JPH01146372A - Superconducting schottky gate field-effect transistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to Schottky gate field effect transistors. More specifically, the present invention relates to a superconducting Schottky gate field effect transistor using a superconductor in the Schottky gate.

2. Description of the Related Art Conventional GaAs Schottky gate field effect transistors have a problem in that the Schottky gate is relatively easily destroyed when a positive voltage is applied to the gate. .

Further, in order to improve the characteristics of the FET, it is sufficient to shorten the gate length, but there is a problem in that the gate resistance increases when the gate length is shortened.

Problems to be Solved by the Invention As mentioned above, in conventional Schottky gate field effect transistors, when a positive voltage is applied to the gate, the Schottky gate is easily destroyed, and when the gate length is shortened, the gate resistance increases. There was a problem with the increase.

Therefore, an object of the present invention is to provide a novel superconducting Schottky gate field effect transistor that solves the problems of the prior art described above.

Means for Solving the Problems According to the present invention, in a MESFET in which a Schottky gate electrode is directly attached to a semiconductor single crystal, the Schottky gate electrode is composed of at least one element α selected from group a elements of the periodic table. , at least one element β selected from group IIIa elements of the periodic table, 1b, nb, I of the periodic table
A composite oxide superconductor containing at least one element γ selected from I[b, IVa, ■a group elements and Au2
A superconducting Schottky gate field effect transistor characterized by having a layered structure is provided.

According to the present invention, any known material can be used as the composite oxide superconductor. In particular, the following general formula: %Formula% (However, α is an element included in the Ho group of the periodic table, and β
is an element included in group 11a of the periodic table, γ is at least one element selected from groups Ib, nb, mb, rva and ■a of the periodic table, and x and ySz are each 0.1≦x ≦0.9.0.4≦y≦3.0.1≦z≦5
A composite oxide represented by the following formula is preferable. These composite oxides are thought to be mainly composed of perovskite-type or oxygen-deficient perovskite-type oxides.

The Group IIa elements α of the periodic table include Ba, Sr,
Ca, Mg, Be, etc. are preferable, for example, Ba,
Sr can be mentioned, and 10 to 80% of this element α is Mg and Ca.

It can also be replaced with one or two elements selected from Sr. Further, the group IIIa element β of the periodic table includes YSLaSSc, Ce5Gd, Ho, Er
%Tm.

Yb, Lu, etc. are preferred, for example Y, La, )t
o, and of this element β, 10 to 80%
can also be replaced with one or two elements selected from Sc or lanthanide elements. The element T is generally Cu, but a part of it is shown in the periodic table rb, nb%
It can also be substituted with other elements selected from group IIIb-1'Va and group II, such as Ti, V, etc.

Further, the semiconductor single crystal used in the present invention is GaAs, In
It may be a single crystal of a group II-V compound such as P, a single crystal of a group II-Vl compound, or a single crystal of a multi-component compound semiconductor.

Function The main feature of the superconducting Schottky gate field effect transistor of the present invention is that the gate electrode has a two-layer structure of a composite oxide superconductor and Au. That is, the idea of using superconductors in field effect transistors has been around for a long time, and some have been experimentally produced using metallic superconductors. However, metal-based superconductors have low superconducting critical temperatures and are not practical.

In the present invention, a practical superconducting Schottky gate field effect transistor is fabricated by using a composite oxide superconductor exhibiting a high superconducting critical temperature as an electrode. The composite oxide superconductor used in the superconducting Schottky gate field effect transistor of the present invention is Y1Ba2C, also called YBCO.
A composite oxide having a multilayer perovskite crystal structure as typified by Us 07-1+ is preferred. However, the present invention is not limited thereto, and any known superconductor may be used.

In the superconducting Schottky gate field effect transistor of the present invention, the gate electrode has a two-layer structure of superconductor and Au, so if the device is cooled and operated in a superconducting state, the gate electrode will have a critical current density exceeding the critical current density. When an excessive current flows, the superconducting state changes to a normal conducting state and the current is suppressed, thereby effectively preventing the Schottky gate electrode from being destroyed. Furthermore, below the critical current density,
Since it acts as a superconductor, the resistance component is only Au, making it possible to realize a low resistance gate.

Further, the semiconductors used in the superconducting Schottky gate field effect transistor of the present invention include Sl, ■-■ group compounds, ■
The semiconductor may be either a -■ group compound or a multi-component compound, and each can be arbitrarily selected depending on the intended use.

A method for manufacturing the superconducting Schottky gate field effect transistor of the present invention will be described below. First, a pair of ohmic electrodes are formed on a semiconductor single crystal substrate, and a gate electrode made of two layers of Au and a composite oxide superconductor is formed between them. The method for forming the composite oxide superconductor layer is preferably a vapor deposition method such as sputtering, ion blating, molecular beam epitaxy, CVD (chemical vapor deposition), or a method similar to a vapor deposition method. At that time, it is preferable to form the composite oxide superconductor layer at a low substrate temperature so as not to impair the physical properties of the semiconductor single crystal.

