Optical characterization of quantum wires and quantum dots

Different optical techniques are described for the characterization of low-dimensional semiconductor structures like quantum wires and quantum dots. The main motivation for the strong interest in these structures stems from the unique properties in terms of tunable electronic structure and related properties. Progress in applications of such quantum structures is, however, limited by the poor control of their geometrical distribution, leading to strong, inhomogeneous broadening. New techniques are thus needed which allow the study of individual quantum structures and, hence, to learn more about the electronic properties. Three main techniques are described: photoluminescence in its macroscopical as well as microscopical form, cathodoluminescence, and luminescence induced by a scanning tunneling microscope. These techniques are illustrated by optical characterization of quantum wire structures grown on patterned substrates and of quantum dots formed by the Stranski-Krastanow mechanism.