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1
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Erbium in Silicon: Possible Light Source for 1.5 μm and Challenge for Defect Physics

100%
Jantsch W., Przybylińska H.
Acta Physica Polonica A
|
1996
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vol. 90
|
issue 4
623-633
EN
The trivalent erbium ion emits at 1.54 μm, independent of the host crystal and temperature. This fact makes Si:Er an interesting candidate for integrated optics in the optimum wavelength regime for fiber optic communication systems. Recent progress in improving the luminescence yield is reviewed and the limiting factors are discussed, namely: the low solubility of different Er centers, thermal quenching of the luminescence above 100 K, the mechanisms for energy transfer from the host crystal to the Er 4f shell and the process induced parasitic recombination channels.
2
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D'yakonov--Perel Spin Relaxation Suppressed by an Applied Magnetic Field

100%
Wilamowski Z., Jantsch W.
Acta Physica Polonica A
|
2003
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vol. 103
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issue 6
671-674
EN
We observe a strong anisotropy of spin relaxation and a decrease in the spin relaxation rate with increasing electron mobility in contrast to predictions of the classical D'yakonov-Perel spin relaxation model. We show that for high electron mobility the cyclotron motion causes an additional modulation of spin-orbit coupling, leading to an effective suppression of the spin relaxation rate.
3
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Ultra-Fast Spin Dynamics in Diluted Magnetic Semiconductors

81%
Wilamowski Z., Buczko R., Karczewski G., Jantsch W.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
969-972
EN
In nano-size antiferromagnetic systems a spatially inhomogeneous field leads to the formation of a staggered magnetization. Thereby the total magnetic moment does not change but the formation of a net magnetic moment at the border of the cluster leads to an energy gain. This type of magnetism is characterised by an ultra-fast dynamics. We suggest it is also responsible for the formation of the exciton magnetic polaron.
4
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Mechanisms of Nonuniform Line Broadening

81%
Wilamowski Ż., Przybylińska H., Jantsch W.
Acta Physica Polonica A
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1995
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vol. 87
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issue 1
181-184
EN
When the spin relaxation time of paramagnetic impurities at different magnetic sites differs by orders of magnitude then instead of resonance line broadening, rather a decay of the line amplitude is expected. In particular, the sp-d coupling of magnetic impurities to shallow impurities leads to a nonuniform distribution of the longitudinal relaxation rates of local spins.
5
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Diluted Magnetic Semimetals - Beyond Heisenberg Coupling

81%
Wilamowski Z., Story T., Jantsch W.
Acta Physica Polonica A
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1995
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vol. 87
|
issue 1
189-192
EN
We analyse effects which cannot be explained assuming the isotropic Heisenberg form of sp-d or of the indirect d-sp-d (RKKY) coupling. Resonance line broadening, a line shift and an enhancement of the magnetic anisotropy in diluted magnetic semimetals are discussed.
6
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Magnesium Acceptor Energy Levels in Cubic GaN

81%
Przybylińska H., Buczko R., Kocher G., Jantsch W.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
683-688
EN
Intra-impurity transitions of the Mg acceptor in cubic phase GaN were measured with the use of photothermal ionization spectroscopy. Apart from the photoionization band several sharp features were detected, related to internal Mg-acceptor transitions. The transitions were identified with the help of effective-mass model calculations involving light- and heavy-hole as well as spin--orbit split-off bands. Transitions to resonant states, associated with the spin-orbit split-off valence band, were also identified. The determined hole binding energy of the Mg acceptor in zinc-blende GaN is 236±1 meV.
7
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Ferromagnetic Behavior of a Short Period Antiferromagnetic Superlattice

