JP2000307198A - Semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the molecular beam quantities which each cell shares so as to reduce the absolute volume of a molecular beam transition response after a shutter is opened by a method wherein material is supplied to the same material of a required layer by the use of molecular beam cells. SOLUTION: An In cell and a P cell are each formed of a single molecular beam cell, a GaInP layer is grown so as to enable its three Ga cells 1, 2, and 3 to emit a molecular beam respectively, a (Al0.5Ga0.5)0.5In0.5P layer is grown so as to enable its a Ga cell 2 and Al cells 1 and 2 to emit a molecular beam respectively, and a (Al0.7Ga0.3)0.5In0.5P layer is grown so as to enable its Ga cells 2 and 3 and an Al cell 2 to emit a molecular beam respectively. Ga cells 1 and 2 are kept at temperatures about 50 deg.C lower than those at which they are grown when (Al0.7Ga0.3)0.5In0.5P layers 13 and 17 are grown. By this setup, the ratio of Al to Ga is instantaneously changed to grow layers of different band gaps successively keeping the ratio of the sum of molecular beams of Al and Ga to a molecular beam of In constant or a lattice constant unchanged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing technique for controlling and forming a thin layer structure of a semiconductor device such as a semiconductor laser device with high precision.

[0002]

2. Description of the Related Art In recent years, semiconductor epitaxial technology has made remarkable progress, and devices utilizing high-performance semiconductor thin films have been put to practical use in various fields. In particular, it is well known that the types of thin layer structures that can be grown have increased due to the practical use of molecular beam epitaxy (MBE) and metal organic vapor deposition (MOCVD).

Above all, the MBE method is excellent in controllability of the thickness of a semiconductor thin layer, and can be controlled and formed with an accuracy of about a monolayer of constituent elements. Therefore, it is particularly advantageous for forming an element using a quantum well structure or a superlattice structure which has been attracting attention and put to practical use in recent years. For this reason, it is becoming mainstream as a thin layer forming technology for high-speed electronic devices.

On the other hand, the MBE method has many difficulties with devices having a complicated thin layer structure, for example, semiconductor lasers, due to the configuration of an apparatus utilizing an ultra-high vacuum. For this reason, the MOCVD method has become the mainstream especially for so-called lattice mismatched materials whose lattice constant changes depending on the composition, such as a red semiconductor laser. However, in the field of red lasers and the like, the use of a quantum well structure is indispensable as the performance of the device becomes higher, and the MBE method that can grow high-quality crystals at a relatively low temperature has excellent controllability of the doping concentration. There is a need for technological innovation in these areas of the MBE method. less than
The problems of the semiconductor laser based on the MBE method are described.

A conventional example of a method for manufacturing an AlGaInP-based red semiconductor laser by the MBE method will be described with reference to FIGS.

As shown in FIG. 6, an n-GaAs buffer layer 31 and an n-Ga buffer layer 31 are formed on an n-GaAs substrate 30 by molecular beam epitaxy.
_0.5 In _0.5 P layer 32, n-Al _0.5 In _0.5 P cladding layer (thickness 1 μm) 3
3, Ga _0.5 In _0.5 P active layer 34, p-Al _0.5 In _0.5 P cladding layer (thickness 1 μm) 35, p-Ga _0.5 In _0.5 P layer 36, p-GaAs cap layer 37
Grow sequentially.

In this case, the n-GaAs buffer layer 31 and the n-Ga _0.5
The growth was stopped between the In _0.5 P layer 32 and between the p-Ga _0.5 In _0.5 P layer 36 and the p-GaAs cap layer 37 for switching the group V molecular beam. However, in others, Ga _0.5 In _0.5 P and Al _0.5 In _0.5 P
Were continuously and alternately grown. The reason for this is that these layers are layers that cause laser oscillation or portions where laser light is concentrated, and when growth is stopped, deterioration in crystallinity due to desorption of phosphorus or mixing of impurities deteriorates laser characteristics. is there.

