Non-equilibrium multi-space density functional simulations of MoS₂ field effect transistors

We describe our recent development of a firstprinciples simulation method for field effect transistors (FETs) within the multi-space constrained-search density functional theory (MS-DFT) formalism. Standard simulation approaches that combine DFT and non-equilibrium Green’s function (NEGF) formalisms employ the grand canonical ensemble and naturally treated the gate electrode as boundary conditions on the electrostatic potential or charge. On the other hand, MS-DFT considers the (micro)canonical ensemble and we impose only the electrochemical potential on the gate electrode. While the method was applied to vertical FET capacitor models within the lateral periodic boundary condition, we here consider the full FET model geometry that includes Ag gate electrode and MoS₂ channel with different channel lengths. We discuss finite-size gate electrode effects as well as short-channel effects.