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Processing and characterization of nanowire arrays for photodetectors

Jain, Vishal LU ; Wallentin, J. LU ; Nowzari, A. LU ; Heurlin, M. LU ; Asoli, D.; Borgström, M. T. LU ; Capasso, F.; Samuelson, L. LU and Pettersson, H. LU (2015) p.511-512
Abstract

We present a fabrication scheme of contacting arrays of vertically standing nanowires (NW) for LEDs (Duan et al. Nature 409:66–69, 2001), photodetectors (Wang et al. Science (NY) 293:1455–1457, 2001) or solar cell applications (Wallentin et al. Science (NY) 339:1057–1060, 2013). Samples were prepared by depositing Au films using nano-imprint lithography (Ma rtensson et al. Nano Lett 4:699–702, 2004) which are used as catalysts for NW growth in a low-pressure metal organic vapour phase epitaxy system where III-V precursors and dopant gases are flown at elevated temperatures which lead to the formation of NWs with different segments (Borgstrom et al. Nano Res 3:264–270, 2010). An insulating SiO2 layer is then deposited and etched from the... (More)

We present a fabrication scheme of contacting arrays of vertically standing nanowires (NW) for LEDs (Duan et al. Nature 409:66–69, 2001), photodetectors (Wang et al. Science (NY) 293:1455–1457, 2001) or solar cell applications (Wallentin et al. Science (NY) 339:1057–1060, 2013). Samples were prepared by depositing Au films using nano-imprint lithography (Ma rtensson et al. Nano Lett 4:699–702, 2004) which are used as catalysts for NW growth in a low-pressure metal organic vapour phase epitaxy system where III-V precursors and dopant gases are flown at elevated temperatures which lead to the formation of NWs with different segments (Borgstrom et al. Nano Res 3:264–270, 2010). An insulating SiO2 layer is then deposited and etched from the top segments of the NWs followed by sputtering of a transparent top conducting oxide and opening up 1 1mm2 device areas through a UV lithography step and etching of the top contact from non-device areas. A second UV lithography step was subsequently carried out to open up smaller windows on the ITO squares for bond pad definition, followed by metallization and lift-off; and the substrate is used as back contact. We also report on the electrical and optical properties of near-infrared p+-i-n+photodetectors/solar cells based on square millimeter ensembles of InP nanowires grown on InP substrates. The study includes a sample series where the p+-segment length was varied between 0 and 250 nm, as well as solar cell samples with 9.3% efficiency with similar design. The NWs have a complex modulated crystal structure of alternating wurtzite and zincblende segments, a polytypism that depends on dopant type. The electrical data for all samples display excellent rectifying behavior with an ideality factor of about 2 at 300 K. From spectrally resolved photocurrent measurements, we conclude that the photocurrent generation process depends strongly on the p+- segment length.Without p+-segment in the NWs, photogenerated carriers funneled from the substrate into the NWs contribute significantly to the photocurrent. Adding a pC-segment shifts the depletion region up into the i -region of the NWs reducing the substrate contribution to photocurrent while strongly improving the collections of carriers generated in the NWs, in agreement with theoretical modeling (Fig. 48.1).

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author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
Infrared (IR), Nanophotonics, Nanowires, Photodetectors, Solar cells
host publication
Nano-Structures for Optics and Photonics
pages
2 pages
publisher
Springer
external identifiers
  • scopus:84943254945
ISBN
9789401791328
9789401791335
DOI
10.1007/978-94-017-9133-5_48
language
English
LU publication?
yes
id
4dc23ce2-6e2a-47d3-8a9f-c6aea2a1629f
date added to LUP
2017-12-13 16:31:20
date last changed
2019-09-27 13:08:04
@inbook{4dc23ce2-6e2a-47d3-8a9f-c6aea2a1629f,
  abstract     = {<p>We present a fabrication scheme of contacting arrays of vertically standing nanowires (NW) for LEDs (Duan et al. Nature 409:66–69, 2001), photodetectors (Wang et al. Science (NY) 293:1455–1457, 2001) or solar cell applications (Wallentin et al. Science (NY) 339:1057–1060, 2013). Samples were prepared by depositing Au films using nano-imprint lithography (Ma rtensson et al. Nano Lett 4:699–702, 2004) which are used as catalysts for NW growth in a low-pressure metal organic vapour phase epitaxy system where III-V precursors and dopant gases are flown at elevated temperatures which lead to the formation of NWs with different segments (Borgstrom et al. Nano Res 3:264–270, 2010). An insulating SiO2 layer is then deposited and etched from the top segments of the NWs followed by sputtering of a transparent top conducting oxide and opening up 1 1mm2 device areas through a UV lithography step and etching of the top contact from non-device areas. A second UV lithography step was subsequently carried out to open up smaller windows on the ITO squares for bond pad definition, followed by metallization and lift-off; and the substrate is used as back contact. We also report on the electrical and optical properties of near-infrared p<sup>+</sup>-i-n<sup>+</sup>photodetectors/solar cells based on square millimeter ensembles of InP nanowires grown on InP substrates. The study includes a sample series where the p<sup>+</sup>-segment length was varied between 0 and 250 nm, as well as solar cell samples with 9.3% efficiency with similar design. The NWs have a complex modulated crystal structure of alternating wurtzite and zincblende segments, a polytypism that depends on dopant type. The electrical data for all samples display excellent rectifying behavior with an ideality factor of about 2 at 300 K. From spectrally resolved photocurrent measurements, we conclude that the photocurrent generation process depends strongly on the p<sup>+</sup>- segment length.Without p<sup>+</sup>-segment in the NWs, photogenerated carriers funneled from the substrate into the NWs contribute significantly to the photocurrent. Adding a pC-segment shifts the depletion region up into the i -region of the NWs reducing the substrate contribution to photocurrent while strongly improving the collections of carriers generated in the NWs, in agreement with theoretical modeling (Fig. 48.1).</p>},
  author       = {Jain, Vishal and Wallentin, J. and Nowzari, A. and Heurlin, M. and Asoli, D. and Borgström, M. T. and Capasso, F. and Samuelson, L. and Pettersson, H.},
  isbn         = {9789401791328},
  keyword      = {Infrared (IR),Nanophotonics,Nanowires,Photodetectors,Solar cells},
  language     = {eng},
  month        = {01},
  pages        = {511--512},
  publisher    = {Springer},
  title        = {Processing and characterization of nanowire arrays for photodetectors},
  url          = {http://dx.doi.org/10.1007/978-94-017-9133-5_48},
  year         = {2015},
}