High photoresponsivity in an all-graphene
p–n vertical junction photodetector
Intensive studies have recently been performed on graphene-based photodetectors (PDs), but most of them are based on field-effect-transistor structures containing mechanically-exfoliated graphene, not suitable for practical large-scale device applications. Here, we firstly report high-efficient PD behaviors of chemical-vapor-deposition-grown all-graphene p-n vertical-type tunneling diodes. The observed unique PD characteristics well follow what are expected from its band structure and the tunneling of current through the interlayer between the metallic p- and n-graphene layers. High detectivity (~1012 cm Hz1/2 W−1) and responsivity (0.4 ~ 1.0 A/W) are achieved in the broad spectral range from ultraviolet to near-infrared and the photoresponse is almost consistent under six month-operations. The high PD performance of the graphene p-n vertical diodes can be understood by the high photocurrent gain and the carrier multiplication arising from impact ionization in graphene.
Keywords: graphene, photodetectors, p-n vertical junction, tunneling diode, carrier multiplication