A Tight-Binding Study of Single-Atom Transistors

Abstract

A detailed theoretical study of the electronic and transport properties of a single atom transistor, where a single phosphorus atom is embedded within a single crystal transistor architecture, is presented. Using a recently reported deterministic single‐atom transistor as a reference, the electronic structure of the device is represented atomistically with a tight‐binding model, and the channel modulation is simulated self‐consistently with a Thomas‐Fermi method. The multi‐scale modeling approach used allows confirmation of the charging energy of the one‐electron donor charge state and explains how the electrostatic environments of the device electrodes affects the donor confinement potential and hence extent in gate voltage of the two‐electron charge state. Importantly, whilst devices are relatively insensitive to dopant ordering in the highly doped leads, a ∼1% variation of the charging energy is observed when a dopant is moved just one lattice spacing within the device. The multi‐scale modeling method presented here lays a strong foundation for the understanding of single‐atom device structures: essential for both classical and quantum information processing.

Probing the Quantum States of a Single Atom Transistor at Microwave Frequencies

“…( < ∼ 5 nm) used to address the donor are quasi-1D, make it difficult, by using simple dc bias spectroscopy, to distinguish the signatures in current related to the excited states of the donor from the features related to the density of the states (DOS). 20,21,31,32 Later we will show how we apply transient current spectroscopy as described in Refs. 23,24 to clarify some of the transport mechanisms that can arise throughout the excited state spectrum of a single atom transistor.…”

Atom‐by‐Atom Fabrication of Single and Few Dopant Quantum Devices

“…While the basic properties of the P atom in Si are not changing in each of these cases (e.g., orbital structure), the electrostatic environment as influenced by the placement and type of electrodes does vary considerably and has been cited as the principle cause for lowering of the addition energy relative to bulk in the FET devices. [32] In the context of these previous measurements, all of the single P atom devices reported show ground state energies above the Fermi level, while all reported STM-fabricated planar devices additionally exhibit electron addition energies above the bulk value.…”

Acceleration of Large-Scale Electronic Structure Simulations with Heterogeneous Parallel Computing

“…The codes are compiled with CUDA 8.0 library, Intel C++ compiler 16.0, and OpenMPI 1.10.2. Si:P quantum dots (QDs), which are defined to be huge silicon (Si) layers encapsulating a single phosphorus (P) atom and are studied with a 10-band TB model for designs of Si-based quantum computers [8,9,23], are used as target devices for all the benchmark tests.…”

“…The spds* 10-band tight-binding (TB) approach, which employs a set of 10 localized orbital bases to describe a single atom, has been extensively used to explain experimental behaviors of various quantum devices [2,[6][7][8][9] through large-scale electronic structure simulations with the well-known nanoelectronics modeling tool (NEMO) [10,11]. As the NEMO only runs in traditional computing clusters of multicore processors, we also have recently released a new software package for TB simulations (Quantum simulation tool for Advanced Nanoscale Devices (Q-AND)), which supports computation with Intel Xeon Phi PCI-E add-in devices and shows enhanced performance compared to the result obtained with clusters of Intel Xeon multicore processors [12].…”