Transport properties of a single pair of coupled self-assembled InAs quantum dots

Electron transport properties of a single pair of strongly and weakly coupled self-assembled InAs quantum dots are investigated using a single electron spectroscopy technique. We fabricated vertical single electron transistors containing just a few pairs of vertically coupled two InAs dot layers embedded in a GaAs matrix. The transport through a single pair of the coupled dots is observed near the pinch-off point of the devices. Thus, observed Coulomb oscillations and Coulomb diamonds show the characteristics just like a single dot for the strongly coupled dots, whereas those for the weakly coupled dots show the irregular features due to the localization of electrons in each dot. In case more than one pair of the coupled dots contributed to the transport, the parallel conduction is proved by observation of two families of Coulomb diamonds.