  The electronic conduction of a novel, three-terminal molecular architecture,
analogous to a heterojunction bipolar transistor is studied. In this
architecture, two diode arms consisting of donor-acceptor molecular wires fuse
through a ring, while a gate modulating wire is a \pi-conjugated wire. The
calculated results show the enhancement or depletion mode of a transistor by
applying a gate field along the positive or negative direction. A small gate
field is required to switch on the current in the proposed architecture. The
changes in the electronic conduction can be attributed to the intrinsic dipolar
molecular architecture in terms of the evolution of molecular wavefunctions,
specifically the one associated with the terphenyl group of the modulating wire
in the presence of the gate field.
