The method of obtaining quantum-size semiconductor structures

 

(57) Abstract:

Use: in the manufacture of quantum-size semiconductor structures. The inventive method includes the formation of quantum-dimensional regions in the process of growing structures by molecular-beam epitaxy. The formation produced by the monochromatization and focusing of the beam of dopant atoms with the subsequent direction of the atom beam on the diffraction element, the selection of the diffracted beam of the first diffraction maximum and its direction on the surface epitaxially patterns. 7 C. p. F.-ly, 1 Il.

The invention relates to microelectronics, in particular to a technology for thin-film epitaxial structures for quantum-well semiconductor devices.

One of the main trends in the development of semiconductor electronics at the present time is to increase speed and reduce power consumption of semiconductor devices (in particular, transistors) with a further increase in the degree of miniaturization.

Effective means of solving these problems is the creation of quantum devices in which the linear dimensions of the IDT-regular electronic States, in which the electron motion is restricted or in two directions ("quantum threads"), or in all three dimensions ("quantum dot") [1]

When electrons are confined in a limited potential barriers in the field of space, comparable in size with the wavelength of the electron, begin to show their wave properties and they can tunnel through restrictive barriers. In addition, there appear two interrelated size quantization effect and resonance. Realization of devices running on these effects, allows to provide the switching speed close to the maximum achievable by tunneling, and low power consumption (due to the small size of the quantum device) because of quantum effects, the current is very sensitive to changes in applied voltage.

This leads to the importance of obtaining quantum-well structures (in particular, epitaxial), in which the conduction electrons are concentrated in the areas of structure, located in the upper layer, and the linear dimensions of which are comparable to the electron wavelength (e.g. 200 for GaAs at T 20aboutC).

A method of obtaining one dimensional conductive about the persons is the following. In politology GaAs substrate implanted Si ions, forming it conductive layer with a width of 20 μm. Then by means of rapid thermal annealing is performed to activate the implanted state, after which the substrate is implanted ions Si2+forming in her high-resistance region with a width of 0.1 μm, limiting conductive layer in a very narrow channel.

Width channel with a one dimensional conductivity ("quantum threads") varied in the range of 0.2 to 1.0 μm. The conductivity of the channel decreased with decreasing width d and reached zero at d of 0.48 μm and very low temperatures (about 1.3 to 2.2).

The disadvantage of this method is the occurrence of a matrix material radiation damage caused by the introduction of foreign ions (in this case, ions of Si in GaAs).

Over time the distribution of defects in the matrix material is changed, which leads, ultimately, to the uncontrolled change of parameters of semiconductor.

As a prototype of the proposed method the chosen method of obtaining quantum-well epitaxial structures ("quantum wires"), which consists in growing the epitaxial substrate structure, with the bulk doping an impurity of Verkhnee surface structure is formed system "quantum wires with cross-sectional dimension of 250-550 nm [3] it should be noted, that the width of electronic channels is smaller than the geometrical width and is about 100-150 nm, which is associated with the production technology.

However, using the technique of photolithography, in particular etching agents for forming the desired pattern on the resist, leads to contamination of the semiconductor material extraneous inclusions and further reduces its parameters.

This method does not allow one dimensional e-channels with preset width (due to the effects of protravlivanija) at the edges of the Windows in the resist width of electronic channels get less than their geometric width equal to the transverse size of the "window").

In addition, the width of the generated electronic channels limited to the above effects, the size of slots in the resist. Using photolithography determines the complexity of this method.

The task of the invention decrease the size and improve the accuracy of formation of quantum-well regions, increasing the purity of the structure and simplification of the way.

The invention consists in that in the method of obtaining quantum-well epitaxial structures, namely in the direction of podlozku areas referred to region to form by monochromatization and focusing of the beam of dopant atoms with the subsequent direction of the beam of atoms on deficieny element, separation of the diffracted beam of the first diffraction maximum and its direction on the surface of the epitaxial structure, and a constant d of the diffraction element selected from a ratio

d , (1) where M is the mass of the atom dopant, kg;

is the diffraction angle, ug. the hail.

T the temperature of the atoms of the beam of dopant, TO;

h the Planck constant, JS;

k Boltzmann's constant, j/K.

Monochromatization atoms beam dopant is carried out by laser cooling.

The beam of dopant atoms incident on the diffraction element, focuses in the form of a point or line (point or line focus) depending on the desired form of quanta of dimensional quantum dot or a quantum filament, respectively.

As a component of the grown epitaxial structure can be used the elements of the III and V groups (e.g., As, and Ga), or the elements of group IV (Si, Ge), and as a dopant of Si and b respectively.

