JPH09326474A - Quantum case memory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quantum case memory filling the role of an optical memory for high density recording, quick recording and low recording energy. SOLUTION: A quantum case memory filling the role of a non-volatile memory furnishing the existance of electron or hole taking localized state in the quantum case is composed of a quantum case QD, barrier layers B encircling the quantum case QD so as to electrically separate the case QD from ambient elements as well as a Schottky junction formed on both surfaces of the barrier layers B as if holding the quantum case QD. At this time, the quantum case QD may be arranged quadratically or three-dimensionally. Furthermore, the electron or the hole is to be inputted, read-out and erased by irradiating the quantum case QD with light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical memory, and more particularly to a quantum box memory using a semiconductor quantum box.

[0002]

2. Description of the Related Art A 1-bit information recording area of a conventional readable / writable optical memory represented by a magneto-optical memory and a phase change memory is about 1 μm ² . Further, in order to record information, it was necessary to irradiate the surface of the memory board with light having a power of several mW for several tens of ns.

[0003]

In the magneto-optical memory and phase change memory using light as described above, the 1-bit recording area is limited by the wavelength for recording or reading, and the 1-bit recording area is set to 1 μm ² or less. Is difficult to do.

Further, according to the conventional principle of information recording, it is necessary to heat the memory board surface to several hundred degrees (Curie temperature or phase transition temperature) or more for recording information, and therefore several meters are required.
It was necessary to irradiate the surface of the memory board for several tens of ns or more with light having a power flux of W / μm ² .

Therefore, an object of the present invention is to provide a quantum box memory that functions as an optical memory with high recording density, high speed recording and low recording energy.

[0006]

In order to achieve the above object, a first invention of the present invention provides a quantum box and a barrier layer surrounding the quantum box so as to electrically isolate the quantum box from the surroundings. A Schottky junction formed on both surfaces of the barrier layer so as to sandwich the box, and the presence or absence of an electron or a hole occupying a localized state in the quantum box is used as bit information and functions as a nonvolatile memory. The quantum box memory is characterized in that

The second invention of the present invention is two-dimensional or three-dimensional.
Quantum boxes arranged in a number of dimensions, a barrier layer that covers the quantum boxes so that each quantum box is electrically isolated from the surroundings, and both surfaces of the barrier layers that sandwich the quantum boxes between them. A quantum box memory having a formed Schottky junction and serving as a non-volatile memory with bit information indicating the presence or absence of electrons or holes occupying a localized state in the quantum box.

According to a third aspect of the present invention, a large number of quantum boxes having different electron-hole pair production energies are arranged two-dimensionally or three-dimensionally, and each quantum box is electrically connected from the surroundings. And a Schottky junction formed on both surfaces of the barrier layer so that they are separated by a Schottky junction, and the presence or absence of an electron or a hole occupying a localized state in the quantum box is used as bit information. , A quantum box memory characterized by functioning as a non-volatile memory.

A fourth invention of the present invention is the third invention according to the third invention, wherein a plurality of dot structures are formed in an island shape by growing a thin film on a substrate which is not lattice-matched as a quantum box.
Alternatively, the quantum box memory uses a large number of dot structures formed by etching the substrate using the island-shaped dot structure as a mask.

According to the basic structure of the quantum box memory of the present invention, a quantum box composed of a semiconductor having a narrow energy gap is covered with a barrier layer composed of a semiconductor having a wide energy gap, and Schottky is formed on both surfaces of the barrier layer. A non-volatile optical memory having a structure having a junction, in which the presence or absence of an electron or a hole occupying a localized state in the quantum box is used as bit information.

