JPH0349263A - Resonance tunnel three-teminal device - Google Patents

Abstract

PURPOSE:To acquire high mutual conductance characteristics and fast switching characteristics by taking a base electrode from a substance which supplies a tunnel level which becomes a quantum well of resonance tunneling diode structure. CONSTITUTION:Thin layers consisting of a substance A, a substance B, a substance C, a substance D, and a substance E are laminated. As a component of substance A to E, thin layers consisting of the substance B and the substance D form a barrier of potential to thin layers consisting of the substance A, the substance C and the substance E. That is, the layer consisting of the substance C selects a material which forms a well of potential to the layer consisting of the substances B and D. Furthermore, a thickness of each of layers consisting of the substance B, the substance C and the substance D is set this enough to realize a quantum level inside the layer consisting of the substance C and to enable resonance tunnelineg. An emitter electrode 1 is taken out of the layer consisting of the substance A, a base electrode 2 is taken out of the layer consisting of the substance C and a collector electrode 3 is taken out of the layer consisting of the substance E.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to electronic devices that apply quantum effects in materials surrounded by potential barriers, and in particular to high transconductance characteristics and high-speed switching characteristics that utilize resonant tunneling effects. , relates to a resonant tunnel three-terminal device characterized by ultra-high frequency oscillation and amplification characteristics.

[Conventional technology]

Conventional resonant tunneling diodes are made of materials A, B,
It has a structure in which thin layers consisting of C, D and E are laminated.

For example, the materials A, C, and E are GaAs, and the material LD is AlGaAs. GaAs and AlG
Due to the difference in electron affinity with aAs, D, substances A, B, C,
When D and E are stacked in this order, the layers made of substances B and D form a potential barrier to electrons, and the layer made of substance C forms a potential well. FIG. 5(a) shows a schematic diagram of energy bands near the conduction band. The thickness of the potential well (thickness of material C) is
When the temperature is below the Broglie wavelength, the energy level E is quantized within the well due to the wave nature of electrons surrounded by a potential barrier. (rl=1°2,...) is formed. The number of empty electron levels at this quantum level is extremely large. Furthermore, based on the principle explained below, if the thickness of the potential barrier formed in the thin layer made of substances B and D in FIG. 5 (al) is made thin enough to allow electrons to tunnel,
A resonant tunneling effect occurs. FIG. 5 (bl is an energy band structure diagram when a bias voltage ■ is applied between the eyebrows made of substances A and E.

As shown in FIG. The electrons in the band tunnel toward the empty level of the object fE via the quantum level E1 in the well. This is a phenomenon in which the tunneling probability increases only for electrons with a certain energy corresponding to a quantum level. That is, transport of carriers is performed by tunnel transition via energy levels within the quantum well. Here, in Figure 6, substances A, B,
10 illustrates trends in current-voltage characteristics when a bias voltage V is applied to a resonant tunnel diode formed by laminating thin layers of C, D, and E (GaAsAj2GaAs is an example). As shown in Figure 6, the current-voltage characteristic is a voltage corresponding to a quantum unit, 2EI /q (q is the amount of charge of an electron, and E is the energy level corresponding to the quantum level E1).
It has negative resistance characteristics with a peak at . This phenomenon is called the resonant tunneling effect because it resonates with the quantum level and increases the probability of electron tunneling.

This effect was proposed by a group at IBM including Ezaki (R, Tsu and L, Ezaki
:Appl, Phys, Lett,
, vol, 22. p, 562.1973. ), experimentally observed (L, L, Chang, L, Eza
ki, and R, Tsu: AppCPh y
s, Lett,, voj! , 24. p,
593. 1974). This effect can be applied to oscillators and analog amplifiers because it exhibits negative resistance, and its response speed is determined by ultra-high-speed tunneling and is thought to be extremely fast. Many studies have been conducted on using it as a terminal element.

As a representative example, (1) MIT's 5ollner observed a large negative resistance region with a Peak/Valley ratio of 6 at liquid nitrogen temperature, and confirmed that the resonant tunneling current followed up to a high frequency of 2.5 THz. (T, C, L, G.

5ollner, W. D., Goodhue, P.

