Просторовий розподіл електрон-діркових пар в Si/Ge гетероструктурах
Photogeneration and transport of nonequilibrium charge carriers, and the determination of photoresponce mechanisms in semiconductor SiGe/Si and SiGe/SiO2/p-Si heterostructures with nanoisland were investigated. The structures were grown by molecular beam epitaxy technique. The work generalizes the r...
Збережено в:
| Дата: | 2015 |
|---|---|
| Автори: | , , , , , , |
| Формат: | Стаття |
| Мова: | Англійська |
| Опубліковано: |
Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2015
|
| Онлайн доступ: | https://surfacezbir.com.ua/index.php/surface/article/view/591 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Surface |
| Завантажити файл: |  |
Репозитарії
Surface| _version_ | 1869291741655334912 |
|---|---|
| author | Lysenko, V. S. Kondratenko, S. V. Melnichuk, Ye. Ye. Terebinska, M. I. Tkachuk, O. I. Kozyrev, Yu. N. Lobanov, V. V. |
| author_facet | Lysenko, V. S. Kondratenko, S. V. Melnichuk, Ye. Ye. Terebinska, M. I. Tkachuk, O. I. Kozyrev, Yu. N. Lobanov, V. V. |
| author_institution_txt_mv | [
{
"author": "V. S. Lysenko",
"institution": "Інститут фізики напіпровідників Національної академії наук України"
},
{
"author": "S. V. Kondratenko",
"institution": "Київський національний університет імені Тараса Шевченка"
},
{
"author": "Ye. Ye. Melnichuk",
"institution": "Київський національний університет імені Тараса Шевченка"
},
{
"author": "M. I. Terebinska",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
},
{
"author": "O. I. Tkachuk",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
},
{
"author": "Yu. N. Kozyrev",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
},
{
"author": "V. V. Lobanov",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
}
] |
| author_sort | Lysenko, V. S. |
| baseUrl_str | |
| collection | OJS |
| datestamp_date | 2018-11-27T09:34:56Z |
| description | Photogeneration and transport of nonequilibrium charge carriers, and the determination of photoresponce mechanisms in semiconductor SiGe/Si and SiGe/SiO2/p-Si heterostructures with nanoisland were investigated. The structures were grown by molecular beam epitaxy technique. The work generalizes the results of studies of morphological, structural, optical and electrical properties of heterostructures with nanoscale objects – quantum dots and quantum wells. It is shown that the photoconductivity of nanoheterostructures SiGe/Si in the infrared range depending on the component composition, size and magnitude of the mechanical stresses in nanoislands Si1-xGex is determined by interband and intraband transitions involving localized states of the valence band of the Ge nanoscale objects. The effects of long-decay photoconductivity and optical quenching of conductivity in SiGe/SiO2/p-Si heterostructures with SiGe nanoclusters was found to be caused by variations of the electrostatic potential in the near-suraface region of p-Si substrate and optically-induced spatial redistribution of trapped positive charges between SiO2/Si interface levels and localized states of Ge nanoislads.
Adsorption complexes of germanium on the reconstructed Si(001)(4×2) surface have been simulated by the Si96Ge2Н84 cluster. For Ge atoms located on the surface layer of the latter, DFT calculations (B3LYP, 6-31G**) of their 3d semicore-level energies have shown a clear-cut correlation between the   chemical shifts and mutual arrangement of Ge atoms. |
| first_indexed | 2025-07-22T19:34:20Z |
| format | Article |
| fulltext |
Поверхность. 2015. Вып. 7(22). С. 285–296 285
UDC 535:016
THE SPATIAL SEPARATION OF ELECTRON-HOLE PAIRS
IN Si/Ge HETEROSTRUCTURES
V.S. Lysenko1, S.V. Kondratenko2, Ye.Ye. Melnichuk2,
M.I. Terebinska3, O.I. Tkachuk3, Yu.N. Kozyrev3, V.V. Lobanov3
1Institute of Semiconductor Physics, 41 Prospect Nauki, 03028, Kyiv, Ukraine
2Taras Shevchenko National University of Kyiv, 64/13 Volodymyrs'ka St., 01601, Kyiv,
Ukraine
3Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine,
17 General Naumov Str. Kyiv, 03164, Ukraine
Photogeneration and transport of nonequilibrium charge carriers, and the determination of
photoresponce mechanisms in semiconductor SiGe/Si and SiGe/SiO2/p-Si heterostructures with
nanoisland were investigated. The structures were grown by molecular beam epitaxy technique. The
work generalizes the results of studies of morphological, structural, optical and electrical properties
of heterostructures with nanoscale objects – quantum dots and quantum wells. It is shown that the
photoconductivity of nanoheterostructures SiGe/Si in the infrared range depending on the component
composition, size and magnitude of the mechanical stresses in nanoislands Si1-xGex is determined by
interband and intraband transitions involving localized states of the valence band of the Ge nanoscale
objects. The effects of long-decay photoconductivity and optical quenching of conductivity in
SiGe/SiO2/p-Si heterostructures with SiGe nanoclusters was found to be caused by variations of the
electrostatic potential in the near-suraface region of p-Si substrate and optically-induced spatial
redistribution of trapped positive charges between SiO2/Si interface levels and localized states of Ge
nanoislads.
Adsorption complexes of germanium on the reconstructed Si(001)(4×2) surface have been
simulated by the Si96Ge2Н84 cluster. For Ge atoms located on the surface layer of the latter, DFT
calculations (B3LYP, 6-31G**) of their 3d semicore-level energies have shown a clear-cut correlation
between the chemical shifts and mutual arrangement of Ge atoms.
Introduction
Germanium nanoclusters grown on/in silicon have been successfully applied in new
optoelectronic, and memory devices. Due to spatial confinement of charge carrier’s motion in
one, two or three directions, respectively, such nanostructures have unique fundamental
properties and technological applications [1, 2]. Of particular interest is attracted by
nanoelectronic devices and systems grown using epitaxy methods - vapor-phase, molecular-
beam and liquid-phase - in which the formation and spatial arrangement of nanoscale
elements was carried out using the effects of self-organization.
In heterosystem Si/Ge with nanoislands distributed across the surface of inherent
nonuniform field of mechanical stresses. Interfaces and their quantum-size classes, wetting
layer (WL) heterogeneity leads to spatial heterogeneity of local electro-physical properties of
Ge nanoclusters and induced spatial variation of the electrostatic potential. These features,
expectedly, will have an impact on the transport of charge carriers along the epitaxial layers.
