Transport properties of gated sub-micron mesas incorporating InAs self-assembled quantum dots that conduct near zero bias

We have fabricated multiple-gate vertical mesa transistors to investigate the Coulomb oscillation and Coulomb diamond-like characteristics of a planar ensemble of self-assembled InAs quantum dots located in the central plane of a single 14 nm Al0.2Ga0.8As tunnel barrier. The current–voltage characteristics are dominated by electron tunneling through the energy levels of just a few (∼10) dots. Since these dots are located at various distances from the mesa side walls, the dot energy levels up-shift at different rates when the gate-adjustable front of the depletion region spreads towards the center of the mesa. This results in Coulomb-diamond apexes with different gate voltage signatures.