Self-Assembly in Semiconductor Epitaxy: From Growth Mechanisms to Device Applications

A key feature of epitaxial semiconductor crystal growth is the possibility of realizing different surface morphological features when growing one material on another. This is driven by many factors, of which the relative lattice mismatch between the materials and the nature of the resultant strain is particularly crucial. Under appropriate conditions, elastic strain relaxation can lead to spontaneous generation of coherent three-dimensional (3D) islands with relatively small size dispersion. These self-assembled islands can be embedded within a material of larger bandgap resulting in 3D quantum confinement of electrons within the island and the formation of quantum dots (QDs). In this chapter we review the strain-driven selfassembly process during semiconductor epitaxy, looking at thermodynamic and kinetic factors that influence the growth as well as specific features of QDs in various materials systems. We highlight the very fundamental correlations between structure and functionality, discuss various characterization techniques, and examine the salient features of the electronic and optical properties of QDs which make them useful for various device applications. We provide a summary of the state of the art in technological applications where the use of QD-based devices has led to improved performance and functionality. Specifically QD-based lasers, superluminescent diodes, infrared photodetectors, memories and single photon sources are discussed, with a focus on materials and growth issues.