Heterojunctions Si / Ge are reffered to the second type , in which there is a limitation of
motion of holes in Ge nanoclusters. That's why Ge nanoclusters can be considered as a long-
term trap for holes, charge which a due to downward band bending in the underlying Si.
Semiconductor heterostructures and especially semiconductor heterostructures with
low-dimensional objects, including quantum wells, quantum wires and quantum dots,
currently comprise the object of intensive study [1, 3]. Of particular interest is attracted by
nanoelectronic devices and systems grown using epitaxy methods - vapor-phase, molecular-
286
beam and liquid-phase - in which the formation and spatial arrangement of nanoscale
elements was carried out using the effects of self-organization. Knowledge of the electronic
spectrum, transport, recombination, and photogeneration in self-organized nanostructures is
essential for creation of novel electronic and photonic devices.
Low-dimensional Ge/Si heterostructures have attracted considerable research interest in
recent years, due to their significant potential to impact new electronic devices which are
compatible with the available silicon technology. Optoelectronic devices based on SiGe dots
grown on a Si substrate have been already proposed [4, 5]. The low-dimensional silicon-
germanium alloys have a wide range of applications, including quantum dot IR
photodetectors, memory cells and spintronic devices. Widespread application of such system
is the arrangement of SiGe quantum dots in the space-charge region of heterojunctions,
Schottky diodes, p-n junctions or metal-oxide-semiconductor structures.
Experiment
The molecular beam epitaxy (MBE) technique (“Katun’-B” set-up, produced in
Novosibirsk, Russia) was used to prepare multilayer Ge-Si(100) nanocluster arrays with the
islands of various sizes and surface density. The (100) oriented wafers of n-Si with 7.5 and 20
Ohmcm resistivity and diameter of 76 mm were used as substrates. In order to prepare
multilayer quantum dot systems with regular nanoisland distribution over the substrate
surface, we have proposed to use a system of Si1-xGex intermediate layers with a sub-critical
thickness [5]. The Ge mole fraction x was gradually increased from layer to layer grown at
gradually decreasing substrate temperature started from Ts=500 ºC. The growth process, in
particular the moment of the 2D3D transition in the Stranski-Krastanov growth regime, was
controlled via RHEED (reflection high energy electron diffraction). To study the surface
morphology, atomic force microscopy (AFM) measurements were carried out using an Ntegra
AFM from NT-MDT with a closed loop scanner. Standard Si cantilevers with tips having a
half opening angle of 10° were employed as probes. The growth of each Si intermediate layer
was continued until a high-contrast Si(100)21 RHEED pattern was produced typical of clean
Si. Thus, the multilayer Ge-Si(100) nanocluster arrays were grown at the temperature
Ts=500 ºC.
The Stranski-Krastanow growth of Ge nanoislands on Si(001) surface is an intermediary
process characterized by both 2D WL and 3D island formation. Transition from the layer-by-
layer epitaxy to nanoisland structure growth occurs at a critical layer thickness which is
highly dependent on surface energies and lattice parameters. Germanium nanoclusters grown
on/in silicon or silicon dioxide have been successfully applied in new nanoelectronic,
optoelectronic and memory devices due to quantum confinement effect and possibility of
integration within Si-based technology.
Micro Raman scattering spectra of the investigated structures were recorded at room
temperature using automated Raman diffraction spectrometer T-64000 Horiba Jobin-Yvon
equipped with CCD detector. The line 488 nm of Ar-Kr laser of 3 mW was used for
excitation. Raman spectra were measured for the geometry z(x,y) - x, where axes x, y, z
correspond to [100], [010] and [001] crystallographic directions, correspondingly. Ohmic Au–
Si contacts of rectangular shape and dimensions of 4x1 mm were welded into epitaxial layers
at 370 0С for lateral photoconductivity measurements. The distance between contacts on the
sample surface was 5 mm. Current-voltage characteristics of the structures studied were found
to be linear in the range from –10 V to +10 V at temperatures between 50 and 290 K. Lateral
photoconductivity spectra were measured at excitation energies ranging from 0.48 to 1.7 eV
under illumination with a 250-W halogen lamp. The corresponding direct photocurrent signal
was registered by a standard amplification technique. Spectral dependences were normalized
to the constant number of exciting quanta using anonselective pyroelectric detector.
287
Non-epitaxial Ge nanoislands which are separated from the substrate attract special
interest due to spatial separation of electron-hole pairs leading to reduction of recombination
rate. NI’s growth at the silicon surface covered with ultrathin silicon oxide layer is mainly
determined by the dynamics of changes of the SiOx film structure and physical properties
during Ge deposition and is principally possible at temperatures below ~400 ºC, when the
formation of voids in ultrathin SiO2 films is suppressed. Epitaxy at such low temperatures
puts some limitations on the crystallinity and structural perfection of the obtained
nanoclusters. Increasing of growth temperature up 430 ºC allows to grow epitaxial crystalline
NI’s on silicon, while silicon oxide is destroyed due to thermal decomposition effect.
Results and discussion
Fig. 1a shows AFM image of the top layer of a typical sample with one layer of
nanoislands large scatter and significant in size. The figure shows that the surface contains
nanoislands size of the basics about 98 nm and a height of about 15 nm. The average surface
density of nanoislands is ~ 1010 cm-2. Composition and values of elastic strains in investigated
Ge/Si heterostructures were estimated using Raman spectroscopy. Typical Raman spectrum
of Ge/Si heterostructure containing 5 layers of Ge quantum dots is given in fig. 1b. It contains
phonon bands corresponding to Ge-Ge, Si-Ge and Si-Si vibrations, which is typical for SiGe
heterostructures with nanoislands, which makes possible to estimate content and strain values
for Ge nanoislands [9]. Thus, Ge mole fraction and elastic strains in Ge nanoislands were
found to be x = 0.91 ± 0.02 and, εxx = - 0.01, correspondingly.
