Graphene-Silicon Schottky Diodes for Photodetection

We present the optoelectronic characterization of graphene/silicon Schottky junctions, fabricated by transferring CVD-graphene on flat and nanotip-patterned n- and p-type Si substrates. We show that medium n- type doping results in the highest rectification. We demonstrate high photoresponsivity, exceeding 2.5 A/W under white light, which we attribute to the contribution of charges photogenerated in the surrounding region of the flat junction or to the internal gain by impact ionization caused by the enhanced field on the nanotips.