Electron-Hole Long-Range Exchange Interaction and Fine Structure of Excitonic
Levels in Semiconductor Quantum Dots
Serguei Goupalov
Department of Electric and Computer Engineering,
Georgia Tech
Electron-hole long-range exchange interaction is one of the main mechanisms
responsible for the fine structure of excitonic levels in various QD systems.
In bulk semiconductors it leads to the longitudinal-transverse splitting
of exciton states which is on the order of 0.1 - 1 meV for A3B5 and A2B6
compounds. However, in QD systems with strong confinement, when the ratio
of the bulk exciton Bohr radius to the QD size is much more than unity,
the exchange interaction is enhanced with respect to its bulk value by
a factor of the ratio in the third power. As a result, the exchange-induced
splittings are on order of several tens of meV. In anisotropic QD systems
with weak confinement, such as islands of QW width fluctuations, the long-range
exchange interaction causes splittings of the exciton radiative levels
to the states linearly polarized along
the system principal axes. An insight to the phenomena will be provided
by a comparison with an alternate treatment where the splittings are due
to interaction of the exciton with the exciton-induced macroscopic longitudinal
electric field.