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1
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Current Fluctuations in Single Barrier Vertical GaAs/AlAs/GaAs Tunneling Devices

100%
Przybytek J., Baj M.
Acta Physica Polonica A
|
2007
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vol. 112
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issue 2
221-226
EN
We report the experimental results of the low temperature (T = 4.2 K) low-frequency current fluctuations measurements in the single-barrier resonant tunneling GaAs/AlAs/GaAs device with Siδ-doping in the center of the 10 nm thick AlAs barrier. The dimensions of the device were 200μm by 200μm. For the biasing voltages 0.1 V<|U|<1 V we observed the Fano factors between F = 0.7 and F = 0.95. We explain it by the existence of the trapping centers/imperfections/resonant levels inside the barrier participating in the transport for this range of voltages. Only for the smallest biasing voltages the Fano factor tends to F = 1, expected for a highly nontransparent barrier.
2
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Stabilization of the Distorted Configuration of the EL2 Defect Induced by the Free Electron Capture in GaAsP

81%
Przybytek J., Baj M., Słupiński T.
Acta Physica Polonica A
|
1995
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vol. 88
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issue 5
881-884
EN
Our results of optical absorption, electronic transport and deep level transient spectroscopy measurements performed on n-type GaAs_{1-x}P_{x} (x ≈ 0.2) strongly suggest that using both an enlarged-gap material (compared to GaAs) and hydrostatic pressure we can push down the acceptor level of the distorted configuration of the EL2 defect, (EL2*)^{–/0}, sufficiently low into the gap that the distorted configuration of the EL2 defect, EL2*, becomes stabilized.
3
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Influence of Intersubband Scattering on the Magnetic Field Dependence of the Conductivity Tensor

81%
Siwiec-Matuszyk J., Baj M., Babiński A., Kasprzak J.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
337-344
EN
In this paper we show that intersubband scattering can lead to apparent inconsistency of the experimental results obtained by means of classical and quantum transport measurements and this discrepancy is entirely connected with the usage of classical formulae to describe magnetic field dependence of a conductivity tensor. We prove that there is no contradiction in our observations and that the models describing quantum oscillations and magnetic-field dependence of the conductivity tensor, which are present in the literature, complement each other.
4
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Pressure-Dependent Coupling of the ^{3}A_{2}(F) and ^{1}T_{2}(D) States of Ni^{2+} in ZnS and ZnSe

81%
Wasik D., Baj M., Liro Z.
Acta Physica Polonica A
|
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.
5
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The Pressure Dependence of Transition Metal-Related Levels in GaAs

81%
Babiński A., Baj M., Hennel A.
Acta Physica Polonica A
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1991
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vol. 79
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issue 2-3
323-327
EN
The hydrostatic pressure coefficients of V^{3+/2+} acceptor level in bulk GaAs and of the 0.48 eV trap (related to Ni^{2+/1+} double acceptor level) in VPE GaAs were measured by means of the DLTS technique. The obtained values are 94 meV/GPa and 196 meV/GPa relative to the bottom of the conduction band. For Ni^{2+/1+} level the strong pressure dependence of the capture cross-section activation energy (60 meV/GPa) was also observed.
6
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Acceptor-Like Level of the EL2 Defect in its Metastable Configuration

81%
Dreszer P., Baj M., Babiński A.
Acta Physica Polonica A
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1991
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vol. 79
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issue 1
129-132
EN
This paper presents for the first time the evident experimental confirmation that EL2 defect, while being in its metastable configuration, traps under hydrostatic pressure an additional electron, i.e. the acceptor-like (EL2*)^{0/-} level enters the energy gap under pressure. We propose that in n-GaAs the EL2 thermal recovery takes always place via the (EL2*)^{-} state.
7
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Hydrostatic Pressure Study of MBE CdMnTe Doped with Bromine

71%
Szczytko J., Wasik D., Przybytek J., Baj M., Waag A.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
933-936
EN
We present Hall effect and resistivity measurements as a function of pressure performed on MBE-grown Cd_{1-x}Mn_{x}Te (with x = 0.14) layer (1 μm) doped with bromine. The experimental data were analysed using positive and negative U model of the Br centres. We found that both models could reproduce the experimental points, but in the case of positive U model - only under assumption that the sample was completely uncompensated.
8
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High-Pressure Magnetotransport Measurements of Resonant Tunnelling via X-Minimum Related States in AlAs Barrier

71%
Gryglas M., Przybytek J., Baj M., Eaves L., Henini M.
Acta Physica Polonica A
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2001
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vol. 100
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issue 3
403-408
EN
In this paper, we present the results of magnetotransport experiments performed on a single barrier GaAs/AlAs/GaAs heterostructures. Tunnel current was measured as a function of magnetic field for different values of bias voltage and hydrostatic pressure. We observed that the amplitude of the magnetooscillations of tunnel current quenched when the requirements for resonant tunnelling were met and it recovered in out-of-resonance conditions. This effect was observed both for tunnelling through donor states and through X-minimum related quasiconfined conduction band states. The fact that also in the latter case the amplitude was restored suggests that this process involved X_z subbands and took place without a participation of phonons (the so-called k_ǁ-conserving process).
9
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Observation of Thermally-Activated Electron Traps in GaAs/AlAs/GaAs Heterostructures in Low-Frequency Noise Measurements

