Hot-Electron Injection in Au Nanorod–ZnO Nanowire
Hybrid Device for Near-Infrared Photodetection
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Abstract
In this Letter, we present a new
class of near-infrared photodetectors
comprising Au nanorods–ZnO nanowire hybrid systems. Fabricated
hybrid FET devices showed a large photoresponse under radiation wavelengths
between 650 and 850 nm, accompanied by an “ultrafast”
transient with a time scale of 250 ms, more than 1 order of magnitude
faster than the ZnO response under radiation above band gap. The generated
photocurrent is ascribed to plasmonic-mediated generation of hot electrons
at the metal–semiconductor Schottky barrier. In the presented
architecture, Au-nanorod-localized surface plasmons were used as active
elements for generating and injecting hot electrons into the wide
band gap ZnO nanowire, functioning as a passive component for charge
collection. A detailed investigation of the hot electron generation
and injection processes is discussed to explain the improved and extended
performance of the hybrid device. The quantum efficiency measured
at 650 nm was calculated to be approximately 3%, more than 30 times
larger than values reported for equivalent metal/semiconductor planar
photodetectors. The presented work is extremely promising for further
development of novel miniaturized, tunable photodetectors and for
highly efficient plasmonic energy conversion devices