The Si1-xGex/Si heterostructures are refered to the second type, in which the potential
well for holes is in the valence band of Si1-xGex (Fig. 2a). Energy diagram of the
heterojunction is primarily determined by the values of the band gap and electron affinity of
the contacting materials. In unstrained Si1-xGex alloys the bandgap decreases monotonically
with increasing of Ge content. Fig. 2b shows the results of numerical calculations of the
energy spectra of holes in Si1-xGex quantum wells with width of 2 nm for different Ge
contents. The analysis shows that the energy position of localized states with respect to top of
Si valence band increases nonlinearly with x due to the dependence of the effective mass of
holes from the strain values in this system. Deep potential well in the valence band favor to
accumulation of holes in Ge nanoislands in the wide temperature range. In the other word, the
Ge nanoislands can be considered as a giant traps for holes. Positive charge of trapped holes
induces downward band bending in the underlying p-Si substrate. Moreover, the band
bending expected to be larger in the region beneath of nanoisland base.
300 350 400 450 500 550
Ge-Ge
= 301.8 sm-1
Si-Ge
= 397.7 sm-1
x = 0.91
xx
= -0.010
c-Si
Ge/Si
In
te
n
si
vi
ty
a
rb
. u
n.
v (sm-1)
a b
Fig. 1. The AFM image of the surface of nanoislands Ge, grown by MBE at 500 º C on the
surface of the substrate p-Si (001) (a) and Raman spectra (b) Si / Ge heterostructure
with nanoislands Si1-xGex on the substrate p-Si (001) (sample 302.03.11).
288
Analyzing the energy diagrams of Si1-xGex/Si heterojunction we can conclude that the
photosensitivity range of these structures is determined by the position of the Fermi level in
the heterostructure, i.e. the concentration dopant in Si substrates and epitaxial films. Interband
optical transitions are realized in the presence of electrons in quantum-sized states of the
valence band nanoislands. For intraband transitions in the valence band, the Fermi level must
be below at least the ground state of nanoislands. Development of efficient optoelectronic
devices requires information on energy, oscillator strengths, and selection rules for interband
and intrabend transitions. Fluorescent measurements do not reflect all transitions possible in
heterogeneous in size and composition of deformations heterostructures. Opportunities of
absorption spectroscopy are severely limited by the fact that the passage of radiation through
nanoscale quantum dot layer is absorbed only by its small part (~ 10-4 - 10-5). As a result, the
direct measurement of the absorption spectra of quantum dots is rather difficult task which
requires a very sensitive technique and long-time measurements. One of methods which
makes possible to study the absorption spectra in nanoscale semiconductor structures is an in-
plane photocurrent spectroscopy. The value of photoconductivity is proportional to the
number of photogenerated charge carriers, and thus the absorption coefficient. Photocurrent
spectroscopy is a direct, sensitive and relatively simple method of studying the shape of
optical absorption spectra and energy and interband transitions possible in heterostructures
with nanoscale objects.
0,3 0,6 0,9
0,1
1
a2
a (
eV
)
Ge content (arb.un.)
Si/Si
1-x
Ge
x
/Si
d = 2 nm
a1
a b
Fig. 2. Energy diagram of Si/Ge heterostructures with Ge nanoislands (a). The activation
energies for localized holes of Si1-xGex quantum wells with width of 2 nm and
different content of Ge (b).
Excitation of nonequilibrium charge carriers in Si/Ge heterostructures with Ge
nanoislands causes conductivity changes in the space charge region of p-Si transport channel.
Photoconductivity spectra (Fig. 3a) measured at excitation and steady temperatures 50-80-120
K contained two components. At hv > εg, Si (1.16 eV at 50 K), the main contribution to the
photoconductivity gives electron-hole pairs photoexcited in the substrate p-Si due to interband
transitions (see transition C in Fig. 2a).
In the spectral region where Si is transparent, photoconductivity originates from
interband electronic transitions involving localized states nanoislands Si1-xGex. The
monopolar photoconductivity was observed in this case. Interband electronic transitions
between localized states of the valence band of SiGe nanoislands and delocalized states of the
conduction band of silicon surrounding can be observed in low-dimentional Si-Ge
heterostructures. The spectral range of interband transitions is determined by Ge contents of
QDs, strain values, and confinement energy for holes in the valence band [10]. Transitions A
289
and B (Fig.2a) are possible if ground states are partially filled by electrons. These transitions
cause the appearance of nonequilibrium electrons in the Si spacer layers and WLs, which are
transport channel, while photoexcited holes are localized in Ge.
0,6 0,8 1,0 1,2 1,4 1,6
0
2
4
6
8
120 K
80 K
P
h
ot
oc
u
rr
en
t(
А
)
hv (еV)
U = 170 мV
50 K
a b
Fig. 3. Photoconductivity spectra of Si / Ge heterostructure with nanoislands Si1-xGex on the
substrate p-Si (001).
Measurements of infrared photoconductivity in Ge-NC/SiO2/Si structures made it
possible to evaluate their electronic spectrum. The PC spectra measured at temperatures 50,
80, and 120 K (Fig.4) give information about energies of electronic transitions in Ge-
NC/SiO2/p-Si structure. The in-plane photocurrent in the range hv > εG,Si is mainly originated
from band-to-band transitions in c-Si. For light excitations with photon energy below band
gap of Si hv < εG,Si (εG,Si=1.17 eV at 77 K ), the electronic transitions from valence band to
conduction band of NCs give main contribution to PC. However, generation of photocurrent
in the range 0.8 < hv < εG,Si for Ge-NC/SiO2/Si is also possible due to transitions between tails
of the density of states in the near-surface c-Si [11], the optical absorption spectra of which
are described by Urbach law. The electron transitions through the states of Ge-NC/SiO2 and
Si/SiO2 interfaces may also be observed, however their contribution to PC is expected to be
small due to high probability for recombination through interface state.
Fig. 4. In-plane PC spectra of Ge-NC/SiO2/Si measured at 50 K, 80 K, and 120 K and HR-
TEM images of Ge NCs grown on silicon oxide.
The contribution of electron-hole pairs photoexcited in Si is observed, when the quanta
energy exceed the band gap value. In the spectral range hv < 1.1 eV, in which c-Si is
transparent, interband indirect transitions take place via the states in the valence and
conduction bands of nanoclusters. Non-equilibrium carriers photoexcited in nanoclusters do
not contribute into carrier transport directly. In order to contribute into the lateral current, the
non-equilibrium electrons and holes should be spatially separated. As for Ge/Si
290
heterojunctions, studied systems referred to type II, where strong confinement for holes in the
region of Ge nanoclusters occurs. In the studied heterostructures, electrons can tunnel through
the oxide SiOx film into the near-surface silicon region and make contribution into
conductivity. At the same time, non-equilibrium holes are localized in the valence band of Ge
nanoclusters, however, they can affect the potential relief in the near-surface region of Si
substrate, and hence, make an indirect effect on the system conductivity.
