Highly strained semiconductors grow epitaxially on mismatched substrates in the
Stranski–Krastanow growth mode, wherein islands are formed after a few monolayers of
layer-by-layer growth. Elastic relaxation on the facet edges, renormalizaton of the surface energy of the facets, and interaction between neighbouring islands via the substrate are the driving forces for self-organized growth. The dimensions of the defect-free islands are of the order of λB, the de Broglie wavelength, and provide three-dimensional quantum confinement of carriers. These self-organized quantum dots, or quantum boxes, are grown by MBE or MOVPE on GaAs, InP, and other substrates, and are being incorporated in microelectronic and optoelectronic devices. The use of strain to produce self-organized quantum dots has become a well-accepted approach and is widely used in III–V semiconductors and other material systems. Much progress has been made in the areas of growth, where the focus has been on size control, and optical characterization, where the goal has been the application to devices.
The collection of articles in this Cluster Issue of Journal of Physics D: Applied Physics, authored by pioneers in the field, portray the tremendous advances that have been made in the epitaxy, the understanding of electronic and optical properties, and the optoelectronic device applications of GaAs- and InP-based self-organized quantum dots. After a general review of this development by Professor D Bimberg, the following articles describe the electronic and optical properties of quantum dots (Mobray and Skolnick), the dynamics of hot carriers in the dots (Norris et al), InP-based lasers (Reithmaier et al), high-performance GaAs-based lasers (Fathpour et al, Su and Lester, Deppe et al), quantum dot amplifiers (Sugawara et al) and quantum dot infrared photodetectors (QDIPs) (Chakrabarti et al, Krishna).
It is hoped that readers will get the sense that self-organized quantum dots are no longer a mere curiosity, but form the active materials for high-performance and novel devices.