JP3263869B2 - Resonant tunnel type hot electron transistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonant tunneling hot electron transistor.

[0002]

2. Description of the Related Art Conventionally, as a resonant tunneling type hot electron transistor, AlGa as shown in FIG.
A device using an As / GaAs heterojunction and a device using an AlSb / InAs heterojunction as shown in FIG. 12 are known. These resonant tunneling type hot electron transistors perform a transistor operation by controlling a resonant tunneling current flowing through a resonant tunneling barrier layer, that is, an AlGaAs layer or an AlSb layer serving as an emitter barrier layer or a collector barrier layer, with a base electrode. is there.

[0003]

In the above-described conventional resonant tunneling hot electron transistor, in order to control the resonant tunneling current with the base electrode, an AlGaAs layer or an AlGaAs layer as an emitter barrier layer or a collector barrier layer is used.
It is necessary to dope the Sb layer with an n-type impurity and supply electrons from the n-type impurity to a GaAs layer or an InAs layer as a base layer. However, when impurities are doped into the emitter barrier layer and the collector barrier layer in this way, the resonance tunnel phenomenon is adversely affected by impurity scattering and the like. In addition, since the doping concentration of the n-type impurity is limited, it is difficult to sufficiently reduce the resistance R of the base layer. Therefore, the resistance R and the capacitance C between the emitter and the base and between the base and the collector are reduced. The operation speed of the transistor is limited by the RC delay caused by the above.

Accordingly, an object of the present invention is to eliminate the necessity of doping the emitter barrier layer and the collector barrier layer with an impurity without adversely affecting the resonance tunnel phenomenon.
In addition, it is an object of the present invention to provide a high-performance resonant tunneling hot electron transistor capable of high-speed operation when a sufficient amount of electrons is present in the base layer.

[0005]

In order to achieve the above object, a resonant tunneling type hot electron transistor according to a first aspect of the present invention has an emitter layer made of a first semiconductor whose energy at the lower end of a conduction band is _Ec1 . (10)
And the energy at the bottom of the conduction band is E _c2 (where E _c2 >
E _c1 ) a second semiconductor emitter barrier layer (8)
And the energy at the bottom of the conduction band and the top of the valence band
The energy is E _c3 (where E _c3 <E _c2 ) and
The first electron supply layer made of a third semiconductor fine E _v3 (7)
And the energy at the bottom of the conduction band is E _c4 (where E _c4 <
E _v3 ) a fourth semiconductor base layer (6);
Energy at the bottom of the band and energy at the top of the valence band
_Are E _c5 and E _v5 (where E _c4 <E _v5 ), respectively.
The second electron supply layer made of a fifth semiconductor (5), conductivity
When the energy at the lower end of the band is E _c6 (where E _c6 > E _c5 )
A collector barrier layer (4) made of a sixth semiconductor and a conduction band
Energy at the lower end of E _c7 (where E _c7 <E _c6 )
And a collector layer (2) made of semiconductor No. 7
It is characterized by having a structure .

[0006] The second resonant tunneling hot electron transistor according to the invention of the present invention, an emitter layer made of a first semiconductor bottom energy of the conduction band is E _c1 (10), the bottom energy of the conduction band is E _c2 (just
And an emitter barrier made of a second semiconductor in which E _c2 > E _c1 )
Layer (8) and energy and valence bands at the bottom of the conduction band
Energy of E _c3 (E _c3 <E
_c2 ) and an electron supply layer comprising a third semiconductor of E _v3
(7) and the energy at the bottom of the conduction band is E _c4 (where
A base layer (6) made of a fourth semiconductor with E _c4 <E _v3 )
And the energy at the bottom of the conduction band is E _c6 (where E _c6 >
E _c4) sixth collector barrier layer made of a semiconductor of (4)
And the energy at the lower end of the conduction band is E _c7 (where E _c7 <
E _c6 ) and the collector layer (2) made of the seventh semiconductor.
It has a next laminated structure .

According to a third aspect of the present invention, there is provided a resonant tunneling hot electron transistor according to the first aspect.
Resonant tunneling hot electron transistor
And the first semiconductor and the seventh semiconductor are AlInAs
Sb, the second semiconductor and the sixth semiconductor are AlSb,
The third semiconductor and the fifth semiconductor are GaSb, the fourth semiconductor.
The body is one that is InAs.

A fourth aspect of the present invention provides a resonant tunneling hot electron transistor according to the second aspect.
Resonant tunneling hot electron transistor
And the first semiconductor and the seventh semiconductor are AlInAs
Sb, the second semiconductor and the sixth semiconductor are AlSb,
The third semiconductor is GaSb, and the fourth semiconductor is InAs.
Things.

