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1
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Improvement of Electrical Properties of Hg_{1-x}Zn_{x}Se upon Doping with Fe

100%
Dobrowolski W., Grodzicka E., Kossut J., Witkowska B.
|
EN
Results of measurements of electron concentration and mobility in mixed crystals of Hg_{1-x}Zn_{x}Se (0 ≤ x ≤ 0.07) doped with resonant Fe donors (0 ≤ n_{Fe} ≤ 5 × 10^{19} cm^{-3}) at liquid helium temperatures are presented. The data show that there is a considerable improvement of the electrical properties of the material when Fe impurities are present. The analysis of the mobility in terms of the scattering from ionized centers (accounting for possible spatial correlation of impurity charges) and the alloy scattering is in agreement with the measured data.
2
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Photovoltaic Effect on PbTe p-n Junction in the Presence of Magnetic Field

88%
Le K., Grodzicka E., Witkowska B., Story T., Gałązka R.
Acta Physica Polonica A
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1993
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vol. 84
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issue 4
721-724
EN
Photovoltaic spectra of PbTe p-n junction have been measured in the infrared spectral region in the temperature range of 8-260 K. The p-n junctions have been formed by cadmium diffusion into the p-type PbTe crystals. From the positions of the photovoltaic maxima the energy gap of the diode material has been determined. In the presence of a magnetic field up to 7 T, a pronounced oscillatory behavior of the photovoltage was observed in the Faraday and Voigt configurations. Experiments were performed as a function of the magnetic field intensity at a constant wavelength of the incident light. The energy of the interband magnetooptical transitions between the Landau levels in PbTe was determined and compared with the theoretical model of Adler, describing the energy band structure for the IV-VI compounds.
3
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Electron Paramagnetic Resonance of Cr in PbTe

88%
Story T., Wilamowski Z., Grodzicka E., Witkowska B., Dobrowolski W.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 4
773-775
EN
We present the results of the low temperature electron paramagnetic resonance (EPR) and transport investigations of the crystals of Pb_{1-x}Cr_{x}Te (x ≤ 0.01). The samples with chromium concentrations x ≥ 0.0015 are all n-type. For these samples we observe the single EPR line with the g-factor decreasing from g = 1.97 till g = 1.93 with increasing carrier concentration. This resonance can be attributed to electrically and magnetically active Cr^{3+} ions. The crystals with Cr concentration x ≤ 0.0015 may be both n- and p-type. The EPR spectrum of these samples consists of two lines: the one discussed above and the other one with g = 1.99 observed only for samples with electron concentration n ≤ 10^{18} cm^{-3}.
4
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Transport and Magnetic Properties of PbTe:Cr and PbSnTe:Cr

88%
Story T., Grodzicka E., Witkowska B., Górecka J., Dobrowolski W.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
879-881
EN
We present the results of the experimental studies of the low temperature transport and magnetic properties of PbTe, Pb_{1-x}Sn_{x}Te (x ≤ 0.3) and SnTe crystals doped with 0.5 at.% of chromium. Cr was found to be a resonant donor in PbTe and PbSnTe. Magnetic susceptibility measurements revealed that PbTe:Cr and Pb_{1-x}Sn_{x}Te:Cr (x ≤ 0.2) are Curie paramagnets whereas SnTe:Cr exhibits van Vleck paramagnetism.
5
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Peculiarities of Electron Transport in PbTe:Cr due to Presence of Resonant Impurity State

88%
Grodzicka E., Dobrowolski W., Kossut J., Story T., Witkowska B.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
599-603
EN
The results of transport investigation of Pb_{1-x}Cr_{x}Te (x ≤ 0.009) in temperature range 3.5-300 K are presented. The obtained electron concentration and electron mobility vs. temperature and Cr concentration data are interpreted and discussed within the model assuming that Cr in PbTe forms a donor state resonant with the conduction band.
6
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Magnetic Properties of EuS/PbS Semiconducting Structures

76%
Stachow-Wójcik A., Twardowski A., Story T., Dobrowolski W., Grodzicka E., Sipatow A.
Acta Physica Polonica A
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1997
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vol. 92
|
issue 5
985-988
EN
We report results of magnetization study of EuS/PbS superstructures with different thicknesses of magnetic and nonmagnetic layers. Reduction of ferromagnetic phase transition temperature was found with decreasing EuS thickness. Reasonable description of this effect is obtained within the model based on the mean field approximation.
7
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Structural and Electrical Properties of Low Concentration SnTe Layers and PbTe/SnTe Heterostructures Grown by MBE