The input and output of such a quantum box memory are
For example, when a bias is applied between both Schottky junctions, a photon having an energy that resonates with the electron-hole pair production energy localized in the quantum box is irradiated, and the electrons or holes generated in the quantum box are irradiated. While pulling one out of the quantum box,
Information is recorded by leaving the other electron or hole in the quantum box. After that, the information is not lost even when the bias is not applied, and the memory functions as a nonvolatile memory. Also,
Irradiation of photons having energy resonating with electron-hole pair formation energy localized in the quantum box without applying the bias voltage, and absorption of the irradiated photons depending on the presence or absence of electrons or holes in the quantum box. Alternatively, the recorded information can be read by observing the presence or absence of light emission.

As described above, the recording of information is carried out by light-based electronic recording.
It is performed by generating a hole pair, and reading is performed by using the difference in light absorption depending on the presence or absence of an electron or a hole. Therefore,
When recording with excitation light of several mW / μm ² , the time required for recording is several tens of ps. Therefore, it is possible to perform recording at higher speed and lower energy than the conventional optical memory.

According to the quantum box memory of the second invention, a large number of quantum boxes are arranged two-dimensionally or three-dimensionally so that each quantum box is electrically isolated from the surroundings. Since it is covered with a barrier layer, it is possible to fabricate, for example, 10 ² to 10 ⁴ quantum boxes in one light spot, and 1 bit of information is converted to 10 ² to 10 ⁴ quantum boxes. It is possible to record simultaneously, and it is possible to improve the reliability of recording 1-bit information.

The quantum box memo according to the third and fourth inventions
According to Re, many electron-hole pair production energies with different energies
By arranging the quantum boxes of two-dimensionally or three-dimensionally
By changing the wavelength of the recording / reading light
For example, 10 in one light spot ^Two-10^ThreeBit information
Since it is possible to record / read
The memory has a recording density of 10 times that of a conventional optical memory.^Two-10
^FourDouble the density is possible.

In addition, Stranski-K is formed into an island shape by growing a thin film on a substrate that is not lattice-matched.
Since the bit structure formed by the rastanow mode growth has a certain degree of random shape and size, by using this bit structure as a quantum box, a large number of quantum boxes with different electron-hole pair production energies can be obtained. It becomes possible to easily arrange two-dimensionally or three-dimensionally and it can be used as the wavelength multiplexing memory.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. The same reference numerals are given to corresponding parts in all the following drawings. [First Embodiment] First, a quantum box memory according to a first embodiment of the present invention will be described.

FIG. 1 is a unit cell structure of the quantum box memory according to the first embodiment, and FIG. 2 is a sectional view taken along the line I--I of FIG. The sectional view taken along the line ΙΙ-ΙΙ in Fig. 1 is also the same as that in Fig. 2. In FIG. 2, QD represents a box-shaped well layer, so-called quantum box. In FIGS. 1 and 2, B is a barrier layer, EL _U and EL _L are Schottky electrodes to the upper and lower portions of the barrier layer B, and O ₁ and O. ₂ indicates the opening of the Schottky electrode opened on the top of the quantum box. Quantum box Q
Examples of the substance that forms D include InAs (or G
aAs, InGaAs, Ge, etc.) and the barrier layer B
As the material forming the, for example, a quantum box is InAs or In
In the case of GaAs, GaAs, AlGaAs, GaSb, A
lGaSb, when the quantum box is GaAs, AlGaAs,
When the quantum box is Ge, Si or the like is used. Quantum box QD
The distances d ₁ and d ₂ from the electrodes EL _U and EL _L are distances at which electrons or holes cannot tunnel (for example, 100 n
m or more). The thickness a of the quantum box in the direction perpendicular to the Schottky electrode is preferably 1 μm or less at which the discretization of the energy levels in the quantum box becomes remarkable.
The smaller a is, the more discrete the energy levels of the quantum boxes are.

Energy in the direction along the line α-α in FIG.
The band diagram is shown in FIG. In FIG. 3, E _V1, E_C1Are each
Energy of valence band edge and conduction band edge of the material forming the barrier layer B
Rugie, EG₁, EG_TwoRespectively form the barrier layer B
Energy gap width of materials, materials forming quantum boxes
Represents the energy gap width of_FFermiener
Represents ghee. Also, φ₁, Φ_TwoIs the barrier layer B, the amount
The electron affinity of the substance forming the child box QD is shown. This
They satisfy the following formula.

