| 1. |
- Bryllert, Tomas, et al.
(författare)
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Designed emitter states in resonant tunneling through quantum dots
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:15, s. 2681-2683
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Tidskriftsartikel (refereegranskat)abstract
- Resonant tunneling through a single layer of self-assembled quantum dots (QDs) is compared to tunneling through two layers of vertically aligned (stacked) dots. The difference can be viewed as going from a two-dimensional emitter to a zero-dimensional emitter. The temperature dependence of current peaks originating in tunneling through individual QDs and individual stacks is used to clarify this point. In addition, we show that the statistical size distribution of self-assembled quantum dots causing the inhomogeneous broadening in luminescence experiments can be analyzed in a resonant tunneling experiment. (C) 2002 American Institute of Physics.
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| 2. |
- Bryllert, Tomas, et al.
(författare)
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Resonant tunneling through coupled self-assembled quantum dots and the influence of inhomogeneous broadening
- 2002
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Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
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Konferensbidrag (refereegranskat)abstract
- Resonant tunneling through a single layer of self-assembled quantum dots (QDs) as well as tunneling through two layers of vertically aligned (stacked) dots is investigated. The difference between single and double layers of QDs can be viewed as going from a two-dimensional emitter to a zero-dimensional emitter. By fabricating small-area devices we are able to probe single stacks of quantum dots, revealing details of the coupling between the stacked dots. Very sharp resonances, with peak-to-valley ratios of several hundred, have been measured in the current-voltage characteristics. We also show that the statistical size distribution of self-assembled quantum dots causing the inhomogeneous broadening in luminescence experiments can be analysed in a resonant tunneling experiment
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| 3. |
- 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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| 4. |
- Ohlsson, Lars, et al.
(författare)
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Slot-Coupled Millimeter-Wave Dielectric Resonator Antenna for High-Efficiency Monolithic Integration
- 2013
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 61:4, s. 1599-1607
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Tidskriftsartikel (refereegranskat)abstract
- A readily mass-producible, flip-chip assembled, and slot-coupled III-V compound semiconductor dielectric resonator antenna operating in the millimeter-wave spectrum has been fabricated and characterized. The antenna has a 6.1% relative bandwidth, deduced from its 10 dB return loss over 58.8-62.5 GHz, located around the resonance at 60.5 GHz. Gating in the delay-domain alleviated the analysis of the complex response from the measured structure. The radiation efficiency is better than -0.1 dB in simulations fed from the on-chip coupling-structure, but reduced by 3.7 dB insertion loss through the measurement assembly feed. Antenna gain measurements show distortion in relation to the simulated pattern, which has a maximum gain of 6 dBi, mainly caused by interference from the electrically large connector used in the assembly. Mode degeneration in the utilized quadratic-footprint resonator was not seen to influence the performance of the antenna. The antenna is intended for on-chip integration and the fabrication technology allows scaling of the operation frequency over the complete millimeter-wave spectrum.
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| 5. |
- Wernersson, Lars-Erik, et al.
(författare)
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Metalorganic vapor phase epitaxy-grown GaP/GaAs/GaP and GaAsP/GaAs/GaAsP n-type resonant tunnelling diodes
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:10, s. 1841-1843
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Tidskriftsartikel (refereegranskat)abstract
- We have studied GaP/GaAs/GaP and GaAsxP1-x/GaAs/GaAsxP1-x double-barrier resonant tunnelling diodes grown by metalorganic vapor phase epitaxy. We find that GaP tensile strained barriers in GaP/GaAs/GaP diodes may be grown with a barrier thickness below the critical thickness of about 12 monolayers. However, a corrugation of the strained barrier is observed by transmission electron microscopy. This variation may explain the low peak-to-valley ratio of the diodes (about 2). In contrast, GaAsxP1-x/GaAs/GaAsxP1-x resonant tunnelling diodes have been grown with a homogeneous thickness of the barriers, consequently showing a substantially improved electrical performance compared to the GaP diodes with peak-to-valley ratios >5.
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| 6. |
- Wernersson, Lars-Erik, et al.
