We report on a quantum dot device design that combines the low disorder properties of undoped SiGe heterostructure materials with an overlapping gate stack in which each electrostatic gate has a dominant and unique function -- control of individual quantum dot occupancies and of lateral tunneling into and between dots. Control of the tunneling rate between a dot and an electron bath is demonstrated over more than nine orders of magnitude and independently confirmed by direct measurement within the bandwidth of our amplifiers. The inter-dot tunnel coupling at the (0,2)<-->(1,1) charge configuration anti-crossing is directly measured to quantify the control of a single inter-dot tunnel barrier gate. A simple exponential dependence is sufficient to describe each of these tunneling processes as a function of the controlling gate voltage.
@article{arxiv.1408.0600,
title = {Undoped accumulation-mode Si/SiGe quantum dots},
author = {Matthew G. Borselli and Kevin Eng and Richard S. Ross and Thomas M. Hazard and Kevin S. Holabird and Biqin Huang and Andrey A. Kiselev and Peter W. Deelman and Leslie D. Warren and Ivan Milosavljevic and Adele E. Schmitz and Marko Sokolich and Mark F. Gyure and Andrew T. Hunter},
journal= {arXiv preprint arXiv:1408.0600},
year = {2014}
}