Mechanisms of manganese-assisted non-radiative recombination in Cd(Mn)Se/Zn(Mn)Se quantum dots

Mechanisms of non-radiative recombination of electron-hole complexes in Cd(Mn)Se/Zn(Mn)Se quantum dots accompanied by interconfigurational excitations of Mn(2+) ions are analyzed within the framework of the single-electron model of deep 3d levels in semiconductors. In addition to the mechanisms caused by Coulomb and exchange interactions, which are related because of the Pauli principle, another mechanism due to sp-d mixing is considered. It is shown that the Coulomb mechanism reduces to long-range dipole-dipole energy transfer from photoexcited quantum dots to Mn(2+) ions. The recombination due to the Coulomb mechanism is allowed for any states of Mn(2+) ions and e-h complexes. In contrast, short-range exchange and sp-d recombinations are subject to spin selection rules, which are the result of strong lh-hh splitting of hole states in quantum dots. Estimates show that efficiency of the sp-d mechanism can considerably exceed that of the Coulomb mechanism. The phonon-assisted recombination and processes involving the upper excited states of Mn(2+) ions are studied. The increase in PL intensity of an ensemble of quantum dots in a magnetic field perpendicular to the sample growth plane observed earlier is analyzed as a possible manifestation of the spin-dependent recombination.