High-Responsivity Near-Infrared Photodetector Using Gate-Modulated Graphene/Germanium Schottky Junction

A high-responsivity near-infrared photodetector is demonstrated using a transparent ZnO top gate-modulated graphene/Ge Schottky junction. The responsivity of a graphene/Ge junction photodetector characterized with a scanning photocurrent microscopy system is improved to 0.75 A W-1. This result is 5 to 35 times higher than the previously reported graphene/Ge photodetectors that did not use gate modulation. The detectivity is also improved to 2.53 x 10(9) cm Hz(1/2) W-1 at V-g = -10 V from 0.43 x 10(9) cm Hz(1/2) W-1 at V-g = 0 V. The performance of this gate-modulated graphene/Ge Schottky junction base infrared (IR) detector is comparable to a commercially available IR photodetector, but the fabrication process is much simpler and compatible with glass or flexible substrates.