Using Light And Heat To Controllably Switch And Reset Disorder Configuration In Nanoscale Devices

Quantum dots exhibit reproducible conductance fluctuations at low temperatures due to electron quantum interference. These fluctuations are not solely determined by dot geometry; they are also highly sensitive to the underlying disorder potential. Here we exploit this sensitivity to better understand the role that background impurities play in the electronic properties of undoped AlGaAs/GaAs heterostructures, and nanoscale devices based thereon. 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 background donor impurities, i.e., DX centers. This "alter and reset" capability is not possible in modulation-doped heterostructures and offers a route to new studies of how background impurities influence transport in nanoscale semiconductor devices.