| 1. |
- Achermann, M, et al.
(författare)
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Nano-scale Schottky contacts: ultrafast drift-diffusion dynamics studied in the optical near field
- 2002
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Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 13:2-4, s. 819-822
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Tidskriftsartikel (refereegranskat)abstract
- We present direct measurements of the ultrafast carrier dynamics around buried nano-scale Schottky contacts with high spatial and time resolution, performed with a novel fermosecond near-field scanning optical microscope, It is shown that high optically excited carrier densities screen the built-in field around a Schottky contact and allow for efficient transport of electrons towards the contact, followed by trapping of electrons into the metal. The experimental results are modeled by a self-consistent treatment of the drift-diffusion equation for the carriers and Poisson's equation for the built-in electric field. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
- Anisimovas, Egidijus
(författare)
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Tunneling spectroscopy of modulated two-dimensional electron systems
- 2002
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Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 12:1-4, s. 307-310
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the tunneling between two parallel modulated two-dimensional electron systems in tilted magnetic fields. The electronic states are described in terms of the magnetic crystal momentum, and tunneling events connect the states whose momenta differ by a shift due to the in-plane component of the field. We use this fact to develop a theory of how the features of the artificial two-dimensional bandstructure can be extracted from the tunneling measurement data.
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| 3. |
- Fasth, Carina, et al.
(författare)
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Effects of breaking current conservation on the phase properties of two-terminal quantum systems
- 2003
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Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 17:1-4, s. 579-583
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Tidskriftsartikel (refereegranskat)abstract
- We study the reflection and transmission phase properties of two-terminal quantum structures coupled to a third lead. The systems are effectively three-terminal and current conservation is broken with regard to the original two-terminal systems. Two structures, a waveguide with an attached stub quantum dot and a waveguide with an inline, double-barrier confined quantum dot, are considered. The transmission and reflection phase properties are calculated for these systems with different couplings to the third lead. The results show that the discontinuous phase shifts seen in the current-conserved two-terminal systems are removed when the third lead is attached. However, as long as the coupling between the quantum systems and the additional lead is weak, sharp but continuous phase drops within narrow energy ranges can still be clearly identified.
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| 4. |
- Gallart, M., et al.
(författare)
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Single photon emission from individual semiconductor nanostructures
- 2003
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Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 17:1-4, s. 568-571
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Konferensbidrag (refereegranskat)abstract
- The correlation between the photons emitted by an optically pumped single quantum dot is investigated. The correlation function on a single dot isolated in a mesa shows that only one photon is emitted at a time at the exciton frequency. These quantum states of light can be generated with a high quantum efficiency, with the use of cavity effects: surrounding the dot by a pillar microcavity not only increases significantly the single photon flux but also allows the preparation of single photons all in the same quantum state (same spatial mode and same polarization). © 2002 Published by Elsevier Science B.V.
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| 5. |
- Gustafson, Boel, et al.
(författare)
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Coupling between lateral modes in a vertical resonant tunneling structure
- 2002
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Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 13:2-4, s. 950-953
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental results and theoretical calculations of the vertical electron transport through a laterally constricted resonant tunneling transistor. Current-voltage measurements at 4.2 K show numerous current peaks that exhibit a complex dependence on the applied gate voltage. A scattering-matrix approach combined with the Landauer formalism was used to perform quantum mechanical calculations of the electron transport through a quantum dot structure with laterally confined emitter and collector regions. The simulations qualitatively reproduce the measured data, suggesting a strong coupling between the lateral modes in the quantum dot and the collector
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| 6. |
- Ohlsson, Jonas, et al.
(författare)
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Growth and characterization of GaAs and InAs nano-whiskers and InAs/GaAs heterostructures
- 2002
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Ingår i: Physica E: Low-dimensional Systems and Nanostructures. - 1386-9477. ; 13:2-4, s. 1126-1130
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Konferensbidrag (refereegranskat)abstract
- Semiconducting InAs and GaAs nano-whiskers have been grown using a chemical beam epitaxy approach in combination with size-selected catalytic Au aerosol particles. The characterization of InAs and GaAs whiskers shows high crystalline quality as seen by transmission electron microscopy. Gate-dependent transport measurements suggests a diffusive electronic transport mechanism. We have also combined these two material systems by growing a very abrupt heterostructure interface within the whiskers, allowing the growth of highly mismatched structures without misfit dislocations. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 7. |
- Xu, Hongqi
(författare)
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A novel electrical property of three-terminal ballistic junctions and its applications in nanoelectronics
- 2002
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Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 13:2-4, s. 942-945
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Tidskriftsartikel (refereegranskat)abstract
- A room-temperature electrical property of three-terminal ballistic junctions (TBJs) is predicted. For a symmetric TBJ. it is shown that when finite voltages F and -V are applied to the left and right branches. the voltage Output V, from the central branch will always be negative. This characteristic appears even when the symmetry in the TBJ is broken. provided that V! is larger than a threshold. Applications of these devices in nanoelectronics are proposed.
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| 8. |
- Zela, Vilma, et al.
(författare)
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Unimodal dome-shaped island population of Ge/Si (001) by step-wise growth in UHV-CVD
- 2002
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Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 13:2-4, s. 1013-1017
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Tidskriftsartikel (refereegranskat)abstract
- This work introduces a new approach to achieve a unimodal dome-shaped island population for the self-assembled Ge/Si (0 0 1) dots grown by ultra-high vacuum chemical vapour deposition at T = 620 degreesC. A step-wise growth mode is applied, consisting of two Ge deposition steps with a short growth interruption in between. In the first step, a "base structure" with pyramids and domes is grown while in the second one, an additional Ge amount at reduced pressure is supplied. Selective "feeding" of only the pyramids and their conversion into domes occurs. Atomic force microscopy and transmission electron microscopy studies indicate that the shape transition starts with nucleation of material onto the {105} facets close to the most strain-relaxed top area of the pyramids.
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| 9. |
- Blomquist, T., et al.
(författare)
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Origin of conductance oscillations in square electron billiards : A semi-classical approach
- 2000
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - 1386-9477 .- 1873-1759. ; 6:1, s. 392-395
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Tidskriftsartikel (refereegranskat)abstract
- We perform semi-classical and quantum mechanical calculations on square billiards and provide a semi-classical interpretation of the conductance oscillations. We outline its relation to the Gutzwiller's picture of periodic orbits. The frequencies of the conductance oscillations are shown to be due to interference of pairs of long trajectories, which in the phase space are typically situated near the corresponding periodic orbit. We identify the pair of trajectories causing the pronounced peak in a recent experiment and from this directly extract the phase coherence length.
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| 10. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Evidence for type I band alignment in GaNAs/GaAs quantum structures by optical spectroscopies
- 2002
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier. - 1386-9477 .- 1873-1759. ; 13:2-4, s. 1074-1077
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Tidskriftsartikel (refereegranskat)abstract
- Type I band line-up in GaNxAs1−x/GaAs multiple quantum wells (MQW) with xless-than-or-equals, slant3% is concluded based on the following experimental results: (i) a comparable radiative decay time of the GaNAs-related photoluminescence (PL) measured from single GaNAs epilayers and the GaNAs/GaAs MQW structures, (ii) the observed PL polarization, and (iii) the spatial confinement of photoexcited holes within the GaNAs layers under resonant excitation of the GaNAs MQW.
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