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Acoustic Transport of Electrons in Parallel Quantum Wires

100%
Cunningham J., Pepper M., Talyanskii V., Ritchie D.
Acta Physica Polonica A
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2005
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vol. 107
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issue 1
38-45
EN
Over the last few years we have developed a new method to control single-electrons by isolating and moving them through a submicron width channel formed in a GaAs/AlGaAs heterostructure using a surface acoustic wave. The acoustic wave acts to push electrons through the depleted submicron channel in packets each containing an integer number of electrons. Our primary motivation for studying this system has been to develop a new standard of dc current for metrological purposes, but our recent focus has widened to investigate the possibility of single-photon emission. Here we show new experimental results which demonstrate acoustoelectric current flow in adjacent 1D wires. These results have relevance both to the use of the system in a single-photon emission scheme, as well as in the creation of a proposed acoustoelectric quantum computer.
2
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Effect in Coherently Strained B-Doped (001)SiGe/Si Heterostructures

100%
Knizhny V. I., Mironov O. A., Makarovskii O. A., Braithwaite G., Mattey N. L., Parker E. H. C., Phillips P. J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
779-782
EN
We report on two methods which illustrate piezoelectric effects in the strained Si (100)Si_{1-x}/Ge_{x} system. The non-contact sound excitation tech­nique has been used to reveal the conversion of a high-frequency electric field E into acoustic waves at 77 K which can also be modulated by a dc applied bias voltage (±30 V). The sample was an MBE grown modulation doped Si_{0.88}Ge_{0.12}/(001)Si structure with a carrier sheet density 2.0 × 10^{11} cm^{-2} and a 4.2 K mobility 10500 cm^{2} V^{-1} s^{-1}. We deduce that the observed high-frequency electric field acoustic wave conversion is associated with a piezoelectric-like effect possibly due to ordering in the strained SiGe alloy or symmetry breaking effect near Si/SiGe interface. Further evidence is pro­vided by the existence of a piezoelectric phonon interaction in the hot hole energy relaxation mechanism determined from high electric field Shubnikov de Haas He^{3} low temperature measurements.
3
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Parametric Amplification in Magnetized Nondegenerate Semiconducting Plasmas

100%
Jat K., Neogi A., Ghosh S.
Acta Physica Polonica A
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1991
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vol. 79
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issue 6
829-841
EN
Using the straightforward coupled-mode theory, the parametric amplification is analytically investigated in magnetized piezoelectric as well as non-piezoelectric semiconductors. The origin of nonlinear interaction is taken to be in the second-order optical susceptibility χ^{(}2) arising from the nonlinear induced current density. The threshold value of the pump electric field E_{0th} is obtained for crystals. E_{0th} is found to decrease with the rise in magnetic field and fall with the rise in scattering angle. Parametric gain constants are obtained for different situations of practical interest, i.e. (i) for piezoelectric coupling only g_{p}, (ii) for deformation potential coupling only g_{d}, (iii) for both the couplings g_{b}. Numerical investigations reveal that the magnetic field increases the gain. Maximum gains are obtained for backward scattered mode. g_{d} is always found to be less than g_{p} and g_{b}. It is also found that g_{p} and g_{b} both are identical up to k ≈ x 10^{7}m^{-1} and for k ≥ 3 x 10^{7}m^{-1}, g_{b} exceeds g_{p}.
4
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Determination of Some Kinetic Parameters of Fast Surface States in Silicon Single Crystals by Means of Surface Acoustic Wave Method

88%
Pustelny T., Opilski A., Pustelny B.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6A
A-183-A-190
EN
The paper presents the acoustic method for determining some parameters of fast surface states in semiconductors. This method uses the interactions of the phonon-electron type for determining both the effective carrier lifetime τ influenced by the fast surface energetic states and the velocity g of the carrier trapped by the surface states. Some experimental results of the parameters τ and g in near-surface region of real Si(111) samples for their various surface treatments, obtained by the offered method, are presented.
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