Thus, photoconductivity of the structures in the range of Si transparency is unipolar –
intrinsic absorption of light in nanoclusters leads to an increase of the electron concentration
in the Si potential well near the SiOx-Si interface and to an increase of the surface
conductance. In this case, the shape of lateral photoconductivity spectra reflects main features
of intrinsic absorption of light in nanoclusters. The edge of PC spectrum of the investigated
structures at 0hv is described by the dependence typical for the indirect band
semiconductors:
2
0
C
hv hv
hv
, (1)
where C is a constant, 0 is the width of the optical band gap. At excitement with quanta
hv<ε0 the Urbach tail is observed due to the crystal structure disorder.
Photocurrent spectroscopy and X-ray diffraction demonstrate that the nanoclusters have the
local structure of body-centred-tetragonal Ge, which exhibit an optical adsorption edge at 0
= 0.48 eV. Taking into account quantum-size effect, this is in a good agreement with the
theoretical calculations of electronic and optical properties of bulk body-centered-tetragonal
Ge and Si, according to which the band gap width for the mentioned polytypes is 0.38 and
0.86 eV, respectively [12].
Influence of the localization of Ge atoms within the Si(001)(4×2) surface layer on
semicore one-electron states. A number of parallel or sequential processes normally occur
as soon as a heterojunction between a germanium quantum dot and reconstructed
Si(001)(42) surface is formed [13, 14]. The most important of those processes is the
formation of >Ge–Ge< surface dimers on the top of a series of asymmetric >Si–Si< species
located on the buckled surface. Taking into account a similarity between Si and Ge covalent
radii (1.17 and 1.22 Å, respectively [16]), a diffusion penetration of Ge atoms into the
crystalline substrate simultaneously with a displacement of an equivalent amount of Si atoms
towards the surface may take place. As the result, a formation of mixed >Si–Ge< surface
dimers is possible. Together with the thermal motion, those processes reduce the abruptness
of the Ge/Si heterojunction [17, 18] and hence deteriorate the robustness of corresponding
solid state electronic devices. Therefore, a reliable location of the Ge sites on the Ge/Si
interface between a germanium quantum dot and Si(001)(42) crystalline substrate presents
an important task.
For such molecular systems as solid-state adsorption complexes, the most precise and
exhausting information on the local environment of atoms can be extracted from
photoelectron spectra [13]. In particular, the latter can be adequately interpreted in terms of
the density of one-electron states over a wide energy range, as soon as corresponding
theoretical models are available [19, 20]. The interpretation of photoelectron spectra is
facilitated by their classification into three regions according to the binding energies of
electrons ( iE ) [19]. The first region (0 ÷ 5 eV) includes a poorly resolvable and rather
complicated structure due to the electrons from valence molecular orbitals (MOs) that mainly
consist of the atomic orbitals (AOs) belonging to partially occupied electron subshells. The
structure of the second region (ca. 15 ÷ 50 eV) is usually well resolved and can be associated
291
with the linear combinations of semicore AOs originating from closed (sub)shells. The latter,
in contrast to valence AOs, in some cases can be combined to so-called internal MOs (IMOs)
[21, 22]. In the case of adsorption complexes, the formation of those IMOs can be monitored
by the exaggerated binding energies of adatoms. Finally, the lines belonging to the third
region of photoelectron spectra (> 50 eV) are almost solely associated with the core-shell
(deep-core) AOs that normally do not contribute to IMOs.
In this paper we report on the calculated densities of one-electron states for a number
of clusters with the same brutto formula Si96Ge2Н84. Thus, so-called cluster A (Fig. 5)
simulates a fragment of the Si(001)(42) relaxed surface with the >Ge–Ge< surface dimer
located over the series of >Si–Si< surface dimers. Clusters А1, А2, А3, and А4 correspond to
different localizations of Ge atoms within the subsurface region of the substrate.
a b c
d e
Fig. 5. a – Configuration of the adsorption complex А (Si96H84•Ge2) with a pure >Ge–Ge<
dimer on the top of a series of surface >Si–Si< dimers; b – Cluster A1; c – Cluster A2;
d– Cluster A3; e – Cluster A4. Clusters A1÷A4 are formed from Cluster A as the
result of a substitution of one or two surface Ge atoms by Si atoms of the substrate.
Calculations of the equilibrium geometry and electronic structure of these clusters
have been performed within the framework of Kohn-Sham density functional theory, using
hybrid B3LYP exchange-correlation functional [23-26] and 6-31 G** basis set. General
Atomic and Molecular Electronic Structure System (GAMESS) suite of programs [27] has
been employed.
We have shown in our previous study [28] that cluster A characterized by a pure >Ge–
Ge< surface dimer is the most stable, while total energies of clusters A1 ÷ A4 with either pure
>Si–Si< surface dimer (A2 and A3) or mixed >Si–Ge< one (A1 and A4) are somewhat
higher. Therefore, the substitution of germanium atoms in a >Ge–Ge< dimer by one or two
substrate silicon atoms is an endothermic process (see Fig. 5 and Table 1).
292
The density of one-electron states of the Si96H84Ge2 cluster (Fig. 6) shows a bimodal
shape for 2s and 3s lines originating from the non-equivalency of Ge atoms within the
>Ge-Ge< surface dimer of the reconstructed Si(001)(42) surface, one of those Ge atoms
being in a so-called down-, and another in up-position [28].
Table 1. Calculated relative energies of Clusters A1÷A4 and chemical shifts for the 5 23d
component of the Ge(3d ) line. Cluster A is taken as the reference (see Fig. 5).
Cluster A1 A2 A3 A4
Relative energy, kcal/mol 1.83 5.15 2.72 5.11
Chemical shift, eV +0.12 -0.08 -0.07 +0.10
a
b
c d
e
Fig. 6. Density of the core one-electron states for Cluster A within the binding-energy ranges
of (a) 2s, (b) 2p, (c) 3s, (d) 3p, and (e) 3d electrons of the Ge atom.
