Single Si nanowire (diameter <= 100 nm) based polarization sensitive near-infrared photodetector with ultra-high responsivity
We report the fabrication and optical response of boron-doped single silicon nanowire-based metal-semiconductor-metal photodetector. Typical single nanowire devices with diameter of ~80-100 nm and electrode spacing of ~1 μm were made using electron-beam lithography from nanowires, grown by a metal-assisted chemical etching process. A high responsivity, of the order of 104 A W-1, was observed even at zero bias in a single nanowire photodetector with peak responsivity in the near-infrared region. The responsivity was found to increase with increasing bias and decreasing nanowire diameter. Finite element based optical simulation was proposed to explain the diameter dependent performance of a single nanowire. The observed photoresponse is sensitive to the polarization of exciting light source, allowing the device to act as a polarization-dependent near-infrared photodetector.