Carrier Dynamics in Quantum Dots

The review of carrier dynamics in quantum dots (QDs) in this chapter often refers to ensembles of QDs, but we will highlight the properties single quantum dots wherever possible. The discussion starts with the capture of carriers into and their relaxation within the QD potential. We examine the phonon-bottleneck problem and continue with the role of Coulomb scattering. This review of ultra-fast relaxation at low densities closes with pointing out the importance of considering polaron formation. With increasing excitation density charged excitons, multi-excitons and Pauli blocking affect the relaxation dynamics. The treatment of the recombination dynamics of electron-hole pairs has to consider first the mostly unwanted effects of blinking, photodarkening and spectral diffusion. Then the focus is on the interpretation of the decay of the photoluminescence signal. A quantitative discussion of intrinsic parameters like lifetime, oscillator strength and dipole moment of various excitonic species is given. We compare these quantities for the various types of quantum dots. Important for the carrier dynamics in QDs is the role of dark states which will be considered in detail. Finally we will highlight the generation of single photons using semiconductor QDs for possible applications in quantum information. This chapter also includes the description of experimental techniques like charge loading of quantum dots or the Hanbury-Brown and Twiss (HBT) correlation experiment.