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Processing and Characterization of Nanowire Arrays for Photodetectors

  • Vishal JainEmail author
  • J. Wallentin
  • A. Nowzari
  • M. Heurlin
  • D. Asoli
  • M. T. Borgström
  • F. Capasso
  • L. Samuelson
  • H. Pettersson
Conference paper
Part of the NATO Science for Peace and Security Series B: Physics and Biophysics book series (NAPSB)

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 (Må 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 (Borgström 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 × 1 mm2 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 p +-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).

Keywords

Nanophotonics Nanowires Infrared (IR) Photodetectors Solar cells 

Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Vishal Jain
    • 1
    • 2
    Email author
  • J. Wallentin
    • 1
  • A. Nowzari
    • 1
  • M. Heurlin
    • 1
  • D. Asoli
    • 3
  • M. T. Borgström
    • 1
  • F. Capasso
    • 4
  • L. Samuelson
    • 1
  • H. Pettersson
    • 1
    • 2
  1. 1.Solid State Physics and the Nanometer Structure ConsortiumLund UniversityLundSweden
  2. 2.Laboratory of Mathematics, Physics and Electrical EngineeringHalmstad UniversityHalmstadSweden
  3. 3.Sol Voltaics AB, Ideon Science ParkLundSweden
  4. 4.School of Engineering and Applied SciencesHarvard UniversityCambridgeUSA

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