hh.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Considering Symmetry Properties of InP Nanowire/Light Incidence Systems to Gain Broadband Absorption
Solid State Physics and NanoLund, Lund University, Lund, Sweden.
Solid State Physics and NanoLund, Lund University, Lund, Sweden.
Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.ORCID iD: 0000-0001-5027-1456
2017 (English)In: IEEE Photonics Journal, ISSN 1097-5764, E-ISSN 1943-0655, Vol. 9, no 3, article id 4501310Article in journal (Refereed) Published
Abstract [en]

Geometrically designed III-V nanowire arrays are promising candidates for disruptive optoelectronics due to the possibility of obtaining a strongly enhanced absorption resulting from nanophotonic resonance effects. With normally incident light on such vertical nanowire arrays, the absorption spectra exhibit peaks that originate from excitation of HE1m waveguide modes in the constituent nanowires. However, the absorption spectra typically show dips between the absorption peaks. Conventionally, such weak absorption has been counteracted by either making the nanowires longer or by decreasing the pitch of the array, both alternatives effectively increasing the volume of absorbing material in the array. Here, we first study two approaches for compensating the absorption dips by exciting additional Mie resonances: 1) oblique light incidence on vertical InP nanowire arrays and 2) normal light incidence on inclined InP nanowire arrays. We then show that branched nanowires offer a novel route to achieve broadband absorption by taking advantage of simultaneous excitations of Mie resonances in the branches and guided HE1m modes in the stem. Finite element method calculations show that the absorption efficiency is enhanced from 0.72 for vertical nanowires to 0.78 for branched nanowires under normal light incidence. Our work provides new insight for the development of novel efficient photovoltaics with high efficiency and reduced active material volume.

Place, publisher, year, edition, pages
Piscataway: IEEE, 2017. Vol. 9, no 3, article id 4501310
Keywords [en]
Nanophotonics, nanowire arrays, absorption, guided modes, Mie resonances, photovoltaics
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:hh:diva-35599DOI: 10.1109/JPHOT.2017.2690313ISI: 000400414300001Scopus ID: 2-s2.0-85018356671OAI: oai:DiVA.org:hh-35599DiVA, id: diva2:1162934
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2018-04-25Bibliographically approved
In thesis
1. Tailoring the Optical Response of III-V Nanowire Arrays
Open this publication in new window or tab >>Tailoring the Optical Response of III-V Nanowire Arrays
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Semiconductor nanowires show a great deal of promise for applications in a wide range of important fields, including photovoltaics, biomedicine, and information technology. Developing these exciting applications is strongly dependent on understanding the fundamental properties of nanowires, such as their optical resonances and absorption spectra. In this thesis we explore optical absorption spectra of arrays of vertical III-V nanowires with a special emphasis on structures optimized to enhance absorption in the solar spectrum. First, we analyze experimentally determined absorption spectra of both indium phosphide (InP) and gallium phosphide (GaP) nanowire arrays. The study provides an intuitive understanding of how the observed absorption resonances in the nanowires may be tuned as a function of their geometrical parameters and crystal structure. As a consequence, the spectral position of absorption resonances can be precisely controlled through the nanowire diameter. However, the results highlight how the blue-shift in the optical absorption resonances as the diameter of the nanowires decreases comes to a halt at low diameters. The stop point is related to the behavior of the refractive indices of the nanowires. The wavelength of the stop is different for nanowire polytypes of similar dimensions due to differences in their refractive indices. We then present a theoretical argument that it is important to consider symmetry properties when tailoring the optical modes excited in the nanowires for enhanced absorption. We show that absorption spectra may be enhanced compared to vertical nanowires at normal incidence by tilting the nanowires with normal incidence light, or by using off-normal incidence with vertical nanowires. This is because additional optical modes inside the nanowires are excited when the symmetry is broken. Looking forward to omnidirectional applications, we consider branched nanowires as a way to enhance the absorption spectra at normal incidence by taking advantage of simultaneous excitation of the spectrally different optical modes in the branches and the stems. Third, we describe in theoretical terms how integrating distributed Bragg reflectors (DBRs) with the nanowires can improve absorption spectra compared to conventional nanowires. DBRs provide a way to employ light trapping mechanisms which increases the optical path length of the excited modes and thereby improves the absorption of the excited modes. At normal incidence, DBR-nanowires improve the absorption efficiency to 78%, compared to 72% for conventional nanowires. We show that the efficiency is increased to 85% for an off-normal incident angle of 50˚. Overall, our results show that studies of optical resonances in nanowires that take the light-matter interaction into account provide opportunities to develop novel optical and optoelectronic functionalities in nanoscience and nanotechnology.

Place, publisher, year, edition, pages
Lund: Lund University, 2017. p. 63
Keywords
III-V nanowires, absorption, optical modes, photovoltaics
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:hh:diva-36683 (URN)978-91-7753-277-4 (ISBN)978-91-7753-278-1 (ISBN)
Public defence
2017-06-02, Rydbergsalen, Fysicum, Sölvegatan 14, Lund, 13:15 (English)
Opponent
Supervisors
Available from: 2018-05-03 Created: 2018-04-25 Last updated: 2018-05-03Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records BETA

Pettersson, Håkan

Search in DiVA

By author/editor
Pettersson, Håkan
By organisation
Halmstad Embedded and Intelligent Systems Research (EIS)
In the same journal
IEEE Photonics Journal
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 59 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf