  InAs/GaAs quantum dots (QDs) and quantum dot molecules (QDMs) are
self-assembled semiconductor nanostructures that can trap a single electron or
hole with well-defined spin projections. QDs and QDMs have excellent optical
properties and have long been of interest for incorporation into quantum
optoelectronic devices ranging from single photon sources to multi-bit quantum
computers. The properties of single QDs, or carriers confined within those QDs,
can be tuned by external electric fields, which provides an important tool for
the development of scalable and tunable devices. Deterministic charging of a QD
with a single electron or hole is an important tool for quantum devices and is
well-established under the application of growth-direction electric fields in a
diode structure. Here, we report a new charging mechanism for a single QD in a
3-electrode device that does not contain a vertical diode and can be used to
control electric field profiles in two dimensions. We fabricate the device with
E-beam lithography and characterize photoluminescence from single QDs under
different bias configurations. Using a combination of experimental data and
COMSOL band structure calculations, we explain how the charging originates in
the electrical-injection of holes induced by lateral electric fields. We
discuss the applications for this device and the potential for full 2-D
electric field control of a single QD and QDM.
