Vertical InGaAs Nanowire Array Photodiodes on Si

We demonstrated vertical InGaAs nanowire (NW) array photodiodes on Si that were optically responsive to visible light (635 nm) and near-infrared light (similar to 1.55 mu m). The vertical NWs were directly grown on Si by selective-area growth. Implementation of a heavily Sn-doped contact layer in the InGaAs NWs improved the diode characteristic because of a lower series resistance, and as a result, a photoresponsivity of 0.25 A/W was obtained at 635 nm, which was twice that before the improvement. Moreover, the photocurrent density of InGaAs-InP core-shell NWs was about 20-fold higher under illumination with light in the 1.55 mu m wavelength band as a result of suppression of surface recombination. These findings are expected to be useful for NW-based photovoltaic applications for optical interconnection and Si platforms.