81%
Wilamowski Ż., Jantsch W., Faschinger W.
Acta Physica Polonica A
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1995
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vol. 87
|
issue 1
185-188
EN
We present a study of short period MnTe/CdTe superlattices by mag­netic resonance. The usually antiferromagnetic structure exhibits critical line broadening above the Néel temperature typical of antiferromagnetic order­ing, but also some ferromagnetic properties at lower temperature. We suggest that the observed ferromagnetic-like moment originates from coupling of the moments of the recently proposed strong magnetic polarons.
8
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Electrically Detected Magnetic Resonance

81%
Fedorych O., Wilamowski Z., Jantsch W., Sadowski J.
Acta Physica Polonica A
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2004
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vol. 105
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issue 6
591-598
EN
We compare the results of electrically detected magnetic resonance in a 2D electron gas in Si/SiGe quantum wells with transport and magnetic resonance measurements on ferromagnetic Ga_{1-x}Mn_xAs. The results lead us to the conclusion that observation of electrically detected magnetic resonance is possible only in the case of a slow spin relaxation, where the microwave resonant absorption leads to a noticeable change of spin magnetization.
9
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DX Puzzle: Where Are We Now?

81%
Wilamowski Z., Suski T., Jantsch W.
Acta Physica Polonica A
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1992
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vol. 82
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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.
10
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Spin Resonance Absorption in a 2D Electron Gas

81%
Ungier W., Jantsch W., Wilamowski Z.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
345-350
EN
We analyze the power absorption at electron spin resonance excited by the Bychkov-Rashba spin-orbit field in a 2D electron gas. We show that, as long as the absorbed power is dissipated by the usual spin lattice relaxation mechanisms, the resonance line shape is expected to be of pure absorption type, i.e., it can be described by the imaginary part of the dynamic magnetic susceptibility. Therefore, the Dysonian line shape observed in ESR of 2D electron gas cannot result from this type of the resonance signal.
11
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Quantum Phenomena in Small Antiferromagnets

81%
Wilamowski Z., Buczko R., Jantsch W.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
379-382
EN
We show that the most characteristic properties of mesoscopic antiferromagnets can be explained in terms of the response on a spatially inhomogeneous perturbation. This concept allows to explain the dynamic properties (quantum resonance, coherence and tunnelling rates) as well as static perturbations which, for increasing size of an antiferromagnet, leads to a transition from the quantum mechanical oscillating system to a classical antiferromagnet with well defined Néel vectors.
12
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Consequences of Spatial Fluctuation of Coulomb Potential in AlGaAs with DX Centers

81%
Wilamowski Z., Kossut J., Jantsch W., Ostermayer G.
Acta Physica Polonica A
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1991
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vol. 80
|
issue 3
385-388
EN
Electric charges on randomly distributed impurities in semiconductors produce a spatially fluctuating potential. When the impurities are partially filled, their occupancy is not random but there appears a spatial correlation of the impurity charges appearing due to the inter-impurity Coulomb interactions. We show that when these interactions are taken into account then (i) the activation energy of the electron concentration, (ii) thermal emission kinetics, (iii) capture kinetics, (iv) persistent photoconductivity kinetics and (v) the electron mobility (in a steady state as well as during transients) in GaAlAs:Si can be explained in a consistent way. The energy diagram con cerning the DX center levels with respect to minima of the conduction band as well as the capture and emission barriers (including the effect of the alloy splitting) is constructed within an approach making use of the notion of the impurity self-screening.
13
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Influence of Coimplantation on Activation of Er Emission in Si

81%
Przybylińska H., Hendorfer G., Jantsch W., Palmetshofer L.
Acta Physica Polonica A
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1995
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vol. 87
|
issue 2
365-368
EN
The results of high resolution photoluminescence studies of erbium im­planted silicon are presented. We show that the apparent enhancement of Er emission by coimplantation with light elements is not due to formation of Er-dopant complexes, but rather to Er forming complexes with defects induced by the implantation process alone.
14
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Erbium Luminescence in Silicon

