Hexagonal boron-nitride (h-BN) provides an ideal substrate for supporting
graphene devices to achieve fascinating transport properties, such as Klein
tunneling, electron optics and other novel quantum transport phenomena.
However, depositing graphene on h-BN creates moir\'e superlattices, whose
electronic properties can be significantly manipulated by controlling the
lattice alignment between layers. In this work, the effects of these moir\'e
structures on the transport properties of graphene are investigated using
atomistic simulations. At large misalignment angles (leading to small moir\'e
cells), the transport properties (most remarkably, Klein tunneling) of pristine
graphene devices are conserved. On the other hand, in the nearly aligned cases,
the moir\'e interaction induces stronger effects, significantly affecting
electron transport in graphene. In particular, Klein tunneling is significantly
degraded. In contrast, strong Fabry-P\'erot interference (accordingly, strong
quantum confinement) effects and non-linear I-V characteristics are observed.
P-N interface smoothness engineering is also considered, suggesting as a
potential way to improve these transport features in graphene/h-BN devices.Comment: 21 pages, 8 figures, Supplementary material