Analysis of optoelectronic properties of TiO₂ nanowiers/Si heterojunction arrays

The optoelectronic properties of n-TiO₂NW/p-Si heterojunction fabricated by depositing TiO₂ nanowires on a p-Si substrate are studied. Under excitation at a wavelength of 370 nm, the TiO₂ nanowires produce a light emission at 435 nm due to the emission of free excitons. The I—V characteristics are measured to investigate the heterojunction effects under the dark environment and ultraviolet (UV) illumination. n-TiO₂NW/p-Si has a p—n junction formed in the n-TiO₂/p-Si heterojunction. TiO₂NW/Si photodiode produces a photocurrent larger than dark current under UV illumination. It is observed that UV photons are absorbed in TiO₂ and the heterojunction shows a 0.034-A/W responsivity at 4-V reverse bias.