E, Tannenwald, C, D, Parker, a.
nd D, D, Peck: Appl, Phys,, L
ett,, voC43, p, 588°1983,), (
2) Same (So7!j!net, etc. has prototyped a resonant tunneling diode that oscillates up to 18 GHz (T,
C, L, G, 5oe7! ner, P, E, Ta
nnenwand, D.D.

Peck, C.D., Parker, and
W.

D. Goodhue: App 7! , Phys.
LetL,, vol, 45. p, 1
319. 1984゜), (3) University of Illinois 3he
Wchuk et al. observed the intrinsic resistance at room temperature (T, J.

Shewchuk, P., C., Chapin, and
P, D, Coffeeman: App7! , Phys., L.
ett,, vol, 46. p, 508.1985). However, in both cases, the studies were conducted on two-terminal elements (diodes), and no idea of application as a three-terminal device was proposed. That is, the specific structure, operating method, operating principle, and specific manufacturing method of a three-terminal device that utilizes the resonant tunneling effect have not yet been proposed.

By using three terminals compared to two terminals, it is possible to control the current-voltage characteristics, and it is thought that the range of applications will expand dramatically.

[Problem to be solved by the invention]

An object of the present invention is to provide a resonant tunnel three-terminal device characterized by having high transconductance characteristics, high-speed switching characteristics, and high-frequency oscillation/amplification characteristics.

[Means to solve the problem]

The most significant feature of the present invention is that the third electrode is taken out from the potential well portion of the resonant tunneling diode to enable operation as a three-terminal device. That is, specifically, for example, in the structure of a resonant tunneling diode formed by stacking thin layers made of substances A, B, C, D, and E, the third layer starts with the layer made of substance C that supplies a tunnel level that becomes a quantum well. An important feature lies in the structure in which the electrode is taken out and used as a control terminal of a three-terminal device to control the current-voltage characteristics flowing between the layers consisting of substance A and substance E. Furthermore, by applying a metal with a high carrier density to material A, we can increase the current density, and by using a metal or a superconductor to material C, we can reduce the base resistance, thereby achieving high-speed LS.
Increasing mutual contactance, which is an important parameter for I switching devices and high frequency devices,
It has the advantage of realizing high-speed/high-frequency oscillation/amplification characteristics and their control.

[For production]

The resonant tunneling three-terminal device of the present invention converts the current peak on the current-voltage characteristic due to the resonant tunneling effect of the resonant tunneling diode to the quantum level E that performs the tunnel transition.
It operates as a three-terminal device, controlled by a voltage applied to a third electrode (base electrode) taken to a thin base layer forming part 1. In order to lower the base resistance, there are various structural ideas such as a structure in which the base layer is multi-layered, or a structure in which the base is made of metal or a superconductor, but the basic operating principle is that a predetermined emitter base By applying a voltage and a base-collector voltage, the quantum level E1 of the layer made of substance C, which becomes the base layer, is changed by tunnel injection from the layer made of substance IA (emitter layer).
A collector current is obtained between the main electrodes by causing most of the tunnel-injected electrons to be further tunnel-injected into the layer made of substance E, while the relaxation process to the conduction band in the base layer The base current is extremely small, resulting in three-terminal operation that provides a large current gain.

A large current can be controlled with a small change in base voltage, resulting in high mutual conductance, high-speed switching performance due to the tunnel effect, and high cut-off frequency performance due to low base resistance, resulting in three-terminal device operation.

〔Example〕

FIGS. 1A and 1B show schematic cross-sectional structural views of resonant tunnel three-terminal devices as first and second embodiments of the present invention.

In FIG. 1(a), substance A, substance fB, and substance C1, respectively.
Structure in which thin layers consisting of substance D and substance E are laminated, first
In the figure (bl), a superlattice formed by thin layers consisting of substance B and substance C2 is sandwiched between layers consisting of substance A and animal matter. Figure 1 (a) and Figure 1 (In the embodiment of bl, the operation is exactly the same, so the structure of FIG. 1(al) will be explained below.

