Silicon nanowire detectors showing phototransistive gain

Nanowire photodetectors are shown to function as phototransistors with high sensitivity. Due to small lateral dimensions, a nanowire detector can have low dark current while showing large phototransistive gain. Planar and vertical silicon nanowire photodetectors fabricated in a top-down approach using an etching process show a phototransistive gain above 35 000 at low light intensities. Simulations show that incident light can be waveguided into vertical nanowires resulting in up to 40 times greater external quantum efficiency above their physical fill factor. Vertical silicon nanowire phototransistors formed by etching are attractive for low light level detection and for integration with silicon electronics. (C) 2008 American Institute of Physics.