JP2004247431A - Quantum semiconductor device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quantum semiconductor device and a method of manufacturing the same device in which the electrical access to the quantum dot is made accurately. <P>SOLUTION: The quantum semiconductor device comprises a quantum dot 12 formed over a semiconductor substrate 10, a semiconductor layer 18 formed to embed the quantum dot 12, and an electrode 22 formed at the area over the quantum dot 12 over the surface of the semiconductor layer 18 due to a stress generated to the semiconductor layer 18 because of existence the quantum dot 12. Accordingly, electrical access is made accurately to the quantum dot 12, and moreover independent electrical access is also made to the quantum dot 12. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a quantum semiconductor device and a method for manufacturing the same, and more particularly, to a quantum semiconductor device having quantum dots and a method for manufacturing the same.
[0002]
[Prior art]
The quantum dots are formed in an island shape apart from each other on a semiconductor substrate, for example, by a formation method using a Transki-Krastanow mode (SK mode). Here, the SK mode is a mode in which a semiconductor crystal to be epitaxially grown grows two-dimensionally (film growth) at the beginning of growth, but grows three-dimensionally at a stage beyond the elastic limit of the film. . By epitaxially growing a film having a different lattice constant from that of the underlying material, quantum dots composed of three-dimensionally grown islands are self-formed.
[0003]
Recently, technologies in the field of quantum information and quantum computation have received a great deal of attention, and the possibility of applying quantum dots has attracted attention. However, for further basic research and application development on quantum dots, there are various technical barriers to overcome.
[0004]
For example, quantum dots are small in size, and quantum dots self-formed using the SK mode are randomly distributed. Until now, no method has been proposed that enables accurate electrical access to each of the self-formed quantum dots in such a randomly dispersed state.
[0005]
On the other hand, by using a process capable of processing in a submicron such as electron beam lithography and reactive ion etching, it is possible to manufacture a conductive pad having a size of about 100 nm. Thus, if the density of the quantum dots is very low, it is possible that such a process could be used to form an electrode on a single quantum dot. That is, an electrode is appropriately formed on a region where a quantum dot will be formed, using a process capable of processing at a submicron. Next, it is checked whether or not quantum dots exist under the electrodes. Thus, by repeating the electrode formation and subsequent checks many times, it may be possible to find the case where a single quantum dot exists under the electrode. However, with such a method, it is almost impossible to capture a single quantum dot when the density of the quantum dots is high. Further, such a stochastic method can be said to be an inefficient method in manufacturing an element.
[0006]
Patent Document 1 proposes a method for electrically accessing quantum dots using an electrode having a fine probe shape. However, in this case, in order to arrange the electrodes on the quantum dots, a special process such as forming the quantum dots in an array state is required. Further, in Patent Document 1, it is considered that the electric field due to the needle-shaped electrode is distributed far more widely than the size of the quantum dot. For this reason, it is assumed that an electric field generated by an electrode arranged on a certain quantum dot affects adjacent quantum dots.
[0007]
[Patent Document 1]
JP-A-7-297381
[0008]
[Problems to be solved by the invention]
As described above, in the related art, no method has been established that enables accurate electrical access to each of the self-formed quantum dots in a randomly dispersed state.
[0009]
Achieving accurate electrical access to each self-formed quantum dot is very important in various aspects of basic research, application development, and the like regarding quantum dots.
[0010]
An object of the present invention is to provide a quantum semiconductor device and a method for manufacturing the same, which enable accurate electrical access to quantum dots.
[0011]
[Means for Solving the Problems]
The object is to form a quantum dot formed on a semiconductor substrate, a semiconductor layer formed so as to embed the quantum dot, and a semiconductor layer formed in a self-aligned manner on a position of a strain generated in the semiconductor layer due to the presence of the quantum dot. The quantum semiconductor device is characterized in that the quantum semiconductor device comprises: As a result, the electrodes can be accurately formed on the quantum dots, so that it is possible to accurately and electrically access the quantum dots via the electrodes. And can be electrically accessed.
[0012]
Further, the object is to form a quantum dot formed on a semiconductor substrate, a semiconductor layer formed so as to embed the quantum dot, and a semiconductor layer formed in a recess formed at a position on the quantum dot on the surface of the semiconductor layer. The quantum semiconductor device is characterized in that the quantum semiconductor device comprises: As a result, the electrodes can be accurately formed on the quantum dots, so that it is possible to accurately and electrically access the quantum dots via the electrodes. And can be electrically accessed.
[0013]
Further, the object is to form a quantum dot formed on a semiconductor substrate, a first semiconductor layer formed so as to embed the quantum dot, and a quantum dot formed at a position on the quantum dot on the first semiconductor layer. Semiconductor dots, a dot-shaped oxide formed by oxidizing a part of the semiconductor dots, a second semiconductor layer formed so as to embed the semiconductor dots, and the second semiconductor layer surface And an electrode formed in a recess formed at a position on the dot-shaped oxide.
[0014]
Further, the object is to form a quantum dot on a semiconductor substrate, a step of forming a semiconductor layer so as to embed the quantum dot, and a step of forming a semiconductor layer in the semiconductor layer due to the presence of the quantum dot. Forming the electrodes in a self-aligned manner.
[0015]
Further, the above object is to form a quantum dot on a semiconductor substrate, a step of forming a semiconductor layer so as to embed the quantum dot, and to form a semiconductor dot at a position on the quantum dot on the semiconductor layer. Forming, and oxidizing the semiconductor dots and the semiconductor layer immediately below the semiconductor dots to form a dot-shaped oxide partly embedded in the semiconductor layer; Forming a concave portion on the surface of the semiconductor layer by removing an oxide of the semiconductor layer, and forming an electrode in the concave portion formed on the surface of the semiconductor layer. This is achieved by a manufacturing method.
[0016]
Further, the object is to form a quantum dot on a semiconductor substrate, to form a first semiconductor layer so as to embed the quantum dot, and to form a first semiconductor layer on the first semiconductor layer. Forming a dot-shaped oxide by oxidizing a part of the semiconductor dot by oxidizing a part of the semiconductor dot at the position; and forming the dot-shaped oxide by oxidizing a part of the semiconductor dot. Forming a second semiconductor layer for embedding the dot-shaped oxide and the semiconductor dots so that a concave portion is formed on the surface at a position on the object; and forming the second semiconductor layer on the surface of the second semiconductor layer. Forming an electrode in the concave portion.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
The quantum semiconductor device and the method for fabricating the quantum semiconductor device according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing the structure of the quantum semiconductor device according to the present embodiment, FIG. 2 is a diagram showing the energy band structure of the quantum semiconductor device according to the present embodiment, and FIG. 3 shows the method for manufacturing the quantum semiconductor device according to the present embodiment. It is a process sectional view.
[0018]
First, the structure of the quantum semiconductor device according to the present embodiment will be explained with reference to FIG.
[0019]
On the semiconductor substrate 10, a quantum dot layer 14 made of a semiconductor including the self-formed quantum dots 12 is formed. The quantum dot layer 14 is composed of a quantum dot 12 composed of a three-dimensional growth island self-formed in the SK mode on the semiconductor substrate 10 and a wetting layer 16 formed on the semiconductor substrate 10 between the quantum dots 12. It is configured.
[0020]
On the quantum dot layer 16, a cap layer, that is, a semiconductor layer 18 is formed. The semiconductor layer 18 on the quantum dot 12 is distorted due to a lattice mismatch between the material of the quantum dot 12 and the material of the semiconductor layer 18. In FIG. 1, a region of the semiconductor layer 18 where distortion occurs is indicated by a dotted line.
[0021]
A granular electrode 22 made of metal is formed on the surface of the semiconductor layer 18 where the strain is generated.
[0022]
In the quantum semiconductor device according to the present embodiment, the electrode 22 is formed in a position where the surface of the semiconductor layer 18 is distorted in a self-aligned manner, that is, a granular electrode made of metal is formed on each quantum dot 12. The main feature is that 22 is formed accurately.
[0023]
As described above, since the electrode 22 is accurately formed on each quantum dot 12 due to the strain generated in the semiconductor layer 18 on the quantum dot 12, the self-formed quantum dot 12 is formed via the electrode 22. Can be accurately electrically accessed. Further, it is possible to electrically access the self-formed quantum dots 12 independently of each other.
[0024]
The energy band structure of the quantum semiconductor device according to the present embodiment is as shown in FIG.
[0025]
Next, the method for fabricating the quantum semiconductor device according to the present embodiment will be explained with reference to FIG.
[0026]
First, the quantum dot layer 14 is formed on the semiconductor substrate 10 by, for example, MBE (Molecular Beam Epitaxy). The quantum dots 12 are self-formed in the quantum dot layer 14 in the SK mode (see FIG. 3A). As a material of the quantum dot layer 14, a material having a different lattice constant from the material of the semiconductor substrate 10 and having a large lattice mismatch is used. For example, when a GaAs substrate is used as the semiconductor substrate 10, for example, InAs can be used as a material of the quantum dot layer 14.
[0027]
Next, the semiconductor layer 18 is formed on the quantum dot layer 14 by, for example, the MBE method (see FIG. 3B). As the material of the semiconductor layer 18, for example, a material having a different lattice constant from the material of the quantum dot layer 14 and having a large lattice mismatch is used. When InAs is used as the material of the quantum dot layer 14, for example, GaAs can be used as the material of the semiconductor layer 18.
