A 3-terminal device with a tunable Schottky barrier controls the charge transport across a
vertically stacked structure named “barristor”- one composed of a graphene/rhenium diselenide
(ReSe2) p-n heterojunction to exploit the advantages of the high mobility of graphene
with tunable ReSe2 for digital applications is reported herein. The CVD-graphene used to
fabricate p-n heterojunction with ReSe2 is p-type doped by DUV irradiation in O2 atmosphere
for 30 min. Density functional theory (DFT) calculations reveals highly anisotropic behavior of
ReSe2, possessing bandgap of 1.17 eV. We demonstrate that the gate-controlled Schottky
barrier can be utilized to modify carrier transport in graphene, resulting in tuning of the
Schottky barrier height. Thus, bymodulating the work function of themonolayered graphene
via the back-gate voltages, the Schottky barrier height at the interface between the graphene
and ReSe2 could be varied by up to 300 meV. A diode showed good rectification behavior with
an ON/OFF current ratio of 102. Furthermore, the barristor exhibits good optoelectronic
characteristics with a sensing range fromvisible (455 nm) to near IR (850 nm) and is capable of
detecting low incident power density. The diode attained photoresponsivity and detectivity
values of 42 AW-1 and 2.2   1012 Jones, respectively, and a rise time of 33.94 ms under 656 nm
laser illumination. Our approach could aid the improved development of high-performance
graphene-based heterojunction devices.