Determining the Location and Cause of Unintentional Quantum Dots in a Nanowire

TL;DR

This study precisely locates unintentional quantum dots in silicon nanowires, revealing their likely fabrication-related causes and suggesting methods to mitigate their occurrence.

Contribution

It introduces a method to accurately determine U-QD locations and identifies their probable origin as fabrication-induced conduction band modulation.

Findings

U-QDs are consistently located in the same regions across devices.

Capacitance comparison enables nanometer-scale localization.

Fabrication processes influence U-QD formation.

Abstract

We determine the locations of unintentional quantum dots (U-QDs) in a silicon nanowire with a precision of a few nanometers by comparing the capacitances to multiple gates with a capacitance simulation. Because we observe U-QDs in the same location of the wire in multiple devices, their cause is likely to be an unintended consequence of the fabrication, not random atomic-scale defects as is typically assumed. The locations of the U-QDs appear consistent with conduction band modulation from strain from the oxide and the gates. This allows us to suggest methods to reduce the frequency of U-QDs.