JPH0366175A - Vertical type point-contact quantum effect device and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a stepwise characteristic according to a quantization state when an electric current is made to flow through a source region 1 and a drain region 3 by a method wherein a first semiconductor layer, a second semiconductor layer and a third semiconductor layer are laminated one after another on a substrate and a semiconductor point-contact region is formed in a very small part inside the second semiconductor layer. CONSTITUTION:An n-type GaAs layer 1 is formed on a semi-insulating substrate 1; a p-type GaAs layer 2 is formed on it; in addition, an n-type GaAs layer 3 is formed. A point-contact region 5 is formed inside the p-type layer 2 to connect the n-type layers 1 and 3. A p-type region 2' is formed inside the n-type layer 3 to extract the p-type layer 2 to the surface. The n-type layer 1 functions as a source region, the p-type layer 2 as a gate region and the n-type layer 3 as a drain region. A gate electrode 12 is formed on the p-type gate region 2'; a drain electrode 13 is formed on the drain region 3; the source region 1 is grounded and extracted to the surface in a different place. A point-contact quantum well device is cooled; a reverse bias voltage is applied to the gate electrode 12 to narrow an effective channel width of the channel region 5; a level inside it is quantized; an electric current is made to flow through the source region 1 and the drain region 3. Thereby, a quantization characteristic can be obtained.

Description

[Detailed Description of the Invention] [Summary] A new structure regarding a point contact quantum effect device in which a source region and a drain region are connected by a point contact channel region in which the carrier level is quantized by reducing the dimensions. The purpose of the present invention is to propose a point contact quantum effect device having a first semiconductor layer of one conductivity type having a main surface, a second semiconductor layer of the opposite conductivity type formed on the main surface, and a second semiconductor layer of the opposite conductivity type formed on the main surface. a third semiconductor layer of the first conductivity type formed on the second semiconductor layer;
a semiconductor point contact region of the first conductivity type formed in the semiconductor layer, connecting the first semiconductor layer and the third semiconductor layer, and having dimensions such that carrier levels are quantized; .

[Industrial Application Field] The present invention relates to a semiconductor device, and in particular to a point contact quantum effect semiconductor device in which a source region and a drain region are connected by a point contact channel region whose carrier level is quantized by reducing the dimensions. Regarding equipment.

[Prior art] Fig. 2 (A), (B), ((l) shows a horizontal point contact quantum effect device according to the prior art.6 Fig. 2 (A)
shows a plan view, and FIG. 2(B) shows a cross-sectional view.

As shown in FIG. 2(A), a gate electrode 5 is placed on the semiconductor surface.
2a and 52b are formed. These gate electrodes 5
A portion sandwiched between 2a and 52b forms a point contact channel region, and a source region 51 is formed on the left side in the figure, and a drain region 53 is formed above.

Referring to the cross-sectional view shown in second (B), semi-insulating (S,
I, ) On the GaAs substrate 54, an intrinsic (i-type)
A GaAs layer 55 is formed on which n-type AlGaA
An s layer 56 is formed. That is, n-type AlGa
As 56 becomes an electron supply layer, and the i-type GaAs layer 55 forms an electron transit layer. In the figure, a layer 58 indicated by a broken line on the surface of the i-type GaAs layer 55 represents a two-dimensional electron gas supplied with electrons from the electron supply layer 56. Gate electrodes [i 52 a, 52 b are arranged forming a Schottky contact. These gate electrodes 52a, 52
When a voltage is applied to b, a depletion layer 59 expands under the gate electrode. In other words, carriers are expelled from the depletion layer and the conductivity is lost. The minute region that did not become a depletion layer becomes a negative layer region and becomes a source region 51.
and the drain region 53 are connected by point contact.

In ``---, the gate electrodes 52a and 52b are, for example,
The width of the thick portion shown in FIG. 12(A) is approximately 1 μm, and the interval between the thick portions is approximately 250 nn+ at the narrowest portion. A bias voltage is applied to the gate electrodes 52a and 52b to form a depletion layer 59.
By growing . . . , the width of the channel region, which is a path for two-dimensional electron gas, is narrowed to less than a submultiple Å. In the channel region whose width is narrowed in this manner, carrier levels are quantized, especially at low temperatures (for example, about 1.2°K).