[0009]

According to the resonant tunneling hot electron transistors according to the first and third _aspects of the present invention, the third semiconductor having the relationship of E _c4 <E _v3 is formed.
A first electron supply layer (7) and a fourth semiconductor
In the heterojunction with the source layer (6), the first electron supply
A phenomenon in which electrons in the valence band of the layer (7) move to the conduction band of the base layer (6) and become semimetalized, that is, a so-called self-
Since doping occurs, the emitter barrier layer (8) and the collector
Even if the barrier layer (4) is not doped with an n-type impurity, a sufficient amount of electrons exists in the base layer (6) . As a result, the base resistance R can be sufficiently reduced, so that the RC delay caused by the base resistance R and the capacitance C between the emitter and the base and between the base and the collector can be reduced. High-speed operation of the hot electron transistor can be achieved. Further, since the emitter barrier layer (8) and the collector barrier layer (4) do not have to be doped with n-type impurities, there is no adverse effect on the resonance tunnel phenomenon. As described above, a high-performance resonant tunneling hot electron transistor can be realized.

According to the resonant tunneling hot electron transistors according to the second and fourth inventions configured as described above, similarly to the first invention, the relationship of E _c4 <E _v3 is satisfied.
A first electron supply layer (7) made of a third semiconductor in
For a heterojunction with the base layer (6) made of the fourth semiconductor
Self-doping occurs in the emitter barrier layer
(8) and the collector barrier layer (4) are doped with n-type impurities.
Even so, there is a sufficient amount of electrons in the base layer (6) . As a result, a high-performance resonant tunneling hot electron transistor can be realized.

[0011]

[0012]

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding portions are denoted by the same reference numerals.

FIG. 1 is an energy band diagram of a resonant tunneling hot electron transistor according to one embodiment of the present invention. In FIG. 1, E _c and E _v indicate the energy at the lower end of the conduction band and the energy at the upper end of the valence band, respectively (the same applies hereinafter).

As shown in FIG. 1, the resonant tunneling hot electron transistor according to this embodiment has an AlInAsSb layer as an emitter layer, an AlSb layer as an emitter barrier layer, a GaSb layer, and an InAs layer as a base layer. , A GaSb layer, an AlSb layer as a collector barrier layer, and an AlInAsSb as a collector layer
It has a structure in which the layers are sequentially in contact. Here, an AlInAsSb layer as an emitter layer and an A
The lInAsSb layer is doped with n-type impurities and is n-type. However, the other layers, ie, an AlSb layer as an emitter barrier layer, a GaSb layer, and an I-type layer as a base layer.
nAs layer, GaSb layer, and A as a collector barrier layer
The lsb layer is not doped with impurities.

The AlInAsSb layer as an emitter layer doped with an n-type impurity and the AlSb layer as an emitter barrier layer, and the AlInAsSb layer as a collector layer doped with an n-type impurity and AlSb as a collector barrier layer A layer as an emitter layer
1InAsSb layer to AlSb as emitter barrier layer
Of n-type impurity into layer and Al as collector layer
In order to prevent the diffusion of n-type impurities from the InAsSb layer to the AlSb layer as the collector barrier layer, for example, an intrinsic (i-type) AlInAsSb layer is preferably provided as a spacer layer as described later.

FIG. 2 shows GaSb / I in the resonant tunneling hot electron transistor according to this embodiment.
FIG. 3 shows an energy band diagram of an nAs heterojunction.

As shown in FIG. 2, this GaSb / InA
In the s heterojunction, the lower end of the conduction band of InAs is lower than the upper end of the valence band of GaSb, so that electrons in the valence band of GaSb move to the conduction band of InAs near the interface of the heterojunction, and Metallize. For this reason,
Many carriers, that is, electrons are present in the InAs layer as the base layer even if n-type impurities are not doped at all. As will be described later, these electrons change the base potential. In this case, the electron exists at the first quantization level E ₀ corresponding to the ground state (see FIG. 1).

Next, the operation of the resonant tunneling type hot electron transistor according to this embodiment having the above-described structure will be described.

A predetermined bias voltage is applied between the emitter and the collector so that the potential of the collector becomes higher than the potential of the emitter. At this time, as shown in FIG. 3, if the quantized first level E ₁ of the InAs layer as the base layer is above the lower end E _c of the conduction band of the AlInAsSb layer as the emitter layer, Through one level E ₁ , a resonant tunneling current passes through an AlSb layer as an emitter barrier layer, an AlSb layer as a collector barrier layer, etc.
Flows between collectors. This is the ON state of the resonant tunneling hot electron transistor.

