Enhancement of the binding energy of charged excitons in disordered quantum wires

Negatively and positively charged excitons are identified in the spatially resolved photoluminescence spectra of quantum wires. We demonstrate that charged excitons are weakly localized in disordered quantum wires. As a consequence, the enhancement of the “binding energy” of a charged exciton is caused, for a significant part, by the recoil energy transferred to the remaining charged carrier during its radiative recombination. We discover that the Coulomb correlation energy is not the sole origin of the “binding energy,” in contrast to charged excitons confined in quantum dots.

Figure 1

Evolution of PL spectra with gate voltage for the thin QWR measured at 10 K through a submicron aperture.

Figure 2

Line shape fitting of the negatively charged exciton line at three temperatures.

Figure 3

Binding energies of negatively and positively charged excitons and spectral positions of neutral exciton line measured in eleven separate apertures for the thin QWR sample. The binding energies are displayed relatively to their mean value (the error is 0.05 meV).

Figure 4

Calculated dependence of the $X^{+}$ and $X^{-}$ binding energies on the length of the square potential. The depth of the potential was fitted to yield the same value of $L$ for the binding energies of aperture no. 5.