The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Hong Sun - One of the best experts on this subject based on the ideXlab platform.
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Energy minigaps in the quantum well wires with periodical Lateral Surface structures
Journal of Materials Science & Technology, 2009Co-Authors: Zhen-yan Deng, Hong SunAbstract:Energy minigaps caused by Lateral Surface structures in quasi-one-dimensional GaAs/AlAs quantum well wires are calculated with the variational and degenerate-perturbational approaches. By a coordinate transformation, the structured interfaces of the wires are transformed into planar ones so that the boundary conditions of the electronic wave functions can be satisfied exactly on the interfaces. The dependence of the energy minigaps on the Lateral Surface structures are discussed
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The Stark effect of excitons in corrugated Lateral Surface superlattices: the effect of centre-of-mass quantization
Journal of Physics: Condensed Matter, 1999Co-Authors: Hong Sun, Jun LeiAbstract:The quantum-confined Stark effect of excitons in GaAs/AlGaAs corrugated Lateral Surface superlattices (CLSSLs) is calculated. New absorption peaks with nearly equal energy spacing appear in the exciton absorption spectra due to the exciton centre-of-mass quantization by the periodically corrugated interfaces of the CLSSLs. The shift of the exciton optical absorption peaks and variation in its absorption strength with the applied electric field, as well the absorption selection rules for the CLSSLs, are discussed.
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The strong Stark effect of intersubband transitions in corrugated Lateral Surface superlattices
Journal of Physics: Condensed Matter, 1998Co-Authors: Hong SunAbstract:Intersubband electro-absorption and electro-refraction index spectra of GaAs/AlAs corrugated Lateral Surface superlattices (CLSSLs) are calculated. Large shifts of intersubband transition energies and Fermi energy levels in the electron occupied subbands induced by applied electric fields result in strong intersubband Stark effects and large refractive index variations in the CLSSLs that we considered with moderate electric fields . Strong intersubband absorptions with normally incident light due to the corrugated interfaces of the CLSSLs which break the in-plane translational symmetry of the systems are predicted. Broadenings of the intersubband electro-absorption and electro-refraction index spectra caused by structural fluctuations of the CLSSLs are discussed.
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Miniband structures and densities of impurity states in Lateral-Surface-superlattice quantum well wires
Journal of Physics: Condensed Matter, 1994Co-Authors: Zhen-yan Deng, Jing-kun Guo, Ting-rong Lai, Hong SunAbstract:We calculate energy miniband structures and densities of impurity states in quasi-one-dimensional GaAs/AlAs quantum well wires with periodic Lateral Surface structures. By a coordinate transformation, the structured interfaces of the wires are transformed into planar interfaces so that the boundary conditions of the electronic wavefunctions can be satisfied exactly on the interfaces. The new optical transition spectral structures associated with minibands and impurities are discussed.
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Magnetopolarons in Lateral Surface superlattices with periodically structured interfaces
Journal of Physics: Condensed Matter, 1993Co-Authors: Hong SunAbstract:An improved Wigner-Brillouin theory, developed by Peeters and Devreese, was extended to the case of Lateral Surface superlattices (LSSLS), where Lateral periodic potentials due to the periodically structured interfaces are introduced into two-dimensional electronic systems. Numerical calculations were carried out for the energy dispersions of the magnetopolarons in GaAs LSSL structures with periodic potentials along the Lateral x direction, such as those produced by deposition of AlAs and GaAs fractional layers on (001) vicinal GaAs substrates. The degenerate magnetopolaron energy levels become dependent on the electron wave vector ky in the y direction, forming magnetopolaron bands. For weak magnetic fields ( omega c, or= omega LO), the effect of the Lateral periodic potentials on the electron-LO-phonon interaction energy must be considered in order to obtain correct magnetopolaron energy dispersions. The transition energy between the first two magnetopolaron energy levels forms a wide band which will broaden greatly the cyclotron resonance absorption spectra of the LSSLS.
Martin Christopher Holland - One of the best experts on this subject based on the ideXlab platform.
