| 1. |
- Bao, Jiming, et al.
(author)
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Optical properties of rotationally twinned InP nanowire heterostructures
- 2008
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 8:3, s. 836-841
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Journal article (peer-reviewed)abstract
- We have developed a technique so that both transmission electron microscopy and microphotoluminescence can be performed on the same semiconductor nanowire over a large range of optical power, thus allowing us to directly correlate structural and optical properties of rotationally twinned zinc blende InP nanowires. We have constructed the energy band diagram of the resulting multiquantum well heterostructure and have performed detailed quantum mechanical calculations of the electron and hole wave functions. The excitation power dependent blue-shift of the photoluminescence can be explained in terms of the predicted staggered band alignment of the rotationally twinned zinc blende/wurzite InP heterostructure and of the concomitant diagonal transitions between localized electron and hole states responsible for radiative recombination. The ability of rotational twinning to introduce a heterostructure in a chemically homogeneous nanowire material and alter in a major way its optical properties opens new possibilities for band-structure engineering.
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| 2. |
- Berg, Alexander, et al.
(author)
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Radial Nanowire Light-Emitting Diodes in the (AlxGa1-x)yIn1-yP Material System
- 2016
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In: Nano letters (Print). - Washington, DC : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 16:1, s. 656-662
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Journal article (peer-reviewed)abstract
- Nanowires have the potential to play an important role for next-generation light-emitting diodes. In this work, we present a growth scheme for radial nanowire quantum-well structures in the AlGaInP material system using a GaInP nanowire core as a template for radial growth with GaInP as the active layer for emission and AlGaInP as charge carrier barriers. The different layers were analyzed by X-ray diffraction to ensure lattice-matched radial structures. Furthermore, we evaluated the material composition and heterojunction interface sharpness by scanning transmission electron microscopy energy dispersive X-ray spectroscopy. The electro-optical properties were investigated by injection luminescence measurements. The presented results can be a valuable track toward radial nanowire light-emitting diodes in the AlGaInP material system in the red/orange/yellow color spectrum. © 2015 American Chemical Society.
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| 3. |
- Borg, Mattias, et al.
(author)
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GaAs/GaSb nanowire heterostructures grown by MOVPE
- 2008
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In: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 310:18, s. 4115-4121
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Journal article (peer-reviewed)abstract
- We report Au-assisted growth of GaAs/GaSb nanowire heterostructures on GaAs(1 1 1)B-substrates by metal-organic vapor phase epitaxy. The growth is studied at various precursor molar fractions and temperatures, in order to optimize the growth conditions for the GaSb nanowire segment. In contrast to most other III-V nanowire systems, the GaSb nanowire growth is Group V-limited under most conditions. We found that depending on the TMSb molar fraction, the seed particle is either supersaturated AuGa or AuGa2 during GaSb growth. The high Ga content in the particle gives a characteristic diameter increase between the GaAs and GaSb segment. From TEM and XEDS measurements we conclude that the GaSb nanowire growth occurs along either the AuGa-GaSb or AuGa2-GaSb pseudo-binaries of the Au-Ga-Sb ternary phase diagram. Finally, the GaSb nanowires exhibit untapered radial growth on the {1 (1) over bar 0} side facets. (C) 2008 Elsevier B.V. All rights reserved.
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| 4. |
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| 5. |
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| 6. |
- Fröberg, Linus, et al.
(author)
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Transients in the Formation of Nanowire Heterostructures.
- 2008
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 8:11, s. 3815-3818
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Journal article (peer-reviewed)abstract
- We present results on the effect of seed particle reconfiguration on the growth of short InAs and InP nanowire segments. The reconfiguration originates in two different steady state alloy compositions of the Au/In seed particle during growth of InAs and InP. From compositional analysis of the seed particle, the In content in the seed particle is determined to be 34 and 44% during InAs and InP growth, respectively. When switching between growing InAs and InP, transient effects dominate during the time period of seed particle reconfiguration. We developed a model that quantitatively explains the effect and with the added understanding we are now able to grow short period (<10 nm) nanowire superlattices.
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| 7. |
- Jacobsson, Daniel, et al.
(author)
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Particle-assisted GaxIn1-xP nanowire growth for designed bandgap structures
- 2012
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 23:24
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Journal article (peer-reviewed)abstract
- Non-tapered vertically straight GaxIn1-xP nanowires were grown in a compositional range from Ga0.2In0.8P to pure GaP in particle-assisted mode by controlling the trimethylindium, trimethylgallium and hydrogen chloride flows in metal-organic vapor phase epitaxy. X-ray energy dispersive spectroscopy in transmission electron microscopy revealed homogeneous radial material composition in single nanowires, whereas variations in the material composition were found along the nanowires. High-resolution x-ray diffraction indicates a variation of the material composition on the order of about 19% measuring an entire sample area, i.e., including edge effects during growth. The non-capped nanowires emit room temperature photoluminescence strongly in the energy range of 1.43-2.16 eV, correlated with the bandgap expected from the material composition.
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| 8. |
- Karlsson, Lisa, et al.
(author)
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Understanding the 3D structure of GaAs nanowires
- 2007
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:48
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Journal article (peer-reviewed)abstract
- The effects of lamellar twinning in epitaxial particle-assisted GaAs <111>B nanowires are investigated in an extensive high resolution electron microscopy (HRTEM) study of the low index zones <-100>, <-1-10>, <1-1-1> and <1-1-2>. As these directions are non-parallel to the (-1-1-1) twin planes we find that the twin segments exhibit two different zone axes as a consequence of twinning. In the first three cases the alternative zones were found to be <1-2-2> <11-4> and <11-5>. These findings are supported by a comparison of experimental HRTEM images and multi-slice simulations along with fast Fourier transform mapping. From the appearance of non-overlapping regions we conclude that the nanowires are bound by {111} facets only. The twin formation and the development of the stable side facets are discussed
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| 9. |
- Larsson, Magnus, et al.
(author)
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Strain mapping in free-standing heterostructured wurtzite InAs/InP nanowires
- 2007
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:1
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Journal article (peer-reviewed)abstract
- The strain distribution in heterostructured wurtzite InAs/InP nanowires is measured by a peak finding technique using high resolution transmission electron microscopy images. We find that nanowires with a diameter of about 20 nm show a 10 nm strained area over the InAs/InP interface and the rest of the wire has a relaxed lattice structure. The lattice parameters and elastic properties for the wurtzite structure of InAs and InP are calculated and a nanowire interface is simulated using finite element calculations. Both the method and the experimental results are validated using a combination of finite element calculations and image simulations.
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| 10. |
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