Monolayer 2D semiconducting tellurides for high-mobility electronics

Discovery and design of two-dimensional (2D) materials with suitable band gaps and high carrier mobility are of vital importance for the photonics, optoelectronics, and high-speed electronics. In this work, based on first principles calculations using density functional theory with Perdew-Burke-Ernzerhof and Heyd-Scuseria-Ernzerhoffunctionals, we introduce a family of monolayer isostructural semiconducting tellurides MN${\mathrm{Te}}_4$, with $M=\left\{\mathrm{Ti},\mathrm{Zr},\mathrm{Hf}\right\}$ and $N=\left\{\mathrm{Si},\mathrm{Ge}\right\}$. These compounds have been identified to possess direct band gaps from 1.0 to 1.31 eV, which are well suited for photonics and optoelectronics applications. Additionally, anisotropic in-plane transport behavior is observed, and small electron and hole $(0.11–0.15m_e)$ effective masses are identified along the dominant transport direction. Ultrahigh carrier mobility is predicted for this family of 2D compounds, which host great promise for potential applications in high-speed electronic devices. Detailed analysis of electronic structures reveals the origins of the promising properties of this unique class of 2D telluride materials.

Figure 1

(a) Top and (b) side view of the relaxed structure of TiSiTe4. The magenta, cyan, and brown balls represent Ti, Si, and Te atoms, respectively. (c) Band structure of TiSiTe4 calculated on the level of HSE06 hybrid functional. High-symmetry $k$ points in the reciprocal space are presented in the figure. (d) Projected density of states of ${\mathrm{TiSiTe}}_4$, showing that the dominant states at the CBM and VBM are contributed by Ti $d$ states and Te $p$ states, respectively.

Figure 2

Top and side view of band decomposed partial charge density of ${\mathrm{TiSiTe}}_4$ at (a) the VBM and (b) the CBM at Γ point in the x-y plane at the $0.0064e{\AA }^{-3}$ isosurface level. The magenta, cyan, and brown balls represent Ti, Si, and Te atoms, respectively.

Figure 3

Projected crystal orbital Hamiltonian population (−pCOHP) between neighboring atoms of ${\mathrm{TiSiTe}}_4$, with the corresponding structure showing the adjacent atoms of which pCOHP is obtained from.