Charge states of a collinearly and laterally coupled vertical triple quantum dot device

Three laterally coupled vertical single quantum dots (tQDs) in a collinear arrangement, with common source and drain electrodes, are investigated. The tQDs are formed inside three connected pillars (mesa1, mesa2, mesa3) with four side gate electrodes (G1, G2 (G2'), G3). Three families of Coulomb oscillation lines corresponding to charges in the numbers of electrons in the three dots are observed, and the few-electron charge configurations can be assigned. We also discuss the separation of adjacent Coulomb peak lines in the stability diagram, indicating that the inter-dot Coulomb energy between adjacent dots (mesa1–mesa2 and mesa2–mesa3) is significantly larger than that between the two non-adjacent dots (mesa1–mesa3).