III-V semiconductor quantum dots with a magnetic impurity

We investigate the hole states in GaAs and InAs quantum dots (QDs) containing a single substitutional Mn impurity, which is a shallow acceptor in the configuration d5+h. For an on-center Mn, in spherical nanocrystals the hole spectrum is found to retain the bulk level scheme, while the binding energy and the sp –d exchange contribution increase rapidly with decreasing QD size. In contrast, in lens-shaped self-assembled QDs the four-fold ground state is split into two well-separated doublets, the confinement-induced enhancement is slower and the effective exchange strength an order-of-magnitude smaller than in the bulk. A preliminary study of the twohole states indicates that the ground state in InAs/GaAs QDs is a singlet, almost uncoupled to the Mn spin. We deduce the zero-field fine structure of the excitonic transitions and compare our results with recently reported photoluminescence spectra (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)