76%
Sadowski J., Grodzicka E., Dynowska E., Adamczewska J., Domagała J., Przedpelski W.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
967-970
EN
We analyse properties of thin SnTe layers and PbTe/SnTe heterostructures grown by MBE on BaF_{2}(111) substrates. Reflection high energy electron diffraction patterns registered during MBE growth of the samples as well as post-growth X-ray diffraction measurements evidence a high structural perfection of 0.6 μm thick SnTe layers and (50 Å PbTe)/(50 Å SnTe) superlattices. The full width at half maximum values of (222) X-ray rocking curves measured for these thin SnTe layers crystallized in the optimal MBE growth conditions are about 300 arcsec; the carrier concentrations can be tuned from 5×10^{19} cm^{-3} to 10^{2 1} cm^{-3} depending on the MBE process parameters.
8
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Cr 3d Surface and Bulk States in Sn_{1-x}Cr_{x}Te/Cr Crystals

76%
Guziewicz E., Szamota-Sadowska K., Kowalski B. J., Grodzicka E., Story T., Orłowski B. A., Johnson R. L.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 4
783-787
EN
We report a new approach to investigate metal-semiconductor interface formation. Photoemission spectroscopy was applied in order to investigate the clean surface of a Sn_{0.97}Cr_{0.03} Te crystal and to observe its changes under sequential deposition of small amounts of Cr atoms. In order to analyse the Cr 3d contribution to the valence band, the Fano-type resonance tuned to the Cr 3p-3d transition was used. The experiment was designed to follow the Sn_{0.97}Cr_{0.03} Te/Cr interface formation process. At the clean Sn_{0.97}Cr_{0.03}Te surface, the Cr 3d states contribution to the valence band was found to be positioned 0.8 eV below the Fermi level. After the Cr deposition processes the contribution shifted to a higher binding energy and another contribution 5.8 eV below the Fermi level was also observed.
9
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Transport and Magnetic Properties of Pb_{1-x-y}Sn_{y}Mn_{x}Te (x ≤ 0.16)

76%
Łazarczyk P., Grodzicka E., Arciszewska M., Witkowska B., Dynowska E., Miotkowska S., Story T.
Acta Physica Polonica A
|
1995
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vol. 87
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issue 2
469-472
EN
Hall constant, conductivity and magnetic susceptibility of Pb_{1-x-y}Sn_{y}Mn_{x}Te semimagnetic semiconductor were investigated as a func­tion of Mn content (x = 0.04, 0.09, 0.16, y = (0.7-0.8)) in the temperature range T = (4 - 300) K. A ferromagnetic phase transition takes place at T = 5 K for samples with x = 0.04, at T = 10 K for x = 0.09 and at T = 20 K for x = 0.16. For crystals with x ≥ 0.09 the strong temper­ature dependence of the Hall constant is observed for temperatures below 40 K. Magnetic field characteristics of the Hall effect is strongly non-linear at T = 4.2 K. No significant temperature or magnetic field dependence of con­ductivity is observed in the whole temperature range studied. The observed transport anomalies are due to the anomalous Hall effect.
10
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PbSe:Cr - New Resonant Donor System

76%
Story T., Wilamowski Ż., Grodzicka E., Dobrowolski W., Witkowska B., Voiron J.
Acta Physica Polonica A
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1995
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vol. 87
|
issue 1
229-232
EN
Hall effect, conductivity, electron paramagnetic resonance and magneti­zation of Pb_{1-x}Cr_{x}Se (x ≤ 0.01) crystals were measured as a function of Cr content and electron concentration. The experimental results suggest that Cr in PbSe creates a resonant donor state with the energy of about 125 meV above the bottom of the conduction band.
11
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Magnetotransport Study of MBE grown Pb_{1-x}Eu_{x}Se Epilayers

