Using light and heat to controllably switch and reset disorder configuration in nanoscale devices

TL;DR

This paper demonstrates a novel method to controllably modify and reset the disorder potential in nanoscale quantum dot devices using light and heat, enabling better study of impurity effects.

Contribution

It introduces a new technique to alter and reset disorder configurations in undoped heterostructures via optical and thermal methods, unlike traditional modulation doping.

Findings

Optical illumination can modify the disorder potential in undoped heterostructures.

Thermal cycling in the dark can reset the disorder to its original state.

Impurities such as C and Si impurities influence the disorder behavior.

Abstract

Quantum dots exhibit reproducible conductance fluctuations at low temperatures due to electron quantum interference. The sensitivity of these fluctuations to the underlying disorder potential has only recently been fully realized. We exploit this sensitivity to obtain a novel tool for better understanding the role that background impurities play in the electrical properties of high-mobility AlGaAs/GaAs heterostructures and nanoscale devices. In particular, we report the remarkable ability to first alter the disorder potential in an undoped AlGaAs/GaAs heterostructure by optical illumination and then reset it back to its initial configuration by room temperature thermal cycling in the dark. We attribute this behavior to a mixture of C background impurities acting as shallow acceptors and deep trapping by Si impurities. This "alter and reset" capability, not possible in modulation-doped heterostructures, offers an exciting route to studying how scattering from even small densities of charged impurities influences the properties of nanoscale semiconductor devices.