Figure 2 (C) shows an example of the characteristics of the source/drain resistance with respect to the gate voltage of a lateral point contact quantum effect device as shown in Figure 2 (A>, (B)). As the value decreases, the source
Train resistance is reduced. In addition, the measurement is approximately 1.2°
I went there. Because the carrier levels are quantized, it is observed that the source/drain resistance changes in a step-like manner. When resistance is converted to conductance, the conductance is 2e for changes in gate voltage.
It can be seen that the level of carriers in the channel region is quantized.

It is expected that various semiconductor devices can be constructed by using such a point contact quantum effect device in which a source region and a drain region are connected by a quantized channel region.

[Problem to be solved by the invention] Point contact quantum effect devices have been proposed, but
In order to fully utilize this possibility, various further studies are required.

The purpose of the present invention is to propose a point contact quantum effect device with a new structure.

Another object of the present invention is to propose a method for manufacturing a point contact quantum effect device having a new structure.

[Means for Solving the Problems] FIG. 1 is a sectional view showing a basic embodiment of the present invention. In the figure, a first semiconductor layer 1 and a second semiconductor layer 2 are provided on a substrate 7.
, a third semiconductor layer 3 are sequentially stacked, and a semiconductor point contact region 5 is formed in a minute portion in the second semiconductor layer 2. The first semiconductor layer 1, the third semiconductor layer 3, and the semiconductor point contact region 5 have one conductivity type, and the second semiconductor layer 2 has the opposite conductivity type. The first semiconductor layer 1 and the third semiconductor layer 3 form the source/drain region, the semiconductor point contact region 5 forms the channel region, and the second semiconductor layer 2 forms the junction gate region.

That is, the W4 structure shown in FIG. 1 as a whole forms a point contact quantum effect device having a vertical junction gate structure. The semiconductor point contact region 5 has dimensions such that carrier levels therein can be easily quantized by applying a reverse bias voltage to the gate region 2.

[Operation 1] A pn junction exists between the gate region 2 and the channel region 5, and the effective width of the depletion layer changes depending on the magnitude of the gate bias voltage. When a reverse bias voltage is applied to the gate region 2 to extend the depletion layer and the width of the conductive channel region 5 is made very narrow, the state of carriers therein becomes quantized. When a current is passed between the source region 1 and the drain region 3 in this state, a stepped characteristic corresponding to the quantization state is obtained.

[Embodiment] FIGS. 3(A) to 3(E) show a vertical point contact quantum effect device according to an embodiment of the present invention.

FIG. 3A shows a single channel vertical point contact quantum effect device. An n-type GaAs layer 1 is formed on a semi-insulating GaAs substrate 7, a p-type GaAs layer 2 is formed thereon, and an n-type GaAs layer 3 is further formed on the surface thereof. A point contact region 5 is formed in the P-type GaAs layer 2 and connects the N-type GaAs layers 1 and 3. Further, a p-type G'aAs region 2° is provided in the n-type GaAs layer 3, and the p-type GaAs layer 2 is led out to the surface. The n-type GaAs layer 1 functions as a source region, the p-type GaAs layer 2 functions as a gate region, and the n-type GaAs layer 3 functions as a drain region. A gate electrode 12 is formed on the p-type gate region 2° on the surface, and a drain electrode @13 is formed on the drain region 3. The source region 1 is grounded and brought out onto the surface at another location.

For example, the n-type source region 1 has a thickness of about 5000 nm and an impurity concentration of about 1 x 10 cm-3.

The n-type channel region 5 has a thickness of about 500mm and a thickness of about 3×101
It has an impurity concentration of 6CI-3. In addition, the n-type drain region 3 has a thickness of about 2000 mm and about 1×10 18 CI-3
It has an impurity concentration of

The single channel point contact quantum effect device shown in FIG. 3(A) is cooled to, for example, liquid helium temperature,
Applying a reverse bias voltage to the gate electrode 12 narrows the effective channel width of the channel region 5, quantizes the level therein, and flows a current between the source region 1 and the drain region 3 to change the quantization characteristic. can be obtained.

FIG. 3(B) shows a multi-channel point contact quantum effect device having a plurality of channels.

Compared to the case of FIG. 3(A), there are a plurality of channel regions including a first channel region 5-1 and a second channel region 502. These plural channel regions 5-
1.5-2 may be arranged close to each other and configured to interfere with each other.