62%
Przybytek J., Stankiewicz R., Gryglas-Borysiewicz M., Baj M., Cavanna A., Faini G.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
723-725
EN
During our investigations of tunneling process in thin 7 nm thick GaAs/AlAs/GaAs vertical single-barrier tunneling structure with Si δ-doping inside the barrier we have observed fluctuations of the tunneling current which exhibited large Lorentzian noise with intensity depending on biasing voltage. We have shown that Lorentzian noise originates from multilevel random telegraph noise of the small number of fluctuators which influence the tunneling process. Time-domain analysis of the current noise measured for temperatures between 4.2 K and 50 K enabled to determine the thermal activation energies of these fluctuators lying between 0.8 and 3 meV.
10
Content available remote

Hydrostatic-Pressure Deep Level Transient Spectroscopy Study of the Heteroantisite Antimony Level in GaAs

62%
Babiński A., Przybytek J., Baj M., Omling P., Samuelson L., Słupiński T.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
841-844
EN
We present some preliminary results of the first hydrostatic-pressure study of the electronic level related to the Sb-heteroantisite defect in GaAs. We studied two kinds of n-type GaAs samples doped with antimony: bulk samples grown by liquid encapsulated Czochralski method and thin layers grown by metalorganic chemical vapour deposition technique. We found strongly nonlinear pressure dependence of the activation energy of the emission rate for the level. Moreover, the results obtained for the bulk material were fairly different from those obtained for thin metalorganic chemical vapour deposition layers. The possible explanation of this difference is presented.
11
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Spectroscopy of a Single Si Donor by the Resonant Tunnelling Experiment

62%
Baj M., Gryglas M., Jouault B., Maude D., Faini G., Gennser U., Cavanna A.
Acta Physica Polonica A
|
2006
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vol. 110
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issue 2
157-162
EN
Resonant tunnelling via single impurities placed in a single barrier was experimentally studied. The typically observed structures in the current-voltage characteristics seem to be paired. Such a pair can be interpreted as ground and excited states of an impurity, related to X_{xy} and X_z valleys, which is in agreement with the results obtained for big mesas. However, it is not clear why X_{xy} states can be seen without any phonon participation.
12
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Transport in GaAs/AlAs/GaAs [111] Tunnel Junctions

62%
Lewińska S., Gryglas-Borysiewicz M., Przybytek J., Baj M., Jouault B., Gennser U., Ouerghi A.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
606-608
EN
Resonant tunneling in single-barrier GaAs/AlAs/GaAs junctions grown in [111] direction was studied for samples with different concentration of silicon δ-doping in AlAs. In the I(V) characteristics, measured at 4 K, two kinds of peaks were observed: related to resonant tunneling via donors states in the barrier, and through X-minimum quantum well subbands. The results are compared to those previously obtained for analogous samples grown along [001] direction. The investigations reveal different symmetry of donor states in both cases.
13
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Visualisation of the extent of damage in a rat spinal cord injury model using MR Microscopy of the water diffusion tensor

62%
Krzyzak A. T., Jasinski A., Weglarz W. P., Adamek D., Sagnowski P., Baj M.
Acta Neurobiologiae Experimentalis
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2005
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vol. 65
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issue 3
255-264
EN
Magnetic Resonance Diffusion Tensor Imaging (DTI) of the control and traumatic injured spinal cord of a rat in vitro is reported. Experiments were performed on excised spinal cords from 10 Wistar rats, using a home-built 6.4 T MR microscope. MRI and histopathological results were compared. Presented results show that DTI of the spinal cord, perfused with formalin 10 minutes after the injury, can detect changes in water diffusion in white matter (WM) and in gray matter (GM), in areas extending well beyond the region of direct impact. Histology of neurons of the GM shows changes that can be attributed to ischemia. This is in agreement with the observed decrease of diffusion in the injured regions, which may be attributed to the cytotoxic edema due to ischemia. However, the diffusion changes in highly anisotropic WM seem to be caused by a direct action of mechanical force of impact, which significantly distorts the nerve fibers.
14
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Spatial Correlations of Donor Charges in MBE CdTe

52%
Suski T., Wiśniewski P., Litwin-Staszewska E., Wasik D., Przybytek J., Baj M., Karczewski G., Wojtowicz T., Zakrzewski A., Kossut J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
929-932
EN
We present experimental evidence that at high pressures indium donors in CdTe localize electrons in spatially correlated manner. We have studied Hall mobility, μ_{H}, as a function of electron concentration, n_{H}, at T=77 K. Changes of n_{H} have been achieved by two methods. High pressure freeze-out of electrons onto localized states of In-donors leads to the mobility enhancement with respect to the situation when n_{H} has been modified by means of a subsequent annealing of the sample. As a result, depending on the degree of spatial correlations in the impurity charges arrangement, different values of μ_{H} correspond to the same value of n_{H}. The variation of mobility with electron concentration suggests that the localized state of In-donor represents likely negatively charged DX state.
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