Next, as the base potential is increased, FIG.
As shown in FIG. 7, when the first quantized level E ₁ of the InAs layer as the base layer becomes lower than the lower end E _c of the conduction band of the AlInAsSb layer as the emitter layer, the first quantized level becomes lower.
The resonance tunnel current via the level E ₁ becomes extremely small (off resonance), and AlS as an emitter barrier layer
The current flowing between the emitter and the collector through the b layer and the AlSb layer as the collector barrier layer is extremely reduced.
This is the off state of the resonant tunneling hot electron transistor.

In this case, since the electrons responsible for the change in the base potential are present at the quantized zero level E ₀ , they do not hinder the resonance tunneling of electrons between the emitter and the collector. Also, the electrons injected from the emitter layer into the base layer reach the collector faster than the transition from the _first quantized level E ₁ to the quantized zero level E ₁ , so that the leakage current to the base is small. Therefore, a high current gain can be obtained.

FIG. 5 shows a specific example of the structure of the resonant tunneling hot electron transistor according to this embodiment.

As shown in FIG. 5, in this resonant tunneling hot electron transistor, for example, an n-type AlIn as a collector layer is formed on a p-type GaSb substrate 1.
AsSb layer 2 and i-type AlInAs as spacer layer
Sb layer 3 and i-type AlSb layer 4 as collector barrier layer
, I-type GaSb layer 5 and i-type InA as base layer
s layer 6, i-type GaSb layer 7, i-type AlSb layer 8 as an emitter barrier layer, and i-type AlI as a spacer layer
nAsSb layer 9 and n-type AlInA as emitter layer
It has a structure in which the sSb layer 10 is sequentially laminated in a predetermined pattern shape. In this case, the i-type GaSb layer 7, the i-type AlSb layer 8 as the emitter barrier layer, the i-type AlInAsSb layer 9 as the spacer layer, and the n-type AlInAsSb layer 10 as the emitter layer have a mesa shape. Then, an n-type AlInAsSb layer 10 as an emitter layer
An emitter electrode E is formed thereon, and I
A base electrode B is formed on the nAs layer 6, and a collector electrode C is formed on the n-type AlInAsSb layer 2 as a collector layer. These emitter electrode E, base electrode B and collector electrode C are formed of metal.

As an example of the thickness of each layer constituting the resonant tunneling hot electron transistor shown in FIG. 5, the i-type AlInAsSb layer 3 and the i-type AlInAsSb layer 9 as spacer layers each have a thickness of about 20 nm and a collector barrier layer. The i-type AlSb layer 4 as an emitter and the i-type AlSb layer 8 as an emitter barrier layer
m, i-type GaSb layer 5 and i-type GaSb layer 7 each have a thickness of about 2 nm, i-type InAs layer 6 as a base layer.
Is about 10 nm.

The p-type GaSb substrate 1, n-type AlIn
AsSb layer 2, i-type AlInAsSb layer 3, i-type AlS
b layer 4, i-type GaSb layer 5, i-type InAs layer 6, i-type G
aSb layer 7, i-type AlSb layer 8, i-type AlInAsSb
The layer 9 and the n-type AlInAsSb layer 10 are lattice-matched to each other, and can be heteroepitaxially grown as described later.

Next, a method for manufacturing the resonant tunneling hot electron transistor shown in FIG. 5 will be described.

First, as shown in FIG. 6, on a p-type GaSb substrate 1, for example, metal organic chemical vapor deposition (MOCVD)
N-type AlInAsSb layer 2, i-type AlInA
sSb layer 3, i-type AlSb layer 4, i-type GaSb layer 5, i
-Type InAs layer 6, i-type GaSb layer 7, i-type AlSb layer 8, i-type AlInAsSb layer 9, and n-type AlInAs
The Sb layer 10 is sequentially epitaxially grown. After this,
A resist pattern 11 having a predetermined shape is formed on the n-type AlInAsSb layer 10. The resist pattern 11 is formed, for example, by irradiating an electron beam having a sufficiently small spot diameter on the n-type AlInAsSb layer 10 in a predetermined source gas atmosphere in a vacuum-evacuated sample chamber of an electron beam irradiation apparatus (not shown). It can be carried out by selectively irradiating and depositing a decomposition product of the raw material gas on the irradiated portion.

