Spectral and spatial transfer and diffusion of excitons in multiple quantum dot structures

Abstract

A formalism is developed for resonant and nonresonant spectral and spatial energy transfer of excitons in disordered semiconductor multiple-quantum-dot structures. Dipole-dipole and photon-exchange energy-transfer mechanisms are considered. For nonresonant transfer, we study two-site transfer rates in a disordered system as a function of the energy mismatch, the temperature, and the distance. The total time-dependent decay rate of the initial spectral intensity excited at a given energy in the inhomogeneous spectral profile is calculated. For resonant transfer, two-site transfer rates are studied as a function of the distance. The diffusion constant is calculated exactly in a regular quantum dot lattice in order to assess the upper limit of the diffusion constant of a disordered system. We find that the total time-dependent spectral decay rate and the diffusion constant are dominated by the weak long-range photon-exchange interaction mechanism over the standard short-range F\"orster (dipole-dipole) mechanism in a uniform macroscopic multi-quantum-dot system due to the long mean-free path of the photons.