  Van der Waal's heterostrucutures allow for novel devices such as
two-dimensional-to-two-dimensional tunnel devices, exemplified by interlayer
tunnel FETs. These devices employ channel/tunnel-barrier/channel geometries.
However, during layer-by-layer exfoliation of these multi-layer materials,
rotational misalignment is the norm and may substantially affect device
characteristics. In this work, by using density functional theory methods, we
consider a reduction in tunneling due to weakened coupling across the
rotationally misaligned interface between the channel layers and the tunnel
barrier. As a prototypical system, we simulate the effects of rotational
misalignment of the tunnel barrier layer between aligned channel layers in a
graphene/hBN/graphene system. We find that rotational misalignment between the
channel layers and the tunnel barrier in this van der Waal's heterostructure
can significantly reduce coupling between the channels by reducing,
specifically, coupling across the interface between the channels and the tunnel
barrier. This weakened coupling in graphene/hBN/graphene with hBN misalignment
may be relevant to all such van der Waal's heterostructures.