Next, using the resist pattern 11 formed as described above as a mask, the n-type AlInAsSb layer 10 and the i-type AlInA are formed by reactive ion etching (RIE) using, for example, a Cl-based etching gas.
sSb layer 9, i-type AlSb layer 8, and i-type GaSb layer 7
Are sequentially etched in the direction perpendicular to the substrate surface. Thereby, as shown in FIG. 7, the n-type AlInAsSb layer 1 is formed.
The i-type AlInAsSb layer 9, the i-type AlSb layer 8, and the i-type GaSb layer 7 are patterned into a quadrangular prism.
Here, in RIE using this Cl-based etching gas, InAs is not etched, so that i-type I
Etching stops automatically when the nAs layer 6 is exposed. That is, at the time of this RIE, the i-type InAs layer 6 serves as an etching stopper.

Next, after the resist pattern 11 is removed, a predetermined portion of the i-type InAs layer 6 is removed by, for example, a wet etching method using another resist pattern (not shown) as a mask, as shown in FIG. I do.

Next, after removing the resist pattern used in etching the i-type InAs layer 6, an RIE method using a Cl-based etching gas is again performed using another resist pattern (not shown) as a mask. By i
GaSb layer 5, i-type AlSb layer 4, i-type AlInAs
The Sb layer 3 and the n-type AlInAsSb layer 2 are sequentially etched in a direction perpendicular to the substrate surface, and the etching is stopped when the n-type AlInAsSb layer 10 is etched by a predetermined thickness. Thereafter, the resist pattern used in this etching is removed. Thus, as shown in FIG. 9, the i-type GaSb layer 5, the i-type AlSb layer 4, the i-type A
The lInAsSb layer 3 and the n-type AlInAsSb layer 2 are patterned into a predetermined shape, and the n-type AlInAsSb layer 2 used as a collector layer is exposed.

Thereafter, as shown in FIG. 5, an emitter electrode E and an i-type InAs layer 6 used as a base layer are formed on an n-type AlInAsSb layer 10 used as an emitter layer.
On top, base electrode B, n-type A used as collector layer
A collector electrode C is formed on each of the lInAsSb layers 2 to complete a desired resonant tunneling hot electron transistor.

As described above, according to the resonant tunneling hot electron transistor of this embodiment, self-doping occurs in the GaSb / InAs heterojunction of the base portion, and the AlSb as the emitter barrier layer and the collector barrier layer is formed. Even if the layer is not doped with an n-type impurity, a large amount of electrons are present in the InAs layer serving as the base layer. Therefore, the base resistance R is reduced to reduce the base resistance R and the capacitance C between the emitter and base and between the base and collector. The RC delay due to the above can be reduced. Therefore, high-speed operation is possible. In addition, since the AlInAsSb layer is used as the emitter layer and the collector layer, the base leakage current can be reduced, and a large current gain can be obtained.

FIG. 10 is an energy band diagram showing a resonant tunneling type hot electron transistor according to another embodiment of the present invention.

As shown in FIG. 10, a resonant tunneling hot electron transistor according to another embodiment is
GaS only on the emitter side of the InAs layer as the base layer
It has the same structure as the above-described resonant tunneling hot electron transistor according to the embodiment shown in FIG. 1 except that there is a b layer and there is no GaSb layer on the collector side.

According to the resonant tunneling hot electron transistor of this embodiment, since the GaSb layer is provided only on one side of the InAs layer as the base layer, the GaSb layer is supplied to the InAs layer by self-doping at the GaSb / InAs heterojunction. Although the amount of electrons to be performed is smaller than that of the resonant tunneling hot electron transistor according to the above-described embodiment, the structure and manufacturing process of the transistor are simplified since the GaSb layer is formed only on one side of the InAs layer. There is an advantage of becoming.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical concept of the present invention are possible.

For example, the resonant tunneling hot electron transistor may be made of a material other than those used in the above-described one embodiment and other embodiments. FIG.
The specific structure of the resonant tunneling hot electron transistor shown in FIG. 1 is merely an example, and a different structure may be used. Similarly, as a manufacturing method of the resonant tunneling hot electron transistor shown in FIG. 5, a manufacturing method different from that described in the above-described embodiment may be used.

[0039]

As described above, according to the present invention,
Even if the emitter barrier layer and the collector barrier layer are not doped with impurities, a sufficient amount of electrons are present in the base layer by self-doping, so that a high-performance resonant tunneling hot electron transistor can be realized.

[Brief description of the drawings]

FIG. 1 is an energy band diagram showing a resonant tunneling hot electron transistor according to one embodiment of the present invention.