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Potential modulation by strain in Lateral Surface superlattices
Physical Review B, 1999Co-Authors: A. R. Long, Ramón Cuscó, E. Skuras, S. Vallis, Ivan A. Larkin, John H. Davies, Martin Christopher HollandAbstract:We have measured the magnitude of the potential modulation below gated one-dimensional Lateral Surface superlattices fabricated with periods between 60 and 600 nm on a range of GaAs/AlGaAs heterostructures. The magnitude of the modulation was obtained by studying the amplitude of the commensurability oscillations in magnetoresistance, and confirmed by analysis of the low field positive magnetoresistance step. Without gate bias applied, the modulation is generated by strain in the gates, coupled piezoelectrically to the two-dimensional electron gas. Both magnitude and harmonic content of the potential are in reasonable agreement with a recent theoretical calculation of this coupling, over the full range of periods and for all the structures studied. Away from zero gate bias electrostatic modulation adds to the piezoelectric component. This differs according to the sign of the applied bias. In depletion it increases roughly linearly with bias and is in good agreement with theoretical estimates, whereas in positive bias it tends to saturate as strong screening in the donor layers develops.
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large periodic potential under Lateral Surface superlattices fabricated from heteroepitaxial stressor layers
Applied Physics Letters, 1998Co-Authors: C J Emeleus, A. R. Long, John H. Davies, Brian Milton, D E Petticrew, Martin Christopher HollandAbstract:We have fabricated Lateral Surface superlattices by etching a strained layer of In0.2Ga0.8As near the Surface of a heterostructure. This provides strong modulation of the electron gas while retaining a high electron mobility. The potential arises mainly from strain and the piezoelectric effect, which depends on orientation, and from the change in the Surface profile. The fundamental components of these two contributions cancel in one orientation to leave a dominant second harmonic. This effectively halves the period of the superlattice from its lithographic value and provides a promising technique for creating potentials with a period comparable to the Fermi wavelength.
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Anisotropic piezoelectric effect in Lateral Surface superlattices
Applied Physics Letters, 1997Co-Authors: E. Skuras, A. R. Long, Ivan A. Larkin, John H. Davies, Martin Christopher HollandAbstract:We have studied the potential induced by Lateral Surface superlattices deposited on a GaAs/AlGaAs heterostructure as a function of bias and orientation of the gates. By using the gates to null the total potential, we extracted the contribution to this potential in the absence of gate bias. Its angular dependence shows that it is dominated by strain from the gates coupled to the electrons by the piezoelectric effect.
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Anharmonic periodic modulation in Lateral Surface superlattices
Surface Science, 1994Co-Authors: Ramón Cuscó, E. Skuras, Martin Christopher Holland, A. R. Long, Ivan A. Larkin, John H. Davies, S.p. BeaumontAbstract:Abstract We have measured the longitudinal magnetoresistance of a Lateral Surface superlattice with a period of 270 nm where the electrons are only 28 nm deep. The commensurability oscillations have a strong second harmonic content. This reflects a non-sinusoidal potential in the two-dimensional electron gas, a consequence of the shallow structure. The shape of the potential cannot be explained by a pinned GaAs Surface and indicates that the Surface charge is frozen or that the electrons feel an elastic strain field from the metal gates.
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Potential modulation under Lateral Surface superlattices
Superlattices and Microstructures, 1994Co-Authors: Ramón Cuscó, E. Skuras, S. Vallis, Martin Christopher Holland, A. R. Long, S.p. Beaumont, Ivan A. Larkin, John H. DaviesAbstract:We have used the commensurability oscillations to make a systematic analysis of the origin and form of the potential under Lateral Surface superlattices with periods down to 100 nm. This potential arises from a combination of mechanical strain and electrostatics, and we have determined its dependence on the gate bias, the period and mark-space ratio of the gate array, and the depth of the electrons.
