Electrical characteristics and photocurrent spectral response of Si nanowires p-i-n junctions

P-i-n junctions were fabricated along silicon nanowires (SiNWs) via the conventional top-down approach using optical lithography. The process is fully CMOS compactable. Each device comprises 500 identical SiNWs connected in parallel, and each SiNW has a length of 1.0 μm and a triangular cross-section with dimensions of ∼6 nm (base) by ∼8 nm (height). Good rectifying electrical characteristics with a low reverse bias current of ∼0.2 fA per SiNW is observed. The photocurrent spectral response of the SiNW p-i-n photodiodes exhibits three peaks between 400 nm to 700 nm, which arise due to local optical field enhancement associated with diffraction by the periodic SiNW array and interference in an air/SiO2/Si cavity.