JPS6332974A - Superconducting semiconductor junction element and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a superconducting semiconductor junction element in which transportation efficiency of quasi-particles is large and implanted electrons are capable of running with high speed, by selecting lattice-matchable materials for electrode thin films composing emitter, base, and collector, a substrate, and a tunnel barrier, and then by forming these thin films in epitaxial process so that electrical characteristics of the thin films themselves can be improved. CONSTITUTION:A superconducting element having a signal-amplified action and a switching operation is composed of a metallic thin film (superconductor or normal conductor) 2, a tunnel barrier 3, a superconducting thin film 4, and compound semiconductor thin film 5, all of which are piled in order on an insulating substrate 1. The first metallic thin film serves as an emitter layer into which quasi-particles are implanted. The second superconductor serves as a base layer. The compound semiconductor serves as a collector layer. Mixed crystal comprising lnAsx Sb1-x or SbGax ln1-x is used for the collector layer. Nitride of Nb, Zr, V, Hf, or single or composite compound composed of Nb, Mo, W carbide, is used for the superconductor. BaF2, MnO, Mn2O3, MnO2, TaO, GeO2, and Pb3O4 are used for the insulating substrate or the tunnel barrier. The whole thin film is thus made to grow in epitaxial process, so that a superconducting semiconductor junction element having high speed and large transportation efficiency can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a superconducting element that performs signal amplification and switching operations, and a method for manufacturing the same.

(Prior Art and Problems to be Solved by the Invention) Since tunnel-type Josephson junctions perform high-speed switching operations, their applicability to integrated circuits has been studied. However, since they do not inherently have an amplification function, they have problems such as a more complex circuit and a smaller operating margin than in the case of semiconductor devices.

In order to improve these problems, a three-terminal device with overlapping Josephson junctions was proposed (S, M, Faris, TJ
.

S-Patent 4+ 334* 158: f
fled 6/6/80). In this device, an intermediate superconductor layer is shared by both junctions, and quasiparticles are injected into the intermediate layer from one junction, thereby controlling the current in the other junction. However, there are drawbacks such as the power amplification factor is small and input/output separation is difficult.

Therefore, a superconducting transistor was proposed that had high-speed operation, low power consumption, and amplification by replacing some of the semiconductors in the structure of a semiconductor bipolar transistor with a superconductor (Japanese Patent Application Laid-Open No. 60-117゜691). : IEEE
Trans, Magn, MAG-21 (198
5)721).

However, even if this element is manufactured, an element with a high amplification factor has not been obtained. The cause of this is low quality, such as disturbances at the interface between the superconductor and semiconductor and poor crystallinity of the film.

For example, the emitter layer is made of GaAS and the base layer is made of N.
bN (superconductor), an element using 1nsb as the collector layer has been proposed, but this element uses the emitter layer as a substrate, NbN on it, and K on top of 1NbN.
It is manufactured by a process of forming 1nSb.

However, good device characteristics have not been obtained with such device structures or combinations of constituent materials. The cause of this is the inconsistency of the lattice.

In other words, the degree of lattice mismatch between bait ho and 1nsb Δa @ /
a6 (where ao is the lattice constant and Δa6 is the difference in the lattice constants) is 4. Although relatively small at lX10, GaA
s and NbN are very large, 0.1, and QaAs
The epitaxial growth of NbN on top becomes insufficient, and as a result, 11'ISb does not become a single crystal film. Furthermore, when a thin film of a superconductor is formed, the initial layer deposited within the film has an irregular arrangement, resulting in a base layer that does not have good superconducting properties.

As described above, with the conventional techniques, it has not been possible to secure the single crystallinity that is essential for operation as a semiconductor and to form a good superconducting thin film.

(Means for resolving gap points) The present invention was proposed to solve the above-mentioned drawbacks, and it solves low quality such as poor crystallinity of thin film properties caused by lattice mismatch. An object of the present invention is to provide a superconducting e-semiconductor junction device that has a large signal amplification factor, high speed, and low power consumption, and a method for manufacturing the same.

In order to achieve the above object, the present invention comprises a base layer made of a superconductor, an emitter layer made of gold IR (superconductor or normal conductor) or a semiconductor in contact with the base layer, and the other side of the base layer. In a superconducting three-terminal device with a compound semiconductor as a collector layer on the side, 1nAsxS is used as the collector layer.
bs-x or SbGaxIn1- is used, and the collector layer, emitter layer, base layer superconductor, tunnel barrier, and insulating substrate of this semiconductor are each made of a lattice-matched material, and the above superconductor Body is Nb
N NbN-TiN NbN-VN NbN-ZrN Nb
N-HfNNbN-NbCNbN-MoCNbN-Lock N
A superconducting material consisting of one of bC-MoCNbC-TaC TaC-MoCTaC-Wc.
The gist of the invention is a method for manufacturing a semiconductor junction device.

