Dynamics of carrier tunneling between vertically aligned double quantum dots

We have directly measured carrier tunneling times between vertically aligned double quantum dots (QD’s) using time-resolved photoluminescence measurement. The vertically aligned double QD structure consists of ${\mathrm{In}}_{0.9}{\mathrm{Al}}_{0.1}\mathrm{As}$ 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 tunneling time on the barrier thickness is in agreement with the Wentzel-Kramers-Brillouin approximation. The nonresonant tunneling rate between QD’s is found to be suppressed to one-tenth of the tunneling rate between quantum wells.