Synthesis of two-dimensional GaSe/MoSe2 misfit heterojunctions by van der Waals epitaxy

Misfit heterojunctions formed by van der Waals (vdW) epitaxial growth of one crystalline metal chalcogenide monolayer on another was demonstrated for the first time to form p-n junctions that exhibit a photovoltaic response.  Such heterojunction bilayers that display Moiré periodicity represent a new type of “building block” with unusual optoelectronic properties suitable for energy generation as well as a wide range of other physical phenomena ranging from interfacial magnetism to superconductivity.

GaSe/MoSe₂ misfit bilayer heterostructures were synthesized by a two-step chemical vapor deposition process and characterized by atomic resolution transmission electron microscopy to reveal the atomistic orientation that generates the periodic Moiré superlattices. First principles modeling of the p-n bilayer heterojunction revealed strong interlayer coupling that explained the observed photovoltaic and photoluminescence behaviors. E-beam lithographic patterning was used to contact heterojunction bilayers for transport and photovoltaic measurements of the heterojunctions.