides, a superconductor with a high pn critical temperature can be obtained. Therefore, it is clear that the same effect can be obtained even if a superconductor in which Ba is replaced with Sr is used.

Furthermore, in this example, n-type GaAs and p-type semiconductors are used.
Ge type was used, but the energy band structure of the second semiconductor has a smaller energy difference from the Fermi level to the conduction band edge than the first semiconductor, and a smaller energy difference from the Fermi level to the valence band edge than the first semiconductor. It is sufficient that the difference is large, and the difference is not limited to these semiconductors.

In this example, a specific value was used as the thickness of the glabellar insulating film, but this thickness may be arbitrary within the range in which the tunnel effect occurs.

In this example, SiO2 was used as the interlayer insulating film, but
It is clear that the invention is not limited to this.

Effects of the Invention As described above, the present invention provides a superconductor on one side of the superconductor with an interlayer insulating film having a thickness that allows tunneling.
A semiconductor having a smaller energy difference from the Fermi level to the conductive band edge than the first semiconductor, and a semiconductor having a smaller energy difference from the Fermi level to the conductive band edge than the first semiconductor and a semiconductor having a smaller energy difference than the first semiconductor through an interlayer insulating film having a thickness that allows tunneling. The present invention provides an element that has a structure including a first semiconductor and a second semiconductor of a different conductivity type, with a large energy difference from the level to the valence band edge, and generates electromagnetic waves of extremely high frequency.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the structure of the present invention, and FIG. 2 is a schematic diagram showing an example of an energy band diagram of the element of the present invention. 1... N-type semiconductor substrate, 2... Interlayer insulating film, 3... Superconductor film, 4... Interlayer insulating film, 5... ...p-type semiconductor film, 6.7...
··electrode.

Claims (1)

[Claims] (1) Having a first semiconductor on one side of the superconductor with an interlayer insulating film thick enough to allow tunneling, and on the other side an interlayer insulating film with a thickness that allows tunneling. wherein the energy difference from the Fermi level to the conduction band edge is smaller than that of the first semiconductor, and the energy difference from the Fermi level to the valence band edge is larger than that of the first semiconductor;
An ultrahigh frequency generating element having a structure including a first semiconductor and a second semiconductor having a different conductivity type.