Graphene/GeTe van der Waals heterostructure: Functional Schottky device with modulated Schottky barriers via external strain and electric field

Abstract

Vertical heterogeneous combinations of two-dimensional (2D) materials have been evident as an effective strategy to design novel photovoltaic and optoelectronic devices. Herein, we perform the first-principles calculations about electronic and optical properties of graphene/GeTe van der Waals heterostructures (vdWHs), accompanied by the efficient modulations about Schottky barriers via an external strain and electric field. A slightly opened band gap of 2.0 meV is obtained for graphene/GeTe vdWH in the equilibrium configuration, and the Dirac point is well preserved at K point. The built-in electric field caused by the charge transfer is devoted to its visible contribution to the efficient hindrance for photoexcited electron-hole pair recombination, consequently increasing the number of carriers and extending their lifetimes. The graphene/GeTe vdWH possesses enhanced optical absorption in the visible region in contrast to the separate GeTe monolayer, indicating its significant potential applications in optoelectronic devices. Besides, the graphene/GeTe vdWH at the equilibrium state exhibits an n-type Schottky contact with n-type Schottky barrier height (SBH) of 0.684 eV. By applying suitable external vertical strains or electric fields, the SBHs can be efficiently tuned, making it of significant possibility to realize the transportations between p-type Schottky contact and n-type Schottky contact, and between Schottky contact and Ohmic contact at the graphene/GeTe interface. These findings together predict the graphene/GeTe vdWH nanocomposite as a competitive candidate in next-generation optoelectronics and Schottky devices.