Moreover, the intensities of 3 22 p and 1 22 p components are essentially the same, as
well as those of 3 23p and 1 23p , that contradicts theoretical expectations based on the
population of the corresponding levels (in contrast to the isolated Ge2 molecule where those
expectations are justified). The Ge(3d) line deviates from the bimodal shape and, to a certain
extent, keeps the shape motif of the corresponding line of Ge2 molecule. It is important to
note that not only the IMO formation but also the abovementioned non-equivalence of Ge
atoms within the >Ge–Ge< surface dimer sophisticates the shape of the Ge(3d) line. That
might indirectly confirm the presence of Ge2 molecules within the adsorption phase of the
Si(001)(42) surface, despite the calculated Ge–Ge bond lengths are 2.16 Å and 2.21 Å in the
>Ge–Ge< surface dimer and in the isolated Ge2 molecule, respectively.
Analysis of the deep-core and semicore-electron densities of states within the energy
ranges of germanium 1s, 2s, 2p, 3s, 3p, and 3d levels indicates the position of 3d level to be
293
the most sensitive one with respect to the mutual arrangement of Ge and Si atoms within all
the clusters under consideration.
Calculated energy shifts of the spin-orbit component 5 23d in Clusters A1A4 relative its
position in Cluster A (Table 1) shows that the migration of germanium atoms from the
>Ge-Ge< surface cluster into the bulk substrate increases the absolute values of 3d binding
energies for Clusters A1 and A4 (one Ge atom is within the mixed >Si–Ge< surface dimer,
and another is in the bulk), but decreases them for Clusters A2 and A3 (pure >Si–Si< surface
dimer and both germanium atoms are in the bulk). Such an effect is less pronounced in the
latter case.
According to the scheme accepted, a binding energy of a semicore electron is
determined by two factors: (i) formal oxidation state of an atom which can be identified with
its formal charge, and (ii) relative donor-acceptor properties of this atom as well as those of
its neighbors.
Two germanium atoms (Nos. 181 and 182) (fig. 5) entering the >Ge–Ge< dimer in
Cluster A are charged negatively, while the sum of charges on their neighbors is positive. In
Cluster A1, Ge(46) atom is embedded into the substrate, and its negative charge increases to -
0.081 atomic units (a. u.) (that of Ge(182)) amounts to -0.065 a. u.), while the positive sum of
charges on the neighboring atoms (0.074 and 0.118 a. u. for Ge(46) and Ge(182),
respectively) increases as well comparing to Cluster A. As the result, a positive chemical shift
of the semicore-electron binding energy relative Cluster A is observed.
Cluster А2 contains Ge(46) and Ge(62) atoms within the crystalline substrate, whose
charges are -0.023 and -0.010 a. u., respectively, while the sum of charges on neighboring
atoms is also positive, but significantly smaller than that for Cluster A. According to the
electrostatic potential approximation, that leads to a negative chemical shift, as one could
expect.
The situation seems to be more complicated for Cluster А3 because of an invariance of
the charge on Ge(46) comparing to Cluster A, and a decrease of the negative charge on
Ge(63) to -0.006 a.u. Together with a negative sum of charges on neighboring atoms, these
circumstances enhance the role donor-acceptor properties of surrounding silicon atoms and
thus explain the negative chemical shift.
In Cluster A4 Ge atoms are directly bonded to each other, while one of them Ge(181)
enters >Si–Ge< mixed dimer and another Ge(46) is located within the crystalline substrate.
The charge of the latter atom amounts to -0.118 a. u., and the sum of charges on its neighbors
is +0.116 a. u. Such a charge distribution (similar to that of Cluster A1) results in a positive
5 23d chemical shift of the Ge 3d line.
Conclusions
The mechanism of photoconductivity in the Ge/Si generally, which are referred to the
second type heterostructures, depends on quantum energy of exciting illumination. The lateral
photoconductivity observed in the range 0.63 – 1.0 еV below fundamental absorption edge of
c-Si was caused by interband transitions from the ground state of a Ge nanoislands to the
conduction band of a silicon surrounding. Photoexcited holes was found to be localized in Ge
nanoislands, while photoelectrons are supposed to be free in the conduction band of Si giving
contribution to the monopolar photoconductivity. In the case of excitation of Ge/SiO2/Si
structures an interband transitions in Ge create localized holes in Ge directly, leading to
optically-induced spatial redistribution of trapped positive charges between SiO2/Si interface
levels and localized states of Ge-NCs, which enhance variation of electrostatic potential in
underlying Si and, therefore, decay of surface conductivity under stationary photoexcitation.
Observed results demonstrate that hole trapping by Ge-NCs and interface states have a
significant effect on in-plane transport in the Ge-NCs/SiO2/Si structures.
294
The comparison semicore-level energy shifts for adsorption complexes simulated by a series
of clusters with the same brutto formula Si96Ge2Н84 but different arrangements of germanium atoms
within the surface layer and bulk with a similar spectrum of the Ge2 molecule has led us to the
following conclusions:
(i) Atomic orbitals from the closed d shell of germanium atom contribute to internal
molecular orbitals that are responsible for a high binding energy of the >Ge–Ge< surface dimer.
(ii) For Si96Ge2Н84 clusters containing one germanium atom embedded in a crystalline
silicon substrate, a 5 23d chemical shift of the Ge(3d ) line is positive (i. e., the binding energy
of the corresponding electrons is higher comparing to that in the cluster containing >Ge–Ge<
surface dimer). For clusters with both germanium atoms embedded in a substrate, such a
chemical shift is negative.
References
1. Brunner K. Si/Ge nanostructures (2002) Rep. Prog. Phys. 65: 27-72.
2. O.G. Schmidt and K. Eberl, Phys. Rev. B 61, 13721(2000).
3. D.Bimberg, M.Grundmann, N.Ledentsov (1999) Quantum dot heterostructures. John
Wiley & Sons, Ltd., Chichester.
4. C. Miesner, O. Röthig, K. Brunner, G. Abstreiter. Intra-valence band photocurrent
spectroscopy of self-assembled Ge dots in Si (2000) Appl. Phys. Lett. 76: 1027-1029.
5. H. Lafontaine, N.L. Rowell, S. Janz, D.-X. Xu. Growth of undulating Si0.5Ge0.5 layers for
photodetectors at λ=1.55 μm (1999) J. Appl. Phys. 86: 1287- 1291.
6. Y. Chen, Y. F. Lu, L. J. Tang, Y. H. Wu, B. J. Cho, X. J. Xu, J. R. Dong, W. D. Song.
Annealing and oxidation of silicon oxide films prepared by plasma-enhanced chemical
vapor deposition (2005) J.Appl.Phys. 97: 014913.