A. R. Long - One of the best experts on this subject based on the ideXlab platform.
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Commensurability oscillations on Lateral Surface superlattices with large periods
Thin Solid Films, 2001Co-Authors: A Abd-el Mongy, A. R. Long, E Belal, K. AliAbstract:Abstract We present for the first time, an investigation of commensurability oscillations (COs) on Lateral Surface superlattice devices with large periods (1 and 2 μm). The observed values of the COs positions are compared with the predicted peaks. In forward bias clear COs are observed. It is noticed that the COs have a strong dominant third harmonic content. The COs are found to vanish with increasing negative bias.
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Importance of symmetry breaking in two-dimensional Lateral-Surface superlattices
Physical Review B, 2000Co-Authors: S. Chowdhury, E. Skuras, A. R. Long, C J Emeleus, B. Milton, J. H. Davies, Giovanni Pennelli, C.r. StanleyAbstract:We have investigated commensurability oscillations in the magnetoresistances of two-dimensional Lateral Surface superlattices with square patterns and periods of 100 nm. In some of our samples the symmetry of the potential was broken by the presence of stress and strong piezoelectric effects. Oscillations were weak in symmetric samples, but became much stronger for transport along the $[011\ifmmode\bar\else\textasciimacron\fi{}]$ direction [on a (100) wafer] when the symmetry was broken. For transport along the $[010]$ and $[001]$ directions in the asymmetric samples, the dominant Fourier component in the potential was at an angle of $45\ifmmode^\circ\else\textdegree\fi{}$ to the transport direction, and the commensurability oscillations had an effective period of $100/\sqrt{2}$ nm. All of these observations are fully in accord with a recent semi-classical theory based on the guiding center drift concept.
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Potential modulation by strain in Lateral Surface superlattices
Physical Review B, 1999Co-Authors: A. R. Long, Ramón Cuscó, E. Skuras, S. Vallis, Ivan A. Larkin, John H. Davies, Martin Christopher HollandAbstract:We have measured the magnitude of the potential modulation below gated one-dimensional Lateral Surface superlattices fabricated with periods between 60 and 600 nm on a range of GaAs/AlGaAs heterostructures. The magnitude of the modulation was obtained by studying the amplitude of the commensurability oscillations in magnetoresistance, and confirmed by analysis of the low field positive magnetoresistance step. Without gate bias applied, the modulation is generated by strain in the gates, coupled piezoelectrically to the two-dimensional electron gas. Both magnitude and harmonic content of the potential are in reasonable agreement with a recent theoretical calculation of this coupling, over the full range of periods and for all the structures studied. Away from zero gate bias electrostatic modulation adds to the piezoelectric component. This differs according to the sign of the applied bias. In depletion it increases roughly linearly with bias and is in good agreement with theoretical estimates, whereas in positive bias it tends to saturate as strong screening in the donor layers develops.
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large periodic potential under Lateral Surface superlattices fabricated from heteroepitaxial stressor layers
Applied Physics Letters, 1998Co-Authors: C J Emeleus, A. R. Long, John H. Davies, Brian Milton, D E Petticrew, Martin Christopher HollandAbstract:We have fabricated Lateral Surface superlattices by etching a strained layer of In0.2Ga0.8As near the Surface of a heterostructure. This provides strong modulation of the electron gas while retaining a high electron mobility. The potential arises mainly from strain and the piezoelectric effect, which depends on orientation, and from the change in the Surface profile. The fundamental components of these two contributions cancel in one orientation to leave a dominant second harmonic. This effectively halves the period of the superlattice from its lithographic value and provides a promising technique for creating potentials with a period comparable to the Fermi wavelength.
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Anisotropic piezoelectric effect in Lateral Surface superlattices
Applied Physics Letters, 1997Co-Authors: E. Skuras, A. R. Long, Ivan A. Larkin, John H. Davies, Martin Christopher HollandAbstract:We have studied the potential induced by Lateral Surface superlattices deposited on a GaAs/AlGaAs heterostructure as a function of bias and orientation of the gates. By using the gates to null the total potential, we extracted the contribution to this potential in the absence of gate bias. Its angular dependence shows that it is dominated by strain from the gates coupled to the electrons by the piezoelectric effect.
