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1
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Fractal Dimensions from Chaotic Oscillations in Semi-Insulating GaAs

100%
Zduniak A., Łusakowski J.
Acta Physica Polonica A
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1993
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vol. 84
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issue 3
575-578
EN
Relaxation and domain current oscillations in undoped semi-insulating GaAs were observed at room temperature for a broad range of voltage applied to a sample. The oscillations were characterized by a reconstruction of an attractor of the system. An analysis of the attractor helped to discriminate between the two likes of oscillations. A transition from one like of oscillations to the other was connected with a chaotization of the current. A chaotic state of the system was analyzed by calculations of fractal dimensions D_{q} for -0.6 < g < 40 and the f(α) function.
2
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Autocorrelation Function and Mutual Information from Short Experimental Time Series

100%
Zduniak A., Łusakowski J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 1
257-260
EN
A nonlinear dynamics of self-generated current oscillations in semi-insu­lating GaAs was studied by the reconstruction of an attractor from a short (14500 points) time series. Two methods of choosing of a time constant (τ) for this reconstruction are compared. One of them assumes τ to be an argu­ment of the first zero of the autocorrelation function and the other takes τ as an argument of the first minimum of the mutual information. It is shown that for periodic oscillations both methods are equivalent, but for chaotic ones only the mutual information gives a time constant which does not depend on a time series used for calculations.
3
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Electron Temperature in Semi-Insulating GaAs for Low Electric Fields

81%
Zduniak A., Łusakowski J., Nowak G.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
777-780
EN
Heating of electrons by electric fields smaller than that required for generation of domain oscillations was investigated in samples of EL2-rich semi-insulating GaAs. Current-voltage characteristics were measured as a function of temperature between 268 K and 330 K. They exhibit a sublinear shape which is interpreted as a result of an enhanced electron capture on the EL2. The capture rate and the electron temperature as a function of the electric field was determined. A fitting procedure gave the value of electron capture cross-section on the EL2 to be 2.7 × 10^{-13} cm^{2} which agrees with literature data.
4
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Universal Behaviour of Magnetoconductance due to Weak Localization in Two-Dimensional Systems - Example of GaInAs Quantum Wells

81%
Zduniak A., Dyakonov M. I., Litwin-Staszewska E., Knap W.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
1053-1057
EN
Weak localization corrections to conductivity of a two-dimensional electron gas are studied by measurements of the magnetic field dependence of the conductivity in GalnAs quantum wells. We observe that, when presented as a function of the normalized magnetic field (x = B/B_{tr}, where B is the magnetic field, B_{tr} = ħ/4eτD, D is the diffusion constant and τ is momentum relaxation time), different samples show very similar high field behaviour. A theoretical description is developed that allows one to describe in a consistent way high and low field behaviour. The theory predicts universal (B^{-1/2}) behaviour of the conductivity correction for all 2D systems in the high field limit (r > 1). Low field behaviour depends strongly on spin and phase relaxation mechanisms. Comparison of the theory with experiment confirms the universal behaviour in the high field limit and allows one to estimate the spin and phase relaxation times for different GaInAs quantum wells.
5
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Weak Antilocalization in Quantum Wells

52%
Knap W., Skierbiszewski C., Litwin-Staszewska E., Kobbi F., Zduniak A., Robert J., Pikus G., Iordanskii S., Mosser V., Zekentes K.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
427-432
EN
Spin relaxation in degenerated two-dimensional (2D) electron gas is studied by measurements of the magnetic field dependence of the weak an­tilocalization corrections to the conductivity in GaInAs quantum wells. Con­sistent quantitative (up to order of magnitude) description of weak antilocal­ization data on GaAs like heterojunctions and quantum wells was obtained. Our results show that spin precession around the effective magnetic field direction as described by the Dyakonov-Perel model is the main spin relax­ation mechanism in degenerated 2D electron gas in semiconductors with no inversion symmetry.
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