(författare)
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Thin layers of GaInP, GaP and GaAsP in metalorganic vapour phase epitaxy-grown resonant tunnelling diodes
- 2002
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Ingår i: Applied Surface Science. - 1873-5584. ; 190:1, s. 252-257
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the epitaxial growth and electrical performance of Al-free, GaAs-based, resonant tunnelling diodes (RTDs) including thin barriers of GaInP, GO, or GaAsxP1-x. n-Type tunnelling diodes have been fabricated and the symmetry in the current-voltage (I-V) characteristics, as well as the peak-to-valley ratios, are found to be sensitive probes for the inter-face quality in the heterostructures. For GaInP RTDs, we show that the introduction of Gap intermediate layers is crucial for the realisation. of a useful tunnelling current. RTDs including thin barriers (less than about 10 monolayers (ML)) of Gap are realised, but the strong mismatch between the materials limit the useful thickness. Finally, RTDs with GaAslambdaP1-x alloys are fabricated showing the best peak-to-valley ratio of the diodes (about 5), as well as a symmetric I-V characteristics. The electrical data are further compared to studies by transmission electron microscopy (TEM) in the various material systems.
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| 7. |
- Lind, Erik, et al.
(författare)
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Tunneling spectroscopy of a quantum dot through a single impurity
- 2003
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 68:3, s. 4-4
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Tidskriftsartikel (refereegranskat)abstract
- A single impurity inside a resonant tunneling diode is used to perform tunneling spectroscopy on an adjacent electrostatically defined vertical quantum dot. This results in tunneling between two zero-dimensional systems, measured as a set of sharp peaks in the current-voltage spectrum for finite bias. Magnetic-field-dependent measurements show that the angular momentum of the tunneling electrons is conserved during the tunneling process. Both ground and excited states are probed. The effect of temperature is also investigated, exhibiting a peak broadening that is smaller than 1 kT.
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| 8. |
- Ohlsson, L., et al.
(författare)
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Slot-Coupled Millimeter-Wave Dielectric Resonator Antenna for High-Efficiency Monolithic Integration
- 2013
-
Ingår i: IEEE Transactions on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-926X .- 1558-2221. ; 61:4, s. 1599-1607
-
Tidskriftsartikel (refereegranskat)abstract
- A readily mass-producible, flip-chip assembled, and slot-coupled III-V compound semiconductor dielectric resonator antenna operating in the millimeter-wave spectrum has been fabricated and characterized. The antenna has a 6.1% relative bandwidth, deduced from its 10 dB return loss over 58.8-62.5 GHz, located around the resonance at 60.5 GHz. Gating in the delay-domain alleviated the analysis of the complex response from the measured structure. The radiation efficiency is better than -0.1 dB in simulations fed from the on-chip coupling-structure, but reduced by 3.7 dB insertion loss through the measurement assembly feed. Antenna gain measurements show distortion in relation to the simulated pattern, which has a maximum gain of 6 dBi, mainly caused by interference from the electrically large connector used in the assembly. Mode degeneration in the utilized quadratic-footprint resonator was not seen to influence the performance of the antenna. The antenna is intended for on-chip integration and the fabrication technology allows scaling of the operation frequency over the complete millimeter-wave spectrum.
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| 9. |
- Sass, T, et al.
(författare)
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Strain in GaP/GaAs and GaAs/GaP resonant tunnelling heterostructures
- 2003
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 248, s. 375-379
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Tidskriftsartikel (refereegranskat)abstract
- We studied the morphology of GaP/(001)GaAs and GaAs/(001)GaP heterostructures grown by metal-organic vapour-phase epitaxy and found wire-like surface undulations elongated in the [110] direction. We attribute this elongation to anisotropic lateral growth rates in the [110] and [110] directions, which are due to a different roughness of monolayer surface steps. In III-V materials grown by molecular beam epitaxy. such surface corrugations are usually elongated in [110]. We explain this difference by the two growth methods having inverted ratios of lateral growth rates in [110] and [110]. Resonant tunnelling diodes fabricated from the GaP/GaAs heterostructures showed very symmetric I-V characteristics. Their peak-to-valley ratio was limited to 2. most probably due to the corrugation of the GaP barriers. (C) 2002 Elsevier Science B.V. All rights reserved.
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