Optical processes in quantum dots and wires

Quantum wires and dots are unique condensed matter systems where electron and hole localization can be achieved by lateral confinement down to quasi 0-dimensions. Here we review how these nanostructures are realized and their optical properties, mainly from an experimental point of view. We discuss changes in the energy and momentum mechanisms as the lateral dimensions are reduced, such as the so-called photon bottleneck, using the example of GaAs-GaAlAs quantum dots and wires. Examples of strain-relief by deep etching in both nominally lattice-matched and strained materials are given. The emission of hot luminescence or resonant Raman scattering from dots and wires is shown to be a fingerprint of exciton localization. Manu-body effects are shown to be important in nanostructures such as GaAs- GaAlAs and Si-SiGe dots and wires. The emergence of ultrathin submonolayer quantum wells has provided further insights into the role of exciton localization in nanostructures, and we discuss here the case of submonolayers of in-As embedded in a GaAs matrix. Considerations for devices are discussed along with future trends in the field.