Quantum dot nanostructures: Paradigm changes in semiconductor physics

Prof.dr. Dieter Bimberg
Institut für Festkörperphysik, PN 5-2, Technische Universität Berlin, Hardenbergstr. 36, D- 10623 Berlin, Germany

Universal self-organization and self-ordering effects at surfaces of semiconductors lead to the formation of coherent zero-dimensional clusters called quantum dots (QDs). A total energy model to explain the hierarchy of ordering is presented. The electronic and optical properties of QDs, being smaller than the de-Broglie-wavelength in all three directions of space are closer to those of atoms in a dielectric cage than of solids. QDs possess a delta-function like density of states, and excitons show an extremely long low-temperature phase relaxation time. Their energy eigenstates are only twofold degenerate and do not depend on momentum, which is no conservable any more. All many particle states are strongly Coulomb correlated. Many particle energies depend on shape and size of the dots, such that negative biexciton binding energies appear and no “free” electron-hole-pairs exist. Quantum dots can be exploited for novel optoelectronic devises, like lasers, amplifiers, single photon sources ... Semiconductor nanotechnologies transform presently to enabling technologies for new economies. It is expected that first commercialization of nanophotonic devices and systems will appear soon.