7. Sutter P. Oblique stacking of three-dimensional dome islands in Ge/Si multilayers / P.
Sutter, E. Mateeva-Sutter, L. Vescan // Appl. Phys. Lett. – 2001. – Vol. 78, № 12. – P.
1736-1738.
8. Kondratenko S.V. Morphology and photoelectric properties of Si-Ge quantum-sized
structures / Yu.N. Kozyrev, M.Yu. Rubezhanska, V.S. Lysenko [та ін.] // International
Workshop "In situ characterization of near-surface processes", Eisenerz, 30 may - 3 June,
2010.: abstract of book. – Eisenerz, Austria, 2010. – Р. 40.
9. S.V. Kondratenko, A.S. Nikolenko, O.V. Vakulenko, M.Ya. Valakh, V.O. Yukhymchuk,
A.V. Dvurechenskii, A.I. Nikiforov // Nanotechnology V. 19, P. 145703 (2008).
10. S. V. Kondratenko, S. L. Golovinskiy, A. S. Nikolenko and O. V. Vakulenko
Semiconductor science and technology 21 (7), 857 (2006).
11. V.S. Lysenko, Yu.V. Gomeniuk, Yu.N. Kozyrev, M.Yu. Rubezhanska, V.K. Sklyar, S.V.
Kondratenko, Ye.Ye. Melnichuk, C. Teichert. Effect of Ge nanoislands on lateral
photoconductivity of Ge-SiOx-Si structures (2011) Advanced Materials Research 276: 179-
186.
12. B.D. Malone, S.G. Louie, M.L. Cohen. Electronic and optical properties of body-centered-
tetragonal Si and Ge (2010) Phys.Rev.B. 81: 115201-115205.
13. Gomoyunova, M. G.; Pronin I. I. Photoelectron spectroscopy of atomic core-shell levels at
silicon surface (Review). Zhurnal Tekhnicheskoi Fiziki 2004, 74, 1–34 (in Russian).
14. Shklyaev, A. A.; Ichikawa, M. Creation of germanium and silicon nanostructures using
scanning tunneling microscope. Uspekhi Fizicheskikh Nauk 2006, 176, 913–930 (in
Russian).
15. Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; 3rd ed.; Wiley: New York,
1972.
295
16. Ratto, F.; Locatelli, A.; Fontana, S.; Kharrazi, S.; Ashtaputre, S.; Kulkarni, S. K.; Heun, S.;
Rosei, F. Diffusion Dynamics during the Nucleation and Grown Ge/Si Nanoctructures on
Si(111). Phys. Rev. Lett. 2006, 96, 1–4.
17. Cohen Simonsen, A.; Schleberger, M.; Tougaard, S.; Hansen, J. L.; Nylandsted Larsen, A.
Nanoctructure of Ge deposited on Si(111): a study by XPS peak shape analysis and AFM
Thin Solid Films 1999, 338, 165–171.
18. Siegbahn, K.; Nordling, C.; Fahlman, A.; et el.; ESCA Atomic, Molecular and Solid State
Structure Studied by Means of Electron Spectroscopy; Upsala, 1967.
19. Briggs, D.; Seah, M. P. Practical Surface Analysis. Auger and X-ray Photoelectron
Spectroscopy; 2nd ed.; Wiley: New York, 1990.
20. Teterin, Yu. A.; Gagarin, S. G. Internal valence molecular orbitals of compounds and
structure of photoelectron spectra. Uspekhi Khimii 1996, 895–917 (in Russian).
21. Ku, W.; Eguiluz, A. G. Band-gap problem in semiconductors revisited: Effects of core
states and many-body self-consistency. Phys. Rev. Lett. 2002, 89, 126401.
22. Becke, A. D. Density-functional thermochemistry. III. The role of exact exchange. J. Chem.
Phys. 1993, 98, 5648-5652
23. Stephens, P. J.; Devlin, F. J.; Chabalowski, C. F.; Frisch, M. J. Ab initio calculation of
vibrational absorption and circular dichroism spectra using density functional force fields. J.
Phys. Chem. 1994, 98, 11623-11627.
24. Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti correlation-energy
formula into a functional of the electron density. Phys. Rev. B 1988, 37, 785-789.
25. Miehlich, B.; Savin, A.; Stoll, H.; Preuss, H. Results obtained with the correlation energy
density functionals of Becke and Lee, Yang and Parr. Chem. Phys. Lett. 1989, 157, 200-206.
26. Schmidt M.W., Baldridge K.K., Boatz J.A. et al. General atomic and molecular electronic-
structure system. Review. J. Comput. Chem. 1993, 14, 1347–1363.
27. Tkachuk O. I., Terebinska M. I., Lobanov V. V. Structure of the dimeric adsorption
complex Ge on the face of Si (001). Surface 2013, 5(20), 26–33 (in Ukrainian).
ПРОСТОРОВИЙ РОЗПОДІЛ ЕЛЕКТРОН-ДІРКОВИХ ПАР
В Si/Ge ГЕТЕРОСТРУКТУРАХ
В.С. Лисенко, С.В. Кондратенко, Є.Є. Мельничук,
М.І. Теребінська, О.І. Ткачук, Ю.М. Козирев, В.В. Лобанов
1Інститут фізики напіпровідників Національної академії наук України,
просп. Науки, 41, Київ, 03028, Україна
2Київський національний університет імені Тараса Шевченка, вул. Толстого,
12, , м. Київ, 01033, Україна
3Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України,
вул. Генерала Наумова, 17, Київ, 03164, Україна
Були досліджені фотогенерація і транспорт нерівноважних носіїв заряду і
визначений механізмфотовідповіді в напівпровідникових SiGe/Si і SiGe/SiO2/Siр-
гетероструктурах з наноострівцями. Зразки були вирощені методом молекулярно-
променевої епітаксії. У роботі узагальнені результати досліджень морфологічних,
структурних, оптичних та електричних властивостей гетероструктур з
нанорозмірними об'єктами – квантовими точками і квантовими ямами. Показано, що
фотопровідність наногетероструктури SiGe/Si в інфрачервоному діапазоні в
залежності від компонентного складу, розмірів і величини механічних напружень в
296
наноострівців Si1-xGex визначається міжзонними і внутрізонними переходами за
участю локалізованих станів валентної зони Ge нанорозмірних об'єктів. Були
встановлені ефекти фото- довгострокового розпаду і оптичного затухання
провідності в SiGe/SiO2/п-Si гетероструктур з SiGe нанокластерами, які викликані
змінами електростатичного потенціалу в приповерхневій зоні р-Si підкладки і
оптично-індукованого просторового перерозподілу захоплених позитивних зарядів між
рівнями межі розділу SiO2/Si і локалізованих станів Ge наноострівців.