Next, FIG. 5 shows the molecular dose of each cell when growing the above-mentioned continuous growth portion. In, Al, Ga, and P cells were used one by one, and a structure without lattice mismatch could be continuously grown. In the case of growing a simple red laser as in this conventional example, there is no particular problem. However, in the case of growing three or more types of compositions, the conventional method uses a method of growing a cell used during growth. Needed to change settings or pause growth. Either of these methods causes deterioration in crystallinity that affects laser characteristics. That is, in the former case, the setting change during the growth causes instability of the lattice constant and deteriorates the reproducibility of crystallinity. In the latter case, crystallinity is degraded due to desorption of phosphorus and mixing of impurities.

Next, a conventional example of a method for growing a more complicated device structure used to solve the above problem will be described with reference to FIGS.

As shown in FIG. 8, an n-GaAs substrate 40 is provided with an MBE method.
N-GaAs buffer layer 41, n-Ga _0.5In_0.5P layer 42, n-
(Al_0.7Ga_0.3)_0.5In_0.5P clad layer (thickness 1μm) 43, (Al
_0.5Ga_{0 .Five})_0.5In_0.5P light guide layer (thickness 30 nm) 44, Ga_0.5In
_0.5P / (Al_0.5Ga_0.5)_0.5In_0.5P multiple quantum well active layer 45, (A
l_0.5Ga_0.5)_0.5In_0.5P light guide layer (thickness 30 nm) 46, p- (Al_0
.7Ga_0.3)_0.5In_0.5P clad layer (thickness 1μm) 47, p-Ga_0.5I
n_0.5A P layer 48 and a p-GaAs cap layer 49 were sequentially grown. here
In the multiple quantum well active layer, Ga_0.5In_0.5P quantum well
3 layers (8 nm thick) 45a, (Al_0.5Ga_0.5)_0.5In_0.5P barrier layer
(Thickness: 5 nm) 45b are alternately laminated in two layers.

In this case, the n-GaAs buffer layer 41 and the n-Ga _0.5
The growth is stopped between the In _0.5 P layer 42 and between the p-Ga _0.5 In _0.5 P layer 48 and the p-GaAs cap layer 49 for switching the group V molecular beam. However, in others, Ga _0.5 In _0.5 P, (Al _0.5 Ga _0.5 )
Layers of three compositions of _0.5 In _0.5 P and (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P are continuously grown. The reason is that these layers are layers that cause laser oscillation or portions where laser light is concentrated,
This is because, when the growth is stopped, deterioration of crystallinity due to desorption of phosphorus or mixing of impurities deteriorates laser characteristics.

Next, FIG. 7 shows the molecular dose of each cell when growing the above-mentioned continuous growth portion. One molecular beam cell is used for each of the In and P cells, but the Ga _0.5 In _0.5 P layer is used for the Ga1 cell, the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer is used for the Ga2 cell and the Al1 cell, and the (Al _0.5 Ga cell). _{The 0.5} ) _0.5 In _0.5 P layer is grown by setting the Ga3 cell and the Al2 cell to emit respective molecular beams.
Therefore, three Ga cells and two Al cells are used.

Thus, the sum of the molecular beams of Al and Ga and In
While the ratio of the molecular beams is kept constant, that is, while the lattice constant is kept constant, the ratio of Al to Ga can be changed instantaneously to continuously grow layers having different band gaps. in this way,
By supplying a molecular beam corresponding to each composition from another molecular beam cell, each composition can be continuously grown even when a device including layers of various compositions is grown.

[0014]

The problems in the above-mentioned improved prior art are listed below. The first problem is
For example, when continuously growing the multiple quantum well active layer 45 in FIGS. 7 and 8, the composition is changed by opening and closing the Ga1 molecular beam cell, the Ga3 molecular beam cell and the Al2 molecular beam cell. But,
The molecular beam intensity when the shutter is opened has a certain transient fluctuation. This is because when the shutter is closed, the heat radiation inside the cell is reflected by the shutter and raises the temperature of the material surface, whereas the reflection of the heat radiation disappears immediately after the shutter is opened, so that the material surface temperature sharply increases. Is to be reduced. The fluctuation of the molecular beam intensity at this time depends on the size of the cell,
Although it depends on the material filling amount, it is often about 10%. In particular, the value is large in a mass production MBE apparatus in which a large material cell needs to be filled with a large amount of material.

