  Graphene-based photodetectors have demonstrated mechanical flexibility, large
operating bandwidth, and broadband spectral response. However, their linear
dynamic range (LDR) is limited by graphene's intrinsichot-carrier dynamics,
which causes deviation from a linear photoresponse at low incident powers. At
the same time, multiplication of hot carriers causes the photoactive region to
be smeared over distances of a few micro-meters, limiting the use of graphene
in high-resolution applications. We present a novel method for engineer-ing
photoactive junctions in FeCl3-intercalated graphene using laser irradiation.
Photocurrent measured at these planar junctions shows an extraordinary linear
response with an LDR value at least 4500 times larger than that of other
graphene devices (44 dB) while maintaining high stability against environmental
contamination without the need for encapsulation. The observed photoresponse is
purely photovoltaic, demonstrating complete quenching of hot-carrier effects.
These results pave the way toward the design of ultrathin photode-tectors with
unprecedented LDR for high-definition imaging and sensing.
