Exciton energy transfer between asymmetric quantum wires: Effect of transfer to an array of wires

Abstract

We study the Stokes exciton transfer rate from a narrow quantum wire (QWR) to a parallel wide QWR separated by a wide barrier and also to a planar array of parallel wide QWRs. The transfer rate is calculated as a function of the distance d between the narrow QWR and the wide QWR and also the array. The dependence of the rate on the temperature and the localization radius is studied for free and localized excitons, respectively. Both the resonant and nonresonant rates are considered. We find that, for energy transfer between two QWRs, the Forster dipole-dipole transfer dominates the transfer rate at short and intermediate distances. The photon-exchange transfer prevails only at an extremely long distance where the rate is negligibly small. This behavior is in contrast with the two-dimensional quantum wells, where the photon-exchange mechanism is dominant except at a very short distance. However, for the energy transfer to an array of QWRs, the photon-exchange transfer rate continues to increase as the array size grows to a macroscopic scale due to its slow range dependence while the dipolar rate saturates quickly with the array size. As a result, the photon-exchange transfer can become dominant in a system consisting of stacks of QWRs or arrays distributed over a wide range. The prediction of the theory is consistent with recent data from V-groove GaAs/AlxGa1-xAs double quantum wires.