  We present the first principle calculations of the electrical properties of
graphene sheet/h-BN heterojunction(GS/h-BN) and 11-armchair graphene nanoribbon
heterojunction(11-AGNR/h-BN), which were carried out using the density
functional theory(DFT) method and the non-equilibrium Green's function(NEGF)
technique. Since 11-AGNR belongs to the conductive (3n-1)-family of AGNR, both
are metallic nanomaterials with two transverse arrays of h-BN, which is a
wide-gap semi-conductor. The two h-BN arrays act as double barriers. The
transmission functions(TF) and I-V characteristics of GS/h-BN and 11-AGNR/h-BN
are calculated by DFT and NEGF, and they show that quantum double barrier
tunneling occurs. The TF becomes very spiky in both materials, and it leads to
step-wise I-V characteristics rather than negative resistance, which is the
typical behavior of double barriers in semiconductors.