This problem is particularly significant in a so-called lattice mismatched material such as an AlGaInP system in which the lattice constant changes depending on the composition. This is because the composition shift due to the transient response of the molecular beam causes crystal transition due to lattice mismatch.

[0016] In addition, a large problem arises when a structure having a layer thickness smaller than the de Broglie wavelength of the carrier, such as a quantum well structure or a superlattice structure, is produced.

This is because the transient response of the molecular beam causes not only the fluctuation of the band gap but also the fluctuation of the growth rate, which makes it difficult to control the thickness of the thin layer which is important in such a structure.

As a second problem, in the conventional example, since the molecular dose of each cell is set to a value corresponding to the composition of each layer even when the shutter is closed, the material necessary for effective growth is set. May consume significantly more material than quantity.
In order to solve this problem, a method of using the same cell in non-adjacent layers and changing the cell temperature during the time during which those layers are grown is also used, but when the composition of each layer is significantly different, A third problem arises in that the value of the temperature change is large and the cell temperature in the layer after the change is not sufficiently stabilized.

The fourth problem is that, as described above, even when the shutter is closed, the molecular dose of each cell is set to a value corresponding to the composition of each layer. May cause an increase in the frequency of replacement of the shutter, scattering of material clusters attached to the shutter, and an increase in surface defects of the grown layer.

The present invention has been made to solve the above-mentioned problems, and the ratio of the molecular beam transient response after the shutter is opened cannot be largely changed because the molecular dose shared by each cell is low. However, the purpose is to drastically reduce the absolute amount.

It is another object of the present invention to reduce the set amount of the molecular beam and improve the stability of the molecular beam when the setting is changed.

[0022]

According to a method of manufacturing a semiconductor device according to the present invention (claim 1), when a plurality of layers are stacked by a molecular beam epitaxial growth method to manufacture a semiconductor device, the same layer as a desired layer is formed. The above object is achieved by supplying a raw material to a material by using a plurality of molecular beam cells.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the first aspect, wherein the plurality of layers have a substantially constant lattice constant and a band gap. The above-mentioned object is achieved by forming these layers in a continuous manner.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to the first aspect, wherein the plurality of layers include multi-element mixed crystal layers having different compositions. The above object is attained by the fact that the multi-element mixed crystal layer is a lattice-mismatched system in which the lattice constant is largely different depending on the composition so as to cause lattice mismatch.

A method of manufacturing a semiconductor device according to the present invention (claim 4) is the method of manufacturing a semiconductor device according to any one of claims 1 to 3, wherein the composition is determined for each layer having a different composition. The above object is achieved by using different numbers of molecular beam cells of the same material.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to any one of the first to fourth aspects, wherein layers having different compositions and not adjacent to each other are formed. The above object is achieved by using the same molecular beam cell when forming.

A method of manufacturing a semiconductor device according to the present invention (claim 6) is the method of manufacturing a semiconductor device according to claim 5, wherein the same molecular beam is formed while forming adjacent layers. The above object is achieved by changing the molecular dose emitted by the cell per unit time.

A method of manufacturing a semiconductor device according to the present invention (claim 7) is the method of manufacturing a semiconductor device according to any one of claims 1 to 6, wherein the temperature of the molecular beam cell in a standby state is set to The above object is achieved by being lower than in use.

In the semiconductor device according to the present invention (claim 8), the thickness of the layer formed by the method for manufacturing a semiconductor device according to any one of claims 1 to 7 is smaller than the de Broglie wavelength of the current carrier. Thereby, the above object is achieved.

That is, in order to solve the above first, second and fourth problems, when a plurality of multi-element mixed crystal layers are grown by the molecular beam epitaxy method, all or some of the layers are grown. The first numerator in total per unit time
A single or a plurality of first molecular beam cells that emit the same molecular dose and a single or a plurality of second molecular beam cells that emit the second molecules by the total second molecular dose are simultaneously operated. A first mixed crystal layer in which the composition ratio of the first molecule to the second molecule is (first molecular dose / second molecular dose), A single or a plurality of first and / or multiple different numbers from the first step of firing the third molecular dose in total
And a first step of firing a second molecule by a fourth molecular dose in total is a single or multiple second
Are simultaneously operated to produce a second mixed crystal layer in which the composition ratio of the first molecule to the second molecule is (third molecular dose / fourth molecular dose).

