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  1. 72 Acta Physica Polonica A

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  1. 7 Kamińska M.

  2. 6 Gasanly N.

  3. 6 Wilamowski Z.

  4. 5 Adamowski J.

  5. 5 Bednarek S.

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1
Content available remote

Infrared Absorption on Shallow Donors in CdF_{2}

100%
Bednarek S., Adamowski J.
Acta Physica Polonica A
|
1991
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vol. 79
|
issue 2-3
393-396
EN
A theoretical description of shallow donor absorption spectra in CdF_{2} in the infrared region is given. The properties of the stable (Y) and bistable (In) donors are analyzed and quantatively described. It is shown that the bistability of donors and the shape of the infrared absorption band have the same origin, which is the combined effect of electron-LO-phonon coupling, conduction band non-parabolicity and short-range central-cell potential.
2
Content available remote

New Donor State of S Symmetry

100%
Bednarek S., Adamowski J.
Acta Physica Polonica A
|
1993
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vol. 84
|
issue 4
820-822
EN
The influence of the short-range potential and the electron-phonon coupling on the donor spectrum is discussed. It is shown that the attractive short-range potential leads to a formation of a single additional state of s symmetry and with energy lying below a weakly perturbed hydrogen-like spectrum, which includes the 1s level. The new state can be called the 0s state. With decreasing short-range attraction, the energy of this state increases crossing over the hydrogen-like levels and, for weak short-range potential, the 0s state disappears. If the electron-phonon coupling is sufficiently strong, the donor hydrogen-like spectrum is perturbed only in a very narrow region of the leve1 crossing.
3
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Anion-Cation Site Dependence of Pressure Coefficients for Donors in GaAs

100%
Bednarek S., Adamowski J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
671-674
EN
The theoretical model, based on the many-band approach, is proposed for the strongly localized donor states in GaAs. The pressure coefficients for the states of A_{1} and Τ-2 symmetry have been calculated for the donors at the anion and cation sites. The obtained results show that these pressure coefficients are different from the conduction-band pressure coefficients and are dependent on the lattice site occupied by the impurity as well as on the symmetry of the donor states.
4
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Conduction Band Influence on the Properties of Bistable Donors

100%
Bednarek S., Adamowski J.
Acta Physica Polonica A
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1991
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vol. 80
|
issue 3
357-360
EN
A theoretical description of bistable donors in polar semiconductors is proposed. The donor states are described within the one-band approximation, which takes into account a finite width and nonparabolicity of the conduction band. The interaction between the defect and the crystal lattice is assumed in the Fröhlich form. For the bistable indium impurity in cadmium fluoride, a coexistence of strongly and weakly localized donor states has been obtained. The calculated energies for both the states and absorption band shape in the 3-eV range are in agreement with experiment.
5
Content available remote

Metastable One- and Two-Electron donor States in GaAs and CdF_{2}

100%
Bednarek S., Adamowski J.
Acta Physica Polonica A
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1996
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vol. 90
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issue 4
719-722
EN
The strongly localized one-electron (D^{0}) and two-electron (D¯) donor states are considered with the lattice deformation around the donor center taken into account. For GaAs, the donor energy levels have been calculated as functions of the hydrostatic pressure. The calculated energy positions and pressure coefficients agree with the experimental data. It is shown that the interaction with phonons reduces the probability of radiative transitions between the states of different localization and leads to the metastability of shallow-level donor states with respect to the D¯ state in GaAs and both the states (D^{0} and D¯) in CdF_{2}.
6
Content available remote

On DLTS Experiments with Extended Defects

100%
Szkiełko W.
Acta Physica Polonica A
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1991
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vol. 79
|
issue 2-3
271-275
EN
It is shown that the line shape of DLTS spectra measured in silicon with a high concentration of extended defects can be consistently explained if the both processes, thermal emission and tunneling of majority carriers from charged defects, are taken into account.
7
Content available remote

Potential Fluctuations in HgSe:Fe,Ga - a Numerical Study

100%
Sobkowicz P., Wilamowski Z., Kossut J.
Acta Physica Polonica A
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1993
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vol. 84
|
issue 4
645-648
EN
We study spatial correlation of donor charges in HgSe:Fe,Ga using a few simple quantities (mean electrostatic energy of various donor sites, fluctuations of the electrostatic potential). The study uses Monte Carlo simulation techniques. We are able to indicate general trends in the behavior of the correlation when proportion of correlating (Fe^{3+}) and noncorrelating (Ga) charged centers in the sample is changed.
8
Content available remote