Furthermore, the present invention includes a base layer made of a superconductor and gold in contact with the base layer! In a superconducting three-terminal device having an emitter layer made of @ (superconductor or normal conductor) or a semiconductor and a collector layer made of a compound semiconductor on the other side of the base layer, 1nAs, cSbt-x or 5bGaxln1 is used in the collector layer. -x mixed crystal, and the collector layer, emitter layer, base layer superconductor, tunnel barrier, and insulating substrate are each made of lattice-matched materials. The gist of the invention is a bonding element.

The present invention focuses on the lattice matching of the semiconductor, insulator, and superconductor materials that make up the device, and forms the device by epitaxial growth from the substrate using a combination of compatible materials, thereby creating a high-quality electrode layer. , is characterized by producing a high-performance superconducting/semiconductor junction device by forming a barrier film and forming an interface without a transition layer at the boundary between each film.

Figure 1 shows the basic structure, in which a thin metal film (superconductor or normal conductor) 2 and a tunnel barrier 3 are formed on an insulating substrate 1.
Next, the element has a superconducting thin film 4 and further a compound semiconductor thin film 5 thereon.

The first thin metal film is the emitter layer into which the quasiparticles are injected, the second superconductor is the base layer, and the compound semiconductor is the collector layer. A semiconductor thin film can be used instead of the emitter metal thin film and tunnel barrier pair.

In order for the quasi-particles to pass through the pace layer ballistically and into the collector layer, the base layer must be 100-500
The quasi-particle resistance must be small and the thin film properties of both the paste and collector layers must be good.

Generally, Nb or V
It is known that when depositing a superconducting thin film with a high melting point such as, the film is of low quality at the initial stage of deposition, and the quality improves as the film thickness increases. In addition to this type of substrate, there is a process for forming a superconducting thin film on an insulator (tunnel barrier) such as an oxide in the production of Josephson devices, and a similar phenomenon occurs in this case as well. Normally, the critical temperature (
A low quality film with low Tc) is formed.

To obtain a high-quality superconducting thin film, it is necessary to form a single-crystal thin film with undisturbed atomic arrangement, ideally from the initial state of deposition.

Further, although a semiconductor thin film is used for the collector layer, it must be a single crystal film in order to obtain high quality characteristics. For example, when the metal emitter layer 2 is in contact with the substrate 1 and the collector layer 5 is formed on top, as in the structure shown in FIG. 1, the first substrate is a single crystal substrate, and the materials of each layer are must be epitaxially formed with lattice matching.

On the other hand, there is a device manufacturing method that is opposite to the above thin film manufacturing order.

That is, a process may be considered in which a collector layer is placed on the substrate side, and a thin film of a base layer and then an emitter layer are sequentially formed thereon. In this case, a superconductor with a high melting point is deposited on a semiconductor with a low melting point. The method of forming a thin film and the method of forming an interface between the emitter layer and the base layer without the presence of a transition layer are important, and lattice matching is also a fundamental issue in this process.

In particular, when a semiconductor is used for the emitter layer, it is essential that the entire thin film be epitaxial.

In any order of lamination of electrodes, it is necessary to combine materials with lattice matching.

There are practical demands for superconducting/semiconductor junction devices. Since this superconducting element is used at the temperature of liquid He, the superconductor must be in a superconducting state at the operating temperature.Furthermore, the injection voltage of quasiparticles is kept as low as possible, and the K
requires the use of narrow gap semiconductors. It is desirable that the gap energy of a semiconductor is approximately the same as that of a superconductor. Conventionally, there was no material composition or process technology for epitaxially growing each thin film from a substrate under such restrictive conditions.
s mixed crystal or 1nSb and Garb mixed crystal, and the superconductor is Nb, Zr, V, Hf nitride or a single compound of Nb, Mo, W carbide or a composite compound thereof, an insulating substrate or a tunnel. BaFxtMno, MnzOs+ Mn01. as a barrier. '
By epitaxially growing the entire thin film using Pb5O4, a superconducting/semiconductor junction device with high speed and high transport efficiency is obtained.