Були вивчені адсорбційні комплекси германію на реконструйованій грані Si (001)
(4×2) на прикладі кластера Si96Ge2H84. Для атомів Ge, локалізованих в приповерхневому
шарі кластера, результати розрахунків методом ТФГ (B3LYP, 6-31G**) положення їх
3d-остовних рівнів свідчить про кореляцію між хімічним зсувом Ge (3d) і хімічним
оточенням атомів германію.
ПРОСТРАНСТВЕННОЕ РАСПРЕДЕЛЕНИЕ ЭЛЕКТРОН-ДЫРОЧНЫХ ПАР
В Si/Ge ГЕТЕРОСТРУКТУРАХ
В.С. Лысенко, С.В. Кондратенко, Е.Е. Мельничук,
М.И. Теребинская, О.И. Ткачук, Ю.Н. Козырев, В.В. Лобанов
1Институт физики полупроводников Национальной академии наук Украины,
просп. Науки, 41, Киев, 03028, Украина
2Киивський национальный университет имени Тараса Шевченко,
ул. Толстого, 12, г.. Киев, 01033, Украина
3Институт химии поверхности им. А.А. Чуйко Национальной академии наук Украины,
ул. Генерала Наумова, 17, Киев, 03164, Украина
Были исследованы фотогенерация и транспорт неравновесных носителей
заряда и определен механизм фотопроводимости в полупроводниковых SiGe/Si и
SiGe/SiO2/Siр-гетероструктурах с наноостровками. Структуры были выращены
методом молекулярно-лучевой эпитаксии. В работе обобщены результаты
исследований морфологических, структурных, оптических и электрических свойств
гетероструктур с наноразмерными объектами – квантовыми точками и квантовыми
ямами. Показано, что фотопроводимость наногетероструктуры SiGe/Si в
инфракрасном диапазоне в зависимости от компонентного состава, размеров и
величины механических напряжений в наноостровках Si1-xGex определяется
межзонными и внутризонными переходами с участием локализованных состояний
валентной зоны Ge наноразмерных объектов. Были установлены эффекты фото
долгосрочного распада и оптического затухания проводимости в SiGe/SiO2/п-Si
гетероструктур с SiGe нанокластерами, которые вызваны изменениями
электростатического потенциала в приповерхностной зоне р-Si подложки и
оптически индуцированного пространственного перераспределения захваченных
положительных зарядов между уровнями границы раздела SiO2/Si и локализованных
состояний Ge наноостровков.
Были изучены адсорбционные комплексы германия на реконструированной грани
Si(001)(4×2) на примере кластера Si96Ge2H84. Для атомов Ge, локализованных в
приповерхностном слое кластера, результаты расчетов методом ТФП (B3LYP,
6-31G**) положения их 3d-остовных уровней свидетельствует о корреляции между
химическим сдвигом Ge(3d) и химическим окружением атомов германия.
|
| id | oai:ojs.pkp.sfu.ca:article-591 |
| institution | Surface |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-03-12T17:15:27Z |
| publishDate | 2015 |
| publisher | Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | surfacezbircomua/98/b4572951a6ef8f2e5047643c64672198.pdf |
| spelling | oai:ojs.pkp.sfu.ca:article-5912018-11-27T09:34:56Z The spatial separation of electron-hole pairs in Si/Ge heterostructures Пространственное распределение электрон-дырочных пар в Si/Ge гетероструктурах Просторовий розподіл електрон-діркових пар в Si/Ge гетероструктурах Lysenko, V. S. Kondratenko, S. V. Melnichuk, Ye. Ye. Terebinska, M. I. Tkachuk, O. I. Kozyrev, Yu. N. Lobanov, V. V. Photogeneration and transport of nonequilibrium charge carriers, and the determination of photoresponce mechanisms in semiconductor SiGe/Si and SiGe/SiO2/p-Si heterostructures with nanoisland were investigated. The structures were grown by molecular beam epitaxy technique. The work generalizes the results of studies of morphological, structural, optical and electrical properties of heterostructures with nanoscale objects – quantum dots and quantum wells. It is shown that the photoconductivity of nanoheterostructures SiGe/Si in the infrared range depending on the component composition, size and magnitude of the mechanical stresses in nanoislands Si1-xGex is determined by interband and intraband transitions involving localized states of the valence band of the Ge nanoscale objects. The effects of long-decay photoconductivity and optical quenching of conductivity in SiGe/SiO2/p-Si heterostructures with SiGe nanoclusters was found to be caused by variations of the electrostatic potential in the near-suraface region of p-Si substrate and optically-induced spatial redistribution of trapped positive charges between SiO2/Si interface levels and localized states of Ge nanoislads. Adsorption complexes of germanium on the reconstructed Si(001)(4×2) surface have been simulated by the Si96Ge2Н84 cluster. For Ge atoms located on the surface layer of the latter, DFT calculations (B3LYP, 6-31G**) of their 3d semicore-level energies have shown a clear-cut correlation between the&nbsp;&nbsp; chemical shifts and mutual arrangement of Ge atoms. Были исследованы фотогенерация и транспорт неравновесных носителей заряда и определен механизм фотопроводимости в полупроводниковых SiGe/Si и SiGe/SiO2/Siр-гетероструктурах с наноостровками. Структуры были выращены методом молекулярно-лучевой эпитаксии. В работе обобщены результаты исследований морфологических, структурных, оптических и электрических свойств гетероструктур с наноразмерными объектами – квантовыми точками и квантовыми ямами. Показано, что фотопроводимость наногетероструктуры SiGe/Si в инфракрасном диапазоне в зависимости от компонентного состава, размеров и величины механических напряжений в наноостровках Si1-xGex определяется межзонными и внутризонными переходами с участием локализованных состояний валентной зоны Ge наноразмерных объектов. Были установлены эффекты фото долгосрочного распада и оптического затухания проводимости в SiGe/SiO2/п-Si гетероструктур с SiGe нанокластерами, которые вызваны изменениями электростатического потенциала в приповерхностной зоне р-Si подложки и оптически индуцированного