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- Buck, P., et al.
(författare)
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The need for and the role of metacognition in teaching and learning the particle model
- 2001
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Ingår i: Research in Science Education - Past, Present, and Future. - 0792367553
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Bokkapitel (populärvet., debatt m.m.)abstract
- The research focus of this symposium on teaching and learning the particle model (discussant: Robin Miller) addressed the following questions: How can misconceptions on atoms be avoided and how can we gain insight into and describe the learning processes involved? Three major influences were identified: metaconceptional awareness, the order in which concepts are learnt and the metaphoric content of language.
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| 4. |
- Landin, L., et al.
(författare)
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Interband transitions in InAs quantum dots in InP studied by photoconductivity and photoluminescence techniques
- 2004
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Ingår i: Journal of Applied Physics. - Melville : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 95:12, s. 8007-8010
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Tidskriftsartikel (refereegranskat)abstract
- We report on a detailed investigation of the interband optics of self-assembled InAs dots embedded in a matrix of InP. In photoconductivity (PC) measurements, we observe optical processes related to the dots and a wetting layer, band-to-band excitation of the InP barrier, as well as to an interesting As-related impurity. In particular, the PC measurements reveal the electronic structure of the dots and strongly suggest that an Auger effect is involved in forming the PC signal. Comparing the PC and photoluminescence (PL) signals, we observe that the fundamental transition is not observed in PC, which we interpret in terms of Pauli blocking due to electrons populating the ground state of the dots. In general, it is demonstrated that the PC technique is in many respects complementary to PL and gives additional insight into the electronic structure of quantum dots.
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| 5. |
- Martin, TP, et al.
(författare)
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The influence of confining wall profile on quantum interference effects in etched Ga0.25In0.75As/InP billiards
- 2003
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036. ; 34:3-6, s. 179-184
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of the potential profile of etched GaInAs/InP billiards and show that their energy gradients are an order of magnitude steeper than those of surface-gated GaAs/AlGaAs billiards. Previously observed in GaAs/AlGaAs billiards, fractal conductance fluctuations are predicted to be critically sensitive to the billiard profile. Here we show that, despite the increase in energy gradient, the fractal conductance fluctuations persist in the harder GaInAs/InP billiards. (C) 2004 Elsevier Ltd. All rights reserved.
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| 6. |
- Ohki, S, et al.
(författare)
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A study of estimation method for conduction band offset in semiconductor heterostructure by using triple-barrier resonant tunneling diodes
- 2002
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Ingår i: Applied Surface Science. - 1873-5584. ; 190:1-4, s. 288-293
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Tidskriftsartikel (refereegranskat)abstract
- A method for evaluating a band offset of a heterojunction is proposed by measuring temperature dependence of current-voltage (I-V) characteristics in triple-barrier resonant tunneling diodes (TBRTDs). The method was applied for investigating a conduction band offset by using GaAs0.25P0.75/GaAs TBRTDs with thin strain heterobarriers grown by MOCVD and DeltaE(c) was estimated as 200-240 meV. In the strain-barrier TBRTDs, negative differential resistance was observed below 100 K. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 7. |
- Song, Aimin, et al.
(författare)
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Quantum behavior as well as room-temperature and 50 GHz operations of novel nonlinear devices and nanomaterials
- 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
- Novel nano-rectifiers based on ballistic electron transport have been fabricated from a high electron-mobility InGaAs/InP wafer. Because of the sufficiently small device size, operations at room temperature are achieved. Furthermore, the devices are shown to work not only up to at least 50 GHz but also with sensitivity to microwave reaching that of the commercial microwave diodes. Based on a similar microscopic mechanism, we have also constructed, to our knowledge, the first artificial electronic nanomaterial that operates at room temperature. Promising possibilities for practical applications, such as microwave detection and second-harmonic generation, are discussed. While the rectifying effect can be well described in the picture of classical ballistic transport, the pronounced output voltage reversal observed at low temperatures strongly suggests that quantum effect may become completely dominant
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| 8. |
- Wernersson, Lars-Erik, et al.
(författare)
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Epitaxially overgrown, stable W-GaAs Schottky contacts with sizes down to 50 nm
- 2002
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Ingår i: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 1520-8567. ; 20:2, s. 580-589
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Tidskriftsartikel (refereegranskat)abstract
- A processing scheme for the fabrication of embedded W-GaAs contacts has been established and the resulting contact characteristics have been evaluated. The main advantage of these contacts is that they are stable during high-temperature epitaxial overgrowth. The fabrication scheme is based on a liftoff process with electron beam evaporation of tungsten and subsequent epitaxial overgrowth using metalorganic vapor phase epitaxy. Various methods were used to characterize the buried contacts. First, the structural properties of GaAs surrounding embedded W features, with widths down to 50 nm, were characterized by high-resolution transmission electron microscopy. Measurements of the conductivity in individual, buried wires were performed in order to study the influence of the overgrowth process on the properties of the tungsten. We also evaluated the current-voltage characteristics for macroscopic contacts, which revealed a clear dependence on processing parameters. Optimized processing conditions could thus be established under which limited contact degradation occurred during overgrowth. Finally, we used the overgrowth technique to perform a detailed investigation of the electrical and optical properties of floating-potential embedded nano-Schottky contacts by space-charge spectroscopy.
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