[0028]
The semiconductor layer 18 on the quantum dots 12 is distorted due to lattice mismatch with the quantum dots 12.
[0029]
It is desirable that the semiconductor layer 18 be formed relatively thin so that the surface thereof is sufficiently distorted. For example, when the upper end of the quantum dot 12 is filled with the semiconductor layer 18, the growth of the semiconductor layer 18 by the MBE method is stopped. The thickness of the semiconductor layer 18 is, for example, 10 nm or less, and more desirably 5 nm or less. The reason why the semiconductor layer 18 should be formed thinner will be described in detail.
[0030]
Next, a metal droplet is deposited on the surface of the semiconductor layer 18 by a droplet epitaxy method to form a granular electrode 22 made of metal. Here, the droplet epitaxy method is a technique for growing fine particles by depositing evaporated metal atoms and molecules on a surface of a material having a lower surface energy than a metal such as an insulator or a semiconductor. That is. In this method, since an action of minimizing the energy of the system occurs, the metal grows into a fine spherical shape so as to minimize the surface area of an insulator or a semiconductor. As a material of the electrode 22, Ga, In, Al, Au, or an alloy thereof can be used.
[0031]
The electrode 22 can be formed in a continuous process after the formation of the semiconductor layer 18 in the epitaxial growth chamber of the film forming apparatus used for forming the semiconductor layer 18.
[0032]
When the semiconductor layer 18 and the electrode 22 are formed in a continuous process, after the formation of the semiconductor layer 18 by the MBE method in the epitaxial growth chamber, the deposition of the semiconductor as the material of the semiconductor layer 18 is stopped.
[0033]
For example, when a group III-V semiconductor is deposited to form the semiconductor layer 18, the supply of the group V element into the epitaxial growth chamber is stopped.
[0034]
By stopping the supply of the group V element, only the metal beam of the group III element is irradiated on the surface of the semiconductor layer 18, and the metal droplet of the group III element is deposited on the surface of the semiconductor layer 18.
[0035]
The metal droplet deposited on the surface of the semiconductor layer 18 by the droplet epitaxy moves to the position of the strain generated on the surface of the semiconductor layer 18.
[0036]
Subsequently, the metal droplet is solidified by cooling after the deposition of the metal droplet is completed, and metal particles are formed. Thus, the granular electrode 22 made of metal is accurately formed at the position where the strain on the surface of the semiconductor layer 18 is generated, that is, on the surface of the semiconductor layer 18 above each of the quantum dots 12 embedded in the semiconductor layer 18. That is, the electrode 22 is formed in a self-aligned manner on the position of the strain generated in the semiconductor layer 18 due to the presence of the quantum dot 12.
[0037]
Conditions for forming the electrode 22 by the droplet epitaxy method may be, for example, as follows. The following conditions are for the case where a GaAs substrate is used as the semiconductor substrate 10.
[0038]
The As partial pressure in the epitaxial growth chamber is, for example, 10 ^-7 The size should be negligible, such as Torr. When depositing In or Ga as a metal droplet, the substrate temperature is, for example, 100 to 200 ° C. When depositing Al as a metal droplet, the substrate temperature is set to, for example, 300 to 400 ° C. The deposition rate is, for example, 0.5 to 3 atomic layers / second, and the total deposition amount is, for example, 1 to 4 atomic layers.
[0039]
The electrode 22 can be set to a desired size in accordance with the size of the quantum dots 12 by appropriately setting conditions for depositing the metal droplets such as the deposition amount.
[0040]
Here, the mechanism by which the granular electrode 22 made of metal formed by the droplet epitaxy method as described above is accurately formed at a position on the quantum dot 12 on the surface of the semiconductor layer 18 will be described.
[0041]
In general, in the droplet epitaxy method described above, it is known that the position of the metal droplet deposited on the surface depends on the surface free energy distribution during the droplet epitaxy process of the surface on which the metal droplet is deposited. Have been.
[0042]
For example, if the surface is treated uniformly, the metal droplets are deposited on the surface in a random arrangement.
[0043]
On the other hand, when the surface state is locally modified, the metal droplet is deposited on a region where the surface state is intentionally modified. When the surface state is locally modified, for example, the surface is locally passivated, locally deposited with impurities, patterned, or locally applied with an electric field. (For example, US Pat. No. 6,383,286, US Pat. No. 6,242,326, US Pat. No. 6,033,972, 245620, JP-A-2000-315654 and the like).
[0044]
In the method for manufacturing the quantum semiconductor device according to the present embodiment, the semiconductor layer 18 is formed thin on the quantum dot layer 14. For this reason, a strain occurs in the semiconductor layer 18 on each quantum dot 12.
[0045]
The portion of the surface of the semiconductor layer 18 where the strain is generated has a higher surface energy than the portion where the strain is not generated. For this reason, metal droplets formed by the droplet epitaxy method are selectively deposited at positions on the quantum dots 12 on the surface of the semiconductor layer 18 where distortion has occurred.
[0046]
As described above, it is desirable to form the semiconductor layer 18 as thin as possible for the following reasons. That is, if the semiconductor layer 18 is formed thicker than the height of the quantum dots 12, sufficient distortion does not occur on the surface of the semiconductor layer 18. For this reason, the surface energy of the portion on the quantum dots 12 on the surface of the semiconductor layer 18 does not largely change from that of other portions, and it is difficult to selectively form metal droplets.
[0047]
As described above, the granular electrode 22 made of metal is accurately formed on the surface of the semiconductor layer 18 on each of the self-formed quantum dots 12 by the droplet epitaxy method.
[0048]
Thus, the quantum semiconductor device according to the present embodiment is manufactured.
[0049]
As described above, according to the present embodiment, due to the strain generated in the semiconductor layer 18 on the quantum dots 12, the granular electrodes 22 made of metal formed by the droplet epitaxy method are positioned on the respective quantum dots 12. Can be accurately formed. This makes it possible to accurately and electrically access the quantum dots 12. In addition, it is possible to electrically access the quantum dots 12 independently of each other.
[0050]
(Modification)
Next, a quantum semiconductor device according to a modification of the present embodiment and a method for manufacturing the same will be described with reference to FIGS. FIG. 4 is a cross-sectional view showing the structure of the quantum semiconductor device according to the present modification, FIG. 5 is a process cross-sectional view showing a method of manufacturing the quantum semiconductor device according to the present modification, and FIG. FIG.
[0051]
First, the structure of the quantum semiconductor device according to the present modification will be described with reference to FIG.
[0052]
The main feature of the quantum semiconductor device according to the present modification is that a wiring 26 electrically connected to the electrode 22 is formed together with the electrode 22.
[0053]
As shown in FIG. 4, a groove 24 is formed on the surface of the semiconductor layer 18. One end of the groove 24 is located in the vicinity of the electrode 22 precisely formed on the surface of the semiconductor layer 18 on the quantum dot 12.
[0054]
In the groove 24, a wiring 26 electrically connected to the electrode 22 is formed.
[0055]
As described above, since the quantum semiconductor device according to the present modification has the wiring 26 electrically connected to the electrode 22, the peripheral circuit for applying a voltage to the quantum dot 12 and the electrode 22 are connected to each other. Electrical connection can be made via the wiring 26. This further facilitates electrical access to the quantum dots 12.
[0056]
Next, a method for manufacturing a quantum semiconductor device according to the present modification will be described with reference to FIGS.
[0057]
3A and 3B, the quantum dot layer 14 and the semiconductor layer 18 are sequentially formed on the semiconductor substrate 10.
[0058]
Next, a semiconductor dot layer 38 is formed on the semiconductor layer 18 by, for example, the MBE method. By epitaxially growing the semiconductor dot layer 38, the semiconductor dots 36 formed of three-dimensionally grown islands are self-formed in the SK mode (see FIG. 5A). The semiconductor dot layer 38 formed here is composed of the semiconductor dots 36 self-formed on the semiconductor layer 18 and the wetting layer 40 formed on the semiconductor layer 18 between the semiconductor dots 36. The semiconductor dots 36 may be quantum dots or antidots. As the material of the semiconductor dot layer 38, a material having a different lattice constant from the material of the semiconductor layer 18 and having a large lattice mismatch is used. For example, when InGaAs is used as the material of the quantum dot layer 14 and GaAs is used as the material of the semiconductor layer 18, AlInAs can be used as the material of the semiconductor dot layer 38.
[0059]
As described above, the semiconductor dots 36 of the semiconductor dot layer 38 laminated and formed in the SK mode on the quantum dot layer 14 via the semiconductor layer 18 are formed on the quantum dots 12 of the quantum dot layer 14. . That is, the positions of the quantum dots 12 in the first quantum dot layer 14 and the positions of the semiconductor dots 36 in the second semiconductor dot layer 38 are aligned in the vertical direction. As described above, the quantum dots 12 and the semiconductor dots 36 are formed so as to overlap each other because, when the semiconductor dot layer is formed on the quantum dot layer on which the quantum dots are formed, the quantum dots overlap with the quantum dots in the semiconductor dot layer. This is because semiconductor dots, which are quantum dots or antidots, tend to be formed.
