Epitaxial growth of radial Si p-i-n junctions for photovoltaic applications

Achieving high quality radial junctions in nanowire arrays with controlled doping profiles is critical for their potential photovoltaic applications. We present a low temperature epitaxial growth process for silicon radial p-n and p-i-n junction arrays on top-down fabricated nanowires using silane-based chemical vapor deposition. Epitaxial growth on [111] oriented nanowires of similar to 300 nm diameter and up to 10 mu m in length exhibits well-defined, single crystalline {110} faceted surfaces at temperatures as low as 710 degrees C. The growth rate G at 810 degrees C for intrinsic Si is greater than that for heavily B- and P-doped Si (G(i)>G(p)>G(n)). Faceted growth morphology at the tip of the nanowires results in well-defined match-head structures for undoped and B-doped growth. Preliminary photovoltaic device arrays of similar to 4 x 10(4) nanowires based on our radial epitaxial p-i-n junction growth approach achieve solar energy conversion efficiencies of 10% under AM 1.5 G illumination. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794541]