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1
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Semimagnetic Semiconductors

100%
Gaj J.
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vol. 96
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issue 5
651-664
EN
This paper contains a description and explanation of selected basic phenomena characteristic of bulk semimagnetic semiconductors: giant Faraday rotation and giant Zeeman splitting, mean field approximation and its limitations, ion-ion interaction, its measurements and its influence on magnetic properties, etc. The basic part is followed by a discussion of a personal choice of new perspectives open by the introduction of diluted magnetic semiconductors in semiconductor quantum structures. In particular, the role of magnetic ions in characterization of semiconductor quantum structures and low-dimensional excitonic systems is analyzed. Particular attention is paid to magnetooptical phenomena and magnetooptical experimental methods in large gap II-VI semimagnetic semiconductors.
2
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Temperature Dependence of the Energy Gap in Cd_{1-x}Fe_{x}Se

52%
Gaj J., Nguyen K., Arciszewska M., Lebecki K.
Acta Physica Polonica A
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1991
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vol. 80
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issue 3
405-407
EN
The energy gap and magnetic susceptibility of Cd_{0.85}Fe_{0.15}Se were measured in function of temperature. Experiments showed that the magnetic contribution to the variation of the energy gap in Cd_{1-x}Fe_{x}Se is not proportional to the product of magnetic susceptibility and temperature as it has been observed in Mn^{++}-containing semiconductors.
3
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Scattering Dynamics of Excitons in ZnSe Based Semimagnetic Semiconductors

52%
Nguyen K., Mac W., Gaj J.
Acta Physica Polonica A
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1992
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vol. 82
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issue 4
634-636
EN
Resonant Raman scattering was measured for (Zn,Fe)Se and (Zn,Cr)Se with the magnetic ion mole fraction below 0.02. LO phonons and intra-Fe^{++} transitions were observed. Polarization measurements versus magnetic field allowed to obtain polarization lifetimes (polariton flight times) in the sub-picosecond range.
4
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Scattering Dynamics of Free Excitons on Fe^{++} Ions in Cd_{1-x}Fe_{x}Se

46%
Gaj J., Nguyen K., Nawrocki M., Golnik A., Lebecki K.
Acta Physica Polonica A
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1991
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vol. 80
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issue 3
409-412
EN
Inelastic scattering of excitons on Fe^{++} ions in Cd_{1-x}Fe_{x}Se was studied by resonant Raman scattering. Polarization measurements were done using a modulation technique, allowing for the first time to determine the full polarization state of the detected light. The obtained results were compared to a simple calculation in an incoherent model of scattering on Fe^{++} ions.
5
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Exchange Interaction in ZnCrSe Semimagnetic Semiconductor

46%
Mac W., Nguyen K., Twardowski A., Gaj J., Demianiuk M.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
902-904
EN
Magnetoreflectance and magnetization of ZnCrSe were measured for B ≤ 5 T and T = 2 K. A linear dependence between exciton splitting and magnetization was found. The s, p-d exchange parameter was estimated: N_{0}α-N_{0}β=0.67eV.
6
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Magnetooptical Analysis of Interface Mixing in Pulsed Laser Evaporation and Epitaxy Grown CdTe/Cd_{0.9}Mn_{0.1}Te Multiple Quantum Well and Superlattice

46%
Lewalski A., Nguyen K., Kossacki P., Gaj J., Dubowski J.
Acta Physica Polonica A
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1993
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vol. 84
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issue 3
571-574
EN
A recently proposed magnetooptical method of determination of interface mixing was applied to CdTe/CdMnTe superstructures grown by pulsed laser evaporation and epitaxy. Diffusion length were found ≈ 5 Å for a multiple quantum well and > 15 Å for a superlattice. Ranges of Mn mole fractions and well width values enabling efficient application of the method were determined.
7
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Femtosecond Dynamics of Neutral and Charged Exciton Absorption in Cd_{1-x}Mn_xTe Quantum Well

40%
Płochocka P., Kossacki P., Maślana W., Radzewicz C., Gaj J., Cibert J., Tatarenko S.
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issue 4-5
679-686
EN
We present a study of time-dependent transmission spectra of a modulation-doped Cd_{1-x}Mn_xTe/Cd_{1-y-z}Zn_yMg_zTe quantum well with variable hole gas concentration. We study the influence of pump pulses on excitonic absorption in subpicosecond time scale. A spectrally broad probe pulse of duration of 40 femtoseconds was used to record the absorption spectra at controlled delay. Studies of temporal evolution of exciton energies revealed coherence decay of linearly polarized excitons and thermalization of non-equilibrium exciton states. We found that a characteristic timescale for thermalization of non-equilibrium populations of photocreated excitons is between 0.8 and 3.6 ps. The timescale of this process depends on the hole concentration in quantum well: for higher hole concentration the decay is faster. Long-lived photo-induced magnetization accompanied by heating of the magnetic system was also observed.
8
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Inter-Dot Coupling in a Self-Assembled Quantum Dot System