Φ ₁ <φ ₂ (1) φ ₁ + EG ₁ > φ ₂ + EG ₂ (2) From these conditions, the quantum box memory of the present embodiment is formed by a type I heterojunction superlattice. There is. As described above, InAs or InGaAs is used as the quantum box QD, and GaAs, AlGaAs, GaSb, A as the barrier layer B.
When lGaSb is used, when GaAs is used as the quantum box QD and AlGaAs is used as the barrier layer B, when Ge is used as the quantum box and Si is used as the barrier layer, the formulas (1) and (2) are satisfied. Has been done.

Further, E ₀ ^e and E ₀ ^h are quantum boxes Q, respectively.
These are the lowest energy level of electrons localized in D and the lowest energy level of holes. Further, φ _B ^e and φ _B ^h respectively represent Schottky barrier heights for electrons and holes at the interface between the external electrode and the barrier layer.

[0021] Since electrons thermally quantum boxes QD from valence band is not _{^{excited, E 0 e -E 0 h>}} k B T ... (3) thermally electrons from the external electrode is not written are excited for the Schottky barrier _{^{conditions, φ B e, φ B h}} > k B T ... (4) ( where, k _B = 1.38 × 10 ²³ [J / K], T: absolute temperature) be the I have to.

In the following description, electrons will be described as particles that carry information. Input to the quantum box memory according to the first embodiment is performed as follows. At the time of input, for example, the lower electrode EL _L is grounded and the bias voltage V _{g is} applied to the upper electrode EL _U.
Is applied to bias the device as shown in FIG. The bias voltage Vg can also be applied by applying an electric field in a non-contact manner by vertically disposing electrodes separated from the quantum box memory.

With the bias voltage thus applied, the frequency ν = (E ₀ ^e −E ₀ ^h ) / h (5) (where, h = 6.63 × 10 ⁻³⁴ J · s) The monochromatic light is irradiated onto the opening O ₁ of the upper electrode EL _U or the opening O ₂ of the lower electrode EL _L. Then, by irradiation of this light,
Electron-hole pairs are generated in the quantum box QD. When the energy levels E ₀ ^e and E ₀ ^h are doubly spin-degenerate, the number of electron-hole pairs generated at this time is two. Since holes of this electron-hole pair are applied with a bias voltage, the thickness of the barrier layer B becomes substantially thin and tunnels and is absorbed by the lower electrode EL _L (FIG. 4). reference). As a result, two electrons are left in the quantum box QD even if the irradiation of the frequency ν light is stopped. As a result, electrons can be input into the quantum box QD. The bias voltage in this case is an electric field such that electrons or holes can tunnel the barrier layer B ₁ which is not normally tunneled, and specifically, the barrier layer B _{1 has} a thickness of 100 nm, for example.
It is about several V per hit.

It should be noted that once the holes are Schottky electrodes EL _U
The barrier layer B is thick enough to prevent tunneling when it is absorbed into the quantum barrier, so that unless holes with thermal energy exceeding the Schottky barrier are excited, the holes recombine with electrons in the quantum box and Never erase. Therefore, if the condition of Expression (3) is satisfied, the information in the quantum box is retained even if the external bias V _{g is set} to zero, and the quantum box functions as a nonvolatile memory.

Next, reading of recorded information from the quantum box memory in the first embodiment is performed as follows. In order to read out the bit information in the quantum box, light having the same frequency ν as the photon used for the input is irradiated and its absorption or emission is observed. If an electron exists in the energy level E ₀ ^e of the quantum box QD, the electron is not resonantly excited by the light of the frequency ν, and the light is absorbed, and light is emitted when the excited electron recombines with the hole. Instead, the light having the frequency ν is transmitted as it is, as shown in FIG. On the other hand, if there is no electron at the energy level E ₀ ^e of the quantum box QD, as shown in FIG. 6, the electron is resonantly excited by the light of the frequency ν, and the absorbed or excited electron of the light is positive. Emission occurs when recombining with the pores.