Doping Properties of Amphoteric C, Si, and Ge Impurities in GaN and AlN

100%
Boguslawski P., Bernholc J.
Acta Physica Polonica A
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1996
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vol. 90
|
issue 4
735-738
EN
Electronic structure of substitutional group-IV impurities C, Si, and Ge in hexagonal GaN and AlN were studied by quantum molecular dynamics. C_{N} is a very shallow acceptor, and thus a promising p-type dopant. Both Si and Ge are excellent donors in GaN. However, in AlGaN alloys the DX configurations are stable for a sufficiently high Al content, which quenches the doping efficiency. Electronic structure of nearest-neighbor X_{cation}-X_{N} pairs is also discussed.
9
Content available remote

Pressure-Dependent Coupling of the ^{3}A_{2}(F) and ^{1}T_{2}(D) States of Ni^{2+} in ZnS and ZnSe

100%
Wasik D., Baj M., Liro Z.
Acta Physica Polonica A
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1991
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vol. 79
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issue 2-3
319-322
EN
We have investigated two close-lying ^{3}A_{2}(F) and ^{1}T_{2}(D) states of Ni^{2+} impurity in ZnS and ZnSe. These states are strongly coupled to each other via the spin-orbit interaction and therefore, small variations of their energies induced by pressure have significantly changed absorption spectra related to them. In order to give a good interpretation to the experimental results we took into account the interaction between both states, their coupling to the lattice vibrations and the pressure-dependent separation between them.
10
Content available remote

Electron Emission from Extended Defects in DLTS Experiment

100%
Figielski T.
Acta Physica Polonica A
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1991
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vol. 79
|
issue 1
137-140
EN
Dislocations parallel to a Schottky junction are considered as an example of well defined extended defects, and their behaviour in DLTS experiment is examined. A possibility of electron hopping between different traps of the defect, and inter-electronic Coulomb interaction are taken into account. Thermal electron emission from the considered defects is no longer exponential with time and consequences of this fact are discussed.
11
Content available remote

Metastability of Localized Neutral Donor State In GaAs

63%
Skierbiszewski C., Jantsch W., Lübke K., Wilamowski Z., Suski T.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
905-908
EN
Investigations of the photoconductivity of GaAs:Ge under hydrostatic pressure show, in addition to the well known persistent photoconductivity due to the DX state, another giant photoconductivity caused by a neutral localised "A₁" state of the donor. We find that the top of the barrier for the electron recapture to the Α₁ state is pinned to the conduction band edge and the capture cross-section σ(T → ∞) is surprisingly small.
12
Content available remote

Evidence for Alloy Splitting of Ge Related DX State in Al_{x}Ga_{1-x}As

63%
Skierbiszewski C., Piotrzkowski R., Lubke K.
Acta Physica Polonica A
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1998
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vol. 94
|
issue 3
531-533
EN
Thermal emission from resonant DX levels in Ge-doped GaAlAs was studied by measuring the temperature transients of free electron concentration. Pressure was used to fill the levels with electrons. Two emission peaks are observed in AlGaAs:Ge. This enables us to confirm that Ge, similarly to Si dopant, is stabilized upon dangling bond C_{3v} configuration in AlGaAs. Analysis of experimental data allows us to determine parameters of two components of the DX multilevel system. Evaluated alloy splitting of ground and top of the barrier states: 45 meV is comparable with determined for Si donor.
13
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Electrical Behavior of Mg in Mg-Implanted 4H-SiC Layer

63%
Matsuura H., Morine T., Nagamachi S.
|
|
vol. 125
|
issue 4
1017-1020
EN
Because Al and B (elements of group III) in SiC are acceptors with deep energy levels and these acceptors cannot reduce the resistivity of p-type SiC very much, Mg (an element of group II) that may emit two holes into the valence band is investigated. Annealing at 1800C makes a Mg-implanted layer p-type. It is found that an Mg acceptor level in 4H-SiC is too deep to reliably determine the density and energy level of the Mg acceptor using the frequently used occupation probability, i.e., the Fermi-Dirac distribution function. Using the distribution function that accounts for the influence of the excited states of a deep-level acceptor, the density and energy level of Mg acceptors can be determined to be approximately 1 × 10^{19} cm^{-3} and 0.6 eV, respectively. These values are considered to be reliable because they agree well with the Mg implantation condition.
14
Content available remote

DX Puzzle: Where Are We Now?