1nSb and 1nAa are O-16ev and 0 at 300K.
．． These are narrow gap semiconductors with an energy gap of 33 eV, but when these are mixed, a mixed crystal with an energy gap of 0.1 eV is obtained. 1nAFlxSk'l-
The mixed crystal of
, = 6.057 A'! varies linearly with the mixed crystal ratio X. On the other hand, the mixed crystal of 5bGa xl nl - is also cubic crystal in the entire region, and from the recommendation of 1nSb = 6.479A, the ao of GaSb = 6.095
Changes up to A. Gap energy is 0 of 1nSb
．． It varies from 16 eV to 0°67 eV for QaSb.

The nitride or carbide superconductors in contact with these semiconductors have a NaC1 (Bl) type structure, and the lattice constant of the simple compound is a, = 4.58 A ~ 4.27 X. These superconductors become compound semiconductors. For matching, the lattice constant of the superconductor, 42Xao, matches the lattice constant of the semiconductor.

On the other hand, as shown in Table 1, insulators can be divided into three groups depending on the size of their lattice constants. As for those belonging to I, ■>Q, MnO*e'l'ao,
It is GeOx and has a lattice constant around 4.4A.

■ consists of BaFm, and a = 6.20^. (2) is composed of MnxOspbsOa and has a lattice constant of around 8.8A.

When these insulators come into contact with the semiconductor on the (001) surface,
■For the insulator, P! On the (061) surface of the S body,
When both a-axes touch each other with a 45° deviation, lattice matching can be achieved. That is, the lattice constant of the insulator is 42Xa, +~6.22
A, and there exists a semiconductor mixed crystal that can achieve lattice matching.

In the insulator (2), mixed crystals with the same lattice constant exist, and lattice matching can be achieved on various identical planes. In the insulator of (2), there is a mixed crystal with a lattice constant of F1'2 x a6 ~ 8.8A, and as in (2), lattice matching must be achieved when both (001') planes are in contact. is possible.

Table 1 Classification and lattice constants of insulators Also, when an insulator is in contact with a superconductor, lattice matching can be achieved on various identical planes by choosing a superconductor with the same lattice constant as the cubic insulator I. It is. In a tetragonal Je M body, lattice matching is possible only in the (ooi) plane. BaF
For z and lattice matching, lattice matching can be achieved in both (ooi) planes by shifting both a-axes by 45'' and touching them.

Although the lattice constant of an insulator cannot be easily changed arbitrarily, it can be changed from 10 to 10 in semiconductors by selecting the mixed crystal ratio, and in superconductors by selecting the type and size of additive elements. Since it is possible to match the degree of matching, it is possible to realize a device in which each layer is completely epitaxially grown.

Next, the present invention will be explained in detail. It should be noted that the embodiments are merely illustrative, and it goes without saying that various changes and improvements may be made without departing from the spirit of the present invention.

<Example 1> FIG. 2 is a schematic diagram of a cross-sectional structure of an element explaining Example 1 of the present invention. BaFm and MnO single crystal substrate 6 ('
001) Nb-10at, %Ti target and Ar-30vo 1. A 200 OA NbN-TiN thin film was deposited at a substrate temperature of 300'C using a mixed gas of
It was manufactured by magnetron sputtering method. The obtained thin film was a single crystal film on any substrate, and Tc was BaF.
2 substrates was 15.6, and MnO was 14.3.

In addition, both the lattice constants of the NbN-TIN thin film are ao =
It was 4.38 A. These thin film 9 substrates were etched to produce an emitter layer pattern 7. Then, S1
An interlayer insulating layer 8 was formed using the same method as above, and windows for the base layer and emitter electrode were opened. Before forming the base layer, BJLF
After forming a tunnel barrier 9 of 3OA using a m or MnO target at a substrate temperature of 250''C, a base layer NbN-TIN thin film was formed by a 35OA DC magnetron method.The base layer pattern 10 was formed by reactive ion etching ( NbN-TI
The N thin film was etched using a CF4-5VO1% can mixed gas under conditions of a total gas pressure of 8 pa and an RF power of 20 W. An insulator S10 was formed on this, and a window was opened on the collector shoulder side using RIE. NbN-TiN
After cleaning the thin film surface with Ar ions and heat treatment at 300@C for 1 hour, a collector layer n-1nAso,
ss Sbo, ss (non-doped) 11' and Te doped n''-1nA804s SbO, sz 11'
was continuously grown epitaxially. The lattice constant of this semiconductor thin film was ao=6-195A. In this case, triethylindium ('l”Ein) is used as the organic metal.
, (CzHs)s in ), 5bHs, AsHs,
T for dope.

As TeI-h, a carrier gas was used.