The drawing shows the e in a vacuum chamber (not shown) of the substrate 1, on which is grown an epitaxial structure, molecular sources 2 component of the grown structures oriented on the substrate 1, the molecular source 3 of dopant atoms, lasers 4 located outside the vacuum chamber, with a system of mirrors 5, the focusing system made in the form of a set of collimating slits 6, the diffraction element 7, the mobile device 8 cooling and movable bounding the aperture 9.

Collimating slits 6 are in the form of a diaphragm with a circular or rectangular holes (the size of a few tenths of a mm) and serve to cut out the beam of dopant atoms areas round or linear cross-section on the surface of the diffraction element 7 (point or line focus). The use of the slits 6 allows you to focus the beam of dopant atoms on different parts of the diffraction element 7 and get further set quatorzieme areas on the substrate 1.

As the diffraction element 7 are used for amplitude or phase grating with a spectral range of 5-20 .

The unit 8 cooling diffraction element 7 is made in the form of cryopanel, allowing Trogo element 7. Based on the ratio of the wolf-Braggot

2d sin = m, (2) where is the diffraction angle (the angle between the direction of the atomic beam and the plane of the diffraction element);

m the order of diffraction peak;

the wavelength de Broglie; expressions for

, (3) where M is the mass of the atom dopant;

V the velocity of the atom dopant;

h is Planck's constant; and the ratio between kinetic and thermal energy of the flow of atoms

kT, (4) where T is the temperature of the atoms in the stream;

k Boltzmann's constant; get

d2(5) or

d (6) 7,010 M-27kg (weight of Si atoms), 10about, T 1, m 1, we have d 10 . This value d is T 15 K, = 3about. The values of T 4 and = 10aboutcorresponds to d 5 .

The proposed method is implemented as follows.

On the substrate 1 are directed molecular flows from sources 2, in which the substrate 1 is formed by epitaxial heterostructure (for example, AlGsAs/ /Gs As). Simultaneously with the formation of the upper layer of the structure is its alloying. Turns on the heater source 3 dopant atoms and, for example Si, proceed into the space between the source 3 and collimating slits 6. Laser 4 that is configured on castoroides using a system of mirrors 5 in beam, propagating towards the atomic beam. Due to the radiation pressure of the laser radiation is slowing and cooling of the atoms of the beam, which minimizes the dispersion of the atoms energy. SelectL<aboutcauses the atoms of the beam will be relative to the laser beam, the required speed and the Doppler shift to strongly absorb the laser light.

The use of laser cooling allows to obtain a beam of atoms with a temperature of several millikelvin (MK). For the proposed method requires a temperature of a few Kelvin (4-10). Next monochromatically beam Si atoms are passed through the collimating slits 6, is supplied to the surface of the diffraction element 7 and is reflected from it in the form of diffraction dots or lines. Aperture 9 highlights of this combination line corresponding to the maximum of the first order, resulting in the surface of the substrate 1 is formed a quantum dot or quantum wire" (depending on the shape of the collimating slits 6) by a few .

The size of the "quantum" field doping is defined as:

L where L is the distance from the diffraction element to the substrate 1;

T temperature is UP>-8and L 10 cm on a substrate can be obtained quantum-dimensional region with transverse size 10 .

1. The METHOD of OBTAINING QUANTUM-SIZE SEMICONDUCTOR STRUCTURES, which includes the cultivation of doped structures by molecular-beam epitaxy and the formation of quantum-dimensional regions, characterized in that the formation of quantum-well regions are produced in the process of growing structures through mohamedsalay and focusing of the beam of dopant atoms with the subsequent direction of the atom beam on the diffraction element, the selection of the diffracted beam of the first diffraction maximum and its direction on the surface of the epitaxial structure, and the constant d of the diffraction element selected from a ratio

< / BR>
where M is the mass of the atom dopant, kg;

q is the diffraction angle, deg;

T is the temperature of the atoms of the beam of dopant, TO;

is the Planck constant, j;

k is the Boltzmann constant, j / K.

2. The method according to p. 1, characterized in that monochromatization beam of dopant atoms is realized by means of laser cooling.

3. The method according to p. 1, characterized in that exercise point picture display ambient is linear focusing of the primary beam of dopant.

5. The method according to p. 1, characterized in that as component of the grown epitaxial structure using the elements of the III and V groups.

6. The method according to PP.1 and 5, characterized in that as the dopant used silicon.

7. The method according to p. 1, characterized in that as component of the grown epitaxial structure using the elements of group IV.

8. The method according to PP.1 and 7, characterized in that as the dopant used Bor.

 

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