[0060]
Next, the wetting layer 40 of the semiconductor dot layer 38 and the surface layer of the semiconductor layer 18 are oxidized by using an AFM (Atomic Force Microscope) oxidation method, thereby forming the linear oxide 28. Here, the linear oxide 28 is formed such that one end of the linear oxide 28 is located at a position near the semiconductor dot 36 formed on the quantum dot 12.
[0061]
The AFM oxidation method is a method in which an AFM probe is brought close to a sample, and a voltage is applied between the AFM probe and the sample to form an oxide on the surface of the sample.
[0062]
In the present modification, for example, in the atmosphere of a humidity of 40 to 60%, the probe 30 of the AFM is brought close to the wetting layer 40 of the semiconductor dot layer 38, a negative bias is applied to the probe 30, and the semiconductor substrate 10 is Apply a positive bias. The probe 30 is scanned in a state of being close to the wetting layer 40 while applying a bias as described above. The probe 30 scans a line on the surface of the wetting layer 40 where the linear oxide 28 is to be formed. Thereby, the wetting layer 40 of the semiconductor dot layer 38 and the surface layer of the semiconductor layer 18 scanned by the probe 30 are oxidized to form the linear oxide 28 (see FIG. 5B).
[0063]
Next, the semiconductor dots 36 and the wetting layer 40 of the semiconductor dot layer 38 and the linear oxide 28 are removed by etching. Thus, the groove 24 is formed on the surface of the semiconductor layer 18 from which the semiconductor dots 36, the wetting layer 40, and the linear oxide 28 have been removed (see FIG. 5C). For example, in the case of the semiconductor dot layer 38 made of InAs, by using HCl as an etchant, the semiconductor dots 36 and the wetting layer 40 and the linear oxide 28 can be removed at the same time.
[0064]
Next, similarly to the above, a metal droplet is deposited on the surface of the semiconductor layer 18 by the droplet epitaxy method. At this time, the metal droplet is formed in the position where the surface of the semiconductor layer 18 is distorted, and is formed in the groove 24.
[0065]
Subsequently, by cooling after the end of the deposition, the metal droplets are solidified and metal particles are formed. In this manner, the wiring 26 formed by continuously connecting the metal particles in the groove 24 is formed together with the granular electrode 22 made of metal (see FIG. 5D).
[0066]
Thus, the quantum semiconductor device according to the present modification is manufactured.
[0067]
After that, as shown in FIG. 6, an electrode pad 32 electrically connected to the wiring 26 may be formed.
[0068]
[Second embodiment]
The quantum semiconductor device according to the second embodiment of the present invention and the method for fabricating the same will be described with reference to FIGS. FIG. 7 is a sectional view illustrating the structure of the quantum semiconductor device according to the present embodiment, and FIG. 8 is a process sectional view illustrating the method of manufacturing the quantum semiconductor device according to the present embodiment. Note that the same components as those of the quantum semiconductor device according to the first embodiment and the method of manufacturing the same are denoted by the same reference numerals, and description thereof will be omitted or simplified.
[0069]
First, the structure of the quantum semiconductor device according to the present embodiment will be explained with reference to FIG.
[0070]
On the semiconductor substrate 10, a quantum dot layer 14 made of a semiconductor including the self-formed quantum dots 12 is formed.
[0071]
On the quantum dot layer 14, a semiconductor layer 18 is formed.
[0072]
A concave portion 34 is formed at a position on the quantum dot 12 on the surface of the semiconductor layer 18. In the recess 34, a granular electrode 22 made of metal is formed.
[0073]
The quantum semiconductor device according to the present embodiment is characterized mainly in that the electrode 22 is formed in a concave portion 34 formed at a position on the quantum dot 12 on the surface of the semiconductor layer 18.
[0074]
As described above, the electrodes 22 are accurately formed on the respective quantum dots 12 by the concave portions 34 formed at the positions on the quantum dots 12 on the surface of the semiconductor layer 18. It is possible to accurately and electrically access the quantum dot 12 thus obtained. Further, it is possible to electrically access the self-formed quantum dots 12 independently of each other.
[0075]
The energy band structure of the quantum semiconductor device according to the present embodiment is substantially the same as that of the quantum semiconductor device according to the first embodiment shown in FIG.
[0076]
Next, the method for fabricating the quantum semiconductor device according to the present embodiment will be explained with reference to FIG.
[0077]
First, the quantum dot layer 14 including the quantum dots 12 and the semiconductor layer 18 are sequentially formed on the semiconductor substrate 10 in the same manner as in the first embodiment (FIGS. 8A and 8B). See).
[0078]
Next, a semiconductor dot layer 38 is formed on the semiconductor layer 18 by, for example, the MBE method. By epitaxially growing the semiconductor dot layer 38, the semiconductor dots 36 formed of three-dimensionally grown islands are self-formed in the SK mode (see FIG. 8C). The semiconductor dot layer 38 formed here is composed of the semiconductor dots 36 self-formed on the semiconductor layer 18 and the wetting layer 40 formed on the semiconductor layer 18 between the semiconductor dots 36. The semiconductor dots 36 may be quantum dots or antidots. As the material of the semiconductor dot layer 38, a material having a different lattice constant from the material of the semiconductor layer 18 and having a large lattice mismatch is used. For example, when InGaAs is used as the material of the quantum dot layer 14 and GaAs is used as the material of the semiconductor layer 18, AlInAs can be used as the material of the semiconductor dot layer 38.
[0079]
As described above, the semiconductor dots 36 of the semiconductor dot layer 38 laminated and formed in the SK mode on the quantum dot layer 14 via the semiconductor layer 18 are formed on the quantum dots 12 of the quantum dot layer 14. . That is, the positions of the quantum dots 12 in the first quantum dot layer 14 and the positions of the semiconductor dots 36 in the second semiconductor dot layer 38 are aligned in the vertical direction. As described above, the quantum dots 12 and the semiconductor dots 36 are formed so as to overlap each other because, when the semiconductor dot layer is formed on the quantum dot layer on which the quantum dots are formed, the quantum dots overlap with the quantum dots in the semiconductor dot layer. This is because semiconductor dots, which are quantum dots or antidots, tend to be formed.
[0080]
Next, the semiconductor dots 36 and the semiconductor layer 18 immediately below the semiconductor dots 36 are oxidized by using the AFM oxidation method. For example, a negative bias is applied to the probe 30 for a predetermined time while the probe 30 of the AFM is close to the semiconductor dot 36 in the air at a humidity of 40 to 60%, and a positive bias is applied to the semiconductor substrate 10. (See FIG. 8D). For example, when the material of the semiconductor dots 36 is InGaAs, a voltage of about 3 to 10 V is applied. As a result, a dot-shaped oxide 42 formed by oxidizing the semiconductor dots 36 and the semiconductor layer 18 immediately below the semiconductor dots 36 is formed. Thus, the dot-shaped oxide 42 is formed so that a part thereof is embedded in the surface layer of the semiconductor layer 18.
[0081]
Note that the semiconductor dots 36 are desirably formed small so that the above-described oxidation can be easily performed. For example, it is desirable to form the semiconductor dots 36 such that the size thereof is about 15 to 30 nm.
[0082]
Next, the dot-shaped oxide 42 is removed by etching. As the etchant, for example, when removing the dot-shaped oxide 42 obtained by oxidizing the semiconductor dots 36 made of InGaAs, diluted HCl or diluted NH is used. ₄ OH or the like is used.
[0083]
Here, the dot-shaped oxide 42 is removed by etching, and the wetting layer 40 is also removed by etching. The order in which the dot-shaped oxide 42 and the wetting layer 40 are removed does not matter. Alternatively, the dot oxide 42 and the wetting layer 40 may be removed at the same time by appropriately selecting an etching solution. For example, by using HCl as an etchant, the dot oxide 42 containing As and the wetting layer 40 made of InAs can be removed at the same time.
[0084]
By removing the dot-shaped oxide 42 in this manner, the concave portion 34 is formed at the position where the semiconductor dot 36 was formed on the surface of the semiconductor layer 18, that is, at the position above each of the quantum dots 12 embedded in the semiconductor layer 18. It is formed (see FIG. 8E).
[0085]
If the height of the semiconductor dot 36 is not sufficiently low and it is difficult to completely oxidize the semiconductor dot 36 by one AFM oxidation method, the concave portion 34 is formed on the surface of the semiconductor layer 18 as follows. May be formed. That is, the step of oxidizing a part of the upper end of the semiconductor dot 36 by the AFM oxidation method and the step of removing the oxidized part of the semiconductor dot 36 by etching are repeated to form the concave portion 34 on the surface of the semiconductor layer 18. You may.
[0086]
Next, as in the case of the first embodiment, metal droplets are deposited on the surface of the semiconductor layer 18 in which the concave portions 34 are formed by the droplet epitaxy method.
[0087]
At this time, the metal droplet deposited on the surface of the semiconductor layer 18 moves to the concave portion 34 formed on the surface of the semiconductor layer 18.
[0088]
Subsequently, the metal droplets are solidified by cooling after the deposition is completed, and metal particles are formed. Thus, the granular electrode 22 made of metal is formed in the recess 34 (see FIG. 8F).
[0089]
In the method for fabricating the quantum semiconductor device according to the present embodiment, even if the semiconductor layer 18 on the quantum dots 12 is not sufficiently distorted, the position on the quantum dots 12 on the surface of the semiconductor layer 18 is changed as described above. Since the recess 34 is formed, the electrode 22 can be accurately formed on the quantum dot 12. As a case where the semiconductor layer 18 on the quantum dot 12 does not have sufficient strain, for example, a case where the lattice mismatch between the quantum dot 12 and the semiconductor layer 18 is small, or a case where the thickness of the semiconductor layer 18 is not thin, for example, 10 nm There are cases.