63%
Wilamowski Z., Suski T., Jantsch W.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 4
561-571
EN
A brief review of the experimental data on the metastable DX-centers in AlGaAs is presented. The experimental proofs of the two-electron nature and of the intermediate, one-electron state of the DX-centers are discussed. We collect the available experimental data on the ground state, electron-emission and capture energies and we discuss the nature of the lattice barrier. The effect of splitting of these energies in AlGaAs alloys and the consequences of the splitting on the capture and emission kinetics are analyzed. The different character of the barrier and of the alloy splitting for donors of the IV and VI group is underlined. The necessity to consider the interdonor Coulomb interaction when discussing the experimental data is also pointed out.
15
Content available remote

Deep Defects in Low-Temperature GaAs

63%
Korona K., Muszalski J., Kamińska M., Weber E.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 5
821-824
EN
Conductivity of GaAs layers grown by molecular beam epitaxy at low substrate temperature (190-200°C) and then annealed at few different temperatures (between 300 and 600°C) were studied. It was confirmed that electron transport is due to hopping between arsenic antisite defects. Parameters describing hopping conductivity and their dependence on temperature of annealing are discussed. Other deep defects with activation energies of 0.105, 0.30, 0.31, 0.47, 0.55 eV were found using photoinduced current transient spectroscopy measurements.
16
Content available remote

FFirst TSC and DLTS Measurements of Low Temperature GaAs

63%
Muszalski J., Babiński A., Korona K., Kamińska E., Piotrowska A., Kamińska M., Weber E.
Acta Physica Polonica A
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1991
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vol. 80
|
issue 3
413-416
EN
The first thermally stimulated current (TSC) and deep level transient spectroscopy (DLTS) studies performed on GaAs grown by molecular beam epitaxy (MBE) at low substrate temperatures (LT GaAs) are reported. TSC experiments, conducted on as grown and 400-580°C annealed layers showed domination of arsenic antisite (EL2-like) defect and supported its key role in hopping conductivity. DLTS studies, performed on Si doped and annealed at 800°C layers revealed substantially lower concentration of EL2-like defect and an electron trap of activation energy ΔE = 0.38 eV was found.
17
Content available remote

DLTS Study of Be-Doped p-Type AlGaAs/GaAs MBE Layers

63%
Szatkowski J., Płaczek-Popko E., Sierański K., Hansen O.
Acta Physica Polonica A
|
1998
|
vol. 94
|
issue 3
565-569
EN
Deep-level transient spectroscopy method was applied to study deep hole traps in p-type Al_{0.5}Ga_{0.5}As grown on GaAs semi-insulating substrate by MBE. Five hole traps labelled by us as H0 to H4 were found. For the traps H1, H3 and H4 thermal activation energies obtained from Arrhenius plots were equal to: E_{H1}=0.15 eV, E_{H3}=0.4 eV, and E_{H4}=0.46 eV. Hole emission from the trap H2 was electric field dependent with the thermal activation energy extrapolated to zero-field equal to 0.37 eV. Capture cross-sections for the traps H1 and H4 were thermally activated with energetic barriers 0.04 eV (for H1) and 0.18 eV (for H4).
18
Content available remote

Deep Levels in Cd_{0.99}Mn_{0.01}Te:Ga

63%
Szatkowski J., Płaczek-Popko E., Sierański K., Bieg B.
Acta Physica Polonica A
|
1998
|
vol. 94
|
issue 3
575-578
EN
Two types of samples were studied. In the material with higher donor concentration four electron traps labelled by us as E1 to E4 were found. For the traps E2 and E3 energies obtained from Arrhenius plots are equal to 0.24 eV and 0.36 eV, respectively. Electric field enhanced electron emission from the levels E1 and E4 was observed and described in terms of Frenkel-Poole mechanism. Capture process from the traps E2 was found to be thermally activated with energetic barriers equal to 0.20 eV for E2.
19
Content available remote

Binding Energy of the Hydrogenic Impurity in CdTe/ZnTe Spherical Quantum Dot

63%
Stojanović D., Kostić R.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 2
234-237
EN
Binding energy of a hydrogenic impurity located at the center of the CdTe/ZnTe spherical quantum dot has been calculated under the effective mass approximation by solving Schrödinger equation analytically. Eigen energies are expressed in terms of the Whittaker function and Coulomb wave function. The results show that impurity binding energy strongly depends on QD size if it is around one effective Bohr radius.
20
Content available remote

Coulomb versus Madelung Gap: Ordering in a System of Point Charges

63%
Sobkowicz P., Wilamowski Z., Kossut J.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
515-518
EN
Spatial correlations of impurity charges in a mixed valence regime are studied with the use of Monte Carlo simulations. The influence of various kinds of disorder on the one-particle density of states is determined. A continuous transitions from a "soft" Coulomb gap (density of states vanishing only at the chemical potential) to a "hard" gap (with a finite range of energies with vanishing density of states) is found, driven by decreasing amount of built-in disorder in the system. The "hard" Coulomb gap resembles the Madelung gap, found in crystalline arrangements of charges. The similarity reflects the fact that both the Coulomb and Madelung gaps are manifestations of the same phenomenon, resulting from ordering of the positions of point charges, the only difference being the range of correlations.
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