Although the point contact quantum effect devices shown in FIGS. 3A and 3B have an inverted structure in which carriers flow from bottom to top, an upright structure can also be formed.

FIG. 3(C) shows an upright point contact quantum effect device. An n-type GaAs layer 21 is formed on a semi-insulating GaAs substrate 7, and a p-type GaAs layer 22 and an n-type GaAs layer 21 are formed on the semi-insulating GaAs substrate 7.
An aAs layer 23 is formed. After that, the p-type GaAs layer 2
The minute portion 25 and the surrounding portion 28, which will become the point contact region of No. 2, are converted to n-type. Furthermore, a p-vacancy region 22' is formed for drawing out the p-type GaAs layer 22 to the surface. A source region is formed by an n-type GaAs layer 23, and a p-type GaAs layer 23 forms a source region.
The gate region is formed by the type GaAs layer 422.22°, and the drain region is formed by the n-type GaAs region 21.28.29. A source electrode 33, a gate t&32, and a drain electrode 31 are formed on each of the source, gate, and train regions. In this way, an upright point contact quantum effect device is formed. Although the case of a single channel is shown, it is obvious that a plurality of channels can be used.

The shape of the channel region is not particularly limited, and may be circular as shown in FIG. 3(D) or as shown in FIG. 3(E).
It is convenient to have a rectangular shape as shown in FIG. here,
By applying a reverse bias voltage to the gate region, the depletion layer is extended and the area of the effective channel region is reduced.
It is necessary to quantize the carrier levels within it. For this reason, the dimensions of the channel region are selected to allow sufficient quantization. For example, the diameter or the length of the short side is about 25,000.

Next, a method for manufacturing the vertical point contact quantum effect device as described above will be explained.

FIGS. 4(A) and 4(B) are cross-sectional views for explaining a method of manufacturing a vertical point contact quantum effect device according to an embodiment of the present invention.

1 2 First, as shown in FIG. 4(A), an n-type GaAs layer 41 is formed on a semi-insulating GaAs substrate 7 by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD).
, an n-type GaAs layer 42, and an n-type GaAs layer 43 are grown epitaxially. A photoresist layer was formed on these epitaxial layers, and a 100nm layer was formed by electron beam exposure.
A minute mask 44 is formed by exposing and developing a minute ion implantation pattern of + or less.

Next, as shown in FIG. 4(B), this minute mask 4 is
Be ions are implanted into the n-type layer 42 through the n-type layer 42.
- converting layer 42 to p+ type; Mask 4 of n-type layer 42
The part excluding the part immediately below 4 is converted to p1 area 45, and n
The type region 41 and the n-type layer 43 are connected by a minute n-type layer 42°.

In this way, a minute channel region can be formed.

For example, the n-type GaAs layer 41 has a thickness of 5,000 layers, an impurity eI degree of collapse of about 1×1018 CI11-3, and an n-type GaAs
The s layer 42 has a thickness of 500 Å and an impurity concentration of 3×10160
The n-type GaAs layer 43 has a thickness of about 2,000 cm and an impurity concentration of about 18 cm, and the p+ type ion implantation region 45 has an impurity concentration of about I x 1018 cm.
It should be about l' or more.

Although a single channel structure has been described, a multichannel structure can also be formed by providing a plurality of masks 44.

In addition, after creating the point contact quantum effect device,
Isolate each device by mesa-etching the surrounding area or implanting inert ions such as oxygen into the surrounding area.

FIGS. 5A and 5B show a method for manufacturing a vertical point contact quantum effect device according to an embodiment of the present invention.

In FIG. 5(A), on a semi-insulating GaAs substrate 7, an n-type GaAs layer 41, a p-type GaAs layer 46, an n-type GaAs
The s-layer 43 is epitaxially grown by MBE or MOCVD. That is, an npn structure is formed on the semi-insulating substrate 7.

For example, the n-type layer 41 has a thickness of 5,000 layers and an impurity concentration of about 1 x 1018 cn+-3, the p-type layer 46 has a thickness of 50 mm and an impurity concentration of about I x 1018 Cl', and the n-type layer 43 has a thickness of 2000 layers. Large, impurity concentration 1×101
It should be about 8CIll-3.

