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Gate capacitance of back-gated nanowire field-effect transistors
Gate capacitances of back-gated nanowire field-effect transistors (NW-FETs)
are calculated by means of finite element methods and the results are compared
with analytical results of the ``metallic cylinder on an infinite metal plate
model''. Completely embedded and non-embedded NW-FETs are considered. It is
shown that the use of the analytical expressions also for non-embedded NW-FETs
gives carrier mobilities that are nearly two times too small. Furthermore, the
electric field amplification of non-embedded NW-FETs and the influence of the
cross-section shape of the nanowires are discussed.Comment: 4 pages, 5 figures, to be published in Appl. Phys. Let
Broadband Quantum Efficiency Enhancement in High Index Nanowires Resonators
Light trapping in sub-wavelength semiconductor nanowires (NWs) offers a
promising approach to simultaneously reducing material consumption and
enhancing photovoltaic performance. Nevertheless, the absorption efficiency of
a NW, defined by the ratio of optical absorption cross section to the NW
diameter, lingers around 1 in existing NW photonic devices, and the absorption
enhancement suffers from a narrow spectral width. Here, we show that the
absorption efficiency can be significantly improved in NWs with higher
refractive indices, by an experimental observation of up to 350% external
quantum efficiency (EQE) in lead sulfide (PbS) NW resonators, a 3-fold increase
compared to Si NWs. Furthermore, broadband absorption enhancement is achieved
in single tapered NWs, where light of various wavelengths is absorbed at
segments with different diameters analogous to a tandem solar cell. Overall,
the single NW Schottky junction solar cells benefit from optical resonance,
near bandgap open circuit voltage, and long minority carrier diffusion length,
demonstrating power conversion efficiency (PCE) comparable to single Si NW
coaxial p-n junction cells11, but with much simpler fabrication processes
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