Therefore, the presence / absence of electrons in the quantum box can be read out by observing the presence / absence of absorption or emission of light of the frequency ν with a photodetector. In this way, the reading is non-destructive, so that no bit information is lost and thus the information can be read many times.

In this case, the photodetector for detecting the absorption of light should be arranged at a position through which the incident light passes, and the photodetector for detecting the light emission should be arranged at a position different from that of the photodetector for detecting the absorption. You can Next, a method of erasing bit information in the quantum box memory according to the first embodiment will be described. To perform erasure-bit information quantum box QD, for example external bias V _g while that was zero phi _B ^h, it illuminates the large photon energy than phi _B ^e. At this time, electrons in the quantum box are excited and absorbed by the external electrode from the quantum box, or holes are injected from the external electrode into the quantum box QD and recombined with electrons in the quantum box, and Erase the electrons (see FIG. 7).

In the above example, of the electron-hole pairs generated at the time of input, the case where holes are extracted and the electrons are treated as information bits has been described. However, the electrons are more easily extracted to the external electrode. In other words, the inequality (potential barrier height of barrier layer for electrons (V _{e in} FIG. 4) × effective mass of electrons) <(potential barrier height of barrier layer for holes (V _{h in} FIG. 4) × hole When the effective mass) is satisfied, holes can be treated as bits of information by replacing “electrons” with “holes” in the above description.

Next, a method of manufacturing the quantum box memory according to the first embodiment will be described with reference to FIG. Here, InGaAs is used as the material forming the well layer W, and GaAs is used as the material forming the barrier layer B. The well layer W is processed through the following process to form the quantum box QD.

First, as shown in FIG. 8A, for example, G
On the aAs substrate S, for example, molecular beam epitaxy (MB
E) method, metalorganic chemical vapor phase (MOCVD) method, metalorganic molecular beam epitaxy (MOMBE) method, etc., to form a barrier layer B made of a GaAs layer and having a thickness a so as to be d ₂ together with the thickness of the substrate. W layer made of InGaAs, thickness d ₁
The barrier layer B made of GaAs is sequentially epitaxially grown. Here, the thickness d of the barrier layer B made of a GaAs layer
₁ , ₁ and ₂ are the thicknesses at which tunneling is not possible. Specifically, for example, 100 nm or more, and the thickness a of the well layer W is a thickness at which the discretization of energy levels in the quantum box becomes remarkable. Yes,
It is typically several nm to several tens of nm.

Next, as shown in FIG. 8B, a mask M having etching resistance is formed on the barrier layer B by using, for example, a photolithography method, an electron beam lithography method, or a scanning tunneling microscope (STM). To do. Specifically, the mask M is formed of, for example, SiO ₂ , Si ₃ N ₄ or the like when using a photolithography method, an electron beam lithography method, or a scanning tunneling microscope (STM).
The area of the mask M is preferably (several nm) ² .

Next, using the mask M, a dry etching method having a strong anisotropy, for example, CH ₄ as an etching gas is used.
+ He or SiCl ₄ + He, Cl ₂ etc. reactive ion etching (RIE) method or electron cyclotron resonance (ECR) reactive ion beam etching (E
The barrier layer B and the well layer W are sequentially etched in the direction perpendicular to the substrate surface by the CR-RIBE method or the like. As a result, the barrier layer B and the well layer W are etched into a rod shape as shown in FIG.