81%
Przybylińska H., Jantsch W., Palmetshofer L.
Acta Physica Polonica A
|
1996
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vol. 90
|
issue 1
83-92
EN
We report on high resolution photoluminescence investigations of Er-implanted Si and demonstrate the variety of Er centers or complexes with impurities and native Si-defects formed depending on the processing parameters. These centers are shown to differ in the efficiency of excitation transfer as well as high temperature photoluminescence yield. The mechanisms responsible for the photoluminescence quenching at different temperature regimes are discussed.
15
Content available remote

Small Antiferromagnetic Clusters

81%
Buczko R., Wilamowski Z., Jantsch W.
Acta Physica Polonica A
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1996
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vol. 90
|
issue 4
747-750
EN
The analysis of the quantum mechanical model of mesoscopic size antiferromagnets shows that small antiferromagnets are characterized by a stronger exchange coupling and by an oscillating character of spins polarizations. Experimental evidence of the quantum character is discussed. We interpret the interlayer coupling in antiferromagnet superlattices and a puzzling resonance observed in nano-size antiferromagnet grains.
16
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Photoconductivity in GaAlAs:Si Proves Negative U of DX Centers

81%
Wilamowski Z., Jantsch W., Ostermayer G.
Acta Physica Polonica A
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1991
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vol. 80
|
issue 2
283-286
EN
The analysis of the temperature dependence of the photoconductivity, amplitude in doped GaAlAs, provides a simple and convincing proof of the negative sign of the Hubbard correlation energy U, strictly speaking of the two-electron nature of the thermal emission process from DX centers. The proof is based on a comparison of the emission activation energy measured per emission event (DLTS) with that measured per electron.
17
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Oscillating Antiferromagnetism of Ultrathin EuTe Layers

81%
Wilamowski Z., Springholz G., Svrcek V., Jantsch W.
Acta Physica Polonica A
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1997
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vol. 92
|
issue 5
1051-1054
EN
We study magnetic resonance on EuTe/PbTe superlattices. Analysis of the magnetic dipole anisotropy in the superlattices and of the EPR amplitude of isolated Eu ions in the PbTe wells shows that the diffusion at interfaces is very small. The real thickness of EuTe can be evaluated with an accuracy better than one monolayer. Since for EuTe layers thicker than 2 monolayers there is no difference in the character of the antiferromagnetic resonance observed for even and odd numbers of monolayers, we conclude that there is no static magnetization of the antiferromagnetic sublattices. Nevertheless, long range antiferromagnetic order is clearly evident.
18
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Localized Spin Relaxation Due To Coupling To Effective Mass States

81%
Wilamowski Z., Dmochowski J., Jantsch W.
Acta Physica Polonica A
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1997
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vol. 92
|
issue 5
1055-1058
EN
The EPR of residual Mn in CdF_{2} doped with Y, In and Ga is investigated. Although these donors are barely seen in EPR, they manifest themselves by a new effect: a drastic resonant reduction in the longitudinal relaxation rate of Mn which occurs only if the Zeeman splitting of the two subsystems coincide. In this situation, the saturation of those of the six Mn hyperfine lines is weakened which coincide with the shallow donor resonance.
19
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Limitations in the Tunability of the Spin Resonance of 2D Electrons in Si by an Electric Current

81%
Wilamowski Z., Malissa H., Glazov M., Jantsch W.
Acta Physica Polonica A
|
2007
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vol. 112
|
issue 2
375-379
EN
We analyse the recently observed effect of an in-plane electric current through a Si quantum well on the conduction electron spin resonance. We find that the ratio of resonance shift and current density is independent of temperature and dissipation processes, but the channel current is reduced due to a parallel electric channel in heavily modulation doped samples. The inhomogeneous current distribution results in some broadening of the ESR line width. In high mobility Si/SiGe layers the current induced increase in the electron temperature is considerably larger than the increase in the lattice temperature. The signal amplitude scales with the square of electron mobility.
20
Content available remote

Metastability of Localized Neutral Donor State In GaAs

71%
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
|
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.
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