The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Masaaki Nakayama - One of the best experts on this subject based on the ideXlab platform.
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electric field effects on reduced effective masses of Minibands at the mini brillouin zone center and edge in a gaas alas superlattice
Journal of Applied Physics, 2012Co-Authors: Masaaki Nakayama, T KawabataAbstract:We have investigated the electric-field-strength dependence of the reduced effective masses of the Minibands in a GaAs/AlAs superlattice embedded in a p-i-n diode structure with use of electroreflectance spectroscopy. Frantz-Keldysh (FK) oscillations are observed in the energy region between the n = 1 heavy hole to electron transition at the mini-Brillouin-zone center (kz = 0: Γ point) and that at the edge (kz = π/D: π point), where D is the superlattice period. Analyzing the FK oscillations, we evaluate the reduced effective masses at the Γ and π points as a function of electric field strength. The evaluated reduced effective masses are consistent with the values estimated from the calculated miniband dispersion relations in a low electric field regime. It is found that the reduced effective masses tend to be heavier at a given electric field strength. Considering the electric-field-strength dependence of eigenstates calculated using a transfer-matrix method, we conclude that an increase of the reduced e...
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Miniband-width effects on Wannier–Stark localization of the first and second quantized states in a GaAs/AlAs superlattice
Journal of Luminescence, 2006Co-Authors: Takayuki Hasegawa, Masaaki NakayamaAbstract:Abstract We performed electroreflectance (ER) measurements in order to reveal the transformation processes from the Minibands to the Wannier–Stark (WS) localization states in a GaAs (6.8 nm)/AlAs (0.9 nm) superlattice. The high sensitivity of ER spectroscopy enabled us to observe the interband optical transitions associated with the second (n=2) Minibands in addition to those associated with the first (n=1) Minibands. It is found that the electric field strengths for the formation of the WS-localization states of the n=2 Minibands are considerably higher than those of the n=1 Minibands. The experimental results are quantitatively analyzed on the basis of the theoretical calculation of the electric-field-strength dependence of the miniband states using a transfer-matrix method. It is concluded that the critical electric field strengths for the formation of the WS-localization states clearly correlate with the miniband widths.
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Electroreflectance Observation of Transformation Processes of the First and Second Minibands to Wannier–Stark Localization States in a GaAs/AlAs Superlattice
Japanese Journal of Applied Physics, 2005Co-Authors: Takayuki Hasegawa, Masaaki NakayamaAbstract:We have investigated the transformation processes of the first (n=1) and second (n=2) Minibands to the Wannier–Stark (WS) localization states in a GaAs (6.8 nm)/AlAs (0.9 nm) superlattice embedded in a p–i–n structure by electroreflectance spectroscopy. The high sensitivity of electroreflectance enabled us to observe the interband optical transitions associated with the n=2 Minibands in addition to those associated with the n=1 Minibands. The systematic results of the electroreflectance spectra as a function of electric field strength demonstrate that the electric field strength for the formation of the WS-localization state of the n=2 miniband is higher than that of the n=1 miniband, which reflects a difference in the energy widths of the n=1 and n=2 Minibands. The experimental results are quantitatively discussed on the basis of the electric-field-strength dependence of the energies and envelope functions of the n=1 and n=2 Minibands calculated using a transfer-matrix method. We find a clear correlation between the miniband widths and the critical electric field strengths for the formation of the WS-localization states.
