  The formation of quantum Hall channels inside the bulk of graphene is studied
using various contact and gate geometries. p-n junctions are created along the
longitudinal direction of samples, and enhanced conductance is observed in the
case of bipolar doping due to new conducting channels forming in the bulk,
whose position, propagating direction and, in one geometry, coupling to
electrodes are determined by the gate-controlled filling factor across the
device. This effect could be exploited to probe the behavior and interaction of
quantum Hall channels protected against uncontrolled scattering at the edges.