As means for solving the second and fourth problems, the cell temperature of the molecular beam cell is set lower in the step where the molecular beam is not emitted than in the step where the molecular beam is emitted. In order to solve the third problem, when a plurality of non-adjacent layers are manufactured in combination with the above-described means,
Using the same molecular beam cell that launches the same type of molecular beam,
While the layers between the non-adjacent layers are being grown, the molecular beam emitted by the molecular beam cell per unit time is changed to produce the adjacent layers.

Hereinafter, the operation of the present invention will be described.

When the above means is used, the ratio of the molecular beam transient response after opening the shutter is not largely changed, but the absolute amount is drastically reduced because the molecular dose shared by each cell is low.

Further, since the set amount of the molecular beam is reduced, the stability of the molecular beam when the setting is changed is improved.

[0035]

<Embodiment 1> Embodiment 1 of a method for manufacturing a red semiconductor laser device according to the present invention will be described with reference to FIGS.
Will be described.

As shown in FIG. 2, an MBE method is formed on an n-GaAs substrate 10.
N-GaAs buffer layer 11, n-Ga _0.5In_0.5P layer 12, n-
(Al_0.7Ga_0.3)_0.5In_0.5P clad layer (thickness 1μm) 13, (Al
_0.5Ga_{0 .Five})_0.5In_0.5P light guide layer (50 nm thick) 14, Ga_0.6In
_0.4P / (Al_0.5Ga_0.5)_0.5In_0.5P multiple quantum well active layer 15, (A
l_0.5Ga_0.5)_0.5In_0.5P light guide layer (thickness: 50 nm) 16, p- (Al_0
.7Ga_0.3)_0.5In_0.5P clad layer (thickness 1μm) 17, p-Ga_0.5I
n_0.5A P layer 18 and a p-GaAs cap layer 19 were sequentially grown. here
In the multiple quantum well active layer, Ga_0.6In_0.4P quantum well
5 layers (thickness: 5 nm) 15a, (Al_0.5Ga_0.5)_0.5In_0.5P barrier layer
(Thickness: 5 nm) 15b are alternately laminated in four layers.

In this embodiment, the n-GaAs buffer layer 11 and n
Although during -ga _0.5 an In _0.5 between the P layer 12 and the p-Ga _0.5 In _{0 .5} P layer 18 and the p-GaAs cap layer 19 has suspended growth for switching the group V molecular beams, in other is Ga _0.5 In _0.5 P, Ga _0.6 In
_0.4 P, (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P, (Al _0.7 Ga _0.3 ) _0.5 In _0.5
Layers having four compositions of P were continuously grown.

Next, FIG. 1 shows the molecular dose of each cell when growing the above-mentioned continuous growth portion, and FIG. 9 shows the transition of the cell temperature at that time. While In and P cells, respectively using molecular beam cells one by one, Ga _0.5 In _0.5 P layer Ga1,
Two or three Ga cells, (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P layer,
Two Al cells of the cell and _{Al1,2, (Al 0.7 Ga 0.3)} 0.5 In 0.5 P
The layers were grown with two Ga cells, Ga2 and 3, and an Al2 cell set to emit their respective molecular beams. Ga1 and Ga2
During growth of the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layers 13 and 17, the cell temperature was set to be about 50 ° C. lower than during the growth. In this example, three Ga cells and two Al cells were used.

In this way, the sum of the molecular beams of Al and Ga and In
While the ratio of the molecular beams was kept constant, that is, while the lattice constant was kept constant, Al was changed in the ratio of Ga instantaneously, and layers having different band gaps could be continuously grown.

As in this embodiment, the supply of the raw material for the same material in the desired layer is performed using a plurality of molecular beam cells, so that the absolute amount of the transient response of the molecular beam intensity when the shutter is opened can be reduced. Could be reduced. In a lattice-mismatched system in which the lattice constant fluctuates depending on the composition as in the present embodiment, when the composition fluctuates greatly due to the transient response, the characteristics of the device are significantly degraded due to the occurrence of crystal dislocation and the like. This problem was solved by applying this embodiment. In particular, in a quantum well active layer having a small layer thickness of 5 nm, the transient response of a molecular beam has a large effect because it causes a change in composition and a change in growth rate.
According to the present embodiment, the structure was stabilized, and the controllability of the oscillation wavelength of the device could be remarkably improved.