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electroreflectance observation of transformation processes of the first and second Minibands to wannier stark localization states in a gaas alas superlattice
Japanese Journal of Applied Physics, 2005Co-Authors: Takayuki Hasegawa, Masaaki NakayamaAbstract:We have investigated the transformation processes of the first (n=1) and second (n=2) Minibands to the Wannier–Stark (WS) localization states in a GaAs (6.8 nm)/AlAs (0.9 nm) superlattice embedded in a p–i–n structure by electroreflectance spectroscopy. The high sensitivity of electroreflectance enabled us to observe the interband optical transitions associated with the n=2 Minibands in addition to those associated with the n=1 Minibands. The systematic results of the electroreflectance spectra as a function of electric field strength demonstrate that the electric field strength for the formation of the WS-localization state of the n=2 miniband is higher than that of the n=1 miniband, which reflects a difference in the energy widths of the n=1 and n=2 Minibands. The experimental results are quantitatively discussed on the basis of the electric-field-strength dependence of the energies and envelope functions of the n=1 and n=2 Minibands calculated using a transfer-matrix method. We find a clear correlation between the miniband widths and the critical electric field strengths for the formation of the WS-localization states.
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Franz–Keldysh oscillations at the above-barrier miniband in a GaAs/AlxGa1 − xAs superlattice
Superlattices and Microstructures, 1999Co-Authors: Masanobu Ando, Masaaki Nakayama, Hitoshi Nishimura, Kenzo FujiwaraAbstract:Abstract We report on the observation of the Franz–Keldysh oscillations associated with the second-electron and heavy-hole Minibands, in which the second-electron miniband lies above the barrier potential, in a GaAs(7.0 nm)/Al0.1Ga0.9As (3.5 nm) superlattice by using electroreflectance spectroscopy. The reduced mass estimated from the Franz–Keldysh oscillations is consistent with that estimated from the miniband–dispersion relation based on the effective mass approximation around a zero-electric field, and becomes heavier with an increase in the electric field. The electric-field dependence of the reduced mass correlates with the localization of the electron envelope function. We discuss these results from an envelope-function forms calculated by a transfer-matrix method.
A. Troper - One of the best experts on this subject based on the ideXlab platform.
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Superlattice vertical transport with high-lying Minibands
Superlattices and Microstructures, 1998Co-Authors: Xiao-wu Lei, I. C. Da Cunha Lima, A. TroperAbstract:We examine the role of high-lying Minibands in superlattice vertical transport using a nonparabolic balance-equation approach. We find that the inclusion of high-lying Minibands results in a decrease of the electron temperature, a reduction of the peak drift velocity and a slow-down of the velocity-drop rate in the negative differential mobility (NDM) regime, in comparison with those predicted by a single miniband model. These effects become significant when the strength of the electric field gets close to or falls in the NDM regime.
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Effect of high-lying Minibands on superlattice vertical transport
Journal of Applied Physics, 1997Co-Authors: Xiao-wu Lei, I. C. Da Cunha Lima, A. TroperAbstract:The role of high-lying Minibands in superlattice vertical transport is investigated using a nonparabolic balance-equation approach extended to include multi-miniband occupation. We find that the existence of high-lying Minibands results in a decrease of the electron temperature, a reduction of the peak drift velocity and a slowdown of the velocity-drop rate in the negative differential mobility (NDM) regime, in comparison with those predicted by a single miniband model. Numerical calculations of steady-state transport in typical GaAs-based superlattices at room temperature, show that these effects become significant when the strength of the electric field gets close to or falls in the NDM regime.
Jian-bai Xia - One of the best experts on this subject based on the ideXlab platform.
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rashba spin splitting of the Minibands of coupled inas gaas pyramid quantum dots
Applied Physics Letters, 2008Co-Authors: X. W. Zhang, Jun-wei Luo, W J Fan, Jian-bai XiaAbstract:The Rashba spin splitting of the Minibands of coupled InAs/GaAs pyramid quantum dots is investigated using the k center dot p method and valence force field model. The Rashba splitting of the two dimensional miniband in the lateral directions is found due to the structure inversion asymmetry in the vertical direction while the miniband in the vertical direction has no Rashba spin splitting. As the space between dots increases, the Rashba coefficients decrease and the conduction-band effective mass increases. This Rashba spin splitting of the Minibands will significantly affect the spin transport properties between quantum dots. (C) 2008 American Institute of Physics.
