Proposal for fast-response radial Schottky junction photodetectors based on silicon nanowires

We propose a silicon-nanowire-based photodetector with a radial metal junction that is predicted to exhibit a significantly reduced response time. The width of the radial depletion layer across the nanowire can be controlled by adjusting the doping concentration of the silicon nanowire. We calculated depletion region widths for silicon nanowires of various diameters and doping concentrations, and then calculated the photogenerated carrier transit time, the RC time constant, and the diffusion time in the nanowire structure. We found that by using the radial junction configuration we could significantly improve the response time to 81 ps. We also found that the diffusion time for the photogenerated carriers depends strongly on the nanowire length and doping concentration.