[0090]
In order to smoothly move the metal droplets deposited by the droplet epitaxy method to the concave portions 34, the semiconductor dots 36 are completely oxidized so that no protrusions remain around the concave portions 34, and the dot shape is formed. It is desirable to form the oxide 42 of this. For the same reason, when the wetting layer 40 is removed by etching, the wetting layer 40 is sufficiently removed by etching so as to prevent the formation of a projection in which the wetting layer 40 remains around the recess 34. It is desirable to keep.
[0091]
Thus, the quantum semiconductor device according to the present embodiment is formed.
[0092]
As described above, according to the present embodiment, the surface of the semiconductor layer 18 on the quantum dot 12 is removed by etching away the dot-shaped oxide 42 formed by oxidizing the semiconductor dot 36 formed on the quantum dot 12. Since the concave portions 34 are formed in the holes and the granular electrodes 22 made of metal are formed by the droplet epitaxy method, the electrodes 22 can be formed accurately at positions on the respective quantum dots 12. This makes it possible to accurately and electrically access the quantum dots 12. In addition, it is possible to electrically access the quantum dots 12 independently of each other.
[0093]
(Modification)
Next, a quantum semiconductor device according to a modification of the present embodiment and a method for manufacturing the same will be described with reference to FIGS. FIG. 9 is a cross-sectional view illustrating the structure of the quantum semiconductor device according to the present modification, and FIG. 10 is a process cross-sectional view illustrating the method of manufacturing the quantum semiconductor device according to the present modification.
[0094]
First, the structure of the quantum semiconductor device according to the present modification will be described with reference to FIG.
[0095]
The main feature of the quantum semiconductor device according to the present modification is that, similarly to the quantum semiconductor device according to the modification of the first embodiment, the electrode 22 and the wiring 26 electrically connected to the electrode 22 are formed. .
[0096]
As shown in FIG. 9, a groove 24 is formed on the surface of the semiconductor layer 18. One end of the groove 24 is located in the vicinity of the concave portion 34 accurately formed at the position on the quantum dot 12 on the surface of the semiconductor layer 18.
[0097]
In the groove 24, a wiring 26 electrically connected to the electrode 22 is formed.
[0098]
As described above, since the quantum semiconductor device according to the present modification has the wiring 26 electrically connected to the electrode 22, the peripheral circuit for applying a voltage to the quantum dot 12 and the electrode 22 are connected to each other. Electrical connection can be made via the wiring 26.
[0099]
Next, a method for manufacturing a quantum semiconductor device according to the present modification will be described with reference to FIGS.
[0100]
8A to 8E, a recess 34 is formed on the surface of the semiconductor layer 18 on the quantum dots 12 (see FIG. 10A).
[0101]
Next, a linear oxide 28 is formed on the surface of the semiconductor layer 18 by the AFM oxidation method. Here, the linear oxide 28 is formed such that one end of the linear oxide 28 is located at the position of the concave portion 34 on the surface of the semiconductor layer 18 (see FIG. 10B).
[0102]
Next, the linear oxide 28 formed on the surface of the semiconductor layer 18 by etching is removed. Thus, a groove 24 is formed on the surface of the semiconductor layer 18 from which the linear oxide 28 has been removed (see FIG. 10C).
[0103]
Next, similarly to the above, a metal droplet is deposited on the surface of the semiconductor layer 18 by the droplet epitaxy method. At this time, the metal droplet is formed in the concave portion 34 on the surface of the semiconductor layer 18 and in the groove 24.
[0104]
Subsequently, the metal droplets are solidified by cooling after the deposition is completed, and metal particles are formed. In this way, the wiring 26 formed by the continuous connection of the metal particles in the groove 24 is formed together with the granular electrode 22 made of metal (see FIG. 10D).
[0105]
Thus, the quantum semiconductor device according to the present modification is manufactured.
[0106]
After that, as in the case of the modification of the first embodiment, the electrode pad 32 electrically connected to the wiring 26 may be formed.
[0107]
[Third embodiment]
The quantum semiconductor device according to the third embodiment of the present invention and the method for fabricating the same will be described with reference to FIGS. FIG. 11 is a sectional view showing the structure of the quantum semiconductor device according to the present embodiment, FIG. 12 is a band energy diagram of the quantum semiconductor device according to the present embodiment, and FIG. 13 is a process sectional view showing the method of manufacturing the quantum semiconductor device according to the present embodiment. It is. The same components as those in the quantum semiconductor device according to the first and second embodiments and the method of manufacturing the same will be denoted by the same reference numerals, and description thereof will be omitted or simplified.
[0108]
First, the structure of the quantum semiconductor device according to the present embodiment will be explained with reference to FIG.
[0109]
On the semiconductor substrate 10, a quantum dot layer 14 made of a semiconductor including the self-formed quantum dots 12 is formed.
[0110]
On the quantum dot layer 14, an intermediate layer, that is, a semiconductor layer 18 is formed.
[0111]
On the semiconductor layer 18, a semiconductor dot layer 46 made of a semiconductor including self-formed semiconductor dots 44 is formed. The semiconductor dot layer 46 is composed of semiconductor dots 44 self-formed on the semiconductor layer 18 and a wetting layer 48 formed on the semiconductor layer 18 between the semiconductor dots 44. The semiconductor dots 44 of the semiconductor dot layer 46 are formed at positions on the quantum dots 12 of the quantum dot layer 14. The semiconductor dots 44 may be antidots or quantum dots.
[0112]
At the upper end of the semiconductor dot 44 of the semiconductor dot layer 46, a dot-shaped oxide 50 formed by oxidizing a part of the upper end of the semiconductor dot 44 is formed.
[0113]
A cap layer, that is, a semiconductor layer 52 is formed on the semiconductor dot layer 46 including the semiconductor dots 44 having the dot-shaped oxide 50 formed on the upper end.
[0114]
A concave portion 54 is formed at a position on the quantum dots 12 and the semiconductor dots 44 that are stacked on the surface of the semiconductor layer 52. The granular electrode 22 made of metal is formed in the recess 54.
[0115]
In the quantum semiconductor device according to the present embodiment, the electrode 22 is formed in the concave portion 54 formed at the position of the surface of the semiconductor layer 52 on the stacked quantum dot 12 and the semiconductor dot 44, that is, each quantum dot The main feature is that the electrodes 22 are accurately formed on the dots 12.
[0116]
As described above, the recesses 54 formed at the positions on the quantum dots 12 on the surface of the semiconductor layer 52 allow the electrodes 22 to be accurately formed on the respective quantum dots 12. It is possible to accurately and electrically access the quantum dot 12 thus obtained. Further, it is possible to electrically access the self-formed quantum dots 12 independently of each other.
[0117]
The quantum semiconductor device according to the present embodiment is also characterized in that a semiconductor layer 52 is formed between the quantum dot 12 and the electrode 22 in addition to the semiconductor layer 18. Since the semiconductor layer 52 is further formed in addition to the semiconductor layer 18, it is possible to prevent the metal in the electrode 22 from diffusing into the quantum dots 12 during heat treatment or the like.
[0118]
The energy band structure of the quantum semiconductor device according to the present embodiment is as shown in FIG.
[0119]
The height and barrier width of the barrier between the quantum dot 12 and the electrode 22 shown in the energy band structure shown in FIG. 12 are the material composition and thickness of the semiconductor layers 18 and 52, the material composition and size of the semiconductor dot 44, A desired value can be set by appropriately setting the size of the dot-shaped oxide 50 and the like.
[0120]
Next, the method for fabricating the quantum semiconductor device according to the present embodiment will be explained with reference to FIG.
[0121]
First, as in the case of the second embodiment, the quantum dot layer 14 and the semiconductor dot layer 46 are formed on the semiconductor substrate 10 with the semiconductor layer 18 interposed therebetween by, for example, the MBE method (see FIG. a)). As the material of the semiconductor dots 44, a material having a different lattice constant from the material of the semiconductor layer 18 and having a large lattice mismatch, and having, for example, a higher ground level energy than the semiconductor layer 18 is selected. In this case, the semiconductor dots 44 become antidots. By selecting such a material for the semiconductor dots 44, the influence of the semiconductor dots 44 on the embedded quantum dots 12 can be reduced. As a material of the semiconductor dots 44, for example, InAlAs, InGaAlAs, or the like can be used.
[0122]
The semiconductor dots 44 need not necessarily be formed small, unlike the second-layer semiconductor dots 36 formed in the method of manufacturing the quantum semiconductor device according to the second embodiment.
[0123]
As described above, the semiconductor dots 44 of the semiconductor dot layer 46 stacked and formed in the SK mode on the quantum dot layer 14 with the semiconductor layer 18 interposed therebetween, as in the case of the second embodiment, It is formed on fourteen quantum dots 12.
[0124]
Next, the semiconductor substrate 10 is taken out of the epitaxial growth chamber.
