Intrinsic and doped coupled quantum dots created by local modulation of implantation in a silicon nanowire

TL;DR

This paper systematically investigates methods to create and tune multi-dot structures in silicon nanowire MOSFETs, focusing on local doping and implantation techniques to control quantum dot formation and coupling.

Contribution

It introduces a novel fabrication approach combining local doping and gate control to realize tunable coupled quantum dots in silicon nanowires.

Findings

Local doping enables independent tuning of tunnel resistances.

Both intrinsic and doped coupled dot structures are achievable.

Device configurations allow precise control of quantum dot coupling.

Abstract

We present a systematic study of various ways (top gates, local doping, substrate bias) to fabricate and tune multi-dot structures in silicon nanowire multigate MOSFETs (metal-oxide-semiconductor field-effect transistors). The carrier concentration profile of the silicon nanowire is a key parameter to control the formation of tunnel barriers and single-electron islands. It is determined both by the doping profile of the nanowire and by the voltages applied to the top gates and to the substrate. Local doping is achieved with the realisation of up to two arsenic implantation steps in combination with gates and nitride spacers acting as a mask. We compare nominally identical devices with different implantations and different voltages applied to the substrate, leading to the realisation of both intrinsic and doped coupled dot structures. We demonstrate devices in which all the tunnel resistances towards the electrodes and between the dots can be independently tuned with the control top gates wrapping the silicon nanowire.