In addition, in order to improve the crystallinity of complex oxide superconductors,
First, a composite oxide superconductor thin film was formed using SrT i 03, Mg
It is also preferable to form the semiconductor single crystal on another suitable substrate such as O1ZrO, sapphire, etc. and grow the semiconductor single crystal on the composite oxide superconductor thin film. In this case, it is preferable to remove the other substrates later.

EXAMPLES Hereinafter, the present invention will be specifically explained by examples, but the following are merely examples of the present invention, and it goes without saying that the scope of the present invention is not limited in any way by the following disclosure. be.

A method for manufacturing the superconducting Schottky gate field effect transistor shown in FIG. 1 will be described below.

On the N-type GaAs active layer of the GaAs semiconductor substrate 5, Au
Two Ge/Ni/Au ohmic electrodes are formed.

The respective electrodes become a source electrode 3 and a drain electrode 4. On the substrate between these electrodes, YBa, Cu307
The superconducting Schottky gate field effect transistor of the present invention is grown by growing a Y1Ba2Cu3O7-X composite oxide superconductor layer 1 using a sintered body powder as a target by a known magnetron sputtering method, and forming an Au layer 2 thereon. be completed. When growing a composite oxide superconductor layer, it is necessary to pay close attention to the substrate temperature so as not to impair the characteristics of the semiconductor. The substrate temperature is 700℃
is preferred.

Effects of the Invention As described in detail above, the superconducting Schottky gate field effect transistor of the present invention is completely novel in that a composite oxide superconductor is used for the superconducting electrode. Furthermore, since the superconducting Schottky gate field effect transistor of the present invention has zero gate resistance, it has excellent initial characteristics even as an FET with a short gate length, and can be expected to be used as a high-speed three-terminal device.

Further, in the superconducting Schottky gate field effect transistor of the present invention, when an excessive current flows through the gate electrode, the superconducting state changes to the normal conducting state, thereby preventing excessive current from flowing.

The present invention further promotes higher speed and higher density of semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a superconducting Schottky gate field effect transistor of the present invention. [Main reference numbers] 1...Superconductor layer, 2...Au layer, 3...Source electrode, 4...Drain electrode, 5...Semiconductor substrate patent applicant Sumitomo Electric Industries, Ltd.

Claims (8)

[Claims] (1) In a MESFET in which a Schottky gate electrode is directly attached to a semiconductor single crystal, the Schottky gate electrode is selected from at least one element α selected from group IIa elements of the periodic table, and an element selected from group IIIa elements of the periodic table. At least one element β, periodic table Ib, IIb, IIIb, IVa,
A superconducting Schottky gate field effect transistor characterized by having a two-layer structure of a composite oxide superconductor containing at least one element γ selected from Group VIIIa elements and Au. (2) The composite oxide superconductor has the general formula: (α_1_−_xβ_x)γ_yO_2 (where α, β, and γ are the elements defined above, x is the atomic ratio of β to α+β, and is 0.1 ≦x≦0.9, and y and z are 0 when (α_1_−_xβ_x) is 1
．． The superconducting Schottky gate field effect according to claim 1, wherein the superconducting Schottky gate field effect is an oxide having a composition represented by transistor. (3) The superconducting Schottky gate field effect transistor according to claim 1 or 2, wherein the composite oxide superconductor has a perovskite crystal structure or an oxygen-deficient perovskite crystal structure. (4) The composite oxide superconductor contains Ba and Y, and further contains Al, Fe, Co, Ni, Zn, Cu, Ag,
At least one selected from the group consisting of Ti
The superconducting Schottky gate field effect transistor according to any one of claims 1 to 3, wherein the superconducting Schottky gate field effect transistor is a composite oxide superconductor containing a seed element. (5) The composite oxide superconductor contains Ba and La, and further contains Al, Fe, Co, Ni, Zn, Cu, Ag.
The superconductor according to any one of claims 1 to 3, wherein the superconductor is a composite oxide superconductor containing at least one element selected from the group consisting of Ti, Ti, and Ti. Schottky gate field effect transistor. (6) The composite oxide superconductor contains Sr and La, and further contains Al, Fe, Co, Ni, Zn, Cu, Ag.
The superconductor according to any one of claims 1 to 3, wherein the superconductor is a composite oxide superconductor containing at least one element selected from the group consisting of Ti, Ti, and Ti. Schottky gate field effect transistor. (7) The composite oxide superconductor contains Ba and Ho, and further contains Al, Fe, Co, Ni, Zn, Cu, Ag.
The superconductor according to any one of claims 1 to 3, wherein the superconductor is a composite oxide superconductor containing at least one element selected from the group consisting of Ti, Ti, and Ti. Schottky gate field effect transistor. (8) The semiconductor according to any one of claims 1 to 7, wherein the semiconductor is a GaAs semiconductor, an InP semiconductor, or a compound semiconductor containing either GaAs or InP. Superconducting Schottky gate field effect transistor.