Next, as shown in FIG. 5(B), from between the surfaces of this structure, a focused ion beal (FIB)
Perform ion implantation using For example, about 100nf in diameter
A silicon ion beam focused on fl is applied to the p-type layer 4 from the surface.
Ions are implanted into the minute portion of No. 6. The Si implanted region is converted to an n-type region 48. In this way, a minute channel region can be formed. Although the case of a single channel has been described, a multi-channel structure can also be formed by performing ion implantation at multiple points using FIB.

Although the present invention has been described above based on the embodiments, the present invention is not limited thereto. For example, various changes, improvements,
It will be obvious to those skilled in the art that combinations and the like are possible.

5 [Effects of the Invention] As explained above, according to the present invention, a vertical point contact quantum effect device is provided.

This vertical point contact quantum effect device can occupy a smaller surface area than a horizontal device, and is expected to be easier to integrate.

Furthermore, since the channel region through which carriers flow is directly surrounded by a Pn junction, it is expected that control can be performed more effectively.

Further, the degree of freedom in designing various circuits together with the surface channel type Schottky gate quantum effect device is increased.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a basic embodiment of the present invention, and FIG. 2 (A
), (B), and (C) are diagrams illustrating a horizontal point contact quantum effect device according to the conventional technology, and FIG.
) is a plan view, FIG. 2(B) is a cross-sectional view, FIG. 2(C) is a graph showing characteristics, and 6 FIGS. 3(A) to (E) are vertical point contact quantum according to embodiments of the present invention. It is a figure explaining an effect device, and the third
Figure (A) is a cross-sectional view of a single-channel quantum effect device, Figure 3 (B) is a cross-sectional view of a multi-channel quantum effect device, and Figure 3 (C) is a cross-section of an upright quantum effect device. Figure, Figure 3 (D),
('E) is a plan view showing the channel shape, and FIGS. 4A and 4B are cross sections of a semiconductor structure showing two steps of a method for manufacturing a vertical point contact quantum effect device according to an embodiment of the present invention. 5A and 5B are cross-sectional views of a semiconductor structure for explaining two steps of a method for manufacturing a vertical point contact quantum effect device according to an embodiment of the present invention. Third semiconductor layer (source/drain region) Semiconductor point 1 to contact region (channel region) In the substrate diagram, 1 first semiconductor layer (source/drain region) 2 second semiconductor layer (gate region) 7 8 FIG. A) Epitaxial growth (A) Epitaxial growth and mask formation 1 (B) Ion implantation (B) Ion implantation by FIB Figure 4 Figure 5

Claims (3)

[Claims] (1), a first conductivity type semiconductor layer having a main surface (1)
and a second semiconductor layer (2) of opposite conductivity type formed on the main surface.
and a third semiconductor layer of the first conductivity type formed on the second semiconductor layer (2).
a semiconductor layer (3), formed in the second semiconductor layer (2) and in the first semiconductor layer (
1) and a third semiconductor layer (3), a vertical point contact quantum effect device comprising a semiconductor point contact region (5) of the first conductivity type having dimensions such that carrier levels are quantized. . (2) forming a second semiconductor layer (2) of an opposite conductivity type on the main surface of the first semiconductor layer (1) of one conductivity type; and forming a second semiconductor layer (2) of the first conductivity type on the second semiconductor layer (2); The third semiconductor layer of the mold (
3), and doping the impurity of the first conductivity type into a minute portion of the second semiconductor layer (2) having a dimension that allows carrier levels to be quantized; A method for manufacturing a vertical point contact quantum effect device, comprising a step of converting the conductivity type to a conductivity type and connecting the first semiconductor layer (1) and the third semiconductor layer (3) with a point contact in the same conductivity type region. (3) forming a second semiconductor layer (2) of one conductivity type with a low impurity concentration on the main surface of the first semiconductor layer (1) of one conductivity type; ) on the third semiconductor layer of the first conductivity type (
3); forming a mask on the third semiconductor layer (3) to cover a minute portion where a point contact is to be formed; and forming a mask on the second semiconductor layer (2) through the mask. a step of doping impurities of a conductivity type and converting the second semiconductor layer (2) to an opposite conductivity type except for a point contact region having dimensions in which carrier levels are quantized. Method for manufacturing an effective device.