NIR photodetector based on p-silicon nanowires/n-cadmium sulfide nanoscale junctions

Abstract

Heterojunction of p-type silicon nanowire and n-type cadmium sulfide (CdS) nanoparticles have been fabricated by deposition of CdS nanoparticles on chemically etched vertically aligned silicon nanowires (SiNWs). The asymmetric current-voltage (I-V) curves confirm the formation of the p-n junction in the SiNW/CdS heterostructures. The growth time of CdS nanoparticles on SiNWs have been optimized for obtaining the best photodiode performance. Variation of current–voltage characteristics with respect to temperature in the range of 200–300 K is also studied and the consequent changes in the barrier height and ideality factor of the p-n junction are observed. Furthermore, from the wavelength vs. current characteristics, the highest current is observed at the near-infrared (NIR) region of the wavelength making it suitable as an NIR detector. The maximum photocurrent (Ip/Id) is calculated to be 6.7 times to dark-current due to photogenerated charge carriers by absorption of photon-energy. The responsivity and detectivity with the variation of light intensities are investigated and the highest values attained by the synthesized samples are 821 mA/W and 1.21 × 1012 Jones respectively, for an NIR source having wavelength of ~ 900 nm and intensity of ~ 8 mW/cm2. Thus SiNW/CdS film can be introduced as a probable candidate for a photo-electronic application.