Self-Organized Semiconductor Quantum Islands in A Semiconducting Matrix

Abstract

Reaching and perusing the quantum limit in conventional devices like memory units is the goal of the current research to allow a further increase in device performance while reducing the device size. While lithographic processes are still widely used for device patterning, these techniques result in corrugated surfaces, inducing undesired surface recombination centers. Thus they are not suitable for high quality, high density quasi-zero dimensional systems with lateral dimensions typically below 30 nm. A self-organization of quantum dots is the alternative. The self-organization of colloidal chalcogenide quantum dots (QD) from liquid solutions or in a glass melt is known since the 1930-ies and has lead to applications like optical absorbers and filters, as the average size of the quantum dot ensemble determines the absorption edge. While a very high density and homogeneity of QD sizes can be achieved, the matrix these QDs are embedded in is generally non-conducting and does not allow to build electrically driven devices. In recent years epitaxial techniques have been developed that allow the embedding of QDs in a semiconducting matrix. These QDs are induced by driving forces that are determined e.g. by the interface energy and the lattice mismatch between the QD and the matrix-material, a perfect crystallinity provided. On the example of CdSe islands embedded in ZnSe we shall discuss the outstanding physical properties of such quasi zero dimensional island structures but also the difficulties in their fabrication.