76%
Dobrowolski W., Grodzicka E., Story T., Lambrecht A., Bottner H., Tacke M.
Acta Physica Polonica A
|
1996
|
vol. 90
|
issue 4
759-762
EN
Hall effect and electron conductivity investigations of MBE grown epilayers of Pb_{1-x}Eu_{x}Se (0 ≤ x ≤ 0.06) as a function of temperature and magnetic field are reported. The strong Hall coefficient dependence on the magnetic field was found for p-type samples grown with Se excess. The possible origins of this effect are discussed.
12
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Transport and Magnetic Study of Gd Ions in Pb_{1-y}Sn_{y}Te

64%
Story T., Arciszewska M., Łazarczyk P., Łusakowski A., Górska M., Dobrowolski W., Witkowska B., Grodzicka E., Gałązka R.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 5
997-1000
EN
Electric conductivity, Hall effect and magnetic susceptibility of Pb_{1-x-y} Sn_{y}Gd_{x}Te mixed crystals with 0.13 ≤ y ≤ 0.93 and 0.001 ≤ x ≤ 0.04 were experimentally studied over the temperature range 4K ≤ T ≤ 300 K. The incorporation of Gd ions into the Pb_{1-y}Sn_{y}Te matrix results in semi-metallic n-type conductivity of the crystals with y < 0.6. For crystals with y > 0.6 one observes only semi-metallic p-type conductivity. We present a model explaining these results in terms of the Sn composition dependence of the location of Gd^{2+/3+} level with respect to the band edges of PbSnGdTe.
13
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Magnetic Properties of Sn_{1-x}Gd_{x}Te (0.002 ≤ x ≤ 0.09)

64%
Story T., Arciszewska M., Dobrowolski W., Gołacki Z., Górska M., Grodzicka E., Łusakowski A., Dynowska E., Witkowska B.
Acta Physica Polonica A
|
1996
|
vol. 90
|
issue 5
935-938
EN
Magnetic, transport and structural properties of bulk crystals of Sn_{1-x}Gd_{x}Te with Gd content 0.002 < x < 0.09 and varying carrier concentrations obtained by an isothermal annealing were studied in the temperature range T = 1.5 - 80 K. We found the effect of resonant increase in antiferromagnetic spin-spin exchange interactions in the crystals with 0.025 ≤ x ≤ 0.05. No effect was found in crystals either with higher (x > 0.05) or with lower (x < 0.025) Gd concentration. The observed Gd composition dependence of the magnetic and transport properties of SnGdTe can be explained in a proposed model relating these experimental properties to the Gd composition induced shift of the position of Gd^{3+/2+} level with respect to the top of the valence band of SnGdTe.
14
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Indium Doping of CdTe Grown by Molecular Beam Epitaxy

64%
Karczewski G., Zakrzewski A., Kutrowski M., Jaroszyński J., Dobrowolski W., Grodzicka E., Janik E., Wojtowicz T., Kossut J., Barcz A.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 1
241-244
EN
We report on n-type indium doping of CdTe films grown by molecular beam epitaxy on (001) GaAs substrates. By adjusting the flux of In atoms we can precisely control the carrier concentration over three orders of magnitude - from 8 × 10^{14} up to 1.3 × 10^{18} cm^{-3}. In agreement with earlier reports we confirmed that Cd overpressure plays an important role in the doping process. The doping appears to be most effective for Cd/Te pressure ratio of 1.5. For this value of Cd/Te pressure ratio essentially 100% efficiency of doping is achieved at low In concentrations (< 10^{18} cm^{-3}). At higher In concentrations acceptor impurities compensate shallow donors limiting the concentration of free carriers.
15
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Resonant State of 4f^{14/13} Yb Ion in Pb_{1-x}Ge_{x}Te

64%
Grodzicka E., Dobrowolski W., Story T., Slynko E., Vygranenko Y. K., Willekens M., Swagten H., de Jonge W.
|
EN
The study of transport and of magnetic properties of Pb_{1-x}Ge_{x}Te:Yb mixed crystals (0 ≤ x ≤ 0.04) is reported. It is shown that Yb forms a donor state resonant with the PbTe valence band. The donor state position may be tuned (shifted relative to the energy gap) by admixture of Ge. The properties of the Yb ion in the Pb_{1-x}Ge_{x}Te matrix makes the system unique from the point of view of magnetic properties. It is demonstrated that the change of the conductivity type from p to n induces transitions from the paramagnetic state to the diamagnetic one.
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