40%
Kazimierczuk T., Nowak S., Suffczyński J., Wojnar P., Golnik A., Gaj J., Kossacki P.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
321-324
EN
We present studies of resonant excitation of self-assembled CdTe/ZnTe quantum dots. Photoluminescence excitation measurements revealed existence of sharp resonances, common for photoluminescence lines attributed to different quantum dot charge states. We conclude from the ensemble of photoluminescence and photoluminescence excitation results that we observe energy transfer in coupled quantum dot pairs.
9
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Long Decays of Excitonic Photoluminescence from CdTe/ZnTe Individual Quantum Dots

40%
Piechal B., Suffczyński J., Trajnerowicz A., Goryca M., Kossacki P., Golnik A., Gaj J.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
831-836
EN
We present time-resolved micro-photoluminescence study of self-assembled CdTe/ZnTe quantum dots. In addition to the fast radiative decay of the exciton, we observe long components, being of the order of a few nanoseconds. We observe that long decays are present for neutral exciton lines as well as on the biexciton ones. The temperature dependent measurements reveal the non-monotonic behaviour. We find also that the long decays are not mono-exponential. We conclude that the dark exciton states cannot be treated as the only source of long decays in the luminescence. We propose other possible explanation, which is the slowing of luminescence by carrier trapping in high energy states in quantum dots and barriers.
10
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Excitonic Giant Zeeman Effect in Wide Gap Diluted Magnetic Semiconductors Based on ZnO and GaN

40%
Pacuski W., Ferrand D., Kossacki P., Marcet S., Cibert J., Gaj J., Golnik A.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
303-309
EN
We present a theoretical description of the excitonic giant Zeeman effect observed in wide gap diluted magnetic semiconductors (Zn,Co)O and (Ga,Mn)N. In these materials, A and B excitons present quite complex energy shifts and change of oscillator strengths under magnetic field. These features can be well reproduced using an excitonic Hamiltonian, taking into account ion-carrier exchange, wurtzite trigonal crystal field, spin-orbit and electron-hole exchange interactions.
11
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Characterization of Self-Assembled CdTe/ZnTe Quantum Dots

40%
Kowalik K., Kudelski A., Golnik A., Gaj J., Karczewski G., Kossut J.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
539-544
EN
We present microluminescence investigations of self-assembled CdTe/ZnTe quantum dots. The dots proprieties resulting from our studies are: values of optical in-plane anisotropy parameters (electron - heavy hole exchange splitting and orientation of anisotropy) and value of effective Lande factor. Parameters giving information about in-plane anisotropy possess random distribution of values with the exchange splitting from 0 to 240 μeV. The effective Lande factor values for our dots are around g^*=-3.2 with a scatter of about 18%. Some PL lines exhibit sudden jumps of energetic position, related to variation of the charge state in their neighborhood.
12
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Magnetoluminescence of a CdTe Quantum Dot with a Single Manganese Ion in Voigt Configuration

40%
Koperski M., Goryca M., Kazimierczuk T., Kossacki P., Wojnar P., Gaj J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
618-620
EN
We present a study of the neutral exciton and negative trion recombination spectra of an individual CdTe quantum dot with a single manganese ion, in magnetic field measured in the Voigt configuration. We describe experimental results and compare with a theoretical model. The quantitative agreement between the model and the experiment allows us to determine separately the electron g-factor.
13
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Exciton Dynamics in ZnTe Based Semimagnetic Semiconductors and CdMnTe Quantum Wells

40%
The Khoi N., Gaj J., Karczewski G., Wojtowicz T., Kossut J., Demianiuk M.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
899-902
EN
Inelastic scattering of excitons on LO phonons in ZnTe based bulk semimagnetic semiconductors with low concentration of paramagnetic ions (Mn^{2+}, Fe^{2+} and Cr^{2+}) was studied. A polarization degree of the LO phonon Raman lines was measured as a function of the exciton splitting in a magnetic field, and allowed us to determine the polarization lifetime (polariton flight time). A similar method was used to investigate multiple Mn^{2+} spin-flip scattering in CdMnTe quantum well. The cascade model seems to be not adequate to interpret the dependence of the polarization degree on the order of scattering.
14
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Numerical Rate Equation Approach to Picosecond Charge State Dynamics in CdTe/ZnTe Quantum Dots

