Tri-layered van der Waals heterostructures based on graphene, gallium selenide and molybdenum selenide

In this work, we propose ultrathin trilayered heterostructures (TL-HTSs) of graphene (G), gallium selenide (GaSe), and molybdenum selenide (⁠$MoSe2$⁠) monolayers and investigate their structural and electronic properties in the framework of first-principles calculations. By calculating the binding energies and interlayer distances and comparing them with those of the typical vdW HTSs, we find that the systems we consider are energetically stable and are characterized by weak vdW interactions. The formation of G, GaSe, and $MoSe2$ monolayers to form $G/GaSe/MoSe2$⁠, $GaSe/G/MoSe2$⁠, and $G/MoSe2/GaSe$ HTSs leads to the opening of a sizable bandgap in graphene at the Dirac point and shows the $p$-type Schottky contact. Among these kinds of TL-HTSs, the $G/GaSe/MoSe2$ has many more advantages than the others due to the lowest binding energy of $−29.47meV/$Ų, the biggest bandgap opening in G of 84.7 meV, and the smallest Schottky barrier height of 0.63 eV. Furthermore, we find that the $p$-type Schottky contact of $G/GaSe/MoSe2$ HTS can be turned into an $n$-type one or into an Ohmic contact when vertical strain or electric field is applied. These results show a potential candidate of the combined HTSs of G, GaSe, and $MoSe2$ monolayers for developing high speed nanoelectronic and optoelectronic devices.