High responsivity sensing of unfocused laser and white light using graphene photodetectors grown by chemical vapor deposition

Graphene photodetectors grown by chemical vapor deposition are fabricated for unfocused laser and white light sensing. The unfocused light enlarges the illuminated graphene area and mimics the real-life sensing conditions, yielding a responsivity of 104 mA/W at room temperature without enhancing absorbance by waveguide and plasmonics. The devices are based on positive photoconductivity from the electron-hole photocarrier pairs and the bolometric-effect-induced negative photoconductivity. The buried off-center local gate induces a net internal potential in the graphene. The relative strength of the two photoconductivities depends on the gate voltage. The technology is scalable, which is a step ahead toward real applications