Quasi van der Waals Epitaxy of Rhombohedral-Stacked Bilayer WSe on GaP(111) Heterostructure.

The growth of bilayers of two-dimensional (2D) materials on conventional 3D semiconductors results in 2D/3D hybrid heterostructures, which can provide additional advantages over more established 3D semiconductors while retaining some specificities of 2D materials. Understanding and exploiting these phenomena hinge on knowing the electronic properties and the hybridization of these structures. Here, we demonstrate that a rhombohedral-stacked bilayer (AB stacking) can be obtained by molecular beam epitaxy growth of tungsten diselenide (WSe) on a gallium phosphide (GaP) substrate. We confirm the presence of 3R-stacking of the WSe bilayer structure using scanning transmission electron microscopy (STEM) and micro-Raman spectroscopy. Also, we report high-resolution angle-resolved photoemission spectroscopy (ARPES) on our rhombohedral-stacked WSe bilayer grown on a GaP(111)B substrate. Our ARPES measurements confirm the expected valence band structure of WSe with the band maximum located at the Γ point of the Brillouin zone. The epitaxial growth of WSe/GaP(111)B helps to understand the fundamental properties of these 2D/3D heterostructures, toward their implementation in future devices.