Next, as shown in FIG. 8D, a material for forming the barrier layer B, for example, GaAs is epitaxially grown and buried in the portion removed by the above-described etching. Next, after selective etching is performed to remove the mask M, a resist pattern having a shape corresponding to the upper electrode EL _U and the lower electrode EL _L is formed (not shown), and a Schottky junction is formed by, for example, a vacuum evaporation method. For example Al
After forming a metal film such as a film or Au film on the upper and lower sides of the element, this resist pattern is removed together with the metal film formed thereon (lift-off). As a result, FIG. 1 and FIG.
An upper power supply E having openings O ₁ and O ₂ as shown in FIG.
L _U and the lower electrode EL _L are formed. The electrodes EL _U and EL _L can also be formed by forming metal films on the top and bottom of the device and then patterning the films by etching or the like. In addition, several tens of nm above and below the device
When it is possible to form a metal thin film or the like having a thickness sufficient to transmit light, the opening O ₁ as shown in FIGS.
And O ₂ may not be formed.

In this way, the quantum box memory according to the first embodiment is formed. As described above, according to the quantum box memory according to the first embodiment, since the recording of 1-bit information is performed by the generation of two electron-hole pairs in the quantum box QD, the energy consumed is extremely high. It is small and the recording speed is extremely fast. Specifically, in the conventional optical memory, 1-bit recording was performed by irradiating light of several mW / μm ² for several tens of ns, but in the present embodiment, irradiation of light of several mW / μm ² for several tens of ps was performed. Good. [Second Embodiment] Next, a quantum box memory according to a second embodiment of the present invention will be described.

FIG. 9 is a sectional view of the quantum box memory according to the second embodiment. As shown in FIG. 9, in the quantum box memory according to the second embodiment, the quantum boxes QD are two-dimensionally arranged in a matrix, and the quantum boxes QD are covered with a barrier layer B. Corresponding metal electrodes EL _U , EL
_An opening O is provided in _L. Therefore, it has a structure in which the quantum box memories according to the first embodiment are arranged in a matrix.

As described above, when the structure in which the quantum boxes are arranged two-dimensionally is used, recording, writing and erasing are performed by light irradiation in the same manner as the quantum box memory according to the first embodiment of the present invention, and the conventional optical memory is used. 2 in the same way as
A disk-type memory can be realized by dimensionally scanning or using a two-dimensional light pattern.

The method of manufacturing the quantum box memory according to the second embodiment of the present invention is the same as the method of manufacturing the first example of the present invention, and therefore will be omitted. Quantum box as above
When it is formed of a semiconductor such as e, InAs, InGaAs, or GaAs, the wavelength of light having the energy required to generate electron-hole pairs is about 1 μm. Therefore, the light spot cannot be narrowed down to several μm ² or less. In this respect, the recording density is 1 bit / μm ² as in the conventional optical memory. On the other hand, the cross-sectional area of the quantum box in the present invention is several hundreds.
Since it is less than nm ² , according to the second embodiment of the present invention, it is possible to produce 10 ² to 10 ⁴ quantum boxes in one light spot. Therefore, 1 bit of information is 1
It is possible to record simultaneously in 0 ² to 10 ⁴ quantum boxes, and it is possible to improve the reliability of recording 1-bit information. Further, as in the first embodiment, the energy of light required for recording 1 bit and the time required for recording are extremely short, so that a disk type memory with low energy consumption and high recording speed can be realized. [Third Embodiment] Next, a quantum box memory according to a third embodiment of the present invention will be described.

10 and 11 show a quantum box according to the third embodiment.
It is sectional drawing of memory. In Fig. 10, the horizontal size is different.
The difference is that a large number of quantum boxes are formed.
The structure is the same as that of FIG. 9 except for. In addition, FIG.
Is a two-dimensional array of many quantum boxes with different shapes and sizes.
A metal electrode film EL having a thickness of several tens of nanometers and transmitting light._U, E
L_LAre provided, there is a difference in vertical and horizontal sizes.
It has the same structure as in FIG. 9 except for and. Figure 10, Figure
11, the quantum box QD _iIs an electron in the quantum box −
The minimum energy required to generate a hole pair is hν_i0=
(E_i0 ^e-E_i0 ^h) (Where E_i0 ^e, E_i0 ^hEach
Re quantum box QD_iEnergies and positives of electrons in
Which represents the quantum box as
I do.