пространственного перераспределения захваченных положительных зарядов между уровнями границы раздела SiO2/Si и локализованных состояний Ge наноостровков. Были изучены адсорбционные комплексы германия на реконструированной грани Si(001)(4×2) на примере кластера Si96Ge2H84. Для атомов &nbsp;Ge, локализованных в приповерхностном слое кластера, результаты расчетов методом ТФП (B3LYP, 6‑31G**) положения их 3d-остовных уровней свидетельствует о корреляции между химическим сдвигом Ge(3d) и химическим окружением атомов германия. Були досліджені фотогенерація і транспорт нерівноважних носіїв заряду і визначений механізмфотовідповіді в напівпровідникових SiGe/Si і SiGe/SiO2/Siр-гетероструктурах з наноострівцями. Зразки були вирощені методом молекулярно-променевої епітаксії. У роботі узагальнені результати досліджень морфологічних, структурних, оптичних та електричних властивостей гетероструктур з нанорозмірними об'єктами – квантовими точками і квантовими ямами. Показано, що фотопровідність наногетероструктури SiGe/Si в інфрачервоному діапазоні в залежності від компонентного складу, розмірів і величини механічних напружень в наноострівців Si1-xGex визначається міжзонними і внутрізонними переходами за участю локалізованих станів валентної зони Ge нанорозмірних об'єктів. Були встановлені ефекти фото- довгострокового розпаду і оптичного затухання провідності в SiGe/SiO2/п-Si гетероструктур з SiGe нанокластерами, які викликані змінами електростатичного потенціалу в приповерхневій зоні р-Si підкладки і оптично-індукованого просторового перерозподілу захоплених позитивних зарядів між рівнями межі розділу SiO2/Si і локалізованих станів Ge наноострівців. Були вивчені адсорбційні комплекси германію на реконструйованій грані Si (001) (4×2) на прикладі кластера Si96Ge2H84. Для атомів Ge, локалізованих в приповерхневому шарі кластера, результати розрахунків методом ТФГ (B3LYP, 6-31G**) положення їх 3d-остовних рівнів свідчить про кореляцію між хімічним зсувом Ge (3d) і хімічним оточенням атомів германію. Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine 2015-09-09 Article Article application/pdf https://surfacezbir.com.ua/index.php/surface/article/view/591 Surface; No. 7(22) (2015): Surface; 285-296 Поверхность; № 7(22) (2015): Поверхность; 285-296 Поверхня; № 7(22) (2015): Поверхня; 285-296 3154-8091 3154-8083 en https://surfacezbir.com.ua/index.php/surface/article/view/591/591 Авторське право (c) 2015 V.S. Lysenko, S.V. Kondratenko, Ye.Ye. Melnichuk, M.I. Terebinska, O.I. Tkachuk, Yu.N. Kozyrev, V.V. Lobanov |
| spellingShingle | Lysenko, V. S. Kondratenko, S. V. Melnichuk, Ye. Ye. Terebinska, M. I. Tkachuk, O. I. Kozyrev, Yu. N. Lobanov, V. V. Просторовий розподіл електрон-діркових пар в Si/Ge гетероструктурах |
| title | Просторовий розподіл електрон-діркових пар в Si/Ge гетероструктурах |
| title_alt | The spatial separation of electron-hole pairs in Si/Ge heterostructures Пространственное распределение электрон-дырочных пар в Si/Ge гетероструктурах |
| title_full | Просторовий розподіл електрон-діркових пар в Si/Ge гетероструктурах |
| title_fullStr | Просторовий розподіл електрон-діркових пар в Si/Ge гетероструктурах |
| title_full_unstemmed | Просторовий розподіл електрон-діркових пар в Si/Ge гетероструктурах |
| title_short | Просторовий розподіл електрон-діркових пар в Si/Ge гетероструктурах |
| title_sort | просторовий розподіл електрон-діркових пар в si/ge гетероструктурах |
| url | https://surfacezbir.com.ua/index.php/surface/article/view/591 |
| work_keys_str_mv | AT lysenkovs thespatialseparationofelectronholepairsinsigeheterostructures AT kondratenkosv thespatialseparationofelectronholepairsinsigeheterostructures AT melnichukyeye thespatialseparationofelectronholepairsinsigeheterostructures AT terebinskami thespatialseparationofelectronholepairsinsigeheterostructures AT tkachukoi thespatialseparationofelectronholepairsinsigeheterostructures AT kozyrevyun thespatialseparationofelectronholepairsinsigeheterostructures AT lobanovvv thespatialseparationofelectronholepairsinsigeheterostructures AT lysenkovs prostranstvennoeraspredelenieélektrondyročnyhparvsigegeterostrukturah AT kondratenkosv prostranstvennoeraspredelenieélektrondyročnyhparvsigegeterostrukturah AT melnichukyeye prostranstvennoeraspredelenieélektrondyročnyhparvsigegeterostrukturah AT terebinskami prostranstvennoeraspredelenieélektrondyročnyhparvsigegeterostrukturah AT tkachukoi prostranstvennoeraspredelenieélektrondyročnyhparvsigegeterostrukturah AT kozyrevyun prostranstvennoeraspredelenieélektrondyročnyhparvsigegeterostrukturah AT lobanovvv prostranstvennoeraspredelenieélektrondyročnyhparvsigegeterostrukturah AT lysenkovs prostorovijrozpodílelektrondírkovihparvsigegeterostrukturah AT kondratenkosv prostorovijrozpodílelektrondírkovihparvsigegeterostrukturah AT melnichukyeye prostorovijrozpodílelektrondírkovihparvsigegeterostrukturah AT terebinskami prostorovijrozpodílelektrondírkovihparvsigegeterostrukturah AT tkachukoi prostorovijrozpodílelektrondírkovihparvsigegeterostrukturah AT kozyrevyun prostorovijrozpodílelektrondírkovihparvsigegeterostrukturah AT lobanovvv prostorovijrozpodílelektrondírkovihparvsigegeterostrukturah AT lysenkovs spatialseparationofelectronholepairsinsigeheterostructures AT kondratenkosv spatialseparationofelectronholepairsinsigeheterostructures AT melnichukyeye spatialseparationofelectronholepairsinsigeheterostructures AT terebinskami spatialseparationofelectronholepairsinsigeheterostructures AT tkachukoi spatialseparationofelectronholepairsinsigeheterostructures AT kozyrevyun spatialseparationofelectronholepairsinsigeheterostructures AT lobanovvv spatialseparationofelectronholepairsinsigeheterostructures |