| 1. |
- Aberg, I, et al.
(författare)
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Nanoscale tungsten aerosol particles embedded in GaAs
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:16, s. 2976-2978
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Tidskriftsartikel (refereegranskat)abstract
- GaAs containing buried nanoscale tungsten particles has been characterized electrically. The particles were produced using a special aerosol process and were embedded in GaAs by epitaxial overgrowth. Two different particle sizes were investigated separately. When the particle concentration was increased, a conductance drop of about 500 times was observed. A simulation model, based on a random distribution of the particles, was developed and used to support our findings. The major advantage of our method is the simplicity and low processing cost.
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| 2. |
- Lind, Erik, et al.
(författare)
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A resonant tunneling permeable base transistor with Al-free tunneling barriers
- 2002
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Ingår i: Device Research Conference (Cat. No.02TH8606). - 0780373170 ; , s. 155-156
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Konferensbidrag (refereegranskat)abstract
- Summary form only given. Resonant tunneling based devices are an intriguing set of devices with promising high speed, low power and high functionality capabilities. We have developed an technology to embed metallic features on the nm-scale inside a semiconductor. By combining such metallic features and heterostructures we have developed a new type of tunneling transistor, the so called Resonant Tunneling Permeable Base Transistor (RT-PBT), where a double barrier heterostructure is placed in close vicinity to a metal grating. A three step fabrication process is described
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| 3. |
- Lind, Erik, et al.
(författare)
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Stacking of heterostructures and metallic elements for a submicron resonant tunneling transistor
- 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
- We have successfully embedded a metal gate in-between two resonant tunneling double barrier heterostructures (RTD), thus realizing a three dimensional resonant tunneling transistor. The gate is placed 30 nm above and 100 below the two RTD's, respectively. The asymmetric gate allows for a unique control of the current-voltage characteristics, not only controlling the peak current but also the peak voltage. We have modeled the transistor with Cadence, a standard simulation package for circuit simulations, achieving good agreement with experimental data
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| 4. |
- 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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| 5. |
- Sass, T, et al.
(författare)
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Oxidation and reduction behavior of Ge/Si islands
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:18, s. 3455-3457
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the oxidation/reduction behavior of dome-shaped three-dimensional islands of Ge on Si(001) grown by ultrabigh vacuum chemical vapor deposition. The oxidation was done by exposing the surfaces to H2O steam in N-2. The reduction was done by H-2, which selectively reduces only the GeO2. The results of the oxidation/reduction processes under varying conditions were analyzed by high-resolution transmission electron microscopy. We found that the selective reduction of such structures does not result in a perfect recovery of the former Ge dots, but results in phase-segregated Ge enrichments. In many cases these enrichments show epitaxial relationship with the underlying Si substrate. These structures are of potential interest for Ge dots embedded in an insulating material as, well as for lateral epitaxial overgrowth of SiO2 / Si(001) by Ge, using the reduced Ge dots as the seeds for epitaxy.
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| 6. |
- 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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| 7. |
- Wernersson, Lars-Erik, et al.
(författare)
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Attractive potential around a buried metallic gate in a Schottky Collector Hot Electron Transistor
- 2002
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Ingår i: Institute of Physics Conference Series. - 0951-3248. ; 170, s. 81-85
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Tidskriftsartikel (refereegranskat)abstract
- We report on the formation of an attractive potential around buried metal wires in a novel design for the Hot Electron Transistor (HET). In this device, the doped base layer in the HET is replaced by an embedded metal grating, which is forward biased beyond flat band conditions in order to efficiently extract carriers from the emitter into the active region. These carriers are collected in a Schottky Collector contact. By tuning the gate and collector voltages, the potential profile around the wires can be repulsive as well as attractive. This is a key result for the realisation of a Biprism device.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- Zela, Vilma, et al.
(författare)
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Oxidation and reduction behaviour of Ge/Si islands
- 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
- We have investigated the oxidation/reduction behaviour of dome-shaped three-dimensional islands of Ge on Si(001) grown by UHV-CVD at 620°C. The oxidation was done by exposing the surfaces to a steam of H2O in N2. The reduction was done in H2, which at T<800 °C selectively reduces GeO2 only. The results of the oxidation/reduction processes under varying conditions were analyzed by high-resolution transmission electron microscopy. We found that the selective reduction of such structures does not result in a perfect recovery of the former Ge dots, but results in phase-segregated Ge-enrichments. In most cases, these enrichments show epitaxial relationship to the underlying Si substrate. These structures are therefore of potential interest for lateral epitaxial overgrowth of the SiO2 by Ge, using the reduced Ge dots as the seeds for epitaxy
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