In the following description, holes are referred to as particles carrying information.
I will explain. The quantum box memory according to the third embodiment
Recording of information is performed in the same way as in the first embodiment, and the via is stored in the quantum box.
Frequency, ν_i0Irradiate the light of. To illuminate this light
Therefore, the quantum box QD is selectively_iElectron-hole pairs only inside
Is generated. Energy level E ₀ ^e, E₀ ^hIs double
When pinned and degenerate, the electrons generated at this time −
There are two hole pairs. Of this electron-hole pair, the electron
Part electrode EL_UIs absorbed by. As a result, the frequency ν_i0Light of
Quantum box QD_iTwo electrons are left in
You. This allows the quantum box QD to be selectively_iOf holes into
You can enter.

It should be noted that once the electrons are absorbed by the Schottky electrode, the barrier of the barrier layer is thick enough to prevent tunneling. Therefore, unless the electrons having energy exceeding the Schottky barrier are excited thermally, the electrons in the quantum box Information is not erased by recombination with holes. Therefore, if the conditional expression (4) is satisfied in each quantum box, the information in the quantum box is retained even if the external bias V _{g is set} to zero, and the quantum box functions as a non-volatile memory.

As described above, there are 10 spots in the light spot.^Two
-10^FourIt is possible to produce individual quantum boxes. Ma
In addition, the energy of electron-hole pair generation depends on the size of the quantum box.
So different. Therefore, 10^Two-10^FourKind of rhino
Quantum box with cavities is created and recorded in one light spot
The frequency of light is 10 in one light spot.^Two-10
^FourBy changing the street, you can
A few μm^TwoWithin 10^Two-10^FourRecord bit information
By doing so, it can be used as a wavelength multiplexing memory.
However, for an electron-hole pair in an excited state in a quantum box
Increase the frequency and record until reaching the generated energy
If you go there, double information will be recorded in the quantum box.
Will be lost. Therefore, the maximum frequency of recording light varies.
The smallest excitation in a quantum box sequence consisting of quantum boxes of various sizes.
Energy of electron-hole pairs in the state / h ”
You. The width of the writing frequency is Δν, which is the maximum in the quantum box.
Has the lowest electron-hole pair production energy and the lowest
The energy difference (non-uniform band width) from the quantum box is ΔE
Then, the number of bits in the quantum box is ΔE / hΔν (here
And h = 6.63 × 10^-34J ・ s).

Next, the reading of the quantum box memory information in the third embodiment of the present invention is carried out as follows in the same manner as in the first embodiment. In order to read the bit information in the quantum box, light with a frequency ν _i0 is irradiated and its absorption or emission is observed. If there is a hole in the energy level E _i0 ^h of quantum boxes QD _i, and electronic absorption of the light is not resonant excitation of the quantum box QD _i by light vibration frequency [nu _i0, excited electrons positive No light emission occurs when recombining with the holes, and the incident light is transmitted as it is. On the other hand, the energy level E of the quantum box QD _i
If there are no holes in _i0 ^h , the electrons in the quantum box QD _i are selectively resonantly excited by the light of the frequency ν _i0 , and when the absorbed or excited electrons of the light recombine with the holes. Light emission occurs.

Therefore, a quantum box having a size of 10 ² to 10 ⁴ is produced in one light spot, and the frequency of light to be read out is 10 ² to 10 ⁴ in one light spot.
Recorded by changing the frequency in 10 ² to 10 ⁴ ways within one light spot, that is, within several μm ² by detecting the presence / absence of absorption / emission for each frequency. Information of 10 ² to 10 ⁴ bits can be read.

