Stark Effect and the Measurement of Electric Fields with Quantum Dot Molecules - Quantum Dot Molecules - page 365

electric field. To induce an opposing field, however, the ionized electrons and holes
must not only separate but also remain within the device region. In our device, this
is most likely done through trapping at impurity sites and materials boundaries (e.g.,
the GaAs/AlGaAs interface, the WLs, or the doped/intrinsic GaAs interface), while
those not trapped will contribute to the measured photocurrent.
Using a gated photon counting technique, the associated temporal response of
F o was measured using a modulated laser excitation with energy above the WL
while continuously monitoring the PL through a CW laser that was below the WL
energy. We observed a relatively long decay time on the order of 110-140

sforthe
temporal response of F o . This can be related to the trapping of carriers at material
interfaces and impurity sites and was consistent with carrier lifetimes in III-V
materials as well as estimates of tunneling rates of the holes through the AlGaAs
barrier. Experiments associated with the variations in the laser power signified that
the decay rate of F o does not have an influence on the number of generated charge
carrier densities. The onset of the optically generated electric field was limited by
the temporal resolution of the experiment (7-8 s). However, the observed results

of the generation rate of F o yielded a frequency response on the order of MHz,
which can possibly be useful for future applications of fast, non-contact, electric
field modulation techniques.

Acknowledgments The authors would like to thank Dan Gammon and Allan Bracker for helpful
discussions. This work was supported by the Ohio University CMSS program and NSF grant
number DMR-1005525.

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