Dynamics of carrier tunneling between vertically aligned double quantum dots

We have directly measured carrier tunneling times between vertically aligne d double quantum dots (QD's) using time-resolved photoluminescence measurem ent. The vertically aligned double QD structure consists of In0.9Al0.1As QD 's, a GaAs barrier layer, and InAs QD's. The tunneling times were measured for the three different barrier thicknesses. The dependence of the tunnelin g time on the barrier thickness is in agreement with the Wentzel-Kramers-Br illouin approximation. The nonresonant tunneling rate between QD's is found to be suppressed to one-tenth of the tunneling rate between quantum wells.