Exciton Spin Dynamics in Semiconductor Quantum Dots

Abstract

AbstractSemiconductor quantum dots are nanometer sized objects that contain typically several thousand atoms of a semiconducting compound resulting in a confinement of the carriers in the three spatial directions. They can be synthesized by a large variety of methods based on colloidal chemistry [1, 2], molecular beam epitaxy or metalorganic chemical vapor deposition. Quantum dots can be formed at interface steps of thin quantum wells [3, 4] or by self-assembly in the Stransky-Krastanov growth mode during molecular beam epitaxy. This process is driven by the strain resulting from the difference in lattice parameter between the matrix (barrier) and the dots, for example 7% for InAs dots in GaAs. The quantum dots obtained in this well-studied system are typically 20 nm in diameter and 5 nm in height and are formed on a thin quantum well referred to as a wetting layer, see Fig. 4.1 for a transmission electron microscope image [5]. Samples used for optical spectroscopy are then covered again by the barrier material. The Stransky-Krastanov growth mode is applied to a large variety of III–V and II–VI compounds [6–8]. An interesting alternative for fabricating GaAs or InAs dots is provided by a technique which is not strain driven, called molecular droplet epitaxy [9]. Quantum dots defined by electrostatic potentials have also shown very interesting effects at very low temperature [10, 11].KeywordsCircular PolarizationDynamical Nuclear PolarizationRadiative LifetimeQuantum BeatAnisotropic ExchangeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.