Further, since one layer is grown using a plurality of molecular beam cells, the set molecular beam intensity of each cell can be reduced to the minimum, so that the material consumption can be reduced, and Material adhesion was also reduced. Further, this effect is more remarkable by lowering the temperature of the Ga1 and 2 cells in the 13th and 17th layers and making them stand by. After waiting at a low temperature, it is necessary to raise the cell temperature to the growth temperature before using the cell. At the time of standby, the above effect can be remarkable if the cell temperature is sufficiently low. However, if the cell temperature is too low compared to the use temperature at the time of subsequent growth, it takes time to stabilize the temperature after the temperature is raised again. The waiting time is short and the effect is small. However, in this embodiment, the set temperature of each cell is 50 times smaller than that of the above-described improved conventional example.
Since the temperature was low by about ° C, this adverse effect could be reduced. <Embodiment 2> In the above-described embodiment 1, three Ga cells were used.
A complex laser structure can be precisely manufactured with one Ga cell. The second embodiment will be described below with reference to FIGS.

As shown in FIG. 4, an MBE method is formed on an n-GaAs substrate 20.
Buffer layer 21, n-Ga _0.5In_0.5P layer 22, n-
(Al_0.7Ga_0.3)_0.5In_0.5P clad layer (thickness 1μm) 23, (Al
_0.5Ga_{0 .Five})_0.5In_0.5P light guide layer (50 nm thick) 24, Ga_0.6In
_0.4P / (Al_0.5Ga_0.5)_0.5In_0.5P multiple quantum well active layer 25, (A
l_0.5Ga_0.5)_0.5In_0.5P light guide layer (50 nm thick) 26, p- (Al_0
.7Ga_0.3)_0.5In_0.5P clad layer (1μm thickness) 27, p-Ga_0.5I
n_0.5A P layer 28 and a p-GaAs cap layer 29 were sequentially grown. here
In the multiple quantum well active layer, Ga_0.6In_0.4P quantum well
5 layers (thickness 5 nm) 25a, (Al_0.5Ga_0.5)_0.5In_0.5P barrier layer
(Thickness: 5 nm) 25b are alternately laminated in four layers.

In this embodiment, the n-GaAs buffer layer 21
And n-Ga _0.5 In _0.5 P layer 22 and p-Ga _0.5 In _0.5 P layer 28 and p-GaAs
Growth was suspended between the cap layers 29 to switch the group V molecular beam, but Ga _0.5 In _0.5 P, Ga _0.6 In
_0.4 P, (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P, (Al _0.7 Ga _0.3 ) _0.5 In _0.5
Layers having four compositions of P were continuously grown.

Next, FIG. 3 shows the molecular dose of each cell when growing the above continuous growth portion. One molecular beam cell was used for each of the In and P cells, but the Ga _0.5 In _0.5 P layer was replaced with two Ga cells, Ga1 and 2, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P
The layer is a Ga1 cell and two Al cells Al1 and 2, (Al _0.5 G
The a _0.5 ) _0.5 In _0.5 P layer was grown with a Ga2 cell and an Al1 cell, and the Ga _0.6 In _0.4 P layer was grown with two Ga cells, Ga1 and 2, each emitting a molecular beam.

During the growth of the (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P layer, the setting of Ga1 was changed so that a required molecular dose was emitted in the next growth layer. Similarly, during the growth of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, the setting of Ga 2 was changed so that the required molecular dose would be emitted in the next growth layer. So in this case, two G
An a cell and two Al cells were used.

