Transport of coupled double quantum dots in series

Results of transport measurements on double quantum dots in series with a weak mutual coupling are presented. Samples have been obtained by delineating two-dimensional electron gas in modulation-doped AlGaAs/GaAs with independently bias-tunable, 100 nm wide, Schottky-gates formed by an electron beam lithography and a lift-off technique. In the Coulomb-blockade regime, Coulomb oscillations with two different periods have been observed, which are probably due to an electrostatic coupling between the remote dot and the bias-sweeping gate. This is confirmed from the transport characteristics of isolated single dots and a simple estimation of the charge degeneracy of the system. Clear Coulomb-staircase structures have also been observed in the double-dot system at a limited high-bias condition.