Electrostatically Doped Silicon Nanowire Arrays for Multispectral Photodetectors.

Nanowires have promising applications as photodetectors with superior ability to tune absorption with morphology. Despite their high optical absorption, the quantum efficiencies of these nanowire photodetectors remain low due to difficulties in fabricating a shallow junction using traditional doping methods. As an alternative, we report nonconventional radial heterojunction photodiodes obtained by conformal coating of an indium oxide layer on silicon nanowire arrays. The indium oxide layer has a high work function which induces a strong inversion in the silicon nanowire and creates a virtual p-n junction. The resulting nanowire photodetectors show efficient carrier separation and collection, leading to an improvement of quantum efficiency up to 0.2. In addition, by controlling the nanowire radii, the spectral responses of the In2O3/Si nanowire photodetectors are tuned over several visible light wavelengths, creating a multispectral detector. Our approach is promising for the development of highly efficient wavelength-selective photodetectors.