Mechanisms of Manganese-Assisted Nonradiative Recombination in Cd(Mn)Se/Zn(Mn)Se Quantum Dots

TL;DR

This paper investigates the mechanisms of nonradiative recombination in Cd(Mn)Se/Zn(Mn)Se quantum dots, highlighting the roles of Coulomb, exchange, and sp-d mixing interactions, and their effects on photoluminescence.

Contribution

It introduces a comprehensive analysis of Mn$^{2+}$-assisted nonradiative recombination mechanisms, including Coulomb, exchange, and sp-d interactions, within a single electron model framework.

Findings

Coulomb mechanism involves long-range dipole-dipole energy transfer.

sp-d mechanism can be more efficient than Coulomb.

Spin selection rules affect exchange and sp-d recombination processes.

Abstract

Mechanisms of nonradiative 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 single electron model of deep {\it 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 {\it 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 {\it e-h} complexes. In contrast, short-range exchange and ${\it sp-d}$ recombinations are subject to spin selection rules, which are the result of strong {\it lh-hh} splitting of hole states in quantum dots. Estimates show that efficiency of the {\it sp-d} mechanism can considerably exceed that of the Coulomb mechanism. The phonon-assisted recombination and processes involving 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.