Optical Spectroscopy on Epitaxially Grown II--VI Single Quantum Dots

Abstract

Spatially resolved optical spectroscopy applied to single non-magnetic and magnetic II--VI semiconductor quantum dots allows one to study optical, electronic and magnetic properties of single quantum objects. A controlled population of the quantum dot eigenstates by single particles can be obtained by laser excitation, in part combined with electrical current injection. This gives access to intrinsic properties of excitons and biexcitons, like phonon or exchange interaction or coupling to the radiation field. It is demonstrated that the eigenstates in single quantum dots can be manipulated in a well-controlled way simply by applying external electric and magnetic fields. This gives insight into the charge distribution and the g-factor of the particles within the dot. Introducing Mn$^{2+}$ions into the crystal matrix results in an efficient spin--spin interaction between carriers and magnetic ions. We discuss giant magneto-optical effects like huge effective g-factors and the formation of quasi-zero-dimensional magnetic polarons and demonstrate how the optical response of a magnetic single quantum dot can be used to monitor nano-scale fluctuations of the magnetization.