[0125]
Then, a part of the upper end of the semiconductor dot 44 of the semiconductor dot layer 46 is oxidized by the AFM oxidation method. For example, a negative bias is applied to the probe 30 for a predetermined time while the probe 30 of the AFM is in proximity to the semiconductor dot 44 in the air at a humidity of 40 to 60%, and a positive bias is applied to the semiconductor substrate 10. Apply. Thus, a dot-shaped oxide 50 formed by oxidizing a part of the upper end of the semiconductor dot 44 is formed (see FIG. 13B).
[0126]
Next, after removing the contaminants adsorbed on the surface and the natural oxide film formed on the surface, the semiconductor substrate 10 is again housed in the epitaxial growth chamber of the film forming apparatus. Note that a cleaning method by irradiation of hydrogen atoms can be used for removing contaminants and the like.
[0127]
Subsequently, the semiconductor layer 52 is formed on the semiconductor dot layer 46 by, for example, the MBE method. As the material of the semiconductor layer 52, for example, the same material as the material of the semiconductor dots 44 or a material having a larger energy gap than the material of the semiconductor dots 44 is selected.
[0128]
In the growth of the semiconductor layer 52, since the dot-shaped oxide 50 is amorphous, the growth rate of the semiconductor layer 52 on the dot-shaped oxide 50 is higher than the growth rate of the semiconductor layer 52 in other regions. Become slow. As a result, a concave portion 54 is formed on the surface of the semiconductor layer 52 on the dot-shaped oxide 50 (see FIG. 13C).
[0129]
In this way, a concave portion 54 is formed at a position on the surface of the semiconductor layer 52 on the quantum dots 12 and the semiconductor dots 44 that are formed by lamination.
[0130]
Next, metal droplets are deposited on the surface of the semiconductor layer 52 in which the concave portions 54 are formed by a droplet epitaxy method. As in the case of the second embodiment, the metal droplet deposited on the surface of the semiconductor layer 52 moves to the recess 54.
[0131]
Subsequently, the metal droplets are solidified by cooling after the deposition is completed, and metal particles are formed. Thus, the granular electrode 22 made of metal is formed in the concave portion 44 on the surface of the semiconductor layer 52 (see FIG. 13D).
[0132]
Thus, the quantum semiconductor device according to the present embodiment is formed.
[0133]
As described above, according to the present embodiment, the growth rate of the semiconductor layer 52 on the dot-shaped oxide 50 obtained by oxidizing a part of the upper end of the semiconductor dot 44 stacked on the quantum dot 12 is reduced. Utilizing this, a concave portion 54 is formed on the surface of the semiconductor layer 52 on the quantum dot 12 and the granular electrode 22 made of metal is formed by a droplet epitaxy method. The electrode 22 can be formed on the substrate. This makes it possible to accurately and electrically access the quantum dots 12. In addition, it is possible to electrically access the quantum dots 12 independently of each other.
[0134]
(Modification)
Next, a quantum semiconductor device according to a modification of the present embodiment and a method for manufacturing the same will be described with reference to FIGS. FIG. 14 is a cross-sectional view illustrating a structure of a quantum semiconductor device according to a modification of the present embodiment, and FIG. 15 is a process cross-sectional view illustrating a method of manufacturing the quantum semiconductor device according to the modification.
[0135]
First, the structure of the quantum semiconductor device according to the present modification will be described with reference to FIG.
[0136]
The quantum semiconductor device according to the present modification is mainly provided with the electrode 22 and the wiring 26 electrically connected to the electrode 22, similarly to the quantum semiconductor device according to the modification of the first and second embodiments. There are features.
[0137]
As shown in FIG. 14, the groove 24 is formed on the surface of the semiconductor layer 52. One end of the groove 24 is located in the vicinity of the concave portion 54 accurately formed at a position on the quantum dot 12 on the surface of the semiconductor layer 52.
[0138]
In the groove 24, a wiring 26 electrically connected to the electrode 22 is formed.
[0139]
As described above, since the quantum semiconductor device according to the present modification has the wiring 26 electrically connected to the electrode 22, the peripheral circuit for applying a voltage to the quantum dot 12 and the electrode 22 are connected to each other. Electrical connection can be made via the wiring 26.
[0140]
Next, a method for manufacturing a quantum semiconductor device according to the present modification will be described with reference to FIGS.
[0141]
As in the cases shown in FIGS. 13A to 13C, a concave portion 54 is formed at a position on the dot-shaped oxide 50 on the surface of the semiconductor layer 52 (see FIG. 15A).
[0142]
Next, a linear oxide 28 is formed on the surface of the semiconductor layer 52 by the AFM oxidation method. Here, the linear oxide 28 is formed such that one end of the linear oxide 28 is located at the position of the concave portion 54 on the surface of the semiconductor layer 52 (see FIG. 15B).
[0143]
Next, the linear oxide 28 formed on the surface of the semiconductor layer 52 by etching is removed. Thus, the groove 24 is formed on the surface of the semiconductor layer 52 from which the linear oxide 28 has been removed (see FIG. 15C).
[0144]
Next, a metal droplet is deposited on the surface of the semiconductor layer 52 by a droplet epitaxy method as described above. At this time, the metal droplet is formed in the recess 24 on the surface of the semiconductor layer 52 and in the groove 24.
[0145]
Subsequently, the metal droplets are solidified by cooling after the deposition is completed, and metal particles are formed. In this way, the wiring 26 formed by the continuous connection of the metal particles in the groove 24 is formed together with the granular electrode 22 made of metal (see FIG. 15D).
[0146]
Thus, the quantum semiconductor device according to the present modification is manufactured.
[0147]
After that, as in the case of the modification of the first embodiment, the electrode pad 32 electrically connected to the wiring 26 may be formed.
[0148]
[Fourth embodiment]
The quantum semiconductor device according to the fourth embodiment of the present invention and the method for fabricating the same will be described with reference to FIGS. FIG. 16 is a sectional view illustrating the structure of the quantum semiconductor device according to the present embodiment, and FIG. 17 is a process sectional view illustrating the method for manufacturing the quantum semiconductor device according to the present embodiment. Note that the same components as those in the quantum semiconductor device according to the first to third embodiments and the method of manufacturing the same will be denoted by the same reference numerals, and description thereof will be omitted or simplified.
[0149]
First, the structure of the quantum semiconductor device according to the present embodiment will be explained with reference to FIG. In the quantum semiconductor device according to the present embodiment, as in the case of the modification of the first embodiment, the wiring is formed together with the electrodes.
[0150]
As shown in FIG. 16, a quantum dot layer 14 made of a semiconductor including self-formed quantum dots 12 is formed on a semiconductor substrate 10.
[0151]
On the quantum dot layer 16, an intermediate layer, that is, a semiconductor layer 18 is formed. In the semiconductor layer 18 on the quantum dots 12, distortion occurs due to lattice mismatch.
[0152]
A granular electrode 22 made of metal is formed on the surface of the semiconductor layer 18 where the strain is generated. A linear oxide 56 is formed on the surface of the semiconductor layer 18. One end of the linear oxide 56 is located near the electrode 22.
[0153]
A cap layer, that is, a semiconductor layer 58 is formed on the semiconductor layer 18 on which the electrode 22 and the linear oxide 56 are formed.
[0154]
An opening 60 reaching the electrode 22 is formed on the electrode 22 of the semiconductor layer 58. The electrode 23 that is electrically connected to the electrode 22 is embedded in the opening 60.
[0155]
In addition, a groove 62 is formed on the surface of the semiconductor layer 58 along the linear oxide 56.
[0156]
In the groove 62, a wiring 64 electrically connected to the electrode 23 is formed.
[0157]
Thus, the main feature of the quantum semiconductor device according to the present embodiment is that the linear oxide 56 is formed below the wiring 64. With the line-shaped oxide 56, a barrier to carriers is formed below the wiring 64, so that leakage current from the wiring 64 can be suppressed.
[0158]
Next, the method for fabricating the quantum semiconductor device according to the present embodiment will be explained with reference to FIGS.
[0159]
First, the electrode 22 is formed at a position on the quantum dot 12 on the surface of the semiconductor layer 18 in the same manner as in the case of the first embodiment shown in FIGS. 3A to 3C.
[0160]
Next, a linear oxide 56 is formed on the surface of the semiconductor layer 18 by AFM oxidation (see FIG. 17A). Here, the linear oxide 56 is formed such that one end of the linear oxide 56 is located near the electrode 22.
[0161]
Next, a semiconductor layer 58 is formed on the semiconductor layer 18 on the surface of which the electrode 22 and the linear oxide 56 are formed, for example, by the MBE method.
[0162]
At this time, the growth rate of the semiconductor layer 58 on the electrode 22 and on the linear oxide 56 is lower than the growth rate of the semiconductor layer 58 in other regions. As a result, a recess 64 is formed at a position on the electrode 22 on the surface of the semiconductor layer 58. Further, a groove 62 is formed on the surface of the semiconductor layer 58 along the linear oxide 56 (see FIG. 17B).
[0163]
Next, the portion of the semiconductor layer 58 where the recess 64 is formed is oxidized by AFM oxidation. Thus, a dot-shaped oxide 66 is formed by oxidizing the portion of the semiconductor layer 58 where the concave portion 64 is formed (see FIG. 17C). Here, the oxidation by the AFM oxidation method is performed until the size of the dot-shaped oxide 66 reaches the electrode 22 thereunder.
[0164]
Next, the dot-shaped oxide 66 formed at the position of the concave portion 64 is removed by etching. Thus, an opening 60 reaching the electrode 22 is formed in the semiconductor layer 58 (see FIG. 17D).