Thus, the sum of the molecular beams of Al and Ga and In
With the molecular beam ratio kept constant, that is, while the lattice constant was kept constant, the layers with different band gaps could be continuously grown by instantaneously changing the ratio of Al to Ga. Where Ga
_The lattice constant of the _0.6 In _0.4 P layer is about 1% smaller than that of the GaAs substrate. As a result, the laser oscillation wavelength can be made shorter, but also in this case, continuous growth is possible while keeping the flux of In and P constant. When such lattice strain is intentionally introduced, the controllability of the composition requires extremely high precision. Therefore, the effect of reducing the influence of the molecular beam transient response of the present invention is particularly useful.

In this embodiment, each layer, particularly the active layer 2
Since the set temperature of the Ga1 cell at 5a can be lowered by about 50 ° C. as compared with the conventional example, the temperature difference for changing the cell setting at the time of standby at the layers 24 and 26 is small. In the conventional example, when the setting was changed between thin layers such as the layers 24 and 26, the Ga cell temperature in the active layer 25a was not stabilized, and the controllability of the composition was poor. Could be avoided.

This embodiment is extremely important for practical use in the MBE method in which the number of cells that can be mounted in the growth chamber is limited.
This embodiment is applicable when a more complicated multilayer structure is manufactured.

[0049]

According to the present invention, MBE, which was conventionally difficult,
The precise composition control at the time of the growth of the complicated multilayer film by the method became possible. This facilitated the growth of a semiconductor laser having a very complicated structure, such as a laser having a SCH quantum well active layer in a lattice mismatched system.

When the present invention is used, the degree of freedom of the multilayer structure becomes extremely large, and a complicated superlattice structure or a structure in which lattice mismatch is intentionally introduced can be easily manufactured. Was. Further, according to the present invention, the amount of material consumption can be reduced, and the amount of unnecessary material attached to the cell shutter can be reduced, so that stable growth can be realized for a long period of time.

[Brief description of the drawings]

FIG. 1 is a diagram showing the molecular dose of each cell in each growth layer of Example 1 of the present invention.

FIG. 2 is a sectional view of a growth layer of the laser structure according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a molecular dose of each cell in each growth layer of Example 2 of the present invention.

FIG. 4 is a diagram showing a cross-sectional view of a growth layer of a laser structure according to Example 2 of the present invention.

FIG. 5 is a diagram showing the molecular dose of each cell in each growth layer of the conventional example.

FIG. 6 is a sectional view of a growth layer of a conventional laser structure.

FIG. 7 is a diagram showing the molecular dose of each cell in each growth layer of another conventional example.

FIG. 8 is a cross-sectional view of a growth layer of another conventional laser structure.

FIG. 9 is a diagram illustrating a temperature transition of a Ga1 cell temperature in each growth layer according to the first embodiment of the present invention.

Claims (8)

[Claims] When manufacturing a semiconductor device by stacking a plurality of layers by a molecular beam epitaxial growth method, a plurality of molecular beam cells are used to supply a raw material for the same material of a desired layer. Semiconductor device manufacturing method. 2. The semiconductor device according to claim 1, wherein the plurality of layers include layers having substantially constant lattice constants and different band gaps, and are formed continuously. Manufacturing method. 3. The lattice-mismatched system according to claim 1, wherein the plurality of layers include a multi-element mixed crystal layer having a different composition, and the multi-element mixed crystal layers differ greatly in lattice constant depending on the composition to such an extent that a lattice mismatch occurs. The method according to claim 1, wherein: 4. The method for manufacturing a semiconductor device according to claim 1, wherein the number of molecular beam cells of the same material that determines the composition is different for each layer having a different composition. A method for manufacturing a semiconductor device, comprising: 5. The method for manufacturing a semiconductor device according to claim 1, wherein the same molecular beam cell is used when forming layers having different compositions and not adjacent to each other. A method for manufacturing a semiconductor device, comprising: 6. The method for manufacturing a semiconductor device according to claim 5, wherein a molecular dose emitted by the same molecular beam cell per unit time is changed while forming adjacent layers. A method of manufacturing a semiconductor device. 7. The method for manufacturing a semiconductor device according to claim 1, wherein a temperature of the molecular beam cell in a standby state is lower than that in a use state of the cell. Semiconductor device manufacturing method. 8. The semiconductor device according to claim 1, wherein the layer formed by the method for manufacturing a semiconductor device according to claim 1 has a thickness smaller than a de Broglie wavelength of a current carrier.