排序方式: 共有76条查询结果,搜索用时 243 毫秒
41.
D. Walker F. Pulizzi A. Patan L. Eaves D. Granados J.M. Garcia M. Henini V.V. Rudenkov P.C.M. Christianen J.C. Maan P. Offermans P.M. Koenraad G. Hill 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):57
We study the effect of a high magnetic field (B) on the current–voltage characteristics, I(V), of a GaAs/(AlGa)As resonant tunneling diode incorporating a layer of ring-shaped quantum dots (QDs) in the quantum well (QW). The dots give rise to a series of four unusual resonances in I(V) which show a high degree of reproducibility across the epitaxial wafer. By combining data for B parallel and perpendicular to the growth axis z, we identify that the unusual resonances arise from resonant tunneling into QD excited states with 2pz-like symmetry. The two series of magneto-oscillations in I for Bz allow us to determine the resonant charging and discharging of the QW with varying bias. 相似文献
42.
Baumgartner A Stock E Patanè A Eaves L Henini M Bimberg D 《Physical review letters》2010,105(25):257401
We image the micro-electroluminescence (EL) spectra of self-assembled InAs quantum dots (QDs) embedded in the intrinsic region of a GaAs p-i-n diode and demonstrate optical detection of carrier injection into a single QD. Tunneling of electrons and holes into the QDs at bias voltages below the flat-band condition leads to a spectrum of sharp EL lines from a small number of bright spots on the diode surface, characteristic of emission from individual QDs. We explain this behavior in terms of Coulomb interaction effects and the selective excitation of a small number of QDs within the ensemble due to preferential tunneling paths for carriers. 相似文献
43.
B. Kh. Bairamov V. A. Voitenko B. P. Zakharchenya V. V. Toporov M. Henini A. J. Kent 《Physics of the Solid State》1999,41(5):763-766
The paper reports the development of a high-sensitivity technique for measurement of inelastic electronic light-scattering
spectra in the near-IR region, which are excited by a stable single-mode cw YAG:Nd laser operating at 1064.4-nm. This technique
has permitted detection for the first time of quasielastic scattering of light by a photoexcited electron-hole plasma generated
in a GaAs layer with an embedded self-organized ensemble of InAs quantum dots. A considerable resonant enhancement of the
quasielastic electronic scattering intensity exceeding the level characteristic of the bulk material by two orders of magnitude
has been revealed. The main scattering mechanism, involving joint diffusion of electrons and holes, has been elucidated.
Fiz. Tverd. Tela (St. Petersburg) 41, 844–847 (May 1999) 相似文献
44.
Quantum oscillations of photoconductivity in p–i–n GaAs/InAs/AlAs quantum-dot heterojunctions have been studied. The dominating effect of the dynamics of charge accumulation of optically excited holes at quantum dots on the oscillation period and on the general evolution of the holes with a change in the illumination power has been shown within a simple electrostatic model. Investigation of the temperature dependence of the oscillating structure of the current–voltage characteristics has confirmed our interpretation. 相似文献
45.
Picosecond acoustic pulses generated by femtosecond laser excitation of a metal film induce a transient current with subnanosecond rise time in a GaAs/Au Schottky diode. The signal consists of components due to the strain pulse crossing the edge of the depletion layer in the GaAs and also the GaAs/Au interface. A theoretical model is presented for the former and is shown to be in very good agreement with the experiment. 相似文献
46.
O.M. Lemine M. Bououdina M. SajieddineA.M. Al-Saie M. ShafiA. Khatab M. Al-hilaliM. Henini 《Physica B: Condensed Matter》2011,406(10):1989-1994
Nanocrystalline zinc ferrite (ZnFe2O4) is synthesized by high-energy ball-milling after 12 h from a powders mixture of zinc oxide (ZnO) and hematite (α-Fe2O3) with balls to powders mass ratio of 20:1. X-ray diffraction, vibrating sample magnetometer (VSM), the Mössbauer spectrometry and photoluminescence (PL) are used to characterize the samples. Rietveld analysis and VSM measurements show that the powder has an average crystallites size of 10 nm and a ferrimagnetic behavior with a saturation magnetization of 30 emu/g. After annealing at 700 °C, the lattice parameter reduces from 8.448 to 8.427 Å and the sample transforms into a superparamagnetic behavior, which was confirmed as well by the room temperature Mössbauer spectrometry. Different mechanisms to explain the obtained results and the correlation between magnetism and structure are discussed. Finally, the broadband visible emission band is observed in the entire PL spectrum and the estimated energy band gap is about 2.13 eV. 相似文献
47.
We have measured the resistance noise of a two-dimensional (2D) hole system in a high mobility GaAs quantum well, around the 2D metal-insulator transition (MIT) at zero magnetic field. The normalized noise power S(R)/R(2) increases strongly when the hole density p(s) is decreased, increases slightly with temperature (T) at the largest densities, and decreases strongly with T at low p(s). The noise scales with the resistance, S(R)/R(2) approximately R2.4, as for a second order phase transition such as a percolation transition. The p(s) dependence of the conductivity is consistent with a critical behavior for such a transition, near a density p(*) which is lower than the observed MIT critical density p(c). 相似文献
48.
Yu. N. Khanin E. E. Vdovin L. Eaves A. Patane M. Henini 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(8):1127-1129
Tunneling transport through a one-barrier GaAs/(AlGa)As/GaAs heterostructure containing self-assembled InAs quantum dots has been investigated at low temperatures. An anomalous increase in the tunneling current through quantum dots in magnetic fields oriented both parallel and perpendicular to the current is observed. This increase is a manifestation of the Fermi-edge singularity in the current as a result of the interaction of a tunneling electron with the electron gas in the emitter. 相似文献
49.
Patanè A Mori N Fowler D Eaves L Henini M Maude DK Hamaguchi C Airey R 《Physical review letters》2004,93(14):146801
We use a magnetic field applied along the axis of a semiconductor superlattice (SL) as a controllable means of creating a one-dimensional band structure. We demonstrate that the current flow through the SL is strongly suppressed when the electron motion perpendicular to the SL axis is strongly confined by the quantizing magnetic field. By modeling this behavior using semiclassical and nonequilibrium Green's function methods, we show that the observed quenching arises from a qualitative change in electron dynamics caused by increasing quantum confinement. 相似文献
50.
Fatma Saad Saoud Jean Claude PlenetMohamed Henini 《Physica B: Condensed Matter》2012,407(6):1008-1013
The structural, electronic and vibrational properties of InN under pressures up to 20 GPa have been investigated using the pseudo-potential plane wave method (PP-PW). The generalized-gradient approximation (GGA) in the frame of density functional theory (DFT) approach has been adopted. It is found that the transition from wurtzite (B4) to rocksalt (B1) phase occurs at a pressure of approximately 12.7 GPa. In addition, a change from a direct to an indirect band gap is observed. The mechanism of these changes is discussed. The phonon frequencies and densities of states (DOS) are derived using the linear response approach and density functional perturbation theory (DFPT). The properties of phonons are described by the harmonic approximation method. Our results show that phonons play an important role in the mechanism of phase transition and in the instability of B4 (wurtzite) just before the pressure of transition. At zero pressure our data agree well with recently reported experimental results. 相似文献