Abstract
We have studied the interaction of light with an array of vertically oriented III-V
semiconductor nanowires both theoretically and experimentally. For the theoretical
studies, electromagnetic modeling has been employed. This modeling shows that with
proper tuning of the nanowire diameter, the absorption per volume semiconductor
material can be 20 times higher in the nanowires than in a corresponding bulk
semiconductor sample. This enhancement occurs when nanophotonic resonances show
up in the nanowires. We have shown that the optical response of a nanowire array can
be described by electrostatics for small-diameter nanowires and by geometrical optics
for large-diameter nanowires. None of these two limit cases showed resonances,
motivating the interest for the intermediate nanophotonic regime where the diameter
of the nanowires is comparable to the wavelength of the incident light.
Supported by theoretical analysis, we have shown experimentally a resonant
photodetection response in an InAsSb nanowire array in the infrared region, which is
of potential interest for thermal imaging and chemical analysis. Furthermore, we have
demonstrated a solar cell based on InP nanowires. The nanowire-array solar cell
showed an efficiency of 13.8 % and converted more than 70 % of the above-bandgap
photons into electron-hole pairs that contributed to the short-circuit current, even
though the nanowires covered only 12 % of the surface.
By combining the electromagnetic modeling with reflectance measurements, we have
developed an optical method for simultaneously measuring both the diameter and the
length of nanowires in large-area arrays. The accuracy of the method is comparable to
that of scanning electron microscopy. Furthermore, we have developed tools for
studying the crystal-phase dependent optical response of III-V materials. The studies
showed that a tuning of the crystal phase, which is possible in the nanowire geometry,
can be used for enabling and disabling strongly absorbing nanophotonic resonances in
nanowire arrays.
semiconductor nanowires both theoretically and experimentally. For the theoretical
studies, electromagnetic modeling has been employed. This modeling shows that with
proper tuning of the nanowire diameter, the absorption per volume semiconductor
material can be 20 times higher in the nanowires than in a corresponding bulk
semiconductor sample. This enhancement occurs when nanophotonic resonances show
up in the nanowires. We have shown that the optical response of a nanowire array can
be described by electrostatics for small-diameter nanowires and by geometrical optics
for large-diameter nanowires. None of these two limit cases showed resonances,
motivating the interest for the intermediate nanophotonic regime where the diameter
of the nanowires is comparable to the wavelength of the incident light.
Supported by theoretical analysis, we have shown experimentally a resonant
photodetection response in an InAsSb nanowire array in the infrared region, which is
of potential interest for thermal imaging and chemical analysis. Furthermore, we have
demonstrated a solar cell based on InP nanowires. The nanowire-array solar cell
showed an efficiency of 13.8 % and converted more than 70 % of the above-bandgap
photons into electron-hole pairs that contributed to the short-circuit current, even
though the nanowires covered only 12 % of the surface.
By combining the electromagnetic modeling with reflectance measurements, we have
developed an optical method for simultaneously measuring both the diameter and the
length of nanowires in large-area arrays. The accuracy of the method is comparable to
that of scanning electron microscopy. Furthermore, we have developed tools for
studying the crystal-phase dependent optical response of III-V materials. The studies
showed that a tuning of the crystal phase, which is possible in the nanowire geometry,
can be used for enabling and disabling strongly absorbing nanophotonic resonances in
nanowire arrays.
| Original language | English |
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| Qualification | Doctor |
| Awarding Institution |
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| Supervisors/Advisors |
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| Award date | 2013 Jun 14 |
| ISBN (Print) | 978-91-7473-550-5 |
| Publication status | Published - 2013 |
Bibliographical note
Defence detailsDate: 2013-06-14
Time: 14:00
Place: Lecture Hall Rydbergsalen, Department of Physics, Professorsgatan 1, Lund University Faculty of Engineering
External reviewer(s)
Name: Yablonovitch, Eli
Title: Professor
Affiliation: University of California, Berkeley, USA
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Subject classification (UKÄ)
- Condensed Matter Physics
Free keywords
- III-V semiconductor materials
- Nanophotonics
- nanowires
- electromagnetic modeling
- Fysicumarkivet A:2013:Anttu