Geometrical control of photocurrent in active Si nanowire devices

SummaryThe growing research in the field of photovoltaics has led to various strategies for increasing the light interaction in absorbers, for instance the use of nanostructures like nanowires where leaky mode resonances enhanced absorption efficiency. Towards this goal, we present a study of the light absorption in single Si nanowires, by means of microphotocurrent spectroscopy combined with transport measurements of carrier diffusion length using the electron beam induced current technique. The study is performed on different diameter nanowires with Schottky junctions created by doping modulation during Chemical Vapor Deposition–Vapor Liquid Solid growth. We show that the photocurrent spectra of single Si nanowires do not follow monotonous profiles as bulk silicon, but rather have steep valleys and peaks whose position and intensity are diameter dependent. These sharp modulations result from a resonant coupling between incident photons and cavity modes of the nanowires. A good agreement between the experiment and the theoretical fit using Mie theory is observed with a red shift in the absorption spectrum with increasing diameters.

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► Optical and electrical characterization of single Si nanowire junctions.
► Diffusion length extracted from Electron Beam Induced Current measurement.
► Single nanowire photoresponse spectra measured by microphotocurrent spectroscopy.
► Good correlation between the analytical Mie calculation and the experimental photoresponse of nanowires.