| 31. |
- Karimi, Mohammad, 1988-, et al.
(författare)
-
Room-temperature InP/InAsP Quantum Discs-in-Nanowire Infrared Photodetectors
- 2017
-
Ingår i: Nano letters (Print). - Washington, DC : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 17:6, s. 3356-3362
-
Tidskriftsartikel (refereegranskat)abstract
- The possibility to engineer nanowire heterostructures with large bandgap variations is particularly interesting for technologically important broadband photodetector applications. Here we report on a combined study of design, fabrication, and optoelectronic properties of infrared photodetectors comprising four million n+–i–n+ InP nanowires periodically ordered in arrays. The nanowires were grown by metal–organic vapor phase epitaxy on InP substrates, with either a single or 20 InAsP quantum discs embedded in the i-segment. By Zn compensation of the residual n-dopants in the i-segment, the room-temperature dark current is strongly suppressed to a level of pA/NW at 1 V bias. The low dark current is manifested in the spectrally resolved photocurrent measurements, which reveal strong photocurrent contributions from the InAsP quantum discs at room temperature with a threshold wavelength of about 2.0 μm and a bias-tunable responsivity reaching 7 A/W@1.38 μm at 2 V bias. Two different processing schemes were implemented to study the effects of radial self-gating in the nanowires induced by the nanowire/SiOx/ITO wrap-gate geometry. Summarized, our results show that properly designed axial InP/InAsP nanowire heterostructures are promising candidates for broadband photodetectors. © 2017 American Chemical Society.
|
|
| 32. |
- Kawaguchi, Kenichi, et al.
(författare)
-
InAs quantum dots and quantum wells grown on stacking-fault controlled InP nanowires with wurtzite crystal structure
- 2011
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 99:13
-
Tidskriftsartikel (refereegranskat)abstract
- Heteroepitaxial growth of InAs was investigated on sidewalls of InP nanowires (NWs) using metal-organic vapor phase epitaxy. InAs quantum wells (QWs) with smooth surface were formed on the InP NWs having perfect wurtzite phase structure. On the other hand, InAs quantum dots (QDs) were formed on wurtzite InP NWs purposely introduced with stacking-fault segments. Photoluminescence from single NWs attributed to both QWs and QDs was observed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3646386]
|
|
| 33. |
- Krishnamachari, U, et al.
(författare)
-
Defect-free InP nanowires grown in [001] direction on InP(001)
- 2004
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 85:11, s. 2077-2079
-
Tidskriftsartikel (refereegranskat)abstract
- We report on [001] InP nanowires grown by metalorganic vapor phase epitaxy directly on (001) InP substrates. Characterization by scanning electron microscopy and transmission electron microscopy reveals wires with nearly square cross sections and a perfect zinc-blende crystalline structure that is free of stacking faults. Photoluminescence measurements of single [001] nanowires exhibit a narrow and intense emission peak at approximately 1.4 eV, whereas <111>B grown reference wires show additional broad luminescence peaks at lower energy. The origin of this uncommon wire growth direction [001] is discussed as a means of controlled formation of [00l]-oriented nanowires on (001) substrates. (C) 2004 American Institute of Physics.
|
|
| 34. |
- Lindelöw, Fredrik, et al.
(författare)
-
Doping evaluation of InP nanowires for tandem junction solar cells
- 2016
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 27:6
-
Tidskriftsartikel (refereegranskat)abstract
- In order to push the development of nanowire-based solar cells further using optimized nanowire diameter and pitch, a doping evaluation of the nanowire geometry is necessary. We report on a doping evaluation of n-type InP nanowires with diameters optimized for light absorption, grown by the use of metal-organic vapor phase epitaxy in particle-assisted growth mode using tetraethyltin (TESn) as the dopant precursor. The charge carrier concentration was evaluated using four-probe resistivity measurements and spatially resolved Hall measurements. In order to reach the highest possible nanowire doping level, we set the TESn molar fraction at a high constant value throughout growth and varied the trimethylindium (TMIn) molar fraction for different runs. Analysis shows that the charge carrier concentration in nanowires grown with the highest TMIn molar fraction (not leading to kinking nanowires) results in a low carrier concentration of approximately 10(16) cm(-3). By decreasing the molar fraction of TMIn, effectively increasing the IV/III ratio, the carrier concentration increases up to a level of about 10(19) cm(-3), where it seems to saturate. Axial carrier concentration gradients along the nanowires are found, which can be correlated to a combination of changes in the nanowire growth rate, measured in situ by optical reflectometry, and polytypism of the nanowires observed in transmission electron microscopy.
|
|
| 35. |
- Lindgren, David, et al.
