ABSTRACT
ABSTRACT : Semiconductors having structures of reduced dimensions as, e.g., quantum dots (QDs) are expected to exhibit special optical and electronic properties leading to new kind of optoelectronic devices. In the past 15 years, the generation of QDs has been attempted using different techniques. However, there was a breakthrough recently initiated by employing of self-ordering mechanisms during the epitaxial growth of lattice-mismatched materials. As an introduction, electronic properties of small islands (0< 30nm) are presented. Principles of the formation of such coherent islands applying the "Stranski-Krastanow" growth mode and further developments in the scope of TEM are briefly demonstrated. The applicability of such quantum structures further can be improved using not single layers of QDs, but, e.g., stacked layers. This has been successfully demonstrated for systems such as GalnAs, SiGe, InAsN. The paper is mainly focused on the formation and properties of InGaAs islands ("dots") in a GaAs matrix, a system showing similar properties as found in other material systems. The goal of TEM investigation of these systems, especially QD layers, is a correlation between morphology/structure and their optical behaviour. TEM techniques applied for such analysis will be discussed.