Next, a method of erasing bit information in the quantum box memory according to the third embodiment will be described. Similar to the method of erasing the bit information in the quantum box memory in the first embodiment, in order to erase the bit information in the quantum box QD _i , electrons or holes are set with the external bias V _{g set} to zero. Irradiate photons with energy greater than the Schottky barrier height between the barrier layer and the outer electrode. At this time, holes in the quantum box are excited and absorbed from the quantum box to the external electrode, or electrons are injected from the external electrode into the quantum box and recombined with holes in the quantum box, Erase the holes.

In the above example, the case where the hole is treated as a carrier of information has been described. However, when the hole is more easily extracted to the external electrode, that is, the inequality (potential barrier height of barrier layer against electron x electron If (effective mass)> (potential barrier height of barrier layer for holes × effective mass of holes) is satisfied, electrons are treated as bits of information by replacing “holes” with “electrons” in the above description. It can be applied in any case.

Next, a method of manufacturing the quantum box memory according to the third embodiment of the present invention will be described. In the fabrication of the structure shown in FIG. 10, the mask M having a different size in the fabrication method of the first embodiment is used for electron beam lithography, metal fine particle formation method from metal thin film, InAs St on GaAs.
ranki-Krastanow growth [G. Yusa
et al. , J. et al. Appl. Phys. 34 11
98 (1995)].

The fabrication of the structure shown in FIG.
Using a crystal growth method such as E or MOCVD, for example, a few atomic layers of InGaAs having no lattice matching with GaAs are grown as well layers on top of GaAs as a barrier layer, and GaAs of the barrier layer is subsequently grown. At this time, InGaA
s grows by a growth mechanism called Stranski-Krastanow mode, and is self-forming several tens nm.
Semiconductor fine particles having a dot structure, which have no diameter defect and are electrically isolated (connected in the drawing but electrically isolated) are formed. The fluctuation of that size is 1
It is about 0%, and the spread of the electron-hole pair generation energy due to the size fluctuation reaches several 10 meV [D. Leonard et al. , App
l. Phys. Lett. 63 3203 (199
3)]. In this case, the dot structure may be formed by increasing the size fluctuation. afterwards,
It is only necessary to form a metal electrode film of several tens of nm that transmits light on the front and back surfaces of the crystal by using a resistance heating vapor deposition method, sputtering or the like.

As a method for producing semiconductor fine particles,
In addition, for example, GaA including a buried AlGaAs layer
After the wet layer of InGaAs fine particles (a layer having a thickness of about 0.5 to 1 nm connecting the fine particles) formed on s as described above is removed by etching with HCl gas,
By etching the GaAs with Cl ₂ gas using the remaining InGaAs fine particles as an etching mask, G
a quantum box of aAs is formed, and then InGaA of the mask is formed.
After removing s, by growing AlGaAs, the G of the dot structure surrounded by AlGaAs of the barrier layer is also formed.
aAs quantum boxes can be formed [G. Yusa
et al. , J. et al. Appl. Phys. 34 119
8 (1995)].

As described above, the quantum box memory realized is not only high-speed recording and low recording energy, but also uses 10 ² to 10 ² as compared with a conventional optical memory by using light of a large frequency for recording light. ⁴ times 10 ² to 10 ⁴ / μ
High density recording of m ² is possible.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the technical idea of the present invention. For example, it goes without saying that the manufacturing method of the quantum box memory described in the first embodiment, the second embodiment, and the third embodiment is only an example, and other manufacturing methods may be used.

[0051]

As described above, according to the present invention,
An optical memory with high recording density, high speed recording and low recording energy becomes possible.

[Brief description of drawings]

FIG. 1 is a perspective view showing a quantum box memory according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line I-I or II-II in FIG.

FIG. 3 is an energy band diagram in a direction along a line α-α of FIG.

FIG. 4 is an energy band diagram for explaining a recording method in the quantum box memory according to the first embodiment of the present invention.

FIG. 5 is an energy band diagram for explaining a reading method of the quantum box memory according to the first embodiment of the present invention.

