Quantum Mechanical Simulation of Electronic Transport in Nanostructured Devices by Efficient Self-consistent Pseudopotential Calculation

TL;DR

This paper introduces an efficient self-consistent pseudopotential method for simulating electronic transport in large nanostructured semiconductor devices, enabling simulations of up to a million atoms on a single processor.

Contribution

The paper presents a novel approach combining empirical pseudopotential calculations with a top of the barrier splitting scheme for non-equilibrium transport simulation.

Findings

Validated TBS scheme against direct scattering calculations in 1D models.

Demonstrated simulation of a 22 nm double-gate FET with results consistent with NEGF tight-binding.

Achieved large-scale simulations of million-atom devices on a single processor.

Abstract

We present a new empirical pseudopotential (EPM) calculation approach to simulate the million atom nanostructured semiconductor devices under potential bias using the periodic boundary conditions. To treat the non-equilibrium condition, instead of directly calculating the scattering states from the source and drain, we calculate the stationary states by the linear combination of bulk band method and then decompose the stationary wave function into source and drain injecting scattering states according to an approximated top of the barrier splitting (TBS) scheme based on physical insight of ballistic and tunneling transport. The decomposed electronic scattering states are then occupied according to the source/drain Fermi-Levels to yield the occupied electron density which is then used to solve the potential, forming a self-consistent loop. The TBS is tested in an one-dimensional effective mass model by comparing with the direct scattering state calculation results. It is also tested in a three-dimensional 22 nm double gate ultra-thin-body field-effect transistor study, by comparing the TBS-EPM result with the non-equilibrium Green's function tight-binding result. We expected the TBS scheme will work whenever the potential in the barrier region is smoother than the wave function oscillations and if it does not have local minimum, thus there is no multiple scattering as in a resonant tunneling diode, and when a three-dimensional problem can be represented as a quasi-one-dimensional problem, e.g., in a variable separation approximation. Using our approach, a million atom non-equilibrium nanostructure device can be simulated with EPM on a single processor computer.