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Rashba spin splitting of the Minibands of coupled InAs∕GaAs pyramid quantum dots
Applied Physics Letters, 2008Co-Authors: X. W. Zhang, Weijun Fan, Jun-wei Luo, Jian-bai XiaAbstract:The Rashba spin splitting of the Minibands of coupled InAs/GaAs pyramid quantum dots is investigated using the k center dot p method and valence force field model. The Rashba splitting of the two dimensional miniband in the lateral directions is found due to the structure inversion asymmetry in the vertical direction while the miniband in the vertical direction has no Rashba spin splitting. As the space between dots increases, the Rashba coefficients decrease and the conduction-band effective mass increases. This Rashba spin splitting of the Minibands will significantly affect the spin transport properties between quantum dots. (C) 2008 American Institute of Physics.
Xiao-wu Lei - One of the best experts on this subject based on the ideXlab platform.
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Superlattice vertical transport with high-lying Minibands
Superlattices and Microstructures, 1998Co-Authors: Xiao-wu Lei, I. C. Da Cunha Lima, A. TroperAbstract:We examine the role of high-lying Minibands in superlattice vertical transport using a nonparabolic balance-equation approach. We find that the inclusion of high-lying Minibands results in a decrease of the electron temperature, a reduction of the peak drift velocity and a slow-down of the velocity-drop rate in the negative differential mobility (NDM) regime, in comparison with those predicted by a single miniband model. These effects become significant when the strength of the electric field gets close to or falls in the NDM regime.
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Effect of high-lying Minibands on superlattice vertical transport
Journal of Applied Physics, 1997Co-Authors: Xiao-wu Lei, I. C. Da Cunha Lima, A. TroperAbstract:The role of high-lying Minibands in superlattice vertical transport is investigated using a nonparabolic balance-equation approach extended to include multi-miniband occupation. We find that the existence of high-lying Minibands results in a decrease of the electron temperature, a reduction of the peak drift velocity and a slowdown of the velocity-drop rate in the negative differential mobility (NDM) regime, in comparison with those predicted by a single miniband model. Numerical calculations of steady-state transport in typical GaAs-based superlattices at room temperature, show that these effects become significant when the strength of the electric field gets close to or falls in the NDM regime.
X. W. Zhang - One of the best experts on this subject based on the ideXlab platform.
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rashba spin splitting of the Minibands of coupled inas gaas pyramid quantum dots
Applied Physics Letters, 2008Co-Authors: X. W. Zhang, Jun-wei Luo, W J Fan, Jian-bai XiaAbstract:The Rashba spin splitting of the Minibands of coupled InAs/GaAs pyramid quantum dots is investigated using the k center dot p method and valence force field model. The Rashba splitting of the two dimensional miniband in the lateral directions is found due to the structure inversion asymmetry in the vertical direction while the miniband in the vertical direction has no Rashba spin splitting. As the space between dots increases, the Rashba coefficients decrease and the conduction-band effective mass increases. This Rashba spin splitting of the Minibands will significantly affect the spin transport properties between quantum dots. (C) 2008 American Institute of Physics.
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Rashba spin splitting of the Minibands of coupled InAs∕GaAs pyramid quantum dots
Applied Physics Letters, 2008Co-Authors: X. W. Zhang, Weijun Fan, Jun-wei Luo, Jian-bai XiaAbstract:The Rashba spin splitting of the Minibands of coupled InAs/GaAs pyramid quantum dots is investigated using the k center dot p method and valence force field model. The Rashba splitting of the two dimensional miniband in the lateral directions is found due to the structure inversion asymmetry in the vertical direction while the miniband in the vertical direction has no Rashba spin splitting. As the space between dots increases, the Rashba coefficients decrease and the conduction-band effective mass increases. This Rashba spin splitting of the Minibands will significantly affect the spin transport properties between quantum dots. (C) 2008 American Institute of Physics.