Transport properties and electrical device characteristics with the TiMeS computational platform: Application in silicon nanowires

Abstract

Nanoelectronics requires the development of a priori technology evaluation for materials and device design that takes into account quantum physical effects and the explicit chemical nature at the atomic scale. Here, we present a cross-platform quantum transport computation tool. Using first-principles electronic structure, it allows for flexible and efficient calculations of materials transport properties and realistic device simulations to extract current-voltage and transfer characteristics. We apply this computational method to the calculation of the mean free path in silicon nanowires with dopant and surface oxygen impurities. The dependence of transport on basis set is established, with the optimized double zeta polarized basis giving a reasonable compromise between converged results and efficiency. The current-voltage characteristics of ultrascaled (3 nm length) nanowire-based transistors with p-i-p and p-n-p doping profiles are also investigated. It is found that charge self-consistency affects the device characteristics more significantly than the choice of the basis set. These devices yield sourced-drain tunneling currents in the range of 0.5 nA (p-n-p junction) to 2 nA (p-i-p junction), implying that junctioned transistor designs at these length scales would likely fail to keep carriers out of the channel in the off-state. (C) 2013 AIP Publishing LLC

Platinum atomic contacts: From tunneling to contact

“…We performed electron transport calculations by means of the NEGF extension of the OpenMX code, 29 which is by now widely used. [38][39][40][41][42][43] The model implemented in this software makes use of periodic boundary conditions. The basis sets employed consist of linear combinations of atomic orbitals generated by a confinement scheme which yields wave functions with zero value beyond a chosen cutoff radius.…”

Real-space method for highly parallelizable electronic transport calculations

“…All calculations used a grid spacing of 0.6 a 0 , giving Hamiltonian dimensions N from 13,000 to 22,000. Also shown are reference calculations using the TIMES transport code 45 to compute T (E) in the linear response regime based on OpenMX 46 electronic structure. The OpenMX calculation used a basis set of 17 orbitals per atom for both the hydrogen and carbon chains.…”

Electrode-molecule energy level offsets in a gold-benzene diamine-gold single molecule tunnel junction

“…It is found that six layers of Au atoms (3 repeat units) form an electrode cell that is sufficiently large to make nextnearest-neighbour interactions between cells negligible. This model of the junction and semi-infinite electrodes are then used with the TiMeS quantum transport program [31] to calculate electron transmission. The TiMeS program uses semi-analytical expressions for the Green's functions in the NEGF formalism for which the limit for the artificial broadening parameter approaching zero has been taken.…”