FIG. 2 shows GaSb / InA in a resonant tunneling hot electron transistor according to one embodiment of the present invention.
FIG. 3 is an energy band diagram of an s heterojunction.

FIG. 3 is an energy band diagram for explaining an operation of the resonant tunneling hot electron transistor according to one embodiment of the present invention.

FIG. 4 is an energy band diagram for explaining an operation of the resonant tunneling hot electron transistor according to one embodiment of the present invention.

FIG. 5 is a perspective view showing a specific structure example of a resonant tunneling hot electron transistor according to one embodiment of the present invention.

FIG. 6 is a perspective view for explaining a method of manufacturing the resonant tunneling hot electron transistor shown in FIG.

FIG. 7 is a perspective view for explaining a method of manufacturing the resonant tunneling hot electron transistor shown in FIG.

FIG. 8 is a perspective view for explaining a method of manufacturing the resonant tunneling hot electron transistor shown in FIG.

9 is a perspective view for explaining a method of manufacturing the resonant tunneling hot electron transistor shown in FIG.

FIG. 10 is an energy band diagram showing a resonant tunneling hot electron transistor according to another embodiment of the present invention.

FIG. 11 is an energy band diagram illustrating an example of a conventional resonant tunneling hot electron transistor.

FIG. 12 is an energy band diagram showing another example of the conventional resonant tunneling hot electron transistor.

[Explanation of symbols]

 1 p-type GaSb substrate 2, 10 n-type AlInAsSb layer 3, 9 i-type AlInAsSb layer 4, 8 i-type AlSb layer 5, 7 i-type GaSb layer 6 i-type InAs layer E Emitter electrode B Base electrode C Collector electrode

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-222478 (JP, A) JP-A-5-206444 (JP, A) JP-A-58-9371 (JP, A) JP-A-61- 158172 (JP, A) JP-A-61-268061 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/331 H01L 29/205 H01L 29/737

Claims (4)

(57) [Claims] An energy at the lower end of the conduction band is the first energy of E _c1 .
An emitter layer made of a semiconductor, the lower end of the energy E _c2 of the conduction band (although, E _c2>
E _c1 ) an emitter barrier layer made of a second semiconductor , energy at the lower end of the conduction band and energy at the upper end of the valence band.
Lugie is E _c3 (where E _c3 <E _c2 ) and E
The energy of the first electron supply layer composed of the third semiconductor of _v3 and the energy of the lower end of the conduction band is E _c4 (where E _c4 <
E _v3 ) a base layer made of a fourth semiconductor , energy at the lower end of the conduction band and energy at the upper end of the valence band.
Lugie is E _c5 and E _v5 (where E _c4 <
E _v5 ), the second electron supply layer made of the fifth semiconductor and the energy at the lower end of the conduction band are E _c6 (where E _c6 >
The energy at the lower end of the conduction band and the collector barrier layer made of the sixth semiconductor of E _c5 ) is E _c7 (where E _c7 <
E _c6 ) and a collector layer made of a seventh semiconductor are sequentially laminated
A resonant tunneling hot electron transistor having a structure as described above . 2. The energy at the lower end of the conduction band is the first energy of E _c1 .
An emitter layer made of a semiconductor, the lower end of the energy E _c2 of the conduction band (although, E _c2>
E _c1 ) an emitter barrier layer made of a second semiconductor , energy at the lower end of the conduction band and energy at the upper end of the valence band.
Lugie is E _c3 (where E _c3 <E _c2 ) and E
The energy of the electron supply layer composed of the third semiconductor of _v3 and the energy of the lower end of the conduction band is E _c4 (where E _c4 <
E _v3 ) The base layer made of the fourth semiconductor and the energy at the lower end of the conduction band are E _c6 (where E _c6 >
The energy at the lower end of the conduction band and the collector barrier layer made of the sixth semiconductor of E _c4 ) is E _c7 (where E _c7 <
E _c6 ) and a collector layer made of a seventh semiconductor are sequentially laminated
A resonant tunneling hot electron transistor having a structure as described above . 3. The first semiconductor and the seventh semiconductor are AlInAsSb, the second semiconductor and the sixth semiconductor are AlSb, the third semiconductor and the fifth semiconductor are GaSb, and the fourth semiconductor is a fourth semiconductor. 2. The resonant tunneling hot electron transistor according to claim 1, wherein said semiconductor is InAs. 4. The first semiconductor and the seventh semiconductor are AlInAsSb, the second semiconductor and the sixth semiconductor are AlSb, the third semiconductor is GaSb,
3. The resonant tunneling hot electron transistor according to claim 2, wherein said fourth semiconductor is InAs.