Speed Is of the Essence

Abstract

APPLIED PHYSICS As the dimensions of electronic devices shrink to the extent where single electrons determine operational behavior, there is an increased need to understand the dynamics of charge motion through a semiconductor device, including the tunneling of electrons into quantum dots. Recent work has shown that coupling the quantum dot to a single electron transistor (SET) could shed some light on the electron tunneling process. As an electron is added to the dot, the potential on the island is changed, which in turn results in an oscillation of the current in the SET. However, the sensitivity of the SET to the proximity of an electron on the dot is such that the bandwidth is limited to about 1 megahertz (MHz). Lu et al. now show that this sensitivity can be increased by more than an order of magnitude with a superconducting SET. They estimate that the greater sensitivity of this technique should allow them to increase the bandwidth to around 100 MHz, or within the realms of individual tunneling events. — ISO Appl. Phys. Lett. 77 , 2746 (2000).