Au was vapor-deposited on the n''-1nAso-as 5bO0sx to form the collector electrode 12.Finally, NbN-TiN was sputtered to form the base electrode 13 and the emitter electrode 14.

The current transmittance α at the grounded base of the superconducting/semiconductor three-terminal junction device fabricated in this way was set to 4.2' K liquid He.
Measured in temperature. When the voltage between the base and the collector is zero, α is 0.8 for a quasi-particle implantation with an emitter-base voltage of 80 mV, and α for a device using B&F wire for the substrate and barrier is 0.8.
3 and using MnO, α was 0.68. N
b-10at, %Nb-4 instead of Ti target,
NbN-VN formed using 5at, %V metal
A superconducting thin film (a=4.38X) also showed similar characteristics. All elements were epitaxially formed and exhibited high α values, but there were differences in α values depending on the substrate. This corresponds to the obtained superconductor NbN-TiN (or 1
The difference in the degree of matching of the lattice constants between BaF2 and MnO (1×104 in the case of BIFm)
For MnO, this is due to K of 1.6 x 10''.

Luck-Nb-30at instead of Ti target, %7.
When a nitride electrode is formed using r or Nb-49at, %Hf target or NbNNbN-5O,
%NbC or TaC targets, the lattice constant of these superconducting electrode thin films is approximately 4.45.
AC! :The degree of lattice matching in this case is better for MnO than for BaFt, and as a semiconductor, InAso, 44
The α of the device using Sbo, 5s (a=6.293 A) is 0.82 for the BaFz substrate and 0.82 for the MnO substrate.
It was 68.

On the other hand, a similar junction element was fabricated using luck instead of the NbN-TiN superconductor, but the Nb thin film at this time was polycrystalline. The α angle of this element was 0.1 to 0.08.

<Example 2> In the same structure as Example 1 of the present invention, an element was produced in which an insulating substrate, a superconductor, and a barrier were combined. T on the board
Single crystal substrates of aO and Mn0t were used.

Further, a tunnel barrier was formed using targets of TaO and MnO2. Using alloy target, substrate temperature 5
A superconducting thin film of 200 OA was fabricated at 00'C by DC magnetron sputtering. 1n as a compound semiconductor
AsxSb+-x and 5bGax1nl-x were used. Both 1nAsSb and 5bGaln were prepared by the same method as in Example 1, but for Ga, triethylgallium (TEGa) was used.

(CzHs)sGa) was used.

When TaO is used for the substrate and tunnel barrier, the superconductor is NbN, where the lattice constant of TaO is ao = 4-42X.
-14mo1. 'XZrN+ NbN-2 mo1.
%HfN, NbNbN-3O1, and %NbC were used.

As a tunnel barrier, Mn is partially used instead of TaO.
tOs was also used. On the other hand, in the case of Mn0z & = 4
．． NbN close to 398 A was used. For semiconductors, Ta
For O, 1nAso, a 4 Sbo, 4s or 5bGao, ssi lno, 40@, Mn0
t, 1nAso, H5ilo-ss or 5b
Gao, ay41nO, szs were adapted.

The current transmittance α of the superconducting/semiconductor three-terminal junction device fabricated in this way with the base grounded was measured at the liquid He temperature. When the voltage between the base and the collector is zero, α is as shown in Table 2 for quasiparticle injection with an emitter-base voltage of 80 mV.

<Example 3> FIG. 3 is a schematic sectional view illustrating Example 3 of the present invention. To-doped n”-1nAssb 1000X n-1nAssb on each (100) plane of 16
Two sets of single crystal layers with different lattice constants, 1nAso, 1Sbo, were grown epitaxially in the same manner as in Example 1.
, ss and 1nA So-s 5bO-st substrates were prepared. A collector layer pattern 16 was formed on these substrates by RIE using Ch bagasse. CI at this time
2 Gas pressure is 3Pa.

The test was conducted under the condition of RF Hower 20W. These 1nAs
Set the Sb substrate on the magnetron sputtering device, and
RF sputter cleaning for 2 minutes at Ar gas pressure of a, vcsb = 50V, then 30 minutes at 300 °C.
Annealed.

1nA80. For st Sbo, 1g substrate, after heating the substrate to about 3000C, Ar-N was applied using a tooth target.
! sputtering with a mixed gas of
X was formed. The NbN thin film at this time showed a good Laue pattern and was confirmed to be a single crystal thin film. The base layer patterning 17 of these NbN superconducting thin films is based on CF
This was carried out by RIE using 4 gases. Next, insulator S
IO was formed. By the lift-off method, S on the base layer
The IO membrane was windowed for the pace electrode and the emitter layer.

