The effect of edge functionalization on the device performance of monolayer Si0.5Ge0.5 nanoribbon transistors

Abstract

Monolayer silicene and germanene have received intensive attention due to their good compatibility with current Si-based electronics. However, the lack of a bandgap severely limits their applications in complex electronic circuits. To overcome this obstacle, we build Si1−xGex superlattices (SLs) and further cleave them into nanoribbons to tune the electrical properties of silicene and germanene, and analyze their transport behavior by means of density functional theory combined with the nonequilibrium Green’s function formalism. Among all the designed Si1−xGex SLs, Si0.5Ge0.5 possesses the widest bandgap of 0.53 eV, as its larger amount of Ge–Si bonds can result in strong absorption of light towards short wavelengths. By edge functionalization with Li, H, and F atoms, the conduction type of the monolayer Si0.5Ge0.5 nanoribbons can be rationally tuned from n-type to ambipolar to p-type. These tunable electronic properties can be attributed to the internal and interfacial charge transfer. The simulated transport behavior of field-effect transistors based on monolayer Si0.5Ge0.5 nanoribbons demonstrates that such edge functionalization could be applied to modulate the conductivity, conduction type, on/off ratio, and carrier concentration effectively. The results of this work reveal the great potential of edge functionalization for tuning the electrical properties of two-dimensional (2D) semiconductors.