[0165]
Next, a metal droplet is deposited on the surface of the semiconductor layer 58 in which the opening 60 and the groove 62 are formed by the droplet epitaxy method. At this time, the metal droplet is formed in the opening 60 reaching the electrode 22 and in the groove 62.
[0166]
Subsequently, the metal droplets are solidified by cooling after the deposition is completed, and metal particles are formed. Thus, together with the granular electrode 23 made of a metal electrically connected to the electrode 22, the wiring 64 formed by continuously connecting the metal particles in the groove 62 is formed (see FIG. 17E).
[0167]
Thus, the quantum semiconductor device according to the present embodiment is formed.
[0168]
After that, as in the case of the modification of the first embodiment, the electrode pad 32 electrically connected to the wiring 26 may be formed.
[0169]
As described above, according to the present embodiment, the wiring 64 is formed in the groove 62 formed on the surface of the semiconductor layer 58 on the linear oxide 56. A barrier to carriers can be formed. Thus, leakage current from the wiring 64 can be suppressed.
[0170]
Note that, in the present embodiment, the case where one layer of the linear oxide 56 is formed has been described. However, by repeating the above steps, a plurality of linear oxides 56 are formed under the wiring 64 by lamination. Is also good. By forming the plurality of linear oxides 56 under the wiring 64, it is possible to more effectively suppress a leak current from the wiring 64.
[0171]
(Modification (Part 1))
A quantum semiconductor device and a method for manufacturing the quantum semiconductor device according to a modification (Part 1) of the present embodiment will be described with reference to FIGS. FIG. 18 is a cross-sectional view illustrating the structure of the quantum semiconductor device according to the present modification, and FIG. 19 is a process cross-sectional view illustrating the method of manufacturing the quantum semiconductor device according to the present modification.
[0172]
First, the structure of the quantum semiconductor device according to the present modification will be described with reference to FIG.
[0173]
In the quantum semiconductor device according to the present modification, the electrodes 22 are formed on the quantum dots 12 as in the case of the second embodiment. That is, as shown in FIG. 18, the electrode 22 is formed in a concave portion 34 formed at a position on the quantum dot 12 on the surface of the semiconductor layer 18.
[0174]
On the surface of the semiconductor layer 18, a linear oxide 56 having one end located near the electrode 22 formed in the concave portion 34 is formed.
[0175]
A semiconductor layer 58 is formed on the semiconductor layer 18 on which the electrode 22 and the linear oxide 56 are formed.
[0176]
Similarly to the above, the electrode 23 electrically connected to the electrode 22 and the wiring 64 electrically connected to the electrode 23 are formed in the semiconductor layer 58.
[0177]
Thus, the quantum semiconductor device according to the present modification is configured.
[0178]
Next, a method for manufacturing a quantum semiconductor device according to the present modification will be described with reference to FIG.
[0179]
First, as in the case of the second embodiment, the electrode 22 is formed in the recess 34 formed at a position on the quantum dot 12 on the surface of the semiconductor layer 18.
[0180]
Next, a linear oxide 56 having one end located near the electrode 22 formed in the recess 34 is formed by AFM oxidation (see FIG. 19A).
[0181]
Next, a semiconductor layer 58 is formed on the semiconductor layer 18 on which the electrode 22 and the linear oxide 56 are formed. Thereafter, an opening 60 reaching the electrode 22 is formed in the semiconductor layer 58 (see FIG. 19B).
[0182]
Next, the electrode 23 is formed in the opening 60 reaching the electrode 22 and the wiring 64 is formed in the groove 62 by the droplet epitaxy method.
[0183]
Thus, the quantum semiconductor device according to the present modification is formed.
[0184]
(Modification (Part 2))
A quantum semiconductor device and a method for manufacturing the quantum semiconductor device according to a modification (Part 2) of the present embodiment will be described with reference to FIGS. FIG. 20 is a cross-sectional view illustrating the structure of the quantum semiconductor device according to the present modification, and FIG. 21 is a process cross-sectional view illustrating the method of manufacturing the quantum semiconductor device according to this modification.
[0185]
First, the structure of the quantum semiconductor device according to the present modification will be described with reference to FIG.
[0186]
In the quantum semiconductor device according to the present modification, the electrodes 22 are formed on the quantum dots 12 as in the case of the third embodiment. That is, as shown in FIG. 20, the electrode 22 is formed in the concave portion 54 formed at a position on the quantum dot 12 and the semiconductor dot 44 on the surface of the semiconductor layer 52.
[0187]
On the surface of the intermediate layer, that is, the semiconductor layer 52, a linear oxide 56 whose one end is located near the electrode 22 formed in the concave portion 54 is formed.
[0188]
On the semiconductor layer 52 on which the electrode 22 and the linear oxide 56 are formed, a cap layer, that is, a semiconductor layer 58 is formed.
[0189]
Similarly to the above, the electrode 23 electrically connected to the electrode 22 and the wiring 64 electrically connected to the electrode 23 are formed in the semiconductor layer 58.
[0190]
Thus, the quantum semiconductor device according to the present modification is configured.
[0191]
Next, a method for manufacturing a quantum semiconductor device according to the present modification will be described with reference to FIG.
[0192]
First, as in the case of the third embodiment, the electrodes 22 are formed in the concave portions 54 formed at positions on the quantum dots 12 and the semiconductor dots 44 on the surface of the semiconductor layer 52.
[0193]
Next, a linear oxide 56 having one end located near the electrode 22 formed in the recess 54 is formed by AFM oxidation (see FIG. 21A).
[0194]
Next, a semiconductor layer 58 is formed on the semiconductor layer 52 on the surface of which the electrode 22 and the linear oxide 56 are formed. Thereafter, an opening 60 reaching the electrode 22 is formed in the semiconductor layer 58 (see FIG. 21B).
[0195]
Next, the electrode 23 is formed in the opening 60 reaching the electrode 22 and the wiring 64 is formed in the groove 62 by the droplet epitaxy method.
[0196]
Thus, the quantum semiconductor device according to the present modification is formed.
[0197]
[Modified embodiment]
The present invention is not limited to the above embodiment, and various modifications are possible.
[0198]
For example, in the above-described embodiment, an example has been described in which an electrode is formed for a quantum dot that is self-formed in the SK mode. However, a quantum dot that forms an electrode is one that is self-formed in the SK mode. It is not limited. For example, the present invention can be applied to a case where electrodes are formed on quantum dots stacked vertically.
[0199]
In the above embodiment, the line-shaped oxide is formed by oxidizing the quantum dots or oxidizing the semiconductor layer by the AFM oxidation method. As long as it is a body, various things can be used. For example, a carbon nanotube can be used as a probe.
[0200]
In the above embodiment, the case where the quantum dots are oxidized or the semiconductor layer is oxidized by the AFM oxidation method has been described as an example, but the oxidation of the quantum dots and the like is not limited to the AFM oxidation. Various methods capable of selectively oxidizing a minute region can be used for oxidizing the quantum dots and the like.
[0201]
(Supplementary Note 1) Quantum dots formed on a semiconductor substrate, a semiconductor layer formed so as to embed the quantum dots, and a semiconductor layer formed in a self-aligned manner on a position of strain generated in the semiconductor layer due to the presence of the quantum dots. A quantum semiconductor device comprising:
[0202]
(Supplementary Note 2) The quantum semiconductor device according to supplementary note 1, wherein the semiconductor layer is made of a material having a different lattice constant from a material of the quantum dots.
[0203]
(Supplementary Note 3) Quantum dots formed on a semiconductor substrate, a semiconductor layer formed so as to embed the quantum dots, and formed in a concave portion formed at a position on the quantum dots on the surface of the semiconductor layer. A quantum semiconductor device comprising: an electrode;
[0204]
(Supplementary Note 4) The quantum semiconductor device according to any one of Supplementary Notes 1 to 3, further comprising a wiring formed in a groove formed on a surface of the semiconductor layer and electrically connected to the electrode. Quantum semiconductor device.
[0205]
(Supplementary Note 5) In the quantum semiconductor device according to any one of Supplementary Notes 1 to 3, a linear oxide formed on the surface of the semiconductor layer and having one end located in the vicinity of the electrode, and the electrode and the linear oxide Another semiconductor layer formed so as to bury an object, another electrode embedded in the other semiconductor layer and electrically connected to the electrode, and the other semiconductor along the linear oxide. And a wiring formed in a groove formed on the surface of the layer and electrically connected to the another electrode.
[0206]
(Supplementary Note 6) A quantum dot formed on a semiconductor substrate, a first semiconductor layer formed so as to embed the quantum dot, and a quantum dot formed at a position on the quantum dot on the first semiconductor layer A semiconductor dot, a dot-shaped oxide formed by oxidizing a part of the semiconductor dot, a second semiconductor layer formed so as to embed the semiconductor dot, and the dot-shaped oxide on the surface of the second semiconductor layer. And an electrode formed in a recess formed at a position on the oxide of the quantum semiconductor device.
[0207]
(Supplementary Note 7) The quantum semiconductor device according to supplementary note 6, wherein the semiconductor dots are quantum dots or antidots.
[0208]
(Supplementary Note 8) The quantum semiconductor device according to supplementary note 6 or 7, further comprising a wiring formed in a groove formed on the surface of the second semiconductor layer and electrically connected to the electrode. Quantum semiconductor device.