Zhen-yan Deng - One of the best experts on this subject based on the ideXlab platform.
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Energy minigaps in the quantum well wires with periodical Lateral Surface structures
Journal of Materials Science & Technology, 2009Co-Authors: Zhen-yan Deng, Hong SunAbstract:Energy minigaps caused by Lateral Surface structures in quasi-one-dimensional GaAs/AlAs quantum well wires are calculated with the variational and degenerate-perturbational approaches. By a coordinate transformation, the structured interfaces of the wires are transformed into planar ones so that the boundary conditions of the electronic wave functions can be satisfied exactly on the interfaces. The dependence of the energy minigaps on the Lateral Surface structures are discussed
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Optical absorption spectra associated with an impurity in Lateral-Surface superlattice quantum well wires
Journal of Physics: Condensed Matter, 1995Co-Authors: Zhen-yan Deng, Jing-kun GuoAbstract:We calculate the optical absorption spectra associated with an impurity in quasi-one-dimensional GaAs/AlAs quantum well wires with periodic Lateral Surface structures. The results indicate that there is an energy-forbidden region for optical transitions from acceptors to conduction minibands, and no forbidden region for optical transitions from valence minibands to donors. The dependence of optical absorption spectra on the interface amplitude is discussed.
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Miniband structures and densities of impurity states in Lateral-Surface-superlattice quantum well wires
Journal of Physics: Condensed Matter, 1994Co-Authors: Zhen-yan Deng, Jing-kun Guo, Ting-rong Lai, Hong SunAbstract:We calculate energy miniband structures and densities of impurity states in quasi-one-dimensional GaAs/AlAs quantum well wires with periodic Lateral Surface structures. By a coordinate transformation, the structured interfaces of the wires are transformed into planar interfaces so that the boundary conditions of the electronic wavefunctions can be satisfied exactly on the interfaces. The new optical transition spectral structures associated with minibands and impurities are discussed.
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ENERGY MINIGAPS IN THE QUANTUM WIRES WITH Lateral Surface-STRUCTURES
Communications in Theoretical Physics, 1993Co-Authors: Zhen-yan Deng, Shi-wei GuAbstract:Energy minigaps caused by Lateral Surface structures in quasi-one-dimensional GaAs/AlAs quantum wires are calculated with the variational and degenerate-perturbational approaches. By a coordinate transformation, the structured interfaces of wires are transformed into planar ones so that the boundary conditions of the electronic wave functions can be satisfied exactly on the interfaces. The dependence of energy minigaps on Lateral Surface structures are discussed.
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Binding energies of hydrogenic impurities in Lateral Surface superlattice quantum well wires
Journal of Physics: Condensed Matter, 1993Co-Authors: Zhen-yan Deng, Hong SunAbstract:A variational calculation of hydrogenic impurity binding energies in quasi-one-dimensional GaAs/AlAs quantum well wires with periodic Lateral Surface structures was carried out. By a coordinate transformation, die structured interfaces of the wires are transformed into planar interfaces so that the boundary conditions of the electronic wavefunctions can be satisfied exactly at the interfaces. The dependences of the binding energies on the positions of the impurities and on the Lateral Surface structures are studied.
Roland Ketzmerick - One of the best experts on this subject based on the ideXlab platform.
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Magnetoresistance due to chaos and nonlinear resonances in Lateral Surface superlattices.
Physical review letters, 1992Co-Authors: Ragnar Fleischmann, Theo Geisel, Roland KetzmerickAbstract:We show that chaos and nonlinear resonances are clearly reflected in the magnetotransport in Lateral Surface superlattices and thereby explain a series of magnetoresistance peaks observed recently in ``antidot'' arrays on semiconductor heterojunctions. We find a mechanism of cyclotron-orbit pinning in an electric field resulting from Kolmogorov-Arnol'd-Moser tori. An experimental verification is suggested in terms of an enhanced cyclotron frequency associated with an anomalously reduced cyclotron radius.