As for the constituent materials of substances A to E, a thin layer consisting of substance B and substance R forms a potential barrier against a thin layer consisting of substance A, animal matter, and substance E, and in other words, a thin layer consisting of substance D and substance C. A material is selected whose layer forms a potential well with respect to the layer consisting of substance B and substance ID. Also,
The thickness of each layer consisting of material B and material C1 is determined by material C.
It is set to be thin enough to create a quantum level in the fuchu consisting of , and to allow resonant tunneling. Emitter electrode l with material A
The base electrode 2 is taken out from the layer made of substance C, and the collector electrode 3 is taken out from the layer made of substance E.

In the structure shown in Figure 1 (bl), the layer made of material C that forms the quantum level for resonance tunneling is sandwiched between thin layers made of material B and material R, and is also formed as a superlattice structure. , and these superlattices are formed in multiple layers.These multilayer superlattices are BCDCCBCD.
... are formed in the order of 13CD. A base electrode 2 as a third electrode is taken out from each layer of these substances C.

FIG. 2 shows a schematic diagram of the energy band near the conduction band of the resonant tunneling three-terminal device as the first embodiment of the present invention, which corresponds to FIG. 1 (al). The figure shows the case where neither the base voltage nor the collector voltage VIC is applied. FIG. In the potential well portion of the layer, there are quantum levels E, (n
=1.2. ) can be done. As shown in Figure 2(b),
When VEI is applied so that the energy level of the conduction band of substance A matches the quantum level E, electrons in substance A tunnel to the quantum level. Most of the electrons that have moved to the quantum level tunnel toward the empty cell value in the substance E and become a collector current 1c. A very small portion moves from the quantum level to the conduction band of substance C, producing base current 8. Therefore, the direct current amplification factor β (-rc/Ie) of the common emitter becomes an extremely large value. Furthermore, since electrons move from the emitter to the collector by tunneling, it is extremely fast, and reflecting the strong nonlinear current/voltage characteristics between the emitter and base, the mutual conductance is large, so high-speed operation is possible. A large current cutoff frequency [i can be realized. Substance A-
E includes the following (A), (B), and (C).

Any material that satisfies the condition (D) may be used. That is, (A
) Substance A, Substance B, Substance C1 Substance and Substance E respectively
In a structure in which thin layers are stacked, or in a structure in which a superlattice formed by thin layers made of substances B and C1 is sandwiched between layers made of substance A and substance E, (B) substances B and The layer of material C forms a potential barrier for electrons with respect to the thin layers of material A, material C, and material E. That is, the layer of material C forms a potential barrier for electrons with respect to the thin layer of material B and material E. (C) The thickness of each layer made of material B and material C1 is set to be thin enough to cause resonant tunneling, and (D) the layer made of material A is set as an emitter electrode, and the layer made of material C is made as thin as possible. Any resonant tunnel three-terminal device may be used as long as it is a resonant tunnel three-terminal device characterized in that a base electrode is taken from a layer made of substance E and a collector electrode is taken from a layer made of substance E.

For example, examples of combinations when each layer consisting of these materials A-E is formed using a semiconductor are shown in Table 1 A-E'. Even in the structure in which a multilayered superlattice consisting of materials B and C1 of the resonant tunnel three-terminal device as Example 2 is sandwiched between materials A and E, a quantum level is created in the superlattice. Therefore, the operating principle is exactly the same.Although the structure is somewhat complicated, since there are multiple layers made of material C, it has the effect of reducing the resistance. The second embodiment of the present invention having the structure shown has the added advantage of further increasing the maximum oscillation frequency fMA compared to the embodiment of FIG. 1fa).

Needless to say, the resonant tunnel three-terminal device according to the present invention can be used to construct ordinary logic circuits and high-frequency analog circuits, but this three-terminal device also has an operation mode as a light-emitting (electromagnetic wave oscillation) switching device.
This corresponds to a third embodiment in which the resonant tunnel three-terminal device according to the present invention is applied to a light-emitting switching device.

The third example will be described below. FIGS. 3(a) and 3(b) are energy band structure diagrams near the conduction band of the resonant tunnel three-terminal device (FIG. 1(a)) having the structure of the first embodiment according to the present invention.
. FIG. 6 shows an energy band structure diagram when the bias conditions of FIG.