[0209]
(Supplementary Note 9) In the quantum semiconductor device according to Supplementary Note 6 or 7, a linear oxide formed on the surface of the second semiconductor layer and having one end located near the electrode, and the electrode and the linear oxide A third semiconductor layer formed so as to fill the third semiconductor layer, another electrode buried in the third semiconductor layer and electrically connected to the electrode, and the third semiconductor layer along the linear oxide. And a wiring formed in a groove formed on the surface of the semiconductor layer and electrically connected to the other electrode.
[0210]
(Supplementary Note 10) In the method of manufacturing a quantum semiconductor device according to any one of Supplementary Notes 1 to 9, the quantum dot is formed of a three-dimensionally grown island self-formed in an SK mode. .
[0211]
(Supplementary Note 11) A step of forming a quantum dot on a semiconductor substrate, a step of forming a semiconductor layer so as to embed the quantum dot, and a self-alignment on a position of a strain generated in the semiconductor layer due to the presence of the quantum dot. Forming an electrode in a specific manner.
[0212]
(Supplementary Note 12) A step of forming a quantum dot on a semiconductor substrate, a step of forming a semiconductor layer so as to embed the quantum dot, and forming a semiconductor dot at a position on the quantum dot on the semiconductor layer. Oxidizing the semiconductor dots and the semiconductor layer immediately below the semiconductor dots to form dot-shaped oxides partially embedded in the semiconductor layer; and Forming a concave portion on the surface of the semiconductor layer by removing an object; and forming an electrode in the concave portion formed on the surface of the semiconductor layer. .
[0213]
(Supplementary Note 13) In the method of manufacturing a quantum semiconductor device according to Supplementary Note 12, in the step of forming the semiconductor dots, a semiconductor dot layer made of a material having a different lattice constant from the semiconductor layer is epitaxially grown, so that the three-dimensional growth island A method for manufacturing a quantum semiconductor device, comprising: forming the semiconductor dots.
[0214]
(Supplementary Note 14) In the method for manufacturing a quantum semiconductor device according to Supplementary Note 12 or 13, in the step of forming the dot-shaped oxide, a needle-shaped conductor is brought close to the semiconductor dot, and the semiconductor substrate and the needle-shaped A semiconductor device and a semiconductor layer immediately below the semiconductor dot are oxidized by applying a voltage between the semiconductor dot and the conductor.
[0215]
(Supplementary Note 15) In the method of manufacturing a quantum semiconductor device according to any one of Supplementary Notes 11 to 14, the semiconductor layer is oxidized before the step of forming the electrode, so that the semiconductor layer is formed on the surface of the semiconductor layer. A step of forming a linear oxide having one end located in the vicinity of the position where the electrode is to be formed, and a step of forming a groove in the semiconductor layer surface by removing the linear oxide. A method of manufacturing a quantum semiconductor device, comprising: forming a wiring electrically connected to the electrode in the groove together with the electrode in the step of forming the electrode.
[0216]
(Supplementary Note 16) In the method for manufacturing a quantum semiconductor device according to any one of Supplementary Notes 11 to 14, the semiconductor layer is oxidized after the step of forming the electrode, so that the surface of the semiconductor layer is A step of forming a linear oxide having one end located in the vicinity of the position where the electrode is to be formed, and forming a concave portion on the surface at a position on the electrode, and forming a groove on the surface along the linear oxide. Forming an electrode and another semiconductor layer for embedding the line-shaped oxide so as to be formed, forming an opening in the recess reaching the electrode, and electrically connecting the electrode in the opening. Forming another electrode electrically connected to the first electrode, and forming the wiring electrically connected to the other electrode in the groove. Law.
[0219]
(Supplementary Note 17) In the method of manufacturing a quantum semiconductor device according to Supplementary Note 16, in the step of forming the opening that reaches the electrode in the recess, a needle-shaped conductor is brought close to the recess, and the semiconductor substrate and the needle are placed close to the recess. The other semiconductor layer in the recess is oxidized by applying a voltage between the opening and the conductor, and the opening reaching the electrode is removed by removing the oxide of the other semiconductor layer in the recess. Forming a quantum semiconductor device.
[0218]
(Supplementary Note 18) In the method of manufacturing a quantum semiconductor device according to any one of Supplementary Notes 15 to 17, in the step of forming the line-shaped oxide, a needle-shaped conductor is brought close to the surface of the semiconductor layer to form the semiconductor. By applying a voltage between the substrate and the needle-shaped conductor and scanning the needle-shaped conductor to oxidize the semiconductor layer surface, the linear oxide is formed. Of manufacturing a quantum semiconductor device.
[0219]
(Supplementary Note 19) A step of forming quantum dots on a semiconductor substrate, a step of forming a first semiconductor layer so as to embed the quantum dots, and a step of forming a first semiconductor layer on the first semiconductor layer. Forming a dot-shaped oxide by oxidizing a part of the semiconductor dot to form a dot-shaped oxide formed by oxidizing a part of the semiconductor dot; Forming a second semiconductor layer in which the dot-shaped oxide and the semiconductor dots are buried so that a concave portion is formed on the surface at a position of the second semiconductor layer; and forming the second semiconductor layer in the concave portion formed on the surface of the second semiconductor layer. Forming an electrode in the semiconductor device.
[0220]
(Supplementary Note 20) In the method of manufacturing a quantum semiconductor device according to Supplementary Note 19, in the step of forming the semiconductor dots, a three-dimensional semiconductor dot layer made of a material having a different lattice constant from the first semiconductor layer is epitaxially grown. A method for manufacturing a quantum semiconductor device, comprising: forming the semiconductor dot comprising a growth island.
[0221]
(Supplementary Note 21) In the method of manufacturing a quantum semiconductor device according to Supplementary Note 19 or 20, in the step of forming the dot-shaped oxide, a needle-shaped conductor is brought close to the semiconductor dot, and the semiconductor substrate and the needle-shaped A method for manufacturing a quantum semiconductor device, comprising oxidizing a part of the semiconductor dot by applying a voltage between the semiconductor dot and the conductor.
[0222]
(Supplementary Note 22) In the method of manufacturing a quantum semiconductor device according to any one of Supplementary Notes 19 to 21, the second semiconductor layer is oxidized before the step of forming the electrode, whereby the second semiconductor layer is oxidized. Forming a line-shaped oxide having one end near a position where the electrode of the second semiconductor layer is to be formed on the surface, and removing the line-shaped oxide to form the second oxide. Forming a groove on the surface of the semiconductor layer, wherein the step of forming the electrode includes forming, in the groove, a wiring electrically connected to the electrode together with the electrode. A method for manufacturing a quantum semiconductor device.
[0223]
(Supplementary Note 23) In the method of manufacturing a quantum semiconductor device according to any one of Supplementary Notes 19 to 21, the second semiconductor layer is oxidized after the step of forming the electrode, so that the surface of the second semiconductor layer is oxidized. Forming a line-shaped oxide having one end near the position where the electrode is to be formed in the second semiconductor layer; and forming a concave portion on a surface at a position on the electrode, wherein the line-shaped oxide is formed. Forming a third semiconductor layer in which the electrode and the linear oxide are buried so that a groove is formed on the surface along the oxide; and forming an opening reaching the electrode in the recess. And forming another electrode electrically connected to the electrode in the opening and forming the wiring electrically connected to the other electrode in the groove. Feature A method for manufacturing a quantum semiconductor device.
[0224]
(Supplementary Note 24) In the method of manufacturing a quantum semiconductor device according to Supplementary Note 23, in the step of forming the opening that reaches the electrode in the recess, a needle-shaped conductor is brought close to the recess, and the semiconductor substrate and the needle are connected. The third semiconductor layer in the recess is oxidized by applying a voltage between the opening and the conductor, and the opening reaching the electrode is removed by removing the oxide of the third semiconductor layer in the recess. Forming a portion, the method for manufacturing a quantum semiconductor device.
[0225]
(Supplementary Note 25) In the method for manufacturing a quantum semiconductor device according to any one of Supplementary Notes 22 to 24, in the step of forming the line-shaped oxide, a needle-shaped conductor is brought close to the surface of the second semiconductor layer. Scanning the needle-shaped conductor while applying a voltage between the semiconductor substrate and the needle-shaped conductor to oxidize the surface of the second semiconductor layer, thereby converting the linear oxide. Forming a quantum semiconductor device.
[0226]
(Supplementary Note 26) In the method for manufacturing a quantum semiconductor device according to any one of Supplementary Notes 11 to 25, in the step of forming the electrode, the electrode is formed by a droplet epitaxy method. Production method.
[0227]
(Supplementary Note 27) In the method of manufacturing a quantum semiconductor device according to any one of Supplementary Notes 11 to 26, in the step of forming the quantum dots, a quantum dot layer made of a material having a different lattice constant from the semiconductor substrate is epitaxially grown. Forming a quantum dot comprising a three-dimensional growth island.
[0228]
(Supplementary Note 28) In the method for manufacturing a quantum semiconductor device according to Supplementary Note 14, 17, 18, 21, 24, or 25, the needle-shaped conductor is a probe of an atomic force microscope. A method for manufacturing a quantum semiconductor device.
