Single-electron tunneling through an individual arsenic dopant in silicon.

V. V. Shorokhov,V. A. Krupenin,D. E. Presnov,S. V. Amitonov,Yu. A. Pashkin

doi:10.1039/c6nr07258e

Abstract

We report the single-electron tunneling behaviour of a silicon nanobridge where the effective island is a single As dopant atom. The device is a gated silicon nanobridge with a thickness and width of ∼20 nm, fabricated from a commercially available silicon-on-insulator wafer, which was first doped with As atoms and then patterned using a unique CMOS-compatible technique. Transport measurements reveal characteristic Coulomb diamonds whose size decreases with gate voltage. Such a dependence indicates that the island of the single-electron transistor created is an individual arsenic dopant atom embedded in the silicon lattice between the source and drain electrodes, and furthermore, can be explained by the increase of the localisation region of the electron wavefunction when the higher energy levels of the dopant As atom become occupied. The charge stability diagram of the device shows features which can be attributed to adjacent dopants, localised in the nanobridge, acting as charge traps. From the measured device transport, we have evaluated the tunnel barrier properties and obtained characteristic device capacitances. The fabrication, control and understanding of such "single-atom" devices marks a further step towards the implementation of single-atom electronics.

Highlights

The remarkable progress of semiconductor industry based on advances in the fabrication of silicon CMOS devices has led to high-speed, ultra-dense and low cost integrated circuits that we use today in our gadgets
The characteristic feature size of semiconductor devices has shrunk to 22 nm in which only a small number of dopant states contribute to the current, and it is expected that in the near future the feature size will approach the minimum possible size – that of a single atom
The fabrication was based on a simple single-layer processing involving conventional lithographic techniques, and followed by controllable etching steps and tests of the device characteristics. This resulted in the planar single-electron transistor whose island is an implanted individual dopant center tunnel coupled to the source and drain electrodes formed by other dopants

Summary

Introduction

The remarkable progress of semiconductor industry based on advances in the fabrication of silicon CMOS devices has led to high-speed, ultra-dense and low cost integrated circuits that we use today in our gadgets. The change of the paradigm for dopants from being passive charge providers in semiconductor microelectronic devices to becoming key elements of single-atom functional devices may have a great impact on future nanoelectronics by advancing both conventional and quantum circuits for information processing, sensing and metrology applications.[2,3]. An important property of individual atoms embedded in a medium is that their quantum confinement energy is of the order of the Coulomb energy, which allows the fabrication of unique single-atom singleelectron tunneling devices as prototypes of quantum bits,[4,5,6] quantum logic gates[7] required for building a quantum processor, logic gates for conventional computers,[8] and charge pumps for quantum metrology.[9,10] Individual dopants in the Si medium were accessed using advanced characterization techniques including tunneling spectroscopy with gated nanowires[11,12,13,14,15,16] and scanning probe structures,[17,18] microwave assisted tunneling[19] capacitance spectroscopy[20] and RF reflectometry.[21]. Lomonosov Moscow State University, Moscow 119991, Russia bDepartment of Physics, Lancaster University, Lancaster LA1 4YB, UK

The physics of the As single-atom single-electron tunneling transistor

Fabrication of the As single-atom single-electron tunneling transistor

Results and discussion

Conclusions