Consider the case where the base-collector voltage ViIC is applied so that the conduction band level of the material fiE becomes quantum order E, thicker (as shown in Figure 3 (al).
By applying the base voltage V□ D, electrons at the conduction band level in the substance A tunnel to the quantum level E1 in the substance C.

However, since there is no level in the material E below the energy level possessed by electrons, the electrons that have tunneled to the quantum level E1 cannot tunnel into the material E and fall into the conduction band of the material C. Therefore, in this relaxation process, the frequency ν(=2π(EI
EC) /h, h blank constant, E,: substance C
light or electromagnetic waves (conduction band energy level) are generated.

On the other hand, if the base-collector voltage ■1 is applied so that the conduction band level in the object [E is smaller than the quantum level E1 as shown in Figure 3 (bl), as explained earlier, the quantum Most of the electrons that have tunneled to level E1 will tunnel to levels in material E, and the probability that they will be relaxed to the conduction band in material C is extremely small.Therefore, no light emission or electromagnetic wave emission will occur.In this way, , the light emission can be switched depending on the magnitude and polarity of the voltage V1.

In this case, as a matter of course, as in the embodiment of the present invention, the base electrode as the third electrode terminal is taken out, and a bias voltage is applied between D and the emitter and collector terminals, respectively, or a current is injected or drawn out. Needless to say, the fact that the light emission switching operation can be controlled as in the present invention is an important feature. Controllability is extremely poor with simple two-terminal operation (resonant tunnel diode).

A fourth example is a case where metal is used as the material constituting the substance A. That is, FIGS. 1(a) and (b)
This is an example in which a metal layer is used as the material constituting the substance A in the structure. Metals have more carriers (electrons) than semiconductors
Due to the high density, the tunneling current density from the emitter to the base can be increased. Therefore, by increasing mutual conductance and load driving force, it is possible to increase D, current cutoff frequency fTO, and achieve high-speed switching characteristics. In this example, substance A is a metal, and the above-mentioned (A) and (B
), (C) and (D), substances A-E
There are many combinations of. However, it is natural that it is more preferable that the quality of the material such as the crystallinity of the amount of substance is good and that an ideal potential structure with few interface states can be realized.

One possible solution for this is the possibility of heteroepitaxial growth between materials, that is, the combination of materials with matched lattice constants. This is a supplementary condition for the constituent materials of the substances realizing each embodiment according to the invention. There are many combinations of materials in terms of lattice constants.

For example, the material constituting material A, material C1 and material E may be Sn, an alloy of Pb, or silicide (C
O3iz, NiSi2, etc.), materials constituting substances B and D include Si, CaFz, GaAs, AAGaA
s, AlAs, etc. These materials have the advantage of having little lattice mismatch with Si, allowing devices to be fabricated on large-area, inexpensive Si substrates.

A fifth example is a case where the object 1c has a structure in which metal is used as the material composing the object 1c. Since the base resistance can be reduced, the maximum oscillation frequency f MAX can be increased. Naturally, the above-mentioned supplementary conditions exist in selecting a material capable of heteroepitaxial growth, and for example, as described above (Sn or Pb alloy, silicide, etc.) can be used.

In the sixth embodiment, a superconductor is used as the material constituting the substance C. FIG. 4 corresponds to a resonant tunnel three-terminal device in which a superconductor material is used for the base layer as a sixth embodiment of the present invention, and shows an energy band structure diagram near the conduction band. Even in a material C (superconductor) surrounded by potential barriers, the quantum levels E,
(n=1.2...) exists, and a superconducting energy gap (indicated by the size 2Δ) exists. There is a quasiparticle state density D at the edge of the superconducting energy gap, and a superconducting pair electron (Cooper bear) exists at the Fermi level.

As shown in Figure 4 (bl), VEII is
When , electrons in substance A tunnel to the quantum level. Most of the electrons that have moved to the quantum level tunnel toward empty units in the substance E, becoming a collector current IC. A very small portion relaxes from the quantum level to the quasi-particle level of the material C (superconductor) and then recombines to form superconducting electron pairs and generate a base current 18. Therefore, the base current is carried by superconducting electron pairs with zero DC resistance. Finally, by eliminating the base resistance, there is an advantage that the maximum oscillation frequency fMAX can be significantly increased. Therefore, when applied as a switching device, it is possible to realize a three-terminal device that has no time delay due to the base resistance, no frequency limitations conventionally limited by the base resistance, and no loss within the base.

