As a type-II heterostructure with exclusive hole confinement GaSb/(Al,Ga)As QDs are an ideal candidate for
a QD based memory device operating at room temperature. We investigated different Antimony-based QDs in
respect of localization energies and storage times with 8-band-k•p calculations as well as time-resolved capacitance
spectroscopy. In addition, we present a memory concept based on self-organized quantum dots (QDs) which could
fuse the advantages of today's main semiconductor memories DRAM and Flash. First results on the performance
of such a memory cell are shown and a closer look at Sb-based QDs as a storage unit is taken.
Efficient generation of polarized single or entangled photons is a crucial requirement for the implementation
of quantum key distribution (QKD) systems. Self-organized semiconductor quantum dots (QDs) are capable of
emitting one polarized photon or an entangled photon pair at a time using appropriate electrical current injection.
We realized highly efficient single photon sources (SPS) based on well established semiconductor technology: In
a pin structure a single electron and a single hole are funneled into a single InAs quantum dot using a submicron
AlOx current aperture. Efficient radiative recombination leads to emission of single polarized photons with an
all-time record purity of the spectrum. Non-classicality of the emitted light without using additional spectral
filtering is demonstrated. Out-coupling efficiency and emission rate are increased by embedding the SPS into a
micro-cavity of Q = 140. The design of the micro-cavity is based on detailed modeling to optimize its performance.
The resulting resonant single-QD diode generates single polarized photons at a repetition rate of 1 GHz exhibiting
a second order correlation function of g(2)(0) = 0.
Eventually, QDs grown on (111) oriented substrate are proposed as source of entangled photon pairs. Intrinsic
symmetry-lowering effects leading to the splitting of the exciton bright states are shown to be absent for this
substrate orientation. As a result the XX → X → 0 recombination cascade of a QD can be used for the generation
of entangled photons without further tuning of the finestructure splitting via QD size and/or shape. We present
first micro-photoluminescence studies on QDs grown on (111) GaAs, demonstrating a fine structure splitting less
than the spectral resolution of our set-up.
Interaction between strongly localized charge carriers in zero-dimensional systems like quantum dots (QD) depends sensitively on the geometrical roperties of the dots. The recently observed monolayer splitting with eight well resolved peaks (in low excitation photoluminescence (PL)) together with eight-band kp theory as the appropriate tool for modeling electronic and optical properties offers direct spectroscopic access to details of the QD morphology. By this achievement it became possible to link single-dot spectra obtained by cathodoluminescence measurements via the exciton transition energy to structural properties of the probed QD. In view of theory this situation constitutes an ideal starting point to study few-particle interactions for realistic InAs QDs as a function of their structural properties. This is done using the configuration interaction method. The wavefunctions are obtained from eight-band kp calculations of single-particle states including explicitly piezoelectric effects in the confinement potential.