Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. The direct growth of such heterostructures is desirable to engineer pristine layers and their combination as van der Waals heterostructures. We reported the direct and epitaxial growth of crystalline tungsten diselenide (WSe2) and molybdenum disulfide (MoS2) monolayer on epitaxial graphene (EG) grown on SiC and the applications on these two single-junctions, WSe2/EG, and MoS2/EG, respectively. With an atomically sharp interface, the vertical transport measurement across the WSe2/EG junction provides evidence that the interlayer gap between the layers adds a barrier to carrier transport, while the photosensing measurements carried out on the MoS2/EG photosensors shows a 20 x increased photon responsibility comparing with bare 1L MoS2 photosensors. In the end, the possibility to directly grow MoS2/WSe2/EG and WSe2/MoS2/EG, the double-junction having strong interlayer coupling due the type-II band alignment is presented.