In forming the emitter layer, the surface of the NbN superconducting thin film is
After cleaning with R, a tunnel barrier 19 of 30A is formed by RF sputtering using a pbsoi or GIOI target, and then an emitter layer 20 is formed.
．． A NbN thin film for the base electrode 21 was deposited at a thickness of 200 OA. Finally, on the windowed n''-1nAssb surface,
A collector electrode 22 of Au was formed.

On the other hand, for the 1nAso, H5bO-sz substrate, N with a lattice constant close to =4-38A is used as a superconducting thin film.
bN-15,4mo1. %MoC, NbN-15mo
1%WC* TaCTaC-4Ornol-9NocT
aC-39,%WC* NbC-65mol,%MoC
,NbCNbC-6O,,9, as a barrier with BaF
A device was produced in the same manner as above using z.

Table 3 shows the combinations of materials for each layer of the superconducting medium semiconductor three-terminal junction device produced in this manner and the characteristics of the device.

The characteristic current transmittance α is the value for quasiparticle injection at an emitter pace voltage of 80 mV when the voltage between the base and the collector is zero. A similar junction device was fabricated using a thin film instead of the superconductor thin film, but the α of this device was 0.0.
It was 8-0.12.

(Effects of the Invention) As explained above, according to the present invention, one of the emitter, base, and collector! By selecting materials that can lattice match the extremely R film, substrate, and tunnel barrier and forming these thin films epitaxially, the atoms in each thin film are arranged regularly from the initial stage of deposition, so the electrical properties of the thin film itself are Moreover, since there is no disordered transition layer at the interface of each electrode, the transport efficiency of quasiparticles is high, and the injected electrons have the advantage of being able to travel at high speed.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a thin film deposition state of a superconducting/semiconductor junction device, and FIGS. 2 and 3 are schematic cross-sectional views of the structure of the superconducting/semiconductor junction device of the present invention. 1... Insulating substrate, 2Φ... Metal thin film (superconducting metal,
Normal conductive metal), 3... Tunnel barrier. 4...-Superconducting thin! , 5---Compound semiconductor, 6--1
Insulating substrate, 7--emitter layer, 8--interlayer insulating layer (StO, etc.), 9--fist/tunnel barrier. 10... Base layer (superconducting metal), 11'φ... Collector layer (low doped compound semiconductor), il'... Collector layer (highly doped compound semiconductor), 12... e collector electrode (Au etc.) , 13...Pase electrode, 14...Emitter electrode, 15...Substrate (highly doped compound semiconductor),
16... Collector layer (low doped compound semiconductor), 17
...Base layer (superconducting gold FJ)elB...Interlayer candy R layer (SIO, etc.), 19...Tunnel barrier 3Q*
me emitter layer, 21 II @ 11 base electrode,
22・φ・Collector electrode i) Figure 1 Figure 2

Claims (3)

[Claims] (1) A base layer made of a superconductor, an emitter layer made of a metal (superconductor or normal conductor) or a semiconductor in contact with the base layer, and a collector layer made of a compound semiconductor on the other side of the base layer. In a superconducting three-terminal device, InAs_xSb_1_-_x or SbG is used in the collector layer.
A mixed crystal of a_xIn_1_-_x is used, and the collector layer, emitter layer, base layer superconductor, tunnel barrier, and insulating substrate of this semiconductor are each made of a lattice-matching material, and the superconductor is NbN NbN -TiN:NbN-VN:NbN-ZrN:Nb
N-HfN:NbN-NbC:NbN-MoC:NbN
-WC:NbC-MoC:NbC-WC:TaC-MoC:TaC-WC:
Manufacturing method of semiconductor junction device (2) Tunnel barrier or insulating substrate is BaF_2
:MnO:Mn_2O_3:MnO_2:TaO:Ge
The method for manufacturing a superconducting/semiconductor junction element according to claim 1, characterized in that it is made of one of O_2:Pb_3O_4 (3) A base layer made of a superconductor, an emitter layer made of a metal (superconductor or normal conductor) or a semiconductor in contact with the base layer, and a collector layer made of a compound semiconductor on the other side of the base layer. In a superconducting three-terminal device, InAs_xSb_1_-_x or SbG is used in the collector layer.
A superconductor that uses a mixed crystal of a_xIn_1_-_x, and that the collector layer, emitter layer, base layer superconductor, tunnel barrier, and insulating substrate of this semiconductor are each made of lattice-matched materials. semiconductor junction device