FIG. 6 is an energy band diagram for explaining a reading method of the quantum box memory according to the first embodiment of the present invention.

FIG. 7 is an energy band diagram for explaining a method of erasing the quantum box memory according to the first embodiment of the present invention.

8A to 8D are cross-sectional views for explaining the method of manufacturing the quantum box memory according to the first embodiment of the present invention.

FIG. 9 is a sectional view showing a quantum box memory according to a second embodiment of the present invention.

FIG. 10 is a sectional view showing a quantum box memory according to a third embodiment of the present invention.

FIG. 11 is a cross-sectional view showing an example of a quantum box having a dot structure formed by Stranski-Krastanow mode growth.

[Explanation of symbols]

EL _U ... Upper electrode, EL _L ... Lower electrode, B to B _{n + 1} ... Barrier layer, QD, QD ₀ , QD ₁ ... Quantum box, O ₁ , O ₂ ... Opening

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichiro Hase 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (8)

[Claims] 1. A quantum box, a barrier layer surrounding the quantum box so as to electrically isolate the quantum box from the surroundings, and a Schottky junction formed on both surfaces of the barrier layer so as to sandwich the quantum box therebetween. A quantum box memory characterized in that the presence or absence of electrons or holes occupying a localized state in the quantum box is used as bit information and functions as a non-volatile memory. 2. An electron generated in the quantum box by irradiating with a photon having an energy that resonates with an electron-hole pair formation energy localized in the quantum box in a state in which a bias is applied between the Schottky junctions. Alternatively, one of the holes is extracted from the quantum box, while the other electron or hole is left in the quantum box to record information, and the electron-hole localized in the quantum box without applying the above bias voltage. The recorded information is read by irradiating a photon having an energy resonating with the pair production energy and observing whether or not the irradiated photon is absorbed or emitted depending on the presence or absence of an electron or a hole in the quantum box. Item 1. The quantum box memory according to item 1. 3. The quantum box memory according to claim 1, wherein electrons or holes in the quantum box are erased by irradiating the quantum box with high-energy photons. 4. The sum of the electron affinity and the band gap difference of the material forming the barrier layer is larger than the sum of the electron affinity and the band gap difference of the material forming the quantum box.
Quantum box memory described. 5. A quantum box between a plurality of quantum boxes arrayed two-dimensionally or three-dimensionally, a barrier layer covering the quantum boxes so that each quantum box is electrically isolated from the surroundings. And a Schottky junction formed on both surfaces of the barrier layer so as to sandwich it, and the presence or absence of an electron or a hole occupying a localized state in the quantum box is used as bit information to function as a nonvolatile memory. Quantum box memory characterized by. 6. A large number of quantum boxes having different electron-hole pair production energies are arranged two-dimensionally or three-dimensionally, and the quantum boxes are barriers so that each quantum box is electrically isolated from the surroundings. It has a Schottky junction formed on both surfaces of the barrier layer and sandwiched between layers, and the presence or absence of an electron or a hole occupying a localized state in the quantum box is used as bit information and functions as a nonvolatile memory. A quantum box memory characterized in that 7. The quantum box is irradiated with photons having multiple energies that resonate with electron-hole pair formation energies localized in the quantum box with a bias applied between the Schottky junctions. One of the generated electrons or holes is extracted from the quantum box, while the other electron or hole is left in the quantum box to record information in a multiplexed manner. Multiple recorded information is read by irradiating photons having multiple energies having hole pair generation energy and observing absorption or emission of the irradiated photons depending on the presence or absence of electrons or holes in the quantum box. The quantum box memory according to claim 6. 8. A quantum box, wherein a large number of island-shaped dot structures are formed by growing a thin film on a substrate not lattice-matched, or the island-shaped dot structure is used as a mask to etch the substrate. 7. The quantum box memory according to claim 6, wherein a large number of dot structures formed by the above are used.