[0229]
(Supplementary Note 29) The method of manufacturing a quantum semiconductor device according to Supplementary Note 14, 17, 18, 21, 24, or 25, wherein the needle-shaped conductor is made of carbon nanotube. Method.
[0230]
【The invention's effect】
As described above, according to the present invention, a quantum dot is formed on a semiconductor substrate, a semiconductor layer is formed so as to embed the quantum dot, and a self-aligned Since the electrodes are formed on the quantum dots, the electrodes can be accurately formed on the respective quantum dots. Therefore, it is possible to accurately and electrically access the quantum dots via such electrodes, and to independently and electrically access the quantum dots.
[0231]
According to the present invention, a quantum dot is formed on a semiconductor substrate, a semiconductor layer is formed so as to embed the quantum dot, and a semiconductor dot is formed at a position on the quantum dot on the semiconductor layer. And the semiconductor layer immediately below the semiconductor dots are oxidized to form a dot-shaped oxide part of which is embedded in the semiconductor layer, and the dot-shaped oxide is removed to form a recess on the surface of the semiconductor layer. Is formed, and the electrode is formed in the concave portion formed on the surface of the semiconductor layer. Therefore, the electrode can be accurately formed on each quantum dot. Therefore, it is possible to accurately and electrically access the quantum dots via such electrodes, and to independently and electrically access the quantum dots.
[0232]
Further, according to the present invention, a quantum dot is formed on a semiconductor substrate, a first semiconductor layer is formed so as to embed the quantum dot, and a semiconductor dot is formed at a position on the quantum dot on the first semiconductor layer. Is formed, and a part of the semiconductor dot is oxidized to form a dot-shaped oxide formed by oxidizing a part of the semiconductor dot, and a concave portion is formed on a surface at a position on the dot-shaped oxide. As described above, the second oxide layer and the second semiconductor layer in which the semiconductor dots are embedded are formed, and the electrodes are formed in the recesses formed in the surface of the second semiconductor layer. Can be formed. Therefore, it is possible to accurately and electrically access the quantum dots via such electrodes, and to independently and electrically access the quantum dots.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a structure of a quantum semiconductor device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an energy band structure of the quantum semiconductor device according to the first embodiment of the present invention.
FIG. 3 is a process sectional view illustrating the method for manufacturing the quantum semiconductor device according to the first embodiment of the present invention;
FIG. 4 is a cross-sectional view illustrating a structure of a quantum semiconductor device according to a modification of the first embodiment of the present invention.
FIG. 5 is a process sectional view illustrating the method for manufacturing the quantum semiconductor device according to the modification of the first embodiment of the present invention.
FIG. 6 is a top view showing a case where a wiring is connected to an electrode pad in the quantum semiconductor device according to a modification of the first embodiment of the present invention.
FIG. 7 is a sectional view illustrating a structure of a quantum semiconductor device according to a second embodiment of the present invention.
FIG. 8 is a process sectional view illustrating the method for manufacturing the quantum semiconductor device according to the second embodiment of the present invention.
FIG. 9 is a cross-sectional view illustrating a structure of a quantum semiconductor device according to a modification of the second embodiment of the present invention.
FIG. 10 is a process sectional view illustrating the method for manufacturing the quantum semiconductor device according to the modification of the second embodiment of the present invention.
FIG. 11 is a sectional view showing the structure of the quantum semiconductor device according to the third embodiment of the present invention.
FIG. 12 is a diagram illustrating an energy band structure of a quantum semiconductor device according to a third embodiment of the present invention.
FIG. 13 is a process sectional view illustrating the method for manufacturing the quantum semiconductor device according to the third embodiment of the present invention.
FIG. 14 is a cross-sectional view illustrating a structure of a quantum semiconductor device according to a modification of the third embodiment of the present invention.
FIG. 15 is a process sectional view illustrating the method for manufacturing the quantum semiconductor device according to the modification of the third embodiment of the present invention.
FIG. 16 is a sectional view showing the structure of the quantum semiconductor device according to a fourth embodiment of the present invention.
FIG. 17 is a process sectional view illustrating the method for manufacturing the quantum semiconductor device according to the fourth embodiment of the present invention;
FIG. 18 is a cross-sectional view illustrating a structure of a quantum semiconductor device according to a modification (Part 1) of the fourth embodiment of the present invention.
FIG. 19 is a process sectional view illustrating the method of manufacturing the quantum semiconductor device according to the modification (Part 1) of the fourth embodiment of the present invention.
FIG. 20 is a cross-sectional view illustrating a structure of a quantum semiconductor device according to a modification (Part 2) of the fourth embodiment of the present invention.
FIG. 21 is a process sectional view illustrating the method of manufacturing the quantum semiconductor device according to the modification (Part 2) of the fourth embodiment of the present invention.
[Explanation of symbols]
10 ... Semiconductor substrate
12 ... Quantum dots
14 Quantum dot layer
16 ... wetting layer
18 ... Semiconductor layer
22, 23 ... electrodes
24 ... groove
26 ... Wiring
28 ... Linear oxide
30 ... Tip
32 ... Electrode pad
34 ... recess
36 ... Semiconductor dots
38 ... Semiconductor dot layer
40 ... wetting layer
42 ... dot-shaped oxide
44 ... Semiconductor dot
46 ... Semiconductor dot layer
48 ... wetting layer
50: dot-shaped oxide
52 ... Semiconductor layer
54 ... recess
56… Linear oxide
58 ... Semiconductor layer
60 ... opening
62 ... groove
64 ... recess
66: dot-shaped oxide

Claims (10)

Quantum dots formed on a semiconductor substrate,
A semiconductor layer formed so as to embed the quantum dots,
A quantum semiconductor device comprising: an electrode formed in a self-aligned manner on a position of a strain generated in the semiconductor layer due to the presence of the quantum dot. Quantum dots formed on a semiconductor substrate,
A semiconductor layer formed so as to embed the quantum dots,
An electrode formed in a recess formed at a position on the quantum dot on the surface of the semiconductor layer. The quantum semiconductor device according to claim 1, wherein
A quantum semiconductor device further comprising a wiring formed in a groove formed on the surface of the semiconductor layer and electrically connected to the electrode. The quantum semiconductor device according to claim 1, wherein
A linear oxide formed on the surface of the semiconductor layer and having one end located near the electrode;
Another semiconductor layer formed so as to embed the electrode and the linear oxide,
Another electrode embedded in the other semiconductor layer and electrically connected to the electrode;
A quantum semiconductor device, further comprising: a wiring formed in a groove formed on the surface of the another semiconductor layer along the linear oxide, and electrically connected to the other electrode. Quantum dots formed on a semiconductor substrate,
A first semiconductor layer formed so as to embed the quantum dots;
A semiconductor dot formed at a position on the quantum dot on the first semiconductor layer;
A dot-shaped oxide obtained by oxidizing a part of the semiconductor dot;
A second semiconductor layer formed so as to embed the semiconductor dots;
An electrode formed in a recess formed at a position on the dot-shaped oxide on the surface of the second semiconductor layer. Forming quantum dots on a semiconductor substrate;
Forming a semiconductor layer so as to embed the quantum dots;
Forming an electrode in a self-aligned manner on a position of a strain generated in the semiconductor layer due to the presence of the quantum dot. Forming quantum dots on a semiconductor substrate;
Forming a semiconductor layer so as to embed the quantum dots;
Forming a semiconductor dot at a position on the quantum dot on the semiconductor layer,
A step of oxidizing the semiconductor dots and the semiconductor layer immediately below the semiconductor dots to form a dot-shaped oxide partially embedded in the semiconductor layer;
Forming a recess on the surface of the semiconductor layer by removing the dot-shaped oxide;
Forming an electrode in the recess formed on the surface of the semiconductor layer. The method for manufacturing a quantum semiconductor device according to claim 6,
By oxidizing the semiconductor layer before the step of forming the electrode, a linear oxide having one end located in the vicinity of a position where the electrode is to be formed on the semiconductor layer is formed on the surface of the semiconductor layer. And further comprising a step of forming a groove in the surface of the semiconductor layer by removing the linear oxide,
The method of manufacturing a quantum semiconductor device, wherein in the step of forming the electrode, a wiring electrically connected to the electrode is formed in the groove together with the electrode. The method for manufacturing a quantum semiconductor device according to claim 6,
Forming a line-shaped oxide having one end located near a position where the electrode of the semiconductor layer is to be formed on the surface of the semiconductor layer by oxidizing the semiconductor layer after the step of forming the electrode; When,
Forming another semiconductor layer for embedding the electrode and the linear oxide such that a concave portion is formed on the surface at a position on the electrode and a groove is formed on the surface along the linear oxide; Process and
Forming an opening in the recess reaching the electrode;
Forming another electrode electrically connected to the electrode in the opening, and forming the wiring electrically connected to the other electrode in the groove. Of manufacturing a quantum semiconductor device. Forming quantum dots on a semiconductor substrate;
Forming a first semiconductor layer so as to embed the quantum dots;
Forming a semiconductor dot at a position on the quantum dot on the first semiconductor layer;
Oxidizing a part of the semiconductor dot to form a dot-shaped oxide formed by oxidizing a part of the semiconductor dot;
Forming a second semiconductor layer for embedding the dot-shaped oxide and the semiconductor dots, such that a concave portion is formed on a surface at a position on the dot-shaped oxide;
Forming an electrode in the recess formed on the surface of the second semiconductor layer.

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