As a superconductor, low T such as Nb type and PB type.

Not only superconductors but also L, which has been discovered one after another since several years ago.
It goes without saying that high T, oxide superconductors abbreviated as a-based, Y-based, Bi-based, etc. can be used.

The embodiments of the present invention are described below.

That is, the present invention provides substance A, substance B, substance C, substance D, and substance E, respectively.
In a structure in which thin layers are stacked, or in a structure in which a superlattice formed by thin layers made of substances B and C1 is sandwiched between layers made of substance A and substance E, substance tB and substance [D Forms a potential barrier for electrons with respect to the thin layers of material A, material C, and material E. In other words, the layer of material C forms a potential well for electrons with respect to the thin layer of material B and material E. ), the thickness of each layer consisting of material B and material C1 is set to be thin enough to cause resonance tunneling,
This invention relates to a resonant tunnel three-terminal device characterized in that an emitter electrode is formed from a layer made of substance A, a base electrode is formed from a layer made of substance C, and a collector electrode is formed from a layer made of substance E.

〔Effect of the invention〕

Compared to a resonant tunneling diode as a conventional three-terminal device, there is an advantage that tunnel injection can be controlled by applying an emitter-base bias voltage and a base-collector bias voltage by taking out the base electrode from the base layer.

By controlling the base electrode, tunnel injection control can be performed at high speed and with high efficiency, so that the above-mentioned high mutual conductance characteristics and high speed switching characteristics can be obtained.

Furthermore, the base resistance can be reduced by not only configuring the base layer as a single layer, but also by configuring it as a multilayer in a superlattice and taking out the base electrode from each layer.
Furthermore, a higher cutoff frequency f can be obtained. In addition, by forming the material C constituting the base layer as a metal layer or a superconductor, the base resistance can be further reduced, making it possible to obtain a switching element without base delay and a three-terminal device without frequency limitations due to base resistance. There are also advantages. Furthermore, since the layer made of substance A or E, which becomes the emitter region or the collector region, is made of metal, there is also the advantage that an element with a larger allowable current value can be realized.

Furthermore, by using three terminals as in the configuration of the embodiment of the present invention, it is possible to perform a light emission switching operation by light emission/cutoff by selecting the base bias condition, and it is possible to realize a high speed and high efficiency light emission switching element. There are advantages.

As explained above, the present invention makes it possible to realize a three-terminal device with high mutual conductance characteristics and high-speed switching characteristics, opening up a wide range of applications such as ultra-high speed LSIs and ultra-high frequency devices.

2 is a schematic diagram of the energy band near the conduction band of the resonant tunnel three-terminal device of the embodiment shown in FIG. 1 (FIG. 1(a)), and FIG. Schematic diagram of the energy band near the conduction band of the terminal device, Figure 4 is the same as Figure 6.
FIG. 2 is a schematic diagram of energy bands near the conduction band of the resonant tunnel three-terminal device of the example.

Fig. 5 is a schematic diagram of the energy band near the conduction band of a conventional resonant tunnel diode, and Fig. 6 shows the current-voltage characteristics of a conventional resonant tunnel diode.

1...emitter electrode, 2...Base electrode, 3...Collector area

[Brief explanation of drawings]

Claims (1)

[Claims] A structure in which thin layers each consisting of substance A, substance B, substance C, substance D, and substance E are laminated, or formed by thin layers consisting of substance B, substance C, and substance D, respectively. In a structure in which a superlattice is sandwiched between layers consisting of substance A and substance E, the layer consisting of substance B and substance D forms a potential barrier to electrons with respect to the thin layer consisting of substance A, substance C, and substance E, The thickness of each layer consisting of substance B, substance C, and substance D is set to be thin enough to cause resonance tunneling, and the layer consisting of substance A is an emitter electrode, the layer consisting of substance C is a base electrode, and the layer consisting of substance E is an emitter electrode. A resonant tunnel three-terminal device characterized by a collector electrode.