40%
Koperski M., Kazimierczuk T., Goryca M., Wojnar P., Golnik A., Kossacki P., Gaj J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
893-895
EN
The rate equation is used for description of photoluminescence dynamics after pulsed excitation of various states of quantum dots. The picosecond dynamics of averaged charge state of quantum dot is described. We compare our simulations with the experiment and come up with the conclusion that probability of carrier capture weakly depends on quantum dot charge state and that electrons and holes are captured non-synchronously.
15
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Anisotropic Exchange Interaction between p-Shell Electron and s-Shell Hole in CdTe/ZnTe Quantum Dots

40%
Kazimierczuk T., Golnik A., Goryca M., Wojnar P., Gaj J., Kossacki P.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
882-884
EN
We study electron-hole exchange interaction in a single CdTe/ZnTe quantum dot by polarization-resolved photoluminescence measurements. We focus on recombination of excitonic states involving p-shell electrons: X^{2-} and XX^-. Recombination lines of X^{2-} and XX^- states exhibit fine structure, which can be consistently explained within a model with four parameters δ_{i}^{αβ} representing strength of iso- and anisotropic parts of interaction between s-hole and s- or p-electron.
16
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Influence of Growth Break before Capping on Photoluminescence Dynamics of CdSe/ZnSe Self-Assembled Quantum Dots

40%
Nowak S., Suffczyński J., Goryca M., Kossacki P., Gaj J., Lee S., Furdyna J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1267-1271
EN
Influence of growth breaks before capping of CdSe self-assembled quantum dot layers on photoluminescence dynamics was examined in three samples. Short (5s) break resulted only in a small blue shift, caused probably by partial strain relaxation and/or Zn interdiffusion. Long (20 min) break induced a strong broadening and red shift of the spectra, combined with a dramatic slow down of the photoluminescence decays. The main result of the long break was identified as introduction of defects (impurities), which generate local electric fields and act as traps of photogenerated carriers.
17
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Control of Local Electric Fields Influencing the Photoluminescence οf an Individual CdTe/ZnTe Quantum Dot

40%
Haas K., Kazimierczuk T., Wojnar P., Golnik A., Gaj J., Kossacki P.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
896-898
EN
We examine the influence of a weak non-resonant illumination on the quantum dot photoluminescence spectrum. We observe that even very weak illumination affects both intensity and spectral position of emission lines in the spectrum. We discover no significant asymmetry in spatial dependence and infer that the observed effects cannot be attributed to a single neighbor center.
18
Content available remote

Faraday Rotation and Photoionization of ZnCrSe Semimagnetic Semiconductor

40%
Mac W., Nguyen K., Gaj J., Twardowski A., Demianiuk M., Stachow-Uciakowska A.
Acta Physica Polonica A
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1993
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vol. 84
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issue 3
567-570
EN
The magnetoabsorption and the Faraday rotation of ZnCrSe were measured for B ≤ 5 T and T = 2 K in the region of photon energies lower than the fundamental absorption edge. The circular dichroism of the photoionization absorption bane was observed and analyzed. The Faraday rotation was interpreted as due to the sum of contributions from interband and photoionization optical transitions.
19
Content available remote

Magnetization Dynamics of a (Cd,Mn)Te Quantum Well in Pulsed Magnetic Field

40%
Kobak J., Goryca M., Kossacki P., Golnik A., Karczewski G., Wojtowicz T., Gaj J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
907-908
EN
In this paper we present studies of magnetization relaxation in a (Cd,Mn)Te quantum well containing 3.2% of Mn, after a pulse of magnetic field. The relaxation was found to be very fast, with dominant component faster than 10 ns. Upon application of static magnetic field the relaxation does not slow down, in contrast with the behavior of very diluted quantum wells or bulk material.
20
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Measurement of Very Small Zeeman Splittings in GaN:Mn,Mg by Faraday Rotation

33%
Wołoś A., Kossacki P., Golnik A., Kamińska M., Gaj J., Twardowski A., Grzegory I., Boćkowski M., Porowski S.
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issue 4-5
695-699
EN
In this work we demonstrate an application of Faraday rotation for measuring an extremely small Zeeman splitting of an Mn related absorption line placed at 1.417 eV in optical absorption spectrum of Mn and Mg doped gallium nitride. Analysis of the collected spectra allowed us to determine the value of the splitting as equal to 0.12±0.01 meV at 6 T. This data should help in establishing the nature of the observed absorption band.
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