(författare)
-
A luminescence study of doping effects in InP-based radial nanowire structures
- 2013
-
Ingår i: Journal of Physics, Conference Series. - : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596. ; 471:1
-
Tidskriftsartikel (refereegranskat)abstract
- We have used micro-photo- and cathodo-luminescence at low temperatures to study the effects of sulphur doping in InP and radial InP/InAs/InP structured nanowires. Samples with pure wurtzite crystal structure, with modulated wurtzite/zincblende crystal structure and with different radial InAs growth times were investigated. We observed a doping concentration gradient along the nanowires, the location of segments of different crystal structure and thickness fluctuations on the monolayer scale of the InAs layer.
|
|
| 36. |
|
|
| 37. |
- Lindgren, David, et al.
(författare)
-
Optical characterization of InAs quantum wells and dots grown radially on wurtzite InP nanowires.
- 2013
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 24:22
-
Tidskriftsartikel (refereegranskat)abstract
- Correlated micro-photoluminescence (μPL) and cathodoluminescence (CL) measurements are reported for single core-shell InP-InAs wurtzite nanowires grown using metal-organic vapor phase epitaxy. Samples covering a radial InAs shell thickness of 1-12 ML were investigated. The effective masses for the wurtzite material were determined from the transition energy dependence of the InAs shell thickness, using a model based on linear deformation potential theory. InP cores with segments of mixed zincblende and wurtzite, on which quantum dots nucleated selectively, were also investigated. Narrow peaks were observed by μPL and the spatial origin of the emission was identified with CL imaging.
|
|
| 38. |
|
|
| 39. |
- Lindgren, David, et al.
(författare)
-
Study of carrier concentration in single InP nanowires by luminescence and Hall measurements
- 2015
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 26:4
-
Tidskriftsartikel (refereegranskat)abstract
- The free electron carrier concentrations in single InP core-shell nanowires are determined by micro-photoluminescence, cathodoluminescence (CL) and Hall effect measurements. The results from luminescence measurements were obtained by solving the Fermi-Dirac integral, as well as by analyzing the peak full width at half maximum (FWHM). Furthermore, the platform used for Hall effect measurements, combined with spot mode CL spectroscopy, is used to determine the carrier concentrations at specific positions along single nanowires. The results obtained via luminescence measurements provide an accurate and rapid feedback technique for the epitaxial development of doping incorporation in nanowires. The technique has been employed on several series of samples in which growth parameters, such as V/III-ratio, temperature and dopant flows, were investigated in an optimization procedure. The correlation between the Hall effect and luminescence measurements for extracting the carrier concentration of different samples were in excellent agreement.
|
|
| 40. |
- Mante, Pierre Adrien, et al.
(författare)
-
Confinement effects on Brillouin scattering in semiconductor nanowire photonic crystal
- 2016
-
Ingår i: Physical Review B. - 1098-0121. ; 94:2
-
Tidskriftsartikel (refereegranskat)abstract
- Scattering of photons by phonons, or Brillouin scattering, enables manipulation and control of light and has led to revolutionary applications, from slow light to saser and cooling of micromechanical resonators. Recently, enhanced light and sound interaction has been demonstrated in waveguides. However, the design of the waveguide geometry tunes and alters the phonon and photon dispersion simultaneously. Here we investigate, through femtosecond pump-probe spectroscopy and theoretical modeling, the light and sound interaction in a bottom-up fabricated vertical nanowire photonic crystal. In such a system, the phonon dispersion can be tuned by varying the geometry of the constituent nanowires. In contrast, the placement of the nanowires in the photonic crystal can be used for tuning optical array modes, without altering the phonon dispersion. We demonstrate the forward and backward scattering, by acoustic phonons in the nanowires, of (1) such optical array modes and (2) guided modes of the constituent nanowires. Furthermore, our results reveal an enhanced interaction of array modes with phonons that we attribute to the specific scattering mechanism. Our results enable the design of a photonic crystal with separately tailored photon and phonon dispersion for Brillouin scattering. We anticipate these advances to be a starting point for enhanced control of light at the nanoscale.
|
|
