The performance limits of monolayer transition metal dichalcogenide transistors are examined with a ballistic MOSFET model. Using ab-initio theory, we calculate the band structures of two-dimensional (2D) transition metal dichalco-genide (MX 2 ). We find the lattice structures of monolayer MX 2 remain the same as the bulk MX 2 . Within the ballistic regime, the performances of monolayer MX 2 transistors are better compared to the silicon transistors if thin high-κ gate insulator is used. This makes monolayer MX 2 promising 2D materials for future nanoelectronic device applications.

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High Frequency potential of graphene field-effect transistors (FETs) is explored by quasi-static self-consistent ballistic and dissipative quantum transport simulations. The unity power gain frequency fMAX and the cut-off frequency fT are modeled at the ballistic limit and in the presence of inelastic phonon scattering for a gate length down to 5 nm. Our major results are (1) with a thin high-κ gate insulator, the intrinsic ballistic fT is above 5 THz at a gate length of 10 nm. (2) Inelastic phonon scattering in graphene FETs lowers both fT and fMAX, mostly due to decrease of the transconductance. (3) fMAX and fT are severely degraded in presence of source and drain contact resistance. (4) To achieve optimum extrinsic fMAX performance, careful choice of DC bias point and gate width is needed.

It was suggested that single-layer MoS2 at the 1T′ phase is a topological insulator whose electronic structure can be modulated by a vertical electric field for field-effect transistor (FET) applications [X. Qian, J. Liu, L. Fu, and J. Li, Science 346, 1344 (2014)]. In this work, performance potential of FETs based on vertical field modulation of the topological edge states is assessed by using quantum transport device simulations. To perform efficient device simulations, a phenomenological Hamiltonian is first proposed and validated to capture the effects of electric fields. Because the ON-state conductance is determined by transport through gapless edge states with a long scattering mean free path and the OFF-state conductance by transport through the gapped bulk states, the ON/OFF ratio is sensitive to the channel length, which is different from conventional FETs. Although a high vertical electric field is required to modulate the topological edge state, a reasonably small subthreshold swing of 131 mV/dec can still be achieved for a practical value of the gate insulator thickness.

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