Atomistic Transport Simulations Research Articles

A computational study of spin Hall effect device based on 2D materials

Efficient spin-charge conversion is indispensable in spintronic computing and memory technologies for achieving low power. Spin Hall and quantum spin Hall effects have been demonstrated in certain atomically thin two-dimensional (2D) materials. In this work, we develop a multiscale simulation method from atomistic quantum transport simulation to the circuit model for the spin Hall effect (SHE) device based on 2D materials. Numerical implementation to speed up atomistic transport simulations with the non-equilibrium Green's function formalism is described for the crossbar SHE device. The multiscale method can treat atomistic scale features and compute the spintronic device performance metrics of the modeled device. As an example, the effect of edge roughness on the SHE devices based on monolayer 2D materials is investigated. The results illustrate that aggressively scaled monolayer SHE devices can efficiently transduce charge to spin in the presence of edge roughness.

Scattering basis representation in ballistic transport simulations of nanowire transistors

The paper presents a basis expansion scheme for atomistic transport simulations in nanowire MOSFETs. Two simple methods are formulated to calculate current carrying states using a low-dimensional device Hamiltonian in the scattering basis representation. The proposed methods are computationally very cheap and their utility is confirmed by test self-consistent calculations in a p-Si nanowire device.

Application of the R-matrix method in quantum transport simulations

The R-matrix method based on a continuous model is generalized as to become applicable to the atomistic transport simulations with a tight-binding device Hamiltonian. The device elements are introduced as arbitrary atomic clusters in the device area and freedom in the device fragmentation can be used to reduce computations. In the ballistic regime, the best computer performance is achieved by taking individual atoms as the device elements. Non-equilibrium current carrying electronic states are constructed by the forward-backward R-matrix propagation scheme which does not require large computer operations and mass storage. The method is applied to quantum transport in p-Si nanowire with random vacancies and surface roughness.

Impact of Strain on Ballistic Current in Si n–i–n Structures

Atomistic transport simulation based on the nonequilibrium Green's function and empirical tight-binding methods has been performed for one-dimensional strained Si n–i–n devices. Simulation results show that the tensile strain enhances the ballistic current and reduces the Zener tunneling current, while the compressive strain gives opposite results.

Effects of Strained Layers on Zener Tunneling in Silicon Nanostructures

An atomistic transport simulation based on the nonequilibrium Green's function and empirical tight-binding methods has been performed for one-dimensional Si n–i–n devices having a thin strained layer in the central i-region. Simulation results show that introducing a strain layer strongly enhances the Zener tunneling current for both tensile and compressive strain.