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Processing and Char...
Abstract
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- 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). © Springer Science+Business Media Dordrecht 2015.
Ämnesord
- NATURVETENSKAP -- Fysik -- Den kondenserade materiens fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Condensed Matter Physics (hsv//eng)
- TEKNIK OCH TEKNOLOGIER -- Nanoteknik -- Nanoteknik (hsv//swe)
- ENGINEERING AND TECHNOLOGY -- Nano-technology -- Nano-technology (hsv//eng)
Nyckelord
- Nanophotonics
- Nanowires
- Infrared (IR)
- Photodetectors
- Solar cells
- Infrared (IR)
- Nanophotonics
- Nanowires
- Photodetectors
- Solar cells
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Jain, Vishal, 19 ...
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Wallentin, J.
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Nowzari, A.
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Heurlin, M.
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Asoli, Damir
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Borgström, M. T.
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Capasso, Federic ...
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Samuelson, L.
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Pettersson, Håka ...
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Högskolan i Halmstad
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Lunds universitet